51
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Control of pancreatic β-cell bioenergetics. Biochem Soc Trans 2018; 46:555-564. [PMID: 29666215 DOI: 10.1042/bst20170505] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 03/06/2018] [Accepted: 03/08/2018] [Indexed: 12/12/2022]
Abstract
The canonical model of glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells predicts a glucose-induced rise in the cytosolic ATP/ADP ratio. Such bioenergetic sensitivity to metabolic fuel is unusual as it implies that ATP flux is governed, to a significant extent, by ATP supply, while it is predominantly demand-driven in other cell types. Metabolic control is generally shared between different processes, but potential control of ATP consumption over β-cell bioenergetics has been largely ignored to date. The present paper offers a brief overview of experimental evidence that demonstrates ATP flux control by glucose-fuelled oxidative phosphorylation. Based on old and new data, it is argued that ATP supply does not hold exclusive control over ATP flux, but shares it with ATP demand, and that the distribution of control is flexible. Quantification of the bioenergetic control distribution will be important from basic and clinical perspectives, but precise measurement of the cytosolic ATP/ADP ratio is complicated by adenine nucleotide compartmentalisation. Metabolic control analysis of β-cell bioenergetics will likely clarify the mechanisms by which glucose and fatty acids amplify and potentiate GSIS, respectively. Moreover, such analysis may offer hints as to how ATP flux control shifts from ATP supply to ATP demand during the development of type 2 diabetes, and why prolonged sulfonylurea treatment causes β-cell deterioration.
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52
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Costford SR, Tattoli I, Duan FT, Volchuk A, Klip A, Philpott DJ, Woo M, Girardin SE. Male Mice Lacking NLRX1 Are Partially Protected From High-Fat Diet-Induced Hyperglycemia. J Endocr Soc 2018; 2:336-347. [PMID: 29577109 PMCID: PMC5855099 DOI: 10.1210/js.2017-00360] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 02/16/2018] [Indexed: 12/27/2022] Open
Abstract
Nod-like receptor (NLR)X1 is an NLR family protein that localizes to the mitochondrial matrix and modulates reactive oxygen species production, possibly by directly interacting with the electron transport chain. Recent work demonstrated that cells lacking NLRX1 have higher oxygen consumption but lower levels of adenosine triphosphate, suggesting that NLRX1 might prevent uncoupling of oxidative phosphorylation. We therefore hypothesized that NLRX1 might regulate whole-body energy metabolism through its effect on mitochondria. Male NLRX1 whole-body knockout (KO) mice and wild-type (WT) C57BL/6N controls were fed a low-fat or a high-fat (HF) diet for 16 weeks from weaning. Contrary to this hypothesis, there were no differences in body weight, adiposity, energy intake, or energy expenditure between HF-fed KO and WT mice, but instead HF KO mice were partially protected from the development of diet-induced hyperglycemia. Additionally, HF KO mice did not present with hyperinsulinemia during the glucose tolerance test, as did HF WT mice. There were no genotype differences in insulin tolerance, which led us to consider a pancreatic phenotype. Histology revealed that KO mice were protected from HF-induced pancreatic lipid accumulation, suggesting a potential role for NLRX1 in pancreatic dysfunction during the development diet-induced type 2 diabetes mellitus. Hence, NLRX1 depletion partially protects against postabsorptive hyperglycemia in obesity that may be linked to the prevention of pancreatic lipid accumulation. Although the actual mechanisms restoring glucose and insulin dynamics remain unknown, NLRX1 emerges as a potentially interesting target to inhibit for the prevention of type 2 diabetes mellitus.
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Affiliation(s)
- Sheila R Costford
- University of Toronto, Toronto, Ontario, Canada.,The Hospital for Sick Children, Toronto, Ontario,Canada
| | | | | | - Allen Volchuk
- University of Toronto, Toronto, Ontario, Canada.,The Hospital for Sick Children, Toronto, Ontario,Canada
| | - Amira Klip
- University of Toronto, Toronto, Ontario, Canada.,The Hospital for Sick Children, Toronto, Ontario,Canada
| | | | - Minna Woo
- University of Toronto, Toronto, Ontario, Canada.,Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
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53
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Guo R, Jiang J, Jing Z, Chen Y, Shi Z, Deng B. Cysteinyl leukotriene receptor 1 regulates glucose-stimulated insulin secretion (GSIS). Cell Signal 2018; 46:129-134. [PMID: 29412178 DOI: 10.1016/j.cellsig.2018.02.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 01/15/2018] [Accepted: 02/01/2018] [Indexed: 01/17/2023]
Abstract
Insulin resistance is an important pathological hallmark of type 2 diabetes mellitus. Glucose-stimulated insulin secretion (GSIS) plays a key role in maintaining blood glucose levels within normal range. Impaired GSIS has been associated with type 2 diabetes, however, the underlying molecular mechanisms remain largely unknown. Cysteinyl leukotriene receptor 1 (cysLT1R) is an important G protein-coupled receptor mediating the biological functions of cysteinyl leukotrienes (cys-LTs). Little is known about the effects of cysLT1R in insulin secretion and pathogenesis of T2DM. In the present study, we aimed to define the physiological functions of cysLT1R in GSIS in MIN6 β-cells. Using reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, we found that cysLT1R was expressed in pancreatic MIN6 β-cells. We also reported that glucose increased the expression of cysLT1R in MIN6 cells. Additionally, the cysLT1R antagonist montelukast promoted GSIS in a dose dependent manner, however, the cysLT1R agonist LD4 inhibited GSIS, suggesting an antagonistic effect of cysLT1R on GSIS. Silencing of cysLT1R by transfection with cysLT1R siRNA enhanced GSIS while overexpression of cysLT1R reduced GSIS in pancreatic MIN6 β-cells. Mechanistically, we found that the Arf6/Cdc42/Rac1 pathway was involved in this process. Collectively, our findings highlight the essential role of cysLT1R in suppressing pancreatic insulin secretion, and potentially provided a new insight into understanding the mechanical regulation of glucose homeostasis.
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Affiliation(s)
- Runmin Guo
- Department of Cardiology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, PR China
| | - Jiamei Jiang
- Department of Cardiology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, PR China
| | - Zhiliang Jing
- Department of Pathology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, PR China
| | - Yonghua Chen
- Department of Pathology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, PR China
| | - Zhizhou Shi
- Department of Endocrinology and Metabolism, Longgang District People's Hospital, Shenzhen 518172, China
| | - Baoping Deng
- Department of cardiovascular surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, 510120, PR China.
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54
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Besseiche A, Riveline JP, Delavallée L, Foufelle F, Gautier JF, Blondeau B. Oxidative and energetic stresses mediate beta-cell dysfunction induced by PGC-1α. DIABETES & METABOLISM 2018; 44:45-54. [DOI: 10.1016/j.diabet.2017.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/18/2017] [Accepted: 01/29/2017] [Indexed: 12/15/2022]
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55
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Broche B, Ben Fradj S, Aguilar E, Sancerni T, Bénard M, Makaci F, Berthault C, Scharfmann R, Alves-Guerra MC, Duvillié B. Mitochondrial Protein UCP2 Controls Pancreas Development. Diabetes 2018; 67:78-84. [PMID: 29079704 DOI: 10.2337/db17-0118] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 10/23/2017] [Indexed: 11/13/2022]
Abstract
The mitochondrial carrier uncoupling protein (UCP) 2 belongs to the family of the UCPs. Despite its name, it is now accepted that UCP2 is rather a metabolite transporter than a UCP. UCP2 can regulate oxidative stress and/or energetic metabolism. In rodents, UCP2 is involved in the control of α- and β-cell mass as well as insulin and glucagon secretion. Our aim was to determine whether the effects of UCP2 observed on β-cell mass have an embryonic origin. Thus, we used Ucp2 knockout mice. We found an increased size of the pancreas in Ucp2-/- fetuses at embryonic day 16.5, associated with a higher number of α- and β-cells. This phenotype was caused by an increase of PDX1+ progenitor cells. Perinatally, an increase in the proliferation of endocrine cells also participates in their expansion. Next, we analyzed the oxidative stress in the pancreata. We quantified an increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2) in the mutant, suggesting an increased production of reactive oxygen species (ROS). Phosphorylation of AKT, an ROS target, was also activated in the Ucp2-/- pancreata. Finally, administration of the antioxidant N-acetyl-l-cysteine to Ucp2-/- pregnant mice alleviated the effect of knocking out UCP2 on pancreas development. Together, these data demonstrate that UCP2 controls pancreas development through the ROS-AKT signaling pathway.
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Affiliation(s)
- Benjamin Broche
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Selma Ben Fradj
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Esther Aguilar
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Tiphaine Sancerni
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Matthieu Bénard
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Fatna Makaci
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Claire Berthault
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Raphaël Scharfmann
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Marie-Clotilde Alves-Guerra
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Bertrand Duvillié
- INSERM, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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56
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From in vivo to in vitro: Major metabolic alterations take place in hepatocytes during and following isolation. PLoS One 2017; 12:e0190366. [PMID: 29284039 PMCID: PMC5746264 DOI: 10.1371/journal.pone.0190366] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 12/13/2017] [Indexed: 12/20/2022] Open
Abstract
The liver plays a key role in maintaining physiological homeostasis and hepatocytes are largely responsible for this. The use of isolated primary hepatocytes has become an essential tool for the study of nutrient physiology, xenobiotic metabolism and several liver pathologies. Since hepatocytes are removed from their normal environment, the isolation procedure and in vitro culture of primary hepatocytes is partially known to induce undesired metabolic changes. We aimed to perform a thorough metabolic profiling of primary cells before, during and after isolation using state-of-the-art techniques. Extensive metabolite measurements using HPLC were performed in situ in the liver, during hepatocyte isolation using the two-step collagenase perfusion method and during in vitro cell culture for up to 48 hours. Assessment of mitochondrial respiratory capacity and ATP-linked respiration of isolated primary hepatocytes was performed using extracellular flux analysis. Primary hepatocytes displayed a drastic decrease in antioxidative-related metabolites (NADPH, NADP, GSH and GSSG) during the isolation procedure when compared to the in situ liver (P<0.001). Parallel assessment of citric acid cycle activity showed a significant decrease of up to 95% in Acetyl-CoA, Isocitrate/Citrate ratio, Succinate, Fumarate and Malate in comparison to the in situ liver (P<0.001). While the levels of several cellular energetic metabolites such as Adenosine, AMP, ADP and ATP were found to be progressively reduced during the isolation procedure and cell culture (P<0.001), higher ATP/ADP ratio and energy charge level were observed when primary cells were cultured in vitro compared to the in situ liver (P<0.05). In addition, a significant decrease in the respiratory capacity occurred after 24 hours in culture. Interestingly, this was not associated with a significant modification of ATP-linked respiration. In conclusion, major metabolic alterations occur immediately after hepatocytes are removed from the liver. These changes persist or increase during in vitro culture. These observations need to be taken into account when using primary hepatocytes for the study of metabolism or liver physiopathology.
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57
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Jouvet N, Estall JL. The pancreas: Bandmaster of glucose homeostasis. Exp Cell Res 2017; 360:19-23. [DOI: 10.1016/j.yexcr.2017.03.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/21/2017] [Accepted: 03/23/2017] [Indexed: 01/02/2023]
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58
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Kuksal N, Chalker J, Mailloux RJ. Progress in understanding the molecular oxygen paradox - function of mitochondrial reactive oxygen species in cell signaling. Biol Chem 2017; 398:1209-1227. [PMID: 28675747 DOI: 10.1515/hsz-2017-0160] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 06/27/2017] [Indexed: 11/15/2022]
Abstract
The molecular oxygen (O2) paradox was coined to describe its essential nature and toxicity. The latter characteristic of O2 is associated with the formation of reactive oxygen species (ROS), which can damage structures vital for cellular function. Mammals are equipped with antioxidant systems to fend off the potentially damaging effects of ROS. However, under certain circumstances antioxidant systems can become overwhelmed leading to oxidative stress and damage. Over the past few decades, it has become evident that ROS, specifically H2O2, are integral signaling molecules complicating the previous logos that oxyradicals were unfortunate by-products of oxygen metabolism that indiscriminately damage cell structures. To avoid its potential toxicity whilst taking advantage of its signaling properties, it is vital for mitochondria to control ROS production and degradation. H2O2 elimination pathways are well characterized in mitochondria. However, less is known about how H2O2 production is controlled. The present review examines the importance of mitochondrial H2O2 in controlling various cellular programs and emerging evidence for how production is regulated. Recently published studies showing how mitochondrial H2O2 can be used as a secondary messenger will be discussed in detail. This will be followed with a description of how mitochondria use S-glutathionylation to control H2O2 production.
