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Mugabo Y, Zhao S, Lamontagne J, Al-Mass A, Peyot ML, Corkey BE, Joly E, Madiraju SRM, Prentki M. Metabolic fate of glucose and candidate signaling and excess-fuel detoxification pathways in pancreatic β-cells. J Biol Chem 2017; 292:7407-7422. [PMID: 28280244 DOI: 10.1074/jbc.m116.763060] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 03/06/2017] [Indexed: 12/28/2022] Open
Abstract
Glucose metabolism promotes insulin secretion in β-cells via metabolic coupling factors that are incompletely defined. Moreover, chronically elevated glucose causes β-cell dysfunction, but little is known about how cells handle excess fuels to avoid toxicity. Here we sought to determine which among the candidate pathways and coupling factors best correlates with glucose-stimulated insulin secretion (GSIS), define the fate of glucose in the β-cell, and identify pathways possibly involved in excess-fuel detoxification. We exposed isolated rat islets for 1 h to increasing glucose concentrations and measured various pathways and metabolites. Glucose oxidation, oxygen consumption, and ATP production correlated well with GSIS and saturated at 16 mm glucose. However, glucose utilization, glycerol release, triglyceride and glycogen contents, free fatty acid (FFA) content and release, and cholesterol and cholesterol esters increased linearly up to 25 mm glucose. Besides being oxidized, glucose was mainly metabolized via glycerol production and release and lipid synthesis (particularly FFA, triglycerides, and cholesterol), whereas glycogen production was comparatively low. Using targeted metabolomics in INS-1(832/13) cells, we found that several metabolites correlated well with GSIS, in particular some Krebs cycle intermediates, malonyl-CoA, and lower ADP levels. Glucose dose-dependently increased the dihydroxyacetone phosphate/glycerol 3-phosphate ratio in INS-1(832/13) cells, indicating a more oxidized state of NAD in the cytosol upon glucose stimulation. Overall, the data support a role for accelerated oxidative mitochondrial metabolism, anaplerosis, and malonyl-CoA/lipid signaling in β-cell metabolic signaling and suggest that a decrease in ADP levels is important in GSIS. The results also suggest that excess-fuel detoxification pathways in β-cells possibly comprise glycerol and FFA formation and release extracellularly and the diversion of glucose carbons to triglycerides and cholesterol esters.
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Affiliation(s)
- Yves Mugabo
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec H3C 3J7, Canada, and
| | - Shangang Zhao
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Medicine and Human Genetics, McGill University, Montreal, Québec H3A 1B1, Canada
| | - Julien Lamontagne
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Anfal Al-Mass
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Medicine and Human Genetics, McGill University, Montreal, Québec H3A 1B1, Canada
| | - Marie-Line Peyot
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Barbara E Corkey
- Department of Medicine, Obesity Research Center, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Erik Joly
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - S R Murthy Madiraju
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Marc Prentki
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada, .,Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec H3C 3J7, Canada, and
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Alquier T, Peyot ML, Latour MG, Kebede M, Sorensen CM, Gesta S, Ronald Kahn C, Smith RD, Jetton TL, Metz TO, Prentki M, Poitout V. Deletion of GPR40 impairs glucose-induced insulin secretion in vivo in mice without affecting intracellular fuel metabolism in islets. Diabetes 2009; 58:2607-15. [PMID: 19720802 PMCID: PMC2768167 DOI: 10.2337/db09-0362] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
OBJECTIVE The G-protein-coupled receptor GPR40 mediates fatty acid potentiation of glucose-stimulated insulin secretion, but its contribution to insulin secretion in vivo and mechanisms of action remain uncertain. This study was aimed to ascertain whether GPR40 controls insulin secretion in vivo and modulates intracellular fuel metabolism in islets. RESEARCH DESIGN AND METHODS Insulin secretion and sensitivity were assessed in GPR40 knockout mice and their wild-type littermates by hyperglycemic clamps and hyperinsulinemic euglycemic clamps, respectively. Transcriptomic analysis, metabolic studies, and lipid profiling were used to ascertain whether GPR40 modulates intracellular fuel metabolism in islets. RESULTS Both glucose- and arginine-stimulated insulin secretion in vivo were decreased by approximately 60% in GPR40 knockout fasted and fed mice, without changes in insulin sensitivity. Neither gene expression profiles nor intracellular metabolism of glucose and palmitate in isolated islets were affected by GPR40 deletion. Lipid profiling of isolated islets revealed that the increase in triglyceride and decrease in lyso-phosphatidylethanolamine species in response to palmitate in vitro was similar in wild-type and knockout islets. In contrast, the increase in intracellular inositol phosphate levels observed in wild-type islets in response to fatty acids in vitro was absent in knockout islets. CONCLUSIONS These results indicate that deletion of GPR40 impairs insulin secretion in vivo not only in response to fatty acids but also to glucose and arginine, without altering intracellular fuel metabolism in islets, via a mechanism that may involve the generation of inositol phosphates downstream of GPR40 activation.
