Selective potentiation of 5-methyl-2-(1-methylcyclohexyl)-4-oxazoleacetic acid (AD-4610) on glucose-induced insulin secretion

In the perfused pancreas from normal SD rats, AD-4610 (0.01-0.1 mM) potentiated biphasic insulin secretion induced by 7.5 mM of glucose. The concentration-response curve of insulin secretion to glucose was shifted leftwards with AD-4610 (0.1 mM) without altering either the threshold concentration of glucose to induce insulin secretion or the maximal insulin response to glucose, indicating increased sensitivity of the pancreatic B-cells to glucose. On the other hand, AD-4610 was 10-fold less effective in altering insulin secretion induced by arginine and glyceraldehyde. The effect of AD-4610 on insulin secretion and glucose metabolism was compared with that of tolbutamide in vivo. AD-4610 (100 mg/kg) potentiated insulin secretion induced by an intravenous glucose load, and also accelerated glucose metabolism without altering basal insulin secretion in normal rats. On the other hand, tolbutamide (20 mg/kg) increased basal insulin secretion, but slightly decreased glucose-induced insulin secretion. In yellow KK mice with hyperglycemia, AD-4610 (10-100 mg/kg) had a dose-dependent hypoglycemic action, but tolbutamide did not. Thus, AD-4610 stimulated insulin secretion in a glucose-dependent fashion and enhanced glucose metabolism in vivo. These results suggest that AD-4610 selectively potentiates glucose-induced insulin secretion by increasing the sensitivity of pancreatic B-cells to glucose and may be useful for treating human NIDDM through a different mechanism than that of tolbutamide.