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Witka BZ, Oktaviani DJ, Marcellino M, Barliana MI, Abdulah R. Type 2 Diabetes-Associated Genetic Polymorphisms as Potential Disease Predictors. Diabetes Metab Syndr Obes 2019; 12:2689-2706. [PMID: 31908510 PMCID: PMC6927489 DOI: 10.2147/dmso.s230061] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 11/19/2019] [Indexed: 12/18/2022] Open
Abstract
Diabetes is a major cause of mortality worldwide. There are several types of diabetes, with type 2 diabetes mellitus (T2DM) being the most common. Many factors, including environmental and genetic factors, are involved in the etiology of the disease. Numerous studies have reported the role of genetic polymorphisms in the initiation and development of T2DM. While genome-wide association studies have identified around more than 200 susceptibility loci, it remains unclear whether these loci are correlated with the pathophysiology of the disease. The present review aimed to elucidate the potential genetic mechanisms underlying T2DM. We found that some genetic polymorphisms were related to T2DM, either in the form of single-nucleotide polymorphisms or direct amino acid changes in proteins. These polymorphisms are potential predictors for the management of T2DM.
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Affiliation(s)
- Beska Z Witka
- Departement of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor, Indonesia
| | - Dede J Oktaviani
- Departement of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor, Indonesia
| | - Marcellino Marcellino
- Departement of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor, Indonesia
| | - Melisa I Barliana
- Departement of Biological Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor, Indonesia
- Center of Excellence in Higher Education for Pharmaceutical Care Innovation, Universitas Padjadjaran, Jatinangor, Indonesia
- Correspondence: Melisa I Barliana Department of Biological Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jl. Raya Bandung Sumedang KM. 21, Jatinangor45363, Indonesia Email
| | - Rizky Abdulah
- Departement of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor, Indonesia
- Center of Excellence in Higher Education for Pharmaceutical Care Innovation, Universitas Padjadjaran, Jatinangor, Indonesia
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Mencarelli M, Zulian A, Cancello R, Alberti L, Gilardini L, Di Blasio AM, Invitti C. A novel missense mutation in the signal peptide of the human POMC gene: a possible additional link between early-onset type 2 diabetes and obesity. Eur J Hum Genet 2012; 20:1290-4. [PMID: 22643178 DOI: 10.1038/ejhg.2012.103] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Rare mutations in several genes have a critical role in the control of homeostatic mechanisms such as food-intake, energy balance and glucose metabolism. In this study, we performed a mutational screening in a 58-year-old woman presenting early-onset type 2 diabetes and central obesity. The entire coding regions of MC4R, MC3R, HNF1A, GCK and POMC (pro-opiomelanocortin) genes were analyzed by direct sequencing. A new missense mutation was identified within the POMC gene signal peptide sequence, resulting in a heterozygous substitution of an arginine for a glycine at codon 15 (p.A15G) that was excluded in 300 healthy normal weight controls. The mutation segregated in the family and was associated with overweight, type 2 diabetes, hypertension and coronary heart disease in the carriers. Functional studies demonstrated that POMC protein was not detectable in β-TC3 cells transfected with A15G-POMC vector as well as in their culture media, despite POMC mRNA levels were comparable for amount and stability to those of wild-type-transfected cells. In silico RNA folding prediction indicated that the mutation gives rise to a different RNA secondary structure, suggesting that it might affect translation and protein synthesis. To the best of our knowledge, this is the first report addressing the functional consequences of a mutation in the signal peptide of POMC. These findings further support the hypothesis that POMC-derived peptides might have a role in the control of peripheral glucose metabolism and suggest that disruption of central POMC secretion might represent an additional link between type 2 diabetes and obesity.