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59
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Upregulation of UCP2 in beta-cells confers partial protection against both oxidative stress and glucotoxicity. Redox Biol 2017; 13:541-549. [PMID: 28755631 PMCID: PMC5537434 DOI: 10.1016/j.redox.2017.07.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 07/19/2017] [Accepted: 07/20/2017] [Indexed: 01/09/2023] Open
Abstract
Deterioration of pancreatic beta-cells plays a critical role in the development of type 2 diabetes. Among the various stressors contributing to these deleterious effects, glucotoxicity and superoxides have been proposed as major players. In this context, the mitochondrial uncoupling protein UCP2 is regularly associated with the stress response. In the present study, we tested the effects of UCP2 upregulation in mouse islets with beta-cell specific overexpression of UCP2 (RIP-UCP2). Islets were subjected to both chronic glucotoxicity (7 days at 30 mM glucose) and acute oxidative stress (200 µM H2O2 for 10 min). Increased UCP2 expression did not alter mitochondrial potential and ATP generation but protected against glucotoxic effects. Glucose-stimulated insulin secretion was altered by both glucotoxicity and oxidative stress, in particular through higher basal insulin release at non-stimulatory glucose concentrations. The secretory response to glucose stimulation was partially preserved in beta-cells overexpressing UCP2. The higher rate of cell death induced by chronic high glucose exposure was lower in RIP-UCP2 islets. Finally, superoxide production was reduced by high glucose, both under acute and chronic conditions, and not modified by UCP2 overexpression. In conclusion, upregulation of UCP2 conferred protective effects to the stressed beta-cell through mechanisms not directly associated with superoxide production. UCP2 upregulation protects pancreatic ß-cells against glucotoxicity. High glucose reduces superoxide production in pancreatic islets. UCP2 upregulation does not change superoxide production. UCP2 upregulation protects ß-cells against oxidative stress.
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60
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Miao Y, Dong Y, Huang P, Zhao X, Huang Z, Yao J, Li H, Xu Q. Increasing UCP2 expression and decreasing NOX1/4 expression maintain chondrocyte phenotype by reducing reactive oxygen species production. Oncotarget 2017; 8:63750-63763. [PMID: 28969026 PMCID: PMC5609958 DOI: 10.18632/oncotarget.18908] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 05/06/2017] [Indexed: 11/26/2022] Open
Abstract
The aim of this study is to demonstrate that improving the mitochondrial function can inhibite the loss of chondrocyte phenotype by regulating the expression of uncoupling protein 2(UCP2) and NADPH oxidase1/4(NOX1/4) to reduce the production of reactive oxygen species(ROS). The effects of mitochondrial biogenesis “master regular” peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), mitochondrial transcriptional factor A (TFAM), UCP2, and NOX1/4 on chondrocyte phenotype was examined. It was found that when the chondrocyte phenotype was lost, PGC-1α, UCP2, and TFAM expression decreased, while NOX1/4 expression increased. Inhibiting UCP2 expression promoted the loss of chondrocyte phenotype, and inhibiting NOX1/4 relieved the loss of the chondrocyte phenotype. After activating the PGC-1α-TFAM pathway, UCP2 increased and NOX1/4 decreased, which suppressed loss of the chondrocyte phenotype. After inhibiting NOX1/4, UCP2 expression increased. Increasing and decreasing UCP2 and NOX1/4 expression, respectively, helps maintain the chondrocyte phenotype and improve mitochondrial functioning by reducing reactive oxygen species production.
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Affiliation(s)
- Yansong Miao
- Department of Orthopaedics, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yuefu Dong
- Department of Joint Surgery, The First People's Hospital of Lianyungang, Lianyungang, China
| | - Ping Huang
- Department of Orthopaedics, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Xiang Zhao
- Department of Orthopaedics, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zhenyu Huang
- Department of Cerebral Surgery, Tong Ren Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jufang Yao
- Department of Animal Facility, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - He Li
- Department of Traditional Chinese Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Qingrong Xu
- Department of Orthopaedics, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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61
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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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62
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Sreedhar A, Zhao Y. Uncoupling protein 2 and metabolic diseases. Mitochondrion 2017; 34:135-140. [PMID: 28351676 PMCID: PMC5477468 DOI: 10.1016/j.mito.2017.03.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/22/2017] [Accepted: 03/24/2017] [Indexed: 02/06/2023]
Abstract
Mitochondria are fascinating organelles involved in various cellular-metabolic activities that are integral for mammalian development. Although they perform diverse, yet interconnected functions, mitochondria are remarkably regulated by complex signaling networks. Therefore, it is not surprising that mitochondrial dysfunction is involved in plethora of diseases, including neurodegenerative and metabolic disorders. One of the many factors that lead to mitochondrial-associated metabolic diseases is the uncoupling protein-2, a family of mitochondrial anion proteins present in the inner mitochondrial membrane. Since their discovery, uncoupling proteins have attracted considerable attention due to their involvement in mitochondrial-mediated oxidative stress and energy metabolism. This review attempts to provide a summary of recent developments in the field of uncoupling protein 2 relating to mitochondrial associated metabolic diseases.
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Affiliation(s)
- Annapoorna Sreedhar
- Department of Pharmacology, Toxicology & Neuroscience, LSU Health Sciences Center in Shreveport, Shreveport, LA 71130, USA
| | - Yunfeng Zhao
- Department of Pharmacology, Toxicology & Neuroscience, LSU Health Sciences Center in Shreveport, Shreveport, LA 71130, USA.
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63
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Seshadri N, Jonasson ME, Hunt KL, Xiang B, Cooper S, Wheeler MB, Dolinsky VW, Doucette CA. Uncoupling protein 2 regulates daily rhythms of insulin secretion capacity in MIN6 cells and isolated islets from male mice. Mol Metab 2017; 6:760-769. [PMID: 28702331 PMCID: PMC5485245 DOI: 10.1016/j.molmet.2017.04.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/16/2017] [Accepted: 04/24/2017] [Indexed: 12/17/2022] Open
Abstract
Objective Upregulation of uncoupling protein 2 (UCP2) is associated with impaired glucose-stimulated insulin secretion (GSIS), which is thought to be an important contributor to pathological β cell failure in obesity and type 2 diabetes (T2D); however, the physiological function of UCP2 in the β cell remains undefined. It has been suggested, but not yet tested, that UCP2 plays a physiological role in β cells by coordinating insulin secretion capacity with anticipated fluctuating nutrient supply, such that upregulation of UCP2 in the inactive/fasted state inhibits GSIS as a mechanism to prevent hypoglycemia. Therefore, we hypothesized that daily cycles of GSIS capacity are dependent on rhythmic and predictable patterns of Ucp2 gene expression such that low Ucp2 in the active/fed phase promotes maximal GSIS capacity, whereas elevated Ucp2 expression in the inactive/fasted phase supresses GSIS capacity. We further hypothesized that rhythmic Ucp2 expression is required for the maintenance of glucose tolerance over the 24 h cycle. Methods We used synchronized MIN6 clonal β cells and isolated mouse islets from wild type (C57BL6) and mice with β cell knockout of Ucp2 (Ucp2-βKO; and respective Ins2-cre controls) to determine the endogenous expression pattern of Ucp2 over 24 h and its impact on GSIS capacity and glucose tolerance over 24 h. Results A dynamic pattern of Ucp2 mRNA expression was observed in synchronized MIN6 cells, which showed a reciprocal relationship with GSIS capacity in a time-of-day-specific manner. GSIS capacity was suppressed in islets isolated from wild type and control mice during the light/inactive phase of the daily cycle; a suppression that was dependent on Ucp2 in the β cell and was lost in islets isolated from Ucp2-βKO mice or wild type islets treated with a UCP2 inhibitor. Finally, suppression of GSIS capacity by UCP2 in the light phase was required for the maintenance of normal patterns of glucose tolerance. Conclusions Our study suggests that Ucp2/UCP2 in the β cell is part of an important, endogenous, metabolic regulator that controls the temporal capacity of GSIS over the course of the day/night cycle, which, in turn, regulates time-of-day glucose tolerance. Targeting Ucp2/UCP2 as a therapeutic in type 2 diabetes or any other metabolic condition must take into account the rhythmic nature of its expression and its impact on glucose tolerance over 24 h, specifically during the inactive/fasted phase. Ucp2 mRNA expression in MIN6 β cells and isolated islets is dynamic and rhythmic over 24 h. Daily cycles of glucose-stimulated insulin secretion capacity are dependent on rhythmic Ucp2 expression and UCP2 activity. Loss of rhythmic Ucp2 mRNA expression triggers glucose intolerance only in the light/inactive phase of the daily cycle. UCP2 is part of an endogenous diurnal metabolic regulator that coordinates islet function with the daily cycle of fasting and feeding.
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Key Words
- GSIS, Glucose-stimulated insulin secretion
- Glucose tolerance
- Glucose-stimulated insulin secretion
- HG, High glucose
- Ins2-cre, Ins2 promoter-driven cre recombinase
- LG, Low glucose
- MIN6, Mouse insulinoma 6
- Pancreatic islets
- T2D, Type 2 diabetes
- UCP2, Uncoupling protein 2
- Ucp2-βKO, β cell-specific Ucp2 knockout
- Uncoupling protein 2
- WT, wild type
- ZT, Zeitgeber time
- i.p.GTT, intraperitoneal glucose tolerance test
- β cells
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Affiliation(s)
- Nivedita Seshadri
- Univerisity of Manitoba, Department of Physiology and Pathophysiology, Winnipeg, MB, R3E 0J9, Canada.,The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada
| | - Michael E Jonasson
- The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada
| | - Kristin L Hunt
- Univerisity of Manitoba, Department of Physiology and Pathophysiology, Winnipeg, MB, R3E 0J9, Canada.,The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada
| | - Bo Xiang
- The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada.,University of Manitoba, Department of Pharmacology & Therapeutics, Winnipeg, MB, R3E 0T6, Canada
| | - Steven Cooper
- The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada
| | - Michael B Wheeler
- University of Toronto, Department of Physiology, Toronto, ON, M5S 1A8, Canada
| | - Vernon W Dolinsky
- The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada.,University of Manitoba, Department of Pharmacology & Therapeutics, Winnipeg, MB, R3E 0T6, Canada
| | - Christine A Doucette
- Univerisity of Manitoba, Department of Physiology and Pathophysiology, Winnipeg, MB, R3E 0J9, Canada.,The Children's Hospital Research Institute of Manitoba, Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme, Winnipeg, MB, R3E 3P4, Canada
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64
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Gerber PA, Rutter GA. The Role of Oxidative Stress and Hypoxia in Pancreatic Beta-Cell Dysfunction in Diabetes Mellitus. Antioxid Redox Signal 2017; 26:501-518. [PMID: 27225690 PMCID: PMC5372767 DOI: 10.1089/ars.2016.6755] [Citation(s) in RCA: 385] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 05/25/2016] [Indexed: 12/16/2022]
Abstract
SIGNIFICANCE Metabolic syndrome is a frequent precursor of type 2 diabetes mellitus (T2D), a disease that currently affects ∼8% of the adult population worldwide. Pancreatic beta-cell dysfunction and loss are central to the disease process, although understanding of the underlying molecular mechanisms is still fragmentary. Recent Advances: Oversupply of nutrients, including glucose and fatty acids, and the subsequent overstimulation of beta cells, are believed to be an important contributor to insulin secretory failure in T2D. Hypoxia has also recently been implicated in beta-cell damage. Accumulating evidence points to a role for oxidative stress in both processes. Although the production of reactive oxygen species (ROS) results from enhanced mitochondrial respiration during stimulation with glucose and other fuels, the expression of antioxidant defense genes is unusually low (or disallowed) in beta cells. CRITICAL ISSUES Not all subjects with metabolic syndrome and hyperglycemia go on to develop full-blown diabetes, implying an important role in disease risk for gene-environment interactions. Possession of common risk alleles at the SLC30A8 locus, encoding the beta-cell granule zinc transporter ZnT8, may affect cytosolic Zn2+ concentrations and thus susceptibility to hypoxia and oxidative stress. FUTURE DIRECTIONS Loss of normal beta-cell function, rather than total mass, is increasingly considered to be the major driver for impaired insulin secretion in diabetes. Better understanding of the role of oxidative changes, its modulation by genes involved in disease risk, and effects on beta-cell identity may facilitate the development of new therapeutic strategies to this disease. Antioxid. Redox Signal. 26, 501-518.
