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Bensellam M, Jonas JC, Laybutt DR. Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions. J Endocrinol 2018; 236:R109-R143. [PMID: 29203573 DOI: 10.1530/joe-17-0516] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 12/04/2017] [Indexed: 12/13/2022]
Abstract
Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.
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Affiliation(s)
- Mohammed Bensellam
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Jean-Christophe Jonas
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - D Ross Laybutt
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- St Vincent's Clinical SchoolUNSW Sydney, Sydney, New South Wales, Australia
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 433] [Impact Index Per Article: 72.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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Han KH. Functional Implications of HMG-CoA Reductase Inhibition on Glucose Metabolism. Korean Circ J 2018; 48:951-963. [PMID: 30334382 PMCID: PMC6196158 DOI: 10.4070/kcj.2018.0307] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 09/27/2018] [Indexed: 02/06/2023] Open
Abstract
HMG-CoA reductase inhibitors, i.e. statins, are effective in reducing cardiovascular disease events but also in cardiac-related and overall mortality. Statins are in general well-tolerated, but currently the concerns are raised if statins may increase the risk of new-onset diabetes mellitus (NOD). In this review, the possible effects of statins on organs/tissues being involved in glucose metabolism, i.e. liver, pancreas, adipose tissue, and muscles, had been discussed. The net outcome seems to be inconsistent and often contradictory, which may be largely affected by in vitro experimental settings or/and in vivo animal conditions. The majority of studies point out statin-induced changes of regulations of isoprenoid metabolites and cell-associated cholesterol contents as predisposing factors related to the statin-induced NOD. On the other hand, it should be considered that dysfunctions of isoprenoid pathway and mitochondrial ATP production and the cholesterol homeostasis are already developed under (pre)diabetic and hypercholesterolemic conditions. In order to connect the basic findings with the clinical manifestation more clearly, further research efforts are needed.
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Affiliation(s)
- Ki Hoon Han
- Department of Internal Medicine, College of Medicine Ulsan University, Asan Medical Center, Seoul, Korea.
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54
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Jensen MV, Gooding J, Ferdaoussi M, Dai XQ, MacDonald PE, Newgard CB. Metabolomics applied to islet nutrient sensing mechanisms. Diabetes Obes Metab 2017; 19 Suppl 1:90-94. [PMID: 28880482 PMCID: PMC5929146 DOI: 10.1111/dom.13010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 05/09/2017] [Accepted: 05/12/2017] [Indexed: 12/16/2022]
Abstract
After multiple decades of investigation, the precise mechanisms involved in fuel-stimulated insulin secretion are still being revealed. One avenue for gaining deeper knowledge is to apply emergent tools of "metabolomics," involving mass spectrometry and nuclear magnetic resonance-based profiling of islet cells in their fuel-stimulated compared with basal states. The current article summarizes recent insights gained from application of metabolomics tools to the specific process of glucose-stimulated insulin secretion, revealing 2 new mechanisms that may provide targets for improving insulin secretion in diabetes.
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Affiliation(s)
- Mette V. Jensen
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701
| | - Jessica Gooding
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701
| | - Mourad Ferdaoussi
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada, T6G2R3
| | - Xiao-Qing Dai
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada, T6G2R3
| | - Patrick E. MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada, T6G2R3
| | - Christopher B. Newgard
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701
- Corresponding Author: Christopher B. Newgard, PhD, Duke Molecular Physiology Institute, 300 North Duke Street, Durham, NC 27701, , Phone: (919) 668-6059
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55
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N-acyl Taurines and Acylcarnitines Cause an Imbalance in Insulin Synthesis and Secretion Provoking β Cell Dysfunction in Type 2 Diabetes. Cell Metab 2017; 25:1334-1347.e4. [PMID: 28591636 DOI: 10.1016/j.cmet.2017.04.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 02/14/2017] [Accepted: 04/13/2017] [Indexed: 02/06/2023]
Abstract
The processes contributing to β cell dysfunction in type 2 diabetes (T2D) are uncertain, largely because it is difficult to access β cells in their intact immediate environment. We examined the pathophysiology of β cells under T2D progression directly in pancreatic tissues. We used MALDI imaging of Langerhans islets (LHIs) within mouse tissues or from human tissues to generate in situ-omics data, which we supported with in vitro experiments. Molecular interaction networks provided information on functional pathways and molecules. We found that stearoylcarnitine accumulated in β cells, leading to arrest of insulin synthesis and energy deficiency via excessive β-oxidation and depletion of TCA cycle and oxidative phosphorylation metabolites. Acetylcarnitine and an accumulation of N-acyl taurines, a group not previously detected in β cells, provoked insulin secretion. Thus, β cell dysfunction results from enhanced insulin secretion combined with an arrest of insulin synthesis.
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Mulder H. Transcribing β-cell mitochondria in health and disease. Mol Metab 2017; 6:1040-1051. [PMID: 28951827 PMCID: PMC5605719 DOI: 10.1016/j.molmet.2017.05.014] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 05/13/2017] [Accepted: 05/22/2017] [Indexed: 12/17/2022] Open
Abstract
Background The recent genome-wide association studies (GWAS) of Type 2 Diabetes (T2D) have identified the pancreatic β-cell as the culprit in the pathogenesis of the disease. Mitochondrial metabolism plays a crucial role in the processes controlling release of insulin and β-cell mass. This notion implies that mechanisms controlling mitochondrial function have the potential to play a decisive pathogenetic role in T2D. Scope of the review This article reviews studies demonstrating that there is indeed mitochondrial dysfunction in islets in T2D, and that GWAS have identified a variant in the gene encoding transcription factor B1 mitochondrial (TFB1M), predisposing to T2D due to mitochondrial dysfunction and impaired insulin secretion. Mechanistic studies of the nature of this pathogenetic link, as well as of other mitochondrial transcription factors, are described. Major conclusions Based on this, it is argued that transcription and translation in mitochondria are critical processes determining mitochondrial function in β-cells in health and disease.
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Key Words
- AMPK, AMP-dependent protein kinase
- ATGL, adipocyte triglyceride lipase
- COX, Cytochrome c oxidase
- CYTB, Cytochrome b
- ERR-α, Estrogen-related receptor-α
- Expression quantitative trait locus (eQTL)
- GDH, Glutamate dehydrogenase
- GSIS, Glucose-stimulated insulin secretion
- GWAS, Genome-wide association study
- Genome-wide association study (GWAS)
- HSL, Hormone-sensitive lipase
- ICDc, Cytosolic isocitrate dehydrogenase
- Insulin secretion
- Islets
- KATP, ATP-dependent K+-channel
- MTERF, Mitochondrial transcription termination factor
- Mitochondria
- ND, NADH dehydrogenase
- NRF, Nuclear respiratory factor
- NSUN4, NOP2/Sun RNA methyltransferase family member 4
- OXPHOS, Oxidative phosphorylation
- PC, Pyruvate carboxylase
- PDH, pyruvate dehydrogenase
- PGC, Peroxisome proliferator-activated receptor-γ co-activator
- POLRMT, Mitochondrial RNA polymerase
- POLγ, DNA polymerase-γ
- PPARγ, Peroxisome proliferator-activated receptor-γ
- PRC, PGC1-related coactivator
- SENP1, Sentrin/SUMO-specific protease-1
- SNP, Single Nucleotide Polymorphism
- SUR1, Sulphonylurea receptor-1
- T2D, Type 2 Diabetes
- TCA, Tricarboxylic acid
- TEFM, Mitochondrial transcription elongation factor
- TFAM, Transcription factor A mitochondrial
- TFB1M, Transcription factor B1 mitochondrial
- TFB2M, Transcription factor B2 mitochondrial
- eQTL, Expression quantitative trait locus
- β-Cell
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Affiliation(s)
- Hindrik Mulder
- Unit of Molecular Metabolism, Lund University Diabetes Centre, Malmö, Sweden
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57
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Petry SF, Sharifpanah F, Sauer H, Linn T. Differential expression of islet glutaredoxin 1 and 5 with high reactive oxygen species production in a mouse model of diabesity. PLoS One 2017; 12:e0176267. [PMID: 28542222 PMCID: PMC5443478 DOI: 10.1371/journal.pone.0176267] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 04/07/2017] [Indexed: 01/14/2023] Open
Abstract
The onset and progression of diabetes mellitus type 2 is highly contingent on the amount of functional beta-cell mass. An underlying cause of beta-cell decay in diabetes is oxidative stress, which markedly affects the insulin producing pancreatic cells due to their poor antioxidant defence capacity. Consequently, disturbances of cellular redox signaling have been implicated to play a major role in beta-cell loss in diabetes mellitus type 2. There is evidence suggesting that the glutaredoxin (Grx) system exerts a protective role for pancreatic islets, but the exact mechanisms have not yet been elucidated. In this study, a mouse model for diabetes mellitus type 2 was used to gain further insight into the significance of Grx for the islets of Langerhans in the diabetic metabolism. We have observed distinct differences in the expression levels of Grx in pancreatic islets between obese, diabetic db mice and lean, non-diabetic controls. This finding is the first report about a decrease of Grx expression levels in pancreatic islets of diabetic mice which was accompanied by declining insulin secretion, increase of reactive oxygen species (ROS) production level, and cell cycle alterations. These data demonstrate the essential role of the Grx system for the beta-cell during metabolic stress which may provide a new target for diabetes mellitus type 2 treatment.
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Affiliation(s)
- Sebastian Friedrich Petry
- Clinical Research Unit, Center of Internal Medicine, Justus Liebig University, Giessen, Germany
- * E-mail:
| | - Fatemeh Sharifpanah
- Department of Physiology, Faculty of Medicine, Justus Liebig University, Giessen, Germany
| | - Heinrich Sauer
- Department of Physiology, Faculty of Medicine, Justus Liebig University, Giessen, Germany
| | - Thomas Linn
- Clinical Research Unit, Center of Internal Medicine, Justus Liebig University, Giessen, Germany
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58
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Abstract
Pancreatic islet β cells secrete insulin in response to nutrient secretagogues, like glucose, dependent on calcium influx and nutrient metabolism. One of the most intriguing qualities of β cells is their ability to use metabolism to amplify the amount of secreted insulin independent of further alterations in intracellular calcium. Many years studying this amplifying process have shaped our current understanding of β cell stimulus-secretion coupling; yet, the exact mechanisms of amplification have been elusive. Recent studies utilizing metabolomics, computational modeling, and animal models have progressed our understanding of the metabolic amplifying pathway of insulin secretion from the β cell. New approaches will be discussed which offer in-roads to a more complete model of β cell function. The development of β cell therapeutics may be aided by such a model, facilitating the targeting of aspects of the metabolic amplifying pathway which are unique to the β cell.
