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Santos JL, Cataldo LR, Cortés-Rivera C, Bravo C, Díaz-Casanova L, Martínez JA, Milagro FI, Galgani J. Plasma lactate and leukocyte mitochondrial DNA copy number as biomarkers of insulin sensitivity in non-diabetic women. J Physiol Biochem 2019; 75:285-297. [DOI: 10.1007/s13105-019-00672-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 02/28/2019] [Indexed: 11/29/2022]
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Dover EN, Patel NY, Stýblo M. Impact of in vitro heavy metal exposure on pancreatic β-cell function. Toxicol Lett 2018; 299:137-144. [PMID: 30300733 PMCID: PMC6214754 DOI: 10.1016/j.toxlet.2018.09.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 09/12/2018] [Accepted: 09/28/2018] [Indexed: 11/24/2022]
Abstract
Susceptibility to type-2 diabetes mellitus (DM) is determined, in part, by a variety of environmental factors, including exposure to metals. Heavy metals including inorganic arsenic (iAs), zinc (Zn), manganese (Mn), and cadmium (Cd) have been reported to affect glucose homeostasis or DM risk in population-based and/or laboratory studies. Previous evidence from our lab has shown that iAs can increase DM risk by impairing mitochondrial metabolism, one of the key steps in the regulation of glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells. The goal of the current study was to compare the effects of iAs on GSIS and mitochondrial function in INS-1 832/13 β-cells with those of Cd, Mn, and Zn, and to evaluate effects of binary mixtures of these metals. As expected, 24-hour exposure to iAs (arsenite, ≥1 μM) significantly inhibited GSIS as did Cd (5 μM) and Mn (12.5, 25, or 50 μM). Zn had no effects on GSIS at concentrations up to 50 μM. Mitochondrial function was assessed by measuring oxygen consumption rate (OCR) after glucose stimulation and during simulated mitochondrial stress. While both iAs and Mn impaired mitochondrial function (inhibiting OCR, maximal respiration, and/or spare respiratory capacity of mitochondria), no significant effects were found in cells exposed to Cd. Interestingly, no additive or synergistic effects on GSIS or OCR were observed in binary mixtures of iAs with either Mn or Cd. These data suggest that Mn, like iAs, may inhibit GSIS by impairing mitochondrial function, whereas Cd may target other mechanisms that regulate GSIS in β-cells.
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Affiliation(s)
- E Nicole Dover
- Curriculum in Toxicology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Naishal Y Patel
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA
| | - Miroslav Stýblo
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA.
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53
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Hennings TG, Chopra DG, DeLeon ER, VanDeusen HR, Sesaki H, Merrins MJ, Ku GM. In Vivo Deletion of β-Cell Drp1 Impairs Insulin Secretion Without Affecting Islet Oxygen Consumption. Endocrinology 2018; 159:3245-3256. [PMID: 30052866 PMCID: PMC6107751 DOI: 10.1210/en.2018-00445] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/16/2018] [Indexed: 01/17/2023]
Abstract
Mitochondria are dynamic organelles that undergo frequent fission and fusion events. Mitochondrial fission is required for ATP production, the tricarboxylic acid cycle, and processes beyond metabolism in a cell-type specific manner. Ex vivo and cell line studies have demonstrated that Drp1, a central regulator of mitochondrial fission, is required for glucose-stimulated insulin secretion (GSIS) in pancreatic β cells. Herein, we set out to interrogate the role of Drp1 in β-cell insulin secretion in vivo. We generated β-cell-specific Drp1 knockout (KO) mice (Drp1β-KO) by crossing a conditional allele of Drp1 to Ins1cre mice, in which Cre recombinase replaces the coding region of the Ins1 gene. Drp1β-KO mice were glucose intolerant due to impaired GSIS but did not progress to fasting hyperglycemia as adults. Despite markedly abnormal mitochondrial morphology, Drp1β-KO islets exhibited normal oxygen consumption rates and an unchanged glucose threshold for intracellular calcium mobilization. Instead, the most profound consequences of β-cell Drp1 deletion were impaired second-phase insulin secretion and impaired glucose-stimulated amplification of insulin secretion. Our data establish Drp1 as an important regulator of insulin secretion in vivo and demonstrate a role for Drp1 in metabolic amplification and calcium handling without affecting oxygen consumption.
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Affiliation(s)
- Thomas G Hennings
- Diabetes Center, University of California, San Francisco, San Francisco, California
- Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, California
| | - Deeksha G Chopra
- Diabetes Center, University of California, San Francisco, San Francisco, California
| | - Elizabeth R DeLeon
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
| | - Halena R VanDeusen
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Matthew J Merrins
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
- William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin
| | - Gregory M Ku
- Diabetes Center, University of California, San Francisco, San Francisco, California
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Francisco, San Francisco, California
- Correspondence: Gregory M. Ku, MD, PhD, 513 Parnassus Avenue, HSW 1027, San Francisco, California 94143. E-mail:
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54
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Xie K, Xu B, Zhang Y, Chen M, Ji Y, Wang J, Huang Z, Zhou K, Xia Y, Tang W. A multi-method evaluation of the effects of Inflammatory cytokines (IL-1β, IFN-γ, TNF-α) on pancreatic β-cells. J Cell Physiol 2018; 233:9375-9382. [PMID: 29923197 DOI: 10.1002/jcp.26518] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 01/30/2018] [Indexed: 01/16/2023]
Abstract
We aimed to explore the effects of Inflammatory cytokines (IL-1β, IFN-γ, TNF-α) on pancreatic β-cells. CCK-8 assay showed that the cell viability decreased after 24 hr treatment of TNF-α, 48 hr of IFN-γ, and 84 hr of IL-1β. EdU assay illustrated that after 24 hr treatment, there were significantly reduced EdU-labeled red fluorescence cells in TNF-α group while not in IFN-γ and IL-1β groups. Flow Cytometry results displayed that TNF-α and IFN-γ groups increased apoptosis while IL-1β group did not. Cell apoptosis results found that there was an increase in the S-phase population of IL-1β and TNF-α groups, however, there was no significant difference in cell cycle between IFN-γ group and the control. TEM images showed that there were reduction in the number of granules and mitochondria in IL-1β and IFN-γ groups, in particular paucity of insulin granules and mitochondria in TNF-α group. Radioimmunoassay results presented that TNF-α inhibited glucose-induced insulin secretion, while there were no significant changes in IL-1β and IFN-γ groups when compared with the control. Metabolomic analysis found amino acid metabolism and Krebs cycle were the most robust altered metabolism pathways after inflammatory cytokines treatments. Overall, the altered amino acid metabolism and Krebs cycle metabolism might be important mechanisms of TNF-α induced mouse pancreatic β-cells dysfuction.
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Affiliation(s)
- Kaipeng Xie
- Nanjing Maternal and Child Health Institute, The Affiliated Obstetrics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, China.,Department of Women Health Care, The Affiliated Obstetrics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, China
| | - Bo Xu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Yuqing Zhang
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Minjian Chen
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Yinwen Ji
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio
| | - Zhenyao Huang
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Kun Zhou
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Yankai Xia
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Wei Tang
- Department of Endocrinology, Islet Cell Senescense and Function Research Laboratory, Jiangsu Province Geriatric Institute, Nanjing, China.,Department of Endocrinology, Jiangyin People's Hospital, School of Medicine, Southeast University, Jiangyin, China
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55
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Dover EN, Beck R, Huang MC, Douillet C, Wang Z, Klett EL, Stýblo M. Arsenite and methylarsonite inhibit mitochondrial metabolism and glucose-stimulated insulin secretion in INS-1 832/13 β cells. Arch Toxicol 2018; 92:693-704. [PMID: 28956099 PMCID: PMC6640649 DOI: 10.1007/s00204-017-2074-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 09/20/2017] [Indexed: 10/18/2022]
Abstract
Growing evidence suggests that exposure to environmental contaminants contributes to the current diabetes epidemic. Inorganic arsenic (iAs), a drinking water and food contaminant, is one of the most widespread environmental diabetogens according to epidemiological studies. Several schemes have been proposed to explain the diabetogenic effects of iAs exposure; however, the exact mechanism remains unknown. We have shown that in vitro exposure to low concentrations of arsenite (iAsIII) or its trivalent methylated metabolites, methylarsonite (MAsIII) and dimethylarsinite (DMAsIII), inhibits glucose-stimulated insulin secretion (GSIS) from isolated pancreatic islets, with little effect on insulin transcription or total insulin content. The goal of this study was to determine if exposure to trivalent arsenicals impairs mitochondrial metabolism, which plays a key role in the regulation of GSIS in β cells. We used a Seahorse extracellular flux analyzer to measure oxygen consumption rate (OCR), a proxy for mitochondrial metabolism, in cultured INS-1 832/13 β cells exposed to iAsIII, MAsIII, or DMAsIII and stimulated with either glucose or pyruvate, a final product of glycolysis and a substrate for the Krebs cycle. We found that 24-h exposure to 2 μM iAsIII or 0.375-0.5 μM MAsIII inhibited OCR in both glucose- and pyruvate-stimulated β cells in a manner that closely paralleled GSIS inhibition. In contrast, 24-h exposure to DMAsIII (up to 2 µM) had no effects on either OCR or GSIS. These results suggest that iAsIII and MAsIII may impair GSIS in β cells by inhibiting mitochondrial metabolism, and that at least one target of these arsenicals is pyruvate decarboxylation or downstream reactions.
