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Meli AP, Fontés G, Avery DT, Leddon SA, Tam M, Elliot M, Ballesteros-Tato A, Miller J, Stevenson MM, Fowell DJ, Tangye SG, King IL. The Integrin LFA-1 Controls T Follicular Helper Cell Generation and Maintenance. Immunity 2017; 45:831-846. [PMID: 27760339 DOI: 10.1016/j.immuni.2016.09.018] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 06/20/2016] [Accepted: 09/22/2016] [Indexed: 01/08/2023]
Abstract
T follicular helper (Tfh) cells are a CD4+ T cell subset critical for long-lived humoral immunity. We hypothesized that integrins play a decisive role in Tfh cell biology. Here we show that Tfh cells expressed a highly active form of leukocyte function-associated antigen-1 (LFA-1) that was required for their survival within the germinal center niche. In addition, LFA-1 promoted expression of Bcl-6, a transcriptional repressor critical for Tfh cell differentiation, and inhibition of LFA-1 abolished Tfh cell generation and prevented protective humoral immunity to intestinal helminth infection. Furthermore, we demonstrated that expression of Talin-1, an adaptor protein that regulates LFA-1 affinity, dictated Tfh versus Th2 effector cell differentiation. Collectively, our results define unique functions for LFA-1 in the Tfh cell effector program and suggest that integrin activity is important in lineage decision-making events in the adaptive immune system.
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Affiliation(s)
- Alexandre P Meli
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Ghislaine Fontés
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Danielle T Avery
- The Immunology Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia
| | - Scott A Leddon
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Mifong Tam
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Michael Elliot
- Sydney Head and Neck Cancer Institute, Camperdown, NSW 2050, Australia
| | - Andre Ballesteros-Tato
- Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jim Miller
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Mary M Stevenson
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Deborah J Fowell
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Stuart G Tangye
- The Immunology Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia
| | - Irah L King
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada.
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Meli AP, Fontés G, Leung Soo C, King IL. T Follicular Helper Cell-Derived IL-4 Is Required for IgE Production during Intestinal Helminth Infection. J Immunol 2017; 199:244-252. [PMID: 28533444 DOI: 10.4049/jimmunol.1700141] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 04/27/2017] [Indexed: 12/15/2022]
Abstract
IgE production plays a crucial role in protective as well as pathogenic type 2 immune responses. Although the cytokine IL-4 is required for the development of IgE-producing plasma cells, the source of IL-4 and cellular requirements for optimal IgE responses remain unclear. Recent evidence suggests that T follicular helper (Tfh) cells are the primary producer of IL-4 in the reactive lymph node during type 2 immune responses. As Tfh cells are also required for the development of plasmablasts derived from germinal center and extrafollicular sources, we hypothesized that this cell subset is essential for the IgE plasmablast response. In this study, we show that during intestinal helminth infection, IL-4 derived from Tfh cells is required for IgE class switching and plasmablast formation. Notably, early IgE class switching did not require germinal center formation. Additionally, Tfh cell-derived IL-4 was required to maintain the Th2 response in the mesenteric lymph nodes of infected mice. Collectively, our results indicate that IL-4-producing Tfh cells are central orchestrators of the type 2 immune response in the reactive lymph nodes during parasitic helminth infection.
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Affiliation(s)
- Alexandre P Meli
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Ghislaine Fontés
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Cindy Leung Soo
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Irah L King
- Department of Microbiology and Immunology, Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec H3A 2B4, Canada
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Ghislain J, Fontés G, Tremblay C, Kebede MA, Poitout V. Dual-Reporter β-Cell-Specific Male Transgenic Rats for the Analysis of β-Cell Functional Mass and Enrichment by Flow Cytometry. Endocrinology 2016; 157:1299-306. [PMID: 26671180 PMCID: PMC4769371 DOI: 10.1210/en.2015-1550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mouse β-cell-specific reporter lines have played a key role in diabetes research. Although the rat provides several advantages, its use has lagged behind the mouse due to the relative paucity of genetic models. In this report we describe the generation and characterization of transgenic rats expressing a Renilla luciferase (RLuc)-enhanced yellow fluorescent protein (YFP) fusion under control of a 9-kb genomic fragment from the rat ins2 gene (RIP7-RLuc-YFP). Analysis of RLuc luminescence and YFP fluorescence revealed that reporter expression is restricted to β-cells in the adult rat. Physiological characteristics including body weight, fat and lean mass, fasting and fed glucose levels, glucose and insulin tolerance, and β-cell mass were similar between two RIP7-RLuc-YFP lines and wild-type littermates. Glucose-induced insulin secretion in isolated islets was indistinguishable from controls in one of the lines, whereas surprisingly, insulin secretion was defective in the second line. Consequently, subsequent studies were limited to the former line. We asked whether transgene activity was responsive to glucose as shown previously for the ins2 gene. Exposing islets ex vivo to high glucose (16.7 mM) or in vivo infusion of glucose for 24 hours increased luciferase activity in islets, whereas the fraction of YFP-positive β-cells after glucose infusion was unchanged. Finally, we showed that fluorescence-activated cell sorting of YFP-positive islet cells can be used to enrich for β-cells. Overall, this transgenic line will enable for the first time the application of both fluorescence and bioluminescence/luminescence-based approaches for the study of rat β-cells.
