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Ivovic A, Yung JHM, Oprescu AI, Vlavcheski F, Mori Y, Rahman SMN, Ye W, Eversley JA, Wheeler MB, Woo M, Tsiani E, Giacca A. β-Cell Insulin Resistance Plays a Causal Role in Fat-Induced β-Cell Dysfunction In Vitro and In Vivo. Endocrinology 2024; 165:bqae044. [PMID: 38578954 PMCID: PMC11033845 DOI: 10.1210/endocr/bqae044] [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: 03/28/2023] [Revised: 03/27/2024] [Accepted: 04/04/2024] [Indexed: 04/07/2024]
Abstract
In the classical insulin target tissues of liver, muscle, and adipose tissue, chronically elevated levels of free fatty acids (FFA) impair insulin signaling. Insulin signaling molecules are also present in β-cells where they play a role in β-cell function. Therefore, inhibition of the insulin/insulin-like growth factor 1 pathway may be involved in fat-induced β-cell dysfunction. To address the role of β-cell insulin resistance in FFA-induced β-cell dysfunction we co-infused bisperoxovanadate (BPV) with oleate or olive oil for 48 hours in rats. BPV, a tyrosine phosphatase inhibitor, acts as an insulin mimetic and is devoid of any antioxidant effect that could prevent β-cell dysfunction, unlike most insulin sensitizers. Following fat infusion, rats either underwent hyperglycemic clamps for assessment of β-cell function in vivo or islets were isolated for ex vivo assessment of glucose-stimulated insulin secretion (GSIS). We also incubated islets with oleate or palmitate and BPV for in vitro assessment of GSIS and Akt (protein kinase B) phosphorylation. Next, mice with β-cell specific deletion of PTEN (phosphatase and tensin homolog; negative regulator of insulin signaling) and littermate controls were infused with oleate for 48 hours, followed by hyperglycemic clamps or ex vivo evaluation of GSIS. In rat experiments, BPV protected against fat-induced impairment of β-cell function in vivo, ex vivo, and in vitro. In mice, β-cell specific deletion of PTEN protected against oleate-induced β-cell dysfunction in vivo and ex vivo. These data support the hypothesis that β-cell insulin resistance plays a causal role in FFA-induced β-cell dysfunction.
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Affiliation(s)
- Aleksandar Ivovic
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Justin Hou Ming Yung
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Andrei I Oprescu
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Filip Vlavcheski
- Department of Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Yusaku Mori
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Division of Diabetes, Metabolism, and Endocrinology, Anti-Glycation Research Section, Department of Medicine, Showa University School of Medicine, Shinagawa, Tokyo 142-8555, Japan
| | - S M Niazur Rahman
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Wenyue Ye
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Judith A Eversley
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Michael B Wheeler
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Minna Woo
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Toronto General Hospital Research Institute, University Health Network, University of Toronto, Toronto, ON M5G 2C4, Canada
- Division of Endocrinology, Department of Medicine, University Health Network, University of Toronto, Toronto, ON M5G 2C4, Canada
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Banting and Best Diabetes Centre, University of Toronto, Toronto, ON M5G 2C4, Canada
| | - Evangelia Tsiani
- Department of Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Adria Giacca
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Banting and Best Diabetes Centre, University of Toronto, Toronto, ON M5G 2C4, Canada
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Lv C, Sun Y, Zhang ZY, Aboelela Z, Qiu X, Meng ZX. β-cell dynamics in type 2 diabetes and in dietary and exercise interventions. J Mol Cell Biol 2022; 14:6656373. [PMID: 35929791 PMCID: PMC9710517 DOI: 10.1093/jmcb/mjac046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 05/07/2022] [Accepted: 08/03/2022] [Indexed: 01/14/2023] Open
Abstract
Pancreatic β-cell dysfunction and insulin resistance are two of the major causes of type 2 diabetes (T2D). Recent clinical and experimental studies have suggested that the functional capacity of β-cells, particularly in the first phase of insulin secretion, is a primary contributor to the progression of T2D and its associated complications. Pancreatic β-cells undergo dynamic compensation and decompensation processes during the development of T2D, in which metabolic stresses such as endoplasmic reticulum stress, oxidative stress, and inflammatory signals are key regulators of β-cell dynamics. Dietary and exercise interventions have been shown to be effective approaches for the treatment of obesity and T2D, especially in the early stages. Whilst the targeted tissues and underlying mechanisms of dietary and exercise interventions remain somewhat vague, accumulating evidence has implicated the improvement of β-cell functional capacity. In this review, we summarize recent advances in the understanding of the dynamic adaptations of β-cell function in T2D progression and clarify the effects and mechanisms of dietary and exercise interventions on β-cell dysfunction in T2D. This review provides molecular insights into the therapeutic effects of dietary and exercise interventions on T2D, and more importantly, it paves the way for future research on the related underlying mechanisms for developing precision prevention and treatment of T2D.
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Affiliation(s)
- Chengan Lv
- Department of Pathology and Pathophysiology and Metabolic Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China,Key Laboratory of Disease Proteomics of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Yuchen Sun
- Department of Pathology and Pathophysiology and Metabolic Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China,Key Laboratory of Disease Proteomics of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou 310058, China,Zhejiang University–University of Edinburgh Institute (ZJE), Zhejiang University, Haining 314400, China
| | - Zhe Yu Zhang
- Department of Pathology and Pathophysiology and Metabolic Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China,Key Laboratory of Disease Proteomics of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Zeyad Aboelela
- Department of Pathology and Pathophysiology and Metabolic Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China,Key Laboratory of Disease Proteomics of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou 310058, China,Bachelors of Surgery, Bachelors of Medicine (MBBS), Zhejiang University School of Medicine, Hangzhou 310003, China
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3
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Antonucci A, Marucci A, Trischitta V, Di Paola R. Role of GALNT2 on Insulin Sensitivity, Lipid Metabolism and Fat Homeostasis. Int J Mol Sci 2022; 23:929. [PMID: 35055114 PMCID: PMC8781516 DOI: 10.3390/ijms23020929] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/11/2022] [Accepted: 01/13/2022] [Indexed: 01/16/2023] Open
Abstract
O-linked glycosylation, the greatest form of post-translational modifications, plays a key role in regulating the majority of physiological processes. It is, therefore, not surprising that abnormal O-linked glycosylation has been related to several human diseases. Recently, GALNT2, which encodes the GalNAc-transferase 2 involved in the first step of O-linked glycosylation, has attracted great attention as a possible player in many highly prevalent human metabolic diseases, including atherogenic dyslipidemia, type 2 diabetes and obesity, all clustered on the common ground of insulin resistance. Data available both in human and animal models point to GALNT2 as a molecule that shapes the risk of the aforementioned abnormalities affecting diverse protein functions, which eventually cause clinically distinct phenotypes (a typical example of pleiotropism). Pathways linking GALNT2 to dyslipidemia and insulin resistance have been partly identified, while those for type 2 diabetes and obesity are yet to be understood. Here, we will provide a brief overview on the present knowledge on GALNT2 function and dysfunction and propose novel insights on the complex pathogenesis of the aforementioned metabolic diseases, which all impose a heavy burden for patients, their families and the entire society.
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Affiliation(s)
- Alessandra Antonucci
- Research Unit of Diabetes and Endocrine Diseases, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), 71013 Foggia, Italy; (A.A.); (A.M.)
| | - Antonella Marucci
- Research Unit of Diabetes and Endocrine Diseases, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), 71013 Foggia, Italy; (A.A.); (A.M.)
| | - Vincenzo Trischitta
- Research Unit of Diabetes and Endocrine Diseases, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), 71013 Foggia, Italy; (A.A.); (A.M.)
- Department of Experimental Medicine, Sapienza University, 00161 Rome, Italy
| | - Rosa Di Paola
- Research Unit of Diabetes and Endocrine Diseases, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), 71013 Foggia, Italy; (A.A.); (A.M.)
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Koneshamoorthy A, Seniveratne-Epa D, Calder G, Sawyer M, Kay TWH, Farrell S, Loudovaris T, Mariana L, McCarthy D, Lyu R, Liu X, Thorn P, Tong J, Chin LK, Zacharin M, Trainer A, Taylor S, MacIsaac RJ, Sachithanandan N, Thomas HE, Krishnamurthy B. Case Report: Hypoglycemia Due to a Novel Activating Glucokinase Variant in an Adult - a Molecular Approach. Front Endocrinol (Lausanne) 2022; 13:842937. [PMID: 35370948 PMCID: PMC8969599 DOI: 10.3389/fendo.2022.842937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 02/17/2022] [Indexed: 11/13/2022] Open
Abstract
We present a case of an obese 22-year-old man with activating GCK variant who had neonatal hypoglycemia, re-emerging with hypoglycemia later in life. We investigated him for asymptomatic hypoglycemia with a family history of hypoglycemia. Genetic testing yielded a novel GCK missense class 3 variant that was subsequently found in his mother, sister and nephew and reclassified as a class 4 likely pathogenic variant. Glucokinase enables phosphorylation of glucose, the rate-limiting step of glycolysis in the liver and pancreatic β cells. It plays a crucial role in the regulation of insulin secretion. Inactivating variants in GCK cause hyperglycemia and activating variants cause hypoglycemia. Spleen-preserving distal pancreatectomy revealed diffuse hyperplastic islets, nuclear pleomorphism and periductular islets. Glucose stimulated insulin secretion revealed increased insulin secretion in response to glucose. Cytoplasmic calcium, which triggers exocytosis of insulin-containing granules, revealed normal basal but increased glucose-stimulated level. Unbiased gene expression analysis using 10X single cell sequencing revealed upregulated INS and CKB genes and downregulated DLK1 and NPY genes in β-cells. Further studies are required to see if alteration in expression of these genes plays a role in the metabolic and histological phenotype associated with glucokinase pathogenic variant. There were more large islets in the patient's pancreas than in control subjects but there was no difference in the proportion of β cells in the islets. His hypoglycemia was persistent after pancreatectomy, was refractory to diazoxide and improved with pasireotide. This case highlights the variable phenotype of GCK mutations. In-depth molecular analyses in the islets have revealed possible mechanisms for hyperplastic islets and insulin hypersecretion.