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Affiliation(s)
- Michael A Kalwat
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States.
| | - Melanie H Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
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59
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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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60
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Santos LR, Muller C, de Souza AH, Takahashi HK, Spégel P, Sweet IR, Chae H, Mulder H, Jonas JC. NNT reverse mode of operation mediates glucose control of mitochondrial NADPH and glutathione redox state in mouse pancreatic β-cells. Mol Metab 2017; 6:535-547. [PMID: 28580284 PMCID: PMC5444111 DOI: 10.1016/j.molmet.2017.04.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/10/2017] [Accepted: 04/18/2017] [Indexed: 11/17/2022] Open
Abstract
Objective The glucose stimulation of insulin secretion (GSIS) by pancreatic β-cells critically depends on increased production of metabolic coupling factors, including NADPH. Nicotinamide nucleotide transhydrogenase (NNT) typically produces NADPH at the expense of NADH and ΔpH in energized mitochondria. Its spontaneous inactivation in C57BL/6J mice was previously shown to alter ATP production, Ca2+ influx, and GSIS, thereby leading to glucose intolerance. Here, we tested the role of NNT in the glucose regulation of mitochondrial NADPH and glutathione redox state and reinvestigated its role in GSIS coupling events in mouse pancreatic islets. Methods Islets were isolated from female C57BL/6J mice (J-islets), which lack functional NNT, and genetically close C57BL/6N mice (N-islets). Wild-type mouse NNT was expressed in J-islets by adenoviral infection. Mitochondrial and cytosolic glutathione oxidation was measured with glutaredoxin 1-fused roGFP2 probes targeted or not to the mitochondrial matrix. NADPH and NADH redox state was measured biochemically. Insulin secretion and upstream coupling events were measured under dynamic or static conditions by standard procedures. Results NNT is largely responsible for the acute glucose-induced rise in islet NADPH/NADP+ ratio and decrease in mitochondrial glutathione oxidation, with a small impact on cytosolic glutathione. However, contrary to current views on NNT in β-cells, these effects resulted from a glucose-dependent reduction in NADPH consumption by NNT reverse mode of operation, rather than from a stimulation of its forward mode of operation. Accordingly, the lack of NNT in J-islets decreased their sensitivity to exogenous H2O2 at non-stimulating glucose. Surprisingly, the lack of NNT did not alter the glucose-stimulation of Ca2+ influx and upstream mitochondrial events, but it markedly reduced both phases of GSIS by altering Ca2+-induced exocytosis and its metabolic amplification. Conclusion These results drastically modify current views on NNT operation and mitochondrial function in pancreatic β-cells.
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Key Words
- AT2, aldrithiol
- C57BL/6J mice
- C57BL/6N mice
- CMV, cytomegalovirus
- DTT, dithiotreitol
- Dz, diazoxide
- FCCP, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone
- GRX1, glutaredoxin 1
- GRX1-roGFP2
- GSIS, glucose stimulation of insulin secretion
- Glucose metabolism
- IDH, isocitrate dehydrogenase
- Insulin secretion
- KRB, Krebs solution
- ME, malic enzyme
- Mitochondrial shuttles
- NNT, nicotinamide nucleotide transhydrogenase
- OCR, oxygen consumption rate
- Pancreatic islet
- Redox-sensitive GFP
- Stimulus-secretion coupling
- WT, wild-type
- [Ca2+]i, intracellular Ca2+ concentration
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Affiliation(s)
- Laila R.B. Santos
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Carole Muller
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Arnaldo H. de Souza
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Hilton K. Takahashi
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Peter Spégel
- Lund University, Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Malmö, 205 02, Sweden
- Lund University, Department of Chemistry, Centre for Analysis and Synthesis, Lund, 221 00, Sweden
| | - Ian R. Sweet
- University of Washington Diabetes Institute, Department of Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Heeyoung Chae
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Hindrik Mulder
- Lund University, Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Malmö, 205 02, Sweden
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
- Corresponding author. Université catholique de Louvain, UCL/SSS/IREC/EDIN, Avenue Hippocrate 55, B1.55.06, B-1200, Brussels, Belgium.Université catholique de LouvainUCL/SSS/IREC/EDINAvenue Hippocrate 55B1.55.06BrusselsB-1200Belgium
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De Marchi U, Hermant A, Thevenet J, Ratinaud Y, Santo-Domingo J, Barron D, Wiederkehr A. A novel ATP-synthase-independent mechanism coupling mitochondrial activation to exocytosis in insulin-secreting cells. J Cell Sci 2017; 130:1929-1939. [PMID: 28404787 DOI: 10.1242/jcs.200741] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/11/2017] [Indexed: 12/16/2022] Open
Abstract
Pancreatic β-cells sense glucose, promoting insulin secretion. Glucose sensing requires the sequential stimulation of glycolysis, mitochondrial metabolism and Ca2+ entry. To elucidate how mitochondrial activation in β-cells contributes to insulin secretion, we compared the effects of glucose and the mitochondrial substrate methylsuccinate in the INS-1E insulin-secreting cell line at the respective concentrations at which they maximally activate mitochondrial respiration. Both substrates induced insulin secretion with distinct respiratory profiles, mitochondrial hyperpolarization, NADH production and ATP-to-ADP ratios. In contrast to glucose, methylsuccinate failed to induce large [Ca2+] rises and exocytosis proceeded largely independently of mitochondrial ATP synthesis. Both glucose- and methylsuccinate-induced secretion was blocked by diazoxide, indicating that Ca2+ is required for exocytosis. Dynamic assessment of the redox state of mitochondrial thiols revealed a less marked reduction in response to methylsuccinate than with glucose. Our results demonstrate that insulin exocytosis can be promoted by two distinct mechanisms one of which is dependent on mitochondrial ATP synthesis and large Ca2+ transients, and one of which is independent of mitochondrial ATP synthesis and relies on small Ca2+ signals. We propose that the combined effects of Ca2+ and redox reactions can trigger insulin secretion by these two mechanisms.
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Affiliation(s)
- Umberto De Marchi
- Mitochondrial Function, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building G, Lausanne CH-1015, Switzerland
| | - Aurelie Hermant
- Mitochondrial Function, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building G, Lausanne CH-1015, Switzerland
| | - Jonathan Thevenet
- Mitochondrial Function, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building G, Lausanne CH-1015, Switzerland
| | - Yann Ratinaud
- Natural Bioactives and screening, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, Lausanne CH-1015, Switzerland
| | - Jaime Santo-Domingo
- Mitochondrial Function, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building G, Lausanne CH-1015, Switzerland
| | - Denis Barron
- Natural Bioactives and screening, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, Lausanne CH-1015, Switzerland
| | - Andreas Wiederkehr
- Mitochondrial Function, Nestlé Institute of Health Sciences, EPFL Innovation Park, Building G, Lausanne CH-1015, Switzerland
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Sphingosine kinase 1-interacting protein is a novel regulator of glucose-stimulated insulin secretion. Sci Rep 2017; 7:779. [PMID: 28396589 PMCID: PMC5429731 DOI: 10.1038/s41598-017-00900-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 03/16/2017] [Indexed: 12/12/2022] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) is essential in keeping blood glucose levels within normal range. GSIS is impaired in type 2 diabetes, and its recovery is crucial in treatment of the disease. We find here that sphingosine kinase 1-interacting protein (SKIP, also called Sphkap) is highly expressed in pancreatic β-cells but not in α-cells. Intraperitoneal glucose tolerance test showed that plasma glucose levels were decreased and insulin levels were increased in SKIP−/− mice compared to SKIP+/+ mice, but exendin-4-enhanced insulin secretion was masked. GSIS was amplified more in SKIP−/− but exendin-4-enhanced insulin secretion was masked compared to that in SKIP+/+ islets. The ATP and cAMP content were similarly increased in SKIP+/+ and SKIP−/− islets; depolarization-evoked, PKA and cAMP-mediated insulin secretion were not affected. Inhibition of PDE activity equally augmented GSIS in SKIP+/+ and SKIP−/− islets. These results indicate that SKIP modulates GSIS by a pathway distinct from that of cAMP-, PDE- and sphingosine kinase-dependent pathways.
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63
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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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Hu X, Chao M, Wu H. Central role of lactate and proton in cancer cell resistance to glucose deprivation and its clinical translation. Signal Transduct Target Ther 2017; 2:16047. [PMID: 29263910 PMCID: PMC5661620 DOI: 10.1038/sigtrans.2016.47] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/21/2016] [Accepted: 12/26/2016] [Indexed: 12/14/2022] Open
Abstract
Targeting common weaknesses of cancer is an important strategy for cancer therapy. Glucose is a nutrient that maintains essential cellular metabolism, supporting cancer cell survival, growth and proliferation. Depriving glucose rapidly kills cancer cells. Most cancer cells possess a feature called Warburg effect, which refers to that cancer cells even with ample oxygen exhibit an exceptionally high glycolysis rate and convert most incoming glucose to lactate. Although it is recognized that Warburg effect confers growth advantage to cancer cells when glucose supply is sufficient, this feature could be considered as a fatal weakness of cancer cells when glucose supply is a problem. As glucose supply in many solid tumors is poor, and as most cancer cells have exceptionally high glycolytic capacity, maximizing cancer cell glycolysis rate would possibly exhaust intratumoral glucose, leading cancer cell to death. Lactate and proton are two common factors in solid tumors, they jointly protect cancer cells against glucose deprivation, and they are also powerful regulators dictating glucose metabolic phenotypes of cancer cells. Disrupting the joint action of lactate and proton, for example, by means of bicarbonate infusion into tumor, could maximize cancer cell glycolytic rate to rapidly use up glucose, expose their vulnerability to glucose deprivation and ultimately kill cancer cells. A pilot clinical study demonstrated that this approach achieved a remarkable improvement in local control of large and huge hepatocellular carcinoma.
