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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Adriaenssens AE, Reimann F, Gribble FM. Distribution and Stimulus Secretion Coupling of Enteroendocrine Cells along the Intestinal Tract. Compr Physiol 2018; 8:1603-1638. [DOI: 10.1002/cphy.c170047] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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53
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Sfairopoulos D, Liatis S, Tigas S, Liberopoulos E. Clinical pharmacology of glucagon-like peptide-1 receptor agonists. Hormones (Athens) 2018; 17:333-350. [PMID: 29949126 DOI: 10.1007/s42000-018-0038-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 05/14/2018] [Indexed: 02/06/2023]
Abstract
Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are an important asset in the armamentarium for the treatment of type 2 diabetes mellitus (type 2 DM). Incretin failure is a critical etiopathogenetic feature of type 2 DM, which, if reversed, results in improved glycaemic control. GLP-1 RAs are injectable peptides that resemble the structure and function of endogenous incretin GLP-1, but as they are not deactivated by the dipeptidyl peptidase-4 (DPP-4), their half-life is prolonged compared with native GLP-1. Based on their ability to activate GLP-1 receptor, GLP-1 RAs are classified as short-acting (exenatide twice-daily and lixisenatide once-daily), and long-acting (liraglutide once-daily and the once-weekly formulations of exenatide extended-release, dulaglutide, and albiglutide). Semaglutide, another long-acting, once-weekly GLP-1 RA, was recently approved by the FDA and EMA. Although all of these agents potently reduce haemoglobin A1C (HbA1c), there are unique features and fundamental differences among them related to fasting and postprandial hyperglycaemia reduction, weight loss potency, cardiovascular protection efficacy, and adverse events profile. It is imperative that current evidence be integrated and applied in the context of an individualised patient-centred approach. This should include not only glucose management but also targeting as many as possible of the pathophysiologic mechanisms responsible for type 2 DM development and progression.
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Affiliation(s)
- Dimitrios Sfairopoulos
- Department of Internal Medicine, School of Medicine, University of Ioannina, Stavrou Niarchou Str, 45110, Ioannina, Greece
| | - Stavros Liatis
- First Department of Propaedeutic and Internal Medicine, Medical School, Laiko General Hospital, National and Kapodistrian University of Athens, 10559, Athens, Greece
| | - Stelios Tigas
- Department of Endocrinology, School of Medicine, University of Ioannina, 45110, Ioannina, Greece
| | - Evangelos Liberopoulos
- Department of Internal Medicine, School of Medicine, University of Ioannina, Stavrou Niarchou Str, 45110, Ioannina, Greece.
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Abstract
The gastrointestinal tract represents the largest interface between the human body and the external environment. It must continuously monitor and discriminate between nutrients that need to be assimilated and harmful substances that need to be expelled. The different cells of the gut epithelium are therefore equipped with a subtle chemosensory system that communicates the sensory information to several effector systems involved in the regulation of appetite, immune responses, and gastrointestinal motility. Disturbances or adaptations in the communication of this sensory information may contribute to the development or maintenance of disease. This is a new emerging research field in which perception of taste can be considered as a novel key player participating in the regulation of gut function. Specific diets or agonists that target these chemosensory signaling pathways may be considered as new therapeutic targets to tune adequate physiological processes in the gut in health and disease.
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Affiliation(s)
- S Steensels
- Translational Research Center for Gastrointestinal Disorders, KU Leuven, 3000 Leuven, Belgium;
| | - I Depoortere
- Translational Research Center for Gastrointestinal Disorders, KU Leuven, 3000 Leuven, Belgium;
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Heeley N, Kirwan P, Darwish T, Arnaud M, Evans ML, Merkle FT, Reimann F, Gribble FM, Blouet C. Rapid sensing of l-leucine by human and murine hypothalamic neurons: Neurochemical and mechanistic insights. Mol Metab 2018; 10:14-27. [PMID: 29439854 PMCID: PMC5985239 DOI: 10.1016/j.molmet.2018.01.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 11/27/2022] Open
Abstract
Objective Dietary proteins are sensed by hypothalamic neurons and strongly influence multiple aspects of metabolic health, including appetite, weight gain, and adiposity. However, little is known about the mechanisms by which hypothalamic neural circuits controlling behavior and metabolism sense protein availability. The aim of this study is to characterize how neurons from the mediobasal hypothalamus respond to a signal of protein availability: the amino acid l-leucine. Methods We used primary cultures of post-weaning murine mediobasal hypothalamic neurons, hypothalamic neurons derived from human induced pluripotent stem cells, and calcium imaging to characterize rapid neuronal responses to physiological changes in extracellular l-Leucine concentration. Results A neurochemically diverse subset of both mouse and human hypothalamic neurons responded rapidly to l-leucine. Consistent with l-leucine's anorexigenic role, we found that 25% of mouse MBH POMC neurons were activated by l-leucine. 10% of MBH NPY neurons were inhibited by l-leucine, and leucine rapidly reduced AGRP secretion, providing a mechanism for the rapid leucine-induced inhibition of foraging behavior in rodents. Surprisingly, none of the candidate mechanisms previously implicated in hypothalamic leucine sensing (KATP channels, mTORC1 signaling, amino-acid decarboxylation) were involved in the acute activity changes produced by l-leucine. Instead, our data indicate that leucine-induced neuronal activation involves a plasma membrane Ca2+ channel, whereas leucine-induced neuronal inhibition is mediated by inhibition of a store-operated Ca2+ current. Conclusions A subset of neurons in the mediobasal hypothalamus rapidly respond to physiological changes in extracellular leucine concentration. Leucine can produce both increases and decreases in neuronal Ca2+ concentrations in a neurochemically-diverse group of neurons, including some POMC and NPY/AGRP neurons. Our data reveal that leucine can signal through novel mechanisms to rapidly affect neuronal activity. A neurochemically diverse group of mouse and human hypothalamic neurons rapidly sense and respond to l-leucine. Leucine can produce neuronal activation or neuronal inhibition via distinct and novel Ca2+ signaling mechanisms. Leucine activates 25% ARH POMC neurons. Leucine inhibits 10% ARH NPY/AGRP neurons and reduces AGRP secretion from fasted mediobasal hypothalamic slices.
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Affiliation(s)
- Nicholas Heeley
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Peter Kirwan
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Tamana Darwish
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Marion Arnaud
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Mark L Evans
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Florian T Merkle
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Frank Reimann
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Fiona M Gribble
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Clemence Blouet
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK.
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Lee JH, Wen X, Cho H, Koo SH. CREB/CRTC2 controls GLP-1-dependent regulation of glucose homeostasis. FASEB J 2018; 32:1566-1578. [PMID: 29118086 DOI: 10.1096/fj.201700845r] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Glucagon-like peptide 1 (GLP-1) is a major incretin that controls glucose homeostasis. The secretion of mature GLP-1 is regulated via GPCRs, including bile acid receptor G protein-coupled bile acid receptor 1, which uses cAMP signaling to enhance the exocytosis of GLP-1-containing vesicles. However, the role of cAMP-mediated transcription has not been clearly demonstrated to date. In this study, we explored the role of cAMP response element-binding protein/CREB-regulated transcription coactivator 2 (CREB/CRTC2)-dependent transcription on GLP-1 secretion in the L cells. We found that the reduced CREB/CRTC2 activity impaired the cAMP-dependent increase in GLP-1 secretion, whereas expression of constitutively active CRTC2 increased GLP-1 exocytosis from the L cells. Close investigation revealed that expression of not only proglucagon but also PC1/3, an endopeptidase for GLP-1 maturation, is transcriptionally regulated by CREB/CRTC2. Furthermore, expression of peroxisome proliferator-activating receptor coactivator 1 α is also reduced upon depletion of CRTC2, leading to the decreased expression of oxidative phosphorylation (OxPhos) genes, reduced ATP levels, and calcium concentrations in the L cells. Finally, we observed that intestine-specific CRTC2 knockout mice displayed reduced GLP-1 expression, leading to the lower plasma GLP-1 levels, impaired glucose tolerance, and decreased insulin-containing β cells in pancreatic islets. Our data show that the CREB/CRTC2-dependent transcriptional pathway is critical for regulating glucose homeostasis by controlling production of GLP-1 from the L cells at the level of transcription, maturation, and exocytosis.-Lee, J.-H., Wen, X., Cho, H., Koo, S.-H. CREB/CRTC2 controls GLP-1-dependent regulation of glucose homeostasis.
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Affiliation(s)
- Ji-Hyun Lee
- Division of Life Sciences, Korea University, Seoul, Korea
| | - Xianlan Wen
- Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hana Cho
- Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Seung-Hoi Koo
- Division of Life Sciences, Korea University, Seoul, Korea
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Psichas A, Larraufie PF, Goldspink DA, Gribble FM, Reimann F. Chylomicrons stimulate incretin secretion in mouse and human cells. Diabetologia 2017; 60:2475-2485. [PMID: 28866808 PMCID: PMC5850988 DOI: 10.1007/s00125-017-4420-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 07/07/2017] [Indexed: 01/05/2023]
Abstract
AIMS/HYPOTHESIS Lipids are a potent stimulus for the secretion of glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic peptide (GIP). Traditionally, this effect was thought to involve the sensing of lipid digestion products by free fatty acid receptor 1 (FFA1) and G-protein coupled receptor 119 (GPR119) on the apical surface of enteroendocrine cells. However, recent evidence suggests that lipids may in fact be sensed basolaterally, and that fatty acid absorption and chylomicron synthesis may be a prerequisite for their stimulatory effect on gut peptide release. Therefore, we investigated the effect of chylomicrons on GLP-1 and GIP secretion in vitro. METHODS The effect of chylomicrons on incretin secretion was investigated using GLUTag cells and duodenal cultures of both murine and human origin. The role of lipoprotein lipase (LPL) and FFA1 in GLUTag cells was assessed by pharmacological inhibition and small (short) interfering RNA (siRNA)-mediated knockdown. The effect of chylomicrons on intracellular calcium concentration ([Ca2+]i) was determined by imaging GLUTag cells loaded with Fura-2. In the primary setting, the contributions of FFA1 and GPR119 were investigated using L cell-specific Gpr119 knockout cultures treated with the FFA1 antagonist GW1100. RESULTS Chylomicrons stimulated GLP-1 release from GLUTag cells, and both GLP-1 and GIP secretion from human and murine duodenal cultures. Chylomicron-triggered GLP-1 secretion from GLUTag cells was largely abolished following lipase inhibition with orlistat or siRNA-mediated knockdown of Lpl. In GLUTag cells, both GW1100 and siRNA-mediated Ffar1 knockdown reduced GLP-1 secretion in response to chylomicrons, and, consistent with FFA1 Gq-coupling, chylomicrons triggered an increase in [Ca2+]i. However, LPL and FFA1 inhibition had no significant effect on chylomicron-mediated incretin secretion in murine cultures. Furthermore, the loss of GPR119 had no impact on GLP-1 secretion in response to chylomicrons, even in the presence of GW1100. CONCLUSIONS/INTERPRETATION Chylomicrons stimulate incretin hormone secretion from GLUTag cells as well as from human and murine duodenal cultures. In GLUTag cells, the molecular pathway was found to involve LPL-mediated lipolysis, leading to the release of lipid species that activated FFA1 and elevated intracellular calcium.