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Affiliation(s)
- Anojian Koneshamoorthy
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Dilan Seniveratne-Epa
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Genevieve Calder
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Matthew Sawyer
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Thomas W. H. Kay
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
- Department of Medicine, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Stephen Farrell
- Department of Surgery, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Thomas Loudovaris
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
| | - Lina Mariana
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
| | - Davis McCarthy
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
- Melbourne Integrative Genomics, Faculty of Science, University of Melbourne, Melbourne, VIC, Australia
| | - Ruqian Lyu
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
| | - Xin Liu
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
- Melbourne Integrative Genomics, Faculty of Science, University of Melbourne, Melbourne, VIC, Australia
| | - Peter Thorn
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Jason Tong
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Lit Kim Chin
- Department of Diabetes and Endocrinology, Royal Children’s Hospital, Melbourne, VIC, Australia
| | - Margaret Zacharin
- Department of Diabetes and Endocrinology, Royal Children’s Hospital, Melbourne, VIC, Australia
| | - Alison Trainer
- Department of Genomic Medicine, Royal Melbourne Hospital, Melbourne, VIC, Australia
| | - Shelby Taylor
- Department of Genomic Medicine, Royal Melbourne Hospital, Melbourne, VIC, Australia
| | - Richard J. MacIsaac
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
- Department of Medicine, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Nirupa Sachithanandan
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
- Department of Medicine, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Helen E. Thomas
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
- Department of Medicine, St. Vincent’s Hospital, Melbourne, VIC, Australia
| | - Balasubramanian Krishnamurthy
- Department of Endocrinology and Diabetes, St. Vincent’s Hospital, Melbourne, VIC, Australia
- St. Vincent’s Institute of Medical Research, Melbourne, VIC, Australia
- Department of Medicine, St. Vincent’s Hospital, Melbourne, VIC, Australia
- *Correspondence: Balasubramanian Krishnamurthy,
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Yang B, Wei X, Luo Y, Kan J. Hypoglycemic effect of low-sugar juice derived from Hovenia dulcis on type 1 diabetes mellitus rats. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2021; 101:4818-4828. [PMID: 33502785 DOI: 10.1002/jsfa.11128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 12/29/2020] [Accepted: 01/27/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Fruit juice is usually rich in monosaccharides and disaccharides. A reverse osmosis separation machine was used to remove monosaccharides and disaccharides from Hovenia dulcis fruit juice, leaving behind most of the bioactive substances in a low-sugar fruit juice (LSFJ), so as to provide a more effective treatment for diabetic patients. METHOD This study was carried out with type 1 diabetes mellitus model induced with high dose of streptozotocin (60 mg kg-1 ), and oral administration of LSFJ for 4 weeks. RESULTS LSFJ treatment led to significant gain in body weight and increased serum insulin level, insulin-like growth factor-1 level, blood urea nitrogen level, creatinine level, and hepatic glycogen level. Meanwhile, fasting blood glucose, fructosamine level, and glucose tolerance were also observably enhanced. Additional, LSFJ treatment significantly improved lipid metabolism, islet quality, and islet oxidative stress. The messenger RNA levels of glucose metabolism genes in the pancreas of diabetic rats decreased in the diabetes model group, whereas messenger RNA expression of these genes was significantly increased with LSFJ treatment. CONCLUSION These findings indicate that LSFJ can improve symptoms associated with type 1 diabetes mellitus. The research also suggests new strategies for diabetes prevention and treatment. © 2021 Society of Chemical Industry.
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Affiliation(s)
- Bing Yang
- College of Food Science, Southwest University, Chongqing, China
- College of Food Science and Technology, Hebei Agricultural University, Baoding, China
- Laboratory of Quality & Safety Risk Assessment for Agro-products on Storage and Preservation (Chongqing), Ministry of Agriculture, Chongqing, China
| | - Xunyu Wei
- College of Food Science, Southwest University, Chongqing, China
- Laboratory of Quality & Safety Risk Assessment for Agro-products on Storage and Preservation (Chongqing), Ministry of Agriculture, Chongqing, China
| | - Yuxin Luo
- College of Food Science, Southwest University, Chongqing, China
| | - Jianquan Kan
- College of Food Science, Southwest University, Chongqing, China
- Laboratory of Quality & Safety Risk Assessment for Agro-products on Storage and Preservation (Chongqing), Ministry of Agriculture, Chongqing, China
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Takatani T, Shirakawa J, Shibue K, Gupta MK, Kim H, Lu S, Hu J, White MF, Kennedy RT, Kulkarni RN. Insulin receptor substrate 1, but not IRS2, plays a dominant role in regulating pancreatic alpha cell function in mice. J Biol Chem 2021; 296:100646. [PMID: 33839150 PMCID: PMC8131928 DOI: 10.1016/j.jbc.2021.100646] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/24/2021] [Accepted: 04/07/2021] [Indexed: 11/29/2022] Open
Abstract
Dysregulated glucagon secretion deteriorates glycemic control in type 1 and type 2 diabetes. Although insulin is known to regulate glucagon secretion via its cognate receptor (insulin receptor, INSR) in pancreatic alpha cells, the role of downstream proteins and signaling pathways underlying insulin's activities are not fully defined. Using in vivo (knockout) and in vitro (knockdown) studies targeting insulin receptor substrate (IRS) proteins, we compared the relative roles of IRS1 and IRS2 in regulating alpha cell function. Alpha cell-specific IRS1-knockout mice exhibited glucose intolerance and inappropriate glucagon suppression during glucose tolerance tests. In contrast, alpha cell-specific IRS2-knockout animals manifested normal glucose tolerance and suppression of glucagon secretion after glucose administration. Alpha cell lines with stable IRS1 knockdown could not repress glucagon mRNA expression and exhibited a reduction in phosphorylation of AKT Ser/Thr kinase (AKT, at Ser-473 and Thr-308). AlphaIRS1KD cells also displayed suppressed global protein translation, including reduced glucagon expression, impaired cytoplasmic Ca2+ response, and mitochondrial dysfunction. This was supported by the identification of novel IRS1-specific downstream target genes, Trpc3 and Cartpt, that are associated with glucagon regulation in alpha cells. These results provide evidence that IRS1, rather than IRS2, is a dominant regulator of pancreatic alpha cell function.
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Affiliation(s)
- Tomozumi Takatani
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Department of Pediatrics, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Jun Shirakawa
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Gunma, Japan
| | - Kimitaka Shibue
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Manoj K Gupta
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Cell Therapy Translational Engine (CTTE), Takeda Pharmaceuticals, Cambridge, Massachusetts, USA
| | - Hyunki Kim
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Shusheng Lu
- Departments of Chemistry and Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jiang Hu
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Morris F White
- Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Robert T Kennedy
- Departments of Chemistry and Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - Rohit N Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts, USA.
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van Vliet S, Koh HCE, Patterson BW, Yoshino M, LaForest R, Gropler RJ, Klein S, Mittendorfer B. Obesity Is Associated With Increased Basal and Postprandial β-Cell Insulin Secretion Even in the Absence of Insulin Resistance. Diabetes 2020; 69:2112-2119. [PMID: 32651241 PMCID: PMC7506835 DOI: 10.2337/db20-0377] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/01/2020] [Indexed: 12/18/2022]
Abstract
We tested the hypothesis that obesity, independent of insulin resistance, is associated with increased insulin secretion. We compared insulin kinetics before and after glucose ingestion in lean healthy people and people with obesity who were matched on multiorgan insulin sensitivity (inhibition of adipose tissue lipolysis and glucose production and stimulation of muscle glucose uptake) as assessed by using a two-stage hyperinsulinemic-euglycemic pancreatic clamp procedure in conjunction with glucose and palmitate tracer infusions and positron emission tomography. We also evaluated the effect of diet-induced weight loss on insulin secretion in people with obesity who did not improve insulin sensitivity despite marked (∼20%) weight loss. Basal and postprandial insulin secretion rates were >50% greater in people with obesity than lean people even though insulin sensitivity was not different between groups. Weight loss in people with obesity decreased insulin secretion by 35% even though insulin sensitivity did not change. These results demonstrate that increased insulin secretion in people with obesity is associated with excess adiposity itself and is not simply a compensatory response to insulin resistance. These findings have important implications regarding the pathogenesis of diabetes because hyperinsulinemia causes insulin resistance and insulin hypersecretion is an independent risk factor for developing diabetes.
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Affiliation(s)
- Stephan van Vliet
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | - Han-Chow E Koh
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO
| | - Bruce W Patterson
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO
| | - Mihoko Yoshino
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO
| | - Richard LaForest
- Mallinckrodt Institute of Radiology at Washington University School of Medicine, St. Louis, MO
| | - Robert J Gropler
- Mallinckrodt Institute of Radiology at Washington University School of Medicine, St. Louis, MO
| | - Samuel Klein
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO
| | - Bettina Mittendorfer
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO
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8
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Rago V, De Rose D, Santoro M, Panza S, Malivindi R, Andò S, D'Agata R, Aquila S. Human Sperm Express the Receptor for Glucagon-like Peptide-1 (GLP-1), Which Affects Sperm Function and Metabolism. Endocrinology 2020; 161:5802751. [PMID: 32157297 DOI: 10.1210/endocr/bqaa031] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 03/09/2020] [Indexed: 12/15/2022]
Abstract
AIM Glucagon-like peptide-1 (GLP-1) produces pleiotropic effects binding to the GLP-1 receptor (GLP1-R), potentiating insulin secretion in the pancreas. GLP1-R is expressed in peripheral tissues and evidence for its role in reproduction has come from knockout mice, although the relationship between GLP-1 and male fertility needs to be clarified. Given that human sperm is an insulin-sensitive and insulin-secreting cell, we hypothesized that the GLP-1/GLP1-R axis may be expressed and functional in these cells. RESULTS AND DISCUSSION We revealed the presence of GLP1-R by Western blotting and immunofluorescence analyses. Because Exendin-4 (Ex-4) displays similar functional properties to native GLP-1, we used this agonist to perform a dose-response study on progressive motility and cholesterol efflux, showing that 300 pM Ex-4 was the most effective treatment. These actions are mediated by GLP1-R and independent from sperm-secreted insulin. The exposure to Ex-4 fueled phosphatidylinositol-3-kinase (PI3K)/AKT signaling and was reversed by H89, indicating a protein kinase A (PKA)-dependence of GLP-1/GLP1-R signaling. It emerged that in sperm, insulin secretion regulated by Ex-4 did not occur in a strictly glucose-dependent manner. A stimulatory action of Ex-4/GLP1-R on lactate dehydrogenase and glucose-6-phosphate dehydrogenase (G6PDH) activities was observed. Ex-4/GLP1-R decreased triglycerides content concomitantly to enhanced lipase and acyl-coenzyme A (acyl-CoA) dehydrogenase activities, addressing a lipolytic effect. CONCLUSION Collectively, we discovered that human sperm is a new GLP1 incretin target, broadening our knowledge about the effects of the GLP1-R agonist in the male reproductive field. Further findings in humans should be conducted in the future to confirm it and to improve the translational aspect of this study.
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Affiliation(s)
- Vittoria Rago
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
| | - Daniela De Rose
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
- Centro Sanitario, University of Calabria Cosenza, Italy
| | - Marta Santoro
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
- Centro Sanitario, University of Calabria Cosenza, Italy
| | - Salvatore Panza
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
- Centro Sanitario, University of Calabria Cosenza, Italy
| | - Rocco Malivindi
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
| | - Sebastiano Andò
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
- Centro Sanitario, University of Calabria Cosenza, Italy
| | - Rosario D'Agata
- Department of Experimental and Clinical Medicine, University of Catania, Catania, Italy
| | - Saveria Aquila
- Department of Pharmacy and Sciences of Health and Nutrition, University of Calabria Cosenza, Italy
- Centro Sanitario, University of Calabria Cosenza, Italy
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9
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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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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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Abstract
Controlling the excess and shortage of energy is a fundamental task for living organisms. Diabetes is a representative metabolic disease caused by the malfunction of energy homeostasis. The islets of Langerhans in the pancreas release long-range messengers, hormones, into the blood to regulate the homeostasis of the primary energy fuel, glucose. The hormone and glucose levels in the blood show rhythmic oscillations with a characteristic period of 5-10 min, and the functional roles of the oscillations are not clear. Each islet has [Formula: see text] and [Formula: see text] cells that secrete glucagon and insulin, respectively. These two counter-regulatory hormones appear sufficient to increase and decrease glucose levels. However, pancreatic islets have a third cell type, [Formula: see text] cells, which secrete somatostatin. The three cell populations have a unique spatial organization in islets, and they interact to perturb their hormone secretions. The mini-organs of islets are scattered throughout the exocrine pancreas. Considering that the human pancreas contains approximately a million islets, the coordination of hormone secretion from the multiple sources of islets and cells within the islets should have a significant effect on human physiology. In this review, we introduce the hierarchical organization of tripartite cell networks, and recent biophysical modeling to systematically understand the oscillations and interactions of [Formula: see text], [Formula: see text], and [Formula: see text] cells. Furthermore, we discuss the functional roles and clinical implications of hormonal oscillations and their phase coordination for the diagnosis of type II diabetes.