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Affiliation(s)
- Xun Hu
- Cancer Institute (a Key Laboratory For Cancer Prevention & Intervention, China National Ministry of Education), The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ming Chao
- Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Hao Wu
- Cancer Institute (a Key Laboratory For Cancer Prevention & Intervention, China National Ministry of Education), The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
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65
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Mugabo Y, Zhao S, Lamontagne J, Al-Mass A, Peyot ML, Corkey BE, Joly E, Madiraju SRM, Prentki M. Metabolic fate of glucose and candidate signaling and excess-fuel detoxification pathways in pancreatic β-cells. J Biol Chem 2017; 292:7407-7422. [PMID: 28280244 DOI: 10.1074/jbc.m116.763060] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 03/06/2017] [Indexed: 12/28/2022] Open
Abstract
Glucose metabolism promotes insulin secretion in β-cells via metabolic coupling factors that are incompletely defined. Moreover, chronically elevated glucose causes β-cell dysfunction, but little is known about how cells handle excess fuels to avoid toxicity. Here we sought to determine which among the candidate pathways and coupling factors best correlates with glucose-stimulated insulin secretion (GSIS), define the fate of glucose in the β-cell, and identify pathways possibly involved in excess-fuel detoxification. We exposed isolated rat islets for 1 h to increasing glucose concentrations and measured various pathways and metabolites. Glucose oxidation, oxygen consumption, and ATP production correlated well with GSIS and saturated at 16 mm glucose. However, glucose utilization, glycerol release, triglyceride and glycogen contents, free fatty acid (FFA) content and release, and cholesterol and cholesterol esters increased linearly up to 25 mm glucose. Besides being oxidized, glucose was mainly metabolized via glycerol production and release and lipid synthesis (particularly FFA, triglycerides, and cholesterol), whereas glycogen production was comparatively low. Using targeted metabolomics in INS-1(832/13) cells, we found that several metabolites correlated well with GSIS, in particular some Krebs cycle intermediates, malonyl-CoA, and lower ADP levels. Glucose dose-dependently increased the dihydroxyacetone phosphate/glycerol 3-phosphate ratio in INS-1(832/13) cells, indicating a more oxidized state of NAD in the cytosol upon glucose stimulation. Overall, the data support a role for accelerated oxidative mitochondrial metabolism, anaplerosis, and malonyl-CoA/lipid signaling in β-cell metabolic signaling and suggest that a decrease in ADP levels is important in GSIS. The results also suggest that excess-fuel detoxification pathways in β-cells possibly comprise glycerol and FFA formation and release extracellularly and the diversion of glucose carbons to triglycerides and cholesterol esters.
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Affiliation(s)
- Yves Mugabo
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec H3C 3J7, Canada, and
| | - Shangang Zhao
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Medicine and Human Genetics, McGill University, Montreal, Québec H3A 1B1, Canada
| | - Julien Lamontagne
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Anfal Al-Mass
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Medicine and Human Genetics, McGill University, Montreal, Québec H3A 1B1, Canada
| | - Marie-Line Peyot
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Barbara E Corkey
- Department of Medicine, Obesity Research Center, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Erik Joly
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - S R Murthy Madiraju
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Marc Prentki
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada, .,Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec H3C 3J7, Canada, and
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66
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Schulze T, Morsi M, Reckers K, Brüning D, Seemann N, Panten U, Rustenbeck I. Metabolic amplification of insulin secretion is differentially desensitized by depolarization in the absence of exogenous fuels. Metabolism 2017; 67:1-13. [PMID: 28081772 DOI: 10.1016/j.metabol.2016.10.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 10/18/2016] [Accepted: 10/20/2016] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The metabolic amplification of insulin secretion is the sequence of events which enables the secretory response to a fuel secretagogue to exceed the secretory response to a purely depolarizing stimulus. The signals in this pathway are incompletely understood. Here, we have characterized an experimental procedure by which the amplifying response to glucose is reversibly desensitized, while the response to α-ketoisocaproic acid (KIC) is unchanged. MATERIALS/METHODS Insulin secretion, NAD(P)H- and FAD-autofluorescence, Fura-2 fluorescence and oxygen consumption were measured in perifused NMRI mouse islets. The ATP- and ADP-contents were measured in statically incubated mouse islets. All islets were freshly isolated. RESULTS While the original observation on the dissociation between glucose- and KIC-amplification was obtained with islets that had been exposed to a high concentration of the sulfonylurea glipizide in the absence of glucose, we now show that in the absence of exogenous fuel a moderate depolarization, irrespective of its mechanism, progressively decreased the amplification in response to both glucose and KIC. However, the amplification in response to glucose declined faster, so a time window exists where glucose was already inefficient, whereas KIC was of unimpaired efficiency. Measurements of adenine nucleotides, NAD(P)H- and FAD-autofluorescence, and oxygen consumption point to a central role of the mitochondrial metabolism in this process. The desensitization could be quickly reversed by increasing oxidative deamination of glutamate and consequently anaplerosis of the citrate cycle. CONCLUSION Depolarization in the absence of exogenous fuel may be a useful model to identify those signals which are indispensable for the generation of metabolic amplification.
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Affiliation(s)
- Torben Schulze
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Mai Morsi
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Kirstin Reckers
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Dennis Brüning
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Nele Seemann
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Uwe Panten
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany.
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67
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Abstract
Metabolomics, or the comprehensive profiling of small molecule metabolites in cells, tissues, or whole organisms, has undergone a rapid technological evolution in the past two decades. These advances have led to the application of metabolomics to defining predictive biomarkers for incident cardiometabolic diseases and, increasingly, as a blueprint for understanding those diseases' pathophysiologic mechanisms. Progress in this area and challenges for the future are reviewed here.
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Affiliation(s)
- Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center, Duke Molecular Physiology Institute, Departments of Pharmacology & Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA.
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68
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de Souza AH, Santos LRB, Roma LP, Bensellam M, Carpinelli AR, Jonas JC. NADPH oxidase-2 does not contribute to β-cell glucotoxicity in cultured pancreatic islets from C57BL/6J mice. Mol Cell Endocrinol 2017; 439:354-362. [PMID: 27664519 DOI: 10.1016/j.mce.2016.09.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/24/2016] [Accepted: 09/20/2016] [Indexed: 11/20/2022]
Abstract
High glucose-induced oxidative stress and increased NADPH oxidase-2 (NOX2) activity may contribute to the progressive decline of the functional β-cell mass in type 2 diabetes. To test that hypothesis, we characterized, in islets from male NOX2 knockout (NOX2-KO) and wild-type (WT) C57BL/6J mice cultured for up to 3 weeks at 10 or 30 mmol/l glucose (G10 or G30), the in vitro effects of glucose on cytosolic oxidative stress using probes sensing glutathione oxidation (GRX1-roGFP2), thiol oxidation (roGFP1) or H2O2 (roGFP2-Orp1), on β-cell stimulus-secretion coupling events and on β-cell apoptosis. After 1-2 days of culture in G10, the glucose stimulation of insulin secretion (GSIS) was ∼1.7-fold higher in NOX2-KO vs. WT islets at 20-30 mmol/l glucose despite similar rises in NAD(P)H and intracellular calcium concentration ([Ca2+]i) and no differences in cytosolic GRX1-roGFP2 oxidation. After long-term culture at G10, roGFP1 and roGFP2-Orp1 oxidation and β-cell apoptosis remained low, and the glucose-induced rises in NAD(P)H, [Ca2+]i and GSIS were similarly preserved in both islet types. After prolonged culture at G30, roGFP1 and roGFP2-Orp1 oxidation increased in parallel with β-cell apoptosis, the glucose sensitivity of the NADPH, [Ca2+]i and insulin secretion responses increased, the maximal [Ca2+]i response decreased, but maximal GSIS was preserved. These responses were almost identical in both islet types. In conclusion, NOX2 is a negative regulator of maximal GSIS in C57BL/6J mouse islets, but it does not detectably contribute to the in vitro glucotoxic induction of cytosolic oxidative stress and alterations of β-cell survival and function.
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Affiliation(s)
- Arnaldo H de Souza
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium; Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Laila R B Santos
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium
| | - Leticia P Roma
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Mohammed Bensellam
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium
| | - Angelo R Carpinelli
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium.
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69
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Ferdaoussi M, MacDonald PE. Toward Connecting Metabolism to the Exocytotic Site. Trends Cell Biol 2016; 27:163-171. [PMID: 27932063 DOI: 10.1016/j.tcb.2016.10.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/28/2016] [Accepted: 10/31/2016] [Indexed: 12/14/2022]
Abstract
Within cells the regulated exocytosis of secretory granules controls multiple physiological functions, including endocrine hormone secretion. Release of the glucose-regulating hormone insulin from pancreatic islet β cells is critical for whole-body metabolic homeostasis. Impaired insulin secretion appears early in the progression to type 2 diabetes (T2D). Key mechanisms that control the β-cell exocytotic response, mediating the long-known but little understood metabolic amplification of insulin secretion, are becoming clearer. Recent insights indicate a convergence of metabolism-driven signals, such as lipid-derived messengers and redox-dependent deSUMOylation, at the plasma membrane to augment Ca2+-dependent insulin exocytosis. These pathways have important implications for the metabolic control of hormone secretion, for the functional compensation that occurs in obesity, and for impaired insulin secretion in diabetes.
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Affiliation(s)
- Mourad Ferdaoussi
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1
| | - Patrick E MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1.
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70
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Pizarro-Delgado J, Deeney JT, Corkey BE, Tamarit-Rodriguez J. Direct Stimulation of Islet Insulin Secretion by Glycolytic and Mitochondrial Metabolites in KCl-Depolarized Islets. PLoS One 2016; 11:e0166111. [PMID: 27851770 PMCID: PMC5112877 DOI: 10.1371/journal.pone.0166111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 10/24/2016] [Indexed: 11/26/2022] Open
Abstract
We have previously demonstrated that islet depolarization with 70 mM KCl opens Cx36 hemichannels and allows diffusion of small metabolites and cofactors through the β-cell plasma membrane. We have investigated in this islet “permeabilized” model whether glycolytic and citric acid cycle intermediates stimulate insulin secretion and how it correlates with ATP production (islet content plus extracellular nucleotide accumulation). Glycolytic intermediates (10 mM) stimulated insulin secretion and ATP production similarly. However, they showed differential sensitivities to respiratory chain or enzyme inhibitors. Pyruvate showed a lower secretory capacity and less ATP production than phosphoenolpyruvate, implicating an important role for glycolytic generation of ATP. ATP production by glucose-6-phosphate was not sensitive to a pyruvate kinase inhibitor that effectively suppressed the phosphoenolpyruvate-induced secretory response and islet ATP rise. Strong suppression of both insulin secretion and ATP production induced by glucose-6-phosphate was caused by 10 μM antimycin A, implicating an important role for the glycerophosphate shuttle in transferring reducing equivalents to the mitochondria. Five citric acid cycle intermediates were investigated for their secretory and ATP production capacity (succinate, fumarate, malate, isocitrate and α-ketoglutarate at 5 mM, together with ADP and/or NADP+ to feed the NADPH re-oxidation cycles). The magnitude of the secretory response was very similar among the different mitochondrial metabolites but α-ketoglutarate showed a more sustained second phase of secretion. Gabaculine (1 mM, a GABA-transaminase inhibitor) suppressed the second phase of secretion and the ATP-production stimulated by α-ketoglutarate, supporting a role for the GABA shuttle in the control of glucose-induced insulin secretion. None of the other citric acid intermediates essayed showed any suppression of both insulin secretion or ATP-production by the presence of gabaculine. We propose that endogenous GABA metabolism in the “GABA-shunt” facilitates ATP production in the citric acid cycle for an optimal insulin secretion.