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Affiliation(s)
- Julien Ghislain
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Ghislaine Fontés
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Caroline Tremblay
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Melkam A Kebede
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
| | - Vincent Poitout
- Montreal Diabetes Research Center (J.G., G.F., C.T., M.A.K., V.P.), Centre de Recherche du Centre Hospitalier de l'Université de Montréal (J.G., G.F., C.T., M.A.K., V.P.), and Departments of Medicine (V.P.) and Biochemistry (V.P.), University of Montreal, Montréal, Québec, Canada H2X 0A9
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Fontés G, Ghislain J, Benterki I, Zarrouki B, Trudel D, Berthiaume Y, Poitout V. The ΔF508 Mutation in the Cystic Fibrosis Transmembrane Conductance Regulator Is Associated With Progressive Insulin Resistance and Decreased Functional β-Cell Mass in Mice. Diabetes 2015; 64:4112-22. [PMID: 26283735 PMCID: PMC4876763 DOI: 10.2337/db14-0810] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 08/10/2015] [Indexed: 01/20/2023]
Abstract
Cystic fibrosis (CF) is the result of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF-related diabetes affects 50% of adult CF patients. How CFTR deficiency predisposes to diabetes is unknown. Herein, we examined the impact of the most frequent cftr mutation in humans, deletion of phenylalanine at position 508 (ΔF508), on glucose homeostasis in mice. We compared ΔF508 mutant mice with wild-type (WT) littermates. Twelve-week-old male ΔF508 mutants had lower body weight, improved oral glucose tolerance, and a trend toward higher insulin tolerance. Glucose-induced insulin secretion was slightly diminished in ΔF508 mutant islets, due to reduced insulin content, but ΔF508 mutant islets were not more sensitive to proinflammatory cytokines than WT islets. Hyperglycemic clamps confirmed an increase in insulin sensitivity with normal β-cell function in 12- and 18-week-old ΔF508 mutants. In contrast, 24-week-old ΔF508 mutants exhibited insulin resistance and reduced β-cell function. β-Cell mass was unaffected at 11 weeks of age but was significantly lower in ΔF508 mutants versus controls at 24 weeks. This was not associated with gross pancreatic pathology. We conclude that the ΔF508 CFTR mutation does not lead to an intrinsic β-cell secretory defect but is associated with insulin resistance and a β-cell mass deficit in aging mutants.
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Affiliation(s)
- Ghislaine Fontés
- Montreal Diabetes Research Center, University of Montreal, Quebec, Canada University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada
| | - Julien Ghislain
- Montreal Diabetes Research Center, University of Montreal, Quebec, Canada University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada
| | - Isma Benterki
- Montreal Diabetes Research Center, University of Montreal, Quebec, Canada University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, Quebec, Canada
| | - Bader Zarrouki
- Montreal Diabetes Research Center, University of Montreal, Quebec, Canada University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada
| | - Dominique Trudel
- University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada Department of Pathology and Cell Biology, University of Montreal, Montreal, Quebec, Canada
| | - Yves Berthiaume
- University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada Department of Medicine, University of Montreal, Montreal, Quebec, Canada
| | - Vincent Poitout
- Montreal Diabetes Research Center, University of Montreal, Quebec, Canada University of Montreal Hospital Research Centre, University of Montreal, Montreal, Quebec, Canada Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, Quebec, Canada Department of Medicine, University of Montreal, Montreal, Quebec, Canada
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Zarrouki B, Benterki I, Fontés G, Peyot ML, Seda O, Prentki M, Poitout V. Epidermal growth factor receptor signaling promotes pancreatic β-cell proliferation in response to nutrient excess in rats through mTOR and FOXM1. Diabetes 2014; 63:982-93. [PMID: 24194502 PMCID: PMC3931394 DOI: 10.2337/db13-0425] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The cellular and molecular mechanisms underpinning the compensatory increase in β-cell mass in response to insulin resistance are essentially unknown. We previously reported that a 72-h coinfusion of glucose and Intralipid (GLU+IL) induces insulin resistance and a marked increase in β-cell proliferation in 6-month-old, but not in 2-month-old, Wistar rats. The aim of the current study was to identify the mechanisms underlying nutrient-induced β-cell proliferation in this model. A transcriptomic analysis identified a central role for the forkhead transcription factor FOXM1 and its targets, and for heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), a ligand of the EGF receptor (EGFR), in nutrient-induced β-cell proliferation. Phosphorylation of ribosomal S6 kinase, a mammalian target of rapamycin (mTOR) target, was increased in islets from GLU+IL-infused 6-month-old rats. HB-EGF induced proliferation of insulin-secreting MIN6 cells and isolated rat islets, and this effect was blocked in MIN6 cells by the EGFR inhibitor AG1478 or the mTOR inhibitor rapamycin. Coinfusion of either AG1478 or rapamycin blocked the increase in FOXM1 signaling, β-cell proliferation, and β-cell mass and size in response to GLU+IL infusion in 6-month-old rats. We conclude that chronic nutrient excess promotes β-cell mass expansion via a pathway that involves EGFR signaling, mTOR activation, and FOXM1-mediated cell proliferation.