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Affiliation(s)
- E N Dover
- Curriculum in Toxicology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - R Beck
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - M C Huang
- Curriculum in Toxicology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - C Douillet
- Department of Nutrition, CB# 74612, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27599-7461, USA
| | - Z Wang
- School of Environmental Science and Engineering, Shandong University, No. 27 Shanda South Road, Jinan, 250100, China
| | - E L Klett
- Department of Nutrition, CB# 74612, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27599-7461, USA
- Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Miroslav Stýblo
- Department of Nutrition, CB# 74612, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27599-7461, USA.
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56
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Cao J, Wu H, Li Z. Recent perspectives of pediatric mitochondrial diseases. Exp Ther Med 2018; 15:13-18. [PMID: 29375674 PMCID: PMC5763647 DOI: 10.3892/etm.2017.5385] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 09/21/2017] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial disorders are amongst the most common groups of inborn errors of metabolism. They are caused by deficiencies in the final pathway of the cellular energy production, the mitochondrial respiratory chain. The disorders are clinically and genetically heterogeneous and the aetiology could be found in the mitochondrial, or in the nuclear genome. We searched important e-databases for the collection of latest literature on the mitochondrial disease especially in pediatric population. Most of the studies in the recent past have focused on the understanding of the clinical phenotypes and pathophysiological mechanisms. Leigh syndrome is a common severe, neurodegenerative disease of early childhood. A defect in the POLG gene is another common observation in most of the cases leading to Alpers syndrome. The review concludes that pediatric mitochondrial disorders are severe, progressive and usually multi-systemic. Further, whole genome sequencing is an excellent diagnostic option.
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Affiliation(s)
- Junhua Cao
- Department of Neonatology, Xuzhou Children's Hospital, Xuzhou, Jiangsu 221002, P.R. China
| | - Hongwei Wu
- Department of Neonatology, Xuzhou Children's Hospital, Xuzhou, Jiangsu 221002, P.R. China
| | - Zhenguang Li
- Department of Neonatology, Xuzhou Children's Hospital, Xuzhou, Jiangsu 221002, P.R. China
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57
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 446] [Impact Index Per Article: 74.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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58
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Skelin Klemen M, Dolenšek J, Slak Rupnik M, Stožer A. The triggering pathway to insulin secretion: Functional similarities and differences between the human and the mouse β cells and their translational relevance. Islets 2017; 9:109-139. [PMID: 28662366 PMCID: PMC5710702 DOI: 10.1080/19382014.2017.1342022] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In β cells, stimulation by metabolic, hormonal, neuronal, and pharmacological factors is coupled to secretion of insulin through different intracellular signaling pathways. Our knowledge about the molecular machinery supporting these pathways and the patterns of signals it generates comes mostly from rodent models, especially the laboratory mouse. The increased availability of human islets for research during the last few decades has yielded new insights into the specifics in signaling pathways leading to insulin secretion in humans. In this review, we follow the most central triggering pathway to insulin secretion from its very beginning when glucose enters the β cell to the calcium oscillations it produces to trigger fusion of insulin containing granules with the plasma membrane. Along the way, we describe the crucial building blocks that contribute to the flow of information and focus on their functional role in mice and humans and on their translational implications.
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Affiliation(s)
- Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Marjan Slak Rupnik
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
- Institute of Physiology; Center for Physiology and Pharmacology; Medical University of Vienna; Vienna, Austria
| | - Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
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59
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Maechler P. Glutamate pathways of the beta-cell and the control of insulin secretion. Diabetes Res Clin Pract 2017; 131:149-153. [PMID: 28743063 DOI: 10.1016/j.diabres.2017.07.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 07/04/2017] [Indexed: 11/29/2022]
Abstract
Pancreatic beta-cells secrete insulin in response to circulating glucose, thereby maintaining euglycemia. Inside the beta-cell, glucose is transformed into intracellular signals stimulating exocytosis. While calcium is an obligatory messenger, this ion is not sufficient to promote the full secretory response. Accordingly, glucose metabolism produces the additive factor glutamate that participates to an amplifying pathway of the calcium signal. Although intracellular glutamate potentiates insulin secretion, extracellular glutamate may activate ionotropic receptors. As a consequence of such activation, insulin exocytosis is slowed down. Therefore, for the beta-cell glutamate is a double-edged sword, an amplifying pathway and a negative feedback, illustrating the principle of homeostasis.
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Affiliation(s)
- Pierre Maechler
- Department of Cell Physiology and Metabolism & Faculty Diabetes Center, University of Geneva Medical Center, Geneva, Switzerland.
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60
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Welters A, Klüppel C, Mrugala J, Wörmeyer L, Meissner T, Mayatepek E, Heiss C, Eberhard D, Lammert E. NMDAR antagonists for the treatment of diabetes mellitus-Current status and future directions. Diabetes Obes Metab 2017; 19 Suppl 1:95-106. [PMID: 28880473 DOI: 10.1111/dom.13017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 05/18/2017] [Accepted: 05/20/2017] [Indexed: 12/16/2022]
Abstract
Diabetes mellitus is characterized by chronically elevated blood glucose levels accelerated by a progressive decline of insulin-producing β-cells in the pancreatic islets. Although medications are available to transiently adjust blood glucose to normal levels, the effects of current drugs are limited when it comes to preservation of a critical mass of functional β-cells to sustainably maintain normoglycemia. In this review, we recapitulate recent evidence on the role of pancreatic N-methyl-D-aspartate receptors (NMDARs) in β-cell physiology, and summarize effects of morphinan-based NMDAR antagonists that are beneficial for insulin secretion, glucose tolerance and islet cell survival. We further discuss NMDAR-mediated molecular pathways relevant for neuronal cell survival, which may also be important for the preservation of β-cell function and mass. Finally, we summarize the literature for evidence on the role of NMDARs in the development of diabetic long-term complications, and highlight beneficial pharmacologic aspects of NMDAR antagonists in diabetic nephropathy, retinopathy as well as neuropathy.
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Affiliation(s)
- Alena Welters
- Institute of Metabolic Physiology, Department of Biology, Heinrich Heine University, Düsseldorf, Germany
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital Düsseldorf, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Carina Klüppel
- Institute of Metabolic Physiology, Department of Biology, Heinrich Heine University, Düsseldorf, Germany
| | - Jessica Mrugala
- Institute for Beta Cell Biology, German Diabetes Center, Leibniz Center for Diabetes Research, Düsseldorf, Germany
- German Center for Diabetes Research, Helmholtz Zentrum München, Neuherberg, Düsseldorf, Germany
| | - Laura Wörmeyer
- Institute of Metabolic Physiology, Department of Biology, Heinrich Heine University, Düsseldorf, Germany
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital Düsseldorf, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Thomas Meissner
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital Düsseldorf, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Ertan Mayatepek
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital Düsseldorf, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Christian Heiss
- Division of Cardiology, Pulmonology, and Vascular Medicine, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Daniel Eberhard
- Institute of Metabolic Physiology, Department of Biology, Heinrich Heine University, Düsseldorf, Germany
| | - Eckhard Lammert
- Institute of Metabolic Physiology, Department of Biology, Heinrich Heine University, Düsseldorf, Germany
- Institute for Beta Cell Biology, German Diabetes Center, Leibniz Center for Diabetes Research, Düsseldorf, Germany
- German Center for Diabetes Research, Helmholtz Zentrum München, Neuherberg, Düsseldorf, Germany
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61
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Silvander JSG, Kvarnström SM, Kumari-Ilieva A, Shrestha A, Alam CM, Toivola DM. Keratins regulate β-cell mitochondrial morphology, motility, and homeostasis. FASEB J 2017; 31:4578-4587. [PMID: 28666985 DOI: 10.1096/fj.201700095r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 06/19/2017] [Indexed: 12/19/2022]
Abstract
Loss of the epithelial intermediate filament protein keratin 8 (K8) in murine β cells leads to irregular insulin vesicles and decreased insulin levels. Because mitochondria are central in glucose-stimulated insulin secretion, the relationship between keratins and β-cell mitochondrial function and morphology was investigated. β cells in murine K8-knockout (K8-/-) islets of Langerhans have increased numbers of mitochondria, which are rounder and have diffuse cristae, as seen by electron microscopy. The mitochondrial network in primary cultured K8-/- β cells is more fragmented compared with K8+/+ mitochondria, correlating with decreased levels of mitofusin 2 and the mitofusin 2- and keratin-binding protein trichoplein. K8-/- β-cell mitochondria have decreased levels of total and mitochondrial cytochrome c, which correlates with a reduction in electron transport complexes I and IV. This provokes loss of mitochondrial membrane potential and reduction of ATP and insulin amount, as seen in K8-/- β cells. Mitochondria in K8 wild-type β cells and MIN6 insulinoma cells overexpressing K8 and 18 are more stationary compared with mitochondria in keratin-deficient cells. In conclusion, keratins, likely through trichoplein-mitofusin interactions, regulate both structural and dynamic functions of β-cell mitochondria, which could have implications for downstream insulin secretion.-Silvander, J. S. G., Kvarnström, S. M., Kumari-Ilieva, A., Shrestha, A., Alam, C. M., Toivola, D. M. Keratins regulate β-cell mitochondrial morphology, motility, and homeostasis.