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Affiliation(s)
- Philipp A. Gerber
- Department of Endocrinology, Diabetes and Clinical Nutrition, University Hospital Zurich, Zurich, Switzerland
| | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, United Kingdom
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UCP2 Expression Is Increased in Pancreas From Brain-Dead Donors and Involved in Cytokine-Induced β Cells Apoptosis. Transplantation 2017; 101:e59-e67. [DOI: 10.1097/tp.0000000000001292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chen X, Kelly AC, Yates DT, Macko AR, Lynch RM, Limesand SW. Islet adaptations in fetal sheep persist following chronic exposure to high norepinephrine. J Endocrinol 2017; 232:285-295. [PMID: 27888197 PMCID: PMC5173394 DOI: 10.1530/joe-16-0445] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 11/25/2016] [Indexed: 11/08/2022]
Abstract
Complications in pregnancy elevate fetal norepinephrine (NE) concentrations. Previous studies in NE-infused sheep fetuses revealed that sustained exposure to high NE resulted in lower expression of α2-adrenergic receptors in islets and increased insulin secretion responsiveness after acutely terminating the NE infusion. In this study, we determined if the compensatory increase in insulin secretion after chronic elevation of NE is independent of hyperglycemia in sheep fetuses and whether it is persistent in conjunction with islet desensitization to NE. After an initial assessment of glucose-stimulated insulin secretion (GSIS) at 129 ± 1 days of gestation, fetuses were continuously infused for seven days with NE and maintained at euglycemia with a maternal insulin infusion. Fetal GSIS studies were performed again on days 8 and 12. Adrenergic sensitivity was determined in pancreatic islets collected at day 12. NE infusion increased (P < 0.01) fetal plasma NE concentrations and lowered (P < 0.01) basal insulin concentrations compared to vehicle-infused controls. GSIS was 1.8-fold greater (P < 0.05) in NE-infused fetuses compared to controls at both one and five days after discontinuing the infusion. Glucose-potentiated arginine-induced insulin secretion was also enhanced (P < 0.01) in NE-infused fetuses. Maximum GSIS in islets isolated from NE-infused fetuses was 1.6-fold greater (P < 0.05) than controls, but islet insulin content and intracellular calcium signaling were not different between treatments. The half-maximal inhibitory concentration for NE was 2.6-fold greater (P < 0.05) in NE-infused islets compared to controls. These findings show that chronic NE exposure and not hyperglycemia produce persistent adaptations in pancreatic islets that augment β-cell responsiveness in part through decreased adrenergic sensitivity.
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Affiliation(s)
- Xiaochuan Chen
- Chongqing Key Laboratory of Forage & HerbivoreCollege of Animal Science and Technology, Southwest University, Chongqing, China
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Amy C Kelly
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Dustin T Yates
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Antoni R Macko
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Ronald M Lynch
- Department of PhysiologyUniversity of Arizona, Tucson, Arizona, USA
| | - Sean W Limesand
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
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Sun W, Zeng C, Liao L, Chen J, Wang Y. Comparison of acarbose and metformin therapy in newly diagnosed type 2 diabetic patients with overweight and/or obesity. Curr Med Res Opin 2016; 32:1389-96. [PMID: 27052634 DOI: 10.1080/03007995.2016.1176013] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
OBJECTIVE To compare the efficacy of acarbose and metformin in overweight and/or obese patients with newly diagnosed type 2 diabetes mellitus (T2DM). METHODS A total of 108 drug-naïve patients with newly diagnosed T2DM, whose hemoglobin A1c (HbA1c) was between 7% and 10% and body mass index was greater than 24 kg/m(2), were enrolled in the First People's Hospital and Municipal Central Hospital of Xiangtan City, Xiangtan, China, from 1 February 2010 to 1 August 2011. Patients were randomly assigned to acarbose (100 mg three times a day) and metformin (1.5 g/day) groups for a predictive follow-up period of 24 weeks. Plasma glucose, insulin, and glucagons at 0, 0.5, and 2 hours after a standardized meal, and HbA1c were measured at baseline and 24 weeks. RESULTS Baseline characteristics of the acarbose and metformin groups were similar. Glucose control improved significantly in both groups at 24 weeks. The percentage of patients achieving HbA1C <6.5% was comparable for acarbose and metformin therapy at 24 weeks. Body weight reduction from baseline to 24 weeks was 3.3 kg in the acarbose group and 2.7 kg in the metformin group, whereas the change in HbA1c and body weight was similar in both groups. The early-phase insulin secretion index improved only in the acarbose group at 24 weeks. After 24 weeks of therapy, fasting glucagon and 0.5 hour postprandial glucagon levels decreased markedly in the acarbose group compared to the metformin group. CONCLUSIONS Twenty-four weeks of therapy with acarbose and metformin induced similar reductions in HbA1c and body weight, but acarbose showed superior efficacy in improving islet α-cell function compared with metformin in overweight/obese patients with newly diagnosed T2DM. However, more large-sample, multicenter, randomized controlled trials are needed to evaluate the efficacy, safety, cost-effectiveness, and glycemic variability of the two drugs.
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Affiliation(s)
- Weiping Sun
- a The First People's Hospital of Xiangtan City , Xiangtan , Hunan , China
| | - Chunping Zeng
- b Affiliated Nanhai Hospital of Southern Medical University , Guangdong , China
| | - Lizhen Liao
- a The First People's Hospital of Xiangtan City , Xiangtan , Hunan , China
| | - Juan Chen
- a The First People's Hospital of Xiangtan City , Xiangtan , Hunan , China
| | - Ying Wang
- c Municipal Central Hospital of Xiangtan City , Xiangtan , Hunan , China
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Cho YS, Lee JH, Jung KH, Park JW, Moon SH, Choe YS, Lee KH. Molecular mechanism of (18)F-FDG uptake reduction induced by genipin in T47D cancer cell and role of uncoupling protein-2 in cancer cell glucose metabolism. Nucl Med Biol 2016; 43:587-92. [PMID: 27451963 DOI: 10.1016/j.nucmedbio.2016.06.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 05/25/2016] [Accepted: 06/04/2016] [Indexed: 12/21/2022]
Abstract
INTRODUCTION Compounds that modulate cancer cell glucose metabolism could open new opportunities for antitumor therapy and for monitoring response using (18)F-FDG PET. Genipin, a natural dietary compound that blocks uncoupling protein 2 (UCP2)-mediated mitochondrial proton leakage, is a potential anticancer agent. We investigated the effect of genipin on glucose metabolism and the mitochondrial function of cancer cells. METHODS Breast and colon cancer cells were assessed for effects of genipin on (18)F-FDG uptake. T47D breast cancer cells were further evaluated for time-dependent and dose-dependent effects on (18)F-FDG uptake, lactate release, oxygen consumption rate (OCR), reactive oxygen species (ROS) production, and mitochondrial membrane potential. The effects of UCP2 knockdown were evaluated using specific siRNA. RESULTS Cancer cells displayed significant reductions in (18)F-FDG uptake by genipin. T47D cells showed the greatest reduction to 32.6±1.0% of controls by 250μM genipin. The effect occurred rapidly, reaching a plateau by 1h that lasted up to 24h. The effect was dose-dependent with a half-inhibitory concentration of 60.8μM. An accompanying decrease in lactate release was consistent with reduced glycolytic flux. OCR was significantly decreased by genipin to 82.2±11.4% of controls, and ROS generation was increased to 156.7±16.0%. These effects were largely reproduced by UCP2 knockdown with specific siRNA. CONCLUSIONS Genipin decreased cancer cell (18)F-FDG uptake by reducing both glycolytic flux and mitochondrial oxidative respiration. This effect appeared to occur by blocking the ability of UCP2 to dissipate energy and restrict ROS production through proton leakage.
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Affiliation(s)
- Young Seok Cho
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
| | - Jin Hee Lee
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kyung-Ho Jung
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Jin-Won Park
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Seung Hwan Moon
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Yearn Seong Choe
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kyung-Han Lee
- Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
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Aharoni-Simon M, Shumiatcher R, Yeung A, Shih AZL, Dolinsky VW, Doucette CA, Luciani DS. Bcl-2 Regulates Reactive Oxygen Species Signaling and a Redox-Sensitive Mitochondrial Proton Leak in Mouse Pancreatic β-Cells. Endocrinology 2016; 157:2270-81. [PMID: 27070098 DOI: 10.1210/en.2015-1964] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In pancreatic β-cells, controlling the levels of reactive oxygen species (ROS) is critical to counter oxidative stress, dysfunction and death under nutrient excess. Moreover, the fine-tuning of ROS and redox balance is important in the regulation of normal β-cell physiology. We recently demonstrated that Bcl-2 and Bcl-xL, in addition to promoting survival, suppress β-cell glucose metabolism and insulin secretion. Here, we tested the hypothesis that the nonapoptotic roles of endogenous Bcl-2 extend to the regulation of β-cell ROS and redox balance. We exposed mouse islet cells and MIN6 cells to the Bcl-2/Bcl-xL antagonist Compound 6 and the Bcl-2-specific antagonist ABT-199 and evaluated ROS levels, Ca(2+) responses, respiratory control, superoxide dismutase activity and cell death. Both acute glucose stimulation and the inhibition of endogenous Bcl-2 progressively increased peroxides and stimulated superoxide dismutase activity in mouse islets. Importantly, conditional β-cell knockout of Bcl-2 amplified glucose-induced formation of peroxides. Bcl-2 antagonism also induced a mitochondrial proton leak that was prevented by the antioxidant N-acetyl-L-cysteine and, therefore, secondary to redox changes. We further established that the proton leak was independent of uncoupling protein 2 but partly mediated by the mitochondrial permeability transition pore. Acutely, inhibitor-induced peroxides promoted Ca(2+) influx, whereas under prolonged Bcl inhibition, the elevated ROS was required for induction of β-cell apoptosis. In conclusion, our data reveal that endogenous Bcl-2 modulates moment-to-moment ROS signaling and suppresses a redox-regulated mitochondrial proton leak in β-cells. These noncanonical roles of Bcl-2 may be important for β-cell function and survival under conditions of high metabolic demand.
