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Filippi BM, Abraham MA, Silva PN, Rasti M, LaPierre MP, Bauer PV, Rocheleau JV, Lam TK. Dynamin-Related Protein 1-Dependent Mitochondrial Fission Changes in the Dorsal Vagal Complex Regulate Insulin Action. Cell Rep 2017; 18:2301-2309. [DOI: 10.1016/j.celrep.2017.02.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 01/26/2017] [Accepted: 02/11/2017] [Indexed: 11/25/2022] Open
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Yue JTY, Abraham MA, Bauer PV, LaPierre MP, Wang P, Duca FA, Filippi BM, Chan O, Lam TKT. Inhibition of glycine transporter-1 in the dorsal vagal complex improves metabolic homeostasis in diabetes and obesity. Nat Commun 2016; 7:13501. [PMID: 27874011 PMCID: PMC5121412 DOI: 10.1038/ncomms13501] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 10/10/2016] [Indexed: 12/14/2022] Open
Abstract
Impaired glucose homeostasis and energy balance are integral to the pathophysiology of diabetes and obesity. Here we show that administration of a glycine transporter 1 (GlyT1) inhibitor, or molecular GlyT1 knockdown, in the dorsal vagal complex (DVC) suppresses glucose production, increases glucose tolerance and reduces food intake and body weight gain in healthy, obese and diabetic rats. These findings provide proof of concept that GlyT1 inhibition in the brain improves glucose and energy homeostasis. Considering the clinical safety and efficacy of GlyT1 inhibitors in raising glycine levels in clinical trials for schizophrenia, we propose that GlyT1 inhibitors have the potential to be repurposed as a treatment of both obesity and diabetes.
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Affiliation(s)
- Jessica T Y Yue
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7
| | - Mona A Abraham
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7.,Departments of Physiology, Toronto, Ontario, Canada M5S 1A8
| | - Paige V Bauer
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7.,Departments of Physiology, Toronto, Ontario, Canada M5S 1A8
| | - Mary P LaPierre
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7.,Departments of Physiology, Toronto, Ontario, Canada M5S 1A8
| | - Peili Wang
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | - Frank A Duca
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7
| | - Beatrice M Filippi
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7
| | - Owen Chan
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | - Tony K T Lam
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, Ontario, Canada M5G 1L7.,Departments of Physiology, Toronto, Ontario, Canada M5S 1A8.,Departments of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada M5G 2C4
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53
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Esterson YB, Carey M, Boucai L, Goyal A, Raghavan P, Zhang K, Mehta D, Feng D, Wu L, Kehlenbrink S, Koppaka S, Kishore P, Hawkins M. Central Regulation of Glucose Production May Be Impaired in Type 2 Diabetes. Diabetes 2016; 65:2569-79. [PMID: 27207526 PMCID: PMC5001178 DOI: 10.2337/db15-1465] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 04/19/2016] [Indexed: 12/21/2022]
Abstract
The challenges of achieving optimal glycemic control in type 2 diabetes highlight the need for new therapies. Inappropriately elevated endogenous glucose production (EGP) is the main source of hyperglycemia in type 2 diabetes. Because activation of central ATP-sensitive potassium (KATP) channels suppresses EGP in nondiabetic rodents and humans, this study examined whether type 2 diabetic humans and rodents retain central regulation of EGP. The KATP channel activator diazoxide was administered in a randomized, placebo-controlled crossover design to eight type 2 diabetic subjects and seven age- and BMI-matched healthy control subjects. Comprehensive measures of glucose turnover and insulin sensitivity were performed during euglycemic pancreatic clamp studies following diazoxide and placebo administration. Complementary rodent clamp studies were performed in Zucker Diabetic Fatty rats. In type 2 diabetic subjects, extrapancreatic KATP channel activation with diazoxide under fixed hormonal conditions failed to suppress EGP, whereas matched control subjects demonstrated a 27% reduction in EGP (P = 0.002) with diazoxide. Diazoxide also failed to suppress EGP in diabetic rats. These results suggest that suppression of EGP by central KATP channel activation may be lost in type 2 diabetes. Restoration of central regulation of glucose metabolism could be a promising therapeutic target to reduce hyperglycemia in type 2 diabetes.
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Affiliation(s)
- Yonah B Esterson
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Michelle Carey
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Laura Boucai
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Akankasha Goyal
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Pooja Raghavan
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Kehao Zhang
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Deeksha Mehta
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Daorong Feng
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Licheng Wu
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Sylvia Kehlenbrink
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Sudha Koppaka
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Preeti Kishore
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Meredith Hawkins
- Diabetes Research and Training Center and Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
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Kullmann S, Heni M, Hallschmid M, Fritsche A, Preissl H, Häring HU. Brain Insulin Resistance at the Crossroads of Metabolic and Cognitive Disorders in Humans. Physiol Rev 2016; 96:1169-209. [PMID: 27489306 DOI: 10.1152/physrev.00032.2015] [Citation(s) in RCA: 341] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ever since the brain was identified as an insulin-sensitive organ, evidence has rapidly accumulated that insulin action in the brain produces multiple behavioral and metabolic effects, influencing eating behavior, peripheral metabolism, and cognition. Disturbances in brain insulin action can be observed in obesity and type 2 diabetes (T2D), as well as in aging and dementia. Decreases in insulin sensitivity of central nervous pathways, i.e., brain insulin resistance, may therefore constitute a joint pathological feature of metabolic and cognitive dysfunctions. Modern neuroimaging methods have provided new means of probing brain insulin action, revealing the influence of insulin on both global and regional brain function. In this review, we highlight recent findings on brain insulin action in humans and its impact on metabolism and cognition. Furthermore, we elaborate on the most prominent factors associated with brain insulin resistance, i.e., obesity, T2D, genes, maternal metabolism, normal aging, inflammation, and dementia, and on their roles regarding causes and consequences of brain insulin resistance. We also describe the beneficial effects of enhanced brain insulin signaling on human eating behavior and cognition and discuss potential applications in the treatment of metabolic and cognitive disorders.