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Affiliation(s)
- Jonas S G Silvander
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Sofie M Kvarnström
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Angeli Kumari-Ilieva
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Anup Shrestha
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Catharina M Alam
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Diana M Toivola
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
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Chau GC, Im DU, Kang TM, Bae JM, Kim W, Pyo S, Moon EY, Um SH. mTOR controls ChREBP transcriptional activity and pancreatic β cell survival under diabetic stress. J Cell Biol 2017; 216:2091-2105. [PMID: 28606928 PMCID: PMC5496625 DOI: 10.1083/jcb.201701085] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 04/05/2017] [Accepted: 05/01/2017] [Indexed: 02/06/2023] Open
Abstract
Through in vivo analyses of mTOR deficiency and in vitro studies of human and mouse pancreatic islets, Chau et al. show that mTOR plays a critical role in β cell survival in diabetes. mTOR associates with and inhibits the transcriptional ChREBP–Mlx complex, suppressing TXNIP expression and β cell death. Impaired nutrient sensing and dysregulated glucose homeostasis are common in diabetes. However, how nutrient-sensitive signaling components control glucose homeostasis and β cell survival under diabetic stress is not well understood. Here, we show that mice lacking the core nutrient-sensitive signaling component mammalian target of rapamycin (mTOR) in β cells exhibit reduced β cell mass and smaller islets. mTOR deficiency leads to a severe reduction in β cell survival and increased mitochondrial oxidative stress in chemical-induced diabetes. Mechanistically, we find that mTOR associates with the carbohydrate-response element–binding protein (ChREBP)–Max-like protein complex and inhibits its transcriptional activity, leading to decreased expression of thioredoxin-interacting protein (TXNIP), a potent inducer of β cell death and oxidative stress. Consistent with this, the levels of TXNIP and ChREBP were highly elevated in human diabetic islets and mTOR-deficient mouse islets. Thus, our results suggest that a nutrient-sensitive mTOR-regulated transcriptional network could be a novel target to improve β cell survival and glucose homeostasis in diabetes.
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Affiliation(s)
- Gia Cac Chau
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do, Korea
| | - Dong Uk Im
- Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea
| | - Tong Mook Kang
- Department of Physiology, Single Cell Network Research Center, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do, Korea
| | - Jeong Mo Bae
- Department of Pathology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul Metropolitan Government Boramae Medical Center, Seoul, Korea
| | - Won Kim
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Seoul National University College of Medicine, Seoul Metropolitan Government Boramae Medical Center, Seoul, Korea
| | - Suhkneung Pyo
- School of Pharmacy, Sungkyunkwan University, Suwon, Gyeonggi-do, Korea
| | - Eun-Yi Moon
- Department of Bioscience and Biotechnology, Sejong University, Seoul, Korea
| | - Sung Hee Um
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do, Korea .,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea
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The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:2712751. [PMID: 28607629 PMCID: PMC5457758 DOI: 10.1155/2017/2712751] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/03/2017] [Accepted: 04/12/2017] [Indexed: 12/14/2022]
Abstract
Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed.
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Abstract
The pancreatic β-cell secretes insulin in response to elevated plasma glucose. This review applies an external bioenergetic critique to the central processes of glucose-stimulated insulin secretion, including glycolytic and mitochondrial metabolism, the cytosolic adenine nucleotide pool, and its interaction with plasma membrane ion channels. The control mechanisms responsible for the unique responsiveness of the cell to glucose availability are discussed from bioenergetic and metabolic control standpoints. The concept of coupling factor facilitation of secretion is critiqued, and an attempt is made to unravel the bioenergetic basis of the oscillatory mechanisms controlling secretion. The need to consider the physiological constraints operating in the intact cell is emphasized throughout. The aim is to provide a coherent pathway through an extensive, complex, and sometimes bewildering literature, particularly for those unfamiliar with the field.
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Affiliation(s)
- David G Nicholls
- Buck Institute for Research on Aging, Novato, California; and Department of Clinical Sciences, Unit of Molecular Metabolism, Lund University Diabetes Centre, Malmo, Sweden
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65
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Santos LR, Muller C, de Souza AH, Takahashi HK, Spégel P, Sweet IR, Chae H, Mulder H, Jonas JC. NNT reverse mode of operation mediates glucose control of mitochondrial NADPH and glutathione redox state in mouse pancreatic β-cells. Mol Metab 2017; 6:535-547. [PMID: 28580284 PMCID: PMC5444111 DOI: 10.1016/j.molmet.2017.04.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/10/2017] [Accepted: 04/18/2017] [Indexed: 11/17/2022] Open
Abstract
Objective The glucose stimulation of insulin secretion (GSIS) by pancreatic β-cells critically depends on increased production of metabolic coupling factors, including NADPH. Nicotinamide nucleotide transhydrogenase (NNT) typically produces NADPH at the expense of NADH and ΔpH in energized mitochondria. Its spontaneous inactivation in C57BL/6J mice was previously shown to alter ATP production, Ca2+ influx, and GSIS, thereby leading to glucose intolerance. Here, we tested the role of NNT in the glucose regulation of mitochondrial NADPH and glutathione redox state and reinvestigated its role in GSIS coupling events in mouse pancreatic islets. Methods Islets were isolated from female C57BL/6J mice (J-islets), which lack functional NNT, and genetically close C57BL/6N mice (N-islets). Wild-type mouse NNT was expressed in J-islets by adenoviral infection. Mitochondrial and cytosolic glutathione oxidation was measured with glutaredoxin 1-fused roGFP2 probes targeted or not to the mitochondrial matrix. NADPH and NADH redox state was measured biochemically. Insulin secretion and upstream coupling events were measured under dynamic or static conditions by standard procedures. Results NNT is largely responsible for the acute glucose-induced rise in islet NADPH/NADP+ ratio and decrease in mitochondrial glutathione oxidation, with a small impact on cytosolic glutathione. However, contrary to current views on NNT in β-cells, these effects resulted from a glucose-dependent reduction in NADPH consumption by NNT reverse mode of operation, rather than from a stimulation of its forward mode of operation. Accordingly, the lack of NNT in J-islets decreased their sensitivity to exogenous H2O2 at non-stimulating glucose. Surprisingly, the lack of NNT did not alter the glucose-stimulation of Ca2+ influx and upstream mitochondrial events, but it markedly reduced both phases of GSIS by altering Ca2+-induced exocytosis and its metabolic amplification. Conclusion These results drastically modify current views on NNT operation and mitochondrial function in pancreatic β-cells.
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Key Words
- AT2, aldrithiol
- C57BL/6J mice
- C57BL/6N mice
- CMV, cytomegalovirus
- DTT, dithiotreitol
- Dz, diazoxide
- FCCP, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone
- GRX1, glutaredoxin 1
- GRX1-roGFP2
- GSIS, glucose stimulation of insulin secretion
- Glucose metabolism
- IDH, isocitrate dehydrogenase
- Insulin secretion
- KRB, Krebs solution
- ME, malic enzyme
- Mitochondrial shuttles
- NNT, nicotinamide nucleotide transhydrogenase
- OCR, oxygen consumption rate
- Pancreatic islet
- Redox-sensitive GFP
- Stimulus-secretion coupling
- WT, wild-type
- [Ca2+]i, intracellular Ca2+ concentration
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Affiliation(s)
- Laila R.B. Santos
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Carole Muller
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Arnaldo H. de Souza
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Hilton K. Takahashi
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Peter Spégel
- Lund University, Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Malmö, 205 02, Sweden
- Lund University, Department of Chemistry, Centre for Analysis and Synthesis, Lund, 221 00, Sweden
| | - Ian R. Sweet
- University of Washington Diabetes Institute, Department of Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Heeyoung Chae
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Hindrik Mulder
- Lund University, Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Malmö, 205 02, Sweden
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
- Corresponding author. Université catholique de Louvain, UCL/SSS/IREC/EDIN, Avenue Hippocrate 55, B1.55.06, B-1200, Brussels, Belgium.Université catholique de LouvainUCL/SSS/IREC/EDINAvenue Hippocrate 55B1.55.06BrusselsB-1200Belgium
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Duvoor C, Dendi VS, Marco A, Shekhawat NS, Chada A, Ravilla R, Musham CK, Mirza W, Chaudhury A. Commentary: ATP: The crucial component of secretory vesicles: Accelerated ATP/insulin exocytosis and prediabetes. Front Physiol 2017; 8:53. [PMID: 28210227 PMCID: PMC5288386 DOI: 10.3389/fphys.2017.00053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/19/2017] [Indexed: 02/03/2023] Open
Affiliation(s)
- Chitharanjan Duvoor
- Department of Endocrinology and Internal Medicine, University of Arkansas for Medical SciencesLittle Rock, AR, USA; GIM FoundationLittle Rock, AR, USA
| | - Vijaya S Dendi
- GIM FoundationLittle Rock, AR, USA; Department of Internal Medicine and Hospital Medicine, Christus Trinity Mother Frances HospitalTyler, TX, USA
| | - Asween Marco
- GIM FoundationLittle Rock, AR, USA; Department of Policy, University of Arkansas for Little RockLittle Rock, AR, USA
| | - Nawal S Shekhawat
- GIM FoundationLittle Rock, AR, USA; Tutwiler ClinicTutwiler, MS, USA
| | - Aditya Chada
- GIM FoundationLittle Rock, AR, USA; Department of Pulmonary and Critical Care Medicine, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Rahul Ravilla
- GIM FoundationLittle Rock, AR, USA; Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Chaitanya K Musham
- GIM FoundationLittle Rock, AR, USA; St. Vincent Infirmary (Catholic Health Initiative)Little Rock, AR, USA
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67
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Abstract
Mitochondria are critical organelles for endocrine health; steroid hormone biosynthesis occurs in these organelles and they provide energy in the form of ATP for hormone production and trafficking. Mitochondrial diseases are multisystem disorders that feature defective oxidative phosphorylation, and are characterized by enormous clinical, biochemical and genetic heterogeneity. To date, mitochondrial diseases have been found to result from >250 monogenic defects encoded across two genomes: the nuclear genome and the ancient circular mitochondrial genome located within mitochondria themselves. Endocrine dysfunction is often observed in genetic mitochondrial diseases and reflects decreased intracellular production or extracellular secretion of hormones. Diabetes mellitus is the most frequently described endocrine disturbance in patients with inherited mitochondrial diseases, but other endocrine manifestations in these patients can include growth hormone deficiency, hypogonadism, adrenal dysfunction, hypoparathyroidism and thyroid disease. Although mitochondrial endocrine dysfunction frequently occurs in the context of multisystem disease, some mitochondrial disorders are characterized by isolated endocrine involvement. Furthermore, additional monogenic mitochondrial endocrine diseases are anticipated to be revealed by the application of genome-wide next-generation sequencing approaches in the future. Understanding the mitochondrial basis of endocrine disturbance is key to developing innovative therapies for patients with mitochondrial diseases.
