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Newgard, Christopher Bang

Overview:

Over its 16 year history, our laboratory has investigated mechanisms of metabolic regulation and fuel homeostasis in mammalian systems. Major projects include: 1) Mechanisms involved in regulation of insulin secretion from pancreatic islet β-cells by glucose and other metabolic fuels; 2) Development of methods for protection of β-cells against immune-mediated damage; 3) Studies on spatial organization and regulation of systems controlling hepatic glucose balance; 4) Studies on the mechanisms involved in lipid-induced impairment of insulin secretion and action in diabetes.

Positions:

W. David and Sarah W. Stedman Professor of Nutrition in the School of Medicine

Pharmacology & Cancer Biology
School of Medicine

Professor of Pharmacology and Cancer Biology

Pharmacology & Cancer Biology
School of Medicine

Director, Sarah W. Stedman Nutrition and Metabolism Center

Sarah Stedman Nutrition & Metabolism Center
School of Medicine

Professor of Biochemistry

Biochemistry
School of Medicine

Professor in Medicine

Medicine, Endocrinology, Metabolism, and Nutrition
School of Medicine

Affiliate, Duke Global Health Institute

Duke Global Health Institute
Institutes and Provost's Academic Units

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 1984

Ph.D. — University of Texas at Dallas

News:

Grants:

Duke Training Grant in Nephrology

Administered By
Medicine, Nephrology
AwardedBy
National Institutes of Health
Role
Preceptor
Start Date
September 20, 1995
End Date
June 30, 2022

Postdoctoral training in genomic medicine research

Administered By
Duke Center for Applied Genomics and Precision Medicine
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
June 14, 2017
End Date
May 31, 2022

A comprehensive research resource to define mechanisms underlying microbial regulation of host metabolism in pediatric obesity and obesity-targeted therapeutics

Administered By
Molecular Genetics and Microbiology
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
September 25, 2016
End Date
August 31, 2021

Multidisciplinary Heart and Vascular Diseases

Administered By
Medicine, Cardiology
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1975
End Date
March 31, 2021

The Effects of a Novel Statin-Induced Protein Modification on Fatty Acid Synthase

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Co-Mentor
Start Date
September 08, 2017
End Date
September 07, 2020

Engineered Glucose Metabolism in Insulin Secreting Cells

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
May 01, 2002
End Date
August 31, 2020

Organization and Function of Cellular Structure

Administered By
Basic Science Departments
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1975
End Date
June 30, 2020

Pharmacological Sciences Training Program

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Participating Faculty Member
Start Date
July 01, 1975
End Date
June 30, 2020

13C-Metabolic Flux Analysis for Understanding Cardiac Energy Homeostasis

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Co-Mentor
Start Date
June 01, 2017
End Date
May 31, 2020

Pharmacology Industry Internships for Ph.D. Students

Administered By
Pharmacology & Cancer Biology
AwardedBy
American Society for Pharmacology and Experimental Therapeutics
Role
Participating Faculty Member
Start Date
January 01, 2017
End Date
December 31, 2019

Endocrinology and Metabolism Training Program

Administered By
Medicine, Endocrinology, Metabolism, and Nutrition
AwardedBy
National Institutes of Health
Role
Co-Director
Start Date
July 01, 2014
End Date
June 30, 2019

Novel SIRT5 Enzymatic Activity Regulates Cellular Mechanisms of Aging and Disease

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
February 01, 2014
End Date
January 31, 2019

Characterization of PDX1-Induced Soluble Factors that Stimulate Beta-Cell Replication

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
American Diabetes Association
Role
Principal Investigator
Start Date
January 01, 2016
End Date
December 31, 2018

Role of Protein Malonylation in Regulating Mitochondrial Function

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
September 30, 2015
End Date
September 29, 2018

Eli Lilly Collaboration

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Eli Lilly and Company
Role
Principal Investigator
Start Date
June 26, 2017
End Date
August 18, 2018

Duke KURe Program

Administered By
Obstetrics and Gynecology, Urogynecology
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
August 01, 2013
End Date
July 31, 2018

HIRN UCSD

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
University of California - San Diego
Role
Principal Investigator
Start Date
April 01, 2017
End Date
June 30, 2018

Metabolomics Core A

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Washington University in St. Louis
Role
Co Investigator
Start Date
September 15, 2014
End Date
June 30, 2018

Project 1

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Washington University in St. Louis
Role
Principal Investigator
Start Date
September 15, 2014
End Date
June 30, 2018

Ethanol-induced Protein Acylation Regulates Metabolism

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Significant Contributor
Start Date
August 05, 2013
End Date
June 30, 2018

Reversible Mitochondrial Protein Acetylation and Metabolic Regulation

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Buck Institute for Research on Aging
Role
Principal Investigator
Start Date
June 01, 2017
End Date
May 31, 2018

Gene expression programs of lactic acidosis in human cancers

Administered By
Molecular Genetics and Microbiology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
July 02, 2007
End Date
April 30, 2018

Duke Research Training Program for Pediatricians

Administered By
Pediatrics, Infectious Diseases
AwardedBy
National Institutes of Health
Role
Training Faculty
Start Date
July 01, 2002
End Date
April 30, 2018

Mitochondrial Protein Acetylation and Energy Metabolism in Muscle

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Co-Sponsor
Start Date
April 29, 2015
End Date
April 28, 2018

Biomarkers of Mental Stress Induced Myocardial Ischemia and CHD Prognosis

Administered By
Psychiatry & Behavioral Sciences, Behavioral Medicine
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
May 09, 2014
End Date
March 31, 2018

Microbiome engineering to affect host nitrogen/amino acid metabolism

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Synlogic
Role
Principal Investigator
Start Date
January 25, 2017
End Date
January 24, 2018

Growth Failure in Extremely Preterm Infants: Microbiomic and Metabolomic Analysis

Administered By
Pediatrics, Neonatology
AwardedBy
Gerber Foundation
Role
Collaborator
Start Date
July 01, 2014
End Date
December 31, 2017

A Biochemical Roadmap of Exercise Signaling

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Broad Institute
Role
Principal Investigator
Start Date
December 14, 2016
End Date
November 30, 2017

The Breast Milk, Gut Microbiome and Immunity (BMMI) Project - Proof of Concept Phase

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Washington University in St. Louis
Role
Principal Investigator
Start Date
November 24, 2015
End Date
November 30, 2017

Center for Molecular & Cellular Studies of Ped Disease

Administered By
Pediatrics
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
April 11, 2003
End Date
November 30, 2017

Metabolomic Biomarkers Predictores of Long-term Success Following Bariatric Surgery

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Columbia University
Role
Principal Investigator
Start Date
September 22, 2015
End Date
June 30, 2017

Development of Novel Therapies for NIDDM

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
April 01, 1984
End Date
April 30, 2017

Reversible Mitochondrial Protein Acetylation and Metabolic Regulation

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Gladstone
Role
Principal Investigator
Start Date
June 01, 2010
End Date
February 28, 2017

Sponsored Research Agreement

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Eli Lilly and Company
Role
Principal Investigator
Start Date
December 18, 2015
End Date
February 17, 2017

Beta cell development and type 2 diabetes: the role of lactogen signaling

Administered By
Pediatrics, Endocrinology
AwardedBy
American Diabetes Association
Role
Consultant
Start Date
January 01, 2014
End Date
December 31, 2016

The Breast Milk, Gut Microbiome and Immunity Project

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Washington University in St. Louis
Role
Principal Investigator
Start Date
November 01, 2013
End Date
October 31, 2016

VA268-15-J-0133

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Durham Veterans Affairs Medical Center
Role
Principal Investigator
Start Date
September 30, 2015
End Date
September 29, 2016

VA240-13-R-0080

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Department of Veterans Affairs
Role
Principal Investigator
Start Date
September 26, 2013
End Date
September 29, 2016

Regulation of Islet Beta-Cell Function via Islet-Derived VGF Peptides

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
September 04, 2013
End Date
June 30, 2016

Metabolomic Quantitative Trait Locus (mQTL) Genetic Mapping in Human CVD

Administered By
Duke Molecular Physiology Institute
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
July 15, 2009
End Date
May 31, 2016

Iron homeostasis in mammalian muscle

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
July 01, 2011
End Date
March 31, 2016

Mass Spectrometry, Immunological and Clinical Chemistry Assessment of Target Metabolomic

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Durham Veterans Affairs Medical Center
Role
Principal Investigator
Start Date
September 30, 2014
End Date
September 29, 2015

Exploiting metabolic vulnerabilities of CD4 T cell subsets to control inflammatory disease

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
April 01, 2015
End Date
August 31, 2015

Metabolic Regulators of Insulin Secretion and Insulin Resistance

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
September 30, 2013
End Date
August 31, 2015

T cell metabolism as a determinant of differentiation in allergic asthma

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
April 08, 2011
End Date
August 31, 2015

Multi-Disciplinary Approaches to Driving Therapeutic Human Beta Cell Replication

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Mount Sinai School of Medicine
Role
Principal Investigator
Start Date
July 01, 2013
End Date
June 30, 2015

Multidisciplinary Neonatal Training Grant

Administered By
Pediatrics, Neonatology
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
April 01, 2010
End Date
June 30, 2015

VA contract Base year

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
Department of Veterans Affairs
Role
Principal Investigator
Start Date
September 26, 2013
End Date
September 27, 2014

Fat Oxidation, Redox Stress and Insulin Resistance in Skeletal Muscle

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Co-Sponsor
Start Date
September 01, 2011
End Date
August 31, 2014

Glucose Transport in Regulation of T Cell Activation and Inflammation

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
August 01, 2012
End Date
July 31, 2014

Glucose metabolism and cell death in cancer

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Significant Contributor
Start Date
April 01, 2007
End Date
January 31, 2014

Hormonal regulation of a Ca2+/AMPK signaling pathway

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
July 01, 1984
End Date
August 31, 2011

Integration of Oncogenic Networks in Cancer Phenotypes

Administered By
Institutes and Centers
AwardedBy
National Institutes of Health
Role
Investigator
Start Date
September 30, 2004
End Date
February 28, 2011

G(alpha)Z signaling in insulin secretion and glucose tolerance

Administered By
Pharmacology & Cancer Biology
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
April 01, 2008
End Date
August 07, 2010

Macrophage Mitochondrial Stress in Inflammation, Insulin Resistance & Obesity

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Co-Mentor
Start Date
August 01, 2007
End Date
January 31, 2010

Regulation and metabolic impact of mitochondrial CD36 in skeletal muscle

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Co-Sponsor
Start Date
December 01, 2006
End Date
November 30, 2009

Mechanisms to Induce Islet Proliferation

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
September 20, 2007
End Date
July 31, 2009

Molecular Genetics of Muscle Specialization

Administered By
Medicine, Cardiology
AwardedBy
National Institutes of Health
Role
Consultant
Start Date
July 01, 2001
End Date
June 30, 2009

Developmental, nutritional and hormonal reg. of Ghrelin

Administered By
Pediatrics, Endocrinology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
September 01, 2005
End Date
May 31, 2009

Engineering of Immunoprotection in B-Cell Lines

Administered By
Sarah Stedman Nutrition & Metabolism Center
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
June 15, 2002
End Date
February 28, 2007
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Awards:

Endocrinology and Metabolism Section Awards/Solomon A. Berson Distinguished Lecture. American Physiological Society.

Type
National
Awarded By
American Physiological Society
Date
January 01, 2003

Publications:

Perinatal western-type diet and associated gestational weight gain alter postpartum maternal mood.

The role of perinatal diet in postpartum maternal mood disorders, including depression and anxiety, remains unclear. We investigated whether perinatal consumption of a Western-type diet (high in fat and branched-chain amino acids [BCAA]) and associated gestational weight gain (GWG) cause serotonin dysregulation in the central nervous system (CNS), resulting in postpartum depression and anxiety (PPD/A).Mouse dams were fed one of four diets (high-fat/high BCAA, low-fat/high BCAA, high-fat, and low-fat) prior to mating and throughout gestation and lactation. Postpartum behavioral assessments were conducted, and plasma and brain tissues assayed. To evaluate potential clinical utility, we conducted preliminary human studies using data from an extant sample of 17 primiparous women with high GWG, comparing across self-reported postpartum mood symptoms using the Edinburgh Postnatal Depression Scale (EPDS) for percent GWG and plasma amino acid levels.Mouse dams fed the high-fat/high BCAA diet gained more weight per kcal consumed, and BCAA-supplemented dams lost weight more slowly postpartum. Dams on BCAA-supplemented diets exhibited increased PPD/A-like behavior, decreased dopaminergic function, and decreased plasma tyrosine and histidine levels when assessed on postnatal day (P)8. Preliminary human data showed that GWG accounted for 29% of the variance in EPDS scores. Histidine was also lower in women with higher EPDS scores.These findings highlight the role of perinatal diet and excess GWG in the development of postpartum mood disorders.

Authors
Bolton, JL; Wiley, MG; Ryan, B; Truong, S; Strait, M; Baker, DC; Yang, NY; Ilkayeva, O; O'Connell, TM; Wroth, SW; Sánchez, CL; Swamy, G; Newgard, C; Kuhn, C; Bilbo, SD; Simmons, LA
MLA Citation
Bolton, JL, Wiley, MG, Ryan, B, Truong, S, Strait, M, Baker, DC, Yang, NY, Ilkayeva, O, O'Connell, TM, Wroth, SW, Sánchez, CL, Swamy, G, Newgard, C, Kuhn, C, Bilbo, SD, and Simmons, LA. "Perinatal western-type diet and associated gestational weight gain alter postpartum maternal mood." Brain and behavior 7.10 (October 2017): e00828-.
PMID
29075574
Source
epmc
Published In
Brain and Behavior
Volume
7
Issue
10
Publish Date
2017
Start Page
e00828
DOI
10.1002/brb3.828

Metabolomics applied to islet nutrient sensing mechanisms.

After multiple decades of investigation, the precise mechanisms involved in fuel-stimulated insulin secretion are still being revealed. One avenue for gaining deeper knowledge is to apply emergent tools of "metabolomics," involving mass spectrometry and nuclear magnetic resonance-based profiling of islet cells in their fuel-stimulated compared with basal states. The current article summarizes recent insights gained from application of metabolomics tools to the specific process of glucose-stimulated insulin secretion, revealing 2 new mechanisms that may provide targets for improving insulin secretion in diabetes.

Authors
Jensen, MV; Gooding, JR; Ferdaoussi, M; Dai, X-Q; Peterson, BS; MacDonald, PE; Newgard, CB
MLA Citation
Jensen, MV, Gooding, JR, Ferdaoussi, M, Dai, X-Q, Peterson, BS, MacDonald, PE, and Newgard, CB. "Metabolomics applied to islet nutrient sensing mechanisms." Diabetes, obesity & metabolism 19 Suppl 1 (September 2017): 90-94. (Review)
PMID
28880482
Source
epmc
Published In
Diabetes Obesity & Metabolism
Volume
19 Suppl 1
Publish Date
2017
Start Page
90
End Page
94
DOI
10.1111/dom.13010

The Prohormone VGF Regulates β Cell Function via Insulin Secretory Granule Biogenesis.

The prohormone VGF is expressed in neuroendocrine and endocrine tissues and regulates nutrient and energy status both centrally and peripherally. We and others have shown that VGF-derived peptides have direct action on the islet β cell as secretagogues and cytoprotective agents; however, the endogenous function of VGF in the β cell has not been described. Here, we demonstrate that VGF regulates secretory granule formation. VGF loss-of-function studies in both isolated islets and conditional knockout mice reveal a profound decrease in stimulus-coupled insulin secretion. Moreover, VGF is necessary to facilitate efficient exit of granule cargo from the trans-Golgi network and proinsulin processing. It also functions to replenish insulin granule stores following nutrient stimulation. Our data support a model in which VGF operates at a critical node of granule biogenesis in the islet β cell to coordinate insulin biosynthesis with β cell secretory capacity.

Authors
Stephens, SB; Edwards, RJ; Sadahiro, M; Lin, W-J; Jiang, C; Salton, SR; Newgard, CB
MLA Citation
Stephens, SB, Edwards, RJ, Sadahiro, M, Lin, W-J, Jiang, C, Salton, SR, and Newgard, CB. "The Prohormone VGF Regulates β Cell Function via Insulin Secretory Granule Biogenesis." Cell reports 20.10 (September 2017): 2480-2489.
PMID
28877479
Source
epmc
Published In
Cell Reports
Volume
20
Issue
10
Publish Date
2017
Start Page
2480
End Page
2489
DOI
10.1016/j.celrep.2017.08.050

Recommendations for Improving Identification and Quantification in Non-Targeted, GC-MS-Based Metabolomic Profiling of Human Plasma.

The field of metabolomics as applied to human disease and health is rapidly expanding. In recent efforts of metabolomics research, greater emphasis has been placed on quality control and method validation. In this study, we report an experience with quality control and a practical application of method validation. Specifically, we sought to identify and modify steps in gas chromatography-mass spectrometry (GC-MS)-based, non-targeted metabolomic profiling of human plasma that could influence metabolite identification and quantification. Our experimental design included two studies: (1) a limiting-dilution study, which investigated the effects of dilution on analyte identification and quantification; and (2) a concentration-specific study, which compared the optimal plasma extract volume established in the first study with the volume used in the current institutional protocol. We confirmed that contaminants, concentration, repeatability and intermediate precision are major factors influencing metabolite identification and quantification. In addition, we established methods for improved metabolite identification and quantification, which were summarized to provide recommendations for experimental design of GC-MS-based non-targeted profiling of human plasma.

Authors
Wang, H; Muehlbauer, MJ; O'Neal, SK; Newgard, CB; Hauser, ER; Bain, JR; Shah, SH
MLA Citation
Wang, H, Muehlbauer, MJ, O'Neal, SK, Newgard, CB, Hauser, ER, Bain, JR, and Shah, SH. "Recommendations for Improving Identification and Quantification in Non-Targeted, GC-MS-Based Metabolomic Profiling of Human Plasma." Metabolites 7.3 (August 25, 2017).
PMID
28841195
Source
epmc
Published In
Metabolites
Volume
7
Issue
3
Publish Date
2017
DOI
10.3390/metabo7030045

Sildenafil Treatment in Heart Failure With Preserved Ejection Fraction: Targeted Metabolomic Profiling in the RELAX Trial.

Phosphodiesterase-5 inhibition with sildenafil compared with a placebo had no effect on the exercise capacity or clinical status of patients with heart failure with preserved ejection fraction (HFpEF) in the PhosphodiesteRasE-5 Inhibition to Improve Clinical Status and Exercise Capacity in Diastolic Heart Failure with Preserved Ejection Fraction (RELAX) clinical trial. Metabolic impairments may explain the neutral results.To test the hypothesis that profiling metabolites in the RELAX trial would clarify the mechanisms of sildenafil effects and identify metabolites associated with clinical outcomes in HFpEF.Paired baseline and 24-week plasma samples of 160 stable outpatient individuals with HFpEF enrolled in the RELAX clinical trial were analyzed using flow injection tandem mass spectrometry (60 metabolites) and conventional assays (5 metabolites).Sildenafil (n = 79) or a placebo (n = 81) administered orally at 20 mg, 3 times daily for 12 weeks, followed by 60 mg, 3 times daily for 12 weeks.The primary measure was metabolite level changes between baseline and 24 weeks stratified by treatments. Secondary measures included correlations between metabolite level changes and clinical biomarkers and associations between baseline metabolite levels and the composite clinical score.No metabolites changed between baseline and 24 weeks in the group treated with a placebo; however, 7 metabolites changed in the group treated with sildenafil, including decreased amino acids (alanine and proline; median change [25th-75th], -38.26 [-100.3 to 28.19] and -28.24 [-56.29 to 12.08], respectively; false discovery rate-adjusted P = .01 and .03, respectively), and increased short-chain dicarboxylacylcarnitines glutaryl carnitine, octenedioyl carnitine, and adipoyl carnitine (median change, 6.19 [-3.37 to 14.18], 2.72 [-3 to 12.57], and 10.72 [-11.23 to 29.57], respectively; false discovery rate-adjusted P = .01, .04, and .05, respectively), and 1 long-chain acylcarnitine metabolite (palmitoyl carnitine; median change, 7.83 [-5.64 to 26.99]; false discovery rate-adjusted P = .03). The increases in long-chain acylarnitine metabolites and short-chain dicarboxylacylcarnitines correlated with increases in endothelin-1 and creatinine/cystatin C, respectively. Higher baseline levels of short-chain dicarboxylacylcarnitine metabolite 3-hydroxyisovalerylcarnitine/malonylcarnitine and asparagine/aspartic acid were associated with worse clinical rank scores in both treatment groups (β, -96.60, P = .001 and β, -0.02, P = .01; after renal adjustment, P = .09 and .02, respectively).Our study provides a potential mechanism for the effects of sildenafil that, through adverse effects on mitochondrial function and endoplasmic reticulum stress, could have contributed to the neutral trial results in RELAX. Short-chain dicarboxylacylcarnitine metabolites and asparagine/aspartic acid could serve as biomarkers associated with adverse clinical outcomes in HFpEF.

Authors
Wang, H; Anstrom, K; Ilkayeva, O; Muehlbauer, MJ; Bain, JR; McNulty, S; Newgard, CB; Kraus, WE; Hernandez, A; Felker, GM; Redfield, M; Shah, SH
MLA Citation
Wang, H, Anstrom, K, Ilkayeva, O, Muehlbauer, MJ, Bain, JR, McNulty, S, Newgard, CB, Kraus, WE, Hernandez, A, Felker, GM, Redfield, M, and Shah, SH. "Sildenafil Treatment in Heart Failure With Preserved Ejection Fraction: Targeted Metabolomic Profiling in the RELAX Trial." JAMA cardiology 2.8 (August 2017): 896-901.
PMID
28492915
Source
epmc
Published In
JAMA Cardiology
Volume
2
Issue
8
Publish Date
2017
Start Page
896
End Page
901
DOI
10.1001/jamacardio.2017.1239

Non-Targeted Metabolomics Analysis of Golden Retriever Muscular Dystrophy-Affected Muscles Reveals Alterations in Arginine and Proline Metabolism, and Elevations in Glutamic and Oleic Acid In Vivo.

Like Duchenne muscular dystrophy (DMD), the Golden Retriever Muscular Dystrophy (GRMD) dog model of DMD is characterized by muscle necrosis, progressive paralysis, and pseudohypertrophy in specific skeletal muscles. This severe GRMD phenotype includes moderate atrophy of the biceps femoris (BF) as compared to unaffected normal dogs, while the long digital extensor (LDE), which functions to flex the tibiotarsal joint and serves as a digital extensor, undergoes the most pronounced atrophy. A recent microarray analysis of GRMD identified alterations in genes associated with lipid metabolism and energy production.We, therefore, undertook a non-targeted metabolomics analysis of the milder/earlier stage disease GRMD BF muscle versus the more severe/chronic LDE using GC-MS to identify underlying metabolic defects specific for affected GRMD skeletal muscle.Untargeted metabolomics analysis of moderately-affected GRMD muscle (BF) identified eight significantly altered metabolites, including significantly decreased stearamide (0.23-fold of controls, p = 2.89 × 10-3), carnosine (0.40-fold of controls, p = 1.88 × 10-2), fumaric acid (0.40-fold of controls, p = 7.40 × 10-4), lactamide (0.33-fold of controls, p = 4.84 × 10-2), myoinositol-2-phosphate (0.45-fold of controls, p = 3.66 × 10-2), and significantly increased oleic acid (1.77-fold of controls, p = 9.27 × 10-2), glutamic acid (2.48-fold of controls, p = 2.63 × 10-2), and proline (1.73-fold of controls, p = 3.01 × 10-2). Pathway enrichment analysis identified significant enrichment for arginine/proline metabolism (p = 5.88 × 10-4, FDR 4.7 × 10-2), where alterations in L-glutamic acid, proline, and carnosine were found. Additionally, multiple Krebs cycle intermediates were significantly decreased (e.g., malic acid, fumaric acid, citric/isocitric acid, and succinic acid), suggesting that altered energy metabolism may be underlying the observed GRMD BF muscle dysfunction. In contrast, two pathways, inosine-5'-monophosphate (VIP Score 3.91) and 3-phosphoglyceric acid (VIP Score 3.08) mainly contributed to the LDE signature, with two metabolites (phosphoglyceric acid and inosine-5'-monophosphate) being significantly decreased. When the BF and LDE were compared, the most significant metabolite was phosphoric acid, which was significantly less in the GRMD BF compared to control and GRMD LDE groups.The identification of elevated BF oleic acid (a long-chain fatty acid) is consistent with recent microarray studies identifying altered lipid metabolism genes, while alterations in arginine and proline metabolism are consistent with recent studies identifying elevated L-arginine in DMD patient sera as a biomarker of disease. Together, these studies demonstrate muscle-specific alterations in GRMD-affected muscle, which illustrate previously unidentified metabolic changes.

Authors
Abdullah, M; Kornegay, JN; Honcoop, A; Parry, TL; Balog-Alvarez, CJ; O'Neal, SK; Bain, JR; Muehlbauer, MJ; Newgard, CB; Patterson, C; Willis, MS
MLA Citation
Abdullah, M, Kornegay, JN, Honcoop, A, Parry, TL, Balog-Alvarez, CJ, O'Neal, SK, Bain, JR, Muehlbauer, MJ, Newgard, CB, Patterson, C, and Willis, MS. "Non-Targeted Metabolomics Analysis of Golden Retriever Muscular Dystrophy-Affected Muscles Reveals Alterations in Arginine and Proline Metabolism, and Elevations in Glutamic and Oleic Acid In Vivo." Metabolites 7.3 (July 29, 2017).
PMID
28758940
Source
epmc
Published In
Metabolites
Volume
7
Issue
3
Publish Date
2017
DOI
10.3390/metabo7030038

Kv2.1 Clustering Contributes to Insulin Exocytosis and Rescues Human β-Cell Dysfunction.

Insulin exocytosis is regulated by ion channels that control excitability and Ca2+ influx. Channels also play an increasingly appreciated role in microdomain structure. In this study, we examine the mechanism by which the voltage-dependent K+ (Kv) channel Kv2.1 (KCNB1) facilitates depolarization-induced exocytosis in INS 832/13 cells and β-cells from human donors with and without type 2 diabetes (T2D). We find that Kv2.1, but not Kv2.2 (KCNB2), forms clusters of 6-12 tetrameric channels at the plasma membrane and facilitates insulin exocytosis. Knockdown of Kv2.1 expression reduces secretory granule targeting to the plasma membrane. Expression of the full-length channel (Kv2.1-wild-type) supports the glucose-dependent recruitment of secretory granules. However, a truncated channel (Kv2.1-ΔC318) that retains electrical function and syntaxin 1A binding, but lacks the ability to form clusters, does not enhance granule recruitment or exocytosis. Expression of KCNB1 appears reduced in T2D islets, and further knockdown of KCNB1 does not inhibit Kv current in T2D β-cells. Upregulation of Kv2.1-wild-type, but not Kv2.1-ΔC318, rescues the exocytotic phenotype in T2D β-cells and increases insulin secretion from T2D islets. Thus, the ability of Kv2.1 to directly facilitate insulin exocytosis depends on channel clustering. Loss of this structural role for the channel might contribute to impaired insulin secretion in diabetes.

Authors
Fu, J; Dai, X; Plummer, G; Suzuki, K; Bautista, A; Githaka, JM; Senior, L; Jensen, M; Greitzer-Antes, D; Manning Fox, JE; Gaisano, HY; Newgard, CB; Touret, N; MacDonald, PE
MLA Citation
Fu, J, Dai, X, Plummer, G, Suzuki, K, Bautista, A, Githaka, JM, Senior, L, Jensen, M, Greitzer-Antes, D, Manning Fox, JE, Gaisano, HY, Newgard, CB, Touret, N, and MacDonald, PE. "Kv2.1 Clustering Contributes to Insulin Exocytosis and Rescues Human β-Cell Dysfunction." Diabetes 66.7 (July 2017): 1890-1900.
PMID
28607108
Source
epmc
Published In
Diabetes
Volume
66
Issue
7
Publish Date
2017
Start Page
1890
End Page
1900
DOI
10.2337/db16-1170

Targeted Metabolomics Demonstrates Distinct and Overlapping Maternal Metabolites Associated With BMI, Glucose, and Insulin Sensitivity During Pregnancy Across Four Ancestry Groups.

We used targeted metabolomics in pregnant mothers to compare maternal metabolite associations with maternal BMI, glycemia, and insulin sensitivity.Targeted metabolomic assays of clinical metabolites, amino acids, and acylcarnitines were performed on fasting and 1-h postglucose serum samples from European ancestry, Afro-Caribbean, Thai, and Mexican American mothers (400 from each ancestry group) who participated in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study and underwent an oral glucose tolerance test at ∼28 weeks gestation.K-means clustering, which identified patterns of metabolite levels across ancestry groups, demonstrated that, at both fasting and 1-h, levels of the majority of metabolites were similar across ancestry groups. Meta-analyses demonstrated association of a broad array of fasting and 1-h metabolites, including lipids and amino acids and their metabolites, with maternal BMI, glucose levels, and insulin sensitivity before and after adjustment for the different phenotypes. At fasting and 1 h, a mix of metabolites was identified that were common across phenotypes or associated with only one or two phenotypes. Partial correlation estimates, which allowed comparison of the strength of association of different metabolites with maternal phenotypes, demonstrated that metabolites most strongly associated with different phenotypes included some that were common across as well as unique to each phenotype.Maternal BMI and glycemia have metabolic signatures that are both shared and unique to each phenotype. These signatures largely remain consistent across different ancestry groups and may contribute to the common and independent effects of these two phenotypes on adverse pregnancy outcomes.

Authors
Jacob, S; Nodzenski, M; Reisetter, AC; Bain, JR; Muehlbauer, MJ; Stevens, RD; Ilkayeva, OR; Lowe, LP; Metzger, BE; Newgard, CB; Scholtens, DM; Lowe, WL; HAPO Study Cooperative Research Group,
MLA Citation
Jacob, S, Nodzenski, M, Reisetter, AC, Bain, JR, Muehlbauer, MJ, Stevens, RD, Ilkayeva, OR, Lowe, LP, Metzger, BE, Newgard, CB, Scholtens, DM, Lowe, WL, and HAPO Study Cooperative Research Group, . "Targeted Metabolomics Demonstrates Distinct and Overlapping Maternal Metabolites Associated With BMI, Glucose, and Insulin Sensitivity During Pregnancy Across Four Ancestry Groups." Diabetes care 40.7 (July 2017): 911-919.
PMID
28637889
Source
epmc
Published In
Diabetes Care
Volume
40
Issue
7
Publish Date
2017
Start Page
911
End Page
919
DOI
10.2337/dc16-2453

Maternal BMI and Glycemia Impact the Fetal Metabolome.

We used targeted metabolomics to determine associations of maternal BMI and glucose levels with cord blood metabolites and associations of cord blood metabolites with newborn birth weight and adiposity in mother-offspring dyads.Targeted metabolomic assays were performed on cord blood serum samples from European ancestry, Afro-Caribbean, Thai, and Mexican American newborns (400 from each ancestry group) whose mothers participated in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study and who had anthropometric measurements at birth.Meta-analysis across the four cohorts demonstrated significant correlation of all cord blood metabolites analyzed with maternal fasting levels of the same metabolites at ∼28 weeks' gestation except for triglycerides, asparagine/aspartate, arginine, and the acylcarnitine C14-OH/C12-DC. Meta-analyses also demonstrated that maternal BMI with or without adjustment for maternal glucose was associated with cord blood metabolites including the branched-chain amino acids and their metabolites as well as phenylalanine. One-hour but not fasting glucose was associated with cord blood 3-hydroxybutyrate and its carnitine ester, a medium-chain acylcarnitine, and glycerol. A number of cord blood metabolites were associated with newborn birth weight and sum of skinfolds, including a negative association of triglycerides and positive association of 3-hydroxybutyrate, its carnitine ester, and serine with both newborn outcomes.Maternal BMI and glycemia are associated with different components of the newborn metabolome, consistent with their independent effects on newborn size at birth. Maternal BMI is associated with a newborn metabolic signature characteristic of insulin resistance and risk of type 2 diabetes in adults.

Authors
Lowe, WL; Bain, JR; Nodzenski, M; Reisetter, AC; Muehlbauer, MJ; Stevens, RD; Ilkayeva, OR; Lowe, LP; Metzger, BE; Newgard, CB; Scholtens, DM; HAPO Study Cooperative Research Group,
MLA Citation
Lowe, WL, Bain, JR, Nodzenski, M, Reisetter, AC, Muehlbauer, MJ, Stevens, RD, Ilkayeva, OR, Lowe, LP, Metzger, BE, Newgard, CB, Scholtens, DM, and HAPO Study Cooperative Research Group, . "Maternal BMI and Glycemia Impact the Fetal Metabolome." Diabetes care 40.7 (July 2017): 902-910.
PMID
28637888
Source
epmc
Published In
Diabetes Care
Volume
40
Issue
7
Publish Date
2017
Start Page
902
End Page
910
DOI
10.2337/dc16-2452

Interrupted Glucagon Signaling Reveals Hepatic α Cell Axis and Role for L-Glutamine in α Cell Proliferation.

Decreasing glucagon action lowers the blood glucose and may be useful therapeutically for diabetes. However, interrupted glucagon signaling leads to α cell proliferation. To identify postulated hepatic-derived circulating factor(s) responsible for α cell proliferation, we used transcriptomics/proteomics/metabolomics in three models of interrupted glucagon signaling and found that proliferation of mouse, zebrafish, and human α cells was mTOR and FoxP transcription factor dependent. Changes in hepatic amino acid (AA) catabolism gene expression predicted the observed increase in circulating AAs. Mimicking these AA levels stimulated α cell proliferation in a newly developed in vitro assay with L-glutamine being a critical AA. α cell expression of the AA transporter Slc38a5 was markedly increased in mice with interrupted glucagon signaling and played a role in α cell proliferation. These results indicate a hepatic α islet cell axis where glucagon regulates serum AA availability and AAs, especially L-glutamine, regulate α cell proliferation and mass via mTOR-dependent nutrient sensing.

Authors
Dean, ED; Li, M; Prasad, N; Wisniewski, SN; Von Deylen, A; Spaeth, J; Maddison, L; Botros, A; Sedgeman, LR; Bozadjieva, N; Ilkayeva, O; Coldren, A; Poffenberger, G; Shostak, A; Semich, MC; Aamodt, KI; Phillips, N; Yan, H; Bernal-Mizrachi, E; Corbin, JD; Vickers, KC; Levy, SE; Dai, C; Newgard, C; Gu, W; Stein, R; Chen, W; Powers, AC
MLA Citation
Dean, ED, Li, M, Prasad, N, Wisniewski, SN, Von Deylen, A, Spaeth, J, Maddison, L, Botros, A, Sedgeman, LR, Bozadjieva, N, Ilkayeva, O, Coldren, A, Poffenberger, G, Shostak, A, Semich, MC, Aamodt, KI, Phillips, N, Yan, H, Bernal-Mizrachi, E, Corbin, JD, Vickers, KC, Levy, SE, Dai, C, Newgard, C, Gu, W, Stein, R, Chen, W, and Powers, AC. "Interrupted Glucagon Signaling Reveals Hepatic α Cell Axis and Role for L-Glutamine in α Cell Proliferation." Cell metabolism 25.6 (June 2017): 1362-1373.e5.
PMID
28591638
Source
epmc
Published In
Cell Metabolism
Volume
25
Issue
6
Publish Date
2017
Start Page
1362
End Page
1373.e5
DOI
10.1016/j.cmet.2017.05.011

Associations of maternal BMI and insulin resistance with the maternal metabolome and newborn outcomes.

Maternal obesity increases the risk for large-for-gestational-age birth and excess newborn adiposity, which are associated with adverse long-term metabolic outcomes in offspring, probably due to effects mediated through the intrauterine environment. We aimed to characterise the maternal metabolic milieu associated with maternal BMI and its relationship to newborn birthweight and adiposity.Fasting and 1 h serum samples were collected from 400 European-ancestry mothers in the Hyperglycaemia and Adverse Pregnancy Outcome Study who underwent an OGTT at ∼28 weeks gestation and whose offspring had anthropometric measurements at birth. Metabolomics assays were performed using biochemical analyses of conventional clinical metabolites, targeted MS-based measurement of amino acids and acylcarnitines and non-targeted GC/MS.Per-metabolite analyses demonstrated broad associations with maternal BMI at fasting and 1 h for lipids, amino acids and their metabolites together with carbohydrates and organic acids. Similar metabolite classes were associated with insulin resistance with unique associations including branched-chain amino acids. Pathway analyses indicated overlapping and unique associations with maternal BMI and insulin resistance. Network analyses demonstrated collective associations of maternal metabolite subnetworks with maternal BMI and newborn size and adiposity, including communities of acylcarnitines, lipids and related metabolites, and carbohydrates and organic acids. Random forest analyses demonstrated contribution of lipids and lipid-related metabolites to the association of maternal BMI with newborn outcomes.Higher maternal BMI and insulin resistance are associated with broad-based changes in maternal metabolites, with lipids and lipid-related metabolites accounting, in part, for the association of maternal BMI with newborn size at birth.

Authors
Sandler, V; Reisetter, AC; Bain, JR; Muehlbauer, MJ; Nodzenski, M; Stevens, RD; Ilkayeva, O; Lowe, LP; Metzger, BE; Newgard, CB; Scholtens, DM; Lowe, WL; HAPO Study Cooperative Research Group,
MLA Citation
Sandler, V, Reisetter, AC, Bain, JR, Muehlbauer, MJ, Nodzenski, M, Stevens, RD, Ilkayeva, O, Lowe, LP, Metzger, BE, Newgard, CB, Scholtens, DM, Lowe, WL, and HAPO Study Cooperative Research Group, . "Associations of maternal BMI and insulin resistance with the maternal metabolome and newborn outcomes." Diabetologia 60.3 (March 2017): 518-530.
PMID
27981358
Source
epmc
Published In
Diabetologia
Volume
60
Issue
3
Publish Date
2017
Start Page
518
End Page
530
DOI
10.1007/s00125-016-4182-2

Mixture model normalization for non-targeted gas chromatography/mass spectrometry metabolomics data.

Metabolomics offers a unique integrative perspective for health research, reflecting genetic and environmental contributions to disease-related phenotypes. Identifying robust associations in population-based or large-scale clinical studies demands large numbers of subjects and therefore sample batching for gas-chromatography/mass spectrometry (GC/MS) non-targeted assays. When run over weeks or months, technical noise due to batch and run-order threatens data interpretability. Application of existing normalization methods to metabolomics is challenged by unsatisfied modeling assumptions and, notably, failure to address batch-specific truncation of low abundance compounds.To curtail technical noise and make GC/MS metabolomics data amenable to analyses describing biologically relevant variability, we propose mixture model normalization (mixnorm) that accommodates truncated data and estimates per-metabolite batch and run-order effects using quality control samples. Mixnorm outperforms other approaches across many metrics, including improved correlation of non-targeted and targeted measurements and superior performance when metabolite detectability varies according to batch. For some metrics, particularly when truncation is less frequent for a metabolite, mean centering and median scaling demonstrate comparable performance to mixnorm.When quality control samples are systematically included in batches, mixnorm is uniquely suited to normalizing non-targeted GC/MS metabolomics data due to explicit accommodation of batch effects, run order and varying thresholds of detectability. Especially in large-scale studies, normalization is crucial for drawing accurate conclusions from non-targeted GC/MS metabolomics data.

Authors
Reisetter, AC; Muehlbauer, MJ; Bain, JR; Nodzenski, M; Stevens, RD; Ilkayeva, O; Metzger, BE; Newgard, CB; Lowe, WL; Scholtens, DM
MLA Citation
Reisetter, AC, Muehlbauer, MJ, Bain, JR, Nodzenski, M, Stevens, RD, Ilkayeva, O, Metzger, BE, Newgard, CB, Lowe, WL, and Scholtens, DM. "Mixture model normalization for non-targeted gas chromatography/mass spectrometry metabolomics data." BMC bioinformatics 18.1 (February 2, 2017): 84-.
PMID
28153035
Source
epmc
Published In
BMC Bioinformatics
Volume
18
Issue
1
Publish Date
2017
Start Page
84
DOI
10.1186/s12859-017-1501-7

Prior Dietary Practices and Connections to a Human Gut Microbial Metacommunity Alter Responses to Diet Interventions.

Ensuring that gut microbiota respond consistently to prescribed dietary interventions, irrespective of prior dietary practices (DPs), is critical for effective nutritional therapy. To address this, we identified DP-associated gut bacterial taxa in individuals either practicing chronic calorie restriction with adequate nutrition (CRON) or without dietary restrictions (AMER). When transplanted into gnotobiotic mice, AMER and CRON microbiota responded predictably to CRON and AMER diets but with variable response strengths. An individual's microbiota is connected to other individuals' communities ("metacommunity") by microbial exchange. Sequentially cohousing AMER-colonized mice with two different groups of CRON-colonized mice simulated metacommunity effects, resulting in enhanced responses to a CRON diet intervention and changes in several metabolic features in AMER animals. This response was driven by an influx of CRON DP-associated taxa. Certain DPs may impair responses to dietary interventions, necessitating the introduction of diet-responsive bacterial lineages present in other individuals and identified using the strategies described.

Authors
Griffin, NW; Ahern, PP; Cheng, J; Heath, AC; Ilkayeva, O; Newgard, CB; Fontana, L; Gordon, JI
MLA Citation
Griffin, NW, Ahern, PP, Cheng, J, Heath, AC, Ilkayeva, O, Newgard, CB, Fontana, L, and Gordon, JI. "Prior Dietary Practices and Connections to a Human Gut Microbial Metacommunity Alter Responses to Diet Interventions." Cell host & microbe 21.1 (January 2017): 84-96.
PMID
28041931
Source
epmc
Published In
Cell Host & Microbe
Volume
21
Issue
1
Publish Date
2017
Start Page
84
End Page
96
DOI
10.1016/j.chom.2016.12.006

Delayed apoptosis allows islet β-cells to implement an autophagic mechanism to promote cell survival.

Increased β-cell death coupled with the inability to replicate existing β-cells drives the decline in β-cell mass observed in the progression of both major forms of diabetes. Understanding endogenous mechanisms of islet cell survival could have considerable value for the development of novel strategies to limit β-cell loss and thereby promote β-cell recovery. Insulinoma cells have provided useful insight into β-cell death pathways but observations made in cell lines sometimes fail to translate to primary islets. Here, we report dramatic differences in the temporal regulation and engagement of the apoptotic program in primary rodent islets relative to the INS-1 derived 832/13 cell line. As expected, 832/13 cells rapidly induced cell stress markers in response to ER stress or DNA damage and were fully committed to apoptosis, resulting in >80% cell death within 24 h. In contrast, primary rat islets were largely refractory to cell death in response to ER stress and DNA damage, despite rapid induction of stress markers, such as XBP-1(s), CHOP, and PUMA. Gene expression profiling revealed a general suppression of pro-apoptotic machinery, such as Apaf-1 and caspase 3, and sustained levels of pro-survival factors, such as cIAP-1, cIAP-2, and XIAP, in rat islets. Furthermore, we observed sustained induction of autophagy following chronic ER stress and found that inhibition of autophagy rendered islet β-cells highly vulnerable to ER stress-induced cell death. We propose that islet β-cells dampen the apoptotic response to delay the onset of cell death, providing a temporal window in which autophagy can be activated to limit cellular damage and promote survival.

Authors
Hayes, HL; Peterson, BS; Haldeman, JM; Newgard, CB; Hohmeier, HE; Stephens, SB
MLA Citation
Hayes, HL, Peterson, BS, Haldeman, JM, Newgard, CB, Hohmeier, HE, and Stephens, SB. "Delayed apoptosis allows islet β-cells to implement an autophagic mechanism to promote cell survival." PloS one 12.2 (January 2017): e0172567-.
PMID
28212395
Source
epmc
Published In
PloS one
Volume
12
Issue
2
Publish Date
2017
Start Page
e0172567
DOI
10.1371/journal.pone.0172567

A Pdx-1-Regulated Soluble Factor Activates Rat and Human Islet Cell Proliferation.

The homeodomain transcription factor Pdx-1 has important roles in pancreas and islet development as well as in β-cell function and survival. We previously reported that Pdx-1 overexpression stimulates islet cell proliferation, but the mechanism remains unclear. Here, we demonstrate that overexpression of Pdx-1 triggers proliferation largely by a non-cell-autonomous mechanism mediated by soluble factors. Consistent with this idea, overexpression of Pdx-1 under the control of a β-cell-specific promoter (rat insulin promoter [RIP]) stimulates proliferation of both α and β cells, and overexpression of Pdx-1 in islets separated by a Transwell membrane from islets lacking Pdx-1 overexpression activates proliferation in the untreated islets. Microarray and gene ontology (GO) analysis identified inhibin beta-B (Inhbb), an activin subunit and member of the transforming growth factor β (TGF-β) superfamily, as a Pdx-1-responsive gene. Overexpression of Inhbb or addition of activin B stimulates rat islet cell and β-cell proliferation, and the activin receptors RIIA and RIIB are required for the full proliferative effects of Pdx-1 in rat islets. In human islets, Inhbb overexpression stimulates total islet cell proliferation and potentiates Pdx-1-stimulated proliferation of total islet cells and β cells. In sum, this study identifies a mechanism by which Pdx-1 induces a soluble factor that is sufficient to stimulate both rat and human islet cell proliferation.

Authors
Hayes, HL; Zhang, L; Becker, TC; Haldeman, JM; Stephens, SB; Arlotto, M; Moss, LG; Newgard, CB; Hohmeier, HE
MLA Citation
Hayes, HL, Zhang, L, Becker, TC, Haldeman, JM, Stephens, SB, Arlotto, M, Moss, LG, Newgard, CB, and Hohmeier, HE. "A Pdx-1-Regulated Soluble Factor Activates Rat and Human Islet Cell Proliferation." Molecular and cellular biology 36.23 (December 2016): 2918-2930.
PMID
27620967
Source
epmc
Published In
Molecular and Cellular Biology
Volume
36
Issue
23
Publish Date
2016
Start Page
2918
End Page
2930
DOI
10.1128/mcb.00103-16

Enhanced GLUT4-Dependent Glucose Transport Relieves Nutrient Stress in Obese Mice Through Changes in Lipid and Amino Acid Metabolism.

Impaired GLUT4-dependent glucose uptake is a contributing factor in the development of whole-body insulin resistance in obese patients and obese animal models. Previously, we demonstrated that transgenic mice engineered to express the human GLUT4 gene under the control of the human GLUT4 promoter (i.e., transgenic [TG] mice) are resistant to obesity-induced insulin resistance. A likely mechanism underlying increased insulin sensitivity is increased glucose uptake in skeletal muscle. The purpose of this study was to investigate the broader metabolic consequences of enhanced glucose uptake into muscle. We observed that the expression of several nuclear and mitochondrially encoded mitochondrial enzymes was decreased in TG mice but that mitochondrial number, size, and fatty acid respiration rates were unchanged. Interestingly, both pyruvate and glutamate respiration rates were decreased in TG mice. Metabolomics analyses of skeletal muscle samples revealed that increased GLUT4 transgene expression was associated with decreased levels of some tricarboxylic acid intermediates and amino acids, whereas the levels of several glucogenic amino acids were elevated. Furthermore, fasting acyl carnitines in obese TG mice were decreased, indicating that increased GLUT4-dependent glucose flux decreases nutrient stress by altering lipid and amino acid metabolism in skeletal muscle.

Authors
Gurley, JM; Ilkayeva, O; Jackson, RM; Griesel, BA; White, P; Matsuzaki, S; Qaisar, R; Van Remmen, H; Humphries, KM; Newgard, CB; Olson, AL
MLA Citation
Gurley, JM, Ilkayeva, O, Jackson, RM, Griesel, BA, White, P, Matsuzaki, S, Qaisar, R, Van Remmen, H, Humphries, KM, Newgard, CB, and Olson, AL. "Enhanced GLUT4-Dependent Glucose Transport Relieves Nutrient Stress in Obese Mice Through Changes in Lipid and Amino Acid Metabolism." Diabetes 65.12 (December 2016): 3585-3597.
PMID
27679559
Source
epmc
Published In
Diabetes
Volume
65
Issue
12
Publish Date
2016
Start Page
3585
End Page
3597
DOI
10.2337/db16-0709

HIV-1 Envelope Mimicry of Host Enzyme Kynureninase Does Not Disrupt Tryptophan Metabolism.

The HIV-1 envelope protein (Env) has evolved to subvert the host immune system, hindering viral control by the host. The tryptophan metabolic enzyme kynureninase (KYNU) is mimicked by a portion of the HIV Env gp41 membrane proximal region (MPER) and is cross-reactive with the HIV broadly neutralizing Ab (bnAb) 2F5. Molecular mimicry of host proteins by pathogens can lead to autoimmune disease. In this article, we demonstrate that neither the 2F5 bnAb nor HIV MPER-KYNU cross-reactive Abs elicited by immunization with an MPER peptide-liposome vaccine in 2F5 bnAb VHDJH and VLJL knock-in mice and rhesus macaques modified KYNU activity or disrupted tissue tryptophan metabolism. Thus, molecular mimicry by HIV-1 Env that promotes the evasion of host anti-HIV-1 Ab responses can be directed toward nonfunctional host protein epitopes that do not impair host protein function. Therefore, the 2F5 HIV Env gp41 region is a key and safe target for HIV-1 vaccine development.

Authors
Bradley, T; Yang, G; Ilkayeva, O; Holl, TM; Zhang, R; Zhang, J; Santra, S; Fox, CB; Reed, SG; Parks, R; Bowman, CM; Bouton-Verville, H; Sutherland, LL; Scearce, RM; Vandergrift, N; Kepler, TB; Moody, MA; Liao, H-X; Alam, SM; McLendon, R; Everitt, JI; Newgard, CB; Verkoczy, L; Kelsoe, G; Haynes, BF
MLA Citation
Bradley, T, Yang, G, Ilkayeva, O, Holl, TM, Zhang, R, Zhang, J, Santra, S, Fox, CB, Reed, SG, Parks, R, Bowman, CM, Bouton-Verville, H, Sutherland, LL, Scearce, RM, Vandergrift, N, Kepler, TB, Moody, MA, Liao, H-X, Alam, SM, McLendon, R, Everitt, JI, Newgard, CB, Verkoczy, L, Kelsoe, G, and Haynes, BF. "HIV-1 Envelope Mimicry of Host Enzyme Kynureninase Does Not Disrupt Tryptophan Metabolism." Journal of immunology (Baltimore, Md. : 1950) 197.12 (December 2016): 4663-4673.
PMID
27849170
Source
epmc
Published In
Journal of immunology (Baltimore, Md. : 1950)
Volume
197
Issue
12
Publish Date
2016
Start Page
4663
End Page
4673
DOI
10.4049/jimmunol.1601484

Branched-chain amino acid restriction in Zucker-fatty rats improves muscle insulin sensitivity by enhancing efficiency of fatty acid oxidation and acyl-glycine export.

A branched-chain amino acid (BCAA)-related metabolic signature is strongly associated with insulin resistance and predictive of incident diabetes and intervention outcomes. To better understand the role that this metabolite cluster plays in obesity-related metabolic dysfunction, we studied the impact of BCAA restriction in a rodent model of obesity in which BCAA metabolism is perturbed in ways that mirror the human condition.Zucker-lean rats (ZLR) and Zucker-fatty rats (ZFR) were fed either a custom control, low fat (LF) diet, or an isonitrogenous, isocaloric LF diet in which all three BCAA (Leu, Ile, Val) were reduced by 45% (LF-RES). We performed comprehensive metabolic and physiologic profiling to characterize the effects of BCAA restriction on energy balance, insulin sensitivity, and glucose, lipid and amino acid metabolism.LF-fed ZFR had higher levels of circulating BCAA and lower levels of glycine compared to LF-fed ZLR. Feeding ZFR with the LF-RES diet lowered circulating BCAA to levels found in LF-fed ZLR. Activity of the rate limiting enzyme in the BCAA catabolic pathway, branched chain keto acid dehydrogenase (BCKDH), was lower in liver but higher in skeletal muscle of ZFR compared to ZLR and was not responsive to diet in either tissue. BCAA restriction had very little impact on metabolites studied in liver of ZFR where BCAA content was low, and BCKDH activity was suppressed. However, in skeletal muscle of LF-fed ZFR compared to LF-fed ZLR, where BCAA content and BCKDH activity were increased, accumulation of fatty acyl CoAs was completely normalized by dietary BCAA restriction. BCAA restriction also normalized skeletal muscle glycine content and increased urinary acetyl glycine excretion in ZFR. These effects were accompanied by lower RER and improved skeletal muscle insulin sensitivity in LF-RES fed ZFR as measured by hyperinsulinemic-isoglycemic clamp.Our data are consistent with a model wherein elevated circulating BCAA contribute to development of obesity-related insulin resistance by interfering with lipid oxidation in skeletal muscle. BCAA-dependent lowering of the skeletal muscle glycine pool appears to contribute to this effect by slowing acyl-glycine export to the urine.

Authors
White, PJ; Lapworth, AL; An, J; Wang, L; McGarrah, RW; Stevens, RD; Ilkayeva, O; George, T; Muehlbauer, MJ; Bain, JR; Trimmer, JK; Brosnan, MJ; Rolph, TP; Newgard, CB
MLA Citation
White, PJ, Lapworth, AL, An, J, Wang, L, McGarrah, RW, Stevens, RD, Ilkayeva, O, George, T, Muehlbauer, MJ, Bain, JR, Trimmer, JK, Brosnan, MJ, Rolph, TP, and Newgard, CB. "Branched-chain amino acid restriction in Zucker-fatty rats improves muscle insulin sensitivity by enhancing efficiency of fatty acid oxidation and acyl-glycine export." Molecular metabolism 5.7 (July 2016): 538-551.
PMID
27408778
Source
epmc
Published In
Molecular Metabolism
Volume
5
Issue
7
Publish Date
2016
Start Page
538
End Page
551
DOI
10.1016/j.molmet.2016.04.006

Proteomic Profiling Reveals Adaptive Responses to Surgical Myocardial Ischemia-Reperfusion in Hibernating Arctic Ground Squirrels Compared to Rats.

Hibernation is an adaptation to extreme environments known to provide organ protection against ischemia-reperfusion (I/R) injury. An unbiased systems approach was utilized to investigate hibernation-induced changes that are characteristic of the hibernator cardioprotective phenotype, by comparing the myocardial proteome of winter hibernating arctic ground squirrels (AGS), summer active AGS, and rats subjected to I/R, and further correlating with targeted metabolic changes.In a well-defined rodent model of I/R by deep hypothermic circulatory arrest followed by 3 or 24 h of reperfusion or sham, myocardial protein abundance in AGS (hibernating summer active) and rats (n = 4 to 5/group) was quantified by label-free proteomics (n = 4 to 5/group) and correlated with metabolic changes.Compared to rats, hibernating AGS displayed markedly reduced plasma levels of troponin I, myocardial apoptosis, and left ventricular contractile dysfunction. Of the 1,320 rat and 1,478 AGS proteins identified, 545 were differentially expressed between hibernating AGS and rat hearts (47% up-regulated and 53% down-regulated). Gene ontology analysis revealed down-regulation in hibernating AGS hearts of most proteins involved in mitochondrial energy transduction, including electron transport chain complexes, acetyl CoA biosynthesis, Krebs cycle, glycolysis, and ketogenesis. Conversely, fatty acid oxidation enzymes and sirtuin-3 were up-regulated in hibernating AGS, with preserved peroxisome proliferator-activated receptor-α activity and reduced tissue levels of acylcarnitines and ceramides after I/R.Natural cardioprotective adaptations in hibernators involve extensive metabolic remodeling, featuring increased expression of fatty acid metabolic proteins and reduced levels of toxic lipid metabolites. Robust up-regulation of sirtuin-3 suggests that posttranslational modifications may underlie organ protection in hibernating mammals.

Authors
Quinones, QJ; Zhang, Z; Ma, Q; Smith, MP; Soderblom, E; Moseley, MA; Bain, J; Newgard, CB; Muehlbauer, MJ; Hirschey, M; Drew, KL; Barnes, BM; Podgoreanu, MV
MLA Citation
Quinones, QJ, Zhang, Z, Ma, Q, Smith, MP, Soderblom, E, Moseley, MA, Bain, J, Newgard, CB, Muehlbauer, MJ, Hirschey, M, Drew, KL, Barnes, BM, and Podgoreanu, MV. "Proteomic Profiling Reveals Adaptive Responses to Surgical Myocardial Ischemia-Reperfusion in Hibernating Arctic Ground Squirrels Compared to Rats." Anesthesiology 124.6 (June 2016): 1296-1310.
PMID
27187119
Source
epmc
Published In
Anesthesiology
Volume
124
Issue
6
Publish Date
2016
Start Page
1296
End Page
1310
DOI
10.1097/aln.0000000000001113

Research Resource: Roles for Calcium/Calmodulin-Dependent Protein Kinase Kinase 2 (CaMKK2) in Systems Metabolism.

A number of epidemiological studies have implicated calcium (Ca(2+)) signaling as a major factor in obesity that contributes to aberrant systems metabolism. Somewhat paradoxically, obesity correlates with decreased circulating Ca(2+) levels, leading to increased release of intracellular Ca(2+) stores from the endoplasmic reticulum. These findings suggest that insulin resistance associated with the obese state is linked to activation of canonical Ca(2+) signaling pathways. Mechanistically, increased intracellular Ca(2+) binds calmodulin (CaM) to activate a set of Ca(2+)/CaM-dependent protein kinases. In this research resource, we explore the metabolic functions and implications of Ca(2+)/CaM-dependent protein kinase kinase 2 (CaMKK2) as a metabolic effector of Ca(2+)/CaM action. We reveal the importance of CaMKK2 for gating insulin release from pancreatic β-cells while concomitantly influencing the sensitivity of insulin-responsive tissues. To provide a better understanding of the metabolic impact of CaMKK2 loss, we performed targeted metabolomic analyses of key metabolic byproducts of glucose, fatty acid, and amino acid metabolism in mice null for CaMKK2. We quantified amino acids and acyl carnitines in 3 insulin-sensitive tissues (liver, skeletal muscle, plasma) isolated from CaMKK2(-/-) mice and their wild-type littermates under conditions of dietary stress (low-fat diet, normal chow, high-fat diet, and fasting), thereby unveiling unique metabolic functions of CaMKK2. Our findings highlight CaMKK2 as a molecular rheostat for insulin action and emphasize the importance of Ca(2+)/CaM/CaMKK2 in regulation of whole-body metabolism. These findings reveal that CaMKK2 may be an attractive therapeutic target for combatting comorbidities associated with perturbed insulin signaling.

Authors
Marcelo, KL; Ribar, T; Means, CR; Tsimelzon, A; Stevens, RD; Ilkayeva, O; Bain, JR; Hilsenbeck, SG; Newgard, CB; Means, AR; York, B
MLA Citation
Marcelo, KL, Ribar, T, Means, CR, Tsimelzon, A, Stevens, RD, Ilkayeva, O, Bain, JR, Hilsenbeck, SG, Newgard, CB, Means, AR, and York, B. "Research Resource: Roles for Calcium/Calmodulin-Dependent Protein Kinase Kinase 2 (CaMKK2) in Systems Metabolism." Molecular Endocrinology 30.5 (May 2016): 557-572.
PMID
27003444
Source
epmc
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
30
Issue
5
Publish Date
2016
Start Page
557
End Page
572
DOI
10.1210/me.2016-1021

Catabolic Defect of Branched-Chain Amino Acids Promotes Heart Failure.

Although metabolic reprogramming is critical in the pathogenesis of heart failure, studies to date have focused principally on fatty acid and glucose metabolism. Contribution of amino acid metabolic regulation in the disease remains understudied.Transcriptomic and metabolomic analyses were performed in mouse failing heart induced by pressure overload. Suppression of branched-chain amino acid (BCAA) catabolic gene expression along with concomitant tissue accumulation of branched-chain α-keto acids was identified as a significant signature of metabolic reprogramming in mouse failing hearts and validated to be shared in human cardiomyopathy hearts. Molecular and genetic evidence identified the transcription factor Krüppel-like factor 15 as a key upstream regulator of the BCAA catabolic regulation in the heart. Studies using a genetic mouse model revealed that BCAA catabolic defect promoted heart failure associated with induced oxidative stress and metabolic disturbance in response to mechanical overload. Mechanistically, elevated branched-chain α-keto acids directly suppressed respiration and induced superoxide production in isolated mitochondria. Finally, pharmacological enhancement of branched-chain α-keto acid dehydrogenase activity significantly blunted cardiac dysfunction after pressure overload.BCAA catabolic defect is a metabolic hallmark of failing heart resulting from Krüppel-like factor 15-mediated transcriptional reprogramming. BCAA catabolic defect imposes a previously unappreciated significant contribution to heart failure.

Authors
Sun, H; Olson, KC; Gao, C; Prosdocimo, DA; Zhou, M; Wang, Z; Jeyaraj, D; Youn, J-Y; Ren, S; Liu, Y; Rau, CD; Shah, S; Ilkayeva, O; Gui, W-J; William, NS; Wynn, RM; Newgard, CB; Cai, H; Xiao, X; Chuang, DT; Schulze, PC; Lynch, C; Jain, MK; Wang, Y
MLA Citation
Sun, H, Olson, KC, Gao, C, Prosdocimo, DA, Zhou, M, Wang, Z, Jeyaraj, D, Youn, J-Y, Ren, S, Liu, Y, Rau, CD, Shah, S, Ilkayeva, O, Gui, W-J, William, NS, Wynn, RM, Newgard, CB, Cai, H, Xiao, X, Chuang, DT, Schulze, PC, Lynch, C, Jain, MK, and Wang, Y. "Catabolic Defect of Branched-Chain Amino Acids Promotes Heart Failure." Circulation 133.21 (May 2016): 2038-2049.
PMID
27059949
Source
epmc
Published In
Circulation
Volume
133
Issue
21
Publish Date
2016
Start Page
2038
End Page
2049
DOI
10.1161/circulationaha.115.020226

Human amylin proteotoxicity impairs protein biosynthesis, and alters major cellular signaling pathways in the heart, brain and liver of humanized diabetic rat model in vivo.

Chronic hypersecretion of the 37 amino acid amylin is common in type 2 diabetics (T2D). Recent studies implicate human amylin aggregates cause proteotoxicity (cell death induced by misfolded proteins) in both the brain and the heart.Identify systemic mechanisms/markers by which human amylin associated with cardiac and brain defects might be identified.We investigated the metabolic consequences of amyloidogenic and cytotoxic amylin oligomers in heart, brain, liver, and plasma using non-targeted metabolomics analysis in a rat model expressing pancreatic human amylin (HIP model).Four metabolites were significantly different in 3 or more of the the four compartments (heart, brain, liver, and plasma) in HIP rats. When compared to a T2D rat model, HIP hearts uniquely had significant DECREASES in five amino acids (lysine, alanine, tyrosine, phenylalanine, serine), with phenylalanine decreased across all four tissues investigated, including plasma. In contrast, significantly INCREASED circulating phenylalanine is reported in diabetics in multiple recent studies.DECREASED phenylalanine may serve as a unique marker of cardiac and brain dysfunction due to hyperamylinemia that can be differentiated from alterations in T2D in the plasma. While the deficiency in phenylalanine was seen across tissues including plasma and could be monitored, reduced tyrosine was seen only in the brain. The 50% reduction in phenylalanine and tyrosine in HIP brains is significant given their role in supporting brain chemistry as a precursor for catecholamines (dopamine, norepinephrine, epinephrine), which may contribute to the increased morbidity and mortality in diabetics at a multi-system level beyond the effects on glucose metabolism.

Authors
Ilaiwy, A; Liu, M; Parry, TL; Bain, JR; Newgard, CB; Schisler, JC; Muehlbauer, MJ; Despa, F; Willis, MS
MLA Citation
Ilaiwy, A, Liu, M, Parry, TL, Bain, JR, Newgard, CB, Schisler, JC, Muehlbauer, MJ, Despa, F, and Willis, MS. "Human amylin proteotoxicity impairs protein biosynthesis, and alters major cellular signaling pathways in the heart, brain and liver of humanized diabetic rat model in vivo." Metabolomics : Official journal of the Metabolomic Society 12.5 (May 2016).
PMID
28775675
Source
epmc
Published In
Metabolomics
Volume
12
Issue
5
Publish Date
2016
DOI
10.1007/s11306-016-1022-9

Integrated Regulation of Hepatic Lipid and Glucose Metabolism by Adipose Triacylglycerol Lipase and FoxO Proteins.

Metabolism is a highly integrated process that is coordinately regulated between tissues and within individual cells. FoxO proteins are major targets of insulin action and contribute to the regulation of gluconeogenesis, glycolysis, and lipogenesis in the liver. However, the mechanisms by which FoxO proteins exert these diverse effects in an integrated fashion remain poorly understood. We report that FoxO proteins also exert important effects on intrahepatic lipolysis and fatty acid oxidation via the regulation of adipose triacylglycerol lipase (ATGL), which mediates the first step in lipolysis, and its inhibitor, the G0/S1 switch 2 gene (G0S2). We also find that ATGL-dependent lipolysis plays a critical role in mediating diverse effects of FoxO proteins in the liver, including effects on gluconeogenic, glycolytic, and lipogenic gene expression and metabolism. These results indicate that intrahepatic lipolysis plays a critical role in mediating and integrating the regulation of glucose and lipid metabolism downstream of FoxO proteins.

Authors
Zhang, W; Bu, SY; Mashek, MT; O-Sullivan, I; Sibai, Z; Khan, SA; Ilkayeva, O; Newgard, CB; Mashek, DG; Unterman, TG
MLA Citation
Zhang, W, Bu, SY, Mashek, MT, O-Sullivan, I, Sibai, Z, Khan, SA, Ilkayeva, O, Newgard, CB, Mashek, DG, and Unterman, TG. "Integrated Regulation of Hepatic Lipid and Glucose Metabolism by Adipose Triacylglycerol Lipase and FoxO Proteins." Cell reports 15.2 (April 2016): 349-359.
PMID
27050511
Source
epmc
Published In
Cell Reports
Volume
15
Issue
2
Publish Date
2016
Start Page
349
End Page
359
DOI
10.1016/j.celrep.2016.03.021

Sialylated Milk Oligosaccharides Promote Microbiota-Dependent Growth in Models of Infant Undernutrition.

Identifying interventions that more effectively promote healthy growth of children with undernutrition is a pressing global health goal. Analysis of human milk oligosaccharides (HMOs) from 6-month-postpartum mothers in two Malawian birth cohorts revealed that sialylated HMOs are significantly less abundant in those with severely stunted infants. To explore this association, we colonized young germ-free mice with a consortium of bacterial strains cultured from the fecal microbiota of a 6-month-old stunted Malawian infant and fed recipient animals a prototypic Malawian diet with or without purified sialylated bovine milk oligosaccharides (S-BMO). S-BMO produced a microbiota-dependent augmentation of lean body mass gain, changed bone morphology, and altered liver, muscle, and brain metabolism in ways indicative of a greater ability to utilize nutrients for anabolism. These effects were also documented in gnotobiotic piglets using the same consortium and Malawian diet. These preclinical models indicate a causal, microbiota-dependent relationship between S-BMO and growth promotion.

Authors
Charbonneau, MR; O'Donnell, D; Blanton, LV; Totten, SM; Davis, JCC; Barratt, MJ; Cheng, J; Guruge, J; Talcott, M; Bain, JR; Muehlbauer, MJ; Ilkayeva, O; Wu, C; Struckmeyer, T; Barile, D; Mangani, C; Jorgensen, J; Fan, Y-M; Maleta, K; Dewey, KG; Ashorn, P; Newgard, CB; Lebrilla, C; Mills, DA; Gordon, JI
MLA Citation
Charbonneau, MR, O'Donnell, D, Blanton, LV, Totten, SM, Davis, JCC, Barratt, MJ, Cheng, J, Guruge, J, Talcott, M, Bain, JR, Muehlbauer, MJ, Ilkayeva, O, Wu, C, Struckmeyer, T, Barile, D, Mangani, C, Jorgensen, J, Fan, Y-M, Maleta, K, Dewey, KG, Ashorn, P, Newgard, CB, Lebrilla, C, Mills, DA, and Gordon, JI. "Sialylated Milk Oligosaccharides Promote Microbiota-Dependent Growth in Models of Infant Undernutrition." Cell 164.5 (February 17, 2016): 859-871.
PMID
26898329
Source
epmc
Published In
Cell
Volume
164
Issue
5
Publish Date
2016
Start Page
859
End Page
871
DOI
10.1016/j.cell.2016.01.024

The Gut Microbiota Modulates Energy Metabolism in the Hibernating Brown Bear Ursus arctos.

Hibernation is an adaptation that helps many animals to conserve energy during food shortage in winter. Brown bears double their fat depots during summer and use these stored lipids during hibernation. Although bears seasonally become obese, they remain metabolically healthy. We analyzed the microbiota of free-ranging brown bears during their active phase and hibernation. Compared to the active phase, hibernation microbiota had reduced diversity, reduced levels of Firmicutes and Actinobacteria, and increased levels of Bacteroidetes. Several metabolites involved in lipid metabolism, including triglycerides, cholesterol, and bile acids, were also affected by hibernation. Transplantation of the bear microbiota from summer and winter to germ-free mice transferred some of the seasonal metabolic features and demonstrated that the summer microbiota promoted adiposity without impairing glucose tolerance, suggesting that seasonal variation in the microbiota may contribute to host energy metabolism in the hibernating brown bear.

Authors
Sommer, F; Ståhlman, M; Ilkayeva, O; Arnemo, JM; Kindberg, J; Josefsson, J; Newgard, CB; Fröbert, O; Bäckhed, F
MLA Citation
Sommer, F, Ståhlman, M, Ilkayeva, O, Arnemo, JM, Kindberg, J, Josefsson, J, Newgard, CB, Fröbert, O, and Bäckhed, F. "The Gut Microbiota Modulates Energy Metabolism in the Hibernating Brown Bear Ursus arctos." Cell reports 14.7 (February 3, 2016): 1655-1661.
PMID
26854221
Source
epmc
Published In
Cell Reports
Volume
14
Issue
7
Publish Date
2016
Start Page
1655
End Page
1661
DOI
10.1016/j.celrep.2016.01.026

Gut bacteria that prevent growth impairments transmitted by microbiota from malnourished children.

Undernourished children exhibit impaired development of their gut microbiota. Transplanting microbiota from 6- and 18-month-old healthy or undernourished Malawian donors into young germ-free mice that were fed a Malawian diet revealed that immature microbiota from undernourished infants and children transmit impaired growth phenotypes. The representation of several age-discriminatory taxa in recipient animals correlated with lean body mass gain; liver, muscle, and brain metabolism; and bone morphology. Mice were cohoused shortly after receiving microbiota from healthy or severely stunted and underweight infants; age- and growth-discriminatory taxa from the microbiota of the former were able to invade that of the latter, which prevented growth impairments in recipient animals. Adding two invasive species, Ruminococcus gnavus and Clostridium symbiosum, to the microbiota from undernourished donors also ameliorated growth and metabolic abnormalities in recipient animals. These results provide evidence that microbiota immaturity is causally related to undernutrition and reveal potential therapeutic targets and agents.

Authors
Blanton, LV; Charbonneau, MR; Salih, T; Barratt, MJ; Venkatesh, S; Ilkaveya, O; Subramanian, S; Manary, MJ; Trehan, I; Jorgensen, JM; Fan, Y-M; Henrissat, B; Leyn, SA; Rodionov, DA; Osterman, AL; Maleta, KM; Newgard, CB; Ashorn, P; Dewey, KG; Gordon, JI
MLA Citation
Blanton, LV, Charbonneau, MR, Salih, T, Barratt, MJ, Venkatesh, S, Ilkaveya, O, Subramanian, S, Manary, MJ, Trehan, I, Jorgensen, JM, Fan, Y-M, Henrissat, B, Leyn, SA, Rodionov, DA, Osterman, AL, Maleta, KM, Newgard, CB, Ashorn, P, Dewey, KG, and Gordon, JI. "Gut bacteria that prevent growth impairments transmitted by microbiota from malnourished children." Science (New York, N.Y.) 351.6275 (February 2016).
PMID
26912898
Source
epmc
Published In
Science
Volume
351
Issue
6275
Publish Date
2016
DOI
10.1126/science.aad3311

Metabolomics applied to the pancreatic islet.

Metabolomics, the characterization of the set of small molecules in a biological system, is advancing research in multiple areas of islet biology. Measuring a breadth of metabolites simultaneously provides a broad perspective on metabolic changes as the islets respond dynamically to metabolic fuels, hormones, or environmental stressors. As a result, metabolomics has the potential to provide new mechanistic insights into islet physiology and pathophysiology. Here we summarize advances in our understanding of islet physiology and the etiologies of type-1 and type-2 diabetes gained from metabolomics studies.

Authors
Gooding, JR; Jensen, MV; Newgard, CB
MLA Citation
Gooding, JR, Jensen, MV, and Newgard, CB. "Metabolomics applied to the pancreatic islet." Archives of biochemistry and biophysics 589 (January 2016): 120-130. (Review)
PMID
26116790
Source
epmc
Published In
Archives of Biochemistry and Biophysics
Volume
589
Publish Date
2016
Start Page
120
End Page
130
DOI
10.1016/j.abb.2015.06.013

Liver receptor homolog-1 is a critical determinant of methyl-pool metabolism.

Balance of labile methyl groups (choline, methionine, betaine, and folate) is important for normal liver function. Quantitatively, a significant use of labile methyl groups is in the production of phosphatidylcholines (PCs), which are ligands for the nuclear liver receptor homolog-1 (LRH-1). We studied the role of LRH-1 in methyl-pool homeostasis and determined its metabolic effects using the methionine and choline-deficient (MCD) diet, which depletes methyl groups and results in a deleterious decrease in the PC-to-phosphatidylethanolamine ratio. We found that MCD diet-fed, liver-specific LRH-1 knockout mice (Lrh-1(-/-) ) do not show the expected decreased methyl-pool and PC/phosphatidylethanolamine ratio and are resistant to the hepatitis and fibrosis normally induced by the diet. Adaptive responses observed in wild-type mice on the MCD diet were also observed in Lrh-1(-/-) mice on a normal diet. This includes reduced expression of the highly active glycine-n-methyltransferase and the biliary phospholipid floppase multidrug-resistance protein 2 (Mdr2/Abcb4), resulting in reduced consumption of methyl groups and biliary PC secretion. In vitro studies confirm that Gnmt and Mdr2 are primary LRH-1 target genes. Additional similarities between hepatic gene expression profiles in MCD diet-fed wild-type and untreated Lrh-1(-/-) mice suggest that methyl-pool deficiency decreases LRH-1 activity, and this was confirmed by in vitro functional results in cells maintained in MCD medium.LRH-1 is a novel transcriptional regulator of methyl-pool balance; when the methyl-pool is depleted, decreased LRH-1 transactivation suppresses expression of key genes to minimize loss of labile methyl groups. (Hepatology 2016;63:95-106).

Authors
Wagner, M; Choi, S; Panzitt, K; Mamrosh, JL; Lee, JM; Zaufel, A; Xiao, R; Wooton-Kee, R; Ståhlman, M; Newgard, CB; Borén, J; Moore, DD
MLA Citation
Wagner, M, Choi, S, Panzitt, K, Mamrosh, JL, Lee, JM, Zaufel, A, Xiao, R, Wooton-Kee, R, Ståhlman, M, Newgard, CB, Borén, J, and Moore, DD. "Liver receptor homolog-1 is a critical determinant of methyl-pool metabolism." Hepatology (Baltimore, Md.) 63.1 (January 2016): 95-106.
PMID
26267291
Source
epmc
Published In
Hepatology
Volume
63
Issue
1
Publish Date
2016
Start Page
95
End Page
106
DOI
10.1002/hep.28124

Diabetes: The good in fat

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Diabetes: The good in fat." Nature 516.7529 (December 4, 2015): 49-50.
Source
scopus
Published In
Nature
Volume
516
Issue
7529
Publish Date
2015
Start Page
49
End Page
50
DOI
10.1038/nature14070

Metabolomic Quantitative Trait Loci (mQTL) Mapping Implicates the Ubiquitin Proteasome System in Cardiovascular Disease Pathogenesis.

Levels of certain circulating short-chain dicarboxylacylcarnitine (SCDA), long-chain dicarboxylacylcarnitine (LCDA) and medium chain acylcarnitine (MCA) metabolites are heritable and predict cardiovascular disease (CVD) events. Little is known about the biological pathways that influence levels of most of these metabolites. Here, we analyzed genetics, epigenetics, and transcriptomics with metabolomics in samples from a large CVD cohort to identify novel genetic markers for CVD and to better understand the role of metabolites in CVD pathogenesis. Using genomewide association in the CATHGEN cohort (N = 1490), we observed associations of several metabolites with genetic loci. Our strongest findings were for SCDA metabolite levels with variants in genes that regulate components of endoplasmic reticulum (ER) stress (USP3, HERC1, STIM1, SEL1L, FBXO25, SUGT1) These findings were validated in a second cohort of CATHGEN subjects (N = 2022, combined p = 8.4x10-6-2.3x10-10). Importantly, variants in these genes independently predicted CVD events. Association of genomewide methylation profiles with SCDA metabolites identified two ER stress genes as differentially methylated (BRSK2 and HOOK2). Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm. Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP. Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

Authors
Kraus, WE; Muoio, DM; Stevens, R; Craig, D; Bain, JR; Grass, E; Haynes, C; Kwee, L; Qin, X; Slentz, DH; Krupp, D; Muehlbauer, M; Hauser, ER; Gregory, SG; Newgard, CB; Shah, SH
MLA Citation
Kraus, WE, Muoio, DM, Stevens, R, Craig, D, Bain, JR, Grass, E, Haynes, C, Kwee, L, Qin, X, Slentz, DH, Krupp, D, Muehlbauer, M, Hauser, ER, Gregory, SG, Newgard, CB, and Shah, SH. "Metabolomic Quantitative Trait Loci (mQTL) Mapping Implicates the Ubiquitin Proteasome System in Cardiovascular Disease Pathogenesis." PLoS genetics 11.11 (November 5, 2015): e1005553-.
Website
http://hdl.handle.net/10161/10957
PMID
26540294
Source
epmc
Published In
PLoS genetics
Volume
11
Issue
11
Publish Date
2015
Start Page
e1005553
DOI
10.1371/journal.pgen.1005553

Non-targeted metabolomics of Brg1/Brm double-mutant cardiomyocytes reveals a novel role for SWI/SNF complexes in metabolic homeostasis.

Mammalian SWI/SNF chromatin-remodeling complexes utilize either BRG1 or Brm as alternative catalytic subunits to alter the position of nucleosomes and regulate gene expression. Genetic studies have demonstrated that SWI/SNF complexes are required during cardiac development and also protect against cardiovascular disease and cancer. However, Brm constitutive null mutants do not exhibit a cardiomyocyte phenotype and inducible Brg1 conditional mutations in cardiomyocyte do not demonstrate differences until stressed with transverse aortic constriction, where they exhibit a reduction in cardiac hypertrophy. We recently demonstrated the overlapping functions of Brm and Brg1 in vascular endothelial cells and sought here to test if this overlapping function occurred in cardiomyocytes. Brg1/Brm double mutants died within 21 days of severe cardiac dysfunction associated with glycogen accumulation and mitochondrial defects based on histological and ultrastructural analyses. To determine the underlying defects, we performed nontargeted metabolomics analysis of cardiac tissue by GC/MS from a line of Brg1/Brm double-mutant mice, which lack both Brg1 and Brm in cardiomyocytes in an inducible manner, and two groups of controls. Metabolites contributing most significantly to the differences between Brg1/Brm double-mutant and control-group hearts were then determined using the variable importance in projection analysis. Increased cardiac linoleic acid and oleic acid suggest alterations in fatty acid utilization or intake are perturbed in Brg1/Brm double mutants. Conversely, decreased glucose-6-phosphate, fructose-6-phosphate, and myoinositol suggest that glycolysis and glycogen formation are impaired. These novel metabolomics findings provide insight into SWI/SNF-regulated metabolic pathways and will guide mechanistic studies evaluating the role of SWI/SNF complexes in homeostasis and cardiovascular disease prevention.

Authors
Banerjee, R; Bultman, SJ; Holley, D; Hillhouse, C; Bain, JR; Newgard, CB; Muehlbauer, MJ; Willis, MS
MLA Citation
Banerjee, R, Bultman, SJ, Holley, D, Hillhouse, C, Bain, JR, Newgard, CB, Muehlbauer, MJ, and Willis, MS. "Non-targeted metabolomics of Brg1/Brm double-mutant cardiomyocytes reveals a novel role for SWI/SNF complexes in metabolic homeostasis." Metabolomics : Official journal of the Metabolomic Society 11.5 (October 2015): 1287-1301.
PMID
26392817
Source
epmc
Published In
Metabolomics
Volume
11
Issue
5
Publish Date
2015
Start Page
1287
End Page
1301
DOI
10.1007/s11306-015-0786-7

Impact of combined resistance and aerobic exercise training on branched-chain amino acid turnover, glycine metabolism and insulin sensitivity in overweight humans.

Obesity is associated with decreased insulin sensitivity (IS) and elevated plasma branched-chain amino acids (BCAAs). The purpose of this study was to investigate the relationship between BCAA metabolism and IS in overweight (OW) individuals during exercise intervention.Whole-body leucine turnover, IS by hyperinsulinaemic-euglycaemic clamp, and circulating and skeletal muscle amino acids, branched-chain α-keto acids and acylcarnitines were measured in ten healthy controls (Control) and nine OW, untrained, insulin-resistant individuals (OW-Untrained). OW-Untrained then underwent a 6 month aerobic and resistance exercise programme and repeated testing (OW-Trained).IS was higher in Control vs OW-Untrained and increased significantly following exercise. IS was lower in OW-Trained vs Control expressed relative to body mass, but was not different from Control when normalised to fat-free mass (FFM). Plasma BCAAs and leucine turnover (relative to FFM) were higher in OW-Untrained vs Control, but did not change on average with exercise. Despite this, within individuals, the decrease in molar sum of circulating BCAAs was the best metabolic predictor of improvement in IS. Circulating glycine levels were higher in Control and OW-Trained vs OW-Untrained, and urinary metabolic profiling suggests that exercise induces more efficient elimination of excess acyl groups derived from BCAA and aromatic amino acid (AA) metabolism via formation of urinary glycine adducts.A mechanism involving more efficient elimination of excess acyl groups derived from BCAA and aromatic AA metabolism via glycine conjugation in the liver, rather than increased BCAA disposal through oxidation and turnover, may mediate interactions between exercise, BCAA metabolism and IS.Clinicaltrials.gov NCT01786941.

Authors
Glynn, EL; Piner, LW; Huffman, KM; Slentz, CA; Elliot-Penry, L; AbouAssi, H; White, PJ; Bain, JR; Muehlbauer, MJ; Ilkayeva, OR; Stevens, RD; Porter Starr, KN; Bales, CW; Volpi, E; Brosnan, MJ; Trimmer, JK; Rolph, TP; Newgard, CB; Kraus, WE
MLA Citation
Glynn, EL, Piner, LW, Huffman, KM, Slentz, CA, Elliot-Penry, L, AbouAssi, H, White, PJ, Bain, JR, Muehlbauer, MJ, Ilkayeva, OR, Stevens, RD, Porter Starr, KN, Bales, CW, Volpi, E, Brosnan, MJ, Trimmer, JK, Rolph, TP, Newgard, CB, and Kraus, WE. "Impact of combined resistance and aerobic exercise training on branched-chain amino acid turnover, glycine metabolism and insulin sensitivity in overweight humans." Diabetologia 58.10 (October 2015): 2324-2335.
PMID
26254576
Source
epmc
Published In
Diabetologia
Volume
58
Issue
10
Publish Date
2015
Start Page
2324
End Page
2335
DOI
10.1007/s00125-015-3705-6

Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells.

Insulin secretion from β cells of the pancreatic islets of Langerhans controls metabolic homeostasis and is impaired in individuals with type 2 diabetes (T2D). Increases in blood glucose trigger insulin release by closing ATP-sensitive K+ channels, depolarizing β cells, and opening voltage-dependent Ca2+ channels to elicit insulin exocytosis. However, one or more additional pathway(s) amplify the secretory response, likely at the distal exocytotic site. The mitochondrial export of isocitrate and engagement with cytosolic isocitrate dehydrogenase (ICDc) may be one key pathway, but the mechanism linking this to insulin secretion and its role in T2D have not been defined. Here, we show that the ICDc-dependent generation of NADPH and subsequent glutathione (GSH) reduction contribute to the amplification of insulin exocytosis via sentrin/SUMO-specific protease-1 (SENP1). In human T2D and an in vitro model of human islet dysfunction, the glucose-dependent amplification of exocytosis was impaired and could be rescued by introduction of signaling intermediates from this pathway. Moreover, islet-specific Senp1 deletion in mice caused impaired glucose tolerance by reducing the amplification of insulin exocytosis. Together, our results identify a pathway that links glucose metabolism to the amplification of insulin secretion and demonstrate that restoration of this axis rescues β cell function in T2D.

Authors
Ferdaoussi, M; Dai, X; Jensen, MV; Wang, R; Peterson, BS; Huang, C; Ilkayeva, O; Smith, N; Miller, N; Hajmrle, C; Spigelman, AF; Wright, RC; Plummer, G; Suzuki, K; Mackay, JP; van de Bunt, M; Gloyn, AL; Ryan, TE; Norquay, LD; Brosnan, MJ; Trimmer, JK; Rolph, TP; Kibbey, RG; Manning Fox, JE; Colmers, WF; Shirihai, OS; Neufer, PD; Yeh, ETH; Newgard, CB; MacDonald, PE
MLA Citation
Ferdaoussi, M, Dai, X, Jensen, MV, Wang, R, Peterson, BS, Huang, C, Ilkayeva, O, Smith, N, Miller, N, Hajmrle, C, Spigelman, AF, Wright, RC, Plummer, G, Suzuki, K, Mackay, JP, van de Bunt, M, Gloyn, AL, Ryan, TE, Norquay, LD, Brosnan, MJ, Trimmer, JK, Rolph, TP, Kibbey, RG, Manning Fox, JE, Colmers, WF, Shirihai, OS, Neufer, PD, Yeh, ETH, Newgard, CB, and MacDonald, PE. "Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells." The Journal of clinical investigation 125.10 (October 2015): 3847-3860.
PMID
26389676
Source
epmc
Published In
Journal of Clinical Investigation
Volume
125
Issue
10
Publish Date
2015
Start Page
3847
End Page
3860
DOI
10.1172/jci82498

Adenylosuccinate Is an Insulin Secretagogue Derived from Glucose-Induced Purine Metabolism.

Pancreatic islet failure, involving loss of glucose-stimulated insulin secretion (GSIS) from islet β cells, heralds the onset of type 2 diabetes (T2D). To search for mediators of GSIS, we performed metabolomics profiling of the insulinoma cell line 832/13 and uncovered significant glucose-induced changes in purine pathway intermediates, including a decrease in inosine monophosphate (IMP) and an increase in adenylosuccinate (S-AMP), suggesting a regulatory role for the enzyme that links the two metabolites, adenylosuccinate synthase (ADSS). Inhibition of ADSS or a more proximal enzyme in the S-AMP biosynthesis pathway, adenylosuccinate lyase, lowers S-AMP levels and impairs GSIS. Addition of S-AMP to the interior of patch-clamped human β cells amplifies exocytosis, an effect dependent upon expression of sentrin/SUMO-specific protease 1 (SENP1). S-AMP also overcomes the defect in glucose-induced exocytosis in β cells from a human donor with T2D. S-AMP is, thus, an insulin secretagogue capable of reversing β cell dysfunction in T2D.