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Affiliation(s)
- Javier Pizarro-Delgado
- Obesity Research Center, Department of Medicine, Boston University School of Medicine, Boston, MA, United States of America
- Biochemistry Department, Medical School, Complutense University, Madrid, Spain
| | - Jude T. Deeney
- Obesity Research Center, Department of Medicine, Boston University School of Medicine, Boston, MA, United States of America
| | - Barbara E. Corkey
- Obesity Research Center, Department of Medicine, Boston University School of Medicine, Boston, MA, United States of America
| | - Jorge Tamarit-Rodriguez
- Obesity Research Center, Department of Medicine, Boston University School of Medicine, Boston, MA, United States of America
- Biochemistry Department, Medical School, Complutense University, Madrid, Spain
- * E-mail:
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71
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Accili D, Talchai SC, Kim-Muller JY, Cinti F, Ishida E, Ordelheide AM, Kuo T, Fan J, Son J. When β-cells fail: lessons from dedifferentiation. Diabetes Obes Metab 2016; 18 Suppl 1:117-22. [PMID: 27615140 PMCID: PMC5021187 DOI: 10.1111/dom.12723] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 05/03/2016] [Indexed: 12/14/2022]
Abstract
Diabetes is caused by a combination of impaired responsiveness to insulin and reduced production of insulin by the pancreas. Until recently, the decline of insulin production had been ascribed to β-cell death. But recent research has shown that β-cells do not die in diabetes, but undergo a silencing process, termed "dedifferentiation." The main implication of this discovery is that β-cells can be revived by appropriate treatments. We have shown that mitochondrial abnormalities are a key step in the progression of β-cell dysfunction towards dedifferentiation. In normal β-cells, mitochondria generate energy required to sustain insulin production and its finely timed release in response to the body's nutritional status. A normal β-cell can adapt its mitochondrial fuel source based on substrate availability, a concept known as "metabolic flexibility." This capability is the first casualty in the progress of β-cell failure. β-Cells lose the ability to select the right fuel for mitochondrial energy production. Mitochondria become overloaded, and accumulate by-products derived from incomplete fuel utilization. Energy production stalls, and insulin production drops, setting the stage for dedifferentiation. The ultimate goal of these investigations is to explore novel treatment paradigms that will benefit people with diabetes.
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Affiliation(s)
- D Accili
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York.
| | - S C Talchai
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - J Y Kim-Muller
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - F Cinti
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - E Ishida
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - A M Ordelheide
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - T Kuo
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - J Fan
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
| | - J Son
- Department of Medicine and Berrie Diabetes Center, Columbia University, New York, New York
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72
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NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) and cytochrome P450 oxidoreductase (CYP450OR) differentially regulate menadione-mediated alterations in redox status, survival and metabolism in pancreatic β-cells. Toxicol Lett 2016; 262:1-11. [PMID: 27558805 DOI: 10.1016/j.toxlet.2016.08.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 07/27/2016] [Accepted: 08/20/2016] [Indexed: 01/08/2023]
Abstract
NQO1 (NAD(P)H-quinone oxidoreductase 1) reduces quinones and xenobiotics to less-reactive compounds via 2-electron reduction, one feature responsible for the role of NQO1 in antioxidant defense in several tissues. In contrast, NADPH cytochrome P450 oxidoreductase (CYP450OR), catalyzes the 1-electron reduction of quinones and xenobiotics, resulting in enhanced superoxide formation. However, to date, the roles of NQO1 and CYP450OR in pancreatic β-cell metabolism under basal conditions and oxidant challenge have not been characterized. Using NQO1 inhibition, over-expression and knock out, we have demonstrated that, in addition to protection of β-cells from toxic concentrations of the redox cycling quinone menadione, NQO1 also regulates the basal level of reduced-to-oxidized nucleotides, suggesting other role(s) beside that of an antioxidant enzyme. In contrast, over-expression of NADPH cytochrome P450 oxidoreductase (CYP450OR) resulted in enhanced redox cycling activity and decreased cellular viability, consistent with the enhanced generation of superoxide and H2O2. Basal expression of NQO1 and CYP450OR was comparable in isolated islets and liver. However, NQO1, but not CYP450OR, was strongly induced in β-cells exposed to menadione. NQO1 and CYP450OR exhibited a reciprocal preference for reducing equivalents in β-cells: while CYP450OR preferentially utilized NADPH, NQO1 primarily utilized NADH. Together, these results demonstrate that NQO1 and CYP450OR reciprocally regulate oxidant metabolism in pancreatic β-cells.
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73
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Lemaire K, Thorrez L, Schuit F. Disallowed and Allowed Gene Expression: Two Faces of Mature Islet Beta Cells. Annu Rev Nutr 2016; 36:45-71. [DOI: 10.1146/annurev-nutr-071715-050808] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Lieven Thorrez
- Gene Expression Unit, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Leuven B3000, Belgium; , ,
| | - Frans Schuit
- Gene Expression Unit, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Leuven B3000, Belgium; , ,
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74
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Brun T, Maechler P. Beta-cell mitochondrial carriers and the diabetogenic stress response. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2540-9. [PMID: 26979549 DOI: 10.1016/j.bbamcr.2016.03.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 01/09/2023]
Abstract
Mitochondria play a central role in pancreatic beta-cells by coupling metabolism of the secretagogue glucose to distal events of regulated insulin exocytosis. This process requires transports of both metabolites and nucleotides in and out of the mitochondria. The molecular identification of mitochondrial carriers and their respective contribution to beta-cell function have been uncovered only recently. In type 2 diabetes, mitochondrial dysfunction is an early event and may precipitate beta-cell loss. Under diabetogenic conditions, characterized by glucotoxicity and lipotoxicity, the expression profile of mitochondrial carriers is selectively modified. This review describes the role of mitochondrial carriers in beta-cells and the selective changes in response to glucolipotoxicity. In particular, we discuss the importance of the transfer of metabolites (pyruvate, citrate, malate, and glutamate) and nucleotides (ATP, NADH, NADPH) for beta-cell function and dysfunction. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Thierry Brun
- Department of Cell Physiology and Metabolism, Faculty Diabetes Center, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, Faculty Diabetes Center, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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75
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Kuo T, Kim-Muller JY, McGraw TE, Accili D. Altered Plasma Profile of Antioxidant Proteins as an Early Correlate of Pancreatic β Cell Dysfunction. J Biol Chem 2016; 291:9648-56. [PMID: 26917725 DOI: 10.1074/jbc.m115.702183] [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: 11/04/2015] [Indexed: 12/22/2022] Open
Abstract
Insulin resistance and β cell dysfunction contribute to the pathogenesis of type 2 diabetes. Unlike insulin resistance, β cell dysfunction remains difficult to predict and monitor, because of the inaccessibility of the endocrine pancreas, the integrated relationship with insulin sensitivity, and the paracrine effects of incretins. The goal of our study was to survey the plasma response to a metabolic challenge in order to identify factors predictive of β cell dysfunction. To this end, we combined (i) the power of unbiased iTRAQ (isobaric tag for relative and absolute quantification) mass spectrometry with (ii) direct sampling of the portal vein following an intravenous glucose/arginine challenge (IVGATT) in (iii) mice with a genetic β cell defect. By so doing, we excluded the effects of peripheral insulin sensitivity as well as those of incretins on β cells, and focused on the first phase of insulin secretion to capture the early pathophysiology of β cell dysfunction. We compared plasma protein profiles with ex vivo islet secretome and transcriptome analyses. We detected changes to 418 plasma proteins in vivo, and detected changes to 262 proteins ex vivo The impairment of insulin secretion was associated with greater overall changes in the plasma response to IVGATT, possibly reflecting metabolic instability. Reduced levels of proteins regulating redox state and neuronal stress markers, as well as increased levels of coagulation factors, antedated the loss of insulin secretion in diabetic mice. These results suggest that a reduced complement of antioxidants in response to a mixed secretagogue challenge is an early correlate of future β cell failure.
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Affiliation(s)
- Taiyi Kuo
- From the Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York 10032 and
| | - Ja Young Kim-Muller
- From the Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York 10032 and
| | - Timothy E McGraw
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065
| | - Domenico Accili
- From the Department of Medicine and Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York 10032 and
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76
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Abstract
Until recently, type 2 diabetes was seen as a disease caused by an impaired ability of insulin to promote the uptake and utilisation of glucose. Work on forkhead box protein O (FOXO) transcription factors revealed new aspects of insulin action that have led us to articulate a liver- and beta cell-centric narrative of diabetes pathophysiology and treatment. FOXO integrate a surprisingly diverse subset of biological functions to promote metabolic flexibility. In the liver, they controls the glucokinase/glucose-6-phosphatase switch and bile acid pool composition, directing carbons to glucose or lipid utilisation, thus providing a unifying mechanism for the two abnormalities of the diabetic liver: excessive glucose production and increased lipid synthesis and secretion. Moreover, FOXO are necessary to maintain beta cell differentiation, and diabetes development is associated with a gradual loss of FOXO function that brings about beta cell dedifferentiation. We proposed that dedifferentiation is the main cause of beta cell failure and conversion into non-beta endocrine cells, and that treatment should restore beta cell differentiation. Our studies investigating these proposals have revealed new dimensions to the pathophysiology of diabetes that can be leveraged to design new therapies.
