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Marhl M. What do stimulated beta cells have in common with cancer cells? Biosystems 2024; 242:105257. [PMID: 38876357 DOI: 10.1016/j.biosystems.2024.105257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 06/11/2024] [Accepted: 06/11/2024] [Indexed: 06/16/2024]
Abstract
This study investigates the metabolic parallels between stimulated pancreatic beta cells and cancer cells, focusing on glucose and glutamine metabolism. Addressing the significant public health challenges of Type 2 Diabetes (T2D) and cancer, we aim to deepen our understanding of the mechanisms driving insulin secretion and cellular proliferation. Our analysis of anaplerotic cycles and the role of NADPH in biosynthesis elucidates their vital functions in both processes. Additionally, we point out that both cell types share an antioxidative response mediated by the Nrf2 signaling pathway, glutathione synthesis, and UCP2 upregulation. Notably, UCP2 facilitates the transfer of C4 metabolites, enhancing reductive TCA cycle metabolism. Furthermore, we observe that hypoxic responses are transient in beta cells post-stimulation but persistent in cancer cells. By synthesizing these insights, the research may suggest novel therapeutic targets for T2D, highlighting the shared metabolic strategies of stimulated beta cells and cancer cells. This comparative analysis not only illuminates the metabolic complexity of these conditions but also emphasizes the crucial role of metabolic pathways in cell function and survival, offering fresh perspectives for tackling T2D and cancer challenges.
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Affiliation(s)
- Marko Marhl
- Faculty of Medicine, University of Maribor, Taborska ulica 8, 2000, Maribor, Slovenia; Faculty of Education, University of Maribor, Koroška cesta 160, 2000, Maribor, Slovenia; Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, 2000, Maribor, Slovenia.
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2
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Luby A, Alves-Guerra MC. UCP2 as a Cancer Target through Energy Metabolism and Oxidative Stress Control. Int J Mol Sci 2022; 23:ijms232315077. [PMID: 36499405 PMCID: PMC9735768 DOI: 10.3390/ijms232315077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 11/25/2022] [Accepted: 11/27/2022] [Indexed: 12/02/2022] Open
Abstract
Despite numerous therapies, cancer remains one of the leading causes of death worldwide due to the lack of markers for early detection and response to treatment in many patients. Technological advances in tumor screening and renewed interest in energy metabolism have allowed us to identify new cellular players in order to develop personalized treatments. Among the metabolic actors, the mitochondrial transporter uncoupling protein 2 (UCP2), whose expression is increased in many cancers, has been identified as an interesting target in tumor metabolic reprogramming. Over the past decade, a better understanding of its biochemical and physiological functions has established a role for UCP2 in (1) protecting cells from oxidative stress, (2) regulating tumor progression through changes in glycolytic, oxidative and calcium metabolism, and (3) increasing antitumor immunity in the tumor microenvironment to limit cancer development. With these pleiotropic roles, UCP2 can be considered as a potential tumor biomarker that may be interesting to target positively or negatively, depending on the type, metabolic status and stage of tumors, in combination with conventional chemotherapy or immunotherapy to control tumor development and increase response to treatment. This review provides an overview of the latest published science linking mitochondrial UCP2 activity to the tumor context.
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Inoue R, Tsuno T, Togashi Y, Okuyama T, Sato A, Nishiyama K, Kyohara M, Li J, Fukushima S, Kin T, Miyashita D, Shiba Y, Atobe Y, Kiyonari H, Bando K, Shapiro AJ, Funakoshi K, Kulkarni RN, Terauchi Y, Shirakawa J. Uncoupling protein 2 and aldolase B impact insulin release by modulating mitochondrial function and Ca 2+ release from the ER. iScience 2022; 25:104603. [PMID: 35800776 PMCID: PMC9253497 DOI: 10.1016/j.isci.2022.104603] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 03/25/2022] [Accepted: 06/08/2022] [Indexed: 02/02/2023] Open
Abstract
Uncoupling protein 2 (UCP2), a mitochondrial protein, is known to be upregulated in pancreatic islets of patients with type 2 diabetes (T2DM); however, the pathological significance of this increase in UCP2 expression is unclear. In this study, we highlight the molecular link between the increase in UCP2 expression in β-cells and β-cell failure by using genetically engineered mice and human islets. β-cell-specific UCP2-overexpressing transgenic mice (βUCP2Tg) exhibited glucose intolerance and a reduction in insulin secretion. Decreased mitochondrial function and increased aldolase B (AldB) expression through oxidative-stress-mediated pathway were observed in βUCP2Tg islets. AldB, a glycolytic enzyme, was associated with reduced insulin secretion via mitochondrial dysfunction and impaired calcium release from the endoplasmic reticulum (ER). Taken together, our findings provide a new mechanism of β-cell dysfunction by UCP2 and AldB. Targeting the UCP2/AldB axis is a promising approach for the recovery of β-cell function.
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Affiliation(s)
- Ryota Inoue
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Takahiro Tsuno
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yu Togashi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Tomoko Okuyama
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Aoi Sato
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
| | - Kuniyuki Nishiyama
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Mayu Kyohara
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Jinghe Li
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Setsuko Fukushima
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
| | - Tatsuya Kin
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, AB T6G2C8, Canada
| | - Daisuke Miyashita
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yusuke Shiba
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yoshitoshi Atobe
- Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama 236-0004, Japan
| | - Hiroshi Kiyonari
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - Kana Bando
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - A.M. James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, AB T6G2C8, Canada
| | - Kengo Funakoshi
- Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama 236-0004, Japan
| | - Rohit N. Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Yasuo Terauchi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Jun Shirakawa
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
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Pancreatic Islets Exhibit Dysregulated Adaptation of Insulin Secretion after Chronic Epinephrine Exposure. Curr Issues Mol Biol 2021; 43:240-250. [PMID: 34071501 PMCID: PMC8929152 DOI: 10.3390/cimb43010020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 01/11/2023] Open
Abstract
Chronic adrenergic stimulation is the dominant factor in impairment of the β-cell function. Sustained adrenergic exposure generates dysregulated insulin secretion in fetal sheep. Similar results have been shown in Min6 under the elevated epinephrine condition, but impairments after adrenergic removal are still unknown and a high rate of proliferation in Min6 has been ignored. Therefore, we incubated primary rats' islets with half maximal inhibitory concentrations of epinephrine for three days, then determined their insulin secretion responsiveness and related signals two days after removal of adrenaline via radioimmunoassay and qPCR. Insulin secretion was not different between the exposure group (1.07 ± 0.04 ng/islet/h) and control (1.23 ± 0.17 ng/islet/h), but total islet insulin content after treatment (5.46 ± 0.87 ng/islet/h) was higher than control (3.17 ± 0.22 ng/islet/h, p < 0.05), and the fractional insulin release was 36% (p < 0.05) lower after the treatment. Meanwhile, the mRNA expression of Gαs, Gαz and Gβ1-2 decreased by 42.8% 19.4% and 24.8%, respectively (p < 0.05). Uncoupling protein 2 (Ucp2), sulphonylurea receptor 1 (Sur1) and superoxide dismutase 2 (Sod2) were significantly reduced (38.5%, 23.8% and 53.8%, p < 0.05). Chronic adrenergic exposure could impair insulin responsiveness in primary pancreatic islets. Decreased G proteins and Sur1 expression affect the regulation of insulin secretion. In conclusion, the sustained under-expression of Ucp2 and Sod2 may further change the function of β-cell, which helps to understand the long-term adrenergic adaptation of pancreatic β-cell.
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Jia X, Luo Z, Gao Y, Liu H, Liu X, Mai W, Liu H, Zheng Q. EGCG Upregulates UCP 3 Levels to Protect MIN 6 Pancreatic Islet Cells from Interleukin-1β-Induced Apoptosis. DRUG DESIGN DEVELOPMENT AND THERAPY 2020; 14:4251-4261. [PMID: 33116413 PMCID: PMC7568641 DOI: 10.2147/dddt.s270345] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 09/06/2020] [Indexed: 11/28/2022]
Abstract
Objective The protective effects of epigallocatechin gallate (EGCG) on interleukin-1β (IL-1β)-induced apoptosis were investigated in murine MIN6 pancreatic β-cells. The role of uncoupling protein-3 (UCP3) signaling in this process was also explored. Methods After treatment with IL-1β and EGCG, cells were collected and analyzed. Cell viability was measured using the CCK8 assay and the function of β-cells was evaluated by analyzing insulin secretion. Detection of mitochondrial function in cells was performed by measuring mitochondrial membrane potential, the concentration of ATP and activity of ROS. Apoptosis was analyzed by Hochest33258 staining and flow cytometry. Expression levels of UCP3 were interrogated using immunohistochemistry, RT-PCR and Western blotting. Results Compared with the control group, IL-1β treatment (20nM) for 24 h significantly decreased cell viability and insulin secretion, damaged mitochondrial function and increased ROS activity. Results also showed increased apoptosis and a decrease in UCP3 expression levels (p<0.01). However, treatment with low (1mM) or high (5mM) concentrations of EGCG significantly decreased IL-1β-induced apoptosis (p<0.01), restored mitochondrial function and subsequently increased UCP3 levels in IL-1β-induced β-cells (p<0.01). Conclusion These results suggest that EGCG protects against IL-1β-induced mitochondrial injury and apoptosis in β-cells through the up-regulation of UCP3.
