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Zhou Q, Peng Y, Ji F, Chen H, Kang W, Chan LS, Gou H, Lin Y, Huang P, Chen D, Wei Q, Su H, Liang C, Zhang X, Yu J, Wong CC. Targeting of SLC25A22 boosts the immunotherapeutic response in KRAS-mutant colorectal cancer. Nat Commun 2023; 14:4677. [PMID: 37542037 PMCID: PMC10403583 DOI: 10.1038/s41467-023-39571-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 06/19/2023] [Indexed: 08/06/2023] Open
Abstract
KRAS is an important tumor intrinsic factor driving immune suppression in colorectal cancer (CRC). In this study, we demonstrate that SLC25A22 underlies mutant KRAS-induced immune suppression in CRC. In immunocompetent male mice and humanized male mice models, SLC25A22 knockout inhibits KRAS-mutant CRC tumor growth with reduced myeloid derived suppressor cells (MDSC) but increased CD8+ T-cells, implying the reversion of mutant KRAS-driven immunosuppression. Mechanistically, we find that SLC25A22 plays a central role in promoting asparagine, which binds and activates SRC phosphorylation. Asparagine-mediated SRC promotes ERK/ETS2 signaling, which drives CXCL1 transcription. Secreted CXCL1 functions as a chemoattractant for MDSC via CXCR2, leading to an immunosuppressive microenvironment. Targeting SLC25A22 or asparagine impairs KRAS-induced MDSC infiltration in CRC. Finally, we demonstrate that the targeting of SLC25A22 in combination with anti-PD1 therapy synergizes to inhibit MDSC and activate CD8+ T cells to suppress KRAS-mutant CRC growth in vivo. We thus identify a metabolic pathway that drives immunosuppression in KRAS-mutant CRC.
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Affiliation(s)
- Qiming Zhou
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Yao Peng
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
- Shenzhen University General Hospital, Shenzhen, China
| | - Fenfen Ji
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Huarong Chen
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
- Department of Anaesthesia and Intensive Care and Peter Hung Pain Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Wei Kang
- Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Lam-Shing Chan
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Hongyan Gou
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Yufeng Lin
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Pingmei Huang
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Danyu Chen
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Qinyao Wei
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Hao Su
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
- Department of Anaesthesia and Intensive Care and Peter Hung Pain Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Cong Liang
- State Key Laboratory of Cellular Stress Biology and School of Life Sciences, Xiamen University, Xiamen, China
| | - Xiang Zhang
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Jun Yu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China.
| | - Chi Chun Wong
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China.
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Sanches JM, Zhao LN, Salehi A, Wollheim CB, Kaldis P. Pathophysiology of type 2 diabetes and the impact of altered metabolic interorgan crosstalk. FEBS J 2023; 290:620-648. [PMID: 34847289 DOI: 10.1111/febs.16306] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 10/14/2021] [Accepted: 11/29/2021] [Indexed: 02/06/2023]
Abstract
Diabetes is a complex and multifactorial disease that affects millions of people worldwide, reducing the quality of life significantly, and results in grave consequences for our health care system. In type 2 diabetes (T2D), the lack of β-cell compensatory mechanisms overcoming peripherally developed insulin resistance is a paramount factor leading to disturbed blood glucose levels and lipid metabolism. Impaired β-cell functions and insulin resistance have been studied extensively resulting in a good understanding of these pathways but much less is known about interorgan crosstalk, which we define as signaling between tissues by secreted factors. Besides hormones and organokines, dysregulated blood glucose and long-lasting hyperglycemia in T2D is associated with changes in metabolism with metabolites from different tissues contributing to the development of this disease. Recent data suggest that metabolites, such as lipids including free fatty acids and amino acids, play important roles in the interorgan crosstalk during the development of T2D. In general, metabolic remodeling affects physiological homeostasis and impacts the development of T2D. Hence, we highlight the importance of metabolic interorgan crosstalk in this review to gain enhanced knowledge of the pathophysiology of T2D, which may lead to new therapeutic approaches to treat this disease.
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Affiliation(s)
| | - Li Na Zhao
- Department of Clinical Sciences, Lund University, Malmö, Sweden
| | - Albert Salehi
- Department of Clinical Sciences, Lund University, Malmö, Sweden
| | - Claes B Wollheim
- Department of Clinical Sciences, Lund University, Malmö, Sweden.,Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Philipp Kaldis
- Department of Clinical Sciences, Lund University, Malmö, Sweden
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Role of Mitochondrial Transporters on Metabolic Rewiring of Pancreatic Adenocarcinoma: A Comprehensive Review. Cancers (Basel) 2023; 15:cancers15020411. [PMID: 36672360 PMCID: PMC9857038 DOI: 10.3390/cancers15020411] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/03/2023] [Accepted: 01/06/2023] [Indexed: 01/11/2023] Open
Abstract
Pancreatic cancer is among the deadliest cancers worldwide and commonly presents as pancreatic ductal adenocarcinoma (PDAC). Metabolic reprogramming is a hallmark of PDAC. Glucose and glutamine metabolism are extensively rewired in order to fulfil both energetic and synthetic demands of this aggressive tumour and maintain favorable redox homeostasis. The mitochondrial pyruvate carrier (MPC), the glutamine carrier (SLC1A5_Var), the glutamate carrier (GC), the aspartate/glutamate carrier (AGC), and the uncoupling protein 2 (UCP2) have all been shown to influence PDAC cell growth and progression. The expression of MPC is downregulated in PDAC and its overexpression reduces cell growth rate, whereas the other four transporters are usually overexpressed and the loss of one or more of them renders PDAC cells unable to grow and proliferate by altering the levels of crucial metabolites such as aspartate. The aim of this review is to comprehensively evaluate the current experimental evidence about the function of these carriers in PDAC metabolic rewiring. Dissecting the precise role of these transporters in the context of the tumour microenvironment is necessary for targeted drug development.
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Ishihara H. Metabolism-secretion coupling in glucose-stimulated insulin secretion. Diabetol Int 2022; 13:463-470. [PMID: 35693987 PMCID: PMC9174369 DOI: 10.1007/s13340-022-00576-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Accepted: 02/27/2022] [Indexed: 01/09/2023]
Abstract
Pancreatic β-cells in the islets of Langerhans secrete insulin in response to blood glucose levels. Precise control of the amount of insulin secreted is of critical importance for maintaining systemic carbohydrate homeostasis. It is now well established that glucose induced production of ATP from ADP and the KATP channel closure elevate cytosolic Ca2+, triggering insulin exocytosis in β-cells. However, for full activation of insulin secretion by glucose, other mechanisms besides Ca2+ elevation are needed. These mechanisms are the targets of current research and include intracellular metabolic pathways branching from glycolysis. They are metabolic pathways originating from the TCA cycle intermediates, the glycerolipid/free fatty acid cycle and the pentose phosphate pathway. Signaling effects of these pathways including degradation (removal) of protein SUMOylation, modulation of insulin vesicular energetics, and lipid modulation of exocytotic machinery may converge to fulfill insulin secretion, though the precise mechanisms have yet to be elucidated. This mini-review summarize recent advances in research on metabolic coupling mechanisms functioning in insulin secretion.
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Affiliation(s)
- Hisamitsu Ishihara
- Division of Diabetes and Metabolism, Nihon University School of Medicine, 30-1 Oyaguchi-kamicho, Itabashi-ku, Tokyo, 173-8610 Japan
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Roca FJ, Whitworth LJ, Prag HA, Murphy MP, Ramakrishnan L. Tumor necrosis factor induces pathogenic mitochondrial ROS in tuberculosis through reverse electron transport. Science 2022; 376:eabh2841. [PMID: 35737799 PMCID: PMC7612974 DOI: 10.1126/science.abh2841] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Tumor necrosis factor (TNF) is a critical host resistance factor against tuberculosis. However, excess TNF produces susceptibility by increasing mitochondrial reactive oxygen species (mROS), which initiate a signaling cascade to cause pathogenic necrosis of mycobacterium-infected macrophages. In zebrafish, we identified the mechanism of TNF-induced mROS in tuberculosis. Excess TNF in mycobacterium-infected macrophages elevates mROS production by reverse electron transport (RET) through complex I. TNF-activated cellular glutamine uptake leads to an increased concentration of succinate, a Krebs cycle intermediate. Oxidation of this elevated succinate by complex II drives RET, thereby generating the mROS superoxide at complex I. The complex I inhibitor metformin, a widely used antidiabetic drug, prevents TNF-induced mROS and necrosis of Mycobacterium tuberculosis-infected zebrafish and human macrophages; metformin may therefore be useful in tuberculosis therapy.
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Affiliation(s)
- Francisco J. Roca
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK
- Current affiliation: Department of Biochemistry and Molecular Biology B and Immunology, Biomedical Research Institute of Murcia (IMIB-Arrixaca), University of Murcia, Murcia 30120, Spain
| | - Laura J. Whitworth
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Hiran A. Prag
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Michael P. Murphy
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Lalita Ramakrishnan
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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Ježek P, Holendová B, Jabůrek M, Dlasková A, Plecitá-Hlavatá L. Contribution of Mitochondria to Insulin Secretion by Various Secretagogues. Antioxid Redox Signal 2022; 36:920-952. [PMID: 34180254 PMCID: PMC9125579 DOI: 10.1089/ars.2021.0113] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Significance: Mitochondria determine glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells by elevating ATP synthesis. As the metabolic and redox hub, mitochondria provide numerous links to the plasma membrane channels, insulin granule vesicles (IGVs), cell redox, NADH, NADPH, and Ca2+ homeostasis, all affecting insulin secretion. Recent Advances: Mitochondrial redox signaling was implicated in several modes of insulin secretion (branched-chain ketoacid [BCKA]-, fatty acid [FA]-stimulated). Mitochondrial Ca2+ influx was found to enhance GSIS, reflecting cytosolic Ca2+ oscillations induced by action potential spikes (intermittent opening of voltage-dependent Ca2+ and K+ channels) or the superimposed Ca2+ release from the endoplasmic reticulum (ER). The ATPase inhibitory factor 1 (IF1) was reported to tune the glucose sensitivity range for GSIS. Mitochondrial protein kinase A was implicated in preventing the IF1-mediated inhibition of the ATP synthase. Critical Issues: It is unknown how the redox signal spreads up to the plasma membrane and what its targets are, what the differences in metabolic, redox, NADH/NADPH, and Ca2+ signaling, and homeostasis are between the first and second GSIS phase, and whether mitochondria can replace ER in the amplification of IGV exocytosis. Future Directions: Metabolomics studies performed to distinguish between the mitochondrial matrix and cytosolic metabolites will elucidate further details. Identifying the targets of cell signaling into mitochondria and of mitochondrial retrograde metabolic and redox signals to the cell will uncover further molecular mechanisms for insulin secretion stimulated by glucose, BCKAs, and FAs, and the amplification of secretion by glucagon-like peptide (GLP-1) and metabotropic receptors. They will identify the distinction between the hub β-cells and their followers in intact and diabetic states. Antioxid. Redox Signal. 36, 920-952.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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Shahroor MA, Lasorsa FM, Porcelli V, Dweikat I, Di Noia MA, Gur M, Agostino G, Shaag A, Rinaldi T, Gasparre G, Guerra F, Castegna A, Todisco S, Abu-Libdeh B, Elpeleg O, Palmieri L. PNC2 (SLC25A36) Deficiency Associated With the Hyperinsulinism/Hyperammonemia Syndrome. J Clin Endocrinol Metab 2022; 107:1346-1356. [PMID: 34971397 DOI: 10.1210/clinem/dgab932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Indexed: 11/19/2022]
Abstract
CONTEXT The hyperinsulinism/hyperammonemia (HI/HA) syndrome, the second-most common form of congenital hyperinsulinism, has been associated with dominant mutations in GLUD1, coding for the mitochondrial enzyme glutamate dehydrogenase, that increase enzyme activity by reducing its sensitivity to allosteric inhibition by GTP. OBJECTIVE To identify the underlying genetic etiology in 2 siblings who presented with the biochemical features of HI/HA syndrome but did not carry pathogenic variants in GLUD1, and to determine the functional impact of the newly identified mutation. METHODS The patients were investigated by whole exome sequencing. Yeast complementation studies and biochemical assays on the recombinant mutated protein were performed. The consequences of stable slc25a36 silencing in HeLa cells were also investigated. RESULTS A homozygous splice site variant was identified in solute carrier family 25, member 36 (SLC25A36), encoding the pyrimidine nucleotide carrier 2 (PNC2), a mitochondrial nucleotide carrier that transports pyrimidine as well as guanine nucleotides across the inner mitochondrial membrane. The mutation leads to a 26-aa in-frame deletion in the first repeat domain of the protein, which abolishes transport activity. Furthermore, knockdown of slc25a36 expression in HeLa cells caused a marked reduction in the mitochondrial GTP content, which likely leads to a hyperactivation of glutamate dehydrogenase in our patients. CONCLUSION We report for the first time a mutation in PNC2/SLC25A36 leading to HI/HA and provide functional evidence of the molecular mechanism responsible for this phenotype. Our findings underscore the importance of mitochondrial nucleotide metabolism and expand the role of mitochondrial transporters in insulin secretion.