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Affiliation(s)
- Thierry Alquier
- Montréal Diabetes Research Center, Research Centre of the Montréal University Hospital, University of Montréal, Montréal, QC, Canada
- Department of Medicine, University of Montréal, Montréal, QC, Canada
| | - Marie-Line Peyot
- Montréal Diabetes Research Center, Research Centre of the Montréal University Hospital, University of Montréal, Montréal, QC, Canada
| | - Martin G. Latour
- Montréal Diabetes Research Center, Research Centre of the Montréal University Hospital, University of Montréal, Montréal, QC, Canada
| | - Melkam Kebede
- Montréal Diabetes Research Center, Research Centre of the Montréal University Hospital, University of Montréal, Montréal, QC, Canada
- Department of Medicine, University of Montréal, Montréal, QC, Canada
| | - Christina M. Sorensen
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington
| | - Stephane Gesta
- Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts
| | - C. Ronald Kahn
- Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts
| | - Richard D. Smith
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington
| | - Thomas L. Jetton
- Division of Endocrinology, Diabetes, and Metabolism, University of Vermont College of Medicine, Burlington, Vermont
| | - Thomas O. Metz
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington
| | - Marc Prentki
- Montréal Diabetes Research Center, Research Centre of the Montréal University Hospital, University of Montréal, Montréal, QC, Canada
- Department of Nutrition, University of Montréal, Montréal, QC, Canada
| | - Vincent Poitout
- Montréal Diabetes Research Center, Research Centre of the Montréal University Hospital, University of Montréal, Montréal, QC, Canada
- Department of Medicine, University of Montréal, Montréal, QC, Canada
- Corresponding author: Vincent Poitout,
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Peyot ML, Gray JP, Lamontagne J, Smith PJS, Holz GG, Madiraju SRM, Prentki M, Heart E. Glucagon-like peptide-1 induced signaling and insulin secretion do not drive fuel and energy metabolism in primary rodent pancreatic beta-cells. PLoS One 2009; 4:e6221. [PMID: 19593440 PMCID: PMC2704866 DOI: 10.1371/journal.pone.0006221] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Accepted: 06/15/2009] [Indexed: 11/24/2022] Open
Abstract
Background Glucagon like peptide-1 (GLP-1) and its analogue exendin-4 (Ex-4) enhance glucose stimulated insulin secretion (GSIS) and activate various signaling pathways in pancreatic β-cells, in particular cAMP, Ca2+ and protein kinase-B (PKB/Akt). In many cells these signals activate intermediary metabolism. However, it is not clear whether the acute amplification of GSIS by GLP-1 involves in part metabolic alterations and the production of metabolic coupling factors. Methodology/Prinicipal Findings GLP-1 or Ex-4 at high glucose caused release (∼20%) of the total rat islet insulin content over 1 h. While both GLP-1 and Ex-4 markedly potentiated GSIS in isolated rat and mouse islets, neither had an effect on β-cell fuel and energy metabolism over a 5 min to 3 h time period. GLP-1 activated PKB without changing glucose usage and oxidation, fatty acid oxidation, lipolysis or esterification into various lipids in rat islets. Ex-4 caused a rise in [Ca2+]i and cAMP but did not enhance energy utilization, as neither oxygen consumption nor mitochondrial ATP levels were altered. Conclusions/Significance The results indicate that GLP-1 barely affects β-cell intermediary metabolism and that metabolic signaling does not significantly contribute to GLP-1 potentiation of GSIS. The data also indicate that insulin secretion is a minor energy consuming process in the β-cell, and that the β-cell is different from most cell types in that its metabolic activation appears to be primarily governed by a “push” (fuel substrate driven) process, rather than a “pull” mechanism secondary to enhanced insulin release as well as to Ca2+, cAMP and PKB signaling.