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Affiliation(s)
- Xu Jia
- Department of Pharmacy, Affiliated Hospital of North Sichuan Medical College, Nanchong 637000, People's Republic of China
| | - Ziren Luo
- School of Pharmacy, North Sichuan Medical College, Nanchong 637000, People's Republic of China
| | - Ying Gao
- Department of Physiology, North Sichuan Medical College, Nanchong 637007, People's Republic of China
| | - Hua Liu
- Department of Physiology, North Sichuan Medical College, Nanchong 637007, People's Republic of China
| | - Xinghai Liu
- Department of Physiology, North Sichuan Medical College, Nanchong 637007, People's Republic of China
| | - Wenli Mai
- Department of Physiology, North Sichuan Medical College, Nanchong 637007, People's Republic of China
| | - Hong Liu
- Department of Physiology, North Sichuan Medical College, Nanchong 637007, People's Republic of China
| | - Qian Zheng
- Department of Physiology, North Sichuan Medical College, Nanchong 637007, People's Republic of China
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Prentki M, Peyot ML, Masiello P, Madiraju SRM. Nutrient-Induced Metabolic Stress, Adaptation, Detoxification, and Toxicity in the Pancreatic β-Cell. Diabetes 2020; 69:279-290. [PMID: 32079704 DOI: 10.2337/dbi19-0014] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 12/20/2019] [Indexed: 11/13/2022]
Abstract
Paraphrasing the Swiss physician and father of toxicology Paracelsus (1493-1541) on chemical agents used as therapeutics, "the dose makes the poison," it is now realized that this aptly applies to the calorigenic nutrients. The case here is the pancreatic islet β-cell presented with excessive levels of nutrients such as glucose, lipids, and amino acids. The short-term effects these nutrients exert on the β-cell are enhanced insulin biosynthesis and secretion and changes in glucose sensitivity. However, chronic fuel surfeit triggers additional compensatory and adaptive mechanisms by β-cells to cope with the increased insulin demand or to protect itself. When these mechanisms fail, toxicity due to the nutrient surplus ensues, leading to β-cell dysfunction, dedifferentiation, and apoptosis. The terms glucotoxicity, lipotoxicity, and glucolipotoxicity have been widely used, but there is some confusion as to what they mean precisely and which is most appropriate for a given situation. Here we address the gluco-, lipo-, and glucolipo-toxicities in β-cells by assessing the evidence both for and against each of them. We also discuss potential mechanisms and defend the view that many of the identified "toxic" effects of nutrient excess, which may also include amino acids, are in fact beneficial adaptive processes. In addition, candidate fuel-excess detoxification pathways are evaluated. Finally, we propose that a more general term should be used for the in vivo situation of overweight-associated type 2 diabetes reflecting both the adaptive and toxic processes to mixed calorigenic nutrients excess: "nutrient-induced metabolic stress" or, in brief, "nutri-stress."
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Affiliation(s)
- Marc Prentki
- Departments of Nutrition and Biochemistry and Molecular Medicine, University of Montreal, and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Quebec, Canada
| | - Marie-Line Peyot
- Departments of Nutrition and Biochemistry and Molecular Medicine, University of Montreal, and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Quebec, Canada
| | - Pellegrino Masiello
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - S R Murthy Madiraju
- Departments of Nutrition and Biochemistry and Molecular Medicine, University of Montreal, and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Quebec, Canada
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Ježek P, Holendová B, Garlid KD, Jabůrek M. Mitochondrial Uncoupling Proteins: Subtle Regulators of Cellular Redox Signaling. Antioxid Redox Signal 2018; 29:667-714. [PMID: 29351723 PMCID: PMC6071544 DOI: 10.1089/ars.2017.7225] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
SIGNIFICANCE Mitochondria are the energetic, metabolic, redox, and information signaling centers of the cell. Substrate pressure, mitochondrial network dynamics, and cristae morphology state are integrated by the protonmotive force Δp or its potential component, ΔΨ, which are attenuated by proton backflux into the matrix, termed uncoupling. The mitochondrial uncoupling proteins (UCP1-5) play an eminent role in the regulation of each of the mentioned aspects, being involved in numerous physiological events including redox signaling. Recent Advances: UCP2 structure, including purine nucleotide and fatty acid (FA) binding sites, strongly support the FA cycling mechanism: UCP2 expels FA anions, whereas uncoupling is achieved by the membrane backflux of protonated FA. Nascent FAs, cleaved by phospholipases, are preferential. The resulting Δp dissipation decreases superoxide formation dependent on Δp. UCP-mediated antioxidant protection and its impairment are expected to play a major role in cell physiology and pathology. Moreover, UCP2-mediated aspartate, oxaloacetate, and malate antiport with phosphate is expected to alter metabolism of cancer cells. CRITICAL ISSUES A wide range of UCP antioxidant effects and participations in redox signaling have been reported; however, mechanisms of UCP activation are still debated. Switching off/on the UCP2 protonophoretic function might serve as redox signaling either by employing/releasing the extra capacity of cell antioxidant systems or by directly increasing/decreasing mitochondrial superoxide sources. Rapid UCP2 degradation, FA levels, elevation of purine nucleotides, decreased Mg2+, or increased pyruvate accumulation may initiate UCP-mediated redox signaling. FUTURE DIRECTIONS Issues such as UCP2 participation in glucose sensing, neuronal (synaptic) function, and immune cell activation should be elucidated. Antioxid. Redox Signal. 29, 667-714.
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Affiliation(s)
- Petr Ježek
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
| | - Blanka Holendová
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
| | - Keith D Garlid
- 2 UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA , Los Angeles, California
| | - Martin Jabůrek
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
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Besseiche A, Riveline JP, Delavallée L, Foufelle F, Gautier JF, Blondeau B. Oxidative and energetic stresses mediate beta-cell dysfunction induced by PGC-1α. DIABETES & METABOLISM 2018; 44:45-54. [DOI: 10.1016/j.diabet.2017.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/18/2017] [Accepted: 01/29/2017] [Indexed: 12/15/2022]
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Upregulation of UCP2 in beta-cells confers partial protection against both oxidative stress and glucotoxicity. Redox Biol 2017; 13:541-549. [PMID: 28755631 PMCID: PMC5537434 DOI: 10.1016/j.redox.2017.07.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 07/19/2017] [Accepted: 07/20/2017] [Indexed: 01/09/2023] Open
Abstract
Deterioration of pancreatic beta-cells plays a critical role in the development of type 2 diabetes. Among the various stressors contributing to these deleterious effects, glucotoxicity and superoxides have been proposed as major players. In this context, the mitochondrial uncoupling protein UCP2 is regularly associated with the stress response. In the present study, we tested the effects of UCP2 upregulation in mouse islets with beta-cell specific overexpression of UCP2 (RIP-UCP2). Islets were subjected to both chronic glucotoxicity (7 days at 30 mM glucose) and acute oxidative stress (200 µM H2O2 for 10 min). Increased UCP2 expression did not alter mitochondrial potential and ATP generation but protected against glucotoxic effects. Glucose-stimulated insulin secretion was altered by both glucotoxicity and oxidative stress, in particular through higher basal insulin release at non-stimulatory glucose concentrations. The secretory response to glucose stimulation was partially preserved in beta-cells overexpressing UCP2. The higher rate of cell death induced by chronic high glucose exposure was lower in RIP-UCP2 islets. Finally, superoxide production was reduced by high glucose, both under acute and chronic conditions, and not modified by UCP2 overexpression. In conclusion, upregulation of UCP2 conferred protective effects to the stressed beta-cell through mechanisms not directly associated with superoxide production. UCP2 upregulation protects pancreatic ß-cells against glucotoxicity. High glucose reduces superoxide production in pancreatic islets. UCP2 upregulation does not change superoxide production. UCP2 upregulation protects ß-cells against oxidative stress.
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Gerber PA, Rutter GA. The Role of Oxidative Stress and Hypoxia in Pancreatic Beta-Cell Dysfunction in Diabetes Mellitus. Antioxid Redox Signal 2017; 26:501-518. [PMID: 27225690 PMCID: PMC5372767 DOI: 10.1089/ars.2016.6755] [Citation(s) in RCA: 385] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 05/25/2016] [Indexed: 12/16/2022]
Abstract
SIGNIFICANCE Metabolic syndrome is a frequent precursor of type 2 diabetes mellitus (T2D), a disease that currently affects ∼8% of the adult population worldwide. Pancreatic beta-cell dysfunction and loss are central to the disease process, although understanding of the underlying molecular mechanisms is still fragmentary. Recent Advances: Oversupply of nutrients, including glucose and fatty acids, and the subsequent overstimulation of beta cells, are believed to be an important contributor to insulin secretory failure in T2D. Hypoxia has also recently been implicated in beta-cell damage. Accumulating evidence points to a role for oxidative stress in both processes. Although the production of reactive oxygen species (ROS) results from enhanced mitochondrial respiration during stimulation with glucose and other fuels, the expression of antioxidant defense genes is unusually low (or disallowed) in beta cells. CRITICAL ISSUES Not all subjects with metabolic syndrome and hyperglycemia go on to develop full-blown diabetes, implying an important role in disease risk for gene-environment interactions. Possession of common risk alleles at the SLC30A8 locus, encoding the beta-cell granule zinc transporter ZnT8, may affect cytosolic Zn2+ concentrations and thus susceptibility to hypoxia and oxidative stress. FUTURE DIRECTIONS Loss of normal beta-cell function, rather than total mass, is increasingly considered to be the major driver for impaired insulin secretion in diabetes. Better understanding of the role of oxidative changes, its modulation by genes involved in disease risk, and effects on beta-cell identity may facilitate the development of new therapeutic strategies to this disease. Antioxid. Redox Signal. 26, 501-518.
