Reduced cytochrome C is an essential regulator of sustained insulin secretion by pancreatic islets |
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Authors: | Jung Seung-Ryoung Kuok Iok Teng Denise Couron Drew Rizzo Norma Margineantu Daciana H Hockenbery David M Kim Francis Sweet Ian R |
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Institution: | Department of Medicine, Diabetes and Obesity Center, University of Washington, Seattle, Washington 98195, USA. |
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Abstract: | Influx of calcium is an essential but insufficient signal in sustained nutrient-stimulated insulin secretion, and increased metabolic rate of the beta cell is also required. The aim of the study was to test the hypothesis that the reduced state of cytochrome c is a metabolic co-factor necessary for insulin secretion, over and above its participation in the ATP-generating function of electron transport/oxidative phosphorylation. We found that nutrient stimulation of insulin secretion by isolated rat islets was strongly correlated with reduced cytochrome c, and agents that acutely and specifically reduced cytochrome c led to increased insulin secretion, even in the face of decreased oxygen consumption and calcium influx. In contrast, neither sites 1 nor 4 of the electron transport chain were both necessary and essential for the stimulation of insulin secretion to occur. Importantly, stimulation of islets with glucose, α-ketoisocaproate, or glyceraldehyde resulted in the appearance of cytochrome c in the cytosol, suggesting a pathway for the regulation of exocytotic machinery by reduction of cytochrome c. The data suggest that the metabolic factor essential for sustained calcium-stimulated insulin secretion to occur is linked to reduction and translocation of cytochrome c. |
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Keywords: | Calcium Cytochrome c Electron Transport Insulin Secretion Pancreatic Islet |
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