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Affiliation(s)
- Monica Mencarelli
- Laboratory of Molecular Biology, Istituto Auxologico Italiano, Milano, Italy
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3
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de Moura EG, Bonomo IT, Nogueira-Neto JF, de Oliveira E, Trevenzoli IH, Reis AM, Passos MCF, Lisboa PC. Maternal prolactin inhibition during lactation programs for metabolic syndrome in adult progeny. J Physiol 2009; 587:4919-29. [PMID: 19736303 DOI: 10.1113/jphysiol.2009.176289] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Neonatal malnutrition is associated with metabolic syndrome in adulthood. Maternal hypoprolactinaemia at the end of lactation (a precocious weaning model) caused obesity, leptin resistance and hypothyroidism in adult offspring, suggesting an association of prolactin (PRL) and programming of metabolic dysfunctions. Metabolic syndrome pathogenesis is still unclear, but abdominal obesity, higher triglycerides, lower high-density lipoprotein (HDL-c) and insulin resistance have been proposed to be important factors involved. We studied the consequences of maternal hypoprolactinaemia during lactation on parameters associated with metabolic syndrome. Lactating Wistar rats were treated with bromocriptine (BRO, 1 mg twice a day) or saline on days 19, 20 and 21 of lactation and their offspring were followed from weaning until 180 days old. Adult BRO offspring had higher body weight (+10%, P < 0.05), total body fat (+41%, P < 0.05), visceral fat (+20%, P < 0.05), subcutaneous fat (+3 times, P < 0.05) and total body protein (+24%, P < 0.05). BRO group presented hyperglycaemia (+16%, P < 0.05), lower muscle glycogen (51%, P < 0.05), higher cholesterol (+30%, P < 0.05), higher low-density lipoprotein (LDL-c) (+1.5 times, P < 0.05), higher triglycerides (+49%, P < 0.05), lower HDL-c (28%, P < 0.05), hyperleptinaemia (+2.9 times, P < 0.05), hypoadiponectinaemia (16%, P < 0.05) and hypoprolactinaemia (54%, P < 0.05) as well as higher insulin resistance index (+24%, P < 0.05). Regarding adrenal function, BRO rats showed hypercorticosteronaemia (+46%, P < 0.05) and higher total catecholamine (+37%, P < 0.05). In the hypothalamus, no change was observed in protein expression of the leptin signalling pathway. Thus, neonatal malnutrition induced by maternal PRL inhibition during late lactation programs for obesity, dyslipidaemia and insulin resistance in adult offspring increasing the risk for metabolic syndrome development.
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Affiliation(s)
- Egberto Gaspar de Moura
- Department of Physiology, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
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Alvarez JA, Bush NC, Hunter GR, Brock DW, Gower BA. Ethnicity and weight status affect the accuracy of proxy indices of insulin sensitivity. Obesity (Silver Spring) 2008; 16:2739-44. [PMID: 18927554 PMCID: PMC2779542 DOI: 10.1038/oby.2008.437] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This study tested the hypotheses that correlations between direct measures of insulin sensitivity and proxy indices of insulin sensitivity derived from fasting values, (i) would not be affected by ethnicity, and (ii) would be stronger in overweight vs. weight-reduced states. We further hypothesized that associations between proxy indices and fat distribution would be similar to those between directly measured insulin sensitivity and fat distribution. Testing was performed in weight-stable conditions in 59 African-American (AA) and 62 white-American (WA) overweight, premenopausal women before and after a weight loss intervention. Subjects were retested 1 year following weight loss. Proxy indices were correlated against the insulin sensitivity index S(I) determined via minimal modeling. Fat distribution was assessed using computed tomography. Correlations between Si and proxy indices were consistently stronger among overweight women (r = 0.44-0.52) vs. weight-reduced women (r = 0.18-0.32), and among AA (r = 0.49-0.56, baseline; 0.24-0.36, weight-reduced) vs. WA (r = 0.38-0.46, baseline; 0.19-0.31, weight-reduced). Among subjects who regained >3 kg after 1 year, correlations between S(I) and proxy indices were similar to those observed at baseline, whereas correlations were weak among women who maintained their reduced body weight. S(I) and all proxy indices were similarly correlated with intra-abdominal adipose tissue (IAAT) at baseline, but not after weight loss. In conclusion, correlations between S(I) and proxy indices were affected by both ethnicity and weight status. If proxy indices are used in multiethnic populations, or in populations including both lean and overweight/obese subjects, data should be interpreted with caution.
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Affiliation(s)
- Jessica A Alvarez
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA.
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5
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Lumeng CN, Bodzin JL, Saltiel AR. Obesity induces a phenotypic switch in adipose tissue macrophage polarization. J Clin Invest 2007; 117:175-84. [PMID: 17200717 PMCID: PMC1716210 DOI: 10.1172/jci29881] [Citation(s) in RCA: 3370] [Impact Index Per Article: 198.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 10/05/2006] [Indexed: 12/11/2022] Open
Abstract
Adipose tissue macrophages (ATMs) infiltrate adipose tissue during obesity and contribute to insulin resistance. We hypothesized that macrophages migrating to adipose tissue upon high-fat feeding may differ from those that reside there under normal diet conditions. To this end, we found a novel F4/80(+)CD11c(+) population of ATMs in adipose tissue of obese mice that was not seen in lean mice. ATMs from lean mice expressed many genes characteristic of M2 or "alternatively activated" macrophages, including Ym1, arginase 1, and Il10. Diet-induced obesity decreased expression of these genes in ATMs while increasing expression of genes such as those encoding TNF-alpha and iNOS that are characteristic of M1 or "classically activated" macrophages. Interestingly, ATMs from obese C-C motif chemokine receptor 2-KO (Ccr2-KO) mice express M2 markers at levels similar to those from lean mice. The antiinflammatory cytokine IL-10, which was overexpressed in ATMs from lean mice, protected adipocytes from TNF-alpha-induced insulin resistance. Thus, diet-induced obesity leads to a shift in the activation state of ATMs from an M2-polarized state in lean animals that may protect adipocytes from inflammation to an M1 proinflammatory state that contributes to insulin resistance.