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Affiliation(s)
- Philipp A. Gerber
- Department of Endocrinology, Diabetes and Clinical Nutrition, University Hospital Zurich, Zurich, Switzerland
| | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, United Kingdom
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UCP2 Expression Is Increased in Pancreas From Brain-Dead Donors and Involved in Cytokine-Induced β Cells Apoptosis. Transplantation 2017; 101:e59-e67. [DOI: 10.1097/tp.0000000000001292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Ježek J, Dlasková A, Zelenka J, Jabůrek M, Ježek P. H₂O₂-Activated Mitochondrial Phospholipase iPLA₂γ Prevents Lipotoxic Oxidative Stress in Synergy with UCP2, Amplifies Signaling via G-Protein-Coupled Receptor GPR40, and Regulates Insulin Secretion in Pancreatic β-Cells. Antioxid Redox Signal 2015; 23:958-72. [PMID: 25925080 PMCID: PMC4623989 DOI: 10.1089/ars.2014.6195] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
AIMS Pancreatic β-cell chronic lipotoxicity evolves from acute free fatty acid (FA)-mediated oxidative stress, unprotected by antioxidant mechanisms. Since mitochondrial uncoupling protein-2 (UCP2) plays antioxidant and insulin-regulating roles in pancreatic β-cells, we tested our hypothesis, that UCP2-mediated uncoupling attenuating mitochondrial superoxide production is initiated by FA release due to a direct H2O2-induced activation of mitochondrial phospholipase iPLA2γ. RESULTS Pro-oxidant tert-butylhydroperoxide increased respiration, decreased membrane potential and mitochondrial matrix superoxide release rates of control but not UCP2- or iPLA2γ-silenced INS-1E cells. iPLA2γ/UCP2-mediated uncoupling was alternatively activated by an H2O2 burst, resulting from palmitic acid (PA) β-oxidation, and it was prevented by antioxidants or catalase overexpression. Exclusively, nascent FAs that cleaved off phospholipids by iPLA2γ were capable of activating UCP2, indicating that the previously reported direct redox UCP2 activation is actually indirect. Glucose-stimulated insulin release was not affected by UCP2 or iPLA2γ silencing, unless pro-oxidant activation had taken place. PA augmented insulin secretion via G-protein-coupled receptor 40 (GPR40), stimulated by iPLA2γ-cleaved FAs (absent after GPR40 silencing). INNOVATION AND CONCLUSION The iPLA2γ/UCP2 synergy provides a feedback antioxidant mechanism preventing oxidative stress by physiological FA intake in pancreatic β-cells, regulating glucose-, FA-, and redox-stimulated insulin secretion. iPLA2γ is regulated by exogenous FA via β-oxidation causing H2O2 signaling, while FAs are cleaved off phospholipids, subsequently acting as amplifying messengers for GPR40. Hence, iPLA2γ acts in eminent physiological redox signaling, the impairment of which results in the lack of antilipotoxic defense and contributes to chronic lipotoxicity.
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Affiliation(s)
- Jan Ježek
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Jaroslav Zelenka
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Petr Ježek
- Department of Membrane Transport Biophysics, Institute of Physiology , Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Babu D, Leclercq G, Goossens V, Vanden Berghe T, Van Hamme E, Vandenabeele P, Lefebvre RA. Mitochondria and NADPH oxidases are the major sources of TNF-α/cycloheximide-induced oxidative stress in murine intestinal epithelial MODE-K cells. Cell Signal 2015; 27:1141-58. [DOI: 10.1016/j.cellsig.2015.02.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 02/22/2015] [Indexed: 01/26/2023]
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Chon S, Riveline JP, Blondeau B, Gautier JF. Incretin-based therapy and pancreatic beta cells. DIABETES & METABOLISM 2014; 40:411-22. [DOI: 10.1016/j.diabet.2014.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/19/2014] [Accepted: 05/21/2014] [Indexed: 01/09/2023]
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Zimmermann A, Bauer MA, Kroemer G, Madeo F, Carmona-Gutierrez D. When less is more: hormesis against stress and disease. MICROBIAL CELL (GRAZ, AUSTRIA) 2014; 1:150-153. [PMID: 28357237 PMCID: PMC5354599 DOI: 10.15698/mic2014.05.148] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 05/03/2014] [Indexed: 12/25/2022]
Abstract
All living organisms need to adapt to ever changing adverse conditions in order to survive. The phenomenon termed hormesis describes an evolutionarily conserved process by which a cell or an entire organism can be preconditioned, meaning that previous exposure to low doses of an insult protects against a higher, normally harmful or lethal dose of the same stressor. Growing evidence suggests that hormesis is directly linked to an organism's (or cell's) capability to cope with pathological conditions such as aging and age-related diseases. Here, we condense the conceptual and potentially therapeutic importance of hormesis by providing a short overview of current evidence in favor of the cytoprotective impact of hormesis, as well as of its underlying molecular mechanisms.
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Affiliation(s)
- Andreas Zimmermann
- Institute of Molecular Biosciences, University of Graz, 8010 Graz,
Austria
| | - Maria A. Bauer
- Institute of Molecular Biosciences, University of Graz, 8010 Graz,
Austria
| | - Guido Kroemer
- Equipe 11 Labellisée Ligue Contre le Cancer, INSERM U1138, Centre de
Recherche des Cordeliers, 15 Rue de l’École de Médecine, 75006 Paris, France
- Metabolomics and Cell Biology Platforms, Institut Gustave Roussy,
Pavillon de Recherche 1, 94805 Villejuif, France
- Université Paris Descartes, Sorbonne Paris Cité, 12 Rue de l’École
de Médecine, 75006 Paris, France
- Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, 20 Rue
Leblanc, 75015 Paris, France
| | - Frank Madeo
- Institute of Molecular Biosciences, University of Graz, 8010 Graz,
Austria
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Donadelli M, Dando I, Fiorini C, Palmieri M. UCP2, a mitochondrial protein regulated at multiple levels. Cell Mol Life Sci 2014; 71:1171-90. [PMID: 23807210 PMCID: PMC11114077 DOI: 10.1007/s00018-013-1407-0] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 05/16/2013] [Accepted: 06/10/2013] [Indexed: 12/11/2022]
Abstract
An ever-increasing number of studies highlight the role of uncoupling protein 2 (UCP2) in a broad range of physiological and pathological processes. The knowledge of the molecular mechanisms of UCP2 regulation is becoming fundamental in both the comprehension of UCP2-related physiological events and the identification of novel therapeutic strategies based on UCP2 modulation. The study of UCP2 regulation is a fast-moving field. Recently, several research groups have made a great effort to thoroughly understand the various molecular mechanisms at the basis of UCP2 regulation. In this review, we describe novel findings concerning events that can occur in a concerted manner at various levels: Ucp2 gene mutation (single nucleotide polymorphisms), UCP2 mRNA and protein expression (transcriptional, translational, and protein turn-over regulation), UCP2 proton conductance (ligands and post-transcriptional modifications), and nutritional and pharmacological regulation of UCP2.
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Affiliation(s)
- Massimo Donadelli
- Section of Biochemistry, Deparment of Life and Reproduction Sciences, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy,
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17
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JEŽEK P, OLEJÁR T, SMOLKOVÁ K, JEŽEK J, DLASKOVÁ A, PLECITÁ-HLAVATÁ L, ZELENKA J, ŠPAČEK T, ENGSTOVÁ H, PAJUELO REGUERA D, JABŮREK M. Antioxidant and Regulatory Role of Mitochondrial Uncoupling Protein UCP2 in Pancreatic β-cells. Physiol Res 2014; 63:S73-91. [DOI: 10.33549/physiolres.932633] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Research on brown adipose tissue and its hallmark protein, mitochondrial uncoupling protein UCP1, has been conducted for half a century and has been traditionally studied in the Institute of Physiology (AS CR, Prague), likewise UCP2 residing in multiple tissues for the last two decades. Our group has significantly contributed to the elucidation of UCP uncoupling mechanism, fully dependent on free fatty acids (FFAs) within the inner mitochondrial membrane. Now we review UCP2 physiological roles emphasizing its roles in pancreatic β-cells, such as antioxidant role, possible tuning of redox homeostasis (consequently UCP2 participation in redox regulations), and fine regulation of glucose-stimulated insulin secretion (GSIS). For example, NADPH has been firmly established as being a modulator of GSIS and since UCP2 may influence redox homeostasis, it likely affects NADPH levels. We also point out the role of phospholipase iPLA2 isoform in providing FFAs for the UCP2 antioxidant function. Such initiation of mild uncoupling hypothetically precedes lipotoxicity in pancreatic β-cells until it reaches the pathological threshold, after which the antioxidant role of UCP2 can be no more cell-protective, for example due to oxidative stress-accumulated mutations in mtDNA. These mechanisms, together with impaired autocrine insulin function belong to important causes of Type 2 diabetes etiology.
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Affiliation(s)
- P. JEŽEK
- Department of Membrane Transport Biophysics, Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic
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18
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Khader H, Solodushko V, Al-Mehdi AB, Audia J, Fouty B. Overlap of Doxycycline Fluorescence with that of the Redox-Sensitive Intracellular Reporter roGFP. J Fluoresc 2013; 24:305-11. [PMID: 24287973 DOI: 10.1007/s10895-013-1331-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 11/20/2013] [Indexed: 11/28/2022]
Abstract
Tetracycline-inducible systems allow for either suppression or induction of transgene expression to facilitate studies of cell physiology. Doxycycline is a preferred inducer for these gene expression systems due to its membrane permeability; however, the heterocyclic structure of doxycycline exhibits fluorogenic properties that can potentially bias measurement of other fluorochromes. Thus the simultaneous use of tetracycline-inducible systems and fluorescent proteins as reporter genes or as intracellular biosensors may lead to potentially confounding results. Herein, using cells which co-express the ratiometric redox sensitive intracellular reporter, roGFP, and a tetracycline-inducible reporter plasmid encoding the reporter gene, mCherry, as a model system, we describe the overlapping intracellular fluorescent signals between doxycycline and commonly used intracellular fluorescent probes. In our cells, the addition of doxycycline to cells caused a dose- and time-dependent increase in cell fluorescence with 405 nm excitation which overlapped with that of the oxidized configuration of roGFP. Incubating cells in concentrations of doxycycline less than 1 μg/mL and removing doxycycline from the media 60 min before performing experiments eliminated fluorescence interference while still maintaining maximal reporter transgene activation.