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Affiliation(s)
- Arianna Psichas
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, WT-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Pierre F Larraufie
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, WT-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Deborah A Goldspink
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, WT-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Fiona M Gribble
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, WT-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK.
| | - Frank Reimann
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, WT-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK.
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Zheng WL, Chu C, Lv YB, Wang Y, Hu JW, Ma Q, Yan Y, Cao YM, Dang XL, Wang KK, Mu JJ. Effect of Salt Intake on Serum Glucagon-Like Peptide-1 Levels in Normotensive Salt-Sensitive Subjects. Kidney Blood Press Res 2017; 42:728-737. [PMID: 29050005 DOI: 10.1159/000484152] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/22/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Excess dietary salt is a critical risk factor of salt-sensitive hypertension. Glucagon-like peptide-1 (GLP-1) , a gut incretin hormone, conferring benefits for blood pressure by natriuresis and diuresis. We implemented a randomized trial to verify the effect of altered salt intake on serum GLP-1 level in human beings. METHODS The 38 subjects were recruited from a rural community of Northern China. All subjects were sequentially maintained a baseline diet period for 3 days, a low-salt diet period for 7 days (3.0g/day of NaCl) , and a high-salt diet period for additional 7 days (18.0g/day of NaCl). RESULTS Serum GLP-1 level increased significantly with the change from the baseline period to the low-salt diet period and decreased with the change from the low-salt to high-salt diet in normotensive salt-sensitive (SS) but not salt-resistant (SR) individuals. There was a significant inverse correlation between the serum GLP-1 level and the MAP in SS subjects. Inverse correlation between the serum GLP-1 level and 24-h urinary sodium excretion was also found among different dietary interventions in SS subjects. CONCLUSIONS Our study indicates that variations in dietary salt intake affect the serum GLP-1 level in normotensive salt-sensitive Chinese adults.
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Chimerel C, Riccio C, Murison K, Gribble FM, Reimann F. Optogenetic Analysis of Depolarization-Dependent Glucagonlike Peptide-1 Release. Endocrinology 2017; 158:3426-3434. [PMID: 28938466 PMCID: PMC5659701 DOI: 10.1210/en.2017-00434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/25/2017] [Indexed: 12/21/2022]
Abstract
Incretin hormones play an important role in the regulation of food intake and glucose homeostasis. Glucagonlike peptide-1 (GLP-1)-secreting cells have been demonstrated to be electrically excitable and to fire action potentials (APs) with increased frequency in response to nutrient exposure. However, nutrients can also be metabolized or activate G-protein-coupled receptors, thus potentially stimulating GLP-1 secretion independent of their effects on the plasma membrane potential. Here we used channelrhodopsins to manipulate the membrane potential of GLUTag cells, a well-established model of GLP-1-secreting enteroendocrine L cells. Using channelrhodopsins with fast or slow on/off kinetics (CheTA and SSFO, respectively), we found that trains of light pulses could trigger APs and calcium elevation in GLUTag cells stably expressing either CheTA or SSFO. Tetrodotoxin reduced light-triggered AP frequency but did not impair calcium responses, whereas further addition of the calcium-channel blockers nifedipine and ω-conotoxin GVIA abolished both APs and calcium transients. Light pulse trains did not trigger GLP-1 secretion from CheTA-expressing cells under basal conditions but were an effective stimulus when cyclic adenosine monophosphate (cAMP) concentrations were elevated by forskolin plus 3-isobutyl 1-methylxanthine. In SSFO-expressing cells, light-stimulated GLP-1 release was observed at resting and elevated cAMP concentrations and was blocked by nifedipine plus ω-conotoxin GVIA but not tetrodotoxin. We conclude that cAMP elevation or cumulative membrane depolarization triggered by SSFO enhances the efficiency of light-triggered action potential firing, voltage-gated calcium entry, and GLP-1 secretion.
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Affiliation(s)
- Catalin Chimerel
- Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom
| | - Cristian Riccio
- Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom
| | - Keir Murison
- Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom
| | - Fiona M. Gribble
- Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom
| | - Frank Reimann
- Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom
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Ghanem SS, Muturi HT, DeAngelis AM, Hu J, Kulkarni RN, Heinrich G, Najjar SM. Age-dependent insulin resistance in male mice with null deletion of the carcinoembryonic antigen-related cell adhesion molecule 2 gene. Diabetologia 2017; 60:1751-1760. [PMID: 28567513 PMCID: PMC5709176 DOI: 10.1007/s00125-017-4307-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 04/21/2017] [Indexed: 10/19/2022]
Abstract
AIMS/HYPOTHESIS Cc2 -/- mice lacking the gene encoding the carcinoembryonic-antigen-related cell adhesion molecule 2 (Cc2 [also known as Ceacam2]) exhibit hyperphagia that leads to obesity and insulin resistance. This starts at 2 months of age in female mice. Male mutants maintain normal body weight and insulin sensitivity until the last age previously examined (7-8 months), owing to increased sympathetic tone to white adipose tissue and energy expenditure. The current study investigates whether insulin resistance develops in mutant male mice at a later age and whether this is accompanied by changes in insulin homeostasis. METHODS Insulin response was assessed by insulin and glucose tolerance tests. Energy balance was analysed by indirect calorimetry. RESULTS Male Cc2 -/- mice developed overt metabolic abnormalities at about 9 months of age. These include elevated global fat mass, hyperinsulinaemia and insulin resistance (as determined by glucose and insulin intolerance, fed hyperglycaemia and decreased insulin signalling pathways). Pair-feeding experiments showed that insulin resistance resulted from hyperphagia. Indirect calorimetry demonstrated that older mutant male mice had compromised energy expenditure. Despite increased insulin secretion caused by Cc2 deletion, chronic hyperinsulinaemia did not develop in mutant male mice until about 9 months of age, at which point insulin clearance began to decline substantially. This was probably mediated by a marked decrease in hepatic CEACAM1 expression. CONCLUSIONS/INTERPRETATION The data demonstrate that at about 9 months of age, Cc2 -/- male mice develop a reduction in energy expenditure and energy imbalance which, combined with a progressive decrease in CEACAM1-dependent hepatic insulin clearance, causes chronic hyperinsulinaemia and sustained age-dependent insulin resistance. This represents a novel mechanistic underpinning of age-related impairment of hepatic insulin clearance.
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Affiliation(s)
- Simona S Ghanem
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, USA
| | - Harrison T Muturi
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Anthony M DeAngelis
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, USA
| | - Jiang Hu
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center and Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA, USA
| | - Rohit N Kulkarni
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center and Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA, USA
| | - Garrett Heinrich
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, 45701-2979, USA
| | - Sonia M Najjar
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, USA.
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA.
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, 45701-2979, USA.
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61
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Signalling in the gut endocrine axis. Physiol Behav 2017; 176:183-188. [DOI: 10.1016/j.physbeh.2017.02.039] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/23/2017] [Accepted: 02/27/2017] [Indexed: 02/06/2023]
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Lee AA, Owyang C. Sugars, Sweet Taste Receptors, and Brain Responses. Nutrients 2017; 9:nu9070653. [PMID: 28672790 PMCID: PMC5537773 DOI: 10.3390/nu9070653] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 06/20/2017] [Accepted: 06/21/2017] [Indexed: 12/25/2022] Open
Abstract
Sweet taste receptors are composed of a heterodimer of taste 1 receptor member 2 (T1R2) and taste 1 receptor member 3 (T1R3). Accumulating evidence shows that sweet taste receptors are ubiquitous throughout the body, including in the gastrointestinal tract as well as the hypothalamus. These sweet taste receptors are heavily involved in nutrient sensing, monitoring changes in energy stores, and triggering metabolic and behavioral responses to maintain energy balance. Not surprisingly, these pathways are heavily regulated by external and internal factors. Dysfunction in one or more of these pathways may be important in the pathogenesis of common diseases, such as obesity and type 2 diabetes mellitus.
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Affiliation(s)
- Allen A Lee
- 1500 East Medical Center Drive, Division of Gastroenterology, Department of Internal Medicine, Michigan Medicine, University of Michigan, Ann Arbor, MI 48109-5362, USA.
| | - Chung Owyang
- 3912 Taubman Center, SPC 5362, Ann Arbor, MI 48109-5362, USA.
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Saltiel MY, Kuhre RE, Christiansen CB, Eliasen R, Conde-Frieboes KW, Rosenkilde MM, Holst JJ. Sweet Taste Receptor Activation in the Gut Is of Limited Importance for Glucose-Stimulated GLP-1 and GIP Secretion. Nutrients 2017; 9:nu9040418. [PMID: 28441725 PMCID: PMC5409757 DOI: 10.3390/nu9040418] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/11/2017] [Accepted: 04/18/2017] [Indexed: 01/14/2023] Open
Abstract
Glucose stimulates the secretion of the incretin hormones: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). It is debated whether the sweet taste receptor (STR) triggers this secretion. We investigated the role of STR activation for glucose-stimulated incretin secretion from an isolated perfused rat small intestine and whether selective STR activation by artificial sweeteners stimulates secretion. Intra-luminal administration of the STR agonists, acesulfame K (3.85% w/v), but not sucralose (1.25% w/v) and stevioside (2.5% w/v), stimulated GLP-1 secretion (acesulfame K: 31 ± 3 pmol/L vs. 21 ± 2 pmol/L, p < 0.05, n = 6). In contrast, intra-arterial administration of sucralose (10 mM) and stevioside (10 mM), but not acesulfame K, stimulated GLP-1 secretion (sucralose: 51 ± 6 pmol/L vs. 34 ± 4 pmol/L, p < 0.05; stevioside: 54 ± 6 pmol/L vs. 32 ± 2 pmol/L, p < 0.05, n = 6), while 0.1 mM and 1 mM sucralose did not affect the secretion. Luminal glucose (20% w/v) doubled GLP-1 and GIP secretion, but basolateral STR inhibition by gurmarin (2.5 µg/mL) or the inhibition of the transient receptor potential cation channel 5 (TRPM5) by triphenylphosphine oxide (TPPO) (100 µM) did not attenuate the responses. In conclusion, STR activation does not drive GIP/GLP-1 secretion itself, nor does it have a role for glucose-stimulated GLP-1 or GIP secretion.
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Affiliation(s)
- Monika Y Saltiel
- NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej, DK-2200, Copenhagen N, Denmark.
| | - Rune E Kuhre
- NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej, DK-2200, Copenhagen N, Denmark.
| | - Charlotte B Christiansen
- NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej, DK-2200, Copenhagen N, Denmark.
| | - Rasmus Eliasen
- Protein & Peptide Chemistry, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Måløv, Denmark.
| | | | - Mette M Rosenkilde
- NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej, DK-2200, Copenhagen N, Denmark.
| | - Jens J Holst
- NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej, DK-2200, Copenhagen N, Denmark.
