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Gambioli R, Montanino Oliva M, Nordio M, Chiefari A, Puliani G, Unfer V. New Insights into the Activities of D-Chiro-Inositol: A Narrative Review. Biomedicines 2021; 9:biomedicines9101378. [PMID: 34680494 PMCID: PMC8533370 DOI: 10.3390/biomedicines9101378] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 12/14/2022] Open
Abstract
D-chiro-inositol (DCI) is a natural compound detectable in cell membranes, which is highly conserved as a biological signaling molecule. In mammals, its function is primarily characterized in the intracellular transduction cascade of insulin. In particular, insulin signal promotes the release of pivotal DCI-containing molecules. In fact, impaired release of DCI is a common feature of insulin-resistant tissues, and insulin-sensitizing pharmaceuticals induce higher concentrations of free DCI. Moreover, it also plays important roles in several other processes. DCI is involved in the regulation of steroidogenesis, due to its regulatory effects on steroidogenic enzymes, including 17α-hydroxylase, 3β-hydroxysteroid dehydrogenase, and aromatase. Such regulation of various enzymes indicates a mechanism by which the body regulates different processes via a single molecule, depending on its concentration. DCI also reduces the expression of integrin β3, which is an adhesion molecule involved in embryo implantation and cellular phenomena such as survival, stemness, and invasiveness. In addition, DCI seems to have important anti-inflammatory activities, like its 3-O-methyl-ether, called pinitol. In vitro evidence demonstrates that treatment with both compounds induces a reduction in pro-inflammatory factors—such as Nf-κB—and cytokines—such as TNF-α. DCI then plays important roles in several fundamental processes in physiology. Therefore, research on such molecule is of primary importance.
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Affiliation(s)
| | - Mario Montanino Oliva
- The Experts Group on Inositol in Basic and Clinical Research (EGOI), 00161 Rome, Italy; (M.M.O.); (M.N.)
- Department of Obstetrics and Gynecology, Santo Spirito Hospital, 00193 Rome, Italy
| | - Maurizio Nordio
- The Experts Group on Inositol in Basic and Clinical Research (EGOI), 00161 Rome, Italy; (M.M.O.); (M.N.)
- Department of Experimental Medicine, Sapienza University, 00185 Rome, Italy
| | - Alfonsina Chiefari
- Oncological Endocrinology Unit, IRCCS Regina Elena National Cancer Institute, 00144 Rome, Italy; (A.C.); (G.P.)
| | - Giulia Puliani
- Oncological Endocrinology Unit, IRCCS Regina Elena National Cancer Institute, 00144 Rome, Italy; (A.C.); (G.P.)
| | - Vittorio Unfer
- The Experts Group on Inositol in Basic and Clinical Research (EGOI), 00161 Rome, Italy; (M.M.O.); (M.N.)
- System Biology Group Lab, 00161 Rome, Italy
- Correspondence:
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2
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Trexler AJ, Taraska JW. Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells. Cell Calcium 2017; 67:1-10. [PMID: 29029784 DOI: 10.1016/j.ceca.2017.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022]
Abstract
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin. Here, we review what is currently known about the molecular mechanisms of protein kinase C action on each of these pathways and how these effects relate to the control of insulin release by exocytosis. We identify remaining challenges in the field and suggest how these challenges might be addressed to advance our understanding of the regulation of insulin release in health and disease.
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Affiliation(s)
- Adam J Trexler
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Justin W Taraska
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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3
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Kaneko YK, Ishikawa T. [Regulation of Lipid Metabolism by Diacylglycerol Kinases in Pancreatic β-cells]. YAKUGAKU ZASSHI 2017; 136:461-5. [PMID: 26935087 DOI: 10.1248/yakushi.15-00246-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The appropriate secretion of insulin from pancreatic β-cells is essential for regulating blood glucose levels. Glucose-stimulated insulin secretion (GSIS) involves the following steps: Glucose uptake by pancreatic β-cells is metabolized to produce ATP. Increased ATP levels result in the closure of ATP-sensitive K(+) (KATP) channels, resulting in membrane depolarization that activates voltage-dependent Ca(2+) channels to subsequently trigger insulin secretion. In addition to this primary mechanism through KATP channels, insulin secretion is regulated by cyclic AMP and diacylglycerol (DAG), which mediate the effects of receptor agonists such as GLP-1 and acetylcholine. Glucose by itself can also increase the levels of these second messengers. Recently, we have shown an obligatory role of diacylglycerol kinase (DGK), an enzyme catalyzing the conversion of DAG to phosphatidic acid, in GSIS. Of the 10 known DGK isoforms, we focused on type-I DGK isoforms (i.e., DGKα, DGKβ, and DGKγ), which are activated by Ca(2+). The protein expression of DGKα and DGKγ was detected in mouse pancreatic islets and the pancreatic β-cell line MIN6. Depletion of these DGKs by a specific inhibitor or siRNA decreased both [Ca(2+)]i and insulin secretion in MIN6 cells. Similar [Ca(2+)]i responses were induced by DiC8, a membrane-permeable DAG analog. These results suggest that DGKα and DGKγ play crucial roles in insulin secretion, and that their depletion impairs insulin secretion through DAG accumulation. In this article, we review the current understanding of the roles of DAG- and DGK-signaling in pancreatic β-cells, and discuss their pathophysiological roles in the progression of type-2 diabetes.
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Affiliation(s)
- Yukiko K Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka
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4
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Chen Y, Song M, Riley JP, Hu CC, Peng X, Scheuner D, Bokvist K, Maiti P, Kahl SD, Montrose-Rafizadeh C, Hamdouchi C, Miller AR. A selective GPR40 (FFAR1) agonist LY2881835 provides immediate and durable glucose control in rodent models of type 2 diabetes. Pharmacol Res Perspect 2016; 4:e00278. [PMID: 28097011 PMCID: PMC5226292 DOI: 10.1002/prp2.278] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 10/11/2016] [Indexed: 11/20/2022] Open
Abstract
LY2881835 is a selective, potent, and efficacious GPR40 agonist. The objective of the studies described here was to examine the pharmacological properties of LY2881835 in preclinical models of T2D. Significant increases in insulin secretion were detected when LY2881835 was tested in primary islets from WT mice but not in islets from GPR40 KO mice. Furthermore, LY2881835 potentiated glucose stimulated insulin secretion in normal lean mice. Acute administration of LY2881835 lowered glucose during OGTTs in WT mice but not in GPR40 KO mice. These findings demonstrate that LY2881835 induces GPR40‐mediated activity ex vivo and in vivo. LY2881835 was administered orally at 10 mg/kg to diet‐induced obese (DIO) mice (an early model of T2D due to insulin resistance) for 14 days. Statistically significant reductions in glucose were seen during OGTTs performed on days 1 and 15. When a study was done for 3 weeks in Zucker fa/fa rats, a rat model of insulin resistance, normalization of blood glucose levels equivalent to those seen in lean rats was observed. A similar study was performed in streptozotocin (STZ)‐treated DIO mice to explore glucose control in a late model of T2D. In this model, pancreatic insulin content was reduced ~80% due to STZ‐treatment plus the mice were insulin resistant due to their high fat diet. Glucose AUCs were significantly reduced during OGTTs done on days 1, 7, and 14 compared to control mice. In conclusion, these results demonstrate that LY2881835 functions as a GPR40‐specific insulin secretagogue mediating immediate and durable glucose control in rodent models of early‐ and late‐stage T2D.
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Affiliation(s)
- Yanyun Chen
- Lilly Research Laboratories Indianapolis Indiana
| | - Min Song
- Lilly Research Laboratories Indianapolis Indiana
| | | | - Charlie C Hu
- Lilly Research Laboratories Indianapolis Indiana
| | - Xianbu Peng
- Lilly Research Laboratories Indianapolis Indiana
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5
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Zhang PP, Zhang G, Zhou W, Weng SJ, Yang XL, Zhong YM. Signaling mechanism for modulation by ATP of glycine receptors on rat retinal ganglion cells. Sci Rep 2016; 6:28938. [PMID: 27357477 PMCID: PMC4928062 DOI: 10.1038/srep28938] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 06/13/2016] [Indexed: 12/30/2022] Open
Abstract
ATP modulates voltage- and ligand-gated channels in the CNS via the activation of ionotropic P2X and metabotropic P2Y receptors. While P2Y receptors are expressed in retinal neurons, the function of these receptors in the retina is largely unknown. Using whole-cell patch-clamp techniques in rat retinal slice preparations, we demonstrated that ATP suppressed glycine receptor-mediated currents of OFF type ganglion cells (OFF-GCs) dose-dependently, and the effect was in part mediated by P2Y1 and P2Y11, but not by P2X. The ATP effect was abolished by intracellular dialysis of a Gq/11 protein inhibitor and phosphatidylinositol (PI)-phospholipase C (PLC) inhibitor, but not phosphatidylcholine (PC)-PLC inhibitor. The ATP effect was accompanied by an increase in [Ca(2+)]i through the IP3-sensitive pathway and was blocked by intracellular Ca(2+)-free solution. Furthermore, the ATP effect was eliminated in the presence of PKC inhibitors. Neither PKA nor PKG system was involved. These results suggest that the ATP-induced suppression may be mediated by a distinct Gq/11/PI-PLC/IP3/Ca(2+)/PKC signaling pathway, following the activation of P2Y1,11 and other P2Y subtypes. Consistently, ATP suppressed glycine receptor-mediated light-evoked inhibitory postsynaptic currents of OFF-GCs. These results suggest that ATP may modify the ON-to-OFF crossover inhibition, thus changing action potential patterns of OFF-GCs.
