Effect of 2-Bromostearate on Glucose-Phosphorylating Activities and the Dynamics of Insulin Secretion in Islets of Langerhans During Fasting

Abstract

Glucose-phosphorylating activity and insulin secretion were measured in homogenates of isolated rat islets and of perfused rat pancreas, respectively. Fasting for 96 h produced a significant decrease of both low-and high-K_m glucose-phosphorylating activities and blocked the insulin secretory response to glucose. In the presence of glucose, 0.25 mM 2-bromostearate, a known inhibitor of fatty acid oxidation, partially restored the insulin response to glucose that was lost during fasting. This effect paralleled the restoration of glucose-phosphorylation activities (primarily the high–K_m component) seen when islets isolated from 96-h-fasted rats were preincubated with 0.25 mM 2-bromostearate. It is concluded that fasting-induced adaptations of glucose-phosphorylating enzymes could account, at least in part, for the reduced insulin secretory response to glucose. 2-Bromostearate, an inhibitor of fatty acid oxidation, is able to restore both insulin secretory response and glucose-phosphorylating activities, suggesting possible interrelations among the correlated impairment in insulin secretion, islet glucose-phosphorylating activity, islet glucose metabolism, and the oxidation of fatty acids in the B-cell during fasting.