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Affiliation(s)
- Taegeun Song
- Department of Physics, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea
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Li X, Xie X, Zhang L, Meng Y, Li N, Wang M, Zhai C, Liu Z, Di T, Zhang L, Li P. Hesperidin inhibits keratinocyte proliferation and imiquimod-induced psoriasis-like dermatitis via the IRS-1/ERK1/2 pathway. Life Sci 2019; 219:311-321. [PMID: 30658103 DOI: 10.1016/j.lfs.2019.01.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 01/06/2019] [Accepted: 01/14/2019] [Indexed: 02/06/2023]
Abstract
AIMS To evaluate the therapeutic benefits of Hesperidin (Hes) using an imiquimod (IMQ)-induced psoriasis-like mouse model and human immortalized keratinocytes (HaCaT) cells stimulated with lipopolysaccharide (LPS). METHODS Mice were treated with IMQ and orally administered Hes (125-500 mg/kg/day), methotrexate (MTX) 1 mg/kg/day or distilled water. HaCaT cells were stimulated with LPS (1 μg/mL) and relevant indices were measured after administration with different concentrations of Hes (5-20 μg/mL) for 24 h. Inflammatory skin lesions in IMQ mice were evaluated using the psoriasis area severity index (PASI) and pathological staining. Proteins in the IRS-1/ERK1/2 pathway and inflammatory factors were assessed using western blotting or quantitative real-time PCR. In addition, factors related to IRS-1 secretion levels were assessed by enzyme-linked immunosorbent assays. Extracellular flux (XF) analysis was used to assess cellular metabolic levels. KEY FINDINGS Hes significantly improved psoriasis-like skin lesions of IMQ-treated mice and inhibited LPS-induced HaCaT cell proliferation. In addition, Hes remarkably decreased PASI scores, reduced epidermal thickness, decreased proliferation and differentiation of epidermal cells, inhibited mRNA expression of inflammatory factors, reduced local skin lesions and serum insulin and glucose levels. Furthermore, Hes modulated the secretion levels of serum Leptin, Adiponectin and Resistin, and inhibited the activation of the IRS-1/ERK1/2 signaling pathway and regulated HaCaT cells metabolism. SIGNIFICANCE This study demonstrated that Hes administration could have significant therapeutic value for the prevention and clinical treatment of psoriasis.
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Affiliation(s)
- Xue Li
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China; Beijing University of Chinese Medicine, Beijing 100029, China
| | - Xinran Xie
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China
| | - Lei Zhang
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China
| | - Yujiao Meng
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China; Beijing University of Chinese Medicine, Beijing 100029, China
| | - Ningfei Li
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China; Beijing University of Chinese Medicine, Beijing 100029, China
| | - Mingxing Wang
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China
| | - Chunyan Zhai
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China
| | - Zhengrong Liu
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China; Beijing University of Chinese Medicine, Beijing 100029, China
| | - Tingting Di
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China
| | - Lu Zhang
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China
| | - Ping Li
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing Institute of Traditional Chinese Medicine, Beijing 100010, China; Beijing Key Laboratory of Clinic and Basic Research with Traditional Chinese Medicine on Psoriasis, Beijing 100010, China; Beijing University of Chinese Medicine, Beijing 100029, China.
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Kowalchuk C, Castellani LN, Chintoh A, Remington G, Giacca A, Hahn MK. Antipsychotics and glucose metabolism: how brain and body collide. Am J Physiol Endocrinol Metab 2019; 316:E1-E15. [PMID: 29969315 DOI: 10.1152/ajpendo.00164.2018] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Since the serendipitous discovery of the first antipsychotic (AP) drug in the 1950s, APs remain the cornerstone of treatment for schizophrenia. A shift over the past two decades away from first-generation, conventional APs to so-called "atypical" (or 2nd/3rd generation) APs parallels acknowledgment of serious metabolic side-effects associated in particular with these newer agents. As will be reviewed, AP drugs and type 2 diabetes are now inextricably linked, contributing to the three- to fivefold increased risk of type 2 diabetes observed in schizophrenia. However, this association is not straightforward. Biological and lifestyle-related illness factors contribute to the association between type 2 diabetes and metabolic disease independently of AP treatment. In addition, APs have a well-established weight gain propensity which could also account for elevated risk of insulin resistance and type 2 diabetes. However, compelling preclinical and clinical evidence now suggests that these drugs can rapidly and directly influence pathways of glucose metabolism independently of weight gain and even in absence of psychiatric illness. Mechanisms of these direct effects remain poorly elucidated but may involve central and peripheral antagonism of neurotransmitters implicated not only in the therapeutic effects of APs but also in glucose homeostasis, possibly via effects on the autonomic nervous system. The clinical relevance of studying "direct" effects of these drugs on glucose metabolism is underscored by the widespread use of these medications, both on and off label, for a growing number of mental illnesses, extending safety concerns well beyond schizophrenia.
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Affiliation(s)
- Chantel Kowalchuk
- Centre for Addiction and Mental Health , Toronto, Ontario , Canada
- Institute of Medical Sciences, University of Toronto , Toronto, Ontario , Canada
| | | | - Araba Chintoh
- Centre for Addiction and Mental Health , Toronto, Ontario , Canada
- Department of Psychiatry, University of Toronto , Toronto, Ontario , Canada
| | - Gary Remington
- Centre for Addiction and Mental Health , Toronto, Ontario , Canada
- Institute of Medical Sciences, University of Toronto , Toronto, Ontario , Canada
- Department of Psychiatry, University of Toronto , Toronto, Ontario , Canada
| | - Adria Giacca
- Institute of Medical Sciences, University of Toronto , Toronto, Ontario , Canada
- Banting and Best Diabetes Centre, University of Toronto , Toronto, Ontario , Canada
- Department of Physiology, University of Toronto , Toronto, Ontario , Canada
- Department of Medicine, University of Toronto , Toronto, Ontario Canada
| | - Margaret K Hahn
- Centre for Addiction and Mental Health , Toronto, Ontario , Canada
- Institute of Medical Sciences, University of Toronto , Toronto, Ontario , Canada
- Department of Psychiatry, University of Toronto , Toronto, Ontario , Canada
- Banting and Best Diabetes Centre, University of Toronto , Toronto, Ontario , Canada
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Hypoglycaemic effect of capsaicinoids via elevation of insulin level and inhibition of glucose absorption in streptozotocin-induced diabetic rats. J Funct Foods 2018. [DOI: 10.1016/j.jff.2018.10.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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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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16
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Lee B, Song T, Lee K, Kim J, Berggren PO, Ryu SH, Jo J. Insulin modulates the frequency of Ca2+ oscillations in mouse pancreatic islets. PLoS One 2017; 12:e0183569. [PMID: 28846705 PMCID: PMC5573301 DOI: 10.1371/journal.pone.0183569] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 08/07/2017] [Indexed: 11/20/2022] Open
Abstract
Pancreatic islets can adapt to oscillatory glucose to produce synchronous insulin pulses. Can islets adapt to other oscillatory stimuli, specifically insulin? To answer this question, we stimulated islets with pulses of exogenous insulin and measured their Ca2+ oscillations. We observed that sufficiently high insulin (> 500 nM) with an optimal pulse period (~ 4 min) could make islets to produce synchronous Ca2+ oscillations. Glucose and insulin, which are key stimulatory factors of islets, modulate islet Ca2+ oscillations differently. Glucose increases the active-to-silent ratio of phases, whereas insulin increases the period of the oscillation. To examine the dual modulation, we adopted a phase oscillator model that incorporated the phase and frequency modulations. This mathematical model showed that out-of-phase oscillations of glucose and insulin were more effective at synchronizing islet Ca2+ oscillations than in-phase stimuli. This finding suggests that a phase shift in glucose and insulin oscillations can enhance inter-islet synchronization.
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Affiliation(s)
- Boah Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | - Taegeun Song
- Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk, Korea
| | - Kayoung Lee
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | - Jaeyoon Kim
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | - Per-Olof Berggren
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institute, Stockholm, Sweden
| | - Sung Ho Ryu
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
| | - Junghyo Jo
- Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk, Korea
- Department of Physics, Pohang University of Science and Technology, Pohang, Gyeongbuk, Korea
- * E-mail:
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Zhang L, Zhou L, Song X, Liang G, Xu Z, Wang F, Huang F, Jiang G. Involvement of exogenous 3‑deoxyglucosone in β‑cell dysfunction induces impaired glucose regulation. Mol Med Rep 2017; 16:2976-2984. [PMID: 28656301 DOI: 10.3892/mmr.2017.6856] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 05/04/2017] [Indexed: 11/05/2022] Open
Abstract
β‑cell dysfunction is the primary cause of type 2 diabetes mellitus (T2DM). 1,2‑dicarbonyl compounds, such as 3‑deoxyglucosone (3DG) have been reported to increase the risk of T2DM. Abnormal elevation of plasma 3DG may impair β‑cell function and thereby, it is linked to T2DM. Previous findings suggest that exogenous 3DG may serve an important role in the development of pre‑diabetes. In the present study, the authors examine whether exogenous 3DG induces impaired glucose regulation in mice by decreasing β‑cell function involving of accumulation of plasma 3DG. At two weeks following administration of 3DG, fasting blood glucose (FBG) levels, oral glucose tolerance (by a glucose meter) and plasma levels of 3DG (by HPLC) and insulin (by radioimmunoassay) were measured. Glucose‑stimulated insulin secretion in cultured pancreas islets and INS‑1 cells was measured by radioimmunoassay. Western blotting was used to examine the expression of the key molecules of the insulin‑PI3K signaling pathway. 3DG treatment increased FBG and fasting blood insulin levels, reduced oral glucose tolerance in conjunction with decreased ∆Ins30‑0/∆G30‑0. In 3DG‑treated mice, an increase in the plasma 3DG level was observed, which was most likely the mechanism for decreased β‑cell function. This idea was further supported by these results that non‑cytotoxic 3DG concentration obviously decreased glucose‑stimulated insulin secretion in cultured pancreas islets and INS‑1 cells exposure to high glucose (25.5 mM). 3DG decreased the expression of GLUT2 and phosphorylation of IRS‑1, PI3K‑p85 and Akt in high glucose‑induced INS‑1 cells. To the best of the authors' knowledge, the present study is the first to demonstrate that exogenous 3DG induced normal mice to develop IGR, resulting from β‑cell dysfunction. Exogenous 3DG administration increased plasma 3DG levels, which participates in inducing β‑cell dysfunction, at least in part, through impairing IRS‑1/PI3K/GLUT2 signaling.
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Affiliation(s)
- Lurong Zhang
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Liang Zhou
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Xiudao Song
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Guoqiang Liang
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Zhongrui Xu
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Fei Wang
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Fei Huang
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
| | - Guorong Jiang
- Suzhou Academy of Wumen Chinese Medicine, Suzhou Hospital of Traditional Chinese Medicine, Nanjing University of Chinese Medicine, Suzhou, Jiangsu 215003, P.R. China
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Chowdhury AI, Bergsten P. GLP-1 analogue recovers impaired insulin secretion from human islets treated with palmitate via down-regulation of SOCS2. Mol Cell Endocrinol 2017; 439:194-202. [PMID: 27566229 DOI: 10.1016/j.mce.2016.08.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Revised: 08/22/2016] [Accepted: 08/22/2016] [Indexed: 12/31/2022]
Abstract
Elevated circulating palmitate levels have been connected with type 2 diabetes mellitus. GLP-1 has favorable effects on beta-cells function. The aim was to identify mechanisms for decreased GSIS after long-term palmitate exposure and restoration by GLP-1 by analyzing changes in G-protein coupled receptor (GPCR) pathway signaling. Insulin secretory response to 20 mM glucose was attenuated after 7 days in islets exposed to palmitate but inclusion of exendin-4 restored secretion. Palmitate treatment altered genes of several GPCR signaling pathways including inflammatory pathways with up-regulated IL-1B, SOCS1 and SOCS2 transcript levels. Protein level of SOCS2 was also up-regulated by palmitate and accompanied by down-regulation of pAkt(T308), which was restored by exendin-4 treatment. When SOCS2 was knocked down, palmitate-induced down-regulation of IRS-1 and pAkt(T308) was prevented and GSIS, proinsulin to insulin ratio and apoptosis was restored. Long-term palmitate treatment up-regulates SOCS2 and reduces PI3K activity, thereby impairing GSIS. GLP-1 reverts the palmitate-induced effects.