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Affiliation(s)
- Michal Aharoni-Simon
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
| | - Rose Shumiatcher
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
| | - Anthony Yeung
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
| | - Alexis Z L Shih
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
| | - Vernon W Dolinsky
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
| | - Christine A Doucette
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
| | - Dan S Luciani
- Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4
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Backe MB, Moen IW, Ellervik C, Hansen JB, Mandrup-Poulsen T. Iron Regulation of Pancreatic Beta-Cell Functions and Oxidative Stress. Annu Rev Nutr 2016; 36:241-73. [PMID: 27146016 DOI: 10.1146/annurev-nutr-071715-050939] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dietary advice is the cornerstone in first-line treatment of metabolic diseases. Nutritional interventions directed at these clinical conditions mainly aim to (a) improve insulin resistance by reducing energy-dense macronutrient intake to obtain weight loss and (b) reduce fluctuations in insulin secretion through avoidance of rapidly absorbable carbohydrates. However, even in the majority of motivated patients selected for clinical trials, massive efforts using this approach have failed to achieve lasting efficacy. Less attention has been given to the role of micronutrients in metabolic diseases. Here, we review the evidence that highlights (a) the importance of iron in pancreatic beta-cell function and dysfunction in diabetes and (b) the integrative pathophysiological effects of tissue iron levels in the interactions among the beta cell, gut microbiome, hypothalamus, innate and adaptive immune systems, and insulin-sensitive tissues. We propose that clinical trials are warranted to clarify the impact of dietary or pharmacological iron reduction on the development of metabolic disorders.
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Affiliation(s)
- Marie Balslev Backe
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark;
| | - Ingrid Wahl Moen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark;
| | - Christina Ellervik
- Department of Laboratory Medicine, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Jakob Bondo Hansen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark;
| | - Thomas Mandrup-Poulsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark;
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Combination of Telmisartan and Linagliptin Preserves Pancreatic Islet Cell Function and Morphology in db/db Mice. Pancreas 2016; 45:584-92. [PMID: 26495783 DOI: 10.1097/mpa.0000000000000505] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVES The present study aimed to investigate the synergistic action of telmisartan and linagliptin in ameliorating pancreatic islet functions and morphology in type 2 diabetes mellitus and to delineate the molecular signaling pathway involved. METHODS db/db mice were given telmisartan (3 mg/kg) or linagliptin (3 mg/kg) alone or in combination, daily for 8 weeks, and were studied in vivo by fasting and random blood glucose tests, oral glucose tolerance tests, and intraperitoneal insulin tolerance tests, as well as ex vivo by glucose-stimulated insulin secretion and morphology of pancreatic islets. The underlying signaling pathways were examined by Western blot, real-time quantitative polymerase chain reaction, and dihydroethidium staining analyses using mouse pancreatic islets and rat β-insulinoma cells. RESULTS Telmisartan/linagliptin combination induced significantly better glucose homeostasis than the monotherapies. Posttreatment reactive oxygen species level was suppressed most significantly after the telmisartan/linagliptin combined therapy, whereas no significant change in peroxisome proliferator-activated receptor γ expressions was observed after treatments. CONCLUSIONS The telmisartan/linagliptin combination preserved pancreatic islet cell functions and morphology via reduction of oxidative stress but independent of the peroxisome proliferator-activated receptor γ pathway. Our data shed light on the therapeutic potential of using the telmisartan/linagliptin combination in the treatment of human type 2 diabetes mellitus and its related complications.
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Liu Y, Prentice KJ, Eversley JA, Hu C, Batchuluun B, Leavey K, Hansen JB, Wei DW, Cox B, Dai FF, Jia W, Wheeler MB. Rapid Elevation in CMPF May Act As a Tipping Point in Diabetes Development. Cell Rep 2016; 14:2889-900. [PMID: 26997281 DOI: 10.1016/j.celrep.2016.02.079] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 12/15/2015] [Accepted: 02/21/2016] [Indexed: 01/09/2023] Open
Abstract
Prediabetes, a state of mild glucose intolerance, can persist for years before a sudden decline in beta cell function and rapid deterioration to overt diabetes. The mechanism underlying this tipping point of beta cell dysfunction remains unknown. Here, the furan fatty acid metabolite CMPF was evaluated in a prospective cohort. Those who developed overt diabetes had a significant increase in CMPF over time, whereas prediabetics maintained chronically elevated levels, even up to 5 years before diagnosis. To evaluate the effect of increasing CMPF on diabetes progression, we used obese, insulin-resistant models of prediabetes. CMPF accelerated diabetes development by inducing metabolic remodeling, resulting in preferential utilization of fatty acids over glucose. This was associated with diminished glucose-stimulated insulin secretion, increased ROS formation, and accumulation of proinsulin, all characteristics of human diabetes. Thus, an increase in CMPF may represent the tipping point in diabetes development by accelerating beta cell dysfunction.
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Affiliation(s)
- Ying Liu
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - Kacey J Prentice
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - Judith A Eversley
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - Cheng Hu
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Battsetseg Batchuluun
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - Katherine Leavey
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3360, Toronto, ON M5S 1A8, Canada
| | - Jakob B Hansen
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - David W Wei
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - Brian Cox
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3360, Toronto, ON M5S 1A8, Canada
| | - Feihan F Dai
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada
| | - Weiping Jia
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China.
| | - Michael B Wheeler
- Department of Physiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 3352, Toronto, ON M5S 1A8, Canada.
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Bronsart LL, Stokes C, Contag CH. Chemiluminescence Imaging of Superoxide Anion Detects Beta-Cell Function and Mass. PLoS One 2016; 11:e0146601. [PMID: 26752052 PMCID: PMC4709142 DOI: 10.1371/journal.pone.0146601] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 12/18/2015] [Indexed: 12/21/2022] Open
Abstract
Superoxide anion is produced during normal cellular respiration and plays key roles in cellular physiology with its dysregulation being associated with a variety of diseases. Superoxide anion is a short-lived molecule and, therefore, its homeostatic regulation and role in biology and disease requires dynamic quantification with fine temporal resolution. Here we validated coelenterazine as a reporter of intracellular superoxide anion concentration and used it as a dynamic measure both in vitro and in vivo. Chemiluminescence was dependent upon superoxide anion levels, including those produced during cellular respiration, and concentrations varied both kinetically and temporally in response to physiologically relevant fluctuations in glucose levels. In vivo imaging with coelenterazine revealed that beta cells of the pancreas have increased levels of superoxide anion, which acted as a measure of beta-cell function and mass and could predict the susceptibility of mice to diabetes mellitus. Glucose response and regulation are key elements of cellular physiology and organismal biology, and superoxide anion appears to play a fundamental and dynamic role in both of these processes.
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Affiliation(s)
- Laura L. Bronsart
- Department of Biology, Stanford University, 318 Campus Drive, Stanford, California 94305, United States of America
- Department of Pediatrics, Stanford University, 318 Campus Drive, Stanford, California 94305, United States of America
| | - Christian Stokes
- Department of Pediatrics, Stanford University, 318 Campus Drive, Stanford, California 94305, United States of America
| | - Christopher H. Contag
- Department of Pediatrics, Stanford University, 318 Campus Drive, Stanford, California 94305, United States of America
- Departments of Radiology, Microbiology & Immunology, Stanford University, 318 Campus Drive, Stanford, California 94305, United States of America
- * E-mail:
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Palmitate-induced impairment of glucose-stimulated insulin secretion precedes mitochondrial dysfunction in mouse pancreatic islets. Biochem J 2015; 473:487-96. [PMID: 26621874 DOI: 10.1042/bj20151080] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 11/30/2015] [Indexed: 01/08/2023]
Abstract
It has been well established that excessive levels of glucose and palmitate lower glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells. This β-cell 'glucolipotoxicity' is possibly mediated by mitochondrial dysfunction, but involvement of bioenergetic failure in the pathological mechanism is the subject of ongoing debate. We show in the present study that increased palmitate levels impair GSIS before altering mitochondrial function. We demonstrate that GSIS defects arise from increased insulin release under basal conditions in addition to decreased insulin secretion under glucose-stimulatory conditions. Real-time respiratory analysis of intact mouse pancreatic islets reveals that mitochondrial ATP synthesis is not involved in the mechanism by which basal insulin is elevated. Equally, mitochondrial lipid oxidation and production of reactive oxygen species (ROS) do not contribute to increased basal insulin secretion. Palmitate does not affect KCl-induced insulin release at a basal or stimulatory glucose level, but elevated basal insulin release is attenuated by palmitoleate and associates with increased intracellular calcium. These findings deepen our understanding of β-cell glucolipotoxicity and reveal that palmitate-induced GSIS impairment is disconnected from mitochondrial dysfunction, a notion that is important when targeting β-cells for the treatment of diabetes and when assessing islet function in human transplants.
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Ježek J, Dlasková A, Zelenka J, Jabůrek M, Ježek P. H₂O₂-Activated Mitochondrial Phospholipase iPLA₂γ Prevents Lipotoxic Oxidative Stress in Synergy with UCP2, Amplifies Signaling via G-Protein-Coupled Receptor GPR40, and Regulates Insulin Secretion in Pancreatic β-Cells. Antioxid Redox Signal 2015; 23:958-72. [PMID: 25925080 PMCID: PMC4623989 DOI: 10.1089/ars.2014.6195] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
AIMS Pancreatic β-cell chronic lipotoxicity evolves from acute free fatty acid (FA)-mediated oxidative stress, unprotected by antioxidant mechanisms. Since mitochondrial uncoupling protein-2 (UCP2) plays antioxidant and insulin-regulating roles in pancreatic β-cells, we tested our hypothesis, that UCP2-mediated uncoupling attenuating mitochondrial superoxide production is initiated by FA release due to a direct H2O2-induced activation of mitochondrial phospholipase iPLA2γ. RESULTS Pro-oxidant tert-butylhydroperoxide increased respiration, decreased membrane potential and mitochondrial matrix superoxide release rates of control but not UCP2- or iPLA2γ-silenced INS-1E cells. iPLA2γ/UCP2-mediated uncoupling was alternatively activated by an H2O2 burst, resulting from palmitic acid (PA) β-oxidation, and it was prevented by antioxidants or catalase overexpression. Exclusively, nascent FAs that cleaved off phospholipids by iPLA2γ were capable of activating UCP2, indicating that the previously reported direct redox UCP2 activation is actually indirect. Glucose-stimulated insulin release was not affected by UCP2 or iPLA2γ silencing, unless pro-oxidant activation had taken place. PA augmented insulin secretion via G-protein-coupled receptor 40 (GPR40), stimulated by iPLA2γ-cleaved FAs (absent after GPR40 silencing). INNOVATION AND CONCLUSION The iPLA2γ/UCP2 synergy provides a feedback antioxidant mechanism preventing oxidative stress by physiological FA intake in pancreatic β-cells, regulating glucose-, FA-, and redox-stimulated insulin secretion. iPLA2γ is regulated by exogenous FA via β-oxidation causing H2O2 signaling, while FAs are cleaved off phospholipids, subsequently acting as amplifying messengers for GPR40. Hence, iPLA2γ acts in eminent physiological redox signaling, the impairment of which results in the lack of antilipotoxic defense and contributes to chronic lipotoxicity.
