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Santos LR, Muller C, de Souza AH, Takahashi HK, Spégel P, Sweet IR, Chae H, Mulder H, Jonas JC. NNT reverse mode of operation mediates glucose control of mitochondrial NADPH and glutathione redox state in mouse pancreatic β-cells. Mol Metab 2017; 6:535-547. [PMID: 28580284 PMCID: PMC5444111 DOI: 10.1016/j.molmet.2017.04.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/10/2017] [Accepted: 04/18/2017] [Indexed: 11/17/2022] Open
Abstract
Objective The glucose stimulation of insulin secretion (GSIS) by pancreatic β-cells critically depends on increased production of metabolic coupling factors, including NADPH. Nicotinamide nucleotide transhydrogenase (NNT) typically produces NADPH at the expense of NADH and ΔpH in energized mitochondria. Its spontaneous inactivation in C57BL/6J mice was previously shown to alter ATP production, Ca2+ influx, and GSIS, thereby leading to glucose intolerance. Here, we tested the role of NNT in the glucose regulation of mitochondrial NADPH and glutathione redox state and reinvestigated its role in GSIS coupling events in mouse pancreatic islets. Methods Islets were isolated from female C57BL/6J mice (J-islets), which lack functional NNT, and genetically close C57BL/6N mice (N-islets). Wild-type mouse NNT was expressed in J-islets by adenoviral infection. Mitochondrial and cytosolic glutathione oxidation was measured with glutaredoxin 1-fused roGFP2 probes targeted or not to the mitochondrial matrix. NADPH and NADH redox state was measured biochemically. Insulin secretion and upstream coupling events were measured under dynamic or static conditions by standard procedures. Results NNT is largely responsible for the acute glucose-induced rise in islet NADPH/NADP+ ratio and decrease in mitochondrial glutathione oxidation, with a small impact on cytosolic glutathione. However, contrary to current views on NNT in β-cells, these effects resulted from a glucose-dependent reduction in NADPH consumption by NNT reverse mode of operation, rather than from a stimulation of its forward mode of operation. Accordingly, the lack of NNT in J-islets decreased their sensitivity to exogenous H2O2 at non-stimulating glucose. Surprisingly, the lack of NNT did not alter the glucose-stimulation of Ca2+ influx and upstream mitochondrial events, but it markedly reduced both phases of GSIS by altering Ca2+-induced exocytosis and its metabolic amplification. Conclusion These results drastically modify current views on NNT operation and mitochondrial function in pancreatic β-cells.
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Key Words
- AT2, aldrithiol
- C57BL/6J mice
- C57BL/6N mice
- CMV, cytomegalovirus
- DTT, dithiotreitol
- Dz, diazoxide
- FCCP, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone
- GRX1, glutaredoxin 1
- GRX1-roGFP2
- GSIS, glucose stimulation of insulin secretion
- Glucose metabolism
- IDH, isocitrate dehydrogenase
- Insulin secretion
- KRB, Krebs solution
- ME, malic enzyme
- Mitochondrial shuttles
- NNT, nicotinamide nucleotide transhydrogenase
- OCR, oxygen consumption rate
- Pancreatic islet
- Redox-sensitive GFP
- Stimulus-secretion coupling
- WT, wild-type
- [Ca2+]i, intracellular Ca2+ concentration
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Affiliation(s)
- Laila R.B. Santos
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Carole Muller
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Arnaldo H. de Souza
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Hilton K. Takahashi
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Peter Spégel
- Lund University, Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Malmö, 205 02, Sweden
- Lund University, Department of Chemistry, Centre for Analysis and Synthesis, Lund, 221 00, Sweden
| | - Ian R. Sweet
- University of Washington Diabetes Institute, Department of Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Heeyoung Chae
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
| | - Hindrik Mulder
- Lund University, Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Malmö, 205 02, Sweden
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, B-1200, Belgium
- Corresponding author. Université catholique de Louvain, UCL/SSS/IREC/EDIN, Avenue Hippocrate 55, B1.55.06, B-1200, Brussels, Belgium.Université catholique de LouvainUCL/SSS/IREC/EDINAvenue Hippocrate 55B1.55.06BrusselsB-1200Belgium
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