Authors
Gooding, JR; Jensen, MV; Dai, X; Wenner, BR; Lu, D; Arumugam, R; Ferdaoussi, M; MacDonald, PE; Newgard, CB
MLA Citation
Gooding, JR, Jensen, MV, Dai, X, Wenner, BR, Lu, D, Arumugam, R, Ferdaoussi, M, MacDonald, PE, and Newgard, CB. "Adenylosuccinate Is an Insulin Secretagogue Derived from Glucose-Induced Purine Metabolism." Cell reports 13.1 (October 2015): 157-167.
PMID
26411681
Source
epmc
Published In
Cell Reports
Volume
13
Issue
1
Publish Date
2015
Start Page
157
End Page
167
DOI
10.1016/j.celrep.2015.08.072

The ubiquitin ligase MuRF1 regulates PPARα activity in the heart by enhancing nuclear export via monoubiquitination.

The transcriptional regulation of peroxisome proliferator-activated receptor (PPAR) α by post-translational modification, such as ubiquitin, has not been described. We report here for the first time an ubiquitin ligase (muscle ring finger-1/MuRF1) that inhibits fatty acid oxidation by inhibiting PPARα, but not PPARβ/δ or PPARγ in cardiomyocytes in vitro. Similarly, MuRF1 Tg+ hearts showed significant decreases in nuclear PPARα activity and acyl-carnitine intermediates, while MuRF1-/- hearts exhibited increased PPARα activity and acyl-carnitine intermediates. MuRF1 directly interacts with PPARα, mono-ubiquitinates it, and targets it for nuclear export to inhibit fatty acid oxidation in a proteasome independent manner. We then identified a previously undescribed nuclear export sequence in PPARα, along with three specific lysines (292, 310, 388) required for MuRF1's targeting of nuclear export. These studies identify the role of ubiquitination in regulating cardiac PPARα, including the ubiquitin ligase that may be responsible for this critical regulation of cardiac metabolism in heart failure.

Authors
Rodríguez, JE; Liao, J-Y; He, J; Schisler, JC; Newgard, CB; Drujan, D; Glass, DJ; Frederick, CB; Yoder, BC; Lalush, DS; Patterson, C; Willis, MS
MLA Citation
Rodríguez, JE, Liao, J-Y, He, J, Schisler, JC, Newgard, CB, Drujan, D, Glass, DJ, Frederick, CB, Yoder, BC, Lalush, DS, Patterson, C, and Willis, MS. "The ubiquitin ligase MuRF1 regulates PPARα activity in the heart by enhancing nuclear export via monoubiquitination." Molecular and cellular endocrinology 413 (September 2015): 36-48.
PMID
26116825
Source
epmc
Published In
Molecular and Cellular Endocrinology
Volume
413
Publish Date
2015
Start Page
36
End Page
48
DOI
10.1016/j.mce.2015.06.008

Induction of miR-132 and miR-212 Expression by Glucagon-Like Peptide 1 (GLP-1) in Rodent and Human Pancreatic β-Cells.

Better understanding how glucagon-like peptide 1 (GLP-1) promotes pancreatic β-cell function and/or mass may uncover new treatment for type 2 diabetes. In this study, we investigated the potential involvement of microRNAs (miRNAs) in the effect of GLP-1 on glucose-stimulated insulin secretion. miRNA levels in INS-1 cells and isolated rodent and human islets treated with GLP-1 in vitro and in vivo (with osmotic pumps) were measured by real-time quantitative PCR. The role of miRNAs on insulin secretion was studied by transfecting INS-1 cells with either precursors or antisense inhibitors of miRNAs. Among the 250 miRNAs surveyed, miR-132 and miR-212 were significantly up-regulated by GLP-1 by greater than 2-fold in INS-1 832/3 cells, which were subsequently reproduced in freshly isolated rat, mouse, and human islets, as well as the islets from GLP-1 infusion in vivo in mice. The inductions of miR-132 and miR-212 by GLP-1 were correlated with cAMP production and were blocked by the protein kinase A inhibitor H-89 but not affected by the exchange protein activated by cAMP activator 8-pCPT-2'-O-Me-cAMP-AM. GLP-1 failed to increase miR-132 or miR-212 expression levels in the 832/13 line of INS-1 cells, which lacks robust cAMP and insulin responses to GLP-1 treatment. Overexpression of miR-132 or miR-212 significantly enhanced glucose-stimulated insulin secretion in both 832/3 and 832/13 cells, and restored insulin responses to GLP-1 in INS-1 832/13 cells. GLP-1 increases the expression of miRNAs 132 and 212 via a cAMP/protein kinase A-dependent pathway in pancreatic β-cells. Overexpression of miR-132 or miR-212 enhances glucose and GLP-1-stimulated insulin secretion.

Authors
Shang, J; Li, J; Keller, MP; Hohmeier, HE; Wang, Y; Feng, Y; Zhou, HH; Shen, X; Rabaglia, M; Soni, M; Attie, AD; Newgard, CB; Thornberry, NA; Howard, AD; Zhou, Y-P
MLA Citation
Shang, J, Li, J, Keller, MP, Hohmeier, HE, Wang, Y, Feng, Y, Zhou, HH, Shen, X, Rabaglia, M, Soni, M, Attie, AD, Newgard, CB, Thornberry, NA, Howard, AD, and Zhou, Y-P. "Induction of miR-132 and miR-212 Expression by Glucagon-Like Peptide 1 (GLP-1) in Rodent and Human Pancreatic β-Cells." Molecular Endocrinology 29.9 (September 2015): 1243-1253.
PMID
26218441
Source
epmc
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
29
Issue
9
Publish Date
2015
Start Page
1243
End Page
1253
DOI
10.1210/me.2014-1335

Left-Biased Spermatogenic Failure in 129/SvJ Dnd1Ter/+ Mice Correlates with Differences in Vascular Architecture, Oxygen Availability, and Metabolites.

Homozygosity for the Ter mutation in the RNA-binding protein Dead end 1 (Dnd1(Ter/Ter)) sensitizes germ cells to degeneration in all mouse strains. In 129/SvJ mice, approximately 10% of Dnd1(Ter/+) heterozygotes develop spermatogenic failure, and 95% of unilateral cases occur in the left testis. The first differences between right and left testes were detected at Postnatal Day 15 when many more spermatogonial stem cells (SSCs) were undergoing apoptosis in the left testis compared to the right. As we detected no significant left/right differences in the molecular pathway associated with body axis asymmetry or in the expression of signals known to promote proliferation, differentiation, and survival of germ cells, we investigated whether physiological differences might account for asymmetry of the degeneration phenotype. We show that left/right differences in vascular architecture are associated with a decrease in hemoglobin saturation and increased levels of HIF-1alpha in the left testis compared to the right. In Dnd1 heterozygotes, lower oxygen availability was associated with metabolic differences, including lower levels of ATP and NADH in the left testis. These experiments suggest a dependence on oxygen availability and metabolic substrates for SSC survival and suggest that Dnd1(Ter/+) SSCs may act as efficient sensors to detect subtle environmental changes that alter SSC fate.

Authors
Bustamante-Marin, XM; Cook, MS; Gooding, J; Newgard, C; Capel, B
MLA Citation
Bustamante-Marin, XM, Cook, MS, Gooding, J, Newgard, C, and Capel, B. "Left-Biased Spermatogenic Failure in 129/SvJ Dnd1Ter/+ Mice Correlates with Differences in Vascular Architecture, Oxygen Availability, and Metabolites." Biology of reproduction 93.3 (September 2015): 78-.
PMID
26224005
Source
epmc
Published In
Biology of Reproduction
Volume
93
Issue
3
Publish Date
2015
Start Page
78
DOI
10.1095/biolreprod.115.128850

MuRF2 regulates PPARγ1 activity to protect against diabetic cardiomyopathy and enhance weight gain induced by a high fat diet.

In diabetes mellitus the morbidity and mortality of cardiovascular disease is increased and represents an important independent mechanism by which heart disease is exacerbated. The pathogenesis of diabetic cardiomyopathy involves the enhanced activation of PPAR transcription factors, including PPARα, and to a lesser degree PPARβ and PPARγ1. How these transcription factors are regulated in the heart is largely unknown. Recent studies have described post-translational ubiquitination of PPARs as ways in which PPAR activity is inhibited in cancer. However, specific mechanisms in the heart have not previously been described. Recent studies have implicated the muscle-specific ubiquitin ligase muscle ring finger-2 (MuRF2) in inhibiting the nuclear transcription factor SRF. Initial studies of MuRF2-/- hearts revealed enhanced PPAR activity, leading to the hypothesis that MuRF2 regulates PPAR activity by post-translational ubiquitination.MuRF2-/- mice were challenged with a 26-week 60% fat diet designed to simulate obesity-mediated insulin resistance and diabetic cardiomyopathy. Mice were followed by conscious echocardiography, blood glucose, tissue triglyceride, glycogen levels, immunoblot analysis of intracellular signaling, heart and skeletal muscle morphometrics, and PPARα, PPARβ, and PPARγ1-regulated mRNA expression.MuRF2 protein levels increase ~20% during the development of diabetic cardiomyopathy induced by high fat diet. Compared to littermate wildtype hearts, MuRF2-/- hearts exhibit an exaggerated diabetic cardiomyopathy, characterized by an early onset systolic dysfunction, larger left ventricular mass, and higher heart weight. MuRF2-/- hearts had significantly increased PPARα- and PPARγ1-regulated gene expression by RT-qPCR, consistent with MuRF2's regulation of these transcription factors in vivo. Mechanistically, MuRF2 mono-ubiquitinated PPARα and PPARγ1 in vitro, consistent with its non-degradatory role in diabetic cardiomyopathy. However, increasing MuRF2:PPARγ1 (>5:1) beyond physiological levels drove poly-ubiquitin-mediated degradation of PPARγ1 in vitro, indicating large MuRF2 increases may lead to PPAR degradation if found in other disease states.Mutations in MuRF2 have been described to contribute to the severity of familial hypertrophic cardiomyopathy. The present study suggests that the lack of MuRF2, as found in these patients, can result in an exaggerated diabetic cardiomyopathy. These studies also identify MuRF2 as the first ubiquitin ligase to regulate cardiac PPARα and PPARγ1 activities in vivo via post-translational modification without degradation.

Authors
He, J; Quintana, MT; Sullivan, J; L Parry, T; J Grevengoed, T; Schisler, JC; Hill, JA; Yates, CC; Mapanga, RF; Essop, MF; Stansfield, WE; Bain, JR; Newgard, CB; Muehlbauer, MJ; Han, Y; Clarke, BA; Willis, MS
MLA Citation
He, J, Quintana, MT, Sullivan, J, L Parry, T, J Grevengoed, T, Schisler, JC, Hill, JA, Yates, CC, Mapanga, RF, Essop, MF, Stansfield, WE, Bain, JR, Newgard, CB, Muehlbauer, MJ, Han, Y, Clarke, BA, and Willis, MS. "MuRF2 regulates PPARγ1 activity to protect against diabetic cardiomyopathy and enhance weight gain induced by a high fat diet." Cardiovascular diabetology 14 (August 5, 2015): 97-.
PMID
26242235
Source
epmc
Published In
Cardiovascular Diabetology
Volume
14
Publish Date
2015
Start Page
97
DOI
10.1186/s12933-015-0252-x

Muscle ring finger-3 protects against diabetic cardiomyopathy induced by a high fat diet.

The pathogenesis of diabetic cardiomyopathy (DCM) involves the enhanced activation of peroxisome proliferator activating receptor (PPAR) transcription factors, including the most prominent isoform in the heart, PPARα. In cancer cells and adipocytes, post-translational modification of PPARs have been identified, including ligand-dependent degradation of PPARs by specific ubiquitin ligases. However, the regulation of PPARs in cardiomyocytes and heart have not previously been identified. We recently identified that muscle ring finger-1 (MuRF1) and MuRF2 differentially inhibit PPAR activities by mono-ubiquitination, leading to the hypothesis that MuRF3 may regulate PPAR activity in vivo to regulate DCM.MuRF3-/- mice were challenged with 26 weeks 60% high fat diet to induce insulin resistance and DCM. Conscious echocardiography, blood glucose, tissue triglyceride, glycogen levels, immunoblot analysis of intracellular signaling, heart and skeletal muscle morphometrics, and PPARα, PPARβ, and PPARγ1 activities were assayed.MuRF3-/- mice exhibited a premature systolic heart failure by 6 weeks high fat diet (vs. 12 weeks in MuRF3+/+). MuRF3-/- mice weighed significantly less than sibling-matched wildtype mice after 26 weeks HFD. These differences may be largely due to resistance to fat accumulation, as MRI analysis revealed MuRF3-/- mice had significantly less fat mass, but not lean body mass. In vitro ubiquitination assays identified MuRF3 mono-ubiquitinated PPARα and PPARγ1, but not PPARβ.These findings suggest that MuRF3 helps stabilize cardiac PPARα and PPARγ1 in vivo to support resistance to the development of DCM. MuRF3 also plays an unexpected role in regulating fat storage despite being found only in striated muscle.

Authors
Quintana, MT; He, J; Sullivan, J; Grevengoed, T; Schisler, J; Han, Y; Hill, JA; Yates, CC; Stansfield, WE; Mapanga, RF; Essop, MF; Muehlbauer, MJ; Newgard, CB; Bain, JR; Willis, MS
MLA Citation
Quintana, MT, He, J, Sullivan, J, Grevengoed, T, Schisler, J, Han, Y, Hill, JA, Yates, CC, Stansfield, WE, Mapanga, RF, Essop, MF, Muehlbauer, MJ, Newgard, CB, Bain, JR, and Willis, MS. "Muscle ring finger-3 protects against diabetic cardiomyopathy induced by a high fat diet." BMC endocrine disorders 15 (July 28, 2015): 36-.
PMID
26215257
Source
epmc
Published In
BMC Endocrine Disorders
Volume
15
Publish Date
2015
Start Page
36
DOI
10.1186/s12902-015-0028-z

Isoprenylcysteine carboxylmethyltransferase regulates mitochondrial respiration and cancer cell metabolism

© 2015 Macmillan Publishers Limited All rights reserved. Isoprenylcysteine carboxylmethyltransferase (Icmt) catalyzes the last of the three-step posttranslational protein prenylation process for the so-called CaaX proteins, which includes many signaling proteins, such as most small GTPases. Despite extensive studies on Icmt and its regulation of cell functions, the mechanisms of much of the impact of Icmt on cellular functions remain unclear. Our recent studies demonstrated that suppression of Icmt results in induction of autophagy, inhibition of cell growth and inhibition of proliferation in various cancer cell types, prompting this investigation of potential metabolic regulation by Icmt. We report here the findings that Icmt inhibition reduces the function of mitochondrial oxidative phosphorylation in multiple cancer cell lines. In-depth oximetry analysis demonstrated that functions of mitochondrial complex I, II and III are subject to Icmt regulation. Consistently, Icmt inhibition decreased cellular ATP and depleted critical tricarboxylic acid cycle metabolites, leading to suppression of cell anabolism and growth, and marked autophagy. Several different approaches demonstrated that the impact of Icmt inhibition on cell proliferation and viability was largely mediated by its effect on mitochondrial respiration. This previously unappreciated function of Icmt, which can be therapeutically exploited, likely has a significant role in the impact of Icmt on tumorigenic processes.

Authors
Teh, JT; Zhu, WL; Ilkayeva, OR; Li, Y; Gooding, J; Casey, PJ; Summers, SA; Newgard, CB; Wang, M
MLA Citation
Teh, JT, Zhu, WL, Ilkayeva, OR, Li, Y, Gooding, J, Casey, PJ, Summers, SA, Newgard, CB, and Wang, M. "Isoprenylcysteine carboxylmethyltransferase regulates mitochondrial respiration and cancer cell metabolism." Oncogene 34.25 (June 20, 2015): 3296-3304.
Source
scopus
Published In
Oncogene: Including Oncogene Reviews
Volume
34
Issue
25
Publish Date
2015
Start Page
3296
End Page
3304
DOI
10.1038/onc.2014.260

Isoprenylcysteine carboxylmethyltransferase regulates mitochondrial respiration and cancer cell metabolism.

Isoprenylcysteine carboxylmethyltransferase (Icmt) catalyzes the last of the three-step posttranslational protein prenylation process for the so-called CaaX proteins, which includes many signaling proteins, such as most small GTPases. Despite extensive studies on Icmt and its regulation of cell functions, the mechanisms of much of the impact of Icmt on cellular functions remain unclear. Our recent studies demonstrated that suppression of Icmt results in induction of autophagy, inhibition of cell growth and inhibition of proliferation in various cancer cell types, prompting this investigation of potential metabolic regulation by Icmt. We report here the findings that Icmt inhibition reduces the function of mitochondrial oxidative phosphorylation in multiple cancer cell lines. In-depth oximetry analysis demonstrated that functions of mitochondrial complex I, II and III are subject to Icmt regulation. Consistently, Icmt inhibition decreased cellular ATP and depleted critical tricarboxylic acid cycle metabolites, leading to suppression of cell anabolism and growth, and marked autophagy. Several different approaches demonstrated that the impact of Icmt inhibition on cell proliferation and viability was largely mediated by its effect on mitochondrial respiration. This previously unappreciated function of Icmt, which can be therapeutically exploited, likely has a significant role in the impact of Icmt on tumorigenic processes.

Authors
Teh, JT; Zhu, WL; Ilkayeva, OR; Li, Y; Gooding, J; Casey, PJ; Summers, SA; Newgard, CB; Wang, M
MLA Citation
Teh, JT, Zhu, WL, Ilkayeva, OR, Li, Y, Gooding, J, Casey, PJ, Summers, SA, Newgard, CB, and Wang, M. "Isoprenylcysteine carboxylmethyltransferase regulates mitochondrial respiration and cancer cell metabolism." Oncogene 34.25 (June 2015): 3296-3304.
PMID
25151967
Source
epmc
Published In
Oncogene: Including Oncogene Reviews
Volume
34
Issue
25
Publish Date
2015
Start Page
3296
End Page
3304
DOI
10.1038/onc.2014.260

HIF-1 Alpha Regulates the Response of Primary Sarcomas to Radiation Therapy through a Cell Autonomous Mechanism.

Hypoxia is a major cause of radiation resistance, which may predispose to local recurrence after radiation therapy. While hypoxia increases tumor cell survival after radiation exposure because there is less oxygen to oxidize damaged DNA, it remains unclear whether signaling pathways triggered by hypoxia contribute to radiation resistance. For example, intratumoral hypoxia can increase hypoxia inducible factor 1 alpha (HIF-1α), which may regulate pathways that contribute to radiation sensitization or radiation resistance. To clarify the role of HIF-1α in regulating tumor response to radiation, we generated a novel genetically engineered mouse model of soft tissue sarcoma with an intact or deleted HIF-1α. Deletion of HIF-1α sensitized primary sarcomas to radiation exposure in vivo. Moreover, cell lines derived from primary sarcomas lacking HIF-1α, or in which HIF-1α was knocked down, had decreased clonogenic survival in vitro, demonstrating that HIF-1α can promote radiation resistance in a cell autonomous manner. In HIF-1α-intact and -deleted sarcoma cells, radiation-induced reactive oxygen species, DNA damage repair and activation of autophagy were similar. However, sarcoma cells lacking HIF-1α had impaired mitochondrial biogenesis and metabolic response after irradiation, which might contribute to radiation resistance. These results show that HIF-1α promotes radiation resistance in a cell autonomous manner.

Authors
Zhang, M; Qiu, Q; Li, Z; Sachdeva, M; Min, H; Cardona, DM; DeLaney, TF; Han, T; Ma, Y; Luo, L; Ilkayeva, OR; Lui, K; Nichols, AG; Newgard, CB; Kastan, MB; Rathmell, JC; Dewhirst, MW; Kirsch, DG
MLA Citation
Zhang, M, Qiu, Q, Li, Z, Sachdeva, M, Min, H, Cardona, DM, DeLaney, TF, Han, T, Ma, Y, Luo, L, Ilkayeva, OR, Lui, K, Nichols, AG, Newgard, CB, Kastan, MB, Rathmell, JC, Dewhirst, MW, and Kirsch, DG. "HIF-1 Alpha Regulates the Response of Primary Sarcomas to Radiation Therapy through a Cell Autonomous Mechanism." Radiation research 183.6 (June 2015): 594-609.
PMID
25973951
Source
epmc
Published In
Radiation Research
Volume
183
Issue
6
Publish Date
2015
Start Page
594
End Page
609
DOI
10.1667/rr14016.1

CAPER is vital for energy and redox homeostasis by integrating glucose-induced mitochondrial functions via ERR-α-Gabpa and stress-induced adaptive responses via NF-κB-cMYC.

Ever since we developed mitochondria to generate ATP, eukaryotes required intimate mito-nuclear communication. In addition, since reactive oxygen species are a cost of mitochondrial oxidative phosphorylation, this demands safeguards as protection from these harmful byproducts. Here we identified a critical transcriptional integrator which eukaryotes share to orchestrate both nutrient-induced mitochondrial energy metabolism and stress-induced nuclear responses, thereby maintaining carbon-nitrogen balance, and preserving life span and reproductive capacity. Inhibition of nutrient-induced expression of CAPER arrests nutrient-dependent cell proliferation and ATP generation and induces autophagy-mediated vacuolization. Nutrient signaling to CAPER induces mitochondrial transcription and glucose-dependent mitochondrial respiration via coactivation of nuclear receptor ERR-α-mediated Gabpa transcription. CAPER is also a coactivator for NF-κB that directly regulates c-Myc to coordinate nuclear transcriptome responses to mitochondrial stress. Finally, CAPER is responsible for anaplerotic carbon flux into TCA cycles from glycolysis, amino acids and fatty acids in order to maintain cellular energy metabolism to counter mitochondrial stress. Collectively, our studies reveal CAPER as an evolutionarily conserved 'master' regulatory mechanism by which eukaryotic cells control vital homeostasis for both ATP and antioxidants via CAPER-dependent coordinated control of nuclear and mitochondrial transcriptomic programs and their metabolisms. These CAPER dependent bioenergetic programs are highly conserved, as we demonstrated that they are essential to preserving life span and reproductive capacity in human cells-and even in C. elegans.

Authors
Kang, YK; Putluri, N; Maity, S; Tsimelzon, A; Ilkayeva, O; Mo, Q; Lonard, D; Michailidis, G; Sreekumar, A; Newgard, CB; Wang, M; Tsai, SY; Tsai, M-J; O'Malley, BW
MLA Citation
Kang, YK, Putluri, N, Maity, S, Tsimelzon, A, Ilkayeva, O, Mo, Q, Lonard, D, Michailidis, G, Sreekumar, A, Newgard, CB, Wang, M, Tsai, SY, Tsai, M-J, and O'Malley, BW. "CAPER is vital for energy and redox homeostasis by integrating glucose-induced mitochondrial functions via ERR-α-Gabpa and stress-induced adaptive responses via NF-κB-cMYC." PLoS genetics 11.4 (April 2015): e1005116-.
PMID
25830341
Source
epmc
Published In
PLoS genetics
Volume
11
Issue
4
Publish Date
2015
Start Page
e1005116
DOI
10.1371/journal.pgen.1005116

Non-targeted metabolomics analysis of cardiac Muscle Ring Finger-1 (MuRF1), MuRF2, and MuRF3 in vivo reveals novel and redundant metabolic changes.

The muscle-specific ubiquitin ligases MuRF1, MuRF2, MuRF3 have been reported to have overlapping substrate specificities, interacting with each other as well as proteins involved in metabolism and cardiac function. In the heart, all three MuRF family proteins have proven critical to cardiac responses to ischemia and heart failure. The non-targeted metabolomics analysis of MuRF1-/-, MuRF2-/-, and MuRF3-/- hearts was initiated to investigate the hypothesis that MuRF1, MuRF2, and MuRF3 have a similarly altered metabolome, representing alterations in overlapping metabolic processes. Ventricular tissue was flash frozen and quantitatively analyzed by GC/MS using a library built upon the Fiehn GC/MS Metabolomics RTL Library. Non-targeted metabolomic analysis identified significant differences (via VIP statistical analysis) in taurine, myoinositol, and stearic acid for the three MuRF-/- phenotypes relative to their matched controls. Moreover, pathway enrichment analysis demonstrated that MuRF1-/- had significant changes in metabolite(s) involved in taurine metabolism and primary acid biosynthesis while MuRF2-/- had changes associated with ascorbic acid/aldarate metabolism (via VIP and t-test analysis vs. sibling-matched wildtype controls). By identifying the functional metabolic consequences of MuRF1, MuRF2, and MuRF3 in the intact heart, non-targeted metabolomics analysis discovered common pathways functionally affected by cardiac MuRF family proteins in vivo. These novel metabolomics findings will aid in guiding the molecular studies delineating the mechanisms that MuRF family proteins regulate metabolic pathways. Understanding these mechanism is an important key to understanding MuRF family proteins' protective effects on the heart during cardiac disease.

Authors
Banerjee, R; He, J; Spaniel, C; Quintana, MT; Wang, Z; Bain, J; Newgard, CB; Muehlbauer, MJ; Willis, MS
MLA Citation
Banerjee, R, He, J, Spaniel, C, Quintana, MT, Wang, Z, Bain, J, Newgard, CB, Muehlbauer, MJ, and Willis, MS. "Non-targeted metabolomics analysis of cardiac Muscle Ring Finger-1 (MuRF1), MuRF2, and MuRF3 in vivo reveals novel and redundant metabolic changes." Metabolomics : Official journal of the Metabolomic Society 11.2 (April 2015): 312-322.
PMID
28325996
Source
epmc
Published In
Metabolomics
Volume
11
Issue
2
Publish Date
2015
Start Page
312
End Page
322
DOI
10.1007/s11306-014-0695-1

Integrated metabolomics and genomics: systems approaches to biomarkers and mechanisms of cardiovascular disease.

The genetic architecture underlying the heritability of cardiovascular disease is incompletely understood. Metabolomics is an emerging technology platform that has shown early success in identifying biomarkers and mechanisms of common chronic diseases. Integration of metabolomics, genetics, and other omics platforms in a systems biology approach holds potential for elucidating novel genetic markers and mechanisms for cardiovascular disease. We review important studies that have used metabolomic profiling in cardiometabolic diseases, approaches for integrating metabolomics with genetics and other molecular profiling platforms, and key studies showing the potential for such studies in deciphering cardiovascular disease genetics, biomarkers, and mechanisms.

Authors
Shah, SH; Newgard, CB
MLA Citation
Shah, SH, and Newgard, CB. "Integrated metabolomics and genomics: systems approaches to biomarkers and mechanisms of cardiovascular disease." Circulation. Cardiovascular genetics 8.2 (April 2015): 410-419. (Review)
PMID
25901039
Source
epmc
Published In
Circulation: Cardiovascular Genetics
Volume
8
Issue
2
Publish Date
2015
Start Page
410
End Page
419
DOI
10.1161/circgenetics.114.000223

Metabolomics in the developmental origins of obesity and its cardiometabolic consequences

Authors
Hivert, MF; Perng, W; Watkins, SM; Newgard, CS; Kenny, LC; Kristal, BS; Patti, ME; Isganaitis, E; DeMeo, DL; Oken, E; Gillman, MW
MLA Citation
Hivert, MF, Perng, W, Watkins, SM, Newgard, CS, Kenny, LC, Kristal, BS, Patti, ME, Isganaitis, E, DeMeo, DL, Oken, E, and Gillman, MW. "Metabolomics in the developmental origins of obesity and its cardiometabolic consequences." Journal of Developmental Origins of Health and Disease 6.02 (April 2015): 65-78.
Source
crossref
Published In
Journal of Developmental Origins of Health and Disease
Volume
6
Issue
02
Publish Date
2015
Start Page
65
End Page
78
DOI
10.1017/S204017441500001X

Metabolomic profile associated with insulin resistance and conversion to diabetes in the Insulin Resistance Atherosclerosis Study.

Metabolomic profiling of amino acids and acylcarnitines has revealed consistent patterns associated with metabolic disease.This study used metabolomic profiling to identify analytes associated with insulin sensitivity (SI) and conversion to type 2 diabetes (T2D).A multiethnic cohort from the Insulin Resistance Atherosclerosis Study.Community-based.A total of 196 subjects (European American, Hispanic, and African American) were selected to represent extremes of the SI distribution and conversion to T2D between baseline and followup exams.Mass spectrometry-based profiling of 69 metabolites. Subjects participated in a frequently sampled i.v. glucose tolerance test to measure SI and acute insulin response. T2D status was determined by a 2-hour oral glucose tolerance test.Logistic regression analysis from 72 high and 75 low SI subjects revealed significantly decreased glycine and increased valine, leucine, phenylalanine, and combined glutamine and glutamate (P = .0079-7.7 × 10(-6)) in insulin-resistant subjects. Ethnic-stratified results were strongest in European Americans. Comparing amino acid profiles between subjects that converted to T2D (76 converters; 70 nonconverters) yielded a similar pattern of associations: decreased glycine and increased valine, leucine, and combined glutamine and glutamate (P = .016-.00010). Importantly, β-cell function as a covariate revealed a similar pattern of association.A distinct pattern of differences in amino acids were observed when comparing subjects with high and low levels of SI. This pattern was associated with conversion to T2D, remaining significant when accounting for β-cell function, emphasizing a link between this metabolic profile and insulin resistance. These results demonstrate a consistent metabolic signature associated with insulin resistance and conversion to T2D, providing potential insight into underlying mechanisms of disease pathogenesis.

Authors
Palmer, ND; Stevens, RD; Antinozzi, PA; Anderson, A; Bergman, RN; Wagenknecht, LE; Newgard, CB; Bowden, DW
MLA Citation
Palmer, ND, Stevens, RD, Antinozzi, PA, Anderson, A, Bergman, RN, Wagenknecht, LE, Newgard, CB, and Bowden, DW. "Metabolomic profile associated with insulin resistance and conversion to diabetes in the Insulin Resistance Atherosclerosis Study." The Journal of Clinical Endocrinology and Metabolism 100.3 (March 2015): E463-E468.
PMID
25423564
Source
epmc
Published In
Journal of Clinical Endocrinology and Metabolism
Volume
100
Issue
3
Publish Date
2015
Start Page
E463
End Page
E468
DOI
10.1210/jc.2014-2357

Coordinated regulatory variation associated with gestational hyperglycaemia regulates expression of the novel hexokinase HKDC1.

Maternal glucose levels during pregnancy impact the developing fetus, affecting metabolic health both early and later on in life. Both genetic and environmental factors influence maternal metabolism, but little is known about the genetic mechanisms that alter glucose metabolism during pregnancy. Here, we report that haplotypes previously associated with gestational hyperglycaemia in the third trimester disrupt regulatory element activity and reduce expression of the nearby HKDC1 gene. We further find that experimentally reducing or increasing HKDC1 expression reduces or increases hexokinase activity, respectively, in multiple cellular models; in addition, purified HKDC1 protein has hexokinase activity in vitro. Together, these results suggest a novel mechanism of gestational glucose regulation in which the effects of genetic variants in multiple regulatory elements alter glucose homeostasis by coordinately reducing expression of the novel hexokinase HKDC1.

Authors
Guo, C; Ludvik, AE; Arlotto, ME; Hayes, MG; Armstrong, LL; Scholtens, DM; Brown, CD; Newgard, CB; Becker, TC; Layden, BT; Lowe, WL; Reddy, TE
MLA Citation
Guo, C, Ludvik, AE, Arlotto, ME, Hayes, MG, Armstrong, LL, Scholtens, DM, Brown, CD, Newgard, CB, Becker, TC, Layden, BT, Lowe, WL, and Reddy, TE. "Coordinated regulatory variation associated with gestational hyperglycaemia regulates expression of the novel hexokinase HKDC1." Nature communications 6 (February 4, 2015): 6069-.
PMID
25648650
Source
epmc
Published In
Nature Communications
Volume
6
Publish Date
2015
Start Page
6069
DOI
10.1038/ncomms7069

Cardiomyocyte glucagon receptor signaling modulates outcomes in mice with experimental myocardial infarction.

Glucagon is a hormone with metabolic actions that maintains normoglycemia during the fasting state. Strategies enabling either inhibition or activation of glucagon receptor (Gcgr) signaling are being explored for the treatment of diabetes or obesity. However, the cardiovascular consequences of manipulating glucagon action are poorly understood.We assessed infarct size and the following outcomes following left anterior descending (LAD) coronary artery ligation; cardiac gene and protein expression, acylcarnitine profiles, and cardiomyocyte survival in normoglycemic non-obese wildtype mice, and in newly generated mice with selective inactivation of the cardiomyocyte Gcgr. Complementary experiments analyzed Gcgr signaling and cell survival in cardiomyocyte cultures and cell lines, in the presence or absence of exogenous glucagon.Exogenous glucagon administration directly impaired recovery of ventricular pressure in ischemic mouse hearts ex vivo, and increased mortality from myocardial infarction after LAD coronary artery ligation in mice in a p38 MAPK-dependent manner. In contrast, cardiomyocyte-specific reduction of glucagon action in adult Gcgr (CM-/-) mice significantly improved survival, and reduced hypertrophy and infarct size following myocardial infarction. Metabolic profiling of hearts from Gcgr (CM-/-) mice revealed a marked reduction in long chain acylcarnitines in both aerobic and ischemic hearts, and following high fat feeding, consistent with an essential role for Gcgr signaling in the control of cardiac fatty acid utilization.Activation or reduction of cardiac Gcgr signaling in the ischemic heart produces substantial cardiac phenotypes, findings with implications for therapeutic strategies designed to augment or inhibit Gcgr signaling for the treatment of metabolic disorders.

Authors
Ali, S; Ussher, JR; Baggio, LL; Kabir, MG; Charron, MJ; Ilkayeva, O; Newgard, CB; Drucker, DJ
MLA Citation
Ali, S, Ussher, JR, Baggio, LL, Kabir, MG, Charron, MJ, Ilkayeva, O, Newgard, CB, and Drucker, DJ. "Cardiomyocyte glucagon receptor signaling modulates outcomes in mice with experimental myocardial infarction." Molecular metabolism 4.2 (February 2015): 132-143.
PMID
25685700
Source
epmc
Published In
Molecular Metabolism
Volume
4
Issue
2
Publish Date
2015
Start Page
132
End Page
143
DOI
10.1016/j.molmet.2014.11.005

Cardiomyocyte glucagon receptor signaling modulates outcomes in mice with experimental myocardial infarction

© 2014 The Authors. Objective: Glucagon is a hormone with metabolic actions that maintains normoglycemia during the fasting state. Strategies enabling either inhibition or activation of glucagon receptor (Gcgr) signaling are being explored for the treatment of diabetes or obesity. However, the cardiovascular consequences of manipulating glucagon action are poorly understood. Methods: We assessed infarct size and the following outcomes following left anterior descending (LAD) coronary artery ligation; cardiac gene and protein expression, acylcarnitine profiles, and cardiomyocyte survival in normoglycemic non-obese wildtype mice, and in newly generated mice with selective inactivation of the cardiomyocyte Gcgr. Complementary experiments analyzed Gcgr signaling and cell survival in cardiomyocyte cultures and cell lines, in the presence or absence of exogenous glucagon. Results: Exogenous glucagon administration directly impaired recovery of ventricular pressure in ischemic mouse hearts exvivo, and increased mortality from myocardial infarction after LAD coronary artery ligation in mice in a p38 MAPK-dependent manner. In contrast, cardiomyocyte-specific reduction of glucagon action in adult Gcgr CM-/- mice significantly improved survival, and reduced hypertrophy and infarct size following myocardial infarction. Metabolic profiling of hearts from Gcgr CM-/- mice revealed a marked reduction in long chain acylcarnitines in both aerobic and ischemic hearts, and following high fat feeding, consistent with an essential role for Gcgr signaling in the control of cardiac fatty acid utilization. Conclusions: Activation or reduction of cardiac Gcgr signaling in the ischemic heart produces substantial cardiac phenotypes, findings with implications for therapeutic strategies designed to augment or inhibit Gcgr signaling for the treatment of metabolic disorders.

Authors
Ali, S; Ussher, JR; Baggio, LL; Kabir, MG; Charron, MJ; Ilkayeva, O; Newgard, CB; Drucker, DJ
MLA Citation
Ali, S, Ussher, JR, Baggio, LL, Kabir, MG, Charron, MJ, Ilkayeva, O, Newgard, CB, and Drucker, DJ. "Cardiomyocyte glucagon receptor signaling modulates outcomes in mice with experimental myocardial infarction." Molecular Metabolism 4.2 (January 1, 2015): 132-143.
Source
scopus
Published In
Molecular Metabolism
Volume
4
Issue
2
Publish Date
2015
Start Page
132
End Page
143
DOI
10.1016/j.molmet.2014.11.005

Compartmentalized acyl-CoA metabolism in skeletal muscle regulates systemic glucose homeostasis.

The impaired capacity of skeletal muscle to switch between the oxidation of fatty acid (FA) and glucose is linked to disordered metabolic homeostasis. To understand how muscle FA oxidation affects systemic glucose, we studied mice with a skeletal muscle-specific deficiency of long-chain acyl-CoA synthetase (ACSL)1. ACSL1 deficiency caused a 91% loss of ACSL-specific activity and a 60-85% decrease in muscle FA oxidation. Acsl1(M-/-) mice were more insulin sensitive, and, during an overnight fast, their respiratory exchange ratio was higher, indicating greater glucose use. During endurance exercise, Acsl1(M-/-) mice ran only 48% as far as controls. At the time that Acsl1(M-/-) mice were exhausted but control mice continued to run, liver and muscle glycogen and triacylglycerol stores were similar in both genotypes; however, plasma glucose concentrations in Acsl1(M-/-) mice were ∼40 mg/dL, whereas glucose concentrations in controls were ∼90 mg/dL. Excess use of glucose and the likely use of amino acids for fuel within muscle depleted glucose reserves and diminished substrate availability for hepatic gluconeogenesis. Surprisingly, the content of muscle acyl-CoA at exhaustion was markedly elevated, indicating that acyl-CoAs synthesized by other ACSL isoforms were not available for β-oxidation. This compartmentalization of acyl-CoAs resulted in both an excessive glucose requirement and severely compromised systemic glucose homeostasis.

Authors
Li, LO; Grevengoed, TJ; Paul, DS; Ilkayeva, O; Koves, TR; Pascual, F; Newgard, CB; Muoio, DM; Coleman, RA
MLA Citation
Li, LO, Grevengoed, TJ, Paul, DS, Ilkayeva, O, Koves, TR, Pascual, F, Newgard, CB, Muoio, DM, and Coleman, RA. "Compartmentalized acyl-CoA metabolism in skeletal muscle regulates systemic glucose homeostasis." Diabetes 64.1 (January 2015): 23-35.
PMID
25071025
Source
epmc
Published In
Diabetes
Volume
64
Issue
1
Publish Date
2015
Start Page
23
End Page
35
DOI
10.2337/db13-1070

Metabolic programming and PDHK1 control CD4+ T cell subsets and inflammation.

Activation of CD4+ T cells results in rapid proliferation and differentiation into effector and regulatory subsets. CD4+ effector T cell (Teff) (Th1 and Th17) and Treg subsets are metabolically distinct, yet the specific metabolic differences that modify T cell populations are uncertain. Here, we evaluated CD4+ T cell populations in murine models and determined that inflammatory Teffs maintain high expression of glycolytic genes and rely on high glycolytic rates, while Tregs are oxidative and require mitochondrial electron transport to proliferate, differentiate, and survive. Metabolic profiling revealed that pyruvate dehydrogenase (PDH) is a key bifurcation point between T cell glycolytic and oxidative metabolism. PDH function is inhibited by PDH kinases (PDHKs). PDHK1 was expressed in Th17 cells, but not Th1 cells, and at low levels in Tregs, and inhibition or knockdown of PDHK1 selectively suppressed Th17 cells and increased Tregs. This alteration in the CD4+ T cell populations was mediated in part through ROS, as N-acetyl cysteine (NAC) treatment restored Th17 cell generation. Moreover, inhibition of PDHK1 modulated immunity and protected animals against experimental autoimmune encephalomyelitis, decreasing Th17 cells and increasing Tregs. Together, these data show that CD4+ subsets utilize and require distinct metabolic programs that can be targeted to control specific T cell populations in autoimmune and inflammatory diseases.

Authors
Gerriets, VA; Kishton, RJ; Nichols, AG; Macintyre, AN; Inoue, M; Ilkayeva, O; Winter, PS; Liu, X; Priyadharshini, B; Slawinska, ME; Haeberli, L; Huck, C; Turka, LA; Wood, KC; Hale, LP; Smith, PA; Schneider, MA; MacIver, NJ; Locasale, JW; Newgard, CB; Shinohara, ML; Rathmell, JC
MLA Citation
Gerriets, VA, Kishton, RJ, Nichols, AG, Macintyre, AN, Inoue, M, Ilkayeva, O, Winter, PS, Liu, X, Priyadharshini, B, Slawinska, ME, Haeberli, L, Huck, C, Turka, LA, Wood, KC, Hale, LP, Smith, PA, Schneider, MA, MacIver, NJ, Locasale, JW, Newgard, CB, Shinohara, ML, and Rathmell, JC. "Metabolic programming and PDHK1 control CD4+ T cell subsets and inflammation." The Journal of clinical investigation 125.1 (January 2015): 194-207.
Website
http://hdl.handle.net/10161/10313
PMID
25437876
Source
epmc
Published In
Journal of Clinical Investigation
Volume
125
Issue
1
Publish Date
2015
Start Page
194
End Page
207
DOI
10.1172/jci76012

Comparison of proteomic and metabolomic profiles of mutants of the mitochondrial respiratory chain in Caenorhabditis elegans.

Single-gene mutations that disrupt mitochondrial respiratory chain function in Caenorhabditis elegans change patterns of protein expression and metabolites. Our goal was to develop useful molecular fingerprints employing adaptable techniques to recognize mitochondrial defects in the electron transport chain. We analyzed mutations affecting complex I, complex II, or ubiquinone synthesis and discovered overarching patterns in the response of C. elegans to mitochondrial dysfunction across all of the mutations studied. These patterns are in KEGG pathways conserved from C. elegans to mammals, verifying that the nematode can serve as a model for mammalian disease. In addition, specific differences exist between mutants that may be useful in diagnosing specific mitochondrial diseases in patients.

Authors
Morgan, PG; Higdon, R; Kolker, N; Bauman, AT; Ilkayeva, O; Newgard, CB; Kolker, E; Steele, LM; Sedensky, MM
MLA Citation
Morgan, PG, Higdon, R, Kolker, N, Bauman, AT, Ilkayeva, O, Newgard, CB, Kolker, E, Steele, LM, and Sedensky, MM. "Comparison of proteomic and metabolomic profiles of mutants of the mitochondrial respiratory chain in Caenorhabditis elegans." Mitochondrion 20 (January 2015): 95-102.
PMID
25530493
Source
epmc
Published In
Mitochondrion
Volume
20
Publish Date
2015
Start Page
95
End Page
102
DOI
10.1016/j.mito.2014.12.004

The good in fat

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "The good in fat." Nature 516.729 (December 4, 2014): 49-50.
Source
scopus
Published In
Nature
Volume
516
Issue
729
Publish Date
2014
Start Page
49
End Page
50
DOI
10.1038/nature14070

Diabetes: The good in fat

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Diabetes: The good in fat." Nature 516.7529 (December 4, 2014): 49-50.
Source
scopus
Published In
Nature
Volume
516
Issue
7529
Publish Date
2014
Start Page
49
End Page
50
DOI
10.1038/nature14070

Diabetes: The good in fat.

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Diabetes: The good in fat." Nature 516.7529 (December 2014): 49-50.
PMID
25409152
Source
epmc
Published In
Nature
Volume
516
Issue
7529
Publish Date
2014
Start Page
49
End Page
50
DOI
10.1038/nature14070

MED13-dependent signaling from the heart confers leanness by enhancing metabolism in adipose tissue and liver.

The heart requires a continuous supply of energy but has little capacity for energy storage and thus relies on exogenous metabolic sources. We previously showed that cardiac MED13 modulates systemic energy homeostasis in mice. Here, we sought to define the extra-cardiac tissue(s) that respond to cardiac MED13 signaling. We show that cardiac overexpression of MED13 in transgenic (MED13cTg) mice confers a lean phenotype that is associated with increased lipid uptake, beta-oxidation and mitochondrial content in white adipose tissue (WAT) and liver. Cardiac expression of MED13 decreases metabolic gene expression in the heart but enhances them in WAT. Although exhibiting increased energy expenditure in the fed state, MED13cTg mice metabolically adapt to fasting. Furthermore, MED13cTg hearts oxidize fuel that is readily available, rendering them more efficient in the fed state. Parabiosis experiments in which circulations of wild-type and MED13cTg mice are joined, reveal that circulating factor(s) in MED13cTg mice promote enhanced metabolism and leanness. These findings demonstrate that MED13 acts within the heart to promote systemic energy expenditure in extra-cardiac energy depots and point to an unexplored metabolic communication system between the heart and other tissues.

Authors
Baskin, KK; Grueter, CE; Kusminski, CM; Holland, WL; Bookout, AL; Satapati, S; Kong, YM; Burgess, SC; Malloy, CR; Scherer, PE; Newgard, CB; Bassel-Duby, R; Olson, EN
MLA Citation
Baskin, KK, Grueter, CE, Kusminski, CM, Holland, WL, Bookout, AL, Satapati, S, Kong, YM, Burgess, SC, Malloy, CR, Scherer, PE, Newgard, CB, Bassel-Duby, R, and Olson, EN. "MED13-dependent signaling from the heart confers leanness by enhancing metabolism in adipose tissue and liver." EMBO molecular medicine 6.12 (December 2014): 1610-1621.
PMID
25422356
Source
epmc
Published In
EMBO Molecular Medicine
Volume
6
Issue
12
Publish Date
2014
Start Page
1610
End Page
1621
DOI
10.15252/emmm.201404218

Brain insulin lowers circulating BCAA levels by inducing hepatic BCAA catabolism.

Circulating branched-chain amino acid (BCAA) levels are elevated in obesity/diabetes and are a sensitive predictor for type 2 diabetes. Here we show in rats that insulin dose-dependently lowers plasma BCAA levels through induction of hepatic protein expression and activity of branched-chain α-keto acid dehydrogenase (BCKDH), the rate-limiting enzyme in the BCAA degradation pathway. Selective induction of hypothalamic insulin signaling in rats and genetic modulation of brain insulin receptors in mice demonstrate that brain insulin signaling is a major regulator of BCAA metabolism by inducing hepatic BCKDH. Short-term overfeeding impairs the ability of brain insulin to lower BCAAs in rats. High-fat feeding in nonhuman primates and obesity and/or diabetes in humans is associated with reduced BCKDH protein in liver. These findings support the concept that decreased hepatic BCKDH is a major cause of increased plasma BCAAs and that hypothalamic insulin resistance may account for impaired BCAA metabolism in obesity and diabetes.

Authors
Shin, AC; Fasshauer, M; Filatova, N; Grundell, LA; Zielinski, E; Zhou, J-Y; Scherer, T; Lindtner, C; White, PJ; Lapworth, AL; Ilkayeva, O; Knippschild, U; Wolf, AM; Scheja, L; Grove, KL; Smith, RD; Qian, W-J; Lynch, CJ; Newgard, CB; Buettner, C
MLA Citation
Shin, AC, Fasshauer, M, Filatova, N, Grundell, LA, Zielinski, E, Zhou, J-Y, Scherer, T, Lindtner, C, White, PJ, Lapworth, AL, Ilkayeva, O, Knippschild, U, Wolf, AM, Scheja, L, Grove, KL, Smith, RD, Qian, W-J, Lynch, CJ, Newgard, CB, and Buettner, C. "Brain insulin lowers circulating BCAA levels by inducing hepatic BCAA catabolism." Cell metabolism 20.5 (November 2014): 898-909.
PMID
25307860
Source
epmc
Published In
Cell Metabolism
Volume
20
Issue
5
Publish Date
2014
Start Page
898
End Page
909
DOI
10.1016/j.cmet.2014.09.003

Hepatic SRC-1 activity orchestrates transcriptional circuitries of amino acid pathways with potential relevance for human metabolic pathogenesis.

Disturbances in amino acid metabolism are increasingly recognized as being associated with, and serving as prognostic markers for chronic human diseases, such as cancer or type 2 diabetes. In the current study, a quantitative metabolomics profiling strategy revealed global impairment in amino acid metabolism in mice deleted for the transcriptional coactivator steroid receptor coactivator (SRC)-1. Aberrations were hepatic in origin, because selective reexpression of SRC-1 in the liver of SRC-1 null mice largely restored amino acids concentrations to normal levels. Cistromic analysis of SRC-1 binding sites in hepatic tissues confirmed a prominent influence of this coregulator on transcriptional programs regulating amino acid metabolism. More specifically, SRC-1 markedly impacted tyrosine levels and was found to regulate the transcriptional activity of the tyrosine aminotransferase (TAT) gene, which encodes the rate-limiting enzyme of tyrosine catabolism. Consequently, SRC-1 null mice displayed low TAT expression and presented with hypertyrosinemia and corneal alterations, 2 clinical features observed in the human syndrome of TAT deficiency. A heterozygous missense variant of SRC-1 (p.P1272S) that is known to alter its coactivation potential, was found in patients harboring idiopathic tyrosinemia-like disorders and may therefore represent one risk factor for their clinical symptoms. Hence, we reinforce the concept that SRC-1 is a central factor in the fine orchestration of multiple pathways of intermediary metabolism, suggesting it as a potential therapeutic target that may be exploitable in human metabolic diseases and cancer.

Authors
Tannour-Louet, M; York, B; Tang, K; Stashi, E; Bouguerra, H; Zhou, S; Yu, H; Wong, L-JC; Stevens, RD; Xu, J; Newgard, CB; O'Malley, BW; Louet, J-F
MLA Citation
Tannour-Louet, M, York, B, Tang, K, Stashi, E, Bouguerra, H, Zhou, S, Yu, H, Wong, L-JC, Stevens, RD, Xu, J, Newgard, CB, O'Malley, BW, and Louet, J-F. "Hepatic SRC-1 activity orchestrates transcriptional circuitries of amino acid pathways with potential relevance for human metabolic pathogenesis." Molecular endocrinology (Baltimore, Md.) 28.10 (October 2014): 1707-1718.
PMID
25148457
Source
epmc
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
28
Issue
10
Publish Date
2014
Start Page
1707
End Page
1718
DOI
10.1210/me.2014-1083

Fatty acid elongase-5 (Elovl5) regulates hepatic triglyceride catabolism in obese C57BL/6J mice.

Nonalcoholic fatty liver disease is a major public health concern in the obese and type 2 diabetic populations. The high-fat lard diet induces obesity and fatty liver in C57BL/6J mice and suppresses expression of the PPAR-target gene, FA elongase 5 (Elovl5). Elovl5 plays a key role in MUFA and PUFA synthesis. Increasing hepatic Elovl5 activity in obese mice lowered hepatic TGs and endoplasmic reticulum stress markers (X-box binding protein 1 and cAMP-dependent transcription factor 6α) and increased TG catabolism and fatty acyl carnitines. Increased hepatic Elovl5 activity did not increase hepatic capacity for β-oxidation. Elovl5 effects on hepatic TG catabolism were linked to increased protein levels of adipocyte TG lipase (ATGL) and comparative gene identification 58 (CGI58). Elevated hepatic Elovl5 activity also induced the expression of some (pyruvate dehydrogenase kinase 4 and fibroblast growth factor 21), but not other cytochrome P450 4A10 (CYP4A10), PPAR-target genes. FA products of Elovl5 activity increased ATGL, but not CGI58, mRNA through PPARβ-dependent mechanisms in human HepG2 cells. Treatment of mouse AML12 hepatocytes with the PPARβ agonist (GW0742) decreased (14)C-18:2,n-6 in TGs but did not affect β-oxidation. These studies establish that Elovl5 activity regulates hepatic levels of FAs controlling PPARβ activity, ATGL expression, and TG catabolism, but not FA oxidation.

Authors
Tripathy, S; Lytle, KA; Stevens, RD; Bain, JR; Newgard, CB; Greenberg, AS; Huang, L-S; Jump, DB
MLA Citation
Tripathy, S, Lytle, KA, Stevens, RD, Bain, JR, Newgard, CB, Greenberg, AS, Huang, L-S, and Jump, DB. "Fatty acid elongase-5 (Elovl5) regulates hepatic triglyceride catabolism in obese C57BL/6J mice." Journal of Lipid Research 55.7 (July 2014): 1448-1464.
PMID
24814977
Source
epmc
Published In
Journal of lipid research
Volume
55
Issue
7
Publish Date
2014
Start Page
1448
End Page
1464
DOI
10.1194/jlr.m050062

Severe acute malnutrition in childhood: hormonal and metabolic status at presentation, response to treatment, and predictors of mortality.

Malnutrition is a major cause of childhood morbidity and mortality. To identify and target those at highest risk, there is a critical need to characterize biomarkers that predict complications prior to and during treatment.We used targeted and nontargeted metabolomic analysis to characterize changes in a broad array of hormones, cytokines, growth factors, and metabolites during treatment of severe childhood malnutrition. Children aged 6 months to 5 years were studied at presentation to Mulago Hospital and during inpatient therapy with milk-based formulas and outpatient supplementation with ready-to-use food. We assessed the relationship between baseline hormone and metabolite levels and subsequent mortality.Seventy-seven patients were enrolled in the study; a subset was followed up from inpatient treatment to the outpatient clinic. Inpatient and outpatient therapies increased weight/height z scores and induced striking changes in the levels of fatty acids, amino acids, acylcarnitines, inflammatory cytokines, and various hormones including leptin, insulin, GH, ghrelin, cortisol, IGF-I, glucagon-like peptide-1, and peptide YY. A total of 12.2% of the patients died during hospitalization; the major biochemical factor predicting mortality was a low level of leptin (P = .0002), a marker of adipose tissue reserve and a critical modulator of immune function.We have used metabolomic analysis to provide a comprehensive hormonal and metabolic profile of severely malnourished children at presentation and during nutritional rehabilitation. Our findings suggest that fatty acid metabolism plays a central role in the adaptation to acute malnutrition and that low levels of the adipose tissue hormone leptin associate with, and may predict, mortality prior to and during treatment.

Authors
Bartz, S; Mody, A; Hornik, C; Bain, J; Muehlbauer, M; Kiyimba, T; Kiboneka, E; Stevens, R; Bartlett, J; St Peter, JV; Newgard, CB; Freemark, M
MLA Citation
Bartz, S, Mody, A, Hornik, C, Bain, J, Muehlbauer, M, Kiyimba, T, Kiboneka, E, Stevens, R, Bartlett, J, St Peter, JV, Newgard, CB, and Freemark, M. "Severe acute malnutrition in childhood: hormonal and metabolic status at presentation, response to treatment, and predictors of mortality." The Journal of clinical endocrinology and metabolism 99.6 (June 2014): 2128-2137.
PMID
24606092
Source
epmc
Published In
Journal of Clinical Endocrinology and Metabolism
Volume
99
Issue
6
Publish Date
2014
Start Page
2128
End Page
2137
DOI
10.1210/jc.2013-4018

Recent progress in metabolic signaling pathways regulating aging and life span.

The NIH Summit, Advances in Geroscience: Impact on Health Span and Chronic Disease, discusses several aspects of cellular degeneration that underlie susceptibility to chronic aging-associated diseases, morbidity, and mortality. In particular, the session on Metabolism focuses on the interrelationship between signal transduction, intermediary metabolism, and metabolic products and byproducts that contribute to pathophysiologic phenotypes and detrimental effects that occur during the aging process, thus leading to susceptibility to disease. Although it is well established that many metabolic pathways (ie, oxidative phosphorylation, insulin-stimulated glucose uptake) decline with age, it often remains uncertain if these are a cause or consequence of the aging process. Moreover, the mechanisms accounting for the decline in metabolic function remain enigmatic. Several novel and unexpected concepts are emerging that will help to define the roles of altered metabolic control in the degenerative mechanisms of aging. This brief review summarizes several of the topics to be discussed in the metabolism of aging session (http://www.geron.org/About%20Us/nih-geroscience-summit).

Authors
Newgard, CB; Pessin, JE
MLA Citation
Newgard, CB, and Pessin, JE. "Recent progress in metabolic signaling pathways regulating aging and life span." The journals of gerontology. Series A, Biological sciences and medical sciences 69 Suppl 1 (June 2014): S21-S27. (Review)
PMID
24833582
Source
epmc
Published In
Journals of Gerontology: Series A
Volume
69 Suppl 1
Publish Date
2014
Start Page
S21
End Page
S27
DOI
10.1093/gerona/glu058

Mechanical unloading promotes myocardial energy recovery in human heart failure.

Impaired bioenergetics is a prominent feature of the failing heart, but the underlying metabolic perturbations are poorly understood.We compared metabolomic, gene transcript, and protein data from 6 paired samples of failing human left ventricular tissue obtained during left ventricular assist device insertion (heart failure samples) and at heart transplant (post-left ventricular assist device samples). Nonfailing left ventricular wall samples procured from explanted hearts of patients with right heart failure served as novel comparison samples. Metabolomic analyses uncovered a distinct pattern in heart failure tissue: 2.6-fold increased pyruvate concentrations coupled with reduced Krebs cycle intermediates and short-chain acylcarnitines, suggesting a global reduction in substrate oxidation. These findings were associated with decreased transcript levels for enzymes that catalyze fatty acid oxidation and pyruvate metabolism and for key transcriptional regulators of mitochondrial metabolism and biogenesis, peroxisome proliferator-activated receptor γ coactivator 1α (PGC1A, 1.3-fold) and estrogen-related receptor α (ERRA, 1.2-fold) and γ (ERRG, 2.2-fold). Thus, parallel decreases in key transcription factors and their target metabolic enzyme genes can explain the decreases in associated metabolic intermediates. Mechanical support with left ventricular assist device improved all of these metabolic and transcriptional defects.These observations underscore an important pathophysiologic role for severely defective metabolism in heart failure, while the reversibility of these defects by left ventricular assist device suggests metabolic resilience of the human heart.

Authors
Gupte, AA; Hamilton, DJ; Cordero-Reyes, AM; Youker, KA; Yin, Z; Estep, JD; Stevens, RD; Wenner, B; Ilkayeva, O; Loebe, M; Peterson, LE; Lyon, CJ; Wong, STC; Newgard, CB; Torre-Amione, G; Taegtmeyer, H; Hsueh, WA
MLA Citation
Gupte, AA, Hamilton, DJ, Cordero-Reyes, AM, Youker, KA, Yin, Z, Estep, JD, Stevens, RD, Wenner, B, Ilkayeva, O, Loebe, M, Peterson, LE, Lyon, CJ, Wong, STC, Newgard, CB, Torre-Amione, G, Taegtmeyer, H, and Hsueh, WA. "Mechanical unloading promotes myocardial energy recovery in human heart failure." Circulation. Cardiovascular genetics 7.3 (June 2014): 266-276.
PMID
24825877
Source
epmc
Published In
Circulation: Cardiovascular Genetics
Volume
7
Issue
3
Publish Date
2014
Start Page
266
End Page
276
DOI
10.1161/circgenetics.113.000404

Obesity and lipid stress inhibit carnitine acetyltransferase activity.

Carnitine acetyltransferase (CrAT) is a mitochondrial matrix enzyme that catalyzes the interconversion of acetyl-CoA and acetylcarnitine. Emerging evidence suggests that this enzyme functions as a positive regulator of total body glucose tolerance and muscle activity of pyruvate dehydrogenase (PDH), a mitochondrial enzyme complex that promotes glucose oxidation and is feedback inhibited by acetyl-CoA. Here, we used tandem mass spectrometry-based metabolic profiling to identify a negative relationship between CrAT activity and muscle content of lipid intermediates. CrAT specific activity was diminished in muscles from obese and diabetic rodents despite increased protein abundance. This reduction in enzyme activity was accompanied by muscle accumulation of long-chain acylcarnitines (LCACs) and acyl-CoAs and a decline in the acetylcarnitine/acetyl-CoA ratio. In vitro assays demonstrated that palmitoyl-CoA acts as a direct mixed-model inhibitor of CrAT. Similarly, in primary human myocytes grown in culture, nutritional and genetic manipulations that promoted mitochondrial influx of fatty acids resulted in accumulation of LCACs but a pronounced decrease of CrAT-derived short-chain acylcarnitines. These results suggest that lipid-induced antagonism of CrAT might contribute to decreased PDH activity and glucose disposal in the context of obesity and diabetes.

Authors
Seiler, SE; Martin, OJ; Noland, RC; Slentz, DH; DeBalsi, KL; Ilkayeva, OR; An, J; Newgard, CB; Koves, TR; Muoio, DM
MLA Citation
Seiler, SE, Martin, OJ, Noland, RC, Slentz, DH, DeBalsi, KL, Ilkayeva, OR, An, J, Newgard, CB, Koves, TR, and Muoio, DM. "Obesity and lipid stress inhibit carnitine acetyltransferase activity." J Lipid Res 55.4 (April 2014): 635-644.
PMID
24395925
Source
pubmed
Published In
Journal of lipid research
Volume
55
Issue
4
Publish Date
2014
Start Page
635
End Page
644
DOI
10.1194/jlr.M043448

Nkx6.1 regulates islet β-cell proliferation via Nr4a1 and Nr4a3 nuclear receptors.

Loss of functional β-cell mass is a hallmark of type 1 and type 2 diabetes, and methods for restoring these cells are needed. We have previously reported that overexpression of the homeodomain transcription factor NK6 homeobox 1 (Nkx6.1) in rat pancreatic islets induces β-cell proliferation and enhances glucose-stimulated insulin secretion, but the pathway by which Nkx6.1 activates β-cell expansion has not been defined. Here, we demonstrate that Nkx6.1 induces expression of the nuclear receptor subfamily 4, group A, members 1 and 3 (Nr4a1 and Nr4a3) orphan nuclear receptors, and that these factors are both necessary and sufficient for Nkx6.1-mediated β-cell proliferation. Consistent with this finding, global knockout of Nr4a1 results in a decrease in β-cell area in neonatal and young mice. Overexpression of Nkx6.1 and the Nr4a receptors results in increased expression of key cell cycle inducers E2F transcription factor 1 and cyclin E1. Furthermore, Nkx6.1 and Nr4a receptors induce components of the anaphase-promoting complex, including ubiquitin-conjugating enzyme E2C, resulting in degradation of the cell cycle inhibitor p21. These studies identify a unique bipartite pathway for activation of β-cell proliferation, suggesting several unique targets for expansion of functional β-cell mass.

Authors
Tessem, JS; Moss, LG; Chao, LC; Arlotto, M; Lu, D; Jensen, MV; Stephens, SB; Tontonoz, P; Hohmeier, HE; Newgard, CB
MLA Citation
Tessem, JS, Moss, LG, Chao, LC, Arlotto, M, Lu, D, Jensen, MV, Stephens, SB, Tontonoz, P, Hohmeier, HE, and Newgard, CB. "Nkx6.1 regulates islet β-cell proliferation via Nr4a1 and Nr4a3 nuclear receptors." Proceedings of the National Academy of Sciences of the United States of America 111.14 (April 2014): 5242-5247.
PMID
24706823
Source
epmc
Published In
Proceedings of the National Academy of Sciences of USA
Volume
111
Issue
14
Publish Date
2014
Start Page
5242
End Page
5247
DOI
10.1073/pnas.1320953111

Postprandial metabolite profiles reveal differential nutrient handling after bariatric surgery compared with matched caloric restriction.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) surgery results in exaggerated postprandial insulin and incretin responses and increased susceptibility to hypoglycemia. OBJECTIVE: We examined whether these features are due to caloric restriction (CR) or altered nutrient handling. METHODS: We performed comprehensive analysis of postprandial metabolite responses during a 2-hour mixed-meal tolerance (MMT) test in 20 morbidly obese subjects with type 2 diabetes who underwent RYGB surgery or matched CR. Acylcarnitines and amino acids (AAs) were measured using targeted mass spectrometry. A linear mixed model was used to determine the main effect of interventions and interaction term to assess the effect of interventions on postprandial kinetics. RESULTS: Two weeks after these interventions, several gut hormones (insulin, glucose-dependent insulinotropic polypeptide, and glucagon-like peptide 1), glucose, and multiple AAs, including branched-chain and aromatic species, exhibited a more rapid rate of appearance and clearance in RYGB surgery subjects than in CR subjects during the MMT test. In the RYGB surgery group, changes in leucine/isoleucine, methionine, phenylalanine, and glucagon-like peptide 1 response were associated with changes in insulin response. Levels of alanine, pyruvate, and lactate decreased significantly at the later stages of meal challenge in RYGB surgery subjects but increased with CR. CONCLUSIONS: RYGB surgery results in improved metabolic flexibility (ie, greater disposal of glucose and AAs and more complete β-oxidation of fatty acids) compared with CR. The changes in the AA kinetics may augment the hormonal responses seen after RYGB surgery. The reduction in key gluconeogenic substrates in the postprandial state may contribute to increased susceptibility to hypoglycemic symptoms in RYGB surgery subjects.

Authors
Khoo, CM; Muehlbauer, MJ; Stevens, RD; Pamuklar, Z; Chen, J; Newgard, CB; Torquati, A
MLA Citation
Khoo, CM, Muehlbauer, MJ, Stevens, RD, Pamuklar, Z, Chen, J, Newgard, CB, and Torquati, A. "Postprandial metabolite profiles reveal differential nutrient handling after bariatric surgery compared with matched caloric restriction." Ann Surg 259.4 (April 2014): 687-693.
PMID
23787216
Source
pubmed
Published In
Annals of Surgery
Volume
259
Issue
4
Publish Date
2014
Start Page
687
End Page
693
DOI
10.1097/SLA.0b013e318296633f

Caffeine stimulates hepatic lipid metabolism by the autophagy-lysosomal pathway in mice.

UNLABELLED: Caffeine is one of the world's most consumed drugs. Recently, several studies showed that its consumption is associated with lower risk for nonalcoholic fatty liver disease (NAFLD), an obesity-related condition that recently has become the major cause of liver disease worldwide. Although caffeine is known to stimulate hepatic fat oxidation, its mechanism of action on lipid metabolism is still not clear. Here, we show that caffeine surprisingly is a potent stimulator of hepatic autophagic flux. Using genetic, pharmacological, and metabolomic approaches, we demonstrate that caffeine reduces intrahepatic lipid content and stimulates β-oxidation in hepatic cells and liver by an autophagy-lysosomal pathway. Furthermore, caffeine-induced autophagy involved down-regulation of mammalian target of rapamycin signaling and alteration in hepatic amino acids and sphingolipid levels. In mice fed a high-fat diet, caffeine markedly reduces hepatosteatosis and concomitantly increases autophagy and lipid uptake in lysosomes. CONCLUSION: These results provide novel insight into caffeine's lipolytic actions through autophagy in mammalian liver and its potential beneficial effects in NAFLD.

Authors
Sinha, RA; Farah, BL; Singh, BK; Siddique, MM; Li, Y; Wu, Y; Ilkayeva, OR; Gooding, J; Ching, J; Zhou, J; Martinez, L; Xie, S; Bay, B-H; Summers, SA; Newgard, CB; Yen, PM
MLA Citation
Sinha, RA, Farah, BL, Singh, BK, Siddique, MM, Li, Y, Wu, Y, Ilkayeva, OR, Gooding, J, Ching, J, Zhou, J, Martinez, L, Xie, S, Bay, B-H, Summers, SA, Newgard, CB, and Yen, PM. "Caffeine stimulates hepatic lipid metabolism by the autophagy-lysosomal pathway in mice." Hepatology 59.4 (April 2014): 1366-1380.
PMID
23929677
Source
pubmed
Published In
Hepatology
Volume
59
Issue
4
Publish Date
2014
Start Page
1366
End Page
1380
DOI
10.1002/hep.26667

BMI, RQ, diabetes, and sex affect the relationships between amino acids and clamp measures of insulin action in humans.

Previous studies have used indirect measures of insulin sensitivity to link circulating amino acids with insulin resistance and identify potential biomarkers of diabetes risk. Using direct measures (i.e., hyperinsulinemic-euglycemic clamps), we examined the relationships between the metabolomic amino acid profile and insulin action (i.e., glucose disposal rate [GDR]). Relationships between GDR and serum amino acids were determined among insulin-sensitive, insulin-resistant, and type 2 diabetic (T2DM) individuals. In all subjects, glycine (Gly) had the strongest correlation with GDR (positive association), followed by leucine/isoleucine (Leu/Ile) (negative association). These relationships were dramatically influenced by BMI, the resting respiratory quotient (RQ), T2DM, and sex. Gly had a strong positive correlation with GDR regardless of BMI, RQ, or sex but became nonsignificant in T2DM. In contrast, Leu/Ile was negatively associated with GDR in nonobese and T2DM subjects. Increased resting fat metabolism (i.e., low RQ) and obesity were observed to independently promote and negate the association between Leu/Ile and insulin resistance, respectively. Additionally, the relationship between Leu/Ile and GDR was magnified in T2DM males. Future studies are needed to determine whether Gly has a mechanistic role in glucose homeostasis and whether dietary Gly enrichment may be an effective intervention in diseases characterized by insulin resistance.

Authors
Thalacker-Mercer, AE; Ingram, KH; Guo, F; Ilkayeva, O; Newgard, CB; Garvey, WT
MLA Citation
Thalacker-Mercer, AE, Ingram, KH, Guo, F, Ilkayeva, O, Newgard, CB, and Garvey, WT. "BMI, RQ, diabetes, and sex affect the relationships between amino acids and clamp measures of insulin action in humans." Diabetes 63.2 (February 2014): 791-800.
PMID
24130332
Source
pubmed
Published In
Diabetes
Volume
63
Issue
2
Publish Date
2014
Start Page
791
End Page
800
DOI
10.2337/db13-0396

Caffeine stimulates hepatic lipid metabolism by the autophagy-lysosomal pathway in mice

Caffeine is one of the world's most consumed drugs. Recently, several studies showed that its consumption is associated with lower risk for nonalcoholic fatty liver disease (NAFLD), an obesity-related condition that recently has become the major cause of liver disease worldwide. Although caffeine is known to stimulate hepatic fat oxidation, its mechanism of action on lipid metabolism is still not clear. Here, we show that caffeine surprisingly is a potent stimulator of hepatic autophagic flux. Using genetic, pharmacological, and metabolomic approaches, we demonstrate that caffeine reduces intrahepatic lipid content and stimulates β-oxidation in hepatic cells and liver by an autophagy-lysosomal pathway. Furthermore, caffeine-induced autophagy involved down-regulation of mammalian target of rapamycin signaling and alteration in hepatic amino acids and sphingolipid levels. In mice fed a high-fat diet, caffeine markedly reduces hepatosteatosis and concomitantly increases autophagy and lipid uptake in lysosomes. Conclusion: These results provide novel insight into caffeine's lipolytic actions through autophagy in mammalian liver and its potential beneficial effects in NAFLD. © 2014 by the American Association for the Study of Liver Diseases.

Authors
Sinha, RA; Farah, BL; Singh, BK; Siddique, MM; Li, Y; Wu, Y; Ilkayeva, OR; Gooding, J; Ching, J; Zhou, J; Martinez, L; Xie, S; Bay, BH; Summers, SA; Newgard, CB; Yen, PM
MLA Citation
Sinha, RA, Farah, BL, Singh, BK, Siddique, MM, Li, Y, Wu, Y, Ilkayeva, OR, Gooding, J, Ching, J, Zhou, J, Martinez, L, Xie, S, Bay, BH, Summers, SA, Newgard, CB, and Yen, PM. "Caffeine stimulates hepatic lipid metabolism by the autophagy-lysosomal pathway in mice." Hepatology 59.4 (January 1, 2014): 1366-1380.
Source
scopus
Published In
Hepatology
Volume
59
Issue
4
Publish Date
2014
Start Page
1366
End Page
1380
DOI
10.1002/hep.26667

Postprandial metabolite profiles reveal differential nutrient handling after bariatric surgery compared with matched caloric restriction

BACKGROUND:: Roux-en-Y gastric bypass (RYGB) surgery results in exaggerated postprandial insulin and incretin responses and increased susceptibility to hypoglycemia. OBJECTIVE:: We examined whether these features are due to caloric restriction (CR) or altered nutrient handling. METHODS:: We performed comprehensive analysis of postprandial metabolite responses during a 2-hour mixed-meal tolerance (MMT) test in 20 morbidly obese subjects with type 2 diabetes who underwent RYGB surgery or matched CR. Acylcarnitines and amino acids (AAs) were measured using targeted mass spectrometry. A linear mixed model was used to determine the main effect of interventions and interaction term to assess the effect of interventions on postprandial kinetics. RESULTS:: Two weeks after these interventions, several gut hormones (insulin, glucose-dependent insulinotropic polypeptide, and glucagon-like peptide 1), glucose, and multiple AAs, including branched-chain and aromatic species, exhibited a more rapid rate of appearance and clearance in RYGB surgery subjects than in CR subjects during the MMT test. In the RYGB surgery group, changes in leucine/isoleucine, methionine, phenylalanine, and glucagon-like peptide 1 response were associated with changes in insulin response. Levels of alanine, pyruvate, and lactate decreased significantly at the later stages of meal challenge in RYGB surgery subjects but increased with CR. CONCLUSIONS:: RYGB surgery results in improved metabolic flexibility (ie, greater disposal of glucose and AAs and more complete β-oxidation of fatty acids) compared with CR. The changes in the AA kinetics may augment the hormonal responses seen after RYGB surgery. The reduction in key gluconeogenic substrates in the postprandial state may contribute to increased susceptibility to hypoglycemic symptoms in RYGB surgery subjects. © 2013 by Lippincott Williams & Wilkins.

Authors
Khoo, CM; Muehlbauer, MJ; Stevens, RD; Pamuklar, Z; Chen, J; Newgard, CB; Torquati, A
MLA Citation
Khoo, CM, Muehlbauer, MJ, Stevens, RD, Pamuklar, Z, Chen, J, Newgard, CB, and Torquati, A. "Postprandial metabolite profiles reveal differential nutrient handling after bariatric surgery compared with matched caloric restriction." Annals of Surgery 259.4 (January 1, 2014): 687-693.
Source
scopus
Published In
Annals of Surgery
Volume
259
Issue
4
Publish Date
2014
Start Page
687
End Page
693
DOI
10.1097/SLA.0b013e318296633f

Brain insulin lowers circulating bcaa levels by inducing hepatic bcaa catabolism

© 2014 Elsevier Inc. Circulating branched-chain amino acid (BCAA) levels are elevated in obesity/diabetes and are a sensitive predictor for type 2 diabetes. Here we show in rats that insulin dose-dependently lowers plasma BCAA levels through induction of hepatic protein expression and activity of branched-chain α-keto acid dehydrogenase (BCKDH), the rate-limiting enzyme in the BCAA degradation pathway. Selective induction of hypothalamic insulin signaling in rats and genetic modulation of brain insulin receptors in mice demonstrate that brain insulin signaling is a major regulator of BCAA metabolism by inducing hepatic BCKDH. Short-term overfeeding impairs the ability of brain insulin to lower BCAAs in rats. High-fat feeding in nonhuman primates and obesity and/or diabetes in humans is associated with reduced BCKDH protein in liver. These findings support the concept that decreased hepatic BCKDH is a major cause of increased plasma BCAAs and that hypothalamic insulin resistance may account for impaired BCAA metabolism in obesity and diabetes.

Authors
Shin, AC; Fasshauer, M; Filatova, N; Grundell, LA; Zielinski, E; Zhou, JY; Scherer, T; Lindtner, C; White, PJ; Lapworth, AL; Ilkayeva, O; Knippschild, U; Wolf, AM; Scheja, L; Grove, KL; Smith, RD; Qian, WJ; Lynch, CJ; Newgard, CB; Buettner, C
MLA Citation
Shin, AC, Fasshauer, M, Filatova, N, Grundell, LA, Zielinski, E, Zhou, JY, Scherer, T, Lindtner, C, White, PJ, Lapworth, AL, Ilkayeva, O, Knippschild, U, Wolf, AM, Scheja, L, Grove, KL, Smith, RD, Qian, WJ, Lynch, CJ, Newgard, CB, and Buettner, C. "Brain insulin lowers circulating bcaa levels by inducing hepatic bcaa catabolism." Cell Metabolism 20.5 (January 1, 2014): 898-909.
Source
scopus
Published In
Cell Metabolism
Volume
20
Issue
5
Publish Date
2014
Start Page
898
End Page
909
DOI
10.1016/j.cmet.2014.09.003

Validation of the association between a branched chain amino acid metabolite profile and extremes of coronary artery disease in patients referred for cardiac catheterization.

OBJECTIVE: To validate independent associations between branched-chain amino acids (BCAA) and other metabolites with coronary artery disease (CAD). METHODS: We conducted mass-spectrometry-based profiling of 63 metabolites in fasting plasma from 1983 sequential patients undergoing cardiac catheterization. Significant CAD was defined as CADindex ≥ 32 (at least one vessel with ≥ 95% stenosis; N = 995) and no CAD as CADindex ≤ 23 and no previous cardiac events (N = 610). Individuals (N = 378) with CAD severity between these extremes were excluded. Principal components analysis (PCA) reduced large numbers of correlated metabolites into uncorrelated factors. Association between metabolite factors and significant CAD vs. no CAD was tested using logistic regression; and between metabolite factors and severity of CAD was tested using linear regression. RESULTS: Of twelve PCA-derived metabolite factors, two were associated with CAD in multivariable models: factor 10, composed of BCAA (adjusted odds ratio, OR, 1.20; 95% CI 1.05-1.35, p = 0.005) and factor 7, composed of short-chain acylcarnitines, which include byproducts of BCAA metabolism (adjusted OR 1.30; 95% CI 1.14-1.48, p = 0.001). After adjustment for glycated albumin (marker of insulin resistance [IR]) both factors 7 (p = 0.0001) and 10 (p = 0.004) remained associated with CAD. Severity of CAD as a continuous variable (including patients with non-obstructive disease) was associated with metabolite factors 2, 3, 6, 7, 8 and 9; only factors 7 and 10 were associated in multivariable models. CONCLUSIONS: We validated the independent association of metabolites involved in BCAA metabolism with CAD extremes. These metabolites may be reporting on novel mechanisms of CAD pathogenesis that are independent of IR and diabetes.

Authors
Bhattacharya, S; Granger, CB; Craig, D; Haynes, C; Bain, J; Stevens, RD; Hauser, ER; Newgard, CB; Kraus, WE; Newby, LK; Shah, SH
MLA Citation
Bhattacharya, S, Granger, CB, Craig, D, Haynes, C, Bain, J, Stevens, RD, Hauser, ER, Newgard, CB, Kraus, WE, Newby, LK, and Shah, SH. "Validation of the association between a branched chain amino acid metabolite profile and extremes of coronary artery disease in patients referred for cardiac catheterization." Atherosclerosis 232.1 (January 2014): 191-196.
PMID
24401236
Source
pubmed
Published In
Atherosclerosis
Volume
232
Issue
1
Publish Date
2014
Start Page
191
End Page
196
DOI
10.1016/j.atherosclerosis.2013.10.036

Effects of HIV infection on the metabolic and hormonal status of children with severe acute malnutrition.

HIV infection occurs in 30% of children with severe acute malnutrition in sub-Saharan Africa. Effects of HIV on the pathophysiology and recovery from malnutrition are poorly understood.We conducted a prospective cohort study of 75 severely malnourished Ugandan children. HIV status/CD4 counts were assessed at baseline; auxologic data and blood samples were obtained at admission and after 14 days of inpatient treatment. We utilized metabolomic profiling to characterize effects of HIV infection on metabolic status and subsequent responses to nutritional therapy.At admission, patients (mean age 16.3 mo) had growth failure (mean W/H z-score -4.27 in non-edematous patients) that improved with formula feeding (mean increase 1.00). 24% (18/75) were HIV-infected. Nine children died within the first 14 days of hospitalization; mortality was higher for HIV-infected patients (33% v. 5%, OR = 8.83). HIV-infected and HIV-negative children presented with elevated NEFA, ketones, and even-numbered acylcarnitines and reductions in albumin and amino acids. Leptin, adiponectin, insulin, and IGF-1 levels were low while growth hormone, cortisol, and ghrelin levels were high. At baseline, HIV-infected patients had higher triglycerides, ketones, and even-chain acylcarnitines and lower leptin and adiponectin levels than HIV-negative patients. Leptin levels rose in all patients following nutritional intervention, but adiponectin levels remained depressed in HIV-infected children. Baseline hypoleptinemia and hypoadiponectinemia were associated with increased mortality.Our findings suggest a critical interplay between HIV infection and adipose tissue storage and function in the adaptation to malnutrition. Hypoleptinemia and hypoadiponectinemia may contribute to high mortality rates among malnourished, HIV-infected children.

Authors
Mody, A; Bartz, S; Hornik, CP; Kiyimba, T; Bain, J; Muehlbauer, M; Kiboneka, E; Stevens, R; St Peter, JV; Newgard, CB; Bartlett, J; Freemark, M
MLA Citation
Mody, A, Bartz, S, Hornik, CP, Kiyimba, T, Bain, J, Muehlbauer, M, Kiboneka, E, Stevens, R, St Peter, JV, Newgard, CB, Bartlett, J, and Freemark, M. "Effects of HIV infection on the metabolic and hormonal status of children with severe acute malnutrition." PloS one 9.7 (January 2014): e102233-.
PMID
25050734
Source
epmc
Published In
PloS one
Volume
9
Issue
7
Publish Date
2014
Start Page
e102233
DOI
10.1371/journal.pone.0102233

Metabolomics reveals broad-scale metabolic perturbations in hyperglycemic mothers during pregnancy.

OBJECTIVE To characterize metabolites across the range of maternal glucose by comparing metabolomic profiles of mothers with high and low fasting plasma glucose (FPG). RESEARCH DESIGN AND METHODS We compared fasting serum from an oral glucose tolerance test at ∼28 weeks' gestation from 67 Northern European ancestry mothers from the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study with high (>90th percentile) FPG with 50 mothers with low (<10th percentile) FPG but comparable BMI. Metabolic data from biochemical analyses of conventional clinical metabolites, targeted mass spectrometry (MS)-based measurement of amino acids, and nontargeted gas chromatography/MS were subjected to per-metabolite analyses and collective pathway analyses using Unipathway annotation. RESULTS High-FPG mothers had a metabolic profile consistent with insulin resistance including higher triglycerides, 3-hydroxybutyrate, and amino acids including alanine, proline, and branched-chain amino acids (false discovery rate [FDR]-adjusted P < 0.05). Lower 1,5-anhydroglucitol in high-FPG mothers suggested recent hyperglycemic excursions (FDR-adjusted P < 0.05). Pathway analyses indicated differences in amino acid degradation pathways for the two groups (FDR-adjusted P < 0.05), consistent with population-based findings in nonpregnant populations. Exploratory analyses with newborn outcomes indicated positive associations for maternal triglycerides with neonatal sum of skinfolds and cord C-peptide and a negative association between maternal glycine and cord C-peptide (P < 0.05). CONCLUSIONS Metabolomics reveals perturbations in metabolism of major macronutrients and amino acid degradation pathways in high- versus low-FPG mothers.

Authors
Scholtens, DM; Muehlbauer, MJ; Daya, NR; Stevens, RD; Dyer, AR; Lowe, LP; Metzger, BE; Newgard, CB; Bain, JR; Lowe, WL; HAPO Study Cooperative Research Group,
MLA Citation
Scholtens, DM, Muehlbauer, MJ, Daya, NR, Stevens, RD, Dyer, AR, Lowe, LP, Metzger, BE, Newgard, CB, Bain, JR, Lowe, WL, and HAPO Study Cooperative Research Group, . "Metabolomics reveals broad-scale metabolic perturbations in hyperglycemic mothers during pregnancy." Diabetes Care 37.1 (2014): 158-166.
PMID
23990511
Source
pubmed
Published In
Diabetes Care
Volume
37
Issue
1
Publish Date
2014
Start Page
158
End Page
166
DOI
10.2337/dc13-0989

SIRT5 regulates the mitochondrial lysine succinylome and metabolic networks.

Reversible posttranslational modifications are emerging as critical regulators of mitochondrial proteins and metabolism. Here, we use a label-free quantitative proteomic approach to characterize the lysine succinylome in liver mitochondria and its regulation by the desuccinylase SIRT5. A total of 1,190 unique sites were identified as succinylated, and 386 sites across 140 proteins representing several metabolic pathways including β-oxidation and ketogenesis were significantly hypersuccinylated in Sirt5(-/-) animals. Loss of SIRT5 leads to accumulation of medium- and long-chain acylcarnitines and decreased β-hydroxybutyrate production in vivo. In addition, we demonstrate that SIRT5 regulates succinylation of the rate-limiting ketogenic enzyme 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) both in vivo and in vitro. Finally, mutation of hypersuccinylated residues K83 and K310 on HMGCS2 to glutamic acid strongly inhibits enzymatic activity. Taken together, these findings establish SIRT5 as a global regulator of lysine succinylation in mitochondria and present a mechanism for inhibition of ketogenesis through HMGCS2.

Authors
Rardin, MJ; He, W; Nishida, Y; Newman, JC; Carrico, C; Danielson, SR; Guo, A; Gut, P; Sahu, AK; Li, B; Uppala, R; Fitch, M; Riiff, T; Zhu, L; Zhou, J; Mulhern, D; Stevens, RD; Ilkayeva, OR; Newgard, CB; Jacobson, MP; Hellerstein, M; Goetzman, ES; Gibson, BW; Verdin, E
MLA Citation
Rardin, MJ, He, W, Nishida, Y, Newman, JC, Carrico, C, Danielson, SR, Guo, A, Gut, P, Sahu, AK, Li, B, Uppala, R, Fitch, M, Riiff, T, Zhu, L, Zhou, J, Mulhern, D, Stevens, RD, Ilkayeva, OR, Newgard, CB, Jacobson, MP, Hellerstein, M, Goetzman, ES, Gibson, BW, and Verdin, E. "SIRT5 regulates the mitochondrial lysine succinylome and metabolic networks." Cell Metab 18.6 (December 3, 2013): 920-933.
PMID
24315375
Source
pubmed
Published In
Cell Metabolism
Volume
18
Issue
6
Publish Date
2013
Start Page
920
End Page
933
DOI
10.1016/j.cmet.2013.11.013

Race and sex differences in small-molecule metabolites and metabolic hormones in overweight and obese adults.

In overweight/obese individuals, cardiometabolic risk factors differ by race and sex categories. Small-molecule metabolites and metabolic hormone levels might also differ across these categories and contribute to risk factor heterogeneity. To explore this possibility, we performed a cross-sectional analysis of fasting plasma levels of 69 small-molecule metabolites and 13 metabolic hormones in 500 overweight/obese adults who participated in the Weight Loss Maintenance trial. Principal-components analysis (PCA) was used for reduction of metabolite data. Race and sex-stratified comparisons of metabolite factors and metabolic hormones were performed. African Americans represented 37.4% of the study participants, and females 63.0%. Of thirteen metabolite factors identified, three differed by race and sex: levels of factor 3 (branched-chain amino acids and related metabolites, p<0.0001), factor 6 (long-chain acylcarnitines, p<0.01), and factor 2 (medium-chain dicarboxylated acylcarnitines, p<0.0001) were higher in males vs. females; factor 6 levels were higher in Caucasians vs. African Americans (p<0.0001). Significant differences were also observed in hormones regulating body weight homeostasis. Among overweight/obese adults, there are significant race and sex differences in small-molecule metabolites and metabolic hormones; these differences may contribute to risk factor heterogeneity across race and sex subgroups and should be considered in future investigations with circulating metabolites and metabolic hormones.

Authors
Patel, MJ; Batch, BC; Svetkey, LP; Bain, JR; Turer, CB; Haynes, C; Muehlbauer, MJ; Stevens, RD; Newgard, CB; Shah, SH
MLA Citation
Patel, MJ, Batch, BC, Svetkey, LP, Bain, JR, Turer, CB, Haynes, C, Muehlbauer, MJ, Stevens, RD, Newgard, CB, and Shah, SH. "Race and sex differences in small-molecule metabolites and metabolic hormones in overweight and obese adults." OMICS 17.12 (December 2013): 627-635.
PMID
24117402
Source
pubmed
Published In
OMICS: A Journal of Integrative Biology
Volume
17
Issue
12
Publish Date
2013
Start Page
627
End Page
635
DOI
10.1089/omi.2013.0031

Circadian clock NAD+ cycle drives mitochondrial oxidative metabolism in mice.