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Affiliation(s)
- Heba Khader
- Department of Pharmacology and the Center for Lung Biology, University of South Alabama School of Medicine, Mobile, AL, 36688, USA
| | - Victor Solodushko
- Department of Pharmacology and the Center for Lung Biology, University of South Alabama School of Medicine, Mobile, AL, 36688, USA
| | - Abu Bakr Al-Mehdi
- Department of Pharmacology and the Center for Lung Biology, University of South Alabama School of Medicine, Mobile, AL, 36688, USA
| | - Jonathon Audia
- Department of Microbiology and Immunology and the Center for Lung Biology, University of South Alabama School of Medicine, Mobile, AL, 36688, USA
| | - Brian Fouty
- Department of Pharmacology and the Center for Lung Biology, University of South Alabama School of Medicine, Mobile, AL, 36688, USA. .,Department of Internal Medicine and Division of Pulmonary and Critical Care Medicine, University of South Alabama, School of Medicine, Mobile, AL, 36688, USA. .,Center for Lung Biology, Department of Pharmacology, MSB 3406, University of South Alabama School of Medicine, Mobile, AL, 36688, USA.
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19
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Redox homeostasis in pancreatic β cells. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:932838. [PMID: 23304259 PMCID: PMC3532876 DOI: 10.1155/2012/932838] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/30/2012] [Indexed: 12/20/2022]
Abstract
We reviewed mechanisms that determine reactive oxygen species (redox) homeostasis, redox information signaling and metabolic/regulatory function of autocrine insulin signaling in pancreatic β cells, and consequences of oxidative stress and dysregulation of redox/information signaling for their dysfunction. We emphasize the role of mitochondrion in β cell molecular physiology and pathology, including the antioxidant role of mitochondrial uncoupling protein UCP2. Since in pancreatic β cells pyruvate cannot be easily diverted towards lactate dehydrogenase for lactate formation, the respiration and oxidative phosphorylation intensity are governed by the availability of glucose, leading to a certain ATP/ADP ratio, whereas in other cell types, cell demand dictates respiration/metabolism rates. Moreover, we examine the possibility that type 2 diabetes mellitus might be considered as an inevitable result of progressive self-accelerating oxidative stress and concomitantly dysregulated information signaling in peripheral tissues as well as in pancreatic β cells. It is because the redox signaling is inherent to the insulin receptor signaling mechanism and its impairment leads to the oxidative and nitrosative stress. Also emerging concepts, admiting participation of redox signaling even in glucose sensing and insulin release in pancreatic β cells, fit in this view. For example, NADPH has been firmly established to be a modulator of glucose-stimulated insulin release.
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20
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Collins S, Pi J, Yehuda-Shnaidman E. Uncoupling and reactive oxygen species (ROS)--a double-edged sword for β-cell function? "Moderation in all things". Best Pract Res Clin Endocrinol Metab 2012; 26:753-8. [PMID: 23168277 DOI: 10.1016/j.beem.2012.08.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The ability of the mitochondrion to (a) manage fuel import to oxidize for adenosine tri-phosphate (ATP) generation while (b) protecting itself and the cellular environment from electron leak, which can generate highly reactive oxygen species (ROS) is a delicate balancing act. ATP is the currency of the cell and as such serves a signaling function as a substrate partner to many kinases and ion channels. While various ROS species have been viewed as a dangerous and toxic group of molecules, it also has a role as a signal derived from mitochondria, as well as other enzymatic sources: a double-edged sword. Current efforts to understand the biochemical mechanisms affected by ROS as a signal--usually noted to be hydrogen peroxide (H(2)O(2))--are exciting, but this duality of ROS effects also pose challenges in managing its levels to protect cells. The mitochondrial uncoupling protein-2 (UCP2), UCP3, and the permeability transition pore have been integral to efforts to try to understand what role mitochondrial-derived ROS have in cells. In this piece we reflect on mitochondrial ROS and uncoupling proteins as signaling regulators. It seems that when it comes to ROS and uncoupling the proverb "Moderation in all things" is apt.
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Affiliation(s)
- Sheila Collins
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, SBMRI-Lake Nona, 6400 Sanger Road, Orlando, FL 32827, USA.
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21
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Stark M, Hodyl N, Butler M, Clifton V. Localisation and characterisation of uncoupling protein-2 (UCP2) in the human preterm placenta. Placenta 2012; 33:1020-5. [DOI: 10.1016/j.placenta.2012.09.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 09/17/2012] [Accepted: 09/19/2012] [Indexed: 10/27/2022]
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22
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Guo QY, Robson-Doucette CA, Allister EM, Wheeler MB. Inducible Deletion of UCP2 in Pancreatic β-Cells Enhances Insulin Secretion. Can J Diabetes 2012. [DOI: 10.1016/j.jcjd.2012.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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23
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Impairment of Proinsulin Processing in β-Cells Exposed to Saturated Free Fatty Acid Is Dependent on Uncoupling Protein-2 Expression. Can J Diabetes 2012. [DOI: 10.1016/j.jcjd.2012.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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24
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Mitochondrial hormesis in pancreatic β cells: does uncoupling protein 2 play a role? OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:740849. [PMID: 23029600 PMCID: PMC3458419 DOI: 10.1155/2012/740849] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 08/07/2012] [Indexed: 12/23/2022]
Abstract
In pancreatic β cells, mitochondrial metabolism translates glucose sensing into signals regulating insulin secretion. Chronic exposure of β cells to excessive nutrients, namely, glucolipotoxicity, impairs β-cell function. This is associated with elevated ROS production from overstimulated mitochondria. Mitochondria are not only the major source of cellular ROS, they are also the primary target of ROS attacks. The mitochondrial uncoupling protein UCP2, even though its uncoupling properties are debated, has been associated with protective functions against ROS toxicity. Hormesis, an adaptive response to cellular stresses, might contribute to the protection against β-cell death, possibly limiting the development of type 2 diabetes. Mitochondrial hormesis, or mitohormesis, is a defense mechanism observed in ROS-induced stress-responses by mitochondria. In β cells, mitochondrial damages induced by sublethal exogenous H2O2 can induce secondary repair and defense mechanisms. In this context, UCP2 is a marker of mitohormesis, being upregulated following stress conditions. When overexpressed in nonstressed naïve cells, UCP2 confers resistance to oxidative stress. Whether treatment with mitohormetic inducers is sufficient to restore or ameliorate secretory function of β cells remains to be determined.
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25
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Supale S, Li N, Brun T, Maechler P. Mitochondrial dysfunction in pancreatic β cells. Trends Endocrinol Metab 2012; 23:477-87. [PMID: 22766318 DOI: 10.1016/j.tem.2012.06.002] [Citation(s) in RCA: 182] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Revised: 06/02/2012] [Accepted: 06/02/2012] [Indexed: 12/17/2022]
Abstract
In pancreatic β cells, mitochondria play a central role in coupling glucose metabolism to insulin exocytosis, thereby ensuring strict control of glucose-stimulated insulin secretion. Defects in mitochondrial function impair this metabolic coupling, and ultimately promote apoptosis and β cell death. Various factors have been identified that may contribute to mitochondrial dysfunction. In this review we address the emerging concept of complex links between these factors. We also discuss the role of the mitochondrial genome and mutations associated with diabetes, the effect of oxidative stress and reactive oxygen species, the sensitivity of mitochondria to lipotoxicity, and the adaptive dynamics of mitochondrial morphology. Better comprehension of the molecular mechanisms contributing to mitochondrial dysfunction will help drive the development of effective therapeutic approaches.
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Affiliation(s)
- Sachin Supale
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, 1211 Geneva 4, Switzerland
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26
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Hals IK, Ogata H, Pettersen E, Ma Z, Björklund A, Skorpen F, Egeberg KW, Grill V. Marked over expression of uncoupling protein-2 in beta cells exerts minor effects on mitochondrial metabolism. Biochem Biophys Res Commun 2012; 423:259-64. [DOI: 10.1016/j.bbrc.2012.05.101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 05/17/2012] [Indexed: 11/17/2022]
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27
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Levendal RA, Schumann D, Donath M, Frost CL. Cannabis exposure associated with weight reduction and β-cell protection in an obese rat model. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2012; 19:575-582. [PMID: 22421529 DOI: 10.1016/j.phymed.2012.02.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 12/15/2011] [Accepted: 02/02/2012] [Indexed: 05/31/2023]
Abstract
The aim of this study was to investigate the effect of an organic cannabis extract on β-cell secretory function in an in vivo diet-induced obese rat model and determine the associated molecular changes within pancreatic tissue. Diet-induced obese Wistar rats and rats fed on standard pellets were subcutaneously injected with an organic cannabis extract or the vehicle over a 28-day period. The effect of diet and treatment was evaluated using the intraperitoneal glucose tolerance tests (IPGTTs) and qPCR analysis on rat pancreata harvested upon termination of the experiment. The cafeteria diet induced an average weight difference of 32g and an overall increase in body weight in the experimental groups occurred at a significantly slower rate than the control groups, irrespective of diet. Area under the curve for glucose (AUC(g)) in the obese group was significantly lower compared to the lean group (p<0.001), with cannabis treatment significantly reducing the AUC(g) in the lean group (p<0.05), and remained unchanged in the obese group, relative to the obese control group. qPCR analysis showed that the cafeteria diet induced down-regulation of the following genes in the obese control group, relative to lean controls: UCP2, c-MYC and FLIP. Cannabis treatment in the obese group resulted in up-regulation of CB1, GLUT2, UCP2 and PKB, relative to the obese control group, while c-MYC levels were down-regulated, relative to the lean control group. Treatment did not significantly change gene expression in the lean group. These results suggest that the cannabis extract protects pancreatic islets against the negative effects of obesity.