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Affiliation(s)
- Stephanie Kullmann
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; German Center for Diabetes Research (DZD e.V.), Tübingen, Germany; Department of Internal Medicine IV, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; and Department of Pharmacy and Biochemistry, Faculty of Science, Eberhard Karls Universität Tübingen, Tübingen, Germany
| | - Martin Heni
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; German Center for Diabetes Research (DZD e.V.), Tübingen, Germany; Department of Internal Medicine IV, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; and Department of Pharmacy and Biochemistry, Faculty of Science, Eberhard Karls Universität Tübingen, Tübingen, Germany
| | - Manfred Hallschmid
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; German Center for Diabetes Research (DZD e.V.), Tübingen, Germany; Department of Internal Medicine IV, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; and Department of Pharmacy and Biochemistry, Faculty of Science, Eberhard Karls Universität Tübingen, Tübingen, Germany
| | - Andreas Fritsche
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; German Center for Diabetes Research (DZD e.V.), Tübingen, Germany; Department of Internal Medicine IV, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; and Department of Pharmacy and Biochemistry, Faculty of Science, Eberhard Karls Universität Tübingen, Tübingen, Germany
| | - Hubert Preissl
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; German Center for Diabetes Research (DZD e.V.), Tübingen, Germany; Department of Internal Medicine IV, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; and Department of Pharmacy and Biochemistry, Faculty of Science, Eberhard Karls Universität Tübingen, Tübingen, Germany
| | - Hans-Ulrich Häring
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; German Center for Diabetes Research (DZD e.V.), Tübingen, Germany; Department of Internal Medicine IV, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; and Department of Pharmacy and Biochemistry, Faculty of Science, Eberhard Karls Universität Tübingen, Tübingen, Germany
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Abstract
In recent years, novel discoveries have reshaped our understanding of the biology of brain glucagon in the regulation of peripheral homeostasis. Here we compare and contrast brain glucagon action in feeding vs glucose regulation and depict the physiological relevance of brain glucagon by reviewing their actions in two key regions of the central nervous system: the mediobasal hypothalamus and the dorsal vagal complex. These novel findings pave the way to future therapeutic strategies aimed at enhancing brain glucagon action for the treatment of diabetes and obesity. This review summarises a presentation given at the 'Novel data on glucagon' symposium at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Young Lee and colleagues, DOI: 10.1007/s00125-016-3965-9 ), and by Russell Miller and Morris Birnbaum, DOI: 10.1007/s00125-016-3955-y ) and an overview by the Session Chair, Isabel Valverde (DOI: 10.1007/s00125-016-3946-z ).
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Affiliation(s)
- Mona A Abraham
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, ON, M5G 1L7, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Tony K T Lam
- Toronto General Hospital Research Institute and Department of Medicine, UHN, Toronto, ON, M5G 1L7, Canada.
- Department of Physiology, University of Toronto, Toronto, ON, Canada.
- Department of Medicine, University of Toronto, Toronto, ON, Canada.
- Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, Canada.
- MaRS Centre, 101 College Street, Toronto Medical Discovery Tower, 10th floor-Room 705, Toronto, ON, M5G 1L7, Canada.
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56
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Abstract
Insulin controls hepatic glucose production (HGP) and maintains glucose homeostasis through the direct action of hepatic insulin receptors, as well as the indirect action of insulin receptors in the central nervous system. Insulin acts on insulin receptors in the hypothalamic arcuate nucleus, activates ATP-sensitive potassium channels in a phosphoinositide 3-kinase (PI3K)-dependent manner, induces hyperpolarization of the hypothalamic neurons, and regulates HGP via the vagus nerve. In the liver, central insulin action augments IL-6 expression in Kupffer cells and activates STAT3 transcription factors in hepatocytes. Activated STAT3 suppresses the gene expression of gluconeogenic enzymes, thereby reducing HGP. It has become evident that nutrients such as glucose, fatty acids, and amino acids act upon the hypothalamus together with insulin, affecting HGP. On the other hand, HGP control by central insulin action is impeded in obesity and impeded by insulin resistance due to disturbance of PI3K signaling and inflammation in the hypothalamus or inhibition of STAT3 signaling in the liver. Although the mechanism of control of hepatic gluconeogenic gene expression by central insulin action is conserved across species, its importance in human glucose metabolism has not been made entirely clear and its elucidation is anticipated in the future.
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Affiliation(s)
- Hiroshi Inoue
- Metabolism and Nutrition Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa 920-8641, Japan
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57
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Xu S, Kim JH, Hwang KH, Das R, Quan X, Nguyen TT, Kim SJ, Cha SK, Park KS. Autocrine insulin increases plasma membrane KATP channel via PI3K-VAMP2 pathway in MIN6 cells. Biochem Biophys Res Commun 2015; 468:752-7. [DOI: 10.1016/j.bbrc.2015.11.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 11/04/2015] [Indexed: 11/24/2022]
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Heni M, Kullmann S, Preissl H, Fritsche A, Häring HU. Impaired insulin action in the human brain: causes and metabolic consequences. Nat Rev Endocrinol 2015; 11:701-11. [PMID: 26460339 DOI: 10.1038/nrendo.2015.173] [Citation(s) in RCA: 178] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Over the past few years, evidence has accumulated that the human brain is an insulin-sensitive organ. Insulin regulates activity in a limited number of specific brain areas that are important for memory, reward, eating behaviour and the regulation of whole-body metabolism. Accordingly, insulin in the brain modulates cognition, food intake and body weight as well as whole-body glucose, energy and lipid metabolism. However, brain imaging studies have revealed that not everybody responds equally to insulin and that a substantial number of people are brain insulin resistant. In this Review, we provide an overview of the effects of insulin in the brain in humans and the relevance of the effects for physiology. We present emerging evidence for insulin resistance of the human brain. Factors associated with brain insulin resistance such as obesity and increasing age, as well as possible pathogenic factors such as visceral fat, saturated fatty acids, alterations at the blood-brain barrier and certain genetic polymorphisms, are reviewed. In particular, the metabolic consequences of brain insulin resistance are discussed and possible future approaches to overcome brain insulin resistance and thereby prevent or treat obesity and type 2 diabetes mellitus are outlined.
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Affiliation(s)
- Martin Heni
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University, Partners in the German Centre for Diabetes Research (DZD), Otfried-Müller-Street 10, 72076 Tübingen, Germany
| | - Stephanie Kullmann
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich at the University of Tübingen, Partners in the German Centre for Diabetes Research (DZD), Otfried-Müller-Street 10, 72076 Tübingen, Germany
| | - Hubert Preissl
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich at the University of Tübingen, Partners in the German Centre for Diabetes Research (DZD), Otfried-Müller-Street 10, 72076 Tübingen, Germany
| | - Andreas Fritsche
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University, Partners in the German Centre for Diabetes Research (DZD), Otfried-Müller-Street 10, 72076 Tübingen, Germany
| | - Hans-Ulrich Häring
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University, Partners in the German Centre for Diabetes Research (DZD), Otfried-Müller-Street 10, 72076 Tübingen, Germany
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59
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LaPierre MP, Abraham MA, Yue JTY, Filippi BM, Lam TKT. Glucagon signalling in the dorsal vagal complex is sufficient and necessary for high-protein feeding to regulate glucose homeostasis in vivo. EMBO Rep 2015; 16:1299-307. [PMID: 26290496 DOI: 10.15252/embr.201540492] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 07/23/2015] [Indexed: 11/09/2022] Open
Abstract
High-protein feeding acutely lowers postprandial glucose concentration compared to low-protein feeding, despite a dichotomous rise of circulating glucagon levels. The physiological role of this glucagon rise has been largely overlooked. We here first report that glucagon signalling in the dorsal vagal complex (DVC) of the brain is sufficient to lower glucose production by activating a Gcgr-PKA-ERK-KATP channel signalling cascade in the DVC of rats in vivo. We further demonstrate that direct blockade of DVC Gcgr signalling negates the acute ability of high- vs. low-protein feeding to reduce plasma glucose concentration, indicating that the elevated circulating glucagon during high-protein feeding acts in the brain to lower plasma glucose levels. These data revise the physiological role of glucagon and argue that brain glucagon signalling contributes to glucose homeostasis during dietary protein intake.