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Affiliation(s)
- Utpal B Pajvani
- Department of Medicine and Naomi Berrie Diabetes Center, Columbia University Medical Center, 1150 St Nicholas Av., New York, NY, 10032, USA.
| | - Domenico Accili
- Department of Medicine and Naomi Berrie Diabetes Center, Columbia University Medical Center, 1150 St Nicholas Av., New York, NY, 10032, USA.
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Zhao S, Poursharifi P, Mugabo Y, Levens EJ, Vivot K, Attane C, Iglesias J, Peyot ML, Joly E, Madiraju SM, Prentki M. α/β-Hydrolase domain-6 and saturated long chain monoacylglycerol regulate insulin secretion promoted by both fuel and non-fuel stimuli. Mol Metab 2015; 4:940-50. [PMID: 26909310 PMCID: PMC4731734 DOI: 10.1016/j.molmet.2015.09.012] [Citation(s) in RCA: 26] [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: 09/03/2015] [Revised: 09/21/2015] [Accepted: 09/28/2015] [Indexed: 01/15/2023] Open
Abstract
Objective α/β-Hydrolase domain-6 (ABHD6) is a newly identified monoacylglycerol (MAG) lipase. We recently reported that it negatively regulates glucose stimulated insulin secretion (GSIS) in the β cells by hydrolyzing lipolysis-derived MAG that acts as a metabolic coupling factor and signaling molecule via exocytotic regulator Munc13-1. Whether ABHD6 and MAG play a role in response to all classes of insulin secretagogues, in particular various fuel and non-fuel stimuli, is unknown. Methods Insulin secretion in response to various classes of secretagogues, exogenous MAG and pharmacological agents was measured in islets of mice deficient in ABHD6 specifically in the β cell (BKO). Islet perifusion experiments and determinations of glucose and fatty acid metabolism, cytosolic Ca2+ and MAG species levels were carried out. Results Deletion of ABHD6 potentiated insulin secretion in response to the fuels glutamine plus leucine and α-ketoisocaproate and to the non-fuel stimuli glucagon-like peptide 1, carbamylcholine and elevated KCl. Fatty acids amplified GSIS in control and BKO mice to the same extent. Exogenous 1-MAG amplified insulin secretion in response to fuel and non-fuel stimuli. MAG hydrolysis activity was greatly reduced in BKO islets without changes in total diacylglycerol and triacylglycerol lipase activity. ABHD6 deletion induced insulin secretion independently from KATP channels and did not alter the glucose induced rise in intracellular Ca2+. Perifusion studies showed elevated insulin secretion during second phase of GSIS in BKO islets that was not due to altered cytosolic Ca2+ signaling or because of changes in glucose and fatty acid metabolism. Glucose increased islet saturated long chain 1-MAG species and ABHD6 deletion caused accumulation of these 1-MAG species at both low and elevated glucose. Conclusion ABHD6 regulates insulin secretion in response to fuel stimuli at large and some non-fuel stimuli by controlling long chain saturated 1-MAG levels that synergize with other signaling pathways for secretion. ABHD6 is the major monoacylglycerol (MAG) hydrolase in pancreatic β cells. 1-MAG level is elevated in islets from β cell specific ABHD6-KO mice (BKO). BKO islets show enhanced fuel and non-fuel induced insulin secretion. ABHD6 accessible 1-MAG synergizes with other signals for insulin secretion.
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Key Words
- 1-OG, 1-oleoylglycerol
- 1-PG, 1-palmitoylglycerol
- 1-SG, 1-stearoylglycerol
- ABHD6, α/β-hydrolase domain-6
- ATGL, adipose triglyceride lipase
- BKO, β cell specific ABHD6-knockout
- Carb, carbamylcholine
- Cytosolic Ca2+
- DAG, diacylglycerol
- FFA, free fatty acid
- Flox, flox/flox
- GL/FFA, glycerolipid/ free fatty acid
- GLP1, glucagon-like peptide 1
- GPCR, G-protein coupled receptor
- GSIS, glucose stimulated insulin secretion
- HSL, hormone sensitive lipase
- Insulin secretion
- KO, knockout
- Kic, α-ketoisocaproate
- MAG, monoacylglycerol
- Monoacylglycerol
- OGTT, oral glucose tolerance test
- Pancreatic islets
- ROS, reactive oxygen species
- TG, triacylglycerol
- WT, wild type
- α/β-Hydrolase domain-6
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - S.R. Murthy Madiraju
- Corresponding author. Montreal Diabetes Research Center, CRCHUM, 900 St-Denis (Viger Tower), Rm R08-414, Montreal, QC H1W 4A4, Canada. Tel.: +1 514 890 8000x23610; fax: +1 514 412 7648.
| | - Marc Prentki
- Corresponding author. Montreal Diabetes Research Center, CRCHUM, 900 St-Denis (Viger Tower), Rm R08-412, Montreal, QC H1W 4A4, Canada. Tel.: +1 514 890 8000x23642; fax: +1 514 412 7648.
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78
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Gooding JR, Jensen MV, Dai X, Wenner BR, Lu D, Arumugam R, Ferdaoussi M, MacDonald PE, Newgard CB. Adenylosuccinate Is an Insulin Secretagogue Derived from Glucose-Induced Purine Metabolism. Cell Rep 2015; 13:157-167. [PMID: 26411681 DOI: 10.1016/j.celrep.2015.08.072] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 08/04/2015] [Accepted: 08/26/2015] [Indexed: 02/05/2023] Open
Abstract
Pancreatic islet failure, involving loss of glucose-stimulated insulin secretion (GSIS) from islet β cells, heralds the onset of type 2 diabetes (T2D). To search for mediators of GSIS, we performed metabolomics profiling of the insulinoma cell line 832/13 and uncovered significant glucose-induced changes in purine pathway intermediates, including a decrease in inosine monophosphate (IMP) and an increase in adenylosuccinate (S-AMP), suggesting a regulatory role for the enzyme that links the two metabolites, adenylosuccinate synthase (ADSS). Inhibition of ADSS or a more proximal enzyme in the S-AMP biosynthesis pathway, adenylosuccinate lyase, lowers S-AMP levels and impairs GSIS. Addition of S-AMP to the interior of patch-clamped human β cells amplifies exocytosis, an effect dependent upon expression of sentrin/SUMO-specific protease 1 (SENP1). S-AMP also overcomes the defect in glucose-induced exocytosis in β cells from a human donor with T2D. S-AMP is, thus, an insulin secretagogue capable of reversing β cell dysfunction in T2D.
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Affiliation(s)
- Jessica R Gooding
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA
| | - Mette V Jensen
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA
| | - Xiaoqing Dai
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Brett R Wenner
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA
| | - Danhong Lu
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA
| | - Ramamani Arumugam
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA
| | - Mourad Ferdaoussi
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Patrick E MacDonald
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, AB T6G 2E1, Canada.
| | - Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University Medical Center, Durham, NC 27701, USA.
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79
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Ferdaoussi M, Dai X, Jensen MV, Wang R, Peterson BS, Huang C, Ilkayeva O, Smith N, Miller N, Hajmrle C, Spigelman AF, Wright RC, Plummer G, Suzuki K, Mackay JP, van de Bunt M, Gloyn AL, Ryan TE, Norquay LD, Brosnan MJ, Trimmer JK, Rolph TP, Kibbey RG, Manning Fox JE, Colmers WF, Shirihai OS, Neufer PD, Yeh ETH, Newgard CB, MacDonald PE. Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells. J Clin Invest 2015; 125:3847-60. [PMID: 26389676 DOI: 10.1172/jci82498] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/24/2015] [Indexed: 01/02/2023] Open
Abstract
Insulin secretion from β cells of the pancreatic islets of Langerhans controls metabolic homeostasis and is impaired in individuals with type 2 diabetes (T2D). Increases in blood glucose trigger insulin release by closing ATP-sensitive K+ channels, depolarizing β cells, and opening voltage-dependent Ca2+ channels to elicit insulin exocytosis. However, one or more additional pathway(s) amplify the secretory response, likely at the distal exocytotic site. The mitochondrial export of isocitrate and engagement with cytosolic isocitrate dehydrogenase (ICDc) may be one key pathway, but the mechanism linking this to insulin secretion and its role in T2D have not been defined. Here, we show that the ICDc-dependent generation of NADPH and subsequent glutathione (GSH) reduction contribute to the amplification of insulin exocytosis via sentrin/SUMO-specific protease-1 (SENP1). In human T2D and an in vitro model of human islet dysfunction, the glucose-dependent amplification of exocytosis was impaired and could be rescued by introduction of signaling intermediates from this pathway. Moreover, islet-specific Senp1 deletion in mice caused impaired glucose tolerance by reducing the amplification of insulin exocytosis. Together, our results identify a pathway that links glucose metabolism to the amplification of insulin secretion and demonstrate that restoration of this axis rescues β cell function in T2D.
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80
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Abstract
Glucose stimulation of insulin secretion in pancreatic β cells involves cell depolarization and subsequent opening of voltage-dependent Ca2+ channels to elicit insulin granule exocytosis. This pathway alone does not account for the entire magnitude of the secretory response in β cells. In this issue, Ferdaoussi, Dai, and colleagues reveal that insulin secretion is amplified by cytosolic isocitrate dehydrogenase-dependent transfer of reducing equivalents, which generates NADPH and reduced glutathione, which in turn activates sentrin/SUMO-specific protease-1 (SENP1). β Cell-specific deletion of Senp1 in murine models reduced the amplification of insulin exocytosis, resulting in impaired glucose tolerance. Further, their studies demonstrate that restoring intracellular NADPH or activating SENP1 improves insulin exocytosis in human β cells from donors with type 2 diabetes, suggesting a potential therapeutic target to augment insulin production.