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Tagliavini A, Pedersen MG. Spatiotemporal Modeling of Triggering and Amplifying Pathways in GLP-1 Secreting Intestinal L Cells. Biophys J 2017; 112:162-171. [PMID: 28076808 PMCID: PMC5232896 DOI: 10.1016/j.bpj.2016.11.3199] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 11/16/2016] [Accepted: 11/29/2016] [Indexed: 01/06/2023] Open
Abstract
Glucagon-like peptide 1 (GLP-1) is secreted by intestinal L-cells, and augments glucose-induced insulin secretion, thus playing an important role in glucose control. The stimulus-secretion pathway in L-cells is still incompletely understood and a topic of debate. It is known that GLP-1 secreting cells can sense glucose to promote electrical activity either by the electrogenic sodium-glucose cotransporter SGLT1, or by closure of ATP-sensitive potassium channels after glucose metabolism. Glucose also has an effect on GLP-1 secretion downstream of electrical activity. An important aspect to take into account is the spatial organization of the cell. Indeed, the glucose transporter GLUT2 is located at the basolateral, vascular side, while SGLT1 is exposed to luminal glucose at the apical side of the cell, suggesting that the two types of transporters play different roles in glucose sensing. Here, we extend our recent model of electrical activity in primary L-cells to include spatiotemporal glucose and Ca2+ dynamics, and GLP-1 secretion. The model confirmed that glucose transportation into the cell through SGLT1 cotransporters can induce Ca2+ influx and release of GLP-1 as a result of electrical activity, while glucose metabolism alone is insufficient to depolarize the cell and evoke GLP-1 secretion in the model, suggesting a crucial role for SGLT1 in triggering GLP-1 release in agreement with experimental studies. We suggest a secondary, but participating, role of GLUT2 and glucose metabolism for GLP-1 secretion via an amplifying pathway that increases the secretion rate at a given Ca2+ level.
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Affiliation(s)
- Alessia Tagliavini
- Department of Information Engineering, University of Padova, Padova, Italy
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65
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Xu Z, Wang W, Nian X, Song G, Zhang X, Xiao H, Zhu X. Dose-dependent effect of glucose on GLP-1 secretion involves sweet taste receptor in isolated perfused rat ileum [Rapid Communication]. Endocr J 2016; 63:1141-1147. [PMID: 27853059 DOI: 10.1507/endocrj.ej16-0390] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Luminal glucose is an important stimulus for glucagon-like peptide 1 (GLP-1) secretion from intestinal endocrine cells. However, the effects of luminal glucose concentration on GLP-1 secretion remain unknown. In this study, we investigated the effect of luminal glucose concentrations (3.5, 5, 10, 15, and 20 mmol/L) on GLP-1 secretion from isolated perfused rat ileum. Results showed that the perfusate glucose concentration dose-dependently stimulated GLP-1 secretion from isolated perfused rat ileum, which was eliminated by the sweet taste receptor inhibitor gurmarin (30 μg/mL), but not inhibited by phloridzin (1 mmol/L), a Na+-coupled glucose transporters inhibitor. We conclude that luminal glucose induced GLP-1 secretion from perfused rat ileum in a concentration-dependent manner. This secretion was mediated by sweet taste receptor transducing signal for GLP-1 release on the gut of rat.
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Affiliation(s)
- Zhiwei Xu
- Institute of Pathogen Biology and Immunology, Department of Biochemistry, North University of Hebei, Zhangjiakou 075000, PR China
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66
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Tian L, Jin T. The incretin hormone GLP-1 and mechanisms underlying its secretion. J Diabetes 2016; 8:753-765. [PMID: 27287542 DOI: 10.1111/1753-0407.12439] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 05/09/2016] [Accepted: 06/02/2016] [Indexed: 12/25/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is a cell type-specific post-translational product of proglucagon. It is encoded by the proglucagon gene and released primarily from intestinal endocrine L-cells in response to hormonal, neuronal, and nutritional stimuli. In addition to serving as an incretin in mediating the effect of meal consumption on insulin secretion, GLP-1 exerts other functions in pancreatic islets, including regulation of β-cell proliferation and protection of β-cells against metabolic stresses. Furthermore, GLP-1 exerts numerous other functions in extrapancreatic organs, whereas brain GLP-1 signaling controls satiety. Herein we review the discovery of two incretins and the development of GLP-1-based drugs. We also describe the development of cellular models for studying mechanisms underlying GLP-1 secretion over the past 30 years. However, the main content of this review is a summary of studies on the exploration of mechanisms underlying GLP-1 secretion. We not only summarize studies conducted over the past three decades on elucidating the role of nutritional components and hormonal factors in regulating GLP-1 secretion, but also present a few very recent studies showing the possible role of dietary polyphenols. Finally, the emerging role of gut microbiota in metabolic homeostasis with the potential implication on GLP-1 secretion is discussed.
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Affiliation(s)
- Lili Tian
- Division of Advanced Diagnostics, Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
- Banting & Best Diabetes Centre, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Tianru Jin
- Division of Advanced Diagnostics, Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada.
- Banting & Best Diabetes Centre, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada.
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67
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Metabolism in mind: New insights into the 'gut-brain axis' spur commercial efforts to target it. Nat Med 2016; 22:697-700. [DOI: 10.1038/nm0716-697] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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68
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Arkhammar P, Wahl P, Gerlach B, Fremming T, Hansen JB. Establishment and Application of in Vitro Membrane Potential Assays in Cell Lines with Endogenous or Recombinant Expression of ATP-Sensitive Potassium Channels (Kir6.2/SUR1) Using a Fluorescent Probe Kit. ACTA ACUST UNITED AC 2016; 9:382-90. [PMID: 15296637 DOI: 10.1177/1087057104263911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The flow of current through the adenosine triphosphate (ATP)-sensitive potassium channel (KATP) of the isoform Kir6.2/SUR1 regulates the resting membrane potential in the pancreatic β-cell. In combination with the cellular glucose metabolism, it is an important minute-to-minute regulator of insulin secretion and whole-body glucose homeostasis. The same KATPisoform is further reported to be present in glucagon-secreting α-cells, intestinal L-cells, and glucose-responsive neurons in the hypothalamus. All in all, this makes Kir6.2/SUR1 an interesting drug target. Using a commercially available fluorescent membrane potential probe kit and a conventional 96-well fluorescence plate reader, the authors have developed and established qualitative membrane potential assays used to screen for potassium channel closers (KCCs) and openers (KCOs) in insulin- and glucagon-secreting cell lines as well as in cells with recombinant expression of the human Kir6.2/SUR1 channel complex. Both glucose- and KCC-induced depolarization could be demonstrated. The magnitudes of these responses and KCO-induced repolarization at high glucose displayed some variation between the different cell lines but a similar rank order of test compounds. Some cell types required the presence of a KCC, such as tolbutamide, to display significant effects of KCOs. The authors find that robust and reliable functional in vitro assays compatible with medium-throughput screening and high-throughput screening can be developed as a base for finding new, more potent, and isoform-selective KCCs and KCOs.
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69
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Lim GE, Piske M, Lulo JE, Ramshaw HS, Lopez AF, Johnson JD. Ywhaz/14-3-3ζ Deletion Improves Glucose Tolerance Through a GLP-1-Dependent Mechanism. Endocrinology 2016; 157:2649-59. [PMID: 27167773 DOI: 10.1210/en.2016-1016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Multiple signaling pathways mediate the actions of metabolic hormones to control glucose homeostasis, but the proteins that coordinate such networks are poorly understood. We previously identified the molecular scaffold protein, 14-3-3ζ, as a critical regulator of in vitro β-cell survival and adipogenesis, but its metabolic roles in glucose homeostasis have not been studied in depth. Herein, we report that Ywhaz gene knockout mice (14-3-3ζKO) exhibited elevated fasting insulin levels while maintaining normal β-cell responsiveness to glucose when compared with wild-type littermate controls. In contrast with our observations after an ip glucose bolus, glucose tolerance was significantly improved in 14-3-3ζKO mice after an oral glucose gavage. This improvement in glucose tolerance was associated with significantly elevated fasting glucagon-like peptide-1 (GLP-1) levels. 14-3-3ζ knockdown in GLUTag L cells elevated GLP-1 synthesis and increased GLP-1 release. Systemic inhibition of the GLP-1 receptor attenuated the improvement in oral glucose tolerance that was seen in 14-3-3ζKO mice. When taken together these findings demonstrate novel roles of 14-3-3ζ in the regulation of glucose homeostasis and suggest that modulating 14-3-3ζ levels in intestinal L cells may have beneficial metabolic effects through GLP-1-dependent mechanisms.
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Affiliation(s)
- Gareth E Lim
- Department of Cellular and Physiological Sciences (G.E.L., M.P., J.D.J.), University of British Columbia, Vancouver, BC, Canada; ALPCO (J.E.L.), Salem, New Hampshire; and The Centre for Cancer Biology (H.S.R., A.F.L.), South Australia Pathology and University of South Australia, Adelaide, Australia
| | - Micah Piske
- Department of Cellular and Physiological Sciences (G.E.L., M.P., J.D.J.), University of British Columbia, Vancouver, BC, Canada; ALPCO (J.E.L.), Salem, New Hampshire; and The Centre for Cancer Biology (H.S.R., A.F.L.), South Australia Pathology and University of South Australia, Adelaide, Australia
| | - James E Lulo
- Department of Cellular and Physiological Sciences (G.E.L., M.P., J.D.J.), University of British Columbia, Vancouver, BC, Canada; ALPCO (J.E.L.), Salem, New Hampshire; and The Centre for Cancer Biology (H.S.R., A.F.L.), South Australia Pathology and University of South Australia, Adelaide, Australia
| | - Hayley S Ramshaw
- Department of Cellular and Physiological Sciences (G.E.L., M.P., J.D.J.), University of British Columbia, Vancouver, BC, Canada; ALPCO (J.E.L.), Salem, New Hampshire; and The Centre for Cancer Biology (H.S.R., A.F.L.), South Australia Pathology and University of South Australia, Adelaide, Australia
| | - Angel F Lopez
- Department of Cellular and Physiological Sciences (G.E.L., M.P., J.D.J.), University of British Columbia, Vancouver, BC, Canada; ALPCO (J.E.L.), Salem, New Hampshire; and The Centre for Cancer Biology (H.S.R., A.F.L.), South Australia Pathology and University of South Australia, Adelaide, Australia
| | - James D Johnson
- Department of Cellular and Physiological Sciences (G.E.L., M.P., J.D.J.), University of British Columbia, Vancouver, BC, Canada; ALPCO (J.E.L.), Salem, New Hampshire; and The Centre for Cancer Biology (H.S.R., A.F.L.), South Australia Pathology and University of South Australia, Adelaide, Australia
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70
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Abstract
Glucagon-like peptide-1 (GLP-1) is a peptide hormone, released from intestinal L-cells in response to hormonal, neural and nutrient stimuli. In addition to potentiation of meal-stimulated insulin secretion, GLP-1 signalling exerts numerous pleiotropic effects on various tissues, regulating energy absorption and disposal, as well as cell proliferation and survival. In Type 2 Diabetes (T2D) reduced plasma levels of GLP-1 have been observed, and plasma levels of GLP-1, as well as reduced numbers of GLP-1 producing cells, have been correlated to obesity and insulin resistance. Increasing endogenous secretion of GLP-1 by selective targeting of the molecular mechanisms regulating secretion from the L-cell has been the focus of much recent research. An additional and promising strategy for enhancing endogenous secretion may be to increase the L-cell mass in the intestinal epithelium, but the mechanisms that regulate the growth, survival and function of these cells are largely unknown. We recently showed that prolonged exposure to high concentrations of the fatty acid palmitate induced lipotoxic effects, similar to those operative in insulin-producing cells, in an in vitro model of GLP-1-producing cells. The mechanisms inducing this lipototoxicity involved increased production of reactive oxygen species (ROS). In this review, regulation of GLP-1-secreting cells is discussed, with a focus on the mechanisms underlying GLP-1 secretion, long-term regulation of growth, differentiation and survival under normal as well as diabetic conditions of hypernutrition.