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Affiliation(s)
- Marie-Line Peyot
- Molecular Nutrition Unit and Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal and Departments of Nutrition and Biochemistry, Université de Montréal, Montréal, Quebec, Canada
| | - Joshua P. Gray
- Department of Chemistry, United States Coast Guard Academy, New London, Connecticut, United States of America
| | - Julien Lamontagne
- Molecular Nutrition Unit and Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal and Departments of Nutrition and Biochemistry, Université de Montréal, Montréal, Quebec, Canada
| | - Peter J. S. Smith
- BioCurrents Research Center (NIH:NCRR), Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - George G. Holz
- State University of New York, Upstate Medical University, Syracuse, New York, United States of America
| | - S. R. Murthy Madiraju
- Molecular Nutrition Unit and Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal and Departments of Nutrition and Biochemistry, Université de Montréal, Montréal, Quebec, Canada
| | - Marc Prentki
- Molecular Nutrition Unit and Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal and Departments of Nutrition and Biochemistry, Université de Montréal, Montréal, Quebec, Canada
- * E-mail:
| | - Emma Heart
- BioCurrents Research Center (NIH:NCRR), Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
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Peyot ML, Guay C, Latour MG, Lamontagne J, Lussier R, Pineda M, Ruderman NB, Haemmerle G, Zechner R, Joly É, Madiraju SRM, Poitout V, Prentki M. Adipose triglyceride lipase is implicated in fuel- and non-fuel-stimulated insulin secretion. J Biol Chem 2009; 284:16848-16859. [PMID: 19389712 DOI: 10.1074/jbc.m109.006650] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Reduced lipolysis in hormone-sensitive lipase-deficient mice is associated with impaired glucose-stimulated insulin secretion (GSIS), suggesting that endogenous beta-cell lipid stores provide signaling molecules for insulin release. Measurements of lipolysis and triglyceride (TG) lipase activity in islets from HSL(-/-) mice indicated the presence of other TG lipase(s) in the beta-cell. Using real time-quantitative PCR, adipose triglyceride lipase (ATGL) was found to be the most abundant TG lipase in rat islets and INS832/13 cells. To assess its role in insulin secretion, ATGL expression was decreased in INS832/13 cells (ATGL-knockdown (KD)) by small hairpin RNA. ATGL-KD increased the esterification of free fatty acid (FFA) into TG. ATGL-KD cells showed decreased glucose- or Gln + Leu-induced insulin release, as well as reduced response to KCl or palmitate at high, but not low, glucose. The K(ATP)-independent/amplification pathway of GSIS was considerably reduced in ATGL-KD cells. ATGL(-/-) mice were hypoinsulinemic and hypoglycemic and showed decreased plasma TG and FFAs. A hyperglycemic clamp revealed increased insulin sensitivity and decreased GSIS and arginine-induced insulin secretion in ATGL(-/-) mice. Accordingly, isolated islets from ATGL(-/-) mice showed reduced insulin secretion in response to glucose, glucose + palmitate, and KCl. Islet TG content and FFA esterification into TG were increased by 2-fold in ATGL(-/-) islets, but glucose usage and oxidation were unaltered. The results demonstrate the importance of ATGL and intracellular lipid signaling for fuel- and non-fuel-induced insulin secretion.
