Salgado, AP, Pereira, FC, Seica, RM, Fernandes, AP, Flatt, Peter, Santos, RM, Rosario, LM and Ramasamy, R (1999) Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells. MOLECULAR AND CELLULAR ENDOCRINOLOGY, 154 (1-2). pp. 79-88. [Journal article]
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Nutrient stimulation of pancreatic beta-cells increases the cellular reduced pyridine nucleotide content, but the specific role of cytosolic redox state in glucose-induced insulin release (GIIR) remains undetermined. The role of cytosolic redox state has been assessed (as reflected by the lactate/pyruvate ratio) in nutrient- and non-nutrient-induced insulin release using a recently established glucose-sensitive clonal beta-cell line (BRIN-BD11). Long-term exposure to the NAD(+) precursor vitamin nicotinic acid (NA, 100 mu M) was used to promote a more oxidized state in the cytosol. Glucose (2-16 mM) evoked a dose-dependent rise in the cytosolic NADH/NAD(+) ratio which was linearly related to the extent of GIIR. NA suppressed the glucose-induced rise in the NADH/NAD(+) ratio and concomitantly reduced GIIR by 44%. It also inhibited, by 47%, the average glucose-induced rise in cytosolic free Ca2+ concentration ([Ca2+](i), assessed by fura-2 microfluorometry from single cells). The latter effect was not accounted for by a reduction in the activity of voltage-sensitive Ca2+ channels, inasmuch as both high K+- and tolbutamide-induced [Ca2+](i) rises remained insensitive to NA exposure. NA did not affect insulin release evoked by any of the depolarizing agents, indicating that steps in the stimulus-secretion coupling cascade distal to Ca2+ influx are insensitive to changes in the cytosolic redox state. It is concluded that GIIR is partially controlled by the cytosolic redox state. Moreover, the impairment in GIIR caused by a shift toward a more oxidized state in the cytosol, originates from an attenuated [Ca2+](i) response. The latter is likely mediated by the influence of cytosolic redox state on specific metabolic pathways (NADH shuttle systems and/or the malonyl-CoA pathway), leading ultimately to enhancement of the activity of ATP-sensitive K+ channels. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.
|Item Type:||Journal article|
|Faculties and Schools:||Faculty of Life and Health Sciences|
Faculty of Life and Health Sciences > School of Biomedical Sciences
|Research Institutes and Groups:||Biomedical Sciences Research Institute|
Biomedical Sciences Research Institute > Diabetes
|Deposited By:||Professor Peter Flatt|
|Deposited On:||13 Jan 2010 14:38|
|Last Modified:||11 Jun 2010 12:49|
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