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Affiliation(s)
- Mary P LaPierre
- Toronto General Research Institute & Department of Medicine UHN, Toronto, Canada Department of Physiology, University of Toronto, Toronto Canada
| | - Mona A Abraham
- Toronto General Research Institute & Department of Medicine UHN, Toronto, Canada Department of Physiology, University of Toronto, Toronto Canada
| | - Jessica T Y Yue
- Toronto General Research Institute & Department of Medicine UHN, Toronto, Canada
| | - Beatrice M Filippi
- Toronto General Research Institute & Department of Medicine UHN, Toronto, Canada
| | - Tony K T Lam
- Toronto General Research Institute & Department of Medicine UHN, Toronto, Canada Department of Physiology, University of Toronto, Toronto Canada Department of Medicine, University of Toronto, Toronto Canada Banting and Best Diabetes Centre, University of Toronto, Toronto, Canada
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Dash S, Xiao C, Morgantini C, Koulajian K, Lewis GF. Is Insulin Action in the Brain Relevant in Regulating Blood Glucose in Humans? J Clin Endocrinol Metab 2015; 100:2525-31. [PMID: 26020765 DOI: 10.1210/jc.2015-1371] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
PURPOSE In addition to its direct action on the liver to lower hepatic glucose production, insulin action in the central nervous system (CNS) also lowers hepatic glucose production in rodents after 4 hours. Although CNS insulin action (CNSIA) modulates hepatic glycogen synthesis in dogs, it has no net effect on hepatic glucose output over a 4-hour period. The role of CNSIA in regulating plasma glucose has recently been examined in humans and is the focus of this review. METHODS AND RESULTS Intransal insulin (INI) administration increases CNS insulin concentration. Hence, INI can address whether CNSIA regulates plasma glucose concentration in humans. We and three other groups have sought to answer this question, with differing conclusions. Here we will review the critical aspects of each study, including its design, which may explain these discordant conclusions. CONCLUSIONS The early glucose-lowering effect of INI is likely due to spillover of insulin into the systemic circulation. In the presence of simultaneous portal and CNS hyperinsulinemia, portal insulin action is dominant. INI administration does lower plasma glucose independent of peripheral insulin concentration (between ∼3 and 6 h after administration), suggesting that CNSIA may play a role in glucose homeostasis in the late postprandial period when its action is likely greatest and portal insulin concentration is at baseline. The potential physiological role and purpose of this pathway are discussed in this review. Because the effects of INI are attenuated in patients with type 2 diabetes and obesity, this is unlikely to be of therapeutic utility.
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Affiliation(s)
- Satya Dash
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, ON M5G 2C4, Canada
| | - Changting Xiao
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, ON M5G 2C4, Canada
| | - Cecilia Morgantini
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, ON M5G 2C4, Canada
| | - Khajag Koulajian
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, ON M5G 2C4, Canada
| | - Gary F Lewis
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, ON M5G 2C4, Canada
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Ribeiro IMR, Ferreira-Neto HC, Antunes VR. Subdiaphragmatic vagus nerve activity and hepatic venous glucose are differentially regulated by the central actions of insulin in Wistar and SHR. Physiol Rep 2015; 3:3/5/e12381. [PMID: 25948821 PMCID: PMC4463817 DOI: 10.14814/phy2.12381] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Glucose is the most important energy substrate for the maintenance of tissues function. The liver plays an essential role in the control of glucose production, since it is able to synthesize, store, and release glucose into the circulation under different situations. Hormones like insulin and catecholamines influence hepatic glucose production (HGP), but little is known about the role of the central actions of physiological doses of insulin in modulating HGP via the autonomic nervous system in nonanesthetized rats especially in SHR where we see a high degree of insulin resistance and metabolic dysfunction. Wistar and SHR received ICV injection of insulin (100 nU/μL) and hepatic venous glucose concentration (HVGC) was monitored for 30 min, as an indirect measure of HGP. At 10 min after insulin injection, HVGC decreased by 27% in Wistar rats, with a negligible change (3%) in SHR. Pretreatment with atropine totally blocked the reduction in HVGC, while pretreatment with propranolol and phentolamine induced a decrease of 8% in HVGC after ICV insulin injection in Wistar. Intracarotid infusion of insulin caused a significant increase in subdiaphragmatic vagus nerve (SVN) activity in Wistar (12 ± 2%), with negligible effects on the lumbar splanchnic sympathetic nerve (LSSN) activity (−6 ± 3%). No change was observed in SVN (−2 ± 2%) and LSSN activities (2 ± 3%) in SHR after ICA insulin infusion. Taken together, these results show, in nonanesthetized animals, the importance of the parasympathetic nervous system in controlling HVGC, and subdiaphragmatic nerve activity following central administration of insulin; a mechanism that is impaired in the SHR.
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Affiliation(s)
- Izabela Martina R Ribeiro
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo (USP), Sao Paulo, Brazil
| | - Hildebrando C Ferreira-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo (USP), Sao Paulo, Brazil
| | - Vagner R Antunes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo (USP), Sao Paulo, Brazil
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Leiria LOS, Arantes-Costa FM, Calixto MC, Alexandre EC, Moura RF, Folli F, Prado CM, Prado MA, Prado VF, Velloso LA, Donato J, Antunes E, Martins MA, Saad MJA. Increased airway reactivity and hyperinsulinemia in obese mice are linked by ERK signaling in brain stem cholinergic neurons. Cell Rep 2015; 11:934-943. [PMID: 25937275 DOI: 10.1016/j.celrep.2015.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Revised: 01/01/2015] [Accepted: 04/03/2015] [Indexed: 01/09/2023] Open
Abstract
Obesity is a major risk factor for asthma, which is characterized by airway hyperreactivity (AHR). In obesity-associated asthma, AHR may be regulated by non-TH2 mechanisms. We hypothesized that airway reactivity is regulated by insulin in the CNS, and that the high levels of insulin associated with obesity contribute to AHR. We found that intracerebroventricular (ICV)-injected insulin increases airway reactivity in wild-type, but not in vesicle acetylcholine transporter knockdown (VAChT KD(HOM-/-)), mice. Either neutralization of central insulin or inhibition of extracellular signal-regulated kinases (ERK) normalized airway reactivity in hyperinsulinemic obese mice. These effects were mediated by insulin in cholinergic nerves located at the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (NA), which convey parasympathetic outflow to the lungs. We propose that increased insulin-induced activation of ERK in parasympathetic pre-ganglionic nerves contributes to AHR in obese mice, suggesting a drug-treatable link between obesity and asthma.
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Affiliation(s)
- Luiz O S Leiria
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil
| | - Fernanda M Arantes-Costa
- Department of Medicine, School of Medicine, University of São Paulo, São Paulo, SP 01246-904, Brazil
| | - Marina C Calixto
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-881, Brazil
| | - Eduardo C Alexandre
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-881, Brazil
| | - Rodrigo F Moura
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil
| | - Franco Folli
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil; Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, TX 78229-3900, USA
| | - Carla M Prado
- Department of Biological Science, Federal University of São Paulo, Diadema, SP 09972-270, Brazil
| | - Marco Antonio Prado
- Robarts Research Institute, Department of Anatomy & Cell Biology and Department of Physiology and Pharmacology, University of Western Ontario, London, ON 5015, Canada
| | - Vania F Prado
- Robarts Research Institute, Department of Anatomy & Cell Biology and Department of Physiology and Pharmacology, University of Western Ontario, London, ON 5015, Canada
| | - Licio A Velloso
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil
| | - José Donato
- Department of Physiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil
| | - Edson Antunes
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-881, Brazil
| | - Milton A Martins
- Department of Medicine, School of Medicine, University of São Paulo, São Paulo, SP 01246-904, Brazil
| | - Mario J A Saad
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP 13083-887, Brazil; Obesity and Comorbidities Research Center (O.C.R.C.), State University of Campinas, Campinas, SP 13083-887, Brazil.