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Affiliation(s)
- Bader Zarrouki
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Montréal, Québec, Canada
| | - Isma Benterki
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Biochemistry, University of Montréal, Montréal, Québec, Canada
| | - Ghislaine Fontés
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
| | - Marie-Line Peyot
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
| | - Ondrej Seda
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
| | - Marc Prentki
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Biochemistry, University of Montréal, Montréal, Québec, Canada
- Department of Nutrition, University of Montréal, Montréal, Québec, Canada
| | - Vincent Poitout
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Montréal, Québec, Canada
- Department of Biochemistry, University of Montréal, Montréal, Québec, Canada
- Department of Nutrition, University of Montréal, Montréal, Québec, Canada
- Corresponding author: Vincent Poitout,
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d'Assignies G, Fontés G, Kauffmann C, Latour M, Gaboury L, Boulanger Y, Van Beers BE, Soulez G, Poitout V, Tang A. Early detection of liver steatosis by magnetic resonance imaging in rats infused with glucose and intralipid solutions and correlation to insulin levels. Metabolism 2013; 62:1850-7. [PMID: 24035445 PMCID: PMC3914148 DOI: 10.1016/j.metabol.2013.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 07/25/2013] [Accepted: 08/09/2013] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Magnetic resonance (MR) techniques allow noninvasive fat quantification. We aimed to investigate the accuracy of MR imaging (MRI), MR spectroscopy (MRS) and histological techniques to detect early-onset liver steatosis in three rat phenotypes assigned to an experimental glucolipotoxic model or a control group. MATERIALS AND METHODS This study was approved by the institutional committee for the protection of animals. Thirty-two rats (13 young Wistar, 6 old Wistar and 13 diabetic Goto-Kakizaki rats) fed a standard diet were assigned to a 72h intravenous infusion of glucose and Intralipid fat emulsion or a saline infusion. Plasma insulin levels were measured. Steatosis was quantified in ex vivo livers with gradient-recalled multi-echo MRI, MRS and histology as fat fractions (FF). RESULTS A significant correlation was found between multi-echo MRI-FF and MRS-FF (r=0.81, p<0.01) and a weaker correlation was found between histology and MRS-FF (r=0.60, p<0.01). MRS and MRI accurately distinguished young Wistar and Goto-Kakizaki rats receiving the glucose+Intralipid infusion from those receiving the saline control whereas histology did not. Significant correlations were found between MRI or MRS and insulin plasma level (r=0.63, p<0.01; r=0.57, p<0.01), and between MRI or MRS and C-peptide concentration (r=0.54, p<0.01; r=0.44, p<0.02). CONCLUSIONS Multi-echo MRI and MRS may be more sensitive to measure early-onset liver steatosis than histology in an experimental glucolipotoxic rat model.
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Affiliation(s)
- Gaspard d'Assignies
- Department of Radiology, University of Montreal, Hôpital Saint-Luc, 1058 rue Saint-Denis, Montreal, Quebec, Canada, H2X 3J4
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
- Department of Radiology, Beaujon Hospital, Université Paris VII, 100 Bd du Général Leclerc, 92118 Clichy, France
| | - Ghislaine Fontés
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
- Montreal Diabetes Research Center, CRCHUM, Technopôle Angus, 2901, Rachel Street East – Room 303, Montreal, Quebec, Canada, H1W 4A4
- Department of Medicine, University of Montreal, Qc, Canada, PO Box 6128, Station Centre-ville, Montreal, Quebec, Canada, H3C 3J7
| | - Claude Kauffmann
- Department of Radiology, University of Montreal, Hôpital Saint-Luc, 1058 rue Saint-Denis, Montreal, Quebec, Canada, H2X 3J4
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
| | - Martin Latour
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
- Montreal Diabetes Research Center, CRCHUM, Technopôle Angus, 2901, Rachel Street East – Room 303, Montreal, Quebec, Canada, H1W 4A4
| | - Louis Gaboury
- Department of anatomo-pathology, Centre hospitalier de l'Université de Montréal (CHUM), 3840 rue St-Urbain, Montreal, Quebec, Canada, H2W 1T8
| | - Yvan Boulanger
- Department of Radiology, University of Montreal, Hôpital Saint-Luc, 1058 rue Saint-Denis, Montreal, Quebec, Canada, H2X 3J4
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
| | - Bernard E. Van Beers
- Department of Radiology, Beaujon Hospital, Université Paris VII, 100 Bd du Général Leclerc, 92118 Clichy, France
| | - Gilles Soulez
- Department of Radiology, University of Montreal, Hôpital Notre-Dame, 1560 rue Sherbrooke Est, Montreal, Quebec, Canada, H2L 4M1
| | - Vincent Poitout
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
- Montreal Diabetes Research Center, CRCHUM, Technopôle Angus, 2901, Rachel Street East – Room 303, Montreal, Quebec, Canada, H1W 4A4
- Department of Medicine, University of Montreal, Qc, Canada, PO Box 6128, Station Centre-ville, Montreal, Quebec, Canada, H3C 3J7
- Department of Nutrition, University of Montreal, Qc, Canada, PO Box 6128, Station Centre-ville, Montreal, Quebec, Canada, H3C 3J7
- Department of Biochemistry, University of Montreal, Qc, Canada, PO Box 6128, Station Centre-ville, Montreal, Quebec, Canada, H3C 3J7
| | - An Tang
- Department of Radiology, University of Montreal, Hôpital Saint-Luc, 1058 rue Saint-Denis, Montreal, Quebec, Canada, H2X 3J4
- Research Center CHUM, Hôpital Saint-Luc, 264, René-Lévesque Blvd. East, Montreal, Quebec, Canada, H2X 1P1
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Zarrouki B, Benterki I, Fontés G, Peyot ML, Seda O, Prentki M, Poitout V. Epidermal Growth Factor Signalling Promotes Pancreatic Beta-Cell Proliferation in Response to Nutrient Excess in Rats Through MTOR And FOXM1. Can J Diabetes 2013. [DOI: 10.1016/j.jcjd.2013.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Semache M, Fontés G, Fogarty S, Kikani C, Rutter J, Poitout V. PAS Kinase Regulates PDX-1 Protein Stability Via Phosphorylation of GSK3β in Pancreatic Beta Cells. Can J Diabetes 2013. [DOI: 10.1016/j.jcjd.2013.08.177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Zarrouki B, Benterki I, Fontés G, Peyot ML, Seda O, Prentki M, Poitout V. Epidermal Growth Factor Signalling Promotes Pancreatic Beta-Cell Proliferation In Response to Nutrient Excess tn Rats Through MTOR And FOXM1. Can J Diabetes 2013. [DOI: 10.1016/j.jcjd.2013.08.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Abstract
Chronic exposure to excessive levels of nutrients is postulated to affect the function of several organs and tissues and to contribute to the development of the many complications associated with obesity and the metabolic syndrome, including type 2 diabetes. To study the mechanisms by which excessive levels of glucose and fatty acids affect the pancreatic beta-cell and the secretion of insulin, we have established a chronic nutrient infusion model in the rat. The procedure consists of catheterizing the right jugular vein and left carotid artery under general anesthesia; allowing a 7-day recuperation period; connecting the catheters to the pumps using a swivel and counterweight system that enables the animal to move freely in the cage; and infusing glucose and/or Intralipid (a soybean oil emulsion which generates a mixture of approximately 80% unsaturated/20% saturated fatty acids when infused with heparin) for 72 hr. This model offers several advantages, including the possibility to finely modulate the target levels of circulating glucose and fatty acids; the option to co-infuse pharmacological compounds; and the relatively short time frame as opposed to dietary models. It can be used to examine the mechanisms of nutrient-induced dysfunction in a variety of organs and to test the effectiveness of drugs in this context.