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81
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Oláhová M, Veal EA. A peroxiredoxin, PRDX-2, is required for insulin secretion and insulin/IIS-dependent regulation of stress resistance and longevity. Aging Cell 2015; 14:558-68. [PMID: 25808059 PMCID: PMC4531070 DOI: 10.1111/acel.12321] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2014] [Indexed: 12/22/2022] Open
Abstract
Peroxiredoxins (Prx) are abundant thiol peroxidases with a conserved anti-ageing role. In contrast to most animals, the nematode worm, Caenorhabditis elegans, encodes a single cytosolic 2-Cys Prx, PRDX-2, rendering it an excellent model for examining how peroxiredoxins affect animal physiology and ageing. Our previous work revealed that, although PRDX-2 protects against the toxicity of peroxides, enigmatically, prdx-2-mutant animals are hyper-resistant to other forms of oxidative stress. Here, we have investigated the basis for this increased resistance. Mammalian FOXO and Nrf2 transcription factors directly promote the expression of a range of detoxification enzymes. We show that the FOXO orthologue, DAF-16, and the Nrf2 orthologue, SKN-1, are required for the increased stress resistance of prdx-2-mutant worms. Our data suggest that PRDX-2 is required for normal levels of insulin secretion and hence the inhibition of DAF-16 and SKN-1 by insulin/IGF-1-like signalling (IIS) under nutrient-rich conditions. Intriguingly, loss of PRDX-2 increases DAF-16 and SKN-1 activities sufficiently to increase arsenite resistance without initiating other IIS-inhibited processes. Together, these data suggest that loss of peroxiredoxin function may increase stress resistance by reducing insulin secretion, but that further changes in insulin signalling are required for the reprogramming of development and fat metabolism. In addition, we reveal that the temperature-dependent prolongevity function of PRDX-2 is required for the extended lifespan associated with several pathways, including further reductions in IIS.
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Affiliation(s)
- Monika Oláhová
- Institute for Cell and Molecular Biosciences Newcastle University Framlington Place Newcastle upon Tyne NE2 4HH UK
| | - Elizabeth A. Veal
- Institute for Cell and Molecular Biosciences Newcastle University Framlington Place Newcastle upon Tyne NE2 4HH UK
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82
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Inhibition of the malate-aspartate shuttle in mouse pancreatic islets abolishes glucagon secretion without affecting insulin secretion. Biochem J 2015; 468:49-63. [PMID: 25731850 DOI: 10.1042/bj20140697] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Altered secretion of insulin as well as glucagon has been implicated in the pathogenesis of Type 2 diabetes (T2D), but the mechanisms controlling glucagon secretion from α-cells largely remain unresolved. Therefore, we studied the regulation of glucagon secretion from αTC1-6 (αTC1 clone 6) cells and compared it with insulin release from INS-1 832/13 cells. We found that INS-1 832/13 and αTC1-6 cells respectively secreted insulin and glucagon concentration-dependently in response to glucose. In contrast, tight coupling of glycolytic and mitochondrial metabolism was observed only in INS-1 832/13 cells. Although glycolytic metabolism was similar in the two cell lines, TCA (tricarboxylic acid) cycle metabolism, respiration and ATP levels were less glucose-responsive in αTC1-6 cells. Inhibition of the malate-aspartate shuttle, using phenyl succinate (PhS), abolished glucose-provoked ATP production and hormone secretion from αTC1-6 but not INS-1 832/13 cells. Blocking the malate-aspartate shuttle increased levels of glycerol 3-phosphate only in INS-1 832/13 cells. Accordingly, relative expression of constituents in the glycerol phosphate shuttle compared with malate-aspartate shuttle was lower in αTC1-6 cells. Our data suggest that the glycerol phosphate shuttle augments the malate-aspartate shuttle in INS-1 832/13 but not αTC1-6 cells. These results were confirmed in mouse islets, where PhS abrogated secretion of glucagon but not insulin. Furthermore, expression of the rate-limiting enzyme of the glycerol phosphate shuttle was higher in sorted primary β- than in α-cells. Thus, suppressed glycerol phosphate shuttle activity in the α-cell may prevent a high rate of glycolysis and consequently glucagon secretion in response to glucose. Accordingly, pyruvate- and lactate-elicited glucagon secretion remains unaffected since their signalling is independent of mitochondrial shuttles.
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83
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Metabolomics applied to the pancreatic islet. Arch Biochem Biophys 2015; 589:120-30. [PMID: 26116790 DOI: 10.1016/j.abb.2015.06.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/19/2015] [Accepted: 06/21/2015] [Indexed: 01/18/2023]
Abstract
Metabolomics, the characterization of the set of small molecules in a biological system, is advancing research in multiple areas of islet biology. Measuring a breadth of metabolites simultaneously provides a broad perspective on metabolic changes as the islets respond dynamically to metabolic fuels, hormones, or environmental stressors. As a result, metabolomics has the potential to provide new mechanistic insights into islet physiology and pathophysiology. Here we summarize advances in our understanding of islet physiology and the etiologies of type-1 and type-2 diabetes gained from metabolomics studies.
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84
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Pancreatic β-cell identity, glucose sensing and the control of insulin secretion. Biochem J 2015; 466:203-18. [PMID: 25697093 DOI: 10.1042/bj20141384] [Citation(s) in RCA: 239] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Insulin release from pancreatic β-cells is required to maintain normal glucose homoeostasis in man and many other animals. Defective insulin secretion underlies all forms of diabetes mellitus, a disease currently reaching epidemic proportions worldwide. Although the destruction of β-cells is responsible for Type 1 diabetes (T1D), both lowered β-cell mass and loss of secretory function are implicated in Type 2 diabetes (T2D). Emerging results suggest that a functional deficiency, involving de-differentiation of the mature β-cell towards a more progenitor-like state, may be an important driver for impaired secretion in T2D. Conversely, at least in rodents, reprogramming of islet non-β to β-cells appears to occur spontaneously in models of T1D, and may occur in man. In the present paper, we summarize the biochemical properties which define the 'identity' of the mature β-cell as a glucose sensor par excellence. In particular, we discuss the importance of suppressing a group of 11 'disallowed' housekeeping genes, including Ldha and the monocarboxylate transporter Mct1 (Slc16a1), for normal nutrient sensing. We then survey the changes in the expression and/or activity of β-cell-enriched transcription factors, including FOXO1, PDX1, NKX6.1, MAFA and RFX6, as well as non-coding RNAs, which may contribute to β-cell de-differentiation and functional impairment in T2D. The relevance of these observations for the development of new approaches to treat T1D and T2D is considered.
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85
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Irles E, Ñeco P, Lluesma M, Villar-Pazos S, Santos-Silva JC, Vettorazzi JF, Alonso-Magdalena P, Carneiro EM, Boschero AC, Nadal Á, Quesada I. Enhanced glucose-induced intracellular signaling promotes insulin hypersecretion: pancreatic beta-cell functional adaptations in a model of genetic obesity and prediabetes. Mol Cell Endocrinol 2015; 404:46-55. [PMID: 25633666 DOI: 10.1016/j.mce.2015.01.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 12/13/2022]
Abstract
Obesity is associated with insulin resistance and is known to be a risk factor for type-2 diabetes. In obese individuals, pancreatic beta-cells try to compensate for the increased insulin demand in order to maintain euglycemia. Most studies have reported that this adaptation is due to morphological changes. However, the involvement of beta-cell functional adaptations in this process needs to be clarified. For this purpose, we evaluated different key steps in the glucose-stimulated insulin secretion (GSIS) in intact islets from female ob/ob obese mice and lean controls. Obese mice showed increased body weight, insulin resistance, hyperinsulinemia, glucose intolerance and fed hyperglycemia. Islets from ob/ob mice exhibited increased glucose-induced mitochondrial activity, reflected by enhanced NAD(P)H production and mitochondrial membrane potential hyperpolarization. Perforated patch-clamp examination of beta-cells within intact islets revealed several alterations in the electrical activity such as increased firing frequency and higher sensitivity to low glucose concentrations. A higher intracellular Ca(2+) mobilization in response to glucose was also found in ob/ob islets. Additionally, they displayed a change in the oscillatory pattern and Ca(2+) signals at low glucose levels. Capacitance experiments in intact islets revealed increased exocytosis in individual ob/ob beta-cells. All these up-regulated processes led to increased GSIS. In contrast, we found a lack of beta-cell Ca(2+) signal coupling, which could be a manifestation of early defects that lead to beta-cell malfunction in the progression to diabetes. These findings indicate that beta-cell functional adaptations are an important process in the compensatory response to obesity.
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Affiliation(s)
- Esperanza Irles
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Patricia Ñeco
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Mónica Lluesma
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Sabrina Villar-Pazos
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Junia Carolina Santos-Silva
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; Department of Structural and Functional Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, Brazil
| | - Jean F Vettorazzi
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; Department of Structural and Functional Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, Brazil
| | - Paloma Alonso-Magdalena
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Everardo M Carneiro
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, Brazil
| | - Antonio C Boschero
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, Brazil
| | - Ángel Nadal
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Ivan Quesada
- Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain.
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86
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Handorf AM, Sollinger HW, Alam T. Genetic Engineering of Surrogate <i>β</i> Cells for Treatment of Type 1 Diabetes Mellitus. ACTA ACUST UNITED AC 2015. [DOI: 10.4236/jdm.2015.54037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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87
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Acute nutrient regulation of the mitochondrial glutathione redox state in pancreatic β-cells. Biochem J 2014; 460:411-23. [PMID: 24678915 DOI: 10.1042/bj20131361] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The glucose stimulation of insulin secretion by pancreatic β-cells depends on increased production of metabolic coupling factors, among which changes in NADPH and ROS (reactive oxygen species) may alter the glutathione redox state (EGSH) and signal through changes in thiol oxidation. However, whether nutrients affect EGSH in β-cell subcellular compartments is unknown. Using redox-sensitive GFP2 fused to glutaredoxin 1 and its mitochondria-targeted form, we studied the acute nutrient regulation of EGSH in the cytosol/nucleus or the mitochondrial matrix of rat islet cells. These probes were mainly expressed in β-cells and reacted to low concentrations of exogenous H2O2 and menadione. Under control conditions, cytosolic/nuclear EGSH was close to -300 mV and unaffected by glucose (from 0 to 30 mM). In comparison, mitochondrial EGSH was less negative and rapidly regulated by glucose and other nutrients, ranging from -280 mV in the absence of glucose to -299 mV in 30 mM glucose. These changes were largely independent from changes in intracellular Ca(2+) concentration and in mitochondrial pH. They were unaffected by overexpression of SOD2 (superoxide dismutase 2) and mitochondria-targeted catalase, but were inversely correlated with changes in NAD(P)H autofluorescence, suggesting that they indirectly resulted from increased NADPH availability rather than from changes in ROS concentration. Interestingly, the opposite regulation of mitochondrial EGSH and NAD(P)H autofluorescence by glucose was also observed in human islets isolated from two donors. In conclusion, the present study demonstrates that glucose and other nutrients acutely reduce mitochondrial, but not cytosolic/nuclear, EGSH in pancreatic β-cells under control conditions.