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71
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Kuhre RE, Wewer Albrechtsen NJ, Deacon CF, Balk-Møller E, Rehfeld JF, Reimann F, Gribble FM, Holst JJ. Peptide production and secretion in GLUTag, NCI-H716, and STC-1 cells: a comparison to native L-cells. J Mol Endocrinol 2016; 56:201-11. [PMID: 26819328 PMCID: PMC7212058 DOI: 10.1530/jme-15-0293] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
GLUTag, NCI-H716, and STC-1 are cell lines that are widely used to study mechanisms underlying secretion of glucagon-like peptide-1 (GLP-1), but the extent to which they resemble native L-cells is unknown. We used validated immunoassays for 14 different hormones to analyze peptide content (lysis samples; n = 9 from different passage numbers) or peptide secretion in response to buffer (baseline), and after stimulation with 50 mM KCl or 10 mM glucose + 10 µM forskolin/3-isobutyl-1-methylxanthine (n = 6 also different passage numbers). All cell lines produced and processed proglucagon into GLP-1, GLP-2, glicentin, and oxyntomodulin in a pattern (prohormone convertase (PC)1/3 dependent) similar to that described for human gut. All three cell lines showed basal secretion of GLP-1 and GLP-2, which increased after stimulation. In contrast to freshly isolated murine L-cells, all cell lines also expressed PC2 and secreted large amounts of pancreatic glucagon. Neurotensin and somatostatin storage was low and secretion was not consistently increased by stimulation. STC-1 cells released more glucose-dependent insulinotropic polypeptide than GLP-1 at baseline (P < 0.01) and KCl elevated its secretion (P < 0.05). Peptide YY, which normally co-localizes with GLP-1 in distal L-cells, was not detected in any of the cell lines. GLUTag and STC-1 cells also expressed vasoactive intestinal peptide, but none expressed pancreatic polypeptide or insulin. GLUTag contained and secreted large amounts of CCK, while NCI-H716 did not store this peptide and STC-1 contained low amounts. Our results show that hormone production in cell line models of the L-cell has limited similarity to the natural L-cells.
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Affiliation(s)
- Rune Ehrenreich Kuhre
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Researchthe Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Nicolai Jacob Wewer Albrechtsen
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Researchthe Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Carolyn Fiona Deacon
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Researchthe Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Emilie Balk-Møller
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Researchthe Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Jens Frederik Rehfeld
- Department of Clinical Biochemistry RigshospitaletUniversity of Copenhagen, Copenhagen, Denmark
| | - Frank Reimann
- Cambridge Institute for Medical Research and MRC Metabolic Diseases UnitUniversity of Cambridge, Cambridge, United Kingdom
| | - Fiona Mary Gribble
- Cambridge Institute for Medical Research and MRC Metabolic Diseases UnitUniversity of Cambridge, Cambridge, United Kingdom
| | - Jens Juul Holst
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Researchthe Panum Institute, University of Copenhagen, Copenhagen, Denmark
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72
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Reimann F, Gribble FM. Mechanisms underlying glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 secretion. J Diabetes Investig 2016; 7 Suppl 1:13-9. [PMID: 27186350 PMCID: PMC4854499 DOI: 10.1111/jdi.12478] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/17/2015] [Accepted: 01/06/2016] [Indexed: 01/10/2023] Open
Abstract
The incretin hormones, glucose‐dependent insulinotropic peptide and glucagon‐like peptide‐1, are secreted from intestinal K‐ and L cells, respectively, with the former being most abundant in the proximal small intestine, whereas the latter increase in number towards the distal gut. Although an overlap between K‐ and L cells can be observed immunohistochemically or in murine models expressing fluorescent markers under the control of the two hormone promoters, the majority (>80%) of labeled cells seems to produce only one of these hormones. Transcriptomic analysis showed a close relationship between small intestinal K‐ and L cells, and glucose sensing mechanisms appear similar in both cell types with a predominant role of electrogenic glucose uptake through sodium‐coupled glucose transporter 1. Similarly, both cell types produce the long‐chain fatty acid sensing G‐protein‐coupled receptors, FFAR1 (GPR40) and FFAR4 (GPR120), but differ in the expression/functionality of other lipid sensing receptors. GPR119 and FFAR2/3, for example, have clearly documented roles in glucagon‐like peptide‐1 secretion, whereas agonists for the endocannabinoid receptor type 1 have been found to show largely selective inhibition of glucose‐dependent insulinotropic peptide secretion. In conclusion, although K‐ and L cell populations overlap and share key molecular nutrient‐sensing mechanisms, subtle differences between the responsiveness of the different cell types might be exploited to differentially modulate glucose‐dependent insulinotropic peptide or glucagon‐like peptide‐1 secretion.
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Affiliation(s)
- Frank Reimann
- University of Cambridge Metabolic Research Laboratories and MRC Metabolic Diseases Unit WT-MRC Institute of Metabolic Science Addenbrooke's Hospital Cambridge UK
| | - Fiona M Gribble
- University of Cambridge Metabolic Research Laboratories and MRC Metabolic Diseases Unit WT-MRC Institute of Metabolic Science Addenbrooke's Hospital Cambridge UK
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73
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Poudyal H. Mechanisms for the cardiovascular effects of glucagon-like peptide-1. Acta Physiol (Oxf) 2016; 216:277-313. [PMID: 26384481 DOI: 10.1111/apha.12604] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 07/25/2015] [Accepted: 09/10/2015] [Indexed: 12/16/2022]
Abstract
Over the past three decades, at least 10 hormones secreted by the enteroendocrine cells have been discovered, which directly affect the cardiovascular system through their innate receptors expressed in the heart and blood vessels or through a neural mechanism. Glucagon-like peptide-1 (GLP-1), an important incretin, is perhaps best studied of these gut-derived hormones with important cardiovascular effects. In this review, I have discussed the mechanism of GLP-1 release from the enteroendocrine L-cells and its physiological effects on the cardiovascular system. Current evidence suggests that GLP-1 has positive inotropic and chronotropic effects on the heart and may be important in preserving left ventricular structure and function by direct and indirect mechanisms. The direct effects of GLP-1 in the heart may be mediated through GLP-1R expressed in atria as well as arteries and arterioles in the left ventricle and mainly involve in the activation of multiple pro-survival kinases and enhanced energy utilization. There is also good evidence to support the involvement of a second, yet to be identified, GLP-1 receptor. Further, GLP-1(9-36)amide, which was previously thought to be the inactive metabolite of the active GLP-1(7-36)amide, may also have direct cardioprotective effects. GLP-1's action on GLP-1R expressed in the central nervous system, kidney, vasculature and the pancreas may indirectly contribute to its cardioprotective effects.
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Affiliation(s)
- H. Poudyal
- Department of Diabetes, Endocrinology and Nutrition; Graduate School of Medicine and Hakubi Centre for Advanced Research; Kyoto University; Kyoto Japan
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74
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Clara R, Langhans W, Mansouri A. Oleic acid stimulates glucagon-like peptide-1 release from enteroendocrine cells by modulating cell respiration and glycolysis. Metabolism 2016; 65:8-17. [PMID: 26892511 DOI: 10.1016/j.metabol.2015.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/22/2015] [Accepted: 10/01/2015] [Indexed: 12/22/2022]
Abstract
OBJECTIVE Glucagon-like peptide-1 (GLP-1) is a potent satiating and incretin hormone released by enteroendocrine L-cells in response to eating. Dietary fat, in particular monounsaturated fatty acids, such as oleic acid (OA), potently stimulates GLP-1 secretion from L-cells. It is, however, unclear whether the intracellular metabolic handling of OA is involved in this effect. METHODS First we determined the optimal medium for the bioenergetics measurements. Then we examined the effect of OA on the metabolism of the immortalized enteroendocrine GLUTag cell model and assessed GLP-1 release in parallel. We measured oxygen consumption rate and extracellular acidification rate in response to OA and to different metabolic inhibitors with the Seahorse extracellular flux analyzer. RESULTS OA increased cellular respiration and potently stimulated GLP-1 release. The fatty acid oxidation inhibitor etomoxir did neither reduce OA-induced respiration nor affect the OA-induced GLP-1 release. In contrast, inhibition of the respiratory chain or of downstream steps of aerobic glycolysis reduced the OA-induced GLP-1 release, and an inhibition of the first step of glycolysis by addition of 2-deoxy-d-glucose even abolished it. CONCLUSION These findings indicate that an indirect stimulation of glycolysis is crucial for the OA-induced release of GLP-1.
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Affiliation(s)
- Rosmarie Clara
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach (Zürich), Switzerland
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach (Zürich), Switzerland
| | - Abdelhak Mansouri
- Physiology and Behavior Laboratory, ETH Zürich, 8603 Schwerzenbach (Zürich), Switzerland.
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75
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Abstract
Glucagon like peptide-1 is an insulinotropic hormone released from intestinal L-cells in response to food ingestion. Here, we investigated mechanisms underlying the sensing of peptones by primary small intestinal L-cells. Meat, casein and vegetable-derived peptones (5 mg/ml), the L-amino acids Phe, Trp, Gln and Ala (20 mM each), and the dipeptide glycine-sarcosine (20 mM) stimulated GLP-1 secretion from primary cultures prepared from the small intestine. Further mechanistic studies were performed with meat peptone, and revealed the elevation of intracellular calcium in L-cells. Inhibition of the calcium sensing receptor (CaSR), transient receptor potential (TRP) channels and Q-type voltage gated calcium channels (VGCC) significantly attenuated peptone-stimulated GLP-1 release and reduced intracellular Ca(2+) responses. CaSR inhibition also attenuated the GLP-1 secretory response to Gln. Targeting these pathways in L-cells could be used to increase endogenous production of GLP-1 and offer exploitable avenues for the development of therapeutics to treat diabetes and obesity.