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Affiliation(s)
- Maher A Shahroor
- Department of Pediatrics and Genetics, Al Makassed Hospital and Al-Quds University, 95908 Jerusalem, Palestine
- Department of Neonatology, Sunnybrook Health Sciences Center, University of Toronto, M4N 3M5 Toronto, Canada
| | - Francesco M Lasorsa
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, 70125 Bari, Italy
| | - Vito Porcelli
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Imad Dweikat
- Metabolic Unit, An-Najah National University, P467 Nablus, Palestine
| | - Maria Antonietta Di Noia
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Michal Gur
- Department of Genetics, Hadassah, Hebrew University Medical Center, 91120 Jerusalem, Israel
| | - Giulia Agostino
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Avraham Shaag
- Department of Genetics, Hadassah, Hebrew University Medical Center, 91120 Jerusalem, Israel
| | - Teresa Rinaldi
- Pasteur Institute-Cenci Bolognetti Foundation, Department of Biology and Biotechnology "Charles Darwin", University of Rome La Sapienza, 00185 Rome, Italy
| | - Giuseppe Gasparre
- Department of Medical and Surgical Sciences (DIMEC), Unit of Medical Genetics and Center for Applied Biomedical Research (CRBA), University of Bologna, 40138 Bologna, Italy
| | - Flora Guerra
- Department of Medical and Surgical Sciences (DIMEC), Unit of Medical Genetics and Center for Applied Biomedical Research (CRBA), University of Bologna, 40138 Bologna, Italy
| | - Alessandra Castegna
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, 70125 Bari, Italy
| | - Simona Todisco
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Bassam Abu-Libdeh
- Department of Pediatrics and Genetics, Al Makassed Hospital and Al-Quds University, 95908 Jerusalem, Palestine
| | - Orly Elpeleg
- Department of Genetics, Hadassah, Hebrew University Medical Center, 91120 Jerusalem, Israel
| | - Luigi Palmieri
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, 70125 Bari, Italy
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Rohli KE, Boyer CK, Blom SE, Stephens SB. Nutrient Regulation of Pancreatic Islet β-Cell Secretory Capacity and Insulin Production. Biomolecules 2022; 12:335. [PMID: 35204835 PMCID: PMC8869698 DOI: 10.3390/biom12020335] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/16/2022] [Accepted: 02/17/2022] [Indexed: 01/27/2023] Open
Abstract
Pancreatic islet β-cells exhibit tremendous plasticity for secretory adaptations that coordinate insulin production and release with nutritional demands. This essential feature of the β-cell can allow for compensatory changes that increase secretory output to overcome insulin resistance early in Type 2 diabetes (T2D). Nutrient-stimulated increases in proinsulin biosynthesis may initiate this β-cell adaptive compensation; however, the molecular regulators of secretory expansion that accommodate the increased biosynthetic burden of packaging and producing additional insulin granules, such as enhanced ER and Golgi functions, remain poorly defined. As these adaptive mechanisms fail and T2D progresses, the β-cell succumbs to metabolic defects resulting in alterations to glucose metabolism and a decline in nutrient-regulated secretory functions, including impaired proinsulin processing and a deficit in mature insulin-containing secretory granules. In this review, we will discuss how the adaptative plasticity of the pancreatic islet β-cell's secretory program allows insulin production to be carefully matched with nutrient availability and peripheral cues for insulin signaling. Furthermore, we will highlight potential defects in the secretory pathway that limit or delay insulin granule biosynthesis, which may contribute to the decline in β-cell function during the pathogenesis of T2D.
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Affiliation(s)
- Kristen E. Rohli
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA 52242, USA; (K.E.R.); (C.K.B.); (S.E.B.)
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Cierra K. Boyer
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA 52242, USA; (K.E.R.); (C.K.B.); (S.E.B.)
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Sandra E. Blom
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA 52242, USA; (K.E.R.); (C.K.B.); (S.E.B.)
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Samuel B. Stephens
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA 52242, USA; (K.E.R.); (C.K.B.); (S.E.B.)
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA
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9
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Shen Y, Zhang Y, Li W, Chen K, Xiang M, Ma H. Glutamine metabolism: from proliferating cells to cardiomyocytes. Metabolism 2021; 121:154778. [PMID: 33901502 DOI: 10.1016/j.metabol.2021.154778] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 04/16/2021] [Accepted: 04/19/2021] [Indexed: 02/06/2023]
Abstract
Glutamine is a major energy source for rapidly dividing cells, such as hematopoietic stem cells and cancer cells. Reliance on glutamine is therefore regarded as a metabolic hallmark of proliferating cells. Moreover, reprogramming glutamine metabolism by various factors, including tissue type, microenvironment, pro-oncogenes, and tumor suppressor genes, can facilitate stem cell fate decisions, tumor recurrence, and drug resistance. However, the significance of glutamine metabolism in cardiomyocytes, an end-differentiated cell type, is not fully understood. Existing evidence suggests important roles of glutamine metabolism in the development of cardiovascular diseases. In this review, we have focused on glutaminolysis and its regulatory network in proliferating cells. We have summarized current findings about the role of glutamine utilization in cardiomyocytes and have discussed possibilities of targeting glutamine metabolism for the treatment of cardiovascular diseases.
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Affiliation(s)
- Yimin Shen
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Yuhao Zhang
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Wudi Li
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Kaijie Chen
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Meixiang Xiang
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China.
| | - Hong Ma
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China.
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10
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Bauchle CJ, Rohli KE, Boyer CK, Pal V, Rocheleau JV, Liu S, Imai Y, Taylor EB, Stephens SB. Mitochondrial Efflux of Citrate and Isocitrate Is Fully Dispensable for Glucose-Stimulated Insulin Secretion and Pancreatic Islet β-Cell Function. Diabetes 2021; 70:1717-1728. [PMID: 34039628 PMCID: PMC8385611 DOI: 10.2337/db21-0037] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 05/22/2021] [Indexed: 11/13/2022]
Abstract
The defining feature of pancreatic islet β-cell function is the precise coordination of changes in blood glucose levels with insulin secretion to regulate systemic glucose homeostasis. While ATP has long been heralded as a critical metabolic coupling factor to trigger insulin release, glucose-derived metabolites have been suggested to further amplify fuel-stimulated insulin secretion. The mitochondrial export of citrate and isocitrate through the citrate-isocitrate carrier (CIC) has been suggested to initiate a key pathway that amplifies glucose-stimulated insulin secretion, though the physiological significance of β-cell CIC-to-glucose homeostasis has not been established. Here, we generated constitutive and adult CIC β-cell knockout (KO) mice and demonstrate that these animals have normal glucose tolerance, similar responses to diet-induced obesity, and identical insulin secretion responses to various fuel secretagogues. Glucose-stimulated NADPH production was impaired in β-cell CIC KO islets, whereas glutathione reduction was retained. Furthermore, suppression of the downstream enzyme cytosolic isocitrate dehydrogenase (Idh1) inhibited insulin secretion in wild-type islets but failed to impact β-cell function in β-cell CIC KO islets. Our data demonstrate that the mitochondrial CIC is not required for glucose-stimulated insulin secretion and that additional complexities exist for the role of Idh1 and NADPH in the regulation of β-cell function.
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Affiliation(s)
- Casey J Bauchle
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA
| | - Kristen E Rohli
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA
| | - Cierra K Boyer
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Department of Pharmacology, University of Iowa, Iowa City, IA
| | - Vidhant Pal
- Institute of Biomedical Engineering, Toronto, Ontario, Canada
- Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Jonathan V Rocheleau
- Institute of Biomedical Engineering, Toronto, Ontario, Canada
- Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Siming Liu
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA
| | - Yumi Imai
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, IA
- Iowa City Veterans Affairs Medical Center, Iowa City, IA
| | - Eric B Taylor
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, IA
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
| | - Samuel B Stephens
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, IA
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, IA
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11
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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12
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Mitochondrial Carriers Regulating Insulin Secretion Profiled in Human Islets upon Metabolic Stress. Biomolecules 2020; 10:biom10111543. [PMID: 33198243 PMCID: PMC7697104 DOI: 10.3390/biom10111543] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/28/2020] [Accepted: 11/10/2020] [Indexed: 12/27/2022] Open
Abstract
Chronic exposure of β-cells to nutrient-rich metabolic stress impairs mitochondrial metabolism and its coupling to insulin secretion. We exposed isolated human islets to different metabolic stresses for 3 days: 0.4 mM oleate or 0.4 mM palmitate at physiological 5.5 mM glucose (lipotoxicity), high 25 mM glucose (glucotoxicity), and high 25 mM glucose combined with 0.4 mM oleate and/or palmitate (glucolipotoxicity). Then, we profiled the mitochondrial carriers and associated genes with RNA-Seq. Diabetogenic conditions, and in particular glucotoxicity, increased expression of several mitochondrial solute carriers in human islets, such as the malate carrier DIC, the α-ketoglutarate-malate exchanger OGC, and the glutamate carrier GC1. Glucotoxicity also induced a general upregulation of the electron transport chain machinery, while palmitate largely counteracted this effect. Expression of different components of the TOM/TIM mitochondrial protein import system was increased by glucotoxicity, whereas glucolipotoxicity strongly upregulated its receptor subunit TOM70. Expression of the mitochondrial calcium uniporter MCU was essentially preserved by metabolic stresses. However, glucotoxicity altered expression of regulatory elements of calcium influx as well as the Na+/Ca2+ exchanger NCLX, which mediates calcium efflux. Overall, the expression profile of mitochondrial carriers and associated genes was modified by the different metabolic stresses exhibiting nutrient-specific signatures.