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Affiliation(s)
- Jasmine Chow
- Department of Paediatrics, Queen Elizabeth Hospital, 30 Gascoigne Road, Kowloon, Hong Kong, China
| | - Joyeeta Rahman
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - John C Achermann
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - Mehul T Dattani
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
- Endocrinology Unit, Great Ormond Street Hospital NHS Foundation Trust, Great Ormond Street, London WC1N 3JH, UK
| | - Shamima Rahman
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
- Metabolic Unit, Great Ormond Street Hospital NHS Foundation Trust, Great Ormond Street, London WC1N 3JH, UK
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de Souza AH, Santos LRB, Roma LP, Bensellam M, Carpinelli AR, Jonas JC. NADPH oxidase-2 does not contribute to β-cell glucotoxicity in cultured pancreatic islets from C57BL/6J mice. Mol Cell Endocrinol 2017; 439:354-362. [PMID: 27664519 DOI: 10.1016/j.mce.2016.09.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/24/2016] [Accepted: 09/20/2016] [Indexed: 11/20/2022]
Abstract
High glucose-induced oxidative stress and increased NADPH oxidase-2 (NOX2) activity may contribute to the progressive decline of the functional β-cell mass in type 2 diabetes. To test that hypothesis, we characterized, in islets from male NOX2 knockout (NOX2-KO) and wild-type (WT) C57BL/6J mice cultured for up to 3 weeks at 10 or 30 mmol/l glucose (G10 or G30), the in vitro effects of glucose on cytosolic oxidative stress using probes sensing glutathione oxidation (GRX1-roGFP2), thiol oxidation (roGFP1) or H2O2 (roGFP2-Orp1), on β-cell stimulus-secretion coupling events and on β-cell apoptosis. After 1-2 days of culture in G10, the glucose stimulation of insulin secretion (GSIS) was ∼1.7-fold higher in NOX2-KO vs. WT islets at 20-30 mmol/l glucose despite similar rises in NAD(P)H and intracellular calcium concentration ([Ca2+]i) and no differences in cytosolic GRX1-roGFP2 oxidation. After long-term culture at G10, roGFP1 and roGFP2-Orp1 oxidation and β-cell apoptosis remained low, and the glucose-induced rises in NAD(P)H, [Ca2+]i and GSIS were similarly preserved in both islet types. After prolonged culture at G30, roGFP1 and roGFP2-Orp1 oxidation increased in parallel with β-cell apoptosis, the glucose sensitivity of the NADPH, [Ca2+]i and insulin secretion responses increased, the maximal [Ca2+]i response decreased, but maximal GSIS was preserved. These responses were almost identical in both islet types. In conclusion, NOX2 is a negative regulator of maximal GSIS in C57BL/6J mouse islets, but it does not detectably contribute to the in vitro glucotoxic induction of cytosolic oxidative stress and alterations of β-cell survival and function.
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Affiliation(s)
- Arnaldo H de Souza
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium; Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Laila R B Santos
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium
| | - Leticia P Roma
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Mohammed Bensellam
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium
| | - Angelo R Carpinelli
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium.
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69
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Alterations in pancreatic β cell function and Trypanosoma cruzi infection: evidence from human and animal studies. Parasitol Res 2016; 116:827-838. [PMID: 28013375 DOI: 10.1007/s00436-016-5350-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 12/11/2016] [Indexed: 01/04/2023]
Abstract
The parasite Trypanosoma cruzi causes a persistent infection, Chagas disease, affecting millions of persons in endemic areas of Latin America. As a result of immigration, this disease has now been diagnosed in non-endemic areas worldwide. Although, the heart and gastrointestinal tract are the most studied, the insulin-secreting β cell of the endocrine pancreas is also a target of infection. In this review, we summarize available clinical and laboratory evidence to determine whether T. cruzi-infection-mediated changes of β cell function is likely to contribute to the development of hyperglycemia and diabetes. Our literature survey indicates that T. cruzi infection of humans and of experimental animals relates to altered secretory behavior of β cells. The mechanistic basis of these observations appears to be a change in stimulus-secretion pathway function rather than the loss of insulin-producing β cells. Whether this attenuated insulin release ultimately contributes to the pathogenesis of diabetes in human Chagas disease, however, remains to be determined. Since the etiologies of diabetes are multifactorial including genetic and lifestyle factors, the use of cell- and animal-based investigations, allowing direct manipulation of these factors, are important tools in testing if reduced insulin secretion has a causal influence on diabetes in the setting of Chagas disease. Long-term clinical investigations will be required to investigate this link in humans.
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70
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Ferdaoussi M, MacDonald PE. Toward Connecting Metabolism to the Exocytotic Site. Trends Cell Biol 2016; 27:163-171. [PMID: 27932063 DOI: 10.1016/j.tcb.2016.10.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/28/2016] [Accepted: 10/31/2016] [Indexed: 12/14/2022]
Abstract
Within cells the regulated exocytosis of secretory granules controls multiple physiological functions, including endocrine hormone secretion. Release of the glucose-regulating hormone insulin from pancreatic islet β cells is critical for whole-body metabolic homeostasis. Impaired insulin secretion appears early in the progression to type 2 diabetes (T2D). Key mechanisms that control the β-cell exocytotic response, mediating the long-known but little understood metabolic amplification of insulin secretion, are becoming clearer. Recent insights indicate a convergence of metabolism-driven signals, such as lipid-derived messengers and redox-dependent deSUMOylation, at the plasma membrane to augment Ca2+-dependent insulin exocytosis. These pathways have important implications for the metabolic control of hormone secretion, for the functional compensation that occurs in obesity, and for impaired insulin secretion in diabetes.
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Affiliation(s)
- Mourad Ferdaoussi
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1
| | - Patrick E MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1.
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71
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Protein malnutrition potentiates the amplifying pathway of insulin secretion in adult obese mice. Sci Rep 2016; 6:33464. [PMID: 27633083 PMCID: PMC5025848 DOI: 10.1038/srep33464] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 08/30/2016] [Indexed: 12/28/2022] Open
Abstract
Pancreatic beta cell (β) dysfunction is an outcome of malnutrition. We assessed the role of the amplifying pathway (AMP PATH) in β cells in malnourished obese mice. C57Bl-6 mice were fed a control (C) or a low-protein diet (R). The groups were then fed a high-fat diet (CH and RH). AMP PATH contribution to insulin secretion was assessed upon incubating islets with diazoxide and KCl. CH and RH displayed increased glucose intolerance, insulin resistance and glucose-stimulated insulin secretion. Only RH showed a higher contribution of the AMP PATH. The mitochondrial membrane potential of RH was decreased, and ATP flux was unaltered. In RH islets, glutamate dehydrogenase (GDH) protein content and activity increased, and the AMP PATH contribution was reestablished when GDH was blunted. Thus, protein malnutrition induces mitochondrial dysfunction in β cells, leading to an increased contribution of the AMP PATH to insulin secretion through the enhancement of GDH content and activity.
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72
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Fatty acids stimulate insulin secretion from human pancreatic islets at fasting glucose concentrations via mitochondria-dependent and -independent mechanisms. Nutr Metab (Lond) 2016; 13:59. [PMID: 27582778 PMCID: PMC5006523 DOI: 10.1186/s12986-016-0119-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 08/19/2016] [Indexed: 12/12/2022] Open
Abstract
Background Free fatty acids (FFAs) acutely stimulate insulin secretion from pancreatic islets. Conflicting results have been presented regarding this effect at non-stimulatory glucose concentration, however. The aim of our study was to investigate how long-chain FFAs affect insulin secretion from isolated human pancreatic islets in the presence of physiologically fasting glucose concentrations and to explore the contribution of mitochondria to the effects on secretion. Methods Insulin secretion from human pancreatic islets was measured from short-term static incubation or perfusion system at fasting glucose concentration (5.5 mM) with or without 4 different FFAs (palmitate, palmitoleate, stearate, and oleate). The contribution of mitochondrial metabolism to the effects of fatty acid-stimulated insulin secretion was explored. Results The average increase in insulin secretion, measured from statically incubated and dynamically perifused human islets, was about 2-fold for saturated free fatty acids (SFAs) (palmitate and stearate) and 3-fold for mono-unsaturated free fatty acids (MUFAs) (palmitoleate and oleate) compared with 5.5 mmol/l glucose alone. Accordingly, MUFAs induced 50 % and SFAs 20 % higher levels of oxygen consumption compared with islets exposed to 5.5 mmol/l glucose alone. The effect was due to increased glycolysis. When glucose was omitted from the medium, addition of the FFAs did not affect oxygen consumption. However, the FFAs still stimulated insulin secretion from the islets although secretion was more than halved. The mitochondria-independent action was via fatty acid metabolism and FFAR1/GPR40 signaling. Conclusions The findings suggest that long-chain FFAs acutely induce insulin secretion from human islets at physiologically fasting glucose concentrations, with MUFAs being more potent than SFAs, and that this effect is associated with increased glycolytic flux and mitochondrial respiration.