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Affiliation(s)
- Azazul Islam Chowdhury
- Department of Medical Cell Biology, Uppsala University, Box 571, SE-75123, Uppsala, Sweden.
| | - Peter Bergsten
- Department of Medical Cell Biology, Uppsala University, Box 571, SE-75123, Uppsala, Sweden
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19
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Markwardt ML, Seckinger KM, Rizzo MA. Regulation of Glucokinase by Intracellular Calcium Levels in Pancreatic β Cells. J Biol Chem 2015; 291:3000-9. [PMID: 26698632 DOI: 10.1074/jbc.m115.692160] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Indexed: 01/01/2023] Open
Abstract
Glucokinase (GCK) controls the rate of glucose metabolism in pancreatic β cells, and its activity is rate-limiting for insulin secretion. Posttranslational GCK activation can be stimulated through either G protein-coupled receptors or receptor tyrosine kinase signaling pathways, suggesting a common mechanism. Here we show that inhibiting Ca(2+) release from the endoplasmic reticulum (ER) decouples GCK activation from receptor stimulation. Furthermore, pharmacological release of ER Ca(2+) stimulates activation of a GCK optical biosensor and potentiates glucose metabolism, implicating rises in cytoplasmic Ca(2+) as a critical regulatory mechanism. To explore the potential for glucose-stimulated GCK activation, the GCK biosensor was optimized using circularly permuted mCerulean3 proteins. This new sensor sensitively reports activation in response to insulin, glucagon-like peptide 1, and agents that raise cAMP levels. Transient, glucose-stimulated GCK activation was observed in βTC3 and MIN6 cells. An ER-localized channelrhodopsin was used to manipulate the cytoplasmic Ca(2+) concentration in cells expressing the optimized FRET-GCK sensor. This permitted quantification of the relationship between cytoplasmic Ca(2+) concentrations and GCK activation. Half-maximal activation of the FRET-GCK sensor was estimated to occur at ∼400 nm Ca(2+). When expressed in islets, fluctuations in GCK activation were observed in response to glucose, and we estimated that posttranslational activation of GCK enhances glucose metabolism by ∼35%. These results suggest a mechanism for integrative control over GCK activation and, therefore, glucose metabolism and insulin secretion through regulation of cytoplasmic Ca(2+) levels.
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Affiliation(s)
- Michele L Markwardt
- From the University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Kendra M Seckinger
- From the University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Mark A Rizzo
- From the University of Maryland School of Medicine, Baltimore, Maryland 21201
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Gao Y, Liao G, Xiang C, Yang X, Cheng X, Ou Y. Effects of phycocyanin on INS-1 pancreatic β-cell mediated by PI3K/Akt/FoxO1 signaling pathway. Int J Biol Macromol 2015; 83:185-94. [PMID: 26616456 DOI: 10.1016/j.ijbiomac.2015.11.054] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 10/22/2015] [Accepted: 11/20/2015] [Indexed: 01/09/2023]
Abstract
The level of methylglyoxal (MG), which is a side-product of metabolic pathways, particularly in glycolysis, is elevated in diabetes. Notably, the accumulation of MG causes a series of pathological changes. Phycocyanin (PC) has been demonstrated to show insulin-sensitizing effect, however, the underlying molecular mechanism remains elusive. The aim of this study was to investigate the protective effects of PC on INS-1 rat insulinoma β-cell against MG-induced cell dysfunction, as well as the underlying mechanisms. PC was preliminarily verified to time-dependently activate PI3-kinase (PI3K) pathway, but the PI3K-specific inhibitor Wortmannin blocked the effect of PC. Glucose-stimulated insulin secretion (GSIS) was impaired in MG-treated INS-1 cells. Furthermore, MG induced dephosphorylation of Akt and FoxO1, resulting in nuclear localization and transactivation of FoxO1. Nevertheless, these effects were all effectively attenuated by PC. The ameliorated insulin secretion was related to the changes of FoxO1 mediated by PC, which demonstrated by RNA interference. And, the dosage used in the above experiments did not affect β-cell viability and apoptosis, although long-term MG induced cell apoptosis and mitochondrial dysfunction. In conclusion, PC was capable to protect INS-1 pancreatic β-cell against MG-induced cell dysfunction through modulating PI3K/Akt pathway and the downstream FoxO1.
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Affiliation(s)
- Yingnv Gao
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Gaoyong Liao
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Chenxi Xiang
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Xuegan Yang
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Xiaodong Cheng
- Department of Integrative Biology & Pharmacology, The University of Texas Health Science Center, Houston, USA.
| | - Yu Ou
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China.
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Oh YS, Shin S, Li HY, Park EY, Lee SM, Choi CS, Lim Y, Jung HS, Jun HS. Betacellulin ameliorates hyperglycemia in obese diabetic db/db mice. J Mol Med (Berl) 2015; 93:1235-45. [PMID: 26070436 DOI: 10.1007/s00109-015-1303-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 04/20/2015] [Accepted: 05/20/2015] [Indexed: 01/08/2023]
Abstract
UNLABELLED We found that administration of a recombinant adenovirus (rAd) expressing betacellulin (BTC) into obese diabetic db/db mice ameliorated hyperglycemia. Exogenous glucose clearance was significantly improved, and serum insulin levels were significantly higher in rAd-BTC-treated mice than rAd-β-gal-treated control mice. rAd-BTC treatment increased insulin/bromodeoxyuridine double-positive cells in the islets, and islets from rAd-BTC-treated mice exhibited a significant increase in the level of G1-S phase-related cyclins as compared with control mice. In addition, BTC treatment increased messenger RNA (mRNA) and protein levels of these cyclins and cyclin-dependent kinases in MIN-6 cells. BTC treatment induced intracellular Ca(2+) levels through phospholipase C-γ1 activation, and upregulated calcineurin B (CnB1) levels as well as calcineurin activity. Upregulation of CnB1 by BTC treatment was observed in isolated islet cells from db/db mice. When treated with CnB1 small interfering RNA (siRNA) in MIN-6 cells and isolated islets, induction of cell cycle regulators by BTC treatment was blocked and consequently reduced BTC-induced cell viability. As well as BTC's effects on cell survival and insulin secretion, our findings demonstrate a novel pathway by which BTC controls beta-cell regeneration in the obese diabetic condition by regulating G1-S phase cell cycle expression through Ca(2+) signaling pathways. KEY MESSAGES Administration of BTC to db/db mice results in amelioration of hyperglycemia. BTC stimulates beta-cell proliferation in db/db mice. Ca(2+) signaling was involved in BTC-induced beta-cell proliferation. BTC has an anti-apoptotic effect and potentiates glucose-stimulated insulin secretion.
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Affiliation(s)
- Yoon Sin Oh
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 7-45 Songdo-dong, Yeonsu-ku, Incheon, Korea.,Gachon Medical Research Institute, Gil Hospital, Incheon, Korea
| | | | - Hui Ying Li
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 7-45 Songdo-dong, Yeonsu-ku, Incheon, Korea.,College of Pharmacy, Gachon University, Incheon, Korea
| | - Eun-Young Park
- College of Pharmacy, Mokpo National University, Jeonnam, Korea
| | - Song Mi Lee
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 7-45 Songdo-dong, Yeonsu-ku, Incheon, Korea.,College of Pharmacy, Gachon University, Incheon, Korea
| | - Cheol Soo Choi
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 7-45 Songdo-dong, Yeonsu-ku, Incheon, Korea.,Gachon Medical Research Institute, Gil Hospital, Incheon, Korea
| | - Yong Lim
- Department of Microbiology, Chosun University College of Medicine, Chonnam, Korea
| | - Hye Seung Jung
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Hee-Sook Jun
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 7-45 Songdo-dong, Yeonsu-ku, Incheon, Korea. .,Gachon Medical Research Institute, Gil Hospital, Incheon, Korea. .,College of Pharmacy, Gachon University, Incheon, Korea.
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22
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Senniappan S, Alexandrescu S, Tatevian N, Shah P, Arya V, Flanagan S, Ellard S, Rampling D, Ashworth M, Brown RE, Hussain K. Sirolimus therapy in infants with severe hyperinsulinemic hypoglycemia. N Engl J Med 2014; 370:1131-7. [PMID: 24645945 DOI: 10.1056/nejmoa1310967] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hyperinsulinemic hypoglycemia is the most common cause of severe, persistent neonatal hypoglycemia. The treatment of hyperinsulinemic hypoglycemia that is unresponsive to diazoxide is subtotal pancreatectomy. We examined the effectiveness of the mammalian target of rapamycin (mTOR) inhibitor sirolimus in four infants with severe hyperinsulinemic hypoglycemia that had been unresponsive to maximal doses of diazoxide (20 mg per kilogram of body weight per day) and octreotide (35 μg per kilogram per day). All the patients had a clear glycemic response to sirolimus, although one patient required a small dose of octreotide to maintain normoglycemia. There were no major adverse events during 1 year of follow-up.
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Affiliation(s)
- Senthil Senniappan
- From the Developmental Endocrinology Research Group, Clinical and Molecular Genetics Unit, Institute of Child Health, University College London (S.S., P.S., V.A., K.H.), and the Departments of Paediatric Endocrinology (S.S., P.S., V.A., K.H.) and Histopathology (D.P., M.A.), Great Ormond Street Hospital for Children, London, and the Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter (S.F., S.E.) - all in the United Kingdom; the Department of Pathology, University of California, San Francisco, San Francisco (S.A.); and the Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston, Houston (N.T., R.E.B.)
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23
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Chowdhury A, Dyachok O, Tengholm A, Sandler S, Bergsten P. Functional differences between aggregated and dispersed insulin-producing cells. Diabetologia 2013; 56:1557-68. [PMID: 23604550 PMCID: PMC3671110 DOI: 10.1007/s00125-013-2903-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 03/12/2013] [Indexed: 11/27/2022]
Abstract
AIMS/HYPOTHESIS Beta cells situated in the islet of Langerhans respond more vigorously to glucose than do dissociated beta cells. Mechanisms for this discrepancy were studied by comparing insulin-producing MIN6 cells aggregated into pseudoislets with MIN6 monolayer cells and mouse and human islets. METHODS MIN6 monolayers, pseudoislets and mouse and human islets were exposed to glucose, α-ketoisocaproic acid (KIC), pyruvate, KIC plus glutamine and the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin. Insulin secretion (ELISA), cytoplasmic Ca(2+) concentration ([Ca(2+)]c; microfluorometry), glucose oxidation (radiolabelling), the expression of genes involved in mitochondrial metabolism (PCR) and the phosphorylation of insulin receptor signalling proteins (western blotting) were measured. RESULTS Insulin secretory responses to glucose, pyruvate, KIC and glutamine were higher in pseudoislets than monolayers and comparable to those of human islets. Glucose oxidation and genes for mitochondrial metabolism were upregulated in pseudoislets compared with single cells and monolayers, respectively. Phosphorylation at the inhibitory S636/639 site of IRS-1 was significantly higher in monolayers and dispersed human and mouse cells than pseudoislets and intact human and mouse islets. PI3K inhibition only slightly attenuated glucose-stimulated insulin secretion from monolayers, but substantially reduced that from pseudoislets and human and mouse islets without suppressing the glucose-induced [Ca(2+)]c response. CONCLUSIONS/INTERPRETATION We propose that islet architecture is critical for proper beta cell mitochondrial metabolism and IRS-1 signalling, and that PI3K regulates insulin secretion at a step distal to the elevation of [Ca(2+)]c.
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Affiliation(s)
- A Chowdhury
- Department of Medical Cell Biology, Uppsala University, Box 571, 75123, Uppsala, Sweden.