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Affiliation(s)
- Jan Ježek
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Jaroslav Zelenka
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Petr Ježek
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Carlessi R, Lemos NE, Dias AL, Oliveira FS, Brondani LA, Canani LH, Bauer AC, Leitão CB, Crispim D. Exendin-4 protects rat islets against loss of viability and function induced by brain death. Mol Cell Endocrinol 2015; 412:239-50. [PMID: 25976662 DOI: 10.1016/j.mce.2015.05.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 05/07/2015] [Accepted: 05/07/2015] [Indexed: 02/01/2023]
Abstract
Islet quality loss after isolation from brain-dead donors still hinders the implementation of human islet transplantation for treatment of type 1 diabetes. In this scenario, systemic inflammation elicited by donor brain death (BD) is among the main factors influencing islet viability and functional impairment. Exendin-4 is largely recognized to promote anti-inflammatory and cytoprotective effects on β-cells. Therefore, we hypothesized that administration of exendin-4 to brain-dead donors might improve islet survival and insulin secretory capabilities. Here, using a rat model of BD, we demonstrate that exendin-4 administration to the brain-dead donors increases both islet viability and glucose-stimulated insulin secretion. In this model, exendin-4 treatment produced a significant decrease in interleukin-1β expression in the pancreas. Furthermore, exendin-4 treatment increased the expression of superoxide dismutase-2 and prevented BD-induced elevation in uncoupling protein-2 expression. Such observations were accompanied by a reduction in gene expression of two genes often associated with endoplasmic reticulum (ER) stress response in freshly isolated islets from treated animals, C/EBP homologous protein and immunoglobulin heavy-chain binding protein. As ER stress response has been shown to be triggered by and to participate in cytokine-induced β-cell death, we suggest that exendin-4 might exert its beneficial effects through alleviation of pancreatic inflammation and oxidative stress, which in turn could prevent islet ER stress and β-cell death. Our findings might unveil a novel strategy to preserve islet quality from brain-dead donors. After testing in the human pancreatic islet transplantation setting, this approach might sum to the ongoing effort to achieve consistent and successful single-donor islet transplantation.
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Affiliation(s)
- Rodrigo Carlessi
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; School of Biomedical Sciences, CHIRI - Biosciences, Curtin University, Perth, Western Australia 6845, Australia
| | - Natália E Lemos
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Ana L Dias
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil
| | - Fernanda S Oliveira
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil
| | - Letícia A Brondani
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Luis H Canani
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Andrea C Bauer
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil
| | - Cristiane B Leitão
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Daisy Crispim
- Laboratory of Human Pancreatic Islet Biology, Endocrine Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Post-Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
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Bandsma RHJ, Ackerley C, Koulajian K, Zhang L, van Zutphen T, van Dijk TH, Xiao C, Giacca A, Lewis GF. A low-protein diet combined with low-dose endotoxin leads to changes in glucose homeostasis in weanling rats. Am J Physiol Endocrinol Metab 2015; 309:E466-73. [PMID: 26152763 DOI: 10.1152/ajpendo.00090.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 07/01/2015] [Indexed: 12/23/2022]
Abstract
Severe malnutrition is a leading cause of global childhood mortality, and infection and hypoglycemia or hyperglycemia are commonly present. The etiology behind the changes in glucose homeostasis is poorly understood. Here, we generated an animal model of severe malnutrition with and without low-grade inflammation to investigate the effects on glucose homeostasis. Immediately after weaning, rats were fed diets containing 5 [low-protein diet (LP)] or 20% protein [control diet (CTRL)], with or without repeated low-dose intraperitoneal lipopolysaccharide (LPS; 2 mg/kg), to mimic inflammation resulting from infections. After 4 wk on the diets, hyperglycemic clamps or euglycemic hyperinsulinemic clamps were performed with infusion of [U-(13)C6]glucose and [2-(13)C]glycerol to assess insulin secretion, action, and hepatic glucose metabolism. In separate studies, pancreatic islets were isolated for further analyses of insulin secretion and islet morphometry. Glucose clearance was reduced significantly by LP feeding alone (16%) and by LP feeding with LPS administration (43.8%) compared with control during the hyperglycemic clamps. This was associated with a strongly reduced insulin secretion in LP-fed rats in vivo as well as ex vivo in islets but signficantly enhanced whole body insulin sensitivity. Gluconeogenesis rates were unaffected by LP feeding, but glycogenolysis was higher after LP feeding. A protein-deficient diet in young rats leads to a susceptibility to low-dose endotoxin-induced impairment in glucose clearance with a decrease in the islet insulin secretory pathway. A protein-deficient diet is associated with enhanced peripheral insulin sensitivity but impaired insulin-mediated suppression of hepatic glycogenolysis.
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Affiliation(s)
- Robert H J Bandsma
- Division of Gastroenterology, Hepatology, and Nutrition, The Hospital for Sick Children, Toronto, Ontario, Canada; Physiology and Experimental Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands;
| | - Cameron Ackerley
- Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Khajag Koulajian
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; and
| | - Ling Zhang
- Physiology and Experimental Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Tim van Zutphen
- Department of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Theo H van Dijk
- Department of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Changting Xiao
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; and Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
| | - Adria Giacca
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; and Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
| | - Gary F Lewis
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; and Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
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78
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Jonasson ME, Wicklow BA, Sellers EAC, Dolinsky VW, Doucette CA. Exploring the role of the HNF-1αG319S polymorphism in β cell failure and youth-onset type 2 diabetes: Lessons from MODY and Hnf-1α-deficient animal models. Biochem Cell Biol 2015; 93:487-94. [PMID: 26176428 DOI: 10.1139/bcb-2015-0021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The prevalence of youth-onset type 2 diabetes (T2D) is rapidly increasing worldwide, disproportionately affecting Indigenous youth with Oji-Cree heritage from central Canada. Candidate gene screening has uncovered a novel and private polymorphism in the Oji-Cree population in the hepatocyte nuclear factor-1 alpha (HNF-1α) gene, where a highly conserved glycine residue at position 319 is changed to a serine (termed HNF-1αG319S or simply G319S). Oji-Cree youth who carry one or two copies of the "S-allele" present at diagnosis with less obesity, reduced indicators of insulin resistance, and lower plasma insulin levels at diagnosis, suggestive of a primary defect in the insulin-secreting β cells. Few studies on the impact of the HNF-1αG319S variant on β cell function have been performed to date; however, much can be learned from other clinical phenotypes of HNF-1α-deficiency, including HNF-1α mutations that cause maturity-onset diabetes of the young 3 (MODY3). In addition, evaluation of Hnf-1α-deficient murine models reveals that HNF-1α plays a central role in the regulation of insulin secretion by regulating the expression of key genes involved in β cell glucose-sensing, mitochondrial function, and the maintenance of the β cell phenotype in differentiated β cells. The overall goal of this minireview is to explore the impact of HNF-1α-deficiency on the β cell to better inform future research into the mechanisms of β cell dysfunction in Oji-Cree youth with T2D.
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Affiliation(s)
- Michael E Jonasson
- d Children's Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg MB R3E 3P4, Canada
| | - Brandy A Wicklow
- b Department of Pediatrics and Child Health, University of Manitoba, CE-208 Childrens Hospital, 840 Sherbrook Street, Health Sciences Centre, Winnipeg, MB R3A 1S1, Canada.,d Children's Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg MB R3E 3P4, Canada
| | - Elizabeth A C Sellers
- b Department of Pediatrics and Child Health, University of Manitoba, CE-208 Childrens Hospital, 840 Sherbrook Street, Health Sciences Centre, Winnipeg, MB R3A 1S1, Canada.,d Children's Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg MB R3E 3P4, Canada
| | - Vernon W Dolinsky
- c Department of Pharmacology and Therapeutics, A203 Chown Bldg., 753 McDermot Avenue, University of Manitoba, Winnipeg, MB R3E 0T6, Canada.,d Children's Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg MB R3E 3P4, Canada
| | - Christine A Doucette
- a College of Medicine, Faculty of Health Sciences, Department of Physiology & Pathophysiology, 432 Basic Medical Sciences Building, 745 Bannatyne Avenue, University of Manitoba, Winnipeg, MB R3E 0J9, Canada.,d Children's Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg MB R3E 3P4, Canada
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Hirschberg Jensen V, Affourtit C. Mitochondrial uncoupling protein-2 is not involved in palmitate-induced impairment of glucose-stimulated insulin secretion in INS-1E insulinoma cells and is not needed for the amplification of insulin release. Biochem Biophys Rep 2015; 1:8-15. [PMID: 26339685 PMCID: PMC4547158 DOI: 10.1016/j.bbrep.2015.03.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/18/2015] [Accepted: 03/19/2015] [Indexed: 11/17/2022] Open
Abstract
We have recently shown that overnight exposure of INS-1E insulinoma cells to palmitate in the presence of high glucose causes defects in both mitochondrial energy metabolism and glucose-stimulated insulin secretion (GSIS). Here we report experiments designed to test the involvement of mitochondrial uncoupling protein-2 (UCP2) in these glucolipotoxic effects. Measuring real-time oxygen consumption in siRNA-transfected INS-1E cells, we show that deleterious effects of palmitate on the glucose sensitivity of mitochondrial respiration and on the coupling efficiency of oxidative phosphorylation are independent of UCP2. Consistently, palmitate impairs GSIS to the same extent in cells with and without UCP2. Furthermore, we knocked down UCP2 in spheroid INS-1E cell clusters (pseudoislets) to test whether or not UCP2 regulates insulin secretion during prolonged glucose exposure. We demonstrate that there are no differences in temporal GSIS kinetics between perifused pseudoislets with and without UCP2. We conclude that UCP2 is not involved in palmitate-induced impairment of GSIS in INS-1E insulinoma cells and is not needed for the amplification of insulin release. These conclusions inform ongoing debate on the disputed biochemical and physiological functions of the beta cell UCP2. UCP2 does not engage with palmitate-induced mitochondrial dysfunction in INS-1E cells. UCP2 does not alter palmitate-induced impairment of insulin secretion in INS-1E cells. UCP2 is not needed for the amplification of insulin secretion in INS-1E pseudoislets.
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Affiliation(s)
- Verena Hirschberg Jensen
- School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK
| | - Charles Affourtit
- School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK
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80
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Besseiche A, Riveline JP, Gautier JF, Bréant B, Blondeau B. Metabolic roles of PGC-1α and its implications for type 2 diabetes. DIABETES & METABOLISM 2015; 41:347-57. [PMID: 25753246 DOI: 10.1016/j.diabet.2015.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 01/07/2015] [Accepted: 02/01/2015] [Indexed: 12/25/2022]
Abstract
PGC-1α is a transcriptional coactivator expressed in brown adipose tissue, liver, pancreas, kidney, skeletal and cardiac muscles, and the brain. This review presents data illustrating how PGC-1α regulates metabolic adaptations and participates in the aetiology of type 2 diabetes (T2D). Studies in mice have shown that increased PGC-1α expression may be beneficial or deleterious, depending on the tissue: in adipose tissue, it promotes thermogenesis and thus protects against energy overload, such as seen in diabetes and obesity; in muscle, PGC-1α induces a change of phenotype towards oxidative metabolism. In contrast, its role is clearly deleterious in the liver and pancreas, where it induces hepatic glucose production and inhibits insulin secretion, changes that promote diabetes. Previous studies by our group have also demonstrated the role of PGC-1α in the fetal origins of T2D. Overexpression of PGC-1α in β cells during fetal life in mice is sufficient to induce β-cell dysfunction in adults, leading to glucose intolerance. PGC-1α also is associated with glucocorticoid receptors in repressing expression of Pdx1, a key β-cell transcription factor. In conclusion, PGC-1α participates in the onset of diabetes through regulation of major metabolic tissues. Yet, it may not represent a useful target for therapeutic strategies against diabetes as it exerts both beneficial and deleterious actions on glucose homoeostasis, and because PGC-1α modulation is involved in neurodegenerative diseases. However, its role in cellular adaptation shows that greater comprehension of PGC-1α actions is needed.