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Affiliation(s)
- Carey N. Lumeng
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, USA.
Department of Pediatrics and Communicable Diseases and
Departments of Internal Medicine and Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Jennifer L. Bodzin
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, USA.
Department of Pediatrics and Communicable Diseases and
Departments of Internal Medicine and Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Alan R. Saltiel
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, USA.
Department of Pediatrics and Communicable Diseases and
Departments of Internal Medicine and Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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6
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Buettner C, Pocai A, Muse ED, Etgen AM, Myers MG, Rossetti L. Critical role of STAT3 in leptin's metabolic actions. Cell Metab 2006; 4:49-60. [PMID: 16814732 PMCID: PMC3638026 DOI: 10.1016/j.cmet.2006.04.014] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/31/2006] [Accepted: 04/27/2006] [Indexed: 01/07/2023]
Abstract
Leptin has pleiotropic effects on glucose homeostasis and feeding behavior. Here, we validate the use of a cell-permeable phosphopeptide that blocks STAT3 activation in vivo. The combination of this biochemical approach with stereotaxic surgical techniques allowed us to pinpoint the contribution of hypothalamic STAT3 to the acute effects of leptin on food intake and glucose homeostasis. Leptin's ability to acutely reduce food intake critically depends on intact STAT3 signaling. Likewise, hypothalamic signaling of leptin through STAT3 is required for the acute effects of leptin on liver glucose fluxes. Lifelong obliteration of STAT3 signaling via the leptin receptor in mice (s/s mice) results in severe hepatic insulin resistance that is comparable to that observed in db/db mice, devoid of leptin receptor signaling. Our results demonstrate that the activation of the hypothalamic STAT3 pathway is an absolute requirement for the effects of leptin on food intake and hepatic glucose metabolism.
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Affiliation(s)
- Christoph Buettner
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
- Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Alessandro Pocai
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
- Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Evan D. Muse
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
- Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Anne M. Etgen
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Martin G. Myers
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109
| | - Luciano Rossetti
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
- Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
- Correspondence:
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7
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Vuguin P, Raab E, Liu B, Barzilai N, Simmons R. Hepatic insulin resistance precedes the development of diabetes in a model of intrauterine growth retardation. Diabetes 2004; 53:2617-22. [PMID: 15448092 DOI: 10.2337/diabetes.53.10.2617] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Intrauterine growth retardation (IUGR) has been linked to the development of type 2 diabetes in adulthood. We developed an IUGR model in rats whereby at age 3-6 months the animals develop a diabetes that is associated with insulin resistance. Hyperinsulinemic-euglycemic clamp studies were performed at age 8 weeks, before the onset of obesity and diabetes. Basal hepatic glucose production (HGP) was significantly higher in IUGR than in control rats (14.6 +/- 0.4 vs. 12.3 +/- 0.3 mg. kg(-1). min(-1); P < 0.05). Insulin suppression of HGP was blunted in IUGR versus control rats (10.4 +/- 0.6 vs. 6.5 +/- 1.0 mg. kg(-1). min(-1); P < 0.01); however, rates of glucose uptake and glycogenolysis were similar between the two groups. Insulin-stimulated insulin receptor substrate 2 and Akt-2 phosphorylation were significantly blunted in IUGR rats. PEPCK and glucose-6-phosphatase mRNA levels were increased at least threefold in liver of IUGR compared with control rats. These studies suggest that an aberrant intrauterine milieu permanently impairs insulin signaling in the liver so that gluconeogenesis is augmented in the IUGR rat. These processes occur early in life, before the onset of hyperglycemia, and indicate that uteroplacental insufficiency causes a primary defect in gene expression and hepatic metabolism that leads to the eventual development of overt hyperglycemia.
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Affiliation(s)
- Patricia Vuguin
- Children's Hospital at Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, USA.