Circadian clocks are self-sustained cellular oscillators that synchronize oxidative and reductive cycles in anticipation of the solar cycle. We found that the clock transcription feedback loop produces cycles of nicotinamide adenine dinucleotide (NAD(+)) biosynthesis, adenosine triphosphate production, and mitochondrial respiration through modulation of mitochondrial protein acetylation to synchronize oxidative metabolic pathways with the 24-hour fasting and feeding cycle. Circadian control of the activity of the NAD(+)-dependent deacetylase sirtuin 3 (SIRT3) generated rhythms in the acetylation and activity of oxidative enzymes and respiration in isolated mitochondria, and NAD(+) supplementation restored protein deacetylation and enhanced oxygen consumption in circadian mutant mice. Thus, circadian control of NAD(+) bioavailability modulates mitochondrial oxidative function and organismal metabolism across the daily cycles of fasting and feeding.

Authors
Peek, CB; Affinati, AH; Ramsey, KM; Kuo, H-Y; Yu, W; Sena, LA; Ilkayeva, O; Marcheva, B; Kobayashi, Y; Omura, C; Levine, DC; Bacsik, DJ; Gius, D; Newgard, CB; Goetzman, E; Chandel, NS; Denu, JM; Mrksich, M; Bass, J
MLA Citation
Peek, CB, Affinati, AH, Ramsey, KM, Kuo, H-Y, Yu, W, Sena, LA, Ilkayeva, O, Marcheva, B, Kobayashi, Y, Omura, C, Levine, DC, Bacsik, DJ, Gius, D, Newgard, CB, Goetzman, E, Chandel, NS, Denu, JM, Mrksich, M, and Bass, J. "Circadian clock NAD+ cycle drives mitochondrial oxidative metabolism in mice." Science 342.6158 (November 1, 2013): 1243417-.
PMID
24051248
Source
pubmed
Published In
Science
Volume
342
Issue
6158
Publish Date
2013
Start Page
1243417
DOI
10.1126/science.1243417

Pdx-1 Activates Islet α- and β-Cell Proliferation via a Mechanism Regulated by Transient Receptor Potential Cation Channels 3 and 6 and Extracellular Signal-Regulated Kinases 1 and 2

The homeodomain transcription factor Pdx-1 has important roles in pancreatic development and β-cell function and survival. In the present study, we demonstrate that adenovirus-mediated overexpression of Pdx-1 in rat or human islets also stimulates cell replication. Moreover, cooverexpression of Pdx-1 with another homeodomain transcription factor, Nkx6.1, has an additive effect on proliferation compared to either factor alone, implying discrete activating mechanisms. Consistent with this, Nkx6.1 stimulates mainly β-cell proliferation, whereas Pdx-1 stimulates both α- and β-cell proliferation. Furthermore, cyclins D1/D2 are upregulated by Pdx-1 but not by Nkx6.1, and inhibition of cdk4 blocks Pdx-1-stimulated but not Nkx6.1-stimulated islet cell proliferation. Genes regulated by Pdx-1 but not Nkx6.1 were identified by microarray analysis. Two members of the transient receptor potential cation (TRPC) channel family, TRPC3 and TRPC6, are upregulated by Pdx-1 overexpression, and small interfering RNA (siRNA)-mediated knockdown of TRPC3/6 or TRPC6 alone inhibits Pdx-1-induced but not Nkx6.1-induced islet cell proliferation. Pdx-1 also stimulates extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, an effect partially blocked by knockdown of TRPC3/6, and blockade of ERK1/2 activation with a MEK1/2 inhibitor partially impairs Pdx-1-stimulated proliferation. These studies define a pathway by which overexpression of Pdx-1 activates islet cell proliferation that is distinct from and additive to a pathway activated by Nkx6.1. © 2013, American Society for Microbiology.

Authors
Hayes, HL; Moss, LG; Schisler, JC; Haldeman, JM; Zhang, Z; Rosenberg, PB; Newgard, CB; Hohmeier, HE
MLA Citation
Hayes, HL, Moss, LG, Schisler, JC, Haldeman, JM, Zhang, Z, Rosenberg, PB, Newgard, CB, and Hohmeier, HE. "Pdx-1 Activates Islet α- and β-Cell Proliferation via a Mechanism Regulated by Transient Receptor Potential Cation Channels 3 and 6 and Extracellular Signal-Regulated Kinases 1 and 2." Molecular and Cellular Biology 33.20 (October 25, 2013): 4017-4029.
Source
scopus
Published In
Molecular and Cellular Biology
Volume
33
Issue
20
Publish Date
2013
Start Page
4017
End Page
4029
DOI
10.1128/MCB.00469-13

Sirt3 regulates metabolic flexibility of skeletal muscle through reversible enzymatic deacetylation.

Sirt3 is an NAD(+)-dependent deacetylase that regulates mitochondrial function by targeting metabolic enzymes and proteins. In fasting mice, Sirt3 expression is decreased in skeletal muscle resulting in increased mitochondrial protein acetylation. Deletion of Sirt3 led to impaired glucose oxidation in muscle, which was associated with decreased pyruvate dehydrogenase (PDH) activity, accumulation of pyruvate and lactate metabolites, and an inability of insulin to suppress fatty acid oxidation. Antibody-based acetyl-peptide enrichment and mass spectrometry of mitochondrial lysates from WT and Sirt3 KO skeletal muscle revealed that a major target of Sirt3 deacetylation is the E1α subunit of PDH (PDH E1α). Sirt3 knockout in vivo and Sirt3 knockdown in myoblasts in vitro induced hyperacetylation of the PDH E1α subunit, altering its phosphorylation leading to suppressed PDH enzymatic activity. The inhibition of PDH activity resulting from reduced levels of Sirt3 induces a switch of skeletal muscle substrate utilization from carbohydrate oxidation toward lactate production and fatty acid utilization even in the fed state, contributing to a loss of metabolic flexibility. Thus, Sirt3 plays an important role in skeletal muscle mitochondrial substrate choice and metabolic flexibility in part by regulating PDH function through deacetylation.

Authors
Jing, E; O'Neill, BT; Rardin, MJ; Kleinridders, A; Ilkeyeva, OR; Ussar, S; Bain, JR; Lee, KY; Verdin, EM; Newgard, CB; Gibson, BW; Kahn, CR
MLA Citation
Jing, E, O'Neill, BT, Rardin, MJ, Kleinridders, A, Ilkeyeva, OR, Ussar, S, Bain, JR, Lee, KY, Verdin, EM, Newgard, CB, Gibson, BW, and Kahn, CR. "Sirt3 regulates metabolic flexibility of skeletal muscle through reversible enzymatic deacetylation." Diabetes 62.10 (October 2013): 3404-3417.
PMID
23835326
Source
pubmed
Published In
Diabetes
Volume
62
Issue
10
Publish Date
2013
Start Page
3404
End Page
3417
DOI
10.2337/db12-1650

Pdx-1 activates islet α- and β-cell proliferation via a mechanism regulated by transient receptor potential cation channels 3 and 6 and extracellular signal-regulated kinases 1 and 2.

The homeodomain transcription factor Pdx-1 has important roles in pancreatic development and β-cell function and survival. In the present study, we demonstrate that adenovirus-mediated overexpression of Pdx-1 in rat or human islets also stimulates cell replication. Moreover, cooverexpression of Pdx-1 with another homeodomain transcription factor, Nkx6.1, has an additive effect on proliferation compared to either factor alone, implying discrete activating mechanisms. Consistent with this, Nkx6.1 stimulates mainly β-cell proliferation, whereas Pdx-1 stimulates both α- and β-cell proliferation. Furthermore, cyclins D1/D2 are upregulated by Pdx-1 but not by Nkx6.1, and inhibition of cdk4 blocks Pdx-1-stimulated but not Nkx6.1-stimulated islet cell proliferation. Genes regulated by Pdx-1 but not Nkx6.1 were identified by microarray analysis. Two members of the transient receptor potential cation (TRPC) channel family, TRPC3 and TRPC6, are upregulated by Pdx-1 overexpression, and small interfering RNA (siRNA)-mediated knockdown of TRPC3/6 or TRPC6 alone inhibits Pdx-1-induced but not Nkx6.1-induced islet cell proliferation. Pdx-1 also stimulates extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, an effect partially blocked by knockdown of TRPC3/6, and blockade of ERK1/2 activation with a MEK1/2 inhibitor partially impairs Pdx-1-stimulated proliferation. These studies define a pathway by which overexpression of Pdx-1 activates islet cell proliferation that is distinct from and additive to a pathway activated by Nkx6.1.

Authors
Hayes, HL; Moss, LG; Schisler, JC; Haldeman, JM; Zhang, Z; Rosenberg, PB; Newgard, CB; Hohmeier, HE
MLA Citation
Hayes, HL, Moss, LG, Schisler, JC, Haldeman, JM, Zhang, Z, Rosenberg, PB, Newgard, CB, and Hohmeier, HE. "Pdx-1 activates islet α- and β-cell proliferation via a mechanism regulated by transient receptor potential cation channels 3 and 6 and extracellular signal-regulated kinases 1 and 2." Mol Cell Biol 33.20 (October 2013): 4017-4029.
PMID
23938296
Source
pubmed
Published In
Molecular and Cellular Biology
Volume
33
Issue
20
Publish Date
2013
Start Page
4017
End Page
4029
DOI
10.1128/MCB.00469-13

Gut microbiota from twins discordant for obesity modulate metabolism in mice.

The role of specific gut microbes in shaping body composition remains unclear. We transplanted fecal microbiota from adult female twin pairs discordant for obesity into germ-free mice fed low-fat mouse chow, as well as diets representing different levels of saturated fat and fruit and vegetable consumption typical of the U.S. diet. Increased total body and fat mass, as well as obesity-associated metabolic phenotypes, were transmissible with uncultured fecal communities and with their corresponding fecal bacterial culture collections. Cohousing mice harboring an obese twin's microbiota (Ob) with mice containing the lean co-twin's microbiota (Ln) prevented the development of increased body mass and obesity-associated metabolic phenotypes in Ob cage mates. Rescue correlated with invasion of specific members of Bacteroidetes from the Ln microbiota into Ob microbiota and was diet-dependent. These findings reveal transmissible, rapid, and modifiable effects of diet-by-microbiota interactions.

Authors
Ridaura, VK; Faith, JJ; Rey, FE; Cheng, J; Duncan, AE; Kau, AL; Griffin, NW; Lombard, V; Henrissat, B; Bain, JR; Muehlbauer, MJ; Ilkayeva, O; Semenkovich, CF; Funai, K; Hayashi, DK; Lyle, BJ; Martini, MC; Ursell, LK; Clemente, JC; Van Treuren, W; Walters, WA; Knight, R; Newgard, CB; Heath, AC; Gordon, JI
MLA Citation
Ridaura, VK, Faith, JJ, Rey, FE, Cheng, J, Duncan, AE, Kau, AL, Griffin, NW, Lombard, V, Henrissat, B, Bain, JR, Muehlbauer, MJ, Ilkayeva, O, Semenkovich, CF, Funai, K, Hayashi, DK, Lyle, BJ, Martini, MC, Ursell, LK, Clemente, JC, Van Treuren, W, Walters, WA, Knight, R, Newgard, CB, Heath, AC, and Gordon, JI. "Gut microbiota from twins discordant for obesity modulate metabolism in mice." Science 341.6150 (September 6, 2013): 1241214-.
PMID
24009397
Source
pubmed
Published In
Science
Volume
341
Issue
6150
Publish Date
2013
Start Page
1241214
DOI
10.1126/science.1241214

Control of voltage-gated potassium channel Kv2.2 expression by pyruvate-isocitrate cycling regulates glucose-stimulated insulin secretion.

Recent studies have shown that the pyruvate-isocitrate cycling pathway, involving the mitochondrial citrate/isocitrate carrier and the cytosolic NADP-dependent isocitrate dehydrogenase (ICDc), is involved in control of glucose-stimulated insulin secretion (GSIS). Here we demonstrate that pyruvate-isocitrate cycling regulates expression of the voltage-gated potassium channel family member Kv2.2 in islet β-cells. siRNA-mediated suppression of ICDc, citrate/isocitrate carrier, or Kv2.2 expression impaired GSIS, and the effect of ICDc knockdown was rescued by re-expression of Kv2.2. Moreover, chronic exposure of β-cells to elevated fatty acids, which impairs GSIS, resulted in decreased expression of Kv2.2. Surprisingly, knockdown of ICDc or Kv2.2 increased rather than decreased outward K(+) current in the 832/13 β-cell line. Immunoprecipitation studies demonstrated interaction of Kv2.1 and Kv2.2, and co-overexpression of the two channels reduced outward K(+) current compared with overexpression of Kv2.1 alone. Also, siRNA-mediated knockdown of ICDc enhanced the suppressive effect of the Kv2.1-selective inhibitor stromatoxin1 on K(+) currents. Our data support a model in which a key function of the pyruvate-isocitrate cycle is to maintain levels of Kv2.2 expression sufficient to allow it to serve as a negative regulator of Kv channel activity.

Authors
Jensen, MV; Haldeman, JM; Zhang, H; Lu, D; Huising, MO; Vale, WW; Hohmeier, HE; Rosenberg, P; Newgard, CB
MLA Citation
Jensen, MV, Haldeman, JM, Zhang, H, Lu, D, Huising, MO, Vale, WW, Hohmeier, HE, Rosenberg, P, and Newgard, CB. "Control of voltage-gated potassium channel Kv2.2 expression by pyruvate-isocitrate cycling regulates glucose-stimulated insulin secretion." J Biol Chem 288.32 (August 9, 2013): 23128-23140.
PMID
23788641
Source
pubmed
Published In
The Journal of biological chemistry
Volume
288
Issue
32
Publish Date
2013
Start Page
23128
End Page
23140
DOI
10.1074/jbc.M113.491654

Effect of Roux-en-Y gastric bypass and laparoscopic adjustable gastric banding on branched-chain amino acid metabolism.

It has been hypothesized that a greater decline in circulating branched-chain amino acids (BCAAs) after weight loss induced by Roux-en-Y gastric bypass (RYGB) surgery than after calorie restriction alone has independent effects on glucose homeostasis, possibly by decreased signaling through the mammalian target of rapamycin (mTOR). We evaluated plasma BCAAs and their C3 and C5 acylcarnitine metabolites, muscle mTOR phosphorylation, and insulin sensitivity (insulin-stimulated glucose Rd) in obese subjects before and after ~20% weight loss induced by RYGB (n = 10, BMI 45.6 ± 6.7 kg/m(2)) or laparoscopic adjustable gastric banding (LAGB) (n = 10, BMI 46.5 ± 8.8 kg/m(2)). Weight loss increased insulin-stimulated glucose Rd by ~55%, decreased total plasma BCAA and C3 and C5 acylcarnitine concentrations by 20-35%, and did not alter mTOR phosphorylation; no differences were detected between surgical groups (all P values for interaction >0.05). Insulin-stimulated glucose Rd correlated negatively with plasma BCAAs and with C3 and C5 acylcarnitine concentrations (r values -0.56 to -0.75, P < 0.05). These data demonstrate that weight loss induced by either LAGB or RYGB causes the same decline in circulating BCAAs and their C3 and C5 acylcarnitine metabolites. Plasma BCAA concentration is negatively associated with skeletal muscle insulin sensitivity, but the mechanism(s) responsible for this relationship is not known.

Authors
Magkos, F; Bradley, D; Schweitzer, GG; Finck, BN; Eagon, JC; Ilkayeva, O; Newgard, CB; Klein, S
MLA Citation
Magkos, F, Bradley, D, Schweitzer, GG, Finck, BN, Eagon, JC, Ilkayeva, O, Newgard, CB, and Klein, S. "Effect of Roux-en-Y gastric bypass and laparoscopic adjustable gastric banding on branched-chain amino acid metabolism." Diabetes 62.8 (August 2013): 2757-2761.
PMID
23610059
Source
pubmed
Published In
Diabetes
Volume
62
Issue
8
Publish Date
2013
Start Page
2757
End Page
2761
DOI
10.2337/db13-0185

Diminished acyl-CoA synthetase isoform 4 activity in INS 832/13 cells reduces cellular epoxyeicosatrienoic acid levels and results in impaired glucose-stimulated insulin secretion.

Glucose-stimulated insulin secretion (GSIS) in pancreatic beta-cells is potentiated by fatty acids (FA). The initial step in the metabolism of intracellular FA is the conversion to acyl-CoA by long chain acyl-CoA synthetases (Acsls). Because the predominantly expressed Acsl isoforms in INS 832/13 cells are Acsl4 and -5, we characterized the role of these Acsls in beta-cell function by using siRNA to knock down Acsl4 or Acsl5. Compared with control cells, an 80% suppression of Acsl4 decreased GSIS and FA-potentiated GSIS by 32 and 54%, respectively. Knockdown of Acsl5 did not alter GSIS. Acsl4 knockdown did not alter FA oxidation or long chain acyl-CoA levels. With Acsl4 knockdown, incubation with 17 mm glucose increased media epoxyeicosatrienoic acids (EETs) and reduced cell membrane levels of EETs. Further, exogenous EETs reduced GSIS in INS 832/13 cells, and in Acsl4 knockdown cells, an EET receptor antagonist partially rescued GSIS. These results strongly suggest that Acsl4 activates EETs to form EET-CoAs that are incorporated into glycerophospholipids, thereby sequestering EETs. Exposing INS 832/13 cells to arachidonate or linoleate reduced Acsl4 mRNA and protein expression and reduced GSIS. These data indicate that Acsl4 modulates GSIS by regulating the levels of unesterified EETs and that arachidonate controls the expression of its activator Acsl4.

Authors
Klett, EL; Chen, S; Edin, ML; Li, LO; Ilkayeva, O; Zeldin, DC; Newgard, CB; Coleman, RA
MLA Citation
Klett, EL, Chen, S, Edin, ML, Li, LO, Ilkayeva, O, Zeldin, DC, Newgard, CB, and Coleman, RA. "Diminished acyl-CoA synthetase isoform 4 activity in INS 832/13 cells reduces cellular epoxyeicosatrienoic acid levels and results in impaired glucose-stimulated insulin secretion." J Biol Chem 288.30 (July 26, 2013): 21618-21629.
PMID
23766516
Source
pubmed
Published In
The Journal of biological chemistry
Volume
288
Issue
30
Publish Date
2013
Start Page
21618
End Page
21629
DOI
10.1074/jbc.M113.481077

Branched chain amino acids are novel biomarkers for discrimination of metabolic wellness.

OBJECTIVE: To identify novel biomarkers through metabolomic profiles that distinguish metabolically well (MW) from metabolically unwell (MUW) individuals, independent of body mass index (BMI). MATERIALS/METHODS: This study was conducted as part of the Measurement to Understand the Reclassification of Disease of Cabarrus/Kannapolis (MURDOCK) project. Individuals from 3 cohorts were classified as lean (BMI<25kg/m²), overweight (BMI≥25kg/m², BMI<30kg/m²) or obese (BMI≥30kg/m²). Cardiometabolic abnormalities were defined as: (1) impaired fasting glucose (≥100mg/dL and ≤126mg/dL); (2) hypertension; (3) triglycerides ≥150mg/dL; (4) HDL-C <40mg/dL in men, <50mg/dL in women; and (5) insulin resistance (calculated Homeostatic Model Assessment (HOMA-IR) index of >5.13). MW individuals were defined as having <2 cardiometabolic abnormalities and MUW individuals had≥two cardiometabolic abnormalities. Targeted profiling of 55 metabolites used mass-spectroscopy-based methods. Principal components analysis (PCA) was used to reduce the large number of correlated metabolites into clusters of fewer uncorrelated factors. RESULTS: Of 1872 individuals, 410 were lean, 610 were overweight, and 852 were obese. Of lean individuals, 67% were categorized as MUW, whereas 80% of overweight and 87% of obese individuals were MUW. PCA-derived factors with levels that differed the most between MW and MUW groups were factors 4 (branched chain amino acids [BCAA]) [p<.0001], 8 (various metabolites) [p<.0001], 9 (C4/Ci4, C3, C5 acylcarnitines) [p<.0001] and 10 (amino acids) [p<.0002]. Further, Factor 4, distinguishes MW from MUW individuals independent of BMI. CONCLUSION: BCAA and related metabolites are promising biomarkers that may aid in understanding cardiometabolic health independent of BMI category.

Authors
Batch, BC; Shah, SH; Newgard, CB; Turer, CB; Haynes, C; Bain, JR; Muehlbauer, M; Patel, MJ; Stevens, RD; Appel, LJ; Newby, LK; Svetkey, LP
MLA Citation
Batch, BC, Shah, SH, Newgard, CB, Turer, CB, Haynes, C, Bain, JR, Muehlbauer, M, Patel, MJ, Stevens, RD, Appel, LJ, Newby, LK, and Svetkey, LP. "Branched chain amino acids are novel biomarkers for discrimination of metabolic wellness." Metabolism 62.7 (July 2013): 961-969.
PMID
23375209
Source
pubmed
Published In
Metabolism: clinical and experimental
Volume
62
Issue
7
Publish Date
2013
Start Page
961
End Page
969
DOI
10.1016/j.metabol.2013.01.007

Metabolomic profiling reveals a role for caspase-2 in lipoapoptosis.

The accumulation of long-chain fatty acids (LCFAs) in non-adipose tissues results in lipid-induced cytotoxicity (or lipoapoptosis). Lipoapoptosis has been proposed to play an important role in the pathogenesis of several metabolic diseases, including non-alcoholic fatty liver disease, diabetes mellitus, and cardiovascular disease. In this report, we demonstrate a novel role for caspase-2 as an initiator of lipoapoptosis. Using a metabolomics approach, we discovered that the activation of caspase-2, the initiator of apoptosis in Xenopus egg extracts, is associated with an accumulation of LCFA metabolites. Metabolic treatments that blocked the buildup of LCFAs potently inhibited caspase-2 activation, whereas adding back an LCFA in this scenario restored caspase activation. Extending these findings to mammalian cells, we show that caspase-2 was engaged and activated in response to treatment with the saturated LCFA palmitate. Down-regulation of caspase-2 significantly impaired cell death induced by saturated LCFAs, suggesting that caspase-2 plays a pivotal role in lipid-induced cytotoxicity. Together, these findings reveal a previously unknown role for caspase-2 as an initiator caspase in lipoapoptosis and suggest that caspase-2 may be an attractive therapeutic target for inhibiting pathological lipid-induced apoptosis.

Authors
Johnson, ES; Lindblom, KR; Robeson, A; Stevens, RD; Ilkayeva, OR; Newgard, CB; Kornbluth, S; Andersen, JL
MLA Citation
Johnson, ES, Lindblom, KR, Robeson, A, Stevens, RD, Ilkayeva, OR, Newgard, CB, Kornbluth, S, and Andersen, JL. "Metabolomic profiling reveals a role for caspase-2 in lipoapoptosis." J Biol Chem 288.20 (May 17, 2013): 14463-14475.
PMID
23553630
Source
pubmed
Published In
The Journal of biological chemistry
Volume
288
Issue
20
Publish Date
2013
Start Page
14463
End Page
14475
DOI
10.1074/jbc.M112.437210

Application of combined omics platforms to accelerate biomedical discovery in diabesity.

Diabesity has become a popular term to describe the specific form of diabetes that develops late in life and is associated with obesity. While there is a correlation between diabetes and obesity, the association is not universally predictive. Defining the metabolic characteristics of obesity that lead to diabetes, and how obese individuals who develop diabetes different from those who do not, are important goals. The use of large-scale omics analyses (e.g., metabolomic, proteomic, transcriptomic, and lipidomic) of diabetes and obesity may help to identify new targets to treat these conditions. This report discusses how various types of omics data can be integrated to shed light on the changes in metabolism that occur in obesity and diabetes.

Authors
Kurland, IJ; Accili, D; Burant, C; Fischer, SM; Kahn, BB; Newgard, CB; Ramagiri, S; Ronnett, GV; Ryals, JA; Sanders, M; Shambaugh, J; Shockcor, J; Gross, SS
MLA Citation
Kurland, IJ, Accili, D, Burant, C, Fischer, SM, Kahn, BB, Newgard, CB, Ramagiri, S, Ronnett, GV, Ryals, JA, Sanders, M, Shambaugh, J, Shockcor, J, and Gross, SS. "Application of combined omics platforms to accelerate biomedical discovery in diabesity." Ann N Y Acad Sci 1287 (May 2013): 1-16.
PMID
23659636
Source
pubmed
Published In
Annals of the New York Academy of Sciences
Volume
1287
Publish Date
2013
Start Page
1
End Page
16
DOI
10.1111/nyas.12116

Pathogenesis of A⁻β⁺ ketosis-prone diabetes.

A⁻β⁺ ketosis-prone diabetes (KPD) is an emerging syndrome of obesity, unprovoked ketoacidosis, reversible β-cell dysfunction, and near-normoglycemic remission. We combined metabolomics with targeted kinetic measurements to investigate its pathophysiology. Fasting plasma fatty acids, acylcarnitines, and amino acids were quantified in 20 KPD patients compared with 19 nondiabetic control subjects. Unique signatures in KPD--higher glutamate but lower glutamine and citrulline concentrations, increased β-hydroxybutyryl-carnitine, decreased isovaleryl-carnitine (a leucine catabolite), and decreased tricarboxylic acid (TCA) cycle intermediates--generated hypotheses that were tested through stable isotope/mass spectrometry protocols in nine new-onset, stable KPD patients compared with seven nondiabetic control subjects. Free fatty acid flux and acetyl CoA flux and oxidation were similar, but KPD had slower acetyl CoA conversion to β-hydroxybutyrate; higher fasting β-hydroxybutyrate concentration; slower β-hydroxybutyrate oxidation; faster leucine oxidative decarboxylation; accelerated glutamine conversion to glutamate without increase in glutamate carbon oxidation; and slower citrulline flux, with diminished glutamine amide-nitrogen transfer to citrulline. The confluence of metabolomic and kinetic data indicate a distinctive pathogenic sequence: impaired ketone oxidation and fatty acid utilization for energy, leading to accelerated leucine catabolism and transamination of α-ketoglutarate to glutamate, with impaired TCA anaplerosis of glutamate carbon. They highlight a novel process of defective energy production and ketosis in A⁻β⁺ KPD.

Authors
Patel, SG; Hsu, JW; Jahoor, F; Coraza, I; Bain, JR; Stevens, RD; Iyer, D; Nalini, R; Ozer, K; Hampe, CS; Newgard, CB; Balasubramanyam, A
MLA Citation
Patel, SG, Hsu, JW, Jahoor, F, Coraza, I, Bain, JR, Stevens, RD, Iyer, D, Nalini, R, Ozer, K, Hampe, CS, Newgard, CB, and Balasubramanyam, A. "Pathogenesis of A⁻β⁺ ketosis-prone diabetes." Diabetes 62.3 (March 2013): 912-922.
PMID
23160531
Source
pubmed
Published In
Diabetes
Volume
62
Issue
3
Publish Date
2013
Start Page
912
End Page
922
DOI
10.2337/db12-0624

Coming of age: molecular drivers of aging and therapeutic opportunities.

Aging is like the weather: everyone talks about it, but no one seems to do anything about it. We believe this may soon change, as an improved understanding of the molecular and genetic pathways underlying aging suggests it is possible to therapeutically target the aging process and increase health span. This Review series focuses on fundamental cellular mechanisms of aging and their relationship to human disease. These pathways include telomere dysfunction in cellular senescence and induction of the senescence-associated secretory phenotype (SASP) in systemic aging, sirtuin family regulation of metabolism and aging-associated diseases, mitochondrial metabolism in aging, the mechanistic target of rapamycin (mTOR) signaling pathway and the use of mTOR inhibitors to increase longevity, the progressive decline of the immune system with age, and aging-associated changes to pancreatic islet β cells that may contribute to diabetes. Together, these articles explore pathways affecting aging and possible interventional targets to slow or delay the onset of age-related pathologies.

Authors
Newgard, CB; Sharpless, NE
MLA Citation
Newgard, CB, and Sharpless, NE. "Coming of age: molecular drivers of aging and therapeutic opportunities." J Clin Invest 123.3 (March 2013): 946-950.
PMID
23454756
Source
pubmed
Published In
Journal of Clinical Investigation
Volume
123
Issue
3
Publish Date
2013
Start Page
946
End Page
950
DOI
10.1172/JCI68833

Branched-chain amino acids alter neurobehavioral function in rats.

Recently, we have described a strong association of branched-chain amino acids (BCAA) and aromatic amino acids (AAA) with obesity and insulin resistance. In the current study, we have investigated the potential impact of BCAA on behavioral functions. We demonstrate that supplementation of either a high-sucrose or a high-fat diet with BCAA induces anxiety-like behavior in rats compared with control groups fed on unsupplemented diets. These behavioral changes are associated with a significant decrease in the concentration of tryptophan (Trp) in brain tissues and a consequent decrease in serotonin but no difference in indices of serotonin synaptic function. The anxiety-like behaviors and decreased levels of Trp in the brain of BCAA-fed rats were reversed by supplementation of Trp in the drinking water but not by administration of fluoxetine, a selective serotonin reuptake inhibitor, suggesting that the behavioral changes are independent of the serotonergic pathway of Trp metabolism. Instead, BCAA supplementation lowers the brain levels of another Trp-derived metabolite, kynurenic acid, and these levels are normalized by Trp supplementation. We conclude that supplementation of high-energy diets with BCAA causes neurobehavioral impairment. Since BCAA are elevated spontaneously in human obesity, our studies suggest a potential mechanism for explaining the strong association of obesity and mood disorders.

Authors
Coppola, A; Wenner, BR; Ilkayeva, O; Stevens, RD; Maggioni, M; Slotkin, TA; Levin, ED; Newgard, CB
MLA Citation
Coppola, A, Wenner, BR, Ilkayeva, O, Stevens, RD, Maggioni, M, Slotkin, TA, Levin, ED, and Newgard, CB. "Branched-chain amino acids alter neurobehavioral function in rats." Am J Physiol Endocrinol Metab 304.4 (February 15, 2013): E405-E413.
PMID
23249694
Source
pubmed
Published In
American journal of physiology. Endocrinology and metabolism
Volume
304
Issue
4
Publish Date
2013
Start Page
E405
End Page
E413
DOI
10.1152/ajpendo.00373.2012

Research resource: tissue- and pathway-specific metabolomic profiles of the steroid receptor coactivator (SRC) family.

The rapidly growing family of transcriptional coregulators includes coactivators that promote transcription and corepressors that harbor the opposing function. In recent years, coregulators have emerged as important regulators of metabolic homeostasis, including the p160 steroid receptor coactivator (SRC) family. Members of the SRC family have been ascribed important roles in control of gluconeogenesis, fat absorption and storage in the liver, and fatty acid oxidation in skeletal muscle. To provide a deeper and more granular understanding of the metabolic impact of the SRC family members, we performed targeted metabolomic analyses of key metabolic byproducts of glucose, fatty acid, and amino acid metabolism in mice with global knockouts (KOs) of SRC-1, SRC-2, or SRC-3. We measured amino acids, acyl carnitines, and organic acids in five tissues with key metabolic functions (liver, heart, skeletal muscle, brain, plasma) isolated from SRC-1, -2, or -3 KO mice and their wild-type littermates under fed and fasted conditions, thereby unveiling unique metabolic functions of each SRC. Specifically, SRC-1 ablation revealed the most significant impact on hepatic metabolism, whereas SRC-2 appeared to impact cardiac metabolism. Conversely, ablation of SRC-3 primarily affected brain and skeletal muscle metabolism. Surprisingly, we identified very few metabolites that changed universally across the three SRC KO models. The findings of this Research Resource demonstrate that coactivator function has very limited metabolic redundancy even within the homologous SRC family. Furthermore, this work also demonstrates the use of metabolomics as a means for identifying novel metabolic regulatory functions of transcriptional coregulators.

Authors
York, B; Sagen, JV; Tsimelzon, A; Louet, J-F; Chopra, AR; Reineke, EL; Zhou, S; Stevens, RD; Wenner, BR; Ilkayeva, O; Bain, JR; Xu, J; Hilsenbeck, SG; Newgard, CB; O'Malley, BW
MLA Citation
York, B, Sagen, JV, Tsimelzon, A, Louet, J-F, Chopra, AR, Reineke, EL, Zhou, S, Stevens, RD, Wenner, BR, Ilkayeva, O, Bain, JR, Xu, J, Hilsenbeck, SG, Newgard, CB, and O'Malley, BW. "Research resource: tissue- and pathway-specific metabolomic profiles of the steroid receptor coactivator (SRC) family." Mol Endocrinol 27.2 (February 2013): 366-380.
PMID
23315938
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
27
Issue
2
Publish Date
2013
Start Page
366
End Page
380
DOI
10.1210/me.2012-1324

The role of voltage-gated potassium channels Kv2.1 and Kv2.2 in the regulation of insulin and somatostatin release from pancreatic islets.

The voltage-gated potassium channels Kv2.1 and Kv2.2 are highly expressed in pancreatic islets, yet their contribution to islet hormone secretion is not fully understood. Here we investigate the role of Kv2 channels in pancreatic islets using a combination of genetic and pharmacologic approaches. Pancreatic β-cells from Kv2.1(-/-) mice possess reduced Kv current and display greater glucose-stimulated insulin secretion (GSIS) relative to WT β-cells. Inhibition of Kv2.x channels with selective peptidyl [guangxitoxin-1E (GxTX-1E)] or small molecule (RY796) inhibitors enhances GSIS in isolated wild-type (WT) mouse and human islets, but not in islets from Kv2.1(-/-) mice. However, in WT mice neither inhibitor improved glucose tolerance in vivo. GxTX-1E and RY796 enhanced somatostatin release in isolated human and mouse islets and in situ perfused pancreata from WT and Kv2.1(-/-) mice. Kv2.2 silencing in mouse islets by adenovirus-small hairpin RNA (shRNA) specifically enhanced islet somatostatin, but not insulin, secretion. In mice lacking somatostatin receptor 5, GxTX-1E stimulated insulin secretion and improved glucose tolerance. Collectively, these data show that Kv2.1 regulates insulin secretion in β-cells and Kv2.2 modulates somatostatin release in δ-cells. Development of selective Kv2.1 inhibitors without cross inhibition of Kv2.2 may provide new avenues to promote GSIS for the treatment of type 2 diabetes.

Authors
Li, XN; Herrington, J; Petrov, A; Ge, L; Eiermann, G; Xiong, Y; Jensen, MV; Hohmeier, HE; Newgard, CB; Garcia, ML; Wagner, M; Zhang, BB; Thornberry, NA; Howard, AD; Kaczorowski, GJ; Zhou, Y-P
MLA Citation
Li, XN, Herrington, J, Petrov, A, Ge, L, Eiermann, G, Xiong, Y, Jensen, MV, Hohmeier, HE, Newgard, CB, Garcia, ML, Wagner, M, Zhang, BB, Thornberry, NA, Howard, AD, Kaczorowski, GJ, and Zhou, Y-P. "The role of voltage-gated potassium channels Kv2.1 and Kv2.2 in the regulation of insulin and somatostatin release from pancreatic islets." J Pharmacol Exp Ther 344.2 (February 2013): 407-416.
PMID
23161216
Source
pubmed
Published In
The Journal of pharmacology and experimental therapeutics
Volume
344
Issue
2
Publish Date
2013
Start Page
407
End Page
416
DOI
10.1124/jpet.112.199083

Suppression of oxidative stress by β-hydroxybutyrate, an endogenous histone deacetylase inhibitor.

Concentrations of acetyl-coenzyme A and nicotinamide adenine dinucleotide (NAD(+)) affect histone acetylation and thereby couple cellular metabolic status and transcriptional regulation. We report that the ketone body d-β-hydroxybutyrate (βOHB) is an endogenous and specific inhibitor of class I histone deacetylases (HDACs). Administration of exogenous βOHB, or fasting or calorie restriction, two conditions associated with increased βOHB abundance, all increased global histone acetylation in mouse tissues. Inhibition of HDAC by βOHB was correlated with global changes in transcription, including that of the genes encoding oxidative stress resistance factors FOXO3A and MT2. Treatment of cells with βOHB increased histone acetylation at the Foxo3a and Mt2 promoters, and both genes were activated by selective depletion of HDAC1 and HDAC2. Consistent with increased FOXO3A and MT2 activity, treatment of mice with βOHB conferred substantial protection against oxidative stress.

Authors
Shimazu, T; Hirschey, MD; Newman, J; He, W; Shirakawa, K; Le Moan, N; Grueter, CA; Lim, H; Saunders, LR; Stevens, RD; Newgard, CB; Farese, RV; de Cabo, R; Ulrich, S; Akassoglou, K; Verdin, E
MLA Citation
Shimazu, T, Hirschey, MD, Newman, J, He, W, Shirakawa, K, Le Moan, N, Grueter, CA, Lim, H, Saunders, LR, Stevens, RD, Newgard, CB, Farese, RV, de Cabo, R, Ulrich, S, Akassoglou, K, and Verdin, E. "Suppression of oxidative stress by β-hydroxybutyrate, an endogenous histone deacetylase inhibitor." Science 339.6116 (January 11, 2013): 211-214.
PMID
23223453
Source
pubmed
Published In
Science
Volume
339
Issue
6116
Publish Date
2013
Start Page
211
End Page
214
DOI
10.1126/science.1227166

Effect of Roux-en-Y gastric bypass and laparoscopic adjustable gastric banding on branched-chain amino acid metabolism

It has been hypothesized that a greater decline in circulating branched-chain amino acids (BCAAs) after weight loss induced by Roux-en-Y gastric bypass (RYGB) surgery than after calorie restriction alone has independent effects on glucose homeostasis, possibly by decreased signaling through the mammalian target of rapamycin (mTOR). We evaluated plasma BCAAs and their C3 and C5 acylcarnitine metabolites, muscle mTOR phosphorylation, and insulin sensitivity (insulin-stimulated glucose Rd) in obese subjects before and after ~20% weight loss induced by RYGB (n = 10, BMI 45.6 ± 6.7 kg/m(2)) or laparoscopic adjustable gastric banding (LAGB) (n = 10, BMI 46.5 ± 8.8 kg/m(2)). Weight loss increased insulin-stimulated glucose Rd by ~55%, decreased total plasma BCAA and C3 and C5 acylcarnitine concentrations by 20-35%, and did not alter mTOR phosphorylation; no differences were detected between surgical groups (all P values for interaction >0.05). Insulin-stimulated glucose Rd correlated negatively with plasma BCAAs and with C3 and C5 acylcarnitine concentrations (r values -0.56 to -0.75, P < 0.05). These data demonstrate that weight loss induced by either LAGB or RYGB causes the same decline in circulating BCAAs and their C3 and C5 acylcarnitine metabolites. Plasma BCAA concentration is negatively associated with skeletal muscle insulin sensitivity, but the mechanism(s) responsible for this relationship is not known.

Authors
Magkos, F; Bradley, D; Schweitzer, GG; Finck, BN; Eagon, JC; Ilkayeva, O; Newgard, CB; Klein, S
MLA Citation
Magkos, F, Bradley, D, Schweitzer, GG, Finck, BN, Eagon, JC, Ilkayeva, O, Newgard, CB, and Klein, S. "Effect of Roux-en-Y gastric bypass and laparoscopic adjustable gastric banding on branched-chain amino acid metabolism." Diabetes 62.8 (2013): 2757-2761.
Source
scival
Published In
Diabetes
Volume
62
Issue
8
Publish Date
2013
Start Page
2757
End Page
2761
DOI
10.2337/db13-0185

Suppression of oxidative stress by β-hydroxybutyrate, an endogenous histone deacetylase inhibitor

Concentrations of acetyl-coenzyme A and nicotinamide adenine dinucleotide (NAD+) affect histone acetylation and thereby couple cellular metabolic status and transcriptional regulation. We report that the ketone body D-β-hydroxybutyrate (βOHB) is an endogenous and specific inhibitor of class I histone deacetylases (HDACs). Administration of exogenous βOHB, or fasting or calorie restriction, two conditions associated with increased βOHB abundance, all increased global histone acetylation in mouse tissues. Inhibition of HDAC by βOHB was correlated with global changes in transcription, including that of the genes encoding oxidative stress resistance factors FOXO3A and MT2. Treatment of cells with βOHB increased histone acetylation at the Foxo3a and Mt2 promoters, and both genes were activated by selective depletion of HDAC1 and HDAC2. Consistent with increased FOXO3A and MT2 activity, treatment of mice with βOHB conferred substantial protection against oxidative stress.

Authors
Shimazu, T; Hirschey, MD; Newman, J; He, W; Shirakawa, K; Moan, NL; Grueter, CA; Lim, H; Saunders, LR; Stevens, RD; Newgard, CB; Jr, RVF; Cabo, RD; Ulrich, S; Akassoglou, K; Verdin, E
MLA Citation
Shimazu, T, Hirschey, MD, Newman, J, He, W, Shirakawa, K, Moan, NL, Grueter, CA, Lim, H, Saunders, LR, Stevens, RD, Newgard, CB, Jr, RVF, Cabo, RD, Ulrich, S, Akassoglou, K, and Verdin, E. "Suppression of oxidative stress by β-hydroxybutyrate, an endogenous histone deacetylase inhibitor." Science 339.6116 (2013): 211-214.
Source
scival
Published In
Science
Volume
339
Issue
6116
Publish Date
2013
Start Page
211
End Page
214
DOI
10.1126/science.1227166

Metabolomic analysis reveals extended metabolic consequences of marginal vitamin B-6 deficiency in healthy human subjects.

Marginal deficiency of vitamin B-6 is common among segments of the population worldwide. Because pyridoxal 5'-phosphate (PLP) serves as a coenzyme in the metabolism of amino acids, carbohydrates, organic acids, and neurotransmitters, as well as in aspects of one-carbon metabolism, vitamin B-6 deficiency could have many effects. Healthy men and women (age: 20-40 y; n = 23) were fed a 2-day controlled, nutritionally adequate diet followed by a 28-day low-vitamin B-6 diet (<0.5 mg/d) to induce marginal deficiency, as reflected by a decline of plasma PLP from 52.6±14.1 (mean ± SD) to 21.5±4.6 nmol/L (P<0.0001) and increased cystathionine from 131±65 to 199±56 nmol/L (P<0.001). Fasting plasma samples obtained before and after vitamin B6 restriction were analyzed by (1)H-NMR with and without filtration and by targeted quantitative analysis by mass spectrometry (MS). Multilevel partial least squares-discriminant analysis and S-plots of NMR spectra showed that NMR is effective in classifying samples according to vitamin B-6 status and identified discriminating features. NMR spectral features of selected metabolites indicated that vitamin B-6 restriction significantly increased the ratios of glutamine/glutamate and 2-oxoglutarate/glutamate (P<0.001) and tended to increase concentrations of acetate, pyruvate, and trimethylamine-N-oxide (adjusted P<0.05). Tandem MS showed significantly greater plasma proline after vitamin B-6 restriction (adjusted P<0.05), but there were no effects on the profile of 14 other amino acids and 45 acylcarnitines. These findings demonstrate that marginal vitamin B-6 deficiency has widespread metabolic perturbations and illustrate the utility of metabolomics in evaluating complex effects of altered vitamin B-6 intake.

Authors
Gregory, JF; Park, Y; Lamers, Y; Bandyopadhyay, N; Chi, Y-Y; Lee, K; Kim, S; da Silva, V; Hove, N; Ranka, S; Kahveci, T; Muller, KE; Stevens, RD; Newgard, CB; Stacpoole, PW; Jones, DP
MLA Citation
Gregory, JF, Park, Y, Lamers, Y, Bandyopadhyay, N, Chi, Y-Y, Lee, K, Kim, S, da Silva, V, Hove, N, Ranka, S, Kahveci, T, Muller, KE, Stevens, RD, Newgard, CB, Stacpoole, PW, and Jones, DP. "Metabolomic analysis reveals extended metabolic consequences of marginal vitamin B-6 deficiency in healthy human subjects. (Published online)" PLoS One 8.6 (2013): e63544-.
PMID
23776431
Source
pubmed
Published In
PloS one
Volume
8
Issue
6
Publish Date
2013
Start Page
e63544
DOI
10.1371/journal.pone.0063544

Application of combined omics platforms to accelerate biomedical discovery in diabesity

Diabesity has become a popular term to describe the specific form of diabetes that develops late in life and is associated with obesity. While there is a correlation between diabetes and obesity, the association is not universally predictive. Defining the metabolic characteristics of obesity that lead to diabetes, and how obese individuals who develop diabetes different from those who do not, are important goals. The use of large-scale omics analyses (e.g., metabolomic, proteomic, transcriptomic, and lipidomic) of diabetes and obesity may help to identify new targets to treat these conditions. This report discusses how various types of omics data can be integrated to shed light on the changes in metabolism that occur in obesity and diabetes. © 2013 New York Academy of Sciences.

Authors
Kurland, IJ; Accili, D; Burant, C; Fischer, SM; Kahn, BB; Newgard, CB; Ramagiri, S; Ronnett, GV; Ryals, JA; Sanders, M; Shambaugh, J; Shockcor, J; Gross, SS
MLA Citation
Kurland, IJ, Accili, D, Burant, C, Fischer, SM, Kahn, BB, Newgard, CB, Ramagiri, S, Ronnett, GV, Ryals, JA, Sanders, M, Shambaugh, J, Shockcor, J, and Gross, SS. "Application of combined omics platforms to accelerate biomedical discovery in diabesity." Annals of the New York Academy of Sciences 1287.1 (2013): 1-16.
Source
scival
Published In
Annals of the New York Academy of Sciences
Volume
1287
Issue
1
Publish Date
2013
Start Page
1
End Page
16
DOI
10.1111/nyas.12116

Branched chain amino acids are novel biomarkers for discrimination of metabolic wellness

Objective To identify novel biomarkers through metabolomic profiles that distinguish metabolically well (MW) from metabolically unwell (MUW) individuals, independent of body mass index (BMI). Materials/Methods This study was conducted as part of the Measurement to Understand the Reclassification of Disease of Cabarrus/Kannapolis (MURDOCK) project. Individuals from 3 cohorts were classified as lean (BMI < 25 kg/m2), overweight (BMI ≥ 25 kg/m2, BMI < 30 kg/m2) or obese (BMI ≥ 30 kg/m 2). Cardiometabolic abnormalities were defined as: (1) impaired fasting glucose (≥ 100 mg/dL and ≤ 126 mg/dL); (2) hypertension; (3) triglycerides ≥ 150 mg/dL; (4) HDL-C < 40 mg/dL in men, < 50 mg/dL in women; and (5) insulin resistance (calculated Homeostatic Model Assessment (HOMA-IR) index of > 5.13). MW individuals were defined as having < 2 cardiometabolic abnormalities and MUW individuals had ≥ two cardiometabolic abnormalities. Targeted profiling of 55 metabolites used mass-spectroscopy-based methods. Principal components analysis (PCA) was used to reduce the large number of correlated metabolites into clusters of fewer uncorrelated factors. Results Of 1872 individuals, 410 were lean, 610 were overweight, and 852 were obese. Of lean individuals, 67% were categorized as MUW, whereas 80% of overweight and 87% of obese individuals were MUW. PCA-derived factors with levels that differed the most between MW and MUW groups were factors 4 (branched chain amino acids [BCAA]) [p <.0001], 8 (various metabolites) [p <.0001], 9 (C4/Ci4, C3, C5 acylcarnitines) [p <.0001] and 10 (amino acids) [p <.0002]. Further, Factor 4, distinguishes MW from MUW individuals independent of BMI. Conclusion BCAA and related metabolites are promising biomarkers that may aid in understanding cardiometabolic health independent of BMI category. © 2013 Elsevier Inc. All rights reserved.

Authors
Batch, BC; Shah, SH; Newgard, CB; Turer, CB; Haynes, C; Bain, JR; Muehlbauer, M; Patel, MJ; Stevens, RD; Appel, LJ; Newby, LK; Svetkey, LP
MLA Citation
Batch, BC, Shah, SH, Newgard, CB, Turer, CB, Haynes, C, Bain, JR, Muehlbauer, M, Patel, MJ, Stevens, RD, Appel, LJ, Newby, LK, and Svetkey, LP. "Branched chain amino acids are novel biomarkers for discrimination of metabolic wellness." Metabolism: Clinical and Experimental 62.7 (2013): 961-969.
Source
scival
Published In
Metabolism
Volume
62
Issue
7
Publish Date
2013
Start Page
961
End Page
969
DOI
10.1016/j.metabol.2013.01.007

Adipose-specific deletion of TFAM increases mitochondrial oxidation and protects mice against obesity and insulin resistance.

Obesity and type 2 diabetes are associated with mitochondrial dysfunction in adipose tissue, but the role for adipose tissue mitochondria in the development of these disorders is currently unknown. To understand the impact of adipose tissue mitochondria on whole-body metabolism, we have generated a mouse model with disruption of the mitochondrial transcription factor A (TFAM) specifically in fat. F-TFKO adipose tissue exhibit decreased mtDNA copy number, altered levels of proteins of the electron transport chain, and perturbed mitochondrial function with decreased complex I activity and greater oxygen consumption and uncoupling. As a result, F-TFKO mice exhibit higher energy expenditure and are protected from age- and diet-induced obesity, insulin resistance, and hepatosteatosis, despite a greater food intake. Thus, TFAM deletion in the adipose tissue increases mitochondrial oxidation that has positive metabolic effects, suggesting that regulation of adipose tissue mitochondria may be a potential therapeutic target for the treatment of obesity.

Authors
Vernochet, C; Mourier, A; Bezy, O; Macotela, Y; Boucher, J; Rardin, MJ; An, D; Lee, KY; Ilkayeva, OR; Zingaretti, CM; Emanuelli, B; Smyth, G; Cinti, S; Newgard, CB; Gibson, BW; Larsson, N-G; Kahn, CR
MLA Citation
Vernochet, C, Mourier, A, Bezy, O, Macotela, Y, Boucher, J, Rardin, MJ, An, D, Lee, KY, Ilkayeva, OR, Zingaretti, CM, Emanuelli, B, Smyth, G, Cinti, S, Newgard, CB, Gibson, BW, Larsson, N-G, and Kahn, CR. "Adipose-specific deletion of TFAM increases mitochondrial oxidation and protects mice against obesity and insulin resistance." Cell Metab 16.6 (December 5, 2012): 765-776.
PMID
23168219
Source
pubmed
Published In
Cell Metabolism
Volume
16
Issue
6
Publish Date
2012
Start Page
765
End Page
776
DOI
10.1016/j.cmet.2012.10.016

Skeletal muscle Nur77 expression enhances oxidative metabolism and substrate utilization.

Mitochondrial dysfunction has been implicated in the pathogenesis of type 2 diabetes. Identifying novel regulators of mitochondrial bioenergetics will broaden our understanding of regulatory checkpoints that coordinate complex metabolic pathways. We previously showed that Nur77, an orphan nuclear receptor of the NR4A family, regulates the expression of genes linked to glucose utilization. Here we demonstrate that expression of Nur77 in skeletal muscle also enhances mitochondrial function. We generated MCK-Nur77 transgenic mice that express wild-type Nur77 specifically in skeletal muscle. Nur77-overexpressing muscle had increased abundance of oxidative muscle fibers and mitochondrial DNA content. Transgenic muscle also exhibited enhanced oxidative metabolism, suggestive of increased mitochondrial activity. Metabolomic analysis confirmed that Nur77 transgenic muscle favored fatty acid oxidation over glucose oxidation, mimicking the metabolic profile of fasting. Nur77 expression also improved the intrinsic respiratory capacity of isolated mitochondria, likely due to the increased abundance of complex I of the electron transport chain. These changes in mitochondrial metabolism translated to improved muscle contractile function ex vivo and improved cold tolerance in vivo. Our studies outline a novel role for Nur77 in the regulation of oxidative metabolism and mitochondrial activity in skeletal muscle.

Authors
Chao, LC; Wroblewski, K; Ilkayeva, OR; Stevens, RD; Bain, J; Meyer, GA; Schenk, S; Martinez, L; Vergnes, L; Narkar, VA; Drew, BG; Hong, C; Boyadjian, R; Hevener, AL; Evans, RM; Reue, K; Spencer, MJ; Newgard, CB; Tontonoz, P
MLA Citation
Chao, LC, Wroblewski, K, Ilkayeva, OR, Stevens, RD, Bain, J, Meyer, GA, Schenk, S, Martinez, L, Vergnes, L, Narkar, VA, Drew, BG, Hong, C, Boyadjian, R, Hevener, AL, Evans, RM, Reue, K, Spencer, MJ, Newgard, CB, and Tontonoz, P. "Skeletal muscle Nur77 expression enhances oxidative metabolism and substrate utilization." J Lipid Res 53.12 (December 2012): 2610-2619.
PMID
23028113
Source
pubmed
Published In
Journal of lipid research
Volume
53
Issue
12
Publish Date
2012
Start Page
2610
End Page
2619
DOI
10.1194/jlr.M029355

Marginal vitamin B-6 deficiency decreases plasma (n-3) and (n-6) PUFA concentrations in healthy men and women.

Previous animal studies showed that severe vitamin B-6 deficiency altered fatty acid profiles of tissue lipids, often with an increase of linoleic acid and a decrease of arachidonic acid. However, little is known about the extent to which vitamin B-6 deficiency affects human fatty acid profiles. The aim of this study was to determine the effects of marginal vitamin B-6 deficiency on fatty acid profiles in plasma, erythrocytes, and peripheral blood mononuclear cells (PBMC) of healthy adults fed a 28-d, low-vitamin B-6 diet. Healthy participants (n = 23) received a 2-d, controlled, vitamin B-6-adequate diet followed by a 28-d, vitamin B-6-restricted diet to induce a marginal deficiency. Plasma HDL and LDL cholesterol concentrations, FFA concentrations, and erythrocyte and PBMC membrane fatty acid compositions did not significantly change from baseline after the 28-d restriction. Plasma total arachidonic acid, EPA, and DHA concentrations decreased from (mean ± SD) 548 ± 96 to 490 ± 94 μmol/L, 37 ± 13 to 32 ± 13 μmol/L, and 121 ± 28 to 109 ± 28 μmol/L [positive false discovery rate (pFDR) adjusted P < 0.05], respectively. The total (n-6):(n-3) PUFA ratio in plasma exhibited a minor increase from 15.4 ± 2.8 to 16.6 ± 3.1 (pFDR adjusted P < 0.05). These data indicate that short-term vitamin B-6 restriction decreases plasma (n-3) and (n-6) PUFA concentrations and tends to increase the plasma (n-6):(n-3) PUFA ratio. Such changes in blood lipids may be associated with the elevated risk of cardiovascular disease in vitamin B-6 insufficiency.

Authors
Zhao, M; Lamers, Y; Ralat, MA; Coats, BS; Chi, Y-Y; Muller, KE; Bain, JR; Shankar, MN; Newgard, CB; Stacpoole, PW; Gregory, JF
MLA Citation
Zhao, M, Lamers, Y, Ralat, MA, Coats, BS, Chi, Y-Y, Muller, KE, Bain, JR, Shankar, MN, Newgard, CB, Stacpoole, PW, and Gregory, JF. "Marginal vitamin B-6 deficiency decreases plasma (n-3) and (n-6) PUFA concentrations in healthy men and women." J Nutr 142.10 (October 2012): 1791-1797.
PMID
22955512
Source
pubmed
Published In
The Journal of nutrition
Volume
142
Issue
10
Publish Date
2012
Start Page
1791
End Page
1797
DOI
10.3945/jn.112.163246

Analysis of serum metabolic profiles in women with endometrial cancer and controls in a population-based case-control study.

CONTEXT: Endometrial cancer is associated with metabolic disturbances related to its underlying risk factors, including obesity and diabetes. Identifying metabolite biomarkers associated with endometrial cancer may have value for early detection, risk assessment, and understanding etiology. OBJECTIVE: The objective of the study was to evaluate the reliable measurement of metabolites in epidemiological studies with nonstandardized blood collection; confirm previously reported correlations of metabolites with body size; and assess differences in metabolite levels between cases and controls. DESIGN: This was the Polish Endometrial Cancer Study (2001-2003). SETTING: This study was a population-based case-control study. PATIENTS: Patients included 250 cases and 250 controls. INTERVENTION: The intervention included the measurement of serum metabolite levels of 15 amino acids, 45 acylcarnitines, and nine fatty acids. MAIN OUTCOME MEASURE: The main outcome measure was endometrial cancer. RESULTS: Body mass index was correlated with levels of valine (r = 0.26, P = 3.4 × 10(-5)), octenoylcarnitine (r = 0.24, P = 1.5 × 10(-4)), palmitic acid (r = 0.26, P = 4.4 × 10(-5)), oleic acid (r = 0.28, P = 9.9 × 10(-6)), and stearic acid (r = 0.26, P = 2.9 × 10(-5)) among controls. Only stearic acid was inversely associated with endometrial cancer case status (quartile 4 vs. quartile 1: odds ratio 0.37, 95% confidence interval 0.20-0.69, P for trend = 1.2 × 10(-4)). Levels of the C5-acylcarnitines, octenoylcarnitine, decatrienoylcarnitine, and linoleic acid were significantly lower in cases than controls (odds ratios ranged from 0.21 to 0.38). CONCLUSIONS: These data demonstrate that previously reported variations in metabolomic profiles with body mass index can be replicated in population-based studies with nonfasting blood collection protocols. We also provide preliminary evidence that large differences in metabolite levels exist between cases and controls, independent of body habitus. Our findings warrant assessment of metabolic profiles, including the candidate markers identified herein, in prospectively collected blood samples to define biomarkers and etiological factors related to endometrial cancer.

Authors
Gaudet, MM; Falk, RT; Stevens, RD; Gunter, MJ; Bain, JR; Pfeiffer, RM; Potischman, N; Lissowska, J; Peplonska, B; Brinton, LA; Garcia-Closas, M; Newgard, CB; Sherman, ME
MLA Citation
Gaudet, MM, Falk, RT, Stevens, RD, Gunter, MJ, Bain, JR, Pfeiffer, RM, Potischman, N, Lissowska, J, Peplonska, B, Brinton, LA, Garcia-Closas, M, Newgard, CB, and Sherman, ME. "Analysis of serum metabolic profiles in women with endometrial cancer and controls in a population-based case-control study." J Clin Endocrinol Metab 97.9 (September 2012): 3216-3223.
PMID
22730518
Source
pubmed
Published In
Journal of Clinical Endocrinology and Metabolism
Volume
97
Issue
9
Publish Date
2012
Start Page
3216
End Page
3223
DOI
10.1210/jc.2012-1490

Rapid and weight-independent improvement of glucose tolerance induced by a peptide designed to elicit apoptosis in adipose tissue endothelium.

A peptide designed to induce apoptosis of endothelium in white adipose tissue (WAT) decreases adiposity. The goal of this work is to determine whether targeting of WAT endothelium results in impaired glucose regulation as a result of impaired WAT function. Glucose tolerance tests were performed on days 2 and 3 of treatment with vehicle (HF-V) or proapoptotic peptide (HF-PP) and mice pair-fed to HF-PP (HF-PF) in obese mice on a high-fat diet (HFD). Serum metabolic variables, including lipid profile, adipokines, individual fatty acids, and acylcarnitines, were measured. Microarray analysis was performed in epididymal fat of lean or obese mice treated with vehicle or proapoptotic peptide (PP). PP rapidly and potently improved glucose tolerance of obese mice in a weight- and food intake-independent manner. Serum insulin and triglycerides were decreased in HF-PP relative to HF-V. Levels of fatty acids and acylcarnitines were distinctive in HF-PP compared with HF-V or HF-PF. Microarray analysis in AT revealed that pathways involved in mitochondrial dysfunction, oxidative phosphorylation, and branched-chain amino acid degradation were changed by exposure to HFD and were reversed by PP administration. These studies suggest a novel role of the AT vasculature in glucose homeostasis and lipid metabolism.

Authors
Kim, D-H; Sartor, MA; Bain, JR; Sandoval, D; Stevens, RD; Medvedovic, M; Newgard, CB; Woods, SC; Seeley, RJ
MLA Citation
Kim, D-H, Sartor, MA, Bain, JR, Sandoval, D, Stevens, RD, Medvedovic, M, Newgard, CB, Woods, SC, and Seeley, RJ. "Rapid and weight-independent improvement of glucose tolerance induced by a peptide designed to elicit apoptosis in adipose tissue endothelium." Diabetes 61.9 (September 2012): 2299-2310.
PMID
22733798
Source
pubmed
Published In
Diabetes
Volume
61
Issue
9
Publish Date
2012
Start Page
2299
End Page
2310
DOI
10.2337/db11-1579

Metabolomic profiling for the identification of novel biomarkers and mechanisms related to common cardiovascular diseases: form and function.

Authors
Shah, SH; Kraus, WE; Newgard, CB
MLA Citation
Shah, SH, Kraus, WE, and Newgard, CB. "Metabolomic profiling for the identification of novel biomarkers and mechanisms related to common cardiovascular diseases: form and function." Circulation 126.9 (August 28, 2012): 1110-1120. (Review)
PMID
22927473
Source
pubmed
Published In
Circulation
Volume
126
Issue
9
Publish Date
2012
Start Page
1110
End Page
1120
DOI
10.1161/CIRCULATIONAHA.111.060368

A VGF-derived peptide attenuates development of type 2 diabetes via enhancement of islet β-cell survival and function.

Deterioration of functional islet β-cell mass is the final step in progression to Type 2 diabetes. We previously reported that overexpression of Nkx6.1 in rat islets has the dual effects of enhancing glucose-stimulated insulin secretion (GSIS) and increasing β-cell replication. Here we show that Nkx6.1 strongly upregulates the prohormone VGF in rat islets and that VGF is both necessary and sufficient for Nkx6.1-mediated enhancement of GSIS. Moreover, the VGF-derived peptide TLQP-21 potentiates GSIS in rat and human islets and improves glucose tolerance in vivo. Chronic injection of TLQP-21 in prediabetic ZDF rats preserves islet mass and slows diabetes onset. TLQP-21 prevents islet cell apoptosis by a pathway similar to that used by GLP-1, but independent of the GLP-1, GIP, or VIP receptors. Unlike GLP-1, TLQP-21 does not inhibit gastric emptying or increase heart rate. We conclude that TLQP-21 is a targeted agent for enhancing islet β-cell survival and function.

Authors
Stephens, SB; Schisler, JC; Hohmeier, HE; An, J; Sun, AY; Pitt, GS; Newgard, CB
MLA Citation
Stephens, SB, Schisler, JC, Hohmeier, HE, An, J, Sun, AY, Pitt, GS, and Newgard, CB. "A VGF-derived peptide attenuates development of type 2 diabetes via enhancement of islet β-cell survival and function." Cell Metab 16.1 (July 3, 2012): 33-43.
PMID
22768837
Source
pubmed
Published In
Cell Metabolism
Volume
16
Issue
1
Publish Date
2012
Start Page
33
End Page
43
DOI
10.1016/j.cmet.2012.05.011

Thyroid hormone stimulates hepatic lipid catabolism via activation of autophagy.

For more than a century, thyroid hormones (THs) have been known to exert powerful catabolic effects, leading to weight loss. Although much has been learned about the molecular mechanisms used by TH receptors (TRs) to regulate gene expression, little is known about the mechanisms by which THs increase oxidative metabolism. Here, we report that TH stimulation of fatty acid β-oxidation is coupled with induction of hepatic autophagy to deliver fatty acids to mitochondria in cell culture and in vivo. Furthermore, blockade of autophagy by autophagy-related 5 (ATG5) siRNA markedly decreased TH-mediated fatty acid β-oxidation in cell culture and in vivo. Consistent with this model, autophagy was altered in livers of mice expressing a mutant TR that causes resistance to the actions of TH as well as in mice with mutant nuclear receptor corepressor (NCoR). These results demonstrate that THs can regulate lipid homeostasis via autophagy and help to explain how THs increase oxidative metabolism.

Authors
Sinha, RA; You, S-H; Zhou, J; Siddique, MM; Bay, B-H; Zhu, X; Privalsky, ML; Cheng, S-Y; Stevens, RD; Summers, SA; Newgard, CB; Lazar, MA; Yen, PM
MLA Citation
Sinha, RA, You, S-H, Zhou, J, Siddique, MM, Bay, B-H, Zhu, X, Privalsky, ML, Cheng, S-Y, Stevens, RD, Summers, SA, Newgard, CB, Lazar, MA, and Yen, PM. "Thyroid hormone stimulates hepatic lipid catabolism via activation of autophagy." J Clin Invest 122.7 (July 2012): 2428-2438.
PMID
22684107
Source
pubmed
Published In
Journal of Clinical Investigation
Volume
122
Issue
7
Publish Date
2012
Start Page
2428
End Page
2438
DOI
10.1172/JCI60580

Deletion of GαZ protein protects against diet-induced glucose intolerance via expansion of β-cell mass.

Insufficient plasma insulin levels caused by deficits in both pancreatic β-cell function and mass contribute to the pathogenesis of type 2 diabetes. This loss of insulin-producing capacity is termed β-cell decompensation. Our work is focused on defining the role(s) of guanine nucleotide-binding protein (G protein) signaling pathways in regulating β-cell decompensation. We have previously demonstrated that the α-subunit of the heterotrimeric G(z) protein, Gα(z), impairs insulin secretion by suppressing production of cAMP. Pancreatic islets from Gα(z)-null mice also exhibit constitutively increased cAMP production and augmented glucose-stimulated insulin secretion, suggesting that Gα(z) is a tonic inhibitor of adenylate cyclase, the enzyme responsible for the conversion of ATP to cAMP. In the present study, we show that mice genetically deficient for Gα(z) are protected from developing glucose intolerance when fed a high fat (45 kcal%) diet. In these mice, a robust increase in β-cell proliferation is correlated with significantly increased β-cell mass. Further, an endogenous Gα(z) signaling pathway, through circulating prostaglandin E activating the EP3 isoform of the E prostanoid receptor, appears to be up-regulated in insulin-resistant, glucose-intolerant mice. These results, along with those of our previous work, link signaling through Gα(z) to both major aspects of β-cell decompensation: insufficient β-cell function and mass.

Authors
Kimple, ME; Moss, JB; Brar, HK; Rosa, TC; Truchan, NA; Pasker, RL; Newgard, CB; Casey, PJ
MLA Citation
Kimple, ME, Moss, JB, Brar, HK, Rosa, TC, Truchan, NA, Pasker, RL, Newgard, CB, and Casey, PJ. "Deletion of GαZ protein protects against diet-induced glucose intolerance via expansion of β-cell mass." J Biol Chem 287.24 (June 8, 2012): 20344-20355.
PMID
22457354
Source
pubmed
Published In
The Journal of biological chemistry
Volume
287
Issue
24
Publish Date
2012
Start Page
20344
End Page
20355
DOI
10.1074/jbc.M112.359745

The problem of establishing relationships between hepatic steatosis and hepatic insulin resistance.

Excessive deposition of fat in the liver (hepatic steatosis) is frequently accompanied by hepatic insulin resistance. Whether this correlation is due to a causal relationship between the conditions has been the subject of considerable debate, and the literature abounds with conflicting data and theories. Here we provide a perspective by defining the problem and its challenges, analyzing the possible causative relationships, and drawing some conclusions.

Authors
Farese, RV; Zechner, R; Newgard, CB; Walther, TC
MLA Citation
Farese, RV, Zechner, R, Newgard, CB, and Walther, TC. "The problem of establishing relationships between hepatic steatosis and hepatic insulin resistance." Cell Metab 15.5 (May 2, 2012): 570-573.
PMID
22560209
Source
pubmed
Published In
Cell Metabolism
Volume
15
Issue
5
Publish Date
2012
Start Page
570
End Page
573
DOI
10.1016/j.cmet.2012.03.004

Ablation of steroid receptor coactivator-3 resembles the human CACT metabolic myopathy.

Oxidation of lipid substrates is essential for survival in fasting and other catabolic conditions, sparing glucose for the brain and other glucose-dependent tissues. Here we show Steroid Receptor Coactivator-3 (SRC-3) plays a central role in long chain fatty acid metabolism by directly regulating carnitine/acyl-carnitine translocase (CACT) gene expression. Genetic deficiency of CACT in humans is accompanied by a constellation of metabolic and toxicity phenotypes including hypoketonemia, hypoglycemia, hyperammonemia, and impaired neurologic, cardiac and skeletal muscle performance, each of which is apparent in mice lacking SRC-3 expression. Consistent with human cases of CACT deficiency, dietary rescue with short chain fatty acids drastically attenuates the clinical hallmarks of the disease in mice devoid of SRC-3. Collectively, our results position SRC-3 as a key regulator of β-oxidation. Moreover, these findings allow us to consider platform coactivators such as the SRCs as potential contributors to syndromes such as CACT deficiency, previously considered as monogenic.

Authors
York, B; Reineke, EL; Sagen, JV; Nikolai, BC; Zhou, S; Louet, J-F; Chopra, AR; Chen, X; Reed, G; Noebels, J; Adesina, AM; Yu, H; Wong, L-JC; Tsimelzon, A; Hilsenbeck, S; Stevens, RD; Wenner, BR; Ilkayeva, O; Xu, J; Newgard, CB; O'Malley, BW
MLA Citation
York, B, Reineke, EL, Sagen, JV, Nikolai, BC, Zhou, S, Louet, J-F, Chopra, AR, Chen, X, Reed, G, Noebels, J, Adesina, AM, Yu, H, Wong, L-JC, Tsimelzon, A, Hilsenbeck, S, Stevens, RD, Wenner, BR, Ilkayeva, O, Xu, J, Newgard, CB, and O'Malley, BW. "Ablation of steroid receptor coactivator-3 resembles the human CACT metabolic myopathy." Cell Metab 15.5 (May 2, 2012): 752-763.
PMID
22560224
Source
pubmed
Published In
Cell Metabolism
Volume
15
Issue
5
Publish Date
2012
Start Page
752
End Page
763
DOI
10.1016/j.cmet.2012.03.020

Interplay between lipids and branched-chain amino acids in development of insulin resistance.

Fatty acids (FA) and FA-derived metabolites have long been implicated in the development of insulin resistance and type 2 diabetes. Surprisingly, application of metabolomics technologies has revealed that branched-chain amino acids (BCAA) and related metabolites are more strongly associated with insulin resistance than many common lipid species. Moreover, the BCAA-related signature is predictive of incident diabetes and intervention outcomes and uniquely responsive to therapeutic interventions. Nevertheless, in animal feeding studies, BCAA supplementation requires the background of a high-fat diet to promote insulin resistance. This Perspective develops a model to explain how lipids and BCAA may synergize to promote metabolic diseases.

Authors
Newgard, CB
MLA Citation
Newgard, CB. "Interplay between lipids and branched-chain amino acids in development of insulin resistance." Cell Metab 15.5 (May 2, 2012): 606-614. (Review)
PMID
22560213
Source
pubmed
Published In
Cell Metabolism
Volume
15
Issue
5
Publish Date
2012
Start Page
606
End Page
614
DOI
10.1016/j.cmet.2012.01.024

Baseline metabolomic profiles predict cardiovascular events in patients at risk for coronary artery disease.

BACKGROUND: Cardiovascular risk models remain incomplete. Small-molecule metabolites may reflect underlying disease and, as such, serve as novel biomarkers of cardiovascular risk. METHODS: We studied 2,023 consecutive patients undergoing cardiac catheterization. Mass spectrometry profiling of 69 metabolites and lipid assessments were performed in fasting plasma. Principal component analysis reduced metabolites to a smaller number of uncorrelated factors. Independent relationships between factors and time-to-clinical events were assessed using Cox modeling. Clinical and metabolomic models were compared using log-likelihood and reclassification analyses. RESULTS: At median follow-up of 3.1 years, there were 232 deaths and 294 death/myocardial infarction (MI) events. Five of 13 metabolite factors were independently associated with mortality: factor 1 (medium-chain acylcarnitines: hazard ratio [HR] 1.12 [95% CI, 1.04-1.21], P = .005), factor 2 (short-chain dicarboxylacylcarnitines: HR 1.17 [1.05-1.31], P = .005), factor 3 (long-chain dicarboxylacylcarnitines: HR 1.14 [1.05-1.25], P = .002); factor 6 (branched-chain amino acids: HR 0.86 [0.75-0.99], P = .03), and factor 12 (fatty acids: HR 1.19 [1.06-1.35], P = .004). Three factors independently predicted death/MI: factor 2 (HR 1.11 [1.01-1.23], P = .04), factor 3 (HR 1.13 [1.04-1.22], P = .005), and factor 12 (HR 1.18 [1.05-1.32], P = .004). For mortality, 27% of intermediate-risk patients were correctly reclassified (net reclassification improvement 8.8%, integrated discrimination index 0.017); for death/MI model, 11% were correctly reclassified (net reclassification improvement 3.9%, integrated discrimination index 0.012). CONCLUSIONS: Metabolic profiles predict cardiovascular events independently of standard predictors.

Authors
Shah, SH; Sun, J-L; Stevens, RD; Bain, JR; Muehlbauer, MJ; Pieper, KS; Haynes, C; Hauser, ER; Kraus, WE; Granger, CB; Newgard, CB; Califf, RM; Newby, LK
MLA Citation
Shah, SH, Sun, J-L, Stevens, RD, Bain, JR, Muehlbauer, MJ, Pieper, KS, Haynes, C, Hauser, ER, Kraus, WE, Granger, CB, Newgard, CB, Califf, RM, and Newby, LK. "Baseline metabolomic profiles predict cardiovascular events in patients at risk for coronary artery disease." Am Heart J 163.5 (May 2012): 844-850.e1.
PMID
22607863
Source
pubmed
Published In
American Heart Journal
Volume
163
Issue
5
Publish Date
2012
Start Page
844
End Page
850.e1
DOI
10.1016/j.ahj.2012.02.005

Metabolic profiles predict adverse events after coronary artery bypass grafting.

OBJECTIVE: Clinical models incompletely predict the outcomes after coronary artery bypass grafting. Novel molecular technologies can identify biomarkers to improve risk stratification. We examined whether metabolic profiles can predict adverse events in patients undergoing coronary artery bypass grafting. METHODS: The study population comprised 478 subjects from the CATHGEN biorepository of patients referred for cardiac catheterization who underwent coronary artery bypass grafting after enrollment. Targeted mass spectrometry-based profiling of 69 metabolites was performed in frozen, fasting plasma samples collected before surgery. Principal components analysis and Cox proportional hazards regression modeling were used to assess the relation between the metabolite factor levels and a composite outcome of postcoronary artery bypass grafting myocardial infarction, the need for percutaneous coronary intervention, repeat coronary artery bypass grafting, and death. RESULTS: During a mean follow-up period of 4.3 ± 2.4 years, 126 subjects (26.4%) experienced an adverse event. Three principal components analysis-derived factors were significantly associated with an adverse outcome on univariate analysis: short-chain dicarboxylacylcarnitines (factor 2, P = .001); ketone-related metabolites (factor 5, P = .02); and short-chain acylcarnitines (factor 6, P = .004). These 3 factors remained independently predictive of an adverse outcome after multivariate adjustment: factor 2 (adjusted hazard ratio, 1.23; 95% confidence interval, 1.10-1.38; P < .001), factor 5 (odds ratio, 1.17; 95% confidence interval, 1.01-1.37; P = .04), and factor 6 (odds ratio, 1.14; 95% confidence interval, 1.02-1.27; P = .03). CONCLUSIONS: Metabolic profiles are independently associated with adverse outcomes after coronary artery bypass grafting. These profiles might represent novel biomarkers of risk that can augment existing tools for risk stratification of coronary artery bypass grafting patients and might elucidate novel biochemical pathways that mediate risk.

Authors
Shah, AA; Craig, DM; Sebek, JK; Haynes, C; Stevens, RC; Muehlbauer, MJ; Granger, CB; Hauser, ER; Newby, LK; Newgard, CB; Kraus, WE; Hughes, GC; Shah, SH
MLA Citation
Shah, AA, Craig, DM, Sebek, JK, Haynes, C, Stevens, RC, Muehlbauer, MJ, Granger, CB, Hauser, ER, Newby, LK, Newgard, CB, Kraus, WE, Hughes, GC, and Shah, SH. "Metabolic profiles predict adverse events after coronary artery bypass grafting." J Thorac Cardiovasc Surg 143.4 (April 2012): 873-878.
PMID
22306227
Source
pubmed
Published In
Journal of Thoracic and Cardiovascular Surgery
Volume
143
Issue
4
Publish Date
2012
Start Page
873
End Page
878
DOI
10.1016/j.jtcvs.2011.09.070

Deletion of CaMKK2 from the liver lowers blood glucose and improves whole-body glucose tolerance in the mouse.

Ca(2+)/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a member of the Ca(2+)/CaM-dependent protein kinase family that is expressed abundantly in brain. Previous work has revealed that CaMKK2 knockout (CaMKK2 KO) mice eat less due to a central nervous system -signaling defect and are protected from diet-induced obesity, glucose intolerance, and insulin resistance. However, here we show that pair feeding of wild-type mice to match food consumption of CAMKK2 mice slows weight gain but fails to protect from diet-induced glucose intolerance, suggesting that other alterations in CaMKK2 KO mice are responsible for their improved glucose metabolism. CaMKK2 is shown to be expressed in liver and acute, specific reduction of the kinase in the liver of high-fat diet-fed CaMKK2(floxed) mice results in lowered blood glucose and improved glucose tolerance. Primary hepatocytes isolated from CaMKK2 KO mice produce less glucose and have decreased mRNA encoding peroxisome proliferator-activated receptor γ coactivator 1-α and the gluconeogenic enzymes glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, and these mRNA fail to respond specifically to the stimulatory effect of catecholamine in a cell-autonomous manner. The mechanism responsible for suppressed gene induction in CaMKK2 KO hepatocytes may involve diminished phosphorylation of histone deacetylase 5, an event necessary in some contexts for derepression of the peroxisome proliferator-activated receptor γ coactivator 1-α promoter. Hepatocytes from CaMKK2 KO mice also show increased rates of de novo lipogenesis and fat oxidation. The changes in fat metabolism observed correlate with steatotic liver and altered acyl carnitine metabolomic profiles in CaMKK2 KO mice. Collectively, these results are consistent with suppressed catecholamine-induced induction of gluconeogenic gene expression in CaMKK2 KO mice that leads to improved whole-body glucose homeostasis despite the presence of increased hepatic fat content.

Authors
Anderson, KA; Lin, F; Ribar, TJ; Stevens, RD; Muehlbauer, MJ; Newgard, CB; Means, AR
MLA Citation
Anderson, KA, Lin, F, Ribar, TJ, Stevens, RD, Muehlbauer, MJ, Newgard, CB, and Means, AR. "Deletion of CaMKK2 from the liver lowers blood glucose and improves whole-body glucose tolerance in the mouse." Mol Endocrinol 26.2 (February 2012): 281-291.
PMID
22240810
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
26
Issue
2
Publish Date
2012
Start Page
281
End Page
291
DOI
10.1210/me.2011-1299

Branched-chain amino acid levels are associated with improvement in insulin resistance with weight loss.

AIMS/HYPOTHESIS: Insulin resistance (IR) improves with weight loss, but this response is heterogeneous. We hypothesised that metabolomic profiling would identify biomarkers predicting changes in IR with weight loss. METHODS: Targeted mass spectrometry-based profiling of 60 metabolites, plus biochemical assays of NEFA, β-hydroxybutyrate, ketones, insulin and glucose were performed in baseline and 6 month plasma samples from 500 participants who had lost ≥4 kg during Phase I of the Weight Loss Maintenance (WLM) trial. Homeostatic model assessment of insulin resistance (HOMA-IR) and change in HOMA-IR with weight loss (∆HOMA-IR) were calculated. Principal components analysis (PCA) and mixed models adjusted for race, sex, baseline weight, and amount of weight loss were used; findings were validated in an independent cohort of patients (n = 22). RESULTS: Mean weight loss was 8.67 ± 4.28 kg; mean ∆HOMA-IR was -0.80 ± 1.73, range -28.9 to 4.82). Baseline PCA-derived factor 3 (branched chain amino acids [BCAAs] and associated catabolites) correlated with baseline HOMA-IR (r = 0.50, p < 0.0001) and independently associated with ∆HOMA-IR (p < 0.0001). ∆HOMA-IR increased in a linear fashion with increasing baseline factor 3 quartiles. Amount of weight loss was only modestly correlated with ∆HOMA-IR (r = 0.24). These findings were validated in the independent cohort, with a factor composed of BCAAs and related metabolites predicting ∆HOMA-IR (p = 0.007). CONCLUSIONS/INTERPRETATION: A cluster of metabolites comprising BCAAs and related analytes predicts improvement in HOMA-IR independent of the amount of weight lost. These results may help identify individuals most likely to benefit from moderate weight loss and elucidate novel mechanisms of IR in obesity.

Authors
Shah, SH; Crosslin, DR; Haynes, CS; Nelson, S; Turer, CB; Stevens, RD; Muehlbauer, MJ; Wenner, BR; Bain, JR; Laferrère, B; Gorroochurn, P; Teixeira, J; Brantley, PJ; Stevens, VJ; Hollis, JF; Appel, LJ; Lien, LF; Batch, B; Newgard, CB; Svetkey, LP
MLA Citation
Shah, SH, Crosslin, DR, Haynes, CS, Nelson, S, Turer, CB, Stevens, RD, Muehlbauer, MJ, Wenner, BR, Bain, JR, Laferrère, B, Gorroochurn, P, Teixeira, J, Brantley, PJ, Stevens, VJ, Hollis, JF, Appel, LJ, Lien, LF, Batch, B, Newgard, CB, and Svetkey, LP. "Branched-chain amino acid levels are associated with improvement in insulin resistance with weight loss." Diabetologia 55.2 (February 2012): 321-330.
PMID
22065088
Source
pubmed
Published In
Diabetologia
Volume
55
Issue
2
Publish Date
2012
Start Page
321
End Page
330
DOI
10.1007/s00125-011-2356-5

Caloric restriction alters the metabolic response to a mixed-meal: results from a randomized, controlled trial.

OBJECTIVES: To determine if caloric restriction (CR) would cause changes in plasma metabolic intermediates in response to a mixed meal, suggestive of changes in the capacity to adapt fuel oxidation to fuel availability or metabolic flexibility, and to determine how any such changes relate to insulin sensitivity (S(I)). METHODS: Forty-six volunteers were randomized to a weight maintenance diet (Control), 25% CR, or 12.5% CR plus 12.5% energy deficit from structured aerobic exercise (CR+EX), or a liquid calorie diet (890 kcal/d until 15% reduction in body weight)for six months. Fasting and postprandial plasma samples were obtained at baseline, three, and six months. A targeted mass spectrometry-based platform was used to measure concentrations of individual free fatty acids (FFA), amino acids (AA), and acylcarnitines (AC). S(I) was measured with an intravenous glucose tolerance test. RESULTS: Over three and six months, there were significantly larger differences in fasting-to-postprandial (FPP) concentrations of medium and long chain AC (byproducts of FA oxidation) in the CR relative to Control and a tendency for the same in CR+EX (CR-3 month P = 0.02; CR-6 month P = 0.002; CR+EX-3 month P = 0.09; CR+EX-6 month P = 0.08). After three months of CR, there was a trend towards a larger difference in FPP FFA concentrations (P = 0.07; CR-3 month P = 0.08). Time-varying differences in FPP concentrations of AC and AA were independently related to time-varying S(I) (P<0.05 for both). CONCLUSIONS: Based on changes in intermediates of FA oxidation following a food challenge, CR imparted improvements in metabolic flexibility that correlated with improvements in S(I). TRIAL REGISTRATION: ClinicalTrials.gov NCT00099151.

Authors
Huffman, KM; Redman, LM; Landerman, LR; Pieper, CF; Stevens, RD; Muehlbauer, MJ; Wenner, BR; Bain, JR; Kraus, VB; Newgard, CB; Ravussin, E; Kraus, WE
MLA Citation
Huffman, KM, Redman, LM, Landerman, LR, Pieper, CF, Stevens, RD, Muehlbauer, MJ, Wenner, BR, Bain, JR, Kraus, VB, Newgard, CB, Ravussin, E, and Kraus, WE. "Caloric restriction alters the metabolic response to a mixed-meal: results from a randomized, controlled trial." PLoS One 7.4 (2012): e28190-.
Website
http://hdl.handle.net/10161/10872
PMID
22523532
Source
pubmed
Published In
PloS one
Volume
7
Issue
4
Publish Date
2012
Start Page
e28190
DOI
10.1371/journal.pone.0028190

Daily variation of serum acylcarnitines and amino acids

To characterize daily variation of amino acids (AAs) and acylcarnitines (ACs) in response to feeding and activity, we measured serum metabolites at various times and after various activities during the day. Subjects were admitted overnight for serial serum sampling, collected in the evening (6-8 p. m., n = 40), before rising from bed or eating (8 a. m., n = 40), 1 h after rising but before eating (9 a. m., n = 20), 1-2 h after rising and breakfast (9-10 a. m., n = 40), and at noon (12 p. m., n = 20). Measurements of 15 AAs and 45 ACs were performed by quantitative tandem mass spectrometry using stable-isotope dilution. Coefficients of variation within and between patients were calculated for individual metabolite values and factors derived from principal components analysis. The change of state between timepoints was evaluated by nearest neighbor non-parametric analysis of values at one timepoint compared to the next subsequent value. Relative to baseline a. m. recumbent concentrations, AA concentrations rose after activity and feeding while AC concentrations rose after activity and decreased with feeding. Furthermore, for all AAs, ACs, and their factors, biological variation was quantifiably evident and distinct from daily variation. This study confirms the daily variation of AAs and provides the first report of daily variation for a large panel of ACs. Although standardization of sample collection is highly desirable to control for daily variation (within a subject due to activity or feeding), this study demonstrated measurable biological variability (across subjects) suggesting that non-standardized sample collections could potentially provide insights into specific AA and AC metabolic pathways and disease mechanisms. © 2011 Springer Science+Business Media, LLC.

Authors
Thompson, DK; Sloane, R; Bain, JR; Stevens, RD; Newgard, CB; Pieper, CF; Kraus, VB
MLA Citation
Thompson, DK, Sloane, R, Bain, JR, Stevens, RD, Newgard, CB, Pieper, CF, and Kraus, VB. "Daily variation of serum acylcarnitines and amino acids." Metabolomics 8.4 (2012): 556-565.
PMID
25067934
Source
scival
Published In
Metabolomics
Volume
8
Issue
4
Publish Date
2012
Start Page
556
End Page
565
DOI
10.1007/s11306-011-0345-9

Mig-6 plays a critical role in the regulation of cholesterol homeostasis and bile acid synthesis.

The disruption of cholesterol homeostasis leads to an increase in cholesterol levels which results in the development of cardiovascular disease. Mitogen Inducible Gene 6 (Mig-6) is an immediate early response gene that can be induced by various mitogens, stresses, and hormones. To identify the metabolic role of Mig-6 in the liver, we conditionally ablated Mig-6 in the liver using the Albumin-Cre mouse model (Alb(cre/+)Mig-6(f/f); Mig-6(d/d)). Mig-6(d/d) mice exhibit hepatomegaly and fatty liver. Serum levels of total, LDL, and HDL cholesterol and hepatic lipid were significantly increased in the Mig-6(d/d) mice. The daily excretion of fecal bile acids was significantly decreased in the Mig-6(d/d) mice. DNA microarray analysis of mRNA isolated from the livers of these mice showed alterations in genes that regulate lipid metabolism, bile acid, and cholesterol synthesis, while the expression of genes that regulate biliary excretion of bile acid and triglyceride synthesis showed no difference in the Mig-6(d/d) mice compared to Mig-6(f/f) controls. These results indicate that Mig-6 plays an important role in cholesterol homeostasis and bile acid synthesis. Mice with liver specific conditional ablation of Mig-6 develop hepatomegaly and increased intrahepatic lipid and provide a novel model system to investigate the genetic and molecular events involved in the regulation of cholesterol homeostasis and bile acid synthesis. Defining the molecular mechanisms by which Mig-6 regulates cholesterol homeostasis will provide new insights into the development of more effective ways for the treatment and prevention of cardiovascular disease.

