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Lewandowski SL, El K, Campbell JE. Evaluating glucose-dependent insulinotropic polypeptide and glucagon as key regulators of insulin secretion in the pancreatic islet. Am J Physiol Endocrinol Metab 2024; 327:E103-E110. [PMID: 38775725 DOI: 10.1152/ajpendo.00360.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 02/27/2024] [Accepted: 05/09/2024] [Indexed: 06/04/2024]
Abstract
The incretin axis is an essential component of postprandial insulin secretion and glucose homeostasis. There are two incretin hormones, glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which exert multiple actions throughout the body. A key cellular target for the incretins are pancreatic β-cells, where they potentiate nutrient-stimulated insulin secretion. This feature of incretins has made this system an attractive target for therapeutic interventions aimed at controlling glycemia. Here, we discuss the role of GIP in both β-cells and α-cells within the islet, to stimulate insulin and glucagon secretion, respectively. Moreover, we discuss how glucagon secretion from α-cells has important insulinotropic actions in β-cells through an axis termed α- to β-cell communication. These recent advances have elevated the potential of GIP and glucagon as a therapeutic targets, coinciding with emerging compounds that pharmacologically leverage the actions of these two peptides in the context of diabetes and obesity.
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Affiliation(s)
- Sophie L Lewandowski
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, United States
| | - Kimberley El
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, United States
| | - Jonathan E Campbell
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, United States
- Division of Endocrinology, Department of Medicine, Duke University, Durham, North Carolina, United States
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, United States
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2
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Alonge KM, Porte D, Schwartz MW. Distinct Roles for Brain and Pancreas in Basal and Postprandial Glucose Homeostasis. Diabetes 2023; 72:547-556. [PMID: 37146276 PMCID: PMC10130484 DOI: 10.2337/db22-0969] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 02/04/2023] [Indexed: 05/07/2023]
Abstract
The glucose homeostasis system ensures that the circulating glucose level is maintained within narrow physiological limits both in the fasting (or basal) state and following a nutrient challenge. Although glucose homeostasis is traditionally conceptualized as a single overarching system, evidence reviewed here suggests that basal glycemia and glucose tolerance are governed by distinct control systems. Specifically, whereas glucose tolerance appears to be determined largely by interactions between insulin secretion and insulin sensitivity, basal-state glucose homeostasis is predominated by insulin-independent mechanisms governed largely by the brain. In addition to a new perspective on how glucose homeostasis is achieved, this "dual control system" hypothesis offers a feasible and testable explanation for observations that are otherwise difficult to reconcile and sheds new light on the integration of central and peripheral metabolic control mechanisms. The implications of this model for the pathogenesis and treatment of impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes are also discussed.
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Affiliation(s)
- Kimberly M. Alonge
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA
| | - Daniel Porte
- Division of Endocrinology, School of Medicine, University of California San Diego, San Diego, CA
| | - Michael W. Schwartz
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA
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3
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A therapeutic convection-enhanced macroencapsulation device for enhancing β cell viability and insulin secretion. Proc Natl Acad Sci U S A 2021; 118:2101258118. [PMID: 34504013 PMCID: PMC8449352 DOI: 10.1073/pnas.2101258118] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2021] [Indexed: 12/30/2022] Open
Abstract
Islet transplantation for type 1 diabetes treatment has been limited by the need for lifelong immunosuppression regimens. This challenge has prompted the development of macroencapsulation devices (MEDs) to immunoprotect the transplanted islets. While promising, conventional MEDs are faced with insufficient transport of oxygen, glucose, and insulin because of the reliance on passive diffusion. Hence, these devices are constrained to two-dimensional, wafer-like geometries with limited loading capacity to maintain cells within a distance of passive diffusion. We hypothesized that convective nutrient transport could extend the loading capacity while also promoting cell viability, rapid glucose equilibration, and the physiological levels of insulin secretion. Here, we showed that convective transport improves nutrient delivery throughout the device and affords a three-dimensional capsule geometry that encapsulates 9.7-fold-more cells than conventional MEDs. Transplantation of a convection-enhanced MED (ceMED) containing insulin-secreting β cells into immunocompetent, hyperglycemic rats demonstrated a rapid, vascular-independent, and glucose-stimulated insulin response, resulting in early amelioration of hyperglycemia, improved glucose tolerance, and reduced fibrosis. Finally, to address potential translational barriers, we outlined future steps necessary to optimize the ceMED design for long-term efficacy and clinical utility.