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8
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Kim SP, Ellmerer M, Van Citters GW, Bergman RN. Primacy of hepatic insulin resistance in the development of the metabolic syndrome induced by an isocaloric moderate-fat diet in the dog. Diabetes 2003; 52:2453-60. [PMID: 14514627 DOI: 10.2337/diabetes.52.10.2453] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Obesity is highly correlated with insulin resistance and the development of type 2 diabetes. Insulin resistance will result in a decrease in insulin's ability to stimulate glucose uptake into peripheral tissue and will suppress glucose production by the liver. However, the development of peripheral and hepatic insulin resistance relative to one another in the context of obesity-associated insulin resistance is not well understood. To examine this phenomena, we used the moderate fat-fed dog model, which has been shown to develop both subcutaneous and visceral adiposity and severe insulin resistance. Six normal dogs were fed an isocaloric diet with a modest increase in fat content for 12 weeks, and they were assessed at weeks 0, 6, and 12 for changes in insulin sensitivity and glucose turnover. By week 12 of the diet, there was a more than twofold increase in trunk adiposity as assessed by magnetic resonance imaging because of an accumulation in both subcutaneous and visceral fat depots with very little change in body weight. Fasting plasma insulin had increased by week 6 (150% of week 0) and remained increased up to week 12 of the study (170% of week 0). Surprisingly, there appeared to be no change in the rates of insulin-stimulated glucose uptake as measured by euglycemic-hyperinsulinemic clamps throughout the course of fat feeding. However, there was an increase in steady-state plasma insulin levels at weeks 6 and 12, indicating a moderate degree of peripheral insulin resistance. In contrast to the moderate defect seen in the periphery, there was a marked impairment in insulin's ability to suppress endogenous glucose production during the clamp such that by week 12 of the study, there was a complete inability of insulin to suppress glucose production. Our results indicate that a diet enriched with a moderate amount of fat results in the development of both subcutaneous and visceral adiposity, hyperinsulinemia, and a modest degree of peripheral insulin resistance. However, there is a complete inability of insulin to suppress hepatic glucose production during the clamp, suggesting that insulin resistance of the liver may be the primary defect in the development of insulin resistance associated with obesity.
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Affiliation(s)
- Stella P Kim
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA
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9
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Abstract
PURPOSE OF REVIEW This review depicts recent developments concerning the role of the liver in control of carbohydrate and lipid utilization from ingestion to storage; it covers the liver's influence on food intake, post-absorptive nutrient metabolism and body weight. The mechanisms involved have implications for the pathogenesis of obesity and type II diabetes. RECENT FINDINGS Recent studies have identified some of the molecular and biochemical mechanisms which control whole body and hepatic carbohydrate and lipid metabolism, thus providing the basis of the liver's role in the control of food intake, metabolism, and body weight. Fatty acids are known to effect gene transcription in various ways. Advances in our understanding of the control of glucose and lipid utilization by the liver include (1). a better functional characterization of some newly discovered transcription factors, (2). new discoveries concerning the physiological and pathophysiological role of hepatic glucokinase and of the glycogen-targeting subunits of protein phosphatase-1, and (3). the demonstration of substantial overlap in the molecular control mechanisms of glucose-lipid utilization. Also, impaired insulin signaling due to a certain gene (Foxo1) has emerged as a possible unifying mechanism for various common metabolic abnormalities of type II diabetes. Finally, recent findings confirm and extend previous knowledge about the important role of hepatic nerves in the control of liver and whole body glucose-lipid utilization. SUMMARY The identification of new molecular and neural mechanisms of the hepatic control of glucose-lipid utilization and body weight provides a focus for future studies and may eventually help to develop new treatments for obesity and type II diabetes.
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Affiliation(s)
- Wolfgang Langhans
- Physiology and Animal Husbandry, Institute of Animal Sciences, Schwerzenbach, Switzerland.
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El-Haschimi K, Dufresne SD, Hirshman MF, Flier JS, Goodyear LJ, Bjørbaek C. Insulin resistance and lipodystrophy in mice lacking ribosomal S6 kinase 2. Diabetes 2003; 52:1340-6. [PMID: 12765942 DOI: 10.2337/diabetes.52.6.1340] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The p90 ribosomal S6 kinase 2 (RSK2) is a serine/threonine kinase with high expression levels in adipose tissue. Numerous in vitro studies show that RSK2 is activated by a broad number of cellular stimuli and suggest that RSK2 is involved in the regulation of a variety of cellular processes. However, the physiological role of RSK2 still remains elusive. We therefore generated rsk2 knockout (KO) mice to better understand the function of RSK2 in vivo. Birth weights of RSK2 KO mice are normal, but the body weight is reduced with age, as compared with wild-type littermates. We found that the difference in body weight was largely caused by a specific loss of white adipose tissue that is accompanied by reduced serum levels of the adipocyte-derived peptide, leptin. KO mice also have impaired glucose tolerance and elevated fasting insulin and glucose levels that are restored following administration of low amounts of leptin, which do not affect food intake. We conclude that RSK2 plays a novel and an important role in regulation of adipose mass in mice and speculate that the reduction in fat tissue may negatively affect insulin sensitivity, as observed in human lipodystrophy, through reduced levels of adipocyte-derived factors, such as leptin.