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Côté CD, Rasmussen BA, Duca FA, Zadeh-Tahmasebi M, Baur JA, Daljeet M, Breen DM, Filippi BM, Lam TKT. Resveratrol activates duodenal Sirt1 to reverse insulin resistance in rats through a neuronal network. Nat Med 2015; 21:498-505. [PMID: 25849131 DOI: 10.1038/nm.3821] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Accepted: 02/06/2015] [Indexed: 12/12/2022]
Abstract
Resveratrol improves insulin sensitivity and lowers hepatic glucose production (HGP) in rat models of obesity and diabetes, but the underlying mechanisms for these antidiabetic effects remain elusive. One process that is considered a key feature of resveratrol action is the activation of the nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase sirtuin 1 (SIRT1) in various tissues. However, the low bioavailability of resveratrol raises questions about whether the antidiabetic effects of oral resveratrol can act directly on these tissues. We show here that acute intraduodenal infusion of resveratrol reversed a 3 d high fat diet (HFD)-induced reduction in duodenal-mucosal Sirt1 protein levels while also enhancing insulin sensitivity and lowering HGP. Further, we found that duodenum-specific knockdown of Sirt1 expression for 14 d was sufficient to induce hepatic insulin resistance in rats fed normal chow. We also found that the glucoregulatory role of duodenally acting resveratrol required activation of Sirt1 and AMP-activated protein kinase (Ampk) in this tissue to initiate a gut-brain-liver neuronal axis that improved hypothalamic insulin sensitivity and in turn, reduced HGP. In addition to the effects of duodenally acting resveratrol in an acute 3 d HFD-fed model of insulin resistance, we also found that short-term infusion of resveratrol into the duodenum lowered HGP in two other rat models of insulin resistance--a 28 d HFD-induced model of obesity and a nicotinamide (NA)-streptozotocin (STZ)-HFD-induced model of mild type 2 diabetes. Together, these studies highlight the therapeutic relevance of targeting duodenal SIRT1 to reverse insulin resistance and improve glucose homeostasis in obesity and diabetes.
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Affiliation(s)
- Clémence D Côté
- 1] Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada. [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Brittany A Rasmussen
- 1] Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada. [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Frank A Duca
- Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada
| | - Melika Zadeh-Tahmasebi
- 1] Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada. [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Joseph A Baur
- Department of Physiology, Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Mira Daljeet
- Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada
| | - Danna M Breen
- Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada
| | - Beatrice M Filippi
- Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada
| | - Tony K T Lam
- 1] Toronto General Research Institute and Department of Medicine, University Health Network, Toronto, Ontario, Canada. [2] Department of Physiology, University of Toronto, Toronto, Ontario, Canada. [3] Department of Medicine, University of Toronto, Toronto, Ontario, Canada. [4] Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
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64
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Metformin activates a duodenal Ampk-dependent pathway to lower hepatic glucose production in rats. Nat Med 2015; 21:506-11. [PMID: 25849133 DOI: 10.1038/nm.3787] [Citation(s) in RCA: 298] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Accepted: 12/12/2014] [Indexed: 12/17/2022]
Abstract
Metformin is a first-line therapeutic option for the treatment of type 2 diabetes, even though its underlying mechanisms of action are relatively unclear. Metformin lowers blood glucose levels by inhibiting hepatic glucose production (HGP), an effect originally postulated to be due to a hepatic AMP-activated protein kinase (AMPK)-dependent mechanism. However, studies have questioned the contribution of hepatic AMPK to the effects of metformin on lowering hyperglycemia, and a gut-brain-liver axis that mediates intestinal nutrient- and hormone-induced lowering of HGP has been identified. Thus, it is possible that metformin affects HGP through this inter-organ crosstalk. Here we show that intraduodenal infusion of metformin for 50 min activated duodenal mucosal Ampk and lowered HGP in a rat 3 d high fat diet (HFD)-induced model of insulin resistance. Inhibition of duodenal Ampk negated the HGP-lowering effect of intraduodenal metformin, and both duodenal glucagon-like peptide-1 receptor (Glp-1r)-protein kinase A (Pka) signaling and a neuronal-mediated gut-brain-liver pathway were required for metformin to lower HGP. Preabsorptive metformin also lowered HGP in rat models of 28 d HFD-induced obesity and insulin resistance and nicotinamide (NA)-streptozotocin (STZ)-HFD-induced type 2 diabetes. In an unclamped setting, inhibition of duodenal Ampk reduced the glucose-lowering effects of a bolus metformin treatment in rat models of diabetes. These findings show that, in rat models of both obesity and diabetes, metformin activates a previously unappreciated duodenal Ampk-dependent pathway to lower HGP and plasma glucose levels.
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65
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Dash S, Xiao C, Morgantini C, Koulajian K, Lewis GF. Intranasal insulin suppresses endogenous glucose production in humans compared with placebo in the presence of similar venous insulin concentrations. Diabetes 2015; 64:766-74. [PMID: 25288674 DOI: 10.2337/db14-0685] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Intranasal insulin (INI) has been shown to modulate food intake and food-related activity in the central nervous system in humans. Because INI increases insulin concentration in the cerebrospinal fluid, these effects have been postulated to be mediated via insulin action in the brain, although peripheral effects of insulin cannot be excluded. INI has been shown to lower plasma glucose in some studies, but whether it regulates endogenous glucose production (EGP) is not known. To assess the role of INI in the regulation of EGP, eight healthy men were studied in a single-blind, crossover study with two randomized visits (one with 40 IU INI and the other with intranasal placebo [INP] administration) 4 weeks apart. EGP was assessed under conditions of an arterial pancreatic clamp, with a primed, constant infusion of deuterated glucose and infusion of 20% dextrose as required to maintain euglycemia. Between 180 and 360 min after administration, INI significantly suppressed EGP by 35.6% compared with INP, despite similar venous insulin concentrations. In conclusion, INI lowers EGP in humans compared with INP, despite similar venous insulin concentrations. INI may therefore be of value in treating excess liver glucose production in diabetes.
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Affiliation(s)
- Satya Dash
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Changting Xiao
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Cecilia Morgantini
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Khajag Koulajian
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Gary F Lewis
- Departments of Medicine and Physiology and the Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada, and Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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66
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Affiliation(s)
- Dale S Edgerton
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Alan D Cherrington
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
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67
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Leiria LOS, Martins MA, Saad MJA. Obesity and asthma: beyond T(H)2 inflammation. Metabolism 2015; 64:172-81. [PMID: 25458831 DOI: 10.1016/j.metabol.2014.10.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 10/01/2014] [Accepted: 10/03/2014] [Indexed: 12/20/2022]
Abstract
Obesity is a major risk factor for asthma. Likewise, obesity is known to increase disease severity in asthmatic subjects and also to impair the efficacy of first-line treatment medications for asthma, worsening asthma control in obese patients. This concept is in agreement with the current understanding that some asthma phenotypes are not accompanied by detectable inflammation, and may not be ameliorated by classical anti-inflammatory therapy. There are growing evidences suggesting that the obesity-related asthma phenotype does not necessarily involve the classical T(H)2-dependent inflammatory process. Hormones involved in glucose homeostasis and in the pathogeneses of obesity likely directly or indirectly link obesity and asthma through inflammatory and non-inflammatory pathways. Furthermore, the endocrine regulation of the airway-related pre-ganglionic nerves likely contributes to airway hyperreactivity (AHR) in obese states. In this review, we focused our efforts on understanding the mechanism underlying obesity-related asthma by exploring the T(H)2-independent mechanisms leading to this disease.
