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Karakaplan ND, Song Y, Laurenti MC, Vella A, Jensen MD. Suppression of Endogenous Insulin Secretion by Euglycemic Hyperinsulinemia. J Clin Endocrinol Metab 2024; 109:e596-e601. [PMID: 37758511 PMCID: PMC10795933 DOI: 10.1210/clinem/dgad563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 09/07/2023] [Accepted: 09/21/2023] [Indexed: 10/03/2023]
Abstract
CONTEXT The impact of insulin, particularly exogenous hyperinsulinemia, on insulin secretion in humans is debated. OBJECTIVE We assessed the effects of exogenous hyperinsulinemia on insulin secretion and whether the response is altered in insulin resistance associated with obesity. METHODS Insulin secretion rates (ISRs) during euglycemic hyperinsulinemic clamp studies (52 volunteers) were calculated using a model that employs plasma C-peptide concentrations. One study involved a 2-step insulin clamp and the other study was a single step insulin clamp. For both studies the goal was to achieve plasma glucose concentrations of 95 mg/dL during the clamp irrespective of fasting glucose concentrations. The percent change in ISR from fasting to the end of the insulin clamp interval was the main outcome. Linear regression and analysis of covariance were used to test for the effects of insulin on ISR and to test for group differences. RESULTS ISR was greater in obese volunteers (P < .001) under fasting and hyperinsulinemic clamp conditions. The change in plasma glucose from baseline to the end of the insulin clamp interval was highly correlated with the change in ISR (r = 0.61, P < .001). From baseline to the end of the clamp we observed a 27% (SD 20) suppression of ISR. The participants who underwent a 2-step insulin clamp had greater suppression of ISR during the second step than the first step (P < .001). The proportional suppression of ISR during euglycemic hyperinsulinemia was not different between nonobese and obese groups (P = .19). CONCLUSION Hyperinsulinemia suppresses endogenous insulin secretion and the relative change in insulin secretion produced by exogenous insulin did not differ between nonobese and obese people.
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Affiliation(s)
- Nesrin Damla Karakaplan
- Endocrine Research Unit, Division of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - Yilin Song
- Endocrine Research Unit, Division of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - Marcello C Laurenti
- Endocrine Research Unit, Division of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - Adrian Vella
- Endocrine Research Unit, Division of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - Michael D Jensen
- Endocrine Research Unit, Division of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
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2
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Cikes D, Atanes P, Cronin SJF, Hagelkrüys A, Huang GC, Persaud SJ, Penninger JM. Neuropeptide Neuromedin B does not alter body weight and glucose homeostasis nor does it act as an insulin-releasing peptide. Sci Rep 2022; 12:9383. [PMID: 35672347 PMCID: PMC9174263 DOI: 10.1038/s41598-022-13060-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 04/15/2022] [Indexed: 11/30/2022] Open
Abstract
Neuromedin B (NMB) is a member of the neuromedin family of neuropeptides with a high level of region-specific expression in the brain. Several GWAS studies on non-obese and obese patients suggested that polymorphisms in NMB predispose to obesity by affecting appetite control and feeding preference. Furthermore, several studies proposed that NMB can act as an insulin releasing peptide. Since the functional study has never been done, the in vivo role of NMB as modulator of weight gain or glucose metabolism remains unclear. Here, we generated Nmb conditional mice and nervous system deficient NmB mice. We then performed olfactory and food preference analysis, as well as metabolic analysis under standard and high fat diet. Additionally, in direct islet studies we evaluated the role of NMB on basal and glucose-stimulated insulin secretion in mouse and humans.
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3
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PI3K and AKT at the Interface of Signaling and Metabolism. Curr Top Microbiol Immunol 2022; 436:311-336. [DOI: 10.1007/978-3-031-06566-8_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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4
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Chen X, Daniels NA, Cottrill D, Cao Y, Wang X, Li Y, Shriwas P, Qian Y, Archer MW, Whitticar NB, Jahan I, Nunemaker CS, Guo A. Natural Compound α-PGG and Its Synthetic Derivative 6Cl-TGQ Alter Insulin Secretion: Evidence for Diminishing Glucose Uptake as a Mechanism. Diabetes Metab Syndr Obes 2021; 14:759-772. [PMID: 33658814 PMCID: PMC7917315 DOI: 10.2147/dmso.s284295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 12/24/2020] [Indexed: 12/17/2022] Open
Abstract
PURPOSE Previously we showed that natural compound α-penta-galloyl-glucose (α-PGG) and its synthetic derivative 6-chloro-6-deoxy-1,2,3,4-tetra-O-galloyl-α-D-glucopyranose (6Cl-TGQ) act to improve insulin signaling in adipocytes by increasing glucose transport. In this study, we investigated the mechanism of actions of α-PGG and 6Cl-TGQ on insulin secretion. METHODS Mouse islets and/or INS-1832/13 beta-cells were used to test the effects of our compounds on glucose-stimulated insulin secretion (GSIS), intracellular calcium [Ca2+]i using fura-2AM, glucose transport activity via a radioactive glucose uptake assay, intracellular ATP/ADP, and extracellular acidification (ECAR) and mitochondrial oxygen consumption rates (OCAR) using Seahorse metabolic analysis. RESULTS Both compounds reduced GSIS in beta-cells without negatively affecting cell viability. The compounds primarily diminished glucose uptake into islets and beta-cells. Despite insulin-like effects in the peripheral tissues, these compounds do not act through the insulin receptor in islets. Further interrogation of the stimulus-secretion pathway showed that all the key metabolic factors involved in GSIS including ECAR, OCAR, ATP/ADP ratios, and [Ca2+]i of INS-1832/13 cells were diminished after the compound treatment. CONCLUSION The compounds suppress glucose uptake of the beta-cells, which consequently slows down the rates of glycolysis and ATP synthesis, leading to decrease in [Ca2+]i and GSIS. The difference between adipocytes and beta-cells in effects on glucose uptake is of great interest. Further structural and functional modifications could produce new compounds with optimized therapeutic potentials for different target cells. The higher potency of synthetic 6Cl-TGQ in enhancing insulin signaling in adipocytes but lower potency in reducing glucose uptake in beta-cells compared to α-PGG suggests the feasibility of such an approach.
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Affiliation(s)
- Xiaozhuo Chen
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Heritage College of Osteopathic Medicine, Athens, OH, 45701, USA
- Interdisciplinary Graduate Program in Molecular and Cellular Biology, Athens, OH, 45701, USA
- Department of Chemistry and Biochemistry, Athens, OH, 45701, USA
| | - Nigel A Daniels
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Heritage College of Osteopathic Medicine, Athens, OH, 45701, USA
- Department of Specialty Medicine, Athens, OH, 45701, USA
| | - David Cottrill
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Yanyang Cao
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Xuan Wang
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Yunsheng Li
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
| | - Pratik Shriwas
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Yanrong Qian
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
| | - Michael W Archer
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
| | - Nicholas B Whitticar
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Translational Biomedical Sciences Program, Ohio University, Athens, OH, 45701, USA
| | - Ishrat Jahan
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
| | - Craig S Nunemaker
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Heritage College of Osteopathic Medicine, Athens, OH, 45701, USA
- Craig S Nunemaker Department of Biomedical Sciences, 1 Ohio University, Athens, OH, 45701, USATel +1 740-593-2387Fax +1 740-593-4795 Email
| | - Aili Guo
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of California at Davis (UC Davis) School of Medicine, UC Davis Health Science, Sacramento, CA, 95817, USA
- Correspondence: Aili Guo Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of California at Davis (UC Davis) School of Medicine, UC Davis Health Science, PSSB, G400, 4150 V St., Sacramento, CA, 95817, USATel +1 916-734-3730Fax +1 916-734-2292 Email
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5
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Marrano N, Biondi G, Cignarelli A, Perrini S, Laviola L, Giorgino F, Natalicchio A. Functional loss of pancreatic islets in type 2 diabetes: How can we halt it? Metabolism 2020; 110:154304. [PMID: 32599081 DOI: 10.1016/j.metabol.2020.154304] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 06/14/2020] [Accepted: 06/25/2020] [Indexed: 02/08/2023]
Abstract
The loss of beta-cell functional mass is a necessary and early condition in the development of type 2 diabetes (T2D). In T2D patients, beta-cell function is already reduced by about 50% at diagnosis and further declines thereafter. Beta-cell mass is also reduced in subjects with T2D, and islets from diabetic donors are smaller compared to non-diabetic donors. Thus, beta-cell regeneration and/or preservation of the functional islet integrity should be highly considered for T2D treatment and possibly cure. To date, the available anti-diabetes drugs have been developed as "symptomatic" medications since they act to primarily reduce elevated blood glucose levels. However, a truly efficient anti-diabetes medication, capable to prevent the onset and progression of T2D, should stop beta-cell loss and/or promote the restoration of fully functional beta-cell mass, independently of reducing hyperglycemia and ameliorating glucotoxicity on the pancreatic islets. This review provides a view of the experimental and clinical evidence on the ability of available anti-diabetes drugs to exert protective effects on beta-cells, with a specific focus on human pancreatic islets and clinical trials. Potential explanations for the lack of concordance between evidence of beta-cell protection in vitro and of persistent amelioration of beta-cell function in vivo are also discussed.
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Affiliation(s)
- Nicola Marrano
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy.
| | - Giuseppina Biondi
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy
| | - Angelo Cignarelli
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy
| | - Sebastio Perrini
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy.
| | - Luigi Laviola
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy.
| | - Francesco Giorgino
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy.
| | - Annalisa Natalicchio
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Bari, Italy.
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6
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Rachdaoui N. Insulin: The Friend and the Foe in the Development of Type 2 Diabetes Mellitus. Int J Mol Sci 2020; 21:ijms21051770. [PMID: 32150819 PMCID: PMC7084909 DOI: 10.3390/ijms21051770] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 02/29/2020] [Accepted: 03/02/2020] [Indexed: 12/14/2022] Open
Abstract
Insulin, a hormone produced by pancreatic β-cells, has a primary function of maintaining glucose homeostasis. Deficiencies in β-cell insulin secretion result in the development of type 1 and type 2 diabetes, metabolic disorders characterized by high levels of blood glucose. Type 2 diabetes mellitus (T2DM) is characterized by the presence of peripheral insulin resistance in tissues such as skeletal muscle, adipose tissue and liver and develops when β-cells fail to compensate for the peripheral insulin resistance. Insulin resistance triggers a rise in insulin demand and leads to β-cell compensation by increasing both β-cell mass and insulin secretion and leads to the development of hyperinsulinemia. In a vicious cycle, hyperinsulinemia exacerbates the metabolic dysregulations that lead to β-cell failure and the development of T2DM. Insulin and IGF-1 signaling pathways play critical roles in maintaining the differentiated phenotype of β-cells. The autocrine actions of secreted insulin on β-cells is still controversial; work by us and others has shown positive and negative actions by insulin on β-cells. We discuss findings that support the concept of an autocrine action of secreted insulin on β-cells. The hypothesis of whether, during the development of T2DM, secreted insulin initially acts as a friend and contributes to β-cell compensation and then, at a later stage, becomes a foe and contributes to β-cell decompensation will be discussed.