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Affiliation(s)
- R-A Levendal
- Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
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28
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Sarre A, Gabrielli J, Vial G, Leverve XM, Assimacopoulos-Jeannet F. Reactive oxygen species are produced at low glucose and contribute to the activation of AMPK in insulin-secreting cells. Free Radic Biol Med 2012; 52:142-50. [PMID: 22064362 DOI: 10.1016/j.freeradbiomed.2011.10.437] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 10/05/2011] [Accepted: 10/10/2011] [Indexed: 01/11/2023]
Abstract
Excess reactive oxygen species (ROS) production is thought to play a key role in the loss of pancreatic β-cell number and/or function, in response to high glucose and/or fatty acids. However, contradictory findings have been reported showing that in pancreatic β cells or insulin-secreting cell lines, ROS are produced under conditions of either high or low glucose. Superoxide production was measured in attached INS1E cells as a function of glucose concentration, by following in real time the oxidation of dihydroethidine. Minimal values of superoxide production were measured at glucose concentrations of 5-20 mM, whereas superoxide generation was maximal at 0-1 mM glucose. Superoxide generation started rapidly (15-30 min) after exposure to low glucose and was suppressed by its addition within minutes. Superoxide was totally suppressed by rotenone, but not myxothiazol, suggesting a role for complex I in this process. Indirect evidence for mitochondrial ROS generation was also provided by a decrease in aconitase activity. Activation of AMPK, a cellular metabolic sensor, and its downstream target ACC by low glucose concentration was largely inhibited by addition of MnTBAP, a MnSOD and catalase mimetic that also totally suppressed superoxide production. Taken together, the data show that low glucose activates AMPK in a superoxide-dependent, AMP-independent way.
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Affiliation(s)
- Alexandre Sarre
- Department of Cell Physiology and Metabolism, Medical Faculty, University of Geneva, Geneva, Switzerland.
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29
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Lee J, Kim MS, Li R, Liu VY, Fu L, Moore DD, Ma K, Yechoor VK. Loss of Bmal1 leads to uncoupling and impaired glucose-stimulated insulin secretion in β-cells. Islets 2011; 3:381-8. [PMID: 22045262 PMCID: PMC3329519 DOI: 10.4161/isl.3.6.18157] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The circadian clock has been shown to regulate metabolic homeostasis. Mice with a deletion of Bmal1, a key component of the core molecular clock, develop hyperglycemia and hypoinsulinemia, suggesting β-cell dysfunction. However, the underlying mechanisms are not fully known. In this study, we investigated the mechanisms underlying the regulation of β-cell function by Bmal1. We studied β-cell function in global Bmal1-/- mice, in vivo and in isolated islets ex vivo, as well as in rat insulinoma cell lines with shRNA-mediated Bmal1 knockdown. Global Bmal1-/- mice develop diabetes secondary to a significant impairment in glucose-stimulated insulin secretion (GSIS). There is a blunting of GSIS in both isolated Bmal1-/- islets and in Bmal1 knockdown cells, as compared to controls, suggesting that this is secondary to a loss of cell-autonomous effect of Bmal1. In contrast to previous studies, in these Bmal1-/- mice on a C57Bl/6 background, the loss of stimulated insulin secretion, interestingly, is with glucose but not to other depolarizing secretagogues, suggesting that events downstream of membrane depolarization are largely normal in Bmal1-/- islets. This defect in GSIS occurs as a result increased mitochondrial uncoupling with consequent impairment of glucose-induced mitochondrial potential generation and ATP synthesis, due to an upregulation of Ucp2. Inhibition of Ucp2, in isolated islets, leads to a rescue of the glucose-induced ATP production and insulin secretion in Bmal1-/- islets. Thus, Bmal1 regulates mitochondrial energy metabolism to maintain normal GSIS and its disruption leads to diabetes due to a loss of GSIS.
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Affiliation(s)
- Jeongkyung Lee
- DERC & Division of Diabetes, Endocrinology & Metabolism; Department of Medicine; Baylor College of Medicine; Houston, TX USA
| | - Mi-Sun Kim
- DERC & Division of Diabetes, Endocrinology & Metabolism; Department of Medicine; Baylor College of Medicine; Houston, TX USA
| | - Rongying Li
- DERC & Division of Diabetes, Endocrinology & Metabolism; Department of Medicine; Baylor College of Medicine; Houston, TX USA
| | - Victoria Y. Liu
- DERC & Division of Diabetes, Endocrinology & Metabolism; Department of Medicine; Baylor College of Medicine; Houston, TX USA
| | - Loning Fu
- CNRC Pediatrics-Nutrition; Baylor College of Medicine; Houston, TX USA
| | - David D. Moore
- Dept of Molecular & Cellular Biology; Baylor College of Medicine; Houston, TX USA
| | - Ke Ma
- Center for Diabetes Research; The Methodist Hospital Research Institute; Houston, TX USA
| | - Vijay K. Yechoor
- DERC & Division of Diabetes, Endocrinology & Metabolism; Department of Medicine; Baylor College of Medicine; Houston, TX USA
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30
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Leloup C, Casteilla L, Carrière A, Galinier A, Benani A, Carneiro L, Pénicaud L. Balancing mitochondrial redox signaling: a key point in metabolic regulation. Antioxid Redox Signal 2011; 14:519-30. [PMID: 20977349 DOI: 10.1089/ars.2010.3424] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mitochondrial reactive oxygen species (mROS) have emerged as signaling molecules in physiology primarily as a result of studies of uncoupling mechanisms in mitochondrial respiration. The discovery that this mechanism negatively regulates mROS generation in many cell types has drawn the attention of the scientific community to the pathological consequences of excess mROS production. From reports of the energetic fluxes in cells grown under normal conditions, the hypothesis that mROS are an integrated physiological signal of the metabolic status of the cell has emerged. Here, we consider recent studies that support this point of view in two key nutrient sensors of the body, beta cells and the hypothalamus, which are the main coordinators of endocrine and nervous controls of energy metabolism and adipose tissue, which is of paramount importance in controlling body weight and, therefore, the development of obesity and type 2 diabetes. In this context, finely balanced mROS production may be at the core of proper metabolic maintenance, and unbalanced mROS production, which is largely documented, might be an important trigger of metabolic disorders.
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Affiliation(s)
- Corinne Leloup
- Centre des Sciences du Goût et de l'Alimentation, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6265-Institut National de Recherche Agronomique 1324, Université de Bourgogne, Dijon, France.
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31
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Vetterli L, Brun T, Giovannoni L, Bosco D, Maechler P. Resveratrol potentiates glucose-stimulated insulin secretion in INS-1E beta-cells and human islets through a SIRT1-dependent mechanism. J Biol Chem 2010; 286:6049-60. [PMID: 21163946 DOI: 10.1074/jbc.m110.176842] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Resveratrol, a polyphenol compound, is known for its effects on energy homeostasis. With properties of energy sensors mediating effects of calorie restriction, sirtuins are targets of resveratrol. The mammalian sirtuin homolog SIRT1 is a protein deacetylase playing a role in glucose metabolism and islet function. Here, we investigated the effects of resveratrol and possible link with SIRT1 in β-cells. Insulinoma INS-1E cells and human islets were cultured with resveratrol before analyzing their physiological responses. Treatment of INS-1E cells for 24 h with 25 μM resveratrol resulted in marked potentiation of glucose-stimulated insulin secretion. This effect was associated with elevated glycolytic flux, resulting in increased glucose oxidation, ATP generation, and mitochondrial oxygen consumption. Such changes correlated with up-regulation of key genes for β-cell function, i.e. Glut2, glucokinase, Pdx-1, Hnf-1α, and Tfam. In human islets, chronic resveratrol treatment similarly increased both the glucose secretory response and expression of the same set of genes, eventually restoring the glucose response in islets obtained from one type 2 diabetic donor. Overexpression of Sirt1 in INS-1E cells potentiated resveratrol effects on insulin secretion. Conversely, inhibition of SIRT1 achieved either by expression of an inactive mutant or by using the EX-527 inhibitor, both abolished resveratrol effects on glucose responses. Treatment of INS-1E cells with EX-527 also prevented resveratrol-induced up-regulation of Glut2, glucokinase, Pdx-1, and Tfam. Resveratrol markedly enhanced the glucose response of INS-1E cells and human islets, even after removal of the compound from the medium. These effects were mediated by and fully dependent on active SIRT1, defining a new role for SIRT1 in the regulation of insulin secretion.
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Affiliation(s)
- Laurène Vetterli
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center and Geneva University Hospitals, 1211 Geneva, Switzerland
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32
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Peyot ML, Pepin E, Lamontagne J, Latour MG, Zarrouki B, Lussier R, Pineda M, Jetton TL, Madiraju SRM, Joly E, Prentki M. Beta-cell failure in diet-induced obese mice stratified according to body weight gain: secretory dysfunction and altered islet lipid metabolism without steatosis or reduced beta-cell mass. Diabetes 2010; 59:2178-87. [PMID: 20547980 PMCID: PMC2927940 DOI: 10.2337/db09-1452] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE C57Bl/6 mice develop obesity and mild hyperglycemia when fed a high-fat diet (HFD). Although diet-induced obesity (DIO) is a widely studied model of type 2 diabetes, little is known about beta-cell failure in these mice. RESEARCH DESIGN AND METHODS DIO mice were separated in two groups according to body weight gain: low- and high-HFD responders (LDR and HDR). We examined whether mild hyperglycemia in HDR mice is due to reduced beta-cell mass or function and studied islet metabolism and signaling. RESULTS HDR mice were more obese, hyperinsulinemic, insulin resistant, and hyperglycemic and showed a more altered plasma lipid profile than LDR. LDR mice largely compensated insulin resistance, whereas HDR showed perturbed glucose homeostasis. Neither LDR nor HDR mice showed reduced beta-cell mass, altered islet glucose metabolism, and triglyceride deposition. Insulin secretion in response to glucose, KCl, and arginine was impaired in LDR and almost abolished in HDR islets. Palmitate partially restored glucose- and KCl-stimulated secretion. The glucose-induced rise in ATP was reduced in both DIO groups, and the glucose-induced rise in Ca(2+) was reduced in HDR islets relatively to LDR. Glucose-stimulated lipolysis was decreased in LDR and HDR islets, whereas fat oxidation was increased in HDR islets only. Fatty acid esterification processes were markedly diminished, and free cholesterol accumulated in HDR islets. CONCLUSIONS beta-Cell failure in HDR mice is not due to reduced beta-cell mass and glucose metabolism or steatosis but to a secretory dysfunction that is possibly due to altered ATP/Ca(2+) and lipid signaling, as well as free cholesterol deposition.