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73
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Li L, Pan ZF, Huang X, Wu BW, Li T, Kang MX, Ge RS, Hu XY, Zhang YH, Ge LJ, Zhu DY, Wu YL, Lou YJ. Junctophilin 3 expresses in pancreatic beta cells and is required for glucose-stimulated insulin secretion. Cell Death Dis 2016; 7:e2275. [PMID: 27336719 PMCID: PMC5143404 DOI: 10.1038/cddis.2016.179] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 05/26/2016] [Accepted: 05/30/2016] [Indexed: 12/15/2022]
Abstract
It is well accepted that junctophilin (JPHs) isoforms act as a physical bridge linking plasma membrane and endoplasmic reticulum (ER) for channel crosstalk in excitable cells. Our purpose is to investigate whether JPHs are involved in the proper communication between Ca(2+) influx and subsequent Ca(2+) amplification in pancreatic beta cells, thereby participating in regulating insulin secretion. The expression of JPH isoforms was examined in human and mouse pancreatic tissues, and JPH3 expression was found in both the beta cells. In mice, knockdown of Jph3 (si-Jph3) in islets decreased glucose-stimulated insulin secretion (GSIS) accompanied by mitochondrial function impairment. Si-Jph3 lowered the insulin secretory response to Ca(2+) signaling in the presence of glucose, and reduced [Ca(2+)]c transient amplitude triggered by caffeine. Si-Jph3 also attenuated mitofusin 2 expression, thereby disturbing the spatial organization of ER-mitochondria contact in islets. These results suggest that the regulation of GSIS by the KATP channel-independent pathways is partly impaired due to decrease of JPH3 expression in mouse islets. JPH3 also binds to type 2 ryanodine receptors (RyR2) in mouse and human pancreatic tissues, which might contribute to Ca(2+) release amplification in GSIS. This study demonstrates some previously unrecognized findings in pancreatic tissues: (1) JPH3 expresses in mouse and human beta cells; (2) si-Jph3 in mouse primary islets impairs GSIS in vitro; (3) impairment in GSIS in si-Jph3 islets is due to changes in RyR2-[Ca(2+)]c transient amplitude and ER-mitochondria contact.
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Affiliation(s)
- L Li
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Department of Pharmacy, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, Zhejiang, China
| | - Z-F Pan
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - X Huang
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Cardiovascular Key Laboratory of Zhejiang Province, The 2nd Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310009, China
| | - B-W Wu
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - T Li
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - M-X Kang
- Department of General Surgery, The 2nd Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310009, China
| | - R-S Ge
- The Population Council at the Rockefeller University, New York 10021, NY, USA
- Institute of Reproductive Biomedicine, the 2nd Affiliated Hospital, Wenzhou Medical University, Wenzhou 325027, China
| | - X-Y Hu
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Cardiovascular Key Laboratory of Zhejiang Province, The 2nd Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310009, China
| | - Y-H Zhang
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - L-J Ge
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - D-Y Zhu
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Y-L Wu
- Department of General Surgery, The 2nd Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310009, China
| | - Y-J Lou
- Insititute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Key Innovation Team for Stem Cell Translational Medicine of Cardiovascular Disease of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
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Abstract
Obesity is closely associated with the development of type 2 diabetes. Many strategies have been used in the past to combat these two conditions, but very few provide for stable and durable glycemic control. Bariatric surgery has emerged as a powerful tool for treating obesity and in over 70 % of cases provides a short-term cure for diabetes. While the acute metabolic effects of surgery are striking, it remains important for us to also consider the long-term effects. This review aims to summarize the chronic or long-term metabolic and physiological effects of Roux-en-Y gastric bypass (RYGB) surgery on pancreatic function, skeletal muscle and hepatic insulin sensitivity, and gastrointestinal remodeling. An increased understanding of the current state of research in these areas can provide the basis for stimulating further research that would contribute to new treatment and management strategies for obesity and diabetes.
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Affiliation(s)
- J David Mosinski
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - John P Kirwan
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA.
- Metabolic Translational Research Center, Cleveland Clinic, Cleveland, OH, 44195, USA.
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75
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Vetterli L, Carobbio S, Frigerio F, Karaca M, Maechler P. The Amplifying Pathway of the β-Cell Contributes to Diet-induced Obesity. J Biol Chem 2016; 291:13063-75. [PMID: 27137930 DOI: 10.1074/jbc.m115.707448] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Indexed: 12/24/2022] Open
Abstract
Efficient energy storage in adipose tissues requires optimal function of the insulin-producing β-cell, whereas its dysfunction promotes diabetes. The associated paradox related to β-cell efficiency is that excessive accumulation of fat in adipose tissue predisposes for type 2 diabetes. Insulin exocytosis is regulated by intracellular metabolic signal transduction, with glutamate dehydrogenase playing a key role in the amplification of the secretory response. Here, we used mice with β-cell-selective glutamate dehydrogenase deletion (βGlud1(-/-)), lacking an amplifying pathway of insulin secretion. As opposed to control mice, βGlud1(-/-) animals fed a high calorie diet maintained glucose tolerance and did not develop diet-induced obesity. Islets of βGlud1(-/-) mice did not increase their secretory response upon high calorie feeding, as did islets of control mice. Inhibited adipose tissue expansion observed in knock-out mice correlated with lower expression of genes responsible for adipogenesis. Rather than being efficiently stored, lipids were consumed at a higher rate in βGlud1(-/-) mice compared with controls, in particular during food intake periods. These results show that reduced β-cell function prior to high calorie feeding prevented diet-induced obesity.
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Affiliation(s)
- Laurène Vetterli
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Stefania Carobbio
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Francesca Frigerio
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Melis Karaca
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Pierre Maechler
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
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76
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Pepin É, Al-Mass A, Attané C, Zhang K, Lamontagne J, Lussier R, Madiraju SRM, Joly E, Ruderman NB, Sladek R, Prentki M, Peyot ML. Pancreatic β-Cell Dysfunction in Diet-Induced Obese Mice: Roles of AMP-Kinase, Protein Kinase Cε, Mitochondrial and Cholesterol Metabolism, and Alterations in Gene Expression. PLoS One 2016; 11:e0153017. [PMID: 27043434 PMCID: PMC4820227 DOI: 10.1371/journal.pone.0153017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 03/22/2016] [Indexed: 12/27/2022] Open
Abstract
Diet induced obese (DIO) mice can be stratified according to their weight gain in response to high fat diet as low responders (LDR) and high responders (HDR). This allows the study of β-cell failure and the transitions to prediabetes (LDR) and early diabetes (HDR). C57BL/6N mice were fed for 8 weeks with a normal chow diet (ND) or a high fat diet and stratified as LDR and HDR. Freshly isolated islets from ND, LDR and HDR mice were studied ex-vivo for mitochondrial metabolism, AMPK activity and signalling, the expression and activity of key enzymes of energy metabolism, cholesterol synthesis, and mRNA profiling. Severely compromised glucose-induced insulin secretion in HDR islets, as compared to ND and LDR islets, was associated with suppressed AMP-kinase activity. HDR islets also showed reduced acetyl-CoA carboxylase activity and enhanced activity of 3-hydroxy-3-methylglutaryl-CoA reductase, which led respectively to elevated fatty acid oxidation and increased cholesterol biosynthesis. HDR islets also displayed mitochondrial membrane hyperpolarization and reduced ATP turnover in the presence of elevated glucose. Expression of protein kinase Cε, which reduces both lipolysis and production of signals for insulin secretion, was elevated in DIO islets. Genes whose expression increased or decreased by more than 1.2-fold were minor between LDR and ND islets (17 differentially expressed), but were prominent between HDR and ND islets (1508 differentially expressed). In HDR islets, particularly affected genes were related to cell cycle and proliferation, AMPK signaling, mitochondrial metabolism and cholesterol metabolism. In conclusion, chronically reduced AMPK activity, mitochondrial dysfunction, elevated cholesterol biosynthesis in islets, and substantial alterations in gene expression accompany β-cell failure in HDR islets. The β-cell compensation process in the prediabetic state (LDR) is largely independent of transcriptional adaptive changes, whereas the transition to early diabetes (HDR) is associated with major alterations in gene expression.