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Affiliation(s)
- Karim El-Haschimi
- Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA
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11
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Dobbins RL, Szczepaniak LS, Zhang W, McGarry JD. Chemical sympathectomy alters regulation of body weight during prolonged ICV leptin infusion. Am J Physiol Endocrinol Metab 2003; 284:E778-87. [PMID: 12626326 DOI: 10.1152/ajpendo.00128.2002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To assess the importance of the sympathetic nervous system in regulating body weight during prolonged leptin infusion, we evaluated food intake, body weight, and physical activity in conscious, unrestrained rats. Initial studies illustrated that prolonged intracerebroventricular (ICV) infusion of leptin enhanced substrate oxidation so that adipose tissue lipid stores were completely ablated, and muscle triglyceride and liver glycogen stores were depleted. After neonatal chemical sympathectomy, changes in weight and food intake were compared in groups of sympathectomized (SYM) and control (CON) adult animals during ICV infusion of leptin. CON animals lost 60 +/- 9 g over 10 days vs. 25 +/- 3 g in the SYM animals when food intake was matched between the two groups. Greater weight loss despite similar energy intake points to an important role of the sympathetic nervous system in stimulating energy expenditure during ICV leptin infusion by increasing the resting metabolic rate, since no differences in physical activity were observed between CON and SYM groups. In conclusion, activation of the SNS by leptin increases energy expenditure by augmenting the resting metabolic rate.
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Affiliation(s)
- Robert L Dobbins
- Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9135, USA.
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12
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Jacobson L. Middle-aged C57BL/6 mice have impaired responses to leptin that are not improved by calorie restriction. Am J Physiol Endocrinol Metab 2002; 282:E786-93. [PMID: 11882498 DOI: 10.1152/ajpendo.00495.2001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Midlife weight gain occurs in many species, suggesting that leptin signaling is impaired at middle age. To test this hypothesis, we measured changes in food intake and body composition in young (Y) and middle-aged (MA) C57BL/6 male mice infused subcutaneously with phosphate-buffered saline or leptin. Leptin-induced decreases in food intake and body fat were delayed in MA mice and associated with catabolism after longer treatment periods. Endogenous plasma leptin levels did not correlate with body fat in MA mice. Calorie restriction (CR) reduced body fat, plasma leptin, and insulin in MA mice to levels in Y mice but did not upregulate leptin sensitivity. CR mice did not respond to leptin doses that inhibited food intake in MA mice and reduced food intake and body fat in Y mice significantly below levels in CR mice. Plasma corticosterone was significantly higher in leptin-treated CR vs. MA mice. We conclude that MA C57BL/6 mice exhibit impaired leptin signaling and that CR, possibly by elevating glucocorticoids, impairs appetite control without improving the metabolic actions of leptin.
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Affiliation(s)
- Lauren Jacobson
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA.
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13
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Abstract
Increased fat mass, abdominal adiposity, and insulin resistance are typical findings in aging mammals and are frequently associated with leptin resistance and increased plasma leptin levels. To examine whether leptin's failure in aging is due to aging per se or to changes in body fat mass or distribution, we studied aging rats that underwent calorie restriction throughout their lives, maintaining their youthful body fat pattern and metabolic profile. Leptin's action was assessed by measuring its ability to regulate food intake, fat mass and its distribution, peripheral and hepatic insulin action, and its own gene expression in fat. Our results show that leptin's action is markedly diminished in aging rats, independently of their body fat pattern. Leptin's failure in this model suggests its causative role in the metabolic decline seen with aging.