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Affiliation(s)
- Ping-Ping Zhang
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Gong Zhang
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Wei Zhou
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Shi-Jun Weng
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Xiong-Li Yang
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Yong-Mei Zhong
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
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6
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Imamura M, Takahashi A, Yamauchi T, Hara K, Yasuda K, Grarup N, Zhao W, Wang X, Huerta-Chagoya A, Hu C, Moon S, Long J, Kwak SH, Rasheed A, Saxena R, Ma RCW, Okada Y, Iwata M, Hosoe J, Shojima N, Iwasaki M, Fujita H, Suzuki K, Danesh J, Jørgensen T, Jørgensen ME, Witte DR, Brandslund I, Christensen C, Hansen T, Mercader JM, Flannick J, Moreno-Macías H, Burtt NP, Zhang R, Kim YJ, Zheng W, Singh JR, Tam CHT, Hirose H, Maegawa H, Ito C, Kaku K, Watada H, Tanaka Y, Tobe K, Kawamori R, Kubo M, Cho YS, Chan JCN, Sanghera D, Frossard P, Park KS, Shu XO, Kim BJ, Florez JC, Tusié-Luna T, Jia W, Tai ES, Pedersen O, Saleheen D, Maeda S, Kadowaki T. Genome-wide association studies in the Japanese population identify seven novel loci for type 2 diabetes. Nat Commun 2016; 7:10531. [PMID: 26818947 PMCID: PMC4738362 DOI: 10.1038/ncomms10531] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 12/22/2015] [Indexed: 12/11/2022] Open
Abstract
Genome-wide association studies (GWAS) have identified more than 80 susceptibility loci for type 2 diabetes (T2D), but most of its heritability still remains to be elucidated. In this study, we conducted a meta-analysis of GWAS for T2D in the Japanese population. Combined data from discovery and subsequent validation analyses (23,399 T2D cases and 31,722 controls) identify 7 new loci with genome-wide significance (P<5 × 10(-8)), rs1116357 near CCDC85A, rs147538848 in FAM60A, rs1575972 near DMRTA1, rs9309245 near ASB3, rs67156297 near ATP8B2, rs7107784 near MIR4686 and rs67839313 near INAFM2. Of these, the association of 4 loci with T2D is replicated in multi-ethnic populations other than Japanese (up to 65,936 T2Ds and 158,030 controls, P<0.007). These results indicate that expansion of single ethnic GWAS is still useful to identify novel susceptibility loci to complex traits not only for ethnicity-specific loci but also for common loci across different ethnicities.
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Affiliation(s)
- Minako Imamura
- Laboratory for Endocrinology, Metabolism and Kidney Diseases, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan
| | - Atsushi Takahashi
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan.,Laboratory for Omics Informatics, Omics Research Center, National Cerebral And Cardiovascular Center, Suita 565-8565, Japan
| | - Toshimasa Yamauchi
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Kazuo Hara
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan.,Department of Diabetes Endocrinology, Metabolism and Rheumatology, Tokyo Medical University, Tokyo 160-0023, Japan
| | - Kazuki Yasuda
- Department of Metabolic Disorder, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo 162-8655, Japan
| | - Niels Grarup
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Wei Zhao
- Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6021, USA
| | - Xu Wang
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore 138672, Singapore
| | - Alicia Huerta-Chagoya
- Unidad de Biología Molecular y Medicina Genómica, Instituto de Investigaciones Biomédicas UNAM/Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City C.P.14000, Mexico
| | - Cheng Hu
- Department of Endocrinology and Metabolism, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Diabetes Institute, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Sanghoon Moon
- Division of Structural and Functional Genomics, Center for Genome Science, National Institute of Health, Chungcheongbuk-do 28159, Korea
| | - Jirong Long
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37203-1738, USA
| | - Soo Heon Kwak
- Department of Internal Medicine, Seoul National University Hospital, Seoul 03080, Korea
| | - Asif Rasheed
- Center for Non-Communicable Diseases, Karachi, Pakistan
| | - Richa Saxena
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Ronald C W Ma
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.,Hong Kong Institute of Diabetes and Obesity, The Chinese University of Hong Kong, Hong Kong, China.,Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Yukinori Okada
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan.,Department of Human Genetics and Disease Diversity, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Minoru Iwata
- First Department of Internal Medicine, University of Toyama, Toyama 930-0194, Japan.,Health Administration Center, University of Toyama, Toyama 930-0194, Japan
| | - Jun Hosoe
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Nobuhiro Shojima
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Minaka Iwasaki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Hayato Fujita
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Ken Suzuki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - John Danesh
- Department of Public Health and Primary Care, University of Cambridge CB1 8RN, UK.,Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus Hinxton, Cambridge CB10 1RQ, UK.,NIHR Blood and Transplant Research Unit in Donor Health and Genomics, Department of Public Health and Primary Care, University of Cambridge, Cambridge CB1 8RN, UK
| | - Torben Jørgensen
- Research Centre for Prevention and Health, Capital Region of Denmark, Glostrup DK-2600, Denmark.,Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen, Copenhagen 2200, Denmark.,Faculty of Medicine, University of Aalborg, Aalborg 9220, Denmark
| | | | - Daniel R Witte
- Department of Public Health, Aarhus University, Aarhus 8000, Denmark.,Danish Diabetes Academy, Odense 5000, Denmark
| | - Ivan Brandslund
- Department of Clinical Biochemistry, Lillebaelt Hospital, Vejle 7100, Denmark.,Institute of Regional Health Research, University of Southern Denmark, Odense 5230, Denmark
| | | | - Torben Hansen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Josep M Mercader
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, USA.,Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Barcelona 08034, Spain.,Center for Human Genetic Research and Diabetes Research Center (Diabetes Unit), Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Jason Flannick
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, USA.,Department of Molecular Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | | | - Noël P Burtt
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, USA
| | - Rong Zhang
- Department of Endocrinology and Metabolism, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Diabetes Institute, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Young Jin Kim
- Division of Structural and Functional Genomics, Center for Genome Science, National Institute of Health, Chungcheongbuk-do 28159, Korea
| | - Wei Zheng
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37203-1738, USA
| | - Jai Rup Singh
- Central University of Punjab, Bathinda, Punjab 151001, India
| | - Claudia H T Tam
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China
| | | | - Hiroshi Maegawa
- Department of Medicine, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Chikako Ito
- Grand Tower Medical Court Life Care Clinic, Hiroshima 730-0012, Japan
| | - Kohei Kaku
- Department of Internal Medicine, Kawasaki Medical School, Kurashiki 701-0192, Japan
| | - Hirotaka Watada
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan.,Sportology Center, Juntendo University Graduate School of Medicine, Tokyo 113-0034, Japan
| | - Yasushi Tanaka
- Division of Metabolism and Endocrinology, Department of Internal Medicine, St Marianna University School of Medicine, Kawasaki 216-8511, Japan
| | - Kazuyuki Tobe
- First Department of Internal Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Ryuzo Kawamori
- Sportology Center, Juntendo University Graduate School of Medicine, Tokyo 113-0034, Japan
| | - Michiaki Kubo
- RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan
| | - Yoon Shin Cho
- Department of Biomedical Science, Hallym University, Chunchon, Gangwon-do 24252, Republic of Korea
| | - Juliana C N Chan
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.,Hong Kong Institute of Diabetes and Obesity, The Chinese University of Hong Kong, Hong Kong, China.,Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Dharambir Sanghera
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.,Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, n
| | | | - Kyong Soo Park
- Department of Internal Medicine, Seoul National University Hospital, Seoul 03080, Korea.,Department of Internal Medicine, Seoul National University College of Medicine, Seoul 03080, Korea.,Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 03080, Korea
| | - Xiao-Ou Shu
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37203-1738, USA
| | - Bong-Jo Kim
- Division of Structural and Functional Genomics, Center for Genome Science, National Institute of Health, Chungcheongbuk-do 28159, Korea
| | - Jose C Florez
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, USA.,Center for Human Genetic Research and Diabetes Research Center (Diabetes Unit), Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Teresa Tusié-Luna
- Unidad de Biología Molecular y Medicina Genómica, Instituto de Investigaciones Biomédicas UNAM/Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City C.P.14000, Mexico
| | - Weiping Jia
- Department of Endocrinology and Metabolism, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Diabetes Institute, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - E Shyong Tai
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore 138672, Singapore.,Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore.,Duke-National University of Singapore Graduate School, Singapore 169857, Singapore
| | - Oluf Pedersen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Danish Saleheen
- Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6021, USA.,Center for Non-Communicable Diseases, Karachi, Pakistan
| | - Shiro Maeda
- Laboratory for Endocrinology, Metabolism and Kidney Diseases, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan.,Department of Advanced Genomic and Laboratory Medicine, Graduate School of Medicine, University of the Ryukyus, Nishihara 903-0215, Japan.,Division of Clinical Laboratory and Blood Transfusion, University of the Ryukyus Hospital, Nishihara 903-0215, Japan
| | - Takashi Kadowaki
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
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7
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Sharma PR, Mackey AJ, Dejene EA, Ramadan JW, Langefeld CD, Palmer ND, Taylor KD, Wagenknecht LE, Watanabe RM, Rich SS, Nunemaker CS. An Islet-Targeted Genome-Wide Association Scan Identifies Novel Genes Implicated in Cytokine-Mediated Islet Stress in Type 2 Diabetes. Endocrinology 2015; 156:3147-56. [PMID: 26018251 PMCID: PMC4541617 DOI: 10.1210/en.2015-1203] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Genome-wide association studies in human type 2 diabetes (T2D) have renewed interest in the pancreatic islet as a contributor to T2D risk. Chronic low-grade inflammation resulting from obesity is a risk factor for T2D and a possible trigger of β-cell failure. In this study, microarray data were collected from mouse islets after overnight treatment with cytokines at concentrations consistent with the chronic low-grade inflammation in T2D. Genes with a cytokine-induced change of >2-fold were then examined for associations between single nucleotide polymorphisms and the acute insulin response to glucose (AIRg) using data from the Genetics Underlying Diabetes in Hispanics (GUARDIAN) Consortium. Significant evidence of association was found between AIRg and single nucleotide polymorphisms in Arap3 (5q31.3), F13a1 (6p25.3), Klhl6 (3q27.1), Nid1 (1q42.3), Pamr1 (11p13), Ripk2 (8q21.3), and Steap4 (7q21.12). To assess the potential relevance to islet function, mouse islets were exposed to conditions modeling low-grade inflammation, mitochondrial stress, endoplasmic reticulum (ER) stress, glucotoxicity, and lipotoxicity. RT-PCR revealed that one or more forms of stress significantly altered expression levels of all genes except Arap3. Thapsigargin-induced ER stress up-regulated both Pamr1 and Klhl6. Three genes confirmed microarray predictions of significant cytokine sensitivity: F13a1 was down-regulated 3.3-fold by cytokines, Ripk2 was up-regulated 1.5- to 3-fold by all stressors, and Steap4 was profoundly cytokine sensitive (167-fold up-regulation). Three genes were thus closely associated with low-grade inflammation in murine islets and also with a marker for islet function (AIRg) in a diabetes-prone human population. This islet-targeted genome-wide association scan identified several previously unrecognized candidate genes related to islet dysfunction during the development of T2D.