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Semache M, Zarrouki B, Fontés G, Fogarty S, Kikani C, Chawki MB, Rutter J, Poitout V. Per-Arnt-Sim kinase regulates pancreatic duodenal homeobox-1 protein stability via phosphorylation of glycogen synthase kinase 3β in pancreatic β-cells. J Biol Chem 2013; 288:24825-33. [PMID: 23853095 DOI: 10.1074/jbc.m113.495945] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In pancreatic β-cells, glucose induces the binding of the transcription factor pancreatic duodenal homeobox-1 (PDX-1) to the insulin gene promoter to activate insulin gene transcription. At low glucose levels, glycogen synthase kinase 3β (GSK3β) is known to phosphorylate PDX-1 on C-terminal serine residues, which triggers PDX-1 proteasomal degradation. We previously showed that the serine/threonine Per-Arnt-Sim domain-containing kinase (PASK) regulates insulin gene transcription via PDX-1. However, the mechanisms underlying this regulation are unknown. In this study, we aimed to identify the role of PASK in the regulation of PDX-1 phosphorylation, protein expression, and stability in insulin-secreting cells and isolated rodent islets of Langerhans. We observed that glucose induces a decrease in overall PDX-1 serine phosphorylation and that overexpression of WT PASK mimics this effect. In vitro, PASK directly phosphorylates GSK3β on its inactivating phosphorylation site Ser(9). Overexpression of a kinase-dead (KD), dominant negative version of PASK blocks glucose-induced Ser(9) phosphorylation of GSK3β. Accordingly, GSK3β Ser(9) phosphorylation is reduced in islets from pask-null mice. Overexpression of WT PASK or KD GSK3β protects PDX-1 from degradation and results in increased PDX-1 protein abundance. Conversely, overexpression of KD PASK blocks glucose-induction of PDX-1 protein. We conclude that PASK phosphorylates and inactivates GSK3β, thereby preventing PDX-1 serine phosphorylation and alleviating GSK3β-mediated PDX-1 protein degradation in pancreatic β-cells.
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Affiliation(s)
- Meriem Semache
- Montreal Diabetes Research Center, CRCHUM, Quebec City H1W4A4, Canada
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Amyot J, Benterki I, Fontés G, Hagman DK, Ferdaoussi M, Teodoro T, Volchuk A, Joly É, Poitout V. Binding of activating transcription factor 6 to the A5/Core of the rat insulin II gene promoter does not mediate its transcriptional repression. J Mol Endocrinol 2011; 47:273-83. [PMID: 21821716 PMCID: PMC3185209 DOI: 10.1530/jme-11-0016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pancreatic β-cells have a well-developed endoplasmic reticulum due to their highly specialized secretory function to produce insulin in response to glucose and nutrients. It has been previously reported that overexpression of activating transcription factor 6 (ATF6) reduces insulin gene expression in part via upregulation of small heterodimer partner. In this study, we investigated whether ATF6 directly binds to the insulin gene promoter, and whether its direct binding represses insulin gene promoter activity. A bioinformatics analysis identified a putative ATF6 binding site in the A5/Core region of the rat insulin II gene promoter. Direct binding of ATF6 was confirmed using several approaches. Electrophoretic mobility shift assays in nuclear extracts from MCF7 cells, isolated rat islets and insulin-secreting HIT-T15 cells showed ATF6 binding to the native A5/Core of the rat insulin II gene promoter. Antibody-mediated supershift analyses revealed the presence of both ATF6 isoforms, ATF6α and ATF6β, in the complex. Chromatin immunoprecipitation assays confirmed the binding of ATF6α and ATF6β to a region encompassing the A5/Core of the rat insulin II gene promoter in isolated rat islets. Overexpression of the active (cleaved) fragment of ATF6α, but not ATF6β, inhibited the activity of an insulin promoter-reporter by 50%. However, the inhibitory effect of ATF6α was insensitive to mutational inactivation or deletion of the A5/Core. Therefore, although ATF6 binds directly to the A5/Core of the rat insulin II gene promoter, this direct binding does not appear to contribute to its repressive activity.