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Affiliation(s)
- Nadia Rachdaoui
- Department of Animal Sciences, Room 108, Foran Hall, Rutgers, the State University of New Jersey, 59 Dudley Rd, New Brunswick, NJ 08901, USA
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7
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Ježek P, Jabůrek M, Plecitá-Hlavatá L. Contribution of Oxidative Stress and Impaired Biogenesis of Pancreatic β-Cells to Type 2 Diabetes. Antioxid Redox Signal 2019; 31:722-751. [PMID: 30450940 PMCID: PMC6708273 DOI: 10.1089/ars.2018.7656] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 11/05/2018] [Indexed: 12/14/2022]
Abstract
Significance: Type 2 diabetes development involves multiple changes in β-cells, related to the oxidative stress and impaired redox signaling, beginning frequently by sustained overfeeding due to the resulting lipotoxicity and glucotoxicity. Uncovering relationships among the dysregulated metabolism, impaired β-cell "well-being," biogenesis, or cross talk with peripheral insulin resistance is required for elucidation of type 2 diabetes etiology. Recent Advances: It has been recognized that the oxidative stress, lipotoxicity, and glucotoxicity cannot be separated from numerous other cell pathology events, such as the attempted compensation of β-cell for the increased insulin demand and dynamics of β-cell biogenesis and its "reversal" at dedifferentiation, that is, from the concomitantly decreasing islet β-cell mass (also due to transdifferentiation) and low-grade islet or systemic inflammation. Critical Issues: At prediabetes, the compensation responses of β-cells, attempting to delay the pathology progression-when exaggerated-set a new state, in which a self-checking redox signaling related to the expression of Ins gene expression is impaired. The resulting altered redox signaling, diminished insulin secretion responses to various secretagogues including glucose, may lead to excretion of cytokines or chemokines by β-cells or excretion of endosomes. They could substantiate putative stress signals to the periphery. Subsequent changes and lasting glucolipotoxicity promote islet inflammatory responses and further pathology spiral. Future Directions: Should bring an understanding of the β-cell self-checking and related redox signaling, including the putative stress signal to periphery. Strategies to cure or prevent type 2 diabetes could be based on the substitution of the "wrong" signal by the "correct" self-checking signal.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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8
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Mizgier ML, Fernández-Verdejo R, Cherfan J, Pinget M, Bouzakri K, Galgani JE. Insights on the Role of Putative Muscle-Derived Factors on Pancreatic Beta Cell Function. Front Physiol 2019; 10:1024. [PMID: 31440170 PMCID: PMC6694406 DOI: 10.3389/fphys.2019.01024] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 07/24/2019] [Indexed: 01/02/2023] Open
Abstract
Skeletal muscle is a main target of insulin action that plays a pivotal role in postprandial glucose disposal. Importantly, skeletal muscle insulin sensitivity relates inversely with pancreatic insulin secretion, which prompted the hypothesis of the existence of a skeletal muscle-pancreas crosstalk mediated through an endocrine factor. The observation that changes in skeletal muscle glucose metabolism are accompanied by altered insulin secretion supports this hypothesis. Meanwhile, a muscle-derived circulating factor affecting in vivo insulin secretion remains elusive. This factor may correspond to peptides/proteins (so called myokines), exosomes and their cargo, and metabolites. We hereby review the most remarkable evidence encouraging the possibility of such inter-organ communication, with special focus on muscle-derived factors that may potentially mediate such skeletal muscle-pancreas crosstalk.
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Affiliation(s)
- Maria L Mizgier
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Strasbourg, France
| | - Rodrigo Fernández-Verdejo
- Departamento de Ciencias de la Salud, Nutrición y Dietética, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Julien Cherfan
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Strasbourg, France
| | - Michel Pinget
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Strasbourg, France
| | - Karim Bouzakri
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Strasbourg, France
| | - Jose E Galgani
- Departamento de Ciencias de la Salud, Nutrición y Dietética, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.,Departamento de Nutrición, Diabetes y Metabolismo, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
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9
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Oakie A, Wang R. β-Cell Receptor Tyrosine Kinases in Controlling Insulin Secretion and Exocytotic Machinery: c-Kit and Insulin Receptor. Endocrinology 2018; 159:3813-3821. [PMID: 30239687 PMCID: PMC6202852 DOI: 10.1210/en.2018-00716] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 09/13/2018] [Indexed: 12/25/2022]
Abstract
Insulin secretion from pancreatic β-cells is initiated through channel-mediated depolarization, cytoskeletal remodeling, and vesicle tethering at the cell membrane, all of which can be regulated through cell surface receptors. Receptor tyrosine kinases (RTKs) promote β-cell development and postnatal signaling to improve β-cell mass and function, yet their activation has also been shown to initiate exocytotic events in β-cells. This review examines the role of RTK signaling in insulin secretion, with a focus on RTKs c-Kit and insulin receptor (IR). Pathways that control insulin release and the potential interplay between c-Kit and IR signaling are discussed, along with clinical implications of RTK therapy on insulin secretion.
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Affiliation(s)
- Amanda Oakie
- Children’s Health Research Institute, Victoria Research Laboratories, London, Ontario, Canada
- Department of Pathology and Laboratory Medicine, University of Western Ontario, London, Ontario, Canada
| | - Rennian Wang
- Children’s Health Research Institute, Victoria Research Laboratories, London, Ontario, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
- Correspondence: Rennian Wang, MD, PhD, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, Ontario N6C 2V5, Canada. E-mail:
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10
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Knocking down Insulin Receptor in Pancreatic Beta Cell lines with Lentiviral-Small Hairpin RNA Reduces Glucose-Stimulated Insulin Secretion via Decreasing the Gene Expression of Insulin, GLUT2 and Pdx1. Int J Mol Sci 2018; 19:ijms19040985. [PMID: 29587416 PMCID: PMC5979368 DOI: 10.3390/ijms19040985] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 03/13/2018] [Accepted: 03/21/2018] [Indexed: 12/18/2022] Open
Abstract
Type 2 diabetes (T2D) is a metabolic disorder characterized by beta cell dysfunction and insulin resistance in fat, muscle and liver cells. Recent studies have shown that the development of insulin resistance in pancreatic beta cell lines may contribute to beta cell dysfunction in T2D. However, there still is a lack of detailed investigations regarding the mechanisms by which insulin deficiency may contribute in diabetes. In this study, we firstly established a stable insulin receptor knockdown cell line in pancreatic beta cells INS-1 (InsRβKD cells) using anti InsRβ small hairpin RNA (InsRβ-shRNA) encoded by lentiviral vectors. The resultant InsRβKD cells demonstrated a significantly reduced expression of InsRβ as determined by real-time PCR and Western blotting analyses. Upon removing glucose from the medium, these cells exhibited a significant decrease in insulin gene expression and protein secretion in response to 20 mM glucose stimulation. In accordance with this insulin reduction, the glucose uptake efficiency as indicated by a 3[H]-2-deoxy-d-glucose assay also decreased. Furthermore, InsRβKD cells showed a dramatic decrease in glucose transporter 2 (GLUT2, encoded by SLC2A2) and pancreatic duodenal homeobox (Pdx1) mRNA expression compared to the controls. These data collectively suggest that pancreatic beta cell insulin resistance contributes to the development of beta cell dysfunction by impairing pancreatic beta cell glucose sensation through the Pdx1- GLUT2 pathway. InsRβKD cells provide a good model to further investigate the mechanism of β-cell dysfunction in T2D.
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11
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Edgerton DS, Kraft G, Smith M, Farmer B, Williams PE, Coate KC, Printz RL, O'Brien RM, Cherrington AD. Insulin's direct hepatic effect explains the inhibition of glucose production caused by insulin secretion. JCI Insight 2017; 2:e91863. [PMID: 28352665 DOI: 10.1172/jci.insight.91863] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Insulin can inhibit hepatic glucose production (HGP) by acting directly on the liver as well as indirectly through effects on adipose tissue, pancreas, and brain. While insulin's indirect effects are indisputable, their physiologic role in the suppression of HGP seen in response to increased insulin secretion is not clear. Likewise, the mechanisms by which insulin suppresses lipolysis and pancreatic α cell secretion under physiologic circumstances are also debated. In this study, insulin was infused into the hepatic portal vein to mimic increased insulin secretion, and insulin's indirect liver effects were blocked either individually or collectively. During physiologic hyperinsulinemia, plasma free fatty acid (FFA) and glucagon levels were clamped at basal values and brain insulin action was blocked, but insulin's direct effects on the liver were left intact. Insulin was equally effective at suppressing HGP when its indirect effects were absent as when they were present. In addition, the inhibition of lipolysis, as well as glucagon and insulin secretion, did not require CNS insulin action or decreased plasma FFA. This indicates that the rapid suppression of HGP is attributable to insulin's direct effect on the liver and that its indirect effects are redundant in the context of a physiologic increase in insulin secretion.
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Affiliation(s)
- Dale S Edgerton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Guillaume Kraft
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Marta Smith
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Ben Farmer
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Phillip E Williams
- Division of Surgical Research, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Katie C Coate
- Samford University, Department of Nutrition and Dietetics, Birmingham, Alabama, USA
| | - Richard L Printz
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Alan D Cherrington
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
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12
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Mizgier ML, Cataldo LR, Gutierrez J, Santos JL, Casas M, Llanos P, Contreras-Ferrat AE, Moro C, Bouzakri K, Galgani JE. Effect of Human Myotubes-Derived Media on Glucose-Stimulated Insulin Secretion. J Diabetes Res 2017; 2017:1328573. [PMID: 28286777 PMCID: PMC5329672 DOI: 10.1155/2017/1328573] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 01/01/2017] [Accepted: 01/17/2017] [Indexed: 12/11/2022] Open
Abstract
Fasting to postprandial transition requires a tight adjustment of insulin secretion to its demand, so tissue (e.g., skeletal muscle) glucose supply is assured while hypo-/hyperglycemia are prevented. High muscle glucose disposal after meals is pivotal for adapting to increased glycemia and might drive insulin secretion through muscle-released factors (e.g., myokines). We hypothesized that insulin influences myokine secretion and then increases glucose-stimulated insulin secretion (GSIS). In conditioned media from human myotubes incubated with/without insulin (100 nmol/L) for 24 h, myokines were qualitatively and quantitatively characterized using an antibody-based array and ELISA-based technology, respectively. C57BL6/J mice islets and Wistar rat beta cells were incubated for 24 h with control and conditioned media from noninsulin- and insulin-treated myotubes prior to GSIS determination. Conditioned media from insulin-treated versus nontreated myotubes had higher RANTES but lower IL6, IL8, and MCP1 concentration. Qualitative analyses revealed that conditioned media from noninsulin- and insulin-treated myotubes expressed 32 and 23 out of 80 myokines, respectively. Islets incubated with conditioned media from noninsulin-treated myotubes had higher GSIS versus control islets (p < 0.05). Meanwhile, conditioned media from insulin-treated myotubes did not influence GSIS. In beta cells, GSIS was similar across conditions. In conclusion, factors being present in noninsulin-stimulated muscle cell-derived media appear to influence GSIS in mice islets.