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Affiliation(s)
- Poonam R Sharma
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Aaron J Mackey
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Eden A Dejene
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - James W Ramadan
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Carl D Langefeld
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Nicholette D Palmer
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Kent D Taylor
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Lynne E Wagenknecht
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Richard M Watanabe
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Stephen S Rich
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Craig S Nunemaker
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
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8
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Leiss V, Flockerzie K, Novakovic A, Rath M, Schönsiegel A, Birnbaumer L, Schürmann A, Harteneck C, Nürnberg B. Insulin secretion stimulated by L-arginine and its metabolite L-ornithine depends on Gα(i2). Am J Physiol Endocrinol Metab 2014; 307:E800-12. [PMID: 25205820 PMCID: PMC4216945 DOI: 10.1152/ajpendo.00337.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bordetella pertussis toxin (PTx), also known as islet-activating protein, induces insulin secretion by ADP-ribosylation of inhibitory G proteins. PTx-induced insulin secretion may result either from inactivation of Gα(o) proteins or from combined inactivation of Gα(o), Gα(i1), Gα(i2), and Gα(i3) isoforms. However, the specific role of Gα(i2) in pancreatic β-cells still remains unknown. In global (Gα(i2)(-/-)) and β-cell-specific (Gα(i2)(βcko)) gene-targeted Gα(i2) mouse models, we studied glucose homeostasis and islet functions. Insulin secretion experiments and intracellular Ca²⁺ measurements were used to characterize Gα(i2) function in vitro. Gα(i2)(-/-) and Gα(i2)(βcko) mice showed an unexpected metabolic phenotype, i.e., significantly lower plasma insulin levels upon intraperitoneal glucose challenge in Gα(i2)(-/-) and Gα(i2)(βcko) mice, whereas plasma glucose concentrations were unchanged in Gα(i2)(-/-) but significantly increased in Gα(i2)(βcko) mice. These findings indicate a novel albeit unexpected role for Gα(i2) in the expression, turnover, and/or release of insulin from islets. Detection of insulin secretion in isolated islets did not show differences in response to high (16 mM) glucose concentrations between control and β-cell-specific Gα(i2)-deficient mice. In contrast, the two- to threefold increase in insulin secretion evoked by L-arginine or L-ornithine (in the presence of 16 mM glucose) was significantly reduced in islets lacking Gα(i2). In accord with a reduced level of insulin secretion, intracellular calcium concentrations induced by the agonistic amino acid L-arginine did not reach control levels in β-cells. The presented analysis of gene-targeted mice provides novel insights in the role of β-cell Gα(i2) showing that amino acid-induced insulin-release depends on Gα(i2).
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MESH Headings
- Animals
- Arginine/metabolism
- Blood Glucose/analysis
- Calcium Signaling
- Crosses, Genetic
- Down-Regulation
- Fluorescent Antibody Technique
- GTP-Binding Protein alpha Subunit, Gi2/agonists
- GTP-Binding Protein alpha Subunit, Gi2/genetics
- GTP-Binding Protein alpha Subunit, Gi2/metabolism
- GTP-Binding Protein alpha Subunits, Gi-Go/agonists
- GTP-Binding Protein alpha Subunits, Gi-Go/genetics
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Hyperglycemia/blood
- Hyperglycemia/metabolism
- Hyperglycemia/prevention & control
- Hypoglycemia/blood
- Hypoglycemia/metabolism
- Hypoglycemia/prevention & control
- Insulin/blood
- Insulin/metabolism
- Insulin Secretion
- Islets of Langerhans/cytology
- Islets of Langerhans/metabolism
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Ornithine/blood
- Ornithine/metabolism
- Specific Pathogen-Free Organisms
- Tissue Culture Techniques
- Up-Regulation
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Affiliation(s)
- Veronika Leiss
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Katarina Flockerzie
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Ana Novakovic
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Michaela Rath
- Department of Experimental Diabetology, German Institute of Human Nutrition, Potsdam-Rehbrücke, Nuthetal, Germany
| | - Annika Schönsiegel
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health/Department of Health and Human Services, Durham, North Carolina
| | - Annette Schürmann
- Department of Experimental Diabetology, German Institute of Human Nutrition, Potsdam-Rehbrücke, Nuthetal, Germany
| | - Christian Harteneck
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Bernd Nürnberg
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany;
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9
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Kyriazis GA, Smith KR, Tyrberg B, Hussain T, Pratley RE. Sweet taste receptors regulate basal insulin secretion and contribute to compensatory insulin hypersecretion during the development of diabetes in male mice. Endocrinology 2014; 155:2112-21. [PMID: 24712876 PMCID: PMC4020927 DOI: 10.1210/en.2013-2015] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
β-Cells rapidly secrete insulin in response to acute increases in plasma glucose but, upon further continuous exposure to glucose, insulin secretion progressively decreases. Although the mechanisms are unclear, this mode of regulation suggests the presence of a time-dependent glucosensory system that temporarily attenuates insulin secretion. Interestingly, early-stage β-cell dysfunction is often characterized by basal (ie, fasting) insulin hypersecretion, suggesting a disruption of these related mechanisms. Because sweet taste receptors (STRs) on β-cells are implicated in the regulation of insulin secretion and glucose is a bona fide STR ligand, we tested whether STRs mediate this sensory mechanism and participate in the regulation of basal insulin secretion. We used mice lacking STR signaling (T1R2(-/-) knockout) and pharmacologic inhibition of STRs in human islets. Mouse and human islets deprived of STR signaling hypersecrete insulin at short-term fasting glucose concentrations. Accordingly, 5-hour fasted T1R2(-/-) mice have increased plasma insulin and lower glucose. Exposure of isolated wild-type islets to elevated glucose levels reduced STR expression, whereas islets from diabetic (db/db) or diet-induced obese mouse models show similar down-regulation. This transcriptional reprogramming in response to hyperglycemia correlates with reduced STR function in these mouse models, leading to insulin hypersecretion. These findings reveal a novel mechanism by which insulin secretion is physiologically regulated by STRs and also suggest that, during the development of diabetes, STR function is compromised by hyperglycemia leading to hyperinsulinemia. These observations further suggest that STRs might be a promising therapeutic target to prevent and treat type 2 diabetes.