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Affiliation(s)
- Émilie Pepin
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
| | - Anfal Al-Mass
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
- Departments of Medicine and Human Genetics, McGill University, Montreal, Québec, Canada
| | - Camille Attané
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
| | - Kezhuo Zhang
- Departments of Medicine and Human Genetics, McGill University, Montreal, Québec, Canada
| | - Julien Lamontagne
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
| | - Roxane Lussier
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
| | - S. R. Murthy Madiraju
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
| | - Erik Joly
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
| | - Neil B. Ruderman
- Departments of Medicine and Physiology and Biophysics, Boston University School of Medicine and Diabetes Unit, Boston Medical Center, Boston, MA, United States of America
| | - Robert Sladek
- Departments of Medicine and Human Genetics, McGill University, Montreal, Québec, Canada
| | - Marc Prentki
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
- Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec, Canada
- * E-mail: (MP); (MLP)
| | - Marie-Line Peyot
- Montreal Diabetes Research Center and Centre de Recherche du CHUM, Montréal, Québec, Canada
- * E-mail: (MP); (MLP)
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77
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Brun T, Maechler P. Beta-cell mitochondrial carriers and the diabetogenic stress response. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2540-9. [PMID: 26979549 DOI: 10.1016/j.bbamcr.2016.03.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 01/09/2023]
Abstract
Mitochondria play a central role in pancreatic beta-cells by coupling metabolism of the secretagogue glucose to distal events of regulated insulin exocytosis. This process requires transports of both metabolites and nucleotides in and out of the mitochondria. The molecular identification of mitochondrial carriers and their respective contribution to beta-cell function have been uncovered only recently. In type 2 diabetes, mitochondrial dysfunction is an early event and may precipitate beta-cell loss. Under diabetogenic conditions, characterized by glucotoxicity and lipotoxicity, the expression profile of mitochondrial carriers is selectively modified. This review describes the role of mitochondrial carriers in beta-cells and the selective changes in response to glucolipotoxicity. In particular, we discuss the importance of the transfer of metabolites (pyruvate, citrate, malate, and glutamate) and nucleotides (ATP, NADH, NADPH) for beta-cell function and dysfunction. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Thierry Brun
- Department of Cell Physiology and Metabolism, Faculty Diabetes Center, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, Faculty Diabetes Center, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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Otter S, Lammert E. Exciting Times for Pancreatic Islets: Glutamate Signaling in Endocrine Cells. Trends Endocrinol Metab 2016; 27:177-188. [PMID: 26740469 DOI: 10.1016/j.tem.2015.12.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/11/2015] [Accepted: 12/14/2015] [Indexed: 01/14/2023]
Abstract
Glutamate represents a key excitatory neurotransmitter in the central nervous system, and also modulates the function and viability of endocrine cells in pancreatic islets. In insulin-secreting beta cells, glutamate acts as an intracellular messenger, and its transport into secretory granules promotes glucose- and incretin-stimulated insulin secretion. Mitochondrial degradation of glutamate also contributes to insulin release when glutamate dehydrogenase is allosterically activated. It also signals extracellularly via glutamate receptors (AMPA and NMDA receptors) to modulate glucagon, insulin and somatostatin secretion, and islet cell survival. Its degradation products, GABA and γ-hydroxybutyrate, are released and also influence islet cell behavior. Thus, islet glutamate receptors, such as the NMDA receptors, might serve as possible drug targets to develop new medications for adjunct treatment of diabetes.
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Affiliation(s)
- Silke Otter
- Institute of Metabolic Physiology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Beta Cell Biology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, and German Center for Diabetes Research (DZD e.V.), Düsseldorf, Germany
| | - Eckhard Lammert
- Institute of Metabolic Physiology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Beta Cell Biology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, and German Center for Diabetes Research (DZD e.V.), Düsseldorf, Germany.
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79
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Juwono J, Martinus RD. Does Hsp60 Provide a Link between Mitochondrial Stress and Inflammation in Diabetes Mellitus? J Diabetes Res 2016; 2016:8017571. [PMID: 27478851 PMCID: PMC4960334 DOI: 10.1155/2016/8017571] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/10/2016] [Accepted: 06/13/2016] [Indexed: 01/22/2023] Open
Abstract
The focus of this review is to summarise the known relationships between the expression of heat shock protein 60 (Hsp60) and its association with the pathogenesis of Type 1 and Type 2 diabetes mellitus. Hsp60 is a mitochondrial stress protein that is induced by mitochondrial impairment. It is known to be secreted from a number of cell types and circulating levels have been documented in both Types 1 and 2 diabetes mellitus patients. The biological significance of extracellular Hsp60, however, remains to be established. We will examine the links between Hsp60 and cellular anti- and proinflammatory processes and specifically address how Hsp60 appears to affect immune inflammation by at least two different mechanisms: as a ligand for innate immune receptors and as an antigen recognised by adaptive immune receptors. We will also look at the role of Hsp60 during immune cell activation in atherosclerosis, a significant risk factor during the pathogenesis of diabetes mellitus.
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Affiliation(s)
- Joshua Juwono
- School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
| | - Ryan D. Martinus
- School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
- *Ryan D. Martinus:
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80
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Roma LP, Duprez J, Jonas JC. Glucokinase activation is beneficial or toxic to cultured rat pancreatic islets depending on the prevailing glucose concentration. Am J Physiol Endocrinol Metab 2015; 309:E632-9. [PMID: 26264555 DOI: 10.1152/ajpendo.00154.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 08/10/2015] [Indexed: 11/22/2022]
Abstract
In rat pancreatic islets, β-cell gene expression, survival, and subsequent acute glucose stimulation of insulin secretion (GSIS) are optimally preserved by prolonged culture at 10 mM glucose (G10) and markedly altered by culture at G5 or G30. Here, we tested whether pharmacological glucokinase (GK) activation prevents these alterations during culture or improves GSIS after culture. Rat pancreatic islets were cultured 1-7 days at G5, G10, or G30 with or without 3 μM of the GK activator Ro 28-0450 (Ro). After culture, β-cell apoptosis and islet gene mRNA levels were measured, and the acute glucose-induced increase in NAD(P)H autofluorescence, intracellular calcium concentration, and insulin secretion were tested in the absence or presence of Ro. Prolonged culture of rat islets at G5 or G30 instead of G10 triggered β-cell apoptosis and reduced their glucose responsiveness. Addition of Ro during culture differently affected β-cell survival and glucose responsiveness depending on the glucose concentration during culture: it was beneficial to β-cell survival and function at G5, detrimental at G10, and ineffective at G30. In contrast, acute GK activation with Ro increased the glucose sensitivity of islets cultured at G10 but failed at restoring β-cell glucose responsiveness after culture at G5 or G30. We conclude that pharmacological GK activation prevents the alteration of β-cell survival and function by long-term culture at G5 but mimics glucotoxicity when added to G10. The complex effects of glucose on the β-cell phenotype result from changes in glucose metabolism and not from an effect of glucose per se.
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Affiliation(s)
- Leticia P Roma
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium; and
| | - Jessica Duprez
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium; and
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium; and Fonds de la recherche scientifique-FNRS, Brussels, Belgium
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81
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Wu J, Yan LJ. Streptozotocin-induced type 1 diabetes in rodents as a model for studying mitochondrial mechanisms of diabetic β cell glucotoxicity. Diabetes Metab Syndr Obes 2015; 8:181-8. [PMID: 25897251 PMCID: PMC4396517 DOI: 10.2147/dmso.s82272] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Chronic hyperglycemia and the corresponding glucotoxicity are the main pathogenic mechanisms of diabetes and its complications. Streptozotocin (STZ)-induced diabetic animal models are useful platforms for the understanding of β cell glucotoxicity in diabetes. As diabetes induced by a single STZ injection is often referred to as type 1 diabetes that is caused by STZ's partial destruction of pancreas, one question often being asked is whether the STZ type 1 diabetes animal model is a good model for studying the mitochondrial mechanisms of β cell glucotoxicity. In this mini review, we provide evidence garnered from the literature that the STZ type 1 diabetes is indeed a suitable model for studying mitochondrial mechanisms of diabetic β cell glucotoxicity. Evidence presented includes: 1) continued β cell derangement is due to chronic hyperglycemia after STZ is completely eliminated out of the body; 2) STZ diabetes can be reversed by insulin treatment, which indicates that β cell responds to treatment and shows ability to regenerate; and 3) STZ diabetes can be ameliorated or alleviated by administration of phytochemicals. In addition, mechanisms of STZ action and fundamental gaps in understanding mitochondrial mechanisms of β cell dysfunction are also discussed.
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Affiliation(s)
- Jinzi Wu
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Liang-Jun Yan
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
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82
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Luo X, Li R, Yan LJ. Roles of Pyruvate, NADH, and Mitochondrial Complex I in Redox Balance and Imbalance in β Cell Function and Dysfunction. J Diabetes Res 2015; 2015:512618. [PMID: 26568959 PMCID: PMC4629043 DOI: 10.1155/2015/512618] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 11/26/2014] [Accepted: 11/27/2014] [Indexed: 12/25/2022] Open
Abstract
Pancreatic β cells not only use glucose as an energy source, but also sense blood glucose levels for insulin secretion. While pyruvate and NADH metabolic pathways are known to be involved in regulating insulin secretion in response to glucose stimulation, the roles of many other components along the metabolic pathways remain poorly understood. Such is the case for mitochondrial complex I (NADH/ubiquinone oxidoreductase). It is known that normal complex I function is absolutely required for episodic insulin secretion after a meal, but the role of complex I in β cells in the diabetic pancreas remains to be investigated. In this paper, we review the roles of pyruvate, NADH, and complex I in insulin secretion and hypothesize that complex I plays a crucial role in the pathogenesis of β cell dysfunction in the diabetic pancreas. This hypothesis is based on the establishment that chronic hyperglycemia overloads complex I with NADH leading to enhanced complex I production of reactive oxygen species. As nearly all metabolic pathways are impaired in diabetes, understanding how complex I in the β cells copes with elevated levels of NADH in the diabetic pancreas may provide potential therapeutic strategies for diabetes.