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Affiliation(s)
- Marie-Line Peyot
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Claudiane Guay
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Martin G Latour
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Julien Lamontagne
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Roxane Lussier
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Marco Pineda
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Neil B Ruderman
- Departments of Medicine and Physiology and Biophysics, Boston University School of Medicine and Diabetes Unit, Section of Endocrinology, Boston University School of Medicine and Boston Medical Center, Boston, Massachusetts 02118
| | - Guenter Haemmerle
- Institute of Molecular Biosciences, Karl-Franzens-University, Graz 8010, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, Karl-Franzens-University, Graz 8010, Austria
| | - Érik Joly
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - S R Murthy Madiraju
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada
| | - Vincent Poitout
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada; Departments of Nutrition, Montreal, Quebec H1W 4A4, Canada; Medicine, University of Montreal, Montreal, Quebec H1W 4A4, Canada
| | - Marc Prentki
- From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada; Departments of Nutrition, Montreal, Quebec H1W 4A4, Canada.
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Zimliki CL, Chenault VM, Mears D. Glucose-dependent and -independent electrical activity in islets of Langerhans of Psammomys obesus, an animal model of nutritionally induced obesity and diabetes. Gen Comp Endocrinol 2009; 161:193-201. [PMID: 19167400 DOI: 10.1016/j.ygcen.2008.12.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 12/17/2008] [Accepted: 12/18/2008] [Indexed: 11/24/2022]
Abstract
Glucose-induced insulin secretion from pancreatic beta-cells involves metabolism-induced membrane depolarization and voltage-dependent Ca(2+) influx. The electrical events in beta-cell glucose sensing have been studied intensely using mouse islets of Langerhans, but data from other species, including models of type 2 diabetes mellitus (T2DM), are lacking. In this work, we made intracellular recordings of electrical activity from cells within islets of the gerbil Psammomys obesus (fat sand rat), a model of dietary-induced T2DM. Most islet cells from lean, non-diabetic sand rats displayed glucose-induced, K(ATP) channel-dependent, oscillatory electrical activity that was similar to the classic "bursting" pattern of mouse beta-cells. However, the oscillations were slower in sand rat islets, and the dose-response curve of electrical activity versus glucose concentration was left-shifted. Of the non-bursting cells, some produced action potentials continuously, while others displayed electrical activity that was largely independent of glucose. The latter activity consisted of continuous or intermittent action potential firing, and persisted for long periods in the absence of glucose. The glucose-insensitive activity was suppressed by diazoxide, indicating that the cells expressed K(ATP) channels. Sand rat islets produced intracellular Ca(2+) oscillations reminiscent of the oscillatory electrical pattern observed in most cells, albeit with a longer period. Finally, we found that the glucose dependence of insulin secretion from sand rat islets closely paralleled that of the bursting electrical activity. We conclude that while subpopulations of K(ATP)-expressing cells in sand rat islets display heterogeneous electrical responses to glucose, insulin secretion most closely follows the oscillatory activity. The ease of recording membrane potential from sand rat islets makes this a useful model for studies of beta-cell electrical signaling during the development of T2DM.