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Affiliation(s)
- Maria L. Mizgier
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Luis R. Cataldo
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan Gutierrez
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - José L. Santos
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Mariana Casas
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Paola Llanos
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Santiago, Chile
| | - Ariel E. Contreras-Ferrat
- Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile
| | - Cedric Moro
- INSERM UMR1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université Paul Sabatier, Toulouse, France
| | - Karim Bouzakri
- Departement de Génétique et Développement, CMU, Université de Genève, Genève, Switzerland
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Strasbourg, France
| | - Jose E. Galgani
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- UDA-Ciencias de la Salud, Carrera de Nutrición y Dietética, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- *Jose E. Galgani:
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Galgani JE, Gómez C, Mizgier ML, Gutierrez J, Santos JL, Olmos P, Mari A. Assessment of the Role of Metabolic Determinants on the Relationship between Insulin Sensitivity and Secretion. PLoS One 2016; 11:e0168352. [PMID: 28002466 PMCID: PMC5176173 DOI: 10.1371/journal.pone.0168352] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 11/30/2016] [Indexed: 12/21/2022] Open
Abstract
Background Insulin secretion correlates inversely with insulin sensitivity, which may suggest the existence of a crosstalk between peripheral organs and pancreas. Such interaction might be mediated through glucose oxidation that may drive the release of circulating factors with action on insulin secretion. Aim To evaluate the association between whole-body carbohydrate oxidation and circulating factors with insulin secretion to consecutive oral glucose loading in non-diabetic individuals. Methods Carbohydrate oxidation was measured after an overnight fast and for 6 hours after two 3-h apart 75-g oral glucose tolerance tests (OGTT) in 53 participants (24/29 males/females; 34±9 y; 27±4 kg/m2). Insulin secretion was estimated by deconvolution of serum C-peptide concentration, β cell function by mathematical modelling and insulin sensitivity from an OGTT. Circulating lactate, free-fatty acids (FFA) and candidate chemokines were assessed before and after OGTT. The effect of recombinant RANTES (regulated on activation, normal T cell expressed and secreted) and IL8 (interleukin 8) on insulin secretion from isolated mice islets was also measured. Results Carbohydrate oxidation assessed over the 6-h period did not relate with insulin secretion (r = -0.11; p = 0.45) or β cell function indexes. Circulating lactate and FFA showed no association with 6-h insulin secretion. Circulating chemokines concentration increased upon oral glucose stimulation. Insulin secretion associated with plasma IL6 (r = 0.35; p<0.05), RANTES (r = 0.30; p<0.05) and IL8 (r = 0.41; p<0.05) determined at 60 min OGTT. IL8 was independently associated with in vivo insulin secretion; however, it did not affect in vitro insulin secretion. Conclusion Whole-body carbohydrate oxidation appears to have no influence on insulin secretion or putative circulating mediators. IL8 may be a potential factor influencing insulin secretion.
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Affiliation(s)
- Jose E. Galgani
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- UDA-Ciencias de la Salud, Carrera de Nutrición y Dietética, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail:
| | - Carmen Gómez
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Maria L. Mizgier
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan Gutierrez
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jose L. Santos
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo Olmos
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Andrea Mari
- Istituto di Neuroscienze, Consiglio Nazionale delle Ricerche, Padova, Italy
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Kolic J, Manning Fox JE, Chepurny OG, Spigelman AF, Ferdaoussi M, Schwede F, Holz GG, MacDonald PE. PI3 kinases p110α and PI3K-C2β negatively regulate cAMP via PDE3/8 to control insulin secretion in mouse and human islets. Mol Metab 2016; 5:459-471. [PMID: 27408772 PMCID: PMC4921792 DOI: 10.1016/j.molmet.2016.05.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 04/26/2016] [Accepted: 05/04/2016] [Indexed: 01/09/2023] Open
Abstract
OBJECTIVES Phosphatidylinositol-3-OH kinase (PI3K) signalling in the endocrine pancreas contributes to glycaemic control. However, the mechanism by which PI3K modulates insulin secretion from the pancreatic beta cell is poorly understood. Thus, our objective was two-fold; to determine the signalling pathway by which acute PI3K inhibition enhances glucose-stimulated insulin secretion (GSIS) and to examine the role of this pathway in islets from type-2 diabetic (T2D) donors. METHODS Isolated islets from mice and non-diabetic or T2D human donors, or INS 832/13 cells, were treated with inhibitors of PI3K and/or phosphodiesterases (PDEs). The expression of PI3K-C2β was knocked down using siRNA. We measured insulin release, single-cell exocytosis, intracellular Ca(2+) responses ([Ca(2+)]i) and Ca(2+) channel currents, intracellular cAMP concentrations ([cAMP]i), and activation of cAMP-dependent protein kinase A (PKA) and protein kinase B (PKB/AKT). RESULTS The non-specific PI3K inhibitor wortmannin amplifies GSIS, raises [cAMP]i and activates PKA, but is without effect in T2D islets. Direct inhibition of specific PDE isoforms demonstrates a role for PDE3 (in humans and mice) and PDE8 (in mice) downstream of PI3K, and restores glucose-responsiveness of T2D islets. We implicate a role for the Class II PI3K catalytic isoform PI3K-C2β in this effect by limiting beta cell exocytosis. CONCLUSIONS PI3K limits GSIS via PDE3 in human islets. While inhibition of p110α or PIK-C2β signalling per se, may promote nutrient-stimulated insulin release, we now suggest that this signalling pathway is perturbed in islets from T2D donors.
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Affiliation(s)
- Jelena Kolic
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada.
| | - Jocelyn E Manning Fox
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
| | - Oleg G Chepurny
- Department of Medicine, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
| | - Aliya F Spigelman
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
| | - Mourad Ferdaoussi
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
| | - Frank Schwede
- BIOLOG Life Science Institute, 28199 Bremen, Germany
| | - George G Holz
- Department of Medicine, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA; Department of Pharmacology, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
| | - Patrick E MacDonald
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
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Arrojo e Drigo R, Ali Y, Diez J, Srinivasan DK, Berggren PO, Boehm BO. New insights into the architecture of the islet of Langerhans: a focused cross-species assessment. Diabetologia 2015. [PMID: 26215305 DOI: 10.1007/s00125-015-3699-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The human genome project and its search for factors underlying human diseases has fostered a major human research effort. Therefore, unsurprisingly, in recent years we have observed an increasing number of studies on human islet cells, including disease approaches focusing on type 1 and type 2 diabetes. Yet, the field of islet and diabetes research relies on the legacy of rodent-based investigations, which have proven difficult to translate to humans, particularly in type 1 diabetes. Whole islet physiology and pathology may differ between rodents and humans, and thus a comprehensive cross-species as well as species-specific view on islet research is much needed. In this review we summarise the current knowledge of interspecies islet cytoarchitecture, and discuss its potential impact on islet function and future perspectives in islet pathophysiology research.
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Affiliation(s)
- Rafael Arrojo e Drigo
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Level 4, 637 553, Singapore, Singapore
| | - Yusuf Ali
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Level 4, 637 553, Singapore, Singapore
| | - Juan Diez
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Level 4, 637 553, Singapore, Singapore
| | - Dinesh Kumar Srinivasan
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Level 4, 637 553, Singapore, Singapore
| | - Per-Olof Berggren
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Level 4, 637 553, Singapore, Singapore.
- Imperial College London, London, UK.
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska University Hospital L1, Karolinska Institutet, SE-171 76, Stockholm, Sweden.
| | - Bernhard O Boehm
- Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, Level 4, 637 553, Singapore, Singapore.
- Imperial College London, London, UK.
- Department of Internal Medicine 1, Ulm University Medical Centre, Ulm, Germany.
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16
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Wuttke A. Lipid Signalling Dynamics at the β-cell Plasma Membrane. Basic Clin Pharmacol Toxicol 2015; 116:281-90. [DOI: 10.1111/bcpt.12369] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/15/2014] [Indexed: 12/26/2022]
Affiliation(s)
- Anne Wuttke
- Department of Medical Cell Biology; Uppsala University; Uppsala Sweden
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Onopchenko OV, Kosiakova GV, Oz M, Klimashevsky VM, Gula NM. N-Stearoylethanolamine Restores Pancreas Lipid Composition in Obesity-Induced Insulin Resistant Rats. Lipids 2014; 50:13-21. [DOI: 10.1007/s11745-014-3960-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 09/29/2014] [Indexed: 12/11/2022]
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McKillop AM, Ng MT, Abdel-Wahab YHA, Flatt PR. Evidence for inhibitory autocrine effects of proinsulin C-peptide on pancreatic β-cell function and insulin secretion. Diabetes Obes Metab 2014; 16:937-46. [PMID: 24702738 DOI: 10.1111/dom.12300] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 02/28/2014] [Accepted: 03/31/2014] [Indexed: 12/21/2022]
Abstract
AIMS Autocrine and paracrine regulatory mechanisms ensure integrated secretion of islet hormones that respond efficiently to changes in metabolic need. As proinsulin C-peptide exerts various biological effects and binds to cell membranes including insulin-secreting β cells, its physiological role in insulin release was examined. METHODS Insulin releasing activity of human and rat C-peptides were studied in the clonal pancreatic cell line, BRIN-BD11, with findings substantiated using isolated islets and in vivo studies employing SWISS TO mice. RESULTS Acute exposure of clonal β cells to human C-peptide resulted in concentration-dependent inhibitory effects on insulin secretion at 5.6 mM (p < 0.05-p < 0.001) and 16.7 mM (p < 0.01-p < 0.001) glucose. At physiologically relevant intra-islet concentrations (10(-9) -10(-6) M), C-peptide suppressed the insulin-secretory responses to a range of secretagogues acting at different points in the β cell stimulus-secretion coupling pathway including alanine (p < 0.05), Ca(2+) (p < 0.001), arginine (p < 0.05), tolbutamide (p < 0.001), glucagon-like peptide 1 (GLP-1) (p < 0.001), isobutylmethylxanthine (IBMX) (p < 0.01) and KCl (p < 0.05). Similar results were obtained using isolated mouse pancreatic islets. Human C-peptide (3 × 10(-7) M, p < 0.001), somatostatin-14 (3 × 10(-7) M, p < 0.01) and diazoxide (300 µM, p < 0.001) reduced both alanine and glucose-stimulated insulin release by 43, 25 and 48%, respectively. The effects of human C-peptide were reproduced using rat C-peptide I and II. C-peptide also inhibited in vivo glucose-stimulated insulin release and impaired glucose tolerance in mice. CONCLUSIONS C-peptide is a biologically active endogenous peptide hormone that exerts inhibitory autocrine effects on pancreatic β-cell function. Mechanisms involving the activation of K(+) channels and a distal effect downstream of increased cytoplasmic Ca(2+) appear to be implicated in the inhibition of insulin secretion.