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13
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Drosophila melanogaster Mitochondrial Carriers: Similarities and Differences with the Human Carriers. Int J Mol Sci 2020; 21:ijms21176052. [PMID: 32842667 PMCID: PMC7504413 DOI: 10.3390/ijms21176052] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/19/2020] [Accepted: 08/19/2020] [Indexed: 12/15/2022] Open
Abstract
Mitochondrial carriers are a family of structurally related proteins responsible for the exchange of metabolites, cofactors and nucleotides between the cytoplasm and mitochondrial matrix. The in silico analysis of the Drosophila melanogaster genome has highlighted the presence of 48 genes encoding putative mitochondrial carriers, but only 20 have been functionally characterized. Despite most Drosophila mitochondrial carrier genes having human homologs and sharing with them 50% or higher sequence identity, D. melanogaster genes display peculiar differences from their human counterparts: (1) in the fruit fly, many genes encode more transcript isoforms or are duplicated, resulting in the presence of numerous subfamilies in the genome; (2) the expression of the energy-producing genes in D. melanogaster is coordinated from a motif known as Nuclear Respiratory Gene (NRG), a palindromic 8-bp sequence; (3) fruit-fly duplicated genes encoding mitochondrial carriers show a testis-biased expression pattern, probably in order to keep a duplicate copy in the genome. Here, we review the main features, biological activities and role in the metabolism of the D. melanogaster mitochondrial carriers characterized to date, highlighting similarities and differences with their human counterparts. Such knowledge is very important for obtaining an integrated view of mitochondrial function in D. melanogaster metabolism.
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14
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Mitochondrial Carriers for Aspartate, Glutamate and Other Amino Acids: A Review. Int J Mol Sci 2019; 20:ijms20184456. [PMID: 31510000 PMCID: PMC6769469 DOI: 10.3390/ijms20184456] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 09/05/2019] [Accepted: 09/06/2019] [Indexed: 12/19/2022] Open
Abstract
Members of the mitochondrial carrier (MC) protein family transport various molecules across the mitochondrial inner membrane to interlink steps of metabolic pathways and biochemical processes that take place in different compartments; i.e., are localized partly inside and outside the mitochondrial matrix. MC substrates consist of metabolites, inorganic anions (such as phosphate and sulfate), nucleotides, cofactors and amino acids. These compounds have been identified by in vitro transport assays based on the uptake of radioactively labeled substrates into liposomes reconstituted with recombinant purified MCs. By using this approach, 18 human, plant and yeast MCs for amino acids have been characterized and shown to transport aspartate, glutamate, ornithine, arginine, lysine, histidine, citrulline and glycine with varying substrate specificities, kinetics, influences of the pH gradient, and capacities for the antiport and uniport mode of transport. Aside from providing amino acids for mitochondrial translation, the transport reactions catalyzed by these MCs are crucial in energy, nitrogen, nucleotide and amino acid metabolism. In this review we dissect the transport properties, phylogeny, regulation and expression levels in different tissues of MCs for amino acids, and summarize the main structural aspects known until now about MCs. The effects of their disease-causing mutations and manipulation of their expression levels in cells are also considered as clues for understanding their physiological functions.
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15
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Amino acid transporters in the regulation of insulin secretion and signalling. Biochem Soc Trans 2019; 47:571-590. [PMID: 30936244 DOI: 10.1042/bst20180250] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 02/24/2019] [Accepted: 02/25/2019] [Indexed: 01/02/2023]
Abstract
Amino acids are increasingly recognised as modulators of nutrient disposal, including their role in regulating blood glucose through interactions with insulin signalling. More recently, cellular membrane transporters of amino acids have been shown to form a pivotal part of this regulation as they are primarily responsible for controlling cellular and circulating amino acid concentrations. The availability of amino acids regulated by transporters can amplify insulin secretion and modulate insulin signalling in various tissues. In addition, insulin itself can regulate the expression of numerous amino acid transporters. This review focuses on amino acid transporters linked to the regulation of insulin secretion and signalling with a focus on those of the small intestine, pancreatic β-islet cells and insulin-responsive tissues, liver and skeletal muscle. We summarise the role of the amino acid transporter B0AT1 (SLC6A19) and peptide transporter PEPT1 (SLC15A1) in the modulation of global insulin signalling via the liver-secreted hormone fibroblast growth factor 21 (FGF21). The role of vesicular vGLUT (SLC17) and mitochondrial SLC25 transporters in providing glutamate for the potentiation of insulin secretion is covered. We also survey the roles SNAT (SLC38) family and LAT1 (SLC7A5) amino acid transporters play in the regulation of and by insulin in numerous affective tissues. We hypothesise the small intestine amino acid transporter B0AT1 represents a crucial nexus between insulin, FGF21 and incretin hormone signalling pathways. The aim is to give an integrated overview of the important role amino acid transporters have been found to play in insulin-regulated nutrient signalling.
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16
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Chen MW, Wu XJ. SLC25A22 Promotes Proliferation and Metastasis of Osteosarcoma Cells via the PTEN Signaling Pathway. Technol Cancer Res Treat 2019; 17:1533033818811143. [PMID: 30482097 PMCID: PMC6259056 DOI: 10.1177/1533033818811143] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Osteosarcoma is a highly malignant bone tumor. However, due to the high complexity of the occurrence and metastasis of osteosarcoma, the exact mechanism promoting its development and progression remains to be elucidated. This study highlights the causal link between solute carrier family 25 member 22 (SLC25A22) and the development, progression, and metastasis of osteosarcoma. SLC25A22 is upregulated in human osteosarcoma and predicts a poor prognosis. The upregulation of SLC25A22 in osteosarcoma tissues was significantly associated with cell proliferation, invasion, and metastasis. Studies of functional gain (overexpression) and loss (knockdown) showed that SLC25A22 significantly increases the ability of osteosarcoma cells to proliferate, as well as invade and metastasize in vitro. At the same time, the expression of SLC25A22 promoted the progression of the cellcycle of osteosarcoma cell lines and inhibited the apoptosis of osteosarcoma cells. Analysis using a mouse xenograft model showed that xenografts of SLC25A22 stable overexpressing osteosarcoma cells had a significant increase in tumor volume and weight compared to the control group. Lung metastasis models in mice showed that expression of SLC25A22 promoted lung metastasis of osteosarcoma in vivo. Furthermore, SLC25A22 inhibited phosphatase and tensin homolog expression and increased phosphorylation of protein kinase b (Akt) and Focal Adhesion Kinase (FAK) in the phosphatase and tensin homolog signaling pathway. In summary, SLC25A22 is highly expressed in osteosarcoma, promoting osteosarcoma cell proliferation and invasion by inhibiting the phosphatase and tensin homolog signaling pathway.
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Affiliation(s)
- Ming-Wei Chen
- 1 Orthopedics department, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan province, China
| | - Xue-Jian Wu
- 1 Orthopedics department, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan province, China
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17
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TAKAHASHI H, YOKOI N, SEINO S. Glutamate as intracellular and extracellular signals in pancreatic islet functions. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2019; 95:246-260. [PMID: 31189778 PMCID: PMC6751295 DOI: 10.2183/pjab.95.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/08/2019] [Indexed: 05/25/2023]
Abstract
l-Glutamate is one of the most abundant amino acids in the body and is a constituent of proteins and a substrate in metabolism. It is well known that glutamate serves as a primary excitatory neurotransmitter and a critical neuromodulator in the brain. Recent studies have shown that in addition to its pivotal role in neural functions, glutamate plays many important roles in a variety of cellular functions, including those as intracellular and extracellular signals. In pancreatic islets, glutamate is now known to be required for the normal regulation of insulin secretion, such as incretin-induced insulin secretion. In this review, we primarily discuss the physiological and pathophysiological roles of glutamate as intracellular and extracellular signals in the functions of pancreatic islets.
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Affiliation(s)
- Harumi TAKAHASHI
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan
| | - Norihide YOKOI
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan
| | - Susumu SEINO
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan
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18
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Porcelli V, Vozza A, Calcagnile V, Gorgoglione R, Arrigoni R, Fontanesi F, Marobbio CMT, Castegna A, Palmieri F, Palmieri L. Molecular identification and functional characterization of a novel glutamate transporter in yeast and plant mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1249-1258. [PMID: 30297026 DOI: 10.1016/j.bbabio.2018.08.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 08/01/2018] [Accepted: 08/02/2018] [Indexed: 11/19/2022]
Abstract
The genome of Saccharomyces cerevisiae encodes 35 members of the mitochondrial carrier family (MCF) and 58 MCF members are coded by the genome of Arabidopsis thaliana, most of which have been functionally characterized. Here two members of this family, Ymc2p from S. cerevisiae and BOU from Arabidopsis, have been thoroughly characterized. These proteins were overproduced in bacteria and reconstituted into liposomes. Their transport properties and kinetic parameters demonstrate that Ymc2p and BOU transport glutamate, and to a much lesser extent L-homocysteinesulfinate, but not other amino acids and many other tested metabolites. Transport catalyzed by both carriers was saturable, inhibited by mercuric chloride and dependent on the proton gradient across the proteoliposomal membrane. The growth phenotype of S. cerevisiae cells lacking the genes ymc2 and agc1, which encodes the only other S. cerevisiae carrier capable to transport glutamate besides aspartate, was fully complemented by expressing Ymc2p, Agc1p or BOU. Mitochondrial extracts derived from ymc2Δagc1Δ cells, reconstituted into liposomes, exhibited no glutamate transport at variance with wild-type, ymc2Δ and agc1Δ cells, showing that S. cerevisiae cells grown in the presence of acetate do not contain additional mitochondrial transporters for glutamate besides Ymc2p and Agc1p. Furthermore, mitochondria isolated from wild-type, ymc2Δ and agc1Δ strains, but not from the double mutant ymc2Δagc1Δ strain, swell in isosmotic ammonium glutamate showing that glutamate is transported by Ymc2p and Agc1p together with a H+. It is proposed that the function of Ymc2p and BOU is to transport glutamate across the mitochondrial inner membrane and thereby play a role in intermediary metabolism, C1 metabolism and mitochondrial protein synthesis.
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Affiliation(s)
- Vito Porcelli
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Angelo Vozza
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Valeria Calcagnile
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Ruggiero Gorgoglione
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Roberto Arrigoni
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Bari, Italy
| | - Flavia Fontanesi
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Carlo M T Marobbio
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy; CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Bari, Italy
| | - Alessandra Castegna
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy; CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Bari, Italy
| | - Ferdinando Palmieri
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy; CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Bari, Italy
| | - Luigi Palmieri
- Laboratory of Biochemistry and Molecular Biology, Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy; CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Bari, Italy.