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Affiliation(s)
- Ilan Gabriely
- Department of Medicine, Division of Endocrinology, Diabetes Research and Training Center. Institute for Aging Research, Albert Einstein College of Medicine, Bronx, New York
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14
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Steinberg GR, Bonen A, Dyck DJ. Fatty acid oxidation and triacylglycerol hydrolysis are enhanced after chronic leptin treatment in rats. Am J Physiol Endocrinol Metab 2002; 282:E593-600. [PMID: 11832362 DOI: 10.1152/ajpendo.00303.2001] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Leptin acutely increases fatty acid (FA) oxidation and triacylglycerol (TG) hydrolysis and decreases TG esterification in oxidative rodent muscle. However, the effects of chronic leptin administration on FA metabolism in skeletal muscle have not been examined. We hypothesized that chronic leptin treatment would enhance TG hydrolysis as well as the capacity to oxidize FA in soleus (SOL) muscle. Female Sprague-Dawley rats were infused for 2 wk with leptin (LEPT; 0.5 mg x kg(-1) x day(-1)) by use of subcutaneously implanted miniosmotic pumps. Control (AD-S) and pair-fed (PF-S) animals received saline-filled implants. Subsequently, FA metabolism was monitored for 45 min in isolated, resting, and contracting (20 tetani/min) SOL muscles by means of pulse-chase procedures. Food intake (-33 +/- 2%, P < 0.01) and body mass (-12.5 +/- 4%, P = 0.01) were reduced in both LEPT and PF-S animals. Leptin levels were elevated (+418 +/- 7%, P < 0.001) in treated animals but reduced in PF-S animals (-73 +/- 8%, P < 0.05) relative to controls. At rest, TG hydrolysis was increased in leptin-treated rats (1.8 +/- 2.2, AD-S vs. 23.5 +/- 8.1 nmol/g wet wt, LEPT; P < 0.001). In contracting SOL muscles, TG hydrolysis (1.5 +/- 0.6, AD-S vs. 3.6 +/- 1.0 micromol/g wet wt, LEPT; P = 0.02) and palmitate oxidation (18.3 +/- 6.7, AD-S vs. 45.7 +/- 9.9 nmol/g wet wt, LEPT; P < 0.05) were both significantly increased by leptin treatment. Chronic leptin treatment had no effect on TG esterification either at rest or during contraction. Markers of overall (citrate synthase) and FA (hydroxyacyl-CoA dehydrogenase) oxidative capacity were unchanged with leptin treatment. Protein expression of hormone-sensitive lipase (HSL) was also unaltered following leptin treatment. Thus leptin-induced increases in lipolysis are likely due to HSL activation (i.e., phosphorylation). Increased FA oxidation secondary to chronic leptin treatment is not due to an enhanced oxidative capacity and may be a result of enhanced flux into the mitochondrion (i.e., carnitine palmitoyltransferase I regulation) or electron transport uncoupling (i.e., uncoupling protein-3 expression).
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Affiliation(s)
- Gregory R Steinberg
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1
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15
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Larkin LM, Reynolds TH, Supiano MA, Kahn BB, Halter JB. Effect of aging and obesity on insulin responsiveness and glut-4 glucose transporter content in skeletal muscle of Fischer 344 x Brown Norway rats. J Gerontol A Biol Sci Med Sci 2001; 56:B486-92. [PMID: 11682570 PMCID: PMC2714732 DOI: 10.1093/gerona/56.11.b486] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This study investigated the metabolic changes with age in the Fischer 344 x Brown Norway rat and its suitability as an animal model of postmaturational insulin resistance. Specifically, we determined whether an age-associated decrease in glucose disposal is associated with diminished whole body insulin responsiveness and/or a decrease in glucose transporter (GLUT-4) protein and mRNA content in medial gastrocnemius muscle of male Fischer 344 x Brown Norway rats of ages 8, 18, and 28 months. Fasting plasma glucose was unchanged with age. There was a significant age effect on visceral adiposity, fasting plasma insulin levels, insulin responsiveness, and GLUT-4 protein content. Insulin responsiveness and GLUT-4 protein were lower in the 18-month-old rats than in the 8-month-old rats. The findings of age-associated increases in visceral adiposity and insulin resistance, and decreases in GLUT-4 in the Fisher 344 x Brown Norway rat, suggest that this rat strain may be an appropriate model for studying the effects of aging on glucose homeostasis.
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Affiliation(s)
- L M Larkin
- Division of Geriatric Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor 48109-0940, USA.
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16
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Obici S, Feng Z, Tan J, Liu L, Karkanias G, Rossetti L. Central melanocortin receptors regulate insulin action. J Clin Invest 2001; 108:1079-85. [PMID: 11581309 PMCID: PMC200952 DOI: 10.1172/jci12954] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Energy balance and insulin action are tightly coregulated. Leptin regulates energy intake and expenditure partly by modulation of the melanocortin pathway in the hypothalamus. Here we demonstrate potent effects of the melanocortin pathway on insulin action and body distribution of adiposity. Conscious rats received week-long infusions of either a melanocortin receptor agonist, alpha-melanocyte-stimulating hormone (alpha-MSH), or antagonist, SHU9119, in the third cerebral ventricle while food intake was maintained constant in each group. alpha-MSH decreased intra-abdominal fat and markedly enhanced the actions of insulin on both glucose uptake and production, while SHU9119 exerted opposite effects. Our findings elucidate a neuroendocrine network that is likely to play a central role in the coupling of energy intake and insulin action.