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Affiliation(s)
- Ramona Pais
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Fiona M Gribble
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
| | - Frank Reimann
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
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76
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Svendsen B, Holst JJ. Regulation of gut hormone secretion. Studies using isolated perfused intestines. Peptides 2016; 77:47-53. [PMID: 26275337 DOI: 10.1016/j.peptides.2015.08.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 07/03/2015] [Accepted: 08/04/2015] [Indexed: 12/28/2022]
Abstract
The incretin hormones glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted from enteroendocrine cells in the intestine along with other gut hormones (PYY, CCK and neurotensin) shown to affect metabolism and/or appetite. The secretion of many gut hormones is highly increased after gastric bypass operations, which have turned out to be an effective therapy of not only obesity but also type 2 diabetes. These effects are likely to be due, at least in part, to increases in the secretion of these gut hormones (except GIP). Therefore, stimulation of the endogenous hormone represents an appealing therapeutic strategy, which has spurred an interest in understanding the regulation of gut hormone secretion and a search for particularly GLP-1 and PYY secretagogues. The secretion of the gut hormones is stimulated by oral intake of nutrients often including carbohydrate, protein and lipid. This review focuses on stimulators of gut hormone secretion, the mechanisms involved, and in particular models used to investigate secretion. A major break-through in this field was the development of methods to identify and isolate specific hormone producing cells, which allow detailed mapping of the expression profiles of these cells, whereas they are less suitable for physiological studies of secretion. Isolated perfused preparations of mouse and rat intestines have proven to be reliable models for dynamic hormone secretion and should be able to bridge the gap between the molecular details derived from the single cells to the integrated patterns observed in the intact animals.
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Affiliation(s)
- Berit Svendsen
- Department of Biomedical Sciences, Faculty of health Sciences, University of Copenhagen, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.
| | - Jens Juul Holst
- Department of Biomedical Sciences, Faculty of health Sciences, University of Copenhagen, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
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77
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Ni Z, Zhang Y, Wang H, Wei Y, Ma B, Hao J, Tu P, Duan H, Li X, Jiang P, Ma X, Wang B, Wu R, Zhu J, Li M. Construction of a Fusion Peptide 5rolGLP-HV and Analysis of its Therapeutic Effect on Type 2 Diabetes Mellitus and Thrombosis in Mice. Appl Biochem Biotechnol 2016; 179:59-74. [DOI: 10.1007/s12010-016-1979-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 01/04/2016] [Indexed: 12/20/2022]
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78
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Kihira Y, Burentogtokh A, Itoh M, Izawa-Ishizawa Y, Ishizawa K, Ikeda Y, Tsuchiya K, Tamaki T. Hypoxia decreases glucagon-like peptide-1 secretion from the GLUTag cell line. Biol Pharm Bull 2016; 38:514-21. [PMID: 25832631 DOI: 10.1248/bpb.b14-00612] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucagon-like peptide-1 (GLP-1), an incretin hormone, is secreted from L cells located in the intestinal epithelium. It is known that intestinal oxygen tension is decreased postprandially. In addition, we found that the expression of hypoxia-inducible factor-1α (HIF-1α), which accumulates in cells under hypoxic conditions, was significantly increased in the colons of mice with food intake, indicating that the oxygen concentration is likely reduced in the colon after eating. Therefore, we hypothesized that GLP-1 secretion is affected by oxygen tension. We found that forskolin-stimulated GLP-1 secretion from GLUTag cells, a model of intestinal L cells, is suppressed in hypoxia (1% O2). Forskolin-stimulated elevations of preproglucagon (ppGCG) and proprotein convertase 1/3 (PC1/3) mRNA expression were decreased under hypoxic conditions. The finding that H89, a protein kinase A (PKA) inhibitor, inhibited the forskolin-stimulated increase of ppGCG and PC1/3 indicated that the cAMP-PKA pathway is involved in the hypoxia-induced suppression of the genes. Hypoxia decreased hexokinase 2 mRNA and protein expression and increased lactate dehydrogenase A mRNA and protein expression. Concomitantly, lactate production was increased and ATP production was decreased. Together, the results indicate that hypoxia decreases glucose utilization for ATP production, which probably causes a decrease in cAMP production and in subsequent GLP-1 production. Our findings suggest that the postprandial decrease in oxygen tension in the intestine attenuates GLP-1 secretion.
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Affiliation(s)
- Yoshitaka Kihira
- Department of Pharmacology, Institute of Health Biosciences, The University of Tokushima Graduate School
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Amouyal C, Andreelli F. Increasing GLP-1 Circulating Levels by Bariatric Surgery or by GLP-1 Receptor Agonists Therapy: Why Are the Clinical Consequences so Different? J Diabetes Res 2016; 2016:5908656. [PMID: 27382574 PMCID: PMC4921140 DOI: 10.1155/2016/5908656] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/18/2016] [Indexed: 12/13/2022] Open
Abstract
The "incretin effect" is used to describe the observation that more insulin is secreted after the oral administration of glucose compared to that after the intravenous administration of the same amount of glucose. During the absorption of meals, the gut is thought to regulate insulin secretion by secreting a specific factor that targets pancreatic beta cells. Additional research confirmed this hypothesis with the discovery of two hormones called incretins: gastric inhibitory peptide (GIP) and glucagon-like peptide 1 (GLP-1). During meals, specific cells in the gut (L and K enteroendocrine cells) secrete incretins, causing an increase in the blood concentrations of, respectively, GLP-1 and GIP. Bariatric surgery is now proposed during the therapeutic management of type 2 diabetes in obese or overweight populations. It has been hypothesized that restoration of endogenous GLP-1 secretion after the surgery may contribute to the postsurgical resolution of diabetes. In 2005, the commercialization of GLP-1 receptor agonists gave the possibility to test this hypothesis. A few years later, it is now accepted that GLP-1 receptor agonists and bariatric surgery differently improve type 2 diabetes. These differences between endogenous and exogenous GLP-1 on glucose homeostasis emphasized the dual properties of GLP-1 as a peptide hormone and as a neurotransmitter.
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Affiliation(s)
- Chloé Amouyal
- Cardiometabolism and Nutrition Institute (ICAN), Heart and Metabolism Department, Pitié-Salpêtrière Hospital (APHP), 75013 Paris, France
- INSERM UMRS U1166 (Eq 6) Nutriomics, UPMC, Pierre et Marie Curie Faculty Paris 6, Sorbonne University, 75013 Paris, France
| | - Fabrizio Andreelli
- Cardiometabolism and Nutrition Institute (ICAN), Heart and Metabolism Department, Pitié-Salpêtrière Hospital (APHP), 75013 Paris, France
- INSERM UMRS U1166 (Eq 6) Nutriomics, UPMC, Pierre et Marie Curie Faculty Paris 6, Sorbonne University, 75013 Paris, France
- *Fabrizio Andreelli:
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80
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Riz M, Pedersen MG. Mathematical Modeling of Interacting Glucose-Sensing Mechanisms and Electrical Activity Underlying Glucagon-Like Peptide 1 Secretion. PLoS Comput Biol 2015; 11:e1004600. [PMID: 26630068 PMCID: PMC4667885 DOI: 10.1371/journal.pcbi.1004600] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 10/13/2015] [Indexed: 01/12/2023] Open
Abstract
Intestinal L-cells sense glucose and other nutrients, and in response release glucagon-like peptide 1 (GLP-1), peptide YY and other hormones with anti-diabetic and weight-reducing effects. The stimulus-secretion pathway in L-cells is still poorly understood, although it is known that GLP-1 secreting cells use sodium-glucose co-transporters (SGLT) and ATP-sensitive K+-channels (K(ATP)-channels) to sense intestinal glucose levels. Electrical activity then transduces glucose sensing to Ca2+-stimulated exocytosis. This particular glucose-sensing arrangement with glucose triggering both a depolarizing SGLT current as well as leading to closure of the hyperpolarizing K(ATP) current is of more general interest for our understanding of glucose-sensing cells. To dissect the interactions of these two glucose-sensing mechanisms, we build a mathematical model of electrical activity underlying GLP-1 secretion. Two sets of model parameters are presented: one set represents primary mouse colonic L-cells; the other set is based on data from the GLP-1 secreting GLUTag cell line. The model is then used to obtain insight into the differences in glucose-sensing between primary L-cells and GLUTag cells. Our results illuminate how the two glucose-sensing mechanisms interact, and suggest that the depolarizing effect of SGLT currents is modulated by K(ATP)-channel activity. Based on our simulations, we propose that primary L-cells encode the glucose signal as changes in action potential amplitude, whereas GLUTag cells rely mainly on frequency modulation. The model should be useful for further basic, pharmacological and theoretical investigations of the cellular signals underlying endogenous GLP-1 and peptide YY release.
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Affiliation(s)
- Michela Riz
- Department of Information Engineering, University of Padua, Padua, Italy
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81
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Ghanem SS, Heinrich G, Lester SG, Pfeiffer V, Bhattacharya S, Patel PR, DeAngelis AM, Dai T, Ramakrishnan SK, Smiley ZN, Jung DY, Lee Y, Kitamura T, Ergun S, Kulkarni RN, Kim JK, Giovannucci DR, Najjar SM. Increased Glucose-induced Secretion of Glucagon-like Peptide-1 in Mice Lacking the Carcinoembryonic Antigen-related Cell Adhesion Molecule 2 (CEACAM2). J Biol Chem 2015; 291:980-8. [PMID: 26586918 DOI: 10.1074/jbc.m115.692582] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Indexed: 01/11/2023] Open
Abstract
Carcinoembryonic antigen-related cell adhesion molecule 2 (CEACAM2) regulates food intake as demonstrated by hyperphagia in mice with the Ceacam2 null mutation (Cc2(-/-)). This study investigated whether CEACAM2 also regulates insulin secretion. Ceacam2 deletion caused an increase in β-cell secretory function, as assessed by hyperglycemic clamp analysis, without affecting insulin response. Although CEACAM2 is expressed in pancreatic islets predominantly in non-β-cells, basal plasma levels of insulin, glucagon and somatostatin, islet areas, and glucose-induced insulin secretion in pooled Cc2(-/-) islets were all normal. Consistent with immunofluorescence analysis showing CEACAM2 expression in distal intestinal villi, Cc2(-/-) mice exhibited a higher release of oral glucose-mediated GLP-1, an incretin that potentiates insulin secretion in response to glucose. Compared with wild type, Cc2(-/-) mice also showed a higher insulin excursion during the oral glucose tolerance test. Pretreating with exendin(9-39), a GLP-1 receptor antagonist, suppressed the effect of Ceacam2 deletion on glucose-induced insulin secretion. Moreover, GLP-1 release into the medium of GLUTag enteroendocrine cells was increased with siRNA-mediated Ceacam2 down-regulation in parallel to an increase in Ca(2+) entry through L-type voltage-dependent Ca(2+) channels. Thus, CEACAM2 regulates insulin secretion, at least in part, by a GLP-1-mediated mechanism, independent of confounding metabolic factors.