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19
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Martinez-Sanchez A, Nguyen-Tu MS, Cebola I, Yavari A, Marchetti P, Piemonti L, de Koning E, Shapiro AMJ, Johnson P, Sakamoto K, Smith DM, Leclerc I, Ashrafian H, Ferrer J, Rutter GA. MiR-184 expression is regulated by AMPK in pancreatic islets. FASEB J 2018; 32:2587-2600. [PMID: 29269398 PMCID: PMC6207280 DOI: 10.1096/fj.201701100r] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
AMPK is a critical energy sensor and target for widely used antidiabetic drugs. In β cells, elevated glucose concentrations lower AMPK activity, and the ablation of both catalytic subunits [β-cell–specific AMPK double-knockout (βAMPKdKO) mice] impairs insulin secretion in vivo and β-cell identity. MicroRNAs (miRNAs) are small RNAs that silence gene expression that are essential for pancreatic β-cell function and identity and altered in diabetes. Here, we have explored the miRNAs acting downstream of AMPK in mouse and human β cells. We identified 14 down-regulated and 9 up-regulated miRNAs in βAMPKdKO vs. control islets. Gene ontology analysis of targeted transcripts revealed enrichment in pathways important for β-cell function and identity. The most down-regulated miRNA was miR-184 (miR-184-3p), an important regulator of β-cell function and compensatory expansion that is controlled by glucose and reduced in diabetes. We demonstrate that AMPK is a potent regulator and an important mediator of the negative effects of glucose on miR-184 expression. Additionally, we reveal sexual dimorphism in miR-184 expression in mouse and human islets. Collectively, these data demonstrate that glucose-mediated changes in AMPK activity are central for the regulation of miR-184 and other miRNAs in islets and provide a link between energy status and gene expression in β cells.—Martinez-Sanchez, A., Nguyen-Tu, M.-S., Cebola, I., Yavari, A., Marchetti, P., Piemonti, L., de Koning, E., Shapiro, A. M. J., Johnson, P., Sakamoto, K., Smith, D. M., Leclerc, I., Ashrafian, H., Ferrer, J., Rutter, G. A. MiR-184 expression is regulated by AMPK in pancreatic islets.
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Affiliation(s)
- Aida Martinez-Sanchez
- Section of Cell Biology and Functional Genomics Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Marie-Sophie Nguyen-Tu
- Section of Cell Biology and Functional Genomics Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Ines Cebola
- Beta Cell Genome Regulation Laboratory, Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Arash Yavari
- Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Piero Marchetti
- Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy
| | - Lorenzo Piemonti
- San Raffaele Diabetes Research Institute (SR-DRI), Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy.,Vita-Salute San Raffaele University, Milan, Italy
| | - Eelco de Koning
- Hubrecht Institute, Utrecht, The Netherlands.,Department of Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - A M James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | - Paul Johnson
- Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom
| | - Kei Sakamoto
- Nestle Institute of Health Sciences, Lausanne, Switzerland
| | - David M Smith
- AstraZeneca Research and Development, Innovative Medicines and Early Development, Discovery Sciences, Cambridge, United Kingdom
| | - Isabelle Leclerc
- Section of Cell Biology and Functional Genomics Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Houman Ashrafian
- Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Jorge Ferrer
- Beta Cell Genome Regulation Laboratory, Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
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20
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Profilo E, Peña-Altamira LE, Corricelli M, Castegna A, Danese A, Agrimi G, Petralla S, Giannuzzi G, Porcelli V, Sbano L, Viscomi C, Massenzio F, Palmieri EM, Giorgi C, Fiermonte G, Virgili M, Palmieri L, Zeviani M, Pinton P, Monti B, Palmieri F, Lasorsa FM. Down-regulation of the mitochondrial aspartate-glutamate carrier isoform 1 AGC1 inhibits proliferation and N-acetylaspartate synthesis in Neuro2A cells. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1422-1435. [DOI: 10.1016/j.bbadis.2017.02.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 02/02/2017] [Accepted: 02/20/2017] [Indexed: 12/26/2022]
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21
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Goubert E, Mircheva Y, Lasorsa FM, Melon C, Profilo E, Sutera J, Becq H, Palmieri F, Palmieri L, Aniksztejn L, Molinari F. Inhibition of the Mitochondrial Glutamate Carrier SLC25A22 in Astrocytes Leads to Intracellular Glutamate Accumulation. Front Cell Neurosci 2017; 11:149. [PMID: 28620281 PMCID: PMC5449474 DOI: 10.3389/fncel.2017.00149] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 05/09/2017] [Indexed: 12/16/2022] Open
Abstract
The solute carrier family 25 (SLC25) drives the import of a large diversity of metabolites into mitochondria, a key cellular structure involved in many metabolic functions. Mutations of the mitochondrial glutamate carrier SLC25A22 (also named GC1) have been identified in early epileptic encephalopathy (EEE) and migrating partial seizures in infancy (MPSI) but the pathophysiological mechanism of GC1 deficiency is still unknown, hampered by the absence of an in vivo model. This carrier is mainly expressed in astrocytes and is the principal gate for glutamate entry into mitochondria. A sufficient supply of energy is essential for the proper function of the brain and mitochondria have a pivotal role in maintaining energy homeostasis. In this work, we wanted to study the consequences of GC1 absence in an in vitro model in order to understand if glutamate catabolism and/or mitochondrial function could be affected. First, short hairpin RNA (shRNA) designed to specifically silence GC1 were validated in rat C6 glioma cells. Silencing GC1 in C6 resulted in a reduction of the GC1 mRNA combined with a decrease of the mitochondrial glutamate carrier activity. Then, primary astrocyte cultures were prepared and transfected with shRNA-GC1 or mismatch-RNA (mmRNA) constructs using the Neon® Transfection System in order to target a high number of primary astrocytes, more than 64%. Silencing GC1 in primary astrocytes resulted in a reduced nicotinamide adenine dinucleotide (Phosphate) (NAD(P)H) formation upon glutamate stimulation. We also observed that the mitochondrial respiratory chain (MRC) was functional after glucose stimulation but not activated by glutamate, resulting in a lower level of cellular adenosine triphosphate (ATP) in silenced astrocytes compared to control cells. Moreover, GC1 inactivation resulted in an intracellular glutamate accumulation. Our results show that mitochondrial glutamate transport via GC1 is important in sustaining glutamate homeostasis in astrocytes. Main Points:The mitochondrial respiratory chain is functional in absence of GC1 Lack of glutamate oxidation results in a lower global ATP level Lack of mitochondrial glutamate transport results in intracellular glutamate accumulation
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Affiliation(s)
| | - Yanina Mircheva
- INMED, INSERM, Aix-Marseille UniversitéMarseille, France.,Centre De Recherche De L'Institut Universitaire En Santé Mentale de QuébecQuebec City, QC, Canada
| | - Francesco M Lasorsa
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
| | | | - Emanuela Profilo
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
| | - Julie Sutera
- INMED, INSERM, Aix-Marseille UniversitéMarseille, France
| | - Hélène Becq
- INMED, INSERM, Aix-Marseille UniversitéMarseille, France
| | - Ferdinando Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
| | - Luigi Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, and CNR Institute of Biomembranes, Bioenergetics and Molecular BiotechnologiesBari, Italy
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22
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Wong CC, Qian Y, Li X, Xu J, Kang W, Tong JH, To KF, Jin Y, Li W, Chen H, Go MYY, Wu JL, Cheng KW, Ng SSM, Sung JJY, Cai Z, Yu J. SLC25A22 Promotes Proliferation and Survival of Colorectal Cancer Cells With KRAS Mutations and Xenograft Tumor Progression in Mice via Intracellular Synthesis of Aspartate. Gastroenterology 2016; 151:945-960.e6. [PMID: 27451147 DOI: 10.1053/j.gastro.2016.07.011] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 06/14/2016] [Accepted: 07/06/2016] [Indexed: 12/17/2022]
Abstract
BACKGROUND & AIMS Many colorectal cancer (CRC) cells contain mutations in KRAS. Analyses of CRC cells with mutations in APC or CTNNB1 and KRAS identified SLC25A22, which encodes mitochondrial glutamate transporter, as a synthetic lethal gene. We investigated the functions of SLC25A22 in CRC cells with mutations in KRAS. METHODS We measured levels of SLC25A22 messenger RNA and protein in paired tumor and nontumor colon tissues collected from 130 patients in Hong Kong and 17 patients in China and compared protein levels with patient survival times. Expression of SLC25A22 was knocked down in KRAS mutant CRC cell lines (DLD1, HCT116, LOVO, SW480, SW620, and SW1116) and CRC cell lines without mutations in KRAS (CACO-2, COLO205, HT29, and SW48); cells were analyzed for colony formation, proliferation, glutaminolysis and aspartate synthesis, and apoptosis in Matrigel and polymerase chain reaction array analyses. DLD1 and HCT116 cells with SLC25A22 knockdown were grown as xenograft tumors in nude mice; tumor growth and metastasis were measured. SLC25A22 was expressed ectopically in HCT116 cells, which were analyzed in vitro and grown as xenograft tumors in nude mice. RESULTS Levels of SLC25A22 messenger RNA and protein were increased in colorectal tumor tissues compared with matched nontumor colon tissues; increased protein levels were associated with shorter survival times of patients (P = .01). Knockdown of SLC25A22 in KRAS mutant CRC cells reduced their proliferation, migration, and invasion in vitro, and tumor formation and metastasis in mice, compared with cells without SLC25A22 knockdown. Knockdown of SLC25A22 reduced aspartate biosynthesis, leading to apoptosis, decreased cell proliferation in KRAS mutant CRC cells. Incubation of KRAS mutant CRC cells with knockdown of SLC25A22 with aspartate increased proliferation and reduced apoptosis, which required GOT1, indicating that oxaloacetate is required for cell survival. Decreased levels of oxaloacetate in cells with knockdown of SLC25A22 reduced regeneration of oxidized nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate. Reduced oxidized nicotinamide adenine dinucleotide inhibited glycolysis and decreased levels of adenosine triphosphate, which inactivated mitogen-activated protein kinase kinase and extracellular signal-regulated kinase signaling via activation of AMP-activated protein kinase. An increased ratio of oxidized nicotinamide adenine dinucleotide phosphate to reduced nicotinamide adenine dinucleotide phosphate induced oxidative stress and glutathione oxidation, which suppressed cell proliferation. Asparagine synthetase mediated synthesis of asparagine from aspartate to promote cell migration. CONCLUSIONS SLC25A22 promotes proliferation and migration of CRC cells with mutations KRAS, and formation and metastasis of CRC xenograft tumors in mice. Patients with colorectal tumors that express increased levels of SLC25A22 have shorter survival times than patients whose tumors have lower levels. SLC25A22 induces intracellular synthesis of aspartate, activation of mitogen-activated protein kinase kinase and extracellular signal-regulated kinase signaling and reduces oxidative stress.