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Aulinger BA, Perabo M, Seeley RJ, Parhofer KG, D'Alessio DA. Rapid hepatic metabolism blunts the endocrine action of portally infused GLP-1 in male rats. Am J Physiol Endocrinol Metab 2020; 318:E189-E197. [PMID: 31743041 PMCID: PMC7052580 DOI: 10.1152/ajpendo.00298.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) is an enteral peptide that contributes to the incretin effect. GLP-1 action is typically described as endocrine, but this mechanism has been questioned because rapid inactivation in the circulation by dipeptidylpeptidase 4 (DPP4) results in a short half-life, limiting the amount of the hormone that can reach the pancreatic islet. An alternative mechanism for GLP-1 to regulate insulin secretion through neuroendocrine signaling originating from sensors in the portal vein has been proposed. We hypothesized that portal infusion of GLP-1 would cause greater glucose-stimulated insulin secretion than equimolar administration into the jugular vein. To test this, hyperglycemic clamps with superimposed graded infusions of GLP-1 into the jugular or portal veins of male rats were performed. These experiments were repeated with pharmacologic DPP4 inhibition to determine the effect of GLP-1 metabolism in the jugular and portal venous beds. Contrary to our hypothesis, we found a higher insulinotropic effect with jugular compared with portal GLP-1, which was associated with higher plasma concentrations of intact GLP-1. The greater insulinotropic effect of jugular venous GLP-1 persisted even with pharmacological DPP4 inhibition. These findings do not support an important role of portal vein GLP-1 signaling for the incretin effect but highlight the hepatoportal bed as a major site of GLP-1 degradation that persists even with pharmacological inhibition. Together, these results support rapid inactivation of enterally released GLP-1 in the liver as limiting endocrine actions on the β-cell and raise questions about the conventional endocrine model of pharmacologic effects of DPP4 inhibitors.
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Affiliation(s)
- Benedikt A Aulinger
- Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio
- Department of Medicine II, University Hospital, LMU Munich, Germany
| | - Marta Perabo
- Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Randy J Seeley
- Department of Surgery, University of Michigan, Ann Arbor, Michigan
| | - Klaus G Parhofer
- Department of Medicine IV, University Hospital, LMU Munich, Germany
| | - David A D'Alessio
- Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
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Yang TY, Gardner JC, Gentile JD, Liang NC. Sex and individual differences in meal patterns mediate the persistency of running-associated high-fat diet avoidance in rats. Am J Physiol Regul Integr Comp Physiol 2018; 316:R130-R143. [PMID: 30403499 DOI: 10.1152/ajpregu.00231.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The modern environment is characterized by convenient access to a variety of high-fat (HF) foods and encourages excess energy intake, which leads to weight gain. While healthier diets and exercise are common interventions that facilitate energy balance, meal patterns also influence body weight and energy metabolism. The current study characterized the association among exercise, diet choice, and meal patterns in rats. Unlike sedentary rats, which prefer a HF to a chow diet, wheel-running rats initially avoid the HF diet. Subsequently, the running-induced HF diet avoidance persists longer in males than in females. We hypothesized that differences in meal patterns contribute to sex differences in the prevalence and persistency of HF diet avoidance. During two-diet choice, rats did not mix chow and HF diet within a meal and consumed discrete meals of each diet. Exercise decreased chow meal size in both sexes (4.5 vs. 5.7 kcal) but decreased total meal frequency only in male rats. Analyses of individual differences revealed WR rats that maintained HF diet avoidance (HF avoiders) had larger chow than HF meals (5.2 vs. 1.3 kcal) upon initial 3 days of diet choice. When compared with rats that reversed HF avoidance (HF eaters), HF avoiders had shorter latency to consume their first meal of HF diet (2.6 vs. 98.9 min) upon initial running and diet choice. Taken together, these results suggest that both sex and individual differences in meal patterns contribute to differences in the persistency of exercise-associated HF diet avoidance.