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Affiliation(s)
- Simona S Ghanem
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Garrett Heinrich
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Sumona G Lester
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Verena Pfeiffer
- the Institut für Anatomie und Zellbiologie, Universität Würzburg, D-97070 Würzburg, Germany
| | - Sumit Bhattacharya
- Neurosciences, College of Medicine and Life Sciences, University of Toledo, Health Science Campus, Toledo, Ohio 43614
| | - Payal R Patel
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Anthony M DeAngelis
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Tong Dai
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Sadeesh K Ramakrishnan
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Zachary N Smiley
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
| | - Dae Y Jung
- the Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Yongjin Lee
- the Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Tadahiro Kitamura
- the Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 371-8512 Gunma, Japan, and
| | - Suleyman Ergun
- the Institut für Anatomie und Zellbiologie, Universität Würzburg, D-97070 Würzburg, Germany
| | - Rohit N Kulkarni
- the Islet Cell and Regenerative Biology, Joslin Diabetes Center and Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02215
| | - Jason K Kim
- the Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - David R Giovannucci
- Neurosciences, College of Medicine and Life Sciences, University of Toledo, Health Science Campus, Toledo, Ohio 43614
| | - Sonia M Najjar
- From the Center for Diabetes and Endocrine Research and Departments of Physiology and Pharmacology and
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82
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Deng Y, Zhang Y, Zheng S, Hong J, Wang C, Liu T, Sun Z, Gu W, Gu Y, Shi J, Yao S, Wang W, Ning G. Postprandial glucose, insulin and incretin responses to different carbohydrate tolerance tests. J Diabetes 2015; 7:820-9. [PMID: 25395350 DOI: 10.1111/1753-0407.12245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 10/28/2014] [Accepted: 11/06/2014] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Few studies have focused on postprandial incretin responses to different carbohydrate meals. Therefore, we designed a study to compare the different effects of two carbohydrates (75 g oral glucose, a monosaccharide and 100 g standard noodle, a polysaccharide, with 75 g carbohydrates equivalently) on postprandial glucose, insulin and incretin responses in different glucose tolerance groups. METHODS This study was an open-label, randomized, two-way crossover clinical trial. 240 participants were assigned to take two carbohydrates in a randomized order separated by a washout period of 5-7 days. The plasma glucose, insulin, c-peptide, glucagon and active glucagon-like peptide-1 (AGLP-1) were measured. The incremental area under curve above baseline from 0 to 120 min of insulin (iAUC(0 -120 min)- INS) and AGLP-1(iAUC(0 -120 min)- AGLP-1) was calculated. RESULTS Compared with standard noodles, the plasma glucose and insulin after consumption of oral glucose were higher at 30 min (both P < 0.001) and 60 min (both P < 0.001), while lower at 180 min (both P < 0.001), but no differences were found at 120 min. The glucagon at 180 min was higher after consumption of oral glucose (P = 0.010). The AGLP-1 response to oral glucose was higher at 30 min (P < 0.001), 60 min (P < 0.001) and 120 min (P = 0.022), but lower at 180 min (P = 0.027). In normal glucose tolerance (NGT), oral glucose elicited a higher insulin response to the corresponding AGLP-1 (P < 0.001), which was represented by iAUC(0 -120 min) -INS /iAUC(0 -120 min)- AGLP-1, while in type 2 diabetes mellitus (T2DM), standard noodles did (P = 0.001). CONCLUSIONS Monosaccharide potentiated more rapid and higher glycemic and insulin responses. Oral glucose of liquid state would elicit a more potent release of AGLP-1. The incretin effect was amplified after consumption of standard noodles in T2DM.
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Affiliation(s)
- Yuying Deng
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Yifei Zhang
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Sheng Zheng
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Jie Hong
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | | | - Ting Liu
- Nutrition and Health Research Institute, COFCO
| | - Zhehao Sun
- R&D Division, China Food Limited, COFCO, Beijing, China
| | - Weiqiong Gu
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Yanyun Gu
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Juan Shi
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Shuangshuang Yao
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Weiqing Wang
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Guang Ning
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of Chinese Health Ministry, Division of Endocrinology of E-Institutes of Shanghai, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
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83
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Abstract
The enteroendocrine system orchestrates how the body responds to the ingestion of foods, employing a diversity of hormones to fine-tune a wide range of physiological responses both within and outside the gut. Recent interest in gut hormones has surged with the realization that they modulate glucose tolerance and food intake through a variety of mechanisms, and such hormones are therefore excellent therapeutic candidates for the treatment of diabetes and obesity. Characterizing the roles and functions of different enteroendocrine cells is an essential step in understanding the physiology, pathophysiology, and therapeutics of the gut-brain-pancreas axis.
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Affiliation(s)
- Fiona M Gribble
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science, and Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom; ,
| | - Frank Reimann
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science, and Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, United Kingdom; ,
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84
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Vasu S, Moffett RC, McClenaghan NH, Flatt PR. Differential molecular and cellular responses of GLP-1 secreting L-cells and pancreatic alpha cells to glucotoxicity and lipotoxicity. Exp Cell Res 2015; 336:100-8. [DOI: 10.1016/j.yexcr.2015.05.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 05/25/2015] [Accepted: 05/26/2015] [Indexed: 12/25/2022]
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85
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Candeias EM, Sebastião IC, Cardoso SM, Correia SC, Carvalho CI, Plácido AI, Santos MS, Oliveira CR, Moreira PI, Duarte AI. Gut-brain connection: The neuroprotective effects of the anti-diabetic drug liraglutide. World J Diabetes 2015; 6:807-827. [PMID: 26131323 PMCID: PMC4478577 DOI: 10.4239/wjd.v6.i6.807] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/30/2015] [Accepted: 05/18/2015] [Indexed: 02/05/2023] Open
Abstract
Long-acting glucagon-like peptide-1 (GLP-1) analogues marketed for type 2 diabetes (T2D) treatment have been showing positive and protective effects in several different tissues, including pancreas, heart or even brain. This gut secreted hormone plays a potent insulinotropic activity and an important role in maintaining glucose homeostasis. Furthermore, growing evidences suggest the occurrence of several commonalities between T2D and neurodegenerative diseases, insulin resistance being pointed as a main cause for cognitive decline and increased risk to develop dementia. In this regard, it has also been suggested that stimulation of brain insulin signaling may have a protective role against cognitive deficits. As GLP-1 receptors (GLP-1R) are expressed throughout the central nervous system and GLP-1 may cross the blood-brain-barrier, an emerging hypothesis suggests that they may be promising therapeutic targets against brain dysfunctional insulin signaling-related pathologies. Importantly, GLP-1 actions depend not only on the direct effect mediated by its receptor activation, but also on the gut-brain axis involving an exchange of signals between both tissues via the vagal nerve, thereby regulating numerous physiological functions (e.g., energy homeostasis, glucose-dependent insulin secretion, as well as appetite and weight control). Amongst the incretin/GLP-1 mimetics class of anti-T2D drugs with an increasingly described neuroprotective potential, the already marketed liraglutide emerged as a GLP-1R agonist highly resistant to dipeptidyl peptidase-4 degradation (thereby having an increased half-life) and whose systemic GLP-1R activity is comparable to that of native GLP-1. Importantly, several preclinical studies showed anti-apoptotic, anti-inflammatory, anti-oxidant and neuroprotective effects of liraglutide against T2D, stroke and Alzheimer disease (AD), whereas several clinical trials, demonstrated some surprising benefits of liraglutide on weight loss, microglia inhibition, behavior and cognition, and in AD biomarkers. Herein, we discuss the GLP-1 action through the gut-brain axis, the hormone’s regulation of some autonomic functions and liraglutide’s neuroprotective potential.
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86
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Ishikawa Y, Hira T, Inoue D, Harada Y, Hashimoto H, Fujii M, Kadowaki M, Hara H. Rice protein hydrolysates stimulate GLP-1 secretion, reduce GLP-1 degradation, and lower the glycemic response in rats. Food Funct 2015; 6:2525-34. [PMID: 26107658 DOI: 10.1039/c4fo01054j] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Rice has historically been consumed in Asia as a major source of carbohydrates, however, little is known regarding the functional roles of rice proteins as dietary factors. In the present study, we investigated whether peptides derived from rice proteins could stimulate GLP-1 secretion, which results in reducing glycemia via the incretin effect in normal rats. Hydrolysates were prepared from the protein fraction of rice endosperm or rice bran, and the effects of these hydrolysates on GLP-1 secretion were examined in a murine enteroendocrine cell line GLUTag. Plasma was collected after oral administration of the rice protein hydrolysates, under anesthesia, or during glucose tolerance tests in rats. In anesthetized rats, plasma dipeptidyl peptidase-IV (DPP-IV) activity was measured after ileal administration of the rice protein hydrolysates. GLP-1 secretion from GLUTag cells was potently stimulated by the rice protein hydrolysates, especially by the peptic digest of rice endosperm protein (REPH) and that of rice bran protein (RBPH). Oral administration of REPH or RBPH elevated plasma GLP-1 concentrations, which resulted in the reduction of glycemia under the intraperitoneal glucose tolerance test. In addition, the plasma DPP-IV activity was attenuated after ileal administration of REPH or RBPH, which resulted in a higher ratio of intact (active) GLP-1 to total GLP-1 in the plasma. These results demonstrate that rice proteins exert potent stimulatory effects on GLP-1 secretion, which could contribute to the reduction of postprandial glycemia. The inhibitory effect of these peptides on the plasma DPP-IV activity may potentiate the incretin effect of GLP-1.
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Affiliation(s)
- Yuki Ishikawa
- Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
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87
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Murovets VO, Bachmanov AA, Zolotarev VA. Impaired Glucose Metabolism in Mice Lacking the Tas1r3 Taste Receptor Gene. PLoS One 2015; 10:e0130997. [PMID: 26107521 PMCID: PMC4479554 DOI: 10.1371/journal.pone.0130997] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 05/27/2015] [Indexed: 01/12/2023] Open
Abstract
The G-protein-coupled sweet taste receptor dimer T1R2/T1R3 is expressed in taste bud cells in the oral cavity. In recent years, its involvement in membrane glucose sensing was discovered in endocrine cells regulating glucose homeostasis. We investigated importance of extraorally expressed T1R3 taste receptor protein in age-dependent control of blood glucose homeostasis in vivo, using nonfasted mice with a targeted mutation of the Tas1r3 gene that encodes the T1R3 protein. Glucose and insulin tolerance tests, as well as behavioral tests measuring taste responses to sucrose solutions, were performed with C57BL/6ByJ (Tas1r3+/+) inbred mice bearing the wild-type allele and C57BL/6J-Tas1r3tm1Rfm mice lacking the entire Tas1r3 coding region and devoid of the T1R3 protein (Tas1r3-/-). Compared with Tas1r3+/+ mice, Tas1r3-/- mice lacked attraction to sucrose in brief-access licking tests, had diminished taste preferences for sucrose solutions in the two-bottle tests, and had reduced insulin sensitivity and tolerance to glucose administered intraperitoneally or intragastrically, which suggests that these effects are due to absence of T1R3. Impairment of glucose clearance in Tas1r3-/- mice was exacerbated with age after intraperitoneal but not intragastric administration of glucose, pointing to a compensatory role of extraoral T1R3-dependent mechanisms in offsetting age-dependent decline in regulation of glucose homeostasis. Incretin effects were similar in Tas1r3+/+ and Tas1r3-/- mice, which suggests that control of blood glucose clearance is associated with effects of extraoral T1R3 in tissues other than the gastrointestinal tract. Collectively, the obtained data demonstrate that the T1R3 receptor protein plays an important role in control of glucose homeostasis not only by regulating sugar intake but also via its extraoral function, probably in the pancreas and brain.