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88
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Boesten DMPHJ, Elie AGIM, Drittij-Reijnders MJ, den Hartog GJM, Bast A. Effect of Nɛ-carboxymethyllysine on oxidative stress and the glutathione system in beta cells. Toxicol Rep 2014; 1:973-980. [PMID: 28962310 PMCID: PMC5598217 DOI: 10.1016/j.toxrep.2014.06.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 06/19/2014] [Accepted: 06/20/2014] [Indexed: 11/25/2022] Open
Abstract
One of the pathways involved in the pathogenesis of diabetic complications is the formation of excessive levels of advanced glycation end (AGE) products. Nɛ-carboxymethyllysine (CML) is one of the best-characterized AGEs. Because little is known about the effects of AGEs on pancreatic beta cells, we investigated the effect of CML on human pancreatic cells and determined the activity and gene expression of glutathione system components. CML at a concentration of 0.5 mM induced cell death in human pancreatic beta cells, which was accompanied by increased intracellular oxidative stress. No changes in the gene expression of the receptor for AGEs (RAGE) were found, although an increase in the level of a target cytokine of RAGE after CML exposure was observed. Additionally we found that CML lowered the levels of GSH and affected the activity and expression of other components of the glutathione system. These changes indicate that the cells are even more vulnerable for oxidative stress after exposure to CML. Since beta cells are low in antioxidant enzymes and repair for oxidized DNA, CML, but most likely also other AGEs, accelerates beta cell dysfunction and increases beta cell death during chronic hyperglycemia.
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Affiliation(s)
| | - Atlanta G I M Elie
- Department of Toxicology, Maastricht University, Maastricht, The Netherlands
| | | | | | - Aalt Bast
- Department of Toxicology, Maastricht University, Maastricht, The Netherlands
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89
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Huang M, Joseph JW. Assessment of the metabolic pathways associated with glucose-stimulated biphasic insulin secretion. Endocrinology 2014; 155:1653-66. [PMID: 24564396 DOI: 10.1210/en.2013-1805] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Biphasic glucose-stimulated insulin secretion involves a rapid first phase followed by a prolonged second phase of insulin secretion. The biochemical pathways that control these 2 phases of insulin secretion are poorly defined. In this study, we used a gas chromatography mass spectroscopy-based metabolomics approach to perform a global analysis of cellular metabolism during biphasic insulin secretion. A time course metabolomic analysis of the clonal β-cell line 832/13 cells showed that glycolytic, tricarboxylic acid, pentose phosphate pathway, and several amino acids were strongly correlated to biphasic insulin secretion. Interestingly, first-phase insulin secretion was negatively associated with L-valine, trans-4-hydroxy-L-proline, trans-3-hydroxy-L-proline, DL-3-aminoisobutyric acid, L-glutamine, sarcosine, L-lysine, and thymine and positively with L-glutamic acid, flavin adenine dinucleotide, caprylic acid, uridine 5'-monophosphate, phosphoglycerate, myristic acid, capric acid, oleic acid, linoleic acid, and palmitoleic acid. Tricarboxylic acid cycle intermediates pyruvate, α-ketoglutarate, and succinate were positively associated with second-phase insulin secretion. Other metabolites such as myo-inositol, cholesterol, DL-3-aminobutyric acid, and L-norleucine were negatively associated metabolites with the second-phase of insulin secretion. These studies provide a detailed analysis of key metabolites that are either negatively or positively associated with biphasic insulin secretion. The insights provided by these data set create a framework for planning future studies in the assessment of the metabolic regulation of biphasic insulin secretion.
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Affiliation(s)
- Mei Huang
- School of Pharmacy, University of Waterloo, Waterloo, Ontario, N2G 1C5, Canada
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90
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Du Y, Zhang H, Montano S, Hegestam J, Ekberg NR, Holmgren A, Brismar K, Ungerstedt JS. Plasma glutaredoxin activity in healthy subjects and patients with abnormal glucose levels or overt type 2 diabetes. Acta Diabetol 2014; 51:225-32. [PMID: 23836328 DOI: 10.1007/s00592-013-0498-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 06/25/2013] [Indexed: 10/26/2022]
Abstract
Oxidative stress induced by hyperglycemia is a key factor in the pathogenesis of diabetes complications. Glutaredoxin 1(Grx1) is a cytosolic redox protein that catalyzes GSH-dependent thiol redox reactions and reversible protein S-glutathionylation. In humans, Grx1 antigen has previously been detected in plasma; however, it has hitherto been unclear if plasma Grx1 is enzymatically active, which would indicate an extracellular function of the protein. Given that glucose overload damages cells through oxidative stress responses, we investigated whether postprandial hyperglycemia induces changes in extracellular Grx1 in patients with abnormal glucose tolerance and healthy subjects. Using a novel sensitive fluorescent substrate assay, we demonstrated that plasma Grx consists of active protein. Grx antigen, activity and total antioxidant capacity were significantly elevated in patients compared to healthy subjects. In response to oral glucose tolerance test, Grx activity and antioxidant capacity increased significantly in healthy volunteers, however, not to the high levels of the patients. In conclusion, these results indicate an extracellular function of plasma Grx in blood glucose metabolism. Thus, Grx may be a marker of increased oxidative stress during hyperglycemia in healthy subjects and may be a risk marker of progression toward diabetes onset.
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Affiliation(s)
- Yatao Du
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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91
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Patterson JN, Cousteils K, Lou JW, Manning Fox JE, MacDonald PE, Joseph JW. Mitochondrial metabolism of pyruvate is essential for regulating glucose-stimulated insulin secretion. J Biol Chem 2014; 289:13335-46. [PMID: 24675076 DOI: 10.1074/jbc.m113.521666] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
It is well known that mitochondrial metabolism of pyruvate is critical for insulin secretion; however, we know little about how pyruvate is transported into mitochondria in β-cells. Part of the reason for this lack of knowledge is that the carrier gene was only discovered in 2012. In the current study, we assess the role of the recently identified carrier in the regulation of insulin secretion. Our studies show that β-cells express both mitochondrial pyruvate carriers (Mpc1 and Mpc2). Using both pharmacological inhibitors and siRNA-mediated knockdown of the MPCs we show that this carrier plays a key role in regulating insulin secretion in clonal 832/13 β-cells as well as rat and human islets. We also show that the MPC is an essential regulator of both the ATP-regulated potassium (KATP) channel-dependent and -independent pathways of insulin secretion. Inhibition of the MPC blocks the glucose-stimulated increase in two key signaling molecules involved in regulating insulin secretion, the ATP/ADP ratio and NADPH/NADP(+) ratio. The MPC also plays a role in in vivo glucose homeostasis as inhibition of MPC by the pharmacological inhibitor α-cyano-β-(1-phenylindol-3-yl)-acrylate (UK5099) resulted in impaired glucose tolerance. These studies clearly show that the newly identified mitochondrial pyruvate carrier sits at an important branching point in nutrient metabolism and that it is an essential regulator of insulin secretion.
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Affiliation(s)
- Jessica N Patterson
- From the School of Pharmacy, University of Waterloo, Waterloo, 10A Victoria Street South, Ontario N2G 1C5, Canada and
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92
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Ding X, Yu Q, Zhang B, Xu N, Jia C, Dong Y, Chen Y, Xing L, Li M. The type II Ca2+/calmodulin-dependent protein kinases are involved in the regulation of cell wall integrity and oxidative stress response in Candida albicans. Biochem Biophys Res Commun 2014; 446:1073-8. [PMID: 24661877 DOI: 10.1016/j.bbrc.2014.03.059] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 03/15/2014] [Indexed: 11/24/2022]
Abstract
The type II Ca(2+)/calmodulin-dependent protein kinases (CaMKs) are thought to play a vital role in cellular regulation in mammalian cells. Two genes CMK1 and CMK2 in the Candida albicans genome encode homologues of mammalian CaMKs. In this work, we constructed the cmk1Δ/Δ, the cmk2Δ/Δ and the cmk1Δ/Δcmk2Δ/Δ mutants and found that CaMKs function in cell wall integrity (CWI) and cellular redox regulation. Loss of either CMK1 or CMK2, or both resulted in increased expression of CWI-related genes under Calcofluor white (CFW) treatment. Besides, CaMKs are essential for the maintenance of cellular redox balance. Disruption of either CMK1 or CMK2, or both not only led to a significant increase of intracellular ROS levels, but also led to a decrease of the mitochondrial membrane potential (MMP), suggesting the important roles that CaMKs play in the maintenance of the mitochondrial function.
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Affiliation(s)
- Xiaohui Ding
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Qilin Yu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Bing Zhang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Ning Xu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Chang Jia
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Yijie Dong
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Yulu Chen
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Laijun Xing
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin, PR China
| | - Mingchun Li
- Department of Microbiology, College of Life Science, Nankai University, Tianjin 300071, PR China..
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93
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Nordgren M, Fransen M. Peroxisomal metabolism and oxidative stress. Biochimie 2014; 98:56-62. [DOI: 10.1016/j.biochi.2013.07.026] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 07/25/2013] [Indexed: 12/25/2022]
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94
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Hanschmann EM, Godoy JR, Berndt C, Hudemann C, Lillig CH. Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling. Antioxid Redox Signal 2013; 19:1539-605. [PMID: 23397885 PMCID: PMC3797455 DOI: 10.1089/ars.2012.4599] [Citation(s) in RCA: 489] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 02/01/2013] [Accepted: 02/07/2013] [Indexed: 12/19/2022]
Abstract
Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.