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24
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Miranda RA, Branco RCS, Gravena C, Barella LF, da Silva Franco CC, Andreazzi AE, de Oliveira JC, Picinato MC, de Freitas Mathias PC. Swim training of monosodium L-glutamate-obese mice improves the impaired insulin receptor tyrosine phosphorylation in pancreatic islets. Endocrine 2013; 43:571-8. [PMID: 22983867 DOI: 10.1007/s12020-012-9798-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 09/06/2012] [Indexed: 12/24/2022]
Abstract
The goal of the present study was to investigate changes on glucose homoeostasis and of the insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) signalling in pancreatic islets from MSG-obese mice submitted to or not submitted to swim training. Swim training of 90-day-old MSG mice was used to evaluate whether signalling pathways of the IR and IRS-1 in islets are involved with the insulin resistance and glucose intolerance observed in this obese animal model. The results showed that IR tyrosine phosphorylation (pIR) was reduced by 42 % in MSG-obese mice (MSG, 6.7 ± 0.2 arbitrary units (a.u.); control, 11.5 ± 0.4 a.u.); on the other hand, exercise training increased pIR by 76 % in MSG mice without affecting control mice (MSG, 11.8 ± 0.3; control, 12.8 ± 0.2 a.u.). Although the treatment with MSG increased IRS-1 tyrosine phosphorylation (pIRS-1) by 96 % (MSG, 17.02 ± 0.6; control, 8.7 ± 0.2 a.u.), exercise training also increased it in both groups (control, 13.6 ± 0.1; MSG, 22.2 ± 1.1 a.u.). Current research shows that the practice of swim training increases the tyrosine phosphorylation of IRS-1 which can modulate the effect caused by obesity in insulin receptors.
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Affiliation(s)
- Rosiane Aparecida Miranda
- Laboratory of Secretion Cell Biology, Department of Cell Biology and Genetics, State University of Maringá/UEM, Block H67, Room 19, Avenue Colombo, 5790, Maringá, PR, 87020-900, Brazil
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25
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Timing of maternal exposure to a high fat diet and development of obesity and hyperinsulinemia in male rat offspring: same metabolic phenotype, different developmental pathways? J Nutr Metab 2013; 2013:517384. [PMID: 23762542 PMCID: PMC3666195 DOI: 10.1155/2013/517384] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 04/08/2013] [Accepted: 04/20/2013] [Indexed: 12/22/2022] Open
Abstract
Objective. Offspring born to mothers either fed an obesogenic diet throughout their life or restricted to pregnancy and lactation demonstrate obesity, hyperinsulinemia, and hyperleptinemia, irrespective of their postweaning diet. We examined whether timing of a maternal obesogenic diet results in differential regulation of pancreatic adipoinsular and inflammatory signaling pathways in offspring. Methods. Female Wistar rats were randomized into 3 groups: (1) control (CONT): fed a control diet preconceptionally and during pregnancy and lactation; (2) maternal high fat (MHF): fed an HF diet throughout their life and during pregnancy and lactation; (3) pregnancy and lactation HF (PLHF): fed a control diet throughout life until mating, then HF diet during pregnancy and lactation. Male offspring were fed the control diet postweaning. Plasma and pancreatic tissue were collected, and mRNA concentrations of key factors regulating adipoinsular axis signaling were determined. Results. MHF and PLHF offspring exhibited increased adiposity and were hyperinsulinemic and hyperleptinemic compared to CONT. Despite a similar anthropometric phenotype, MHF and PLHF offspring exhibited distinctly different expression for key pancreatic genes, dependent upon maternal preconceptional nutritional background. Conclusions. These data suggest that despite using differential signaling pathways, obesity in offspring may be an adaptive outcome of early life exposure to HF during critical developmental windows.
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26
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Zhang Z, Liu C, Gan Z, Wang X, Yi Q, Liu Y, Wang Y, Lu B, Du H, Shao J, Wang J. Improved Glucose-Stimulated Insulin Secretion by Selective Intraislet Inhibition of Angiotensin II Type 1 Receptor Expression in Isolated Islets of db/db Mice. Int J Endocrinol 2013; 2013:319586. [PMID: 24371439 PMCID: PMC3859026 DOI: 10.1155/2013/319586] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 10/13/2013] [Accepted: 10/31/2013] [Indexed: 12/20/2022] Open
Abstract
Recent evidence supported the presence of a local renin-angiotensin system (RAS) in the pancreas, which is implicated in many physiological and pathophysiological processes. We utilized small interfering RNA (siRNA) to investigate the effects of angiotensin II type 1 receptor (AT1R) knockdown on glucose-stimulated insulin secretion (GSIS) in isolated islets of db/db mice and to explore the potential mechanisms involved. We found that Ad-siAT1R treatment resulted in a significant decrease both in AT1R mRNA level and in AT1R protein expression level. With downexpression of AT1R, notable increased insulin secretion and decreased glucagon secretion levels were found by perifusion. Simultaneously, significant increased protein levels of IRS-1 (by 85%), IRS-2 (by 95%), PI3K(85) (by 112.5%), and p-Akt2 (by 164%) were found by western blot. And upregulation of both GLUT-2 (by 190%) and GCK (by 121%) was achieved after AT1R inhibition by Ad-siAT1R. Intraislet AT1R expression level is a crucial physiological regulator of insulin sensitivity of β cell itself and thus affects glucose-induced insulin and glucagon release. Therefore, the characteristics of AT1R inhibitors could make it a potential novel therapeutics for prevention and treatment of type 2 diabetes.
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Affiliation(s)
- Zhen Zhang
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Chunyan Liu
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Zhenhua Gan
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Xinyi Wang
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Qiuyan Yi
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Yanqing Liu
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Yingzhijie Wang
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Bin Lu
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Hong Du
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Jiaqing Shao
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
- *Jiaqing Shao: and
| | - Jun Wang
- Department of Cardiology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
- *Jun Wang:
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27
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Jiang F, Wang C, Li R, Sheng Q, Hu C, Zhang R, Fang Q, Bao Y, Xiang K, Zeng R, Jia W. Serum Proteome Changes in Healthy Subjects with Different Genotypes of NOS1AP in the Chinese Population. J Diabetes Res 2013; 2013:357630. [PMID: 23671866 PMCID: PMC3647583 DOI: 10.1155/2013/357630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 03/12/2013] [Indexed: 11/24/2022] Open
Abstract
Type 2 diabetes and its chronic complications have become a worldwide epidemic nowadays. However, its molecular mechanism is still unknown. We have previously identified a novel variant rs12742393 of NOS1AP for type 2 diabetes susceptibility in the Chinese population. In this study, we analyzed the total serum profiling among three genotypes of rs12742393 to discover potential crosstalk under the variant and the disease through proteomic analyses for the first time. We used OFFGEL peptide fractionation, LC-MS/MS analysis, and label-free quantification to profile the fasting human serum samples of the genotypes in rs12742393 (n = 4, for CC, AC, and AA, resp.). Four proteins were identified, including apoA4, alpha1-ACT, HABP2, and keratin 10, with blood levels changed significantly between CC and AA homozygotes of rs12742393. Compared with AA group, the levels of apoA4 increased (P = 0.000265), whereas the concentration of alpha1-ACT, HABP2, and keratin 10 decreased in CC group (P = 0.011116, 0.021175, and 0.015661, resp.). Then we selected additional fasting serum samples for ELISA and western blot validation. However, no significant differences were identified by neither ELISA nor western blot (P > 0.05). The protein profiling changes between the genotypes of rs12742393 indicated that this SNP might play a role in the development of type 2 diabetes.
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Affiliation(s)
- Feng Jiang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Congrong Wang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Rongxia Li
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China
| | - Quanhu Sheng
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China
| | - Cheng Hu
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Rong Zhang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Qichen Fang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Yuqian Bao
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Kunsan Xiang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
| | - Rong Zeng
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China
| | - Weiping Jia
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, 600 Yishan Road, Shanghai 200233, China
- *Weiping Jia:
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28
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Goldfine AB, Kulkarni RN. Modulation of β-cell function: a translational journey from the bench to the bedside. Diabetes Obes Metab 2012; 14 Suppl 3:152-60. [PMID: 22928576 DOI: 10.1111/j.1463-1326.2012.01647.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Both decreased insulin secretion and action contribute to the pathogenesis of type 2 diabetes (T2D) in humans. The insulin receptor and insulin signalling proteins are present in the rodent and human β-cell and modulate cell growth and function. Insulin receptors and insulin signalling proteins in β-cells are critical for compensatory islet growth in response to insulin resistance. Rodents with tissue-specific knockout of the insulin receptor in the β-cell (βIRKO) show reduced first-phase glucose-stimulated insulin secretion (GSIS) and with aging develop glucose intolerance and diabetes, phenotypically similar to the process seen in human T2D. Expression of multiple insulin signalling proteins is reduced in islets of patients with T2D. Insulin potentiates GSIS in isolated human β-cells. Recent studies in humans in vivo show that pre-exposure to insulin increases GSIS, and this effect is diminished in persons with insulin resistance or T2D. β-Cell function correlates to whole-body insulin sensitivity. Together, these findings suggest that pancreatic β-cell dysfunction could be caused by a defect in insulin signalling within β-cell, and β-cell insulin resistance may lead to a loss of β-cell function and/or mass, contributing to the pathophysiology of T2D.
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Affiliation(s)
- A B Goldfine
- Section of Clinical Research, Joslin Diabetes Center, Boston, MA 02215, USA.
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29
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Wang R. Physiological implications of hydrogen sulfide: a whiff exploration that blossomed. Physiol Rev 2012; 92:791-896. [PMID: 22535897 DOI: 10.1152/physrev.00017.2011] [Citation(s) in RCA: 1372] [Impact Index Per Article: 114.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The important life-supporting role of hydrogen sulfide (H(2)S) has evolved from bacteria to plants, invertebrates, vertebrates, and finally to mammals. Over the centuries, however, H(2)S had only been known for its toxicity and environmental hazard. Physiological importance of H(2)S has been appreciated for about a decade. It started by the discovery of endogenous H(2)S production in mammalian cells and gained momentum by typifying this gasotransmitter with a variety of physiological functions. The H(2)S-catalyzing enzymes are differentially expressed in cardiovascular, neuronal, immune, renal, respiratory, gastrointestinal, reproductive, liver, and endocrine systems and affect the functions of these systems through the production of H(2)S. The physiological functions of H(2)S are mediated by different molecular targets, such as different ion channels and signaling proteins. Alternations of H(2)S metabolism lead to an array of pathological disturbances in the form of hypertension, atherosclerosis, heart failure, diabetes, cirrhosis, inflammation, sepsis, neurodegenerative disease, erectile dysfunction, and asthma, to name a few. Many new technologies have been developed to detect endogenous H(2)S production, and novel H(2)S-delivery compounds have been invented to aid therapeutic intervention of diseases related to abnormal H(2)S metabolism. While acknowledging the challenges ahead, research on H(2)S physiology and medicine is entering an exponential exploration era.
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Affiliation(s)
- Rui Wang
- Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada.
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30
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Koh DS, Cho JH, Chen L. Paracrine interactions within islets of Langerhans. J Mol Neurosci 2012; 48:429-40. [PMID: 22528452 DOI: 10.1007/s12031-012-9752-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 03/12/2012] [Indexed: 01/05/2023]
Abstract
Glucose supply fluctuates between meal and fasting periods and its consumption by the body varies greatly depending on bodily metabolism. Pancreatic islets of Langerhans secrete various endocrine hormones including insulin and glucagon to keep blood glucose level relatively constant. Additionally, islet hormones regulate activity of neighboring cells as local autocrine or paracrine modulators. Moreover, islet cells release neurotransmitters such as glutamate and γ-aminobutyric acid (GABA) to gain more precise regulation of hormones release kinetics. Excitatory glutamate is co-released with glucagon from α-cells and activates glutamate receptors in the neighboring cells. GABA released from β-cells was shown to inhibit α-cells but to activate β-cells by acting GABA(A) receptors. This review summarizes the recent progress in understanding the paracrine/autocrine interactions in islets.