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Affiliation(s)
- A M McKillop
- SAAD Centre for Pharmacy & Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, UK
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Li L, Li X, Zhu Y, Zhang M, Yin D, Lu J, Liu F, Wang C, Jia W. Growth receptor binding protein 10 inhibits glucose-stimulated insulin release from pancreatic β-cells associated with suppression of the insulin/insulin-like growth factor-1 signalling pathway. Clin Exp Pharmacol Physiol 2014; 40:841-7. [PMID: 23937793 DOI: 10.1111/1440-1681.12160] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Revised: 07/22/2013] [Accepted: 08/08/2013] [Indexed: 01/30/2023]
Abstract
Growth receptor binding protein 10 (Grb10) is an adaptor protein that interacts with the insulin receptor and insulin-like growth factor (IGF)-1 receptor. Overexpression of Grb10 in muscle cells and adipocytes inhibits insulin signalling, and transgenic mice overexpressing Grb10 exhibit impaired glucose tolerance. However, the roles of Grb10 in β-cells remain unknown. The aim of the present study was to explore the effect of Grb10 on β-cell function. The effects of Grb10 on glucose-stimulated insulin secretion (GSIS) and the insulin/IGF-1 signalling pathway were investigated in rat islets and/or dispersed islet cells with Grb10 overexpresion by adenovirus transfection. Protein expression was detected by western blot analysis. We found that Grb10 was expressed in both human and rat pancreas. Expression of Grb10 was increased in islets isolated from rats fed a high-fat plus high-sugar diet compared with islets isolated from rats fed normal chow diet, as well as in INS 832/13 cells exposed to high levels of glucose (20 mmol/L), palmitate (1 mmol/L) and interleukin-1β (50 U/mL). Overexpression of Grb10 in INS 832/13 cells or rat islets impaired GSIS compared with the respective control (all P < 0.05). Moreover, inhibition of GSIS by Grb10 overexpression was associated with a decrease in insulin- and IGF-1-induced Akt and extracellular signal-regulated kinase 1/2 phosphorylation. The results of the present study demonstrate that Grb10 is an important negative regulator of insulin/IGF-1 signalling in pancreatic β-cells and a potential target to improve β-cell function.
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Affiliation(s)
- Ling Li
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China; Diabetes Institute, Shanghai Jiao Tong University, Shanghai, China; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai, China
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JEŽEK P, OLEJÁR T, SMOLKOVÁ K, JEŽEK J, DLASKOVÁ A, PLECITÁ-HLAVATÁ L, ZELENKA J, ŠPAČEK T, ENGSTOVÁ H, PAJUELO REGUERA D, JABŮREK M. Antioxidant and Regulatory Role of Mitochondrial Uncoupling Protein UCP2 in Pancreatic β-cells. Physiol Res 2014; 63:S73-91. [DOI: 10.33549/physiolres.932633] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Research on brown adipose tissue and its hallmark protein, mitochondrial uncoupling protein UCP1, has been conducted for half a century and has been traditionally studied in the Institute of Physiology (AS CR, Prague), likewise UCP2 residing in multiple tissues for the last two decades. Our group has significantly contributed to the elucidation of UCP uncoupling mechanism, fully dependent on free fatty acids (FFAs) within the inner mitochondrial membrane. Now we review UCP2 physiological roles emphasizing its roles in pancreatic β-cells, such as antioxidant role, possible tuning of redox homeostasis (consequently UCP2 participation in redox regulations), and fine regulation of glucose-stimulated insulin secretion (GSIS). For example, NADPH has been firmly established as being a modulator of GSIS and since UCP2 may influence redox homeostasis, it likely affects NADPH levels. We also point out the role of phospholipase iPLA2 isoform in providing FFAs for the UCP2 antioxidant function. Such initiation of mild uncoupling hypothetically precedes lipotoxicity in pancreatic β-cells until it reaches the pathological threshold, after which the antioxidant role of UCP2 can be no more cell-protective, for example due to oxidative stress-accumulated mutations in mtDNA. These mechanisms, together with impaired autocrine insulin function belong to important causes of Type 2 diabetes etiology.
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Affiliation(s)
- P. JEŽEK
- Department of Membrane Transport Biophysics, Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic
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21
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Kolic J, Spigelman AF, Plummer G, Leung E, Hajmrle C, Kin T, Shapiro AMJ, Manning Fox JE, MacDonald PE. Distinct and opposing roles for the phosphatidylinositol 3-OH kinase catalytic subunits p110α and p110β in the regulation of insulin secretion from rodent and human beta cells. Diabetologia 2013; 56:1339-49. [PMID: 23568272 DOI: 10.1007/s00125-013-2882-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/18/2013] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS Phosphatidylinositol 3-OH kinases (PI3Ks) regulate beta cell mass, gene transcription, and function, although the contribution of the specific isoforms is unknown. As reduced type 1A PI3K signalling is thought to contribute to impaired insulin secretion, we investigated the role of the type 1A PI3K catalytic subunits α and β (p110α and -β) in insulin granule recruitment and exocytosis in rodent and human islets. METHODS The p110α and p110β subunits were inhibited pharmacologically or by small hairpin (sh)RNA-mediated knockdown, and were directly infused or overexpressed in mouse and human islets, beta cells and INS-1 832/13 cells. Glucose-stimulated insulin secretion (GSIS), single-cell exocytosis, Ca(2+) signalling, plasma membrane granule localisation, and actin density were monitored. RESULTS Inhibition or knockdown of p110α increased GSIS. This was not due to altered Ca(2+) responses, depolymerisation of cortical actin or increased cortical granule density, but to enhanced Ca(2+)-dependent exocytosis. Intracellular infusion of recombinant PI3Kα (p110α/p85β) blocked exocytosis. Conversely, knockdown (but not pharmacological inhibition) of p110β blunted GSIS, reduced cortical granule density and impaired exocytosis. Exocytosis was rescued by direct intracellular infusion of recombinant PI3Kβ (p110β/p85β) even when p110β catalytic activity was inhibited. Conversely, both the wild-type p110β and a catalytically inactive mutant directly facilitated exocytosis. CONCLUSIONS/INTERPRETATION Type 1A PI3K isoforms have distinct and opposing roles in the acute regulation of insulin secretion. While p110α acts as a negative regulator of beta cell exocytosis and insulin secretion, p110β is a positive regulator of insulin secretion through a mechanism separate from its catalytic activity.
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Affiliation(s)
- J Kolic
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada T6G 2E1
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Redox homeostasis in pancreatic β cells. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:932838. [PMID: 23304259 PMCID: PMC3532876 DOI: 10.1155/2012/932838] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/30/2012] [Indexed: 12/20/2022]
Abstract
We reviewed mechanisms that determine reactive oxygen species (redox) homeostasis, redox information signaling and metabolic/regulatory function of autocrine insulin signaling in pancreatic β cells, and consequences of oxidative stress and dysregulation of redox/information signaling for their dysfunction. We emphasize the role of mitochondrion in β cell molecular physiology and pathology, including the antioxidant role of mitochondrial uncoupling protein UCP2. Since in pancreatic β cells pyruvate cannot be easily diverted towards lactate dehydrogenase for lactate formation, the respiration and oxidative phosphorylation intensity are governed by the availability of glucose, leading to a certain ATP/ADP ratio, whereas in other cell types, cell demand dictates respiration/metabolism rates. Moreover, we examine the possibility that type 2 diabetes mellitus might be considered as an inevitable result of progressive self-accelerating oxidative stress and concomitantly dysregulated information signaling in peripheral tissues as well as in pancreatic β cells. It is because the redox signaling is inherent to the insulin receptor signaling mechanism and its impairment leads to the oxidative and nitrosative stress. Also emerging concepts, admiting participation of redox signaling even in glucose sensing and insulin release in pancreatic β cells, fit in this view. For example, NADPH has been firmly established to be a modulator of glucose-stimulated insulin release.
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Abstract
Impaired insulin secretion from pancreatic β-cells is a major factor in the pathogenesis of type 2 diabetes. The main regulator of insulin secretion is the plasma glucose concentration. Insulin secretion is modified by other nutrients, circulating hormones and the autonomic nervous system, as well as local paracrine and autocrine signals. Autocrine signalling involves diffusible molecules that bind to receptors on the same cell from which they have been released. The first transmitter to be implicated in the autocrine regulation of β-cell function was insulin itself. The importance of autocrine insulin signalling is underscored by the finding that mice lacking insulin receptors in β-cells are glucose intolerant. In addition to insulin, β-cells secrete a variety of additional substances, including peptides (e.g. amylin, chromogranin A and B and their cleavage products), neurotransmitters (ATP and γ-aminobutyric acid) and ions (e.g. zinc). Here we review the autocrine effects of substances secreted from β-cells, with a focus on acute effects in stimulus-secretion coupling, present some novel data and discuss the general significance of autocrine signals for the regulation of insulin secretion.
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Affiliation(s)
- M Braun
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada.
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Hauge-Evans AC, Anderson RL, Persaud SJ, Jones PM. Delta cell secretory responses to insulin secretagogues are not mediated indirectly by insulin. Diabetologia 2012; 55:1995-2004. [PMID: 22526610 DOI: 10.1007/s00125-012-2546-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/09/2012] [Indexed: 10/28/2022]
Abstract
AIMS/HYPOTHESIS Somatostatin from islet delta cells inhibits insulin and glucagon secretion, but knowledge of the regulation of pancreatic somatostatin release is limited. Some insulin secretagogues stimulate somatostatin secretion, and here we investigated whether delta cell secretory responses are indirectly regulated in a paracrine manner by insulin released from beta cells. METHODS Hormone release from static incubations of primary mouse islets or somatostatin-secreting TGP52 cells was measured by RIA. mRNA expression was assessed by RT-PCR. RESULTS Glucose and a range of other physiological and pharmacological agents stimulated insulin and somatostatin release, and insulin receptor mRNA was expressed in islets, MIN6 beta cells and TGP52 cells. However, exogenous insulin did not modulate basal or glucose-induced somatostatin secretion from islets, nor did pre-incubation with an antibody against the insulin receptor or with the insulin receptor tyrosine kinase inhibitor, HNMPA(AM)(3). Glucose and tolbutamide stimulated somatostatin release from TGP52 cells, whereas a range of receptor-operating agents had no effect, the latter being consistent with a lack of corresponding receptor mRNA expression in these cells. Parasympathetic activation stimulated insulin, but inhibited somatostatin release from mouse islets in accordance with differences in muscarinic receptor mRNA expression in islets, MIN6 and TGP52 cells. The inhibitory effect on somatostatin secretion was reversed by pertussis toxin or the muscarinic receptor 2 antagonist, methoctramine. CONCLUSIONS/INTERPRETATIONS A number of insulin secretagogues have analogous effects on insulin and somatostatin release, but this similarity of response is not mediated by an indirect, paracrine action of insulin on delta cells.
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Affiliation(s)
- A C Hauge-Evans
- Diabetes Research Group, Division of Diabetes and Nutritional Sciences, School of Medicine, King's College London, Guy's Campus, London Bridge, London SE1 1UL, UK.
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Abstract
Insulin secretion is one of the most characteristic features of β-cell physiology. As it plays a central role in glucose regulation, a number of experimental and theoretical studies have been performed since the discovery of the pancreatic β-cell. This review article aims to give an overview of the mathematical approaches to insulin secretion. Beginning with the bursting electrical activity in pancreatic β-cells, we describe effects of the gap-junction coupling between β-cells on the dynamics of insulin secretion. Then, implications of paracrine interactions among such islet cells as α-, β-, and δ-cells are discussed. Finally, we present mathematical models which incorporate effects of glycolysis and mitochondrial glucose metabolism on the control of insulin secretion.