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MESH Headings
- Animals
- Glucose/metabolism
- Hypothalamus/metabolism
- Insulin/metabolism
- Insulin Receptor Substrate Proteins
- Intracellular Signaling Peptides and Proteins
- Male
- Melanocyte-Stimulating Hormones/adverse effects
- Melanocyte-Stimulating Hormones/pharmacology
- Oligodeoxyribonucleotides, Antisense
- Phosphoproteins/metabolism
- Phosphorylation
- Rats
- Rats, Sprague-Dawley
- Receptor, Melanocortin, Type 3
- Receptor, Melanocortin, Type 4
- Receptors, Corticotropin/agonists
- Receptors, Corticotropin/antagonists & inhibitors
- Receptors, Corticotropin/metabolism
- Receptors, Peptide/agonists
- Receptors, Peptide/antagonists & inhibitors
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Signal Transduction
- alpha-MSH/adverse effects
- alpha-MSH/pharmacology
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Affiliation(s)
- S Obici
- Diabetes Research and Training Center, Albert Einstein College of Medicine, Bronx, New York, USA 10461
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17
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Ye JM, Doyle PJ, Iglesias MA, Watson DG, Cooney GJ, Kraegen EW. Peroxisome proliferator-activated receptor (PPAR)-alpha activation lowers muscle lipids and improves insulin sensitivity in high fat-fed rats: comparison with PPAR-gamma activation. Diabetes 2001; 50:411-7. [PMID: 11272155 DOI: 10.2337/diabetes.50.2.411] [Citation(s) in RCA: 262] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Peroxisome proliferator-activated receptor (PPAR)-alpha agonists lower circulating lipids, but the consequences for muscle lipid metabolism and insulin sensitivity are not clear. We investigated whether PPAR-alpha activation improves insulin sensitivity in insulin-resistant rats and compared the effects with PPAR-gamma activation. Three-week high fat-fed male Wistar rats were untreated or treated with the specific PPAR-alpha agonist WY14643 or the PPAR-gamma agonist pioglitazone (both 3 mg x kg(-1) x day(-1)) for the last 2 weeks of high-fat feeding. Like pioglitazone, WY14643 lowered basal plasma levels of glucose, triglycerides (-16% vs. untreated), and leptin (-52%), and also muscle triglyceride (-34%) and total long-chain acyl-CoAs (LCACoAs) (-41%) (P < 0.05). In contrast to pioglitazone, WY14643 substantially reduced visceral fat weight and total liver triglyceride content (P < 0.01) without increasing body weight gain. WY14643 and pioglitazone similarly enhanced whole-body insulin sensitivity (clamp glucose infusion rate increased 35 and 37% and glucose disposal 22 and 15%, respectively, vs. untreated). Both agents enhanced insulin-mediated muscle glucose metabolic index (Rg') and reduced muscle triglyceride and LCACoA accumulation (P < 0.05). Although pioglitazone had more potent effects than WY14643 on muscle insulin sensitization, this was associated with its greater effect to reduce muscle LCACoA accumulation. Overall insulin-mediated muscle Rg' was inversely correlated with the content of LCACoAs (r = -0.74, P = 0.001) and with plasma triglyceride levels (r = -0.77, P < 0.001). We conclude that even though WY14643 and pioglitazone, representing PPAR-alpha and PPAR-gamma activation, respectively, may alter muscle lipid supply by different mechanisms, both significantly improve muscle insulin action in the high fat-fed rat model of insulin resistance, and this effect is proportional to the degree to which they reduce muscle lipid accumulation.
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Affiliation(s)
- J M Ye
- Garvan Institute of Medical Research, Sydney, Australia.
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18
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Yaspelkis BB, Davis JR, Saberi M, Smith TL, Jazayeri R, Singh M, Fernandez V, Trevino B, Chinookoswong N, Wang J, Shi ZQ, Levin N. Leptin administration improves skeletal muscle insulin responsiveness in diet-induced insulin-resistant rats. Am J Physiol Endocrinol Metab 2001; 280:E130-42. [PMID: 11120667 DOI: 10.1152/ajpendo.2001.280.1.e130] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In addition to suppressing appetite, leptin may also modulate insulin secretion and action. Leptin was administered here to insulin-resistant rats to determine its effects on secretagogue-stimulated insulin release, whole body glucose disposal, and insulin-stimulated skeletal muscle glucose uptake and transport. Male Wistar rats were fed either a normal (Con) or a high-fat (HF) diet for 3 or 6 mo. HF rats were then treated with either vehicle (HF), leptin (HF-Lep, 10 mg. kg(-1). day(-1) sc), or food restriction (HF-FR) for 12-15 days. Glucose tolerance and skeletal muscle glucose uptake and transport were significantly impaired in HF compared with Con. Whole body glucose tolerance and rates of insulin-stimulated skeletal muscle glucose uptake and transport in HF-Lep were similar to those of Con and greater than those of HF and HF-FR. The insulin secretory response to either glucose or tolbutamide (a pancreatic beta-cell secretagogue) was not significantly diminished in HF-Lep. Total and plasma membrane skeletal muscle GLUT-4 protein concentrations were similar in Con and HF-Lep and greater than those in HF and HF-FR. The findings suggest that chronic leptin administration reversed a high-fat diet-induced insulin-resistant state, without compromising insulin secretion.