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Affiliation(s)
- A Besseiche
- Inserm, UMR-S 1138, Centre de Recherche des Cordeliers, 75006 Paris, France; Université Pierre-et-Marie-Curie - Paris 6, UMR-S 1138, 75006 Paris, France; Université Paris Descartes, UMR-S 1138, 75006 Paris, France
| | - J-P Riveline
- Inserm, UMR-S 1138, Centre de Recherche des Cordeliers, 75006 Paris, France; Université Pierre-et-Marie-Curie - Paris 6, UMR-S 1138, 75006 Paris, France; Université Paris Descartes, UMR-S 1138, 75006 Paris, France; University Center of Diabetes and Complications in Lariboisière hospital, Université Paris-Diderot Paris-7, Public Assistance-Paris Hospitals, 75010 Paris, France
| | - J-F Gautier
- Inserm, UMR-S 1138, Centre de Recherche des Cordeliers, 75006 Paris, France; Université Pierre-et-Marie-Curie - Paris 6, UMR-S 1138, 75006 Paris, France; Université Paris Descartes, UMR-S 1138, 75006 Paris, France; University Center of Diabetes and Complications in Lariboisière hospital, Université Paris-Diderot Paris-7, Public Assistance-Paris Hospitals, 75010 Paris, France
| | - B Bréant
- Inserm, UMR-S 1138, Centre de Recherche des Cordeliers, 75006 Paris, France; Université Pierre-et-Marie-Curie - Paris 6, UMR-S 1138, 75006 Paris, France; Université Paris Descartes, UMR-S 1138, 75006 Paris, France
| | - B Blondeau
- Inserm, UMR-S 1138, Centre de Recherche des Cordeliers, 75006 Paris, France; Université Pierre-et-Marie-Curie - Paris 6, UMR-S 1138, 75006 Paris, France; Université Paris Descartes, UMR-S 1138, 75006 Paris, France.
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81
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Novel insights into pancreatic β-cell glucolipotoxicity from real-time functional analysis of mitochondrial energy metabolism in INS-1E insulinoma cells. Biochem J 2015; 456:417-26. [PMID: 24099598 DOI: 10.1042/bj20131002] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
High circulating glucose and non-esterified (free) fatty acid levels can cause pancreatic β-cell failure. The molecular mechanisms of this β-cell glucolipotoxicity are yet to be established conclusively. In the present paper we report on the involvement of mitochondrial dysfunction in fatty-acid-induced β-cell failure. We have used state-of-the-art extracellular flux technology to functionally probe mitochondrial energy metabolism in intact INS-1E insulinoma cells in real-time. We show that 24-h palmitate exposure at high glucose attenuates the glucose-sensitivity of mitochondrial respiration and lowers coupling efficiency of glucose-stimulated oxidative phosphorylation. These mitochondrial defects coincide with an increased level of ROS (reactive oxygen species), impaired GSIS (glucose-stimulated insulin secretion) and decreased cell viability. Palmitate lowers absolute glucose-stimulated respiration coupled to ATP synthesis, but does not affect mitochondrial proton leak. Palmitate is not toxic when administered at low glucose unless fatty acid β-oxidation is inhibited. Palmitoleate, on the other hand, does not affect mitochondrial respiration, ROS levels, GSIS or cell viability. Although palmitoleate protects against the palmitate-induced ROS increase and cell viability loss, it does not protect against respiratory and insulin secretory defects. We conclude that mitochondrial dysfunction contributes to fatty-acid-induced GSIS impairment, and that glucolipotoxic cell viability and GSIS phenotypes are mechanistically distinct.
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Kaufman BA, Li C, Soleimanpour SA. Mitochondrial regulation of β-cell function: maintaining the momentum for insulin release. Mol Aspects Med 2015; 42:91-104. [PMID: 25659350 PMCID: PMC4404204 DOI: 10.1016/j.mam.2015.01.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 01/29/2015] [Accepted: 01/29/2015] [Indexed: 01/15/2023]
Abstract
All forms of diabetes share the common etiology of insufficient pancreatic β-cell function to meet peripheral insulin demand. In pancreatic β-cells, mitochondria serve to integrate the metabolism of exogenous nutrients into energy output, which ultimately leads to insulin release. As such, mitochondrial dysfunction underlies β-cell failure and the development of diabetes. Mitochondrial regulation of β-cell function occurs through many diverse pathways, including metabolic coupling, generation of reactive oxygen species, maintenance of mitochondrial mass, and through interaction with other cellular organelles. In this chapter, we will focus on the importance of enzymatic regulators of mitochondrial fuel metabolism and control of mitochondrial mass to pancreatic β-cell function, describing how defects in these pathways ultimately lead to diabetes. Furthermore, we will examine the factors responsible for mitochondrial biogenesis and degradation and their roles in the balance of mitochondrial mass in β-cells. Clarifying the causes of β-cell mitochondrial dysfunction may inform new approaches to treat the underlying etiologies of diabetes.
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Affiliation(s)
- Brett A Kaufman
- Division of Cardiology, Vascular Medicine Institute, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Changhong Li
- Division of Endocrinology and Diabetes, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Scott A Soleimanpour
- Division of Metabolism, Endocrinology & Diabetes and Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
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83
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Liu L, Liu J, Gao Y, Yu X, Xu G, Huang Y. Uncoupling protein-2 mediates the protective action of berberine against oxidative stress in rat insulinoma INS-1E cells and in diabetic mouse islets. Br J Pharmacol 2015; 171:3246-54. [PMID: 24588674 DOI: 10.1111/bph.12666] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 02/27/2014] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE Uncoupling protein-2 (UCP2) may regulate glucose-stimulated insulin secretion. The current study investigated the effects of berberine, an alkaloid found in many medicinal plants, on oxidative stress and insulin secretion through restoration of UCP2 expression in high glucose (HG)-treated INS-1E cells and rat islets or in db/db mouse islets. EXPERIMENTAL APPROACH Mouse and rat pancreatic islets were isolated. Nitrotyrosine, superoxide dismutase (SOD)-1 and UCP2 expression and AMPK phosphorylation were examined by Western blotting. Insulin secretion was measured by ELISA. Mitochondrial reactive oxygen species (ROS) production was detected by confocal microscopy. KEY RESULTS Incubation of INS-1E cells and rat islets with HG (30 mmol·L(-1); 8 h) elevated nitrotyrosine level, reduced SOD-1 and UCP2 expression and AMPK phosphorylation, and inhibited glucose-stimulated insulin secretion. HG also increased mitochondrial ROS in INS-1E cells. Co-treatment with berberine inhibited such effects. The AMPK inhibitor compound C, the UCP2 inhibitor genipin and adenovirus ucp2 shRNA inhibited these protective effects of berberine. Furthermore, compound C normalized berberine-stimulated UCP2 expression but genipin did not affect AMPK phosphorylation. Islets from db/db mice exhibited elevated nitrotyrosine levels, reduced expression of SOD-1 and UCP2 and AMPK phosphorylation, and decreased insulin secretion compared with those from db/m(+) mice. Berberine also improved these defects in diabetic islets and genipin blocked the effects of berberine. CONCLUSIONS AND IMPLICATIONS Berberine inhibited oxidative stress and restored insulin secretion in HG-treated INS-IE cells and diabetic mouse islets by activating AMPK and UCP2. UCP2 is an important signalling molecule in mediating anti-diabetic effects of berberine.
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Affiliation(s)
- Limei Liu
- Department of Physiology and Pathophysiology, Peking University Health Science Center, Peking, China
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84
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Kibbey RG, Choi CS, Lee HY, Cabrera O, Pongratz RL, Zhao X, Birkenfeld AL, Li C, Berggren PO, Stanley C, Shulman GI. Mitochondrial GTP insensitivity contributes to hypoglycemia in hyperinsulinemia hyperammonemia by inhibiting glucagon release. Diabetes 2014; 63:4218-29. [PMID: 25024374 PMCID: PMC4237996 DOI: 10.2337/db14-0783] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mitochondrial GTP (mtGTP)-insensitive mutations in glutamate dehydrogenase (GDH(H454Y)) result in fasting and amino acid-induced hypoglycemia in hyperinsulinemia hyperammonemia (HI/HA). Surprisingly, hypoglycemia may occur in this disorder despite appropriately suppressed insulin. To better understand the islet-specific contribution, transgenic mice expressing the human activating mutation in β-cells (H454Y mice) were characterized in vivo. As in the humans with HI/HA, H454Y mice had fasting hypoglycemia, but plasma insulin concentrations were similar to the controls. Paradoxically, both glucose- and glutamine-stimulated insulin secretion were severely impaired in H454Y mice. Instead, lack of a glucagon response during hypoglycemic clamps identified impaired counterregulation. Moreover, both insulin and glucagon secretion were impaired in perifused islets. Acute pharmacologic inhibition of GDH restored both insulin and glucagon secretion and normalized glucose tolerance in vivo. These studies support the presence of an mtGTP-dependent signal generated via β-cell GDH that inhibits α-cells. As such, in children with activating GDH mutations of HI/HA, this insulin-independent glucagon suppression may contribute importantly to symptomatic hypoglycemia. The identification of a human mutation causing congenital hypoglucagonemic hypoglycemia highlights a central role of the mtGTP-GDH-glucagon axis in glucose homeostasis.
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Affiliation(s)
- Richard G Kibbey
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT
| | - Cheol Soo Choi
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Hui-Young Lee
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Over Cabrera
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL Department of Molecular Medicine and Surgery, The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Rebecca L Pongratz
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Xiaojian Zhao
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Andreas L Birkenfeld
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Changhong Li
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, PA
| | - Per-Olof Berggren
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL Department of Molecular Medicine and Surgery, The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Charles Stanley
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, PA
| | - Gerald I Shulman
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT
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85
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Barlow J, Hirschberg Jensen V, Affourtit C. Uncoupling protein-2 attenuates palmitoleate protection against the cytotoxic production of mitochondrial reactive oxygen species in INS-1E insulinoma cells. Redox Biol 2014; 4:14-22. [PMID: 25482405 PMCID: PMC4309862 DOI: 10.1016/j.redox.2014.11.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 11/21/2014] [Accepted: 11/24/2014] [Indexed: 01/23/2023] Open
Abstract
High glucose and fatty acid levels impair pancreatic beta cell function. We have recently shown that palmitate-induced loss of INS-1E insulinoma cells is related to increased reactive oxygen species (ROS) production as both toxic effects are prevented by palmitoleate. Here we show that palmitate-induced ROS are mostly mitochondrial: oxidation of MitoSOX, a mitochondria-targeted superoxide probe, is increased by palmitate, whilst oxidation of the equivalent non-targeted probe is unaffected. Moreover, mitochondrial respiratory inhibition with antimycin A stimulates palmitate-induced MitoSOX oxidation. We also show that palmitate does not change the level of mitochondrial uncoupling protein-2 (UCP2) and that UCP2 knockdown does not affect palmitate-induced MitoSOX oxidation. Palmitoleate does not influence MitoSOX oxidation in INS-1E cells ±UCP2 and largely prevents the palmitate-induced effects. Importantly, UCP2 knockdown amplifies the preventive effect of palmitoleate on palmitate-induced ROS. Consistently, viability effects of palmitate and palmitoleate are similar between cells ±UCP2, but UCP2 knockdown significantly augments the palmitoleate protection against palmitate-induced cell loss at high glucose. We conclude that UCP2 neither mediates palmitate-induced mitochondrial ROS generation and the associated cell loss, nor protects against these deleterious effects. Instead, UCP2 dampens palmitoleate protection against palmitate toxicity.
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Affiliation(s)
- Jonathan Barlow
- School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK
| | - Verena Hirschberg Jensen
- School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK
| | - Charles Affourtit
- School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK.
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86
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Kong W, Chen LL, Zheng J, Zhang HH, Hu X, Zeng TS, Hu D. Resveratrol supplementation restores high-fat diet-induced insulin secretion dysfunction by increasing mitochondrial function in islet. Exp Biol Med (Maywood) 2014; 240:220-9. [PMID: 25228148 DOI: 10.1177/1535370214548998] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Resveratrol (RSV), a natural compound, is known for its effects on energy homeostasis. Here we investigated the effects of RSV and possible mechanism in insulin secretion of high-fat diet rats. Rats were randomly divided into three groups as follows: NC group (animals were fed ad libitum with normal chow for 8 weeks), HF group (animals were fed ad libitum with high-fat diet for 8 weeks), and HFR group (animals were treated with high-fat diet and administered with RSV for 8 weeks). Insulin secretion ability of rats was assessed by hyperglycemic clamp. Mitochondrial biogenesis genes, mitochondrial respiratory chain activities, reactive oxidative species (ROS), and several mitochondrial antioxidant enzyme activities were evaluated in islet. We found that HF group rats clearly showed low insulin secretion and mitochondrial complex dysfunction. Expression of silent mating type information regulation 2 homolog- 1 (SIRT1) and related mitochondrial biogenesis were significantly decreased. However, RSV administration group (HFR) showed a marked potentiation of glucose-stimulated insulin secretion. This effect was associated with elevated SIRT1 protein expression and antioxidant enzyme activities, resulting in increased mitochondrial respiratory chain activities and decreased ROS level. This study suggests that RSV may increase islet mitochondrial complex activities and antioxidant function to restore insulin secretion dysfunction induced by high-fat diet.