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Affiliation(s)
- Tiffany Y Yang
- Department of Psychology, University of Illinois at Urbana-Champaign , Champaign, Illinois
| | - Jennie C Gardner
- Department of Psychology, University of Illinois at Urbana-Champaign , Champaign, Illinois
| | | | - Nu-Chu Liang
- Department of Psychology, University of Illinois at Urbana-Champaign , Champaign, Illinois.,Neuroscience Program, University of Illinois at Urbana-Champaign , Urbana, Illinois.,Division of Nutritional Sciences, University of Illinois at Urbana-Champaign , Urbana, Illinois
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Shi X, Chacko S, Li F, Li D, Burrin D, Chan L, Guan X. Acute activation of GLP-1-expressing neurons promotes glucose homeostasis and insulin sensitivity. Mol Metab 2017; 6:1350-1359. [PMID: 29107283 PMCID: PMC5681239 DOI: 10.1016/j.molmet.2017.08.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 08/20/2017] [Accepted: 08/23/2017] [Indexed: 01/10/2023] Open
Abstract
OBJECTIVE Glucagon-like peptides are co-released from enteroendocrine L cells in the gut and preproglucagon (PPG) neurons in the brainstem. PPG-derived GLP-1/2 are probably key neuroendocrine signals for the control of energy balance and glucose homeostasis. The objective of this study was to determine whether activation of PPG neurons per se modulates glucose homeostasis and insulin sensitivity in vivo. METHODS We generated glucagon (Gcg) promoter-driven Cre transgenic mice and injected excitatory hM3Dq-mCherry AAV into their brainstem NTS. We characterized the metabolic impact of PPG neuron activation on glucose homeostasis and insulin sensitivity using stable isotopic tracers coupled with hyperinsulinemic euglycemic clamp. RESULTS We showed that after ip injection of clozapine N-oxide, Gcg-Cre lean mice transduced with hM3Dq in the brainstem NTS downregulated basal endogenous glucose production and enhanced glucose tolerance following ip glucose tolerance test. Moreover, acute activation of PPG neuronsNTS enhanced whole-body insulin sensitivity as indicated by increased glucose infusion rate as well as augmented insulin-suppression of endogenous glucose production and gluconeogenesis. In contrast, insulin-stimulation of glucose disposal was not altered significantly. CONCLUSIONS We conclude that acute activation of PPG neurons in the brainstem reduces basal glucose production, enhances intraperitoneal glucose tolerance, and augments hepatic insulin sensitivity, suggesting an important physiological role of PPG neurons-mediated circuitry in promoting glycemic control and insulin sensitivity.
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Affiliation(s)
- Xuemei Shi
- Department of Respiratory and Critical Care Medicine, Binzhou Medical University Hospital, Binzhou, Shangdong 256603, China; USDA-ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Shaji Chacko
- USDA-ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Feng Li
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Depei Li
- Department of Critical Care, the University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Douglas Burrin
- USDA-ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lawrence Chan
- Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xinfu Guan
- School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang 325000, China; USDA-ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA; Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
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Jessen L, Smith EP, Ulrich-Lai Y, Herman JP, Seeley RJ, Sandoval D, D’Alessio D. Central Nervous System GLP-1 Receptors Regulate Islet Hormone Secretion and Glucose Homeostasis in Male Rats. Endocrinology 2017; 158:2124-2133. [PMID: 28430981 PMCID: PMC5505222 DOI: 10.1210/en.2016-1826] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 04/13/2017] [Indexed: 02/07/2023]
Abstract
The glucagon-like peptide 1 (GLP-1) system plays an important role in blood glucose regulation, in great part through coordinate control of insulin and glucagon secretion. These effects are generally attributed to GLP-1 produced in peripheral sites, principally the intestine. GLP-1 is also produced in hindbrain neurons that signal through GLP-1 receptors (GLP-1rs) expressed in brain regions involved in metabolic regulation. GLP-1 in the central nervous system (CNS) induces satiety, visceral illness, and stress responses. However, recent evidence suggests CNS GLP-1 is also involved in glucose regulation. To test the hypothesis that central GLP-1 regulates islet hormone secretion, conscious rats were given intracerebroventricular (ICV) GLP-1, GLP-1r antagonist exendin-[9-39] (Ex-9), or saline during fasting or hyperglycemia from intravenous glucose. Administration of CNS GLP-1 increased fasting glucose, glucagon, corticosterone, and epinephrine and blunted insulin secretion in response to hyperglycemia. Paradoxically, GLP-1r blockade with ICV Ex-9 also reduced glucose-stimulated insulin secretion, and administration of ICV Ex-9 to freely feeding rats caused mild glucose intolerance. Thus, direct administration of CNS GLP-1 affected islet hormone secretion counter to what is seen with peripherally administered GLP-1, an effect likely due to stimulation of sympathetic nervous system activity. In contrast, blockade of brain GLP-1r supports a role for CNS GLP-1 on glucose-stimulated insulin secretion and glucose control after a meal. These findings suggest a model in which activation of CNS GLP-1r by endogenous peptide promotes glucose tolerance, an effect that can be overridden by stress responses stimulated by exogenous GLP-1.