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Affiliation(s)
- George A Kyriazis
- Diabetes and Obesity Research Center (G.A.K., K.R.S., B.T., T.H., R.E.P.) Sanford-Burnham Medical Research Institute, Orlando, Florida 32827; Translational Research Institute for Metabolism and Diabetes (G.A.K., R.E.P.), Florida Hospital, Orlando, Florida 32804; and Translational Science (B.T.), Cardiovascular and Metabolic Disease, Mölndal, AstraZeneca, Sweden
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10
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Mikami S, Kitamura S, Negoro N, Sasaki S, Suzuki M, Tsujihata Y, Miyazaki T, Ito R, Suzuki N, Miyazaki J, Santou T, Kanzaki N, Funami M, Tanaka T, Yasuma T, Momose Y. Discovery of phenylpropanoic acid derivatives containing polar functionalities as potent and orally bioavailable G protein-coupled receptor 40 agonists for the treatment of type 2 diabetes. J Med Chem 2012; 55:3756-76. [PMID: 22428944 DOI: 10.1021/jm2016123] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As part of a program to identify potent GPR40 agonists with drug-like properties suitable for clinical development, the incorporation of polar substituents was explored with the intention of decreasing the lipophilicity of our recently disclosed phenylpropanoic acid derivative 1. This incorporation would allow us to mitigate the cytotoxicity issues observed with compound 1 and enable us to move away from the multifunctional free fatty acid-like structure. Substitutions on the 2',6'-dimethylbiphenyl ring were initially undertaken, which revealed the feasibility of introducing polar functionalities at the biphenyl 4'-position. Further optimization of this position and the linker led to the discovery of several 4'-alkoxybiphenyl derivatives, which showed potent GPR40 agonist activities with the best balance in terms of improved cytotoxicity profiles and favorable pharmacokinetic properties. Among them, 3-{2-fluoro-4-[({4'-[(4-hydroxy-1,1-dioxidotetrahydro-2H-thiopyran-4-yl)methoxy]-2',6'-dimethylbiphenyl-3-yl}methyl)amino]phenyl}propanoic acid (35) exhibited a robust plasma glucose-lowering effect and insulinotropic action during an oral glucose tolerance test in rats with impaired glucose tolerance.
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Affiliation(s)
- Satoshi Mikami
- Pharmaceutical Research Division, Takeda Pharmaceutical Company, Ltd., 26-1 Muraoka-higashi, 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
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11
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Wang Y, Park S, Bajpayee NS, Nagaoka Y, Boulay G, Birnbaumer L, Jiang M. Augmented glucose-induced insulin release in mice lacking G(o2), but not G(o1) or G(i) proteins. Proc Natl Acad Sci U S A 2011; 108:1693-8. [PMID: 21220323 PMCID: PMC3029743 DOI: 10.1073/pnas.1018903108] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Insulin secretion by pancreatic β cells is a complex and highly regulated process. Disruption of this process can lead to diabetes mellitus. One of the various pathways involved in the regulation of insulin secretion is the activation of heterotrimeric G proteins. Bordetella pertussis toxin (PTX) promotes insulin secretion, suggesting the involvement of one or more of three G(i) and/or two G(o) proteins as suppressors of insulin secretion from β cells. However, neither the mechanism of this inhibitory modulation of insulin secretion nor the identity of the G(i/o) proteins involved has been elucidated. Here we show that one of the two splice variants of G(o), G(o2), is a key player in the control of glucose-induced insulin secretion by β cells. Mice lacking G(o2)α, but not those lacking α subunits of either G(o1) or any G(i) proteins, handle glucose loads more efficiently than wild-type (WT) mice, and do so by increased glucose-induced insulin secretion. We thus provide unique genetic evidence that the G(o2) protein is a transducer in an inhibitory pathway that prevents damaging oversecretion of insulin.
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Affiliation(s)
- Ying Wang
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095; and
| | - Sangeun Park
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095; and
| | - Neil S. Bajpayee
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095; and
| | - Yoshiko Nagaoka
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095; and
| | - Guylain Boulay
- Laboratory of Neurobiology, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
| | - Meisheng Jiang
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095; and
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12
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Yamazaki H, Zawalich KC, Zawalich WS. Physiologic implications of phosphoinositides and phospholipase C in the regulation of insulin secretion. J Nutr Sci Vitaminol (Tokyo) 2010; 56:1-8. [PMID: 20354339 DOI: 10.3177/jnsv.56.1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The secretion of insulin from the pancreatic beta-cell must be commensurate to satisfy the insulin requirements of the organism. This cell has a great flexibility to meet these requirements which are increased not only by the ingestion of nutrients (increase of plasma glucose) but also by the sensitivity of target tissues to insulin as well. The insulin secretion is a complex biochemical event regulated by a host of potential second messenger molecules acting alone or in concert. These events include the cation calcium, which gains access to the beta-cell via the opening of voltage-regulated channels, cAMP and phosphoinositide-derived second messenger molecules, generated as a consequence of phospholipase C (PLC) activation. In this review, we focused on phosphoinositides, PLC/Phosphokinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) cascade in the regulation of insulin secretion. We also described our studies on the mechanism of the beta-cell desensitization using perifused islets. It is suggested that a failure of the signaling events contribute to the pathogenesis of diabetes in which the beta-cell can no longer secrete the required amounts of insulin. It has been observed that chronic exposure to high glucose desensitizes the beta-cells to subsequent stimulation. We suggested that the failure of PLC activation can be attributed in the impairment of insulin secretion by chronic sustained glucose exposure. It may contribute to the vicious circle of impaired insulin secretion leading up to diabetes.
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Affiliation(s)
- Hanae Yamazaki
- Laboratory of Ajinomoto Integrative Research for Advanced Dieting, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
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13
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Malmgren S, Nicholls DG, Taneera J, Bacos K, Koeck T, Tamaddon A, Wibom R, Groop L, Ling C, Mulder H, Sharoyko VV. Tight coupling between glucose and mitochondrial metabolism in clonal beta-cells is required for robust insulin secretion. J Biol Chem 2009; 284:32395-404. [PMID: 19797055 DOI: 10.1074/jbc.m109.026708] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The biochemical mechanisms underlying glucose-stimulated insulin secretion from pancreatic beta-cells are not completely understood. To identify metabolic disturbances in beta-cells that impair glucose-stimulated insulin secretion, we compared two INS-1-derived clonal beta-cell lines, which are glucose-responsive (832/13 cells) or glucose-unresponsive (832/2 cells). To this end, we analyzed a number of parameters in glycolytic and mitochondrial metabolism, including mRNA expression of genes involved in cellular energy metabolism. We found that despite a marked impairment of glucose-stimulated insulin secretion, 832/2 cells exhibited a higher rate of glycolysis. Still, no glucose-induced increases in respiratory rate, ATP production, or respiratory chain complex I, III, and IV activities were seen in the 832/2 cells. Instead, 832/2 cells, which expressed lactate dehydrogenase A, released lactate regardless of ambient glucose concentrations. In contrast, the glucose-responsive 832/13 line lacked lactate dehydrogenase and did not produce lactate. Accordingly, in 832/2 cells mRNA expression of genes for glycolytic enzymes were up-regulated, whereas mitochondria-related genes were down-regulated. This could account for a Warburg-like effect in the 832/2 cell clone, lacking in 832/13 cells as well as primary beta-cells. In human islets, mRNA expression of genes such as lactate dehydrogenase A and hexokinase I correlated positively with HbA(1c) levels, reflecting perturbed long term glucose homeostasis, whereas that of Slc2a2 (glucose transporter 2) correlated negatively with HbA(1c) and thus better metabolic control. We conclude that tight metabolic regulation enhancing mitochondrial metabolism and restricting glycolysis in 832/13 cells is required for clonal beta-cells to secrete insulin robustly in response to glucose. Moreover, a similar expression pattern of genes controlling glycolytic and mitochondrial metabolism in clonal beta-cells and human islets was observed, suggesting that a similar prioritization of mitochondrial metabolism is required in healthy human beta-cells. The 832 beta-cell lines may be helpful tools to resolve metabolic perturbations occurring in Type 2 diabetes.
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Affiliation(s)
- Siri Malmgren
- Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Lund University Diabetes Centre, 205 02 Malmö, Sweden
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14
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Zawalich WS, Zawalich KC. Enhanced activation of phospholipase C and insulin secretion from islets incubated in fatty acid-free bovine serum albumin. Metabolism 2008; 57:290-8. [PMID: 18191063 PMCID: PMC2275802 DOI: 10.1016/j.metabol.2007.09.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 09/28/2007] [Indexed: 11/18/2022]
Abstract
Incubation in 100 micromol/L fatty acid-free bovine serum albumin (FAF-BSA) significantly amplifies insulin secretion from isolated, perifused rat islets. When compared with the responses of control islets incubated in 100 micromol/L radioimmunoassay-grade BSA, insulin secretion rates were increased 2- to 3-fold when these islets were stimulated with 10 mmol/L glucose alone or with the combination of 10 mmol/L glucose, 15 mmol/L KCl, and 100 micromol/L diazoxide. These amplified secretory responses were paralleled by significant increases in the phospholipase C (PLC) activation monitored by fractional increases in (3)H-inositol efflux from these same islets. Amplified PLC responses were also observed with the cholinergic agonist carbachol (50 micromol/L). No differences in the secretory responses to the protein kinase C activator phorbol 12-myristate 13-acetate (200 nmol/L) could be detected between control and FAF-BSA-pretreated rat islets. Mouse islets were also immune to the amplifying impact of this treatment protocol. These findings demonstrate that short-term incubation in FAF-BSA significantly augments the activation of PLC in rat islets by a number of agonists. This proximal event provides the impetus for the distal activation of protein kinase C. If applicable to human islets, this manipulation may provide a mechanism to enhance the secretory responses from islets destined for transplantation, thus improving their in vivo secretory capacity.