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Affiliation(s)
- Julie Amyot
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
- Department of Biochemistry, Université de Montréal, C.P. 6128, succursale Centre-ville, QC, Canada, H3C 3J7
| | - Isma Benterki
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
- Department of Biochemistry, Université de Montréal, C.P. 6128, succursale Centre-ville, QC, Canada, H3C 3J7
| | - Ghislaine Fontés
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
| | - Derek K. Hagman
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
| | - Mourad Ferdaoussi
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
| | - Tracy Teodoro
- Division of Cellular and Molecular Biology, Toronto General Research Institute, University Health Network, 101 College Street, TMDT 10-706, Toronto, ON, Canada, M5G1L7
| | - Allen Volchuk
- Division of Cellular and Molecular Biology, Toronto General Research Institute, University Health Network, 101 College Street, TMDT 10-706, Toronto, ON, Canada, M5G1L7
| | - Érik Joly
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
| | - Vincent Poitout
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada, H1W 4A4
- Department of Biochemistry, Université de Montréal, C.P. 6128, succursale Centre-ville, QC, Canada, H3C 3J7
- Department of Medicine, Université de Montréal, C.P. 6128, succursale Centre-ville, QC, Canada, H3C 3J7
- Department of Nutrition, Université de Montréal, C.P. 6128, succursale Centre-ville, QC, Canada, H3C 3J7
- Corresponding author: Montreal Diabetes Research Center, CRCHUM, Technopole Angus, 2901 Rachel Est, Montréal, QC, H1W 4A4, Canada, Tel: +1 514 890-8000 Ext: 23603, Fax: +1 514 412-7648,
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Semplici F, Vaxillaire M, Fogarty S, Semache M, Bonnefond A, Fontés G, Philippe J, Meur G, Diraison F, Sessions RB, Rutter J, Poitout V, Froguel P, Rutter GA. Human mutation within Per-Arnt-Sim (PAS) domain-containing protein kinase (PASK) causes basal insulin hypersecretion. J Biol Chem 2011; 286:44005-44014. [PMID: 22065581 PMCID: PMC3243507 DOI: 10.1074/jbc.m111.254995] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
PAS kinase (PASK) is a glucose-regulated protein kinase involved in the control of pancreatic islet hormone release and insulin sensitivity. We aimed here to identify mutations in the PASK gene that may be associated with young-onset diabetes in humans. We screened 18 diabetic probands with unelucidated maturity-onset diabetes of the young (MODY). We identified two rare nonsynonymous mutations in the PASK gene (p.L1051V and p.G1117E), each of which was found in a single MODY family. Wild type or mutant PASKs were expressed in HEK 293 cells. Kinase activity of the affinity-purified proteins was assayed as autophosphorylation at amino acid Thr307 or against an Ugp1p-derived peptide. Whereas the PASK p.G1117E mutant displayed a ∼25% increase with respect to wild type PASK in the extent of autophosphorylation, and a ∼2-fold increase in kinase activity toward exogenous substrates, the activity of the p.L1051V mutant was unchanged. Amino acid Gly1117 is located in an α helical region opposing the active site of PASK and may elicit either: (a) a conformational change that increases catalytic efficiency or (b) a diminished inhibitory interaction with the PAS domain. Mouse islets were therefore infected with adenoviruses expressing wild type or mutant PASK and the regulation of insulin secretion was examined. PASK p.G1117E-infected islets displayed a 4-fold decrease in glucose-stimulated (16.7 versus 3 mM) insulin secretion, chiefly reflecting a 4.5-fold increase in insulin release at low glucose. In summary, we have characterized a rare mutation (p.G1117E) in the PASK gene from a young-onset diabetes family, which modulates glucose-stimulated insulin secretion.
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Affiliation(s)
- Francesca Semplici
- Department of Medicine, Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Imperial College London, London SW7 2AZ, United Kingdom
| | - Martine Vaxillaire
- CNRS-UMR-8199, Pasteur Institute of Lille, BP245 59019 Lille Cedex, France; Lille Nord de France University, BP245 59019 Lille Cedex, France
| | - Sarah Fogarty
- University of Utah School of Medicine, Salt Lake City, Utah 84132-3201
| | - Meriem Semache
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
| | - Amélie Bonnefond
- CNRS-UMR-8199, Pasteur Institute of Lille, BP245 59019 Lille Cedex, France; Lille Nord de France University, BP245 59019 Lille Cedex, France
| | - Ghislaine Fontés
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
| | - Julien Philippe
- CNRS-UMR-8199, Pasteur Institute of Lille, BP245 59019 Lille Cedex, France; Lille Nord de France University, BP245 59019 Lille Cedex, France
| | - Gargi Meur
- Department of Medicine, Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Imperial College London, London SW7 2AZ, United Kingdom
| | - Frederique Diraison
- Centre for Research in Biomedicine, Faculty of Health and Life Sciences, University of the West of England, Bristol BS16 1QY, United Kingdom
| | - Richard B Sessions
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jared Rutter
- University of Utah School of Medicine, Salt Lake City, Utah 84132-3201
| | - Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada; Department of Medicine, University of Montréal, Montréal QC H1W 4A4 Québec, Canada
| | - Philippe Froguel
- CNRS-UMR-8199, Pasteur Institute of Lille, BP245 59019 Lille Cedex, France; Lille Nord de France University, BP245 59019 Lille Cedex, France; Department of Genomics of Common Disease, School of Public Health, Imperial College London, London SW7 2AZ, United Kingdom
| | - Guy A Rutter
- Department of Medicine, Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Imperial College London, London SW7 2AZ, United Kingdom.