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Affiliation(s)
- Luiz O S Leiria
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP, Brazil
| | - Milton A Martins
- Department of Medicine, School of Medicine, University de São Paulo, São Paulo, SP, Brazil
| | - Mário J A Saad
- Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas, Campinas, SP, Brazil.
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68
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Yue JTY, Abraham MA, LaPierre MP, Mighiu PI, Light PE, Filippi BM, Lam TKT. A fatty acid-dependent hypothalamic–DVC neurocircuitry that regulates hepatic secretion of triglyceride-rich lipoproteins. Nat Commun 2015; 6:5970. [DOI: 10.1038/ncomms6970] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 11/26/2014] [Indexed: 12/31/2022] Open
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69
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Scarlett JM, Schwartz MW. Gut-brain mechanisms controlling glucose homeostasis. F1000PRIME REPORTS 2015; 7:12. [PMID: 25705395 PMCID: PMC4311273 DOI: 10.12703/p7-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Our current understanding of glucose homeostasis is centered on glucose-induced secretion of insulin from pancreatic islets and insulin action on glucose metabolism in peripheral tissues. In addition, however, recent evidence suggests that neurocircuits located within a brain-centered glucoregulatory system work cooperatively with pancreatic islets to promote glucose homeostasis. Among key observations is evidence that, in addition to insulin-dependent mechanisms, the brain has the capacity to potently lower blood glucose levels via mechanisms that are insulin-independent, some of which are activated by signals emanating from the gastrointestinal tract. This review highlights evidence supporting a key role for a “gut-brain-liver axis” in control of glucose homeostasis by the brain-centered glucoregulatory system and the implications of this regulatory system for diabetes pathogenesis and treatment.
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Affiliation(s)
- Jarrad M. Scarlett
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington at South Lake Union850 Republican Street, N335, Box 358055, Seattle, WA 98195USA
- Department of Pediatric Gastroenterology and Hepatology, Seattle Children's HospitalOB.9.620.1, P.O. Box 5371, Seattle, WA 98105USA
| | - Michael W. Schwartz
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington at South Lake Union850 Republican Street, N335, Box 358055, Seattle, WA 98195USA
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70
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Heni M, Wagner R, Kullmann S, Veit R, Mat Husin H, Linder K, Benkendorff C, Peter A, Stefan N, Häring HU, Preissl H, Fritsche A. Central insulin administration improves whole-body insulin sensitivity via hypothalamus and parasympathetic outputs in men. Diabetes 2014; 63:4083-8. [PMID: 25028522 DOI: 10.2337/db14-0477] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Animal studies suggest that insulin action in the brain is involved in the regulation of peripheral insulin sensitivity. Whether this holds true in humans is unknown. Using intranasal application of insulin to the human brain, we studied the impacts of brain insulin action on whole-body insulin sensitivity and the mechanisms involved in this process. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic glucose clamp before and after intranasal application of insulin and placebo in randomized order in lean and obese men. After insulin spray application in lean subjects, a higher glucose infusion rate was necessary to maintain euglycemia compared with placebo. Accordingly, clamp-derived insulin sensitivity index improved after insulin spray. In obese subjects, this insulin-sensitizing effect could not be detected. Change in the high-frequency band of heart rate variability, an estimate of parasympathetic output, correlated positively with change in whole-body insulin sensitivity after intranasal insulin. Improvement in whole-body insulin sensitivity correlated with the change in hypothalamic activity as assessed by functional magnetic resonance imaging. Intranasal insulin improves peripheral insulin sensitivity in lean but not in obese men. Furthermore, brain-derived peripheral insulin sensitization is associated with hypothalamic activity and parasympathetic outputs. Thus, the findings provide novel insights into the regulation of insulin sensitivity and the pathogenesis of insulin resistance in humans.
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Affiliation(s)
- Martin Heni
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Robert Wagner
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Stephanie Kullmann
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Ralf Veit
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Haliza Mat Husin
- Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Katarzyna Linder
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Charlotte Benkendorff
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Andreas Peter
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Norbert Stefan
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Hans-Ulrich Häring
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Hubert Preissl
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Andreas Fritsche
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
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71
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Xiao F, Xia T, Lv Z, Zhang Q, Xiao Y, Yu J, Liu H, Deng J, Guo Y, Wang C, Li K, Liu B, Chen S, Guo F. Central prolactin receptors (PRLRs) regulate hepatic insulin sensitivity in mice via signal transducer and activator of transcription 5 (STAT5) and the vagus nerve. Diabetologia 2014; 57:2136-44. [PMID: 25064125 DOI: 10.1007/s00125-014-3336-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 06/24/2014] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS Recent studies have revealed the crucial role of the central nervous system (CNS), especially the hypothalamus, in the regulation of insulin sensitivity in peripheral tissues. The aim of our current study was to investigate the possible involvement of hypothalamic prolactin receptors (PRLRs) in the regulation of hepatic insulin sensitivity. METHODS We employed overexpression of PRLRs in mouse hypothalamus via intracerebroventricular injection of adenovirus expressing PRLR and inhibition of PRLRs via adenovirus expressing short-hairpin RNA (shRNA) specific for PRLRs in vivo. Selective hepatic vagotomy was employed to verify the important role of the vagus nerve in mediating signals from the brain to peripheral organs. In addition, a genetic insulin-resistant animal model, the db/db mouse, was used in our study to investigate the role of hypothalamic PRLRs in regulating whole-body insulin sensitivity. RESULTS Overexpression of PRLRs in the hypothalamus improved hepatic insulin sensitivity in mice and inhibition of hypothalamic PRLRs had the opposite effect. In addition, we demonstrated that hypothalamic PRLR-improved insulin sensitivity was significantly attenuated by inhibiting the activity of signal transducer and activator of transcription 5 (STAT5) in the CNS and by selective hepatic vagotomy. Finally, overexpression of PRLRs significantly ameliorated insulin resistance in db/db mice. CONCLUSIONS/INTERPRETATION Our study identifies a novel central pathway involved in the regulation of hepatic insulin sensitivity, mediated by hypothalamic PRLR/STAT5 signalling and the vagus nerve, thus demonstrating an important role for hypothalamic PRLRs under conditions of insulin resistance.