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Affiliation(s)
- Chi Chun Wong
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
| | - Yun Qian
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China; Department of Gastroenterology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Zhejiang, China
| | - Xiaona Li
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China
| | - Jiaying Xu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Wei Kang
- Department of Anatomical and Cellular Pathology, State Key Laboratory of Oncology in South China, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Joanna H Tong
- Department of Anatomical and Cellular Pathology, State Key Laboratory of Oncology in South China, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Ka-Fai To
- Department of Anatomical and Cellular Pathology, State Key Laboratory of Oncology in South China, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
| | - Ye Jin
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Weilin Li
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Huarong Chen
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Minnie Y Y Go
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Jian-Lin Wu
- State Key Laboratory for Quality Research in Chinese Medicines, Macau University of Science and Technology, Macau, China
| | - Ka Wing Cheng
- College of Engineering, Peking University, Peking, China
| | - Simon S M Ng
- Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China
| | - Joseph J Y Sung
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China
| | - Zongwei Cai
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China
| | - Jun Yu
- Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
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Vetterli L, Carobbio S, Frigerio F, Karaca M, Maechler P. The Amplifying Pathway of the β-Cell Contributes to Diet-induced Obesity. J Biol Chem 2016; 291:13063-75. [PMID: 27137930 DOI: 10.1074/jbc.m115.707448] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Indexed: 12/24/2022] Open
Abstract
Efficient energy storage in adipose tissues requires optimal function of the insulin-producing β-cell, whereas its dysfunction promotes diabetes. The associated paradox related to β-cell efficiency is that excessive accumulation of fat in adipose tissue predisposes for type 2 diabetes. Insulin exocytosis is regulated by intracellular metabolic signal transduction, with glutamate dehydrogenase playing a key role in the amplification of the secretory response. Here, we used mice with β-cell-selective glutamate dehydrogenase deletion (βGlud1(-/-)), lacking an amplifying pathway of insulin secretion. As opposed to control mice, βGlud1(-/-) animals fed a high calorie diet maintained glucose tolerance and did not develop diet-induced obesity. Islets of βGlud1(-/-) mice did not increase their secretory response upon high calorie feeding, as did islets of control mice. Inhibited adipose tissue expansion observed in knock-out mice correlated with lower expression of genes responsible for adipogenesis. Rather than being efficiently stored, lipids were consumed at a higher rate in βGlud1(-/-) mice compared with controls, in particular during food intake periods. These results show that reduced β-cell function prior to high calorie feeding prevented diet-induced obesity.
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Affiliation(s)
- Laurène Vetterli
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Stefania Carobbio
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Francesca Frigerio
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Melis Karaca
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
| | - Pierre Maechler
- From the Department of Cell Physiology and Metabolism and Faculty Diabetes Center, Geneva University Medical Centre, 1211 Geneva 4, Switzerland
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24
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Yokoi N, Gheni G, Takahashi H, Seino S. β-Cell glutamate signaling: Its role in incretin-induced insulin secretion. J Diabetes Investig 2016; 7 Suppl 1:38-43. [PMID: 27186354 PMCID: PMC4854503 DOI: 10.1111/jdi.12468] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 12/17/2015] [Accepted: 12/21/2015] [Indexed: 11/30/2022] Open
Abstract
Insulin secretion from the pancreatic β-cell (referred to as β-cell hereafter) plays a central role in glucose homeostasis. Impaired insulin secretion is a major factor contributing to the development of diabetes and, therefore, is an important target for treatment of the disease. Cyclic adenosine monophosphate is a key second messenger in β-cells that amplifies insulin secretion. Incretins released by the gut potentiate insulin secretion through cyclic adenosine monophosphate signaling in β-cells, which is the basis for the incretin-based diabetes therapies now being used worldwide. Despite its importance, the interaction between glucose metabolism and incretin/cyclic adenosine monophosphate signaling in β-cells has long been unknown. A recent study showed that cytosolic glutamate produced by glucose metabolism in β-cells is a key signal in incretin-induced insulin secretion. Here we review the physiological and pathophysiological roles of β-cell glutamate signaling in incretin-induced insulin secretion.
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Affiliation(s)
- Norihide Yokoi
- Division of Molecular and Metabolic Medicine Kobe University Graduate School of Medicine Kobe Japan
| | - Ghupurjan Gheni
- Division of Molecular and Metabolic Medicine Kobe University Graduate School of Medicine Kobe Japan
| | - Harumi Takahashi
- Division of Molecular and Metabolic Medicine Kobe University Graduate School of Medicine Kobe Japan
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine Kobe University Graduate School of Medicine Kobe Japan
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25
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Brun T, Maechler P. Beta-cell mitochondrial carriers and the diabetogenic stress response. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2540-9. [PMID: 26979549 DOI: 10.1016/j.bbamcr.2016.03.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 01/09/2023]
Abstract
Mitochondria play a central role in pancreatic beta-cells by coupling metabolism of the secretagogue glucose to distal events of regulated insulin exocytosis. This process requires transports of both metabolites and nucleotides in and out of the mitochondria. The molecular identification of mitochondrial carriers and their respective contribution to beta-cell function have been uncovered only recently. In type 2 diabetes, mitochondrial dysfunction is an early event and may precipitate beta-cell loss. Under diabetogenic conditions, characterized by glucotoxicity and lipotoxicity, the expression profile of mitochondrial carriers is selectively modified. This review describes the role of mitochondrial carriers in beta-cells and the selective changes in response to glucolipotoxicity. In particular, we discuss the importance of the transfer of metabolites (pyruvate, citrate, malate, and glutamate) and nucleotides (ATP, NADH, NADPH) for beta-cell function and dysfunction. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Thierry Brun
- Department of Cell Physiology and Metabolism, Faculty Diabetes Center, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, Faculty Diabetes Center, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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26
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Palmieri F, Monné M. Discoveries, metabolic roles and diseases of mitochondrial carriers: A review. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2362-78. [PMID: 26968366 DOI: 10.1016/j.bbamcr.2016.03.007] [Citation(s) in RCA: 159] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 02/29/2016] [Accepted: 03/01/2016] [Indexed: 12/25/2022]
Abstract
Mitochondrial carriers (MCs) are a superfamily of nuclear-encoded proteins that are mostly localized in the inner mitochondrial membrane and transport numerous metabolites, nucleotides, cofactors and inorganic anions. Their unique sequence features, i.e., a tripartite structure, six transmembrane α-helices and a three-fold repeated signature motif, allow MCs to be easily recognized. This review describes how the functions of MCs from Saccharomyces cerevisiae, Homo sapiens and Arabidopsis thaliana (listed in the first table) were discovered after the genome sequence of S. cerevisiae was determined in 1996. In the genomic era, more than 50 previously unknown MCs from these organisms have been identified and characterized biochemically using a method consisting of gene expression, purification of the recombinant proteins, their reconstitution into liposomes and transport assays (EPRA). Information derived from studies with intact mitochondria, genetic and metabolic evidence, sequence similarity, phylogenetic analysis and complementation of knockout phenotypes have guided the choice of substrates that were tested in the transport assays. In addition, the diseases associated to defects of human MCs have been briefly reviewed. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Ferdinando Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy.
| | - Magnus Monné
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy; Department of Sciences, University of Basilicata, Via Ateneo Lucano 10, 85100 Potenza, Italy
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27
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Otter S, Lammert E. Exciting Times for Pancreatic Islets: Glutamate Signaling in Endocrine Cells. Trends Endocrinol Metab 2016; 27:177-188. [PMID: 26740469 DOI: 10.1016/j.tem.2015.12.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/11/2015] [Accepted: 12/14/2015] [Indexed: 01/14/2023]
Abstract
Glutamate represents a key excitatory neurotransmitter in the central nervous system, and also modulates the function and viability of endocrine cells in pancreatic islets. In insulin-secreting beta cells, glutamate acts as an intracellular messenger, and its transport into secretory granules promotes glucose- and incretin-stimulated insulin secretion. Mitochondrial degradation of glutamate also contributes to insulin release when glutamate dehydrogenase is allosterically activated. It also signals extracellularly via glutamate receptors (AMPA and NMDA receptors) to modulate glucagon, insulin and somatostatin secretion, and islet cell survival. Its degradation products, GABA and γ-hydroxybutyrate, are released and also influence islet cell behavior. Thus, islet glutamate receptors, such as the NMDA receptors, might serve as possible drug targets to develop new medications for adjunct treatment of diabetes.
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Affiliation(s)
- Silke Otter
- Institute of Metabolic Physiology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Beta Cell Biology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, and German Center for Diabetes Research (DZD e.V.), Düsseldorf, Germany
| | - Eckhard Lammert
- Institute of Metabolic Physiology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Beta Cell Biology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, and German Center for Diabetes Research (DZD e.V.), Düsseldorf, Germany.
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28
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Tattikota SG, Rathjen T, Hausser J, Khedkar A, Kabra UD, Pandey V, Sury M, Wessels HH, Mollet IG, Eliasson L, Selbach M, Zinzen RP, Zavolan M, Kadener S, Tschöp MH, Jastroch M, Friedländer MR, Poy MN. miR-184 Regulates Pancreatic β-Cell Function According to Glucose Metabolism. J Biol Chem 2015; 290:20284-94. [PMID: 26152724 DOI: 10.1074/jbc.m115.658625] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Indexed: 02/03/2023] Open
Abstract
In response to fasting or hyperglycemia, the pancreatic β-cell alters its output of secreted insulin; however, the pathways governing this adaptive response are not entirely established. Although the precise role of microRNAs (miRNAs) is also unclear, a recurring theme emphasizes their function in cellular stress responses. We recently showed that miR-184, an abundant miRNA in the β-cell, regulates compensatory proliferation and secretion during insulin resistance. Consistent with previous studies showing miR-184 suppresses insulin release, expression of this miRNA was increased in islets after fasting, demonstrating an active role in the β-cell as glucose levels lower and the insulin demand ceases. Additionally, miR-184 was negatively regulated upon the administration of a sucrose-rich diet in Drosophila, demonstrating strong conservation of this pathway through evolution. Furthermore, miR-184 and its target Argonaute2 remained inversely correlated as concentrations of extracellular glucose increased, underlining a functional relationship between this miRNA and its targets. Lastly, restoration of Argonaute2 in the presence of miR-184 rescued suppression of miR-375-targeted genes, suggesting these genes act in a coordinated manner during changes in the metabolic context. Together, these results highlight the adaptive role of miR-184 according to glucose metabolism and suggest the regulatory role of this miRNA in energy homeostasis is highly conserved.