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Affiliation(s)
- Marie-Line Peyot
- Montreal Diabetes Research Center and CRCHUM, Montreal, QC, Canada.
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Yang J, Chi Y, Burkhardt BR, Guan Y, Wolf BA. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells. Nutr Rev 2010; 68:270-9. [PMID: 20500788 DOI: 10.1111/j.1753-4887.2010.00282.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Leucine, a branched-chain amino acid that must be supplied in the daily diet, plays an important role in controlling protein synthesis and regulating cell metabolism in various cell types. In pancreatic beta cells, leucine acutely stimulates insulin secretion by serving as both metabolic fuel and allosteric activator of glutamate dehydrogenase to enhance glutaminolysis. Leucine has also been shown to regulate gene transcription and protein synthesis in pancreatic islet beta cells via both mTOR-dependent and -independent pathways at physiological concentrations. Long-term treatment with leucine has been shown to improve insulin secretory dysfunction of human diabetic islets via upregulation of certain key metabolic genes. In vivo, leucine administration improves glycemic control in humans and rodents with type 2 diabetes. This review summarizes and discusses the recent findings regarding the effects of leucine metabolism on pancreatic beta-cell function.
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Affiliation(s)
- Jichun Yang
- Department of Physiology and Pathophysiology, Peking University Diabetes Center, Peking University Health Science Center, Beijing, China.
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Drews G, Krippeit-Drews P, Düfer M. Oxidative stress and beta-cell dysfunction. Pflugers Arch 2010; 460:703-18. [PMID: 20652307 DOI: 10.1007/s00424-010-0862-9] [Citation(s) in RCA: 188] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 06/23/2010] [Accepted: 06/25/2010] [Indexed: 12/11/2022]
Abstract
Diabetes mellitus type 1 and 2 (T1DM and T2DM) are complex multifactorial diseases. Loss of beta-cell function caused by reduced secretory capacity and enhanced apoptosis is a key event in the pathogenesis of both diabetes types. Oxidative stress induced by reactive oxygen and nitrogen species is critically involved in the impairment of beta-cell function during the development of diabetes. Because of their low antioxidant capacity, beta-cells are extremely sensitive towards oxidative stress. In beta-cells, important targets for an oxidant insult are cell metabolism and K(ATP) channels. The oxidant-evoked alterations of K(ATP) channel activity seem to be critical for oxidant-induced dysfunction because genetic ablation of K(ATP) channels attenuates the effects of oxidative stress on beta-cell function. Besides the effects on metabolism, interference of oxidants with mitochondria induces key events in apoptosis. Consequently, increasing antioxidant defence is a promising strategy to delay beta cell failure in (pre)-diabetic patients or during islet transplantation. Knock-out of K(ATP) channels has beneficial effects on oxidant-induced inhibition of insulin secretion and cell death. Interestingly, these effects can be mimicked by sulfonylureas that have been used in the treatment of T2DM for many years. Loss of functional K(ATP) channels leads to up-regulation of antioxidant enzymes, a process that depends on cytosolic Ca(2+). These observations are of great importance for clinical intervention because they show a possibility to protect beta-cells at an early stage before dramatic changes of the secretory capacity and loss of cell mass become manifest and lead to glucose intolerance or even overt diabetes.
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Affiliation(s)
- Gisela Drews
- Department of Pharmacology and Clinical Pharmacy, University of Tübingen, Auf der Morgenstelle 8, Tübingen, Germany.
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Mookerjee SA, Divakaruni AS, Jastroch M, Brand MD. Mitochondrial uncoupling and lifespan. Mech Ageing Dev 2010; 131:463-72. [PMID: 20363244 PMCID: PMC2924931 DOI: 10.1016/j.mad.2010.03.010] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2009] [Revised: 03/17/2010] [Accepted: 03/29/2010] [Indexed: 12/21/2022]
Abstract
The quest to understand why we age has given rise to numerous lines of investigation that have gradually converged to include metabolic control by mitochondrial activity as a major player. That is, the ideal balance between nutrient uptake, its transduction into usable energy, and the mitigation of damaging byproducts can be regulated by mitochondrial respiration and output (ATP, reactive oxygen species (ROS), and heat). Mitochondrial inefficiency through proton leak, which uncouples substrate oxidation from ADP phosphorylation, can comprise as much as 30% of the basal metabolic rate. This uncoupling is hypothesized to protect cells from conditions that favor ROS production. Uncoupling can also occur through pharmacological induction of proton leak and activity of the uncoupling proteins. Mitochondrial uncoupling is implicated in lifespan extension through its effects on metabolic rate and ROS production. However, evidence to date does not suggest a consistent role for uncoupling in lifespan. The purpose of this review is to discuss recent work examining how mitochondrial uncoupling impacts lifespan.
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36
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Emre Y, Nübel T. Uncoupling protein UCP2: When mitochondrial activity meets immunity. FEBS Lett 2010; 584:1437-42. [DOI: 10.1016/j.febslet.2010.03.014] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Revised: 02/20/2010] [Accepted: 03/10/2010] [Indexed: 11/26/2022]
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Lacraz G, Figeac F, Movassat J, Kassis N, Portha B. Diabetic GK/Par rat beta-cells are spontaneously protected against H2O2-triggered apoptosis. A cAMP-dependent adaptive response. Am J Physiol Endocrinol Metab 2010; 298:E17-27. [PMID: 19843875 DOI: 10.1152/ajpendo.90871.2008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The alteration of the beta-cell population in the Goto-Kakizaki rat (GK/Par line), a model of spontaneous type 2 diabetes, has been ascribed to significantly decreased beta-cell replication and neogenesis, while beta-cell apoptosis is surprisingly not enhanced and remains in the normal range. To gain insight into the mechanisms by which those beta-cells are protected from death, we studied ex vivo the apoptotic activity and the expression of a large set of pro/antiapoptotic and pro/antioxidant genes in GK/Par islet cells. This was done in vitro in freshly isolated islets as well as in response to culture conditions and calibrated reactive oxygen species (ROS) exposure (i.e., H2O2). We also investigated the intracellular mechanisms of the diabetic beta-cell response to ROS, the role if any of the intracellular cAMP metabolism, and finally the kinetic of ROS response, taking advantage of the GK/Par rat normoglycemia until weaning. Our results show that the peculiar GK/Par beta-cell phenotype was correlated with an increased expression of a large panel of antioxidant genes as well as pro/antiapoptotic genes. We demonstrate that such combination confers resistance to cytotoxic H2O2 exposure in vitro, raising the possibility that at least some of the activated stress/defense genes have protective effects against H2O2-triggered beta-cell death. We also present some evidence that the GK/Par beta-cell resistance to H2O2 is at least partly cAMP dependent. Finally, we show that such a phenotype is not innate but is spontaneously acquired after diabetes onset as the result of an adaptive response to the diabetic environment.
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MESH Headings
- Adaptation, Physiological/physiology
- Animals
- Apoptosis/drug effects
- Apoptosis/physiology
- Apoptosis Regulatory Proteins/genetics
- Apoptosis Regulatory Proteins/metabolism
- Cell Division/physiology
- Cells, Cultured
- Cyclic AMP/metabolism
- Cyclin D1/genetics
- Cyclin D1/metabolism
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Disease Models, Animal
- Heme Oxygenase-1/genetics
- Heme Oxygenase-1/metabolism
- Hydrogen Peroxide/pharmacology
- Hypoxia-Inducible Factor 1, alpha Subunit/genetics
- Hypoxia-Inducible Factor 1, alpha Subunit/metabolism
- Insulin-Secreting Cells/metabolism
- Insulin-Secreting Cells/pathology
- Male
- Oxidants/pharmacology
- Proto-Oncogene Proteins c-myc/genetics
- Proto-Oncogene Proteins c-myc/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Mutant Strains
- Rats, Wistar
- Reactive Oxygen Species/metabolism
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Affiliation(s)
- Grégory Lacraz
- Laboratoire Biologie et Pathologie du Pancréas Endocrine, Unité Biologie Fonctionnelle et Adaptive, Equipe 1, Université Paris-Diderot et CNRS EAC-4413, Paris, France
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38
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Role of mitochondria in beta-cell function and dysfunction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:193-216. [PMID: 20217499 DOI: 10.1007/978-90-481-3271-3_9] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Pancreatic beta-cells are poised to sense glucose and other nutrient secretagogues to regulate insulin exocytosis, thereby maintaining glucose homeostasis. This process requires translation of metabolic substrates into intracellular messengers recognized by the exocytotic machinery. Central to this metabolism-secretion coupling, mitochondria integrate and generate metabolic signals, thereby connecting glucose recognition to insulin exocytosis. In response to a glucose rise, nucleotides and metabolites are generated by mitochondria and participate, together with cytosolic calcium, to the stimulation of insulin release. This review describes the mitochondrion-dependent pathways of regulated insulin secretion. Mitochondrial defects, such as mutations and reactive oxygen species production, are discussed in the context of beta-cell failure that may participate to the etiology of diabetes.