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Affiliation(s)
- Kyungreem Han
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul, South Korea
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Aldibbiat A, Huang GC, Zhao M, Holliman GN, Ferguson L, Hughes S, Brigham K, Wardle J, Williams R, Dickinson A, White SA, Johnson PRV, Manas D, Amiel SA, Shaw JAM. Validation of Islet Transport From a Geographically Distant Isolation Center Enabling Equitable Access and National Health Service Funding of a Clinical Islet Transplant Program for England. CELL MEDICINE 2011; 2:97-104. [PMID: 27004135 DOI: 10.3727/215517911x617905] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Islet transplantation has become established as a successful treatment for type 1 diabetes complicated by recurrent severe hypoglycemia. In the UK access has been limited to a few centrally located units. Our goal was to validate a quality-assured system for safe/effective transport of human islets in the UK and to successfully undertake the first transplants with transported islets. Pancreases were retrieved from deceased donors in the north of England and transported to King's College London using two-layer method (TLM) or University of Wisconsin solution alone. Islets were isolated and transported back to Newcastle in standard blood transfusion or gas-permeable bags with detailed evaluation pre- and posttransport. In the preclinical phase, islets were isolated from 10 pancreases with mean yield of 258,000 islet equivalents. No significant differences were seen between TLM and University of Wisconsin solution organ preservation. A significant loss of integrity was demonstrated in islets shipped in gas-permeable bags, whereas sterility, number, purity, and viability were maintained in blood transfusion bags. Maintenance of secretory granules and glucose-stimulated insulin secretion was confirmed following transport. A Standard Operating Procedure enabling final pretransplant quality control from a simple side-arm sample was validated. Moreover, levels of insulin and cytokines in transport medium were low, enabling transplant without centrifugation/resuspension at the recipient site. Six clinical transplants of transported islets were undertaken in five recipients with 100% primary graft function and resolution of severe hypoglycemia. Safe and clinically effective islet transport has been established facilitating sustainable NHS funding of a clinical islet transplant program for the UK.
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Affiliation(s)
- Ali Aldibbiat
- Institute of Cellular Medicine, Newcastle University , Newcastle upon Tyne , UK
| | - Guo Cai Huang
- † Division of Diabetes and Nutritional Sciences, King's College London , London , UK
| | - Min Zhao
- † Division of Diabetes and Nutritional Sciences, King's College London , London , UK
| | - Graham N Holliman
- Institute of Cellular Medicine, Newcastle University , Newcastle upon Tyne , UK
| | - Linda Ferguson
- Institute of Cellular Medicine, Newcastle University , Newcastle upon Tyne , UK
| | - Stephen Hughes
- ‡ Nuffield Department of Surgical Sciences, University of Oxford , Oxford , UK
| | - Ken Brigham
- § Department of Haematology, Newcastle University , Newcastle upon Tyne , UK
| | - Julie Wardle
- ¶ Institute of Transplantation, Freeman Hospital , Newcastle upon Tyne , UK
| | - Rob Williams
- ¶ Institute of Transplantation, Freeman Hospital , Newcastle upon Tyne , UK
| | - Anne Dickinson
- § Department of Haematology, Newcastle University , Newcastle upon Tyne , UK
| | - Steven A White
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK; ¶Institute of Transplantation, Freeman Hospital, Newcastle upon Tyne, UK
| | - Paul R V Johnson
- ‡ Nuffield Department of Surgical Sciences, University of Oxford , Oxford , UK
| | - Derek Manas
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK; ¶Institute of Transplantation, Freeman Hospital, Newcastle upon Tyne, UK
| | - Stephanie A Amiel
- † Division of Diabetes and Nutritional Sciences, King's College London , London , UK
| | - James A M Shaw
- Institute of Cellular Medicine, Newcastle University , Newcastle upon Tyne , UK
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Bansal P, Wang S, Liu S, Xiang YY, Lu WY, Wang Q. GABA coordinates with insulin in regulating secretory function in pancreatic INS-1 β-cells. PLoS One 2011; 6:e26225. [PMID: 22031825 PMCID: PMC3198728 DOI: 10.1371/journal.pone.0026225] [Citation(s) in RCA: 43] [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: 07/13/2011] [Accepted: 09/22/2011] [Indexed: 11/18/2022] Open
Abstract
Pancreatic islet β-cells produce large amounts of γ-aminobutyric acid (GABA), which is co-released with insulin. GABA inhibits glucagon secretion by hyperpolarizing α-cells via type-A GABA receptors (GABA(A)Rs). We and others recently reported that islet β-cells also express GABA(A)Rs and that activation of GABA(A)Rs increases insulin release. Here we investigate the effects of insulin on the GABA-GABA(A)R system in the pancreatic INS-1 cells using perforated-patch recording. The results showed that GABA produces a rapid inward current and depolarizes INS-1 cells. However, pre-treatment of the cell with regular insulin (1 µM) suppressed the GABA-induced current (I(GABA)) by 43%. Zinc-free insulin also suppressed I(GABA) to the same extent of inhibition by regular insulin. The inhibition of I(GABA) occurs within 30 seconds after application of insulin. The insulin-induced inhibition of I(GABA) persisted in the presence of PI3-kinase inhibitor, but was abolished upon inhibition of ERK, indicating that insulin suppresses GABA(A)Rs through a mechanism that involves ERK activation. Radioimmunoassay revealed that the secretion of C-peptide was enhanced by GABA, which was blocked by pre-incubating the cells with picrotoxin (50 µM, p<0.01) and insulin (1 µM, p<0.01), respectively. Together, these data suggest that autocrine GABA, via activation of GABA(A)Rs, depolarizes the pancreatic β-cells and enhances insulin secretion. On the other hand, insulin down-regulates GABA-GABA(A)R signaling presenting a feedback mechanism for fine-tuning β-cell secretion.
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Affiliation(s)
- Paul Bansal
- Departments of Physiology and Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Endocrinology and Metabolism, The Keenan Research Centre in the Li Ka-Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Shuanglian Wang
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
| | - Shenghao Liu
- Departments of Physiology and Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Endocrinology and Metabolism, The Keenan Research Centre in the Li Ka-Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Yun-Yan Xiang
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
| | - Wei-Yang Lu
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
- * E-mail: (W-YL); (QW)
| | - Qinghua Wang
- Departments of Physiology and Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Endocrinology and Metabolism, The Keenan Research Centre in the Li Ka-Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
- * E-mail: (W-YL); (QW)
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Meng R, Götz C, Montenarh M. The role of protein kinase CK2 in the regulation of the insulin production of pancreatic islets. Biochem Biophys Res Commun 2010; 401:203-6. [DOI: 10.1016/j.bbrc.2010.09.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 09/05/2010] [Indexed: 10/19/2022]
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Drews G, Krippeit-Drews P, Düfer M. Electrophysiology of islet cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:115-63. [PMID: 20217497 DOI: 10.1007/978-90-481-3271-3_7] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Stimulus-Secretion Coupling (SSC) of pancreatic islet cells comprises electrical activity. Changes of the membrane potential (V(m)) are regulated by metabolism-dependent alterations in ion channel activity. This coupling is best explored in beta-cells. The effect of glucose is directly linked to mitochondrial metabolism as the ATP/ADP ratio determines the open probability of ATP-sensitive K(+) channels (K(ATP) channels). Nucleotide sensitivity and concentration in the direct vicinity of the channels are controlled by several factors including phospholipids, fatty acids, and kinases, e.g., creatine and adenylate kinase. Closure of K(ATP) channels leads to depolarization of beta-cells via a yet unknown depolarizing current. Ca(2+) influx during action potentials (APs) results in an increase of the cytosolic Ca(2+) concentration ([Ca(2+)](c)) that triggers exocytosis. APs are elicited by the opening of voltage-dependent Na(+) and/or Ca(2+) channels and repolarized by voltage- and/or Ca(2+)-dependent K(+) channels. At a constant stimulatory glucose concentration APs are clustered in bursts that are interrupted by hyperpolarized interburst phases. Bursting electrical activity induces parallel fluctuations in [Ca(2+)](c) and insulin secretion. Bursts are terminated by I(Kslow) consisting of currents through Ca(2+)-dependent K(+) channels and K(ATP) channels. This review focuses on structure, characteristics, physiological function, and regulation of ion channels in beta-cells. Information about pharmacological drugs acting on K(ATP) channels, K(ATP) channelopathies, and influence of oxidative stress on K(ATP) channel function is provided. One focus is the outstanding significance of L-type Ca(2+) channels for insulin secretion. The role of less well characterized beta-cell channels including voltage-dependent Na(+) channels, volume sensitive anion channels (VSACs), transient receptor potential (TRP)-related channels, and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels is discussed. A model of beta-cell oscillations provides insight in the interplay of the different channels to induce and maintain electrical activity. Regulation of beta-cell electrical activity by hormones and the autonomous nervous system is discussed. alpha- and delta-cells are also equipped with K(ATP) channels, voltage-dependent Na(+), K(+), and Ca(2+) channels. Yet the SSC of these cells is less clear and is not necessarily dependent on K(ATP) channel closure. Different ion channels of alpha- and delta-cells are introduced and SSC in alpha-cells is described in special respect of paracrine effects of insulin and GABA secreted from beta-cells.
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Affiliation(s)
- Gisela Drews
- Institute of Pharmacy, Department of Pharmacology and Clinical Pharmacy, University of Tübingen, 72076 Tübingen, Germany.
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30
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Tengholm A, Gylfe E. Oscillatory control of insulin secretion. Mol Cell Endocrinol 2009; 297:58-72. [PMID: 18706473 DOI: 10.1016/j.mce.2008.07.009] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 05/30/2008] [Accepted: 07/10/2008] [Indexed: 11/17/2022]
Abstract
Pancreatic beta-cells possess an inherent ability to generate oscillatory signals that trigger insulin release. Coordination of the secretory activity among beta-cells results in pulsatile insulin secretion from the pancreas, which is considered important for the action of the hormone in the target tissues. This review focuses on the mechanisms underlying oscillatory control of insulin secretion at the level of the individual beta-cell. Recent studies have demonstrated that oscillations of the cytoplasmic Ca(2+) concentration are synchronized with oscillations in beta-cell metabolism, intracellular cAMP concentration, phospholipase C activity and plasma membrane phosphoinositide lipid concentrations. There are complex interdependencies between the different messengers and signalling pathways that contribute to amplitude regulation and shaping of the insulin secretory response to nutrient stimuli and neurohormonal modulators. Several of these pathways may be important pharmacological targets for improving pulsatile insulin secretion in type 2 diabetes.
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Affiliation(s)
- Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-75123 Uppsala, Sweden.