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Affiliation(s)
- Wen Kong
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Lu-lu Chen
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Juan Zheng
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Hao-hao Zhang
- Department of Endocrinology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Xiang Hu
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Tian-shu Zeng
- Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Di Hu
- Department of Gastroenterology, Jingzhou Central Hospital, Jingzhou 434020, China
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87
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The furan fatty acid metabolite CMPF is elevated in diabetes and induces β cell dysfunction. Cell Metab 2014; 19:653-66. [PMID: 24703697 DOI: 10.1016/j.cmet.2014.03.008] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 12/30/2013] [Accepted: 02/26/2014] [Indexed: 02/02/2023]
Abstract
Gestational diabetes (GDM) results from failure of the β cells to adapt to increased metabolic demands; however, the cause of GDM and the extremely high rate of progression to type 2 diabetes (T2D) remains unknown. Using metabolomics, we show that the furan fatty acid metabolite 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) is elevated in the plasma of humans with GDM, as well as impaired glucose-tolerant and T2D patients. In mice, diabetic levels of plasma CMPF induced glucose intolerance, impaired glucose-stimulated insulin secretion, and decreased glucose utilization. Mechanistically, we show that CMPF acts directly on the β cell, causing impaired mitochondrial function, decreasing glucose-induced ATP accumulation, and inducing oxidative stress, resulting in dysregulation of key transcription factors and ultimately reduced insulin biosynthesis. Importantly, specifically blocking its transport through OAT3 or antioxidant treatment could prevent CMPF-induced β cell dysfunction. Thus, CMPF provides a link between β cell dysfunction and GDM/T2D that could be targeted therapeutically.
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88
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Hansen JB, Moen IW, Mandrup-Poulsen T. Iron: the hard player in diabetes pathophysiology. Acta Physiol (Oxf) 2014; 210:717-32. [PMID: 24521359 DOI: 10.1111/apha.12256] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 01/09/2014] [Accepted: 02/03/2014] [Indexed: 12/14/2022]
Abstract
The interest in the role of ferrous iron in diabetes pathophysiology has been revived by recent evidence of iron as an important determinant of pancreatic islet inflammation and as a biomarker of diabetes risk and mortality. The iron metabolism in the β-cell is complex. Excess free iron is toxic, but at the same time, iron is required for normal β-cell function and thereby glucose homeostasis. In the pathogenesis of diabetes, iron generates reactive oxygen species (ROS) by participating in the Fenton chemistry, which can induce oxidative damage and apoptosis. The aim of this review is to present and discuss recent evidence, suggesting that iron is a key pathogenic factor in both type 1 and type 2 diabetes with a focus on inflammatory pathways. Pro-inflammatory cytokine-induced β-cell death is not fully understood, but may include iron-induced ROS formation resulting in dedifferentiation by activation of transcription factors, activation of the mitochondrial apoptotic machinery or of other cell death mechanisms. The pro-inflammatory cytokine IL-1β facilitates divalent metal transporter 1 (DMT1)-induced β-cell iron uptake and consequently ROS formation and apoptosis, and we propose that this mechanism provides the relay between inflammation and oxidative β-cell damage. Iron chelation may be a potential therapeutic approach to reduce disease severity and mortality among diabetes patients. However, the therapeutic effect and safety of iron reduction need to be tested in clinical trials before dietary interventions or the use of iron chelation therapy titrated to avoid anaemia.
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Affiliation(s)
- J. B. Hansen
- Section for Endocrinological Research; Department of Biomedical Sciences; University of Copenhagen; Copenhagen Denmark
- Department of Physiology; University of Toronto; Toronto ON Canada
| | - I. W. Moen
- Section for Endocrinological Research; Department of Biomedical Sciences; University of Copenhagen; Copenhagen Denmark
| | - T. Mandrup-Poulsen
- Section for Endocrinological Research; Department of Biomedical Sciences; University of Copenhagen; Copenhagen Denmark
- Department of Molecular Medicine and Surgery; Karolinska Institutet; Stockholm Sweden
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89
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JEŽEK P, OLEJÁR T, SMOLKOVÁ K, JEŽEK J, DLASKOVÁ A, PLECITÁ-HLAVATÁ L, ZELENKA J, ŠPAČEK T, ENGSTOVÁ H, PAJUELO REGUERA D, JABŮREK M. Antioxidant and Regulatory Role of Mitochondrial Uncoupling Protein UCP2 in Pancreatic β-cells. Physiol Res 2014; 63:S73-91. [DOI: 10.33549/physiolres.932633] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Research on brown adipose tissue and its hallmark protein, mitochondrial uncoupling protein UCP1, has been conducted for half a century and has been traditionally studied in the Institute of Physiology (AS CR, Prague), likewise UCP2 residing in multiple tissues for the last two decades. Our group has significantly contributed to the elucidation of UCP uncoupling mechanism, fully dependent on free fatty acids (FFAs) within the inner mitochondrial membrane. Now we review UCP2 physiological roles emphasizing its roles in pancreatic β-cells, such as antioxidant role, possible tuning of redox homeostasis (consequently UCP2 participation in redox regulations), and fine regulation of glucose-stimulated insulin secretion (GSIS). For example, NADPH has been firmly established as being a modulator of GSIS and since UCP2 may influence redox homeostasis, it likely affects NADPH levels. We also point out the role of phospholipase iPLA2 isoform in providing FFAs for the UCP2 antioxidant function. Such initiation of mild uncoupling hypothetically precedes lipotoxicity in pancreatic β-cells until it reaches the pathological threshold, after which the antioxidant role of UCP2 can be no more cell-protective, for example due to oxidative stress-accumulated mutations in mtDNA. These mechanisms, together with impaired autocrine insulin function belong to important causes of Type 2 diabetes etiology.
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Affiliation(s)
- P. JEŽEK
- Department of Membrane Transport Biophysics, Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic
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90
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Luu L, Dai FF, Prentice KJ, Huang X, Hardy AB, Hansen JB, Liu Y, Joseph JW, Wheeler MB. The loss of Sirt1 in mouse pancreatic beta cells impairs insulin secretion by disrupting glucose sensing. Diabetologia 2013; 56:2010-20. [PMID: 23783352 DOI: 10.1007/s00125-013-2946-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 04/29/2013] [Indexed: 10/26/2022]
Abstract
AIMS/HYPOTHESIS Sirtuin 1 (SIRT1) has emerged as a key metabolic regulator of glucose homeostasis and insulin secretion. Enhanced SIRT1 activity has been shown to be protective against diabetes, although the mechanisms remain largely unknown. The aim of this study was to determine how SIRT1 regulates insulin secretion in the pancreatic beta cell. METHODS Pancreatic beta cell-specific Sirt1 deletion was induced by tamoxifen injection in 9-week-old Pdx1CreER:floxSirt1 mice (Sirt1BKO). Controls were injected with vehicle. Mice were assessed metabolically via glucose challenge, insulin tolerance tests and physical variables. In parallel, Sirt1 short interfering RNA-treated MIN6 cells (SIRT1KD) and isolated Sirt1BKO islets were used to investigate the effect of SIRT1 inactivation on insulin secretion and gene expression. RESULTS OGTTs showed impaired glucose disposal in Sirt1BKO mice due to insufficient insulin secretion. Isolated Sirt1BKO islets and SIRT1KD MIN6 cells also exhibited impaired glucose-stimulated insulin secretion. Subsequent analyses revealed impaired α-ketoisocaproic acid-induced insulin secretion and attenuated glucose-induced Ca(2+) influx, but normal insulin granule exocytosis in Sirt1BKO beta cells. Microarray studies revealed a large cluster of mitochondria-related genes, the expression of which was dysregulated in SIRT1KD MIN6 cells. Upon further analysis, we demonstrated an explicit defect in mitochondrial function: the inability to couple nutrient metabolism to mitochondrial membrane hyperpolarisation and reduced oxygen consumption rates. CONCLUSIONS/INTERPRETATION Taken together, these findings indicate that in beta cells the deacetylase SIRT1 regulates the expression of specific mitochondria-related genes that control metabolic coupling, and that a decrease in beta cell Sirt1 expression impairs glucose sensing and insulin secretion.
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Affiliation(s)
- L Luu
- Department of Physiology, University of Toronto, 1 King's College Circle Room 3352, Toronto, ON M5S 1A8, Canada
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91
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Abstract
The pancreatic islet β cell senses circulating levels of calorigenic nutrients to secrete insulin according to the needs of the organism. Altered insulin secretion is linked to various disorders such as diabetes, hypoglycemic states, and cardiometabolic diseases. Fuel stimuli, including glucose, free fatty acids, and amino acids, promote insulin granule exocytosis primarily via their metabolism in β cells and the production of key signaling metabolites. This paper reviews our current knowledge of the pathways involved in both positive and negative metabolic signaling for insulin secretion and assesses the role of established and candidate metabolic coupling factors, keeping recent developments in focus.
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Affiliation(s)
- Marc Prentki
- Molecular Nutrition Unit, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, QC, Canada.
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92
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Allister EM, Robson-Doucette CA, Prentice KJ, Hardy AB, Sultan S, Gaisano HY, Kong D, Gilon P, Herrera PL, Lowell BB, Wheeler MB. UCP2 regulates the glucagon response to fasting and starvation. Diabetes 2013; 62:1623-33. [PMID: 23434936 PMCID: PMC3636632 DOI: 10.2337/db12-0981] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Glucagon is important for maintaining euglycemia during fasting/starvation, and abnormal glucagon secretion is associated with type 1 and type 2 diabetes; however, the mechanisms of hypoglycemia-induced glucagon secretion are poorly understood. We previously demonstrated that global deletion of mitochondrial uncoupling protein 2 (UCP2(-/-)) in mice impaired glucagon secretion from isolated islets. Therefore, UCP2 may contribute to the regulation of hypoglycemia-induced glucagon secretion, which is supported by our current finding that UCP2 expression is increased in nutrient-deprived murine and human islets. Further to this, we created α-cell-specific UCP2 knockout (UCP2AKO) mice, which we used to demonstrate that blood glucose recovery in response to hypoglycemia is impaired owing to attenuated glucagon secretion. UCP2-deleted α-cells have higher levels of intracellular reactive oxygen species (ROS) due to enhanced mitochondrial coupling, which translated into defective stimulus/secretion coupling. The effects of UCP2 deletion were mimicked by the UCP2 inhibitor genipin on both murine and human islets and also by application of exogenous ROS, confirming that changes in oxidative status and electrical activity directly reduce glucagon secretion. Therefore, α-cell UCP2 deletion perturbs the fasting/hypoglycemic glucagon response and shows that UCP2 is necessary for normal α-cell glucose sensing and the maintenance of euglycemia.