Authors
Ku, BJ; Kim, TH; Lee, JH; Buras, ED; White, LD; Stevens, RD; Ilkayeva, OR; Bain, JR; Newgard, CB; DeMayo, FJ; Jeong, J-W
MLA Citation
Ku, BJ, Kim, TH, Lee, JH, Buras, ED, White, LD, Stevens, RD, Ilkayeva, OR, Bain, JR, Newgard, CB, DeMayo, FJ, and Jeong, J-W. "Mig-6 plays a critical role in the regulation of cholesterol homeostasis and bile acid synthesis." PLoS One 7.8 (2012): e42915-.
PMID
22912762
Source
pubmed
Published In
PloS one
Volume
7
Issue
8
Publish Date
2012
Start Page
e42915
DOI
10.1371/journal.pone.0042915

Metabolomic profiling reveals mitochondrial-derived lipid biomarkers that drive obesity-associated inflammation.

Obesity has reached epidemic proportions worldwide. Several animal models of obesity exist, but studies are lacking that compare traditional lard-based high fat diets (HFD) to "Cafeteria diets" (CAF) consisting of nutrient poor human junk food. Our previous work demonstrated the rapid and severe obesogenic and inflammatory consequences of CAF compared to HFD including rapid weight gain, markers of Metabolic Syndrome, multi-tissue lipid accumulation, and dramatic inflammation. To identify potential mediators of CAF-induced obesity and Metabolic Syndrome, we used metabolomic analysis to profile serum, muscle, and white adipose from rats fed CAF, HFD, or standard control diets. Principle component analysis identified elevations in clusters of fatty acids and acylcarnitines. These increases in metabolites were associated with systemic mitochondrial dysfunction that paralleled weight gain, physiologic measures of Metabolic Syndrome, and tissue inflammation in CAF-fed rats. Spearman pairwise correlations between metabolites, physiologic, and histologic findings revealed strong correlations between elevated markers of inflammation in CAF-fed animals, measured as crown like structures in adipose, and specifically the pro-inflammatory saturated fatty acids and oxidation intermediates laurate and lauroyl carnitine. Treatment of bone marrow-derived macrophages with lauroyl carnitine polarized macrophages towards the M1 pro-inflammatory phenotype through downregulation of AMPK and secretion of pro-inflammatory cytokines. Results presented herein demonstrate that compared to a traditional HFD model, the CAF diet provides a robust model for diet-induced human obesity, which models Metabolic Syndrome-related mitochondrial dysfunction in serum, muscle, and adipose, along with pro-inflammatory metabolite alterations. These data also suggest that modifying the availability or metabolism of saturated fatty acids may limit the inflammation associated with obesity leading to Metabolic Syndrome.

Authors
Sampey, BP; Freemerman, AJ; Zhang, J; Kuan, P-F; Galanko, JA; O'Connell, TM; Ilkayeva, OR; Muehlbauer, MJ; Stevens, RD; Newgard, CB; Brauer, HA; Troester, MA; Makowski, L
MLA Citation
Sampey, BP, Freemerman, AJ, Zhang, J, Kuan, P-F, Galanko, JA, O'Connell, TM, Ilkayeva, OR, Muehlbauer, MJ, Stevens, RD, Newgard, CB, Brauer, HA, Troester, MA, and Makowski, L. "Metabolomic profiling reveals mitochondrial-derived lipid biomarkers that drive obesity-associated inflammation." PLoS One 7.6 (2012): e38812-.
PMID
22701716
Source
pubmed
Published In
PloS one
Volume
7
Issue
6
Publish Date
2012
Start Page
e38812
DOI
10.1371/journal.pone.0038812

SRC-2 coactivator deficiency decreases functional reserve in response to pressure overload of mouse heart.

A major component of the cardiac stress response is the simultaneous activation of several gene regulatory networks. Interestingly, the transcriptional regulator steroid receptor coactivator-2, SRC-2 is often decreased during cardiac failure in humans. We postulated that SRC-2 suppression plays a mechanistic role in the stress response and that SRC-2 activity is an important regulator of the adult heart gene expression profile. Genome-wide microarray analysis, confirmed with targeted gene expression analyses revealed that genetic ablation of SRC-2 activates the "fetal gene program" in adult mice as manifested by shifts in expression of a) metabolic and b) sarcomeric genes, as well as associated modulating transcription factors. While these gene expression changes were not accompanied by changes in left ventricular weight or cardiac function, imposition of transverse aortic constriction (TAC) predisposed SRC-2 knockout (KO) mice to stress-induced cardiac dysfunction. In addition, SRC-2 KO mice lacked the normal ventricular hypertrophic response as indicated through heart weight, left ventricular wall thickness, and blunted molecular signaling known to activate hypertrophy. Our results indicate that SRC-2 is involved in maintenance of the steady-state adult heart transcriptional profile, with its ablation inducing transcriptional changes that mimic a stressed heart. These results further suggest that SRC-2 deletion interferes with the timing and integration needed to respond efficiently to stress through disruption of metabolic and sarcomeric gene expression and hypertrophic signaling, the three key stress responsive pathways.

Authors
Reineke, EL; York, B; Stashi, E; Chen, X; Tsimelzon, A; Xu, J; Newgard, CB; Taffet, GE; Taegtmeyer, H; Entman, ML; O'Malley, BW
MLA Citation
Reineke, EL, York, B, Stashi, E, Chen, X, Tsimelzon, A, Xu, J, Newgard, CB, Taffet, GE, Taegtmeyer, H, Entman, ML, and O'Malley, BW. "SRC-2 coactivator deficiency decreases functional reserve in response to pressure overload of mouse heart." PLoS One 7.12 (2012): e53395-.
PMID
23300926
Source
pubmed
Published In
PloS one
Volume
7
Issue
12
Publish Date
2012
Start Page
e53395
DOI
10.1371/journal.pone.0053395

Effect of heparin administration on metabolomic profiles in samples obtained during cardiac catheterization.

BACKGROUND: Metabolic profiling holds promise for early detection of coronary artery disease and assessing risk for ischemic events. Heparin is frequently administered (1) to treat acute coronary syndromes; and (2) during routine cardiac catheterization procedures. Because it stimulates lipolysis, heparin is a potential confounder of metabolic profiling in these populations. METHODS AND RESULTS: Using mass spectrometry and conventional immunoassays, we evaluated how unfractionated heparin administration affected 69 peripheral blood metabolites (acylcarnitines, amino acids, nonesterified fatty acids and their oxidation byproducts, conventional lipids, glucose, and C-reactive protein) in samples obtained pre- and postcardiac catheterization from 19 patients who received heparin and 10 patients who did not. Using unpaired t tests, we compared the changes in mean metabolite levels before and after the procedure between the nonheparin and heparin groups. Clinical characteristics of the nonheparin and heparin groups, indication for cardiac catheterization, procedure performed, and other periprocedural variables were similar. The mean change between pre- and postprocedure β-hydroxybutyrate (5.43 versus 66.84 μmol/L; P=0.009), ketones (21.17 versus 98.49 μmol/L; P=0.009), nonesterified fatty acids (0.37 versus 1.20 mmol/L; P=0.017), and triglycerides (-9.33 versus -36.50 mg/dL; P=0.007) was significantly different between the nonheparin and heparin groups, respectively. There were no significant differences between groups in the other metabolites measured. CONCLUSIONS: Heparin administration during cardiac catheterization induced changes in peripheral blood metabolites that were consistent with known lipolytic effects of heparin and define a metabolite signature associated with heparin administration. These findings are important for accurate interpretation of future metabolic profiling studies in populations exposed to heparin.

Authors
Brunner, MP; Shah, SH; Craig, DM; Stevens, RD; Muehlbauer, MJ; Bain, JR; Newgard, CB; Kraus, WE; Granger, CB; Sketch, MH; Newby, LK
MLA Citation
Brunner, MP, Shah, SH, Craig, DM, Stevens, RD, Muehlbauer, MJ, Bain, JR, Newgard, CB, Kraus, WE, Granger, CB, Sketch, MH, and Newby, LK. "Effect of heparin administration on metabolomic profiles in samples obtained during cardiac catheterization." Circ Cardiovasc Genet 4.6 (December 2011): 695-700.
PMID
22010138
Source
pubmed
Published In
Circulation: Cardiovascular Genetics
Volume
4
Issue
6
Publish Date
2011
Start Page
695
End Page
700
DOI
10.1161/CIRCGENETICS.111.960575

The impact of a consortium of fermented milk strains on the gut microbiome of gnotobiotic mice and monozygotic twins.

Understanding how the human gut microbiota and host are affected by probiotic bacterial strains requires carefully controlled studies in humans and in mouse models of the gut ecosystem where potentially confounding variables that are difficult to control in humans can be constrained. Therefore, we characterized the fecal microbiomes and metatranscriptomes of adult female monozygotic twin pairs through repeated sampling 4 weeks before, 7 weeks during, and 4 weeks after consumption of a commercially available fermented milk product (FMP) containing a consortium of Bifidobacterium animalis subsp. lactis, two strains of Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis subsp. cremoris, and Streptococcus thermophilus. In addition, gnotobiotic mice harboring a 15-species model human gut microbiota whose genomes contain 58,399 known or predicted protein-coding genes were studied before and after gavage with all five sequenced FMP strains. No significant changes in bacterial species composition or in the proportional representation of genes encoding known enzymes were observed in the feces of humans consuming the FMP. Only minimal changes in microbiota configuration were noted in mice after single or repeated gavage with the FMP consortium. However, RNA-Seq analysis of fecal samples and follow-up mass spectrometry of urinary metabolites disclosed that introducing the FMP strains into mice results in significant changes in expression of microbiome-encoded enzymes involved in numerous metabolic pathways, most prominently those related to carbohydrate metabolism. B. animalis subsp. lactis, the dominant persistent member of the FMP consortium in gnotobiotic mice, up-regulates a locus in vivo that is involved in the catabolism of xylooligosaccharides, a class of glycans widely distributed in fruits, vegetables, and other foods, underscoring the importance of these sugars to this bacterial species. The human fecal metatranscriptome exhibited significant changes, confined to the period of FMP consumption, that mirror changes in gnotobiotic mice, including those related to plant polysaccharide metabolism. These experiments illustrate a translational research pipeline for characterizing the effects of FMPs on the human gut microbiome.

Authors
McNulty, NP; Yatsunenko, T; Hsiao, A; Faith, JJ; Muegge, BD; Goodman, AL; Henrissat, B; Oozeer, R; Cools-Portier, S; Gobert, G; Chervaux, C; Knights, D; Lozupone, CA; Knight, R; Duncan, AE; Bain, JR; Muehlbauer, MJ; Newgard, CB; Heath, AC; Gordon, JI
MLA Citation
McNulty, NP, Yatsunenko, T, Hsiao, A, Faith, JJ, Muegge, BD, Goodman, AL, Henrissat, B, Oozeer, R, Cools-Portier, S, Gobert, G, Chervaux, C, Knights, D, Lozupone, CA, Knight, R, Duncan, AE, Bain, JR, Muehlbauer, MJ, Newgard, CB, Heath, AC, and Gordon, JI. "The impact of a consortium of fermented milk strains on the gut microbiome of gnotobiotic mice and monozygotic twins." Sci Transl Med 3.106 (October 26, 2011): 106ra106-.
PMID
22030749
Source
pubmed
Published In
Science Translational Medicine
Volume
3
Issue
106
Publish Date
2011
Start Page
106ra106
DOI
10.1126/scitranslmed.3002701

SIRT3 deficiency and mitochondrial protein hyperacetylation accelerate the development of the metabolic syndrome.

Acetylation is increasingly recognized as an important metabolic regulatory posttranslational protein modification, yet the metabolic consequence of mitochondrial protein hyperacetylation is unknown. We find that high-fat diet (HFD) feeding induces hepatic mitochondrial protein hyperacetylation in mice and downregulation of the major mitochondrial protein deacetylase SIRT3. Mice lacking SIRT3 (SIRT3KO) placed on a HFD show accelerated obesity, insulin resistance, hyperlipidemia, and steatohepatitis compared to wild-type (WT) mice. The lipogenic enzyme stearoyl-CoA desaturase 1 is highly induced in SIRT3KO mice, and its deletion rescues both WT and SIRT3KO mice from HFD-induced hepatic steatosis and insulin resistance. We further identify a single nucleotide polymorphism in the human SIRT3 gene that is suggestive of a genetic association with the metabolic syndrome. This polymorphism encodes a point mutation in the SIRT3 protein, which reduces its overall enzymatic efficiency. Our findings show that loss of SIRT3 and dysregulation of mitochondrial protein acetylation contribute to the metabolic syndrome.

Authors
Hirschey, MD; Shimazu, T; Jing, E; Grueter, CA; Collins, AM; Aouizerat, B; Stančáková, A; Goetzman, E; Lam, MM; Schwer, B; Stevens, RD; Muehlbauer, MJ; Kakar, S; Bass, NM; Kuusisto, J; Laakso, M; Alt, FW; Newgard, CB; Farese, RV; Kahn, CR; Verdin, E
MLA Citation
Hirschey, MD, Shimazu, T, Jing, E, Grueter, CA, Collins, AM, Aouizerat, B, Stančáková, A, Goetzman, E, Lam, MM, Schwer, B, Stevens, RD, Muehlbauer, MJ, Kakar, S, Bass, NM, Kuusisto, J, Laakso, M, Alt, FW, Newgard, CB, Farese, RV, Kahn, CR, and Verdin, E. "SIRT3 deficiency and mitochondrial protein hyperacetylation accelerate the development of the metabolic syndrome." Mol Cell 44.2 (October 21, 2011): 177-190.
PMID
21856199
Source
pubmed
Published In
Molecular Cell
Volume
44
Issue
2
Publish Date
2011
Start Page
177
End Page
190
DOI
10.1016/j.molcel.2011.07.019

Cafeteria diet is a robust model of human metabolic syndrome with liver and adipose inflammation: comparison to high-fat diet.

Obesity has reached epidemic proportions worldwide and reports estimate that American children consume up to 25% of calories from snacks. Several animal models of obesity exist, but studies are lacking that compare high-fat diets (HFD) traditionally used in rodent models of diet-induced obesity (DIO) to diets consisting of food regularly consumed by humans, including high-salt, high-fat, low-fiber, energy dense foods such as cookies, chips, and processed meats. To investigate the obesogenic and inflammatory consequences of a cafeteria diet (CAF) compared to a lard-based 45% HFD in rodent models, male Wistar rats were fed HFD, CAF or chow control diets for 15 weeks. Body weight increased dramatically and remained significantly elevated in CAF-fed rats compared to all other diets. Glucose- and insulin-tolerance tests revealed that hyperinsulinemia, hyperglycemia, and glucose intolerance were exaggerated in the CAF-fed rats compared to controls and HFD-fed rats. It is well-established that macrophages infiltrate metabolic tissues at the onset of weight gain and directly contribute to inflammation, insulin resistance, and obesity. Although both high fat diets resulted in increased adiposity and hepatosteatosis, CAF-fed rats displayed remarkable inflammation in white fat, brown fat and liver compared to HFD and controls. In sum, the CAF provided a robust model of human metabolic syndrome compared to traditional lard-based HFD, creating a phenotype of exaggerated obesity with glucose intolerance and inflammation. This model provides a unique platform to study the biochemical, genomic and physiological mechanisms of obesity and obesity-related disease states that are pandemic in western civilization today.

Authors
Sampey, BP; Vanhoose, AM; Winfield, HM; Freemerman, AJ; Muehlbauer, MJ; Fueger, PT; Newgard, CB; Makowski, L
MLA Citation
Sampey, BP, Vanhoose, AM, Winfield, HM, Freemerman, AJ, Muehlbauer, MJ, Fueger, PT, Newgard, CB, and Makowski, L. "Cafeteria diet is a robust model of human metabolic syndrome with liver and adipose inflammation: comparison to high-fat diet." Obesity (Silver Spring) 19.6 (June 2011): 1109-1117.
PMID
21331068
Source
pubmed
Published In
Obesity
Volume
19
Issue
6
Publish Date
2011
Start Page
1109
End Page
1117
DOI
10.1038/oby.2011.18

Branching out for detection of type 2 diabetes.

Type 2 diabetes is an epidemic disease worldwide, but it is difficult to predict its appearance in the general population. A recent study demonstrates that circulating concentrations of a small group of essential amino acids predict risk for diabetes, contributing to a recent resurgence of interest in these common analytes.

Authors
Shah, SH; Svetkey, LP; Newgard, CB
MLA Citation
Shah, SH, Svetkey, LP, and Newgard, CB. "Branching out for detection of type 2 diabetes." Cell Metab 13.5 (May 4, 2011): 491-492.
PMID
21531330
Source
pubmed
Published In
Cell Metabolism
Volume
13
Issue
5
Publish Date
2011
Start Page
491
End Page
492
DOI
10.1016/j.cmet.2011.04.003

Plasma acylcarnitines are associated with physical performance in elderly men.

BACKGROUND: Metabolic profiling might provide insight into the biologic underpinnings of disability in older adults. METHODS: A targeted mass spectrometry-based platform was used to identify and quantify 45 plasma acylcarnitines in 77 older men with a mean age of 79 years and average body mass index of 28.4 kg/m(2). To control for type I error inherent in a test of multiple analytes, principal components analysis was employed to reduce the acylcarnitines from 45 separate metabolites, into a single "acylcarnitine factor." We then tested for an association between this acylcarnitine factor and multiple indices of physical performance and self-reported function. RESULTS: The acylcarnitine factor accounted for 40% of the total variance in 45 acylcarnitines. Of the metabolites analyzed, those that contributed most to our one-factor solution were even-numbered medium and long-chain species with side chains containing 10-18 carbons (factor loadings ≥0.70). Odd-numbered chain species, in contrast, had factor loadings 0.50 or less. Acylcarnitine factor scores were inversely related to physical performance as measured by the Short Physical Performance Battery total score, two of its three component scores (gait and chair stands Short Physical Performance Battery), and usual and maximal gait speeds (ρ = -0.324, -0.348, -0.309, -0.241, and -0.254, respectively; p < .05). CONCLUSIONS: Higher acylcarnitine factor scores were associated with lower levels of objectively measured physical performance in this group of older, largely overweight men. Metabolic profiles of rodents exhibiting lipid-induced mitochondrial dysfunction show a similar phenotypic predominance of medium- and long-chain acylcarnitines.

Authors
Lum, H; Sloane, R; Huffman, KM; Kraus, VB; Thompson, DK; Kraus, WE; Bain, JR; Stevens, R; Pieper, CF; Taylor, GA; Newgard, CB; Cohen, HJ; Morey, MC
MLA Citation
Lum, H, Sloane, R, Huffman, KM, Kraus, VB, Thompson, DK, Kraus, WE, Bain, JR, Stevens, R, Pieper, CF, Taylor, GA, Newgard, CB, Cohen, HJ, and Morey, MC. "Plasma acylcarnitines are associated with physical performance in elderly men." J Gerontol A Biol Sci Med Sci 66.5 (May 2011): 548-553.
PMID
21367961
Source
pubmed
Published In
Journals of Gerontology: Series A
Volume
66
Issue
5
Publish Date
2011
Start Page
548
End Page
553
DOI
10.1093/gerona/glr006

Differential metabolic impact of gastric bypass surgery versus dietary intervention in obese diabetic subjects despite identical weight loss.

Glycemic control is improved more after gastric bypass surgery (GBP) than after equivalent diet-induced weight loss in patients with morbid obesity and type 2 diabetes mellitus. We applied metabolomic profiling to understand the mechanisms of this better metabolic response after GBP. Circulating amino acids (AAs) and acylcarnitines (ACs) were measured in plasma from fasted subjects by targeted tandem mass spectrometry before and after a matched 10-kilogram weight loss induced by GBP or diet. Total AAs and branched-chain AAs (BCAAs) decreased after GBP, but not after dietary intervention. Metabolites derived from BCAA oxidation also decreased only after GBP. Principal components (PC) analysis identified two major PCs, one composed almost exclusively of ACs (PC1) and another with BCAAs and their metabolites as major contributors (PC2). PC1 and PC2 were inversely correlated with pro-insulin concentrations, the C-peptide response to oral glucose, and the insulin sensitivity index after weight loss, whereas PC2 was uniquely correlated with levels of insulin resistance (HOMA-IR). These data suggest that the enhanced decrease in circulating AAs after GBP occurs by mechanisms other than weight loss and may contribute to the better improvement in glucose homeostasis observed with the surgical intervention.

Authors
Laferrère, B; Reilly, D; Arias, S; Swerdlow, N; Gorroochurn, P; Bawa, B; Bose, M; Teixeira, J; Stevens, RD; Wenner, BR; Bain, JR; Muehlbauer, MJ; Haqq, A; Lien, L; Shah, SH; Svetkey, LP; Newgard, CB
MLA Citation
Laferrère, B, Reilly, D, Arias, S, Swerdlow, N, Gorroochurn, P, Bawa, B, Bose, M, Teixeira, J, Stevens, RD, Wenner, BR, Bain, JR, Muehlbauer, MJ, Haqq, A, Lien, L, Shah, SH, Svetkey, LP, and Newgard, CB. "Differential metabolic impact of gastric bypass surgery versus dietary intervention in obese diabetic subjects despite identical weight loss." Sci Transl Med 3.80 (April 27, 2011): 80re2-.
PMID
21525399
Source
pubmed
Published In
Science Translational Medicine
Volume
3
Issue
80
Publish Date
2011
Start Page
80re2
DOI
10.1126/scitranslmed.3002043

Regulation of mitochondrial morphology by APC/CCdh1-mediated control of Drp1 stability.

Homeostatic maintenance of cellular mitochondria requires a dynamic balance between fission and fusion, and controlled changes in morphology are important for processes such as apoptosis and cellular division. Interphase mitochondria have been described as an interconnected network that fragments as cells enter mitosis, and this mitotic mitochondrial fragmentation is known to be regulated by the dynamin-related GTPase Drp1 (dynamin-related protein 1), a key component of the mitochondrial division machinery. Loss of Drp1 function and the subsequent failure of mitochondrial division during mitosis lead to incomplete cytokinesis and the unequal distribution of mitochondria into daughter cells. During mitotic exit and interphase, the mitochondrial network reforms. Here we demonstrate that changes in mitochondrial dynamics as cells exit mitosis are driven in part through ubiquitylation of Drp1, catalyzed by the APC/C(Cdh1) (anaphase-promoting complex/cyclosome and its coactivator Cdh1) E3 ubiquitin ligase complex. Importantly, inhibition of Cdh1-mediated Drp1 ubiquitylation and proteasomal degradation during interphase prevents the normal G1 phase regrowth of mitochondrial networks following cell division.

Authors
Horn, SR; Thomenius, MJ; Johnson, ES; Freel, CD; Wu, JQ; Coloff, JL; Yang, C-S; Tang, W; An, J; Ilkayeva, OR; Rathmell, JC; Newgard, CB; Kornbluth, S
MLA Citation
Horn, SR, Thomenius, MJ, Johnson, ES, Freel, CD, Wu, JQ, Coloff, JL, Yang, C-S, Tang, W, An, J, Ilkayeva, OR, Rathmell, JC, Newgard, CB, and Kornbluth, S. "Regulation of mitochondrial morphology by APC/CCdh1-mediated control of Drp1 stability." Mol Biol Cell 22.8 (April 15, 2011): 1207-1216.
PMID
21325626
Source
pubmed
Published In
Molecular Biology of the Cell
Volume
22
Issue
8
Publish Date
2011
Start Page
1207
End Page
1216
DOI
10.1091/mbc.E10-07-0567

Ubiquitin fold modifier 1 (UFM1) and its target UFBP1 protect pancreatic beta cells from ER stress-induced apoptosis.

UFM1 is a member of the ubiquitin like protein family. While the enzymatic cascade of UFM1 conjugation has been elucidated in recent years, the biological function remains largely unknown. In this report we demonstrate that the recently identified C20orf116, which we name UFM1-binding protein 1 containing a PCI domain (UFBP1), and CDK5RAP3 interact with UFM1. Components of the UFM1 conjugation pathway (UFM1, UFBP1, UFL1 and CDK5RAP3) are highly expressed in pancreatic islets of Langerhans and some other secretory tissues. Co-localization of UFM1 with UFBP1 in the endoplasmic reticulum (ER) depends on UFBP1. We demonstrate that ER stress, which is common in secretory cells, induces expression of Ufm1, Ufbp1 and Ufl1 in the beta-cell line INS-1E. siRNA-mediated Ufm1 or Ufbp1 knockdown enhances apoptosis upon ER stress. Silencing the E3 enzyme UFL1, results in similar outcomes, suggesting that UFM1-UFBP1 conjugation is required to prevent ER stress-induced apoptosis. Together, our data suggest that UFM1-UFBP1 participate in preventing ER stress-induced apoptosis in protein secretory cells.

Authors
Lemaire, K; Moura, RF; Granvik, M; Igoillo-Esteve, M; Hohmeier, HE; Hendrickx, N; Newgard, CB; Waelkens, E; Cnop, M; Schuit, F
MLA Citation
Lemaire, K, Moura, RF, Granvik, M, Igoillo-Esteve, M, Hohmeier, HE, Hendrickx, N, Newgard, CB, Waelkens, E, Cnop, M, and Schuit, F. "Ubiquitin fold modifier 1 (UFM1) and its target UFBP1 protect pancreatic beta cells from ER stress-induced apoptosis. (Published online)" PLoS One 6.4 (April 6, 2011): e18517-.
PMID
21494687
Source
pubmed
Published In
PloS one
Volume
6
Issue
4
Publish Date
2011
Start Page
e18517
DOI
10.1371/journal.pone.0018517

Effect of caloric restriction with and without exercise on metabolic intermediates in nonobese men and women.

OBJECTIVES: The objective of the study was to evaluate whether serum concentrations of metabolic intermediates are related to adiposity and insulin sensitivity (Si) in overweight healthy subjects and compare changes in metabolic intermediates with similar weight loss achieved by diet only or diet plus exercise. DESIGN: This was a randomized controlled trial. PARTICIPANTS AND INTERVENTION: The cross-sectional study included 46 (aged 36.8 ± 1.0 yr) overweight (body mass index 27.8 ± 0.7 kg/m(2)) subjects enrolled in a 6-month study of calorie restriction. To determine the effect of diet only or diet plus exercise on metabolic intermediates, 35 subjects were randomized to control (energy intake at 100% of energy requirements); CR (25% calorie restriction), or CR+EX: (12.5% CR plus 12.5% increase in energy expenditure by exercise). MAIN OUTCOME MEASURES: Serum concentrations of eight fatty acids, 15 amino acids, and 45 acylcarnitines (ACs) measured by targeted mass spectrometry. RESULTS: In overweight subjects, the concentrations of C2 AC and long-chain ACs were positively associated with percent fat (R(2) = 0.75, P = 0.0001) and Si (R(2) = 0.12, P = 0.05). The percent fat (R(2) = 0.77, P < 0.0001), abdominal visceral fat (R(2) = 0.64, P < 0.0001), and intrahepatic fat (R(2) = 0.30, P = 0.0002) were positively associated with fatty acid concentrations. There was a significant increase in an AC factor (comprised of C2 and several medium chain ACs) in the CR group (P = 0.01). CONCLUSION: In nonobese subjects, fasted serum ACs are associated with Si and fat mass. Despite similar weight loss, serum ACs increase with CR alone but not CR+EX. A greater improvement in Si with weight loss during CR+EX interventions may be related to improved coupling of β-oxidation and tricarboxylic acid cycle flux induced by exercise.

Authors
Redman, LM; Huffman, KM; Landerman, LR; Pieper, CF; Bain, JR; Muehlbauer, MJ; Stevens, RD; Wenner, BR; Kraus, VB; Newgard, CB; Kraus, WE; Ravussin, E
MLA Citation
Redman, LM, Huffman, KM, Landerman, LR, Pieper, CF, Bain, JR, Muehlbauer, MJ, Stevens, RD, Wenner, BR, Kraus, VB, Newgard, CB, Kraus, WE, and Ravussin, E. "Effect of caloric restriction with and without exercise on metabolic intermediates in nonobese men and women." J Clin Endocrinol Metab 96.2 (February 2011): E312-E321.
PMID
21123443
Source
pubmed
Published In
Journal of Clinical Endocrinology and Metabolism
Volume
96
Issue
2
Publish Date
2011
Start Page
E312
End Page
E321
DOI
10.1210/jc.2010-1971

The metabolic phenotype of Prader-Willi syndrome (PWS) in childhood: heightened insulin sensitivity relative to body mass index.

CONTEXT: Insulin sensitivity is higher in patients with Prader-Willi syndrome (PWS) than in body mass index-matched obese controls (OCs). Factors contributing to the heightened insulin sensitivity of PWS remain obscure. We compared the fasting levels of various hormones, cytokines, lipids, and liver function tests in 14 PWS patients and 14 OCs with those in 14 age- and gender-matched lean children (LC). We hypothesized that metabolic profiles of children with PWS are comparable with those of LC, but different from those of OCs. RESULTS: Leptin levels were comparable in PWS patients and OCs, suggesting comparable degrees of adiposity. Glucose levels were comparable among groups. However, fasting insulin concentrations and homeostasis model assessment insulin resistance index were lower in PWS patients than in OCs (P < 0.05) and similar to LC. Moreover, high-density lipoprotein levels were lower and triglycerides higher in OCs (P < 0.05) but not PWS patients. Total adiponectin, high-molecular-weight (HMW) adiponectin and the HMW to total adiponectin ratio were higher in PWS patients (P < 0.05) than in OCs and similar to LC. High-sensitivity C-reactive protein and IL-6 levels were higher in OCs than in PWS patients or LC (P < 0.05). Nevertheless, PAI-1 levels were elevated in both OC and PWS patients. There were no group differences in glucagon-like peptide-1, macrophage chemoattractant protein-1, TNFα, IL-2, IL-8, IL-10, IL-12p40, IL-18, resistin, total or low-density lipoprotein cholesterol, aspartate aminotransferase, or alanine aminotransferase. CONCLUSIONS: The heightened insulin sensitivity of PWS patients relative to OCs is associated with higher levels of adiponectin and lower levels of high-sensitivity C-reactive protein and IL-6. Future studies will determine whether PWS children are protected from obesity comorbidities such as type 2 diabetes, hyperlipidemia, and nonalcoholic fatty liver disease.

Authors
Haqq, AM; Muehlbauer, MJ; Newgard, CB; Grambow, S; Freemark, M
MLA Citation
Haqq, AM, Muehlbauer, MJ, Newgard, CB, Grambow, S, and Freemark, M. "The metabolic phenotype of Prader-Willi syndrome (PWS) in childhood: heightened insulin sensitivity relative to body mass index." J Clin Endocrinol Metab 96.1 (January 2011): E225-E232.
PMID
20962018
Source
pubmed
Published In
Journal of Clinical Endocrinology and Metabolism
Volume
96
Issue
1
Publish Date
2011
Start Page
E225
End Page
E232
DOI
10.1210/jc.2010-1733

Exercise-induced changes in metabolic intermediates, hormones, and inflammatory markers associated with improvements in insulin sensitivity.

OBJECTIVE: To understand relationships between exercise training-mediated improvements in insulin sensitivity (S(I)) and changes in circulating concentrations of metabolic intermediates, hormones, and inflammatory mediators. RESEARCH DESIGN AND METHODS: Targeted mass spectrometry and enzyme-linked immunosorbent assays were used to quantify metabolic intermediates, hormones, and inflammatory markers at baseline, after 6 months of exercise training, and 2 weeks after exercise training cessation (n = 53). A principal components analysis (PCA) strategy was used to relate changes in these intermediates to changes in S(I). RESULTS: PCA reduced the number of intermediates from 90 to 24 factors composed of biologically related components. With exercise training, improvements in S(I) were associated with reductions in by-products of fatty acid oxidation and increases in glycine and proline (P < 0.05, R² = 0.59); these relationships were retained 15 days after cessation of exercise training (P < 0.05, R² = 0.34). CONCLUSIONS: These observations support prior observations in animal models that exercise training promotes more efficient mitochondrial β-oxidation and challenges current hypotheses regarding exercise training and glycine metabolism.

Authors
Huffman, KM; Slentz, CA; Bateman, LA; Thompson, D; Muehlbauer, MJ; Bain, JR; Stevens, RD; Wenner, BR; Kraus, VB; Newgard, CB; Kraus, WE
MLA Citation
Huffman, KM, Slentz, CA, Bateman, LA, Thompson, D, Muehlbauer, MJ, Bain, JR, Stevens, RD, Wenner, BR, Kraus, VB, Newgard, CB, and Kraus, WE. "Exercise-induced changes in metabolic intermediates, hormones, and inflammatory markers associated with improvements in insulin sensitivity." Diabetes Care 34.1 (January 2011): 174-176.
Website
http://hdl.handle.net/10161/10882
PMID
20921216
Source
pubmed
Published In
Diabetes Care
Volume
34
Issue
1
Publish Date
2011
Start Page
174
End Page
176
DOI
10.2337/dc10-0709

Hepatic acyl-CoA:Diacylglcyerol acyltransferase (DGAT) overexpression, diacylglycerol, and insulin sensitivity

Authors
Monetti, M; Levin, MC; Watt, MJ; Hubbard, BK; Newgard, C; Sr, RVF; Hevener, AL; Jr, RVF
MLA Citation
Monetti, M, Levin, MC, Watt, MJ, Hubbard, BK, Newgard, C, Sr, RVF, Hevener, AL, and Jr, RVF. "Hepatic acyl-CoA:Diacylglcyerol acyltransferase (DGAT) overexpression, diacylglycerol, and insulin sensitivity." Proceedings of the National Academy of Sciences of the United States of America 108.34 (2011): E523-.
PMID
21807991
Source
scival
Published In
Proceedings of the National Academy of Sciences of USA
Volume
108
Issue
34
Publish Date
2011
Start Page
E523
DOI
10.1073/pnas.1108505108

The coactivator SRC-1 is an essential coordinator of hepatic glucose production.

Gluconeogenesis makes a major contribution to hepatic glucose production, a process critical for survival in mammals. In this study, we identify the p160 family member, SRC-1, as a key coordinator of the hepatic gluconeogenic program in vivo. SRC-1-null mice displayed hypoglycemia secondary to a deficit in hepatic glucose production. Selective re-expression of SRC-1 in the liver restored blood glucose levels to a normal range. SRC-1 was found induced upon fasting to coordinate in a cell-autonomous manner, the gene expression of rate-limiting enzymes of the gluconeogenic pathway. At the molecular level, the main role of SRC-1 was to modulate the expression and the activity of C/EBPα through a feed-forward loop in which SRC-1 used C/EBPα to transactivate pyruvate carboxylase, a crucial gene for initiation of the gluconeogenic program. We propose that SRC-1 acts as a critical mediator of glucose homeostasis in the liver by adjusting the transcriptional activity of key genes involved in the hepatic glucose production machinery.

Authors
Louet, J-F; Chopra, AR; Sagen, JV; An, J; York, B; Tannour-Louet, M; Saha, PK; Stevens, RD; Wenner, BR; Ilkayeva, OR; Bain, JR; Zhou, S; DeMayo, F; Xu, J; Newgard, CB; O'Malley, BW
MLA Citation
Louet, J-F, Chopra, AR, Sagen, JV, An, J, York, B, Tannour-Louet, M, Saha, PK, Stevens, RD, Wenner, BR, Ilkayeva, OR, Bain, JR, Zhou, S, DeMayo, F, Xu, J, Newgard, CB, and O'Malley, BW. "The coactivator SRC-1 is an essential coordinator of hepatic glucose production." Cell Metab 12.6 (December 1, 2010): 606-618.
PMID
21109193
Source
pubmed
Published In
Cell Metabolism
Volume
12
Issue
6
Publish Date
2010
Start Page
606
End Page
618
DOI
10.1016/j.cmet.2010.11.009

Dissecting the in vivo metabolic potential of two human gut acetogens.

Fermenting microbial communities generate hydrogen; its removal through the production of acetate, methane, or hydrogen sulfide modulates the efficiency of energy extraction from available nutrients in many ecosystems. We noted that pathway components for acetogenesis are more abundantly and consistently represented in the gut microbiomes of monozygotic twins and their mothers than components for methanogenesis or sulfate reduction and subsequently analyzed the metabolic potential of two sequenced human gut acetogens, Blautia hydrogenotrophica and Marvinbryantia formatexigens in vitro and in the intestines of gnotobiotic mice harboring a prominent saccharolytic bacterium. To do so, we developed a generally applicable method for multiplex sequencing of expressed microbial mRNAs (microbial RNA-Seq) and, together with mass spectrometry of metabolites, showed that these organisms have distinct patterns of substrate utilization. B. hydrogenotrophica targets aliphatic and aromatic amino acids. It increases the efficiency of fermentation by consuming reducing equivalents, thereby maintaining a high NAD(+)/NADH ratio and boosting acetate production. In contrast, M. formatexigens consumes oligosaccharides, does not impact the redox state of the gut, and boosts the yield of succinate. These findings have strategic implications for those who wish to manipulate the hydrogen economy of gut microbial communities in ways that modulate energy harvest.

Authors
Rey, FE; Faith, JJ; Bain, J; Muehlbauer, MJ; Stevens, RD; Newgard, CB; Gordon, JI
MLA Citation
Rey, FE, Faith, JJ, Bain, J, Muehlbauer, MJ, Stevens, RD, Newgard, CB, and Gordon, JI. "Dissecting the in vivo metabolic potential of two human gut acetogens." J Biol Chem 285.29 (July 16, 2010): 22082-22090.
PMID
20444704
Source
pubmed
Published In
The Journal of biological chemistry
Volume
285
Issue
29
Publish Date
2010
Start Page
22082
End Page
22090
DOI
10.1074/jbc.M110.117713

Lower brain-derived neurotrophic factor in patients with prader-willi syndrome compared to obese and lean control subjects.

CONTEXT: Brain-derived neurotrophic factor (BDNF) haploinsufficiency is associated with hyperphagia and obesity in both animals and humans. BDNF appears to function downstream of the leptin-melanocortin signaling pathway to control energy balance. The potential role of BDNF in the etiology of the severe hyperphagia associated with PWS has not been previously explored. OBJECTIVE: The aim was to compare BDNF concentrations in subjects with PWS and obese controls (OC) and lean controls (LC). DESIGN AND SETTING: We conducted a cross-sectional study at an outpatient clinical research center. PARTICIPANTS: We studied 13 subjects with PWS [five females and eight males; mean + or - sd: age, 11.0 + or - 4.1 yr; body mass index (BMI)-Z, 2.05 + or - 0.78], 13 OC (eight females, five males; age, 12.3 + or - 2.7 yr; BMI-Z, 2.18 + or - 0.61), and 13 LC (six females, seven males; age, 12.4 + or - 2.6 yr; BMI-Z, -0.57 + or - 0.73). MAIN OUTCOME MEASURE: BDNF was measured in serum and plasma by ELISA. Analysis of covariance adjusted for age, sex, and BMI-Z. RESULTS: All groups were comparable for age (P = 0.50) and sex distribution (P = 0.49). BMI-Z was comparable between PWS and OC (P = 0.89) and lower in LC (P < 0.001). Adjusted serum BDNF was comparable (P = 0.35) in OC (mean + or - sem: 13.5 + or - 1.2 ng/ml) and LC (19.2 + or - 1.3 ng/ml), but lower in PWS (8.3 + or - 1.2 ng/ml; P = 0.01 vs. OC; P = 0.03 vs. LC). Adjusted plasma BDNF in PWS (217 + or - 130 pg/ml) was lower than OC (422 + or - 126 pg/ml; P = 0.02), but statistically comparable with LC (540 + or - 143 pg/ml; P = 0.10). CONCLUSIONS: Lower BDNF in PWS suggests insufficient central BDNF production because BDNF in peripheral circulation is believed to reflect cerebral BDNF output. Decreased BDNF may be a potential cause for the disordered satiety and morbid obesity associated with PWS. Further studies are needed to confirm this preliminary pilot study in a larger cohort of patients with PWS.

Authors
Han, JC; Muehlbauer, MJ; Cui, HN; Newgard, CB; Haqq, AM
MLA Citation
Han, JC, Muehlbauer, MJ, Cui, HN, Newgard, CB, and Haqq, AM. "Lower brain-derived neurotrophic factor in patients with prader-willi syndrome compared to obese and lean control subjects." J Clin Endocrinol Metab 95.7 (July 2010): 3532-3536.
PMID
20427492
Source
pubmed
Published In
Journal of Clinical Endocrinology and Metabolism
Volume
95
Issue
7
Publish Date
2010
Start Page
3532
End Page
3536
DOI
10.1210/jc.2010-0127

Energetics and metabolism in the failing heart: important but poorly understood.

PURPOSE OF REVIEW: Profound abnormalities in myocardial energy metabolism occur in heart failure and correlate with clinical symptoms and survival. Available comprehensive human metabolic data come from small studies, enrolling patients across heart failure causes, at different disease stages, and using different methodologies, and is often contradictory. Remaining fundamental gaps in knowledge include whether observed shifts in cardiac substrate utilization are adaptive or maladaptive, causal or an epiphenomenon of heart failure. RECENT FINDINGS: Recent studies have characterized the temporal changes in myocardial substrate metabolism involved in progression of heart failure, the role of insulin resistance, and the mechanisms of mitochondrial dysfunction in heart failure. The concept of metabolic inflexibility has been proposed to explain the lack of energetic and mechanical reserve in the failing heart. SUMMARY: Despite current therapies, which provide substantial benefits to patients, heart failure remains a progressive disease, and new approaches to treatment are necessary. Developing metabolic interventions would be facilitated by systems-level integration of current knowledge on myocardial metabolic control. Although preliminary evidence suggests that metabolic modulators inducing a shift towards carbohydrate utilization seem generally beneficial in the failing heart, such interventions should be matched to the stage of metabolic deregulation in the progression of heart failure.

Authors
Turer, AT; Malloy, CR; Newgard, CB; Podgoreanu, MV
MLA Citation
Turer, AT, Malloy, CR, Newgard, CB, and Podgoreanu, MV. "Energetics and metabolism in the failing heart: important but poorly understood." Curr Opin Clin Nutr Metab Care 13.4 (July 2010): 458-465. (Review)
PMID
20453645
Source
pubmed
Published In
Current Opinion in Clinical Nutrition and Metabolic Care
Volume
13
Issue
4
Publish Date
2010
Start Page
458
End Page
465
DOI
10.1097/MCO.0b013e32833a55a5

The mitochondrial 2-oxoglutarate carrier is part of a metabolic pathway that mediates glucose- and glutamine-stimulated insulin secretion.

Glucose-stimulated insulin secretion from pancreatic islet beta-cells is dependent in part on pyruvate cycling through the pyruvate/isocitrate pathway, which generates cytosolic alpha-ketoglutarate, also known as 2-oxoglutarate (2OG). Here, we have investigated if mitochondrial transport of 2OG through the 2-oxoglutarate carrier (OGC) participates in control of nutrient-stimulated insulin secretion. Suppression of OGC in clonal pancreatic beta-cells (832/13 cells) and isolated rat islets by adenovirus-mediated delivery of small interfering RNA significantly decreased glucose-stimulated insulin secretion. OGC suppression also reduced insulin secretion in response to glutamine plus the glutamate dehydrogenase activator 2-amino-2-norbornane carboxylic acid. Nutrient-stimulated increases in glucose usage, glucose oxidation, glutamine oxidation, or ATP:ADP ratio were not affected by OGC knockdown, whereas suppression of OGC resulted in a significant decrease in the NADPH:NADP(+) ratio during stimulation with glucose but not glutamine + 2-amino-2-norbornane carboxylic acid. Finally, OGC suppression reduced insulin secretion in response to a membrane-permeant 2OG analog, dimethyl-2OG. These data reveal that the OGC is part of a mechanism of fuel-stimulated insulin secretion that is common to glucose, amino acid, and organic acid secretagogues, involving flux through the pyruvate/isocitrate cycling pathway. Although the components of this pathway must remain intact for appropriate stimulus-secretion coupling, production of NADPH does not appear to be the universal second messenger signal generated by these reactions.

Authors
Odegaard, ML; Joseph, JW; Jensen, MV; Lu, D; Ilkayeva, O; Ronnebaum, SM; Becker, TC; Newgard, CB
MLA Citation
Odegaard, ML, Joseph, JW, Jensen, MV, Lu, D, Ilkayeva, O, Ronnebaum, SM, Becker, TC, and Newgard, CB. "The mitochondrial 2-oxoglutarate carrier is part of a metabolic pathway that mediates glucose- and glutamine-stimulated insulin secretion." J Biol Chem 285.22 (May 28, 2010): 16530-16537.
PMID
20356834
Source
pubmed
Published In
The Journal of biological chemistry
Volume
285
Issue
22
Publish Date
2010
Start Page
16530
End Page
16537
DOI
10.1074/jbc.M109.092593

Rap1 promotes multiple pancreatic islet cell functions and signals through mammalian target of rapamycin complex 1 to enhance proliferation.

Recent studies have implicated Epac2, a guanine-nucleotide exchange factor for the Rap subfamily of monomeric G proteins, as an important regulator of insulin secretion from pancreatic beta-cells. Although the Epac proteins were originally identified as cAMP-responsive activators of Rap1 GTPases, the role of Rap1 in beta-cell biology has not yet been defined. In this study, we examined the direct effects of Rap1 signaling on beta-cell biology. Using the Ins-1 rat insulinoma line, we demonstrate that activated Rap1A, but not related monomeric G proteins, promotes ribosomal protein S6 phosphorylation. Using isolated rat islets, we show that this signaling event is rapamycin-sensitive, indicating that it is mediated by the mammalian target of rapamycin complex 1-p70 S6 kinase pathway, a known growth regulatory pathway. This newly defined beta-cell signaling pathway acts downstream of cAMP, in parallel with the stimulation of cAMP-dependent protein kinase, to drive ribosomal protein S6 phosphorylation. Activated Rap1A promotes glucose-stimulated insulin secretion, islet cell hypertrophy, and islet cell proliferation, the latter exclusively through mammalian target of rapamycin complex 1, suggesting that Rap1 is an important regulator of beta-cell function. This newly defined signaling pathway may yield unique targets for the treatment of beta-cell dysfunction in diabetes.

Authors
Kelly, P; Bailey, CL; Fueger, PT; Newgard, CB; Casey, PJ; Kimple, ME
MLA Citation
Kelly, P, Bailey, CL, Fueger, PT, Newgard, CB, Casey, PJ, and Kimple, ME. "Rap1 promotes multiple pancreatic islet cell functions and signals through mammalian target of rapamycin complex 1 to enhance proliferation." J Biol Chem 285.21 (May 21, 2010): 15777-15785.
PMID
20339002
Source
pubmed
Published In
The Journal of biological chemistry
Volume
285
Issue
21
Publish Date
2010
Start Page
15777
End Page
15785
DOI
10.1074/jbc.M109.069112

Regulation of skeletal muscle oxidative capacity and insulin signaling by the mitochondrial rhomboid protease PARL.

Type 2 diabetes mellitus (T2DM) and aging are characterized by insulin resistance and impaired mitochondrial energetics. In lower organisms, remodeling by the protease pcp1 (PARL ortholog) maintains the function and lifecycle of mitochondria. We examined whether variation in PARL protein content is associated with mitochondrial abnormalities and insulin resistance. PARL mRNA and mitochondrial mass were both reduced in elderly subjects and in subjects with T2DM. Muscle knockdown of PARL in mice resulted in malformed mitochondrial cristae, lower mitochondrial content, decreased PGC1alpha protein levels, and impaired insulin signaling. Suppression of PARL protein in healthy myotubes lowered mitochondrial mass and insulin-stimulated glycogen synthesis and increased reactive oxygen species production. We propose that lower PARL expression may contribute to the mitochondrial abnormalities seen in aging and T2DM.

Authors
Civitarese, AE; MacLean, PS; Carling, S; Kerr-Bayles, L; McMillan, RP; Pierce, A; Becker, TC; Moro, C; Finlayson, J; Lefort, N; Newgard, CB; Mandarino, L; Cefalu, W; Walder, K; Collier, GR; Hulver, MW; Smith, SR; Ravussin, E
MLA Citation
Civitarese, AE, MacLean, PS, Carling, S, Kerr-Bayles, L, McMillan, RP, Pierce, A, Becker, TC, Moro, C, Finlayson, J, Lefort, N, Newgard, CB, Mandarino, L, Cefalu, W, Walder, K, Collier, GR, Hulver, MW, Smith, SR, and Ravussin, E. "Regulation of skeletal muscle oxidative capacity and insulin signaling by the mitochondrial rhomboid protease PARL." Cell Metab 11.5 (May 5, 2010): 412-426.
PMID
20444421
Source
pubmed
Published In
Cell Metabolism
Volume
11
Issue
5
Publish Date
2010
Start Page
412
End Page
426
DOI
10.1016/j.cmet.2010.04.004

Association of a peripheral blood metabolic profile with coronary artery disease and risk of subsequent cardiovascular events.

BACKGROUND: Molecular tools may provide insight into cardiovascular risk. We assessed whether metabolites discriminate coronary artery disease (CAD) and predict risk of cardiovascular events. METHODS AND RESULTS: We performed mass-spectrometry-based profiling of 69 metabolites in subjects from the CATHGEN biorepository. To evaluate discriminative capabilities of metabolites for CAD, 2 groups were profiled: 174 CAD cases and 174 sex/race-matched controls ("initial"), and 140 CAD cases and 140 controls ("replication"). To evaluate the capability of metabolites to predict cardiovascular events, cases were combined ("event" group); of these, 74 experienced death/myocardial infarction during follow-up. A third independent group was profiled ("event-replication" group; n=63 cases with cardiovascular events, 66 controls). Analysis included principal-components analysis, linear regression, and Cox proportional hazards. Two principal components analysis-derived factors were associated with CAD: 1 comprising branched-chain amino acid metabolites (factor 4, initial P=0.002, replication P=0.01), and 1 comprising urea cycle metabolites (factor 9, initial P=0.0004, replication P=0.01). In multivariable regression, these factors were independently associated with CAD in initial (factor 4, odds ratio [OR], 1.36; 95% CI, 1.06 to 1.74; P=0.02; factor 9, OR, 0.67; 95% CI, 0.52 to 0.87; P=0.003) and replication (factor 4, OR, 1.43; 95% CI, 1.07 to 1.91; P=0.02; factor 9, OR, 0.66; 95% CI, 0.48 to 0.91; P=0.01) groups. A factor composed of dicarboxylacylcarnitines predicted death/myocardial infarction (event group hazard ratio 2.17; 95% CI, 1.23 to 3.84; P=0.007) and was associated with cardiovascular events in the event-replication group (OR, 1.52; 95% CI, 1.08 to 2.14; P=0.01). CONCLUSIONS: Metabolite profiles are associated with CAD and subsequent cardiovascular events.

Authors
Shah, SH; Bain, JR; Muehlbauer, MJ; Stevens, RD; Crosslin, DR; Haynes, C; Dungan, J; Newby, LK; Hauser, ER; Ginsburg, GS; Newgard, CB; Kraus, WE
MLA Citation
Shah, SH, Bain, JR, Muehlbauer, MJ, Stevens, RD, Crosslin, DR, Haynes, C, Dungan, J, Newby, LK, Hauser, ER, Ginsburg, GS, Newgard, CB, and Kraus, WE. "Association of a peripheral blood metabolic profile with coronary artery disease and risk of subsequent cardiovascular events." Circ Cardiovasc Genet 3.2 (April 2010): 207-214.
Website
http://hdl.handle.net/10161/5964
PMID
20173117
Source
pubmed
Published In
Circulation: Cardiovascular Genetics
Volume
3
Issue
2
Publish Date
2010
Start Page
207
End Page
214
DOI
10.1161/CIRCGENETICS.109.852814

Insulin resistance is associated with a metabolic profile of altered protein metabolism in Chinese and Asian-Indian men.

AIMS/HYPOTHESIS: Insulin resistance (IR) is associated with obesity, but can also develop in individuals with normal body weight. We employed comprehensive profiling methods to identify metabolic events associated with IR, while controlling for obesity. METHODS: We selected 263 non-obese (BMI approximately 24 kg/m2) Asian-Indian and Chinese men from a large cross-sectional study carried out in Singapore. Individuals taking medication for diabetes or hyperlipidaemia were excluded. Participants were separated into lower and upper tertiles of IR based on HOMA indices of < or =1.06 or > or =1.93, respectively. MS-based metabolic profiling of acylcarnitines, amino acids and organic acids was combined with hormonal and cytokine profiling in all participants. RESULTS: After controlling for BMI, commonly accepted risk factors for IR, including circulating fatty acids and inflammatory cytokines, did not discriminate the upper and lower quartiles of insulin sensitivity in either Asian- Indian or Chinese men. Instead, IR was correlated with increased levels of alanine, proline, valine, leucine/isoleucine, phenylalanine, tyrosine, glutamate/glutamine and ornithine, and a cluster of branched-chain and related amino acids identified by principal components analysis. These changes were not due to increased protein intake by individuals in the upper quartile of IR. Increased abdominal adiposity and leptin, and decreased adiponectin and IGF-binding protein 1 were also correlated with IR. CONCLUSIONS/INTERPRETATION: These findings demonstrate that perturbations in amino acid homeostasis, but not inflammatory markers or NEFAs, are associated with IR in individuals of relatively low body mass.

Authors
Tai, ES; Tan, MLS; Stevens, RD; Low, YL; Muehlbauer, MJ; Goh, DLM; Ilkayeva, OR; Wenner, BR; Bain, JR; Lee, JJM; Lim, SC; Khoo, CM; Shah, SH; Newgard, CB
MLA Citation
Tai, ES, Tan, MLS, Stevens, RD, Low, YL, Muehlbauer, MJ, Goh, DLM, Ilkayeva, OR, Wenner, BR, Bain, JR, Lee, JJM, Lim, SC, Khoo, CM, Shah, SH, and Newgard, CB. "Insulin resistance is associated with a metabolic profile of altered protein metabolism in Chinese and Asian-Indian men." Diabetologia 53.4 (April 2010): 757-767.
PMID
20076942
Source
pubmed
Published In
Diabetologia
Volume
53
Issue
4
Publish Date
2010
Start Page
757
End Page
767
DOI
10.1007/s00125-009-1637-8

Getting biological about the genetics of diabetes.

New technology has provided methods for collecting large amounts of data reflecting gene expression, metabolite and protein abundance, and post-translational modification of proteins. Integration of these various data sets enable the genetic mapping of many new phenotypes and facilitates the creation of network models that link genetic variation with intermediate traits leading to human disease. The first round of genome-wide association studies has not accounted for common human diseases to the extent that was expected. New phenotyping approaches and methods of data integration should bring these studies closer to their promised goals.

Authors
Newgard, CB; Attie, AD
MLA Citation
Newgard, CB, and Attie, AD. "Getting biological about the genetics of diabetes." Nat Med 16.4 (April 2010): 388-391.
PMID
20376050
Source
pubmed
Published In
Nature Medicine
Volume
16
Issue
4
Publish Date
2010
Start Page
388
End Page
391
DOI
10.1038/nm0410-388

Comprehensive metabolic analysis for understanding of obesity and diabetes mechanisms

Authors
Newgard, CB
MLA Citation
Newgard, CB. "Comprehensive metabolic analysis for understanding of obesity and diabetes mechanisms." FASEB JOURNAL 24 (April 2010).
Source
wos-lite
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
24
Publish Date
2010

Leptin therapy in insulin-deficient type I diabetes.

In nonobese diabetic mice with uncontrolled type 1 diabetes, leptin therapy alone or combined with low-dose insulin reverses the catabolic state through suppression of hyperglucagonemia. Additionally, it mimics the anabolic actions of insulin monotherapy and normalizes hemoglobin A1c with far less glucose variability. We show that leptin therapy, like insulin, normalizes the levels of a wide array of hepatic intermediary metabolites in multiple chemical classes, including acylcarnitines, organic acids (tricarboxylic acid cycle intermediates), amino acids, and acyl CoAs. In contrast to insulin monotherapy, however, leptin lowers both lipogenic and cholesterologenic transcription factors and enzymes and reduces plasma and tissue lipids. The results imply that leptin administration may have multiple short- and long-term advantages over insulin monotherapy for type 1 diabetes.

Authors
Wang, M-Y; Chen, L; Clark, GO; Lee, Y; Stevens, RD; Ilkayeva, OR; Wenner, BR; Bain, JR; Charron, MJ; Newgard, CB; Unger, RH
MLA Citation
Wang, M-Y, Chen, L, Clark, GO, Lee, Y, Stevens, RD, Ilkayeva, OR, Wenner, BR, Bain, JR, Charron, MJ, Newgard, CB, and Unger, RH. "Leptin therapy in insulin-deficient type I diabetes." Proc Natl Acad Sci U S A 107.11 (March 16, 2010): 4813-4819.
PMID
20194735
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
107
Issue
11
Publish Date
2010
Start Page
4813
End Page
4819
DOI
10.1073/pnas.0909422107

Cholinergic augmentation of insulin release requires ankyrin-B.

Parasympathetic stimulation of pancreatic islets augments glucose-stimulated insulin secretion by inducing inositol trisphosphate receptor (IP(3)R)-mediated calcium ion (Ca2+) release. Ankyrin-B binds to the IP(3)R and is enriched in pancreatic beta cells. We found that ankyrin-B-deficient islets displayed impaired potentiation of insulin secretion by the muscarinic agonist carbachol, blunted carbachol-mediated intracellular Ca2+ release, and reduced the abundance of IP3R. Ankyrin-B-haploinsufficient mice exhibited hyperglycemia after oral ingestion but not after intraperitoneal injection of glucose, consistent with impaired parasympathetic potentiation of glucose-stimulated insulin secretion. The R1788W mutation of ankyrin-B impaired its function in pancreatic islets and is associated with type 2 diabetes in Caucasians and Hispanics. Thus, defective glycemic regulation through loss of ankyrin-B-dependent stabilization of IP3R is a potential risk factor for type 2 diabetes.

Authors
Healy, JA; Nilsson, KR; Hohmeier, HE; Berglund, J; Davis, J; Hoffman, J; Kohler, M; Li, L-S; Berggren, P-O; Newgard, CB; Bennett, V
MLA Citation
Healy, JA, Nilsson, KR, Hohmeier, HE, Berglund, J, Davis, J, Hoffman, J, Kohler, M, Li, L-S, Berggren, P-O, Newgard, CB, and Bennett, V. "Cholinergic augmentation of insulin release requires ankyrin-B. (Published online)" Sci Signal 3.113 (March 16, 2010): ra19-.
PMID
20234002
Source
pubmed
Published In
Science Signaling
Volume
3
Issue
113
Publish Date
2010
Start Page
ra19
DOI
10.1126/scisignal.2000771

Gp93, the Drosophila GRP94 ortholog, is required for gut epithelial homeostasis and nutrient assimilation-coupled growth control.

GRP94, the endoplasmic reticulum Hsp90, is a metazoan-restricted chaperone essential for early development in mammals, yet dispensable for mammalian cell viability. This dichotomy suggests that GRP94 is required for the functional expression of secretory and/or membrane proteins that enable the integration of cells into tissues. To explore this hypothesis, we have identified the Drosophila ortholog of GRP94, Gp93, and report that Gp93 is an essential gene in Drosophila. Loss of zygotic Gp93 expression is late larval-lethal and causes prominent defects in the larval midgut, the sole endoderm-derived larval tissue. Gp93 mutant larvae display pronounced defects in the midgut epithelium, with aberrant copper cell structure, markedly reduced gut acidification, atypical septate junction structure, depressed gut motility, and deficits in intestinal nutrient uptake. The metabolic consequences of the loss of Gp93-expression are profound; Gp93 mutant larvae exhibit a starvation-like metabolic phenotype, including suppression of insulin signaling and extensive mobilization of amino acids and triglycerides. The defects in copper cell structure/function accompanying loss of Gp93 expression resemble those reported for mutations in labial, an endodermal homeotic gene required for copper cell specification, and alpha-spectrin, thus suggesting an essential role for Gp93 in the functional expression of secretory/integral membrane protein-encoding lab protein target genes and/or integral membrane protein(s) that interact with the spectrin cytoskeleton to confer epithelial membrane specialization.

Authors
Maynard, JC; Pham, T; Zheng, T; Jockheck-Clark, A; Rankin, HB; Newgard, CB; Spana, EP; Nicchitta, CV
MLA Citation
Maynard, JC, Pham, T, Zheng, T, Jockheck-Clark, A, Rankin, HB, Newgard, CB, Spana, EP, and Nicchitta, CV. "Gp93, the Drosophila GRP94 ortholog, is required for gut epithelial homeostasis and nutrient assimilation-coupled growth control." Dev Biol 339.2 (March 15, 2010): 295-306.
PMID
20044986
Source
pubmed
Published In
Developmental Biology
Volume
339
Issue
2
Publish Date
2010
Start Page
295
End Page
306
DOI
10.1016/j.ydbio.2009.12.023

SIRT3 regulates mitochondrial fatty-acid oxidation by reversible enzyme deacetylation.

Sirtuins are NAD(+)-dependent protein deacetylases. They mediate adaptive responses to a variety of stresses, including calorie restriction and metabolic stress. Sirtuin 3 (SIRT3) is localized in the mitochondrial matrix, where it regulates the acetylation levels of metabolic enzymes, including acetyl coenzyme A synthetase 2 (refs 1, 2). Mice lacking both Sirt3 alleles appear phenotypically normal under basal conditions, but show marked hyperacetylation of several mitochondrial proteins. Here we report that SIRT3 expression is upregulated during fasting in liver and brown adipose tissues. During fasting, livers from mice lacking SIRT3 had higher levels of fatty-acid oxidation intermediate products and triglycerides, associated with decreased levels of fatty-acid oxidation, compared to livers from wild-type mice. Mass spectrometry of mitochondrial proteins shows that long-chain acyl coenzyme A dehydrogenase (LCAD) is hyperacetylated at lysine 42 in the absence of SIRT3. LCAD is deacetylated in wild-type mice under fasted conditions and by SIRT3 in vitro and in vivo; and hyperacetylation of LCAD reduces its enzymatic activity. Mice lacking SIRT3 exhibit hallmarks of fatty-acid oxidation disorders during fasting, including reduced ATP levels and intolerance to cold exposure. These findings identify acetylation as a novel regulatory mechanism for mitochondrial fatty-acid oxidation and demonstrate that SIRT3 modulates mitochondrial intermediary metabolism and fatty-acid use during fasting.

Authors
Hirschey, MD; Shimazu, T; Goetzman, E; Jing, E; Schwer, B; Lombard, DB; Grueter, CA; Harris, C; Biddinger, S; Ilkayeva, OR; Stevens, RD; Li, Y; Saha, AK; Ruderman, NB; Bain, JR; Newgard, CB; Farese, RV; Alt, FW; Kahn, CR; Verdin, E
MLA Citation
Hirschey, MD, Shimazu, T, Goetzman, E, Jing, E, Schwer, B, Lombard, DB, Grueter, CA, Harris, C, Biddinger, S, Ilkayeva, OR, Stevens, RD, Li, Y, Saha, AK, Ruderman, NB, Bain, JR, Newgard, CB, Farese, RV, Alt, FW, Kahn, CR, and Verdin, E. "SIRT3 regulates mitochondrial fatty-acid oxidation by reversible enzyme deacetylation." Nature 464.7285 (March 4, 2010): 121-125.
PMID
20203611
Source
pubmed
Published In
Nature
Volume
464
Issue
7285
Publish Date
2010
Start Page
121
End Page
125
DOI
10.1038/nature08778

Adenovirus-mediated leptin expression normalises hypertension associated with diet-induced obesity.

In our previous study, moderate increases in plasma leptin levels achieved via administration of recombinant adenovirus containing the rat leptin cDNA were shown to correct the abnormal metabolic profile in rats with diet-induced obesity, suggesting that these animals had developed resistance to the metabolic effects of leptin, which could be reversed by leptin gene over-expression. However, the effect of this therapeutic strategy on blood pressure was not investigated. The present study aimed to determine whether a moderate increase of endogenous plasma leptin levels affected arterial blood pressure in rats with diet-induced obesity and hypertension. The major finding from the present study was that the natural rise in plasma leptin with weight-gain is insufficient to counterbalance high blood pressure associated with obesity, additional increases of circulating leptin levels with adenoviral leptin gene therapy led to normalisation of blood pressure in high-fat diet-induced obese and hypertensive rats. Mechanistically, the reduction of blood pressure by leptin in obese rats was likely independent of alpha-adrenergic and acetylcholinergic receptor mediation. This is the first study to demonstrate that further increases in circulating leptin levels by leptin gene transfer during obesity could reduce blood pressure.

Authors
Zhang, W; Telemaque, S; Augustyniak, RA; Anderson, P; Thomas, GD; An, J; Wang, Z; Newgard, CB; Victor, RG
MLA Citation
Zhang, W, Telemaque, S, Augustyniak, RA, Anderson, P, Thomas, GD, An, J, Wang, Z, Newgard, CB, and Victor, RG. "Adenovirus-mediated leptin expression normalises hypertension associated with diet-induced obesity." J Neuroendocrinol 22.3 (March 2010): 175-180.
PMID
20059648
Source
pubmed
Published In
Journal of Neuroendocrinology
Volume
22
Issue
3
Publish Date
2010
Start Page
175
End Page
180
DOI
10.1111/j.1365-2826.2010.01953.x

Contamination with E1A-positive wild-type adenovirus accounts for species-specific stimulation of islet cell proliferation by CCK: a cautionary note.

We have previously reported that adenovirus-mediated expression of preprocholecystokin (CCK) stimulates human and mouse islet cell proliferation. In follow-up studies, we became concerned that the CCK adenovirus might have been contaminated with a wild-type E1A-containing adenovirus. Here we show conclusively that the proliferative effects reported in the original paper in mouse and human islets were not due to CCK expression but rather to a contaminating E1A-expressing wild-type adenovirus. We also show, however, that CCK expression does have a proliferative effect in rat islets. We hope that our report of the steps taken to detect the wild-type virus contamination, and purification of the contributing viral stocks, will be helpful to other investigators, and that our experience will serve as a cautionary tale for use of adenovirus vectors, especially for studies on cellular replication.

Authors
Lavine, JA; Raess, PW; Davis, DB; Rabaglia, ME; Presley, BK; Keller, MP; Beinfeld, MC; Kopin, AS; Newgard, CB; Attie, AD
MLA Citation
Lavine, JA, Raess, PW, Davis, DB, Rabaglia, ME, Presley, BK, Keller, MP, Beinfeld, MC, Kopin, AS, Newgard, CB, and Attie, AD. "Contamination with E1A-positive wild-type adenovirus accounts for species-specific stimulation of islet cell proliferation by CCK: a cautionary note." Mol Endocrinol 24.2 (February 2010): 464-467.
PMID
20081104
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
24
Issue
2
Publish Date
2010
Start Page
464
End Page
467
DOI
10.1210/me.2009-0384

Overexpression of pre-pro-cholecystokinin stimulates β-cell proliferation in mouse and human islets with retention of islet function (Molecular Endocrinology (2008) 22, (2716-2728))

Authors
Lavine, JA; Raess, PW; Davis, DB; Rabaglia, ME; Presley, BK; Keller, MP; Beinfeld, MC; Kopin, AS; Newgard, CB; Attie, AD
MLA Citation
Lavine, JA, Raess, PW, Davis, DB, Rabaglia, ME, Presley, BK, Keller, MP, Beinfeld, MC, Kopin, AS, Newgard, CB, and Attie, AD. "Overexpression of pre-pro-cholecystokinin stimulates β-cell proliferation in mouse and human islets with retention of islet function (Molecular Endocrinology (2008) 22, (2716-2728))." Molecular Endocrinology 24.2 (2010): 472--.
Source
scival
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
24
Issue
2
Publish Date
2010
Start Page
472-

Comprehensive Metabolic Analysis for Understanding of Disease

Comprehensive measurement of intermediary metabolites and changes in metabolic activity lead to the improved detection and understanding of diseases. Metabolomics is increasingly getting integrated with genomic and transcriptomic profiling methods. This chapter describes current methodologies for metabolic profiling and flux analysis and discusses the instrumentation for measurement of large groups of intermediary metabolites as well as computational methods for analyzing such data. Instrumentation for measurement of large groups of intermediary metabolites as well as computational methods for analyzing such data are emerging. This surge in development of metabolomics technologies confers a number of potential advantages for disease research. Human beings contain approximately 5000 discrete small molecule metabolites, far less than the estimate of 25,000 genes and 100,000 proteins. This makes metabolomics the most tractable of the "omics" sciences. It also measures changes in metabolic or chemical milieu that are downstream of genomic and proteomic alterations, potentially providing the most integrated picture of biological status. Further, the identification of metabolic fingerprints for specific diseases has practical utility for development of therapies because metabolic changes immediately suggest enzymatic drug targets. Thus, metabolomics is likely to be a powerful and precise tool for discerning mechanisms of action and possible toxicological effects of drug therapies. © 2010 Copyright © 2010 Elsevier Inc. All rights reserved.

Authors
Newgard, CB; Stevens, RD; Wenner, BR; Burgess, SC; Ilkayeva, O; Muehlbauer, MJ; Sherry, AD; Bain, JR
MLA Citation
Newgard, CB, Stevens, RD, Wenner, BR, Burgess, SC, Ilkayeva, O, Muehlbauer, MJ, Sherry, AD, and Bain, JR. "Comprehensive Metabolic Analysis for Understanding of Disease." Essentials of Genomic and Personalized Medicine (2010): 97-107.
Source
scival
Published In
Essentials of Genomic and Personalized Medicine
Publish Date
2010
Start Page
97
End Page
107
DOI
10.1016/B978-0-12-374934-5.00009-X

Insulin resistance and altered systemic glucose metabolism in mice lacking Nur77.

OBJECTIVE: Nur77 is an orphan nuclear receptor with pleotropic functions. Previous studies have identified Nur77 as a transcriptional regulator of glucose utilization genes in skeletal muscle and gluconeogenesis in liver. However, the net functional impact of these pathways is unknown. To examine the consequence of Nur77 signaling for glucose metabolism in vivo, we challenged Nur77 null mice with high-fat feeding. RESEARCH DESIGN AND METHODS: Wild-type and Nur77 null mice were fed a high-fat diet (60% calories from fat) for 3 months. We determined glucose tolerance, tissue-specific insulin sensitivity, oxygen consumption, muscle and liver lipid content, muscle insulin signaling, and expression of glucose and lipid metabolism genes. RESULTS: Mice with genetic deletion of Nur77 exhibited increased susceptibility to diet-induced obesity and insulin resistance. Hyperinsulinemic-euglycemic clamp studies revealed greater high-fat diet-induced insulin resistance in both skeletal muscle and liver of Nur77 null mice compared with controls. Loss of Nur77 expression in skeletal muscle impaired insulin signaling and markedly reduced GLUT4 protein expression. Muscles lacking Nur77 also exhibited increased triglyceride content and accumulation of multiple even-chained acylcarnitine species. In the liver, Nur77 deletion led to hepatic steatosis and enhanced expression of lipogenic genes, likely reflecting the lipogenic effect of hyperinsulinemia. CONCLUSIONS: Collectively, these data demonstrate that loss of Nur77 influences systemic glucose metabolism and highlight the physiological contribution of muscle Nur77 to this regulatory pathway.

Authors
Chao, LC; Wroblewski, K; Zhang, Z; Pei, L; Vergnes, L; Ilkayeva, OR; Ding, SY; Reue, K; Watt, MJ; Newgard, CB; Pilch, PF; Hevener, AL; Tontonoz, P
MLA Citation
Chao, LC, Wroblewski, K, Zhang, Z, Pei, L, Vergnes, L, Ilkayeva, OR, Ding, SY, Reue, K, Watt, MJ, Newgard, CB, Pilch, PF, Hevener, AL, and Tontonoz, P. "Insulin resistance and altered systemic glucose metabolism in mice lacking Nur77." Diabetes 58.12 (December 2009): 2788-2796.
PMID
19741162
Source
pubmed
Published In
Diabetes
Volume
58
Issue
12
Publish Date
2009
Start Page
2788
End Page
2796
DOI
10.2337/db09-0763

Cooperative transcriptional regulation of the essential pancreatic islet gene NeuroD1 (beta2) by Nkx2.2 and neurogenin 3.

Nkx2.2 and NeuroD1 are two critical regulators of pancreatic beta cell development. Nkx2.2 is a homeodomain transcription factor that is essential for islet cell type specification and mature beta cell function. NeuroD1 is a basic helix-loop-helix transcription factor that is critical for islet beta cell maturation and maintenance. Although both proteins influence beta cell development directly downstream of the endocrine progenitor factor, neurogenin3 (Ngn3), a connection between the two proteins in the regulation of beta cell fate and function has yet to be established. In this study, we demonstrate that Nkx2.2 transcriptional activity is required to facilitate the activation of NeuroD1 by Ngn3. Furthermore, Nkx2.2 is necessary to maintain high levels of NeuroD1 expression in developing mouse and zebrafish islets and in mature beta cells. Interestingly, Nkx2.2 regulates NeuroD1 through two independent promoter elements, one that is bound and activated directly by Nkx2.2 and one that appears to be regulated by Nkx2.2 through an indirect mechanism. Together, these findings suggest that Nkx2.2 coordinately activates NeuroD1 with Ngn3 within the endocrine progenitor cell and also plays a role in the maintenance of NeuroD1 expression to regulate beta cell function in the mature islet. Collectively, these findings further define the conserved regulatory networks involved in islet beta cell formation and function.

Authors
Anderson, KR; Torres, CA; Solomon, K; Becker, TC; Newgard, CB; Wright, CV; Hagman, J; Sussel, L
MLA Citation
Anderson, KR, Torres, CA, Solomon, K, Becker, TC, Newgard, CB, Wright, CV, Hagman, J, and Sussel, L. "Cooperative transcriptional regulation of the essential pancreatic islet gene NeuroD1 (beta2) by Nkx2.2 and neurogenin 3." J Biol Chem 284.45 (November 6, 2009): 31236-31248.
PMID
19759004
Source
pubmed
Published In
The Journal of biological chemistry
Volume
284
Issue
45
Publish Date
2009
Start Page
31236
End Page
31248
DOI
10.1074/jbc.M109.048694

Activation of nuclear receptor CAR ameliorates diabetes and fatty liver disease.

Constitutive androstane receptor CAR (NR1I3) has been identified as a central mediator of coordinate responses to xenobiotic and endobiotic stress. Here we use leptin-deficient mice (ob/ob) and ob/ob, CAR(-/-) double mutant mice to identify a metabolic role of CAR in type 2 diabetes. Activation of CAR significantly reduces serum glucose levels and improves glucose tolerance and insulin sensitivity. Gene expression analyses and hyperinsulinemic euglycemic clamp results suggest that CAR activation ameliorates hyperglycemia by suppressing glucose production and stimulating glucose uptake and usage in the liver. In addition, CAR activation dramatically improves fatty liver by both inhibition of hepatic lipogenesis and induction of beta-oxidation. We conclude that CAR activation improves type 2 diabetes, and that these actions of CAR suggest therapeutic approaches to the disease.

Authors
Dong, B; Saha, PK; Huang, W; Chen, W; Abu-Elheiga, LA; Wakil, SJ; Stevens, RD; Ilkayeva, O; Newgard, CB; Chan, L; Moore, DD
MLA Citation
Dong, B, Saha, PK, Huang, W, Chen, W, Abu-Elheiga, LA, Wakil, SJ, Stevens, RD, Ilkayeva, O, Newgard, CB, Chan, L, and Moore, DD. "Activation of nuclear receptor CAR ameliorates diabetes and fatty liver disease." Proc Natl Acad Sci U S A 106.44 (November 3, 2009): 18831-18836.
PMID
19850873
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
106
Issue
44
Publish Date
2009
Start Page
18831
End Page
18836
DOI
10.1073/pnas.0909731106

Metabolomics applied to diabetes research: moving from information to knowledge.

Authors
Bain, JR; Stevens, RD; Wenner, BR; Ilkayeva, O; Muoio, DM; Newgard, CB
MLA Citation
Bain, JR, Stevens, RD, Wenner, BR, Ilkayeva, O, Muoio, DM, and Newgard, CB. "Metabolomics applied to diabetes research: moving from information to knowledge." Diabetes 58.11 (November 2009): 2429-2443.
PMID
19875619
Source
pubmed
Published In
Diabetes
Volume
58
Issue
11
Publish Date
2009
Start Page
2429
End Page
2443
DOI
10.2337/db09-0580

Relationships between circulating metabolic intermediates and insulin action in overweight to obese, inactive men and women.

OBJECTIVE: To determine whether circulating metabolic intermediates are related to insulin resistance and beta-cell dysfunction in individuals at risk for type 2 diabetes. RESEARCH DESIGN AND METHODS: In 73 sedentary, overweight to obese, dyslipidemic individuals, insulin action was derived from a frequently sampled intravenous glucose tolerance test. Plasma concentrations of 75 amino acids, acylcarnitines, free fatty acids, and conventional metabolites were measured with a targeted, mass spectrometry-based platform. Principal components analysis followed by backward stepwise linear regression was used to explore relationships between measures of insulin action and metabolic intermediates. RESULTS: The 75 metabolic intermediates clustered into 19 factors comprising biologically related intermediates. A factor containing large neutral amino acids was inversely related to insulin sensitivity (S(I)) (R(2) = 0.26). A factor containing fatty acids was inversely related to the acute insulin response to glucose (R(2) = 0.12). Both of these factors, age, and a factor containing medium-chain acylcarnitines and glucose were inversely and independently related to the disposition index (DI) (R(2) = 0.39). Sex differences were found for metabolic predictors of S(I) and DI. CONCLUSIONS: In addition to the well-recognized risks for insulin resistance, elevated concentrations of large, neutral amino acids were independently associated with insulin resistance. Fatty acids were inversely related to the pancreatic response to glucose. Both large neutral amino acids and fatty acids were related to an appropriate pancreatic response, suggesting that these metabolic intermediates might play a role in the progression to type 2 diabetes, one by contributing to insulin resistance and the other to pancreatic failure. These intermediates might exert sex-specific effects on insulin action.

Authors
Huffman, KM; Shah, SH; Stevens, RD; Bain, JR; Muehlbauer, M; Slentz, CA; Tanner, CJ; Kuchibhatla, M; Houmard, JA; Newgard, CB; Kraus, WE
MLA Citation
Huffman, KM, Shah, SH, Stevens, RD, Bain, JR, Muehlbauer, M, Slentz, CA, Tanner, CJ, Kuchibhatla, M, Houmard, JA, Newgard, CB, and Kraus, WE. "Relationships between circulating metabolic intermediates and insulin action in overweight to obese, inactive men and women." Diabetes Care 32.9 (September 2009): 1678-1683.
PMID
19502541
Source
pubmed
Published In
Diabetes Care
Volume
32
Issue
9
Publish Date
2009
Start Page
1678
End Page
1683
DOI
10.2337/dc08-2075

Fasting-induced hepatic production of DHEA is regulated by PGC-1alpha, ERRalpha, and HNF4alpha.

The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1alpha is involved in the coordinate induction of changes in gene expression in the liver that enable a homeostatic response to alterations in metabolic state, environmental cues, and nutrient availability. In exploring the specific pathways under PGC-1alpha regulation in the liver, we have made the surprising observation that this coactivator can induce the expression of CYP11A1 and CYP17A1, key rate-limiting enzymes involved in the initial steps of steroidogenesis. Both of these enzymes function to produce C(19)-steroids, converting cholesterol into pregnenolone, and then to dehydroepiandrosterone (DHEA). Estrogen-related receptor (ERR)-alpha mediates PGC-1alpha's induction of CYP11A1 and binds within the first intron of the CYP11A1 gene. Both ERR-alpha and hepatocyte nuclear factor-4alpha are required for PGC-1alpha-mediated induction of CYP17A1, and specific binding sites for these receptors have been identified in the regulatory regions of this gene. The potential physiological significance of these observations was highlighted in rats where fasting induced hepatic expression of PGC-1alpha and CYP17A1 and was associated with an increase in hepatic levels of DHEA. These data suggest that DHEA could be playing a role as an intracellular signaling molecule involved in modulating hepatic activity in response to fasting conditions.

Authors
Grasfeder, LL; Gaillard, S; Hammes, SR; Ilkayeva, O; Newgard, CB; Hochberg, RB; Dwyer, MA; Chang, C-Y; McDonnell, DP
MLA Citation
Grasfeder, LL, Gaillard, S, Hammes, SR, Ilkayeva, O, Newgard, CB, Hochberg, RB, Dwyer, MA, Chang, C-Y, and McDonnell, DP. "Fasting-induced hepatic production of DHEA is regulated by PGC-1alpha, ERRalpha, and HNF4alpha." Mol Endocrinol 23.8 (August 2009): 1171-1182.
PMID
19389810
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
23
Issue
8
Publish Date
2009
Start Page
1171
End Page
1182
DOI
10.1210/me.2009-0024

Increased insulin sensitivity in mice lacking collectrin, a downstream target of HNF-1alpha.

Collectrin is a downstream target of the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha), which is mutated in maturity-onset diabetes of the young subtype 3 (MODY3). Evidence from transgenic mouse models with collectrin overexpression in pancreatic islets suggests divergent roles for collectrin in influencing beta-cell mass and insulin exocytosis. To clarify the function of collectrin in the pancreas, we used a mouse line with targeted deletion of the gene. We examined pancreas morphology, glucose homeostasis by ip glucose tolerance testing (IPGTT) and insulin tolerance testing (IPITT), and pancreas function by in vivo acute-phase insulin response determination and glucose-stimulated insulin secretion from isolated islets. We find no difference in either pancreas morphology or function between wild-type and collectrin-deficient animals (Tmem27(-/y)). However, we note that by 6 months of age, Tmem27(-/y) mice exhibit increased insulin sensitivity by IPITT and decreased adiposity by dual-energy x-ray absorptiometry scanning compared with wild-type. We have previously reported that Tmem27(-/y) mice exhibit profound aminoaciduria due to failed renal recovery. We now demonstrate that Tmem27(-/y) animals also display inappropriate excretion of some short-chain acylcarnitines derived from amino acid and fatty acid oxidation. We provide further evidence for compensatory up-regulation of oxidative metabolism in Tmem27(-/y) mice, along with enhanced protein turnover associated with preserved lean mass even out to 1.5 yr of age. Our studies suggest that collectrin-deficient mice activate a number of adaptive mechanisms to defend energy homeostasis in the setting of ongoing nutrient losses.

Authors
Malakauskas, SM; Kourany, WM; Zhang, XY; Lu, D; Stevens, RD; Koves, TR; Hohmeier, HE; Muoio, DM; Newgard, CB; Le, TH
MLA Citation
Malakauskas, SM, Kourany, WM, Zhang, XY, Lu, D, Stevens, RD, Koves, TR, Hohmeier, HE, Muoio, DM, Newgard, CB, and Le, TH. "Increased insulin sensitivity in mice lacking collectrin, a downstream target of HNF-1alpha." Mol Endocrinol 23.6 (June 2009): 881-892.
PMID
19246514
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
23
Issue
6
Publish Date
2009
Start Page
881
End Page
892
DOI
10.1210/me.2008-0274

Biochemistry. A glucose-to-gene link.

Authors
Rathmell, JC; Newgard, CB
MLA Citation
Rathmell, JC, and Newgard, CB. "Biochemistry. A glucose-to-gene link." Science 324.5930 (May 22, 2009): 1021-1022.
PMID
19460991
Source
pubmed
Published In
Science
Volume
324
Issue
5930
Publish Date
2009
Start Page
1021
End Page
1022
DOI
10.1126/science.1174665

Metabolomic profiling reveals distinct patterns of myocardial substrate use in humans with coronary artery disease or left ventricular dysfunction during surgical ischemia/reperfusion.

BACKGROUND: Human myocardial metabolism has been incompletely characterized in the setting of surgical cardioplegic arrest and ischemia/reperfusion. Furthermore, the effect of preexisting ventricular state on ischemia-induced metabolic derangements has not been established. METHODS AND RESULTS: We applied a mass spectrometry-based platform to profile 63 intermediary metabolites in serial paired peripheral arterial and coronary sinus blood effluents obtained from 37 patients undergoing cardiac surgery, stratified by presence of coronary artery disease and left ventricular dysfunction. The myocardium was a net user of a number of fuel substrates before ischemia, with significant differences between patients with and without coronary artery disease. After reperfusion, significantly lower extraction ratios of most substrates were found, as well as significant release of 2 specific acylcarnitine species, acetylcarnitine and 3-hydroxybutyryl-carnitine. These changes were especially evident in patients with impaired ventricular function, who exhibited profound limitations in extraction of all forms of metabolic fuels. Principal component analysis highlighted several metabolic groupings as potentially important in the postoperative clinical course. CONCLUSIONS: The preexisting ventricular state is associated with significant differences in myocardial fuel uptake at baseline and after ischemia/reperfusion. The dysfunctional ventricle is characterized by global suppression of metabolic fuel uptake and limited myocardial metabolic reserve and flexibility after global ischemia/reperfusion stress in the setting of cardiac surgery. Altered metabolic profiles after ischemia/reperfusion are associated with postoperative hemodynamic course and suggest a role for perioperative metabolic monitoring and targeted optimization in cardiac surgical patients.

Authors
Turer, AT; Stevens, RD; Bain, JR; Muehlbauer, MJ; van der Westhuizen, J; Mathew, JP; Schwinn, DA; Glower, DD; Newgard, CB; Podgoreanu, MV
MLA Citation
Turer, AT, Stevens, RD, Bain, JR, Muehlbauer, MJ, van der Westhuizen, J, Mathew, JP, Schwinn, DA, Glower, DD, Newgard, CB, and Podgoreanu, MV. "Metabolomic profiling reveals distinct patterns of myocardial substrate use in humans with coronary artery disease or left ventricular dysfunction during surgical ischemia/reperfusion." Circulation 119.13 (April 7, 2009): 1736-1746.
PMID
19307475
Source
pubmed
Published In
Circulation
Volume
119
Issue
13
Publish Date
2009
Start Page
1736
End Page
1746
DOI
10.1161/CIRCULATIONAHA.108.816116

A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance.

Metabolomic profiling of obese versus lean humans reveals a branched-chain amino acid (BCAA)-related metabolite signature that is suggestive of increased catabolism of BCAA and correlated with insulin resistance. To test its impact on metabolic homeostasis, we fed rats on high-fat (HF), HF with supplemented BCAA (HF/BCAA), or standard chow (SC) diets. Despite having reduced food intake and a low rate of weight gain equivalent to the SC group, HF/BCAA rats were as insulin resistant as HF rats. Pair-feeding of HF diet to match the HF/BCAA animals or BCAA addition to SC diet did not cause insulin resistance. Insulin resistance induced by HF/BCAA feeding was accompanied by chronic phosphorylation of mTOR, JNK, and IRS1Ser307 and by accumulation of multiple acylcarnitines in muscle, and it was reversed by the mTOR inhibitor, rapamycin. Our findings show that in the context of a dietary pattern that includes high fat consumption, BCAA contributes to development of obesity-associated insulin resistance.

Authors
Newgard, CB; An, J; Bain, JR; Muehlbauer, MJ; Stevens, RD; Lien, LF; Haqq, AM; Shah, SH; Arlotto, M; Slentz, CA; Rochon, J; Gallup, D; Ilkayeva, O; Wenner, BR; Yancy, WS; Eisenson, H; Musante, G; Surwit, RS; Millington, DS; Butler, MD; Svetkey, LP
MLA Citation
Newgard, CB, An, J, Bain, JR, Muehlbauer, MJ, Stevens, RD, Lien, LF, Haqq, AM, Shah, SH, Arlotto, M, Slentz, CA, Rochon, J, Gallup, D, Ilkayeva, O, Wenner, BR, Yancy, WS, Eisenson, H, Musante, G, Surwit, RS, Millington, DS, Butler, MD, and Svetkey, LP. "A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance." Cell Metab 9.4 (April 2009): 311-326.
PMID
19356713
Source
pubmed
Published In
Cell Metabolism
Volume
9
Issue
4
Publish Date
2009
Start Page
311
End Page
326
DOI
10.1016/j.cmet.2009.02.002

Glucose metabolism as a target of histone deacetylase inhibitors.