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Affiliation(s)
- Xiaoting Luo
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
- Department of Biochemistry and Molecular Biology, Gannan Medical University, Ganzhou, Jiangxi 341000, China
| | - Rongrong Li
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
| | - Liang-Jun Yan
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
- *Liang-Jun Yan:
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83
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Peinado JR, Diaz-Ruiz A, Frühbeck G, Malagon MM. Mitochondria in metabolic disease: getting clues from proteomic studies. Proteomics 2014; 14:452-66. [PMID: 24339000 DOI: 10.1002/pmic.201300376] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Revised: 11/08/2013] [Accepted: 11/21/2013] [Indexed: 01/11/2023]
Abstract
Mitochondria play a key role as major regulators of cellular energy homeostasis, but in the context of mitochondrial dysfunction, mitochondria may generate reactive oxidative species and induce cellular apoptosis. Indeed, altered mitochondrial status has been linked to the pathogenesis of several metabolic disorders and specially disorders related to insulin resistance, such as obesity, type 2 diabetes, and other comorbidities comprising the metabolic syndrome. In the present review, we summarize information from various mitochondrial proteomic studies of insulin-sensitive tissues under different metabolic states. To that end, we first focus our attention on the pancreas, as mitochondrial malfunction has been shown to contribute to beta cell failure and impaired insulin release. Furthermore, proteomic studies of mitochondria obtained from liver, muscle, and adipose tissue are summarized, as these tissues constitute the primary insulin target metabolic tissues. Since recent advances in proteomic techniques have exposed the importance of PTMs in the development of metabolic disease, we also present information on specific PTMs that may directly affect mitochondria during the pathogenesis of metabolic disease. Specifically, mitochondrial protein acetylation, phosphorylation, and other PTMs related to oxidative damage, such as nitrosylation and carbonylation, are discussed.
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Affiliation(s)
- Juan R Peinado
- Department of Medical Sciences, Faculty of Medicine, Ciudad Real, Spain
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84
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Lo JC, Ljubicic S, Leibiger B, Kern M, Leibiger IB, Moede T, Kelly ME, Chatterjee Bhowmick D, Murano I, Cohen P, Banks AS, Khandekar MJ, Dietrich A, Flier JS, Cinti S, Blüher M, Danial NN, Berggren PO, Spiegelman BM. Adipsin is an adipokine that improves β cell function in diabetes. Cell 2014; 158:41-53. [PMID: 24995977 DOI: 10.1016/j.cell.2014.06.005] [Citation(s) in RCA: 252] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 03/19/2014] [Accepted: 04/10/2014] [Indexed: 02/07/2023]
Abstract
A hallmark of type 2 diabetes mellitus (T2DM) is the development of pancreatic β cell failure, which results in insulinopenia and hyperglycemia. We show that the adipokine adipsin has a beneficial role in maintaining β cell function. Animals genetically lacking adipsin have glucose intolerance due to insulinopenia; isolated islets from these mice have reduced glucose-stimulated insulin secretion. Replenishment of adipsin to diabetic mice treated hyperglycemia by boosting insulin secretion. We identify C3a, a peptide generated by adipsin, as a potent insulin secretagogue and show that the C3a receptor is required for these beneficial effects of adipsin. C3a acts on islets by augmenting ATP levels, respiration, and cytosolic free Ca(2+). Finally, we demonstrate that T2DM patients with β cell failure are deficient in adipsin. These findings indicate that the adipsin/C3a pathway connects adipocyte function to β cell physiology, and manipulation of this molecular switch may serve as a therapy in T2DM.
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Affiliation(s)
- James C Lo
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Sanda Ljubicic
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Barbara Leibiger
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Matthias Kern
- Department of Medicine, University of Leipzig, Leipzig 04103, Germany
| | - Ingo B Leibiger
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Tilo Moede
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Molly E Kelly
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Diti Chatterjee Bhowmick
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Incoronata Murano
- Department of Experimental and Clinical Medicine, University of Ancona, 60020 Ancona, Italy
| | - Paul Cohen
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Alexander S Banks
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Melin J Khandekar
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Arne Dietrich
- Department of Surgery, University of Leipzig, Leipzig 04103, Germany
| | | | - Saverio Cinti
- Department of Experimental and Clinical Medicine, University of Ancona, 60020 Ancona, Italy
| | - Matthias Blüher
- Department of Medicine, University of Leipzig, Leipzig 04103, Germany
| | - Nika N Danial
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Bruce M Spiegelman
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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85
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De Long NE, Hyslop JR, Raha S, Hardy DB, Holloway AC. Fluoxetine-induced pancreatic beta cell dysfunction: New insight into the benefits of folic acid in the treatment of depression. J Affect Disord 2014; 166:6-13. [PMID: 25012404 DOI: 10.1016/j.jad.2014.04.063] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 04/25/2014] [Indexed: 01/10/2023]
Abstract
BACKGROUND Major depressive disorder is a common psychiatric illness with reported prevalence rates of 12-16% in persons aged 12 and over. Depression is also associated with a high risk of new onset of type 2 diabetes (T2D). This relationship between depression and diabetes may be related to depression itself and/or drugs prescribed. Importantly, the use of selective serotonin reuptake inhibitors (SSRIs), the most commonly prescribed class of antidepressants, increases the risk of developing T2D. However, the mechanism(s) underlying this association remains elusive. METHODS Here we examine the effects of the SSRI fluoxetine (Prozac®) on beta cell function utilizing INS-1E cells, a rat beta cell line, to elucidate the underlying molecular mechanisms. RESULTS Fluoxetine treatment significantly reduced glucose stimulated insulin secretion (GSIS). This decreased beta cell function was concomitant with an increased production of reactive oxygen species and oxidative damage which may contribute to decreased mitochondrial electron transport chain enzyme (ETC) activity. Importantly the fluoxetine-induced deficits in beta cell function were prevented by the addition of the antioxidant folic acid. LIMITATIONS These studies were conducted in vitro; the in vivo relevance remains to be determined. CONCLUSIONS These findings suggest that use of SSRI antidepressants may increase the risk of new-onset T2D by causing oxidative stress in pancreatic beta cells. However, folic acid supplementation in patients taking SSRIs may reduce the risk of new onset diabetes via protection of normal beta cell function.
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Affiliation(s)
- Nicole E De Long
- Department of Obstetrics and Gynecology, McMaster University, RM HSC-3N52 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
| | - Jillian R Hyslop
- Department of Obstetrics and Gynecology, McMaster University, RM HSC-3N52 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
| | - Sandeep Raha
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada L8S 4K1
| | - Daniel B Hardy
- Departments of Obstetrics and Gynecology and Physiology and Pharmacology, Western University, London, ON, Canada N6A5C1
| | - Alison C Holloway
- Department of Obstetrics and Gynecology, McMaster University, RM HSC-3N52 1280 Main Street West, Hamilton, ON, Canada L8S 4K1.
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86
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Kaludercic N, Deshwal S, Di Lisa F. Reactive oxygen species and redox compartmentalization. Front Physiol 2014; 5:285. [PMID: 25161621 PMCID: PMC4130307 DOI: 10.3389/fphys.2014.00285] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 07/11/2014] [Indexed: 01/01/2023] Open
Abstract
Reactive oxygen species (ROS) formation and signaling are of major importance and regulate a number of processes in physiological conditions. A disruption in redox status regulation, however, has been associated with numerous pathological conditions. In recent years it has become increasingly clear that oxidative and reductive modifications are confined in a spatio-temporal manner. This makes ROS signaling similar to that of Ca(2+) or other second messengers. Some subcellular compartments are more oxidizing (such as lysosomes or peroxisomes) whereas others are more reducing (mitochondria, nuclei). Moreover, although more reducing, mitochondria are especially susceptible to oxidation, most likely due to the high number of exposed thiols present in that compartment. Recent advances in the development of redox probes allow specific measurement of defined ROS in different cellular compartments in intact living cells or organisms. The availability of these tools now allows simultaneous spatio-temporal measurements and correlation between ROS generation and organelle and/or cellular function. The study of ROS compartmentalization and microdomains will help elucidate their role in physiology and disease. Here we will examine redox probes currently available and how ROS generation may vary between subcellular compartments. Furthermore, we will discuss ROS compartmentalization in physiological and pathological conditions focusing our attention on mitochondria, since their vulnerability to oxidative stress is likely at the basis of several diseases.
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Affiliation(s)
- Nina Kaludercic
- Neuroscience Institute, National Research Council of Italy (CNR) Padova, Italy
| | - Soni Deshwal
- Department of Biomedical Sciences, University of Padova Padova, Italy
| | - Fabio Di Lisa
- Neuroscience Institute, National Research Council of Italy (CNR) Padova, Italy ; Department of Biomedical Sciences, University of Padova Padova, Italy
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Acute nutrient regulation of the mitochondrial glutathione redox state in pancreatic β-cells. Biochem J 2014; 460:411-23. [PMID: 24678915 DOI: 10.1042/bj20131361] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The glucose stimulation of insulin secretion by pancreatic β-cells depends on increased production of metabolic coupling factors, among which changes in NADPH and ROS (reactive oxygen species) may alter the glutathione redox state (EGSH) and signal through changes in thiol oxidation. However, whether nutrients affect EGSH in β-cell subcellular compartments is unknown. Using redox-sensitive GFP2 fused to glutaredoxin 1 and its mitochondria-targeted form, we studied the acute nutrient regulation of EGSH in the cytosol/nucleus or the mitochondrial matrix of rat islet cells. These probes were mainly expressed in β-cells and reacted to low concentrations of exogenous H2O2 and menadione. Under control conditions, cytosolic/nuclear EGSH was close to -300 mV and unaffected by glucose (from 0 to 30 mM). In comparison, mitochondrial EGSH was less negative and rapidly regulated by glucose and other nutrients, ranging from -280 mV in the absence of glucose to -299 mV in 30 mM glucose. These changes were largely independent from changes in intracellular Ca(2+) concentration and in mitochondrial pH. They were unaffected by overexpression of SOD2 (superoxide dismutase 2) and mitochondria-targeted catalase, but were inversely correlated with changes in NAD(P)H autofluorescence, suggesting that they indirectly resulted from increased NADPH availability rather than from changes in ROS concentration. Interestingly, the opposite regulation of mitochondrial EGSH and NAD(P)H autofluorescence by glucose was also observed in human islets isolated from two donors. In conclusion, the present study demonstrates that glucose and other nutrients acutely reduce mitochondrial, but not cytosolic/nuclear, EGSH in pancreatic β-cells under control conditions.