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Affiliation(s)
- Sudhir G Tattikota
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany
| | - Thomas Rathjen
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany
| | - Jean Hausser
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Aditya Khedkar
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany
| | - Uma D Kabra
- Institute for Diabetes and Obesity, Helmholtz Centre for Health and Environment and Division of Metabolic Diseases, Technical University Munich, 85748 Munich, Germany
| | - Varun Pandey
- Biological Chemistry Department, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Matthias Sury
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany
| | | | - Inês G Mollet
- Islet cell exocytosis, Lund University Diabetes Center, CRC 91-11, Jan Waldenströms gata 35, 20502 Malmö, Sweden, and
| | - Lena Eliasson
- Islet cell exocytosis, Lund University Diabetes Center, CRC 91-11, Jan Waldenströms gata 35, 20502 Malmö, Sweden, and
| | - Matthias Selbach
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany
| | - Robert P Zinzen
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany
| | - Mihaela Zavolan
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Sebastian Kadener
- Biological Chemistry Department, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Matthias H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Centre for Health and Environment and Division of Metabolic Diseases, Technical University Munich, 85748 Munich, Germany
| | - Martin Jastroch
- Institute for Diabetes and Obesity, Helmholtz Centre for Health and Environment and Division of Metabolic Diseases, Technical University Munich, 85748 Munich, Germany
| | - Marc R Friedländer
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 17121 Stockholm, Sweden
| | - Matthew N Poy
- From the Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany,
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29
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Brun T, Li N, Jourdain AA, Gaudet P, Duhamel D, Meyer J, Bosco D, Maechler P. Diabetogenic milieus induce specific changes in mitochondrial transcriptome and differentiation of human pancreatic islets. Hum Mol Genet 2015; 24:5270-84. [PMID: 26123492 DOI: 10.1093/hmg/ddv247] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 06/23/2015] [Indexed: 01/09/2023] Open
Abstract
In pancreatic β-cells, mitochondria play a central role in coupling glucose metabolism to insulin secretion. Chronic exposure of β-cells to metabolic stresses impairs their function and potentially induces apoptosis. Little is known on mitochondrial adaptation to metabolic stresses, i.e. high glucose, fatty acids or oxidative stress; being all highlighted in the pathogenesis of type 2 diabetes. Here, human islets were exposed for 3 days to 25 mm glucose, 0.4 mm palmitate, 0.4 mm oleate and transiently to H2O2. Culture at physiological 5.6 mm glucose served as no-stress control. Expression of mitochondrion-associated genes was quantified, including the transcriptome of mitochondrial inner membrane carriers. Targets of interest were further evaluated at the protein level. Three days after acute oxidative stress, no significant alteration in β-cell function or apoptosis was detected in human islets. Palmitate specifically increased expression of the pyruvate carriers MPC1 and MPC2, whereas the glutamate carrier GC1 and the aspartate/glutamate carrier AGC1 were down-regulated by palmitate and oleate, respectively. High glucose decreased mRNA levels of key transcription factors (HNF4A, IPF1, PPARA and TFAM) and energy-sensor SIRT1. High glucose also reduced expression of 11 mtDNA-encoded respiratory chain subunits. Interestingly, transcript levels of the carriers for aspartate/glutamate AGC2, malate DIC and malate/oxaloacetate/aspartate UCP2 were increased by high glucose, a profile suggesting important mitochondrial anaplerotic/cataplerotic activities and NADPH-generating shuttles. Chronic exposure to high glucose impaired glucose-stimulated insulin secretion, decreased insulin content, promoted caspase-3 cleavage and cell death, revealing glucotoxicity. Overall, expression profile of mitochondrion-associated genes was selectively modified by glucose, delineating a glucotoxic-specific signature.
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Affiliation(s)
- Thierry Brun
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland,
| | - Ning Li
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland
| | - Alexis A Jourdain
- Department of Cell Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - Pascale Gaudet
- Swiss Institute of Bioinformatics (SIB), Geneva, Switzerland, University of Geneva, Medical Center, Geneva, Switzerland and
| | - Dominique Duhamel
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland
| | - Jérémy Meyer
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospital, Geneva, Switzerland
| | - Domenico Bosco
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospital, Geneva, Switzerland
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland,
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30
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Glutamate acts as a key signal linking glucose metabolism to incretin/cAMP action to amplify insulin secretion. Cell Rep 2014; 9:661-73. [PMID: 25373904 PMCID: PMC4536302 DOI: 10.1016/j.celrep.2014.09.030] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 08/19/2014] [Accepted: 09/15/2014] [Indexed: 11/29/2022] Open
Abstract
Incretins, hormones released by the gut after meal ingestion, are essential for maintaining systemic glucose homeostasis by stimulating insulin secretion. The effect of incretins on insulin secretion occurs only at elevated glucose concentrations and is mediated by cAMP signaling, but the mechanism linking glucose metabolism and cAMP action in insulin secretion is unknown. We show here, using a metabolomics-based approach, that cytosolic glutamate derived from the malate-aspartate shuttle upon glucose stimulation underlies the stimulatory effect of incretins and that glutamate uptake into insulin granules mediated by cAMP/PKA signaling amplifies insulin release. Glutamate production is diminished in an incretin-unresponsive, insulin-secreting β cell line and pancreatic islets of animal models of human diabetes and obesity. Conversely, a membrane-permeable glutamate precursor restores amplification of insulin secretion in these models. Thus, cytosolic glutamate represents the elusive link between glucose metabolism and cAMP action in incretin-induced insulin secretion. Glutamate is derived from the malate-aspartate shuttle upon glucose stimulation Shuttle-derived glutamate is crucial for incretin-induced insulin secretion Cytosolic glutamate is transported into insulin granules via cAMP/PKA signaling Glutamate production by glucose is defective in incretin-unresponsive β cells
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31
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Li C, Gowan S, Anil A, Beck BH, Thongda W, Kucuktas H, Kaltenboeck L, Peatman E. Discovery and validation of gene-linked diagnostic SNP markers for assessing hybridization between Largemouth bass (Micropterus salmoides) and Florida bass (M. floridanus). Mol Ecol Resour 2014; 15:395-404. [DOI: 10.1111/1755-0998.12308] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/17/2014] [Accepted: 07/18/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Chao Li
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
| | - Spencer Gowan
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
| | - Ammu Anil
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
| | - Benjamin H. Beck
- United States Department of Agriculture; Agricultural Research Service; Stuttgart National Aquaculture Research Center; Stuttgart AR 72160 USA
| | - Wilawan Thongda
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
| | - Huseyin Kucuktas
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
| | - Ludmilla Kaltenboeck
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
| | - Eric Peatman
- School of Fisheries; Aquaculture and Aquatic Sciences; Auburn University; Auburn AL 36849 USA
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32
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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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Argonaute2 mediates compensatory expansion of the pancreatic β cell. Cell Metab 2014; 19:122-34. [PMID: 24361012 PMCID: PMC3945818 DOI: 10.1016/j.cmet.2013.11.015] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Revised: 07/26/2013] [Accepted: 11/10/2013] [Indexed: 12/31/2022]
Abstract
Pancreatic β cells adapt to compensate for increased metabolic demand during insulin resistance. Although the microRNA pathway has an essential role in β cell proliferation, the extent of its contribution is unclear. Here, we report that miR-184 is silenced in the pancreatic islets of insulin-resistant mouse models and type 2 diabetic human subjects. Reduction of miR-184 promotes the expression of its target Argonaute2 (Ago2), a component of the microRNA-induced silencing complex. Moreover, restoration of miR-184 in leptin-deficient ob/ob mice decreased Ago2 and prevented compensatory β cell expansion. Loss of Ago2 during insulin resistance blocked β cell growth and relieved the regulation of miR-375-targeted genes, including the growth suppressor Cadm1. Lastly, administration of a ketogenic diet to ob/ob mice rescued insulin sensitivity and miR-184 expression and restored Ago2 and β cell mass. This study identifies the targeting of Ago2 by miR-184 as an essential component of the compensatory response to regulate proliferation according to insulin sensitivity.
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Groschner LN, Alam MR, Graier WF. Metabolism-secretion coupling and mitochondrial calcium activities in clonal pancreatic β-cells. VITAMINS AND HORMONES 2014; 95:63-86. [PMID: 24559914 DOI: 10.1016/b978-0-12-800174-5.00003-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pancreatic β-cells are the only cells capable of lowering blood glucose by secreting insulin. The β-cell continuously adjusts its secretory activity to substrate availability in order to keep blood glucose levels within the physiological range--a process called metabolism-secretion coupling. Glucose is readily taken up by the β-cell and broken down into intermediates that fuel oxidative metabolism inside the mitochondria to generate ATP. The resulting increase in the ATP/ADP ratio causes closure of plasma membrane KATP channels, thereby depolarizing the cell and triggering the opening of voltage-gated Ca²⁺ channels. Consequential oscillations of cytosolic Ca²⁺ not only mediate the exocytosis of insulin granules but are also relayed to other subcellular compartments including the mitochondria, where Ca²⁺ is required to accelerate mitochondrial metabolism in response to nutrient stimulation. The mitochondrial Ca²⁺ uptake machinery plays a fundamental role in this feed-forward mechanism that guarantees sustained insulin secretion and, thus, represents a promising therapeutic target for type 2 diabetes.
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Affiliation(s)
- Lukas N Groschner
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Muhammad Rizwan Alam
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria.
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Brun T, Scarcia P, Li N, Gaudet P, Duhamel D, Palmieri F, Maechler P. Changes in mitochondrial carriers exhibit stress-specific signatures in INS-1Eβ-cells exposed to glucose versus fatty acids. PLoS One 2013; 8:e82364. [PMID: 24349266 PMCID: PMC3861392 DOI: 10.1371/journal.pone.0082364] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 10/22/2013] [Indexed: 11/19/2022] Open
Abstract
Chronic exposure of β-cells to metabolic stresses impairs their function and potentially induces apoptosis. Mitochondria play a central role in coupling glucose metabolism to insulin secretion. However, little is known on mitochondrial responses to specific stresses; i.e. low versus high glucose, saturated versus unsaturated fatty acids, or oxidative stress. INS-1E cells were exposed for 3 days to 5.6 mM glucose, 25 mM glucose, 0.4 mM palmitate, and 0.4 mM oleate. Culture at standard 11.1 mM glucose served as no-stress control and transient oxidative stress (200 µM H2O2 for 10 min at day 0) served as positive stressful condition. Mito-array analyzed transcripts of 60 mitochondrion-associated genes with special focus on members of the Slc25 family. Transcripts of interest were evaluated at the protein level by immunoblotting. Bioinformatics analyzed the expression profiles to delineate comprehensive networks. Chronic exposure to the different metabolic stresses impaired glucose-stimulated insulin secretion; revealing glucotoxicity and lipo-dysfunction. Both saturated and unsaturated fatty acids increased expression of the carnitine/acylcarnitine carrier CAC, whereas the citrate carrier CIC and energy sensor SIRT1 were specifically upregulated by palmitate and oleate, respectively. High glucose upregulated CIC, the dicarboxylate carrier DIC and glutamate carrier GC1. Conversely, it reduced expression of energy sensors (AMPK, SIRT1, SIRT4), metabolic genes, transcription factor PDX1, and anti-apoptotic Bcl2. This was associated with caspase-3 cleavage and cell death. Expression levels of GC1 and SIRT4 exhibited positive and negative glucose dose-response, respectively. Expression profiles of energy sensors and mitochondrial carriers were selectively modified by the different conditions, exhibiting stress-specific signatures.
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Affiliation(s)
- Thierry Brun
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland
- * E-mail: (TB); (PM)
| | - Pasquale Scarcia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Ning Li
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland
| | - Pascale Gaudet
- Swiss Institute of Bioinformatics (SIB) and University of Geneva, Medical Center, Geneva, Switzerland
| | - Dominique Duhamel
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland
| | - Ferdinando Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
- Center of Excellence in Comparative Genomics (CEGBA), University of Bari, Bari, Italy
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, Geneva, Switzerland
- * E-mail: (TB); (PM)
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Abstract
The mitochondrion relies on compartmentalization of certain enzymes, ions and metabolites for the sake of efficient metabolism. In order to fulfil its activities, a myriad of carriers are properly expressed, targeted and folded in the inner mitochondrial membrane. Among these carriers, the six-transmembrane-helix mitochondrial SLC25 (solute carrier family 25) proteins facilitate transport of solutes with disparate chemical identities across the inner mitochondrial membrane. Although their proper function replenishes building blocks needed for metabolic reactions, dysfunctional SLC25 proteins are involved in pathological states. It is the purpose of the present review to cover the current knowledge on the role of SLC25 transporters in health and disease.
