Reduced cytochrome C is an essential regulator of sustained insulin secretion by pancreatic islets.

Publication Type:

Journal Article

Source:

The Journal of biological chemistry, Volume 286, Issue 20, p.17422-34 (2011)

Keywords:

2011, Adenosine Triphosphate, Animals, Calcium, Clinical Research Division, Cytochromes c, Electron Transport Chain Complex Proteins, Insulin, Islets of Langerhans, Oxidation-Reduction, Oxygen Consumption, Rats, Rats, Sprague-Dawley

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.