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Fontés G, Zarrouki B, Hagman DK, Latour MG, Semache M, Roskens V, Moore PC, Prentki M, Rhodes CJ, Jetton TL, Poitout V. Glucolipotoxicity age-dependently impairs beta cell function in rats despite a marked increase in beta cell mass. Diabetologia 2010; 53:2369-79. [PMID: 20628728 PMCID: PMC2947580 DOI: 10.1007/s00125-010-1850-5] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 06/18/2010] [Indexed: 01/25/2023]
Abstract
AIMS/HYPOTHESIS Prolonged exposure of pancreatic beta cells to excessive levels of glucose and fatty acids, referred to as glucolipotoxicity, is postulated to contribute to impaired glucose homeostasis in patients with type 2 diabetes. However, the relative contribution of defective beta cell function vs diminished beta cell mass under glucolipotoxic conditions in vivo remains a subject of debate. We therefore sought to determine whether glucolipotoxicity in rats is due to impaired beta cell function and/or reduced beta cell mass, and whether older animals are more susceptible to glucolipotoxic condition. METHODS Wistar rats (2 and 6 months old) received a 72 h infusion of glucose + intravenous fat emulsion or saline control. In vivo insulin secretion and sensitivity were assessed by hyperglycaemic clamps. Ex vivo insulin secretion, insulin biosynthesis and gene expression were measured in isolated islets. Beta cell mass and proliferation were examined by immunohistochemistry. RESULTS A 72 h infusion of glucose + intravenous fat emulsion in 2-month-old Wistar rats did not affect insulin sensitivity, insulin secretion or beta cell mass. In 6-month-old rats by contrast it led to insulin resistance and reduced insulin secretion in vivo, despite an increase in beta cell mass and proliferation. This was associated with: (1) diminished glucose-stimulated second-phase insulin secretion and proinsulin biosynthesis; (2) lower insulin content; and (3) reduced expression of beta cell genes in isolated islets. CONCLUSIONS/INTERPRETATION In this in vivo model, glucolipotoxicity is characterised by an age-dependent impairment of glucose-regulated beta cell function despite a marked increase in beta cell mass.
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Affiliation(s)
- G. Fontés
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4
- Department of Medicine, University of Montreal, Montreal, QC, Canada
| | - B. Zarrouki
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4
- Department of Medicine, University of Montreal, Montreal, QC, Canada
| | - D. K. Hagman
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4
- Department of Medicine, University of Montreal, Montreal, QC, Canada
| | - M. G. Latour
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4
| | - M. Semache
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4
- Department of Biochemistry, University of Montreal, Montreal, QC, Canada
| | - V. Roskens
- Division of Endocrinology, Diabetes and Metabolism, University of Vermont College of Medicine, Burlington, VT, USA
| | - P. C. Moore
- Kovler Diabetes Center, University of Chicago, Chicago, IL, USA
| | - M. Prentki
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4
- Department of Nutrition, University of Montreal, Montreal, QC, Canada
- Department of Biochemistry, University of Montreal, Montreal, QC, Canada
| | - C. J. Rhodes
- Kovler Diabetes Center, University of Chicago, Chicago, IL, USA
| | - T. L. Jetton
- Division of Endocrinology, Diabetes and Metabolism, University of Vermont College of Medicine, Burlington, VT, USA
| | - V. Poitout
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- CRCHUM–Technopole Angus, 2901 Rachel Est, Montréal, QC, Canada H1W 4A4,
- Department of Medicine, University of Montreal, Montreal, QC, Canada
- Department of Nutrition, University of Montreal, Montreal, QC, Canada
- Department of Biochemistry, University of Montreal, Montreal, QC, Canada
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Fontés G, Semache M, Hagman DK, Tremblay C, Shah R, Rhodes CJ, Rutter J, Poitout V. Involvement of Per-Arnt-Sim Kinase and extracellular-regulated kinases-1/2 in palmitate inhibition of insulin gene expression in pancreatic beta-cells. Diabetes 2009; 58:2048-58. [PMID: 19502418 PMCID: PMC2731539 DOI: 10.2337/db08-0579] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Prolonged exposure of pancreatic beta-cells to simultaneously elevated levels of fatty acids and glucose (glucolipotoxicity) impairs insulin gene transcription. However, the intracellular signaling pathways mediating these effects are mostly unknown. This study aimed to ascertain the role of extracellular-regulated kinases (ERKs)1/2, protein kinase B (PKB), and Per-Arnt-Sim kinase (PASK) in palmitate inhibition of insulin gene expression in pancreatic beta-cells. RESEARCH DESIGN AND METHODS MIN6 cells and isolated rat islets were cultured in the presence of elevated glucose, with or without palmitate or ceramide. ERK1/2 phosphorylation, PKB phosphorylation, and PASK expression were examined by immunoblotting and real-time PCR. The role of these kinases in insulin gene expression was assessed using pharmacological and molecular approaches. RESULTS Exposure of MIN6 cells and islets to elevated glucose induced ERK1/2 and PKB phosphorylation, which was further enhanced by palmitate. Inhibition of ERK1/2, but not of PKB, partially prevented the inhibition of insulin gene expression in the presence of palmitate or ceramide. Glucose-induced expression of PASK mRNA and protein levels was reduced in the presence of palmitate. Overexpression of wild-type PASK increased insulin and pancreatic duodenal homeobox-1 gene expression in MIN6 cells and rat islets incubated with glucose and palmitate, whereas overexpression of a kinase-dead PASK mutant in rat islets decreased expression of insulin and pancreatic duodenal homeobox-1 and increased C/EBPbeta expression. CONCLUSIONS Both the PASK and ERK1/2 signaling pathways mediate palmitate inhibition of insulin gene expression. These findings identify PASK as a novel mediator of glucolipotoxicity on the insulin gene in pancreatic beta-cells.