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Maechler P. Mitochondrial function and insulin secretion. Mol Cell Endocrinol 2013; 379:12-8. [PMID: 23792187 DOI: 10.1016/j.mce.2013.06.019] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 06/12/2013] [Accepted: 06/12/2013] [Indexed: 10/26/2022]
Abstract
In the endocrine fraction of the pancreas, the β-cell rapidly reacts to fluctuations in blood glucose concentrations by adjusting the rate of insulin secretion. Glucose-sensing coupled to insulin exocytosis depends on transduction of metabolic signals into intracellular messengers recognized by the secretory machinery. Mitochondria play a central role in this process by connecting glucose metabolism to insulin release. Mitochondrial activity is primarily regulated by metabolic fluxes, but also by dynamic morphology changes and free Ca(2+) concentrations. Recent advances of mitochondrial Ca(2+) homeostasis are discussed; in particular the roles of the newly-identified mitochondrial Ca(2+) uniporter MCU and its regulatory partner MICU1, as well as the mitochondrial Na(+)-Ca(2+) exchanger. This review describes how mitochondria function both as sensors and generators of metabolic signals; such as NADPH, long chain acyl-CoA, glutamate. The coupling factors are additive to the Ca(2+) signal and participate to the amplifying pathway of glucose-stimulated insulin secretion.
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Affiliation(s)
- Pierre Maechler
- Department of Cell Physiology and Metabolism, Geneva University Medical Centre, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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Supale S, Thorel F, Merkwirth C, Gjinovci A, Herrera PL, Scorrano L, Meda P, Langer T, Maechler P. Loss of prohibitin induces mitochondrial damages altering β-cell function and survival and is responsible for gradual diabetes development. Diabetes 2013; 62:3488-99. [PMID: 23863811 PMCID: PMC3781460 DOI: 10.2337/db13-0152] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Prohibitins are highly conserved proteins mainly implicated in the maintenance of mitochondrial function and architecture. Their dysfunctions are associated with aging, cancer, obesity, and inflammation. However, their possible role in pancreatic β-cells remains unknown. The current study documents the expression of prohibitins in human and rodent islets and their key role for β-cell function and survival. Ablation of Phb2 in mouse β-cells sequentially resulted in impairment of mitochondrial function and insulin secretion, loss of β-cells, progressive alteration of glucose homeostasis, and, ultimately, severe diabetes. Remarkably, these events progressed over a 3-week period of time after weaning. Defective insulin supply in β-Phb2(-/-) mice was contributed by both β-cell dysfunction and apoptosis, temporarily compensated by increased β-cell proliferation. At the molecular level, we observed that deletion of Phb2 caused mitochondrial abnormalities, including reduction of mitochondrial DNA copy number and respiratory chain complex IV levels, altered mitochondrial activity, cleavage of L-optic atrophy 1, and mitochondrial fragmentation. Overall, our data demonstrate that Phb2 is essential for metabolic activation of mitochondria and, as a consequence, for function and survival of β-cells.
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Affiliation(s)
- Sachin Supale
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, Geneva, Switzerland
| | - Fabrizio Thorel
- Department of Genetic Medicine and Development, University of Geneva Medical Centre, Geneva, Switzerland
| | | | - Asllan Gjinovci
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, Geneva, Switzerland
| | - Pedro L. Herrera
- Department of Genetic Medicine and Development, University of Geneva Medical Centre, Geneva, Switzerland
| | - Luca Scorrano
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, Geneva, Switzerland
| | - Paolo Meda
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, Geneva, Switzerland
| | - Thomas Langer
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, Geneva, Switzerland
- Corresponding author: Pierre Maechler,
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Morita S, Horii T, Kimura M, Hatada I. MiR-184 regulates insulin secretion through repression of Slc25a22. PeerJ 2013; 1:e162. [PMID: 24109547 PMCID: PMC3792180 DOI: 10.7717/peerj.162] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 08/27/2013] [Indexed: 11/20/2022] Open
Abstract
Insulin secretion from pancreatic β-cells plays an essential role in blood glucose homeostasis and type 2 diabetes. Many genes are involved in the secretion of insulin and most of these genes can be targeted by microRNAs (miRNAs). However, the role of miRNAs in insulin secretion and type 2 diabetes has not been exhaustively studied. The expression miR-184, a miRNA enriched in pancreatic islets, negatively correlates with insulin secretion, suggesting that it is a good candidate for miRNA-mediated regulation of insulin secretion. Here we report that miR-184 inhibits insulin secretion in the MIN6 pancreatic β-cell line through the repression of its target Slc25a22, a mitochondrial glutamate carrier. Our study provides new insight into the regulation of insulin secretion by glutamate transport in mitochondria.
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Affiliation(s)
- Sumiyo Morita
- Laboratory of Genome Science, Biosignal Genome Resource Center, Institute for Molecular and Cellular Regulation, Gunma University , Japan
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Mitochondrial glutamate carriers from Drosophila melanogaster: biochemical, evolutionary and modeling studies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:1245-55. [PMID: 23850633 DOI: 10.1016/j.bbabio.2013.07.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 06/26/2013] [Accepted: 07/02/2013] [Indexed: 12/13/2022]
Abstract
The mitochondrial carriers are members of a family of transport proteins that mediate solute transport across the inner mitochondrial membrane. Two isoforms of the glutamate carriers, GC1 and GC2 (encoded by the SLC25A22 and SLC25A18 genes, respectively), have been identified in humans. Two independent mutations in SLC25A22 are associated with severe epileptic encephalopathy. In the present study we show that two genes (CG18347 and CG12201) phylogenetically related to the human GC encoding genes are present in the D. melanogaster genome. We have functionally characterized the proteins encoded by CG18347 and CG12201, designated as DmGC1p and DmGC2p respectively, by overexpression in Escherichia coli and reconstitution into liposomes. Their transport properties demonstrate that DmGC1p and DmGC2p both catalyze the transport of glutamate across the inner mitochondrial membrane. Computational approaches have been used in order to highlight residues of DmGC1p and DmGC2p involved in substrate binding. Furthermore, gene expression analysis during development and in various adult tissues reveals that CG18347 is ubiquitously expressed in all examined D. melanogaster tissues, while the expression of CG12201 is strongly testis-biased. Finally, we identified mitochondrial glutamate carrier orthologs in 49 eukaryotic species in order to attempt the reconstruction of the evolutionary history of the glutamate carrier function. Comparison of the exon/intron structure and other key features of the analyzed orthologs suggests that eukaryotic glutamate carrier genes descend from an intron-rich ancestral gene already present in the common ancestor of lineages that diverged as early as bilateria and radiata.
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Beiroa D, Romero-Picó A, Langa C, Bernabeu C, López M, López-Novoa JM, Nogueiras R, Diéguez C. Heterozygous deficiency of endoglin decreases insulin and hepatic triglyceride levels during high fat diet. PLoS One 2013; 8:e54591. [PMID: 23336009 PMCID: PMC3545959 DOI: 10.1371/journal.pone.0054591] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 12/14/2012] [Indexed: 12/30/2022] Open
Abstract
Endoglin is a transmembrane auxiliary receptor for transforming growth factor-beta (TGF-beta) that is predominantly expressed on proliferating endothelial cells. It plays a wide range of physiological roles but its importance on energy balance or insulin sensitivity has been unexplored. Endoglin deficient mice die during midgestation due to cardiovascular defects. Here we report for first time that heterozygous endoglin deficiency in mice decreases high fat diet-induced hepatic triglyceride content and insulin levels. Importantly, these effects are independent of changes in body weight or adiposity. At molecular level, we failed to detect relevant changes in the insulin signalling pathway at basal levels in liver, muscle or adipose tissues that could explain the insulin-dependent effect. However, we found decreased triglyceride content in the liver of endoglin heterozygous mice fed a high fat diet in comparison to their wild type littermates. Overall, our findings indicate that endoglin is a potentially important physiological mediator of insulin levels and hepatic lipid metabolism.
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Affiliation(s)
- Daniel Beiroa
- Department of Physiology, School of Medicine-CIMUS – Instituto de Investigaciones Sanitarias (IDIS), CIBER Fisiopatologia de la Obesidad y Nutricion (CIBERobn), University of Santiago de Compostela, Santiago de Compostela, A Coruña, Spain
| | - Amparo Romero-Picó
- Department of Physiology, School of Medicine-CIMUS – Instituto de Investigaciones Sanitarias (IDIS), CIBER Fisiopatologia de la Obesidad y Nutricion (CIBERobn), University of Santiago de Compostela, Santiago de Compostela, A Coruña, Spain
| | - Carmen Langa
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Carmelo Bernabeu
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Miguel López
- Department of Physiology, School of Medicine-CIMUS – Instituto de Investigaciones Sanitarias (IDIS), CIBER Fisiopatologia de la Obesidad y Nutricion (CIBERobn), University of Santiago de Compostela, Santiago de Compostela, A Coruña, Spain
| | - José M. López-Novoa
- Renal and Cardiovascular Physiopathology Unit, Department of Physiology and Pharmacology, University of Salamanca and Instituto de Investigaciones Biomédicas de Salamanca (IBSAL), Campus Miguel de Unamuno, Salamanca, Spain
| | - Ruben Nogueiras
- Department of Physiology, School of Medicine-CIMUS – Instituto de Investigaciones Sanitarias (IDIS), CIBER Fisiopatologia de la Obesidad y Nutricion (CIBERobn), University of Santiago de Compostela, Santiago de Compostela, A Coruña, Spain
| | - Carlos Diéguez
- Department of Physiology, School of Medicine-CIMUS – Instituto de Investigaciones Sanitarias (IDIS), CIBER Fisiopatologia de la Obesidad y Nutricion (CIBERobn), University of Santiago de Compostela, Santiago de Compostela, A Coruña, Spain
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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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Abstract
In the endocrine fraction of the pancreas, the task of the beta-cell is to continuously and perfectly adjust insulin secretion to fluctuating blood glucose levels, thereby maintaining glycemia and nutrient homeostasis. This glucose sensing coupled to insulin exocytosis depends on transduction of metabolic signals into intracellular messengers recognized by the exocytotic machinery. Central to this metabolism-secretion coupling, mitochondrial signal transduction refers to both integration and generation of metabolic signals, connecting glucose sensing to insulin exocytosis. In response to a glucose rise, nucleotides and metabolites are generated by mitochondria and participate, together with cytosolic calcium, in the stimulation of insulin release. This review describes the role of mitochondria in metabolic signal transduction regulating insulin secretion.
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Affiliation(s)
- Pierre Maechler
- Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, rue Michel-Servet 1, CH-1211 Geneva 4, Switzerland.