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31
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Tengholm A, Idevall-Hagren O. Spatio-temporal dynamics of phosphatidylinositol-3,4,5-trisphosphate signalling. VITAMINS AND HORMONES 2009; 80:287-311. [PMID: 19251042 DOI: 10.1016/s0083-6729(08)00611-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Many effects of insulin, insulin-like growth factors and other receptor stimuli are mediated via the phospholipid second messenger phosphatidylinositol-3,4,5-trisphosphate (PIP(3)). PIP(3) is formed by the activity of phosphoinositide 3-kinases in the plasma membrane, where it serves to recruit signalling proteins. These proteins coordinate complex events leading to changes in cell metabolism, growth, movement and survival. Over the past decade, new techniques for measurements of PIP(3) in the plasma membrane of individual living cells have markedly improved our understanding of the role of this messenger in a variety of cellular processes. This review summarises the mechanisms involved in formation and degradation of PIP(3) in insulin-responsive cells, how PIP(3) can be measured in individual cells as well as accumulating evidence that the plasma membrane PIP(3) concentration undergoes complex spatio-temporal patterns in many types of cells, with particular emphasis on autocrine insulin-induced PIP(3) oscillations in pancreatic beta-cells.
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Affiliation(s)
- Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Uppsala, Sweden
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32
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Abstract
Studies in transgenic animals, rodent insulin-secreting cell lines and rodent islets suggest that insulin acts in an autocrine manner to regulate beta-cell mass and gene expression. Very little is known about the in vitro roles played by insulin in human islets, and the regulatory role of insulin in protecting against beta-cell apoptosis. We have identified mRNAs encoding IRs (insulin receptors) and downstream signalling elements in dissociated human islet beta-cells by single-cell RT (reverse transcription)-PCR, and perifusion studies have indicated that insulin does not have an autocrine role to regulate insulin secretion from human islets, but activation of the closely related IGF-1 (insulin-like growth factor 1) receptors is linked to inhibition of insulin secretion. Knockdown of IR mRNA by siRNAs (small interfering RNAs) decreased IR protein expression without affecting IGF-1 receptor levels, and blocked glucose stimulation of preproinsulin gene expression. Similar results were obtained when human islet IRS (IR substrate)-2 was knocked down, whereas depletion of IRS-1 caused an increase in preproinsulin mRNA levels. Studies using the mouse MIN6 beta-cell line indicated that glucose protected beta-cells from undergoing apoptosis and that this was a consequence, at least in part, of insulin release in response to elevated glucose. IGF-1 also exerted anti-apoptotic effects. These data indicate that insulin can exert autocrine effects in human islets through receptors on beta-cells. It protects beta-cells against apoptosis and increases preproinsulin mRNA synthesis, but does not affect insulin secretion.
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Abstract
The appropriate function of insulin-producing pancreatic beta-cells is crucial for the regulation of glucose homeostasis, and its impairment leads to diabetes mellitus, the most common metabolic disorder in man. In addition to glucose, the major nutrient factor, inputs from the nervous system, humoral components, and cell-cell communication within the islet of Langerhans act together to guarantee the release of appropriate amounts of insulin in response to changes in blood glucose levels. Data obtained within the past decade in several laboratories have revitalized controversy over the autocrine feedback action of secreted insulin on beta-cell function. Although insulin historically has been suggested to exert a negative effect on beta-cells, recent data provide evidence for a positive role of insulin in transcription, translation, ion flux, insulin secretion, proliferation, and beta-cell survival. Current insights on the role of insulin on pancreatic beta-cell function are discussed.
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Affiliation(s)
- Ingo B Leibiger
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden.
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34
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Activation of the Na+/K+-ATPase by insulin and glucose as a putative negative feedback mechanism in pancreatic beta-cells. Pflugers Arch 2008; 457:1351-60. [PMID: 18836740 DOI: 10.1007/s00424-008-0592-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 09/14/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
Pancreatic beta-cells of sulfonylurea receptor type 1 knock-out (SUR1(-/-)) mice exhibit an oscillating membrane potential (V (m)) demonstrating that hyper-polarisation occurs despite the lack of K(ATP) channels. We hypothesize that glucose activates the Na(+)/K(+)-ATPase thus increasing a hyper-polarising current. Elevating glucose in SUR1(-/-) beta-cells resulted in a transient fall in V (m) and [Ca(2+)](c) independent of sarcoplasmic and endoplasmic reticulum Ca(2+)-activated ATPase (SERCA) activation. This was not affected by K(+) channel blockade but inhibited by ATP depletion and by ouabain. Increasing glucose also reduced [Na(+)](c), an effect reversed by ouabain. Exogenously applied insulin decreased [Na(+)](c) and hyper-polarised V (m). Inhibiting insulin signalling in SUR1(-/-) beta-cells blunted the glucose-induced decrease of [Ca(2+)](c). Tolbutamide (1 mmol/l) disclosed the SERCA-independent effect of glucose on [Ca(2+)](c) in wild-type beta-cells. The data show that in SUR1(-/-) beta-cells, glucose activates the Na(+)/K(+)-ATPase presumably by increasing [ATP](c). Insulin can also stimulate the pump and potentiate the effect of glucose. Pathways involving the pump may thus serve as potential drug targets in certain metabolic disorders.
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35
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Zhao M, Muiesan P, Amiel SA, Srinivasan P, Asare-Anane H, Fairbanks L, Persaud S, Jones P, Jones J, Ashraf S, Littlejohn W, Rela M, Heaton N, Huang GC. Human islets derived from donors after cardiac death are fully biofunctional. Am J Transplant 2007; 7:2318-25. [PMID: 17845565 DOI: 10.1111/j.1600-6143.2007.01937.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Islets from brain-dead donors (BDDs) are being used in the treatment of Type 1 diabetes. However, both donor numbers and islet survival are limited. We explored the clinical potential for islets from non-heart-beating donors (NHBDs), who have lower circulating cytokines, by comparing islets from 10 NHBDs against 12 identically-isolated islets from BDDs over the same time period. The quantity and quality of islets from NHBDs was good. NHBD yielded approximately 12.6% more islets than those of BDDs (505,000 +/- 84,230 vs. 400,970 +/- 172,430 islet equivalent number [IEQ]/pancreas, p = 0.01) with comparable viability. ATP and GTP contents were lower (6.026 +/- 3.076 vs. 18.105 +/- 7.8 nM/mg protein, p = 0.01 and 1.52 +/- 0.87 vs. 3.378 +/- 0.83 nM/mg protein, p = 0.04) and correlated negatively to warm ischemia time (R(2)= 0.8022 and R(2)= 0.7996, respectively). Islets from NHBDs took longer to control hyperglycemia in diabetic mice, but were equally able to sustain euglycemia. With a warm ischemia time (WIT) of <or=25 min, islets from NHBDs are at least as competent as islets from BDDs and should be suitable for clinical use.
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Affiliation(s)
- M Zhao
- Diabetes Research Group, King's College London School of Medicine, London, UK
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36
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Hee-Park S, Lim B, Baek WK, Bae JH, Song DK. Negative and positive feedback regulation of insulin in glucose-stimulated Ca2+ response in pancreatic beta cells. Diabetes Res Clin Pract 2007; 77 Suppl 1:S143-9. [PMID: 17467844 DOI: 10.1016/j.diabres.2007.02.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/02/2007] [Indexed: 10/23/2022]
Abstract
Secreted insulin from pancreatic beta cells exerts autocrine and paracrine effects within the islets. The present study has evaluated how exogenous insulin participates in cytosolic Ca(2+) response to high glucose, according to glucose concentration at which insulin is applied. When 100 nM insulin was pretreated to the bath solution containing islet cells in the presence of basal level of glucose, the elevation of cytosolic Ca(2+) concentration ([Ca(2+)](c)) by subsequently applied 10mM glucose was remarkably attenuated. In contrast, the glucose-stimulated [Ca(2+)](c) elevation was more potentiated when insulin was superimposed on the high glucose stimulation. These insulin actions were modestly inhibited by the application of LY294002, the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor, but not completely, suggesting that another mechanism is also involved. By 100 nM insulin, phosphorylated form of AMP-activated protein kinases (p-AMPK) was dramatically decreased in basal glucose but increased in high glucose, when compared with their reciprocal controls. These results may suggest that the extent of AMPK activation may be a tool for insulin receptors to monitor blood glucose level, with which insulin-induced insulin receptor activation determines the way to go negatively or positively toward [Ca(2+)](c).
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Affiliation(s)
- Sung Hee-Park
- Department of Physiology, Keimyung University School of Medicine and Chronic Disease Research Center, 194, Dongsan-Dong, Jung-Gu, Daegu 700-712, Korea
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37
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Vagn Korsgaard T, Colding-Jørgensen M. Time-dependent mechanisms in beta-cell glucose sensing. J Biol Phys 2006; 32:289-306. [PMID: 19669468 DOI: 10.1007/s10867-006-9017-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 04/21/2006] [Accepted: 04/28/2006] [Indexed: 12/22/2022] Open
Abstract
The relation between plasma glucose and insulin release from pancreatic beta-cells is not stationary in the sense that a given glucose concentration leads to a specific rate of insulin secretion. A number of time-dependent mechanisms appear to exist that modify insulin release both on a short and a longer time scale. Typically, two phases are described. The first phase, lasting up to 10 min, is a pulse of insulin release in response to fast changes in glucose concentration. The second phase is a more steady increase of insulin release over minutes to hours, if the elevated glucose concentration is sustained. The paper describes the glucose sensing mechanism via the complex dynamics of the key enzyme glucokinase, which controls the first step in glucose metabolism: phosphorylation of glucose to glucose-6-phosphate. Three time-dependent phenomena (mechanisms) are described. The fastest, corresponding to the first phase, is a delayed negative feedback regulating the glucokinase activity. Due to the delay, a rapid glucose increase will cause a burst of activity in the glucose sensing system, before the glucokinase is down-regulated. The second mechanism corresponds to the translocation of glucokinase from an inactive to an active form. As the translocation is controlled by the product(s) of the glucokinase reaction rather than by the substrate glucose, this mechanism gives a positive, but saturable, feedback. Finally, the release of the insulin granules is assumed to be enhanced by previous glucose exposure, giving a so-called glucose memory to the beta-cells. The effect depends on the insulin release of the cells, and this mechanism constitutes a second positive, saturable feedback system. Taken together, the three phenomena describe most of the glucose sensing behaviour of the beta-cells. The results indicate that the insulin release is not a precise function of the plasma glucose concentration. It rather looks as if the beta-cells just increase the insulin production, until the plasma glucose has returned to normal. This type of integral control has the advantage that the precise glucose sensitivity of the beta-cells is not important for normal glucose homeostasis.