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Affiliation(s)
- Fei Xiao
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, People's Republic of China
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72
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Abraham MA, Filippi BM, Kang GM, Kim MS, Lam TKT. Insulin action in the hypothalamus and dorsal vagal complex. Exp Physiol 2014; 99:1104-9. [DOI: 10.1113/expphysiol.2014.079962] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Mona A. Abraham
- Toronto General Research Institute and Department of Medicine; University Health Network; Toronto Ontario Canada
- Department of Physiology; University of Toronto; Toronto Ontario Canada
| | - Beatrice M. Filippi
- Toronto General Research Institute and Department of Medicine; University Health Network; Toronto Ontario Canada
| | - Gil Myoung Kang
- Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - Min-Seon Kim
- Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - Tony K. T. Lam
- Toronto General Research Institute and Department of Medicine; University Health Network; Toronto Ontario Canada
- Department of Physiology; University of Toronto; Toronto Ontario Canada
- Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
- Department of Medicine; University of Toronto; Toronto Ontario Canada
- Banting and Best Diabetes Centre; University of Toronto; Toronto Ontario Canada
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73
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Rojas JM, Schwartz MW. Control of hepatic glucose metabolism by islet and brain. Diabetes Obes Metab 2014; 16 Suppl 1:33-40. [PMID: 25200294 PMCID: PMC4191916 DOI: 10.1111/dom.12332] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 04/18/2014] [Indexed: 12/19/2022]
Abstract
Dysregulation of hepatic glucose uptake (HGU) and inability of insulin to suppress hepatic glucose production (HGP) contribute to hyperglycaemia in patients with type 2 diabetes (T2D). Growing evidence suggests that insulin can inhibit HGP not only through a direct effect on the liver but also through a mechanism involving the brain. Yet, the notion that insulin action in the brain plays a physiological role in the control of HGP continues to be controversial. Although studies in dogs suggest that the direct hepatic effect of insulin is sufficient to explain day-to-day control of HGP, a surprising outcome has been revealed by recent studies in mice, investigating whether the direct hepatic action of insulin is necessary for normal HGP: when the hepatic insulin signalling pathway was genetically disrupted, HGP was maintained normally even in the absence of direct input from insulin. Here, we present evidence that points to a potentially important role of the brain in the physiological control of both HGU and HGP in response to input from insulin as well as other hormones and nutrients.
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Affiliation(s)
- Jennifer M. Rojas
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Michael W. Schwartz
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington, Seattle, Washington, USA
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74
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Blake CB, Smith BN. cAMP-dependent insulin modulation of synaptic inhibition in neurons of the dorsal motor nucleus of the vagus is altered in diabetic mice. Am J Physiol Regul Integr Comp Physiol 2014; 307:R711-20. [PMID: 24990858 DOI: 10.1152/ajpregu.00138.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Pathologies in which insulin is dysregulated, including diabetes, can disrupt central vagal circuitry, leading to gastrointestinal and other autonomic dysfunction. Insulin affects whole body metabolism through central mechanisms and is transported into the brain stem dorsal motor nucleus of the vagus (DMV) and nucleus tractus solitarius (NTS), which mediate parasympathetic visceral regulation. The NTS receives viscerosensory vagal input and projects heavily to the DMV, which supplies parasympathetic vagal motor output. Normally, insulin inhibits synaptic excitation of DMV neurons, with no effect on synaptic inhibition. Modulation of synaptic inhibition in DMV, however, is often sensitive to cAMP-dependent mechanisms. We hypothesized that an effect of insulin on GABAergic synaptic transmission may be uncovered by elevating resting cAMP levels in GABAergic terminals. We used whole cell patch-clamp recordings in brain stem slices from control and diabetic mice to identify insulin effects on inhibitory neurotransmission in the DMV in the presence of forskolin to elevate cAMP levels. In the presence of forskolin, insulin decreased the frequency of inhibitory postsynaptic currents (IPSCs) and the paired-pulse ratio of evoked IPSCs in DMV neurons from control mice. This effect was blocked by brefeldin-A, a Golgi-disrupting agent, or indinavir, a GLUT4 blocker, indicating that protein trafficking and glucose transport were involved. In streptozotocin-treated, diabetic mice, insulin did not affect IPSCs in DMV neurons in the presence of forskolin. Results suggest an impairment of cAMP-induced insulin effects on GABA release in the DMV, which likely involves disrupted protein trafficking in diabetic mice. These findings provide insight into mechanisms underlying vagal dysregulation associated with diabetes.
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Affiliation(s)
- Camille B Blake
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
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75
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Evans MC, Rizwan M, Mayer C, Boehm U, Anderson GM. Evidence that insulin signalling in gonadotrophin-releasing hormone and kisspeptin neurones does not play an essential role in metabolic regulation of fertility in mice. J Neuroendocrinol 2014; 26:468-79. [PMID: 24824308 DOI: 10.1111/jne.12166] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 04/23/2014] [Accepted: 05/08/2014] [Indexed: 12/31/2022]
Abstract
Insulin in the brain plays an important role in regulating reproductive function, as demonstrated via conditional brain-specific insulin receptor (Insr) deletion (knockout). However, the specific neuronal target cells mediating the central effects of insulin on the reproductive axis remain unidentified. We first investigated whether insulin can act via direct effects on gonadotrophin-releasing hormone (GnRH) neurones. After clearly detecting Insr mRNA in an immunopurified GnRH cell fraction, we confirmed the presence of insulin receptor protein (InsR) in approximately 82% of GnRH neurones using dual-label immunohistochemistry. However, we did not observe any insulin-induced phospho-Akt (pAkt) or phospho-extracellular-signal-regulated kinase 1/2 in GnRH neurones, and therefore we investigated whether insulin signals via kisspeptin neurones to modulate GnRH release. Using dual-label immunohistochemistry, InsRs were detected only in approximately 5% of kisspeptin-immunoreactive cells. Insulin-induced pAkt was not observed in any kisspeptin-immunoreactive cells in either the rostral periventricular region of the third ventricle or arcuate nucleus in response to 200 mU of insulin treatment, although a more pharmacological dose (10 U) induced pronounced (> 20%) pAkt-kisspeptin coexpression in both regions. To confirm that insulin signalling via kisspeptin neurones does not critically modulate reproductive function, we generated kisspeptin-specific InsR knockout (KIRKO) mice and assessed multiple reproductive and metabolic parameters. No significant differences in puberty onset, oestrous cyclicity or reproductive competency were observed in the female or male KIRKO mice compared to their control littermates. However, significantly decreased fasting insulin (P < 0.05) and a nonsignificant trend towards reduced body weight were observed in male KIRKO mice. Thus, InsR signalling in kisspeptin cells is not critical for puberty onset or reproductive competency, although it may have a small metabolic effect in males.