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15
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Zawalich WS, Yamazaki H, Zawalich KC. Biphasic insulin secretion from freshly isolated or cultured, perifused rodent islets: comparative studies with rats and mice. Metabolism 2008; 57:30-9. [PMID: 18078856 PMCID: PMC2214880 DOI: 10.1016/j.metabol.2007.07.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 07/23/2007] [Indexed: 11/19/2022]
Abstract
In the present report, we compared the insulin secretory responses of freshly isolated, perifused rat and mouse islets to glucose. Prestimulatory glucose levels were changed to assess their influence on the subsequent secretory responses. Additional studies included experiments with the incretin factor glucagon-like peptide-1 (GLP-1), the cholinergic agonist carbachol, and the alpha2 agonist epinephrine. Our findings demonstrate that under conditions where glucose (8.5-11.1 mmol/L) evokes a dramatic biphasic insulin secretory response from perifused rat islets, mouse islets exhibit little response. Increasing the prestimulatory glucose level to 8.5 mmol/L dramatically distorts subsequently measured glucose-induced insulin secretion from rat islets but allows the evocation of a modest but clear biphasic response from mouse islets in response to 30 mmol/L, but not 11.1 or 16.7 mmol/L, glucose. In the presence of a minimally effective glucose level (10 mmol/L), mouse islets remain exquisitely sensitive to the combined stimulatory effects of GLP-1 (2.5 nmol/L) plus carbachol (0.5 micromol/L) and to the inhibitory influence of epinephrine (10 nmol/L). Short-term culture of rat islets in CMRL 1066 containing 5.6 mmol/L glucose resulted in a significant decrease in the secretory response to 11.1 mmol/L glucose, whereas the same manipulation improved mouse islet responses. It is concluded that the process of collagenase isolating islets does not alter mouse islet sensitivity in any adverse way and that increasing the prestimulatory glucose level can indeed alter the pattern of insulin secretion in either a positive or negative manner depending upon the species being investigated. Prior short-term culture of rodent islets differentially affects secretion from these 2 species.
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16
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Yamazaki H, Zawalich KC, Zawalich WS. Desensitization of the pancreatic beta-cell: effects of sustained physiological hyperglycemia and potassium. Am J Physiol Endocrinol Metab 2006; 291:H1381-7. [PMID: 16868227 DOI: 10.1152/ajpendo.00137.2006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The impact of modest but prolonged (3 h) exposure to high physiological glucose concentrations and hyperkalemia on the insulin secretory and phospholipase C (PLC) responses of rat pancreatic islets was determined. In acute studies, glucose (5-20 mM) caused a dose-dependent increase in secretion with maximal release rates 25-fold above basal secretion. When measured after 3 h of exposure to 5-10 mM glucose, subsequent stimulation of islets with 10-20 mM glucose during a dynamic perifusion resulted in dose-dependent decrements in secretion and PLC activation. Acute hyperkalemia (15-30 mM) stimulated calcium-dependent increases in both insulin secretion and PLC activation; however, prolonged hyperkalemia resulted in a biochemical and secretory lesion similar to that induced by sustained modest hyperglycemia. Glucose- (8 mM) desensitized islets retained significant sensitivity to stimulation by either carbachol or glucagon-like peptide-1. These findings emphasize the vulnerability of the beta-cell to even moderate sustained hyperglycemia and provide a biochemical rationale for achieving tight glucose control in diabetic patients. They also suggest that PLC activation plays a critically important role in the physiological regulation of glucose-induced secretion and in the desensitization of release that follows chronic hyperglycemia or hyperkalemia.
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Affiliation(s)
- Hanae Yamazaki
- Yale University School of Nursing, New Haven, CT 06536-0740, USA
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17
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Yamazaki H, Philbrick W, Zawalich KC, Zawalich WS. Acute and chronic effects of glucose and carbachol on insulin secretion and phospholipase C activation: studies with diazoxide and atropine. Am J Physiol Endocrinol Metab 2006; 290:E26-E33. [PMID: 16105864 DOI: 10.1152/ajpendo.00149.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The acute and chronic effects of 20 mM glucose and 10 microM carbachol on beta-cell responses were investigated. Acute exposure of rat islets to 20 mM glucose increased glucose usage rates and resulted in a large insulin-secretory response during a dynamic perifusion. The secretory, but not the metabolic, effect of 20 mM glucose was abolished by simultaneous exposure to 100 microM diazoxide. Glucose (20 mM) significantly increased inositol phosphate (IP) accumulation, an index of phospholipase C (PLC) activation, from [(3)H]inositol-prelabeled islets. Diazoxide, but not atropine, abolished this effect as well. Unlike 20 mM glucose, 10 microM carbachol (in the presence of 5 mM glucose) increased IP accumulation but had no effect on insulin secretion or glucose (5 mM) metabolism. The IP effect was abolished by 50 microM atropine but not by diazoxide. Chronic 3-h exposure of islets to 20 mM glucose or 10 microM carbachol profoundly reduced both the insulin-secretory and PLC responses to a subsequent 20 mM glucose stimulus. The adverse effects of chronic glucose exposure were abolished by diazoxide but not by atropine. In contrast, the adverse effects of carbachol were abolished by atropine but not by diazoxide. Prior 3 h of exposure to 20 mM glucose or carbachol had no inhibitory effect on glucose metabolism. Significant secretory responses could be evoked from 20 mM glucose- or carbachol-pretreated islets by the inclusion of forskolin. These findings support the concept that an early event in the evolution of beta-cell desensitization is the impaired activation of islet PLC.
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Affiliation(s)
- Hanae Yamazaki
- Yale University School of Nursing, New Haven, CT 06536-0740, USA
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18
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Tamarina NA, Kuznetsov A, Rhodes CJ, Bindokas VP, Philipson LH. Inositol (1,4,5)-trisphosphate dynamics and intracellular calcium oscillations in pancreatic beta-cells. Diabetes 2005; 54:3073-81. [PMID: 16249428 DOI: 10.2337/diabetes.54.11.3073] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucose-stimulated insulin secretion is associated with transients of intracellular calcium concentration ([Ca2+]i) in the pancreatic beta-cell. We tested the hypothesis that inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] [Ca2+]i release is incorporated in glucose-induced [Ca2+]i oscillations in mouse islets and MIN6 cells. We found that depletion of intracellular Ca2+ stores with thapsigargin increased the oscillation frequency by twofold and inhibited the slow recovery phase of [Ca2+]i oscillations. We employed a pleckstrin homology domain-containing fluorescent biosensor, phospholipase C partial differential pleckstrin homology domain-enhanced green fluorescent protein, to visualize Ins(1,4,5)P3 dynamics in insulin-secreting MIN6 cells and mouse islets in real time using a video-rate confocal system. In both types of cells, stimulation with carbamoylcholine (CCh) and depolarization with KCl results in an increase in Ins(1,4,5)P3 accumulation in the cytoplasm. When stimulated with glucose, the Ins(1,4,5)P3 concentration in the cytoplasm oscillates in parallel with oscillations of [Ca2+]i. Maximal accumulation of Ins(1,4,5)P3 in these oscillations coincides with the peak of [Ca2+]i and tracks changes in frequencies induced by the voltage-gated K+ channel blockade. We show that Ins(1,4,5)P3 release in insulin-secreting cells can be stimulated by depolarization-induced Ca2+ flux. We conclude that Ins(1,4,5)P3 concentration oscillates in parallel with [Ca2+]i in response to glucose stimulation, but it is not the driving force for [Ca2+]i oscillations.
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Affiliation(s)
- Natalia A Tamarina
- Department of Medicine, MC 1027, University of Chicago, Chicago, IL 60637, USA
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19
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Johnson DE, Yamazaki H, Ward KM, Schmidt AW, Lebel WS, Treadway JL, Gibbs EM, Zawalich WS, Rollema H. Inhibitory effects of antipsychotics on carbachol-enhanced insulin secretion from perifused rat islets: role of muscarinic antagonism in antipsychotic-induced diabetes and hyperglycemia. Diabetes 2005; 54:1552-8. [PMID: 15855345 DOI: 10.2337/diabetes.54.5.1552] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Treatment with the atypical antipsychotics olanzapine and clozapine has been associated with an increased risk for deterioration of glucose homeostasis, leading to hyperglycemia, ketoacidosis, and diabetes, in some cases independent of weight gain. Because these events may be a consequence of their ability to directly alter insulin secretion from pancreatic beta-cells, we determined the effects of several antipsychotics on cholinergic- and glucose-stimulated insulin secretion from isolated rat islets. At concentrations encompassing therapeutically relevant levels, olanzapine and clozapine reduced insulin secretion stimulated by 10 micromol/l carbachol plus 7 mmol/l glucose. This inhibition of insulin secretion was paralleled by significant reductions in carbachol-potentiated inositol phosphate accumulation. In contrast, risperidone or ziprasidone had no adverse effect on cholinergic-induced insulin secretion or inositol phosphate accumulation. None of the compounds tested impaired the islet secretory responses to 8 mmol/l glucose alone. Finally, in vitro binding and functional data show that olanzapine and clozapine (unlike risperidone, ziprasidone, and haloperidol) are potent muscarinic M3 antagonists. These findings demonstrate that low concentrations of olanzapine and clozapine can markedly and selectively impair cholinergic-stimulated insulin secretion by blocking muscarinic M3 receptors, which could be one of the contributing factors to their higher risk for producing hyperglycemia and diabetes in humans.