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Poitout V, Amyot J, Semache M, Zarrouki B, Hagman D, Fontés G. Glucolipotoxicity of the pancreatic beta cell. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1801:289-98. [PMID: 19715772 DOI: 10.1016/j.bbalip.2009.08.006] [Citation(s) in RCA: 269] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/13/2009] [Accepted: 08/13/2009] [Indexed: 02/07/2023]
Abstract
The concept of glucolipotoxicity refers to the combined, deleterious effects of elevated glucose and fatty acid levels on pancreatic beta-cell function and survival. Significant progress has been made in recent years towards a better understanding of the cellular and molecular basis of glucolipotoxicity in the beta cell. The permissive effect of elevated glucose on the detrimental actions of fatty acids stems from the influence of glucose on intracellular fatty acid metabolism, promoting the synthesis of cellular lipids. The combination of excessive levels of fatty acids and glucose therefore leads to decreased insulin secretion, impaired insulin gene expression, and beta-cell death by apoptosis, all of which probably have distinct underlying mechanisms. Recent studies from our laboratory have identified several pathways implicated in fatty acid inhibition of insulin gene expression, including the extracellular-regulated kinase (ERK1/2) pathway, the metabolic sensor Per-Arnt-Sim kinase (PASK), and the ATF6 branch of the unfolded protein response. We have also confirmed in vivo in rats that the decrease in insulin gene expression is an early defect which precedes any detectable abnormality in insulin secretion. While the role of glucolipotoxicity in humans is still debated, the inhibitory effects of chronically elevated fatty acid levels has been clearly demonstrated in several studies, at least in individuals genetically predisposed to developing type 2 diabetes. It is therefore likely that glucolipotoxicity contributes to beta-cell failure in type 2 diabetes as well as to the decline in beta-cell function observed after the onset of the disease.
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Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, Montreal, QC, Canada.
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40
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Li N, Brun T, Cnop M, Cunha DA, Eizirik DL, Maechler P. Transient oxidative stress damages mitochondrial machinery inducing persistent beta-cell dysfunction. J Biol Chem 2009; 284:23602-12. [PMID: 19546218 DOI: 10.1074/jbc.m109.024323] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Transient exposure of beta-cells to oxidative stress interrupts the transduction of signals normally coupling glucose metabolism to insulin secretion. We investigated putative persistence of effects induced by one transient oxidative stress (200 microm H(2)O(2), 10 min) on insulin secreting cells following recovery periods of days and weeks. Three days after oxidative stress INS-1E cells and rat islets exhibited persistent dysfunction. In particular, the secretory response to 15 mm glucose was reduced by 40% in INS-1E cells stressed 3 days before compared with naïve cells. Compared with non-stressed INS-1E cells, we observed reduced oxygen consumption (-43%) and impaired glucose-induced ATP generation (-46%). These parameters correlated with increased mitochondrial reactive oxygen species formation (+60%) accompanied with down-regulation of subunits of the respiratory chain and decreased expression of genes responsible for mitochondrial biogenesis (TFAM, -24%; PGC-1alpha, -67%). Three weeks after single oxidative stress, both mitochondrial respiration and secretory responses were recovered. Moreover, such recovered INS-1E cells exhibited partial resistance to a second transient oxidative stress and up-regulation of UCP2 (+78%) compared with naïve cells. In conclusion, one acute oxidative stress induces beta-cell dysfunction lasting over days, explained by persistent damages in mitochondrial components.
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Affiliation(s)
- Ning Li
- Department of Cell Physiology, Faculty of Medicine, University of Geneva, rue Michel-Servet 1, CH-1211 Geneva 4, Switzerland
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41
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Leloup C, Tourrel-Cuzin C, Magnan C, Karaca M, Castel J, Carneiro L, Colombani AL, Ktorza A, Casteilla L, Pénicaud L. Mitochondrial reactive oxygen species are obligatory signals for glucose-induced insulin secretion. Diabetes 2009; 58:673-81. [PMID: 19073765 PMCID: PMC2646066 DOI: 10.2337/db07-1056] [Citation(s) in RCA: 255] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Insulin secretion involves complex events in which the mitochondria play a pivotal role in the generation of signals that couple glucose detection to insulin secretion. Studies on the mitochondrial generation of reactive oxygen species (ROS) generally focus on chronic nutrient exposure. Here, we investigate whether transient mitochondrial ROS production linked to glucose-induced increased respiration might act as a signal for monitoring insulin secretion. RESEARCH DESIGN AND METHODS ROS production in response to glucose was investigated in freshly isolated rat islets. ROS effects were studied using a pharmacological approach and calcium imaging. RESULTS Transient glucose increase from 5.5 to 16.7 mmol/l stimulated ROS generation, which was reversed by antioxidants. Insulin secretion was dose dependently blunted by antioxidants and highly correlated with ROS levels. The incapacity of beta-cells to secrete insulin in response to glucose with antioxidants was associated with a decrease in ROS production and in contrast to the maintenance of high levels of ATP and NADH. Then, we investigated the mitochondrial origin of ROS (mROS) as the triggering signal. Insulin release was mimicked by the mitochondrial-complex blockers, antimycin and rotenone, that generate mROS. The adding of antioxidants to mitochondrial blockers or to glucose was used to lower mROS reversed insulin secretion. Finally, calcium imaging on perifused islets using glucose stimulation or mitochondrial blockers revealed that calcium mobilization was completely reversed using the antioxidant trolox and that it was of extracellular origin. No toxic effects were present using these pharmacological approaches. CONCLUSIONS Altogether, these complementary results demonstrate that mROS production is a necessary stimulus for glucose-induced insulin secretion.
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Affiliation(s)
- Corinne Leloup
- Department of Metabolism, Plasticity, and Mitochondria, Unité Mixte de Recherche 5241, Centre National de la Recherche Scientifique-Université Paul Sabatier, Institut Fédératif de Recherche 31, Toulouse, France.
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Mutations in UCP2 in congenital hyperinsulinism reveal a role for regulation of insulin secretion. PLoS One 2008; 3:e3850. [PMID: 19065272 PMCID: PMC2588657 DOI: 10.1371/journal.pone.0003850] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 11/10/2008] [Indexed: 12/21/2022] Open
Abstract
Although the most common mechanism underlying congenital hyperinsulinism is dysfunction of the pancreatic ATP-sensitive potassium channel, the pathogenesis and genetic origins of this disease remains largely unexplained in more than half of all patients. UCP2 knockout mice exhibit an hyperinsulinemic hypoglycemia, suggesting an involment of UCP2 in insulin secretion. However, a possible pathogenic role for UCP2 protein in the development of human congenital hyperinsulinism or of any human disease has not yet been investigated. We studied ten children exhibiting congenital hyperinsulinism, without detectable mutations in the known congenital hyperinsulinism-causing genes. Parental-inherited heterozygous UCP2 variants encoding amino-acid changes were found in two unrelated children with congenital hyperinsulinism. Functional assays in yeast and in insulin-secreting cells revealed an impaired activity of UCP2 mutants. Therefore, we report the finding of UCP2 coding variants in human congenital hyperinsulinism, which reveals a role for this gene in the regulation of insulin secretion and glucose metabolism in humans. Our results show for the first time a direct association between UCP2 amino acid alteration and human disease and highlight a role for mitochondria in hormone secretion.
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43
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Carobbio S, Frigerio F, Rubi B, Vetterli L, Bloksgaard M, Gjinovci A, Pournourmohammadi S, Herrera PL, Reith W, Mandrup S, Maechler P. Deletion of glutamate dehydrogenase in beta-cells abolishes part of the insulin secretory response not required for glucose homeostasis. J Biol Chem 2008; 284:921-9. [PMID: 19015267 DOI: 10.1074/jbc.m806295200] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin exocytosis is regulated in pancreatic ss-cells by a cascade of intracellular signals translating glucose levels into corresponding secretory responses. The mitochondrial enzyme glutamate dehydrogenase (GDH) is regarded as a major player in this process, although its abrogation has not been tested yet in animal models. Here, we generated transgenic mice, named betaGlud1(-/-), with ss-cell-specific GDH deletion. Our results show that GDH plays an essential role in the full development of the insulin secretory response. In situ pancreatic perfusion revealed that glucose-stimulated insulin secretion was reduced by 37% in betaGlud1(-/-). Furthermore, isolated islets with either constitutive or acute adenovirus-mediated knock-out of GDH showed a 49 and 38% reduction in glucose-induced insulin release, respectively. Adenovirus-mediated re-expression of GDH in betaGlud1(-/-) islets fully restored glucose-induced insulin release. Thus, GDH appears to account for about 40% of glucose-stimulated insulin secretion and to lack redundant mechanisms. In betaGlud1(-/-) mice, the reduced secretory capacity resulted in lower plasma insulin levels in response to both feeding and glucose load, while body weight gain was preserved. The results demonstrate that GDH is essential for the full development of the secretory response in beta-cells. However, maximal secretory capacity is not required for maintenance of glucose homeostasis in normo-caloric conditions.
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44
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Exercise-induced synaptogenesis in the hippocampus is dependent on UCP2-regulated mitochondrial adaptation. J Neurosci 2008; 28:10766-71. [PMID: 18923051 DOI: 10.1523/jneurosci.2744-08.2008] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Mitochondria are essential organelles in neurons providing appropriate energetic needs to maintain resting and action potentials as well as to modulate synaptic plasticity. Although neuronal events underlie various behavioral events, the behavior itself, such as voluntary exercise, feeds back to affect neuronal morphology and function as well as glial morphology and function. The hippocampal formation is a main site of synaptic plasticity induced by voluntary exercise. Here we show that voluntary exercise induces uncoupling protein 2 (UCP2) mRNA expression and mitochondrial oxygen consumption in coupled as well as uncoupled respiratory states in the hippocampus. These changes in mitochondrial metabolism coincided with an increase in mitochondrial number and dendritic spine synapses in granule cells of the dentate gyrus and the stratum radiatum of the CA1 region and were dependent on UCP2 expression, because in UCP2 knock-out mice such changes were not observed. Together, these observations reveal that a mitochondrial mechanism related to UCP2 function is essential for appropriate bioenergetic adaptation of neurons to increased neuronal activity and synaptic plasticity in response to exercise.