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Affiliation(s)
- Ghislaine Fontés
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Québec, Canada
| | - Meriem Semache
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
| | - Derek K. Hagman
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Québec, Canada
| | - Caroline Tremblay
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
| | - Ramila Shah
- Kovler Diabetes Center, University of Chicago, Chicago, Illinois
| | | | - Jared Rutter
- Division of Endocrinology, University of Utah School of Medicine, Salt Lake City, Utah
| | - Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Québec, Canada
- Corresponding author: Vincent Poitout,
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Poitout V, Amyot J, Semache M, Zarrouki B, Hagman D, Fontés G. Glucolipotoxicity of the pancreatic beta cell. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1801:289-98. [PMID: 19715772 DOI: 10.1016/j.bbalip.2009.08.006] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/13/2009] [Accepted: 08/13/2009] [Indexed: 02/07/2023]
Abstract
The concept of glucolipotoxicity refers to the combined, deleterious effects of elevated glucose and fatty acid levels on pancreatic beta-cell function and survival. Significant progress has been made in recent years towards a better understanding of the cellular and molecular basis of glucolipotoxicity in the beta cell. The permissive effect of elevated glucose on the detrimental actions of fatty acids stems from the influence of glucose on intracellular fatty acid metabolism, promoting the synthesis of cellular lipids. The combination of excessive levels of fatty acids and glucose therefore leads to decreased insulin secretion, impaired insulin gene expression, and beta-cell death by apoptosis, all of which probably have distinct underlying mechanisms. Recent studies from our laboratory have identified several pathways implicated in fatty acid inhibition of insulin gene expression, including the extracellular-regulated kinase (ERK1/2) pathway, the metabolic sensor Per-Arnt-Sim kinase (PASK), and the ATF6 branch of the unfolded protein response. We have also confirmed in vivo in rats that the decrease in insulin gene expression is an early defect which precedes any detectable abnormality in insulin secretion. While the role of glucolipotoxicity in humans is still debated, the inhibitory effects of chronically elevated fatty acid levels has been clearly demonstrated in several studies, at least in individuals genetically predisposed to developing type 2 diabetes. It is therefore likely that glucolipotoxicity contributes to beta-cell failure in type 2 diabetes as well as to the decline in beta-cell function observed after the onset of the disease.
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Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, Montreal, QC, Canada.
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Amyot J, Hagman D, Fontés G, Poitout V. A role for ER stress and JNK in fatty acid inhibition of the insulin gene. Can J Diabetes 2009. [DOI: 10.1016/s1499-2671(09)31017-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Abstract
Miniglucagon (glucagon 19-29) is the ultimate processing product of proglucagon, present in the glucagon-secreting granules of the alpha cells, at a close vicinity of the insulin-secreting beta cells. Co-released with glucagon and thanks to its original mode of action and its huge potency, it suppresses, inside the islet of Langerhans, the detrimental effect of glucagon on insulin secretion, while it leaves untouched the beneficial effect of glucagon on glucose competence of the beta cell. At the periphery, miniglucagon is processed at the surface of glucagon- and insulin-sensitive cells from circulating glucagon. At that level, it acts via a cellular pathway which uses initial molecular steps distinct from that of insulin which, when impaired, are involved in insulin resistence. This bypass allows miniglucagon to act as an insulin-like component, a characteristic which makes this peptide of particular interest from a pathophysiological and pharmacological point of views in understanding and treating metabolic diseases, such as the type 2 diabetes.
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Affiliation(s)
- Dominique Bataille
- INSERM U 376, CHU Arnaud-de-Villeneuve, 34295 Montpellier Cedex 05, France.
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Fontés G, Lajoix AD, Bergeron F, Cadel S, Prat A, Foulon T, Gross R, Dalle S, Le-Nguyen D, Tribillac F, Bataille D. Miniglucagon (MG)-generating endopeptidase, which processes glucagon into MG, is composed of N-arginine dibasic convertase and aminopeptidase B. Endocrinology 2005; 146:702-12. [PMID: 15539558 DOI: 10.1210/en.2004-0853] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Miniglucagon (MG), the C-terminal glucagon fragment, processed from glucagon by the MG-generating endopeptidase (MGE) at the Arg17-Arg18 dibasic site, displays biological effects opposite to that of the mother-hormone. This secondary processing occurs in the glucagon- and MG-producing alpha-cells of the islets of Langerhans and from circulating glucagon. We first characterized the enzymatic activities of MGE in culture media from glucagon and MG-secreting alphaTC1.6 cells as made of a metalloendoprotease and an aminopeptidase. We observed that glucagon is a substrate for N-arginine dibasic convertase (NRDc), a metalloendoprotease, and that aminopeptidase B cleaves in vitro the intermediate cleavage products sequentially, releasing mature MG. Furthermore, immunodepletion of either enzyme resulted in the disappearance of the majority of MGE activity from the culture medium. We found RNAs and proteins corresponding to both enzymes in different cell lines containing a MGE activity (mouse alphaTC1.6 cells, rat hepatic FaO, and rat pituitary GH4C1). Using confocal microscopy, we observed a granular immunostaining of both enzymes in the alphaTC1.6 and native rat alpha-cells from islets of Langerhans. By immunogold electron microscopy, both enzymes were found in the mature secretory granules of alpha-cells, close to their substrate (glucagon) and their product (MG). Finally, we found NRDc only in the fractions from perfused pancreas that contain glucagon and MG after stimulation by hypoglycemia. We conclude that MGE is composed of NRDc and aminopeptidase B acting sequentially, providing a molecular basis for this uncommon regulatory process, which should be now addressed in both physiological and pathophysiological situations.