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88
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Stroh M, Swerdlow RH, Zhu H. Common defects of mitochondria and iron in neurodegeneration and diabetes (MIND): a paradigm worth exploring. Biochem Pharmacol 2014; 88:573-83. [PMID: 24361914 PMCID: PMC3972369 DOI: 10.1016/j.bcp.2013.11.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 11/25/2013] [Accepted: 11/25/2013] [Indexed: 12/19/2022]
Abstract
A popular, if not centric, approach to the study of an event is to first consider that of the simplest cause. When dissecting the underlying mechanisms governing idiopathic diseases, this generally takes the form of an ab initio genetic approach. To date, this genetic 'smoking gun' has remained elusive in diabetes mellitus and for many affected by neurodegenerative diseases. With no single gene, or even subset of genes, conclusively causative in all cases, other approaches to the etiology and treatment of these diseases seem reasonable, including the correlation of a systems' predisposed sensitivity to particular influence. In the cases of diabetes mellitus and neurodegenerative diseases, overlapping themes of mitochondrial influence or dysfunction and iron dyshomeostasis are apparent and relatively consistent. This mini-review discusses the influence of mitochondrial function and iron homeostasis on diabetes mellitus and neurodegenerative disease, namely Alzheimer's disease. Also discussed is the incidence of diabetes accompanied by neuropathy and neurodegeneration along with neurodegenerative disorders prone to development of diabetes. Mouse models containing multiple facets of this overlap are also described alongside current molecular trends attributed to both diseases. As a way of approaching the idiopathic and complex nature of these diseases we are proposing the consideration of a MIND (mitochondria, iron, neurodegeneration, and diabetes) paradigm in which systemic metabolic influence, iron homeostasis, and respective genetic backgrounds play a central role in the development of disease.
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Affiliation(s)
- Matthew Stroh
- Neuroscience Graduate Program, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Russell H Swerdlow
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
| | - Hao Zhu
- Neuroscience Graduate Program, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Clinical Laboratory Sciences, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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89
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Abstract
The growing epidemic of type 2 diabetes mellitus (T2DM) and obesity is largely attributed to the current lifestyle of over-consumption and physical inactivity. As the primary platform controlling metabolic and energy homeostasis, mitochondria show aberrant changes in T2DM and obese subjects. While the underlying mechanism is under extensive investigation, epigenetic regulation is now emerging to play an important role in mitochondrial biogenesis, function, and dynamics. In line with lifestyle modifications preventing mitochondrial alterations and metabolic disorders, exercise has been shown to change DNA methylation of the promoter of PGC1α to favor gene expression responsible for mitochondrial biogenesis and function. In this article we discuss the epigenetic mechanism of mitochondrial alteration in T2DM and obesity, and the effects of lifestyle on epigenetic regulation. Future studies designed to further explore and integrate the epigenetic mechanisms with lifestyle modification may lead to interdisciplinary interventions and novel preventive options for mitochondrial alteration and metabolic disorders.
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Affiliation(s)
- Zhiyong Cheng
- Department of Human Nutrition, Foods, and Exercise; Fralin Translational Obesity Research Center; Fralin Life Science Institute; College of Agriculture and Life Sciences; Virginia Tech; Blacksburg, VA USA
| | - Fabio A Almeida
- Department of Human Nutrition, Foods, and Exercise; Fralin Translational Obesity Research Center; Fralin Life Science Institute; College of Agriculture and Life Sciences; Virginia Tech; Blacksburg, VA USA
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90
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Abstract
Mathematical modeling of the electrical activity of the pancreatic β-cell has been extremely important for understanding the cellular mechanisms involved in glucose-stimulated insulin secretion. Several models have been proposed over the last 30 y, growing in complexity as experimental evidence of the cellular mechanisms involved has become available. Almost all the models have been developed based on experimental data from rodents. However, given the many important differences between species, models of human β-cells have recently been developed. This review summarizes how modeling of β-cells has evolved, highlighting the proposed physiological mechanisms underlying β-cell electrical activity.
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Key Words
- ADP, adenosine diphosphate
- ATP, adenosine triphosphate
- CK, Chay-Keizer
- CRAC, calcium release-activated current
- Ca2+, calcium ions
- DOM, dual oscillator model
- ER, endoplasmic reticulum
- F6P, fructose-6-phosphate
- FBP, fructose-1,6-bisphosphate
- GLUT, glucose transporter
- GSIS, glucose-stimulated insulin secretion
- HERG, human eter à-go-go related gene
- IP3R, inositol-1,4,5-trisphosphate receptors
- KATP, ATP-sensitive K+ channels
- KCa, Ca2+-dependent K+ channels
- Kv, voltage-dependent K+ channels
- MCU, mitochondrial Ca2+ uniporter
- NCX, Na+/Ca2+ exchanger
- PFK, phosphofructokinase
- PMCA, plasma membrane Ca2+-ATPase
- ROS, reactive oxygen species
- RyR, ryanodine receptors
- SERCA, sarco-endoplasmic reticulum Ca2+-ATPase
- T2D, Type 2 Diabetes
- TCA, trycarboxylic acid cycle
- TRP, transient receptor potential
- VDCC, voltage-dependent Ca2+ channels
- Vm, membrane potential
- [ATP]i, cytosolic ATP
- [Ca2+]i, intracellular calcium concentration
- [Ca2+]m, mitochondrial calcium
- [Na+], Na+ concentration
- action potentials
- bursting
- cAMP, cyclic AMP
- calcium
- electrical activity
- ion channels
- mNCX, mitochondrial Na+/Ca2+ exchanger
- mathematical model
- β-cell
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Affiliation(s)
- Gerardo J Félix-Martínez
- Department of Electrical Engineering; Universidad
Autónoma Metropolitana-Iztapalapa; México, DF,
México
- Correspondence to: Gerardo J
Félix-Martínez;
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91
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Jenstad M, Chaudhry FA. The Amino Acid Transporters of the Glutamate/GABA-Glutamine Cycle and Their Impact on Insulin and Glucagon Secretion. Front Endocrinol (Lausanne) 2013; 4:199. [PMID: 24427154 PMCID: PMC3876026 DOI: 10.3389/fendo.2013.00199] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 12/16/2013] [Indexed: 12/21/2022] Open
Abstract
Intercellular communication is pivotal in optimizing and synchronizing cellular responses to keep homeostasis and to respond adequately to external stimuli. In the central nervous system (CNS), glutamatergic and GABAergic signals are postulated to be dependent on the glutamate/GABA-glutamine cycle for vesicular loading of neurotransmitters, for inactivating the signal and for the replenishment of the neurotransmitters. Islets of Langerhans release the hormones insulin and glucagon, but share similarities with CNS cells in for example transcriptional control of development and differentiation, and chromatin methylation. Interestingly, CNS proteins involved in secretion of the neurotransmitters and emitting their responses as well as the regulation of these processes, are also found in islet cells. Moreover, high levels of glutamate, GABA, and glutamine and their respective vesicular and plasma membrane transporters have been shown in the islet cells and there is emerging support for these amino acids and their transporters playing important roles in the maturation and secretion of insulin and glucagon. In this review, we will discuss the feasibility of recent data in the field in relation to the biophysical properties of the transporters (Slc1, Slc17, Slc32, and Slc38) and physiology of hormone secretion in islets of Langerhans.
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Affiliation(s)
- Monica Jenstad
- Institute for Medical Informatics, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
- *Correspondence: Monica Jenstad, Institute for Medical Informatics, Oslo University Hospital, Radiumhospitalet, PO Box 4953 Nydalen, Oslo NO-0424, Norway e-mail:
| | - Farrukh Abbas Chaudhry
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
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92
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Horan MP, Cooper DN. The emergence of the mitochondrial genome as a partial regulator of nuclear function is providing new insights into the genetic mechanisms underlying age-related complex disease. Hum Genet 2013; 133:435-58. [DOI: 10.1007/s00439-013-1402-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 11/23/2013] [Indexed: 12/17/2022]
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Morita S, Horii T, Kimura M, Hatada I. MiR-184 regulates insulin secretion through repression of Slc25a22. PeerJ 2013; 1:e162. [PMID: 24109547 PMCID: PMC3792180 DOI: 10.7717/peerj.162] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 08/27/2013] [Indexed: 11/20/2022] Open
Abstract
Insulin secretion from pancreatic β-cells plays an essential role in blood glucose homeostasis and type 2 diabetes. Many genes are involved in the secretion of insulin and most of these genes can be targeted by microRNAs (miRNAs). However, the role of miRNAs in insulin secretion and type 2 diabetes has not been exhaustively studied. The expression miR-184, a miRNA enriched in pancreatic islets, negatively correlates with insulin secretion, suggesting that it is a good candidate for miRNA-mediated regulation of insulin secretion. Here we report that miR-184 inhibits insulin secretion in the MIN6 pancreatic β-cell line through the repression of its target Slc25a22, a mitochondrial glutamate carrier. Our study provides new insight into the regulation of insulin secretion by glutamate transport in mitochondria.
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Affiliation(s)
- Sumiyo Morita
- Laboratory of Genome Science, Biosignal Genome Resource Center, Institute for Molecular and Cellular Regulation, Gunma University , Japan
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