The therapeutic efficacy of histone deacetylase inhibitors (HDACI) is generally attributed to their ability to alter gene expression secondary to their effects on the acetylation status of transcription factors and histones. However, because HDACIs exhibit similar transcriptional effects in most cells, the molecular basis for their therapeutic selectivity toward malignant cells is largely unknown. In this study, we report that HDACI, of distinct chemotypes, quantitatively inhibit glucose transporter 1 (GLUT1)-mediated glucose transport into multiple myeloma cells through both down-regulation of GLUT1 and inhibition of hexokinase 1 (HXK1) enzymatic activity. Unexpectedly, however, this inhibition of glucose utilization is accompanied by an increase in amino acid catabolism with no increase in fatty acid oxidation. Our findings suggest that an HDACI-induced change in carbon source preference could contribute to the therapeutic efficacy of these drugs by creating a pattern of fuel utilization that is incompatible with rapid tumor growth and survival. Furthermore, these results, which implicate glucose metabolism as a target of HDACI, suggest that caution should be exercised in attributing effects of this class of drug to primary alterations in gene transcription.

Authors
Wardell, SE; Ilkayeva, OR; Wieman, HL; Frigo, DE; Rathmell, JC; Newgard, CB; McDonnell, DP
MLA Citation
Wardell, SE, Ilkayeva, OR, Wieman, HL, Frigo, DE, Rathmell, JC, Newgard, CB, and McDonnell, DP. "Glucose metabolism as a target of histone deacetylase inhibitors." Mol Endocrinol 23.3 (March 2009): 388-401.
PMID
19106193
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
23
Issue
3
Publish Date
2009
Start Page
388
End Page
401
DOI
10.1210/me.2008-0179

Moderate dietary vitamin B-6 restriction raises plasma glycine and cystathionine concentrations while minimally affecting the rates of glycine turnover and glycine cleavage in healthy men and women.

Glycine is a precursor of purines, protein, glutathione, and 1-carbon units as 5,10-methylenetetrahydrofolate. Glycine decarboxylation through the glycine cleavage system (GCS) and glycine-serine transformation by serine hydroxymethyltransferase (SHMT) require pyridoxal 5'-phosphate (PLP; active form of vitamin B-6) as a coenzyme. The intake of vitamin B-6 is frequently low in humans. Therefore, we determined the effects of vitamin B-6 restriction on whole-body glycine flux, the rate of glycine decarboxylation, glycine-to-serine conversion, use of glycine carbons in nucleoside synthesis, and other aspects of 1-carbon metabolism. We used a primed, constant infusion of [1,2-(13)C(2)]glycine and [5,5,5-(2)H(3)]leucine to quantify in vivo kinetics in healthy adults (7 males, 6 females; 20-39 y) of normal vitamin B-6 status or marginal vitamin B-6 deficiency. Vitamin B-6 restriction lowered the plasma PLP concentration from 55 +/- 4 nmol/L (mean +/- SEM) to 23 +/- 1 nmol/L (P < 0.0001), which is consistent with marginal deficiency, whereas the plasma glycine concentration increased (P < 0.01). SHMT-mediated conversion of glycine to serine increased from 182 +/- 7 to 205 +/- 9 micromol x kg(-1) x h(-1) (P < 0.05), but serine production using a GCS-derived 1-carbon unit (93 +/- 9 vs. 91 +/- 6 micromol x kg(-1) x h(-1)) and glycine cleavage (163 +/- 11 vs. 151 +/- 8 micromol x kg(-1) x h(-1)) were not changed by vitamin B-6 restriction. The GCS produced 1-carbon units at a rate (approximately 140-170 micromol x kg(-1) x h(-1)) that greatly exceeds the demand for remethylation and transmethylation processes (approximately 4-7 micromol x kg(-1) x h(-1)). We conclude that the in vivo GCS and SHMT reactions are quite resilient to the effects of marginal vitamin B-6 deficiency, presumably through a compensatory effect of increasing substrate concentration.

Authors
Lamers, Y; Williamson, J; Ralat, M; Quinlivan, EP; Gilbert, LR; Keeling, C; Stevens, RD; Newgard, CB; Ueland, PM; Meyer, K; Fredriksen, A; Stacpoole, PW; Gregory, JF
MLA Citation
Lamers, Y, Williamson, J, Ralat, M, Quinlivan, EP, Gilbert, LR, Keeling, C, Stevens, RD, Newgard, CB, Ueland, PM, Meyer, K, Fredriksen, A, Stacpoole, PW, and Gregory, JF. "Moderate dietary vitamin B-6 restriction raises plasma glycine and cystathionine concentrations while minimally affecting the rates of glycine turnover and glycine cleavage in healthy men and women." J Nutr 139.3 (March 2009): 452-460.
PMID
19158217
Source
pubmed
Published In
The Journal of nutrition
Volume
139
Issue
3
Publish Date
2009
Start Page
452
End Page
460
DOI
10.3945/jn.108.099184

The STEDMAN project: biophysical, biochemical and metabolic effects of a behavioral weight loss intervention during weight loss, maintenance, and regain.

The Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) Project uses comprehensive metabolic profiling to probe biochemical mechanisms of weight loss in humans. Measurements at baseline, 2 and 4 weeks, 6 and 12 months included diet, body composition, metabolic rate, hormones, and 80 intermediary metabolites measured by mass spectrometry. In 27 obese adults in a behavioral weight loss intervention, median weight decreased 13.9 lb over the first 6 months, then reverted towards baseline by 12 months. Insulin resistance (HOMA) was partially ameliorated in the first 6 months and showed sustained improvement at 12 months despite weight regain. Ghrelin increased with weight loss and reverted to baseline, whereas leptin and PYY fell at 6 months and remained persistently low. NPY levels did not change. Factors possibly contributing to sustained improvement in insulin sensitivity despite weight regain include adiponectin (increased by 12 months), IGF-1 (increased during weight loss and continued to increase during weight regain), and visceral fat (fell at 6 months but did not change thereafter). We observed a persistent reduction in free fatty acids, branched chain amino acids, and related metabolites that may contribute to improved insulin action. These findings provide evidence for sustained benefits of weight loss in obese humans and insights into mechanisms.

Authors
Lien, LF; Haqq, AM; Arlotto, M; Slentz, CA; Muehlbauer, MJ; McMahon, RL; Rochon, J; Gallup, D; Bain, JR; Ilkayeva, O; Wenner, BR; Stevens, RD; Millington, DS; Muoio, DM; Butler, MD; Newgard, CB; Svetkey, LP
MLA Citation
Lien, LF, Haqq, AM, Arlotto, M, Slentz, CA, Muehlbauer, MJ, McMahon, RL, Rochon, J, Gallup, D, Bain, JR, Ilkayeva, O, Wenner, BR, Stevens, RD, Millington, DS, Muoio, DM, Butler, MD, Newgard, CB, and Svetkey, LP. "The STEDMAN project: biophysical, biochemical and metabolic effects of a behavioral weight loss intervention during weight loss, maintenance, and regain." OMICS 13.1 (February 2009): 21-35.
PMID
19290809
Source
pubmed
Published In
OMICS: A Journal of Integrative Biology
Volume
13
Issue
1
Publish Date
2009
Start Page
21
End Page
35
DOI
10.1089/omi.2008.0035

The liver--a potential new player in islet regeneration?

Pancreatic islet beta cell mass expands in response to certain physiological conditions such as pregnancy and obesity, but the signaling pathways involved are not well understood. Possible insights come from a newly described regulatory circuit through which obesity-enhanced kinase signaling in the liver triggers expansion of islet mass and enhanced insulin secretion.

Authors
Moss, LG; Newgard, CB
MLA Citation
Moss, LG, and Newgard, CB. "The liver--a potential new player in islet regeneration?." Cell Metab 9.1 (January 7, 2009): 5-6.
PMID
19117540
Source
pubmed
Published In
Cell Metabolism
Volume
9
Issue
1
Publish Date
2009
Start Page
5
End Page
6
DOI
10.1016/j.cmet.2008.12.009

Neuropeptide Y gene polymorphisms confer risk of early-onset atherosclerosis.

Neuropeptide Y (NPY) is a strong candidate gene for coronary artery disease (CAD). We have previously identified genetic linkage to familial CAD in the genomic region of NPY. We performed follow-up genetic, biostatistical, and functional analysis of NPY in early-onset CAD. In familial CAD (GENECARD, N = 420 families), we found increased microsatellite linkage to chromosome 7p14 (OSA LOD = 4.2, p = 0.004) in 97 earliest age-of-onset families. Tagged NPY SNPs demonstrated linkage to CAD of a 6-SNP block (LOD = 1.58-2.72), family-based association of this block with CAD (p = 0.02), and stronger linkage to CAD in the earliest age-of-onset families. Association of this 6-SNP block with CAD was validated in: (a) 556 non-familial early-onset CAD cases and 256 controls (OR 1.46-1.65, p = 0.01-0.05), showing stronger association in youngest cases (OR 1.84-2.20, p = 0.0004-0.09); and (b) GENECARD probands versus non-familial controls (OR 1.79-2.06, p = 0.003-0.02). A promoter SNP (rs16147) within this 6-SNP block was associated with higher plasma NPY levels (p = 0.04). To assess a causal role of NPY in atherosclerosis, we applied the NPY1-receptor-antagonist BIBP-3226 adventitially to endothelium-denuded carotid arteries of apolipoprotein E-deficient mice; treatment reduced atherosclerotic neointimal area by 50% (p = 0.03). Thus, NPY variants associate with atherosclerosis in two independent datasets (with strong age-of-onset effects) and show allele-specific expression with NPY levels, while NPY receptor antagonism reduces atherosclerosis in mice. We conclude that NPY contributes to atherosclerosis pathogenesis.

Authors
Shah, SH; Freedman, NJ; Zhang, L; Crosslin, DR; Stone, DH; Haynes, C; Johnson, J; Nelson, S; Wang, L; Connelly, JJ; Muehlbauer, M; Ginsburg, GS; Crossman, DC; Jones, CJH; Vance, J; Sketch, MH; Granger, CB; Newgard, CB; Gregory, SG; Goldschmidt-Clermont, PJ; Kraus, WE; Hauser, ER
MLA Citation
Shah, SH, Freedman, NJ, Zhang, L, Crosslin, DR, Stone, DH, Haynes, C, Johnson, J, Nelson, S, Wang, L, Connelly, JJ, Muehlbauer, M, Ginsburg, GS, Crossman, DC, Jones, CJH, Vance, J, Sketch, MH, Granger, CB, Newgard, CB, Gregory, SG, Goldschmidt-Clermont, PJ, Kraus, WE, and Hauser, ER. "Neuropeptide Y gene polymorphisms confer risk of early-onset atherosclerosis." PLoS Genet 5.1 (January 2009): e1000318-.
PMID
19119412
Source
pubmed
Published In
PLoS genetics
Volume
5
Issue
1
Publish Date
2009
Start Page
e1000318
DOI
10.1371/journal.pgen.1000318

Restoration of hepatic glucokinase expression corrects hepatic glucose flux and normalizes plasma glucose in zucker diabetic fatty rats.

OBJECTIVE: We examined in 20-week-old Zucker diabetic fatty (ZDF) rats whether restoration of hepatic glucokinase (GK) expression would alter hepatic glucose flux and improve hyperglycemia. RESEARCH DESIGN AND METHODS: ZDF rats were treated at various doses with an adenovirus that directs the expression of rat liver GK (AdvCMV-GKL) dose dependently, and various metabolic parameters were compared with those of nondiabetic lean littermates (ZCL rats) before and during a hyperglycemic clamp. Viral infection per se did not affect hepatic GK activity, since expression of a catalytically inactive form of GK did not alter endogenous hepatic GK activity. RESULTS: ZDF rats compared with ZCL rats have lower hepatic GK activity (11.6 +/- 1.9 vs. 32.5 +/- 3.2 mU/mg protein), marked hyperglycemia (23.9 +/- 1.2 vs. 7.4 +/- 0.3 mmol/l), higher endogenous glucose production (80 +/- 3 vs. 38 +/- 3 micromol x kg(-1) x min(-1)), increased glucose-6-phosphatase flux (150 +/- 11 vs. 58 +/- 8 micromol x kg(-1) x min(-1)), and during a hyperglycemic clamp, a failure to suppress endogenous glucose production (80 +/- 7 vs. -7 +/- 4 micromol x kg(-1) x min(-1)) and promote glucose incorporation into glycogen (15 +/- 5 vs. 43 +/- 3 micromol/g liver). Treatment of ZDF rats with different doses of AdvCMV-GKL, which restored hepatic GK activity to one to two times that of ZCL rats, normalized plasma glucose levels and endogenous glucose production. During a hyperglycemic clamp, glucose production was suppressed and glucose incorporation into glycogen was normal. CONCLUSIONS: Alteration of hepatic GK activity in ZDF rats has profound effects on plasma glucose and hepatic glucose flux.

Authors
Torres, TP; Catlin, RL; Chan, R; Fujimoto, Y; Sasaki, N; Printz, RL; Newgard, CB; Shiota, M
MLA Citation
Torres, TP, Catlin, RL, Chan, R, Fujimoto, Y, Sasaki, N, Printz, RL, Newgard, CB, and Shiota, M. "Restoration of hepatic glucokinase expression corrects hepatic glucose flux and normalizes plasma glucose in zucker diabetic fatty rats." Diabetes 58.1 (January 2009): 78-86.
PMID
18952838
Source
pubmed
Published In
Diabetes
Volume
58
Issue
1
Publish Date
2009
Start Page
78
End Page
86
DOI
10.2337/db08-1119

High heritability of metabolomic profiles in families burdened with premature cardiovascular disease.

Integration of genetic and metabolic profiling holds promise for providing insight into human disease. Coronary artery disease (CAD) is strongly heritable, but the heritability of metabolomic profiles has not been evaluated in humans. We performed quantitative mass spectrometry-based metabolic profiling in 117 individuals within eight multiplex families from the GENECARD study of premature CAD. Heritabilities were calculated using variance components. We found high heritabilities for amino acids (arginine, ornithine, alanine, proline, leucine/isoleucine, valine, glutamate/glutamine, phenylalanine and glycine; h(2)=0.33-0.80, P=0.005-1.9 x 10(-16)), free fatty acids (arachidonic, palmitic, linoleic; h(2)=0.48-0.59, P=0.002-0.00005) and acylcarnitines (h(2)=0.23-0.79, P=0.05-0.0000002). Principal components analysis was used to identify metabolite clusters. Reflecting individual metabolites, several components were heritable, including components comprised of ketones, beta-hydroxybutyrate and C2-acylcarnitine (h(2)=0.61); short- and medium-chain acylcarnitines (h(2)=0.39); amino acids (h(2)=0.44); long-chain acylcarnitines (h(2)=0.39) and branched-chain amino acids (h(2)=0.27). We report a novel finding of high heritabilities of metabolites in premature CAD, establishing a possible genetic basis for these profiles. These results have implications for understanding CAD pathophysiology and genetics.

Authors
Shah, SH; Hauser, ER; Bain, JR; Muehlbauer, MJ; Haynes, C; Stevens, RD; Wenner, BR; Dowdy, ZE; Granger, CB; Ginsburg, GS; Newgard, CB; Kraus, WE
MLA Citation
Shah, SH, Hauser, ER, Bain, JR, Muehlbauer, MJ, Haynes, C, Stevens, RD, Wenner, BR, Dowdy, ZE, Granger, CB, Ginsburg, GS, Newgard, CB, and Kraus, WE. "High heritability of metabolomic profiles in families burdened with premature cardiovascular disease." Mol Syst Biol 5 (2009): 258-.
PMID
19357637
Source
pubmed
Published In
Molecular systems biology
Volume
5
Publish Date
2009
Start Page
258
DOI
10.1038/msb.2009.11

A Branched-Chain Amino Acid-Related Metabolic Signature that Differentiates Obese and Lean Humans and Contributes to Insulin Resistance (DOI:10.1016/j.cmet.2009.02.002)

Authors
Newgard, CB; An, J; Bain, JR; Muehlbauer, MJ; Stevens, RD; Lien, LF; Haqq, AM; Shah, SH; Arlotto, M; Slentz, CA; Rochon, J; Gallup, D; Ilkayeva, O; Wenner, BR; Jr, WSY; Eisenson, H; Musante, G; Surwit, R; Millington, DS; Butler, MD; Svetkey, LP
MLA Citation
Newgard, CB, An, J, Bain, JR, Muehlbauer, MJ, Stevens, RD, Lien, LF, Haqq, AM, Shah, SH, Arlotto, M, Slentz, CA, Rochon, J, Gallup, D, Ilkayeva, O, Wenner, BR, Jr, WSY, Eisenson, H, Musante, G, Surwit, R, Millington, DS, Butler, MD, and Svetkey, LP. "A Branched-Chain Amino Acid-Related Metabolic Signature that Differentiates Obese and Lean Humans and Contributes to Insulin Resistance (DOI:10.1016/j.cmet.2009.02.002)." Cell Metabolism 9.6 (2009): 565-566.
Source
scival
Published In
Cell Metabolism
Volume
9
Issue
6
Publish Date
2009
Start Page
565
End Page
566
DOI
10.1016/j.cmet.2009.05.001

Ghrelin concentrations in Prader-Willi syndrome (PWS) infants and children: changes during development.

BACKGROUND: Prader-Willi syndrome (PWS) is associated with failure to thrive in infancy and progressive hyperphagia and obesity in childhood. This progressive weight gain is associated with hyperghrelinaemia and increased insulin sensitivity. The role of ghrelin excess in the pathogenesis of obesity is unclear. OBJECTIVE: To determine if high ghrelin levels precede the onset of obesity in young PWS children. DESIGN AND METHODS: A cross-sectional study of 33 infants with PWS and 28 healthy control subjects (C). Fasting ghrelin and other satiety hormones were measured. RESULTS: Median total serum ghrelin in young children with PWS trended higher, but did not differ significantly from those in C of similar age, weight-for-age z-score and sex. However, there was more variability in ghrelin concentrations of young PWS. Eleven of 33 PWS subjects had ghrelin levels greater than the 95th percentile for ghrelin values in the C subjects (> 2871 pg/ml). Six of the PWS subjects with high ghrelin levels had weight-for-age z-scores < 0. Ghrelin concentrations in PWS and C infants exceeded those in older children. In youngsters with PWS, leptin was higher, suggesting a relative excess of fat to lean body mass and plasma adiponectin was increased. CONCLUSIONS: Young infants with PWS who have not yet developed hyperphagia or obesity have median fasting ghrelin levels similar to controls. However, a subset (33%) of young PWS is hyperghrelinaemic; approximately one-half of those with hyperghrelinaemia have BMI z-score < 0. The age-related decline in ghrelin is blunted in PWS.

Authors
Haqq, AM; Grambow, SC; Muehlbauer, M; Newgard, CB; Svetkey, LP; Carrel, AL; Yanovski, JA; Purnell, JQ; Freemark, M
MLA Citation
Haqq, AM, Grambow, SC, Muehlbauer, M, Newgard, CB, Svetkey, LP, Carrel, AL, Yanovski, JA, Purnell, JQ, and Freemark, M. "Ghrelin concentrations in Prader-Willi syndrome (PWS) infants and children: changes during development." Clin Endocrinol (Oxf) 69.6 (December 2008): 911-920.
PMID
18710462
Source
pubmed
Published In
Clinical Endocrinology
Volume
69
Issue
6
Publish Date
2008
Start Page
911
End Page
920
DOI
10.1111/j.1365-2265.2008.03385.x

Metabolic cycling in control of glucose-stimulated insulin secretion.

Glucose-stimulated insulin secretion (GSIS) is central to normal control of metabolic fuel homeostasis, and its impairment is a key element of beta-cell failure in type 2 diabetes. Glucose exerts its effects on insulin secretion via its metabolism in beta-cells to generate stimulus/secretion coupling factors, including a rise in the ATP/ADP ratio, which serves to suppress ATP-sensitive K(+) (K(ATP)) channels and activate voltage-gated Ca(2+) channels, leading to stimulation of insulin granule exocytosis. Whereas this K(ATP) channel-dependent mechanism of GSIS has been broadly accepted for more than 30 years, it has become increasingly apparent that it does not fully describe the effects of glucose on insulin secretion. More recent studies have demonstrated an important role for cyclic pathways of pyruvate metabolism in control of insulin secretion. Three cycles occur in islet beta-cells: the pyruvate/malate, pyruvate/citrate, and pyruvate/isocitrate cycles. This review discusses recent work on the role of each of these pathways in control of insulin secretion and builds a case for the particular relevance of byproducts of the pyruvate/isocitrate cycle, NADPH and alpha-ketoglutarate, in control of GSIS.

Authors
Jensen, MV; Joseph, JW; Ronnebaum, SM; Burgess, SC; Sherry, AD; Newgard, CB
MLA Citation
Jensen, MV, Joseph, JW, Ronnebaum, SM, Burgess, SC, Sherry, AD, and Newgard, CB. "Metabolic cycling in control of glucose-stimulated insulin secretion." Am J Physiol Endocrinol Metab 295.6 (December 2008): E1287-E1297. (Review)
PMID
18728221
Source
pubmed
Published In
American journal of physiology. Endocrinology and metabolism
Volume
295
Issue
6
Publish Date
2008
Start Page
E1287
End Page
E1297
DOI
10.1152/ajpendo.90604.2008

Overexpression of pre-pro-cholecystokinin stimulates beta-cell proliferation in mouse and human islets with retention of islet function.

Type 1 and type 2 diabetes result from a deficit in insulin production and beta-cell mass. Methods to expand beta-cell mass are under intensive investigation for the treatment of type 1 and type 2 diabetes. We tested the hypothesis that cholecystokinin (CCK) can promote beta-cell proliferation. We treated isolated mouse and human islets with an adenovirus containing the CCK cDNA (AdCMV-CCK). We measured [(3)H]thymidine and BrdU incorporation into DNA and additionally, performed flow cytometry analysis to determine whether CCK overexpression stimulates beta-cell proliferation. We studied islet function by measuring glucose-stimulated insulin secretion and investigated the cell cycle regulation of proliferating beta-cells by quantitative RT-PCR and Western blot analysis. Overexpression of CCK stimulated [(3)H]thymidine incorporation into DNA 5.0-fold and 15.8-fold in mouse and human islets, respectively. AdCMV-CCK treatment also stimulated BrdU incorporation into DNA 10-fold and 21-fold in mouse and human beta-cells, respectively. Glucose-stimulated insulin secretion was unaffected by CCK expression. Analysis of cyclin and cdk mRNA and protein abundance revealed that CCK overexpression increased cyclin A, cyclin B, cyclin E, cdk1, and cdk2 with no change in cyclin D1, cyclin D2, cyclin D3, cdk4, or cdk6 in mouse and human islets. Additionally, AdCMV-CCK treatment of CCK receptor knockout and wild-type mice resulted in equal [(3)H]thymidine incorporation. CCK is a beta-cell proliferative factor that is effective in both mouse and human islets. CCK triggers beta-cell proliferation without disrupting islet function, up-regulates a distinct set of cell cycle regulators in islets, and signals independently of the CCK receptors.

Authors
Lavine, JA; Raess, PW; Davis, DB; Rabaglia, ME; Presley, BK; Keller, MP; Beinfeld, MC; Kopin, AS; Newgard, CB; Attie, AD
MLA Citation
Lavine, JA, Raess, PW, Davis, DB, Rabaglia, ME, Presley, BK, Keller, MP, Beinfeld, MC, Kopin, AS, Newgard, CB, and Attie, AD. "Overexpression of pre-pro-cholecystokinin stimulates beta-cell proliferation in mouse and human islets with retention of islet function." Mol Endocrinol 22.12 (December 2008): 2716-2728.
PMID
18845673
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
22
Issue
12
Publish Date
2008
Start Page
2716
End Page
2728
DOI
10.1210/me.2008-0255

Absence of the SRC-2 coactivator results in a glycogenopathy resembling Von Gierke's disease.

Hepatic glucose production is critical for basal brain function and survival when dietary glucose is unavailable. Glucose-6-phosphatase (G6Pase) is an essential, rate-limiting enzyme that serves as a terminal gatekeeper for hepatic glucose release into the plasma. Mutations in G6Pase result in Von Gierke's disease (glycogen storage disease-1a), a potentially fatal genetic disorder. We have identified the transcriptional coactivator SRC-2 as a regulator of fasting hepatic glucose release, a function that SRC-2 performs by controlling the expression of hepatic G6Pase. SRC-2 modulates G6Pase expression directly by acting as a coactivator with the orphan nuclear receptor RORalpha. In addition, SRC-2 ablation, in both a whole-body and liver-specific manner, resulted in a Von Gierke's disease phenotype in mice. Our results position SRC-2 as a critical regulator of mammalian glucose production.

Authors
Chopra, AR; Louet, J-F; Saha, P; An, J; Demayo, F; Xu, J; York, B; Karpen, S; Finegold, M; Moore, D; Chan, L; Newgard, CB; O'Malley, BW
MLA Citation
Chopra, AR, Louet, J-F, Saha, P, An, J, Demayo, F, Xu, J, York, B, Karpen, S, Finegold, M, Moore, D, Chan, L, Newgard, CB, and O'Malley, BW. "Absence of the SRC-2 coactivator results in a glycogenopathy resembling Von Gierke's disease." Science 322.5906 (November 28, 2008): 1395-1399.
PMID
19039140
Source
pubmed
Published In
Science
Volume
322
Issue
5906
Publish Date
2008
Start Page
1395
End Page
1399
DOI
10.1126/science.1164847

Silencing of cytosolic or mitochondrial isoforms of malic enzyme has no effect on glucose-stimulated insulin secretion from rodent islets.

We have previously demonstrated a role for pyruvate cycling in glucose-stimulated insulin secretion (GSIS). Some of the possible pyruvate cycling pathways are completed by conversion of malate to pyruvate by malic enzyme. Using INS-1-derived 832/13 cells, it has recently been shown by other laboratories that NADP-dependent cytosolic malic enzyme (MEc), but not NAD-dependent mitochondrial malic enzyme (MEm), regulates GSIS. In the current study, we show that small interfering RNA-mediated suppression of either MEm or MEc results in decreased GSIS in both 832/13 cells and a new and more glucose- and incretin-responsive INS-1-derived cell line, 832/3. The effect of MEm to suppress GSIS in these cell lines was linked to a substantial decrease in cell growth, whereas MEc suppression resulted in decreased NADPH, shown previously to be correlated with GSIS. However, adenovirus-mediated delivery of small interfering RNAs specific to MEc and MEm to isolated rat islets, while leading to effective suppression of the targets transcripts, had no effect on GSIS. Furthermore, islets isolated from MEc-null MOD1(-/-) mice exhibit normal glucose- and potassium-stimulated insulin secretion. These results indicate that pyruvate-malate cycling does not control GSIS in primary rodent islets.

Authors
Ronnebaum, SM; Jensen, MV; Hohmeier, HE; Burgess, SC; Zhou, Y-P; Qian, S; MacNeil, D; Howard, A; Thornberry, N; Ilkayeva, O; Lu, D; Sherry, AD; Newgard, CB
MLA Citation
Ronnebaum, SM, Jensen, MV, Hohmeier, HE, Burgess, SC, Zhou, Y-P, Qian, S, MacNeil, D, Howard, A, Thornberry, N, Ilkayeva, O, Lu, D, Sherry, AD, and Newgard, CB. "Silencing of cytosolic or mitochondrial isoforms of malic enzyme has no effect on glucose-stimulated insulin secretion from rodent islets." J Biol Chem 283.43 (October 24, 2008): 28909-28917.
PMID
18755687
Source
pubmed
Published In
The Journal of biological chemistry
Volume
283
Issue
43
Publish Date
2008
Start Page
28909
End Page
28917
DOI
10.1074/jbc.M804665200

Fatty acid oxidation and insulin action: when less is more.

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Fatty acid oxidation and insulin action: when less is more." Diabetes 57.6 (June 2008): 1455-1456.
PMID
18511446
Source
pubmed
Published In
Diabetes
Volume
57
Issue
6
Publish Date
2008
Start Page
1455
End Page
1456
DOI
10.2337/db08-0281

Chronic suppression of acetyl-CoA carboxylase 1 in beta-cells impairs insulin secretion via inhibition of glucose rather than lipid metabolism.

Acetyl-CoA carboxylase 1 (ACC1) currently is being investigated as a target for treatment of obesity-associated dyslipidemia and insulin resistance. To investigate the effects of ACC1 inhibition on insulin secretion, three small interfering RNA (siRNA) duplexes targeting ACC1 (siACC1) were transfected into the INS-1-derived cell line, 832/13; the most efficacious duplex was also cloned into an adenovirus and used to transduce isolated rat islets. Delivery of the siACC1 duplexes decreased ACC1 mRNA by 60-80% in 832/13 cells and islets and enzyme activity by 46% compared with cells treated with a non-targeted siRNA. Delivery of siACC1 decreased glucose-stimulated insulin secretion (GSIS) by 70% in 832/13 cells and by 33% in islets. Surprisingly, siACC1 treatment decreased glucose oxidation by 49%, and the ATP:ADP ratio by 52%, accompanied by clear decreases in pyruvate cycling activity and tricarboxylic acid cycle intermediates. Exposure of siACC1-treated cells to the pyruvate cycling substrate dimethylmalate restored GSIS to normal without recovery of the depressed ATP:ADP ratio. In siACC1-treated cells, glucokinase protein levels were decreased by 25%, which correlated with a 36% decrease in glycogen synthesis and a 33% decrease in glycolytic flux. Furthermore, acute addition of the ACC1 inhibitor 5-(tetradecyloxy)-2-furoic acid (TOFA) to beta-cells suppressed [(14)C]glucose incorporation into lipids but had no effect on GSIS, whereas chronic TOFA administration suppressed GSIS and glucose metabolism. In sum, chronic, but not acute, suppression of ACC1 activity impairs GSIS via inhibition of glucose rather than lipid metabolism. These findings raise concerns about the use of ACC inhibitors for diabetes therapy.

Authors
Ronnebaum, SM; Joseph, JW; Ilkayeva, O; Burgess, SC; Lu, D; Becker, TC; Sherry, AD; Newgard, CB
MLA Citation
Ronnebaum, SM, Joseph, JW, Ilkayeva, O, Burgess, SC, Lu, D, Becker, TC, Sherry, AD, and Newgard, CB. "Chronic suppression of acetyl-CoA carboxylase 1 in beta-cells impairs insulin secretion via inhibition of glucose rather than lipid metabolism." J Biol Chem 283.21 (May 23, 2008): 14248-14256.
PMID
18381287
Source
pubmed
Published In
The Journal of biological chemistry
Volume
283
Issue
21
Publish Date
2008
Start Page
14248
End Page
14256
DOI
10.1074/jbc.M800119200

Stimulation of human and rat islet beta-cell proliferation with retention of function by the homeodomain transcription factor Nkx6.1.

The homeodomain transcription factor Nkx6.1 plays an important role in pancreatic islet beta-cell development, but its effects on adult beta-cell function, survival, and proliferation are not well understood. In the present study, we demonstrated that treatment of primary rat pancreatic islets with a cytomegalovirus promoter-driven recombinant adenovirus containing the Nkx6.1 cDNA (AdCMV-Nkx6.1) causes dramatic increases in [methyl-(3)H] thymidine and 5-bromo-2'-deoxyuridine (BrdU) incorporation and in the number of cells per islet relative to islets treated with a control adenovirus (AdCMV-betaGAL), whereas suppression of Nkx6.1 expression reduces thymidine incorporation. Immunocytochemical studies reveal that >80% of BrdU-positive cells in AdCMV-Nkx6.1-treated islets are beta cells. Microarray, real-time PCR, and immunoblot analyses reveal that overexpression of Nkx6.1 in rat islets causes concerted upregulation of a cadre of cell cycle control genes, including those encoding cyclins A, B, and E, and several regulatory kinases. Cyclin E is upregulated earlier than the other cyclins, and adenovirus-mediated overexpression of cyclin E is shown to be sufficient to activate islet cell proliferation. Moreover, chromatin immunoprecipitation assays demonstrate direct interaction of Nkx6.1 with the cyclin A2 and B1 genes. Overexpression of Nkx6.1 in rat islets caused a clear enhancement of glucose-stimulated insulin secretion (GSIS), whereas overexpression of Nkx6.1 in human islets caused an increase in the level of [(3)H]thymidine incorporation that was twice the control level, along with complete retention of GSIS. We conclude that Nkx6.1 is among the very rare factors capable of stimulating beta-cell replication with retention or enhancement of function, properties that may be exploitable for expansion of beta-cell mass in treatment of both major forms of diabetes.

Authors
Schisler, JC; Fueger, PT; Babu, DA; Hohmeier, HE; Tessem, JS; Lu, D; Becker, TC; Naziruddin, B; Levy, M; Mirmira, RG; Newgard, CB
MLA Citation
Schisler, JC, Fueger, PT, Babu, DA, Hohmeier, HE, Tessem, JS, Lu, D, Becker, TC, Naziruddin, B, Levy, M, Mirmira, RG, and Newgard, CB. "Stimulation of human and rat islet beta-cell proliferation with retention of function by the homeodomain transcription factor Nkx6.1." Mol Cell Biol 28.10 (May 2008): 3465-3476.
PMID
18347054
Source
pubmed
Published In
Molecular and Cellular Biology
Volume
28
Issue
10
Publish Date
2008
Start Page
3465
End Page
3476
DOI
10.1128/MCB.01791-07

Trefoil factor 3 stimulates human and rodent pancreatic islet beta-cell replication with retention of function.

Both major forms of diabetes involve a decline in beta-cell mass, mediated by autoimmune destruction of insulin-producing cells in type 1 diabetes and by increased rates of apoptosis secondary to metabolic stress in type 2 diabetes. Methods for controlled expansion of beta-cell mass are currently not available but would have great potential utility for treatment of these diseases. In the current study, we demonstrate that overexpression of trefoil factor 3 (TFF3) in rat pancreatic islets results in a 4- to 5-fold increase in [(3)H]thymidine incorporation, with full retention of glucose-stimulated insulin secretion. This increase was almost exclusively due to stimulation of beta-cell replication, as demonstrated by studies of bromodeoxyuridine incorporation and co-immunofluorescence analysis with anti-bromodeoxyuridine and antiinsulin or antiglucagon antibodies. The proliferative effect of TFF3 required the presence of serum or 0.5 ng/ml epidermal growth factor. The ability of TFF3 overexpression to stimulate proliferation of rat islets in serum was abolished by the addition of epidermal growth factor receptor antagonist AG1478. Furthermore, TFF3-induced increases in [3H]thymidine incorporation in rat islets cultured in serum was blocked by overexpression of a dominant-negative Akt protein or treatment with triciribine, an Akt inhibitor. Finally, overexpression of TFF3 also caused a doubling of [3H]thymidine incorporation in human islets. In summary, our findings reveal a novel TFF3-mediated pathway for stimulation of beta-cell replication that could ultimately be exploited for expansion or preservation of islet beta-cell mass.

Authors
Fueger, PT; Schisler, JC; Lu, D; Babu, DA; Mirmira, RG; Newgard, CB; Hohmeier, HE
MLA Citation
Fueger, PT, Schisler, JC, Lu, D, Babu, DA, Mirmira, RG, Newgard, CB, and Hohmeier, HE. "Trefoil factor 3 stimulates human and rodent pancreatic islet beta-cell replication with retention of function." Mol Endocrinol 22.5 (May 2008): 1251-1259.
PMID
18258687
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
22
Issue
5
Publish Date
2008
Start Page
1251
End Page
1259
DOI
10.1210/me.2007-0500

Genetic networks of liver metabolism revealed by integration of metabolic and transcriptional profiling.

Although numerous quantitative trait loci (QTL) influencing disease-related phenotypes have been detected through gene mapping and positional cloning, identification of the individual gene(s) and molecular pathways leading to those phenotypes is often elusive. One way to improve understanding of genetic architecture is to classify phenotypes in greater depth by including transcriptional and metabolic profiling. In the current study, we have generated and analyzed mRNA expression and metabolic profiles in liver samples obtained in an F2 intercross between the diabetes-resistant C57BL/6 leptin(ob/ob) and the diabetes-susceptible BTBR leptin(ob/ob) mouse strains. This cross, which segregates for genotype and physiological traits, was previously used to identify several diabetes-related QTL. Our current investigation includes microarray analysis of over 40,000 probe sets, plus quantitative mass spectrometry-based measurements of sixty-seven intermediary metabolites in three different classes (amino acids, organic acids, and acyl-carnitines). We show that liver metabolites map to distinct genetic regions, thereby indicating that tissue metabolites are heritable. We also demonstrate that genomic analysis can be integrated with liver mRNA expression and metabolite profiling data to construct causal networks for control of specific metabolic processes in liver. As a proof of principle of the practical significance of this integrative approach, we illustrate the construction of a specific causal network that links gene expression and metabolic changes in the context of glutamate metabolism, and demonstrate its validity by showing that genes in the network respond to changes in glutamine and glutamate availability. Thus, the methods described here have the potential to reveal regulatory networks that contribute to chronic, complex, and highly prevalent diseases and conditions such as obesity and diabetes.

Authors
Ferrara, CT; Wang, P; Neto, EC; Stevens, RD; Bain, JR; Wenner, BR; Ilkayeva, OR; Keller, MP; Blasiole, DA; Kendziorski, C; Yandell, BS; Newgard, CB; Attie, AD
MLA Citation
Ferrara, CT, Wang, P, Neto, EC, Stevens, RD, Bain, JR, Wenner, BR, Ilkayeva, OR, Keller, MP, Blasiole, DA, Kendziorski, C, Yandell, BS, Newgard, CB, and Attie, AD. "Genetic networks of liver metabolism revealed by integration of metabolic and transcriptional profiling. (Published online)" PLoS Genet 4.3 (March 14, 2008): e1000034-.
PMID
18369453
Source
pubmed
Published In
PLoS genetics
Volume
4
Issue
3
Publish Date
2008
Start Page
e1000034
DOI
10.1371/journal.pgen.1000034

Mechanisms of disease:Molecular and metabolic mechanisms of insulin resistance and beta-cell failure in type 2 diabetes.

Nearly unlimited supplies of energy-dense foods and technologies that encourage sedentary behaviour have introduced a new threat to the survival of our species: obesity and its co-morbidities. Foremost among the co-morbidities is type 2 diabetes, which is projected to afflict 300 million people worldwide by 2020. Compliance with lifestyle modifications such as reduced caloric intake and increased physical activity has proved to be difficult for the general population, meaning that pharmacological intervention may be the only recourse for some. This epidemiological reality heightens the urgency for gaining a deeper understanding of the processes that cause metabolic failure of key tissues and organ systems in type 2 diabetes, as reviewed here.

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Mechanisms of disease:Molecular and metabolic mechanisms of insulin resistance and beta-cell failure in type 2 diabetes." Nat Rev Mol Cell Biol 9.3 (March 2008): 193-205. (Review)
PMID
18200017
Source
pubmed
Published In
Nature Reviews Molecular Cell Biology
Volume
9
Issue
3
Publish Date
2008
Start Page
193
End Page
205
DOI
10.1038/nrm2327

Galphaz negatively regulates insulin secretion and glucose clearance.

Relatively little is known about the in vivo functions of the alpha subunit of the heterotrimeric G protein Gz (Galphaz). Clues to one potential function recently emerged with the finding that activation of Galphaz inhibits glucose-stimulated insulin secretion in an insulinoma cell line (Kimple, M. E., Nixon, A. B., Kelly, P., Bailey, C. L., Young, K. H., Fields, T. A., and Casey, P. J. (2005) J. Biol. Chem. 280, 31708-31713). To extend this study in vivo, a Galphaz knock-out mouse model was utilized to determine whether Galphaz function plays a role in the inhibition of insulin secretion. No differences were discovered in the gross morphology of the pancreatic islets or in the islet DNA, protein, or insulin content between Galphaz-null and wild-type mice. There was also no difference between the insulin sensitivity of Galphaz-null mice and wild-type controls, as measured by insulin tolerance tests. Galphaz-null mice did, however, display increased plasma insulin concentrations and a corresponding increase in glucose clearance following intraperitoneal and oral glucose challenge as compared with wild-type controls. The increased plasma insulin observed in Galphaz-null mice is most likely a direct result of enhanced insulin secretion, since pancreatic islets isolated from Galphaz-null mice exhibited significantly higher glucose-stimulated insulin secretion than those of wild-type mice. Finally, the increased insulin secretion observed in Galphaz-null islets appears to be due to the relief of a tonic inhibition of adenylyl cyclase, as cAMP production was significantly increased in Galphaz-null islets in the absence of exogenous stimulation. These findings indicate that Galphaz may be a potential new target for therapeutics aimed at ameliorating beta-cell dysfunction in Type 2 diabetes.

Authors
Kimple, ME; Joseph, JW; Bailey, CL; Fueger, PT; Hendry, IA; Newgard, CB; Casey, PJ
MLA Citation
Kimple, ME, Joseph, JW, Bailey, CL, Fueger, PT, Hendry, IA, Newgard, CB, and Casey, PJ. "Galphaz negatively regulates insulin secretion and glucose clearance." J Biol Chem 283.8 (February 22, 2008): 4560-4567.
PMID
18096703
Source
pubmed
Published In
The Journal of biological chemistry
Volume
283
Issue
8
Publish Date
2008
Start Page
4560
End Page
4567
DOI
10.1074/jbc.M706481200

Gαz negatively regulates insulin secretion and glucose clearance

Relatively little is known about the in vivo functions of the α subunit of the heterotrimeric G protein G z (Gα z ). Clues to one potential function recently emerged with the finding that activation of Gα z inhibits glucose-stimulated insulin secretion in an insulinoma cell line (Kimple, M. E., Nixon, A. B., Kelly, P., Bailey, C. L., Young, K. H., Fields, T. A., and Casey, P. J. (2005) J. Biol. Chem. 280, 31708-31713). To extend this study in vivo, a Gα z knock-out mouse model was utilized to determine whether Gα z function plays a role in the inhibition of insulin secretion. No differences were discovered in the gross morphology of the pancreatic islets or in the islet DNA, protein, or insulin content between Gα z -null and wild-type mice. There was also no difference between the insulin sensitivity of Gα z -null mice and wild-type controls, as measured by insulin tolerance tests. Gα z -null mice did, however, display increased plasma insulin concentrations and a corresponding increase in glucose clearance following intraperitoneal and oral glucose challenge as compared with wild-type controls. The increased plasma insulin observed in Gα z -null mice is most likely a direct result of enhanced insulin secretion, since pancreatic islets isolated from Gα z -null mice exhibited significantly higher glucose-stimulated insulin secretion than those of wild-type mice. Finally, the increased insulin secretion observed in Gα z -null islets appears to be due to the relief of a tonic inhibition of adenylyl cyclase, as cAMP production was significantly increased in Gα z -null islets in the absence of exogenous stimulation. These findings indicate that Gα z may be a potential new target for therapeutics aimed at ameliorating β-cell dysfunction in Type 2 diabetes. © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.

Authors
Kimple, ME; Joseph, JW; Bailey, CL; Fueger, PT; Hendry, IA; Newgard, CB; Casey, PJ
MLA Citation
Kimple, ME, Joseph, JW, Bailey, CL, Fueger, PT, Hendry, IA, Newgard, CB, and Casey, PJ. "Gαz negatively regulates insulin secretion and glucose clearance." Journal of Biological Chemistry 283.8 (February 22, 2008): 4560-4567.
Source
scopus
Published In
The Journal of biological chemistry
Volume
283
Issue
8
Publish Date
2008
Start Page
4560
End Page
4567
DOI
10.1074/jbc.M706481200

Mitochondrial overload and incomplete fatty acid oxidation contribute to skeletal muscle insulin resistance.

Previous studies have suggested that insulin resistance develops secondary to diminished fat oxidation and resultant accumulation of cytosolic lipid molecules that impair insulin signaling. Contrary to this model, the present study used targeted metabolomics to find that obesity-related insulin resistance in skeletal muscle is characterized by excessive beta-oxidation, impaired switching to carbohydrate substrate during the fasted-to-fed transition, and coincident depletion of organic acid intermediates of the tricarboxylic acid cycle. In cultured myotubes, lipid-induced insulin resistance was prevented by manipulations that restrict fatty acid uptake into mitochondria. These results were recapitulated in mice lacking malonyl-CoA decarboxylase (MCD), an enzyme that promotes mitochondrial beta-oxidation by relieving malonyl-CoA-mediated inhibition of carnitine palmitoyltransferase 1. Thus, mcd(-/-) mice exhibit reduced rates of fat catabolism and resist diet-induced glucose intolerance despite high intramuscular levels of long-chain acyl-CoAs. These findings reveal a strong connection between skeletal muscle insulin resistance and lipid-induced mitochondrial stress.

Authors
Koves, TR; Ussher, JR; Noland, RC; Slentz, D; Mosedale, M; Ilkayeva, O; Bain, J; Stevens, R; Dyck, JRB; Newgard, CB; Lopaschuk, GD; Muoio, DM
MLA Citation
Koves, TR, Ussher, JR, Noland, RC, Slentz, D, Mosedale, M, Ilkayeva, O, Bain, J, Stevens, R, Dyck, JRB, Newgard, CB, Lopaschuk, GD, and Muoio, DM. "Mitochondrial overload and incomplete fatty acid oxidation contribute to skeletal muscle insulin resistance." Cell Metab 7.1 (January 2008): 45-56.
PMID
18177724
Source
pubmed
Published In
Cell Metabolism
Volume
7
Issue
1
Publish Date
2008
Start Page
45
End Page
56
DOI
10.1016/j.cmet.2007.10.013

Hepatic regulation of fuel metabolism

It has been recognized for more than a century that the liver plays an important role in maintaining metabolic fuel homeostasis. The purpose of this chapter is to summarize mechanisms by which circulating glucose and lipid concentrations are controlled by hepatic metabolic activities. © 2007 Landes Bioscience and Springer Science+Business Media, LLC.

Authors
Clark, C; Newgard, CB
MLA Citation
Clark, C, and Newgard, CB. "Hepatic regulation of fuel metabolism." (December 1, 2007): 90-109. (Chapter)
Source
scopus
Publish Date
2007
Start Page
90
End Page
109
DOI
10.1007/978-0-387-72204-7_5

Altered distribution of adiponectin isoforms in children with Prader-Willi syndrome (PWS): association with insulin sensitivity and circulating satiety peptide hormones.

OBJECTIVE: Prader-Willi syndrome (PWS) is a genetic syndrome characterized by relative hypoinsulinaemia and normal or increased insulin sensitivity despite profound obesity. We hypothesized that this increased insulin sensitivity is mediated by increased levels of total and high molecular weight adiponectin and associated with changes in levels of satiety hormones. DESIGN, PATIENTS AND MEASUREMENTS: We measured total adiponectin and its isoforms [high molecular weight (HMW), middle molecular weight (MMW) and low molecular weight (LMW) adiponectin] and satiety hormones in 14 children with PWS [median age 11.35 years, body mass index (BMI) Z-score 2.15] and 14 BMI-matched controls (median age 11.97 years, BMI Z-score 2.34). RESULTS: Despite comparable BMI Z-scores and leptin levels, the PWS children exhibited lower fasting insulin and HOMA-IR (homeostasis model assessment of insulin resistance) scores compared to obese controls. For any given BMI Z-score, the PWS children showed higher concentrations of fasting total and HMW adiponectin and higher HMW/total adiponectin ratios. The HMW/total adioponectin ratio was preserved in children with PWS at high degrees of obesity. In PWS children, fasting plasma total adiponectin, HMW adiponectin and HMW/total adiponectin ratio correlated negatively with age (P < 0.05), HOMA-IR (P < 0.01), BMI Z-score (P < 0.05), insulin (P < 0.01) and leptin (P < 0.05). In addition to higher fasting ghrelin concentrations, the PWS children showed significantly higher fasting levels of total peptide YY (PYY) and gastric inhibitory polypeptide (GIP) compared to obese controls. CONCLUSIONS: Relative to controls of similar age and BMI Z-score, the PWS children had significantly higher levels of total and HMW adiponectin, and increased ratios of HMW/total adiponectin. These findings may explain in part the heightened insulin sensitivity of PWS children relative to BMI-matched controls.

Authors
Haqq, AM; Muehlbauer, M; Svetkey, LP; Newgard, CB; Purnell, JQ; Grambow, SC; Freemark, MS
MLA Citation
Haqq, AM, Muehlbauer, M, Svetkey, LP, Newgard, CB, Purnell, JQ, Grambow, SC, and Freemark, MS. "Altered distribution of adiponectin isoforms in children with Prader-Willi syndrome (PWS): association with insulin sensitivity and circulating satiety peptide hormones." Clin Endocrinol (Oxf) 67.6 (December 2007): 944-951.
PMID
17666087
Source
pubmed
Published In
Clinical Endocrinology
Volume
67
Issue
6
Publish Date
2007
Start Page
944
End Page
951
DOI
10.1111/j.1365-2265.2007.02991.x

Increased lipid accumulation and insulin resistance in transgenic mice expressing DGAT2 in glycolytic (type II) muscle.

Insulin resistance and type 2 diabetes are frequently accompanied by lipid accumulation in skeletal muscle. However, it is unknown whether primary lipid deposition in skeletal muscle is sufficient to cause insulin resistance or whether the type of muscle fiber, oxidative or glycolytic fiber, is an important determinant of lipid-mediated insulin resistance. Here we utilized transgenic mice to test the hypothesis that lipid accumulation specifically in glycolytic muscle promotes insulin resistance. Overexpression of DGAT2, which encodes an acyl-CoA:diacylglycerol acyltransferase that catalyzes triacylglycerol (TG) synthesis, in glycolytic muscle of mice increased the content of TG, ceramides, and unsaturated long-chain fatty acyl-CoAs in young adult mice. This lipid accumulation was accompanied by impaired insulin signaling and insulin-mediated glucose uptake in glycolytic muscle and impaired whole body glucose and insulin tolerance. We conclude that DGAT2-mediated lipid deposition specifically in glycolytic muscle promotes insulin resistance in this tissue and may contribute to the development of diabetes.

Authors
Levin, MC; Monetti, M; Watt, MJ; Sajan, MP; Stevens, RD; Bain, JR; Newgard, CB; Farese, RV; Farese, RV
MLA Citation
Levin, MC, Monetti, M, Watt, MJ, Sajan, MP, Stevens, RD, Bain, JR, Newgard, CB, Farese, RV, and Farese, RV. "Increased lipid accumulation and insulin resistance in transgenic mice expressing DGAT2 in glycolytic (type II) muscle." Am J Physiol Endocrinol Metab 293.6 (December 2007): E1772-E1781.
PMID
17940217
Source
pubmed
Published In
American journal of physiology. Endocrinology and metabolism
Volume
293
Issue
6
Publish Date
2007
Start Page
E1772
End Page
E1781
DOI
10.1152/ajpendo.00158.2007

Normal flux through ATP-citrate lyase or fatty acid synthase is not required for glucose-stimulated insulin secretion.

It has been proposed that de novo synthesis of long-chain acyl-CoA (LC-CoA) is a signal for glucose-stimulated insulin secretion (GSIS). Key enzymes involved in synthesis of fatty acids from glucose include ATP-citrate lyase (CL) and fatty acid synthase (FAS). An inhibitor of CL, hydroxycitrate (HC), has been reported to inhibit insulin secretion in some laboratories but not in others. Here we show that high concentrations of NaCl created during preparation of HC by standard methods explain the inhibition of GSIS, and that removal of the excess NaCl prevents the effect. To further investigate the role of CL, two small interfering RNA adenoviruses (Ad-siCL2 and Ad-siCL3) were generated. Ad-siCL3 reduced CL mRNA levels by 92 +/- 6% and CL protein levels by 75 +/- 4% but did not affect GSIS in 832/13 cells compared with cells treated with a control adenovirus (Ad-siControl). Similar results were obtained with Ad-siCL2. Ad-siCL3-treated cells also exhibited a 52 +/- 7% reduction in cytosolic oxaloacetate, an 83 +/- 4% reduction in malonyl-CoA levels, and inhibition of [U-(14)C]glucose incorporation into lipid by 43 +/- 4%, all expected metabolic out-comes of CL suppression. Similarly, treatment of 832/13 cells with a recombinant adenovirus specific to FAS (Ad-siFAS) reduced FAS mRNA levels by 81 +/- 2% in 832/13 cells, resulting in a 59 +/- 4% decrease in [U-(14)C]glucose incorporation into lipid, without affecting GSIS. Finally, treatment of primary rat islets with Ad-siCL3 or Ad-siFAS reduced CL and FAS mRNA levels by 65 +/- 4% and 52 +/- 3%, respectively, but had no effect on GSIS relative to Ad-siControl-treated islets. These findings demonstrate that a normal rate of flux of glucose carbons through CL and FAS is not required for GSIS in insulinoma cell lines or rat islets.

Authors
Joseph, JW; Odegaard, ML; Ronnebaum, SM; Burgess, SC; Muehlbauer, J; Sherry, AD; Newgard, CB
MLA Citation
Joseph, JW, Odegaard, ML, Ronnebaum, SM, Burgess, SC, Muehlbauer, J, Sherry, AD, and Newgard, CB. "Normal flux through ATP-citrate lyase or fatty acid synthase is not required for glucose-stimulated insulin secretion." J Biol Chem 282.43 (October 26, 2007): 31592-31600.
PMID
17823126
Source
pubmed
Published In
The Journal of biological chemistry
Volume
282
Issue
43
Publish Date
2007
Start Page
31592
End Page
31600
DOI
10.1074/jbc.M706080200

Expression and glycogenic effect of glycogen-targeting protein phosphatase 1 regulatory subunit GL in cultured human muscle.

Glycogen-targeting PP1 (protein phosphatase 1) subunit G(L) (coded for by the PPP1R3B gene) is expressed in human, but not rodent, skeletal muscle. Its effects on muscle glycogen metabolism are unknown. We show that G(L) mRNA levels in primary cultured human myotubes are similar to those in freshly excised muscle, unlike subunits G(M) (gene PPP1R3A) or PTG (protein targeting to glycogen; gene PPP1R3C), which decrease strikingly. In cultured myotubes, expression of the genes coding for G(L), G(M) and PTG is not regulated by glucose or insulin. Overexpression of G(L) activates myotube GS (glycogen synthase), glycogenesis in glucose-replete and -depleted cells and glycogen accumulation. Compared with overexpressed G(M), G(L) has a more potent activating effect on glycogenesis, while marked enhancement of their combined action is only observed in glucose-replete cells. G(L) does not affect GP (glycogen phosphorylase) activity, while co-overexpression with muscle GP impairs G(L) activation of GS in glucose-replete cells. G(L) enhances long-term glycogenesis additively to glucose depletion and insulin, although G(L) does not change the phosphorylation of GSK3 (GS kinase 3) on Ser9 or its upstream regulator kinase Akt/protein kinase B on Ser473, nor its response to insulin. In conclusion, in cultured human myotubes, the G(L) gene is expressed as in muscle tissue and is unresponsive to glucose or insulin, as are G(M) and PTG genes. G(L) activates GS regardless of glucose, does not regulate GP and stimulates glycogenesis in combination with insulin and glucose depletion.

Authors
Montori-Grau, M; Guitart, M; Lerin, C; Andreu, AL; Newgard, CB; García-Martínez, C; Gómez-Foix, AM
MLA Citation
Montori-Grau, M, Guitart, M, Lerin, C, Andreu, AL, Newgard, CB, García-Martínez, C, and Gómez-Foix, AM. "Expression and glycogenic effect of glycogen-targeting protein phosphatase 1 regulatory subunit GL in cultured human muscle." Biochem J 405.1 (July 1, 2007): 107-113.
PMID
17555403
Source
pubmed
Published In
The Biochemical journal
Volume
405
Issue
1
Publish Date
2007
Start Page
107
End Page
113
DOI
10.1042/BJ20061572

Dissociation of hepatic steatosis and insulin resistance in mice overexpressing DGAT in the liver.

Hepatic steatosis, the accumulation of lipids in the liver, is widely believed to result in insulin resistance. To test the causal relationship between hepatic steatosis and insulin resistance, we generated mice that overexpress acyl-CoA:diacylglycerol acyltransferase 2 (DGAT2), which catalyzes the final step of triacylglycerol (TG) biosynthesis, in the liver (Liv-DGAT2 mice). Liv-DGAT2 mice developed hepatic steatosis, with increased amounts of TG, diacylglycerol, ceramides, and unsaturated long-chain fatty acyl-CoAs in the liver. However, they had no abnormalities in plasma glucose and insulin levels, glucose and insulin tolerance, rates of glucose infusion and hepatic glucose production during hyperinsulinemic-euglycemic clamp studies, or activities of insulin-stimulated signaling proteins in the liver. DGAT1 overexpression in the liver also failed to induce glucose or insulin intolerance. Our results indicate that DGAT-mediated lipid accumulation in the liver is insufficient to cause insulin resistance and show that hepatic steatosis can occur independently of insulin resistance.

Authors
Monetti, M; Levin, MC; Watt, MJ; Sajan, MP; Marmor, S; Hubbard, BK; Stevens, RD; Bain, JR; Newgard, CB; Farese, RV; Hevener, AL; Farese, RV
MLA Citation
Monetti, M, Levin, MC, Watt, MJ, Sajan, MP, Marmor, S, Hubbard, BK, Stevens, RD, Bain, JR, Newgard, CB, Farese, RV, Hevener, AL, and Farese, RV. "Dissociation of hepatic steatosis and insulin resistance in mice overexpressing DGAT in the liver." Cell Metab 6.1 (July 2007): 69-78.
PMID
17618857
Source
pubmed
Published In
Cell Metabolism
Volume
6
Issue
1
Publish Date
2007
Start Page
69
End Page
78
DOI
10.1016/j.cmet.2007.05.005

Hepatic overexpression of glycerol-sn-3-phosphate acyltransferase 1 in rats causes insulin resistance.

Fatty liver is commonly associated with insulin resistance and type 2 diabetes, but it is unclear whether triacylglycerol accumulation or an excess flux of lipid intermediates in the pathway of triacyglycerol synthesis are sufficient to cause insulin resistance in the absence of genetic or diet-induced obesity. To determine whether increased glycerolipid flux can, by itself, cause hepatic insulin resistance, we used an adenoviral construct to overexpress glycerol-sn-3-phosphate acyltransferase-1 (Ad-GPAT1), the committed step in de novo triacylglycerol synthesis. After 5-7 days, food intake, body weight, and fat pad weight did not differ between Ad-GPAT1 and Ad-enhanced green fluorescent protein control rats, but the chow-fed Ad-GPAT1 rats developed fatty liver, hyperlipidemia, and insulin resistance. Liver was the predominant site of insulin resistance; Ad-GPAT1 rats had 2.5-fold higher hepatic glucose output than controls during a hyperinsulinemic-euglycemic clamp. Hepatic diacylglycerol and lysophosphatidate were elevated in Ad-GPAT1 rats, suggesting a role for these lipid metabolites in the development of hepatic insulin resistance, and hepatic protein kinase Cepsilon was activated, providing a potential mechanism for insulin resistance. Ad-GPAT1-treated rats had 50% lower hepatic NF-kappaB activity and no difference in expression of tumor necrosis factor-alpha and interleukin-beta, consistent with hepatic insulin resistance in the absence of increased hepatic inflammation. Glycogen synthesis and uptake of 2-deoxyglucose were reduced in skeletal muscle, suggesting mild peripheral insulin resistance associated with a higher content of skeletal muscle triacylglycerol. These results indicate that increased flux through the pathway of hepatic de novo triacylglycerol synthesis can cause hepatic and systemic insulin resistance in the absence of obesity or a lipogenic diet.

Authors
Nagle, CA; An, J; Shiota, M; Torres, TP; Cline, GW; Liu, Z-X; Wang, S; Catlin, RL; Shulman, GI; Newgard, CB; Coleman, RA
MLA Citation
Nagle, CA, An, J, Shiota, M, Torres, TP, Cline, GW, Liu, Z-X, Wang, S, Catlin, RL, Shulman, GI, Newgard, CB, and Coleman, RA. "Hepatic overexpression of glycerol-sn-3-phosphate acyltransferase 1 in rats causes insulin resistance." J Biol Chem 282.20 (May 18, 2007): 14807-14815.
PMID
17389595
Source
pubmed
Published In
The Journal of biological chemistry
Volume
282
Issue
20
Publish Date
2007
Start Page
14807
End Page
14815
DOI
10.1074/jbc.M611550200

The role of AMPK and mTOR in nutrient sensing in pancreatic beta-cells.

The AMP-activated protein kinase (AMPK) is a central regulator of the energy status of the cell, based on its unique ability to respond directly to fluctuations in the ratio of AMP:ATP. Because glucose and amino acids stimulate insulin release from pancreatic beta-cells by the regulation of metabolic intermediates, AMPK represents an attractive candidate for control of beta-cell function. Here, we show that inhibition of AMPK in beta-cells by high glucose inversely correlates with activation of the mammalian Target of Rapamycin (mTOR) pathway, another cellular sensor for nutritional conditions. Forced activation of AMPK by AICAR, phenformin, or oligomycin significantly blocked phosphorylation of p70S6K, a downstream target of mTOR, in response to the combination of glucose and amino acids. Amino acids also suppressed the activity of AMPK, and this at a minimum required the presence of leucine and glutamine. It is unlikely that the ability of AMPK to sense both glucose and amino acids plays a role in regulation of insulin secretion, as inhibition of AMPK by amino acids did not influence insulin secretion. Moreover, activation of AMPK by AICAR or phenformin did not antagonize glucose-stimulated insulin secretion, and insulin secretion was also unaffected in response to suppression of AMPK activity by expression of a dominant negative AMPK construct (K45R). Taken together, these results suggest that the inhibition of AMPK activity by glucose and amino acids might be an important component of the mechanism for nutrient-stimulated mTOR activity but not insulin secretion in the beta-cell.

Authors
Gleason, CE; Lu, D; Witters, LA; Newgard, CB; Birnbaum, MJ
MLA Citation
Gleason, CE, Lu, D, Witters, LA, Newgard, CB, and Birnbaum, MJ. "The role of AMPK and mTOR in nutrient sensing in pancreatic beta-cells." J Biol Chem 282.14 (April 6, 2007): 10341-10351.
PMID
17287212
Source
pubmed
Published In
The Journal of biological chemistry
Volume
282
Issue
14
Publish Date
2007
Start Page
10341
End Page
10351
DOI
10.1074/jbc.M610631200

Chemical knockout of pantothenate kinase reveals the metabolic and genetic program responsible for hepatic coenzyme A homeostasis.

Coenzyme A (CoA) is the major acyl group carrier in intermediary metabolism. Hopantenate (HoPan), a competitive inhibitor of the pantothenate kinases, was used to chemically antagonize CoA biosynthesis. HoPan dramatically reduced liver CoA and mice developed severe hypoglycemia. Insulin was reduced, glucagon and corticosterone were elevated, and fasting accelerated hypoglycemia. Metabolic profiling revealed a large increase in acylcarnitines, illustrating the role of carnitine in buffering acyl groups to maintain the nonesterified CoASH level. HoPan triggered significant changes in hepatic gene expression that substantially increased the thioesterases, which liberate CoASH from acyl-CoA, and increased pyruvate dehydrogenase kinase 1, which prevents the conversion of CoASH to acetyl-CoA. These results identify the metabolic rearrangements that maintain the CoASH pool which is critical to mitochondrial functions, including gluconeogenesis, fatty acid oxidation, and the tricarboxylic acid and urea cycles.

Authors
Zhang, Y-M; Chohnan, S; Virga, KG; Stevens, RD; Ilkayeva, OR; Wenner, BR; Bain, JR; Newgard, CB; Lee, RE; Rock, CO; Jackowski, S
MLA Citation
Zhang, Y-M, Chohnan, S, Virga, KG, Stevens, RD, Ilkayeva, OR, Wenner, BR, Bain, JR, Newgard, CB, Lee, RE, Rock, CO, and Jackowski, S. "Chemical knockout of pantothenate kinase reveals the metabolic and genetic program responsible for hepatic coenzyme A homeostasis." Chem Biol 14.3 (March 2007): 291-302.
PMID
17379144
Source
pubmed
Published In
Chemistry & Biology
Volume
14
Issue
3
Publish Date
2007
Start Page
291
End Page
302
DOI
10.1016/j.chembiol.2007.01.013

Functional genomics of the beta-cell: short-chain 3-hydroxyacyl-coenzyme A dehydrogenase regulates insulin secretion independent of K+ currents.

Recent advances in functional genomics afford the opportunity to interrogate the expression profiles of thousands of genes simultaneously and examine the function of these genes in a high-throughput manner. In this study, we describe a rational and efficient approach to identifying novel regulators of insulin secretion by the pancreatic beta-cell. Computational analysis of expression profiles of several mouse and cellular models of impaired insulin secretion identified 373 candidate genes involved in regulation of insulin secretion. Using RNA interference, we assessed the requirements of 10 of these candidates and identified four genes (40%) as being essential for normal insulin secretion. Among the genes identified was Hadhsc, which encodes short-chain 3-hydroxyacyl-coenzyme A dehydrogenase (SCHAD), an enzyme of mitochondrial beta-oxidation of fatty acids whose mutation results in congenital hyperinsulinism. RNA interference-mediated gene suppression of Hadhsc in insulinoma cells and primary rodent islets revealed enhanced basal but normal glucose-stimulated insulin secretion. This increase in basal insulin secretion was not attenuated by the opening of the KATP channel with diazoxide, suggesting that SCHAD regulates insulin secretion through a KATP channel-independent mechanism. Our results suggest a molecular explanation for the hyperinsulinemia hypoglycemic seen in patients with SCHAD deficiency.

Authors
Hardy, OT; Hohmeier, HE; Becker, TC; Manduchi, E; Doliba, NM; Gupta, RK; White, P; Stoeckert, CJ; Matschinsky, FM; Newgard, CB; Kaestner, KH
MLA Citation
Hardy, OT, Hohmeier, HE, Becker, TC, Manduchi, E, Doliba, NM, Gupta, RK, White, P, Stoeckert, CJ, Matschinsky, FM, Newgard, CB, and Kaestner, KH. "Functional genomics of the beta-cell: short-chain 3-hydroxyacyl-coenzyme A dehydrogenase regulates insulin secretion independent of K+ currents." Mol Endocrinol 21.3 (March 2007): 765-773.
PMID
17185391
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
21
Issue
3
Publish Date
2007
Start Page
765
End Page
773
DOI
10.1210/me.2006-0411

The promoter for the gene encoding the catalytic subunit of rat glucose-6-phosphatase contains two distinct glucose-responsive regions.

Glucose homeostasis requires the proper expression and regulation of the catalytic subunit of glucose-6-phosphatase (G-6-Pase), which hydrolyzes glucose 6-phosphate to glucose in glucose-producing tissues. Glucose induces the expression of G-6-Pase at the transcriptional and posttranscriptional levels by unknown mechanisms. To better understand this metabolic regulation, we mapped the cis-regulatory elements conferring glucose responsiveness to the rat G-6-Pase gene promoter in glucose-responsive cell lines. The full-length (-4078/+64) promoter conferred a moderate glucose response to a reporter construct in HL1C rat hepatoma cells, which was dependent on coexpression of glucokinase. The same construct provided a robust glucose response in 832/13 INS-1 rat insulinoma cells, which are not glucogenic. Glucose also strongly increased endogenous G-6-Pase mRNA levels in 832/13 cells and in rat pancreatic islets, although the induced levels from islets were still markedly lower than in untreated primary hepatocytes. A distal promoter region was glucose responsive in 832/13 cells and contained a carbohydrate response element with two E-boxes separated by five base pairs. Carbohydrate response element-binding protein bound this region in a glucose-dependent manner in situ. A second, proximal promoter region was glucose responsive in both 832/13 and HL1C cells, with a hepatocyte nuclear factor 1 binding site and two cAMP response elements required for glucose responsiveness. Expression of dominant-negative versions of both cAMP response element-binding protein and CAAT/enhancer-binding protein blocked the glucose response of the proximal region in a dose-dependent manner. We conclude that multiple, distinct cis-regulatory promoter elements are involved in the glucose response of the rat G-6-Pase gene.

Authors
Pedersen, KB; Zhang, P; Doumen, C; Charbonnet, M; Lu, D; Newgard, CB; Haycock, JW; Lange, AJ; Scott, DK
MLA Citation
Pedersen, KB, Zhang, P, Doumen, C, Charbonnet, M, Lu, D, Newgard, CB, Haycock, JW, Lange, AJ, and Scott, DK. "The promoter for the gene encoding the catalytic subunit of rat glucose-6-phosphatase contains two distinct glucose-responsive regions." Am J Physiol Endocrinol Metab 292.3 (March 2007): E788-E801.
PMID
17106062
Source
pubmed
Published In
American journal of physiology. Endocrinology and metabolism
Volume
292
Issue
3
Publish Date
2007
Start Page
E788
End Page
E801
DOI
10.1152/ajpendo.00510.2006

Erratum: Expression and glycogenic effect of glycogen-targeting protein phosphatase 1 regulatory subunit GL in cultured human muscle (Biochemical Journal (2007) 405, (107-113))

Authors
Montori-Grau, M; Guitart, M; Lerin, C; Andreu, AL; Newgard, CB; García-Martínez, C; Gómez-Foix, AM
MLA Citation
Montori-Grau, M, Guitart, M, Lerin, C, Andreu, AL, Newgard, CB, García-Martínez, C, and Gómez-Foix, AM. "Erratum: Expression and glycogenic effect of glycogen-targeting protein phosphatase 1 regulatory subunit GL in cultured human muscle (Biochemical Journal (2007) 405, (107-113))." Biochemical Journal 405.3 (2007): 625--.
Source
scival
Published In
The Biochemical journal
Volume
405
Issue
3
Publish Date
2007
Start Page
625-

Overexpression of rat long chain acyl-coa synthetase 1 alters fatty acid metabolism in rat primary hepatocytes.

Long chain acyl-CoA synthetases (ACSL) activate fatty acids (FA) and provide substrates for both anabolic and catabolic pathways. We have hypothesized that each of the five ACSL isoforms partitions FA toward specific downstream pathways. Acsl1 mRNA is increased in cells under both lipogenic and oxidative conditions. To elucidate the role of ACSL1 in hepatic lipid metabolism, we overexpressed an Acsl1 adenovirus construct (Ad-Acsl1) in rat primary hepatocytes. Ad-ACSL1, located on the endoplasmic reticulum but not on mitochondria or plasma membrane, increased ACS specific activity 3.7-fold. With 100 or 750 mum [1-(14)C]oleate, Ad-Acsl1 increased oleate incorporation into diacylglycerol and phospholipids, particularly phosphatidylethanolamine and phosphatidylinositol, and decreased incorporation into cholesterol esters and secreted triacylglycerol. Ad-Acsl1 did not alter oleate incorporation into triacylglycerol, beta-oxidation products, or total amount of FA metabolized. In pulse-chase experiments to examine the effects of Ad-Acsl1 on lipid turnover, more labeled triacylglycerol and phospholipid, but less labeled diacylglycerol, remained in Ad-Acsl1 cells, suggesting that ACSL1 increased reacylation of hydrolyzed oleate derived from triacylglycerol and diacylglycerol. In addition, less hydrolyzed oleate was used for cholesterol ester synthesis and beta-oxidation. The increase in [1,2,3-(3)H]glycerol incorporation into diacylglycerol and phospholipid was similar to the increase with [(14)C]oleate labeling suggesting that ACSL1 increased de novo synthesis. Labeling Ad-Acsl1 cells with [(14)C]acetate increased triacylglycerol synthesis but did not channel endogenous FA away from cholesterol ester synthesis. Thus, consistent with the hypothesis that individual ACSLs partition FA, Ad-Acsl1 increased FA reacylation and channeled FA toward diacylglycerol and phospholipid synthesis and away from cholesterol ester synthesis.

Authors
Li, LO; Mashek, DG; An, J; Doughman, SD; Newgard, CB; Coleman, RA
MLA Citation
Li, LO, Mashek, DG, An, J, Doughman, SD, Newgard, CB, and Coleman, RA. "Overexpression of rat long chain acyl-coa synthetase 1 alters fatty acid metabolism in rat primary hepatocytes." J Biol Chem 281.48 (December 1, 2006): 37246-37255.
PMID
17028193
Source
pubmed
Published In
The Journal of biological chemistry
Volume
281
Issue
48
Publish Date
2006
Start Page
37246
End Page
37255
DOI
10.1074/jbc.M604427200

The mitochondrial citrate/isocitrate carrier plays a regulatory role in glucose-stimulated insulin secretion.

Glucose-stimulated insulin secretion (GSIS) is mediated in part by glucose metabolism-driven increases in ATP/ADP ratio, but by-products of mitochondrial glucose metabolism also play an important role. Here we investigate the role of the mitochondrial citrate/isocitrate carrier (CIC) in regulation of GSIS. Inhibition of CIC activity in INS-1-derived 832/13 cells or primary rat islets by the substrate analogue 1,2,3-benzenetricarboxylate (BTC) resulted in potent inhibition of GSIS, involving both first and second phase secretion. A recombinant adenovirus containing a CIC-specific siRNA (Ad-siCIC) dose-dependently reduced CIC expression in 832/13 cells and caused parallel inhibitory effects on citrate accumulation in the cytosol. Ad-siCIC treatment did not affect glucose utilization, glucose oxidation, or ATP/ADP ratio but did inhibit glucose incorporation into fatty acids and glucose-induced increases in NADPH/NADP+ ratio relative to cells treated with a control siRNA virus (Ad-siControl). Ad-siCIC also inhibited GSIS in 832/13 cells, whereas overexpression of CIC enhanced GSIS and raised cytosolic citrate levels. In normal rat islets, Ad-siCIC treatment also suppressed CIC mRNA levels and inhibited GSIS. We conclude that export of citrate and/or isocitrate from the mitochondria to the cytosol is an important step in control of GSIS.

Authors
Joseph, JW; Jensen, MV; Ilkayeva, O; Palmieri, F; Alárcon, C; Rhodes, CJ; Newgard, CB
MLA Citation
Joseph, JW, Jensen, MV, Ilkayeva, O, Palmieri, F, Alárcon, C, Rhodes, CJ, and Newgard, CB. "The mitochondrial citrate/isocitrate carrier plays a regulatory role in glucose-stimulated insulin secretion." J Biol Chem 281.47 (November 24, 2006): 35624-35632.
PMID
17001083
Source
pubmed
Published In
The Journal of biological chemistry
Volume
281
Issue
47
Publish Date
2006
Start Page
35624
End Page
35632
DOI
10.1074/jbc.M602606200

A pyruvate cycling pathway involving cytosolic NADP-dependent isocitrate dehydrogenase regulates glucose-stimulated insulin secretion.

Glucose-stimulated insulin secretion (GSIS) from pancreatic islet beta-cells is central to control of mammalian fuel homeostasis. Glucose metabolism mediates GSIS in part via ATP-regulated K+ (KATP) channels, but multiple lines of evidence suggest participation of other signals. Here we investigated the role of cytosolic NADP-dependent isocitrate dehydrogenase (ICDc) in control of GSIS in beta-cells. Delivery of small interfering RNAs specific for ICDc caused impairment of GSIS in two independent robustly glucose-responsive rat insulinoma (INS-1-derived) cell lines and in primary rat islets. Suppression of ICDc also attenuated the glucose-induced increments in pyruvate cycling activity and in NADPH levels, a predicted by-product of pyruvate cycling pathways, as well as the total cellular NADP(H) content. Metabolic profiling of eight organic acids in cell extracts revealed that suppression of ICDc caused increases in lactate production in both INS-1-derived cell lines and primary islets, consistent with the attenuation of pyruvate cycling, with no significant changes in other intermediates. Based on these studies, we propose that a pyruvate cycling pathway involving ICDc plays an important role in control of GSIS.

Authors
Ronnebaum, SM; Ilkayeva, O; Burgess, SC; Joseph, JW; Lu, D; Stevens, RD; Becker, TC; Sherry, AD; Newgard, CB; Jensen, MV
MLA Citation
Ronnebaum, SM, Ilkayeva, O, Burgess, SC, Joseph, JW, Lu, D, Stevens, RD, Becker, TC, Sherry, AD, Newgard, CB, and Jensen, MV. "A pyruvate cycling pathway involving cytosolic NADP-dependent isocitrate dehydrogenase regulates glucose-stimulated insulin secretion." J Biol Chem 281.41 (October 13, 2006): 30593-30602.
PMID
16912049
Source
pubmed
Published In
The Journal of biological chemistry
Volume
281
Issue
41
Publish Date
2006
Start Page
30593
End Page
30602
DOI
10.1074/jbc.M511908200

Compensatory responses to pyruvate carboxylase suppression in islet beta-cells. Preservation of glucose-stimulated insulin secretion.

We have previously reported that glucose-stimulated insulin secretion (GSIS) is tightly correlated with pyruvate carboxylase (PC)-catalyzed anaplerotic flux into the tricarboxylic acid cycle and stimulation of pyruvate cycling activity. To further evaluate the role of PC in beta-cell function, we constructed a recombinant adenovirus containing a small interfering RNA (siRNA) specific to PC (Ad-siPC). Ad-siPC reduced PC mRNA levels by 83 and 64% and PC protein by 56 and 35% in INS-1-derived 832/13 cells and primary rat islets, respectively. Surprisingly, this manipulation did not impair GSIS in rat islets. In Ad-siPC-treated 832/13 cells, GSIS was slightly increased, whereas glycolytic rate and glucose oxidation were unaffected. Flux through PC at high glucose was decreased by only 20%, suggesting an increase in PC-specific activity. Acetyl carnitine, a surrogate for acetyl-CoA, an allosteric activator of PC, was increased by 36% in Ad-siPC-treated cells, suggesting a mechanism by which PC enzymatic activity is maintained with suppressed PC protein levels. In addition, the NADPH:NADP ratio, a proposed coupling factor for GSIS, was unaffected in Ad-siPC-treated cells. We conclude that beta-cells activate compensatory mechanisms in response to suppression of PC expression that prevent impairment of anaplerosis, pyruvate cycling, NAPDH production, and GSIS.

Authors
Jensen, MV; Joseph, JW; Ilkayeva, O; Burgess, S; Lu, D; Ronnebaum, SM; Odegaard, M; Becker, TC; Sherry, AD; Newgard, CB
MLA Citation
Jensen, MV, Joseph, JW, Ilkayeva, O, Burgess, S, Lu, D, Ronnebaum, SM, Odegaard, M, Becker, TC, Sherry, AD, and Newgard, CB. "Compensatory responses to pyruvate carboxylase suppression in islet beta-cells. Preservation of glucose-stimulated insulin secretion." J Biol Chem 281.31 (August 4, 2006): 22342-22351.
PMID
16740637
Source
pubmed
Published In
The Journal of biological chemistry
Volume
281
Issue
31
Publish Date
2006
Start Page
22342
End Page
22351
DOI
10.1074/jbc.M604350200

FoxA2, Nkx2.2, and PDX-1 regulate islet beta-cell-specific mafA expression through conserved sequences located between base pairs -8118 and -7750 upstream from the transcription start site.

The MafA transcription factor is both critical to islet beta-cell function and has a unique pancreatic cell-type-specific expression pattern. To localize the potential transcriptional regulatory region(s) involved in directing expression to the beta cell, areas of identity within the 5' flanking region of the mouse, human, and rat mafA genes were found between nucleotides -9389 and -9194, -8426 and -8293, -8118 and -7750, -6622 and -6441, -6217 and -6031, and -250 and +56 relative to the transcription start site. The identity between species was greater than 75%, with the highest found between bp -8118 and -7750 ( approximately 94%, termed region 3). Region 3 was the only upstream mammalian conserved region found in chicken mafA (88% identity). In addition, region 3 uniquely displayed beta-cell-specific activity in cell-line-based reporter assays. Important regulators of beta-cell formation and function, PDX-1, FoxA2, and Nkx2.2, were shown to specifically bind to region 3 in vivo using the chromatin immunoprecipitation assay. Mutational and functional analyses demonstrated that FoxA2 (bp -7943 to -7910), Nkx2.2 (bp -7771 to -7746), and PDX-1 (bp -8087 to -8063) mediated region 3 activation. Consistent with a role in transcription, small interfering RNA-mediated knockdown of PDX-1 led to decreased mafA mRNA production in INS-1-derived beta-cell lines (832/13 and 832/3), while MafA expression was undetected in the pancreatic epithelium of Nkx2.2 null animals. These results suggest that beta-cell-type-specific mafA transcription is principally controlled by region 3-acting transcription factors that are essential in the formation of functional beta cells.

Authors
Raum, JC; Gerrish, K; Artner, I; Henderson, E; Guo, M; Sussel, L; Schisler, JC; Newgard, CB; Stein, R
MLA Citation
Raum, JC, Gerrish, K, Artner, I, Henderson, E, Guo, M, Sussel, L, Schisler, JC, Newgard, CB, and Stein, R. "FoxA2, Nkx2.2, and PDX-1 regulate islet beta-cell-specific mafA expression through conserved sequences located between base pairs -8118 and -7750 upstream from the transcription start site." Mol Cell Biol 26.15 (August 2006): 5735-5743.
PMID
16847327
Source
pubmed
Published In
Molecular and Cellular Biology
Volume
26
Issue
15
Publish Date
2006
Start Page
5735
End Page
5743
DOI
10.1128/MCB.00249-06

Efficient gene delivery to pancreatic islets with ultrasonic microbubble destruction technology.

This study describes a method of gene delivery to pancreatic islets of adult, living animals by ultrasound targeted microbubble destruction (UTMD). The technique involves incorporation of plasmids into the phospholipid shell of gas-filled microbubbles, which are then infused into rats and destroyed within the pancreatic microcirculation with ultrasound. Specific delivery of genes to islet beta cells by UTMD was achieved by using a plasmid containing a rat insulin 1 promoter (RIP), and reporter gene expression was regulated appropriately by glucose in animals that received a RIP-luciferase plasmid. To demonstrate biological efficacy, we used UTMD to deliver RIP-human insulin and RIP-hexokinase I plasmids to islets of adult rats. Delivery of the former plasmid resulted in clear increases in circulating human C-peptide and decreased blood glucose levels, whereas delivery of the latter plasmid resulted in a clear increase in hexokinase I protein expression in islets, increased insulin levels in blood, and decreased circulating glucose levels. We conclude that UTMD allows relatively noninvasive delivery of genes to pancreatic islets with an efficiency sufficient to modulate beta cell function in adult animals.

Authors
Chen, S; Ding, J-H; Bekeredjian, R; Yang, B-Z; Shohet, RV; Johnston, SA; Hohmeier, HE; Newgard, CB; Grayburn, PA
MLA Citation
Chen, S, Ding, J-H, Bekeredjian, R, Yang, B-Z, Shohet, RV, Johnston, SA, Hohmeier, HE, Newgard, CB, and Grayburn, PA. "Efficient gene delivery to pancreatic islets with ultrasonic microbubble destruction technology." Proc Natl Acad Sci U S A 103.22 (May 30, 2006): 8469-8474.
PMID
16709667
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
103
Issue
22
Publish Date
2006
Start Page
8469
End Page
8474
DOI
10.1073/pnas.0602921103

Pro- and antiapoptotic proteins regulate apoptosis but do not protect against cytokine-mediated cytotoxicity in rat islets and beta-cell lines.

Type 1 diabetes results from islet beta-cell death and dysfunction induced by an autoimmune mechanism. Proinflammatory cytokines such as interleukin-1beta and gamma-interferon are mediators of this beta-cell cytotoxicity, but the mechanism by which damage occurs is not well understood. In the current study, we present multiple lines of evidence supporting the conclusion that cytokine-induced killing of rat beta-cells occurs predominantly by a nonapoptotic mechanism, including the following: 1) A rat beta-cell line selected for resistance to cytokine-induced cytotoxicity (833/15) is equally sensitive to killing by the apoptosis-inducing agents camptothecin and etoposide as a cytokine-sensitive cell line (832/13). 2) Overexpression of a constitutively active form of the antiapoptotic protein kinase Akt1 in 832/13 cells provides significant protection against cell killing induced by camptothecin and etoposide but no protection against cytokine-mediated damage. 3) Small interfering RNA-mediated suppression of the proapoptotic protein Bax enhances viability of 832/13 cells upon exposure to the known apoptosis-inducing drugs but not the inflammatory cytokines. 4) Exposure of primary rat islets or 832/13 cells to the inflammatory cytokines causes cell death as evidenced by the release of adenylate kinase activity into the cell medium, with no attendant increase in caspase 3 activation or annexin V staining. In contrast, camptothecin- and etoposide-induced killing is associated with robust increases in caspase 3 activation and annexin V staining. 5) Camptothecin increases cellular ATP levels, whereas inflammatory cytokines lower ATP levels in both beta-cell lines and primary islets. We conclude that proinflammatory cytokines cause beta-cell cytotoxicity primarily through a nonapoptotic mechanism linked to a decline in ATP levels.

Authors
Collier, JJ; Fueger, PT; Hohmeier, HE; Newgard, CB
MLA Citation
Collier, JJ, Fueger, PT, Hohmeier, HE, and Newgard, CB. "Pro- and antiapoptotic proteins regulate apoptosis but do not protect against cytokine-mediated cytotoxicity in rat islets and beta-cell lines." Diabetes 55.5 (May 2006): 1398-1406.
PMID
16644697
Source
pubmed
Published In
Diabetes
Volume
55
Issue
5
Publish Date
2006
Start Page
1398
End Page
1406

Obesity-related derangements in metabolic regulation.

An epidemic surge in the incidence of obesity has occurred worldwide over the past two decades. This alarming trend has been triggered by lifestyle habits that encourage overconsumption of energy-rich foods while also discouraging regular physical activity. These environmental influences create a chronic energy imbalance that leads to persistent weight gain in the form of body fat and a host of other abnormalities in metabolic homeostasis. As adiposity increases, so does the risk of developing comorbidities such as diabetes, hypertension, and cardiovascular disease. The intimate association between obesity and systemic metabolic dysregulation has inspired a new area of biochemistry research in which scientists are seeking to understand the molecular mechanisms that link chronic lipid oversupply to tissue dysfunction and disease development. The purpose of this chapter is to review recent findings in this area, placing emphasis on lipid-induced functional impairments in the major peripheral organs that control energy flux: adipose tissue, the liver, skeletal muscle, and the pancreas.

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Obesity-related derangements in metabolic regulation." Annu Rev Biochem 75 (2006): 367-401. (Review)
PMID
16756496
Source
pubmed
Published In
Annual Review of Biochemistry
Volume
75
Publish Date
2006
Start Page
367
End Page
401
DOI
10.1146/annurev.biochem.75.103004.142512

TRB3 links the E3 ubiquitin ligase COF1 to lipid metabolism

During fasting, increased concentrations of circulating catecholamines promote the mobilization of lipid stores from adipose tissue in part by phosphorylating and inactivating acetyl-coenzyme A carboxylase (ACC), the rate-limiting enzyme in fatty acid synthesis. Here, we describe a parallel pathway, in which the pseudokinase Tribbles 3 (TRB3), whose abundance is increased during fasting, stimulates lipolysis by triggering the degradation of ACC in adipose tissue. TRB3 promoted ACC ubiquitination through an association with the E3 ubiquitin ligase constitutive photomorphogenic protein 1 (COP1). Indeed, adipocytes deficient in TRB3 accumulated larger amounts of ACC protein than did wild-type cells. Because transgenic mice expressing TRB3 in adipose tissue are protected from diet-induced obesity due to enhanced fatty acid oxidation, these results demonstrate how phosphorylation and ubiquitination pathways converge on a key regulator of lipid metabolism to maintain energy homeostasis.

Authors
Qi, L; Heredia, JE; Altarejos, JY; Screaton, R; Goebel, N; Niessen, S; MacLeod, IX; Liew, CW; Kulkarni, RN; Bain, J; Newgard, C; Welson, M; Evans, RM; Yates, J; Montminy, M
MLA Citation
Qi, L, Heredia, JE, Altarejos, JY, Screaton, R, Goebel, N, Niessen, S, MacLeod, IX, Liew, CW, Kulkarni, RN, Bain, J, Newgard, C, Welson, M, Evans, RM, Yates, J, and Montminy, M. "TRB3 links the E3 ubiquitin ligase COF1 to lipid metabolism." Science 312.5781 (2006): 1763-1766.
PMID
16794074
Source
scival
Published In
Science
Volume
312
Issue
5781
Publish Date
2006
Start Page
1763
End Page
1766
DOI
10.1126/science.1123374

The Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) weight loss project: Rationale and design.