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Affiliation(s)
- Charles L Zimliki
- Department of Anatomy, Physiology & Genetics, Uniformed Services University School of Medicine, Bethesda, MD 20814, USA
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Pechhold K, Koczwara K, Zhu X, Harrison VS, Walker G, Lee J, Harlan DM. Blood glucose levels regulate pancreatic beta-cell proliferation during experimentally-induced and spontaneous autoimmune diabetes in mice. PLoS One 2009; 4:e4827. [PMID: 19287497 PMCID: PMC2654100 DOI: 10.1371/journal.pone.0004827] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 02/02/2009] [Indexed: 12/20/2022] Open
Abstract
Background Type 1 diabetes mellitus is caused by immune-mediated destruction of pancreatic β-cells leading to insulin deficiency, impaired intermediary metabolism, and elevated blood glucose concentrations. While at autoimmune diabetes onset a limited number of β-cells persist, the cells' regenerative potential and its regulation have remained largely unexplored. Using two mouse autoimmune diabetes models, this study examined the proliferation of pancreatic islet ß-cells and other endocrine and non-endocrine subsets, and the factors regulating that proliferation. Methodology and Principal Findings We adapted multi-parameter flow cytometry techniques (including DNA-content measurements and 5′-bromo-2′-deoxyuridine [BrdU] incorporation) to study pancreatic islet single cell suspensions. These studies demonstrate that β-cell proliferation rapidly increases at diabetes onset, and that this proliferation is closely correlated with the diabetic animals' elevated blood glucose levels. For instance, we show that when normoglycemia is restored by exogenous insulin or islet transplantation, the β-cell proliferation rate returns towards low levels found in control animals, yet surges when hyperglycemia recurs. In contrast, other-than-ß endocrine islet cells did not exhibit the same glucose-dependent proliferative responses. Rather, disease-associated alterations of BrdU-incorporation rates of δ-cells (minor decrease), and non-endocrine islet cells (slight increase) were not affected by blood glucose levels, or were inversely related to glycemia control after diabetes onset (α-cells). Conclusion We conclude that murine β-cells' ability to proliferate in response to metabolic need (i.e. rising blood glucose concentrations) is remarkably well preserved during severe, chronic β-cell autoimmunity. These data suggest that timely control of the destructive immune response after disease manifestation could allow spontaneous regeneration of sufficient β-cell mass to restore normal glucose homeostasis.
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Affiliation(s)
- Klaus Pechhold
- Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD, USA.
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Francini F, Gagliardino JJ, Borelli MI. Decreased islet sensitivity to insulin in hamsters with dietary-induced insulin resistance. Life Sci 2008; 82:817-22. [DOI: 10.1016/j.lfs.2008.01.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 12/21/2007] [Accepted: 01/21/2008] [Indexed: 10/22/2022]
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Borelli MI, Stoppiglia LF, Rezende LF, Flores LE, Del Zotto H, Boschero AC, Gagliardino JJ. INGAP-related pentadecapeptide: its modulatory effect upon insulin secretion. ACTA ACUST UNITED AC 2005; 131:97-102. [PMID: 16084603 DOI: 10.1016/j.regpep.2005.07.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 06/02/2005] [Accepted: 07/14/2005] [Indexed: 11/21/2022]
Abstract
We examined the effects of a pentadecapeptide having the 104-118 aminoacid sequence of islet neogenesis-associated protein (INGAP-PP) on insulin secretion, and the morphological characteristics of adult and neonatal pancreatic rat islets cultured in RPMI and 10 mM glucose for 4 days, with or without different INGAP-PP concentrations (0.1-100 mug/ml). A scrambled 15 aminoacid peptide was used as control for the specificity of INGAP-PP effect. Cultured neonatal and adult islets released insulin in response to glucose (2.8-16.7 mM) in a dose-dependent manner, and to leucine and arginine (10 mM). In all cases, the response was greater in adult islets. INGAP-PP added to the culture medium significantly enhanced glucose- and aminoacid-induced insulin release in both adult and newborn rats; however, no changes were observed with the scrambled peptide. Similar results were obtained incubating freshly isolated adult rat islets with INGAP-PP. Whereas INGAP-PP did not induce significant changes in islet survival rate or proportion/number of islet cells, it increased significantly beta-cell size. This first demonstration of the enhancing effect of INGAP-PP on the beta-cell secretory response of adult and newborn islets opens a new avenue to study its production mechanism and potential use to increase the secretory capacity of endogenous islets in intact animals or of islets preserved for future transplants.
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Affiliation(s)
- María I Borelli
- CENEXA-Center of Experimental and Applied Endocrinology (UNLP-CONICET, PAHO/WHO Collaborating Center), National University of La Plata School of Medicine, La Plata, Argentina
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