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Affiliation(s)
- Emma M. Allister
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | | | - Kacey J. Prentice
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Alexandre B. Hardy
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Sobia Sultan
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Herbert Y. Gaisano
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Dong Kong
- Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - Patrick Gilon
- Pôle d’endocrinologie, diabète et nutrition, Institut de recherche expérimentale et clinique, Université catholique de Louvain, Brussels, Belgium
| | - Pedro L. Herrera
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Bradford B. Lowell
- Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - Michael B. Wheeler
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Corresponding author: Michael B. Wheeler,
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93
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Lortz S, Gurgul-Convey E, Naujok O, Lenzen S. Overexpression of the antioxidant enzyme catalase does not interfere with the glucose responsiveness of insulin-secreting INS-1E cells and rat islets. Diabetologia 2013; 56:774-82. [PMID: 23306382 DOI: 10.1007/s00125-012-2823-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 12/12/2012] [Indexed: 10/27/2022]
Abstract
AIMS/HYPOTHESIS Hydrogen peroxide (H2O2)-inactivating enzymes such as catalase are produced in extraordinarily low levels in beta cells. Whether this low expression might be related to a signalling function of H2O2 within the beta cell is unknown. A high level of H2O2-inactivating enzymes could potentially be incompatible with glucose-induced insulin secretion. Therefore the effect of catalase overexpression on mitochondrial function and physiological insulin secretion was studied in insulin-secreting INS-1E and primary islet cells. METHODS INS-1E and rat islet cells were lentivirally transduced to overexpress catalase in the cytosol (CytoCat) or in mitochondria (MitoCat). Cell viability and caspase-3 activation were assessed after cytokine incubation and hypoxia. Insulin secretion was quantified and expression of the gene encoding the mitochondrial uncoupling protein 2 (Ucp2) was measured in parallel to mitochondrial membrane potential and reactive oxygen species (ROS) formation. RESULTS The ability to secret insulin in a glucose-dependent manner was not suppressed by catalase overexpression, although the glucose-dependent increase in the mitochondrial membrane potential was attenuated in MitoCat cells along with an increased Ucp2 expression and reduced mitochondrial ROS formation. In addition, MitoCat overexpressing cells were significantly more resistant against pro-inflammatory cytokines and hypoxia than CytoCat and control cells. CONCLUSIONS/INTERPRETATION The results demonstrate that an improved antioxidative defence status of insulin-secreting cells allowing efficient H2O2 inactivation is not incompatible with proper insulin secretory responsiveness to glucose stimulation and provide no support for a signalling role of H2O2 in insulin-secreting cells. Interestingly, the results also document for the first time that the decreased ROS formation with increasing glucose concentrations is of mitochondrial origin.
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Affiliation(s)
- S Lortz
- Institute of Clinical Biochemistry, Hannover Medical School, 30623 Hannover, Germany
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94
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Mailloux RJ, Xuan JY, Beauchamp B, Jui L, Lou M, Harper ME. Glutaredoxin-2 is required to control proton leak through uncoupling protein-3. J Biol Chem 2013; 288:8365-8379. [PMID: 23335511 DOI: 10.1074/jbc.m112.442905] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Glutathionylation has emerged as a key modification required for controlling protein function in response to changes in cell redox status. Recently, we showed that the glutathionylation state of uncoupling protein-3 (UCP3) modulates the leak of protons back into the mitochondrial matrix, thus controlling reactive oxygen species production. However, whether or not UCP3 glutathionylation is mediated enzymatically has remained unknown because previous work relied on the use of pharmacological agents, such as diamide, to alter the UCP3 glutathionylation state. Here, we demonstrate that glutaredoxin-2 (Grx2), a matrix oxidoreductase, is required to glutathionylate and inhibit UCP3. Analysis of bioenergetics in skeletal muscle mitochondria revealed that knock-out of Grx2 (Grx2(-/-)) increased proton leak in a UCP3-dependent manner. These effects were reversed using diamide, a glutathionylation catalyst. Importantly, the increased leak did not compromise coupled respiration. Knockdown of Grx2 augmented proton leak-dependent respiration in primary myotubes from wild type mice, an effect that was absent in UCP3(-/-) cells. These results confirm that Grx2 deactivates UCP3 by glutathionylation. To our knowledge, this is the first enzyme identified to regulate UCP3 by glutathionylation and is the first study on the role of Grx2 in the regulation of energy metabolism.
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Affiliation(s)
- Ryan J Mailloux
- Department of Biochemistry, Immunology, and Microbiology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Jian Ying Xuan
- Department of Biochemistry, Immunology, and Microbiology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Brittany Beauchamp
- Department of Biochemistry, Immunology, and Microbiology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Linda Jui
- Department of Biochemistry, Immunology, and Microbiology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Marjorie Lou
- Center of Redox Biology and School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska 68583
| | - Mary-Ellen Harper
- Department of Biochemistry, Immunology, and Microbiology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
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95
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Abstract
Beta cell dysfunction and insulin resistance are inherently complex with their interrelation for triggering the pathogenesis of diabetes also somewhat undefined. Both pathogenic states induce hyperglycemia and therefore increase insulin demand. Beta cell dysfunction results from inadequate glucose sensing to stimulate insulin secretion therefore elevated glucose concentrations prevail. Persistently elevated glucose concentrations above the physiological range result in the manifestation of hyperglycemia. With systemic insulin resistance, insulin signaling within glucose recipient tissues is defective therefore hyperglycemia perseveres. Beta cell dysfunction supersedes insulin resistance in inducing diabetes. Both pathological states influence each other and presumably synergistically exacerbate diabetes. Preserving beta cell function and insulin signaling in beta cells and insulin signaling in the glucose recipient tissues will maintain glucose homeostasis.
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Affiliation(s)
- Marlon E. Cerf
- Diabetes Discovery Platform, South African Medical Research CouncilCape Town, South Africa
- *Correspondence: Marlon E. Cerf, Diabetes Discovery Platform, South African Medical Research Council, PO Box 19070, Tygerberg, Cape Town 7505, South Africa. e-mail:
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96
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Barlow J, Hirschberg V, Brand MD, Affourtit C. Measuring Mitochondrial Uncoupling Protein-2 Level and Activity in Insulinoma Cells. Methods Enzymol 2013; 528:257-67. [DOI: 10.1016/b978-0-12-405881-1.00015-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
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97
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Liu J, Li J, Li WJ, Wang CM. The role of uncoupling proteins in diabetes mellitus. J Diabetes Res 2013; 2013:585897. [PMID: 23841103 PMCID: PMC3687498 DOI: 10.1155/2013/585897] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 05/21/2013] [Indexed: 01/04/2023] Open
Abstract
Uncoupling proteins (UCPs) are anion carriers expressed in the mitochondrial inner membrane that uncouple oxygen consumption by the respiratory chain from ATP synthesis. The physiological functions of UCPs have long been debated since the new UCPs (UCP2 to 5) were discovered, and the role of UCPs in the pathogeneses of diabetes mellitus is one of the hottest topics. UCPs are thought to be activated by superoxide and then decrease mitochondrial free radicals generation; this may provide a protective effect on diabetes mellitus that is under the oxidative stress conditions. UCP1 is considered to be a candidate gene for diabetes because of its role in thermogenesis and energy expenditure. UCP2 is expressed in several tissues and acts in the negative regulation of insulin secretion by β-cells and in fatty acid metabolism. UCP3 plays a role in fatty acid metabolism and energy homeostasis and modulates insulin sensitivity. Several gene polymorphisms of UCP1, UCP2, and UCP3 were reported to be associated with diabetes. The progress in the role of UCP1, UCP2, and UCP3 on diabetes mellitus is summarized in this review.
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Affiliation(s)
- Jing Liu
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Ji Li
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY 14214, USA
| | - Wen-Jian Li
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Chun-Ming Wang
- School of Life Sciences, Lanzhou University, Lanzhou 730000, China
- *Chun-Ming Wang:
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98
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Redox homeostasis in pancreatic β cells. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:932838. [PMID: 23304259 PMCID: PMC3532876 DOI: 10.1155/2012/932838] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/30/2012] [Indexed: 12/20/2022]
Abstract
We reviewed mechanisms that determine reactive oxygen species (redox) homeostasis, redox information signaling and metabolic/regulatory function of autocrine insulin signaling in pancreatic β cells, and consequences of oxidative stress and dysregulation of redox/information signaling for their dysfunction. We emphasize the role of mitochondrion in β cell molecular physiology and pathology, including the antioxidant role of mitochondrial uncoupling protein UCP2. Since in pancreatic β cells pyruvate cannot be easily diverted towards lactate dehydrogenase for lactate formation, the respiration and oxidative phosphorylation intensity are governed by the availability of glucose, leading to a certain ATP/ADP ratio, whereas in other cell types, cell demand dictates respiration/metabolism rates. Moreover, we examine the possibility that type 2 diabetes mellitus might be considered as an inevitable result of progressive self-accelerating oxidative stress and concomitantly dysregulated information signaling in peripheral tissues as well as in pancreatic β cells. It is because the redox signaling is inherent to the insulin receptor signaling mechanism and its impairment leads to the oxidative and nitrosative stress. Also emerging concepts, admiting participation of redox signaling even in glucose sensing and insulin release in pancreatic β cells, fit in this view. For example, NADPH has been firmly established to be a modulator of glucose-stimulated insulin release.
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99
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Collins S, Pi J, Yehuda-Shnaidman E. Uncoupling and reactive oxygen species (ROS)--a double-edged sword for β-cell function? "Moderation in all things". Best Pract Res Clin Endocrinol Metab 2012; 26:753-8. [PMID: 23168277 DOI: 10.1016/j.beem.2012.08.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The ability of the mitochondrion to (a) manage fuel import to oxidize for adenosine tri-phosphate (ATP) generation while (b) protecting itself and the cellular environment from electron leak, which can generate highly reactive oxygen species (ROS) is a delicate balancing act. ATP is the currency of the cell and as such serves a signaling function as a substrate partner to many kinases and ion channels. While various ROS species have been viewed as a dangerous and toxic group of molecules, it also has a role as a signal derived from mitochondria, as well as other enzymatic sources: a double-edged sword. Current efforts to understand the biochemical mechanisms affected by ROS as a signal--usually noted to be hydrogen peroxide (H(2)O(2))--are exciting, but this duality of ROS effects also pose challenges in managing its levels to protect cells. The mitochondrial uncoupling protein-2 (UCP2), UCP3, and the permeability transition pore have been integral to efforts to try to understand what role mitochondrial-derived ROS have in cells. In this piece we reflect on mitochondrial ROS and uncoupling proteins as signaling regulators. It seems that when it comes to ROS and uncoupling the proverb "Moderation in all things" is apt.
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Affiliation(s)
- Sheila Collins
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, SBMRI-Lake Nona, 6400 Sanger Road, Orlando, FL 32827, USA.
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Novotny GW, Lundh M, Backe MB, Christensen DP, Hansen JB, Dahllöf MS, Pallesen EMH, Mandrup-Poulsen T. Transcriptional and translational regulation of cytokine signaling in inflammatory β-cell dysfunction and apoptosis. Arch Biochem Biophys 2012; 528:171-84. [PMID: 23063755 DOI: 10.1016/j.abb.2012.09.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/20/2012] [Accepted: 09/22/2012] [Indexed: 12/19/2022]
Abstract
Disease is conventionally viewed as the chaotic inappropriate outcome of deranged tissue function resulting from aberrancies in cellular processes. Yet the patho-biology of cellular dysfunction and death encompasses a coordinated network no less sophisticated and regulated than maintenance of homeostatic balance. Cellular demise is far from passive subordination to stress but requires controlled coordination of energy-requiring activities including gene transcription and protein translation that determine the graded transition between defensive mechanisms, cell cycle regulation, dedifferentiation and ultimately to the activation of death programmes. In fact, most stressors stimulate both homeostasis and regeneration on one hand and impairment and destruction on the other, depending on the ambient circumstances. Here we illustrate this bimodal ambiguity in cell response by reviewing recent progress in our understanding of how the pancreatic β cell copes with inflammatory stress by changing gene transcription and protein translation by the differential and interconnected action of reactive oxygen and nitric oxide species, microRNAs and posttranslational protein modifications.
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Affiliation(s)
- Guy W Novotny
- Section of Endocrinological Research, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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