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Affiliation(s)
- David E Johnson
- Pfizer Global Research and Development, Department of Neuroscience, Groton Laboratories, MS 8220-4159, Eastern Point Road, Groton, CT 06340, USA
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20
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Aizawa T, Komatsu M. Rab27a: a new face in beta cell metabolism-secretion coupling. J Clin Invest 2005; 115:227-30. [PMID: 15690078 PMCID: PMC546431 DOI: 10.1172/jci24269] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In pancreatic beta cells, not only insulin exocytosis per se, but translocation of beta granules toward the plasma membrane--an event upstream of exocytosis--are under the control of glucose. However, the molecular basis of this translocation has been poorly understood. Rab27a-mediated translocation of glucose-induced beta granules is reported in this issue of the JCI. Rab27a or its effector molecule may constitute a novel pharmacological target because potentiation of the Rab27a pathway is expected to restore beta cell glucose competency in patients with diabetes mellitus.
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Affiliation(s)
- Toru Aizawa
- Center for Health, Safety, and Environmental Management and Graduate School of Medicine, Department of Aging Medicine and Geriatrics, Shinshu University, Matsumoto, Japan.
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21
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Mari A, Gastaldelli A, Natali A, Ostergard T, Schmitz O, Ferrannini E. Characterization of beta-cell function impairment in first-degree relatives of type 2 diabetic subjects: modeling analysis of 24-h triple-meal tests. Am J Physiol Endocrinol Metab 2005; 288:E541-6. [PMID: 15522997 DOI: 10.1152/ajpendo.00175.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate early secretory defects in prediabetes, we evaluated beta-Cell function and insulin sensitivity (M value, by euglycemic clamp) in 26 normotolerant first-degree relatives of type 2 diabetic patients (FDR) and 17 age- and weight-matched control subjects. beta-Cell function was assessed by modeling analysis of glucose and C-peptide concentrations measured during 24 h of standardized living conditions. Fasting and total insulin secretion (ISR) were increased in FDR, as was ISR at a reference 5 mM glucose level (ISR5, 107 +/- 6 vs. 87 +/- 6 pmol x min(-1) x m(-2), P < 0.05). ISR5 was inversely related to M in controls (ISR5 = k/M1.23, rho = -0.74, P < 0.005) but not in FDR; when M was accounted for (by calculating a compensation index ISR5 x M1.23), compensation for insulin resistance was impaired in FDR (10.8 +/- 1.0 vs. 13.4 +/- 0.6 units, P < 0.05). Potentiation of ISR, expressing relative transient increases in glucose-stimulated ISR during meals, was impaired in FDR (1.29 +/- 0.08 vs. 1.62 +/- 0.08 during 1st meal, P < 0.02). Moreover, the potentiation time course was related to glucose-dependent insulin-releasing polypeptide (GIP) concentrations in both groups, and the sensitivity of potentiation to GIP derived from this relationship tended to be impaired in FDR. Compensation index, potentiation, and sensitivity to GIP were interrelated parameters (P < 0.05 or less). beta-Cell function parameters were also related to mean 24-h glucose levels (r2 = 0.63, P < 0.0001, multivariate model). In conclusion, although in absolute terms ISR is increased in insulin-resistant FDR, beta-cell function shows a cluster of interrelated abnormalities involving compensation for insulin resistance, potentiation, and sensitivity to GIP, suggesting a beta-cell defect in the amplifying pathway of insulin secretion.
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Affiliation(s)
- Andrea Mari
- Consiglio Nazionale delle Ricerche Institute of Biomedical Engineering, Padua, Italy.
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22
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Straub SG, Sharp GWG. Massive augmentation of stimulated insulin secretion induced by fatty acid-free BSA in rat pancreatic islets. Diabetes 2004; 53:3152-8. [PMID: 15561945 DOI: 10.2337/diabetes.53.12.3152] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Incubation of rat pancreatic islets for 4-6 h with 100 micromol/l fatty acid-free BSA induced a 3- to 10-fold enhancement of insulin release to a subsequent challenge with 16.7 mmol/l glucose, without changing the typical biphasic pattern of the response. A similar enhancement was observed with other stimuli, such as leucine, depolarizing concentrations of KCl and tolbutamide, pointing to a general phenomenon and common mechanism for the augmentation. Norepinephrine completely blocked the stimulated response. The protein kinase C (PKC) inhibitor Ro 31-8220, which acts at the ATP-binding site and inhibits all PKC isoforms, strongly inhibited the enhancement of a subsequent glucose challenge when present during the BSA pretreatment period. In contrast, Go 6976, an inhibitor of conventional PKC isoforms, was without effect, even at the high concentration of 1 micromol/l. Preincubation with calphostin C, which competes for the diacylglycerol (DAG)-binding site, therefore inhibiting conventional, novel, and PKC isoforms of the PKD type, completely abolished the enhancing effect of the BSA but did not affect secretion in islets treated with 10 micromol/l fatty acid-free BSA. We conclude that the remarkable enhancement of insulin release is due to a change in glucose signaling and activation of a novel PKC isoform or a DAG-binding protein.
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Affiliation(s)
- Susanne G Straub
- Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
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23
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Winzell MS, Pacini G, Wollheim CB, Ahrén B. Beta-cell-targeted expression of a dominant-negative mutant of hepatocyte nuclear factor-1alpha in mice: diabetes model with beta-cell dysfunction partially rescued by nonglucose secretagogues. Diabetes 2004; 53 Suppl 3:S92-6. [PMID: 15561929 DOI: 10.2337/diabetes.53.suppl_3.s92] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We studied islet function in mice with beta-cell-targeted expression of a dominant-negative mutant of hepatocyte nuclear factor (HNF)-1alpha. At age 2-3 months, anesthetized transgenic and wild-type male mice underwent an intravenous glucose (1 g/kg) tolerance test (IVGTT). It was found that transgenic mice had an abolished insulin response in association with severe glucose intolerance. In other tests, the 5-min insulin response to intravenous arginine was impaired by 79% (P=0.032) and the 15-min insulin response to gastric glucose was suppressed by 97% (P=0.006). In islets incubated for 60 min, the insulin response to glucose (3.3-22.2 mmol/l) was impaired by >80% in transgenic mice. In contrast, insulin responses to nonglucose secretagogues were only partially suppressed (to GLP-1 [100 nmol/l] by 40%, to carbachol [1 micromol/l] by 20%, and to palmitate [0.5 mmol/l] by 15%), whereas the response to depolarization by KCl (50 mmol/l) was not reduced. Finally, the IVGTT data insulin sensitivity in transgenic mice was not significantly different from that of wild-type mice. Thus, mice with targeted suppression of beta-cell HNF-1alpha represent a good diabetes model exhibiting severely impaired insulin secretion after glucose with marked glucose intolerance. In contrast, the insulin responses to nonglucose stimuli are not suppressed when the islet insulin content is taken into account.
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24
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Ramanadham S, Song H, Hsu FF, Zhang S, Crankshaw M, Grant GA, Newgard CB, Bao S, Ma Z, Turk J. Pancreatic islets and insulinoma cells express a novel isoform of group VIA phospholipase A2 (iPLA2 beta) that participates in glucose-stimulated insulin secretion and is not produced by alternate splicing of the iPLA2 beta transcript. Biochemistry 2004; 42:13929-40. [PMID: 14636061 PMCID: PMC3716001 DOI: 10.1021/bi034843p] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Many cells express a group VIA 84 kDa phospholipase A(2) (iPLA(2)beta) that is sensitive to inhibition by a bromoenol lactone (BEL) suicide substrate. Inhibition of iPLA(2)beta in pancreatic islets and insulinoma cells suppresses, and overexpression of iPLA(2)beta in INS-1 insulinoma cells amplifies, glucose-stimulated insulin secretion, suggesting that iPLA(2)beta participates in secretion. Western blotting analyses reveal that glucose-responsive 832/13 INS-1 cells express essentially no 84 kDa iPLA(2)beta-immunoreactive protein but predominantly express a previously unrecognized immunoreactive iPLA(2)beta protein in the 70 kDa region that is not generated by a mechanism of alternate splicing of the iPLA(2)beta transcript. To determine if the 70 kDa-immunoreactive protein is a short isoform of iPLA(2)beta, protein from the 70 kDa region was digested with trypsin and analyzed by mass spectrometry. Such analyses reveal several peptides with masses and amino acid sequences that exactly match iPLA(2)beta tryptic peptides. Peptide sequences identified in the 70 kDa tryptic digest include iPLA(2)beta residues 7-53, suggesting that the N-terminus is preserved. We also report here that the 832/13 INS-1 cells express iPLA(2)beta catalytic activity and that BEL inhibits secretagogue-stimulated insulin secretion from these cells but not the incorporation of arachidonic acid into membrane PC pools of these cells. These observations suggest that the catalytic iPLA(2)beta activity expressed in 832/13 INS-1 cells is attributable to a short isoform of iPLA(2)beta and that this isoform participates in insulin secretory but not in membrane phospholipid remodeling pathways. Further, the finding that pancreatic islets also express predominantly a 70 kDa iPLA(2)beta-immunoreactive protein suggests that a signal transduction role of iPLA(2)beta in the native beta-cell might be attributable to a 70 kDa isoform of iPLA(2)beta.