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Affiliation(s)
- M C Evans
- Centre for Neuroendocrinology and Department of Anatomy, University of Otago School of Medical Sciences, Dunedin, New Zealand
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76
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LaPierre MP, Abraham MA, Filippi BM, Yue JTY, Lam TKT. Glucagon and lipid signaling in the hypothalamus. Mamm Genome 2014; 25:434-41. [DOI: 10.1007/s00335-014-9510-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 03/25/2014] [Indexed: 12/12/2022]
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77
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Filippi BM, Bassiri A, Abraham MA, Duca FA, Yue JTY, Lam TKT. Insulin signals through the dorsal vagal complex to regulate energy balance. Diabetes 2014; 63:892-9. [PMID: 24270985 DOI: 10.2337/db13-1044] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin signaling in the hypothalamus regulates food intake and hepatic glucose production in rodents. Although it is known that insulin also activates insulin receptor in the dorsal vagal complex (DVC) to lower glucose production through an extracellular signal-related kinase 1/2 (Erk1/2)-dependent and phosphatidylinositol 3-kinase (PI3K)-independent pathway, it is unknown whether DVC insulin action regulates food intake. We report here that a single acute infusion of insulin into the DVC decreased food intake in healthy male rats. Chemical and molecular inhibition of Erk1/2 signaling in the DVC negated the acute anorectic effect of insulin in healthy rats, while DVC insulin acute infusion failed to lower food intake in high fat-fed rats. Finally, molecular disruption of Erk1/2 signaling in the DVC of healthy rats per se increased food intake and induced obesity over a period of 2 weeks, whereas a daily repeated acute DVC insulin infusion for 12 days conversely decreased food intake and body weight in healthy rats. In summary, insulin activates Erk1/2 signaling in the DVC to regulate energy balance.
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Affiliation(s)
- Beatrice M Filippi
- Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
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78
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Xu E, Schwab M, Marette A. Role of protein tyrosine phosphatases in the modulation of insulin signaling and their implication in the pathogenesis of obesity-linked insulin resistance. Rev Endocr Metab Disord 2014; 15:79-97. [PMID: 24264858 DOI: 10.1007/s11154-013-9282-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Insulin resistance is a major disorder that links obesity to type 2 diabetes mellitus (T2D). It involves defects in the insulin actions owing to a reduced ability of insulin to trigger key signaling pathways in major metabolic tissues. The pathogenesis of insulin resistance involves several inhibitory molecules that interfere with the tyrosine phosphorylation of the insulin receptor and its downstream effectors. Among those, growing interest has been developed toward the protein tyrosine phosphatases (PTPs), a large family of enzymes that can inactivate crucial signaling effectors in the insulin signaling cascade by dephosphorylating their tyrosine residues. Herein we briefly review the role of several PTPs that have been shown to be implicated in the regulation of insulin action, and then focus on the Src homology 2 (SH2) domain-containing SHP1 and SHP2 enzymes, since recent reports have indicated major roles for these PTPs in the control of insulin action and glucose metabolism. Finally, the therapeutic potential of targeting PTPs for combating insulin resistance and alleviating T2D will be discussed.
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Affiliation(s)
- Elaine Xu
- Department of Medicine, Cardiology Axis of the Institut Universitaire de Cardiologie et de Pneumologie de Québec (Hôpital Laval), Ste-Foy, Québec, Canada, G1V 4G2
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79
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Rasmussen BA, Breen DM, Duca FA, Côté CD, Zadeh-Tahmasebi M, Filippi BM, Lam TKT. Jejunal leptin-PI3K signaling lowers glucose production. Cell Metab 2014; 19:155-61. [PMID: 24361011 DOI: 10.1016/j.cmet.2013.11.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 10/08/2013] [Accepted: 11/11/2013] [Indexed: 10/25/2022]
Abstract
The fat-derived hormone leptin binds to its hypothalamic receptors to regulate glucose homeostasis. Leptin is also synthesized in the stomach and subsequently binds to its receptors expressed in the intestine, although the functional relevance of such activation remains largely unknown. We report here that intrajejunal leptin administration activates jejunal leptin receptors and signals through a phosphatidylinositol 3-kinase (PI3K)-dependent and signal transducer and activator of transcription 3 (STAT3)-independent signaling pathway to lower glucose production in healthy rodents. Jejunal leptin action is sufficient to lower glucose production in uncontrolled diabetic and high-fat-fed rodents and contributes to the early antidiabetic effect of duodenal-jejunal bypass surgery. These data unveil a glucoregulatory site of leptin action and suggest that enhancing leptin-PI3K signaling in the jejunum lowers plasma glucose concentrations in diabetes.
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Affiliation(s)
- Brittany A Rasmussen
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Danna M Breen
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Frank A Duca
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Clémence D Côté
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Melika Zadeh-Tahmasebi
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Beatrice M Filippi
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Tony K T Lam
- Toronto General Research Institute, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada; Banting and Best Diabetes Centre, University of Toronto, Toronto, ON M5G 2C4, Canada.
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80
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Zhang ZG, Qin CY. Sirt6 suppresses hepatocellular carcinoma cell growth via inhibiting the extracellular signal‑regulated kinase signaling pathway. Mol Med Rep 2013; 9:882-8. [PMID: 24366394 DOI: 10.3892/mmr.2013.1879] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 12/17/2013] [Indexed: 12/15/2022] Open
Abstract
Sirt6, a member of the mammalian sirtuin family, is a protein that is located in the nucleus and is an NAD+‑dependent deacetylase important in the control of metabolic activity and genome stability. Recently, several studies have demonstrated the potential role of Sirt6 in tumor biology; however, the role of Sirt6 in hepatocellular carcinoma (HCC) remains unclear. In the present study, Sirt6 protein expression was found to be downregulated in human HCC tissue compared with adjacent normal tissue. Knockdown of Sirt6 promoted growth of the HepG2 HCC cell line, whereas overexpression of Sirt6 inhibited the growth of HepG2 cells. Overexpression of Sirt6 induced apoptosis in HepG2 cells, which was demonstrated by a terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay and cleaved caspase-3 immunoblotting. Furthermore, overexpression of Sirt6 decreased intracellular reactive oxygen species and superoxide anion levels. Finally, overexpression of Sirt6 inhibited phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2), and blocking the ERK1/2 pathway with chemical-specific inhibitor U0126, attenuated the tumor suppressive effect of overexpression of Sirt6. Collectively, these data suggest that Sirt6 is a tumor suppressor in HCC cells and may be a promising therapeutic target in HCC.
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Affiliation(s)
- Zhi-Gao Zhang
- Department of Gastroenterology, Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Cheng-Yong Qin
- Department of Gastroenterology, Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
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81
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Filippi BM, Abraham MA, Yue JTY, Lam TKT. Insulin and glucagon signaling in the central nervous system. Rev Endocr Metab Disord 2013; 14:365-75. [PMID: 23959343 DOI: 10.1007/s11154-013-9258-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The prevalence of the obesity and diabetes epidemic has triggered tremendous research investigating the role of the central nervous system (CNS) in the regulation of food intake, body weight gain and glucose homeostasis. This invited review focuses on the role of two pancreatic hormones--insulin and glucagon--that trigger signaling pathways in the brain to regulate energy and glucose homeostasis. Unlike in the periphery, insulin and glucagon signaling in the CNS does not seem to have opposing metabolic effects, as both hormones exert a suppressive effect on food intake and weight gain. They signal through different pathways and alter different neuronal populations suggesting a complementary action of the two hormones in regulating feeding behavior. Similar to its systemic effect, insulin signaling in the brain lowers glucose production. However, the ability of glucagon signaling in the brain to regulate glucose production remains unknown. Future studies that aim to dissect insulin and glucagon signaling in the CNS that regulate energy and glucose homeostasis could unveil novel signaling molecules to lower body weight and glucose levels in obesity and diabetes.