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Affiliation(s)
- Duk-Su Koh
- University of Washington, Seattle, WA, USA.
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31
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Halperin F, Lopez X, Manning R, Kahn CR, Kulkarni RN, Goldfine AB. Insulin augmentation of glucose-stimulated insulin secretion is impaired in insulin-resistant humans. Diabetes 2012; 61:301-9. [PMID: 22275085 PMCID: PMC3266415 DOI: 10.2337/db11-1067] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Type 2 diabetes (T2D) is characterized by insulin resistance and pancreatic β-cell dysfunction, the latter possibly caused by a defect in insulin signaling in β-cells. We hypothesized that insulin's effect to potentiate glucose-stimulated insulin secretion (GSIS) would be diminished in insulin-resistant persons. To evaluate the effect of insulin to modulate GSIS in insulin-resistant compared with insulin-sensitive subjects, 10 participants with impaired glucose tolerance (IGT), 11 with T2D, and 8 healthy control subjects were studied on two occasions. The insulin secretory response was assessed by the administration of dextrose for 80 min following a 4-h clamp with either saline infusion (sham) or an isoglycemic-hyperinsulinemic clamp using B28-Asp-insulin (which can be distinguished immunologically from endogenous insulin) that raised insulin concentrations to high physiologic concentrations. Pre-exposure to insulin augmented GSIS in healthy persons. This effect was attenuated in insulin-resistant cohorts, both those with IGT and those with T2D. Insulin potentiates glucose-stimulated insulin secretion in insulin-resistant subjects to a lesser degree than in normal subjects. This is consistent with an effect of insulin to regulate β-cell function in humans in vivo with therapeutic implications.
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Affiliation(s)
- Florencia Halperin
- Joslin Diabetes Center, Boston, Massachusetts
- Brigham and Women’s Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Ximena Lopez
- Joslin Diabetes Center, Boston, Massachusetts
- Brigham and Women’s Hospital, Boston, Massachusetts
- University of Texas Southwestern Medical Center, Dallas, Texas
| | | | - C. Ronald Kahn
- Joslin Diabetes Center, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Rohit N. Kulkarni
- Joslin Diabetes Center, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Allison B. Goldfine
- Joslin Diabetes Center, Boston, Massachusetts
- Brigham and Women’s Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
- Corresponding author: Allison B. Goldfine,
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32
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Lopez X, Cypess A, Manning R, O'Shea S, Kulkarni RN, Goldfine AB. Exogenous insulin enhances glucose-stimulated insulin response in healthy humans independent of changes in free fatty acids. J Clin Endocrinol Metab 2011; 96:3811-21. [PMID: 21956413 PMCID: PMC3232618 DOI: 10.1210/jc.2011-0627] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Islet β-cells express both insulin receptors and insulin signaling proteins. Recent studies suggest insulin signaling is physiologically important for glucose sensing. OBJECTIVE Preexposure to insulin enhances glucose-stimulated insulin secretion (GSIS) in healthy humans. We evaluated whether the effect of insulin to potentiate GSIS is modulated through regulation of free fatty acids (FFA). DESIGN AND SETTING Subjects were studied on three occasions in this single-site study at an academic institution clinical research center. PATIENTS Subjects included nine healthy volunteers. INTERVENTIONS Glucose-induced insulin response was assessed on three occasions after 4 h saline (low insulin/sham) or isoglycemic-hyperinsulinemic (high insulin) clamps with or without intralipid and heparin infusion, using B28 Asp-insulin that could be distinguished from endogenous insulin immunologically. During the last 80 min of all three clamps, additional glucose was administered to stimulate insulin secretion (GSIS) with glucose concentrations maintained at similar concentrations during all studies. MAIN OUTCOME MEASURE β-Cell response to glucose stimulation was assessed. RESULTS Preexposure to exogenous insulin increased the endogenous insulin-secretory response to glucose by 32% compared with sham clamp (P = 0.001). This was accompanied by a drop in FFA during hyperinsulinemic clamp compared with the sham clamp (0.06 ± 0.02 vs. 0.60 ± 0.09 mEq/liter, respectively), which was prevented during the hyperinsulinemic clamp with intralipid/heparin infusion (1.27 ± 0.17 mEq/liter). After preexposure to insulin with intralipid/heparin infusion to maintain FFA concentration, GSIS was 21% higher compared with sham clamp (P < 0.04) and similar to preexposure to insulin without intralipid/heparin (P = 0.2). CONCLUSIONS Insulin potentiates glucose-stimulated insulin response independent of FFA concentrations in healthy humans.
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Affiliation(s)
- Ximena Lopez
- Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Fiory F, Lombardi A, Miele C, Giudicelli J, Beguinot F, Van Obberghen E. Methylglyoxal impairs insulin signalling and insulin action on glucose-induced insulin secretion in the pancreatic beta cell line INS-1E. Diabetologia 2011; 54:2941-52. [PMID: 21861178 DOI: 10.1007/s00125-011-2280-8] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 07/18/2011] [Indexed: 12/13/2022]
Abstract
AIMS/HYPOTHESIS Chronic hyperglycaemia aggravates insulin resistance, at least in part, by increasing the formation of advanced glycation end-products (AGEs). Methylglyoxal (MGO) is the most reactive AGE precursor and its abnormal accumulation participates in damage in various tissues and organs. Here we investigated the ability of MGO to interfere with insulin signalling and to affect beta cell functions in the INS-1E beta cell line. METHODS INS-1E cells were incubated with MGO and then exposed to insulin or to glucose. Western blotting was used to study signalling pathways, and real-time PCR to analyse gene expression; insulin levels were determined by radioimmunoassay. RESULTS Non-cytotoxic MGO concentrations inhibited insulin-induced IRS tyrosine phosphorylation and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) pathway activation independently from reactive oxygen species (ROS) production. Concomitantly, formation of AGE adducts on immunoprecipitated IRS was observed. Aminoguanidine reversed MGO inhibitory effects and the formation of AGE adducts on IRS. Further, the insulin- and glucose-induced expression of Ins1, Gck and Pdx1 mRNA was abolished by MGO. Finally, MGO blocked glucose-induced insulin secretion and PI3K/PKB pathway activation. These MGO effects were abolished by LiCl, which inhibits glycogen synthase kinase-3 (GSK-3). CONCLUSIONS/INTERPRETATION MGO exerted major damaging effects on INS-1E cells impairing both insulin action and secretion. An important actor in these noxious MGO effects appears to be GSK-3. In conclusion, MGO participates not only in the pathogenesis of the debilitating complications of type 2 diabetes, but also in worsening of the diabetic state by favouring beta cell failure.
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Affiliation(s)
- F Fiory
- Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università degli Studi di Napoli Federico II, Naples, Italy
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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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Marquez AG, Pietri JE, Smithers HM, Nuss A, Antonova Y, Drexler AL, Riehle MA, Brown MR, Luckhart S. Insulin-like peptides in the mosquito Anopheles stephensi: identification and expression in response to diet and infection with Plasmodium falciparum. Gen Comp Endocrinol 2011; 173:303-12. [PMID: 21703270 PMCID: PMC3153599 DOI: 10.1016/j.ygcen.2011.06.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 05/30/2011] [Accepted: 06/05/2011] [Indexed: 12/17/2022]
Abstract
Insulin-like peptides (ILPs) regulate a multitude of biological processes, including metabolism and immunity to infection, and share similar structural motifs across widely divergent taxa. Insulin/insulin-like growth factor signaling (IIS) pathway elements are similarly conserved. We have shown that IIS regulates reproduction, innate immunity, and lifespan in female Anopheles stephensi, a major mosquito vector of human malaria. To further explore IIS regulation of these processes, we identified genes encoding five ILPs in this species and characterized their expression in tissues. Antisera to ILP homologs in Anopheles gambiae were used to identify cellular sources in An. stephensi females by immunocytochemistry. We analyzed tissue-specific ILP transcript expression in young and older females, in response to different feeding regimens, and in response to infection with Plasmodiumfalciparum with quantitative reverse transcriptase-PCR assays. While some ILP transcript changes were evident in older females and in response to blood feeding, significant changes were particularly notable in response to hormonal concentrations of ingested human insulin and to P. falciparum infection. These changes suggest that ILP secretion and action may be similarly responsive in Plasmodium-infected females and potentially alter metabolism and innate immunity.
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Affiliation(s)
- Alexander G. Marquez
- Department of Medical Microbiology and Immunology, 3437 Tupper Hall, One Shields Avenue, School of Medicine, University of California, Davis, CA 95616
| | - Jose E. Pietri
- Department of Medical Microbiology and Immunology, 3437 Tupper Hall, One Shields Avenue, School of Medicine, University of California, Davis, CA 95616
| | - Hannah M. Smithers
- Department of Medical Microbiology and Immunology, 3437 Tupper Hall, One Shields Avenue, School of Medicine, University of California, Davis, CA 95616
| | - Andrew Nuss
- Department of Entomology, 413 Biological Sciences Building, University of Georgia, Athens, GA 30602
| | - Yevgeniya Antonova
- Department of Entomology, 410 Forbes Building, University of Arizona, Tucson, AZ 85721
| | - Anna L. Drexler
- Department of Medical Microbiology and Immunology, 3437 Tupper Hall, One Shields Avenue, School of Medicine, University of California, Davis, CA 95616
| | - Michael A. Riehle
- Department of Entomology, 410 Forbes Building, University of Arizona, Tucson, AZ 85721
| | - Mark R. Brown
- Department of Entomology, 413 Biological Sciences Building, University of Georgia, Athens, GA 30602
| | - Shirley Luckhart
- Department of Medical Microbiology and Immunology, 3437 Tupper Hall, One Shields Avenue, School of Medicine, University of California, Davis, CA 95616
- Corresponding author: Department of Medical Microbiology and Immunology, School of Medicine, 1 Shields Avenue, University of California, Davis, CA USA 95616, , Tel: (530) 754-6963, Fax: (530) 752-8692
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Di Paola R, Caporarello N, Marucci A, Dimatteo C, Iadicicco C, Del Guerra S, Prudente S, Sudano D, Miele C, Parrino C, Piro S, Beguinot F, Marchetti P, Trischitta V, Frittitta L. ENPP1 affects insulin action and secretion: evidences from in vitro studies. PLoS One 2011; 6:e19462. [PMID: 21573217 PMCID: PMC3088669 DOI: 10.1371/journal.pone.0019462] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 03/30/2011] [Indexed: 12/20/2022] Open
Abstract
The aim of this study was to deeper investigate the mechanisms through which
ENPP1, a negative modulator of insulin receptor (IR) activation, plays a role on
insulin signaling, insulin secretion and eventually glucose metabolism. ENPP1
cDNA (carrying either K121 or Q121 variant) was transfected in HepG2 liver-, L6
skeletal muscle- and INS1E beta-cells. Insulin-induced IR-autophosphorylation
(HepG2, L6, INS1E), Akt-Ser473,
ERK1/2-Thr202/Tyr204 and GSK3-beta Ser9
phosphorylation (HepG2, L6), PEPCK mRNA levels (HepG2) and
2-deoxy-D-glucose uptake (L6) was studied. GLUT 4 mRNA
(L6), insulin secretion and caspase-3 activation (INS1E) were also investigated.
Insulin-induced IR-autophosphorylation was decreased in HepG2-K, L6-K, INS1E-K
(20%, 52% and 11% reduction vs. untransfected cells) and
twice as much in HepG2-Q, L6-Q, INS1E-Q (44%, 92% and 30%).