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Affiliation(s)
- Sasanka Ramanadham
- Mass Spectrometry Resource, Division of Endocrinology, Diabetes, and Metabolism, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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25
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Yaney GC, Corkey BE. Fatty acid metabolism and insulin secretion in pancreatic beta cells. Diabetologia 2003; 46:1297-312. [PMID: 13680127 DOI: 10.1007/s00125-003-1207-4] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Revised: 07/14/2003] [Indexed: 01/16/2023]
Abstract
Increases in glucose or fatty acids affect metabolism via changes in long-chain acyl-CoA formation and chronically elevated fatty acids increase total cellular CoA. Understanding the response of pancreatic beta cells to increased amounts of fuel and the role that altered insulin secretion plays in the development and maintenance of obesity and Type 2 diabetes is important. Data indicate that the activated form of fatty acids acts as an effector molecule in stimulus-secretion coupling. Glucose increases cytosolic long-chain acyl-CoA because it increases the "switch" compound malonyl-CoA that blocks mitochondrial beta-oxidation, thus implementing a shift from fatty acid to glucose oxidation. We present arguments in support of the following: (i) A source of fatty acid either exogenous or endogenous (derived by lipolysis of triglyceride) is necessary to support normal insulin secretion; (ii) a rapid increase of fatty acids potentiates glucose-stimulated secretion by increasing fatty acyl-CoA or complex lipid concentrations that act distally by modulating key enzymes such as protein kinase C or the exocytotic machinery; (iii) a chronic increase of fatty acids enhances basal secretion by the same mechanism, but promotes obesity and a diminished response to stimulatory glucose; (iv) agents which raise cAMP act as incretins, at least in part, by stimulating lipolysis via beta-cell hormone-sensitive lipase activation. Furthermore, increased triglyceride stores can give higher rates of lipolysis and thus influence both basal and stimulated insulin secretion. These points highlight the important roles of NEFA, LC-CoA, and their esterified derivatives in affecting insulin secretion in both normal and pathological states.
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Affiliation(s)
- G C Yaney
- Boston University School of Medicine, Obesity Research Center, 650 Albany Street, Boston, MA 02118, USA
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26
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Miguel JC, Abdel-Wahab YHA, Green BD, Mathias PCF, Flatt PR. Cooperative enhancement of insulinotropic action of GLP-1 by acetylcholine uncovers paradoxical inhibitory effect of beta cell muscarinic receptor activation on adenylate cyclase activity. Biochem Pharmacol 2003; 65:283-92. [PMID: 12504804 DOI: 10.1016/s0006-2952(02)01482-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The cooperative effect of glucagon-like peptide 1 (GLP-1) and acetylcholine (ACh) was evaluated in a beta cell line model (BRIN BD11). GLP-1 (20 nM) and ACh (100 microM) increased insulin secretion by 24-47%, whereas in combination there was a further 89% enhancement of insulin release. Overnight culture with 100 ng/mL pertussis toxin (PTX) or 10nM PMA significantly reduced the combined insulinotropic action (P<0.05 and P<0.001, respectively) and the sole stimulatory effects of GLP-1 (PTX treatment; P<0.01) or ACh (PMA treatment; P<0.05). Under control conditions, ACh (50nM-1mM) concentration-dependently inhibited by up to 40% (P<0.001) the 10-fold (P<0.001) elevation of cyclic 3',5'-adenosine monophosphate (cAMP) induced by 20 nM GLP-1. The paradoxical inhibitory action of ACh was abolished by PTX pre-treatment, suggesting involvement of G(i) and/or G(o) G protein alpha subunit. Effects of selective muscarinic receptor antagonists on the concentration-dependent insulinotropic actions of ACh (50 nM-1 mM) on 20 nM GLP-1 induced insulin secretion revealed inhibition by rho-FHHSiD (M3 antagonist, P<0.05), stimulation with pirenzepine (M1 antagonist, P<0.001) and no significant effects of either methoctramine (M2 antagonist) or MT-3 (M4 antagonist). Antagonism of M2, M3 and M4 muscarinic receptor effects with methoctramine (3-100 nM), rho-FHHSiD (3-30 nM) or MT-3 (10-300 nM) did not significantly affect the inhibitory action of ACh on GLP-1 stimulated cAMP production. In contrast, M1 receptor antagonism with pirenzepine (3-30 0nM) resulted in a concentration-dependent decrease in the inhibitory action of ACh on GLP-1 stimulated cAMP production (P<0.001). These data indicate an important functional cooperation between the cholinergic neurotransmitter ACh and the incretin hormone GLP-1 on insulin secretion mediated through the M3 muscarinic receptor subtype. However, the insulinotropic action of ACh was associated with a paradoxical inhibitory effect on GLP-1 stimulated cAMP production, achieved through a novel PTX- and pirenzepine-sensitive M1 muscarinic receptor activated pathway. An imbalance between these pathways may contribute to dysfunctional insulin secretion.
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Affiliation(s)
- João C Miguel
- School of Biomedical Sciences, University of Ulster, Coleraine, Co Londonderry, Northern Ireland, BT52 1SA, UK.
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27
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Barker CJ, Leibiger IB, Leibiger B, Berggren PO. Phosphorylated inositol compounds in beta -cell stimulus-response coupling. Am J Physiol Endocrinol Metab 2002; 283:E1113-22. [PMID: 12424101 DOI: 10.1152/ajpendo.00088.2002] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pancreatic beta-cell function is essential for the regulation of glucose homeostasis in humans, and its impairment leads to the development of type 2 diabetes. Inputs from glucose and cell surface receptors act together to initiate the beta-cell stimulus-response coupling that ultimately leads to the release of insulin. Phosphorylated inositol compounds have recently emerged as key players at all levels of the stimulus-secretion coupling process. In this current review, we seek to highlight recent advances in beta-cell phosphoinositide research by dividing our examination into two sections. The first involves the events that lead to insulin secretion. This includes both new roles for inositol polyphosphates, particularly inositol hexakisphosphate, and both conventional and 3-phosphorylated inositol lipids. In the second section, we deal with the more novel concept of the autocrine role of insulin. Here, released insulin initiates signal transduction cascades, principally through the activity of phosphatidylinositol 3-kinase. This new round of signal transduction has been established to activate key beta-cell genes, particularly the insulin gene itself. More controversially, this insulin feedback has also been suggested to either terminate or enhance insulin secretion events.
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Affiliation(s)
- Christopher J Barker
- Department of Molecular Medicine, The Rolf Luft Center for Diabetes Research, Karolinska Institutet, S-171 76 Stockholm, Sweden
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28
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Yaney GC, Fairbanks JM, Deeney JT, Korchak HM, Tornheim K, Corkey BE. Potentiation of insulin secretion by phorbol esters is mediated by PKC-alpha and nPKC isoforms. Am J Physiol Endocrinol Metab 2002; 283:E880-8. [PMID: 12376314 DOI: 10.1152/ajpendo.00474.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Culturing clonal beta-cells (HIT-T15) overnight in the presence of phorbol ester [phorbol myristate acetate (PMA)] enhanced insulin secretion while causing downregulation of some protein kinase C (PKC) isoforms and most PKC activity. We show here that this enhanced secretion required the retention of PMA in the cell. Hence, it could not be because of long-lived phosphorylation of cellular substrates by the isoforms that were downregulated, namely PKC-alpha, -betaII, and -epsilon, but could be because of the continued activation of the two remaining diacylglycerol-sensitive isoforms delta and mu. The enhanced secretion did not involve changes in glucose metabolism, cell membrane potential, or intracellular Ca2+ handling, suggesting a distal effect. PMA washout caused the loss of the enhanced response, but secretion was then stimulated by acute readdition of PMA or bombesin. The magnitude of this restimulation appeared dependent on the mass of PKC-alpha, which was rapidly resynthesized during PMA washout. Therefore, stimulation of insulin secretion by PMA, and presumably by endogenous diacylglycerol, involves the activation of PKC isoforms delta and/or mu, and also PKC-alpha.
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Affiliation(s)
- Gordon C Yaney
- Obesity Research Center, Evans Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
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Ahmed M, Grapengiesser E. Ca2+ handling of rat pancreatic beta-cells exposed to ryanodine, caffeine, and glucagon. Endocrine 2002; 17:103-8. [PMID: 12041911 DOI: 10.1385/endo:17:2:103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2001] [Revised: 12/26/2001] [Accepted: 12/26/2001] [Indexed: 11/11/2022]
Abstract
Reported species differences in the stimulus-secretion coupling of insulin release made it important to compare the Ca2+ handling of rat beta-cells with that previously observed in mice. Single beta-cells and small aggregates were prepared from pancreatic islets of Wistar rats, attached to cover slips and then used for measuring the cytoplasmic Ca2+ concentration ([Ca2+]i) with the ratiometric fura-2 technique. Glucose (11 mM) induced slow oscillations of [Ca2+]i similar to those seen in other species, including humans. Comparison of the oscillations in rat beta-cells with those previously described in mouse revealed that there was a slightly lower frequency and an increased tendency to transformation into sustained [Ca2+]i in response to glucagon or caffeine. Ryanodine (5-20 microM) did not affect existing oscillations but sometimes restored rhythmic activity in the presence of caffeine. Stimulation with glucose resulted not only in oscillations but also in transients of [Ca2+]i sometimes appearing in synchrony in adjacent beta-cells and disappearing after the addition of 200 nM thapsigargin or 20 mM caffeine. The frequency of transients recorded in a medium containing glucagon and methoxyverapamil was higher than seen under similar conditions in mouse beta-cells. Although exhibiting some differences compared with mouse beta-cells, rat beta-cells also have an intrinsic ability to oscillate and to generate the transients of [Ca2+] that are supposed to synchronize the rhythmicity of the islets in the pancreas.