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82
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Abraham MA, Yue JTY, LaPierre MP, Rutter GA, Light PE, Filippi BM, Lam TKT. Hypothalamic glucagon signals through the KATP channels to regulate glucose production. Mol Metab 2013; 3:202-8. [PMID: 24634823 DOI: 10.1016/j.molmet.2013.11.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 11/18/2013] [Accepted: 11/20/2013] [Indexed: 12/11/2022] Open
Abstract
Insulin, leptin and GLP-1 signal in the mediobasal hypothalamus (MBH) to lower hepatic glucose production (GP). MBH glucagon action also inhibits GP but the downstream signaling mediators remain largely unknown. In parallel, a lipid-sensing pathway involving MBH AMPK→malonyl-CoA→CPT-1→LCFA-CoA→PKC-δ leading to the activation of KATP channels lowers GP. Given that glucagon signals through the MBH PKA to lower GP, and PKA inhibits AMPK in hypothalamic cell lines, a possibility arises that MBH glucagon-PKA inhibits AMPK, elevates LCFA-CoA levels to activate PKC-δ, and activates KATP channels to lower GP. We here report that neither molecular or chemical activation of MBH AMPK nor inhibition of PKC-δ negated the effect of MBH glucagon. In contrast, molecular and chemical inhibition of MBH KATP channels negated MBH glucagon's effect to lower GP. Thus, MBH glucagon signals through a lipid-sensing independent but KATP channel-dependent pathway to regulate GP.
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Affiliation(s)
- Mona A Abraham
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Physiology, University of Toronto, Toronto, Canada
| | - Jessica T Y Yue
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Medicine, University of Toronto, Toronto, Canada
| | - Mary P LaPierre
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Physiology, University of Toronto, Toronto, Canada
| | - Guy A Rutter
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College of London, South Kensington, London, UK
| | - Peter E Light
- Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Beatrice M Filippi
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Medicine, University of Toronto, Toronto, Canada
| | - Tony K T Lam
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Physiology, University of Toronto, Toronto, Canada ; Departments of Medicine, University of Toronto, Toronto, Canada ; Banting and Best Diabetes Centre, University of Toronto, Toronto, Canada
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83
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Carey M, Kehlenbrink S, Hawkins M. Evidence for central regulation of glucose metabolism. J Biol Chem 2013; 288:34981-8. [PMID: 24142701 DOI: 10.1074/jbc.r113.506782] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Evidence for central regulation of glucose homeostasis is accumulating from both animal and human studies. Central nutrient and hormone sensing in the hypothalamus appears to coordinate regulation of whole body metabolism. Central signals activate ATP-sensitive potassium (KATP) channels, thereby down-regulating glucose production, likely through vagal efferent signals. Recent human studies are consistent with this hypothesis. The contributions of direct and central inputs to metabolic regulation are likely of comparable magnitude, with somewhat delayed central effects and more rapid peripheral effects. Understanding central regulation of glucose metabolism could promote the development of novel therapeutic approaches for such metabolic conditions as diabetes mellitus.
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Affiliation(s)
- Michelle Carey
- From the Department of Medicine and Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
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84
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Rupprecht LE, Mietlicki-Baase EG, Zimmer DJ, McGrath LE, Olivos DR, Hayes MR. Hindbrain GLP-1 receptor-mediated suppression of food intake requires a PI3K-dependent decrease in phosphorylation of membrane-bound Akt. Am J Physiol Endocrinol Metab 2013; 305:E751-9. [PMID: 23900416 PMCID: PMC3761195 DOI: 10.1152/ajpendo.00367.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) receptors (GLP-1R) expressed in the nucleus tractus solitarius (NTS) are physiologically required for the control of feeding. Recently, NTS GLP-1R-mediated suppression of feeding was shown to occur via a rapid PKA-induced suppression of AMPK and activation of MAPK signaling. Unknown are the additional intracellular signaling pathways that account for the long-term hypophagic effects of GLP-1R activation. Because cAMP/PKA activity can promote PI3K/PIP3-dependent translocation of Akt to the plasma membrane, we hypothesize that hindbrain GLP-1R-mediated control of feeding involves a PI3K-Akt-dependent pathway. Importantly, the novel evidence presented here challenges the dogmatic view that PI3K phosphorylation results in an obligatory activation of Akt and instead supports a growing body of literature showing that activation of cAMP/PKA can inhibit Akt phosphorylation at the plasma membrane. Behavioral data show that inhibition of hindbrain PI3K activity by a fourth icv administration of LY-294002 (3.07 μg) attenuated the food intake- and body weight-suppressive effects of a fourth icv administration of the GLP-1R agonist exendin-4 (0.3 μg) in rats. Hindbrain administration of triciribine (10 μg), an inhibitor of PIP3-dependent translocation of Akt to the cell membrane, also attenuated the intake-suppressive effects of a fourth icv injection of exendin-4. Immunoblot analyses of ex vivo NTS tissue lysates and in vitro GLP-1R-expressing neurons (GT1-7) support the behavioral findings and show that GLP-1R activation decreases phosphorylation of Akt in a time-dependent fashion. Current data reveal the requirement of PI3K activation, PIP3-dependent translocation of Akt to the plasma membrane, and suppression in phosphorylation of membrane-bound Akt to mediate the food intake-suppressive effects of hindbrain GLP-1R activation.
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Affiliation(s)
- Laura E Rupprecht
- Translational Neuroscience Program, Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
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85
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Diepenbroek C, Serlie MJ, Fliers E, Kalsbeek A, la Fleur SE. Brain areas and pathways in the regulation of glucose metabolism. Biofactors 2013; 39:505-13. [PMID: 23913677 DOI: 10.1002/biof.1123] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 05/28/2013] [Indexed: 11/11/2022]
Abstract
Glucose is the most important source of fuel for the brain and its concentration must be kept within strict boundaries to ensure the organism's optimal fitness. To maintain glucose homeostasis, an optimal balance between glucose uptake and glucose output is required. Besides managing acute changes in plasma glucose concentrations, the brain controls a daily rhythm in glucose concentrations. The various nuclei within the hypothalamus that are involved in the control of both these processes are well known. However, novel studies indicate an additional role for brain areas that are originally appreciated in other processes than glucose metabolism. Therefore, besides the classic hypothalamic pathways, we will review cortico-limbic brain areas and their role in glucose metabolism.
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Affiliation(s)
- Charlene Diepenbroek
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
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86
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Sugar for the brain: the role of glucose in physiological and pathological brain function. Trends Neurosci 2013; 36:587-97. [PMID: 23968694 DOI: 10.1016/j.tins.2013.07.001] [Citation(s) in RCA: 903] [Impact Index Per Article: 82.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 06/30/2013] [Accepted: 07/08/2013] [Indexed: 12/13/2022]
Abstract
The mammalian brain depends upon glucose as its main source of energy, and tight regulation of glucose metabolism is critical for brain physiology. Consistent with its critical role for physiological brain function, disruption of normal glucose metabolism as well as its interdependence with cell death pathways forms the pathophysiological basis for many brain disorders. Here, we review recent advances in understanding how glucose metabolism sustains basic brain physiology. We synthesize these findings to form a comprehensive picture of the cooperation required between different systems and cell types, and the specific breakdowns in this cooperation that lead to disease.
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87
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Hypothalamic glucagon signaling inhibits hepatic glucose production. Nat Med 2013; 19:766-72. [DOI: 10.1038/nm.3115] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 01/31/2013] [Indexed: 01/28/2023]
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