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Affiliation(s)
- Ghislaine Fontés
- Institut National de la Santé et de la Recherche Médicale Unité 376, Centre Hospitalier Universitaire Arnaud de Villeneuve, 371, Rue du Doyen G. Giraud, 34295 Montpellier, Cedex 5, France
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Dalle S, Longuet C, Costes S, Broca C, Faruque O, Fontés G, Hani EH, Bataille D. Glucagon promotes cAMP-response element-binding protein phosphorylation via activation of ERK1/2 in MIN6 cell line and isolated islets of Langerhans. J Biol Chem 2004; 279:20345-55. [PMID: 14988413 DOI: 10.1074/jbc.m312483200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
By using the MIN6 cell line and pancreatic islets, we show that in the presence of a low glucose concentration, corresponding to physiological glucagon release from alpha cells, glucagon treatment of the beta cell caused a rapid, time-dependent phosphorylation and activation of p44/p42 mitogen-activated protein kinase (ERK1/2) independently from extracellular calcium influx. Inhibition of either cAMP-dependent protein kinase (PKA) or MEK completely blocked ERK1/2 activation by glucagon. However, no significant activation of several upstream activators of MEK, including Shc-p21(Ras) and phosphatidylinositol 3-kinase, was observed in response to glucagon treatment. Chelation of intracellular calcium (intracellular [Ca(2+)]) reduced glucagon-mediated ERK1/2 activation. In addition, internalization of glucagon receptors through clathrin-coated pits formation is required for ERK1/2 activation. Remarkably, glucagon promotes the nuclear translocation of ERK1/2 and induces the phosphorylation of cAMP-response element-binding protein (CREB). Miniglucagon, produced from glucagon and released together with the mother hormone from the alpha cells in low glucose situations, blocks the insulinotropic effect of glucagon, whereas it does not inhibit the glucagon-induced PKA/ERK1/2/CREB pathway. We conclude that glucagon-induced ERK1/2 activation is mediated by PKA and that an increase in [Ca(2+)](i) is required for maximal ERK activation. Our results uncover a novel mechanism by which the PKA/ERK1/2 signaling network engaged by glucagon, in situation of low glucose concentration, regulates phosphorylation of CREB, a transcription factor crucial for normal beta cell function and survival.
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Affiliation(s)
- Stéphane Dalle
- Unité INSERM U376, CHU Arnaud-de-Villeneuve, 371 Rue du Doyen Gaston Giraud, 34295 Montpellier Cedex 5, France
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Bataille D, Dalle S, Hani EH, Longuet C, Costes S, Fontés G. Physiopathologie de la sécrétion du glucagon. Annales d'Endocrinologie 2004; 65:24-7. [PMID: 15122088 DOI: 10.1016/s0003-4266(04)95626-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- D Bataille
- CHU Arnaud-de-Villeneuve, INSERM U 376, Endocrinologie des peptides et diabète, 34295 Montpellier Cedex 5, France.
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Bataille D, Fontés G, Costes S, Longuet C, Dalle S. [Miniglucagon: is the precursor a traitor to its family or a genius? ]. Journ Annu Diabetol Hotel Dieu 2004:139-49. [PMID: 15259312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Affiliation(s)
- D Bataille
- Inserm U 376, CHU Arnaud-de-Villeneuve, Montpellier
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Dalle S, Fontés G, Lajoix AD, LeBrigand L, Gross R, Ribes G, Dufour M, Barry L, LeNguyen D, Bataille D. Miniglucagon (glucagon 19-29): a novel regulator of the pancreatic islet physiology. Diabetes 2002; 51:406-12. [PMID: 11812748 DOI: 10.2337/diabetes.51.2.406] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Miniglucagon, the COOH-terminal (19-29) fragment processed from glucagon, is a potent and efficient inhibitor of insulin secretion from the MIN 6 beta-cell line. Using the rat isolated-perfused pancreas, we investigated the inhibitory effect of miniglucagon on insulin secretion and evaluated the existence of an inhibitory tone exerted by this peptide inside the islet. Miniglucagon dose-dependently inhibited insulin secretion stimulated by 8.3 mol/l glucose, with no change in the perfusion flow rate. A concentration of 1 nmol/l miniglucagon had a significant inhibitory effect on a 1 nmol/l glucagon-like peptide 1 (7-36) amide-potentiated insulin secretion. A decrease in extracellular glucose concentration simultaneously stimulated glucagon and miniglucagon secretion from pancreatic alpha-cells. Using confocal and electron microscopy analysis, we observed that miniglucagon is colocalized with glucagon in mature secretory granules of alpha-cells. Perfusion of an anti-miniglucagon antiserum directed against the biologically active moiety of the peptide resulted in a more pronounced effect of a glucose challenge on insulin secretion, indicating that miniglucagon exerts a local inhibitory tone on beta-cells. We concluded that miniglucagon is a novel local regulator of the pancreatic islet physiology and that any abnormal inhibitory tone exerted by this peptide on the beta-cell would result in an impaired insulin secretion, as observed in type 2 diabetes.
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Affiliation(s)
- Stéphane Dalle
- Institut National de la Santé et de la Recherche Médicale, Montpellier, France
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