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Affiliation(s)
- Thomas Vagn Korsgaard
- Development Projects Management, Novo Nordisk A/S, Novo Allè, 2880 Bagsvaerd, Denmark
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38
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Hagren OI, Tengholm A. Glucose and insulin synergistically activate phosphatidylinositol 3-kinase to trigger oscillations of phosphatidylinositol 3,4,5-trisphosphate in beta-cells. J Biol Chem 2006; 281:39121-7. [PMID: 17074763 DOI: 10.1074/jbc.m607445200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In insulin-secreting beta-cells, activation of phosphatidylinositol 3'-OH-kinase with resulting formation of phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) has been implicated in the regulation of ion channels, insulin secretion, and gene transcription as well as in cell growth and survival, but the kinetics of PIP(3) signals following physiological stimulation of insulin secretion is unknown. Using evanescent wave microscopy and a green fluorescent protein-tagged PIP(3)-binding protein domain for real-time monitoring of plasma membrane PIP(3) concentration in single MIN6 beta-cells, we now demonstrate that glucose stimulation of insulin secretion results in pronounced PIP(3) oscillations via autocrine stimulation of insulin receptors. Glucose lacked effect when insulin secretion was prevented with the hyperpolarizing agent diazoxide, but the sugar dose dependently enhanced the PIP(3) response to maximal insulin stimulation without affecting the rate of PIP(3) degradation. We conclude that glucose is an important co-activator of phosphatidylinositol-3'-OH-kinase and that the plasma membrane PIP(3) concentration in beta-cells undergoes oscillations due to pulsatile release of insulin.
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Affiliation(s)
- Olof Idevall Hagren
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-751 23 Uppsala, Sweden
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39
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Kang H, Jo J, Kim HJ, Choi MY, Rhee SW, Koh DS. Glucose metabolism and oscillatory behavior of pancreatic islets. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:051905. [PMID: 16383643 DOI: 10.1103/physreve.72.051905] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2004] [Revised: 08/15/2005] [Indexed: 05/05/2023]
Abstract
A variety of oscillations are observed in pancreatic islets. We establish a model incorporating two oscillatory systems of different time scales: One is the well-known bursting model in pancreatic cells and the other is the glucose-insulin feedback model which considers direct and indirect feedback of secreted insulin. These two are coupled to interact with each other in the combined model, and two basic assumptions are made on the basis of biological observations: The conductance gK(ATP) for the ATP-dependent potassium current is a decreasing function of the glucose concentration whereas the insulin secretion rate is given by a function of the intracellular calcium concentration. Obtained via extensive numerical simulations are complex oscillations including clusters of bursts, slow and fast calcium oscillations, and so on. We also consider how the intracellular glucose concentration depends upon the extracellular glucose concentration, and examine the inhibitory effects of insulin.
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Affiliation(s)
- H Kang
- Department of Physics and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
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40
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Luciani DS, Johnson JD. Acute effects of insulin on beta-cells from transplantable human islets. Mol Cell Endocrinol 2005; 241:88-98. [PMID: 16099589 DOI: 10.1016/j.mce.2005.06.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Revised: 06/28/2005] [Accepted: 06/29/2005] [Indexed: 11/15/2022]
Abstract
The functional role of autocrine insulin signaling remains unclear despite considerable investigation. In the present study, we tested the effects of high and low doses of exogenous insulin on Ca2+ signaling, insulin synthesis and insulin secretion in dispersed human islet cells using a combination of imaging, radioimmunoassay and patch-clamp electrophysiology. Although 200 nM insulin stimulated Ca2+ signals with larger amplitudes, the percentage of responding cells was lower when compared with 0.2 nM insulin. However, both 0.2 nM insulin and 200 nM insulin led to a transient increase in accessible cellular insulin content under conditions that glucose did not. This pool of insulin likely reflected de novo synthesis as it could be blocked by cyclohexamide or actinomycin D. Blocking endogenous autocrine insulin signaling in quiescent beta-cells with the insulin receptor inhibitor HMNPA led to a reduction in insulin synthesis, suggesting some degree of basal activity of this positive feed-forward loop. Unlike exposure to high glucose, acute treatment with insulin did not stimulate robust insulin exocytosis, as estimated by C-peptide release and capacitance measurements from single beta-cells. Together these data provide further evidence that autocrine insulin signaling can regulate the function of human pancreatic beta-cells. Our findings suggest autocrine insulin signaling directly controls insulin protein levels, but not exocytosis, in beta-cells and demonstrate the functional specificity of insulin signaling and glucose signaling in human islet cells.
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Affiliation(s)
- Dan S Luciani
- Department of Cellular and Physiological Science, University of British Columbia, Vancouver, 2350 Health Sciences Mall, Vancouver, BC, Canada
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41
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Kulkarni RN. New insights into the roles of insulin/IGF-I in the development and maintenance of beta-cell mass. Rev Endocr Metab Disord 2005; 6:199-210. [PMID: 16151624 DOI: 10.1007/s11154-005-3051-y] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Rohit N Kulkarni
- Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA.
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Zhou S, Lechpammer S, Greenberger JS, Glowacki J. Hypoxia inhibition of adipocytogenesis in human bone marrow stromal cells requires transforming growth factor-beta/Smad3 signaling. J Biol Chem 2005; 280:22688-96. [PMID: 15845540 PMCID: PMC1242109 DOI: 10.1074/jbc.m412953200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Although hypoxia and transforming growth factor-beta (TGF-beta) inhibit differentiation of adipocytes from preadipocytes and bone marrow-derived cells in several species, the relationship between hypoxia and TGF-beta signaling in adipocytogenesis is unknown. In this study, we evaluated the mechanisms of inhibition of adipocyte differentiation by hypoxia and TGF-beta in human and murine marrow stromal cells (MSCs) and the role of TGF-beta/Smad signaling in the inhibition of adipocytogenesis by hypoxia. Both hypoxia-mimetic deferoxamine mesylate (DFO) and TGF-beta1 inhibited adipocyte differentiation (1.0% versus the control at 15 microm DFO and 1.4% versus the control at 1 ng/ml TGF-beta1) and adipocyte gene expression (peroxisome proliferator-activated receptor-gamma2 and lipoprotein lipase) in human MSCs after 21 days of treatment. Hypoxia (2% O(2)) and DFO (but not TGF-beta1) increased hypoxia-inducible factor-1alpha as shown by Western blotting. Macroarrays and Western and Northern blot analyses showed that hypoxia activated the TGF-beta/Smad signaling pathway and that both hypoxia and TGF-beta1 modulated adipocyte differentiation pathways such as the insulin-, peroxisome proliferator-activated receptor-gamma-, phosphatidylinositol 3-kinase-, and MAPK-associated signaling pathways. Studies with mouse marrow stromal cell lines derived from Smad3(+/+) or Smad3(-/-) mice revealed that the TGF-beta type I receptor (ALK-5) and its intracellular signaling molecule Smad3 were necessary for the inhibition of adipocyte differentiation by both TGF-beta and hypoxia-mimetic DFO. Thus, the TGF-beta/Smad signaling pathway is required for hypoxia-mediated inhibition of adipocyte differentiation in MSCs.
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Affiliation(s)
- Shuanhu Zhou
- Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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Al-Majed HT, Squires PE, Persaud SJ, Huang GCC, Amiel S, Whitehouse BJ, Jones PM. Effect of 17beta-estradiol on insulin secretion and cytosolic calcium in Min6 mouse insulinoma cells and human islets of Langerhans. Pancreas 2005; 30:307-13. [PMID: 15841038 DOI: 10.1097/01.mpa.0000161886.17492.22] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVE Female gonadal steroids can exert an insulinotropic effect in vivo. The objective of this study was to investigate the effects in vitro of 17-beta-estradiol (17beta-E2) on changes in cytosolic calcium ([Ca]i) and on insulin secretion from the MIN6 mouse insulinoma cell line and human primary islets of Langerhans. METHODS Stimulus-induced changes in [Ca]i were measured in Fura-2-loaded cells by single cell microfluorimetry. The effects of 17beta-E2 on insulin secretion were measured in static incubation experiments, and the rate and pattern of secretory responses were studied in multi-channel perifusion experiments. RESULTS 17Beta-E2 (1-100 nmol/L) enhanced basal (2 mmol/L glucose) insulin secretion but had no effect on secretory responses to 20 mmol/L glucose or to depolarizing stimuli (100 micromol/L tolbutamide, 20 mmol/L KCl). Approximately 60% of MIN6 cells responded to 17beta-E2 (1-100 nmol/L) with a small but sustained increase in [Ca]i, whereas 98% of MIN6 cells responded to tolbutamide (100 micromol/L). Similar effects were observed in experiments using human primary beta cells. In contrast, 17beta-E2 had no detectable effect on the increases in [Ca]i evoked by tolbutamide (100 micromol/L) or glucose (20 mmol/L). CONCLUSIONS Our observations are consistent with a rapid effect of 17beta-E2 to depolarize beta cells leading to an influx of extracellular Ca and the initiation of insulin secretion by the consequent elevations in [Ca]i. We suggest that this may offer a mechanism through which circulating estradiol can influence beta-cell responsiveness to other signals.
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Affiliation(s)
- Hana T Al-Majed
- Division of Reproductive Health, Endocrinology and Development, King's College London, London, United Kingdom
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Jimenez-Feltstrom J, Lundquist I, Obermuller S, Salehi A. Insulin feedback actions: complex effects involving isoforms of islet nitric oxide synthase. ACTA ACUST UNITED AC 2005; 122:109-18. [PMID: 15380928 DOI: 10.1016/j.regpep.2004.06.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 05/19/2004] [Accepted: 06/01/2004] [Indexed: 11/18/2022]
Abstract
The present study examined the effects of exogenous insulin on C-peptide release in relation to islet activities of neural constitutive nitric oxide synthase (ncNOS) and inducible NOS (iNOS). The dose-response curves for glucose-stimulated insulin and C-peptide release from isolated islets were practically identical: 0.05-0.1 nmol/l insulin stimulated, 1-100 nmol/l had no effect, whereas concentrations >/=250 nmol/l ("high insulin"), inhibited C-peptide release. Both the stimulatory and inhibitory effects were abolished by the phosphatidylinositol 3'-kinase inhibitor wortmannin. Addition of a NOS inhibitor partially reversed the inhibitory action of high insulin, but had no effect on the stimulatory action of low insulin (0.1 nmol/l). Moreover, high insulin markedly increased islet ncNOS activity and induced a strong iNOS activity. As shown biochemically and with confocal microscopy, the stimulatory action of high insulin on NOS activities and the associated inhibition of C-peptide release were reversed by raising cyclic AMP through addition of either glucagon-like peptide 1 (GLP-1) or dibutyryl cyclic AMP (Bt(2)cAMP) to the incubated islets. We conclude that the positive feedback mechanisms of action of insulin are independent of islet NOS activities and remain unclear. The negative feedback action of insulin, however, can be explained by its ability to stimulate both islet ncNOS activity and the expression and activity of iNOS. The effects on iNOS are most likely transduced through phosphatidylinositol 3'-kinase and are counteracted by raising islet cyclic AMP levels.
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Affiliation(s)
- Javier Jimenez-Feltstrom
- Institute of Physiological Sciences, Department of Pharmacology, University of Lund, BMC F13 S-221 84 Lund, Sweden.