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Affiliation(s)
- Vladimir O. Murovets
- Department of physiology of digestion, Pavlov Institute of Physiology, Saint-Petersburg, Russia
| | | | - Vasiliy A. Zolotarev
- Department of physiology of digestion, Pavlov Institute of Physiology, Saint-Petersburg, Russia
- * E-mail:
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88
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Sandoval DA, D'Alessio DA. Physiology of proglucagon peptides: role of glucagon and GLP-1 in health and disease. Physiol Rev 2015; 95:513-48. [PMID: 25834231 DOI: 10.1152/physrev.00013.2014] [Citation(s) in RCA: 310] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The preproglucagon gene (Gcg) is expressed by specific enteroendocrine cells (L-cells) of the intestinal mucosa, pancreatic islet α-cells, and a discrete set of neurons within the nucleus of the solitary tract. Gcg encodes multiple peptides including glucagon, glucagon-like peptide-1, glucagon-like peptide-2, oxyntomodulin, and glicentin. Of these, glucagon and GLP-1 have received the most attention because of important roles in glucose metabolism, involvement in diabetes and other disorders, and application to therapeutics. The generally accepted model is that GLP-1 improves glucose homeostasis indirectly via stimulation of nutrient-induced insulin release and by reducing glucagon secretion. Yet the body of literature surrounding GLP-1 physiology reveals an incompletely understood and complex system that includes peripheral and central GLP-1 actions to regulate energy and glucose homeostasis. On the other hand, glucagon is established principally as a counterregulatory hormone, increasing in response to physiological challenges that threaten adequate blood glucose levels and driving glucose production to restore euglycemia. However, there also exists a potential role for glucagon in regulating energy expenditure that has recently been suggested in pharmacological studies. It is also becoming apparent that there is cross-talk between the proglucagon derived-peptides, e.g., GLP-1 inhibits glucagon secretion, and some additive or synergistic pharmacological interaction between GLP-1 and glucagon, e.g., dual glucagon/GLP-1 agonists cause more weight loss than single agonists. In this review, we discuss the physiological functions of both glucagon and GLP-1 by comparing and contrasting how these peptides function, variably in concert and opposition, to regulate glucose and energy homeostasis.
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Affiliation(s)
- Darleen A Sandoval
- Division of Endocrinology and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - David A D'Alessio
- Division of Endocrinology and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio
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89
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Sato T, Hayashi H, Hiratsuka M, Hirasawa N. Glucocorticoids decrease the production of glucagon-like peptide-1 at the transcriptional level in intestinal L-cells. Mol Cell Endocrinol 2015; 406:60-7. [PMID: 25700603 DOI: 10.1016/j.mce.2015.02.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 01/13/2015] [Accepted: 02/13/2015] [Indexed: 01/28/2023]
Abstract
Glucocorticoids are widely used as anti-inflammatory or immunosuppressive drugs, but often induce hyperglycemia as a side effect. Glucagon-like peptide-1 (GLP-1) is secreted from intestinal L cells and plays crucial roles in maintaining glucose homeostasis. However, the direct effects of glucocorticoids on the GLP-1 production pathway in L cells remain unclear. We investigated the effects of glucocorticoids on GLP-1 production in vitro and in vivo. In L cell lines, glucocorticoids decreased GLP-1 release and expression of the precursor, proglucagon, at protein and mRNA levels, which were inhibited by mifepristone. The administration of dexamethasone or budesonide to mice significantly decreased the mRNA expression of proglucagon in the ileum and partially decreased glucose-stimulated GLP-1 secretion. Compound A, a dissociated glucocorticoid receptor modulator, did not affect the expression of proglucagon in vitro. These results suggested that glucocorticoids directly reduced GLP-1 production at the transcriptional level in L cells through a glucocorticoid receptor dimerization-dependent mechanism.
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Affiliation(s)
- Taiki Sato
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Hiroto Hayashi
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Masahiro Hiratsuka
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Noriyasu Hirasawa
- Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
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90
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Gagnon J, Baggio LL, Drucker DJ, Brubaker PL. Ghrelin Is a Novel Regulator of GLP-1 Secretion. Diabetes 2015; 64:1513-21. [PMID: 25412624 DOI: 10.2337/db14-1176] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 11/15/2014] [Indexed: 12/16/2022]
Abstract
GLP-1 is a gastrointestinal L-cell hormone that enhances glucose-stimulated insulin secretion. Hence, strategies that prevent GLP-1 degradation or activate the GLP-1 receptor are used to treat patients with type 2 diabetes. GLP-1 secretion occurs after a meal and is partly regulated by other circulating hormones. Ghrelin is a stomach-derived hormone that plays a key role in whole-body energy metabolism. Because ghrelin levels peak immediately before mealtimes, we hypothesized that ghrelin plays a role in priming the intestinal L-cell for nutrient-induced GLP-1 release. The intraperitoneal injection of ghrelin into mice 15 min before the administration of oral glucose enhanced glucose-stimulated GLP-1 release and improved glucose tolerance, whereas the ghrelin receptor antagonist D-Lys GHRP-6 reduced plasma levels of GLP-1 and insulin and diminished oral glucose tolerance. The ghrelin-mediated improvement in glucose tolerance was lost in mice coinjected with a GLP-1 receptor antagonist as well as in Glp1r(-/-) mice lacking the GLP-1 receptor. The impaired oral glucose tolerance in diet-induced obese mice was also improved by ghrelin preadministration. Importantly, ghrelin directly stimulated GLP-1 release from L-cell lines (murine GLUTag, human NCI-H716) through an extracellular signal-related kinase 1/2-dependent pathway. These studies demonstrate a novel role for ghrelin in enhancing the GLP-1 secretory response to ingested nutrients.
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Affiliation(s)
- Jeffrey Gagnon
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Laurie L Baggio
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada Lunenfeld-Tanenbaum Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - Daniel J Drucker
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada Lunenfeld-Tanenbaum Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - Patricia L Brubaker
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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91
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Nagamine R, Ueno S, Tsubata M, Yamaguchi K, Takagaki K, Hira T, Hara H, Tsuda T. Dietary sweet potato (Ipomoea batatas L.) leaf extract attenuates hyperglycaemia by enhancing the secretion of glucagon-like peptide-1 (GLP-1). Food Funct 2015; 5:2309-16. [PMID: 25066255 DOI: 10.1039/c4fo00032c] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
'Suioh', a sweet potato (Ipomoea batatas L.) cultivar developed in Japan, has edible leaves and stems. The sweet potato leaves contain polyphenols such as caffeoylquinic acid (CQA) derivatives. It has multiple biological functions and may help to regulate the blood glucose concentration. In this study, we first examined whether sweet potato leaf extract powder (SP) attenuated hyperglycaemia in type 2 diabetic mice. Administration of dietary SP for 5 weeks significantly lowered glycaemia in type 2 diabetic mice. Second, we conducted in vitro experiments, and found that SP and CQA derivatives significantly enhanced glucagon-like peptide-1 (GLP-1) secretion. Third, pre-administration of SP significantly stimulated GLP-1 secretion and was accompanied by enhanced insulin secretion in rats, which resulted in a reduced glycaemic response after glucose injection. These results indicate that oral SP attenuates postprandial hyperglycaemia, possibly through enhancement of GLP-1 secretion.
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Affiliation(s)
- Rika Nagamine
- Research and Development Division, Toyo Shinyaku Co., Ltd., 7-28 Yayoigaoka, Tosu-shi, Saga 841-0005, Japan.
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92
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Emery EC, Diakogiannaki E, Gentry C, Psichas A, Habib AM, Bevan S, Fischer MJM, Reimann F, Gribble FM. Stimulation of GLP-1 secretion downstream of the ligand-gated ion channel TRPA1. Diabetes 2015; 64:1202-10. [PMID: 25325736 PMCID: PMC4375100 DOI: 10.2337/db14-0737] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Stimulus-coupled incretin secretion from enteroendocrine cells plays a fundamental role in glucose homeostasis and could be targeted for the treatment of type 2 diabetes. Here, we investigated the expression and function of transient receptor potential (TRP) ion channels in enteroendocrine L cells producing GLP-1. By microarray and quantitative PCR analysis, we identified trpa1 as an L cell-enriched transcript in the small intestine. Calcium imaging of primary L cells and the model cell line GLUTag revealed responses triggered by the TRPA1 agonists allyl-isothiocyanate (mustard oil), carvacrol, and polyunsaturated fatty acids, which were blocked by TRPA1 antagonists. Electrophysiology in GLUTag cells showed that carvacrol induced a current with characteristics typical of TRPA1 and triggered the firing of action potentials. TRPA1 activation caused an increase in GLP-1 secretion from primary murine intestinal cultures and GLUTag cells, an effect that was abolished in cultures from trpa1(-/-) mice or by pharmacological TRPA1 inhibition. These findings present TRPA1 as a novel sensory mechanism in enteroendocrine L cells, coupled to the facilitation of GLP-1 release, which may be exploitable as a target for treating diabetes.
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Affiliation(s)
- Edward C Emery
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, U.K
| | | | - Clive Gentry
- Wolfson Centre for Age-Related Diseases, King's College London, London, U.K
| | - Arianna Psichas
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, U.K
| | - Abdella M Habib
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London, U.K
| | - Stuart Bevan
- Wolfson Centre for Age-Related Diseases, King's College London, London, U.K
| | - Michael J M Fischer
- Institute of Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Frank Reimann
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, U.K.
| | - Fiona M Gribble
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, U.K.
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93
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Cao Y, Cao X, Liu XM. Expression of cholecystokinin2-receptor in rat and human L cells and the stimulation of glucagon-like peptide-1 secretion by gastrin treatment. Acta Histochem 2015; 117:205-10. [PMID: 25601282 DOI: 10.1016/j.acthis.2014.12.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 11/30/2014] [Accepted: 12/18/2014] [Indexed: 12/21/2022]
Abstract
Gastrin is a gastrointestinal hormone secreted by G cells. Hypergastrinemia can improve blood glucose and glycosylated hemoglobin levels. These positive effects are primarily due to the trophic effects of gastrin on β-cells. In recent years, many receptors that regulate secretion of glucagon-like peptide 1 (GLP-1) have been identified in enteroendocrine L cell lines. This led us to hypothesize that, in addition to the trophic effects of gastrin on β-cells, L cells also express cholecystokinin2-receptor (CCK2R), which may regulate GLP-1 secretion and have synergistic effects on glucose homeostasis. Our research provides a preliminary analysis of CCK2R expression and the stimulating effect of gastrin treatment on GLP-1 secretion in a human endocrine L cell line, using RT-PCR, Western blot, immunocytochemistry, and ELISA analyses. The expression of proglucagon and prohormone convertase 3, which regulate GLP-1 biosynthesis, were also analyzed by real-time PCR. Double immunofluorescence labeling was utilized to assess the intracellular localization of CCK2R and GLP-1 in L cells harvested from rat colon tissue. Our results showed that CCK2R was expressed in both the human L cell line and the rat L cells. We also showed that treatment with gastrin, a CCK2R agonist, stimulated the secretion of GLP-1, and that this effect was likely due to increased expression of proglucagon and PCSK1 (also known as prohormone convertase 3 (PC3 gene)). These results not only provide a basis for the role gastrin may play in intestinal L cells, and may also provide the basis for the development of a method of gastrin-mediated glycemic regulation.