This paper outlines the rationale and design of the Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) weight loss project, in which detailed biologic profiling of three hundred and fifty obese individuals (body mass index (BMI): 30-50 kg/m(2)) will be conducted as they lose weight via seven distinct interventions. These profiles will be compared to those of fifty normal, healthy, control participants (BMI: 18.5-24.9 kg/m(2)). The interventions include the following: Roux-en-Y gastric bypass surgery, dietary interventions of differing macronutrient composition and diverse pharmacologic interventions. Outcome variables include eight conventional metabolites and CRP measured by standard clinical chemistry techniques, twenty hormones of energy balance and fuel homeostasis measured by radioimmunoassay (RIA) or by enzyme-linked Immunosorbent assay (ELISA), ten pro- and anti-inflammatory cytokines measured using Luminex xMAP technology, one hundred and one intermediary metabolites measured by targeted mass-spectrometry-based methods, and physiologic variables such as body composition measured by dual energy X-ray absorptiometry (DEXA), air displacement plethysmography, and abdominal computerized tomography (CT), insulin sensitivity measured by intravenous glucose tolerance test (IV-GTT) and metabolic rate measured by indirect calorimetry. Results from this study will expand our knowledge of the biology of obesity and weight regulation and may lead to targeted strategies for its treatment and control.

Authors
Haqq, AM; Lien, LF; Boan, J; Arlotto, M; Slentz, CA; Muehlbauer, MJ; Rochon, J; Gallup, D; McMahon, RL; Bain, JR; Stevens, R; Millington, D; Butler, MD; Newgard, CB; Svetkey, LP
MLA Citation
Haqq, AM, Lien, LF, Boan, J, Arlotto, M, Slentz, CA, Muehlbauer, MJ, Rochon, J, Gallup, D, McMahon, RL, Bain, JR, Stevens, R, Millington, D, Butler, MD, Newgard, CB, and Svetkey, LP. "The Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) weight loss project: Rationale and design." Contemp Clin Trials 26.6 (December 2005): 616-625.
PMID
16239128
Source
pubmed
Published In
Contemporary Clinical Trials
Volume
26
Issue
6
Publish Date
2005
Start Page
616
End Page
625
DOI
10.1016/j.cct.2005.09.003

Islets for all?

Authors
Hohmeier, HE; Newgard, CB
MLA Citation
Hohmeier, HE, and Newgard, CB. "Islets for all?." Nat Biotechnol 23.10 (October 2005): 1231-1232.
PMID
16211061
Source
pubmed
Published In
Nature Biotechnology
Volume
23
Issue
10
Publish Date
2005
Start Page
1231
End Page
1232
DOI
10.1038/nbt1005-1231

Peroxisome proliferator-activated receptor-gamma co-activator 1alpha-mediated metabolic remodeling of skeletal myocytes mimics exercise training and reverses lipid-induced mitochondrial inefficiency.

Peroxisome proliferator-activated receptor-gamma co-activator 1alpha (PGC1alpha) is a promiscuous co-activator that plays a key role in regulating mitochondrial biogenesis and fuel homeostasis. Emergent evidence links decreased skeletal muscle PGC1alpha activity and coincident impairments in mitochondrial performance to the development of insulin resistance in humans. Here we used rodent models to demonstrate that muscle mitochondrial efficiency is compromised by diet-induced obesity and is subsequently rescued by exercise training. Chronic high fat feeding caused accelerated rates of incomplete fatty acid oxidation and accumulation of beta-oxidative intermediates. The capacity of muscle mitochondria to fully oxidize a heavy influx of fatty acid depended on factors such as fiber type and exercise training and was positively correlated with expression levels of PGC1alpha. Likewise, an efficient lipid-induced substrate switch in cultured myocytes depended on adenovirus-mediated increases in PGC1alpha expression. Our results supported a novel paradigm in which a high lipid supply, occurring under conditions of low PGC1alpha, provokes a disconnect between mitochondrial beta-oxidation and tricarboxylic acid cycle activity. Conversely, the metabolic remodeling that occurred in response to PGC1alpha overexpression favored a shift from incomplete to complete beta-oxidation. We proposed that PGC1alpha enables muscle mitochondria to better cope with a high lipid load, possibly reflecting a fundamental metabolic benefit of exercise training.

Authors
Koves, TR; Li, P; An, J; Akimoto, T; Slentz, D; Ilkayeva, O; Dohm, GL; Yan, Z; Newgard, CB; Muoio, DM
MLA Citation
Koves, TR, Li, P, An, J, Akimoto, T, Slentz, D, Ilkayeva, O, Dohm, GL, Yan, Z, Newgard, CB, and Muoio, DM. "Peroxisome proliferator-activated receptor-gamma co-activator 1alpha-mediated metabolic remodeling of skeletal myocytes mimics exercise training and reverses lipid-induced mitochondrial inefficiency." J Biol Chem 280.39 (September 30, 2005): 33588-33598.
PMID
16079133
Source
pubmed
Published In
The Journal of biological chemistry
Volume
280
Issue
39
Publish Date
2005
Start Page
33588
End Page
33598
DOI
10.1074/jbc.M507621200

Metabolism: A is for adipokine.

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Metabolism: A is for adipokine." Nature 436.7049 (July 21, 2005): 337-338.
PMID
16034406
Source
pubmed
Published In
Nature
Volume
436
Issue
7049
Publish Date
2005
Start Page
337
End Page
338
DOI
10.1038/436337a

Peptide-mediated targeting of the islets of Langerhans.

Strategies for restoring beta-cell function in diabetic patients would be greatly aided by the ability to target genes, proteins, or small molecules specifically to these cells. Furthermore, the ability to direct imaging agents specifically to beta-cells would facilitate diagnosis and monitoring of disease progression. To isolate ligands that can home to beta-cells in vivo, we have panned a random phage-displayed 20-mer peptide library on freshly isolated rat islets. We have isolated two 20-mer peptides that bind to islets ex vivo. One of these peptides preferentially homes to the islets of Langerhans in a normal rat with clear differentiation between the endocrine and exocrine cells of the pancreas. Furthermore, this peptide does not target beta-cells in a type 2 diabetes animal model, suggesting that the peptide can discriminate between glucose-stimulated insulin secretion-functional and -dysfunctional beta-cells.

Authors
Samli, KN; McGuire, MJ; Newgard, CB; Johnston, SA; Brown, KC
MLA Citation
Samli, KN, McGuire, MJ, Newgard, CB, Johnston, SA, and Brown, KC. "Peptide-mediated targeting of the islets of Langerhans." Diabetes 54.7 (July 2005): 2103-2108.
PMID
15983211
Source
pubmed
Published In
Diabetes
Volume
54
Issue
7
Publish Date
2005
Start Page
2103
End Page
2108

Isolation of a mycoplasma-specific binding peptide from an unbiased phage-displayed peptide library.

An important goal in medicine is the development of methods for cell-specific targeting of therapeutic molecules to pathogens or pathogen-infected cells. However, little progress has been made in cell-specific targeting of bacterially infected cells. Using a phage display approach, we have isolated a 20-mer peptide that binds to Mycoplasma arginini infected pancreatic beta-cells in tissue culture. This peptide binds to M. arginini infected beta-cells 200 times better than a control phage and is specific for the infected cells. Furthermore, transferring the M. arginini contamination to another cell line renders the newly infected cell line susceptible to peptide binding. Immunolocalization experiments suggest that the peptide is binding to M. arginini adhered to the cell surface. The free synthetic peptide retains its binding in the absence of the phage vehicle and tetramerization of the peptide increases its affinity for the infected cells. Efforts have been made to use this peptide to eliminate Mycoplasma from infected cell lines using ferromagnetic beads coated with the selected peptide. A ten-fold reduction of infection was accomplished with one fractionation via this approach. Our results suggest that this peptide, isolated from an unbiased selection, may be of utility for the detection and reduction of Mycoplasma infection in cultured cells. Furthermore, a general implication of our findings is that phage display methods may be useful for identifying peptides that target a broad array of other biological pathogens in a specific fashion.

Authors
De, J; Chang, Y-C; Samli, KN; Schisler, JC; Newgard, CB; Johnston, SA; Brown, KC
MLA Citation
De, J, Chang, Y-C, Samli, KN, Schisler, JC, Newgard, CB, Johnston, SA, and Brown, KC. "Isolation of a mycoplasma-specific binding peptide from an unbiased phage-displayed peptide library." Mol Biosyst 1.2 (July 2005): 149-157.
PMID
16880978
Source
pubmed
Published In
Molecular BioSystems
Volume
1
Issue
2
Publish Date
2005
Start Page
149
End Page
157
DOI
10.1039/b504572j

The Nkx6.1 homeodomain transcription factor suppresses glucagon expression and regulates glucose-stimulated insulin secretion in islet beta cells.

We have previously described rat insulinoma INS-1-derived cell lines with robust or poor glucose-stimulated insulin secretion (GSIS). In the current study, we have further resolved these lines into three classes: class 1, glucose-unresponsive/glucagon-expressing; class 2, glucose-unresponsive/glucagon-negative; and class 3, glucose-responsive/glucagon-negative. The transcription factor Nkx2.2 was expressed with relative abundance of 3.3, 1.0, and 1.0 in class 1, class 2, and class 3 cells, respectively, whereas Nkx6.1 expression had the opposite trend: 1.0, 2.6, and 6.4 in class 1, class 2, and class 3 cells, respectively. In class 1 cells, overexpressed Nkx6.1 suppressed glucagon expression but did not affect the levels of several other prominent beta cell transcription factors. RNA interference (RNAi)-mediated suppression of Nkx6.1 in class 3 cells resulted in a doubling of glucagon mRNA, with no effect on Pdx1 levels, whereas suppression of Pdx1 in class 3 cells caused a 12-fold increase in glucagon transcript levels, demonstrating independent effects of Nkx6.1 and Pdx1 on glucagon expression in beta cell lines. RNAi-mediated suppression of Nkx6.1 expression in class 3 cells also caused a decrease in GSIS from 13.9- to 3.7-fold, whereas suppression of Pdx1 reduced absolute amounts of insulin secretion without affecting fold response. Finally, RNAi-mediated suppression of Nkx6.1 mRNA in primary rat islets was accompanied by a significant decrease in GSIS relative to control cells. In sum, our studies have revealed roles for Nkx6.1 in suppression of glucagon expression and control of GSIS in islet beta cells.

Authors
Schisler, JC; Jensen, PB; Taylor, DG; Becker, TC; Knop, FK; Takekawa, S; German, M; Weir, GC; Lu, D; Mirmira, RG; Newgard, CB
MLA Citation
Schisler, JC, Jensen, PB, Taylor, DG, Becker, TC, Knop, FK, Takekawa, S, German, M, Weir, GC, Lu, D, Mirmira, RG, and Newgard, CB. "The Nkx6.1 homeodomain transcription factor suppresses glucagon expression and regulates glucose-stimulated insulin secretion in islet beta cells." Proc Natl Acad Sci U S A 102.20 (May 17, 2005): 7297-7302.
PMID
15883383
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
102
Issue
20
Publish Date
2005
Start Page
7297
End Page
7302
DOI
10.1073/pnas.0502168102

Mechanism of insulin gene regulation by the pancreatic transcription factor Pdx-1: application of pre-mRNA analysis and chromatin immunoprecipitation to assess formation of functional transcriptional complexes.

The homeodomain factor Pdx-1 regulates an array of genes in the developing and mature pancreas, but whether regulation of each specific gene occurs by a direct mechanism (binding to promoter elements and activating basal transcriptional machinery) or an indirect mechanism (via regulation of other genes) is unknown. To determine the mechanism underlying regulation of the insulin gene by Pdx-1, we performed a kinetic analysis of insulin transcription following adenovirus-mediated delivery of a small interfering RNA specific for pdx-1 into insulinoma cells and pancreatic islets to diminish endogenous Pdx-1 protein. insulin transcription was assessed by measuring both a long half-life insulin mRNA (mature mRNA) and a short half-life insulin pre-mRNA species by real-time reverse transcriptase-PCR. Following progressive knock-down of Pdx-1 levels, we observed coordinate decreases in pre-mRNA levels (to about 40% of normal levels at 72 h). In contrast, mature mRNA levels showed strikingly smaller and delayed declines, suggesting that the longer half-life of this species underestimates the contribution of Pdx-1 to insulin transcription. Chromatin immunoprecipitation assays revealed that the decrease in insulin transcription was associated with decreases in the occupancies of Pdx-1 and p300 at the proximal insulin promoter. Although there was no corresponding change in the recruitment of RNA polymerase II to the proximal promoter, its recruitment to the insulin coding region was significantly reduced. Our results suggest that Pdx-1 directly regulates insulin transcription through formation of a complex with transcriptional coactivators on the proximal insulin promoter. This complex leads to enhancement of elongation by the basal transcriptional machinery.

Authors
Iype, T; Francis, J; Garmey, JC; Schisler, JC; Nesher, R; Weir, GC; Becker, TC; Newgard, CB; Griffen, SC; Mirmira, RG
MLA Citation
Iype, T, Francis, J, Garmey, JC, Schisler, JC, Nesher, R, Weir, GC, Becker, TC, Newgard, CB, Griffen, SC, and Mirmira, RG. "Mechanism of insulin gene regulation by the pancreatic transcription factor Pdx-1: application of pre-mRNA analysis and chromatin immunoprecipitation to assess formation of functional transcriptional complexes." J Biol Chem 280.17 (April 29, 2005): 16798-16807.
PMID
15743769
Source
pubmed
Published In
The Journal of biological chemistry
Volume
280
Issue
17
Publish Date
2005
Start Page
16798
End Page
16807
DOI
10.1074/jbc.M414381200

Hyperlipidemic effects of dietary saturated fats mediated through PGC-1beta coactivation of SREBP.

The PGC-1 family of coactivators stimulates the activity of certain transcription factors and nuclear receptors. Transcription factors in the sterol responsive element binding protein (SREBP) family are key regulators of the lipogenic genes in the liver. We show here that high-fat feeding, which induces hyperlipidemia and atherogenesis, stimulates the expression of both PGC-1beta and SREBP1c and 1a in liver. PGC-1beta coactivates the SREBP transcription factor family and stimulates lipogenic gene expression. Further, PGC-1beta is required for SREBP-mediated lipogenic gene expression. However, unlike SREBP itself, PGC-1beta reduces fat accumulation in the liver while greatly increasing circulating triglycerides and cholesterol in VLDL particles. The stimulation of lipoprotein transport upon PGC-1beta expression is likely due to the simultaneous coactivation of the liver X receptor, LXRalpha, a nuclear hormone receptor with known roles in hepatic lipid transport. These data suggest a mechanism through which dietary saturated fats can stimulate hyperlipidemia and atherogenesis.

Authors
Lin, J; Yang, R; Tarr, PT; Wu, P-H; Handschin, C; Li, S; Yang, W; Pei, L; Uldry, M; Tontonoz, P; Newgard, CB; Spiegelman, BM
MLA Citation
Lin, J, Yang, R, Tarr, PT, Wu, P-H, Handschin, C, Li, S, Yang, W, Pei, L, Uldry, M, Tontonoz, P, Newgard, CB, and Spiegelman, BM. "Hyperlipidemic effects of dietary saturated fats mediated through PGC-1beta coactivation of SREBP." Cell 120.2 (January 28, 2005): 261-273.
PMID
15680331
Source
pubmed
Published In
Cell
Volume
120
Issue
2
Publish Date
2005
Start Page
261
End Page
273
DOI
10.1016/j.cell.2004.11.043

Cell lines derived from pancreatic islets.

The islets of Langerhans play a major role in control of metabolic fuel homeostasis. The rapid increase in incidence of diabetes worldwide has spurred renewed interest in islet cell biology. However, gaining a detailed understanding of islet function at a molecular and biochemical level has been complicated by the difficulty and high cost associated with isolation of pancreatic islets. Until recently, islet-derived cell lines have represented sub-optimal surrogates for primary cells for functional studies due to their undifferentiated or unstable phenotypic features. New approaches have resulted in isolation and characterization of rodent insulinoma cell lines that retain many key functional attributes of normal islets and have become useful tools in the study of islet cell biology.

Authors
Hohmeier, HE; Newgard, CB
MLA Citation
Hohmeier, HE, and Newgard, CB. "Cell lines derived from pancreatic islets." Mol Cell Endocrinol 228.1-2 (December 30, 2004): 121-128. (Review)
PMID
15541576
Source
pubmed
Published In
Molecular and Cellular Endocrinology
Volume
228
Issue
1-2
Publish Date
2004
Start Page
121
End Page
128
DOI
10.1016/j.mce.2004.04.017

Biomedicine. Insulin resistance takes a trip through the ER.

Authors
Muoio, DM; Newgard, CB
MLA Citation
Muoio, DM, and Newgard, CB. "Biomedicine. Insulin resistance takes a trip through the ER." Science 306.5695 (October 15, 2004): 425-426.
PMID
15486283
Source
pubmed
Published In
Science
Volume
306
Issue
5695
Publish Date
2004
Start Page
425
End Page
426
DOI
10.1126/science.1104680

An adenovirus vector for efficient RNA interference-mediated suppression of target genes in insulinoma cells and pancreatic islets of langerhans.

Silencing gene expression by RNA interference (RNAi) can provide insight into gene function but requires efficient delivery of small interfering RNAs (siRNAs) into cells. Introduction of exogenous nucleic acids can be especially difficult in cultured pancreatic islets. This article describes a method for making recombinant adenoviruses that efficiently drive expression of siRNAs in islet beta-cells and a beta-cell-derived cell line. Transduction with a virus expressing an siRNA specific for GLUT2 reduced GLUT2 mRNA and protein levels by 80% in the INS-1-derived beta-cell line, 832/13, and GLUT2 protein levels by >90% in primary rat islets. Another virus expressing an siRNA specific for glucokinase (GK) caused 80% suppression of GK mRNA and 50% suppression of GK protein levels in 832/13 cells. These experiments validate recombinant adenoviral RNAi vectors as a useful tool for suppression of the expression of specific genes in pancreatic islets and beta-cell lines. Advantages of this approach include 1) the high efficiency of adenovirus-mediated gene transfer in insulinoma cell lines and rat islets and 2) the rapidity with which RNAi constructs can be prepared and tested relative to stable-transfection strategies.

Authors
Bain, JR; Schisler, JC; Takeuchi, K; Newgard, CB; Becker, TC
MLA Citation
Bain, JR, Schisler, JC, Takeuchi, K, Newgard, CB, and Becker, TC. "An adenovirus vector for efficient RNA interference-mediated suppression of target genes in insulinoma cells and pancreatic islets of langerhans." Diabetes 53.9 (September 2004): 2190-2194.
PMID
15331526
Source
pubmed
Published In
Diabetes
Volume
53
Issue
9
Publish Date
2004
Start Page
2190
End Page
2194

Biochemical mechanism of lipid-induced impairment of glucose-stimulated insulin secretion and reversal with a malate analogue.

Hyperlipidemia appears to play an integral role in loss of glucose-stimulated insulin secretion (GSIS) in type 2 diabetes. This impairment can be simulated in vitro by chronic culture of 832/13 insulinoma cells with high concentrations of free fatty acids, or by study of lipid-laden islets from Zucker diabetic fatty rats. Here we show that impaired GSIS is not a simple result of saturation of lipid storage pathways, as adenovirus-mediated overexpression of a cytosolically localized variant of malonyl-CoA decarboxylase in either cellular model results in dramatic lowering of cellular triglyceride stores but no improvement in GSIS. Instead, the glucose-induced increment in "pyruvate cycling" activity (pyruvate exchange with tricarboxylic acid cycle intermediates measured by (13)C NMR), previously shown to play an important role in GSIS, is completely ablated in concert with profound suppression of GSIS in lipid-cultured 832/13 cells, whereas glucose oxidation is unaffected. Moreover, GSIS is partially restored in both lipid-cultured 832/13 cells and islets from Zucker diabetic fatty rats by addition of a membrane permeant ester of a pyruvate cycling intermediate (dimethyl malate). We conclude that chronic exposure of islet beta-cells to fatty acids grossly alters a mitochondrial pathway of pyruvate metabolism that is important for normal GSIS.

Authors
Boucher, A; Lu, D; Burgess, SC; Telemaque-Potts, S; Jensen, MV; Mulder, H; Wang, M-Y; Unger, RH; Sherry, AD; Newgard, CB
MLA Citation
Boucher, A, Lu, D, Burgess, SC, Telemaque-Potts, S, Jensen, MV, Mulder, H, Wang, M-Y, Unger, RH, Sherry, AD, and Newgard, CB. "Biochemical mechanism of lipid-induced impairment of glucose-stimulated insulin secretion and reversal with a malate analogue." J Biol Chem 279.26 (June 25, 2004): 27263-27271.
PMID
15073188
Source
pubmed
Published In
The Journal of biological chemistry
Volume
279
Issue
26
Publish Date
2004
Start Page
27263
End Page
27271
DOI
10.1074/jbc.M401167200

Hepatic expression of malonyl-CoA decarboxylase reverses muscle, liver and whole-animal insulin resistance.

Lipid infusion or ingestion of a high-fat diet results in insulin resistance, but the mechanism underlying this phenomenon remains unclear. Here we show that, in rats fed a high-fat diet, whole-animal, muscle and liver insulin resistance is ameliorated following hepatic overexpression of malonyl-coenzyme A (CoA) decarboxylase (MCD), an enzyme that affects lipid partitioning. MCD overexpression decreased circulating free fatty acid (FFA) and liver triglyceride content. In skeletal muscle, levels of triglyceride and long-chain acyl-CoA (LC-CoA)-two candidate mediators of insulin resistance-were either increased or unchanged. Metabolic profiling of 36 acylcarnitine species by tandem mass spectrometry revealed a unique decrease in the concentration of one lipid-derived metabolite, beta-OH-butyrate, in muscle of MCD-overexpressing animals. The best explanation for our findings is that hepatic expression of MCD lowered circulating FFA levels, which led to lowering of muscle beta-OH-butyrate levels and improvement of insulin sensitivity.

Authors
An, J; Muoio, DM; Shiota, M; Fujimoto, Y; Cline, GW; Shulman, GI; Koves, TR; Stevens, R; Millington, D; Newgard, CB
MLA Citation
An, J, Muoio, DM, Shiota, M, Fujimoto, Y, Cline, GW, Shulman, GI, Koves, TR, Stevens, R, Millington, D, and Newgard, CB. "Hepatic expression of malonyl-CoA decarboxylase reverses muscle, liver and whole-animal insulin resistance." Nat Med 10.3 (March 2004): 268-274.
PMID
14770177
Source
pubmed
Published In
Nature Medicine
Volume
10
Issue
3
Publish Date
2004
Start Page
268
End Page
274
DOI
10.1038/nm995

Understanding of basic mechanisms of beta-cell function and survival: prelude to new diabetes therapies.

Type 1 and type 2 diabetes are both diseases of insulin insufficiency, although they develop by distinct pathways. The recent surge in the incidence of type 2 diabetes and the chronic ailments confronted by patients with either form of the disease highlight the need for better understanding of beta-cell biology. In this review, we present recent work focused on this goal. Our hope is that basic research being conducted in this and other laboratories will ultimately contribute to the development of methods for enhancing beta-cell function and survival in the context of both major forms of diabetes. Our strategy for understanding the beta-cell involves a multidisciplinary approach in which tools from the traditional fields of biochemistry, enzymology, and physiology are teamed with newer technologies from the fields of molecular biology, gene discovery, cell and developmental biology, and biophysical chemistry. We have focused on two important aspects of beta-cell biology in our studies: beta-cell function, specifically the metabolic regulatory mechanisms involved in glucose-stimulated insulin secretion, and beta-cell resistance to immune attack, with emphasis on resistance to inflammatory cytokines and reactive oxygen species.

Authors
Newgard, CB; Hohmeier, HE; Lu, D; Jensen, MV; Tran, VV; Chen, G; Burgess, S; Sherry, AD
MLA Citation
Newgard, CB, Hohmeier, HE, Lu, D, Jensen, MV, Tran, VV, Chen, G, Burgess, S, and Sherry, AD. "Understanding of basic mechanisms of beta-cell function and survival: prelude to new diabetes therapies." Cell Biochem Biophys 40.3 Suppl (2004): 159-168. (Review)
PMID
15289651
Source
pubmed
Published In
Cell Biochemistry and Biophysics
Volume
40
Issue
3 Suppl
Publish Date
2004
Start Page
159
End Page
168

Pancreatic islets and insulinoma cells express a novel isoform of group VIA phospholipase A2 (iPLA2 beta) that participates in glucose-stimulated insulin secretion and is not produced by alternate splicing of the iPLA2 beta transcript.

Many cells express a group VIA 84 kDa phospholipase A(2) (iPLA(2)beta) that is sensitive to inhibition by a bromoenol lactone (BEL) suicide substrate. Inhibition of iPLA(2)beta in pancreatic islets and insulinoma cells suppresses, and overexpression of iPLA(2)beta in INS-1 insulinoma cells amplifies, glucose-stimulated insulin secretion, suggesting that iPLA(2)beta participates in secretion. Western blotting analyses reveal that glucose-responsive 832/13 INS-1 cells express essentially no 84 kDa iPLA(2)beta-immunoreactive protein but predominantly express a previously unrecognized immunoreactive iPLA(2)beta protein in the 70 kDa region that is not generated by a mechanism of alternate splicing of the iPLA(2)beta transcript. To determine if the 70 kDa-immunoreactive protein is a short isoform of iPLA(2)beta, protein from the 70 kDa region was digested with trypsin and analyzed by mass spectrometry. Such analyses reveal several peptides with masses and amino acid sequences that exactly match iPLA(2)beta tryptic peptides. Peptide sequences identified in the 70 kDa tryptic digest include iPLA(2)beta residues 7-53, suggesting that the N-terminus is preserved. We also report here that the 832/13 INS-1 cells express iPLA(2)beta catalytic activity and that BEL inhibits secretagogue-stimulated insulin secretion from these cells but not the incorporation of arachidonic acid into membrane PC pools of these cells. These observations suggest that the catalytic iPLA(2)beta activity expressed in 832/13 INS-1 cells is attributable to a short isoform of iPLA(2)beta and that this isoform participates in insulin secretory but not in membrane phospholipid remodeling pathways. Further, the finding that pancreatic islets also express predominantly a 70 kDa iPLA(2)beta-immunoreactive protein suggests that a signal transduction role of iPLA(2)beta in the native beta-cell might be attributable to a 70 kDa isoform of iPLA(2)beta.

Authors
Ramanadham, S; Song, H; Hsu, F-F; Zhang, S; Crankshaw, M; Grant, GA; Newgard, CB; Bao, S; Ma, Z; Turk, J
MLA Citation
Ramanadham, S, Song, H, Hsu, F-F, Zhang, S, Crankshaw, M, Grant, GA, Newgard, CB, Bao, S, Ma, Z, and Turk, J. "Pancreatic islets and insulinoma cells express a novel isoform of group VIA phospholipase A2 (iPLA2 beta) that participates in glucose-stimulated insulin secretion and is not produced by alternate splicing of the iPLA2 beta transcript." Biochemistry 42.47 (December 2, 2003): 13929-13940.
PMID
14636061
Source
pubmed
Published In
Biochemistry
Volume
42
Issue
47
Publish Date
2003
Start Page
13929
End Page
13940
DOI
10.1021/bi034843p

Inflammatory mechanisms in diabetes: lessons from the beta-cell.

Inflammation plays an important role in the destruction of pancreatic islet beta-cells that leads to type I diabetes. This involves infiltration of T-cells and macrophages into the islets and local production of inflammatory cytokines such as interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma. Our laboratory has developed several strategies for protecting beta-cells against oxidative stress and cytokine-induced cytotoxicity. These include a cytokine selection strategy that results in cell lines that are resistant to the combined effects of IL-1 beta+IFN-gamma. More recently, we have combined the cytokine selection procedure with overexpression of the antiapoptotic gene bcl-2, resulting in cell lines with greater resistance to oxidative stress and cytokine-induced damage than achieved with either procedure alone. This article summarizes this work and the remarkably divergent mechanisms by which protection is achieved in the different model systems. We also discuss the potential relevance of insights gained from these approaches for enhancing islet cell survival and function in both major forms of diabetes.

Authors
Hohmeier, HE; Tran, VV; Chen, G; Gasa, R; Newgard, CB
MLA Citation
Hohmeier, HE, Tran, VV, Chen, G, Gasa, R, and Newgard, CB. "Inflammatory mechanisms in diabetes: lessons from the beta-cell." Int J Obes Relat Metab Disord 27 Suppl 3 (December 2003): S12-S16. (Review)
PMID
14704737
Source
pubmed
Published In
Int J Obes Relat Metab Disord
Volume
27 Suppl 3
Publish Date
2003
Start Page
S12
End Page
S16
DOI
10.1038/sj.ijo.0802493

Regulation and function of the muscle glycogen-targeting subunit of protein phosphatase 1 (GM) in human muscle cells depends on the COOH-terminal region and glycogen content.

G(M), the muscle-specific glycogen-targeting subunit of protein phosphatase 1 (PP1) targeted to the sarcoplasmic reticulum, was proposed to regulate recovery of glycogen in exercised muscle, whereas mutation truncation of its COOH-terminal domain is known to be associated with type 2 diabetes. Here, we demonstrate differential effects of G(M) overexpression in human muscle cells according to glycogen concentration. Adenovirus-mediated delivery of G(M) slightly activated glycogen synthase (GS) and inactivated glycogen phosphorylase (GP) in glycogen-replete cells, causing an overaccumulation of glycogen and impairment of glycogenolysis after glucose deprivation. Differently, in glycogen-depleted cells, G(M) strongly increased GS activation with no further enhancement of early glycogen resynthesis and without affecting GP. Effects of G(M) on GS and GP were abrogated by treatment with dibutyryl cyclic AMP. Expression of a COOH-terminal deleted-mutant (G(M) Delta C), lacking the membrane binding sequence to sarcoplasmic reticulum, failed to activate GS in glycogen-depleted cells, while behaving similar to native G(M) in glycogen-replete cells. This is explained by loss of stability of the G(M) Delta C protein following glycogen-depletion. In summary, G(M) promotes glycogen storage and inversely regulates GS and GP activities, while, specifically, synthase phosphatase activity of G(M)-PP1 is inhibited by glycogen. The conditional loss of function of the COOH-terminal deleted G(M) construct may help to explain the reported association of truncation mutation of G(M) with insulin resistance in human subjects.

Authors
Lerín, C; Montell, E; Nolasco, T; Clark, C; Brady, MJ; Newgard, CB; Gómez-Foix, AM
MLA Citation
Lerín, C, Montell, E, Nolasco, T, Clark, C, Brady, MJ, Newgard, CB, and Gómez-Foix, AM. "Regulation and function of the muscle glycogen-targeting subunit of protein phosphatase 1 (GM) in human muscle cells depends on the COOH-terminal region and glycogen content." Diabetes 52.9 (September 2003): 2221-2226.
PMID
12941760
Source
pubmed
Published In
Diabetes
Volume
52
Issue
9
Publish Date
2003
Start Page
2221
End Page
2226

PGC-1beta in the regulation of hepatic glucose and energy metabolism.

Peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) is a transcriptional coactivator that regulates multiple aspects of cellular energy metabolism, including mitochondrial biogenesis, hepatic gluconeogenesis, and beta-oxidation of fatty acids. PGC-1alpha mRNA levels are increased in both type-1 and type-2 diabetes and may contribute to elevated hepatic glucose production in diabetic states. We have recently described PGC-1beta, a novel transcriptional coactivator that is a homolog of PGC-1alpha. Although PGC-1beta shares significant sequence similarity and tissue distribution with PGC-1alpha, the biological activities of PGC-1beta in the regulation of cellular metabolism is unknown. In this study, we used an adenoviral-mediated expression system to study the function of PGC-1beta both in cultured hepatocytes and in the liver of rats. PGC-1beta, like PGC-1alpha, potently induces the expression of an array of mitochondrial genes involved in oxidative metabolism. However, in contrast to PGC-1alpha, PGC-1beta poorly activates the expression of gluconeogenic genes in hepatocytes or liver in vivo, illustrating that these two coactivators play distinct roles in hepatic glucose metabolism. The reduced ability of PGC-1beta to induce gluconeogenic genes is due, at least in part, to its inability to physically associate with and coactivate hepatic nuclear receptor 4alpha (HNF4alpha) and forkhead transcription factor O1 (FOXO1), two critical transcription factors that mediate the activation of gluconeogenic gene expression by PGC-1alpha. These data illustrate that PGC-1beta and PGC-1alpha have distinct arrays of activities in hepatic energy metabolism.

Authors
Lin, J; Tarr, PT; Yang, R; Rhee, J; Puigserver, P; Newgard, CB; Spiegelman, BM
MLA Citation
Lin, J, Tarr, PT, Yang, R, Rhee, J, Puigserver, P, Newgard, CB, and Spiegelman, BM. "PGC-1beta in the regulation of hepatic glucose and energy metabolism." J Biol Chem 278.33 (August 15, 2003): 30843-30848.
PMID
12807885
Source
pubmed
Published In
The Journal of biological chemistry
Volume
278
Issue
33
Publish Date
2003
Start Page
30843
End Page
30848
DOI
10.1074/jbc.M303643200

Bioenergetic analysis of peroxisome proliferator-activated receptor gamma coactivators 1alpha and 1beta (PGC-1alpha and PGC-1beta) in muscle cells.

Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha is a coactivator of nuclear receptors and other transcription factors that regulates several components of energy metabolism, particularly certain aspects of adaptive thermogenesis in brown fat and skeletal muscle, hepatic gluconeogenesis, and fiber type switching in skeletal muscle. PGC-1alpha has been shown to induce mitochondrial biogenesis when expressed in muscle cells, and preliminary analysis has suggested that this molecule may specifically increase the fraction of uncoupled versus coupled respiration. In this paper, we have performed detailed bioenergetic analyses of the function of PGC-1alpha and its homolog PGC-1beta in muscle cells by monitoring simultaneously oxygen consumption and membrane potential. Cells expressing PGC-1alpha or PGC-1beta display higher proton leak rates at any given membrane potential than control cells. However, cells expressing PGC-1alpha have a higher proportion of their mitochondrial respiration linked to proton leak than cells expressing PGC-1beta. Although these two proteins cause a similar increase in the expression of many mitochondrial genes, PGC-1beta preferentially induces certain genes involved in the removal of reactive oxygen species, recently recognized as activators of uncoupling proteins. Together, these data indicate that PGC-1alpha and PGC-1beta profoundly alter mitochondrial metabolism and suggest that these proteins are likely to play different physiological functions.

Authors
St-Pierre, J; Lin, J; Krauss, S; Tarr, PT; Yang, R; Newgard, CB; Spiegelman, BM
MLA Citation
St-Pierre, J, Lin, J, Krauss, S, Tarr, PT, Yang, R, Newgard, CB, and Spiegelman, BM. "Bioenergetic analysis of peroxisome proliferator-activated receptor gamma coactivators 1alpha and 1beta (PGC-1alpha and PGC-1beta) in muscle cells." J Biol Chem 278.29 (July 18, 2003): 26597-26603.
PMID
12734177
Source
pubmed
Published In
The Journal of biological chemistry
Volume
278
Issue
29
Publish Date
2003
Start Page
26597
End Page
26603
DOI
10.1074/jbc.M301850200

Suppression of beta cell energy metabolism and insulin release by PGC-1alpha.

beta cell dysfunction is an important component of type 2 diabetes, but the molecular basis for this defect is poorly understood. The transcriptional coactivator PGC-1alpha mRNA and protein levels are significantly elevated in islets from multiple animal models of diabetes; adenovirus-mediated expression of PGC-1alpha to levels similar to those present in diabetic rodents produces a marked inhibition of glucose-stimulated insulin secretion from islets in culture and in live mice. This inhibition coincides with changes in metabolic gene expression associated with impaired beta cell function, including the induction of glucose-6-phosphatase and suppression of GLUT2, glucokinase, and glycerol-3-phosphate dehydrogenase. These changes result in blunting of the glucose-induced rise in cellular ATP levels and membrane electrical activity responsible for Ca(2+) influx and insulin exocytosis. These results strongly suggest that PGC-1alpha plays a key functional role in the beta cell and is involved in the pathogenesis of the diabetic phenotype.

Authors
Yoon, JC; Xu, G; Deeney, JT; Yang, S-N; Rhee, J; Puigserver, P; Levens, AR; Yang, R; Zhang, C-Y; Lowell, BB; Berggren, P-O; Newgard, CB; Bonner-Weir, S; Weir, G; Spiegelman, BM
MLA Citation
Yoon, JC, Xu, G, Deeney, JT, Yang, S-N, Rhee, J, Puigserver, P, Levens, AR, Yang, R, Zhang, C-Y, Lowell, BB, Berggren, P-O, Newgard, CB, Bonner-Weir, S, Weir, G, and Spiegelman, BM. "Suppression of beta cell energy metabolism and insulin release by PGC-1alpha." Dev Cell 5.1 (July 2003): 73-83.
PMID
12852853
Source
pubmed
Published In
Developmental Cell
Volume
5
Issue
1
Publish Date
2003
Start Page
73
End Page
83

Hepatic expression of a targeting subunit of protein phosphatase-1 in streptozotocin-diabetic rats reverses hyperglycemia and hyperphagia despite depressed glucokinase expression.

Glycogen-targeting subunits of protein phosphatase-1 (PP-1) are scaffolding proteins that facilitate the regulation of key enzymes of glycogen metabolism by PP-1. In the current study, we have tested the effects of hepatic expression of GMDeltaC, a truncated version of the muscle-targeting subunit isoform, in rats rendered insulin-deficient via injection of a single moderate dose of streptozotocin (STZ). Three key findings emerged. First, GMDeltaC expression in liver was sufficient to fully normalize blood glucose levels (from 335 +/- 31 mg/dl prior to viral injection to 109 +/- 28 mg/dl 6 days after injection) and liver glycogen content in STZ-injected rats. Second, this normalization occurred despite very low levels of liver glucokinase expression in the insulin-deficient STZ-injected rats. Finally, the hyperphagia induced by STZ injection was completely reversed by GMDeltaC expression in liver. In contrast to these findings with GMDeltaC, overexpression of another targeting subunit, GL, in STZ-injected rats caused a large increase in liver glycogen stores but only a transient decrease in food intake and blood glucose levels. The surprising demonstration of a glucose-lowering effect of GMDeltaC in the background of depressed hepatic glucokinase expression suggests that controlled stimulation of liver glycogen storage may be an effective mechanism for improving glucose homeostasis, even when normal pathways of glucose disposal are impaired.

Authors
Yang, R; Newgard, CB
MLA Citation
Yang, R, and Newgard, CB. "Hepatic expression of a targeting subunit of protein phosphatase-1 in streptozotocin-diabetic rats reverses hyperglycemia and hyperphagia despite depressed glucokinase expression." J Biol Chem 278.26 (June 27, 2003): 23418-23425.
PMID
12697773
Source
pubmed
Published In
The Journal of biological chemistry
Volume
278
Issue
26
Publish Date
2003
Start Page
23418
End Page
23425
DOI
10.1074/jbc.M213112200

Discrete and complementary mechanisms of protection of beta-cells against cytokine-induced and oxidative damage achieved by bcl-2 overexpression and a cytokine selection strategy.

We have been investigating the potential utility of engineered cell lines as surrogates for primary islet cells in treatment of type 1 diabetes. To this end, two strategies that have emerged for procuring cell lines with resistance to immune-mediated damage are 1) selection of cytokine-resistant cell lines by growth of INS-1 insulinoma cells in iteratively increasing concentrations of interleukin (IL)-1beta + gamma-interferon (IFN-gamma), and 2) stable overexpression of the anti-apoptotic gene bcl-2 in INS-1 cells. Herein, we show that bcl-2-overexpressing cells are resistant to the cytotoxic effects of reactive oxygen and nitrogen species (ROS/RNS), but are only modestly protected against high concentrations of IL-1beta + INF-gamma, whereas the converse is true in cytokine selected cells. We also found that the combination of bcl-2 expression and cytokine selection confers a broader spectrum of resistance than either procedure alone, such that the resultant cells are highly resistant to cytokines and ROS/RNS, with no impairment in glucose-stimulated insulin secretion. INS-1-derived cells with combined bcl-2 expression and cytokine selection are also more resistant to damage induced by coculture with mitogen-activated peripheral blood mononuclear cells. Surprisingly, application of the cytokine selection procedure to bcl-2-overexpressing cells does not result in impairment of nuclear factor-kappaB translocation, iNOS expression, and NO production, as clearly occurs upon application of the selection procedure to cells without bcl-2 overexpression. Further investigation of the diverse pathways involved in the development of cytokine and ROS/RNS resistance may define simplified and specific strategies for preservation of beta-cell mass.

Authors
Tran, VV; Chen, G; Newgard, CB; Hohmeier, HE
MLA Citation
Tran, VV, Chen, G, Newgard, CB, and Hohmeier, HE. "Discrete and complementary mechanisms of protection of beta-cells against cytokine-induced and oxidative damage achieved by bcl-2 overexpression and a cytokine selection strategy." Diabetes 52.6 (June 2003): 1423-1432.
PMID
12765953
Source
pubmed
Published In
Diabetes
Volume
52
Issue
6
Publish Date
2003
Start Page
1423
End Page
1432

Stimulus/secretion coupling factors in glucose-stimulated insulin secretion: insights gained from a multidisciplinary approach.

There is a growing appreciation for the complexity of the pathways involved in glucose-stimulated insulin secretion (GSIS) from pancreatic islet beta-cells. In our laboratory, this has stimulated the development of an interdisciplinary approach to the problem. In this study, we review recent studies combining the tools of recombinant adenovirus for gene delivery, the development of novel cell lines that exhibit either robust or weak GSIS, and nuclear magnetic resonance imaging for metabolic fingerprinting of glucose-stimulated cells. Using these tools, we demonstrate a potentially important role for pyruvate carboxylase-mediated pyruvate cycling pathways in the control of GSIS, and discuss potential coupling factors produced by such pathways.

Authors
Newgard, CB; Lu, D; Jensen, MV; Schissler, J; Boucher, A; Burgess, S; Sherry, AD
MLA Citation
Newgard, CB, Lu, D, Jensen, MV, Schissler, J, Boucher, A, Burgess, S, and Sherry, AD. "Stimulus/secretion coupling factors in glucose-stimulated insulin secretion: insights gained from a multidisciplinary approach." Diabetes 51 Suppl 3 (December 2002): S389-S393. (Review)
PMID
12475781
Source
pubmed
Published In
Diabetes
Volume
51 Suppl 3
Publish Date
2002
Start Page
S389
End Page
S393

While tinkering with the beta-cell...metabolic regulatory mechanisms and new therapeutic strategies: American Diabetes Association Lilly Lecture, 2001.

A common feature of the two major forms of human diabetes is the partial or complete loss of insulin secretion from beta-cells in the pancreatic islets of Langerhans. In this article, we review the development of a set of tools for studying beta-cell biology and their application to understanding of fuel-mediated insulin secretion and enhancement of beta-cell survival. Insights into these basic issues are likely to be useful for the design of new drug and cell-based diabetes therapies.

Authors
Newgard, CB
MLA Citation
Newgard, CB. "While tinkering with the beta-cell..metabolic regulatory mechanisms and new therapeutic strategies: American Diabetes Association Lilly Lecture, 2001." Diabetes 51.11 (November 2002): 3141-3150.
PMID
12401704
Source
pubmed
Published In
Diabetes
Volume
51
Issue
11
Publish Date
2002
Start Page
3141
End Page
3150

A futile metabolic cycle activated in adipocytes by antidiabetic agents.

Thiazolidinediones (TZDs) are effective therapies for type 2 diabetes, which has reached epidemic proportions in industrialized societies. TZD treatment reduces circulating free fatty acids (FFAs), which oppose insulin actions in skeletal muscle and other insulin target tissues. Here we report that TZDs, acting as ligands for the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-gamma, markedly induce adipocyte glycerol kinase (GyK) gene expression. This is surprising, as standard textbooks indicate that adipocytes lack GyK and thereby avoid futile cycles of triglyceride breakdown and resynthesis from glycerol and FFAs. By inducing GyK, TZDs markedly stimulate glycerol incorporation into triglyceride and reduce FFA secretion from adipocytes. The 'futile' fuel cycle resulting from expression of GyK in adipocytes is thus a novel mechanism contributing to reduced FFA levels and perhaps insulin sensitization by antidiabetic therapies.

Authors
Guan, H-P; Li, Y; Jensen, MV; Newgard, CB; Steppan, CM; Lazar, MA
MLA Citation
Guan, H-P, Li, Y, Jensen, MV, Newgard, CB, Steppan, CM, and Lazar, MA. "A futile metabolic cycle activated in adipocytes by antidiabetic agents." Nat Med 8.10 (October 2002): 1122-1128.
PMID
12357248
Source
pubmed
Published In
Nature Medicine
Volume
8
Issue
10
Publish Date
2002
Start Page
1122
End Page
1128
DOI
10.1038/nm780

Mitochondrial metabolism sets the maximal limit of fuel-stimulated insulin secretion in a model pancreatic beta cell: a survey of four fuel secretagogues.

The precise metabolic steps that couple glucose catabolism to insulin secretion in the pancreatic beta cell are incompletely understood. ATP generated from glycolytic metabolism in the cytosol, from mitochondrial metabolism, and/or from the hydrogen shuttles operating between cytosolic and mitochondrial compartments has been implicated as an important coupling factor. To identify the importance of each of these metabolic pathways, we have compared the fates of four fuel secretagogues (glucose, pyruvate, dihydroxyacetone, and glycerol) in the INS1-E beta cell line. Two of these fuels, dihydroxyacetone and glycerol, are normally ineffective as secretagogues but are enabled by adenovirus-mediated expression of glycerol kinase. Comparison of these two particular fuels allows the effect of redox state on insulin secretion to be evaluated since the phosphorylated products dihydroxyacetone phosphate and glycerol phosphate lie on opposite sides of the NADH-consuming glycerophosphate dehydrogenase reaction. Based upon measurements of glycolytic metabolites, mitochondrial oxidation, mitochondrial matrix calcium, and mitochondrial membrane potential, we find that insulin secretion most tightly correlates with mitochondrial metabolism for each of the four fuels. In the case of glucose stimulation, the high control strength of glucose phosphorylation sets the pace of glucose metabolism and thus the rate of insulin secretion. However, bypassing this reaction with pyruvate, dihydroxyacetone, or glycerol uncovers constraints imposed by mitochondrial metabolism, each of which attains a similar maximal limit of insulin secretion. More specifically, we found that the hyperpolarization of the mitochondrial membrane, related to the proton export from the mitochondrial matrix, correlates well with insulin secretion. Based on these findings, we propose that fuel-stimulated secretion is in fact limited by the inherent thermodynamic constraints of proton gradient formation.

Authors
Antinozzi, PA; Ishihara, H; Newgard, CB; Wollheim, CB
MLA Citation
Antinozzi, PA, Ishihara, H, Newgard, CB, and Wollheim, CB. "Mitochondrial metabolism sets the maximal limit of fuel-stimulated insulin secretion in a model pancreatic beta cell: a survey of four fuel secretagogues." J Biol Chem 277.14 (April 5, 2002): 11746-11755.
PMID
11821387
Source
pubmed
Published In
The Journal of biological chemistry
Volume
277
Issue
14
Publish Date
2002
Start Page
11746
End Page
11755
DOI
10.1074/jbc.M108462200

13C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS).

Cellular metabolism of glucose is required for stimulation of insulin secretion from pancreatic beta cells, but the precise metabolic coupling factors involved in this process are not known. In an effort to better understand mechanisms of fuel-mediated insulin secretion, we have adapted 13C NMR and isotopomer methods to measure influx of metabolic fuels into the tricarboxylic acid (TCA) cycle in insulinoma cells. Mitochondrial metabolism of [U-13C3]pyruvate, derived from [U-13C6]glucose, was compared in four clonal rat insulinoma cell 1-derived cell lines with varying degrees of glucose responsiveness. A 13C isotopomer analysis of glutamate isolated from these cells showed that the fraction of acetyl-CoA derived from [U-13C6]glucose was the same in all four cell lines (44 +/- 5%, 70 +/- 3%, and 84 +/- 4% with 3, 6, or 12 mM glucose, respectively). The 13C NMR spectra also demonstrated the existence of two compartmental pools of pyruvate, one that exchanges with TCA cycle intermediates and a second pool derived from [U-13C6]glucose that feeds acetyl-CoA into the TCA cycle. The 13C NMR spectra were consistent with a metabolic model where the two pyruvate pools do not randomly mix. Flux between the mitochondrial intermediates and the first pool of pyruvate (pyruvate cycling) varied in proportion to glucose responsiveness in the four cell lines. Furthermore, stimulation of pyruvate cycling with dimethylmalate or its inhibition with phenylacetic acid led to proportional changes in insulin secretion. These findings indicate that exchange of pyruvate with TCA cycle intermediates, rather than oxidation of pyruvate via acetyl-CoA, correlates with glucose-stimulated insulin secretion.

Authors
Lu, D; Mulder, H; Zhao, P; Burgess, SC; Jensen, MV; Kamzolova, S; Newgard, CB; Sherry, AD
MLA Citation
Lu, D, Mulder, H, Zhao, P, Burgess, SC, Jensen, MV, Kamzolova, S, Newgard, CB, and Sherry, AD. "13C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS)." Proc Natl Acad Sci U S A 99.5 (March 5, 2002): 2708-2713.
PMID
11880625
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
99
Issue
5
Publish Date
2002
Start Page
2708
End Page
2713
DOI
10.1073/pnas.052005699

Effects of modulation of glycerol kinase expression on lipid and carbohydrate metabolism in human muscle cells.

Glycerol is taken up by human muscle in vivo and incorporated into lipids, but little is known about regulation of glycerol metabolism in this tissue. In this study, we have analyzed the role of glycerol kinase (GlK) in the regulation of glycerol metabolism in primary cultured human muscle cells. Isolated human muscle cells exhibited lower GlK activity than fresh muscle explants, but the activity in cultured cells was increased by exposure to insulin. [U-(14)C]Glycerol was incorporated into cellular phospholipids and triacylglycerides (TAGs), but little or no increase in TAG content or lactate release was observed in response to changes in the medium glycerol concentration. Adenovirus-mediated delivery of the Escherichia coli GlK gene (AdCMV-GlK) into muscle cells caused a 30-fold increase in GlK activity, which was associated with a marked rise in the labeling of phospholipid or TAG from [U-(14)C]glycerol compared with controls. Moreover, GlK overexpression caused [U-(14)C]glycerol to be incorporated into glycogen, which was dependent on the activation of glycogen synthase. Co-incubation of AdCMV-GlK-treated muscle cells with glycerol and oleate resulted in a large accumulation of TAG and an increase in lactate production. We conclude that GlK is the limiting step in muscle cell glycerol metabolism. Glycerol 3-phosphate is readily used for TAG synthesis but can also be diverted to form glycolytic intermediates that are in turn converted to glycogen or lactate. Given the high levels of glycerol in muscle interstitial fluid, these finding suggest that changes in GlK activity in muscle can exert important influences on fuel deposition in this tissue.

Authors
Montell, E; Lerín, C; Newgard, CB; Gómez-Foix, AM
MLA Citation
Montell, E, Lerín, C, Newgard, CB, and Gómez-Foix, AM. "Effects of modulation of glycerol kinase expression on lipid and carbohydrate metabolism in human muscle cells." J Biol Chem 277.4 (January 25, 2002): 2682-2686.
PMID
11714702
Source
pubmed
Published In
The Journal of biological chemistry
Volume
277
Issue
4
Publish Date
2002
Start Page
2682
End Page
2686
DOI
10.1074/jbc.M107227200

Glycogen-targeting subunits and glucokinase differentially affect pathways of glycogen metabolism and their regulation in hepatocytes.

Overexpression of the glucose-phosphorylating enzyme glucokinase (GK) or members of the family of glycogen-targeting subunits of protein phosphatase-1 increases hepatic glucose disposal and glycogen synthesis. This study was undertaken to evaluate the functional properties of a novel, truncated glycogen-targeting subunit derived from the skeletal muscle isoform G(M)/R(Gl) and to compare pathways of glycogen metabolism and their regulation in cells with overexpressed targeting subunits and GK. When overexpressed in hepatocytes, truncated G(M)/R(Gl) (G(M)DeltaC) was approximately twice as potent as full-length G(M)/R(Gl) in stimulation of glycogen synthesis, but clearly less potent than GK or two other native glycogen-targeting subunits, G(L) and PTG. We also found that cells with overexpressed G(M)DeltaC are unique in that glycogen was efficiently degraded in response to lowering of media glucose concentrations, stimulation with forskolin, or a combination of both maneuvers, whereas cells with overexpressed G(L), PTG, or GK exhibited impairment in one or both of these glycogenolytic signaling pathways. (2)H NMR analysis of purified glycogen revealed that hepatocytes with overexpressed GK synthesized a larger portion of their glycogen from triose phosphates and a smaller portion from tricarboxylic acid cycle intermediates than cells with overexpressed glycogen-targeting subunits. Additional evidence for activation of distinct pathways of glycogen synthesis by GK and targeting subunits is provided by the additive effect of co-overexpression of the two types of proteins upon glycogen synthesis and a much larger stimulation of glucose utilization, glucose transport, and lactate production elicited by GK. We conclude that overexpression of the novel targeting subunit G(M)DeltaC confers unique regulation of glycogen metabolism. Furthermore, targeting subunits and GK stimulate glycogen synthesis by distinct pathways.

Authors
Yang, R; Cao, L; Gasa, R; Brady, MJ; Sherry, AD; Newgard, CB
MLA Citation
Yang, R, Cao, L, Gasa, R, Brady, MJ, Sherry, AD, and Newgard, CB. "Glycogen-targeting subunits and glucokinase differentially affect pathways of glycogen metabolism and their regulation in hepatocytes." J Biol Chem 277.2 (January 11, 2002): 1514-1523.
PMID
11600496
Source
pubmed
Published In
The Journal of biological chemistry
Volume
277
Issue
2
Publish Date
2002
Start Page
1514
End Page
1523
DOI
10.1074/jbc.M107001200

Reversal of diet-induced glucose intolerance by hepatic expression of a variant glycogen-targeting subunit of protein phosphatase-1.

Glycogen-targeting subunits of protein phosphatase-1 facilitate interaction of the phosphatase with enzymes of glycogen metabolism. Expression of one family member, PTG, in the liver of normal rats improves glucose tolerance without affecting other plasma variables but leaves animals unable to reduce hepatic glycogen stores in response to fasting. In the current study, we have tested whether expression of other targeting subunit isoforms, such as the liver isoform G(L), the muscle isoform G(M)/R(Gl), or a truncated version of G(M)/R(Gl) termed G(M)DeltaC in liver ameliorates glucose intolerance in rats fed on a high fat diet (HF). HF animals overexpressing G(M)DeltaC, but not G(L) or G(M)/R(Gl), exhibited a decline in blood glucose of 35-44 mg/dl relative to control HF animals during an oral glucose tolerance test (OGTT) such that levels were indistinguishable from those of normal rats fed on standard chow at all but one time point. Hepatic glycogen levels were 2.1-2.4-fold greater in G(L)- and G(M)DeltaC-overexpressing HF rats compared with control HF animals following OGTT. In a second set of studies on fed and 20-h fasted HF animals, G(M)DeltaC-overexpressing rats lowered their liver glycogen levels by 57% (from 402 +/- 54 to 173 +/- 27 microg of glycogen/mg of protein) in the fasted versus fed states compared with only 44% in G(L)-overexpressing animals (from 740 +/- 35 to 413 +/- 141 microg of glycogen/mg of protein). Since the OGTT studies were performed on 20-h fasted rats, this meant that G(M)DeltaC-overexpressing rats synthesized much more glycogen than G(L)-overexpressing HF rats during the OGTT (419 versus 117 microg of glycogen/mg of protein, respectively), helping to explain why G(M)DeltaC preferentially enhanced glucose clearance. We conclude that G(M)DeltaC has a unique combination of glycogenic potency and responsiveness to glycogenolytic signals that allows it to be used to lower blood glucose levels in diabetes.

Authors
Gasa, R; Clark, C; Yang, R; DePaoli-Roach, AA; Newgard, CB
MLA Citation
Gasa, R, Clark, C, Yang, R, DePaoli-Roach, AA, and Newgard, CB. "Reversal of diet-induced glucose intolerance by hepatic expression of a variant glycogen-targeting subunit of protein phosphatase-1." J Biol Chem 277.2 (January 11, 2002): 1524-1530.
PMID
11707447
Source
pubmed
Published In
The Journal of biological chemistry
Volume
277
Issue
2
Publish Date
2002
Start Page
1524
End Page
1530
DOI
10.1074/jbc.M107744200

Increasing fructose 2,6-bisphosphate overcomes hepatic insulin resistance of type 2 diabetes.

Hepatic glucose production is increased as a metabolic consequence of insulin resistance in type 2 diabetes. Because fructose 2,6-bisphosphate is an important regulator of hepatic glucose production, we used adenovirus-mediated enzyme overexpression to increase hepatic fructose 2,6-bisphosphate to determine if the hyperglycemia in KK mice, polygenic models of type 2 diabetes, could be ameliorated by reduction of hepatic glucose production. Seven days after treatment with virus encoding a mutant 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase designed to increase fructose 2,6-bisphosphate levels, plasma glucose, lipids, and insulin were significantly reduced in KK/H1J and KK.Cg-A(y)/J mice. Moreover, high fructose 2,6-bisphosphate levels downregulated glucose-6-phosphatase and upregulated glucokinase gene expression, thereby reversing the insulin-resistant pattern of hepatic gene expression of these two key glucose-metabolic enzymes. The increased hepatic fructose 2,6-bisphosphate also reduced adiposity in both KK mice. These results clearly indicate that increasing hepatic fructose 2,6-bisphosphate overcomes the impairment of insulin in suppressing hepatic glucose production, and it provides a potential therapy for type 2 diabetes.

Authors
Wu, C; Okar, DA; Newgard, CB; Lange, AJ
MLA Citation
Wu, C, Okar, DA, Newgard, CB, and Lange, AJ. "Increasing fructose 2,6-bisphosphate overcomes hepatic insulin resistance of type 2 diabetes." Am J Physiol Endocrinol Metab 282.1 (January 2002): E38-E45.
PMID
11739081
Source
pubmed
Published In
American journal of physiology. Endocrinology and metabolism
Volume
282
Issue
1
Publish Date
2002
Start Page
E38
End Page
E45

Glucokinase gene transfer to skeletal muscle of diabetic Zucker fatty rats improves insulin-sensitive glucose uptake.

Skeletal muscle has a prime role in glucose homeostasis. We have previously demonstrated that adenovirus-mediated glucokinase (GK) gene transfer to skeletal muscle of Wistar rats enhances muscle glucose uptake and whole body glucose disposal under conditions of hyperglycemia and hyperinsulinemia. In this study, we have tested whether GK gene transfer to the muscle of the Zucker Diabetic Fatty rat (ZDF), a genetic model of obesity and type 2 diabetes, could improve glycemic control and prevent the onset of hyperglycemia in obese males. We show that GK delivery results in a doubling of total gastrocnemius muscle glucose phosphorylating activity 9 weeks after gene transfer. GK-treated rats exhibited slightly reduced weight and normal insulin-sensitive glucose uptake, as assessed during an insulin tolerance test, whereas age-matched rats treated with a control virus were clearly insulin resistant. The improved glucose uptake in GK-expressing rats was associated with higher gastrocnemius lactate content, whereas glycogen and triacylglyceride (TAG) levels were unmodified. Remarkably, GK-treated rats showed increased expression of both hexokinase II (HKII) and GLUT4, in accordance with a glucose-dependent regulation of these proteins. Thus, our data show that delivery of GK, despite improving insulin-sensitive glucose disposal in muscle, is not sufficient to prevent or delay the appearance of elevated glucose and insulin levels associated with severe obesity in male ZDF animals.

Authors
Jiménez-Chillarón, JC; Telemaque-Potts, S; Gómez-Valadés, AG; Anderson, P; Newgard, CB; Gómez-Foix, AM
MLA Citation
Jiménez-Chillarón, JC, Telemaque-Potts, S, Gómez-Valadés, AG, Anderson, P, Newgard, CB, and Gómez-Foix, AM. "Glucokinase gene transfer to skeletal muscle of diabetic Zucker fatty rats improves insulin-sensitive glucose uptake." Metabolism 51.1 (January 2002): 121-126.
PMID
11782883
Source
pubmed
Published In
Metabolism
Volume
51
Issue
1
Publish Date
2002
Start Page
121
End Page
126

Increasing fructose 2,6-bisphosphate overcomes hepatic insulin resistance of type 2 diabetes

Hepatic glucose production is increased as a metabolic consequence of insulin resistance in type 2 diabetes. Because fructose 2,6-bisphosphate is an important regulator of hepatic glucose production, we used adenovirus-mediated enzyme overexpression to increase hepatic fructose 2,6-bisphosphate to determine if the hyperglycemia in KK mice, polygenic models of type 2 diabetes, could be ameliorated by reduction of hepatic glucose production. Seven days after treatment with virus encoding a mutant 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase designed to increase fructose 2,6-bisphosphate levels, plasma glucose, lipids, and insulin were significantly reduced in KK/H1J and KK.Cg-AY/J mice. Moreover, high fructose 2,6-bisphosphate levels downregulated glucose-6-phosphatase and upregulated glucokinase gene expression, thereby reversing the insulin-resistant pattern of hepatic gene expression of these two key glucose-metabolic enzymes. The increased hepatic fructose 2,6-bisphosphate also reduced adiposity in both KK mice. These results clearly indicate that increasing hepatic fructose 2,6-bisphosphate overcomes the impairment of insulin in suppressing hepatic glucose production, and it provides a potential therapy for type 2 diabetes.

Authors
Wu, C; Okar, DA; Newgard, CB; Lange, AJ
MLA Citation
Wu, C, Okar, DA, Newgard, CB, and Lange, AJ. "Increasing fructose 2,6-bisphosphate overcomes hepatic insulin resistance of type 2 diabetes." American Journal of Physiology - Endocrinology and Metabolism 282.1 45-1 (2002): E38-E45.
Source
scival
Published In
American journal of physiology. Endocrinology and metabolism
Volume
282
Issue
1 45-1
Publish Date
2002
Start Page
E38
End Page
E45

Control of hepatic gluconeogenesis through the transcriptional coactivator PGC-1.

Blood glucose levels are maintained by the balance between glucose uptake by peripheral tissues and glucose secretion by the liver. Gluconeogenesis is strongly stimulated during fasting and is aberrantly activated in diabetes mellitus. Here we show that the transcriptional coactivator PGC-1 is strongly induced in liver in fasting mice and in three mouse models of insulin action deficiency: streptozotocin-induced diabetes, ob/ob genotype and liver insulin-receptor knockout. PGC-1 is induced synergistically in primary liver cultures by cyclic AMP and glucocorticoids. Adenoviral-mediated expression of PGC-1 in hepatocytes in culture or in vivo strongly activates an entire programme of key gluconeogenic enzymes, including phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, leading to increased glucose output. Full transcriptional activation of the PEPCK promoter requires coactivation of the glucocorticoid receptor and the liver-enriched transcription factor HNF-4alpha (hepatic nuclear factor-4alpha) by PGC-1. These results implicate PGC-1 as a key modulator of hepatic gluconeogenesis and as a central target of the insulin-cAMP axis in liver.

Authors
Yoon, JC; Puigserver, P; Chen, G; Donovan, J; Wu, Z; Rhee, J; Adelmant, G; Stafford, J; Kahn, CR; Granner, DK; Newgard, CB; Spiegelman, BM
MLA Citation
Yoon, JC, Puigserver, P, Chen, G, Donovan, J, Wu, Z, Rhee, J, Adelmant, G, Stafford, J, Kahn, CR, Granner, DK, Newgard, CB, and Spiegelman, BM. "Control of hepatic gluconeogenesis through the transcriptional coactivator PGC-1." Nature 413.6852 (September 13, 2001): 131-138.
PMID
11557972
Source
pubmed
Published In
Nature
Volume
413
Issue
6852
Publish Date
2001
Start Page
131
End Page
138
DOI
10.1038/35093050

Protein synthesis. The perks of balancing glucose.

What do the regulation of translation initiation and glucose metabolism have to do with each other? Quite a lot, it seems, according to Sonenberg and Newgard in their Perspective. They discuss new findings that identify the kinase responsible for inactivating eIF2--a factor that is required for translation initiation (and hence protein synthesis)--when the endoplasmic reticulum is under stress. Loss of this kinase results in destruction of insulin-producing b cells in the pancreas and dysregulation of glucose homeostasis.

Authors
Sonenberg, N; Newgard, CB
MLA Citation
Sonenberg, N, and Newgard, CB. "Protein synthesis. The perks of balancing glucose." Science 293.5531 (August 3, 2001): 818-819.
PMID
11486079
Source
pubmed
Published In
Science
Volume
293
Issue
5531
Publish Date
2001
Start Page
818
End Page
819
DOI
10.1126/science.1062937

Overexpression of the P46 (T1) translocase component of the glucose-6-phosphatase complex in hepatocytes impairs glycogen accumulation via hydrolysis of glucose 1-phosphate.

The final step of gluconeogenesis and glycogenolysis is catalyzed by the glucose-6-phosphatase (Glc-6-Pase) enzyme complex, located in the endoplasmic reticulum. The complex consists of a 36-kDa catalytic subunit (P36), a 46-kDa glucose 6-phosphate translocase (P46), and putative glucose and inorganic phosphate transporters. Mutations in the genes encoding P36 or P46 have been linked to glycogen storage diseases type Ia and type Ib, respectively. However, the relative roles of these two proteins in control of the rate of glucose 6-phosphate hydrolysis have not been defined. To gain insight into this area, we have constructed a recombinant adenovirus containing the cDNA encoding human P46 (AdCMV-P46) and treated rat hepatocytes with this virus, or a virus encoding P36 (AdCMV-P36), or the combination of both viruses, resulting in large and equivalent increases in expression of the transgenes within 8-24 h of viral treatment. The overexpressed P46 protein was appropriately targeted to hepatocyte microsomes and caused a 58% increase in glucose 6-phosphate hydrolysis in nondetergent-treated (intact) microsomal preparations relative to controls, whereas overexpression of P36 caused a 3.6-fold increase. Overexpression of P46 caused a 50% inhibition of glycogen accumulation in hepatocytes from fasted rats incubated at 25 mm glucose relative to cells treated with a control virus (AdCMV-betaGAL). Furthermore, in hepatocytes from fed rats cultured at 25 mm glucose and then exposed to 15 mm glucose, AdCMV-P46 treatment activated glycogenolysis, as indicated by a 50% reduction in glycogen content relative to AdCMV-betaGAL-treated controls. In contrast, overexpression of P46 had only small effects on glycolysis, whereas overexpression of P36 had large effects on both glycogen metabolism and glycolysis, even in the presence of co-overexpressed glucokinase. Finally, P46 overexpression enhanced glucose 1-phosphate but not fructose 6-phosphate hydrolysis in intact microsomes, providing a mechanism by which P46 overexpression may exert its preferential effects on glycogen metabolism.

Authors
An, J; Li, Y; van De Werve, G; Newgard, CB
MLA Citation
An, J, Li, Y, van De Werve, G, and Newgard, CB. "Overexpression of the P46 (T1) translocase component of the glucose-6-phosphatase complex in hepatocytes impairs glycogen accumulation via hydrolysis of glucose 1-phosphate." J Biol Chem 276.14 (April 6, 2001): 10722-10729.
PMID
11148207
Source
pubmed
Published In
The Journal of biological chemistry
Volume
276
Issue
14
Publish Date
2001
Start Page
10722
End Page
10729
DOI
10.1074/jbc.M009525200

Overexpression of a modified human malonyl-CoA decarboxylase blocks the glucose-induced increase in malonyl-CoA level but has no impact on insulin secretion in INS-1-derived (832/13) beta-cells.

The long-chain acyl-CoA (LC-CoA) model of glucose-stimulated insulin secretion (GSIS) holds that secretion is linked to a glucose-induced increase in malonyl-CoA level and accumulation of LC-CoA in the cytosol. We have previously tested the validity of this proposal by overexpressing goose malonyl-CoA decarboxylase (MCD) in INS-1 cells, but these studies have been criticized due to: 1) the small insulin secretion response (2-4-fold) of the INS-1 cells used; 2) unknown contribution of the ATP-sensitive K(+) (K(ATP)) channel-independent pathway of GSIS in INS-1 cells, which has been implicated as the site at which lipids regulate insulin granule exocytosis; and 3) deletion of the N-terminal mitochondrial targeting sequence, but not the C-terminal peroxisomal targeting sequence in the goose MCD construct, raising the possibility that a significant fraction of the overexpressed enzyme was localized to peroxisomes. To address these outstanding concerns, INS-1-derived 832/13 cells, which exhibit robust K(ATP) channel-dependent and -independent pathways of GSIS, were treated with a new adenovirus encoding human MCD lacking both its mitochondrial and peroxisomal targeting sequences (AdCMV-MCD Delta 5), resulting in large increases in cytosolic MCD activity. Treatment of 832/13 cells with AdCMV-MCD Delta 5 completely blocked the glucose-induced rise in malonyl-CoA and attenuated the inhibitory effect of glucose on fatty acid oxidation. However, MCD overexpression had no effect on K(ATP) channel-dependent or -independent GSIS in 832/13 cells. Furthermore, combined treatment of 832/13 cells with AdCMV-MCD Delta 5 and triacsin C, an inhibitor of long chain acyl-CoA synthetase that reduces LC-CoA levels, did not impair GSIS. These findings extend our previous observations and are not consistent with the LC-CoA hypothesis as originally set forth.

Authors
Mulder, H; Lu, D; Finley, J; An, J; Cohen, J; Antinozzi, PA; McGarry, JD; Newgard, CB
MLA Citation
Mulder, H, Lu, D, Finley, J, An, J, Cohen, J, Antinozzi, PA, McGarry, JD, and Newgard, CB. "Overexpression of a modified human malonyl-CoA decarboxylase blocks the glucose-induced increase in malonyl-CoA level but has no impact on insulin secretion in INS-1-derived (832/13) beta-cells." J Biol Chem 276.9 (March 2, 2001): 6479-6484.
PMID
11113153
Source
pubmed
Published In
The Journal of biological chemistry
Volume
276
Issue
9
Publish Date
2001
Start Page
6479
End Page
6484
DOI
10.1074/jbc.M010364200

Expression of the transcription factor STAT-1 alpha in insulinoma cells protects against cytotoxic effects of multiple cytokines.

Destruction of pancreatic islet beta-cells in type 1 diabetes appears to result from direct contact with infiltrating T-cells and macrophages and exposure to inflammatory cytokines such as interferon (IFN)-gamma, interleukin (IL)-1 beta, and tumor necrosis factor TNF-alpha that such cells produce. We recently reported on a method for selection of insulinoma cells that are resistant to the cytotoxic effects of inflammatory cytokines (INS-1(res)), involving their growth in progressively increasing concentrations of IL-1 beta plus IFN-gamma, and selection of surviving cells. In the current study, we have investigated the molecular mechanism of cytokine resistance in INS-1(res) cells. By focusing on the known components of the IFN-gamma receptor signaling pathway, we have discovered that expression levels of signal transducer and activator of transcription (STAT)-1 alpha are closely correlated with the cytokine-resistant and -sensitive phenotypes. That STAT-1 alpha is directly involved in development of cytokine resistance is demonstrated by an increase of viability from 10 +/- 2% in control cells to 50 +/- 6% in cells with adenovirus-mediated overexpression of STAT-1 alpha (p < 0.001) after culture of both cell groups in the presence of 100 units/ml IFN-gamma plus 10 ng/ml IL-1 beta for 48 h. The resistance to IL-1 beta plus IFN-gamma in STAT-1 alpha-expressing cells is due in part to interference with IL-1 beta-mediated stimulation of inducible nitric-oxide synthase expression and nitric oxide production. Furthermore, overexpression of STAT-1 alpha does not impair robust glucose-stimulated insulin secretion in the INS-1-derived cell line 832/13. We conclude that expression of STAT-1 alpha may be a means of protecting insulin-producing cell lines from cytokine damage, which, in conjunction with appropriate cell-impermeant macroencapsulation devices, may allow such cells to be used for insulin replacement in type 1 diabetes.

Authors
Chen, G; Hohmeier, HE; Newgard, CB
MLA Citation
Chen, G, Hohmeier, HE, and Newgard, CB. "Expression of the transcription factor STAT-1 alpha in insulinoma cells protects against cytotoxic effects of multiple cytokines." J Biol Chem 276.1 (January 5, 2001): 766-772.
PMID
11024034
Source
pubmed
Published In
The Journal of biological chemistry
Volume
276
Issue
1
Publish Date
2001
Start Page
766
End Page
772
DOI
10.1074/jbc.M008330200

Overexpression of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase in mouse liver lowers blood glucose by suppressing hepatic glucose production.

Hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase is an important regulatory enzyme of glucose metabolism. By controlling the level of fructose-2,6-bisphosphate, an allosteric activator of the glycolytic enzyme 6-phosphofructo-1-kinase and an inhibitor of the gluconeogenic enzyme fructose-1,6-bisphosphatase, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase regulates hepatic glucose output. We studied the effects of adenovirus-mediated overexpression of this enzyme on hepatic glucose metabolism in normal or diabetic mice. These animals were treated with virus encoding either wild-type or bisphosphatase activity-deficient 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase. Seven days after virus injection, hepatic fructose-2,6-bisphosphate levels increased significantly in both normal and diabetic mice, with larger increases observed in animals with overexpression of the mutant enzyme. Blood glucose levels in normal mice overexpressing either enzyme were lowered, accompanied by increased plasma lactate, triglycerides, and FFAs. Blood glucose levels were markedly reduced in diabetic mice overexpressing the wild-type enzyme, and still more so in mice overexpressing the mutant form of the enzyme. The lower blood glucose levels in diabetic mice were accompanied by partially normalized plasma triglycerides and FFAs, increased plasma lactate, and increased liver glycogen levels, relative to diabetic mice treated with a control adenovirus. Our findings underscore the critical role played by hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in control of fuel homeostasis and suggest that this enzyme may be considered as a therapeutic target in diabetes.

Authors
Wu, C; Okar, DA; Newgard, CB; Lange, AJ
MLA Citation
Wu, C, Okar, DA, Newgard, CB, and Lange, AJ. "Overexpression of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase in mouse liver lowers blood glucose by suppressing hepatic glucose production." J Clin Invest 107.1 (January 2001): 91-98.
PMID
11134184
Source
pubmed
Published In
Journal of Clinical Investigation
Volume
107
Issue
1
Publish Date
2001
Start Page
91
End Page
98
DOI
10.1172/JCI11103

Glucose activates mitogen-activated protein kinase (extracellular signal-regulated kinase) through proline-rich tyrosine kinase-2 and the Glut1 glucose transporter.

Glucose serves as both a nutrient and regulator of physiological and pathological processes. Presently, we found that glucose and certain sugars rapidly activated extracellular signal-regulated kinase (ERK) by a mechanism that was: (a) independent of glucose uptake/metabolism and protein kinase C but nevertheless cytochalasin B-inhibitable; (b) dependent upon proline-rich tyrosine kinase-2 (PYK2), GRB2, SOS, RAS, RAF, and MEK1; and (c) amplified by overexpression of the Glut1, but not Glut2, Glut3, or Glut4, glucose transporter. This amplifying effect was independent of glucose uptake but dependent on residues 463-468, IASGFR, in the Glut1 C terminus. Accordingly, glucose effects on ERK were amplified by expression of Glut4/Glut1 or Glut2/Glut1 chimeras containing IASGFR but not by Glut1/Glut4 or Glut1/Glut2 chimeras lacking these residues. Also, deletion of Glut1 residues 469-492 was without effect, but mutations involving serine 465 or arginine 468 yielded dominant-negative forms that inhibited glucose-dependent ERK activation. Glucose stimulated the phosphorylation of tyrosine residues 402 and 881 in PYK2 and binding of PYK2 to Myc-Glut1. Our findings suggest that: (a) glucose activates the GRB2/SOS/RAS/RAF/MEK1/ERK pathway by a mechanism that requires PYK2 and residues 463-468, IASGFR, in the Glut1 C terminus and (b) Glut1 serves as a sensor, transducer, and amplifier for glucose signaling to PYK2 and ERK.

Authors
Bandyopadhyay, G; Sajan, MP; Kanoh, Y; Standaert, ML; Burke, TR; Quon, MJ; Reed, BC; Dikic, I; Noel, LE; Newgard, CB; Farese, R
MLA Citation
Bandyopadhyay, G, Sajan, MP, Kanoh, Y, Standaert, ML, Burke, TR, Quon, MJ, Reed, BC, Dikic, I, Noel, LE, Newgard, CB, and Farese, R. "Glucose activates mitogen-activated protein kinase (extracellular signal-regulated kinase) through proline-rich tyrosine kinase-2 and the Glut1 glucose transporter." J Biol Chem 275.52 (December 29, 2000): 40817-40826.
PMID
11007796
Source
pubmed
Published In
The Journal of biological chemistry
Volume
275
Issue
52
Publish Date
2000
Start Page
40817
End Page
40826
DOI
10.1074/jbc.M007920200

Overexpression of protein targeting to glycogen in cultured human muscle cells stimulates glycogen synthesis independent of glycogen and glucose 6-phosphate levels.

There is growing evidence that glycogen targeting subunits of protein phosphatase-1 play a critical role in regulation of glycogen metabolism. In the current study, we have investigated the effects of adenovirus-mediated overexpression of a specific glycogen targeting subunit known as protein targeting to glycogen (PTG) in cultured human muscle cells. PTG was overexpressed both in muscle cells cultured at high glucose (glycogen replete) or in cells incubated for 18 h in the absence of glucose and then incubated in high glucose (glycogen re-synthesizing). In both glycogen replete and glycogen resynthesizing cells, PTG overexpression caused glycogen to be synthesized at a linear rate 1-5 days after viral treatment, while in cells treated with a virus lacking a cDNA insert (control virus), glycogen content reached a plateau at day 1 with no further increase. In the glycogen replete PTG overexpressing cells, glycogen content was 20 times that in controls at day 5. Furthermore, in cells undergoing glycogen resynthesis, PTG overexpression caused a doubling of the initial rate of glycogen synthesis over the first 24 h relative to cells treated with control virus. In both sets of experiments, the effects of PTG on glycogen synthesis were correlated with a 2-3-fold increase in glycogen synthase activity state, with no changes in glycogen phosphorylase activity. The alterations in glycogen synthase activity were not accompanied by changes in the intracellular concentration of glucose 6-phosphate. We conclude that PTG overexpression activates glycogen synthesis in a glucose 6-phosphate-independent manner in human muscle cells while overriding glycogen-mediated inhibition. Our findings suggest that modulation of PTG expression in muscle may be a mechanism for enhancing muscle glucose disposal and improving glucose tolerance in diabetes.

Authors
Lerín, C; Montell, E; Berman, HK; Newgard, CB; Gómez-Foix, AM
MLA Citation
Lerín, C, Montell, E, Berman, HK, Newgard, CB, and Gómez-Foix, AM. "Overexpression of protein targeting to glycogen in cultured human muscle cells stimulates glycogen synthesis independent of glycogen and glucose 6-phosphate levels." J Biol Chem 275.51 (December 22, 2000): 39991-39995.
PMID
10998419
Source
pubmed
Published In
The Journal of biological chemistry
Volume
275
Issue
51
Publish Date
2000
Start Page
39991
End Page
39995
DOI
10.1074/jbc.M006251200

Organizing glucose disposal: emerging roles of the glycogen targeting subunits of protein phosphatase-1.

Glucose is stored in mammalian tissues in the form of glycogen. Glycogen levels are markedly reduced in liver or muscle cells of patients with insulin-resistant or insulin-deficient forms of diabetes, suggesting that impaired glycogen synthesis may contribute to development of hyperglycemia. Recently, interest in this area has been further stimulated by new insights into the spatial organization of metabolic enzymes within cells and the importance of such organization in regulation of glycogen metabolism. It is now clear that a four-member family of glycogen targeting subunits of protein phosphatase-1 (PP1) plays a major role in coordinating these events. These proteins target PP1 to the glycogen particle and also bind differentially to glycogen synthase, glycogen phosphorylase, and phosphorylase kinase, thereby serving as molecular scaffolds. Moreover, the various glycogen-targeting subunits have distinct tissue expression patterns and can influence regulation of glycogen metabolism in response to glycogenic and glycogenolytic signals. The purpose of this article is to summarize new insights into the structure, function, regulation, and metabolic effects of the glycogen-targeting subunits of PP1 and to evaluate the possibility that these molecules could serve as therapeutic targets for lowering of blood glucose in diabetes.

Authors
Newgard, CB; Brady, MJ; O'Doherty, RM; Saltiel, AR
MLA Citation
Newgard, CB, Brady, MJ, O'Doherty, RM, and Saltiel, AR. "Organizing glucose disposal: emerging roles of the glycogen targeting subunits of protein phosphatase-1." Diabetes 49.12 (December 2000): 1967-1977. (Review)
PMID
11117996
Source
pubmed
Published In
Diabetes
Volume
49
Issue
12
Publish Date
2000
Start Page
1967
End Page
1977

Glucose down-regulates the expression of the peroxisome proliferator-activated receptor-alpha gene in the pancreatic beta -cell.

To better understand the action of glucose on fatty acid metabolism in the beta-cell and the link between chronically elevated glucose or fatty acids and beta-cell decompensation in adipogenic diabetes, we investigated whether glucose regulates peroxisomal proliferator-activated receptor (PPAR) gene expression in the beta-cell. Islets or INS(832/13) beta-cells exposed to high glucose show a 60-80% reduction in PPARalpha mRNA expression. Oleate, either in the absence or presence of glucose, has no effect. The action of glucose is dose-dependent in the 6-20 mm range and maximal after 6 h. Glucose also causes quantitatively similar reductions in PPARalpha protein and DNA binding activity of this transcription factor. The effect of glucose is blocked by the glucokinase inhibitor mannoheptulose, is partially mimicked by 2-deoxyglucose, and is not blocked by the 3-O-methyl or the 6-deoxy analogues of the sugar that are not phosphorylated. Chronic elevated glucose reduces the expression levels of the PPAR target genes, uncoupling protein 2 and acyl-CoA oxidase, which are involved in fat oxidation and lipid detoxification. A 3-day exposure of INS-1 cells to elevated glucose results in a permanent rise in malonyl-CoA, the inhibition of fat oxidation, and the promotion of fatty acid esterification processes and causes elevated insulin secretion at low glucose. The results suggest that a reduction in PPARalpha gene expression together with a rise in malonyl-CoA plays a role in the coordinated adaptation of beta-cell glucose and lipid metabolism to hyperglycemia and may be implicated in the mechanism of beta-cell "glucolipotoxicity."

Authors
Roduit, R; Morin, J; Massé, F; Segall, L; Roche, E; Newgard, CB; Assimacopoulos-Jeannet, F; Prentki, M
MLA Citation
Roduit, R, Morin, J, Massé, F, Segall, L, Roche, E, Newgard, CB, Assimacopoulos-Jeannet, F, and Prentki, M. "Glucose down-regulates the expression of the peroxisome proliferator-activated receptor-alpha gene in the pancreatic beta -cell." J Biol Chem 275.46 (November 17, 2000): 35799-35806.
PMID
10967113
Source
pubmed
Published In
The Journal of biological chemistry
Volume
275
Issue
46
Publish Date
2000
Start Page
35799
End Page
35806
DOI
10.1074/jbc.M006001200

Distinctive regulatory and metabolic properties of glycogen-targeting subunits of protein phosphatase-1 (PTG, GL, GM/RGl) expressed in hepatocytes.

Glycogen-targeting subunits of protein phosphatase-1 facilitate interaction of the phosphatase with enzymes of glycogen metabolism. We have shown that overexpression of one member of the family, protein targeting to glycogen (PTG), causes large increases in glycogen storage in isolated hepatocytes or intact rat liver. In the current study, we have compared the metabolic and regulatory properties of PTG (expressed in many tissues), with two other members of the gene family, G(L) (expressed primarily in liver) and G(M)/R(Gl) (expressed primarily in striated muscle). Adenovirus-mediated expression of these proteins in hepatocytes led to the following key observations. 1) G(L) has the highest glycogenic potency among the three forms studied. 2) Glycogen synthase activity ratio is much higher in G(L)-overexpressing cells than in PTG or G(M)/R(Gl)-overexpressing cells. Thus, at moderate levels of G(L) overexpression, glycogen synthase activity is increased by insulin treatment, but at higher levels of G(L) expression, insulin is no longer required to achieve maximal synthase activity. In contrast, cells with high levels of PTG overexpression retain dose-dependent regulation of glycogen synthesis and glycogen synthase enzyme activity by insulin. 3) G(L)- and G(M)/R(Gl)-overexpressing cells exhibit a strong glycogenolytic response to forskolin, whereas PTG-overexpressing cells are less responsive. This difference may be explained in part by a lesser forskolin-induced increase in glycogen phosphorylase activity in PTG-overexpressing cells. Based on these results, we suggest that expression of either G(L) or G(M)/R(Gl) in liver of diabetic animals may represent a strategy for lowering of blood glucose levels in diabetes.

Authors
Gasa, R; Jensen, PB; Berman, HK; Brady, MJ; DePaoli-Roach, AA; Newgard, CB
MLA Citation
Gasa, R, Jensen, PB, Berman, HK, Brady, MJ, DePaoli-Roach, AA, and Newgard, CB. "Distinctive regulatory and metabolic properties of glycogen-targeting subunits of protein phosphatase-1 (PTG, GL, GM/RGl) expressed in hepatocytes." J Biol Chem 275.34 (August 25, 2000): 26396-26403.
PMID
10862764
Source
pubmed
Published In
The Journal of biological chemistry
Volume
275
Issue
34
Publish Date
2000
Start Page
26396
End Page
26403
DOI
10.1074/jbc.M002427200

Selection of insulinoma cell lines with resistance to interleukin-1beta- and gamma-interferon-induced cytotoxicity.

Engineered insulinoma cell lines may represent an alternative to isolated islets for transplantation therapy of type 1 diabetes. Success of this approach may require development of cell lines that can withstand cytokine-mediated damage. To this end, we have cultured INS-1 insulinoma cells in increasing concentrations of interleukin-1beta (IL-1beta) + gamma-interferon (IFN-gamma), with approximate weekly iterations over an 8-week period. Based on the C,N diphenyl-N'-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium+ ++ bromide (MTT) viability assay, the selected cells, termed INS-1res, were 100% viable after 5 days of treatment with 10 ng/ml of IL-1beta. These cells were also 78 +/- 1.2% viable after 5 days of exposure to the combination of 10 ng/ml IL-1beta and 100 U/ml IFN-gamma, whereas parental INS-1 cells treated in the same manner were only 0.3 +/- 0.03% viable. INS-1res cells were also resistant to treatment with supernatants from activated rat peripheral blood mononuclear cells, whereas only 20% of parental INS-1 cells survived such treatment. The resistance to IL-1beta conferred by this procedure was stable, whereas the partial resistance to IFN-gamma was transient but reinducible by culture in the presence of cytokines. Stable transfection of INS-1res cells with a plasmid containing the human insulin cDNA and expansion of the transfected colonies in the absence of cytokines produced cell lines that were on average more resistant to IL-1beta + IFN-gamma (53 +/- 11%) than similarly transfected clones derived from parental INS-1 cells (15 +/- 7%). Importantly, several INS-1res-derived clones retained the capacity to secrete insulin in response to glucose concentrations over the normal physiological range. With regard to the mechanism by which selection was conferred, we found normal levels of IFN-gamma receptor mRNA, but a 60% reduction in expression of the IL-1 receptor type I (IL-1RI) in INS-1res cells compared with parental INS-1 cells. IL-1beta signaling through p38 MAP kinase was found to be normal in INS-1res cells, suggesting that their expression of IL-1RI is sufficient to maintain cytokine action. However, normal IL-1beta-mediated translocation of NF-kappaB and induction of inducible nitric oxide synthase expression and nitric oxide production was severely impaired in the INS-1res cell lines, suggesting a mechanism for the IL-1beta resistance. In sum, this study defines a strategy for isolation of cytokine-resistant beta-cell lines and provides a new system for studying the mechanisms by which such resistance can be achieved.