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45
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The sensitivity of pancreatic β-cells to mitochondrial injuries triggered by lipotoxicity and oxidative stress. Biochem Soc Trans 2008; 36:930-4. [DOI: 10.1042/bst0360930] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Pancreatic β-cells are essential for the maintenance of glucose homoeostasis, and dysfunction of these insulin-secreting cells results in the development of diabetes. In the course of events leading from obesity to Type 2 diabetes, several mechanisms are currently envisaged. Among them, lipids and oxidative stress are considered as toxic candidates for the β-cell. The cellular link between fatty acids and ROS (reactive oxygen species) is essentially the mitochondrion, a key organelle for the control of insulin secretion. Mitochondria are the main source of ROS and are also the primary target of oxidative attacks. The present review presents the current knowledge of lipotoxicity related to oxidative stress in the context of mitochondrial function in the β-cell.
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46
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Shen W, Liu K, Tian C, Yang L, Li X, Ren J, Packer L, Head E, Sharman E, Liu J. Protective effects of R-alpha-lipoic acid and acetyl-L-carnitine in MIN6 and isolated rat islet cells chronically exposed to oleic acid. J Cell Biochem 2008; 104:1232-43. [PMID: 18260126 DOI: 10.1002/jcb.21701] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Mitochondrial dysfunction due to oxidative stress and concomitant impaired beta-cell function may play a key role in type 2 diabetes. Preventing and/or ameliorating oxidative mitochondrial dysfunction with mitochondria-specific nutrients may have preventive or therapeutic potential. In the present study, the oxidative mechanism of mitochondrial dysfunction in pancreatic beta-cells exposed to sublethal levels of oleic acid (OA) and the protective effects of mitochondrial nutrients [R-alpha-lipoic acid (LA) and acetyl-L-carnitine (ALC)] were investigated. Chronic exposure (72 h) of insulinoma MIN6 cells to OA (0.2-0.8 mM) increased intracellular oxidant formation, decreased mitochondrial membrane potential (MMP), enhanced uncoupling protein-2 (UCP-2) mRNA and protein expression, and consequently, decreased glucose-induced ATP production and suppressed glucose-stimulated insulin secretion. Pretreatment with LA and/or ALC reduced oxidant formation, increased MMP, regulated UCP-2 mRNA and protein expression, increased glucose-induced ATP production, and restored glucose-stimulated insulin secretion. The key findings on ATP production and insulin secretion were verified with isolated rat islets. These results suggest that mitochondrial dysfunction is involved in OA-induced pancreatic beta-cell dysfunction and that pretreatment with mitochondrial protective nutrients could be an effective strategy to prevent beta-cell dysfunction.
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Affiliation(s)
- Weili Shen
- Institute for Nutritional Sciences, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, PR China
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47
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UCP2 is highly expressed in pancreatic alpha-cells and influences secretion and survival. Proc Natl Acad Sci U S A 2008; 105:12057-62. [PMID: 18701716 DOI: 10.1073/pnas.0710434105] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
In pancreatic beta-cells, uncoupling protein 2 (UCP2) influences mitochondrial oxidative phosphorylation and insulin secretion. Here, we show that alpha-cells express significantly higher levels of UCP2 than do beta-cells. Greater mitochondrial UCP2-related uncoupling was observed in alpha-cells compared with beta-cells and was accompanied by a lower oxidative phosphorylation efficiency (ATP/O). Conversely, reducing UCP2 activity in alpha-cells was associated with higher mitochondrial membrane potential generated by glucose oxidation and with increased ATP synthesis, indicating more efficient metabolic coupling. In vitro, the suppression of UCP2 activity led to reduced glucagon secretion in response to low glucose; however, in vivo, fasting glucagon levels were normal in UCP2(-/-) mice. In addition to its effects on secretion, UCP2 played a cytoprotective role in islets, with UCP2(-/-) alpha-cells being more sensitive to specific death stimuli. In summary, we demonstrate a direct role for UCP2 in maintaining alpha-cell function at the level of glucose metabolism, glucagon secretion, and cytoprotection.
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48
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Galetti S, Sarre A, Perreten H, Produit-Zengaffinen N, Muzzin P, Assimacopoulos-Jeannet F. Fatty acids do not activate UCP2 in pancreatic beta cells: comparison with UCP1. Pflugers Arch 2008; 457:931-40. [PMID: 18626658 DOI: 10.1007/s00424-008-0548-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Accepted: 06/14/2008] [Indexed: 01/29/2023]
Abstract
UCP2 is expressed in pancreatic beta cells where its postulated uncoupling activity will modulate glucose-induced changes in ATP/ADP ratio and insulin secretion. The consequences of UCP2 over/underexpression on beta-cell function has mainly been studied in the basal state; however, a UCP has no uncoupling activity unless stimulated by fatty acids and/or reactive oxygen species. Here, UCP2 was overexpressed in INS-1 cells and parameters reflecting mitochondrial coupling measured in the basal state and after stimulation by fatty acids. For comparison, UCP1 was expressed to similar levels and the same parameters measured. Neither UCP1 expression nor UCP2 overexpression modified basal or glucose-stimulated metabolic changes. Upon addition of fatty acids, UCP1-expressing cells displayed the expected mitochondrial uncoupling effect, while UCP2 did not elicit any measurable change in mitochondrial function. Taken together, our data demonstrate that, in pancreatic beta-cells, UCP2 has no uncoupling activity in the basal state or after fatty acid stimulation.
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Affiliation(s)
- Sandrine Galetti
- Department of Cell Physiology and Metabolism, Medical Faculty, University of Geneva, 1 rue Michel Servet, 1211, Geneva 4, Switzerland
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Shen W, Hao J, Tian C, Ren J, Yang L, Li X, Luo C, Cotma CW, Liu J. A combination of nutriments improves mitochondrial biogenesis and function in skeletal muscle of type 2 diabetic Goto-Kakizaki rats. PLoS One 2008; 3:e2328. [PMID: 18523557 PMCID: PMC2391295 DOI: 10.1371/journal.pone.0002328] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 04/26/2008] [Indexed: 12/25/2022] Open
Abstract
Background Recent evidence indicates that insulin resistance in skeletal muscle may be related to reduce mitochondrial number and oxidation capacity. However, it is not known whether increasing mitochondrial number and function improves insulin resistance. In the present study, we investigated the effects of a combination of nutrients on insulin resistance and mitochondrial biogenesis/function in skeletal muscle of type 2 diabetic Goto–Kakizaki rats. Methodology/Principal Findings We demonstrated that defect of glucose and lipid metabolism is associated with low mitochondrial content and reduced mitochondrial enzyme activity in skeletal muscle of the diabetic Goto-Kakizaki rats. The treatment of combination of R-α-lipoic acid, acetyl-L-carnitine, nicotinamide, and biotin effectively improved glucose tolerance, decreased the basal insulin secretion and the level of circulating free fatty acid (FFA), and prevented the reduction of mitochondrial biogenesis in skeletal muscle. The nutrients treatment also significantly increased mRNA levels of genes involved in lipid metabolism, including peroxisome proliferator–activated receptor-α (Pparα), peroxisome proliferator–activated receptor-δ (Pparδ), and carnitine palmitoyl transferase-1 (Mcpt-1) and activity of mitochondrial complex I and II in skeletal muscle. All of these effects of mitochondrial nutrients are comparable to that of the antidiabetic drug, pioglitazone. In addition, the treatment with nutrients, unlike pioglitazone, did not cause body weight gain. Conclusions/Significance These data suggest that a combination of mitochondrial targeting nutrients may improve skeletal mitochondrial dysfunction and exert hypoglycemic effects, without causing weight gain.
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MESH Headings
- Animals
- DNA, Mitochondrial/metabolism
- Diabetes Mellitus, Experimental/physiopathology
- Diabetes Mellitus, Type 2/physiopathology
- Dietary Supplements
- Fatty Acids, Nonesterified/blood
- Glucose Tolerance Test
- Mitochondria, Muscle/drug effects
- Mitochondria, Muscle/metabolism
- Mitochondria, Muscle/physiology
- Muscle Proteins/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/physiopathology
- Rats
- Rats, Mutant Strains
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Affiliation(s)
- Weili Shen
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jiejie Hao
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
- Graduate School of the Chinese Academy of Sciences, Beijing, China
| | - Chuan Tian
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
- Graduate School of the Chinese Academy of Sciences, Beijing, China
| | - Jinmin Ren
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Lu Yang
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Xuesen Li
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
- Graduate School of the Chinese Academy of Sciences, Beijing, China
| | - Cheng Luo
- Institute for Nutritional Science, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Carl W. Cotma
- Institute for Brain Aging and Dementia, University of California Irvine, Irvine, California, United States of America
| | - Jiankang Liu
- Institute for Brain Aging and Dementia, University of California Irvine, Irvine, California, United States of America
- * E-mail:
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Abstract
Glucotoxicity, lipotoxicity, and glucolipotoxicity are secondary phenomena that are proposed to play a role in all forms of type 2 diabetes. The underlying concept is that once the primary pathogenesis of diabetes is established, probably involving both genetic and environmental forces, hyperglycemia and very commonly hyperlipidemia ensue and thereafter exert additional damaging or toxic effects on the beta-cell. In addition to their contribution to the deterioration of beta-cell function after the onset of the disease, elevations of plasma fatty acid levels that often accompany insulin resistance may, as glucose levels begin to rise outside of the normal range, also play a pathogenic role in the early stages of the disease. Because hyperglycemia is a prerequisite for lipotoxicity to occur, the term glucolipotoxicity, rather than lipotoxicity, is more appropriate to describe deleterious effects of lipids on beta-cell function. In vitro and in vivo evidence supporting the concept of glucotoxicity is presented first, as well as a description of the underlying mechanisms with an emphasis on the role of oxidative stress. Second, we discuss the functional manifestations of glucolipotoxicity on insulin secretion, insulin gene expression, and beta-cell death, and the role of glucose in the mechanisms of glucolipotoxicity. Finally, we attempt to define the role of these phenomena in the natural history of beta-cell compensation, decompensation, and failure during the course of type 2 diabetes.
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Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CR-CHUM, Technopole Angus, 2901 Rachel Est, Montreal, Quebec, Canada H1W 4A4.
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