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Affiliation(s)
- Yang Cao
- Department of Endocrinology, First Affiliated Hospital of Harbin Medical University, Harbin 150001, Heilongjiang Province, China
| | - Xun Cao
- Department of Endocrinology, First Affiliated Hospital of Harbin Medical University, Harbin 150001, Heilongjiang Province, China
| | - Xiao-Min Liu
- Department of Endocrinology, First Affiliated Hospital of Harbin Medical University, Harbin 150001, Heilongjiang Province, China.
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94
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Harada Y, Hiasa M. Immunological identification of vesicular nucleotide transporter in intestinal L cells. Biol Pharm Bull 2015; 37:1090-5. [PMID: 24989000 DOI: 10.1248/bpb.b14-00275] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is well established that vesicular nucleotide transporter (VNUT) is responsible for vesicular storage of nucleotides such as ATP, and that VNUT-expressing cells can secrete nucleotides upon exocytosis, playing an important role in purinergic chemical transmission. In the present study, we show that VNUT is expressed in intestinal L cells. Immunohistochemical evidence indicated that VNUT is present in glucagon-like peptide 1 (GLP-1) containing cells in rat intestine. VNUT immunoreactivity is not co-localized with GLP-1, a marker for secretory granules, and synaptophysin, a marker for synaptic-like microvesicles (SLMVs). Essentially the same results were obtained for GLUTag clonal L cells. Sucrose density gradient analysis confirmed that VNUT is present the light fraction, unlike secretory granules. These results demonstrate that intestinal L cells express VNUT in either the unidentified organelles at light density other than secretory granules and SLMVs or a subpopulation of SLMVs, and suggest that L cells are purinergic in nature and secrete nucleotides independent of GLP-1 secretion.
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Affiliation(s)
- Yuika Harada
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences
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95
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Rutter GA, Hodson DJ. Beta cell connectivity in pancreatic islets: a type 2 diabetes target? Cell Mol Life Sci 2015; 72:453-467. [PMID: 25323131 PMCID: PMC11113448 DOI: 10.1007/s00018-014-1755-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/30/2014] [Accepted: 10/01/2014] [Indexed: 12/12/2022]
Abstract
Beta cell connectivity describes the phenomenon whereby the islet context improves insulin secretion by providing a three-dimensional platform for intercellular signaling processes. Thus, the precise flow of information through homotypically interconnected beta cells leads to the large-scale organization of hormone release activities, influencing cell responses to glucose and other secretagogues. Although a phenomenon whose importance has arguably been underappreciated in islet biology until recently, a growing number of studies suggest that such cell-cell communication is a fundamental property of this micro-organ. Hence, connectivity may plausibly be targeted by both environmental and genetic factors in type 2 diabetes mellitus (T2DM) to perturb normal beta cell function and insulin release. Here, we review the mechanisms that contribute to beta cell connectivity, discuss how these may fail during T2DM, and examine approaches to restore insulin secretion by boosting cell communication.
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Affiliation(s)
- Guy A Rutter
- Section of Cell Biology, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK.
| | - David J Hodson
- Section of Cell Biology, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
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96
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Kuhre RE, Frost CR, Svendsen B, Holst JJ. Molecular mechanisms of glucose-stimulated GLP-1 secretion from perfused rat small intestine. Diabetes 2015; 64:370-82. [PMID: 25157092 DOI: 10.2337/db14-0807] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucose is an important stimulus for glucagon-like peptide 1 (GLP-1) secretion, but the mechanisms of secretion have not been investigated in integrated physiological models. We studied glucose-stimulated GLP-1 secretion from isolated perfused rat small intestine. Luminal glucose (5% and 20% w/v) stimulated the secretion dose dependently, but vascular glucose was without significant effect at 5, 10, 15, and 25 mmol/L. GLP-1 stimulation by luminal glucose (20%) secretion was blocked by the voltage-gated Ca channel inhibitor, nifedipine, or by hyperpolarization with diazoxide. Luminal administration (20%) of the nonmetabolizable sodium-glucose transporter 1 (SGLT1) substrate, methyl-α-D-glucopyranoside (α-MGP), stimulated release, whereas the SGLT1 inhibitor phloridzin (luminally) abolished responses to α-MGP and glucose. Furthermore, in the absence of luminal NaCl, luminal glucose (20%) did not stimulate a response. Luminal glucose-stimulated GLP-1 secretion was also sensitive to luminal GLUT2 inhibition (phloretin), but in contrast to SGLT1 inhibition, phloretin did not eliminate the response, and luminal glucose (20%) stimulated larger GLP-1 responses than luminal α-MGP in matched concentrations. Glucose transported by GLUT2 may act after metabolization, closing KATP channels similar to sulfonylureas, which also stimulated secretion. Our data indicate that SGLT1 activity is the driving force for glucose-stimulated GLP-1 secretion and that KATP-channel closure is required to stimulate a full-blown glucose-induced response.
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Affiliation(s)
- Rune E Kuhre
- Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, the Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Charlotte R Frost
- Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, the Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Berit Svendsen
- Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, the Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Jens J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, the Panum Institute, University of Copenhagen, Copenhagen, Denmark
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97
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Toyooka N, Adachi I, Minehira D, Takeda D, Miyawaki S, Kato A, Miyazaki A, Miyatake R, Umezaki M, Miura K, Kitahara Y, Sugimoto K, Matsuya Y. Synthesis and Evaluations of GLP-1 Secretion and Anti-Diabetic Effect in KKAy Mice of New Tricyclic Compounds. HETEROCYCLES 2015. [DOI: 10.3987/com-14-s(k)29] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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98
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Abstract
Although GLP-1 (glucagon like peptide-1) based therapies (GLP-1 agonists and dipeptidyl peptidase-4 inhibitors) is currently playing a cornerstone role in the treatment of type 2 diabetes, dilemma does exist about some of its basic physiology. So far, we know that GLP-1 is secreted by the direct actions of luminal contents on the L cells in distal jejunum and proximal ileum. However, there is growing evidence now, which suggest that other mechanism via "neural" or "upper gut" signals may be playing a second fiddle and could stimulate GLP-1 secretion even before the luminal contents have reached into the proximities of L cells. Therefore, the contribution of direct and indirect mechanism to GLP-1 secretion remains elusive. Furthermore, no clear consensus exists about the pattern of GLP-1 secretion, although many believe it is monophasic. One of the most exciting issues in incretin science is GLP-1 level and GLP-1 responsiveness. It is not exactly known as to what happens to endogenous GLP-1 with progressive worsening of dysglycemia from normal glucose tolerance to impaired glucose to frank diabetes and furthermore with increasing duration of diabetes. Although, conventional wisdom suggests that there may be a decrease in endogenous GLP-1 level with the worsening of dysglycemia, literature showed discordant results. Furthermore, there is emerging evidence to suggest that GLP-1 response can vary with ethnicity. This mini review is an attempt to put a brief perspective on all these issues.
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Affiliation(s)
- Awadhesh Kumar Singh
- Senior Consultant Endocrinologist, G.D Diabetes Hospital, Kolkata, West Bengal, India
- Sun Valley Diabetes Hospital, Guwahati, Assam, India
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99
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Bacterial metabolite indole modulates incretin secretion from intestinal enteroendocrine L cells. Cell Rep 2014; 9:1202-8. [PMID: 25456122 PMCID: PMC4308618 DOI: 10.1016/j.celrep.2014.10.032] [Citation(s) in RCA: 347] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 09/22/2014] [Accepted: 10/10/2014] [Indexed: 12/25/2022] Open
Abstract
It has long been speculated that metabolites, produced by gut microbiota, influence host metabolism in health and diseases. Here, we reveal that indole, a metabolite produced from the dissimilation of tryptophan, is able to modulate the secretion of glucagon-like peptide-1 (GLP-1) from immortalized and primary mouse colonic L cells. Indole increased GLP-1 release during short exposures, but it reduced secretion over longer periods. These effects were attributed to the ability of indole to affect two key molecular mechanisms in L cells. On the one hand, indole inhibited voltage-gated K+ channels, increased the temporal width of action potentials fired by L cells, and led to enhanced Ca2+ entry, thereby acutely stimulating GLP-1 secretion. On the other hand, indole slowed ATP production by blocking NADH dehydrogenase, thus leading to a prolonged reduction of GLP-1 secretion. Our results identify indole as a signaling molecule by which gut microbiota communicate with L cells and influence host metabolism. Bacterial metabolite indole modulates secretion of incretin peptide GLP-1 Indole widens the width of action potentials fired by L cells and elevates GLP-1 Prolonged exposure to indole inhibits ATP production and thus GLP-1 secretion
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100
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Kim KS, Egan JM, Jang HJ. Denatonium induces secretion of glucagon-like peptide-1 through activation of bitter taste receptor pathways. Diabetologia 2014; 57:2117-25. [PMID: 25016595 PMCID: PMC5160131 DOI: 10.1007/s00125-014-3326-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 06/16/2014] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS This study was designed to ascertain whether human enteroendocrine cells express bitter taste receptors, and whether activation of these receptors with bitter-tasting ligands induces secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). METHODS We used human enteroendocrine NCI-H716 cells, isolated duodenal segments from mice, and whole mice as our experimental systems for investigating stimuli and mechanisms underlying GLP-1- and PYY-stimulated release. We measured hormone levels by ELISA and determined bitter taste receptor expression by real-time quantitative PCR. We adopted a pharmacological approach using inhibitors and enhancers of downstream signalling pathways known to be involved in bitter taste transduction in taste bud cells to investigate these pathways in NCI-H716 cells. RESULTS Using a pharmacological approach, we identified signalling pathways triggered by the denatonium benzoate (DB)-activated bitter receptors. This involved activation of α-gustducin (Gαgust)-the specific G-protein subunit that is also present in taste bud cells-reduction of intracellular cAMP levels and enhancement of phospholipase C (PLC) activity, which ultimately led to increased intracellular calcium concentrations and hormone release. Gavage of DB, followed by gavage of glucose, to db/db mice stimulated GLP-1 and subsequent insulin secretion, leading to lower blood glucose levels. CONCLUSIONS/INTERPRETATION Our study demonstrates that activation of gut-expressed bitter taste receptors stimulates GLP-1 secretion in a PLC-dependent manner. In diabetic mice, DB (a ligand of bitter taste receptor cells), when given via gavage, lowers blood glucose levels in diabetic mice after oral glucose administration, through increased secretion of GLP-1.
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Affiliation(s)
- Ki-Suk Kim
- Department of Biochemistry, College of Korean Medicine, Kyung Hee University, Hoegi-Dong, Dongdaemun-Gu, Seoul, 130-701, Republic of Korea
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