Similar data were obtained with Akt-Ser473,
ERK1/2-Thr202/Tyr204 and GSK3-beta Ser9 in
HepG2 and L6. Insulin-induced reduction of PEPCK mRNA was progressively lower in
untransfected, HepG2-K and HepG2-Q cells (65%, 54%, 23%).
Insulin-induced glucose uptake in untransfected L6 (60% increase over
basal), was totally abolished in L6-K and L6-Q cells. GLUT 4 mRNA was slightly
reduced in L6-K and twice as much in L6-Q (13% and 25% reduction
vs. untransfected cells). Glucose-induced insulin secretion was 60%
reduced in INS1E-K and almost abolished in INS1E-Q. Serum deficiency activated
caspase-3 by two, three and four folds in untransfected INS1E, INS1E-K and
INS1E-Q. Glyburide-induced insulin secretion was reduced by 50% in
isolated human islets from homozygous QQ donors as compared to those from KK and
KQ individuals. Our data clearly indicate that ENPP1, especially when the Q121
variant is operating, affects insulin signaling and glucose metabolism in
skeletal muscle- and liver-cells and both function and survival of insulin
secreting beta-cells, thus representing a strong pathogenic factor predisposing
to insulin resistance, defective insulin secretion and glucose metabolism
abnormalities.
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Affiliation(s)
- Rosa Di Paola
- Research Unit of Diabetes and Endocrine
Diseases, IRCCS “Casa Sollievo della Sofferenza”, San Giovanni
Rotondo, Italy
- * E-mail: (RDP); (VT); (LF)
| | - Nunzia Caporarello
- Unit of Endocrinology, Department of Clinical
and Molecular Biomedicine, University of Catania Medical School, Garibaldi
Hospital, Catania, Italy
| | - Antonella Marucci
- Research Unit of Diabetes and Endocrine
Diseases, IRCCS “Casa Sollievo della Sofferenza”, San Giovanni
Rotondo, Italy
| | - Claudia Dimatteo
- Research Unit of Diabetes and Endocrine
Diseases, IRCCS “Casa Sollievo della Sofferenza”, San Giovanni
Rotondo, Italy
| | - Claudia Iadicicco
- Dipartimento di Biologia e Patologia Cellulare
e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del CNR,
Università degli Studi di Napoli Federico II, Naples, Italy
| | - Silvia Del Guerra
- Department of Endocrinology and Metabolism,
University of Pisa, Pisa, Italy
| | - Sabrina Prudente
- IRCCS “Casa Sollievo della Sofferenza,
Mendel Laboratory”, San Giovanni Rotondo, Italy
| | - Dora Sudano
- Unit of Endocrinology, Department of Clinical
and Molecular Biomedicine, University of Catania Medical School, Garibaldi
Hospital, Catania, Italy
| | - Claudia Miele
- Dipartimento di Biologia e Patologia Cellulare
e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del CNR,
Università degli Studi di Napoli Federico II, Naples, Italy
| | - Cristina Parrino
- Unit of Endocrinology, Department of Clinical
and Molecular Biomedicine, University of Catania Medical School, Garibaldi
Hospital, Catania, Italy
| | - Salvatore Piro
- Unit of Internal Medicine, Department of
Clinical and Molecular Biomedicine, University of Catania Medical School,
Garibaldi Hospital, Catania, Italy
| | - Francesco Beguinot
- Dipartimento di Biologia e Patologia Cellulare
e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del CNR,
Università degli Studi di Napoli Federico II, Naples, Italy
| | - Piero Marchetti
- Department of Endocrinology and Metabolism,
University of Pisa, Pisa, Italy
| | - Vincenzo Trischitta
- Research Unit of Diabetes and Endocrine
Diseases, IRCCS “Casa Sollievo della Sofferenza”, San Giovanni
Rotondo, Italy
- IRCCS “Casa Sollievo della Sofferenza,
Mendel Laboratory”, San Giovanni Rotondo, Italy
- Department of Experimental Medicine, Sapienza
University, Rome, Italy
- * E-mail: (RDP); (VT); (LF)
| | - Lucia Frittitta
- Unit of Endocrinology, Department of Clinical
and Molecular Biomedicine, University of Catania Medical School, Garibaldi
Hospital, Catania, Italy
- * E-mail: (RDP); (VT); (LF)
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Insulin/phosphoinositide 3-kinase pathway accelerates the glucose-induced first-phase insulin secretion through TrpV2 recruitment in pancreatic β-cells. Biochem J 2010; 432:375-86. [PMID: 20854263 DOI: 10.1042/bj20100864] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Functional insulin receptor and its downstream effector PI3K (phosphoinositide 3-kinase) have been identified in pancreatic β-cells, but their involvement in the regulation of insulin secretion from β-cells remains unclear. In the present study, we investigated the physiological role of insulin and PI3K in glucose-induced biphasic insulin exocytosis in primary cultured β-cells and insulinoma Min6 cells using total internal reflection fluorescent microscopy. The pretreatment of β-cells with insulin induced the rapid increase in intracellular Ca2+ levels and accelerated the exocytotic response without affecting the second-phase insulin secretion. The inhibition of PI3K not only abolished the insulin-induced rapid development of the exocytotic response, but also potentiated the second-phase insulin secretion. The rapid development of Ca2+ and accelerated exocytotic response induced by insulin were accompanied by the translocation of the Ca2+-permeable channel TrpV2 (transient receptor potential V2) in a PI3K-dependent manner. Inhibition of TrpV2 by the selective blocker tranilast, or the expression of shRNA (short-hairpin RNA) against TrpV2 suppressed the effect of insulin in the first phase, but the second phase was not affected. Thus our results demonstrate that insulin treatment induced the acceleration of the exocytotic response during the glucose-induced first-phase response by the insertion of TrpV2 into the plasma membrane in a PI3K-dependent manner.
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38
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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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Arredouani A, Evans AM, Ma J, Parrington J, Zhu MX, Galione A. An emerging role for NAADP-mediated Ca2+ signaling in the pancreatic β-cell. Islets 2010; 2:323-30. [PMID: 21099331 PMCID: PMC3230560 DOI: 10.4161/isl.2.5.12747] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Several recent reports, including one in this journal, have reignited the debate about whether the calcium-mobilizing messenger, nicotinic adenine nucleotide diphosphate (NAADP) plays a central role in the regulation of calcium signalling in pancreatic β-cell. These studies have highlighted a role for NAADP-induced Ca(2+) mobilization not only in mediating the effects of the incretin, GLP-1 and the autocrine proliferative effects of insulin, but also possibly a fundamental role in glucose-mediated insulin secretion in the pancreatic β-cell.
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Affiliation(s)
| | - A Mark Evans
- Centre for Integrative Physiology; College of Medicine and Veterinary Medicine; University of Edinburgh; Edinburgh, Scotland UK
| | - Jianjie Ma
- Department of Physiology and Biophysics; UMDNJ-Robert Wood Johnson Medical School; Piscataway, NJ USA
| | - John Parrington
- Department of Pharmacology; University of Oxford; Oxford, UK
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology; The University of Texas Health Science Center in Houston; Houston, TX USA
| | - Antony Galione
- Department of Pharmacology; University of Oxford; Oxford, UK
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40
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Filiputti E, Rafacho A, Araújo EP, Silveira LR, Trevisan A, Batista TM, Curi R, Velloso LA, Quesada I, Boschero AC, Carneiro EM. Augmentation of insulin secretion by leucine supplementation in malnourished rats: possible involvement of the phosphatidylinositol 3-phosphate kinase/mammalian target protein of rapamycin pathway. Metabolism 2010; 59:635-44. [PMID: 19913855 DOI: 10.1016/j.metabol.2009.09.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 09/03/2009] [Accepted: 09/04/2009] [Indexed: 01/01/2023]
Abstract
A regimen of low-protein diet induces a reduction of pancreatic islet function that is associated with development of metabolic disorders including diabetes and obesity afterward. In the present study, the influence of leucine supplementation on metabolic parameters, insulin secretion to glucose and to amino acids, as well as the levels of proteins that participate in the phosphatidylinositol 3-phosphate kinase (PI3K) pathway was investigated in malnourished rats. Four groups were fed with different diets for 12 weeks: a normal protein diet (17%) without (NP) or with leucine supplementation (NPL) or a low (6%)-protein diet without (LP) or with leucine supplementation (LPL). Leucine was given in the drinking water during the last 4 weeks. As indicated by the intraperitoneal glucose tolerance test, LPL rats exhibited increased glucose tolerance as compared with NPL group. Both NPL and LPL rats had higher circulating insulin levels than controls. The LPL rats also showed increased insulin secretion by pancreatic islets in response to glucose or arginine compared with those observed in islets from LP animals. Glucose oxidation was significantly reduced in NPL, LP, and LPL isolated islets as compared with NP; but no alteration was observed for leucine and glutamate oxidation among the 4 groups. Western blotting analysis demonstrated increased PI3K and mammalian target protein of rapamycin protein contents in LPL compared with LP islets. A significant increase in insulin-induced insulin receptor substrate 1-associated PI3K activation was also observed in LPL compared with LP islets. These findings indicate that leucine supplementation can augment islet function in malnourished rats and that activation of the PI3K/mammalian target protein of rapamycin pathway may play a role in this process.
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Affiliation(s)
- Eliane Filiputti
- Department of Anatomy, Cell Biology and Physiology and Biophysics, Institute of Biology, State University of Campinas (UNICAMP), Campinas, SP, Brazil
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41
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Insulin enhances glucose-stimulated insulin secretion in healthy humans. Proc Natl Acad Sci U S A 2010; 107:4770-5. [PMID: 20176932 DOI: 10.1073/pnas.1000002107] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Islet beta-cells express both insulin receptors and insulin-signaling proteins. Recent evidence from rodents in vivo and from islets isolated from rodents or humans suggests that the insulin signaling pathway is physiologically important for glucose sensing. We evaluated whether insulin regulates beta-cell function in healthy humans in vivo. Glucose-induced insulin secretion was assessed in healthy humans following 4-h saline (low insulin/sham clamp) or isoglycemic-hyperinsulinemic (high insulin) clamps using B28-Asp insulin that could be immunologically distinguished from endogenous insulin. Insulin and C-peptide clearance were evaluated to understand the impact of hyperinsulinemia on estimates of beta-cell function. Preexposure to exogenous insulin increased the endogenous insulin secretory response to glucose by approximately 40%. C-peptide response also increased, although not to the level predicted by insulin. Insulin clearance was not saturated at hyperinsulinemia, but metabolic clearance of C-peptide, assessed by infusion of stable isotope-labeled C-peptide, increased modestly during hyperinsulinemic clamp. These studies demonstrate that insulin potentiates glucose-stimulated insulin secretion in vivo in healthy humans. In addition, hyperinsulinemia increases C-peptide clearance, which may lead to modest underestimation of beta-cell secretory response when using these methods during prolonged dynamic testing.