Authors
Chen, G; Hohmeier, HE; Gasa, R; Tran, VV; Newgard, CB
MLA Citation
Chen, G, Hohmeier, HE, Gasa, R, Tran, VV, and Newgard, CB. "Selection of insulinoma cell lines with resistance to interleukin-1beta- and gamma-interferon-induced cytotoxicity." Diabetes 49.4 (April 2000): 562-570.
PMID
10871193
Source
pubmed
Published In
Diabetes
Volume
49
Issue
4
Publish Date
2000
Start Page
562
End Page
570

Isolation of INS-1-derived cell lines with robust ATP-sensitive K+ channel-dependent and -independent glucose-stimulated insulin secretion.

The biochemical mechanisms involved in regulation of insulin secretion are not completely understood. The rat INS-1 cell line has been used to gain insight in this area because it secretes insulin in response to glucose concentrations in the physiological range. However, the magnitude of the response is far less than that seen in freshly isolated rat islets. In the current study, we have stably transfected INS-1 cells with a plasmid containing the human proinsulin gene. After antibiotic selection and clonal expansion, 67% of the resultant clones were found to be poorly responsive to glucose in terms of insulin secretion (< or =2-fold stimulation by 15 mmol/l compared with 3 mmol/l glucose), 17% of the clones were moderately responsive (2- to 5-fold stimulation), and 16% were strongly responsive (5- to 13-fold stimulation). The differences in responsiveness could not be ascribed to differences in insulin content. Detailed analysis of one of the strongly responsive lines (832/13) revealed that its potent response to glucose (average of 10-fold) was stable over 66 population doublings (approximately 7.5 months of tissue culture) with half-maximal stimulation at 6 mmol/l glucose. Furthermore, in the presence of 15 mmol/l glucose, insulin secretion was potentiated significantly by 100 pmol/l isobutylmethylxanthine (320%), 1 mmol/l oleate/palmitate (77%), and 50 nmol/l glucagon-like peptide 1 (60%), whereas carbachol had no effect. Glucose-stimulated insulin secretion was also potentiated by the sulfonylurea tolbutamide (threefold at 3 mmol/l glucose and 50% at 15 mmol/l glucose) and was abolished by diazoxide, which demonstrates the operation of the ATP-sensitive K+ channel (K(ATP)) in 832/13 cells. Moreover, when the K(ATP) channel was bypassed by incubation of cells in depolarizing K+ (35 mmol/l), insulin secretion was more effectively stimulated by glucose in 832/13 cells than in parental INS-1 cells, which demonstrates the presence of a K(ATP) channel-independent pathway of glucose sensing. We conclude that clonal selection of INS-1 cells allows isolation of cell lines that exhibit markedly enhanced and stable responsiveness to glucose and several of its known potentiators. These lines may be attractive new vehicles for studies of beta-cell function.

Authors
Hohmeier, HE; Mulder, H; Chen, G; Henkel-Rieger, R; Prentki, M; Newgard, CB
MLA Citation
Hohmeier, HE, Mulder, H, Chen, G, Henkel-Rieger, R, Prentki, M, and Newgard, CB. "Isolation of INS-1-derived cell lines with robust ATP-sensitive K+ channel-dependent and -independent glucose-stimulated insulin secretion." Diabetes 49.3 (March 2000): 424-430.
PMID
10868964
Source
pubmed
Published In
Diabetes
Volume
49
Issue
3
Publish Date
2000
Start Page
424
End Page
430

Correction of diet-induced hyperglycemia, hyperinsulinemia, and skeletal muscle insulin resistance by moderate hyperleptinemia.

Human obesity and high fat feeding in rats are associated with the development of insulin resistance and perturbed carbohydrate and lipid metabolism. It has been proposed that these metabolic abnormalities may be reversible by interventions that increase plasma leptin. Up to now, studies in nongenetic animal models of obesity and in human obesity have concentrated on multiple injection therapy with mixed results. Our study sought to determine whether a sustained, moderate increase in plasma leptin, achieved by administration of a recombinant adenovirus containing the leptin cDNA (AdCMV-leptin) would be effective in reversing the metabolic abnormalities of the obese phenotype. Wistar rats fed a high-fat diet (HF) were heavier (P < 0.05), had increased fat mass and intramuscular triglycerides (mTG), and had elevated plasma glucose, insulin, triglyceride, and free fatty acids compared with standard chow-fed (SC) control animals (all P < 0.01). HF rats also had impaired glucose tolerance and were markedly insulin resistant, as demonstrated by a 40% reduction in insulin-stimulated muscle glucose uptake (P < 0.001). Increasing plasma leptin levels to 29.0 +/- 1.5 ng/ml (from 7.0 +/- 1.4 ng/ml, P < 0.001) for a period of 6 days decreased adipose mass by 40% and normalized plasma glucose and insulin levels. In addition, insulin-stimulated skeletal muscle glucose uptake was normalized in hyperleptinemic rats, an effect that correlated closely with a 60% (P < 0.001) decrease in mTG. Importantly, HF rats that received a control adenovirus containing the beta-galactosidase cDNA and were calorically matched to AdCMV-leptin-treated animals remained hyperglycemic, hyperinsulinemic, insulin resistant, and maintained elevated mTG. We conclude that a gene-therapeutic intervention that elevates plasma leptin moderately for a sustained period reverses diet-induced hyperglycemia, hyperinsulinemia, and skeletal muscle insulin resistance, and that these improvements are tightly linked to leptin-induced reductions in mTG.

Authors
Buettner, R; Newgard, CB; Rhodes, CJ; O'Doherty, RM
MLA Citation
Buettner, R, Newgard, CB, Rhodes, CJ, and O'Doherty, RM. "Correction of diet-induced hyperglycemia, hyperinsulinemia, and skeletal muscle insulin resistance by moderate hyperleptinemia." Am J Physiol Endocrinol Metab 278.3 (March 2000): E563-E569.
PMID
10710512
Source
pubmed
Published In
American journal of physiology. Endocrinology and metabolism
Volume
278
Issue
3
Publish Date
2000
Start Page
E563
End Page
E569

Activation of direct and indirect pathways of glycogen synthesis by hepatic overexpression of protein targeting to glycogen.

Glycogen-targeting subunits of protein phosphatase-1, such as protein targeting to glycogen (PTG), direct the phosphatase to the glycogen particle, where it stimulates glycogenesis. We have investigated the metabolic impact of overexpressing PTG in liver of normal rats. After administration of PTG cDNA in a recombinant adenovirus, animals were fasted or allowed to continue feeding for 24 hours. Liver glycogen was nearly completely depleted in fasted control animals, whereas glycogen levels in fasted or fed PTG-overexpressing animals were 70% higher than in fed controls. Nevertheless, transgenic animals regulated plasma glucose, triglycerides, FFAs, ketones, and insulin normally in the fasted and fed states. Fasted PTG-overexpressing animals receiving an oral bolus of [U-(13)C]glucose exhibited a large increase in hepatic glycogen content and a 70% increase in incorporation of [(13)C]glucose into glycogen. However, incorporation of labeled glucose accounted for only a small portion of the glycogen synthesized in PTG-overexpressing animals, consistent with our earlier finding that PTG promotes glycogen synthesis from gluconeogenic precursors. We conclude that hepatic PTG overexpression activates both direct and indirect pathways of glycogen synthesis. Because of its ability to enhance glucose storage without affecting other metabolic indicators, the glycogen-targeting subunit may prove valuable in controlling blood glucose levels in diabetes.

Authors
O'Doherty, RM; Jensen, PB; Anderson, P; Jones, JG; Berman, HK; Kearney, D; Newgard, CB
MLA Citation
O'Doherty, RM, Jensen, PB, Anderson, P, Jones, JG, Berman, HK, Kearney, D, and Newgard, CB. "Activation of direct and indirect pathways of glycogen synthesis by hepatic overexpression of protein targeting to glycogen." J Clin Invest 105.4 (February 2000): 479-488.
PMID
10683377
Source
pubmed
Published In
Journal of Clinical Investigation
Volume
105
Issue
4
Publish Date
2000
Start Page
479
End Page
488
DOI
10.1172/JCI8673

Correction of diet-induced hyperglycemia, hyperinsulinemia, and skeletal muscle insulin resistance by moderate hyperleptinemia

Human obesity and high fat feeding in rats are associated with the development of insulin resistance and perturbed carbohydrate and lipid metabolism. It has been proposed that these metabolic abnormalities may be reversible by interventions that increase plasma leptin. Up to now, studies in nongenetic animal models of obesity and in human obesity have concentrated on multiple injection therapy with mixed results. Our study sought to determine whether a sustained, moderate increase in plasma leptin, achieved by administration of a recombinant adenovirus containing the leptin cDNA (AdCMV-leptin) would be effective in reversing the metabolic abnormalities of the obese phenotype. Wistar rats fed a high-fat diet (HF) were heavier (P < 0.05), had increased fat mass and intramuscular triglycerides (mTG), and had elevated plasma glucose, insulin, triglyceride, and free fatty acids compared with standard chow-fed (SC) control animals (all P < 0.01). HF rats also had impaired glucose tolerance and were markedly insulin resistant, as demonstrated by a 40% reduction in insulin-stimulated muscle glucose uptake (P < 0.001). Increasing plasma leptin levels to 29.0 ± 1.5 ng/ml (from 7.0 ± 1.4 ng/ml, P < 0.001) for a period of 6 days decreased adipose mass by 40% and normalized plasma glucose and insulin levels. In addition, insulin- stimulated skeletal muscle glucose uptake was normalized in hyperleptinemic rats, an effect that correlated closely with a 60% (P 0.001) decrease in mTG. Importantly, HF rats that received a control adenovirus containing the β- galactosidase cDNA and were calorically matched to AdCMV-leptin-treated animals remained hyperglycemic, hyperinsulinemic, insulin resistant, and maintained elevated mTG. We conclude that a gene-therapeutic intervention that elevates plasma leptin moderately for a sustained period reverses diet- induced hyperglycemia, hyperinsulinemia, and skeletal muscle insulin resistance, and that these improvements are tightly linked to leptin-induced reductions in mTG.

Authors
Buettner, R; Newgard, CB; Rhodes, CJ; O'Doherty, RM
MLA Citation
Buettner, R, Newgard, CB, Rhodes, CJ, and O'Doherty, RM. "Correction of diet-induced hyperglycemia, hyperinsulinemia, and skeletal muscle insulin resistance by moderate hyperleptinemia." American Journal of Physiology - Endocrinology and Metabolism 278.3 41-3 (2000): E563-E569.
Source
scival
Published In
American journal of physiology. Endocrinology and metabolism
Volume
278
Issue
3 41-3
Publish Date
2000
Start Page
E563
End Page
E569

New lessons in the regulation of glucose metabolism taught by the glucose 6-phosphatase system

The operation of glucose 6-phosphatase (EC 3.1.3.9) (Glc6Pase) stems from the interaction of at least two highly hydrophobic proteins embedded in the ER membrane, a heavily glycosylated catalytic subunit of m 36 kDa (P36) and a 46-kDa putative glucose 6-phosphate (Glc6P) translocase (P46). Topology studies of P36 and P46 predict, respectively, nine and ten transmembrane domains with the N-terminal end of P36 oriented towards the lumen of the ER and both termini of P46 oriented towards the cytoplasm. P36 gene expression is increased by glucose, fructose 2,6-bisphosphate (Fru-2,6-P2) and free fatty acids, as well as by glucocorticoids and cyclic AMP; the latter are counteracted by insulin. P46 gene expression is affected by glucose, insulin and cyclic AMP in a manner similar to P36. Accordingly, several response elements for glucocorticoids, cyclic AMP and insulin regulated by hepatocyte nuclear factors were found in the Glc6Pase promoter. Mutations in P36 and P46 lead to glycogen storage disease (GSD) type-1a and type-1 non a (formerly 1b and 1c), respectively. Adenovirusmediated overexpression of P36 in hepatocytes and in vivo impairs glycogen metabolism and glycolysis and increases glucose production; P36 overexpression in INS-1 cells results in decreased glycolysis and glucoseinduced insulin secretion. The nature of the interaction between P36 and P46 in controling Glc6Pase activity remains to be defined. The latter might also have functions other than Glc6P transport that are related to Glc6P metabolism.

Authors
Werve, GVD; Lange, A; Newgard, C; Méchin, M-C; Li, Y; Berteloot, A
MLA Citation
Werve, GVD, Lange, A, Newgard, C, Méchin, M-C, Li, Y, and Berteloot, A. "New lessons in the regulation of glucose metabolism taught by the glucose 6-phosphatase system." European Journal of Biochemistry 267.6 (2000): 1533-1549.
PMID
10712583
Source
scival
Published In
European journal of biochemistry / FEBS
Volume
267
Issue
6
Publish Date
2000
Start Page
1533
End Page
1549
DOI
10.1046/j.1432-1327.2000.01160.x

Increased glucose disposal induced by adenovirus-mediated transfer of glucokinase to skeletal muscle in vivo.

In non-insulin-dependent diabetes mellitus, insulin-stimulated glucose uptake is impaired in muscle, contributing in a major way to development of hyperglycemia. We previously showed that expression of the glucose phosphorylating enzyme glucokinase (GK) in cultured human myocytes improved glucose storage and disposal, suggesting that GK delivery to muscle in situ could potentially enhance glucose clearance. Here we have tested this idea directly by intramuscular delivery of an adenovirus containing the liver GK cDNA (AdCMV-GKL) into one hind limb. We injected an adenovirus containing the beta-galactosidase gene (AdCMV-lacZ) into the hind limb of newborn rats. beta-Galactosidase activity was localized in muscle for as long as 1 month after delivery, with a large percentage of fibers staining positive in the gastrocnemius. Using the same approach with AdCMV-GKL, GK protein content was increased from zero to 50-400% of the GK in normal liver sample, and total glucose phosphorylating activity was increased in GK-expressing muscles relative to the counterpart uninfected muscle. Expression of GK in muscle improved glucose tolerance rather than changing basal glycemic control. Glucose levels were reduced by approximately 35% 10 min after administration of a glucose bolus to fed animals treated with AdCMV-GKL relative to AdCMV-lacZ-treated controls. The enhanced rate of glucose clearance was reflected in increases in muscle 2-deoxy glucose uptake and blood lactate levels. We conclude that restricted expression of GK in muscle leads to an enhanced capacity for muscle glucose disposal and whole body glucose tolerance under conditions of maximal glucose-insulin stimulation, suggesting that under these conditions glucose phosphorylation becomes rate-limiting. Our findings also show that gene delivery to a fraction of the whole body is sufficient to improve glucose disposal, providing a rationale for the development of new therapeutic strategies for treatment of diabetes.-Jiménez-Chillarón, J. C., Newgard, C. B., Gómez-Foix, A. M. Increased glucose disposal induced by adenovirus-mediated transfer of glucokinase to skeletal muscle in vivo.

Authors
Jiménez-Chillarón, JC; Newgard, CB; Gómez-Foix, AM
MLA Citation
Jiménez-Chillarón, JC, Newgard, CB, and Gómez-Foix, AM. "Increased glucose disposal induced by adenovirus-mediated transfer of glucokinase to skeletal muscle in vivo." FASEB J 13.15 (December 1999): 2153-2160.
PMID
10593862
Source
pubmed
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
13
Issue
15
Publish Date
1999
Start Page
2153
End Page
2160

Glucokinase overexpression restores glucose utilization and storage in cultured hepatocytes from male Zucker diabetic fatty rats.

Zucker diabetic fatty rats develop type 2 diabetes concomitantly with peripheral insulin resistance. Hepatocytes from these rats and their control lean counterparts have been cultured, and a number of key parameters of glucose metabolism have been determined. Glucokinase activity was 4.5-fold lower in hepatocytes from diabetic rats than in hepatocytes from healthy ones. In contrast, hexokinase activity was about 2-fold higher in hepatocytes from diabetic animals than in healthy ones. Glucose-6-phosphatase activity was not significantly different. Despite the altered ratios of glucokinase to hexokinase activity, intracellular glucose 6-phosphate concentrations were similar in the two types of cells when they where incubated with 1-25 mM glucose. However, glycogen levels and glycogen synthase activity ratio were lower in hepatocytes from diabetic animals. Total pyruvate kinase activity and its activity ratio as well as fructose 2,6-bisphosphate concentration and lactate production were also lower in cells from diabetic animals. All of these data indicate that glucose metabolism is clearly impaired in hepatocytes from Zucker diabetic fatty rats. Glucokinase overexpression using adenovirus restored glucose metabolism in diabetic hepatocytes. In glucokinase-overexpressing cells, glucose 6-phosphate levels increased. Moreover, glycogen deposition was greatly enhanced due to the activation of glycogen synthase. Pyruvate kinase was also activated, and fructose-2,6-bisphosphate concentration and lactate production were increased in glucokinase-overexpressing diabetic hepatocytes. Overexpression of hexokinase I did not increase glycogen deposition. In conclusion, hepatocytes from Zucker diabetic fatty rats showed depressed glycogen and glycolytic metabolism, but glucokinase overexpression improved their glucose utilization and storage.

Authors
Seoane, J; Barberà, A; Télémaque-Potts, S; Newgard, CB; Guinovart, JJ
MLA Citation
Seoane, J, Barberà, A, Télémaque-Potts, S, Newgard, CB, and Guinovart, JJ. "Glucokinase overexpression restores glucose utilization and storage in cultured hepatocytes from male Zucker diabetic fatty rats." J Biol Chem 274.45 (November 5, 1999): 31833-31838.
PMID
10542207
Source
pubmed
Published In
The Journal of biological chemistry
Volume
274
Issue
45
Publish Date
1999
Start Page
31833
End Page
31838

Metabolic impact of glucokinase overexpression in liver: lowering of blood glucose in fed rats is accompanied by hyperlipidemia.

The balance between hepatic glucose uptake and production is perturbed in both major forms of diabetes. It has been suggested that pharmacologic or genetic methods for enhancing glucokinase (GK) enzymatic activity in liver might be a means of increasing glucose disposal and lowering blood glucose in diabetic patients. To better evaluate this possibility, we used a recombinant adenovirus containing the cDNA encoding GK (AdCMV-GKL) to achieve overexpression of the enzyme at different levels in liver of normal rats. In a first set of experiments, in rats fasted for 18 h, AdCMV-GKL infusion caused a 211% increase in hepatic GK activity relative to animals infused with a control virus (AdCMV-betaGAL). AdCMV-GKL-treated fasted rats exhibited no significant changes in circulating glucose, free fatty acids (FFAs), lactate, beta-hydroxybutyrate, or insulin levels relative to controls, whereas triglyceride (TG) levels were slightly increased (53%). In a second set of studies, in rats fed ad libitum, GK was overexpressed in liver by 3- and 6.4-fold. Animals with the lower degree of GK overexpression exhibited no significant changes in circulating glucose, FFAs, insulin, TG, or lactate levels relative to controls that received a virus encoding a catalytically inactive mutant GK (AdCMV-GK203), but did show a modest increase in lactate (58%) relative to AdCMV-betaGAL-infused controls. In contrast, the higher level of GK overexpression caused a 38% decrease in blood glucose levels and a 67% decrease in circulating insulin levels relative to AdCMV-GK203-infused animals. The decline in glucose levels was accompanied by a 190% increase in circulating TG and a 310% increase in circulating FFAs; total plasma cholesterol was unaffected. Finally, fasted animals treated with AdCMV-GKL had 5.4 times as much liver glycogen as AdCMV-betaGAL-treated controls; no significant increases in liver glycogen were observed at either level of GK overexpression in ad libitum-fed rats relative to fed controls. In sum, levels of hepatic GK overexpression associated with a decline in blood glucose are accompanied by equally dramatic increases in FFAs and TG, raising concerns about manipulation of liver GK activity as a viable strategy for treatment of diabetes.

Authors
O'Doherty, RM; Lehman, DL; Télémaque-Potts, S; Newgard, CB
MLA Citation
O'Doherty, RM, Lehman, DL, Télémaque-Potts, S, and Newgard, CB. "Metabolic impact of glucokinase overexpression in liver: lowering of blood glucose in fed rats is accompanied by hyperlipidemia." Diabetes 48.10 (October 1999): 2022-2027.
PMID
10512368
Source
pubmed
Published In
Diabetes
Volume
48
Issue
10
Publish Date
1999
Start Page
2022
End Page
2027

Sparing effect of leptin on liver glycogen stores in rats during the fed-to-fasted transition.

The effect of moderate hyperleptinemia ( approximately 20 ng/ml) on liver and skeletal muscle glycogen metabolism was examined in Wistar rats. Animals were studied approximately 90 h after receiving recombinant adenoviruses encoding rat leptin (AdCMV-leptin) or beta-galactosidase (AdCMV-betaGal). Liver and skeletal muscle glycogen levels in the fed and fasted (18 h) states were similar in AdCMV-leptin- and AdCMV-betaGal-treated rats. However, after delivery of a glucose bolus, liver glycogen levels were significantly greater in AdCMV-leptin compared with AdCMV-betaGal rats (P < 0.05). To investigate the mechanism(s) of these differences, glycogen levels were measured immediately after the cessation of a 3- or 6-h glucose infusion or 3, 6, and 9 h after the cessation of a 6-h glucose infusion. Similar increases in liver and skeletal muscle glycogen occurred in hyperleptinemic and control rats in response to glucose infusions. However, 3 and 6 h after the cessation of a glucose infusion, liver glycogen levels were approximately twofold greater (P < 0.05) in AdCMV-leptin-treated compared with AdCMV-betaGal-treated animals. Skeletal muscle glycogen levels were similar in AdCMV-leptin-treated and AdCMV-betaGal-treated animals at the same time points. Glycogen phosphorylase, phosphodiesterase 3B, and glycogen synthase activities were unaltered by hyperleptinemia. We conclude that moderate increases in plasma leptin levels decrease liver glycogen degradation during the fed-to-fasted transition.

Authors
O'Doherty, RM; Anderson, PR; Zhao, AZ; Bornfeldt, KE; Newgard, CB
MLA Citation
O'Doherty, RM, Anderson, PR, Zhao, AZ, Bornfeldt, KE, and Newgard, CB. "Sparing effect of leptin on liver glycogen stores in rats during the fed-to-fasted transition." Am J Physiol 277.3 Pt 1 (September 1999): E544-E550.
PMID
10484368
Source
pubmed
Published In
The American journal of physiology
Volume
277
Issue
3 Pt 1
Publish Date
1999
Start Page
E544
End Page
E550

Glucose-6-phosphatase overexpression lowers glucose 6-phosphate and inhibits glycogen synthesis and glycolysis in hepatocytes without affecting glucokinase translocation. Evidence against feedback inhibition of glucokinase.

In hepatocytes glucokinase (GK) and glucose-6-phosphatase (Glc-6-Pase)(1) have converse effects on glucose 6-phosphate (and fructose 6-phosphate) levels. To establish whether hexose 6-phosphate regulates GK binding to its regulatory protein, we determined the effects of Glc-6-Pase overexpression on glucose metabolism and GK compartmentation. Glc-6-Pase overexpression (4-fold) decreased glucose 6-phosphate levels by 50% and inhibited glycogen synthesis and glycolysis with a greater negative control coefficient on glycogen synthesis than on glycolysis, but it did not affect the response coefficients of glycogen synthesis or glycolysis to glucose, and it did not increase the control coefficient of GK or cause dissociation of GK from its regulatory protein, indicating that in hepatocytes fructose 6-phosphate does not regulate GK translocation by feedback inhibition. GK overexpression increases glycolysis and glycogen synthesis with a greater control coefficient on glycogen synthesis than on glycolysis. On the basis of the similar relative control coefficients of GK and Glc-6-Pase on glycogen synthesis compared with glycolysis, and the lack of effect of Glc-6-Pase overexpression on GK translocation or the control coefficient of GK, it is concluded that the main regulatory function of Glc-6-Pase is to buffer the glucose 6-phosphate concentration. This is consistent with recent findings that hyperglycemia stimulates Glc-6-Pase gene transcription.

Authors
Aiston, S; Trinh, KY; Lange, AJ; Newgard, CB; Agius, L
MLA Citation
Aiston, S, Trinh, KY, Lange, AJ, Newgard, CB, and Agius, L. "Glucose-6-phosphatase overexpression lowers glucose 6-phosphate and inhibits glycogen synthesis and glycolysis in hepatocytes without affecting glucokinase translocation. Evidence against feedback inhibition of glucokinase." J Biol Chem 274.35 (August 27, 1999): 24559-24566.
PMID
10455119
Source
pubmed
Published In
The Journal of biological chemistry
Volume
274
Issue
35
Publish Date
1999
Start Page
24559
End Page
24566

Snare protein expression and adenoviral transfection of amphicrine AR42J.

The amphicrine AR42J acinar cell line is an excellent model to study both exocrine and neuroendocrine exocytotic mechanisms. As a first step toward this goal, we determined the specific isoforms of the v- and t-SNARE and Munc18 families expressed in these cells. In addition, we show that dexamethasone-induced differentiation toward the exocrine phenotype causes an upregulation of several of these proteins. AR42J is notoriously difficult to transfect, limiting its usefulness as a model. However, we have now overcome this obstacle by acheiving high efficiency expression of a beta-galactosidase reporter gene and truncated SNAP-25 gene using adenoviral infection techniques. The AR42J cells can now be used to pursue and elucidate the distinct functions of individual SNARE isoforms used in endocrine and exocrine secretion within a single cell line.

Authors
Gaisano, HY; Huang, X; Sheu, L; Ghai, M; Newgard, CB; Trinh, KY; Trimble, WS
MLA Citation
Gaisano, HY, Huang, X, Sheu, L, Ghai, M, Newgard, CB, Trinh, KY, and Trimble, WS. "Snare protein expression and adenoviral transfection of amphicrine AR42J." Biochem Biophys Res Commun 260.3 (July 14, 1999): 781-784.
PMID
10403842
Source
pubmed
Published In
Biochemical and Biophysical Research Communications
Volume
260
Issue
3
Publish Date
1999
Start Page
781
End Page
784
DOI
10.1006/bbrc.1999.0987

Increase in PDX-1 levels suppresses insulin gene expression in RIN 1046-38 cells.

RIN1046-38 cells (RIN-38) exhibit a passage-dependent reduction in both basal and glucose-regulated insulin secretion, accompanied by decreased insulin content. In an attempt to explain the mechanism of the gradual decrease in insulin production in cultured cells, we analyzed the insulin promoter activity and the levels of an important trans-activator of the insulin gene, PDX-1, as a function of aging in culture. We demonstrate that the decrease in insulin content and secretion is reflected in decreased promoter activity and is associated with a decrease in E47 and BETA2 nuclear factors, but with a paradoxical 3-fold increase in PDX-1 protein levels. To dissect the effect of increased PDX-1 from the decrease in the additional transcription factors on insulin promoter activity, we overexpressed PDX-1 protein in low passage RIN-38 cells by recombinant adenovirus technology. PDX-1 overexpression did not reduce E47 and BETA2 levels, but was sufficient to suppress rat insulin promoter activity in a dose-dependent manner. The fact that PDX-1 levels participate in trans-activation of insulin promoter activity was demonstrated in HIT-T15 cells. Treating HIT-T15 cells with 1-2 multiplicity of infection of AdCMV-PDX-1 increased rat insulin promoter activity, whereas higher doses repressed insulin promoter activity in these cells as in RIN-38 cells. Our data demonstrate that PDX-1 regulates transcription of the insulin gene in a dose-dependent manner. Depending on its nuclear dosage and the levels of additional cooperating transcription factors, PDX-1 may act as an activator or a repressor of insulin gene expression, such that low as well as high doses may be deleterious to insulin production.

Authors
Seijffers, R; Ben-David, O; Cohen, Y; Karasik, A; Berezin, M; Newgard, CB; Ferber, S
MLA Citation
Seijffers, R, Ben-David, O, Cohen, Y, Karasik, A, Berezin, M, Newgard, CB, and Ferber, S. "Increase in PDX-1 levels suppresses insulin gene expression in RIN 1046-38 cells." Endocrinology 140.7 (July 1999): 3311-3317.
PMID
10385428
Source
pubmed
Published In
Endocrinology
Volume
140
Issue
7
Publish Date
1999
Start Page
3311
End Page
3317
DOI
10.1210/endo.140.7.6796

Overexpression of G11alpha and isoforms of phospholipase C in islet beta-cells reveals a lack of correlation between inositol phosphate accumulation and insulin secretion.

It has been suggested that insulin secretion from pancreatic islets may be mediated in part by activation of phospholipases C (PLCs) and phosphoinositide hydrolysis. The purpose of this study was to determine whether the relatively modest fuel-stimulated insulin secretion responses of rodent beta-cell lines might be explained by inadequate expression or activation of PLC isoforms. We have found that two insulinoma cell lines, INS-1 and betaG 40/110, completely lack PLC-delta1 expression but have levels of expression of PLC-beta1, -beta2, -beta3, -delta2, and -gamma1 that are similar to or slightly reduced from those found in fresh rat islets. Adenovirus-mediated overexpression of PLC-delta1, -beta1, or -beta3 in INS-1 or betaG 40/110 cells results in little or no enhancement in inositol phosphate (IP) accumulation and no improvement in insulin secretion when the cells are stimulated with glucose or carbachol, despite the fact that the overexpressed proteins are fully active in cell extracts. Overexpression of PLC-beta1 or -beta3 in normal rat islets elicits a larger increase in IP accumulation but, again, has no effect on insulin secretion. Because the effect of carbachol on insulin secretion is thought to be mediated through muscarinic receptors that link to the Gq/11 class of heterotrimeric G proteins, we also overexpressed G11alpha in INS-1 cells, either alone or in concert with overexpression of PLC-beta1 or -beta3. Overexpression of G11alpha enhances IP accumulation, an effect slightly potentiated by co-overexpression of PLC-beta1 or -beta3, but these maneuvers do not affect glucose or carbachol-stimulated insulin secretion. In sum, our studies show a lack of correlation between IP accumulation and insulin secretion in INS-1 cells, betaG 40/110 cells, or cultured rat islets. We conclude that overexpression of PLC isoforms and/or G11alpha is not an effective means of enhancing fuel responsiveness in the insulinoma cell lines studied.

Authors
Gasa, R; Trinh, KY; Yu, K; Wilkie, TM; Newgard, CB
MLA Citation
Gasa, R, Trinh, KY, Yu, K, Wilkie, TM, and Newgard, CB. "Overexpression of G11alpha and isoforms of phospholipase C in islet beta-cells reveals a lack of correlation between inositol phosphate accumulation and insulin secretion." Diabetes 48.5 (May 1999): 1035-1044.
PMID
10331408
Source
pubmed
Published In
Diabetes
Volume
48
Issue
5
Publish Date
1999
Start Page
1035
End Page
1044

Adenovirus-mediated overexpression of uncoupling protein-2 in pancreatic islets of Zucker diabetic rats increases oxidative activity and improves beta-cell function.

The discovery of uncoupling protein (UCP)-2, a ubiquitously expressed protein homologous to UCP-1, has raised the possibility that energy balance of cells might be regulated in tissues other than brown adipocytes. In normal pancreatic islets, UCP-2 is upregulated by leptin and is low in leptin-resistant islets of ZDF rats. To determine whether UCP-2 does, in fact, have uncoupling activity and, if so, whether such activity would favorably influence the abnormalities in leptin-unresponsive UCP-2-underexpressing islets of diabetic ZDF rats, we transferred the UCP-2 gene to the islets of diabetic ZDF rats and lean (+/+) ZDF control rats. Although ATP was reduced by 23% in both groups of islets, the ATP:ADP ratio increased by 42 and 141%, respectively. [3H]palmitate oxidation was increased by 50%, and [3H]glucose oxidation was 42-63% higher. Preproinsulin mRNA was 2.9-fold above control levels, and glucose-stimulated insulin secretion, which was negligible in control ZDF rat islets, was improved in UCP-2-overexpressing islets. The high fat content of the islets was not reduced, however. We conclude that UCP-2 has uncoupling function when overexpressed in leptin-insensitive islets and that its overexpression corrects the underexpression of the insulin gene and ameliorates glucose-stimulated insulin secretion, possibly by increasing the ATP:ADP ratio.

Authors
Wang, MY; Shimabukuro, M; Lee, Y; Trinh, KY; Chen, JL; Newgard, CB; Unger, RH
MLA Citation
Wang, MY, Shimabukuro, M, Lee, Y, Trinh, KY, Chen, JL, Newgard, CB, and Unger, RH. "Adenovirus-mediated overexpression of uncoupling protein-2 in pancreatic islets of Zucker diabetic rats increases oxidative activity and improves beta-cell function." Diabetes 48.5 (May 1999): 1020-1025.
PMID
10331406
Source
pubmed
Published In
Diabetes
Volume
48
Issue
5
Publish Date
1999
Start Page
1020
End Page
1025

Reversing adipocyte differentiation: implications for treatment of obesity.

Conventional treatment of obesity reduces fat in mature adipocytes but leaves them with lipogenic enzymes capable of rapid resynthesis of fat, a likely factor in treatment failure. Adenovirus-induced hyperleptinemia in normal rats results in rapid nonketotic fat loss that persists after hyperleptinemia disappears, whereas pair-fed controls regain their weight in 2 weeks. We report here that the hyperleptinemia depletes adipocyte fat while profoundly down-regulating lipogenic enzymes and their transcription factor, peroxisome proliferator-activated receptor (PPAR)gamma in epididymal fat; enzymes of fatty acid oxidation and their transcription factor, PPARalpha, normally low in adipocytes, are up-regulated, as are uncoupling proteins 1 and 2. This transformation of adipocytes from cells that store triglycerides to fatty acid-oxidizing cells is accompanied by loss of the adipocyte markers, adipocyte fatty acid-binding protein 2, tumor necrosis factor alpha, and leptin, and by the appearance of the preadipocyte marker Pref-1. These findings suggest a strategy for the treatment of obesity by alteration of the adipocyte phenotype.

Authors
Zhou, YT; Wang, ZW; Higa, M; Newgard, CB; Unger, RH
MLA Citation
Zhou, YT, Wang, ZW, Higa, M, Newgard, CB, and Unger, RH. "Reversing adipocyte differentiation: implications for treatment of obesity." Proc Natl Acad Sci U S A 96.5 (March 2, 1999): 2391-2395.
PMID
10051652
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
96
Issue
5
Publish Date
1999
Start Page
2391
End Page
2395

Metabolic engineering with recombinant adenoviruses.

Fuel homeostasis in mammals is accomplished by the interplay between tissues and organs with distinct metabolic roles. These regulatory mechanisms are disrupted in obesity and diabetes, leading to a renewed emphasis on discovery of molecular and pharmacologic methods for reversing metabolic disorders. In this chapter, we review the use of recombinant adenoviral vectors as tools for delivering metabolic regulatory genes to cells in culture and to tissues of intact animals. Included are studies on the use of these vectors for gaining insights into the biochemical mechanisms that regulate glucose-stimulated insulin secretion from pancreatic islet beta-cells. We also highlight their use for understanding the function of newly discovered genes that regulate glycogen metabolism in liver and other tissues, and for evaluating "candidate" genes such as glucose-6-phosphatase, which may contribute to development of metabolic dysfunction in pancreatic islets and liver. Finally, we discuss the use of adenoviral and related vectors for causing chronic increases in the levels of circulating hormones. These examples serve to highlight the power of viral gene transfer vectors as tools for understanding metabolic regulatory mechanisms.

Authors
Antinozzi, PA; Berman, HK; O'Doherty, RM; Newgard, CB
MLA Citation
Antinozzi, PA, Berman, HK, O'Doherty, RM, and Newgard, CB. "Metabolic engineering with recombinant adenoviruses." Annu Rev Nutr 19 (1999): 511-544. (Review)
PMID
10448535
Source
pubmed
Published In
Annual Review of Nutrition
Volume
19
Publish Date
1999
Start Page
511
End Page
544
DOI
10.1146/annurev.nutr.19.1.511

Sparing effect of leptin on liver glycogen stores in rats during the fed-to-fasted transition

The effect of moderate hyperleptinemia (~20 ng/ml) on liver and skeletal muscle glycogen metabolism was examined in Wistar rats. Animals were studied ~90 h after receiving recombinant adenoviruses encoding rat leptin (AdCMV-leptin) or β-galactosidase (AdCMV-βGal). Liver and skeletal muscle glycogen levels in the fed and fasted (18 h) states were similar in AdCMV- leptin-and AdCMV-βGal-treated rats. However, after delivery of a glucose bolus, liver glycogen levels were significantly greater in AdCMV-leptin compared with AdCMV-βGal rats (P < 0.05). To investigate the mechanism(s) of these differences, glycogen levels were measured immediately after the cessation of a 3- or 6-h glucose infusion or 3, 6, and 9 h after the cessation of a 6-h glucose infusion. Similar increases in liver and skeletal muscle glycogen occurred in hyperleptinemic and control rats in response to glucose infusions. However, 3 and 6 h after the cessation of a glucose infusion, liver glycogen levels were approximately twofold greater (P < 0.05) in AdCMV-leptin-treated compared with AdCMV-βGal-treated animals. Skeletal muscle glycogen levels were similar in AdCMV-leptin-treated and AdCMV-βGal- treated animals at the same time points. Glycogen phosphorylase, phosphodiesterase 3B, and glycogen synthase activities were unaltered by hyperleptinemia. We conclude that moderate increases in plasma leptin levels decrease liver glycogen degradation during the fed-to-fasted transition.

Authors
O'Doherty, RM; Anderson, PR; Zhao, AZ; Bornfeldt, KE; Newgard, CB
MLA Citation
O'Doherty, RM, Anderson, PR, Zhao, AZ, Bornfeldt, KE, and Newgard, CB. "Sparing effect of leptin on liver glycogen stores in rats during the fed-to-fasted transition." American Journal of Physiology - Endocrinology and Metabolism 277.3 40-3 (1999): E544-E550.
Source
scival
Published In
American journal of physiology. Endocrinology and metabolism
Volume
277
Issue
3 40-3
Publish Date
1999
Start Page
E544
End Page
E550

Lipoapoptosis in beta-cells of obese prediabetic fa/fa rats. Role of serine palmitoyltransferase overexpression.

We reported that the lipoapoptosis of beta-cells observed in fat-laden islets of obese fa/fa Zucker Diabetic Fatty (ZDF) rats results from overproduction of ceramide, an initiator of the apoptotic cascade and is induced by long-chain fatty acids (FA). Whereas the ceramide of cytokine-induced apoptosis may be derived from sphingomyelin hydrolysis, FA-induced ceramide overproduction seems to be derived from FA. We therefore semiquantified mRNA of serine palmitoyltransferase (SPT), which catalyzes the first step in ceramide synthesis. It was 2-3-fold higher in fa/fa islets than in +/+ controls. [3H]Ceramide formation from [3H]serine was 2.2-4. 5-fold higher in fa/fa islets. Triacsin-C, which blocks palmitoyl-CoA synthesis, and L-cycloserine, which blocks SPT activity, completely blocked [3H]ceramide formation from [3H]serine. Islets of fa/fa rats are unresponsive to the lipopenic action of leptin, which normally depletes fat and prevents FA up-regulation of SPT. To determine the role of leptin unresponsiveness in the SPT overexpression, we transferred wild type OB-Rb cDNA to their islets; now leptin completely blocked the exaggerated FA-induced increase of SPT mRNA while reducing the fat content. Beta-cell lipoapoptosis was partially prevented in vivo by treating prediabetic ZDF rats with L-cycloserine for 2 weeks. Ceramide content and DNA fragmentation both declined 40-50%. We conclude that lipoapoptosis of ZDF rats is mediated by enhanced ceramide synthesis from FA and that blockade by SPT inhibitors prevents lipoapoptosis.

Authors
Shimabukuro, M; Higa, M; Zhou, YT; Wang, MY; Newgard, CB; Unger, RH
MLA Citation
Shimabukuro, M, Higa, M, Zhou, YT, Wang, MY, Newgard, CB, and Unger, RH. "Lipoapoptosis in beta-cells of obese prediabetic fa/fa rats. Role of serine palmitoyltransferase overexpression." J Biol Chem 273.49 (December 4, 1998): 32487-32490.
PMID
9829981
Source
pubmed
Published In
The Journal of biological chemistry
Volume
273
Issue
49
Publish Date
1998
Start Page
32487
End Page
32490

Perturbation of fuel homeostasis caused by overexpression of the glucose-6-phosphatase catalytic subunit in liver of normal rats.

The terminal step in hepatic gluconeogenesis is catalyzed by glucose-6-phosphatase, an enzyme activity residing in the endoplasmic reticulum and consisting of a catalytic subunit (glucose-6-phosphatase (G6Pase)) and putative accessory transport proteins. We show that Zucker diabetic fatty rats (fa/fa), which are known to exhibit impaired suppression of hepatic glucose output, have 2.4-fold more glucose-6-phosphatase activity in liver than lean controls. To define the potential contribution of increased hepatic G6Pase to development of diabetes, we infused recombinant adenoviruses containing the G6Pase cDNA (AdCMV-G6Pase) or the beta-galactosidase gene into normal rats. Animals were studied by one of three protocols as follows: protocol 1, fed ad libitum for 7 days; protocol 2, fed ad libitum for 5 days, fasted overnight, and subjected to an oral glucose tolerance test; protocol 3, fed ad libitum for 4 days, fasted for 48 h, subjected to oral glucose tolerance test, and then allowed to refeed overnight. Hepatic glucose-6-phosphatase enzymatic activity was increased by 1.6-3-fold in microsomes isolated from AdCMV-G6Pase-treated animals in all three protocols, and the resultant metabolic profile was similar in each case. AdCMV-G6Pase-treated animals exhibited several of the abnormalities associated with early stage non-insulin-dependent diabetes mellitus, including glucose intolerance, hyperinsulinemia, decreased hepatic glycogen content, and increased peripheral (muscle) triglyceride stores. These animals also exhibited significant decreases in circulating free fatty acids and triglycerides, changes not normally associated with the disease. Our studies show that overexpression of G6Pase in liver is sufficient to perturb whole animal glucose and lipid homeostasis, possibly contributing to the development of metabolic abnormalities associated with diabetes.

Authors
Trinh, KY; O'Doherty, RM; Anderson, P; Lange, AJ; Newgard, CB
MLA Citation
Trinh, KY, O'Doherty, RM, Anderson, P, Lange, AJ, and Newgard, CB. "Perturbation of fuel homeostasis caused by overexpression of the glucose-6-phosphatase catalytic subunit in liver of normal rats." J Biol Chem 273.47 (November 20, 1998): 31615-31620.
PMID
9813078
Source
pubmed
Published In
The Journal of biological chemistry
Volume
273
Issue
47
Publish Date
1998
Start Page
31615
End Page
31620

Overexpression of protein targeting to glycogen (PTG) in rat hepatocytes causes profound activation of glycogen synthesis independent of normal hormone- and substrate-mediated regulatory mechanisms.

Protein targeting to glycogen (PTG), also known as PPP1R5, is a widely expressed member of a growing family of proteins that target protein phosphatase-1 (PP-1) to glycogen particles. Because PTG also binds to glycogen synthase and phosphorylase kinase, it has been suggested that it serves as a "scaffold" for efficient activation of glycogen synthesis. However, very little is known about the metabolic effects of PTG. In this study, we have used recombinant adenovirus to overexpress PTG in primary rat hepatocytes, a cell type with high glycogenic capacity. We find that overexpression of PTG potently activates glycogen synthesis in cultured hepatocytes. Surprisingly, the glycogenic effect of PTG is observed even in the complete absence of carbohydrates or insulin in the culture medium. Furthermore, glycogenolytic agents such as forskolin or glucagon are largely ineffective at activating glycogen degradation in PTG overexpressing hepatocytes, even though large increases in cAMP levels are demonstrated. These metabolic effects of PTG overexpression are accompanied by a 3.6-fold increase in glycogen synthase activation state and a 40% decrease in glycogen phosphorylase activity. Our results are consistent with a model in which PTG overexpression "locks" the hepatocyte in a glycogenic mode, presumably via its ability to promote interaction of enzymes of glycogen metabolism with PP-1.

Authors
Berman, HK; O'Doherty, RM; Anderson, P; Newgard, CB
MLA Citation
Berman, HK, O'Doherty, RM, Anderson, P, and Newgard, CB. "Overexpression of protein targeting to glycogen (PTG) in rat hepatocytes causes profound activation of glycogen synthesis independent of normal hormone- and substrate-mediated regulatory mechanisms." J Biol Chem 273.41 (October 9, 1998): 26421-26425.
PMID
9756875
Source
pubmed
Published In
The Journal of biological chemistry
Volume
273
Issue
41
Publish Date
1998
Start Page
26421
End Page
26425

Overexpression of leptin receptors in pancreatic islets of Zucker diabetic fatty rats restores GLUT-2, glucokinase, and glucose-stimulated insulin secretion.

The high-Km glucose transporter, GLUT-2, and the high-Km hexokinase of beta cells, glucokinase (GK), are required for glucose-stimulated insulin secretion (GSIS). GLUT-2 expression in beta cells of Zucker diabetic fatty (ZDF) rats is profoundly reduced at the onset of beta-cell dysfunction of diabetes. Because ZDF rats are homozygous for a mutation in their leptin receptor (OB-R) gene and are therefore leptin-insensitive, we expressed the wild-type OB-R gene in diabetic islets by infusing a recombinant adenovirus (AdCMV-OB-Rb) to determine whether this reversed the abnormalities. Leptin induced a rise in phosphorylated STAT3, indicating that the transferred wild-type OB-R was functional. GLUT-2 protein rose 17-fold in AdCMV-OB-Rb-treated ZDF islets without leptin, and leptin caused no further rise. GK protein rose 7-fold without and 12-fold with leptin. Preproinsulin mRNA increased 64% without leptin and rose no further with leptin, but leptin was required to restore GSIS. Clofibrate and 9-cis-retinoic acid, the partner ligands for binding to peroxisome proliferator-activator receptor alpha (PPARalpha) and retinoid X receptor, up-regulated GLUT-2 expression in islets of normal rats, but not in ZDF rats, in which PPARalpha is very low. Because the fat content of islets of diabetic ZDF rats remains high unless they are treated with leptin, it appears that restoration of GSIS requires normalization of intracellular nutrient homeostasis, whereas up-regulation of GLUT-2 and GK is leptin-independent, requiring only high expression of OB-Rb.

Authors
Wang, MY; Koyama, K; Shimabukuro, M; Mangelsdorf, D; Newgard, CB; Unger, RH
MLA Citation
Wang, MY, Koyama, K, Shimabukuro, M, Mangelsdorf, D, Newgard, CB, and Unger, RH. "Overexpression of leptin receptors in pancreatic islets of Zucker diabetic fatty rats restores GLUT-2, glucokinase, and glucose-stimulated insulin secretion." Proc Natl Acad Sci U S A 95.20 (September 29, 1998): 11921-11926.
PMID
9751766
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
95
Issue
20
Publish Date
1998
Start Page
11921
End Page
11926

The repression of hormone-activated PEPCK gene expression by glucose is insulin-independent but requires glucose metabolism.

Phosphoenolpyruvate carboxykinase (PEPCK) is a rate-controlling enzyme in hepatic gluconeogenesis, and it therefore plays a central role in glucose homeostasis. The rate of transcription of the PEPCK gene is increased by glucagon (via cAMP) and glucocorticoids and is inhibited by insulin. Under certain circumstances glucose also decreases PEPCK gene expression, but the mechanism of this effect is poorly understood. The glucose-mediated stimulation of a number of glycolytic and lipogenic genes requires the expression of glucokinase (GK) and increased glucose metabolism. HL1C rat hepatoma cells are a stably transfected line of H4IIE rat hepatoma cells that express a PEPCK promoter-chloramphenicol acetyltransferase fusion gene that is regulated in the same manner as the endogenous PEPCK gene. These cells do not express GK and do not normally exhibit a response of either the endogenous PEPCK gene, or of the trans-gene, to glucose. A recombinant adenovirus that directs the expression of glucokinase (AdCMV-GK) was used to increase glucose metabolism in HL1C cells to test whether increased glucose flux is also required for the repression of PEPCK gene expression. In AdCMV-GK-treated cells glucose strongly inhibits hormone-activated transcription of the endogenous PEPCK gene and of the expressed fusion gene. The glucose effect on PEPCK gene promoter activity is blocked by 5 mM mannoheptulose, a specific inhibitor of GK activity. The glucose analog, 2-deoxyglucose mimics the glucose response, but this effect does not require GK expression. 3-O-methylglucose is ineffective. Glucose exerts its effect on the PEPCK gene within 4 h, at physiologic concentrations, and with an EC50 of 6.5 mM, which approximates the Km of glucokinase. The effects of glucose and insulin on PEPCK gene expression are additive, but only at suboptimal concentrations of both agents. The results of these studies demonstrate that, by inhibiting PEPCK gene transcription, glucose participates in a feedback control loop that governs its production from gluconeogenesis.

Authors
Scott, DK; O'Doherty, RM; Stafford, JM; Newgard, CB; Granner, DK
MLA Citation
Scott, DK, O'Doherty, RM, Stafford, JM, Newgard, CB, and Granner, DK. "The repression of hormone-activated PEPCK gene expression by glucose is insulin-independent but requires glucose metabolism." J Biol Chem 273.37 (September 11, 1998): 24145-24151.
PMID
9727036
Source
pubmed
Published In
The Journal of biological chemistry
Volume
273
Issue
37
Publish Date
1998
Start Page
24145
End Page
24151

Expression of glucokinase in cultured human muscle cells confers insulin-independent and glucose concentration-dependent increases in glucose disposal and storage.

Insulin resistance, as is found in skeletal muscle of individuals with obesity and NIDDM, appears to involve a reduced capacity of the hormone to stimulate glucose uptake and/or phosphorylation. The glucose phosphorylation step, as catalyzed by hexokinase II, has been described as rate limiting for glucose disposal in muscle, but overexpression of this enzyme under control of a muscle-specific promoter in transgenic mice has had limited metabolic impact. In the current study, we investigated in a cultured muscle model whether expression of glucokinase, which in contrast to hexokinase II is not inhibited by glucose-6-phosphate (G-6-P), would have a pronounced metabolic impact. We used a recombinant adenovirus containing the cDNA-encoding rat liver glucokinase (AdCMV-GKL) to increase the glucose phosphorylating activity in cultured human muscle cells by fourfold. G-6-P levels increased in AdCMV-GKL-treated cells in a glucose concentration-dependent manner over the range of 1-30 mmol/l, whereas the much smaller increases in G-6-P in control cells were maximal at glucose concentrations <5 mmol/l. Further, cells expressing glucokinase accumulated 17 times more 2-deoxyglucose-6-phosphate than control cells. In AdCMV-GKL-treated cells, the time-dependent rise in G-6-P correlated with an increase in the activity ratio of glycogen synthase. AdCMV-GKL-treated cells also exhibited a 2.5- to 3-fold increase in glycogen content and a four- to fivefold increase in glycolytic flux, proportional to the increase in glucose phosphorylating capacity. All of these observations were made in the absence of insulin. Thus we concluded that expression of glucokinase in cultured human muscle cells results in proportional increases in insulin-independent glucose disposal, and that muscle glucose storage and utilization becomes controlled in a glucose concentration-dependent manner in AdCMV-GKL-treated cells. These results encourage testing whether delivery of glucokinase to muscle in vivo has an impact on glycemic control, which could be a method for circumventing the failure of insulin to stimulate glucose uptake and/or phosphorylation in muscle normally in insulin-resistant subjects.

Authors
Baqué, S; Montell, E; Guinovart, JJ; Newgard, CB; Gómez-Foix, AM
MLA Citation
Baqué, S, Montell, E, Guinovart, JJ, Newgard, CB, and Gómez-Foix, AM. "Expression of glucokinase in cultured human muscle cells confers insulin-independent and glucose concentration-dependent increases in glucose disposal and storage." Diabetes 47.9 (September 1998): 1392-1398.
PMID
9726226
Source
pubmed
Published In
Diabetes
Volume
47
Issue
9
Publish Date
1998
Start Page
1392
End Page
1398

Resistance to adenovirally induced hyperleptinemia in rats. Comparison of ventromedial hypothalamic lesions and mutated leptin receptors.

Leptin regulates appetite and body weight via hypothalamic targets, but it can act directly on cultured pancreatic islets to regulate their fat metabolism. To obtain in vivo evidence that leptin may act peripherally as well as centrally, we compared the effect of adenovirally induced hyperleptinemia on food intake, body weight, and islet fat content in ventromedial hypothalamic-lesioned (VMHL) rats, sham-lesioned (SL) controls, and Zucker Diabetic Fatty (ZDF) rats in which the leptin receptor is mutated. Infusion with recombinant adenovirus containing the rat leptin cDNA increased plasma leptin by approximately 20 ng/ml in VMHL and ZDF rats but had no effect on their food intake, body weight, or fat tissue weight. Caloric matching of hyperphagic VMHL rats to SL controls did not reduce their resistance to hyperleptinemia. Whereas prediabetic ZDF rats had a fourfold elevation in islet fat, in VMHL rats islet fat was normal and none of them became diabetic. Isolated islets from ZDF rats were completely resistant to the lipopenic action of leptin, while VMHL islets exhibited 50% of the normal response; caloric matching of VMHL rats to SL controls increased leptin responsiveness of their islets to 92% of controls. We conclude that leptin regulation of adipocyte fat requires an intact VMH but that islet fat content is regulated independently of the VMH.

Authors
Koyama, K; Shimabukuro, M; Chen, G; Wang, MY; Lee, Y; Kalra, PS; Dube, MG; Kalra, SP; Newgard, CB; Unger, RH
MLA Citation
Koyama, K, Shimabukuro, M, Chen, G, Wang, MY, Lee, Y, Kalra, PS, Dube, MG, Kalra, SP, Newgard, CB, and Unger, RH. "Resistance to adenovirally induced hyperleptinemia in rats. Comparison of ventromedial hypothalamic lesions and mutated leptin receptors." J Clin Invest 102.4 (August 15, 1998): 728-733.
PMID
9710441
Source
pubmed
Published In
Journal of Clinical Investigation
Volume
102
Issue
4
Publish Date
1998
Start Page
728
End Page
733
DOI
10.1172/JCI3353

Protection against lipoapoptosis of beta cells through leptin-dependent maintenance of Bcl-2 expression.

Obesity causes its complications through functional and morphologic damage to remotely situated tissues via undetermined mechanisms. In one rodent model of obesity, the Zucker diabetic fatty fa/fa rat, overaccumulation of triglycerides in the pancreatic islets may be responsible for a gradual depletion of beta cells, leading to the most common complication of obesity, non-insulin-dependent diabetes mellitus. At the onset of non-insulin-dependent diabetes mellitus, the islets from fa/fa rats contain up to 100 times the fat content of islets from normal lean rats. Ultimately, about 75% of the beta cells disappear from these fat-laden islets as a consequence of apoptosis induced by long-chain fatty acids (FA). Here we quantify Bcl-2, the anti-apoptosis factor in these islets, and find that Bcl-2 mRNA and protein are, respectively, 85% and 70% below controls. In normal islets cultured in 1 mM FA, Bcl-2 mRNA declined by 68% and completely disappeared in fa/fa islets cultured in FA. In both groups, suppression was completely blocked by the fatty acyl-CoA synthetase inhibitor, triacsin C, evidence of its mediation by fatty acyl-CoA. To determine whether leptin action blocked FA-induced apoptosis, we cultured normal and fa/fa islets in 1 mM FA with or without leptin. Leptin completely blocked FA-induced Bcl-2 suppression in normal islets but had no effect on islets from fa/fa rats, which are unresponsive to leptin because of a mutation in their leptin receptors (OB-R). However, when wild-type OB-R is overexpressed in fa/fa islets, leptin completely prevented FA-induced Bcl-2 suppression and DNA fragmentation.

Authors
Shimabukuro, M; Wang, MY; Zhou, YT; Newgard, CB; Unger, RH
MLA Citation
Shimabukuro, M, Wang, MY, Zhou, YT, Newgard, CB, and Unger, RH. "Protection against lipoapoptosis of beta cells through leptin-dependent maintenance of Bcl-2 expression." Proc Natl Acad Sci U S A 95.16 (August 4, 1998): 9558-9561.
PMID
9689119
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
95
Issue
16
Publish Date
1998
Start Page
9558
End Page
9561

Role of peroxisome proliferator-activated receptor alpha in disease of pancreatic beta cells.

Expression of peroxisome proliferator-activated receptor alpha (PPARalpha) and enzymes of fatty acid (FA) oxidation is markedly reduced in the fat-laden, dysfunctional islets of obese, prediabetic Zucker diabetic fatty (fa/fa) rats with mutated leptin receptors (OB-R). Leptin, PPARalpha/retinoid x receptor ligands, and FA all up-regulate PPARalpha and enzymes of FA oxidation and stimulate [3H]-palmitate oxidation in normal islets but not in islets from fa/fa rats. Overexpression of normal OB-R in islets of fa/fa rats corrects all of the foregoing abnormalities and reverses the diabetic phenotype. PPARalpha is a OB-R-dependent factor required for normal fat homeostasis in islet cells.

Authors
Zhou, YT; Shimabukuro, M; Wang, MY; Lee, Y; Higa, M; Milburn, JL; Newgard, CB; Unger, RH
MLA Citation
Zhou, YT, Shimabukuro, M, Wang, MY, Lee, Y, Higa, M, Milburn, JL, Newgard, CB, and Unger, RH. "Role of peroxisome proliferator-activated receptor alpha in disease of pancreatic beta cells." Proc Natl Acad Sci U S A 95.15 (July 21, 1998): 8898-8903.
PMID
9671776
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
95
Issue
15
Publish Date
1998
Start Page
8898
End Page
8903

Molecular or pharmacologic perturbation of the link between glucose and lipid metabolism is without effect on glucose-stimulated insulin secretion. A re-evaluation of the long-chain acyl-CoA hypothesis.

The mechanism by which glucose stimulates insulin secretion from the pancreatic islets of Langerhans is incompletely understood. It has been suggested that malonyl-CoA plays a regulatory role by inhibiting fatty acid oxidation and promoting accumulation of cytosolic long-chain acyl-CoA (LC-CoA). In the current study, we have re-evaluated this "long-chain acyl-CoA hypothesis" by using molecular and pharmacologic methods to perturb lipid metabolism in INS-1 insulinoma cells or rat islets during glucose stimulation. First, we constructed a recombinant adenovirus containing the cDNA encoding malonyl-CoA decarboxylase (AdCMV-MCD), an enzyme that decarboxylates malonyl-CoA to acetyl-CoA. INS-1 cells treated with AdCMV-MCD had dramatically lowered intracellular malonyl CoA levels compared with AdCMV-betaGal-treated cells at both 3 and 20 mM glucose. Further, at 20 mM glucose, AdCMV-MCD-treated cells were less effective at suppressing [1-14C]palmitate oxidation and incorporated 43% less labeled palmitate and 50% less labeled glucose into cellular lipids than either AdCMV-betaGAL-treated or untreated INS-1 cells. Despite the large metabolic changes caused by expression of MCD, insulin secretion in response to glucose was unaltered relative to controls. The alternative, pharmacologic approach for perturbing lipid metabolism was to use triacsin C to inhibit long-chain acyl-CoA synthetase. This agent caused potent attenuation of palmitate oxidation and glucose or palmitate incorporation into cellular lipids and also caused a 47% decrease in total LC-CoA. Despite this, the drug had no effect on glucose-stimulated insulin secretion in islets or INS-1 cells. We conclude that significant disruption of the link between glucose and lipid metabolism does not impair glucose-stimulated insulin secretion in pancreatic islets or INS-1 cells.

Authors
Antinozzi, PA; Segall, L; Prentki, M; McGarry, JD; Newgard, CB
MLA Citation
Antinozzi, PA, Segall, L, Prentki, M, McGarry, JD, and Newgard, CB. "Molecular or pharmacologic perturbation of the link between glucose and lipid metabolism is without effect on glucose-stimulated insulin secretion. A re-evaluation of the long-chain acyl-CoA hypothesis." J Biol Chem 273.26 (June 26, 1998): 16146-16154.
PMID
9632669
Source
pubmed
Published In
The Journal of biological chemistry
Volume
273
Issue
26
Publish Date
1998
Start Page
16146
End Page
16154

Stable expression of manganese superoxide dismutase (MnSOD) in insulinoma cells prevents IL-1beta- induced cytotoxicity and reduces nitric oxide production.

The fact that insulin-producing islet beta-cells are susceptible to the cytotoxic effects of inflammatory cytokines represents a potential hinderance to the use of such cells for transplantation therapy of insulin-dependent diabetes mellitus (IDDM). In the current study, we show that IL-1beta induces destruction of INS-1 insulinoma cells, while having no effect on a second insulinoma cell line RIN1046-38 and its engineered derivatives, and that this difference is correlated with a higher level of expression of manganese superoxide dismutase (MnSOD) in the latter cells. Stable overexpression of MnSOD in INS-1 cells provides complete protection against IL-1beta-mediated cytotoxicity, and also results in markedly reduced killing when such cells are exposed to conditioned media from activated human or rat PBMC. Further, overexpression of MnSOD in either RIN- or INS-1-derived lines results in a sharp reduction in IL-1beta-induced nitric oxide (NO) production, a finding that correlates with reduced levels of the inducible form of nitric oxide synthase (iNOS). Treatment of INS-1 cells with L-NMMA, an inhibitor of iNOS, provides the same degree of protection against IL-1beta or supernatants from LPS-activated rat PBMC as MnSOD overexpression, supporting the idea that MnSOD protects INS-1 cells by interfering with the normal IL-1beta-mediated increase in iNOS. Because NO and its derivatives have been implicated as critical mediators of beta-cell destruction in IDDM, we conclude that well regulated insulinoma cell lines engineered for MnSOD overexpression may be an attractive alternative to isolated islets as vehicles for insulin replacement in autoimmune diabetes.

Authors
Hohmeier, HE; Thigpen, A; Tran, VV; Davis, R; Newgard, CB
MLA Citation
Hohmeier, HE, Thigpen, A, Tran, VV, Davis, R, and Newgard, CB. "Stable expression of manganese superoxide dismutase (MnSOD) in insulinoma cells prevents IL-1beta- induced cytotoxicity and reduces nitric oxide production." J Clin Invest 101.9 (May 1, 1998): 1811-1820.
PMID
9576743
Source
pubmed
Published In
Journal of Clinical Investigation
Volume
101
Issue
9
Publish Date
1998
Start Page
1811
End Page
1820
DOI
10.1172/JCI1489

Fundamental metabolic differences between hepatocytes and islet beta-cells revealed by glucokinase overexpression.

Adenovirus-mediated overexpression of the glucose phosphorylating enzyme glucokinase causes large changes in glycolytic flux and glucose storage in isolated rat hepatocytes, but not in pancreatic islets. We have used the well-differentiated insulinoma cell line INS-1 to investigate the basis for these apparent cell-type specific differences. We find that 2- or 5-[3H]glucose usage is increased at low (

Authors
Berman, HK; Newgard, CB
MLA Citation
Berman, HK, and Newgard, CB. "Fundamental metabolic differences between hepatocytes and islet beta-cells revealed by glucokinase overexpression." Biochemistry 37.13 (March 31, 1998): 4543-4552.
PMID
9521775
Source
pubmed
Published In
Biochemistry
Volume
37
Issue
13
Publish Date
1998
Start Page
4543
End Page
4552
DOI
10.1021/bi9726133

OB-Rb gene transfer to leptin-resistant islets reverses diabetogenic phenotype.

In obese Zucker diabetic fatty (ZDF) rats with mutant leptin receptors, pancreatic islets have an approximately 50-fold increase in fat (TG), overproduce nitric oxide (NO), and lack a normal proinsulin mRNA response to fatty acids. We overexpressed the wild-type full-length "b" isoform of the leptin receptor (OB-Rb) in ZDF islets by perfusing ZDF pancreata with recombinant adenovirus containing the cDNA encoding OB-Rb. In cultured islets isolated from these animals, leptin lowered islet TG by 87% and completely blocked TG formation from free fatty acids. Overproduction of NO was reduced, and the preproinsulin mRNA response to free fatty acids was restored. This establishes defective leptin action as the proximate cause of lipotoxic diabetes in ZDF rats.

Authors
Wang, MY; Koyama, K; Shimabukuro, M; Newgard, CB; Unger, RH
MLA Citation
Wang, MY, Koyama, K, Shimabukuro, M, Newgard, CB, and Unger, RH. "OB-Rb gene transfer to leptin-resistant islets reverses diabetogenic phenotype." Proc Natl Acad Sci U S A 95.2 (January 20, 1998): 714-718.
PMID
9435258
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
95
Issue
2
Publish Date
1998
Start Page
714
End Page
718

Metabolic impact of adenovirus-mediated overexpression of the glucose-6-phosphatase catalytic subunit in hepatocytes.

Glucose-6-phosphatase (G6Pase) catalyzes the hydrolysis of glucose 6-phosphate (Glu-6-P) to free glucose and, as the last step in gluconeogenesis and glycogenolysis in liver, is thought to play an important role in glucose homeostasis. G6Pase activity appears to be conferred by a set of proteins localized to the endoplasmic reticulum, including a glucose-6-phosphate translocase, a G6Pase phosphohydrolase or catalytic subunit, and glucose and inorganic phosphate transporters in the endoplasmic reticulum membrane. In the current study, we used a recombinant adenovirus containing the cDNA encoding the G6Pase catalytic subunit (AdCMV-G6Pase) to evaluate the metabolic impact of overexpression of the enzyme in primary hepatocytes. We found that AdCMV-G6Pase-treated liver cells contain significantly less glycogen and Glu-6-P, but unchanged UDP-glucose levels, relative to control cells. Further, the glycogen synthase activity state was closely correlated with Glu-6-P levels over a wide range of glucose concentrations in both G6Pase-overexpressing and control cells. The reduction in glycogen synthesis in AdCMV-G6Pase-treated hepatocytes is therefore not a function of decreased substrate availability but rather occurs because of the regulatory effects of Glu-6-P on glycogen synthase activity. We also found that AdCMV-G6Pase-treated-cells had significantly lower rates of lactate production and [3-3H]glucose usage, coupled with enhanced rates of gluconeogenesis and Glu-6-P hydrolysis. We conclude that overexpression of the G6Pase catalytic subunit alone is sufficient to activate flux through the G6Pase system in liver cells. Further, hepatocytes treated with AdCMV-G6Pase exhibit a metabolic profile resembling that of liver cells from patients or animals with non-insulin-dependent diabetes mellitus, suggesting that dysregulation of the catalytic subunit of G6Pase could contribute to the etiology of the disease.

Authors
Seoane, J; Trinh, K; O'Doherty, RM; Gómez-Foix, AM; Lange, AJ; Newgard, CB; Guinovart, JJ
MLA Citation
Seoane, J, Trinh, K, O'Doherty, RM, Gómez-Foix, AM, Lange, AJ, Newgard, CB, and Guinovart, JJ. "Metabolic impact of adenovirus-mediated overexpression of the glucose-6-phosphatase catalytic subunit in hepatocytes." J Biol Chem 272.43 (October 24, 1997): 26972-26977.
PMID
9341134
Source
pubmed
Published In
The Journal of biological chemistry
Volume
272
Issue
43
Publish Date
1997
Start Page
26972
End Page
26977

Adenovirus-mediated expression of the catalytic subunit of glucose-6-phosphatase in INS-1 cells. Effects on glucose cycling, glucose usage, and insulin secretion.

Glucose-6-phosphatase (Glu-6-Pase) catalyzes the terminal step of gluconeogenesis, the conversion of glucose 6-phosphate (Glu-6-P) to free glucose. This enzyme activity is thought to be conferred by a complex of proteins residing in the endoplasmic reticulum (ER), including a Glu-6-P translocase that transports Glu-6-P into the lumen of the ER, a phosphohydrolase catalytic subunit residing in the lumen, and putative glucose and inorganic phosphate transporters that allow exit of the products of the reaction. In this study, we have investigated the effect of adenovirus-mediated overexpression of the Glu-6-Pase catalytic subunit on glucose metabolism and insulin secretion, using a well differentiated insulinoma cell line, INS-1. We found that the overexpressed Glu-6-Pase catalytic subunit was normally glycosylated, correctly sorted to the ER, and caused a 10-fold increase in Glu-6-Pase enzymatic activity in in vitro assays. Consistent with these findings, a 4.2-fold increase in 3H2O incorporation into glucose was observed in INS-1 cells treated with the recombinant adenovirus containing the Glu-6-Pase catalytic subunit cDNA (AdCMV-Glu-6-Pase). 3-[3H]Glucose usage was decreased by 32% in AdCMV-Glu-6-Pase-treated cells relative to controls, resulting in a proportional 30% decrease in glucose-stimulated insulin secretion. Our findings indicate that overexpression of the Glu-6-Pase catalytic subunit significantly impacts glucose metabolism and insulin secretion in islet beta-cells. However, INS-1 cells treated with AdCMV-Glu-6-Pase do not exhibit the severe alterations of beta-cell function and metabolism associated with islets from rodent models of obesity and non-insulin-dependent diabetes mellitus, suggesting the involvement of genes in addition to the catalytic subunit of Glu-6-Pase in the etiology of such beta-cell dysfunction.

Authors
Trinh, K; Minassian, C; Lange, AJ; O'Doherty, RM; Newgard, CB
MLA Citation
Trinh, K, Minassian, C, Lange, AJ, O'Doherty, RM, and Newgard, CB. "Adenovirus-mediated expression of the catalytic subunit of glucose-6-phosphatase in INS-1 cells. Effects on glucose cycling, glucose usage, and insulin secretion." J Biol Chem 272.40 (October 3, 1997): 24837-24842.
PMID
9312082
Source
pubmed
Published In
The Journal of biological chemistry
Volume
272
Issue
40
Publish Date
1997
Start Page
24837
End Page
24842

beta-cell function in normal rats made chronically hyperleptinemic by adenovirus-leptin gene therapy.

Leptin was overexpressed in the liver of normal Wistar rats by infusing recombinant adenovirus containing the cDNA encoding leptin. Plasma leptin levels rose to 12-24 ng/ml (vs. <2 ng/ml in control rats), and food intake and body weight fell. Visible fat disappeared within 7 days. Plasma insulin fell to <50% of normal in association with hypoglycemia, suggesting enhanced insulin sensitivity. Although beta-cells appeared histologically normal, the pancreases were unresponsive to perfusion with stimulatory levels of glucose and arginine. Since islet triglyceride content was 0, compared with 14 ng/islet in pair-fed control rats, we coperfused a 2:1 oleate:palmitate mixture (0.5 mmol/l). This restored insulin responses to supranormal levels. When normal islets were cultured with 20 ng/ml of leptin, they too became triglyceride-depleted and failed to respond when perifused with glucose or arginine. Perifusion of fatty acids restored both responses. We conclude that in normal rats, hyperleptinemia for 2 weeks causes reversible beta-cell dysfunction by depleting tissue lipids, thereby depriving beta-cells of a lipid-derived signal required for the insulin response to other fuels.

Authors
Koyama, K; Chen, G; Wang, MY; Lee, Y; Shimabukuro, M; Newgard, CB; Unger, RH
MLA Citation
Koyama, K, Chen, G, Wang, MY, Lee, Y, Shimabukuro, M, Newgard, CB, and Unger, RH. "beta-cell function in normal rats made chronically hyperleptinemic by adenovirus-leptin gene therapy." Diabetes 46.8 (August 1997): 1276-1280.
PMID
9231651
Source
pubmed
Published In
Diabetes
Volume
46
Issue
8
Publish Date
1997
Start Page
1276
End Page
1280

Engineered cell lines for insulin replacement in diabetes: current status and future prospects.

The recently completed diabetes complications and control trial has highlighted the need for improvement of insulin delivery systems for treatment of insulin-dependent diabetes mellitus. Despite steady improvement in methods for islet and whole pancreas transplantation over the past three decades, the broad-scale applicability of these approaches remains uncertain due in part to the difficulty and expense associated with procurement of functional tissue. To address this concern, we and others have been using the tools of molecular biology to develop cell lines with regulated insulin secretion that might serve as a surrogate for primary islets or pancreas tissue in transplantation therapy. This article seeks to provide a brief summary of the current status of this growing field, with a particular emphasis on progress in producing cell lines with appropriate glucose-stimulated insulin secretion.

Authors
Newgard, CB; Clark, S; BeltrandelRio, H; Hohmeier, HE; Quaade, C; Normington, K
MLA Citation
Newgard, CB, Clark, S, BeltrandelRio, H, Hohmeier, HE, Quaade, C, and Normington, K. "Engineered cell lines for insulin replacement in diabetes: current status and future prospects." Diabetologia 40 Suppl 2 (July 1997): S42-S47. (Review)
PMID
9248700
Source
pubmed
Published In
Diabetologia
Volume
40 Suppl 2
Publish Date
1997
Start Page
S42
End Page
S47

Engineering of glycerol-stimulated insulin secretion in islet beta cells. Differential metabolic fates of glucose and glycerol provide insight into mechanisms of stimulus-secretion coupling.

Insulin secretion from beta cells in the islets of Langerhans can be stimulated by a number of metabolic fuels, including glucose and glyceraldehyde, and is thought to be mediated by metabolism of the secretagogues and an attendant increase in the ATP:ADP ratio. Curiously, glycerol fails to stimulate insulin secretion, even though it has been reported that islets contain abundant glycerol kinase activity and oxidize glycerol efficiently. We have reinvestigated this point and find that rat islets and the well differentiated insulinoma cell line INS-1 contain negligible glycerol kinase activity. A recombinant adenovirus containing the bacterial glycerol kinase gene (AdCMV-GlpK) was constructed and used to express the enzyme in islets and INS-1 cells, resulting in insulin secretion in response to glycerol. In AdCMV-GlpK-treated INS-1 cells a greater proportion of glycerol is converted to lactate and a lesser proportion is oxidized compared with glucose. The two fuels are equally potent as insulin secretagogues, despite the fact that oxidation of glycerol at its maximally effective dose (2-5 mM) occurs at a rate that is similar to the rate of glucose oxidation at its basal, nonstimulatory concentration (3 mM). We also investigated the possibility that glycerol may signal via expansion of the glycerol phosphate pool to allow enhanced fatty acid esterification and formation of complex lipids. Addition of Triacsin-C, an inhibitor of long-chain acyl-CoA synthetase, to AdCMV-GlpK-treated INS-1 cells did not inhibit glycerol-stimulated insulin secretion despite the fact that it blocked glycerol incorporation into cellular lipids. We conclude from these studies that glycerol kinase expression is sufficient to activate glycerol signaling in beta cells, showing that the failure of normal islets to respond to this substrate is due to a lack of this enzyme activity. Further, our studies show that glycerol signaling is not linked to esterification or oxidation of the substrate, but is likely mediated by its metabolism in the glycerol phosphate shuttle and/or the distal portion of the glycolytic pathway, either of which can lead to production of ATP and an increased ATP:ADP ratio.

Authors
Noel, RJ; Antinozzi, PA; McGarry, JD; Newgard, CB
MLA Citation
Noel, RJ, Antinozzi, PA, McGarry, JD, and Newgard, CB. "Engineering of glycerol-stimulated insulin secretion in islet beta cells. Differential metabolic fates of glucose and glycerol provide insight into mechanisms of stimulus-secretion coupling." The Journal of biological chemistry 272.30 (July 1997): 18621-18627.
PMID
9228030
Source
epmc
Published In
The Journal of biological chemistry
Volume
272
Issue
30
Publish Date
1997
Start Page
18621
End Page
18627
DOI
10.1074/jbc.272.30.18621

Induction by leptin of uncoupling protein-2 and enzymes of fatty acid oxidation.

We have studied mechanisms by which leptin overexpression, which reduces body weight via anorexic and thermogenic actions, induces triglyceride depletion in adipocytes and nonadipocytes. Here we show that leptin alters in pancreatic islets the mRNA of the genes encoding enzymes of free fatty acid metabolism and uncoupling protein-2 (UCP-2). In animals infused with a recombinant adenovirus containing the leptin cDNA, the levels of mRNAs encoding enzymes of mitochondrial and peroxisomal oxidation rose 2- to 3-fold, whereas mRNA encoding an enzyme of esterification declined in islets from hyperleptinemic rats. Islet UCP-2 mRNA rose 6-fold. All in vivo changes occurred in vitro in normal islets cultured with recombinant leptin, indicating direct extraneural effects. Leptin overexpression increased UCP-2 mRNA by more than 10-fold in epididymal, retroperitoneal, and subcutaneous fat tissue of normal, but not of leptin-receptor-defective obese rats. By directly regulating the expression of enzymes of free fatty acid metabolism and of UCP-2, leptin controls intracellular triglyceride content of certain nonadipocytes, as well as adipocytes.

Authors
Zhou, YT; Shimabukuro, M; Koyama, K; Lee, Y; Wang, MY; Trieu, F; Newgard, CB; Unger, RH
MLA Citation
Zhou, YT, Shimabukuro, M, Koyama, K, Lee, Y, Wang, MY, Trieu, F, Newgard, CB, and Unger, RH. "Induction by leptin of uncoupling protein-2 and enzymes of fatty acid oxidation." Proc Natl Acad Sci U S A 94.12 (June 10, 1997): 6386-6390.
PMID
9177227
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
94
Issue
12
Publish Date
1997
Start Page
6386
End Page
6390

Regulation of insulin secretion from novel engineered insulinoma cell lines.

In the accompanying article, we describe the creation of novel cell lines derived from RIN 1046-38 rat insulinoma cells by stable transfection with combinations of genes encoding human insulin, GLUT2, and glucokinase. Herein we describe the regulation of insulin secretion and glucose metabolism in these new cell lines. A cell line (betaG I/17) expressing only the human proinsulin transgene exhibits a clear increase in basal insulin production (measured in the absence of secretagogues) relative to parental RIN 1046-38 cells. betaG I/17 cells engineered for high levels of GLUT2 expression and a twofold increase in glucokinase activity (betaG 49/206) or engineered for a 10-fold increase in glucokinase activity alone (betaG 40/110) exhibit a 66% and 80% suppression in basal insulin secretion relative to betaG I/17 cells, respectively. As a result, betaG 49/206 and betaG 40/110 cells exhibit potent insulin-secretory responses to glucose alone (6.1- and 7.6-fold, respectively) or to glucose plus isobutylmethylxanthine (10.8- and 15.1-fold, respectively) that are clearly larger than the corresponding responses of betaG I/17 or parental RIN 1046-38 cells. betaG 49/206 and betaG 40/110 cells also exhibit a rapid and sustained response to glucose plus isobutyl-methylxanthine in perifusion studies that is clearly larger in magnitude than that of the two control lines. Glucose dose-response studies show that both engineered and non-engineered lines respond maximally to submillimolar concentrations of glucose and that betaG 49/206 cells are the most sensitive to low concentrations of the hexose, consistent with their clearly elevated rate of [5-3H]glucose usage. Finally, 5-thioglucose, a potent inhibitor of low-K(m) hexokinases, most effectively normalizes glucose concentration dependence for insulin secretion in the cell line with highest glucokinase expression (betaG 40/110). We conclude that GLUT2 and/or glucokinase expression imposes tight regulation of basal insulin secretion in cell lines that overexpress human proinsulin, allowing a marked improvement in the range of secretagogue responsiveness in such cells.

Authors
Hohmeier, HE; BeltrandelRio, H; Clark, SA; Henkel-Rieger, R; Normington, K; Newgard, CB
MLA Citation
Hohmeier, HE, BeltrandelRio, H, Clark, SA, Henkel-Rieger, R, Normington, K, and Newgard, CB. "Regulation of insulin secretion from novel engineered insulinoma cell lines." Diabetes 46.6 (June 1997): 968-977.
PMID
9166667
Source
pubmed
Published In
Diabetes
Volume
46
Issue
6
Publish Date
1997
Start Page
968
End Page
977

Novel insulinoma cell lines produced by iterative engineering of GLUT2, glucokinase, and human insulin expression.

Cellular engineering studies in our group are directed at creating insulin-secreting cell lines that simulate the performance of the normal islet beta-cell. The strategy described in this article involves the stepwise stable introduction of genes relevant to beta-cell performance into the RIN 1046-38 insulinoma cell line, a process that we term "iterative engineering." RIN cells stably engineered to contain multiple copies of the human insulin gene exhibit a large increase in insulin content, such that they approach the content of human islets assayed in parallel. Analysis by high-performance liquid chromatography demonstrates that these engineered cell lines process human proinsulin to mature insulin with high efficiency. Cell lines that are further engineered to express the GLUT2 and glucokinase genes demonstrate stable expression of the three transgenes for the full lifetime of the lines produced to date (6 months to 1 year in continuous culture). Transplantation of the engineered cell lines into nude rats reveals that stably integrated genes are expressed at constant levels in the in vivo environment over the full duration of experiments performed (48 days). Several endogenous genes expressed in normal beta-cells, including rat insulin, amylin, sulfonylurea receptor, and glucokinase, are stably expressed in the insulinoma lines during these in vivo studies. Endogenous GLUT2 expression, in contrast, is rapidly extinguished during in vivo passage. The loss of GLUT2 is overcome in engineered cell ines in which transporter expression is provided by a stably transfected transgene. These results suggest that a potential advantage of the iterative engineering approach may be to preserve stability of function and phenotype, particularly in the in vivo setting.

Authors
Clark, SA; Quaade, C; Constandy, H; Hansen, P; Halban, P; Ferber, S; Newgard, CB; Normington, K
MLA Citation
Clark, SA, Quaade, C, Constandy, H, Hansen, P, Halban, P, Ferber, S, Newgard, CB, and Normington, K. "Novel insulinoma cell lines produced by iterative engineering of GLUT2, glucokinase, and human insulin expression." Diabetes 46.6 (June 1997): 958-967.
PMID
9166666
Source
pubmed
Published In
Diabetes
Volume
46
Issue
6
Publish Date
1997
Start Page
958
End Page
967

Stimulation of glucose-6-phosphatase gene expression by glucose and fructose-2,6-bisphosphate.

Glucose-6-phosphatase, a key enzyme in the homeostatic regulation of blood glucose concentration, catalyzes the terminal step in gluconeogenesis and glycogenolysis. Glucose, the product of the glucose-6-phosphatase reaction, dramatically increases the level of glucose-6-phosphatase mRNA transcripts in primary hepatocytes (20-fold), and the maximum response is obtained at a glucose concentration as low as 11 mM. Glucose specifically increases glucose-6-phosphatase mRNA and L-type pyruvate kinase mRNA. In the rat hepatoma-derived cell line, Fao, glucose increases the glucose-6-phosphatase mRNA only modestly (3-fold). In the presence of high glucose concentrations, overexpression of glucokinase in Fao cells via recombinant adenovirus vectors increases lactate production to the level found in primary hepatocytes and increases glucose-6-phosphatase gene expression by 21-fold. Similar overexpression of hexokinase I in Fao cells with high levels of glucose does not increase lactate production nor does it change the response of glucose-6-phosphatase mRNA to glucose. Glucokinase overexpression in Fao cells blunts the previously reported inhibitory effect of insulin on glucose-6-phosphatase gene expression in these cells. Raising the cellular concentration of fructose-2,6-bisphosphate, a potent effector of the direction of carbon flux through the gluconeogenic and glycolytic pathways, also stimulated glucose-6-phosphatase gene expression in Fao cells. Increasing the fructose-2,6-bisphosphate concentration over a 15-fold range (12 +/- 1 to 187 +/- 17 pmol/plate) via an adenoviral vector overexpression system, led to a 6-fold increase (0.32 +/- 0. 03 to 2.2 +/- 0.33 arbitrary units of mRNA) in glucose-6-phosphatase gene expression with a concomitant increase in glycolysis and a decrease in gluconeogenesis. Also, the effects of fructose-2, 6-bisphosphate concentrations on fructose-1,6-bisphosphatase gene expression were stimulatory, leading to a 5-6-fold increase in mRNA level over a 15-fold range in fructose-2,6-bisphosphate level. Liver pyruvate kinase and phosphoenolpyruvate carboxykinase mRNA were unchanged by the manipulation of fructose-2,6-bisphosphate level.

Authors
Argaud, D; Kirby, TL; Newgard, CB; Lange, AJ
MLA Citation
Argaud, D, Kirby, TL, Newgard, CB, and Lange, AJ. "Stimulation of glucose-6-phosphatase gene expression by glucose and fructose-2,6-bisphosphate." J Biol Chem 272.19 (May 9, 1997): 12854-12861.
PMID
9139747
Source
pubmed
Published In
The Journal of biological chemistry
Volume
272
Issue
19
Publish Date
1997
Start Page
12854
End Page
12861

Structural domains that contribute to substrate specificity in facilitated glucose transporters are distinct from those involved in kinetic function: studies with GLUT-1/GLUT-2 chimeras.

GLUT-2 differs from other members of the facilitated glucose transporter family because it transports a wider range of substrates and exhibits a higher Km for transport of glucose analogs such as 2-deoxyglucose (2-DOG). In order to investigate the structural determinants of the unique substrate specificity and kinetic function of GLUT-2, recombinant adenoviruses were used to express native, mutant, and chimeric glucose transporters in the kidney cell line CV-1, yielding the following key observations. (1) A chimera consisting of GLUT-1 with the C-terminal tail of GLUT-2 had a Km for 2-DOG of 9.9 +/- 1.5 that was intermediate between that of native GLUT-1 (3.7 +/- 0.4) and native GLUT-2 (26.3 +/- 3.3). In contrast to the effect of the GLUT-2 C terminus on Km for 2-DOG, this substitution did not confer enhanced uptake of three alternative substrates (fructose, arabinose, or streptozotocin) which are transported efficiently by native GLUT-2 but not by GLUT-1. (2) A chimera consisting of GLUT-2 with the N-terminal 87 amino acids of GLUT-1 exhibited no change in Km for 2-DOG relative to native GLUT-2 but exhibited a significant reduction in capacity for transport of the three alternative substrates. (3) Mutation of asparagine 62 in GLUT-2 to glutamine produced a transporter lacking its N-linked oligosaccharide that exhibited a 2.5-fold increase in Km for 2-DOG but equally efficient transport of the three alternative substrates relative to native GLUT-2. These data provide insight into structural domains that affect substrate specificity in facilitated glucose transporters and demonstrate that they are distinct from elements involved in glucose transport kinetics.

Authors
Noel, LE; Newgard, CB
MLA Citation
Noel, LE, and Newgard, CB. "Structural domains that contribute to substrate specificity in facilitated glucose transporters are distinct from those involved in kinetic function: studies with GLUT-1/GLUT-2 chimeras." Biochemistry 36.18 (May 6, 1997): 5465-5475.
PMID
9154929
Source
pubmed
Published In
Biochemistry
Volume
36
Issue
18
Publish Date
1997
Start Page
5465
End Page
5475
DOI
10.1021/bi9630624

Direct antidiabetic effect of leptin through triglyceride depletion of tissues.

Leptin is currently believed to control body composition largely, if not entirely, via hypothalamic receptors that regulate food intake and thermogenesis. Here we demonstrate direct extraneural effects of leptin to deplete fat content of both adipocytes and nonadipocytes to levels far below those of pairfed controls. In cultured pancreatic islets, leptin lowered triglyceride (TG) content by preventing TG formation from free fatty acids (FFA) and by increasing FFA oxidation. In vivo hyperleptinemia, induced in normal rats by adenovirus gene transfer, depleted TG content in liver, skeletal muscle, and pancreas without increasing plasma FFA or ketones, suggesting intracellular oxidation. In islets of obese Zucker Diabetic Fatty rats with leptin receptor mutations, leptin had no effect in vivo or in vitro. The TG content was approximately 20 times normal, and esterification capacity was increased 3- to 4-fold. Thus, in rats with normal leptin receptors but not in Zucker Diabetic Fatty rats, nonadipocytes and adipocytes esterify FFA, store them as TG, and later oxidize them intracellularly via an "indirect pathway" of intracellular fatty acid metabolism controlled by leptin. By maintaining insulin sensitivity and preventing islet lipotoxicity, this activity of leptin may prevent adipogenic diabetes.