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Affiliation(s)
- B B Yaspelkis
- Exercise Biochemistry Laboratory, Department of Kinesiology, California State University Northridge, Northridge, California 91330-8287, USA.
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19
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Enevoldsen LH, Stallknecht B, Fluckey JD, Galbo H. Effect of exercise training on in vivo lipolysis in intra-abdominal adipose tissue in rats. Am J Physiol Endocrinol Metab 2000; 279:E585-92. [PMID: 10950826 DOI: 10.1152/ajpendo.2000.279.3.e585] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intra-abdominal obesity is associated with cardiovascular disease and non-insulin-dependent diabetes mellitus, and physical training has been suggested to alleviate these conditions. We compared epinephrine-stimulated lipolysis in vivo in three intra-abdominal adipose tissues (ATs: retroperitoneal, parametrial, and mesenteric) and in subcutaneous AT, and we also studied the effect of physical training. Moreover, we studied the effect of physical training on epinephrine-stimulated lipolysis in muscle in vivo. Female rats were either swim trained (15 wk, n = 8) or sedentary (n = 7). Under anesthesia, a two-stage intravenous epinephrine infusion (60 min of 80 and 200 ng. kg(-1). min(-1), respectively) was carried out, and local interstitial glycerol concentration was measured by the microdialysis technique. Blood flow was measured by microspheres. Training increased blood flow in all ATs [on average: 73 +/- 12 (trained) vs. 14 +/- 4 (sedentary) ml. 100 g(-1). min(-1), P < 0. 05]; nevertheless, epinephrine-stimulated interstitial glycerol concentrations were increased or unchanged. Interstitial glycerol concentration was higher in intra-abdominal than in subcutaneous AT in both trained and sedentary rats. In skeletal muscle, interstitial glycerol concentration and blood flow did not differ between trained and sedentary rats. In conclusion, in vivo lipolysis is higher both in the basal state and during epinephrine-stimulation in intra-abdominal than in subcutaneous AT, and training may be beneficial in alleviating intra-abdominal obesity by enhancing lipolysis in intra-abdominal fat depots.
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Affiliation(s)
- L H Enevoldsen
- Department of Medical Physiology, The Panum Institute, University of Copenhagen and Copenhagen Muscle Research Centre, National University Hospital, Denmark.
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Gupta G, Cases JA, She L, Ma XH, Yang XM, Hu M, Wu J, Rossetti L, Barzilai N. Ability of insulin to modulate hepatic glucose production in aging rats is impaired by fat accumulation. Am J Physiol Endocrinol Metab 2000; 278:E985-91. [PMID: 10826999 DOI: 10.1152/ajpendo.2000.278.6.e985] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Increased total fat mass (FM) and visceral fat (VF) may account in part for age-associated decrease in hepatic insulin action. This study determined whether preventing the changes in body fat distribution abolished this defect throughout aging. We studied the F(1) hybrid of Brown Norway-Fischer 344 rats (n = 29), which we assigned to caloric restriction (CR) or fed ad libitum (AL). CR (55% of the calories consumed by AL) was initiated and used at 2 mo to prevent age-dependent increases in FM and VF. AL rats were studied at 2, 8, and 20 mo; CR rats were studied at 8 and 20 mo. VF and FM remained unchanged throughout aging in CR rats. AL-fed rats at 8 and 20 mo had over fourfold higher FM and VF compared with both CR groups. Insulin clamp studies (3 mU. kg(-1). min(-1) with somatostatin) were performed to assess hepatic insulin sensitivity. Prevention of fat accretion resulted in a marked improvement in insulin action in the suppression of hepatic glucose production (HGP) (6.3 +/- 0.3 and 7.2 +/- 1.2 mg. kg(-1). min(-1) in 8- and 20-mo CR rats vs. 8.3 +/- 0.5 and 10.8 +/- 0.9 mg. kg(-1). min(-1) in 8- and 20-mo AL rats, respectively). The rate of gluconeogenesis (by enrichment of hepatic uridine diphosphate glucose and phosphoenolpyruvate pools by [(14)C]lactate) was unchanged in all groups. The improvement in hepatic insulin action in the CR group was mostly due to effective suppression of glycogenolysis (4.4 +/- 0.3 and 4.9 +/- 0.3 mg. kg(-1). min(-1) in 8- and 20-mo CR rats vs. 5.8 +/- 0.6 and 8.2 +/- 1.0 mg. kg(-1). min(-1) in 8- and 20-mo AL rats, respectively). The results demonstrated the preservation of hepatic insulin action in aging CR rats. Therefore, body fat and its distribution are major determinants of age-associated hepatic insulin resistance.
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Affiliation(s)
- G Gupta
- Department of Medicine, and the Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York 10461, USA
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