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Affiliation(s)
- Lene Jessen
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45219
| | - Eric P. Smith
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45219
| | - Yvonne Ulrich-Lai
- Department of Psychiatry and Behavioral Neursocience, University of Cincinnati, Cincinnati, Ohio 45219
| | - James P. Herman
- Department of Psychiatry and Behavioral Neursocience, University of Cincinnati, Cincinnati, Ohio 45219
| | - Randy J. Seeley
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45219
| | - Darleen Sandoval
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45219
| | - David D’Alessio
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45219
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Schmitz J, Evers N, Awazawa M, Nicholls HT, Brönneke HS, Dietrich A, Mauer J, Blüher M, Brüning JC. Obesogenic memory can confer long-term increases in adipose tissue but not liver inflammation and insulin resistance after weight loss. Mol Metab 2016; 5:328-339. [PMID: 27110485 PMCID: PMC4837291 DOI: 10.1016/j.molmet.2015.12.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 12/11/2015] [Accepted: 12/16/2015] [Indexed: 12/11/2022] Open
Abstract
Objective Obesity represents a major risk factor for the development of type 2 diabetes mellitus, atherosclerosis and certain cancer entities. Treatment of obesity is hindered by the long-term maintenance of initially reduced body weight, and it remains unclear whether all pathologies associated with obesity are fully reversible even upon successfully maintained weight loss. Methods We compared high fat diet-fed, weight reduced and lean mice in terms of body weight development, adipose tissue and liver insulin sensitivity as well as inflammatory gene expression. Moreover, we assessed similar parameters in a human cohort before and after bariatric surgery. Results Compared to lean animals, mice that demonstrated successful weight reduction showed increased weight gain following exposure to ad libitum control diet. However, pair-feeding weight-reduced mice with lean controls efficiently stabilized body weight, indicating that hyperphagia was the predominant cause for the observed weight regain. Additionally, whereas glucose tolerance improved rapidly after weight loss, systemic insulin resistance was retained and ameliorated only upon prolonged pair-feeding. Weight loss enhanced insulin action and resolved pro-inflammatory gene expression exclusively in the liver, whereas visceral adipose tissue displayed no significant improvement of metabolic and inflammatory parameters compared to obese mice. Similarly, bariatric surgery in humans (n = 55) resulted in massive weight reduction, improved hepatic inflammation and systemic glucose homeostasis, while adipose tissue inflammation remained unaffected and adipocyte-autonomous insulin action only exhibit minor improvements in a subgroup of patients (42%). Conclusions These results demonstrate that although sustained weight loss improves systemic glucose homeostasis, primarily through improved inflammation and insulin action in liver, a remarkable obesogenic memory can confer long-term increases in adipose tissue inflammation and insulin resistance in mice as well as in a significant subpopulation of obese patients. Upon weight loss in mice liver insulin sensitivity rapidly improves. Upon weight loss in mice fat retains metabolic inflammation and insulin resistance. Weight gain upon successful weight reduction in mice is driven by increased food intake. A proportion of human subjects undergoing bariatric surgery retain AT-inflammation.
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Affiliation(s)
- J Schmitz
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany
| | - N Evers
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany
| | - M Awazawa
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany
| | - H T Nicholls
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany
| | - H S Brönneke
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany
| | - A Dietrich
- Department of Surgery, University of Leipzig, Leipzig, Germany
| | - J Mauer
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany
| | - M Blüher
- Department of Medicine, University of Leipzig, Leipzig, Germany
| | - J C Brüning
- Max Planck Institute for Metabolism Research, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Gleueler Str. 50, D-50931 Cologne, Germany.
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