Authors
Shimabukuro, M; Koyama, K; Chen, G; Wang, MY; Trieu, F; Lee, Y; Newgard, CB; Unger, RH
MLA Citation
Shimabukuro, M, Koyama, K, Chen, G, Wang, MY, Trieu, F, Lee, Y, Newgard, CB, and Unger, RH. "Direct antidiabetic effect of leptin through triglyceride depletion of tissues." Proc Natl Acad Sci U S A 94.9 (April 29, 1997): 4637-4641.
PMID
9114043
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
94
Issue
9
Publish Date
1997
Start Page
4637
End Page
4641

Regulation of overexpressed hexokinases in liver and islet cells.

Authors
Newgard, CB; Becker, TC; Berman, HK; O'Doherty, RM
MLA Citation
Newgard, CB, Becker, TC, Berman, HK, and O'Doherty, RM. "Regulation of overexpressed hexokinases in liver and islet cells." Biochem Soc Trans 25.1 (February 1997): 118-122. (Review)
PMID
9056855
Source
pubmed
Published In
Biochemical Society transactions
Volume
25
Issue
1
Publish Date
1997
Start Page
118
End Page
122

Evidence that potentiation of insulin secretion is mediated by free rather than CoA-activated fatty acids

Authors
Antinozzi, PA; Jr, RM; Newgard, CB
MLA Citation
Antinozzi, PA, Jr, RM, and Newgard, CB. "Evidence that potentiation of insulin secretion is mediated by free rather than CoA-activated fatty acids." Experimental and Clinical Endocrinology and Diabetes 105.4 (1997): A44-.
Source
scival
Published In
Experimental and Clinical Endocrinology & Diabetes
Volume
105
Issue
4
Publish Date
1997
Start Page
A44

β-Cell function in normal rats made chronically hyperleptinemic by adenovirus-leptin gene therapy

Leptin was overexpressed in the liver of normal Wistar rats by infusing recombinant adenovirus containing the cDNA encoding leptin. Plasma leptin levels rose to 12-24 ng/ml (vs. <2 ng/ml in control rats), and food intake and body weight fell. Visible fat disappeared within 7 days. Plasma insulin fell to <50% of normal in association with hypoglycemia, suggesting enhanced insulin sensitivity. Although β-cells appeared histologically normal, the pancreases were unresponsive to perfusion with stimulatory levels of glucose and arginine. Since islet triglyceride content was 0, compared with 14 ng/islet in pair-fed control rats, we coperfused a 2:1 oleate:palmitate mixture (0.5 mmol/l). This restored insulin responses to supranormal levels. When normal islets were cultured with 20 ng/ml of leptin, they too became triglyceride-depleted and failed to respond when perifused with glucose or arginine. Perifusion of fatty acids restored both responses. We conclude that in normal rats, hyperleptinemia for 2 weeks causes reversible β-cell dysfunction by depleting tissue lipids, thereby depriving β-cells of a lipid-derived signal required for the insulin response to other fuels.

Authors
Koyama, K; Chen, G; Wang, M-Y; Lee, Y; Shimabukuro, M; Newgard, CB; Unger, RH
MLA Citation
Koyama, K, Chen, G, Wang, M-Y, Lee, Y, Shimabukuro, M, Newgard, CB, and Unger, RH. "β-Cell function in normal rats made chronically hyperleptinemic by adenovirus-leptin gene therapy." Diabetes 46.8 (1997): 1276-1280.
Source
scival
Published In
Diabetes
Volume
46
Issue
8
Publish Date
1997
Start Page
1276
End Page
1280

Disappearance of body fat in normal rats induced by adenovirus-mediated leptin gene therapy.

Sustained hyperleptinemia of 8 ng/ml was induced for 28 days in normal Wistar rats by infusing a recombinant adenovirus containing the rat leptin cDNA (AdCMV-leptin). Hyperleptinemic rats exhibited a 30-50% reduction in food intake and gained only 22 g over the experimental period versus 115-132 g in control animals that received saline infusions or a recombinant virus containing the beta-galactosidase gene (AdCMV-beta Gal). Body fat was absent in hyperleptinemic rats, whereas control rats pair-fed to the hyperleptinemic rats retained approximately 50% body fat. Further, plasma triglycerides and insulin levels were significantly lower in hyperleptinemic versus pair-fed controls, while fatty acid and glucose levels were similar in the two groups, suggestive of enhanced insulin sensitivity in the hyperleptinemic animals. Thus, despite equivalent reductions in food intake and weight gain in hyperleptinemic and pair-fed animals, identifiable fat tissue was completely ablated only in the former group, raising the possibility of a specific lipoatrophic activity for leptin.

Authors
Chen, G; Koyama, K; Yuan, X; Lee, Y; Zhou, YT; O'Doherty, R; Newgard, CB; Unger, RH
MLA Citation
Chen, G, Koyama, K, Yuan, X, Lee, Y, Zhou, YT, O'Doherty, R, Newgard, CB, and Unger, RH. "Disappearance of body fat in normal rats induced by adenovirus-mediated leptin gene therapy." Proc Natl Acad Sci U S A 93.25 (December 10, 1996): 14795-14799.
PMID
8962134
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
93
Issue
25
Publish Date
1996
Start Page
14795
End Page
14799

Evidence for a role of glucose-induced translocation of glucokinase in the control of hepatic glycogen synthesis.

Glucokinase reversibly partitions between a bound and a free state in the hepatocyte in response to the metabolic status of the cell. Maximum binding occurs at low [glucose] (<5 mM) and minimum binding at high [glucose] or in the presence of sorbitol or fructose. In this study we determined the binding characteristics of glucokinase in the hepatocyte in situ, by adenovirus-mediated glucokinase overexpression combined with the digitonin-permeabilization technique. We also determined the sensitivity of glycogen synthesis to changes in either total glucokinase overexpression or in free glucokinase activity. Glucokinase overexpression is associated with an increase in both free and bound activity, with an overall decrease in the proportion of bound activity. In hepatocytes incubated at low [glucose] (0-5 mM), glucokinase binding involves a high-affinity binding site with a Kd of approximately 0.1 microM and a binding capacity of approximately 3 pmol/mg total cell protein and low-affinity binding with a Kd of approximately 1.6 microM. Increasing glucose concentration to 20 mM causes a dose-dependent increase in the Kd of the high- affinity site to approximately 0.6 microM, and this effect was mimicked by 50 microM sorbitol, a precursor of fructose 1-P, confirming that this site is the regulatory protein of glucokinase. Glycogen synthesis determined from the incorporation of [2-3H,U-14C]glucose into glycogen at 5 mM or 10 mM glucose was very sensitive to small increases in total glucokinase activity and correlated more closely with the increase in free glucokinase activity. The relation between glycogenic flux and glucokinase activity is sigmoidal. Expression of the sensitivity of glycogen synthesis to glucokinase activity as the control coefficient reveals that the coefficient is greater for the incorporation of 2-tritium (which occurs exclusively by the direct pathway) than for incorporation of 14C label (which involves direct and indirect pathways) and is greater at 5 mM glucose (when glucokinase is maximally sequestered at its high-affinity site) than at 10 mM glucose. The results support the hypothesis that compartmentation of glucokinase in the hepatocyte increases the sensitivity of glycogen synthesis to small changes in total glucokinase activity and that glucose-induced translocation of glucokinase has a major role in the acute control of glycogen synthesis.

Authors
Agius, L; Peak, M; Newgard, CB; Gomez-Foix, AM; Guinovart, JJ
MLA Citation
Agius, L, Peak, M, Newgard, CB, Gomez-Foix, AM, and Guinovart, JJ. "Evidence for a role of glucose-induced translocation of glucokinase in the control of hepatic glycogen synthesis." J Biol Chem 271.48 (November 29, 1996): 30479-30486.
PMID
8940014
Source
pubmed
Published In
The Journal of biological chemistry
Volume
271
Issue
48
Publish Date
1996
Start Page
30479
End Page
30486

Glucose 6-phosphate produced by glucokinase, but not hexokinase I, promotes the activation of hepatic glycogen synthase.

In a previous study (O'Doherty, R. M., Lehman, D. L., Seoane, J., Gómez-Foix, A. M., Guinovart, J. J., and Newgard, C.B. (1996) J. Biol. Chem. 271, 20524-20530), we demonstrated that adenovirus-mediated overexpression of glucokinase but not hexokinase I has a potent enhancing effect on glycogen synthesis in primary hepatocytes. In an effort to understand the underlying mechanism of this differential effect of the two hexokinase isoforms, we have investigated changes in key intracellular metabolites and the activation state of glycogen synthase in cells treated with recombinant adenoviruses expressing the liver isoform of glucokinase (AdCMV-GKL) or hexokinase I (AdCMV-HKI). Glucose 6-phosphate (Glu-6-P) levels are elevated from approximately 1.5 nmol/mg protein to 8-10 nmol/mg protein in both AdCMV-GKL- and AdCMV-HKI-treated hepatocytes as glucose is raised from 1 to 5 mM, levels four times higher than those in untreated cells. In AdCMV-GKL-treated cells, Glu-6-P continues to accumulate at glucose levels greater than 5 mM, reaching a maximum of 120 nmol/mg protein in cells incubated at 25 mM glucose, a value 10 and 50 times greater than the maximal levels achieved in AdCMV-HKI-treated and untreated cells, respectively. In parallel with the changes observed in Glu-6-P levels, increases in UDP-Glc in AdCMV-HKI- and AdCMV-GKL-treated cells were most pronounced at low (1-5 mM) and high (25 mM) glucose levels, respectively. Despite the significant increases in Glu-6-P and UDP-Glc achieved in AdCMV-HKI-treated cells, only AdCMV-GKL-treated cells exhibited increases in glycogen synthase activity ratio and translocation of the enzyme from a soluble to a particulate form relative to untreated control cells. We conclude that Glu-6-P produced by overexpressed glucokinase is glycogenic because it effectively promotes activation of glycogen synthase. Glu-6-P produced by overexpressed hexokinase, in contrast, appears to be unable to exert the same regulatory effects, probably due to the different subcellular distribution of the two glucose-phosphorylating enzymes.

Authors
Seoane, J; Gómez-Foix, AM; O'Doherty, RM; Gómez-Ara, C; Newgard, CB; Guinovart, JJ
MLA Citation
Seoane, J, Gómez-Foix, AM, O'Doherty, RM, Gómez-Ara, C, Newgard, CB, and Guinovart, JJ. "Glucose 6-phosphate produced by glucokinase, but not hexokinase I, promotes the activation of hepatic glycogen synthase." J Biol Chem 271.39 (September 27, 1996): 23756-23760.
PMID
8798601
Source
pubmed
Published In
The Journal of biological chemistry
Volume
271
Issue
39
Publish Date
1996
Start Page
23756
End Page
23760

A novel leptin receptor isoform in rat.

Five mouse and human leptin receptors (Ob-R) have recently been identified, a long isoform (Ob-Rb), preferentially expressed in hypothalamus, and 4 short isoforms, Ob-Ra, Ob-Rc, Ob-Rd, and Ob-Re. We have identified a new short isoform in the rat, r-OB-Rf, with 6 C-terminal amino acids and a 3' untranslated region without homology to other Ob-R isoforms. Its higher expression in rat liver and spleen compared to brain, stomach, kidney, thymus, heart, lung and hypothalamus, contrasts with Ob-Ra and Ob-Rb homologues and raises possibilities of as yet unidentified roles for members of the growing Ob-R gene family.

Authors
Wang, MY; Zhou, YT; Newgard, CB; Unger, RH
MLA Citation
Wang, MY, Zhou, YT, Newgard, CB, and Unger, RH. "A novel leptin receptor isoform in rat." FEBS Lett 392.2 (August 26, 1996): 87-90.
PMID
8772180
Source
pubmed
Published In
FEBS Letters
Volume
392
Issue
2
Publish Date
1996
Start Page
87
End Page
90

Differential metabolic effects of adenovirus-mediated glucokinase and hexokinase I overexpression in rat primary hepatocytes.

The first step of glucose metabolism is the phosphorylation of glucose, catalyzed by the hexokinase family of enzymes. To address the metabolic impact of increasing glucose phosphorylation capacity in liver, rat primary hepatocytes were treated with recombinant adenoviruses containing the cDNAs encoding either rat liver glucokinase (AdCMV-GKL) or rat hexokinase I (AdCMV-HKI). Maximal glucose phosphorylation in AdCMV-GKL- and AdCMV-HKI-treated hepatocytes was increased 7.1 +/- 1.2- and 6.3 +/- 0.8-fold, respectively, over hepatocytes treated with an adenovirus expressing beta-galactosidase. Glucose usage (measured with 3 and 20 m 2-[3H]glucose and 5-[3H]glucose) was significantly increased in AdCMV-GKL-treated cells preincubated in 1 or 25 mM glucose. Treatment of hepatocytes with AdCMV-HKI also caused enhanced glucose utilization, but the increases were smaller and were less apparent in cells preincubated in high (25 mM) glucose. AdCMV-GKL-treated hepatocytes incubated for 48 h in the presence of variable glucose concentrations had glycogen levels that were maximally 15.0 +/- 0. 6-fold greater than levels in corresponding control cells. AdCMV-HKI-treated hepatocytes incubated under similar conditions had unchanged glycogen levels relative to controls. In AdCMV-GKL-treated cells, lactate output was increased to a maximum of 3.0 +/- 0.4-fold (at 25 mM glucose), glucose oxidation was increased 3.5 +/- 0.3-fold, and triglyceride production was unchanged relative to untreated cells. Among these three parameters, only lactate production was increased in AdCMV-HKI-treated cells, and then only at low glucose concentrations. We conclude that overexpression of glucokinase has potent effects on glucose storage and utilization in hepatocytes and that these effects are not matched by overexpression of hexokinase I.

Authors
O'Doherty, RM; Lehman, DL; Seoane, J; Gómez-Foix, AM; Guinovart, JJ; Newgard, CB
MLA Citation
O'Doherty, RM, Lehman, DL, Seoane, J, Gómez-Foix, AM, Guinovart, JJ, and Newgard, CB. "Differential metabolic effects of adenovirus-mediated glucokinase and hexokinase I overexpression in rat primary hepatocytes." J Biol Chem 271.34 (August 23, 1996): 20524-20530.
PMID
8702794
Source
pubmed
Published In
The Journal of biological chemistry
Volume
271
Issue
34
Publish Date
1996
Start Page
20524
End Page
20530

Insulin secretory cells for the therapy of diabetes mellitus

Even with intensive insulin therapy it is impossible to reach physiological blood glucose levels in insulin-dependent diabetes mellitus. Because of the high costs and technical problems involved in islet cell transplantation broad applicability of this therapy seems uncertain. An alternative approach is the development of molecular-engineered insulin-producing clonal cell lines. The main interest is in rodent insulinoma cell lines and neuroendocrine AtT-20ins cells. This paper reviews the current knowledge about glucose-stimulated insulin secretion and the problems that have to be solved before these cells can be used for therapy in diabetes mellitus.

Authors
Schnedl, WJ; Hohmeier, HE; Newgard, CB
MLA Citation
Schnedl, WJ, Hohmeier, HE, and Newgard, CB. "Insulin secretory cells for the therapy of diabetes mellitus." Naturwissenschaften 83.1 (February 7, 1996): 1-5. (Review)
Source
scopus
Published In
Naturwissenschaften
Volume
83
Issue
1
Publish Date
1996
Start Page
1
End Page
5
DOI
10.1007/s001140050238

Differential effects of overexpressed glucokinase and hexokinase I in isolated islets. Evidence for functional segregation of the high and low Km enzymes.

Glucose-stimulated insulin secretion is believed to require metabolism of the sugar via a high Km pathway in which glucokinase (hexokinase IV) is rate-limiting. In this study, we have used recombinant adenoviruses to overexpress the liver and islet isoforms of glucokinase as well as low Km hexokinase I in isolated rat islets of Langerhans. Glucose phosphorylating activity increased by up to 20-fold in extracts from islets treated with adenoviruses containing the cDNAs encoding either tissue isoform of glucokinase, but such cells exhibited no increase in 2- or 5-[3H]glucose usage, lactate production, glycogen content, or glucose oxidation. Furthermore, glucokinase overexpression enhanced insulin secretion in response to stimulatory glucose or glucose plus arginine by only 36-53% relative to control islets. In contrast to the minimal effects of overexpressed glucokinases, overexpression of hexokinase I caused a 2.5-4-fold enhancement in all metabolic parameters except glycogen content when measured at a basal glucose concentration (3 mM). Based on measurement of glucose phosphorylation in intact cells, overexpressed glucokinase is clearly active in a non-islet cell line (CV-1) but not within islet cells. That this result cannot be ascribed to the levels of glucokinase regulatory protein in islets is shown by direct measurement of its activity and mRNA. These data provide evidence for functional partitioning of glucokinase and hexokinase and suggest that overexpressed glucokinase must interact with factors found in limiting concentration in the islet cell in order to become activated and engage in productive metabolic signaling.

Authors
Becker, TC; Noel, RJ; Johnson, JH; Lynch, RM; Hirose, H; Tokuyama, Y; Bell, GI; Newgard, CB
MLA Citation
Becker, TC, Noel, RJ, Johnson, JH, Lynch, RM, Hirose, H, Tokuyama, Y, Bell, GI, and Newgard, CB. "Differential effects of overexpressed glucokinase and hexokinase I in isolated islets. Evidence for functional segregation of the high and low Km enzymes." J Biol Chem 271.1 (January 5, 1996): 390-394.
PMID
8550593
Source
pubmed
Published In
The Journal of biological chemistry
Volume
271
Issue
1
Publish Date
1996
Start Page
390
End Page
394

[Insulin producing cells as therapy in diabetes mellitus].

Even with intensive insulin therapy it is impossible to reach physiological blood glucose levels in insulin-dependent diabetes mellitus. Because of the high costs and technical problems involved in islet cell transplantation broad applicability of this therapy seems uncertain. An alternative approach is the development of molecular-engineered insulin-producing clonal cell lines. The main interest is in rodent insulinoma cell lines and neuroendocrine AtT-20ins cells. This paper reviews the current knowledge about glucose-stimulated insulin secretion and the problems that have to be solved before these cells can be used for therapy in diabetes mellitus.

Authors
Schnedl, WJ; Hohmeier, HE; Newgard, CB
MLA Citation
Schnedl, WJ, Hohmeier, HE, and Newgard, CB. "[Insulin producing cells as therapy in diabetes mellitus]." Naturwissenschaften 83.1 (January 1996): 1-5. (Review)
PMID
8637602
Source
pubmed
Published In
Naturwissenschaften
Volume
83
Issue
1
Publish Date
1996
Start Page
1
End Page
5

Regulatory role of glucose transport and phosphorylation in pancreatic islet β-cells

Insulin secretion is largely controlled by the level of circulating glucose. The mechanism by which glucose stimulates insulin release from pancreatic islet β-cells has been an important but difficult area of investigation. In recent years, the tools of molecular biology have been applied to test a concept previously developed from physiological studies that glucose transport and phosphorylation represent key regulatory steps for glucose-stimulated insulin secretion. This article summarizes the recent molecular studies, deals with controversial issues that have arisen in the area, and highlights the role of defects in glucose transport and phosphorylation in certain forms of diabetes.

Authors
Newgard, CB
MLA Citation
Newgard, CB. "Regulatory role of glucose transport and phosphorylation in pancreatic islet β-cells." Diabetes Reviews 4.2 (1996): 191-206.
Source
scival
Published In
Diabetes Reviews
Volume
4
Issue
2
Publish Date
1996
Start Page
191
End Page
206

Erratum: A novel leptin receptor isoform in rat (FEBS Letters 392 (1996) (87-90)) (PII S0014579396007909)

Authors
Wang, M-Y; Zhou, YT; Newgard, CB; Unger, RH
MLA Citation
Wang, M-Y, Zhou, YT, Newgard, CB, and Unger, RH. "Erratum: A novel leptin receptor isoform in rat (FEBS Letters 392 (1996) (87-90)) (PII S0014579396007909)." FEBS Letters 398.2-3 (1996): 344--.
Source
scival
Published In
FEBS Letters
Volume
398
Issue
2-3
Publish Date
1996
Start Page
344-

Insulin secretory cells for the therapy of diabetes mellitus

Even with intensive insulin therapy it is impossible to reach physiological blood glucose levels in insulin-dependent diabetes mellitus. Because of the high costs and technical problems involved in islet cell transplantation broad applicability of this therapy seems uncertain. An alternative approach is the development of molecular-engineered insulin-producing clonal cell lines. The main interest is in rodent insulinoma cell lines and neuroendocrine AtT-20ins cells. This paper reviews the current knowledge about glucose-stimulated insulin secretion and the problems that have to be solved before these cells can be used for therapy in diabetes mellitus.

Authors
Schnedl, WJ; Hohmeier, HE; Newgard, CB
MLA Citation
Schnedl, WJ, Hohmeier, HE, and Newgard, CB. "Insulin secretory cells for the therapy of diabetes mellitus." Naturwissenschaften 83.1 (1996): 1-5.
Source
scival
Published In
Naturwissenschaften
Volume
83
Issue
1
Publish Date
1996
Start Page
1
End Page
5
DOI
10.1007/s001140050238

Insulinsezernierende Zellen zur Therapie des Diabetes mellitus

Even with intensive insulin therapy it is impossible to reach physiological blood glucose levels in insulin-dependent diabetes mellitus. Because of the high costs and technical problems involved in islet cell transplantation broad applicability of this therapy seems uncertain. An alternative approach is the development of molecular-engineered insulin-producing clonal cell lines. The main interest is in rodent insulinoma cell lines and neuroendocrine AtT-20ins cells. This paper reviews the current knowledge about glucose-stimulated insulin secretion and the problems that have to be solved before these cells can be used for therapy in diabetes mellitus.

Authors
Schnedl, WJ; Hohmeier, HE; Newgard, CB
MLA Citation
Schnedl, WJ, Hohmeier, HE, and Newgard, CB. "Insulinsezernierende Zellen zur Therapie des Diabetes mellitus." Naturwissenschaften 83.1 (1996): 1-5.
Source
scival
Published In
Naturwissenschaften
Volume
83
Issue
1
Publish Date
1996
Start Page
1
End Page
5

Adenoviral-mediated glucokinase overexpression in rat primary hepatocytes increases the efficiency of glycogen accumulation and lactate production at physiologic glucose concentrations

Glucokinase (GK) catalyses the conversion of glucose to glucose-6-phosphate, and is vital to the liver's role in maintaining glucose homeostasis. To address the effects of altered GK expression on liver carbohydrate metabolism, rat primary hepatocytes were treated with a recombmant adenovirus containing the cDNA of rat liver GK (AdCMVGKL+), and cultured in 1, 3, 5, 10, 15, or 25 mM glucose. GK activity in AdCMVGKL+ hepatocytes was 8.34±0.90-fold (p<0.01, n=9) higher than in controls (untreated hepatocytes, or hepatocytes treated with an adenoviral vector expressing β-galactosidase), and was unaffected by glucose culture conditions. Fold Increase of Glycogen and Lactate in AdCMVCKL+ Over Untreated Hepatocytes 1 3 5 10 15 25 (Glucose (mM)) Glycogen 1.1±0.2 1.7±0.1 4.6±10 18.1±4.1 25.3±3.6 1 5.7±1 .8 Lactae 3.0±0.2 4 9±0-5 5.1±0.3 6.5±0.3 4.7±0.3 3.7±0.2 Importantly, the levels of glycogen and lactate in AdCMVGKL+ hepatocytes cultured in 5mM glucose (230.0±50.0ug/mg protein and 14.94±0.98mM, respectively) were comparable to those observed in controls cultured in 25mM glucose (150.0±20.0ug/mg protein and 7.90±0.36mM, respectively), suggesting that increased glucose phosphorylation due to GK over expression increases the efficiency of glycogen synthesis and glycolysis at physiologic glucose concentrations.

Authors
O'Doherty, RM; Lehman, DL; Newgard, CB
MLA Citation
O'Doherty, RM, Lehman, DL, and Newgard, CB. "Adenoviral-mediated glucokinase overexpression in rat primary hepatocytes increases the efficiency of glycogen accumulation and lactate production at physiologic glucose concentrations." FASEB Journal 10.3 (1996): A461-.
Source
scival
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
10
Issue
3
Publish Date
1996
Start Page
A461

Adenovirus-mediated overexpression of liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in gluconeogenic rat hepatoma cells. Paradoxical effect on Fru-2,6-P2 levels.

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase has been postulated to be a metabolic signaling enzyme, which acts as a switch between glycolysis and gluconeogenesis in mammalian liver by regulating the level of fructose 2,6-bisphosphate. The effect of overexpressing the bifunctional enzyme was studied in FAO cells transduced with recombinant adenoviral constructs of either the wild-type enzyme or a double mutant that has no bisphosphatase activity or protein kinase phosphorylation site. With both constructs, the mRNA and protein were overexpressed by 150- and 40-fold, respectively. Addition of cAMP to cells overexpressing the wild-type enzyme increased the S0.5 for fructose 6-phosphate of the kinase by 1.5-fold but had no effect on the overexpressed double mutant. When the wild-type enzyme was overexpressed, there was a decrease in fructose 2,6-bisphosphate levels, even though 6-phosphofructo-2-kinase maximal activity increased more than 22-fold and was in excess of fructose-2,6-bisphosphatase maximal activity. The kinase:bisphosphatase maximal activity ratio was decreased, indicating that the overexpressed enzyme was phosphorylated by cAMP-dependent protein kinase. Overexpression of the double mutant resulted in a 28-fold increase in kinase maximal activity and a 3-4-fold increase in fructose 2,6-bisphosphate levels. Overexpression of this form inhibited the rate of glucose production from dihydroxyacetone by 90% and stimulated the rate of lactate plus pyruvate production by 200%. In contrast, overexpression of the wild-type enzyme enhanced glucose production and inhibited lactate plus pyruvate production. These results provide direct support for fructose 2,6-bisphosphate as a regulator of gluconeogenic/glycolytic pathway flux and suggest that regulation of bifunctional enzyme activities by covalent modification is more important than the amount of the protein.

Authors
Argaud, D; Lange, AJ; Becker, TC; Okar, DA; el-Maghrabi, MR; Newgard, CB; Pilkis, SJ
MLA Citation
Argaud, D, Lange, AJ, Becker, TC, Okar, DA, el-Maghrabi, MR, Newgard, CB, and Pilkis, SJ. "Adenovirus-mediated overexpression of liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in gluconeogenic rat hepatoma cells. Paradoxical effect on Fru-2,6-P2 levels." J Biol Chem 270.41 (October 13, 1995): 24229-24236.
PMID
7592629
Source
pubmed
Published In
The Journal of biological chemistry
Volume
270
Issue
41
Publish Date
1995
Start Page
24229
End Page
24236

Pancreatic beta-cells in obesity. Evidence for induction of functional, morphologic, and metabolic abnormalities by increased long chain fatty acids.

To elucidate the mechanism of the basal hyperinsulinemia of obesity, we perfused pancreata from obese Zucker and lean Wistar rats with substimulatory concentrations of glucose. Insulin secretion at 4.2 and 5.6 mM glucose was approximately 10 times that of controls, whereas beta-cell volume fraction was increased only 4-fold and DNA per islet 3.5-fold. We therefore compared glucose usage at 1.4, 2.8, and 5.6 mM. Usage was 8-11.4 times greater in Zucker islets at 1.4 and 2.8 mM and 4 times greater at 5.6 mM; glucose oxidation at 2.8 and 5.6 mM glucose was > 12 times lean controls. To determine if the high free fatty acid (FFA) levels of obesity induce these abnormalities, normal Wistar islets were cultured with 0, 1, or 2 mM long chain FFA for 7 days. Compared to islets cultured without FFA insulin secretion by FFA-cultured islets (2 mM) perifused with 1.4, 3, or 5.6 mM glucose was increased more than 2-fold, bromodeoxyuridine incorporation was increased 3-fold, and glucose usage at 2.8 and 5.6 mM glucose was increased approximately 2-fold (1 mM FFA) and 3-fold (2 mM FFA). We conclude that hypersecretion of insulin by islets of obese Zucker fatty rats is associated with, and probably caused by, enhanced low Km glucose metabolism and beta-cell hyperplasia, abnormalities that can be induced in normal islets by increased FFA.

Authors
Milburn, JL; Hirose, H; Lee, YH; Nagasawa, Y; Ogawa, A; Ohneda, M; BeltrandelRio, H; Newgard, CB; Johnson, JH; Unger, RH
MLA Citation
Milburn, JL, Hirose, H, Lee, YH, Nagasawa, Y, Ogawa, A, Ohneda, M, BeltrandelRio, H, Newgard, CB, Johnson, JH, and Unger, RH. "Pancreatic beta-cells in obesity. Evidence for induction of functional, morphologic, and metabolic abnormalities by increased long chain fatty acids." J Biol Chem 270.3 (January 20, 1995): 1295-1299.
PMID
7836394
Source
pubmed
Published In
The Journal of biological chemistry
Volume
270
Issue
3
Publish Date
1995
Start Page
1295
End Page
1299

Metabolic coupling factors in pancreatic beta-cell signal transduction.

This chapter focuses on the biochemical mechanisms that mediate glucose-stimulated insulin secretion (GSIS) from beta-cells of the islets of Langerhans and the potentiating role played by fatty acids. We summarize evidence supporting the idea that glucose metabolism is required for GSIS and that the GLUT-2 facilitated glucose transporter and the glucose phosphorylating enzyme glucokinase play important roles in measuring changes in extracellular glucose concentration. The idea that glucose metabolism is linked to insulin secretion through a sequence of events involving changes in ATP:ADP ratio, inhibition of ATP-sensitive K+ channels, and activation of voltage-gated Ca2+ channels is critically reviewed, and the relative importance of ATP generated from glycolytic versus mitochondrial metabolism is evaluated. We also present the growing concept that an important signal for insulin secretion may reside at the linkage between glucose and lipid metabolism, specifically the generation of the regulatory molecule malonyl CoA that promotes fatty acid esterification and inhibits oxidation. Finally, we show that in contrast to its short term potentiating effect on GSIS, long-term exposure of islets to high levels of fatty acids results in beta-cell dysfunction, suggesting that hyperlipidemia associated with obesity may play a causal role in the diminished GSIS characteristic of non insulin-dependent diabetes mellitus (NIDDM).

Authors
Newgard, CB; McGarry, JD
MLA Citation
Newgard, CB, and McGarry, JD. "Metabolic coupling factors in pancreatic beta-cell signal transduction." Annu Rev Biochem 64 (1995): 689-719. (Review)
PMID
7574498
Source
pubmed
Published In
Annual Review of Biochemistry
Volume
64
Publish Date
1995
Start Page
689
End Page
719
DOI
10.1146/annurev.bi.64.070195.003353

Adenovirus-mediated delivery into myocytes of muscle glycogen phosphorylase, the enzyme deficient in patients with glycogen-storage disease type V.

The feasibility of using adenovirus as a vector for the introduction of glycogen phosphorylase activity into myocytes has been examined. We used the C2C12 myoblast cell line to assay the impact of phosphorylase gene transfer on myocyte glycogen metabolism and to reproduce in vitro the two strategies proposed for the treatment of muscle genetic diseases, myoblast transplantation and direct DNA delivery. In this study, a recombinant adenovirus containing the muscle glycogen phosphorylase cDNA transcribed from the cytomegalovirus promoter (AdCMV-MGP) was used to transduce both differentiating myoblasts and nondividing mature myotube cells. Muscle glycogen phosphorylase mRNA levels and total phosphorylase activity were increased in both cell types after viral treatment although more efficiently in the differentiated myotubes. The increase in phosphorylase activity was transient (15 days) in myoblasts whereas in myotubes higher levels of phosphorylase gene expression and activity were reached, which remained above control levels for the duration of the study (20 days). The introduction of muscle phosphorylase into myotubes enhanced their glycogenolytic capacity. AdCMV MGP-transduced myotubes had lower glycogen levels under basal conditions. In addition, these engineered cells showed more extensive glycogenolysis in response to both adrenaline, which stimulates glycogen phosphorylase phosphorylation, and carbonyl cyanide m-chlorophenylhydrazone, a metabolic uncoupler. In conclusion, transfer of the muscle glycogen phosphorylase cDNA into myotubes confers an enhanced and regulatable glycogenolytic capacity. Thus this system might be useful for delivery of muscle glycogen phosphorylase and restoration of glycogenolysis in muscle cells from patients with muscle phosphorylase deficiency (McArdle's disease).

Authors
Baqué, S; Newgard, CB; Gerard, RD; Guinovart, JJ; Gómez-Foix, AM
MLA Citation
Baqué, S, Newgard, CB, Gerard, RD, Guinovart, JJ, and Gómez-Foix, AM. "Adenovirus-mediated delivery into myocytes of muscle glycogen phosphorylase, the enzyme deficient in patients with glycogen-storage disease type V." Biochem J 304 ( Pt 3) (December 15, 1994): 1009-1014.
PMID
7818463
Source
pubmed
Published In
The Biochemical journal
Volume
304 ( Pt 3)
Publish Date
1994
Start Page
1009
End Page
1014

STZ transport and cytotoxicity. Specific enhancement in GLUT2-expressing cells.

The glucose analog streptozotocin (STZ) has long been used as a tool for creating experimental diabetes because of its relatively specific beta-cell cytotoxic effect, but the mechanism by which systemic injection of STZ causes beta-cell destruction is not well understood. In the current study, we have used insulinoma (RIN) and AtT-20ins cell lines engineered for overexpression of GLUT2 or GLUT1 to investigate the role of glucose transporter isoforms in mediating STZ cytotoxicity. The in vivo effects of STZ were evaluated by implantation of RIN cells expressing or lacking GLUT2 into athymic nude rats. The drug had a potent cytotoxic effect on RIN cells expressing GLUT2, but had no effect on cells lacking GLUT2 expression, as indicated by histological analysis and measurement of the blood glucose levels of treated animals. The preferential cytotoxic effect of STZ on GLUT2-expressing cell lines was confirmed by in vitro analysis of GLUT2-expressing and untransfected RIN cells, as well as GLUT2- and GLUT1-overexpressing AtT-20ins cells. Consistent with these data, only GLUT2-expressing RIN or AtT-20ins cells transported STZ efficiently. We conclude that expression of GLUT2 is required for efficient killing of neuroendocrine cells by STZ, and this effect is related to specific recognition of the drug as a transported substrate by GLUT2 but not GLUT1.

Authors
Schnedl, WJ; Ferber, S; Johnson, JH; Newgard, CB
MLA Citation
Schnedl, WJ, Ferber, S, Johnson, JH, and Newgard, CB. "STZ transport and cytotoxicity. Specific enhancement in GLUT2-expressing cells." Diabetes 43.11 (November 1994): 1326-1333.
PMID
7926307
Source
pubmed
Published In
Diabetes
Volume
43
Issue
11
Publish Date
1994
Start Page
1326
End Page
1333

Overexpression of hexokinase I in isolated islets of Langerhans via recombinant adenovirus. Enhancement of glucose metabolism and insulin secretion at basal but not stimulatory glucose levels.

Glucose metabolism and glucose-stimulated insulin secretion are thought to be controlled at the level of glucose phosphorylation in pancreatic islet beta-cells. In the current study we have investigated the importance of glucose phosphorylation by using recombinant adenovirus as a gene delivery system for isolated rat islets. Treatment of islets with a virus containing the cDNA encoding the Escherichia coli beta-galactosidase gene (AdCMV-beta GAL) resulted in efficiencies of gene transfer of 70.3 +/- 2.5 and 61.2 +/- 2.2% in two independent experiments. Treatment of islets with a virus containing the cDNA encoding rat hexokinase I (AdCMV-HKI) resulted in a 10.7-fold increase in immunodetectable hexokinase protein and a similar increase in enzyme activity. A large percentage of the overexpressed hexokinase activity was associated with a cell fraction enriched in mitochondria. These changes in enzyme level were accompanied by a 2-fold increase in insulin release and [5-3H]glucose usage at basal glucose concentrations (3 mM). The rate of glucose usage at 20 mM glucose and the magnitude of the insulin secretory response to this stimulatory level of the sugar were unchanged relative to control islets. Overexpression of hexokinase I in isolated islets therefore creates a phenotype of elevated basal insulin release similar to that seen in islets from obese and insulin-resistant mammals. The discrepancy between the large increase in hexokinase activity and the small increase in glucose usage and insulin release may indicate, however, that other steps in glucose metabolism become rate-limiting after only modest increases in glucose-phosphorylating activity.

Authors
Becker, TC; BeltrandelRio, H; Noel, RJ; Johnson, JH; Newgard, CB
MLA Citation
Becker, TC, BeltrandelRio, H, Noel, RJ, Johnson, JH, and Newgard, CB. "Overexpression of hexokinase I in isolated islets of Langerhans via recombinant adenovirus. Enhancement of glucose metabolism and insulin secretion at basal but not stimulatory glucose levels." J Biol Chem 269.33 (August 19, 1994): 21234-21238.
PMID
8063745
Source
pubmed
Published In
The Journal of biological chemistry
Volume
269
Issue
33
Publish Date
1994
Start Page
21234
End Page
21238

GLUT-2 gene transfer into insulinoma cells confers both low and high affinity glucose-stimulated insulin release. Relationship to glucokinase activity.

The rat insulinoma cell line RIN 1046-38 loses glucose-stimulated insulin secretion as a function of time in culture. We found that the loss of glucose sensing in these cells was correlated with the loss of expression of GLUT-2 and glucokinase. Stable transfection of RIN cells with a plasmid containing the GLUT-2 cDNA conferred glucose-stimulated insulin release in intermediate but not high passage cells, with the near-maximal 3-fold increase occurring at 50 microM glucose. GLUT-2 expressing cells also exhibited a larger response to the combination of 5 mM glucose + 1 microM forskolin than untransfected cells (7.9 versus 1.6-2.7-fold, respectively). GLUT-2 expressing intermediate passage, but not high passage, RIN cells exhibited a 4-fold increase in glucokinase enzymatic activity relative to nonexpressing controls. Glucokinase activity was also increased by transfer of the GLUT-2 gene into intermediate passage RIN cells via recombinant adenovirus. Preincubation of GLUT-2 expressing intermediate passage RIN cells with 2-deoxyglucose to inhibit low Km hexokinases resulted in a glucose-stimulated insulin secretion response that was shifted toward the physiologic range. These studies indicate that GLUT-2 expression confers both a high and low affinity glucose-stimulated insulin secretion response to intermediate passage RIN cells.

Authors
Ferber, S; BeltrandelRio, H; Johnson, JH; Noel, RJ; Cassidy, LE; Clark, S; Becker, TC; Hughes, SD; Newgard, CB
MLA Citation
Ferber, S, BeltrandelRio, H, Johnson, JH, Noel, RJ, Cassidy, LE, Clark, S, Becker, TC, Hughes, SD, and Newgard, CB. "GLUT-2 gene transfer into insulinoma cells confers both low and high affinity glucose-stimulated insulin release. Relationship to glucokinase activity." J Biol Chem 269.15 (April 15, 1994): 11523-11529.
PMID
8157682
Source
pubmed
Published In
The Journal of biological chemistry
Volume
269
Issue
15
Publish Date
1994
Start Page
11523
End Page
11529

Molecular strategies for the treatment of diabetes.

Authors
Ferber, S; Schnedl, WJ; BeltrandelRio, H; Irminger, JC; Halban, P; Newgard, CB
MLA Citation
Ferber, S, Schnedl, WJ, BeltrandelRio, H, Irminger, JC, Halban, P, and Newgard, CB. "Molecular strategies for the treatment of diabetes." Transplant Proc 26.2 (April 1994): 363-365. (Review)
PMID
8171464
Source
pubmed
Published In
Transplantation Proceedings
Volume
26
Issue
2
Publish Date
1994
Start Page
363
End Page
365

Cellular engineering and gene therapy strategies for insulin replacement in diabetes.

In diabetes, insulin secretion is either completely absent (insulin-dependent diabetes mellitus [IDDM]) or inappropriately regulated (non-insulin-dependent diabetes mellitus [NIDDM]). In recent years, new insights into the molecular and biochemical mechanism(s) of fuel-mediated insulin release coupled with advances in gene transfer technology have led to the investigation of molecular strategies for replacement of normal insulin delivery function. Such initiatives have included attempts to engineer glucose-stimulated insulin secretion in cell lines that might serve as surrogates for islets in IDDM. The development of DNA virus gene transfer systems of remarkable efficiency also has suggested ways in which the beta-cell dysfunction of NIDDM might ultimately be repaired by gene therapy. The emerging work in these areas and implications for the future are summarized in this perspective.

Authors
Newgard, CB
MLA Citation
Newgard, CB. "Cellular engineering and gene therapy strategies for insulin replacement in diabetes." Diabetes 43.3 (March 1994): 341-350. (Review)
PMID
8314006
Source
pubmed
Published In
Diabetes
Volume
43
Issue
3
Publish Date
1994
Start Page
341
End Page
350

Use of recombinant adenovirus for metabolic engineering of mammalian cells.

Authors
Becker, TC; Noel, RJ; Coats, WS; Gómez-Foix, AM; Alam, T; Gerard, RD; Newgard, CB
MLA Citation
Becker, TC, Noel, RJ, Coats, WS, Gómez-Foix, AM, Alam, T, Gerard, RD, and Newgard, CB. "Use of recombinant adenovirus for metabolic engineering of mammalian cells." Methods Cell Biol 43 Pt A (1994): 161-189. (Review)
PMID
7823861
Source
pubmed
Published In
Methods in cell biology
Volume
43 Pt A
Publish Date
1994
Start Page
161
End Page
189

Glucose-stimulated insulin secretion in cell lines

Because islet β-cells are expensive and difficult to isolate, islet transplantation may have limited applicability for insulin replacement in insulin-dependent diabetes mellitus. Knowledge of glucose sensing guides the development of clonal cell lines that behave Like β-cells. High-K(m) glucose transport and glucose phosphorylation both contribute to glucose-stimulated insulin secretion in clonal cells and β-cells. Introduction of these and other key molecular components of the β-cell into clonal lines may eventually result in glucose-responsive, insulin-secreting cell implants for human use.

Authors
Cassidy, LE; Newgard, CB
MLA Citation
Cassidy, LE, and Newgard, CB. "Glucose-stimulated insulin secretion in cell lines." Diabetes, Nutrition and Metabolism - Clinical and Experimental 7.4 (1994): 189-195.
Source
scival
Published In
Diabetes, Nutrition and Metabolism - Clinical and Experimental
Volume
7
Issue
4
Publish Date
1994
Start Page
189
End Page
195

Use of recombinant adenovirus for metabolic engineering of mammalian cells.

Authors
Becker, TC; Noel, RJ; Coats, WS; Gómez-Foix, AM; Alam, T; Gerard, RD; Newgard, CB
MLA Citation
Becker, TC, Noel, RJ, Coats, WS, Gómez-Foix, AM, Alam, T, Gerard, RD, and Newgard, CB. "Use of recombinant adenovirus for metabolic engineering of mammalian cells." Methods in cell biology 43 Pt A (1994): 161-189.
Source
scival
Published In
Methods in cell biology
Volume
43 Pt A
Publish Date
1994
Start Page
161
End Page
189
DOI
10.1016/S0091-679X(08)60603-2

Molecular engineering of the pancreatic beta-cell.

Authors
Newgard, CB; Hughes, SD; Quaade, C; Beltrandelrio, H; Gomez-Foix, AM; Ferber, S
MLA Citation
Newgard, CB, Hughes, SD, Quaade, C, Beltrandelrio, H, Gomez-Foix, AM, and Ferber, S. "Molecular engineering of the pancreatic beta-cell." J Lab Clin Med 122.4 (October 1993): 356-363. (Review)
PMID
8228550
Source
pubmed
Published In
Journal of Laboratory and Clinical Medicine
Volume
122
Issue
4
Publish Date
1993
Start Page
356
End Page
363

Transfection of AtT-20ins cells with GLUT-2 but not GLUT-1 confers glucose-stimulated insulin secretion. Relationship to glucose metabolism.

Glucose is thought to stimulate insulin release from islet beta-cells through generation of metabolic signals. In the current study we have introduced the genes encoding the facilitated glucose transporters known as GLUT-1 and GLUT-2 into AtT-20ins cells to assess their impact on glucose-stimulated insulin release and glucose metabolism. We find that transfection of AtT-20ins cells with GLUT-2, but not GLUT-1, confers glucose-stimulated insulin release in both static incubation and perifusion studies. Cells transfected with GLUT-1 have a Km for 3-O-methyl glucose uptake of 4 mM and a Vmax of 5-6 mmol/min/liter cell space. These values are increased compared to untransfected AtT-20ins cells (Km = 2 mM; Vmax = 0.5 mmol/min/liter cell space), but are less than observed in GLUT-2-transfected lines (Km = 16-17 mM; Vmax = 17-25 mmol/min/liter cell space). Despite these dramatic differences in glucose transport affinity and capacity, the rates of [5-3H]glucose usage are not different in the control and transfected lines over a range of glucose concentrations from 10 microM to 20 mM. We conclude that the specific effect of GLUT-2 on glucose-stimulated insulin release in AtT-20ins cells is not related to changes in the overall rate of glucose metabolism and may instead involve physical coupling of GLUT-2 with cellular proteins and/or structures involved in glucose signaling.

Authors
Hughes, SD; Quaade, C; Johnson, JH; Ferber, S; Newgard, CB
MLA Citation
Hughes, SD, Quaade, C, Johnson, JH, Ferber, S, and Newgard, CB. "Transfection of AtT-20ins cells with GLUT-2 but not GLUT-1 confers glucose-stimulated insulin secretion. Relationship to glucose metabolism." J Biol Chem 268.20 (July 15, 1993): 15205-15212.
PMID
8325893
Source
pubmed
Published In
The Journal of biological chemistry
Volume
268
Issue
20
Publish Date
1993
Start Page
15205
End Page
15212

Autoantibodies to the GLUT-2 glucose transporter of beta cells in insulin-dependent diabetes mellitus of recent onset.

Purified immunoglobulin G (IgG) from the serum of patients with insulin-dependent diabetes mellitus (IDDM) of recent onset inhibits high-Km uptake of 3-O-methyl-beta-D-glucose by rat pancreatic islets. To determine if the inhibition is the result of antibodies against GLUT-2, the high-Km glucose transporter of beta cells, we incubated IDDM sera with rat islet cells and with AtT-20ins cells transfected to express GLUT-2. IDDM sera inhibited glucose uptake in islet cells and in GLUT-2-expressing AtT-20ins cells but not in AtT-20ins cells transfected to express the low-Km isoform, GLUT-1. In 24 of 30 (77%) patients with newly diagnosed IDDM, IgG binding as measured by immunofluorescence and flow cytometry of the cells transfected to express GLUT-2 was > 2 standard deviations from the mean of the nondiabetic population; 29 of 31 (96%) of nondiabetic children were negative (P < 0.0001). Increased IgG binding could be removed by absorption with GLUT-2-expressing cells but not with GLUT-1-expressing cells. We conclude that most patients with IDDM of recent onset have autoantibodies to GLUT-2.

Authors
Inman, LR; McAllister, CT; Chen, L; Hughes, S; Newgard, CB; Kettman, JR; Unger, RH; Johnson, JH
MLA Citation
Inman, LR, McAllister, CT, Chen, L, Hughes, S, Newgard, CB, Kettman, JR, Unger, RH, and Johnson, JH. "Autoantibodies to the GLUT-2 glucose transporter of beta cells in insulin-dependent diabetes mellitus of recent onset." Proc Natl Acad Sci U S A 90.4 (February 15, 1993): 1281-1284.
PMID
8433987
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
90
Issue
4
Publish Date
1993
Start Page
1281
End Page
1284

Adenovirus-mediated transfer of the muscle glycogen phosphorylase gene into hepatocytes confers altered regulation of glycogen metabolism.

The muscle isozyme of glycogen phosphorylase is potently activated by the allosteric ligand AMP, whereas the liver isozyme is not. In this study we have investigated the metabolic impact of expression of muscle phosphorylase in liver cells. To this end, we constructed a replication-defective, recombinant adenovirus containing the muscle glycogen phosphorylase cDNA (termed AdCMV-MGP) and used this system to infect hepatocytes in culture. AMP-activatable glycogen phosphorylase activity was increased 46-fold 6 days after infection of primary liver cells with AdCMV-MGP. Despite large increases in phosphorylase activity, glycogen levels were only slightly reduced in AdCMV-MGP-infected liver cells compared to uninfected cells or cells infected with wild-type adenovirus. The lack of correlation of phosphorylase activity and glycogen content suggests that the liver cell environment can inhibit the muscle phosphorylase isozyme. This inhibition can be overcome, however, by addition of carbonyl cyanide m-chlorophenylhydrazone (CCCP), which increases AMP levels by 30-fold and causes a much larger decrease in glycogen levels in AdCMV-MGP-infected cells than in uninfected or wild-type adenovirus-infected controls. CCCP treatment also caused a preferential decrease in glycogen content relative to glucagon treatment in AdCMV-MGP-infected hepatocytes (74% versus 11%, respectively), even though the two drugs caused equal increases in phosphorylase a activity. Introduction of muscle phosphorylase into hepatocytes therefore confers a capacity for glycogenolytic response to effectors that is not provided by the endogenous liver phosphorylase isozyme. The remarkable efficiency of adenovirus-mediated gene transfer into primary hepatocytes and the demonstration of altered regulation of glycogen metabolism as a consequence of expression of a non-cognate phosphorylase isozyme may have implications for gene therapy of glycogen storage diseases.

Authors
Gómez-Foix, AM; Coats, WS; Baqué, S; Alam, T; Gerard, RD; Newgard, CB
MLA Citation
Gómez-Foix, AM, Coats, WS, Baqué, S, Alam, T, Gerard, RD, and Newgard, CB. "Adenovirus-mediated transfer of the muscle glycogen phosphorylase gene into hepatocytes confers altered regulation of glycogen metabolism." J Biol Chem 267.35 (December 15, 1992): 25129-25134.
PMID
1334082
Source
pubmed
Published In
The Journal of biological chemistry
Volume
267
Issue
35
Publish Date
1992
Start Page
25129
End Page
25134

Cellular engineering for the treatment of metabolic disorders: prospects for therapy in diabetes.

Significant advances in the areas of identification of disease susceptibility genes and gene transfer technologies have fueled new initiatives in cellular engineering as a means for treating metabolic disease. This article utilizes new findings from such work as the blueprint for a discussion of the prospects for gene therapy in diabetes mellitus.

Authors
Newgard, CB
MLA Citation
Newgard, CB. "Cellular engineering for the treatment of metabolic disorders: prospects for therapy in diabetes." Biotechnology (N Y) 10.10 (October 1992): 1112-1120.
PMID
1369396
Source
pubmed
Published In
Biotechnology
Volume
10
Issue
10
Publish Date
1992
Start Page
1112
End Page
1120

Engineering of glucose-stimulated insulin secretion and biosynthesis in non-islet cells.

The high-capacity glucose transporter known as GLUT-2 and the glucose phosphorylating enzyme glucokinase are thought to be key components of the "glucose-sensing apparatus" that regulates insulin release from the beta cells of the islets of Langerhans in response to changes in external glucose concentration. AtT-20ins cells are derived from anterior pituitary cells and are like beta cells in that they express glucokinase and have been engineered to secrete correctly processed insulin in response to analogs of cAMP, but, unlike beta cells, they fail to respond to glucose and lack GLUT-2 expression. Herein we demonstrate that stable transfection of AtT-20ins cells with the GLUT-2 cDNA confers glucose-stimulated insulin secretion and glucose regulation of insulin biosynthesis and also results in glucose potentiation of the secretory response to non-glucose secretagogues. This work represents a first step toward creation of a genetically engineered "artificial beta cell."

Authors
Hughes, SD; Johnson, JH; Quaade, C; Newgard, CB
MLA Citation
Hughes, SD, Johnson, JH, Quaade, C, and Newgard, CB. "Engineering of glucose-stimulated insulin secretion and biosynthesis in non-islet cells." Proc Natl Acad Sci U S A 89.2 (January 15, 1992): 688-692.
PMID
1309953
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
89
Issue
2
Publish Date
1992
Start Page
688
End Page
692

Factors regulating islet regeneration in the post-insulinoma NEDH rat.

Authors
Chen, L; Appel, MC; Alam, T; Miyaura, C; Sestak, A; O'Neil, J; Unger, RH; Newgard, CB
MLA Citation
Chen, L, Appel, MC, Alam, T, Miyaura, C, Sestak, A, O'Neil, J, Unger, RH, and Newgard, CB. "Factors regulating islet regeneration in the post-insulinoma NEDH rat." Adv Exp Med Biol 321 (1992): 71-80. (Review)
PMID
1449084
Source
pubmed
Published In
Advances in experimental medicine and biology
Volume
321
Publish Date
1992
Start Page
71
End Page
80

Cellular engineering for the treatment of metabolic disorders: Prospects for therapy in diabetes

Authors
Newgard, CB
MLA Citation
Newgard, CB. "Cellular engineering for the treatment of metabolic disorders: Prospects for therapy in diabetes." Bio/Technology 10.10 (1992): 1112-1120.
Source
scival
Published In
Biotechnology
Volume
10
Issue
10
Publish Date
1992
Start Page
1112
End Page
1120
DOI
10.1038/nbt1092-1112

Developmental expression of glycogenolytic enzymes in rabbit tissues: possible relationship to fetal lung maturation.

Glycogen can be degraded in mammalian tissues by one of three isozymes of glycogen phosphorylase, termed muscle (M), liver (L) and brain (B) after the tissues in which they are preferentially expressed in adult animals, or by members of the family of alpha-glucosidases. In the current study, we have examined the developmental expression of these enzymes and their respective mRNAs in rabbit tissues, with particular emphasis on the developing lung, a tissue in which glycogen serves as an important source of carbon for surfactant phospholipid biosynthesis. Native gel activity assays and RNA blot hybridization analysis revealed that the B isoform of glycogen phosphorylase predominates in fetal and adult lung tissues, accompanied by a low level of expression of the M isoform. Total B and M phosphorylase activities increased during fetal lung development, with a peak at day 28 of gestation, then decreased to the adult level at term. This peak in activity coincided with the peak period of glycogen degradation in developing lung. While the increase in M isozyme activity was correlated with an increase in the level of its mRNA, B isoform mRNA showed no significant alteration during development, suggesting that the increase in B isoform activity is determined by a posttranscriptional mechanism. Analysis of phosphorylase mRNA levels in developing liver, skeletal muscle, brain and heart revealed a diverse expression pattern. The L isozyme mRNA was predominant at all time points in liver, the M isozyme was predominant at all time points in muscle, the B isozyme was predominant at all time points in brain, and heart contained a mixture of B and M mRNA in roughly equal ratios at all time points. Thus, our studies of phosphorylase mRNA in the rabbit provide no evidence for general predominance of the B isozyme in fetal tissues, or for isozyme 'switching' from the B to the L or M forms during development, as has been suggested by others. In addition to the increase in phosphorylase activity, acid, but not neutral alpha-glucosidase activity was found to increase significantly during fetal lung development, again with a peak at day 28 of gestation. Interestingly, RNA blot hybridization analysis with a probe for lysosomal alpha-glucosidase revealed no change in the level of expression of its 4 kb transcript in developing lung. Instead, we observed induction of a structurally related mRNA of 7.4 kb that peaked at day 28 of gestation. Hybridization with a sucrase/isomaltase-specific oligonucleotide excluded the possibility that the 7.4 kb transcript encodes this protein.(ABSTRACT TRUNCATED AT 400 WORDS)

Authors
Newgard, CB; Norkiewicz, B; Hughes, SD; Frenkel, RA; Coats, WS; Martiniuk, F; Johnston, JM
MLA Citation
Newgard, CB, Norkiewicz, B, Hughes, SD, Frenkel, RA, Coats, WS, Martiniuk, F, and Johnston, JM. "Developmental expression of glycogenolytic enzymes in rabbit tissues: possible relationship to fetal lung maturation." Biochim Biophys Acta 1090.3 (November 11, 1991): 333-342.
PMID
1954255
Source
pubmed
Published In
Biochimica et Biophysica Acta: international journal of biochemistry and biophysics
Volume
1090
Issue
3
Publish Date
1991
Start Page
333
End Page
342

An engineered liver glycogen phosphorylase with AMP allosteric activation.

Liver and muscle glycogen phosphorylases, which are products of distinct genes, are both activated by covalent phosphorylation, but in the unphosphorylated (b) state, only the muscle isozyme is efficiently activated by the allosteric activator AMP. The different responsiveness of the phosphorylase isozymes to allosteric ligands is important for the maintenance of tissue and whole body glucose homeostasis. In an attempt to understand the structural determinants of differential sensitivity of the muscle and liver isozymes to AMP, we have developed a bacterial expression system for the liver enzyme, allowing native and engineered proteins to be expressed and characterized. Engineering of the single amino acid substitutions Thr48Pro, Met197Thr and the double mutant Thr48Pro, Met197Thr in liver phosphorylase, and Pro48Thr in muscle phosphorylase, did not qualitatively change the response of the two isozymes to AMP. These sites had previously been implicated in the configuration of the AMP binding site. However, when nine amino acids among the first 48 in liver phosphorylase were replaced with the corresponding muscle phosphorylase residues (L1M2-48L49-846), the engineered liver enzyme was activated by AMP to a higher maximal activity than native liver phosphorylase. Interestingly, the homotropic cooperativity of AMP binding was unchanged in the engineered phosphorylase b protein, and heterotropic cooperativity between the glucose-1-phosphate and AMP sites was only slightly enhanced. The native liver, native muscle and L1M2-48L49-846 phosphorylases were converted to the a form by treatment with purified phosphorylase kinase; the maximal activity of the chimeric a enzyme was greater than the native liver a enzyme and approached that of muscle phosphorylase a. From these results we suggest that tissue-specific phosphorylase isozymes have evolved a complex mechanism in which the N-terminal 48 amino acids modulate intrinsic activity (Vmax), probably by affecting subunit interactions, and other, as yet undefined regions specify the allosteric interactions with ligands and substrates.

Authors
Coats, WS; Browner, MF; Fletterick, RJ; Newgard, CB
MLA Citation
Coats, WS, Browner, MF, Fletterick, RJ, and Newgard, CB. "An engineered liver glycogen phosphorylase with AMP allosteric activation." J Biol Chem 266.24 (August 25, 1991): 16113-16119.
PMID
1874749
Source
pubmed
Published In
The Journal of biological chemistry
Volume
266
Issue
24
Publish Date
1991
Start Page
16113
End Page
16119

Analysis of the protein products encoded by variant glucokinase transcripts via expression in bacteria.

Five variant transcripts of the single rat glucokinase gene have been described that are naturally expressed in islets of Langerhans, liver and anterior pituitary. Four of these were prepared as cDNA and expressed in bacteria in order to begin to address their physiological roles. Expression of constructs pGKB1 (normal islet/pituitary glucokinase) and pGKL1 (normal liver glucokinase) resulted in a glucose-dependent, glucokinase-like activity, 7-fold and 45-fold, respectively, above background. Expression of pGKB3 (variant islet/pituitary glucokinase) and pGKL2 (variant liver glucokinase) in contrast, did not result in any glucokinase-like activity.

Authors
Quaade, C; Hughes, SD; Coats, WS; Sestak, AL; Iynedjian, PB; Newgard, CB
MLA Citation
Quaade, C, Hughes, SD, Coats, WS, Sestak, AL, Iynedjian, PB, and Newgard, CB. "Analysis of the protein products encoded by variant glucokinase transcripts via expression in bacteria." FEBS Lett 280.1 (March 11, 1991): 47-52.
PMID
2009966
Source
pubmed
Published In
FEBS Letters
Volume
280
Issue
1
Publish Date
1991
Start Page
47
End Page
52

Expression of normal and novel glucokinase mRNAs in anterior pituitary and islet cells.

The glucose-phosphorylating enzyme glucokinase likely plays an important role in regulating glucose-stimulated insulin secretion from the islets of Langerhans and has previously been thought to be expressed only in that tissue and in liver. In this study, we demonstrate high levels of glucokinase mRNA in the anterior pituitary cell line AtT20ins, which has been engineered to secrete correctly processed insulin, as well as in primary anterior pituitary tissue. Unlike islet or liver cells, expression of glucokinase mRNA in anterior pituitary cells was not accompanied by expression of the high Km glucose transporter (GLUT-2) mRNA. The glucokinase transcript in anterior pituitary cells was similar in size to islet glucokinase mRNA, which has a unique, elongated 5'-end relative to the liver glucokinase message. Amplification and sequence analysis of the glucokinase mRNA expressed in islets, RIN1046-38 cells, and anterior pituitary cells confirmed that the glucokinase transcripts in these cell types contain the same 5'-sequence. In addition, a novel alternative transcript was identified that contains a 52-nucleotide deletion and that predicts a 58-amino acid peptide as a result of a frame shift. Both the deleted and undeleted transcripts were found in islets, RIN cells, and AtT20ins cells, whereas only the deleted product was identified in primary anterior pituitary tissue. An antibody prepared against a peptide found at the N terminus of the islet isoform of glucokinase easily detected a protein with a size predicted by the undeleted transcript in extracts prepared from islets, RIN1046-38 cells, and AtT20ins cells. Since both the glucokinase protein and mRNA are naturally expressed in AtT20ins and RIN1046-38 cells, we compared the effect of varying concentrations of glucose on insulin secretion from the two lines. Insulin secretion from RIN1046-38 cells was stimulated by glucose in a dose-dependent manner over the range 0-2.5 mM, where it reached a maximum. AtT20ins cells, in contrast, exhibited no response to glucose at any concentration tested, despite the fact that insulin secretion from both cell lines was stimulated by incubation with dibutyryl cAMP. We conclude that glucokinase expression in AtT20ins cells may be necessary, but is not sufficient to confer glucose-stimulated insulin secretion.

Authors
Hughes, SD; Quaade, C; Milburn, JL; Cassidy, L; Newgard, CB
MLA Citation
Hughes, SD, Quaade, C, Milburn, JL, Cassidy, L, and Newgard, CB. "Expression of normal and novel glucokinase mRNAs in anterior pituitary and islet cells." J Biol Chem 266.7 (March 5, 1991): 4521-4530.
PMID
1999433
Source
pubmed
Published In
The Journal of biological chemistry
Volume
266
Issue
7
Publish Date
1991
Start Page
4521
End Page
4530

Expression of reg/PSP, a pancreatic exocrine gene: relationship to changes in islet beta-cell mass.

A cDNA termed reg was recently isolated by differential screening of a library prepared from regenerating islets isolated from pancreatic remnants of rats subjected to 90% pancreatectomy and nicotinamide treatment. This led to speculation that this gene may be involved in expansion of beta-cell mass. In the current study we have measured reg expression after implantation and resection of a solid insulinoma tumor into rats, maneuvers known, respectively, to reduce and reexpand the volume of beta-cells in the islet. Animals with an implanted insulinoma tumor became profoundly hypoglycemic. Islet beta-cells declined from the normal 75% of total islet volume to less than 30%, in concert with a marked reduction in the reg mRNA level. Removal of the tumor resulted in a sharp increase in beta-cell replication, as measured by [3H]thymidine incorporation and a return to normal beta-cell volume within 4 days of tumor resection. This was associated with a transient induction in reg expression compared to that in tumor-bearing animals, effectively returning the amount of reg mRNA to the levels found in normal animals within 48 h; at later time points after tumor removal (3-7 days) reg expression declined, but then rose toward normal. In situ hybridization analysis localized the initial induction in reg mRNA expression to the exocrine pancreas. Continuous infusion of insulin into normal rats for 4 days, a maneuver that does not significantly reduce beta-cell mass, resulted in dramatically reduced insulin mRNA in islets, but no change in the levels of reg mRNA. We conclude that the diminution in pancreatic beta-cell mass caused by subcutaneous implantation of an insulinoma is associated with reduced reg gene expression and that the increase in beta-cell replication after resection of the tumor is preceded by return of reg gene expression toward normal.

Authors
Miyaura, C; Chen, L; Appel, M; Alam, T; Inman, L; Hughes, SD; Milburn, JL; Unger, RH; Newgard, CB
MLA Citation
Miyaura, C, Chen, L, Appel, M, Alam, T, Inman, L, Hughes, SD, Milburn, JL, Unger, RH, and Newgard, CB. "Expression of reg/PSP, a pancreatic exocrine gene: relationship to changes in islet beta-cell mass." Mol Endocrinol 5.2 (February 1991): 226-234.
PMID
2038344
Source
pubmed
Published In
Molecular endocrinology (Baltimore, Md.)
Volume
5
Issue
2
Publish Date
1991
Start Page
226
End Page
234
DOI
10.1210/mend-5-2-226

Evidence that down-regulation of beta-cell glucose transporters in non-insulin-dependent diabetes may be the cause of diabetic hyperglycemia.

Non-insulin-dependent diabetes mellitus (NIDDM) is attributed to a failure of pancreatic beta cells to maintain insulin secretion at a level sufficient to compensate for underlying insulin resistance. In the ZDF rat, a model of NIDDM that closely resembles the human syndrome, we have previously reported profound underexpression of GLUT-2, the high-Km facilitative glucose transporter expressed by beta cells of normal animals. Here we report that islets of diabetic rats exhibit a marked decrease in the volume of GLUT-2-positive beta cells and a reduction at the electron-microscopic level in the number of GLUT-2-immunoreactive sites per unit of beta-cell plasma membrane. The deficiency of GLUT-2 cannot be induced in normal beta cells by in vivo or in vitro exposure to high levels of glucose nor can it be prevented in beta cells of prediabetic ZDF rats by elimination of hyperglycemia. We conclude that this dearth of immunodetectable GLUT-2 in NIDDM is not secondary to hyperglycemia and therefore that it may well play a causal role in the development of hyperglycemia.

Authors
Orci, L; Ravazzola, M; Baetens, D; Inman, L; Amherdt, M; Peterson, RG; Newgard, CB; Johnson, JH; Unger, RH
MLA Citation
Orci, L, Ravazzola, M, Baetens, D, Inman, L, Amherdt, M, Peterson, RG, Newgard, CB, Johnson, JH, and Unger, RH. "Evidence that down-regulation of beta-cell glucose transporters in non-insulin-dependent diabetes may be the cause of diabetic hyperglycemia." Proc Natl Acad Sci U S A 87.24 (December 1990): 9953-9957.
PMID
2263645
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
87
Issue
24
Publish Date
1990
Start Page
9953
End Page
9957

Underexpression of beta cell high Km glucose transporters in noninsulin-dependent diabetes.

The role of defective glucose transport in the pathogenesis of noninsulin-dependent diabetes (NIDDM) was examined in Zucker diabetic fatty rats, a model of NIDDM. As in human NIDDM, insulin secretion was unresponsive to 20 mM glucose. Uptake of 3-O-methylglucose by islet cells was less than 19% of controls. The beta cell glucose transporter (GLUT-2) immunoreactivity and amount of GLUT-2 messenger RNA were profoundly reduced. Whenever fewer than 60% of beta cells were GLUT-2-positive, the response to glucose was absent and hyperglycemia exceeded 11 mM plasma glucose. We conclude that in NIDDM underexpression of GLUT-2 messenger RNA lowers high Km glucose transport in beta cells, and thereby impairs glucose-stimulated insulin secretion and prevents correction of hyperglycemia.

Authors
Johnson, JH; Ogawa, A; Chen, L; Orci, L; Newgard, CB; Alam, T; Unger, RH
MLA Citation
Johnson, JH, Ogawa, A, Chen, L, Orci, L, Newgard, CB, Alam, T, and Unger, RH. "Underexpression of beta cell high Km glucose transporters in noninsulin-dependent diabetes." Science 250.4980 (October 26, 1990): 546-549.
PMID
2237405
Source
pubmed
Published In
Science
Volume
250
Issue
4980
Publish Date
1990
Start Page
546
End Page
549

Glucokinase and glucose transporter expression in liver and islets: implications for control of glucose homoeostasis.

Authors
Newgard, CB; Quaade, C; Hughes, SD; Milburn, JL
MLA Citation
Newgard, CB, Quaade, C, Hughes, SD, and Milburn, JL. "Glucokinase and glucose transporter expression in liver and islets: implications for control of glucose homoeostasis." Biochem Soc Trans 18.5 (October 1990): 851-853.
PMID
2083694
Source
pubmed
Published In
Biochemical Society transactions
Volume
18
Issue
5
Publish Date
1990
Start Page
851
End Page
853

Regulation of beta-cell glucose transporter gene expression.

It has been postulated that a glucose transporter of beta cells (GLUT-2) may be important in glucose-stimulated insulin secretion. To determine whether this transporter is constitutively expressed or regulated, we subjected conscious unrestrained Wistar rats to perturbations in glucose homeostasis and quantitated beta-cell GLUT-2 mRNA by in situ hybridization. After 3 hr of hypoglycemia (glucose at 29 +/- 5 mg/dl), GLUT-2 and proinsulin mRNA signal densities were reduced by 25% of the level in control rats. After 4 days (blood glucose at 57 +/- 7 mg/dl vs. 120 +/- 10 mg/dl in saline-infused control rats), GLUT-2 and proinsulin mRNA densities were reduced by 85% and 65%, respectively (P = 0.001). After 12 days (glucose at 54 +/- 8 mg/dl), GLUT-2 mRNA signal density was undetectable whereas proinsulin mRNA was reduced by 51%. After 12 days of hypoglycemia, the Km for 3-O-methyl-D-glucose transport in isolated rat islets, normally 18-20 mM, was 2.5 mM. This provides functional evidence of a profound reduction of high Km glucose transporter in beta cells. In contrast, GLUT-2 was only slightly reduced by hypoglycemia in liver. To determine the effect of prolonged hyperglycemia, we also infused animals with 50% (wt/vol) glucose for 5 days (glucose at 200 +/- 50 mg/dl). Hyperglycemic clamping increased GLUT-2 mRNA by 46% (P = 0.001) whereas proinsulin mRNA doubled (P = 0.001). We conclude that GLUT-2 expression in beta cells, but not liver, is subject to regulation by certain perturbations in blood glucose homeostasis.

Authors
Chen, L; Alam, T; Johnson, JH; Hughes, S; Newgard, CB; Unger, RH
MLA Citation
Chen, L, Alam, T, Johnson, JH, Hughes, S, Newgard, CB, and Unger, RH. "Regulation of beta-cell glucose transporter gene expression." Proc Natl Acad Sci U S A 87.11 (June 1990): 4088-4092.
PMID
2190214
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
87
Issue
11
Publish Date
1990
Start Page
4088
End Page
4092

The high Km glucose transporter of islets of Langerhans is functionally similar to the low affinity transporter of liver and has an identical primary sequence.

The liver has been shown to contain a facilitated diffusion glucose transporter with high Km for glucose that is structurally distinct from the low Km glucose transporters found in most other tissues. We find that 3-O-methyl glucose is greater than 90% equilibrated across dispersed islet cells within 60 s, consistent with a facilitated diffusion transport mechanism. L-Glucose uptake was minimal throughout the time course, indicating stereospecificity. Measurement of glucose transport over a range of 3-O-methyl glucose concentrations from 0.05 to 60 mM revealed the presence of a component of glucose transport with an apparent Km of 17 mM, a value essentially identical to that previously reported for liver. Interestingly, a second component of glucose transport was also observed with an apparent Km of 1.4 mM, as has been reported for other tissues such as erythrocytes that are known to contain the "HepG2" or "erythroid/brain" type glucose transporter. Further evidence for the existence of two transport components is provided by the observation that a low concentration of cytochalasin B (0.4 microM) completely inhibits the low Km transport activity but has no effect on the high Km transporter. The kinetic similarity of high Km glucose transport in liver and islets is readily understood in light of our structural analysis. Sequence analysis of cDNA clones indicates that the liver and islet glucose transporters have identical sequences and, thus, are the products of the same gene.

Authors
Johnson, JH; Newgard, CB; Milburn, JL; Lodish, HF; Thorens, B
MLA Citation
Johnson, JH, Newgard, CB, Milburn, JL, Lodish, HF, and Thorens, B. "The high Km glucose transporter of islets of Langerhans is functionally similar to the low affinity transporter of liver and has an identical primary sequence." J Biol Chem 265.12 (April 25, 1990): 6548-6551.
PMID
2182619
Source
pubmed
Published In
The Journal of biological chemistry
Volume
265
Issue
12
Publish Date
1990
Start Page
6548
End Page
6551

Erratum: Underexpression of β cell high K(m) glucose transporters in noninsulin-dependent diabetes (Science (26 Oct. 1990) (546))

Authors
Johnson, JH; Ogawa, A; Chen, L; Alam, T; Unger, RH; Orci, L; Newgard, CB
MLA Citation
Johnson, JH, Ogawa, A, Chen, L, Alam, T, Unger, RH, Orci, L, and Newgard, CB. "Erratum: Underexpression of β cell high K(m) glucose transporters in noninsulin-dependent diabetes (Science (26 Oct. 1990) (546))." Science 250.4985 (1990): 1195--.
Source
scival
Published In
Science
Volume
250
Issue
4985
Publish Date
1990
Start Page
1195-

Differential expression and regulation of the glucokinase gene in liver and islets of Langerhans.

Glucokinase, a key regulatory enzyme of glucose metabolism in mammals, provides an interesting model of tissue-specific gene expression. The single-copy gene is expressed principally in liver, where it gives rise to a 2.4-kilobase mRNA. The islets of Langerhans of the pancreas also contain glucokinase. Using a cDNA complementary to rat liver glucokinase mRNA, we show that normal pancreatic islets and tumoral islet cells contain a glucokinase mRNA species approximately 400 nucleotides longer than hepatic mRNA. Hybridization with synthetic oligonucleotides and primer-extension analysis show that the liver and islet glucokinase mRNAs differ in the 5' region. Glucokinase mRNA is absent from the livers of fasted rats and is strongly induced within hours by an oral glucose load. In contrast, islet glucokinase mRNA is expressed at a constant level during the fasting-refeeding cycle. The level of glucokinase protein in islets measured by immunoblotting is unaffected by fasting and refeeding, whereas a 3-fold increase in the amount of enzyme occurs in liver during the transition from fasting to refeeding. From these data, we conclude (i) that alternative splicing and/or the use of distinct tissue-specific promoters generate structurally distinct mRNA species in liver and islets of Langerhans and (ii) that tissue-specific transcription mechanisms result in inducible expression of the glucokinase gene in liver but not in islets during the fasting-refeeding transition.

Authors
Iynedjian, PB; Pilot, PR; Nouspikel, T; Milburn, JL; Quaade, C; Hughes, S; Ucla, C; Newgard, CB
MLA Citation
Iynedjian, PB, Pilot, PR, Nouspikel, T, Milburn, JL, Quaade, C, Hughes, S, Ucla, C, and Newgard, CB. "Differential expression and regulation of the glucokinase gene in liver and islets of Langerhans." Proc Natl Acad Sci U S A 86.20 (October 1989): 7838-7842.
PMID
2682629
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
86
Issue
20
Publish Date
1989
Start Page
7838
End Page
7842

Rat amylin: cloning and tissue-specific expression in pancreatic islets.

Amyloid deposits in the islets of Langerhans of the pancreas are a common finding in non-insulin-dependent diabetes mellitus. The main protein constituent of these deposits is a 37-amino acid peptide known as amylin that resembles calcitonin gene-related peptide, a neuropeptide. We have isolated cDNA clones corresponding to the rat amylin precursor from an islet cDNA library and we show that this peptide is encoded in a 0.9-kilobase mRNA that is translated to yield a 93-amino acid precursor. The amylin peptide is bordered by dibasic residues, suggesting that it is proteolyzed like calcitonin gene-related peptide. The peptide sequences flanking the amylin sequence do not resemble the calcitonin gene-related peptide flanking sequences. RNA hybridization studies show that amylin mRNA is abundant in the islets of Langerhans but is not present in the brain or seven other tissues examined. Dietary changes, such as fasting or fasting and refeeding, have little effect on amylin mRNA expression. This tissue specificity suggests that amylin is involved in specific signaling pathways related to islet function.

Authors
Leffert, JD; Newgard, CB; Okamoto, H; Milburn, JL; Luskey, KL
MLA Citation
Leffert, JD, Newgard, CB, Okamoto, H, Milburn, JL, and Luskey, KL. "Rat amylin: cloning and tissue-specific expression in pancreatic islets." Proc Natl Acad Sci U S A 86.9 (May 1989): 3127-3130.
PMID
2654937
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
86
Issue
9
Publish Date
1989
Start Page
3127
End Page
3130

The family of glycogen phosphorylases: structure and function.

Glycogen phosphorylase plays a central role in the mobilization of carbohydrate reserves in a wide variety of organisms and tissues. While rabbit muscle phosphorylase remains the most studied and best characterized of phosphorylases, recombinant DNA techniques have led to the recent appearance of primary sequence data for a wide variety of phosphorylase enzymes. The functional properties of rabbit muscle phosphorylases are reviewed and then compared to properties of phosphorylases from other tissues and organisms. Tissue expression patterns and the chromosomal localization of mammalian phosphorylases are described. Differences in functional properties among phosphorylases are related to new structural information. Evolutionary relationships among phosphorylases as afforded by comparative analysis of proteins and gene sequences are discussed.

Authors
Newgard, CB; Hwang, PK; Fletterick, RJ
MLA Citation
Newgard, CB, Hwang, PK, and Fletterick, RJ. "The family of glycogen phosphorylases: structure and function." Crit Rev Biochem Mol Biol 24.1 (1989): 69-99. (Review)
PMID
2667896
Source
pubmed
Published In
Critical Reviews in Biochemistry and Molecular Biology (Informa)
Volume
24
Issue
1
Publish Date
1989
Start Page
69
End Page
99
DOI
10.3109/10409238909082552

Human brain glycogen phosphorylase. Cloning, sequence analysis, chromosomal mapping, tissue expression, and comparison with the human liver and muscle isozymes.

We have cloned the cDNA encoding a new isozyme of glycogen phosphorylase (1,4-D-glucan:orthosphosphate D-glucosyltransferase, EC 2.4.1.1) from a cDNA library prepared from a human brain astrocytoma cell line. Blot-hybridization analysis reveals that this message is preferentially expressed in human brain, but is also found at a low level in human fetal liver and adult liver and muscle tissues. Although previous studies have suggested that the major isozyme of phosphorylase found in all fetal tissues is the brain type, our data show that the predominant mRNA in fetal liver (24-week gestation) is the adult liver form. The protein sequence deduced from the nucleotide sequence of the brain phosphorylase cDNA is 862 amino acids long compared with 846 and 841 amino acids for the liver and muscle isozymes, respectively; the greater length of brain phosphorylase is entirely due to an extension at the far C-terminal portion of the protein. The muscle and brain isozymes share greater identity with regard to nucleotide and deduced amino acid sequences, codon usage, and nucleotide composition than either do with the liver sequence, suggesting a closer evolutionary relationship between them. Spot blot hybridization of the brain phosphorylase cDNA to laser-sorted human chromosome fractions, and Southern blot analysis of hamster/human hybrid cell line DNA reveals that the exact homolog of the newly cloned cDNA maps to chromosome 20, but that a slightly less homologous gene is found on chromosome 10 as well. The liver and muscle genes have previously been localized to chromosomes 14 and 11, respectively. This suggests that the phosphorylase genes evolved by duplication and translocation of a common ancestral gene, leading to divergence of elements controlling gene expression and of structural features of the phosphorylase proteins that confer tissue-specific functional properties.

Authors
Newgard, CB; Littman, DR; van Genderen, C; Smith, M; Fletterick, RJ
MLA Citation
Newgard, CB, Littman, DR, van Genderen, C, Smith, M, and Fletterick, RJ. "Human brain glycogen phosphorylase. Cloning, sequence analysis, chromosomal mapping, tissue expression, and comparison with the human liver and muscle isozymes." J Biol Chem 263.8 (March 15, 1988): 3850-3857.
PMID
3346228
Source
pubmed
Published In
The Journal of biological chemistry
Volume
263
Issue
8
Publish Date
1988
Start Page
3850
End Page
3857

The polymorphic locus for glycogen storage disease VI (liver glycogen phosphorylase) maps to chromosome 14.

Human liver glycogen phosphorylase deficiency, also known as glycogen storage disease type VI (GSD VI) or Hers disease, is characterized by hepatomegaly and reduced or absent glycogenolytic response to the injection of glucagon. The recently isolated cDNA encoding the liver isozyme of glycogen phosphorylase was used to map the gene and identify restriction-fragment polymorphisms in normal Caucasians as a prerequisite for detecting linked GSD VI abnormalities. Results of restriction-enzyme analysis using a downstream fragment of the liver glycogen phosphorylase cDNA indicated the existence of a single gene copy per haploid genome. Hybridization of this downstream liver phosphorylase probe to dual laser-excited, sorted human chromosomes localized the gene to human chromosome 14. When the downstream probe was tested on genomic DNA cut with seven different restriction enzymes, a single MspI restriction-fragment-length polymorphism (RFLP) was observed in a single individual. In contrast, similar Southern blots performed with an upstream portion of the cDNA encoding liver phosphorylase revealed common RFLPs for four of eight enzymes tested, with minor polymorphic allele frequencies ranging from 33% to 44%. One of the four enzymes (TaqI) revealed two independent polymorphisms. If random distribution of these haplotypes among normal and disease loci, is assumed, approximately 92% of fetuses at risk for Hers disease will be informative when tested with the upstream liver phosphorylase probe.

Authors
Newgard, CB; Fletterick, RJ; Anderson, LA; Lebo, RV
MLA Citation
Newgard, CB, Fletterick, RJ, Anderson, LA, and Lebo, RV. "The polymorphic locus for glycogen storage disease VI (liver glycogen phosphorylase) maps to chromosome 14." Am J Hum Genet 40.4 (April 1987): 351-364.
PMID
2883891
Source
pubmed
Published In
The American Journal of Human Genetics
Volume
40
Issue
4
Publish Date
1987
Start Page
351
End Page
364

Modeling the biochemical differences between rabbit muscle and human liver phosphorylase.

Glycogen phosphorylases catalyze the regulated breakdown of glycogen to glucose-1-phosphate. In mammals, glycogen phosphorylase occurs in three different isozymes called liver, muscle, and brain after the tissues in which they are preferentially expressed. The muscle isozyme binds and is activated cooperatively by AMP. In contrast, the liver enzyme binds AMP noncooperatively and is poorly activated. The amino acid sequence of human liver phosphorylase is 80% identical with rabbit muscle phosphorylase, and those residues which contact AMP are conserved. Using computer graphics software, we replaced side chains of the known rabbit muscle structure with those of human liver phosphorylase and interpreted the effects of these changes in order to account for the biochemical differences between them. We have identified two substitutions in liver phosphorylase potentially important in altering the cooperative binding and activation of this isozyme by AMP.

Authors
Rath, VL; Newgard, CB; Sprang, SR; Goldsmith, EJ; Fletterick, RJ
MLA Citation
Rath, VL, Newgard, CB, Sprang, SR, Goldsmith, EJ, and Fletterick, RJ. "Modeling the biochemical differences between rabbit muscle and human liver phosphorylase." Proteins 2.3 (1987): 225-235.
PMID
3447179
Source
pubmed
Published In
Proteins: Structure, Function and Bioinformatics
Volume
2
Issue
3
Publish Date
1987
Start Page
225
End Page
235
DOI
10.1002/prot.340020307

From dietary glucose to liver glycogen: the full circle round.

Authors
McGarry, JD; Kuwajima, M; Newgard, CB; Foster, DW; Katz, J
MLA Citation
McGarry, JD, Kuwajima, M, Newgard, CB, Foster, DW, and Katz, J. "From dietary glucose to liver glycogen: the full circle round." Annu Rev Nutr 7 (1987): 51-73. (Review)
PMID
3038155
Source
pubmed
Published In
Annual Review of Nutrition
Volume
7
Publish Date
1987
Start Page
51
End Page
73
DOI
10.1146/annurev.nu.07.070187.000411

Sequence analysis of the cDNA encoding human liver glycogen phosphorylase reveals tissue-specific codon usage.

We have cloned the cDNA encoding glycogen phosphorylase (1,4-alpha-D-glucan:orthophosphate alpha-D-glucosyl-transferase, EC 2.4.1.1) from human liver. Blot-hybridization analysis using a large fragment of the cDNA to probe mRNA from rabbit brain, muscle, and liver tissues shows preferential hybridization to liver RNA. Determination of the entire nucleotide sequence of the liver message has allowed a comparison with the previously determined rabbit muscle phosphorylase sequence. Despite an amino acid identity of 80%, the two cDNAs exhibit a remarkable divergence in G+C content. In the muscle phosphorylase sequence, 86% of the nucleotides at the third codon position are either deoxyguanosine or deoxycytidine residues, while in the liver homolog the figure is only 60%, resulting in a strikingly different pattern of codon usage throughout most of the sequence. The liver phosphorylase cDNA appears to represent an evolutionary mosaic; the segment encoding the N-terminal 80 amino acids contains greater than 90% G+C at the third codon position. A survey of other published mammalian cDNA sequences reveals that the data for liver and muscle phosphorylases reflects a bias in codon usage patterns in liver and muscle coding sequences in general.

Authors
Newgard, CB; Nakano, K; Hwang, PK; Fletterick, RJ
MLA Citation
Newgard, CB, Nakano, K, Hwang, PK, and Fletterick, RJ. "Sequence analysis of the cDNA encoding human liver glycogen phosphorylase reveals tissue-specific codon usage." Proc Natl Acad Sci U S A 83.21 (November 1986): 8132-8136.
PMID
2877458
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
83
Issue
21
Publish Date
1986
Start Page
8132
End Page
8136

The glucose-phosphorylating capacity of liver as measured by three independent assays. Implications for the mechanism of hepatic glycogen synthesis.

In the fasted to fed transition liver glycogen derives mainly from gluconeogenic precursors. Why glucose is not used efficiently as a direct precursor of glycogen has become a controversial issue, in part because of disagreement over the question of how well liver can phosphorylate glucose under conditions prevailing postprandially. To try to resolve the matter the relative merits of two recently described assays, one spectrophotometric (A), the other isotopic (B), for monitoring rates of glucose phosphorylation in the high speed supernatant fraction of liver have been rigorously evaluated. A third method, also isotopic (C), was developed for use with unfractionated as well as fractionated liver homogenates. Using fasted rats and mice from different nutritional backgrounds the glucose-phosphorylating capacity of liver extracts was measured and compared with rates of hepatic glycogen synthesis observed during refeeding. Two of the assays (A and C) provided reliable data at all concentrations of glucose tested (5-100 mM), while method B exhibited shortcomings at lower substrate concentrations. The results clearly establish that in both rats and mice the ability of the liver to phosphorylate glucose at physiological concentrations is sufficient to support only 25-30% of postprandial glycogen synthesis. A limited capacity for glucose phosphorylation probably accounts for the fact that two-thirds of glycogen synthesized with refeeding after a fast is formed by the indirect (gluconeogenic) pathway.

Authors
Kuwajima, M; Newgard, CB; Foster, DW; McGarry, JD
MLA Citation
Kuwajima, M, Newgard, CB, Foster, DW, and McGarry, JD. "The glucose-phosphorylating capacity of liver as measured by three independent assays. Implications for the mechanism of hepatic glycogen synthesis." J Biol Chem 261.19 (July 5, 1986): 8849-8853.
PMID
3722176
Source
pubmed
Published In
The Journal of biological chemistry
Volume
261
Issue
19
Publish Date
1986
Start Page
8849
End Page
8853

Structural relationships in glycogen phosphorylases.

Authors
Fletterick, RJ; Burke, JA; Hwang, PK; Nakano, K; Newgard, CB
MLA Citation
Fletterick, RJ, Burke, JA, Hwang, PK, Nakano, K, and Newgard, CB. "Structural relationships in glycogen phosphorylases." Ann N Y Acad Sci 478 (1986): 220-232. (Review)
PMID
3541750
Source
pubmed
Published In
Annals of the New York Academy of Sciences
Volume
478
Publish Date
1986
Start Page
220
End Page
232

Structure of mammalia