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Affiliation(s)
- Meftun Ahmed
- Department of Medical Cell Biology, Uppsala University, Sweden
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30
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Abstract
Rapid and sustained stimulation of beta-cells with glucose induces biphasic insulin secretion. The two phases appear to reflect a characteristic of stimulus-secretion coupling in each beta-cell rather than heterogeneity in the time-course of the response between beta-cells or islets. There is no evidence indicating that biphasic secretion can be attributed to an intrinsically biphasic metabolic signal. In contrast, the biphasic rise in cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) induced by glucose is important to shape the two phases of secretion. The first phase requires a rapid and marked elevation of [Ca(2+)](i) and corresponds to the release of insulin granules from a limited pool. The magnitude of the second phase is determined by the elevation of [Ca(2+)](i), but its development requires production of another signal. This signal corresponds to the amplifying action of glucose and may serve to replenish the pool of granules that are releasable at the prevailing [Ca(2+)](i). The species characteristics of biphasic insulin secretion and its perturbations in pathological situations are discussed.
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Affiliation(s)
- Jean-Claude Henquin
- Unité d'Endocrinologie et Métabolisme, University of Louvain School of Medicine, UCL 55.30, B-1200 Brussels, Belgium.
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Suga S, Wu J, Ogawa Y, Takeo T, Kanno T, Wakui M. Phorbol ester impairs electrical excitation of rat pancreatic beta-cells through PKC-independent activation of KATP channels. BMC Pharmacol 2001; 1:3. [PMID: 11560763 PMCID: PMC55693 DOI: 10.1186/1471-2210-1-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2001] [Accepted: 08/16/2001] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Phorbol 12-myristate 13-acetate (PMA) is often used as an activating phorbol ester of protein kinase C (PKC) to investigate the roles of the kinase in cellular functions. Accumulating lines of evidence indicate that in addition to activating PKC, PMA also produces some regulatory effects in a PKC-independent manner. In this study, we investigated the non-PKC effects of PMA on electrical excitability of rat pancreatic beta-cells by using patch-clamp techniques. RESULTS In current-clamp recording, PMA (80 nM) reversibly inhibited 15 mM glucose-induced action potential spikes superimposed on a slow membrane depolarization and this inhibition can not be prevented by pre-treatment of the cell with a specific PKC inhibitor, bisindolylmaleimide (BIM, 1 microM). In the presence of a subthreshold concentration (5.5 mM) of glucose, PMA hyperpolarized beta-cells in a concentration-dependent manner (0.8-240 nM), even in the presence of BIM. Based on cell-attached single channel recordings, PMA increased ATP-sensitive K+ channel (KATP) activity. Based on inside-out patch-clamp recordings, PMA had little effect on KATP activity if no ATP was in the bath, while PMA restored KATP activity that was suppressed by 10 microM ATP in the bath. In voltage-clamp recording, PMA enhanced tolbutamide-sensitive membrane currents elicited by repetitive ramp pulses from -90 to -50 mV in a concentration-dependent manner, and this potentiation could not be prevented by pre-treatment of cell with BIM. 4alpha-phorbol 12,13-didecanoate (4alpha-PDD), a non-PKC-activating phorbol ester, mimicked the effect of PMA on both current-clamp and voltage-clamp recording configurations. With either 5.5 or 16.6 mM glucose in the extracellular solution, PMA (80 nM) increased insulin secretion from rat islets. However, in islets pretreated with BIM (1 microM), PMA did not increase, but rather reduced insulin secretion. CONCLUSION In rat pancreatic beta-cells, PMA modulates insulin secretion through a mixed mechanism: increases insulin secretion by activation of PKC, and meanwhile decrease insulin secretion by impairing beta-cell excitability in a PKC-independent manner. The enhancement of KATP activity by reducing sensitivity of KATP to ATP seems to underlie the PMA-induced impairment of beta-cells electrical excitation in response to glucose stimulation.
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Affiliation(s)
- Sechiko Suga
- Department of Physiology, Hirosaki University School of Medicine, Hirosaki, 036-8562, Japan
| | - Jie Wu
- Devision of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013-4496, USA
| | - Yoshiji Ogawa
- The Third Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, 036-8562, Japan
| | - Teruko Takeo
- Department of Physiology, Hirosaki University School of Medicine, Hirosaki, 036-8562, Japan
| | - Takahiro Kanno
- Department of Physiology, Hirosaki University School of Medicine, Hirosaki, 036-8562, Japan
| | - Makoto Wakui
- Department of Physiology, Hirosaki University School of Medicine, Hirosaki, 036-8562, Japan
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Zawalich WS, Zawalich KC, Tesz GJ, Sterpka JA, Philbrick WM. Insulin secretion and IP levels in two distant lineages of the genus Mus: comparisons with rat islets. Am J Physiol Endocrinol Metab 2001; 280:E720-8. [PMID: 11287354 DOI: 10.1152/ajpendo.2001.280.5.e720] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Islet responses of two different Mus geni, the laboratory mouse (Mus musculus) and a phylogenetically more ancient species (Mus caroli), were measured and compared with the responses of islets from rats (Rattus norvegicus). A minimal and flat second-phase response to 20 mM glucose was evoked from M. musculus islets, whereas a large rising second-phase response characterized rat islets. M. caroli responses were intermediate between these two extremes; a modest rising second-phase response to 20 mM glucose was observed. Prior, brief stimulation of rat islets with 20 mM glucose results in an amplified insulin secretory response to a subsequent 20 mM glucose challenge. No such potentiation or priming was observed from M. musculus islets. In contrast, M. caroli islets displayed a modest twofold potentiated first-phase response upon subsequent restimulation with 20 mM glucose. Inositol phosphate (IP) accumulation in response to 20 mM glucose stimulation in [(3)H]inositol-prelabeled rat or mouse islets paralleled the insulin secretory responses. The divergence in 20 mM glucose-induced insulin release between these species may be attributable to differences in phospholipase C-mediated IP accumulation in islets.
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Affiliation(s)
- W S Zawalich
- Yale University School of Nursing, New Haven, Connecticut 06536, USA.
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Barbosa RM, Silva AM, Tomé AR, Stamford JA, Santos RM, Rosário LM. Control of pulsatile 5-HT/insulin secretion from single mouse pancreatic islets by intracellular calcium dynamics. J Physiol 1998; 510 ( Pt 1):135-43. [PMID: 9625872 PMCID: PMC2231018 DOI: 10.1111/j.1469-7793.1998.135bz.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. Glucose-induced insulin release from single islets of Langerhans is pulsatile. We have investigated the correlation between changes in cytosolic free calcium concentration ([Ca2+]i) and oscillatory insulin secretion from single mouse islets, in particular examining the basis for differences in secretory responses to intermediate and high glucose concentrations. Insulin release was monitored in real time through the amperometric detection of the surrogate insulin marker 5-hydroxytryptamine (5-HT) via carbon fibre microelectrodes. The [Ca2+]i was simultaneously recorded by whole-islet fura-2 microfluorometry. 2. In 82 % of the experiments, exposure to 11 mM glucose evoked regular high-frequency (average, 3.4 min-1) synchronous oscillations in amperometric current and [Ca2+]i. In the remaining experiments (18 %), 11 mM glucose induced an oscillatory pattern consisting of high-frequency [Ca2+]i oscillations that were superimposed on low-frequency (average, 0.32 min-1) [Ca2+]i waves. Intermittent high-frequency [Ca2+]i oscillations gave rise to a similar pattern of pulsatile 5-HT release. 3. Raising the glucose concentration from 11 to 20 mM increased the duration of the steady-state [Ca2+]i oscillations without increasing their amplitude. In contrast, both the duration and amplitude of the associated 5-HT transients were increased by glucose stimulation. The amount of 5-HT released per secretion cycle was linearly related to the duration of the underlying [Ca2+]i oscillations in both 11 and 20 mM glucose. The slopes of the straight lines were identical, indicating that there is no significant difference between the ability of calcium oscillations to elicit 5-HT/insulin release in 11 and 20 mM glucose. 4. In situ 5-HT microamperometry has the potential to resolve the high-frequency oscillatory component of the second phase of glucose-induced insulin secretion. This component appears to reflect primarily the duration of the underlying [Ca2+]i oscillations, suggesting that glucose metabolism and/or access to glucose metabolites is not rate limiting to fast pulsatile insulin release.
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Affiliation(s)
- R M Barbosa
- Centre for Neurosciences of Coimbra, Laboratory of Instrumental Analysis, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
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