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Affiliation(s)
- Eva-Maria Hanschmann
- Institute for Medical Biochemistry and Molecular Biology, University Medicine, Ernst-Moritz Arndt University, Greifswald, Germany
| | - José Rodrigo Godoy
- Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine, Vienna, Austria
| | - Carsten Berndt
- Department of Neurology, Medical Faculty, Heinrich-Heine University, Duesseldorf, Germany
| | - Christoph Hudemann
- Institute of Laboratory Medicine, Molecular Diagnostics, Philipps University, Marburg, Germany
| | - Christopher Horst Lillig
- Institute for Medical Biochemistry and Molecular Biology, University Medicine, Ernst-Moritz Arndt University, Greifswald, Germany
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95
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Maechler P. Mitochondrial function and insulin secretion. Mol Cell Endocrinol 2013; 379:12-8. [PMID: 23792187 DOI: 10.1016/j.mce.2013.06.019] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 06/12/2013] [Accepted: 06/12/2013] [Indexed: 10/26/2022]
Abstract
In the endocrine fraction of the pancreas, the β-cell rapidly reacts to fluctuations in blood glucose concentrations by adjusting the rate of insulin secretion. Glucose-sensing coupled to insulin exocytosis depends on transduction of metabolic signals into intracellular messengers recognized by the secretory machinery. Mitochondria play a central role in this process by connecting glucose metabolism to insulin release. Mitochondrial activity is primarily regulated by metabolic fluxes, but also by dynamic morphology changes and free Ca(2+) concentrations. Recent advances of mitochondrial Ca(2+) homeostasis are discussed; in particular the roles of the newly-identified mitochondrial Ca(2+) uniporter MCU and its regulatory partner MICU1, as well as the mitochondrial Na(+)-Ca(2+) exchanger. This review describes how mitochondria function both as sensors and generators of metabolic signals; such as NADPH, long chain acyl-CoA, glutamate. The coupling factors are additive to the Ca(2+) signal and participate to the amplifying pathway of glucose-stimulated insulin secretion.
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Affiliation(s)
- Pierre Maechler
- Department of Cell Physiology and Metabolism, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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96
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Guay C, Joly É, Pepin É, Barbeau A, Hentsch L, Pineda M, Madiraju SRM, Brunengraber H, Prentki M. A role for cytosolic isocitrate dehydrogenase as a negative regulator of glucose signaling for insulin secretion in pancreatic ß-cells. PLoS One 2013; 8:e77097. [PMID: 24130841 PMCID: PMC3795013 DOI: 10.1371/journal.pone.0077097] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 08/30/2013] [Indexed: 01/24/2023] Open
Abstract
Cytosolic NADPH may act as one of the signals that couple glucose metabolism to insulin secretion in the pancreatic ß-cell. NADPH levels in the cytoplasm are largely controlled by the cytosolic isoforms of malic enzyme and isocitrate dehydrogenase (IDHc). Some studies have provided evidence for a role of malic enzyme in glucose-induced insulin secretion (GIIS) via pyruvate cycling, but the role of IDHc in ß-cell signaling is unsettled. IDHc is an established component of the isocitrate/α-ketoglutarate shuttle that transfers reducing equivalents (NADPH) from the mitochondrion to the cytosol. This shuttle is energy consuming since it is coupled to nicotinamide nucleotide transhydrogenase that uses the mitochondrial proton gradient to produce mitochondrial NADPH and NAD(+) from NADP(+) and NADH. To determine whether flux through IDHc is positively or negatively linked to GIIS, we performed RNAi knockdown experiments in ß-cells. Reduced IDHc expression in INS 832/13 cells and isolated rat islet ß-cells resulted in enhanced GIIS. This effect was mediated at least in part via the KATP-independent amplification arm of GIIS. IDHc knockdown in INS 832/13 cells did not alter glucose oxidation but it reduced fatty acid oxidation and increased lipogenesis from glucose. Metabolome profiling in INS 832/13 cells showed that IDHc knockdown increased isocitrate and NADP(+) levels. It also increased the cellular contents of several metabolites linked to GIIS, in particular some Krebs cycle intermediates, acetyl-CoA, glutamate, cAMP and ATP. The results identify IDHc as a component of the emerging pathways that negatively regulate GIIS.
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Affiliation(s)
- Claudiane Guay
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - Érik Joly
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - Émilie Pepin
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - Annie Barbeau
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - Lisa Hentsch
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - Marco Pineda
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - S. R. Murthy Madiraju
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
| | - Henri Brunengraber
- Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United State of America
| | - Marc Prentki
- Molecular Nutrition Unit and the Montreal Diabetes Research Center at the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, CR-CHUM, Montreal, Quebec, Canada
- Departments of Nutrition and Biochemistry, University of Montreal, Montreal, Quebec, Canada
- * E-mail:
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97
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Panten U, Willenborg M, Schumacher K, Hamada A, Ghaly H, Rustenbeck I. Acute metabolic amplification of insulin secretion in mouse islets is mediated by mitochondrial export of metabolites, but not by mitochondrial energy generation. Metabolism 2013; 62:1375-86. [PMID: 23790612 DOI: 10.1016/j.metabol.2013.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 04/22/2013] [Accepted: 05/08/2013] [Indexed: 12/26/2022]
Abstract
OBJECTIVE The β-cell metabolism of glucose and of some other fuels (e.g. α-ketoisocaproate) generates signals triggering and acutely amplifying insulin secretion. As the pathway coupling metabolism with amplification is largely unknown, we aimed to narrow down the putative amplifying signals. MATERIALS/METHODS An experimental design was used which previously prevented glucose-induced, but not α-ketoisocaproate-induced insulin secretion. Isolated mouse islets were pretreated for one hour with medium devoid of fuels and containing the sulfonylurea glipizide in high concentration which closed all ATP-sensitive K(+) channels. This concentration was also applied during the subsequent examination of fuel-induced effects. In perifused or incubated islets, insulin secretion and metabolic parameters were measured. RESULTS The pretreatment decreased the islet ATP/ADP ratio. Whereas glucose and α-ketoisovalerate were ineffective or weakly effective, respectively, when tested separately, their combination strongly enhanced the insulin secretion. Compared with glucose, the strong amplifier α-ketoisocaproate caused less increase in NAD(P)H-fluorescence and less mitochondrial hyperpolarization. Compared with α-ketoisovalerate, α-ketoisocaproate caused greater increase in NAD(P)H-fluorescence and greater mitochondrial hyperpolarization. Neither α-ketoacid anion enhanced the islet ATP/ADP ratio during onset of the insulin secretion. α-Ketoisocaproate induced a higher pyruvate content than glucose, slowly elevated the citrate content which was not changed by glucose and generated a much higher acetoacetate content than other fuels. α-Ketoisovalerate alone or in combination with glucose did not increase the citrate content. CONCLUSIONS In β-cells, mitochondrial energy generation does not mediate acute metabolic amplification, but mitochondrial production of acetyl-CoA and supplemental acetoacetate supplies cytosolic metabolites which induce the generation of specific amplifying signals.
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Affiliation(s)
- Uwe Panten
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technical University of Braunschweig, Mendelssohnstrasse 1, D-38106 Braunschweig, Germany.
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98
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Gonzalez A, Merino B, Marroquí L, Ñeco P, Alonso-Magdalena P, Caballero-Garrido E, Vieira E, Soriano S, Gomis R, Nadal A, Quesada I. Insulin hypersecretion in islets from diet-induced hyperinsulinemic obese female mice is associated with several functional adaptations in individual β-cells. Endocrinology 2013; 154:3515-24. [PMID: 23867214 DOI: 10.1210/en.2013-1424] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Insulin resistance and hyperinsulinemia are generally associated with obesity. Obese nondiabetic individuals develop a compensatory β-cell response to adjust insulin levels to the increased demand, maintaining euglycemia. Although several studies indicate that this compensation relies on structural changes, the existence of β-cell functional adaptations is incompletely understood. Here, we fed female mice with a high-fat diet (HFD) for 12 weeks. These animals became obese, hyperinsulinemic, insulin-resistant, and mildly glucose-intolerant while fed, and fasting glycemia was comparable in HFD and control mice. Islets from HFD animals exhibited increased β-cell mass and hypertrophy. Additionally, they had enhanced insulin gene expression and content and augmented glucose-induced insulin secretion. Electrophysiological examination of β-cells from both groups showed no differences in KATP channel open probability and conductance. However, action potentials elicited by glucose had larger amplitude in obese mice. Glucose-induced Ca²⁺ signals in intact islets, in isolated β-cells, and individual β-cells within islets were also increased in HFD mice. Additionally, a higher proportion of glucose-responsive cells was present in obese mice. In contrast, whole-cell Ca²⁺ current densities were similar in both groups. Capacitance measurements showed that depolarization-evoked exocytosis was enhanced in HFD β-cells compared with controls. Although this augment was not significant when capacitance increases of the whole β-cell population were normalized to cell size, the exocytotic output varied significantly when β-cells were distributed by size ranges. All these findings indicate that β-cell functional adaptations are present in the islet compensatory response to obesity.
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Affiliation(s)
- Alejandro Gonzalez
- Universidad Miguel Hernández, Avenida de la Universidad s/n, 03202 Elche, Spain.
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99
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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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100
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Jensen MV, Haldeman JM, Zhang H, Lu D, Huising MO, Vale WW, Hohmeier HE, Rosenberg P, Newgard CB. Control of voltage-gated potassium channel Kv2.2 expression by pyruvate-isocitrate cycling regulates glucose-stimulated insulin secretion. J Biol Chem 2013; 288:23128-40. [PMID: 23788641 DOI: 10.1074/jbc.m113.491654] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Recent studies have shown that the pyruvate-isocitrate cycling pathway, involving the mitochondrial citrate/isocitrate carrier and the cytosolic NADP-dependent isocitrate dehydrogenase (ICDc), is involved in control of glucose-stimulated insulin secretion (GSIS). Here we demonstrate that pyruvate-isocitrate cycling regulates expression of the voltage-gated potassium channel family member Kv2.2 in islet β-cells. siRNA-mediated suppression of ICDc, citrate/isocitrate carrier, or Kv2.2 expression impaired GSIS, and the effect of ICDc knockdown was rescued by re-expression of Kv2.2. Moreover, chronic exposure of β-cells to elevated fatty acids, which impairs GSIS, resulted in decreased expression of Kv2.2. Surprisingly, knockdown of ICDc or Kv2.2 increased rather than decreased outward K(+) current in the 832/13 β-cell line. Immunoprecipitation studies demonstrated interaction of Kv2.1 and Kv2.2, and co-overexpression of the two channels reduced outward K(+) current compared with overexpression of Kv2.1 alone. Also, siRNA-mediated knockdown of ICDc enhanced the suppressive effect of the Kv2.1-selective inhibitor stromatoxin1 on K(+) currents. Our data support a model in which a key function of the pyruvate-isocitrate cycle is to maintain levels of Kv2.2 expression sufficient to allow it to serve as a negative regulator of Kv channel activity.
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Affiliation(s)
- Mette V Jensen
- Duke Institute of Molecular Physiology, Duke University Medical Center, Durham, North Carolina 27704, USA
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