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Alejandro EU, Kalynyak TB, Taghizadeh F, Gwiazda KS, Rawstron EK, Jacob KJ, Johnson JD. Acute insulin signaling in pancreatic beta-cells is mediated by multiple Raf-1 dependent pathways. Endocrinology 2010; 151:502-12. [PMID: 20056832 PMCID: PMC2817610 DOI: 10.1210/en.2009-0678] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Insulin enhances the proliferation and survival of pancreatic beta-cells, but its mechanisms remain unclear. We hypothesized that Raf-1, a kinase upstream of both ERK and Bad, might be a critical target of insulin in beta-cells. To test this hypothesis, we treated human and mouse islets as well as MIN6 beta-cells with multiple insulin concentrations and examined putative downstream targets using immunoblotting, immunoprecipitation, quantitative fluorescent imaging, and cell death assays. Low doses of insulin rapidly activated Raf-1 by dephosphorylating serine 259 and phosphorylating serine 338 in human islets, mouse islets, and MIN6 cells. The phosphorylation of ERK by insulin was eliminated by exposure to a Raf inhibitor (GW5074) or transfection with a dominant-negative Raf-1 mutant. Insulin also enhanced the interaction between mitochondrial Raf-1 and Bcl-2 agonist of cell death (Bad), promoting Bad inactivation via its phosphorylation on serine 112. Insulin-stimulated ERK phosphorylation was abrogated by calcium chelation, calcineurin and calmodulin-dependent protein kinase II inhibitors, and Ned-19, a nicotinic acid adenine dinucleotide phosphate receptor (NAADPR) antagonist. Blocking Raf-1 and Ca(2+) signaling resulted in nonadditive beta-cell death. Autocrine insulin signaling partly accounted for the effects of glucose on ERK phosphorylation. Our results demonstrate that Raf-1 is a critical target of insulin in primary beta-cells. Activation of Raf-1 leads to both an ERK-dependent pathway that involves nicotinic acid adenine dinucleotide phosphate-sensitive Ca(2+) stores and Ca(2+)-dependent phosphorylation events, and an ERK-independent pathway that involves Bad inactivation at the mitochondria. Together our findings identify a novel insulin signaling pathway in beta-cells and shed light on insulin's antiapoptotic and mitogenic mechanisms.
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Affiliation(s)
- Emilyn U Alejandro
- Department of Cellular and Physiological Sciences, University of British Columbia, 5358 Life Sciences Building, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada
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Prudente S, Morini E, Trischitta V. Insulin signaling regulating genes: effect on T2DM and cardiovascular risk. Nat Rev Endocrinol 2009; 5:682-93. [PMID: 19924153 DOI: 10.1038/nrendo.2009.215] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is a complex disorder that has a heterogeneous genetic and environmental background. In this Review, we discuss the role of relatively infrequent polymorphisms of genes that regulate insulin signaling (including the K121Q polymorphism of ENPP1, the G972R polymorphism of IRS1 and the Q84R polymorphism of TRIB3) in T2DM and other conditions related to insulin resistance. The biological relevance of these three polymorphisms has been very thoroughly characterized both in vitro and in vivo and the available data indicate that they all affect insulin signaling and action as well as insulin secretion. They also affect insulin-mediated regulation of endothelial cell function. In addition, several reports indicate that the effects of all three polymorphisms on the risk of T2DM and cardiovascular diseases related to insulin resistance depend on the clinical features of the individual, including their body weight and age at disease onset. Thus, these polymorphisms might be used to demonstrate how difficult it is to ascertain the contribution of relatively infrequent genetic variants with heterogeneous effects on disease susceptibility. Unraveling the role of such variants might be facilitated by improving disease definition and focusing on specific subsets of patients.
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Affiliation(s)
- Sabrina Prudente
- IRCCS Casa Sollievo della Sofferenza, Mendel Institute, Rome, Italy
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44
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Pigeau GM, Kolic J, Ball BJ, Hoppa MB, Wang YW, Rückle T, Woo M, Manning Fox JE, MacDonald PE. Insulin granule recruitment and exocytosis is dependent on p110gamma in insulinoma and human beta-cells. Diabetes 2009; 58:2084-92. [PMID: 19549714 PMCID: PMC2731529 DOI: 10.2337/db08-1371] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE Phosphatidylinositol 3-OH kinase (PI3K) has a long-recognized role in beta-cell mass regulation and gene transcription and is implicated in the modulation of insulin secretion. The role of nontyrosine kinase receptor-activated PI3K isoforms is largely unexplored. We therefore investigated the role of the G-protein-coupled PI3Kgamma and its catalytic subunit p110gamma in the regulation of insulin granule recruitment and exocytosis. RESEARCH DESIGN AND METHODS The expression of p110gamma was knocked down by small-interfering RNA, and p110gamma activity was selectively inhibited with AS605240 (40 nmol/l). Exocytosis and granule recruitment was monitored by islet perifusion, whole-cell capacitance, total internal reflection fluorescence microscopy, and electron microscopy in INS-1 and human beta-cells. Cortical F-actin was examined in INS-1 cells and human islets and in mouse beta-cells lacking the phosphatase and tensin homolog (PTEN). RESULTS Knockdown or inhibition of p110gamma markedly blunted depolarization-induced insulin secretion and exocytosis and ablated the exocytotic response to direct Ca(2+) infusion. This resulted from reduced granule localization to the plasma membrane and was associated with increased cortical F-actin. Inhibition of p110gamma had no effect on F-actin in beta-cells lacking PTEN. Finally, the effect of p110gamma inhibition on granule localization and exocytosis could be rapidly reversed by agents that promote actin depolymerization. CONCLUSIONS The G-protein-coupled PI3Kgamma is an important determinant of secretory granule trafficking to the plasma membrane, at least in part through the negative regulation of cortical F-actin. Thus, p110gamma activity plays an important role in maintaining a membrane-docked, readily releasable pool of secretory granules in insulinoma and human beta-cells.
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Affiliation(s)
- Gary M. Pigeau
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Jelena Kolic
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Brandon J. Ball
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Michael B. Hoppa
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Headington, Oxford, U.K
| | - Ying W. Wang
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Thomas Rückle
- Geneva Research Center, Merck Serono, Geneva, Switzerland
| | - Minna Woo
- Department of Medicine, Medical Biophysics, Institute of Medical Science, Ontario Cancer Institute, University of Toronto, Toronto, Ontario, Canada
| | - Jocelyn E. Manning Fox
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E. MacDonald
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Patrick E. MacDonald,
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Abstract
OBJECTIVE To investigate the action of palmitate on insulin receptor (IR) signaling pathway in rat pancreatic islets. The following proteins were studied: IR substrate-1 and -2 (IRS1 and IRS2), phosphatidylinositol 3-kinase, extracellular signal-regulated protein kinase-1 and -2 (ERK1/2), and signal transducer and activator of transcription 3 (STAT3). METHODS Immunoblotting and immunoprecipitation assays were used to evaluate the phosphorylation states of IRS1 and IRS2 (tyrosine [Tyr]), ERK1/2 (threonine 202 [Thr202]/Tyr204), and STAT3 (serine [Ser727]). RESULTS The exposure of rat pancreatic islets to 0.1-mmol/L palmitate for up to 30 minutes produced a significant increase of Tyr phosphorylation in IRS2 but not in IRS1. The association of phosphatidylinositol 3-kinase with IRS2 was also upregulated by palmitate. Exposure to 5.6-mmol/L glucose caused a gradual decrease in ERK1/2 (Thr202/Tyr204) and STAT3 (serine [Ser727]) phosphorylations after 30-minute incubation. The addition of palmitate (0.1 mmol/L), associated with 5.6-mmol/L glucose, abolished these latter effects of glucose after 15-minute incubation. CONCLUSIONS Palmitate at physiological concentration associated with 5.6-mmol/L glucose activates IR signaling pathway in pancreatic beta cells.
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46
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Regulation of glucose-dependent insulin secretion by insulin: Possible role of AMP-activated protein kinase. Life Sci 2009; 85:178-83. [DOI: 10.1016/j.lfs.2009.05.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 05/07/2009] [Accepted: 05/16/2009] [Indexed: 11/18/2022]
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Chang TJ, Chen WP, Yang C, Lu PH, Liang YC, Su MJ, Lee SC, Chuang LM. Serine-385 phosphorylation of inwardly rectifying K+ channel subunit (Kir6.2) by AMP-dependent protein kinase plays a key role in rosiglitazone-induced closure of the K(ATP) channel and insulin secretion in rats. Diabetologia 2009; 52:1112-21. [PMID: 19357830 DOI: 10.1007/s00125-009-1337-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 02/26/2009] [Indexed: 11/27/2022]
Abstract
AIMS/HYPOTHESIS Rosiglitazone, an insulin sensitiser, not only improves insulin sensitivity but also enhances insulin secretory capacity by ameliorating gluco- and lipotoxicity in beta cells. Rosiglitazone can stimulate insulin secretion at basal and high glucose levels via a phosphatidylinositol 3-kinase (PI3K)-dependent pathway. We hypothesised that regulation of phosphorylation of the ATP-sensitive potassium (K(ATP)) channel might serve as a key step in the regulation of insulin secretion. METHODS Insulin secretory responses were studied in an isolated pancreas perfusion system, cultured rat islets and MIN6 and RINm5F beta cells. Signal transduction pathways downstream of PI3K were explored to link rosiglitazone to K(ATP) channel conductance with patch clamp techniques and insulin secretion measured by ELISA. RESULTS Rosiglitazone stimulated AMP-activated protein kinase (AMPK) activity and induced inhibition of the K(ATP) channel conductance in islet beta cells; both effects were blocked by the PI3K inhibitor LY294002. Following stimulation of AMPK by 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a pharmacological activator, both AICAR-stimulated insulin secretion and inhibition of K(ATP) channel conductance were unaffected by LY294002, indicating that AMPK activation occurs at a site downstream of PI3K activity. The serine residue at amino acid position 385 of Kir6.2 was found to be the substrate phosphorylation site of AMPK when activated by rosiglitazone or AICAR. CONCLUSIONS/INTERPRETATION Our data indicate that PI3K-dependent activation of AMPK is required for rosiglitazone-stimulated insulin secretion in pancreatic beta cells. Phosphorylation of the Ser(385) residue of the Kir6.2 subunit of the K(ATP) channel by AMPK may play a role in insulin secretion.
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Affiliation(s)
- T-J Chang
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
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48
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Prudente S, Morini E, Trischitta V. The emerging role of TRIB3 as a gene affecting human insulin resistance and related clinical outcomes. Acta Diabetol 2009; 46:79-84. [PMID: 19139803 DOI: 10.1007/s00592-008-0087-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 11/10/2008] [Indexed: 01/18/2023]
Abstract
Type 2 diabetes is becoming epidemic. The personal and social burden imposed by diabetes will increase in the close future as its prevalence is expected to double in the next 15-20 years. Type 2 diabetes is caused by the combination of resistance to insulin action and inadequate insulin secretion. Despite the role of profound changes in individual environmental exposure is incontrovertible, several findings clearly indicate that type 2 diabetes and insulin resistance are also heritable. Among the several inhibitors of insulin signalling, which have been recently proposed as determinants of insulin resistance, is TRIB3, a mammalian tribbles homolog which affects insulin signalling at the level of Akt-2, a key modulator of insulin action in target cells. We here report data on a prevalent Q84R TRIB3 missense single nucleotide polymorphism (rs2295490) we first described few years ago. Several lines of evidences indicate that this amino-acid change is, in fact, a gain of function mutation with the potential to affect insulin signalling and thus, to increase the risk of insulin resistance and related clinical outcomes.
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Affiliation(s)
- Sabrina Prudente
- CSS-Mendel Institute, Viale Regina Margherita 261, 00198, Rome, Italy.
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49
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Abstract
Type 1 and type 2 diabetes mellitus together are predicted to affect over 300 million people worldwide by the year 2020. A relative or absolute paucity of functional β-cells is a central feature of both types of disease, and identifying the pathways that mediate the embryonic origin of new β-cells and mechanisms that underlie the proliferation of existing β-cells are major efforts in the fields of developmental and islet biology. A poor secretory response of existing β-cells to nutrients and hormones and the defects in hormone processing also contribute to the hyperglycemia observed in type 2 diabetes and has prompted studies aimed at enhancing β-cell function. The factors that contribute to a greater susceptibility in aging individuals to develop diabetes is currently unclear and may be linked to a poor turnover of β-cells and/or enhanced susceptibility of β-cells to apoptosis. This review is an update on the recent work in the areas of islet/β-cell regeneration and hormone processing that are relevant to the pathophysiology of the endocrine pancreas in type 1, type 2 and obesity-associated diabetes.
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Affiliation(s)
- Anke Assmann
- Research Division, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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50
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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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