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Collier JJ, White SM, Dick GM, Scott DK. Phosphatidylinositol 3-kinase inhibitors reveal a unique mechanism of enhancing insulin secretion in 832/13 rat insulinoma cells. Biochem Biophys Res Commun 2004; 324:1018-23. [PMID: 15485656 DOI: 10.1016/j.bbrc.2004.09.149] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Indexed: 11/22/2022]
Abstract
Hyperinsulinemia exists before the onset of overt type 2 diabetes mellitus. This response is at least partly due to enhanced insulin release from pancreatic beta-cells. Increased insulin secretion can be mimicked in vitro by acute culture of 832/13 rat insulinoma cells with phosphatidylinositol 3-kinase (PI-3K) inhibitors, a treatment that would theoretically simulate insulin resistance. We demonstrate in this study that while the PI-3K inhibitors Wortmannin and LY294002 both block Akt phosphorylation, only LY29002 significantly augments insulin secretion. LY294002 treatment potentiates insulin secretion over both basal and stimulatory glucose concentrations. This effect correlates with a significant increase in action potential duration. There was no change in resting or peak membrane potential under any of the treatment conditions, demonstrating that the cells remain healthy under the acute treatments used in this study. By contrast, Wortmannin has no effect on action potential duration. A partial explanation for these findings is that LY294002 potently inhibits voltage-dependent potassium channels, but does not affect voltage-gated calcium currents. We conclude that while PI-3K may play a role in regulating insulin secretion, there are diverse effects of the established inhibitors of this enzyme on beta-cell insulin secretory responses.
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Affiliation(s)
- J Jason Collier
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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46
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Ohsugi M, Cras-Méneur C, Zhou Y, Bernal-Mizrachi E, Johnson JD, Luciani DS, Polonsky KS, Permutt MA. Reduced expression of the insulin receptor in mouse insulinoma (MIN6) cells reveals multiple roles of insulin signaling in gene expression, proliferation, insulin content, and secretion. J Biol Chem 2004; 280:4992-5003. [PMID: 15546857 DOI: 10.1074/jbc.m411727200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of insulin signaling in pancreatic beta cells has become increasingly apparent. Stably transformed insulinoma cell lines (MIN6) were created with small interfering RNA resulting in the reduction of insulin receptor (IR) expression up to 80% (insulin receptor knockdown, IRKDDelta80). Functionally perturbed IR signaling was confirmed with the absence of insulin-stimulated insulin receptor substrate 1 tyrosine phosphorylation. Additionally, Akt phosphorylation was reduced and responded poorly to glucose stimulation. Gene expression profiling revealed that reduced IR expression was associated with alterations in expression of >1,500 genes with diverse functions. IRKD cells exhibited low rate of proliferation due to delay in transition from G0/G1 to S phase, whereas susceptibility to apoptosis did not differ from that of control cells. Insulin content was reduced in proportion to the reduction of IR. IRKD cells maintained glucose responsiveness as measured by NADPH generation, whereas Ca2+ responses and insulin secretion were enhanced. IRKDDelta80 and control cells were treated with glucose (25 mm) or insulin (100 nm) for 45 min, and gene expression profiles were assessed. Transcriptional activation of several hundred early response genes common to both glucose and insulin stimulation was observed in control cells. In IRKDDelta80 cells, insulin failed to activate any genes as anticipated. Importantly, glucose stimulation of gene expression in IRKDDelta80 cells showed that most genes previously activated by glucose were no longer activated, suggesting a major autocrine/paracrine effect of insulin on glucose-regulated gene expression. On the other hand, there were a number of glucose-regulated genes in the IRKDDelta80 cells that were not previously observed in control cells, suggesting a feedback regulation of insulin signaling on glucose-regulated gene expression. These results demonstrate important roles of the insulin receptor in islet beta cell gene expression and function and may serve to elucidate molecular defects in animal models with diminished beta cell insulin signaling.
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Affiliation(s)
- Mitsuru Ohsugi
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Broca C, Breil V, Cruciani-Guglielmacci C, Manteghetti M, Rouault C, Derouet M, Rizkalla S, Pau B, Petit P, Ribes G, Ktorza A, Gross R, Reach G, Taouis M. Insulinotropic agent ID-1101 (4-hydroxyisoleucine) activates insulin signaling in rat. Am J Physiol Endocrinol Metab 2004; 287:E463-71. [PMID: 15082420 DOI: 10.1152/ajpendo.00163.2003] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
ID-1101 (4-hydroxyisoleucine), an amino acid extracted from fenugreek seeds, exhibits an interesting glucose-dependent insulin-stimulating activity. The present study was undertaken to investigate a possible extrapancreatic effect of ID-1101 on insulin signaling and action besides its previously described insulinotropic action. Insulin-sensitizing effects of ID-1101 were investigated in rat in vivo by three different approaches: 1) using euglycemic hyperinsulinemic clamps in two different rat models of insulin resistance, i.e., Zucker fa/fa rats and rats fed a sucrose-lipid diet; 2) measuring liver and muscle phosphatidylinositol (PI) 3-kinase activity after an acute injection of ID-1101 in normal and insulin-resistant diabetic rats; and 3) after chronic treatment in two rat models of insulin resistance. Euglycemic hyperinsulinemic clamp experiments revealed that ID-1101 can improve insulin resistance through an increase of peripheral glucose utilization rate in sucrose-lipid-fed rats and by decreasing hepatic glucose production in Zucker fa/fa rats. Moreover, we demonstrated that a single injection of ID-1101 activates the PI 3-kinase activity in liver and muscle from normal rats but also in muscle from diabetic rats. Finally, chronic ID-1101 treatment significantly reduced insulinemia in type 2 diabetic rats and reduced the progression of hyperinsulinemia in insulin-resistant obese Zucker fa/fa rats. These findings clearly demonstrate that ID-1101 can reduce insulin resistance through activation of the early steps of insulin signaling in peripheral tissues and in liver. In summary, ID-1101, besides its insulinotropic effect, directly improves insulin sensitivity, making it a potentially very valuable therapeutic agent for diabetes treatment.
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Affiliation(s)
- Christophe Broca
- Laboratoire de Pharmacologie, Centre de Pharmacologie et Biotechnologies pour la Santé-Unite Mixte de Recherche 5160 Centre National de la Recherche Scientifique, Faculté de Médecine, 34060 Montpellier, France.
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Braun M, Wendt A, Buschard K, Salehi A, Sewing S, Gromada J, Rorsman P. GABAB receptor activation inhibits exocytosis in rat pancreatic beta-cells by G-protein-dependent activation of calcineurin. J Physiol 2004; 559:397-409. [PMID: 15235087 PMCID: PMC1665126 DOI: 10.1113/jphysiol.2004.066563] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We have investigated the regulation of hormone secretion from rat pancreatic islets by the GABAB receptors (GABABRs). Inclusion of the specific GABABR antagonist CGP 55845 in the extracellular medium increased glucose-stimulated insulin secretion 1.6-fold but did not affect the release of glucagon and somatostatin. Conversely, addition of the GABABR agonist baclofen inhibited glucose-stimulated insulin secretion by approximately 60%. Using RT-PCR, transcription of GABABR1a-c,f and GABABR2 subunits was detected in beta-cells. Measurements of membrane currents and cell capacitance were applied to single beta-cells to investigate the mechanisms by which GABABR activation inhibits insulin secretion. In perforated-patch measurements, baclofen inhibited exocytosis elicited by 500-ms voltage-clamp depolarizations to 0 mV by < or = 80% and voltage-gated Ca2+ entry by only approximately 30%. Both effects were concentration-dependent with IC50 values of approximately 2 microm. The inhibitory action of baclofen was abolished in the presence of CGP 55845. The ability of baclofen to suppress exocytosis was prevented by pre-treatment with pertussis toxin and by inclusion of GDPbetaS in the intracellular medium, and became irreversible in the presence of GTPgammaS as expected for a process involving inhibitory G-proteins (Gi/o-proteins). The inhibitory effect of baclofen resulted from activation of the serine/threonine protein phosphatase calcineurin and pre-treatment with cyclosporin A or intracellular application of calcineurin autoinhibitory peptide abolished the effect. Addition of baclofen had no effect on [Ca2+]i and electrical activity in glucose-stimulated beta-cells. These data indicate that GABA released from beta-cells functions as an autocrine inhibitor of insulin secretion in pancreatic islets and that the effect is principally due to direct suppression of exocytosis.
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Affiliation(s)
- Matthias Braun
- Department of Physiological Sciences, BMC B11, SE-221 84 Lund, Sweden.
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Nunemaker CS, Zhang M, Satin LS. Insulin feedback alters mitochondrial activity through an ATP-sensitive K+ channel-dependent pathway in mouse islets and beta-cells. Diabetes 2004; 53:1765-72. [PMID: 15220200 DOI: 10.2337/diabetes.53.7.1765] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Recent work suggests that insulin may exert both positive and negative feedback directly on pancreatic beta-cells. To investigate the hypothesis that insulin modulates beta-cell metabolism, mouse islets and beta-cell clusters were loaded with rhodamine 123 to dynamically monitor mitochondrial membrane potential (DeltaPsi(m)). Spontaneous oscillations in DeltaPsi(m) (period: 218 +/- 26 s) were observed in 17 of 30 islets exposed to 11.1 mmol/l glucose. Acute insulin application (100 nmol/l) hyperpolarized DeltaPsi(m), indicating a change in mitochondrial activity. The ATP-sensitive K(+) (K(ATP)) channel opener diazoxide or the l-type calcium channel blocker nifedipine mimicked the effect of insulin, suggesting that insulin activates K(ATP) channels to hyperpolarize DeltaPsi(m) by inhibiting calcium influx. Treatment with forskolin, which increases endogenous insulin secretion, also mimicked the effect of exogenous insulin, suggesting physiological feedback. Pretreatment with nifedipine or the K(ATP) inhibitor glyburide prevented insulin action, further implicating a K(ATP) channel pathway. Together, these data suggest a feedback mechanism whereby insulin receptor activation opens K(ATP) channels to inhibit further secretion. The resulting reduction in beta-cell calcium increases the energy stored in the mitochondrial gradient that drives ATP production. Insulin feedback onto mitochondria may thus help to calibrate the energy needs of the beta-cell on a minute-to-minute basis.
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Affiliation(s)
- Craig S Nunemaker
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, USA
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Kobayashi H, Mitsui T, Nomura S, Ohno Y, Kadomatsu K, Muramatsu T, Nagasaka T, Mizutani S. Expression of glucose transporter 4 in the human pancreatic islet of Langerhans. Biochem Biophys Res Commun 2004; 314:1121-5. [PMID: 14751249 DOI: 10.1016/j.bbrc.2004.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Glucose transporter 4 (GLUT4) is the main insulin-responsive glucose transporter in skeletal muscle and adipose tissue of human and rodent, and is translocated to the plasma membrane in response to insulin. GLUT2 is well known as the main glucose transporter in pancreatic islets and could highly regulate glucose-stimulated insulin secretion by B-cells as a glucose sensor. We confirmed the presence of GLUT4 mRNA and GLUT4 protein in pancreas in the human. Indirect immunohistochemistry showed that the pancreatic islets of human and rat were conspicuously labeled by anti-GLUT4 antibody. The presence of placental leucine aminopeptidase (P-LAP), a homologue of insulin-regulated aminopeptidase (IRAP), was also shown in the human pancreatic islet. IRAP/P-LAP is thought to be involved in glucose metabolism. This study provides the first evidence that GLUT4 is present in human and rat pancreatic islets and may suggest its specific role in glucose homeostasis in conjunction with IRAP/P-LAP.
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Affiliation(s)
- Honami Kobayashi
- Department of Obstetrics and Gynecology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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