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44
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Vetterli L, Carobbio S, Pournourmohammadi S, Martin-Del-Rio R, Skytt DM, Waagepetersen HS, Tamarit-Rodriguez J, Maechler P. Delineation of glutamate pathways and secretory responses in pancreatic islets with β-cell-specific abrogation of the glutamate dehydrogenase. Mol Biol Cell 2012; 23:3851-62. [PMID: 22875990 PMCID: PMC3459861 DOI: 10.1091/mbc.e11-08-0676] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The amino acid profile and the secretory responses of glutamate dehydrogenase (GDH)-deficient β-cells are characterized. This study shows that GDH is essential for both insulin release and net glutamate synthesis evoked by glucose. Adding cellular glutamate restored the full development of glucose-stimulated insulin secretion, showing the requirement for permissive glutamate levels. In pancreatic β-cells, glutamate dehydrogenase (GDH) modulates insulin secretion, although its function regarding specific secretagogues is unclear. This study investigated the role of GDH using a β-cell–specific GDH knockout mouse model, called βGlud1−/−. The absence of GDH in islets isolated from βGlud1–/– mice resulted in abrogation of insulin release evoked by glutamine combined with 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid or l-leucine. Reintroduction of GDH in βGlud1–/– islets fully restored the secretory response. Regarding glucose stimulation, insulin secretion in islets isolated from βGlud1–/– mice exhibited half of the response measured in control islets. The amplifying pathway, tested at stimulatory glucose concentrations in the presence of KCl and diazoxide, was markedly inhibited in βGlud1–/– islets. On glucose stimulation, net synthesis of glutamate from α-ketoglutarate was impaired in GDH-deficient islets. Accordingly, glucose-induced elevation of glutamate levels observed in control islets was absent in βGlud1–/– islets. Parallel biochemical pathways, namely alanine and aspartate aminotransferases, could not compensate for the lack of GDH. However, the secretory response to glucose was fully restored by the provision of cellular glutamate when βGlud1–/– islets were exposed to dimethyl glutamate. This shows that permissive levels of glutamate are required for the full development of glucose-stimulated insulin secretion and that GDH plays an indispensable role in this process.
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Affiliation(s)
- Laurène Vetterli
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center, Geneva, Switzerland
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45
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da Silva PMR, Batista TM, Ribeiro RA, Zoppi CC, Boschero AC, Carneiro EM. Decreased insulin secretion in islets from protein malnourished rats is associated with impaired glutamate dehydrogenase function: effect of leucine supplementation. Metabolism 2012; 61:721-32. [PMID: 22078937 DOI: 10.1016/j.metabol.2011.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 08/27/2011] [Accepted: 09/27/2011] [Indexed: 02/06/2023]
Abstract
We herein studied the role of glutamate dehydrogenase (GDH), in response to leucine (LEU) supplementation, upon insulin secretion of malnourished rats. Weaned male Wistar rats were fed normal-protein (17%) or low-protein diet (6%, LP) for 8 weeks. Half of the rats of each group were supplemented with LEU (1.5%) in the drinking water for the following 4 weeks. Gene and protein expressions, static insulin secretion, and cytoplasmic Ca(2+) oscillations were measured. Glutamate dehydrogenase messenger RNA was 58% lower in LP islets, and LEU supplementation augmented it in 28%. The LP islets secreted less insulin when exposed to 20 mmol/L LEU, 20 mmol/L LEU + 2 mmol/L glutamine (with or without 5 mmol/L aminooxyacetic acid, a branched chain aminotransferase inhibitor, or 20 μmol/L epigallocatechin gallate, a GDH inhibitor), 20 mmol/L α-ketoisocaproate, glutamine + 20 mmol/L β-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (a GDH activator), and 22.2 mmol/L glucose. Leucine supplementation augmented insulin secretion to levels found in normal-protein islets in all the above conditions, an effect that was blunted when islets were incubated with epigallocatechin gallate. The glutamine + β-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid-induced increased [Ca(2+)](i) and oscillations were higher than those for LP islets. Leucine supplementation normalized these parameters in LP islets. Impaired GDH function was associated with lower insulin release in LP islets, and LEU supplementation normalized insulin secretion via restoration of GDH function. In addition, GDH may contribute to insulin secretion through ameliorations of Ca(2+) handling in LP islets.
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Affiliation(s)
- Priscilla Muniz Ribeiro da Silva
- Department of Anatomy, Cellular Biology and Physiology and Biophysics, Institute of Biology, University of Campinas,PO Box 6109, CEP 13083-970 Campinas, SP, Brazil
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46
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Huypens PR, Huang M, Joseph JW. Overcoming the spatial barriers of the stimulus secretion cascade in pancreatic β-cells. Islets 2012; 4:1-116. [PMID: 22143007 DOI: 10.4161/isl.18338] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The ability of the pancreatic β-cells to adapt the rate of insulin release in accordance to changes in circulating glucose levels is essential for glucose homeostasis. Two spatial barriers imposed by the plasma membrane and inner mitochondrial membrane need to be overcome in order to achieve stringent coupling between the different steps in the stimulus-secretion cascade. The first spatial barrier is overcome by the presence of a glucose transporter (GLUT) in the plasma membrane, whereas a low affinity hexokinase IV (glucokinase, GK) in the cytosol conveys glucose availability into a metabolic flux that triggers and accelerates insulin release. The mitochondrial inner membrane comprises a second spatial barrier that compartmentalizes glucose metabolism into glycolysis (cytosol) and tricarboxylate (TCA) cycle (mitochondrial matrix). The exchange of metabolites between cytosol and mitochondrial matrix is mediated via a set of mitochondrial carriers, including the aspartate-glutamate carrier (aralar1), α- ketoglutarate carrier (OGC), ATP/ADP carrier (AAC), glutamate carrier (GC1), dicarboxylate carrier (DIC) and citrate/isocitrate carrier (CIC). The scope of this review is to provide an overview of the role these carriers play in stimulus-secretion coupling and discuss the importance of these findings in the context of the exquisite glucose responsive state of the pancreatic β-cell.
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Affiliation(s)
- Peter R Huypens
- School of Pharmacy; Health Science Campus; University of Waterloo; Kitchener, CN Canada
| | - Mei Huang
- School of Pharmacy; Health Science Campus; University of Waterloo; Kitchener, CN Canada
| | - Jamie W Joseph
- School of Pharmacy; Health Science Campus; University of Waterloo; Kitchener, CN Canada
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47
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Sugden MC, Holness MJ. The pyruvate carboxylase-pyruvate dehydrogenase axis in islet pyruvate metabolism: Going round in circles? Islets 2011; 3:302-19. [PMID: 21934355 PMCID: PMC3329512 DOI: 10.4161/isl.3.6.17806] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Pyruvate is the major product of glycolysis in pancreatic β-cells, and its ultimate metabolic fate depends on the relative activities of two enzymes. The first, pyruvate carboxylase (PC) replenishes oxaloacetate withdrawn from the tricarboxylic acid (TCA) cycle via the carboxylation of pyruvate to form oxaloacetate. Flux via PC is also involved in the formation of NADPH, one of several important coupling factors for insulin secretion. In most tissues, PC activity is enhanced by increased acetyl-CoA. The alternative fate of pyruvate is its oxidative decarboxylation to form acetyl-CoA via the pyruvate dehydrogenase complex (PDC). The ultimate fate of acetyl-CoA carbon is oxidation to CO2 via the TCA cycle, and so the PDC reaction results of the irreversible loss of glucose-derived carbon. Thus, PDC activity is stringently regulated. The mechanisms controlling PDC activity include end-product inhibition by increased acetyl-CoA, NADH and ATP, and its phosphorylation (inactivation) by a family of pyruvate dehydrogenase kinases (PDHKs 1-4). Here we review new developments in the regulation of the activities and expression of PC, PDC and the PDHKs in the pancreatic islet in relation to islet pyruvate disposition and glucose-stimulated insulin secretion (GSIS).
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Affiliation(s)
- Mary C Sugden
- Centre for Diabetes, Blizard Institute, Bart's and the London School of Medicine and Dentistry, London, UK.
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48
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Role of mitochondrial phosphate carrier in metabolism-secretion coupling in rat insulinoma cell line INS-1. Biochem J 2011; 435:421-30. [PMID: 21265734 DOI: 10.1042/bj20101708] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In pancreatic β-cells, glucose-induced mitochondrial ATP production plays an important role in insulin secretion. The mitochondrial phosphate carrier PiC is a member of the SLC25 (solute carrier family 25) family and transports Pi from the cytosol into the mitochondrial matrix. Since intramitochondrial Pi is an essential substrate for mitochondrial ATP production by complex V (ATP synthase) and affects the activity of the respiratory chain, Pi transport via PiC may be a rate-limiting step for ATP production. We evaluated the role of PiC in metabolism-secretion coupling in pancreatic β-cells using INS-1 cells manipulated to reduce PiC expression by siRNA (small interfering RNA). Consequent reduction of the PiC protein level decreased glucose (10 mM)-stimulated insulin secretion, the ATP:ADP ratio in the presence of 10 mM glucose and elevation of intracellular calcium concentration in response to 10 mM glucose without affecting the mitochondrial membrane potential (Δψm) in INS-1 cells. In experiments using the mitochondrial fraction of INS-1 cells in the presence of 1 mM succinate, PiC down-regulation decreased ATP production at various Pi concentrations ranging from 0.001 to 10 mM, but did not affect Δψm at 3 mM Pi. In conclusion, the Pi supply to mitochondria via PiC plays a critical role in ATP production and metabolism-secretion coupling in INS-1 cells.
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Karaca M, Frigerio F, Maechler P. From pancreatic islets to central nervous system, the importance of glutamate dehydrogenase for the control of energy homeostasis. Neurochem Int 2011; 59:510-7. [DOI: 10.1016/j.neuint.2011.03.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 03/21/2011] [Accepted: 03/23/2011] [Indexed: 11/25/2022]
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Jitrapakdee S, Wutthisathapornchai A, Wallace JC, MacDonald MJ. Regulation of insulin secretion: role of mitochondrial signalling. Diabetologia 2010; 53:1019-32. [PMID: 20225132 PMCID: PMC2885902 DOI: 10.1007/s00125-010-1685-0] [Citation(s) in RCA: 216] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Accepted: 01/06/2010] [Indexed: 12/23/2022]
Abstract
Pancreatic beta cells are specialised endocrine cells that continuously sense the levels of blood sugar and other fuels and, in response, secrete insulin to maintain normal fuel homeostasis. During postprandial periods an elevated level of plasma glucose rapidly stimulates insulin secretion to decrease hepatic glucose output and promote glucose uptake into other tissues, principally muscle and adipose tissues. Beta cell mitochondria play a key role in this process, not only by providing energy in the form of ATP to support insulin secretion, but also by synthesising metabolites (anaplerosis) that can act, both intra- and extramitochondrially, as factors that couple glucose sensing to insulin granule exocytosis. ATP on its own, and possibly modulated by these coupling factors, triggers closure of the ATP-sensitive potassium channel, resulting in membrane depolarisation that increases intracellular calcium to cause insulin secretion. The metabolic imbalance caused by chronic hyperglycaemia and hyperlipidaemia severely affects mitochondrial metabolism, leading to the development of impaired glucose-induced insulin secretion in type 2 diabetes. It appears that the anaplerotic enzyme pyruvate carboxylase participates directly or indirectly in several metabolic pathways which are important for glucose-induced insulin secretion, including: the pyruvate/malate cycle, the pyruvate/citrate cycle, the pyruvate/isocitrate cycle and glutamate-dehydrogenase-catalysed alpha-ketoglutarate production. These four pathways enable 'shuttling' or 'recycling' of these intermediate(s) into and out of mitochondrion, allowing continuous production of intracellular messenger(s). The purpose of this review is to present an account of recent progress in this area of central importance in the realm of diabetes and obesity research.
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Affiliation(s)
- S Jitrapakdee
- Molecular Metabolism Research Group, Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Road, Phya-Thai, Bangkok 10400, Thailand.
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