1,5-Anhydroglucitol stimulates insulin release in insulinoma cell lines

Concentrations of 1,5-anhydroglucitol (1,5-AG), which is a major circulating polyol, decrease in patients with diabetes mellitus. In both insulinoma-derived RINr and MIN6 cells, 1,5-AG stimulated insulin release within the range of 0.03-0.61 mM in a dose-dependent manner. Insulin release was maximally stimulated by 1,5-AG to levels that reached 25% and 100% greater than that of control (1,5-AG-free group) in RINr and MIN6 cells, respectively. A physiological concentration of 1,5-AG stimulated insulin release after a 5-min incubation and this action was maintained for 60 min. In addition, at approximately 1/200 the concentration of glucose, 1,5-AG had additive action with 20 mM glucose. The action of 1,5-AG on insulin secretion with other types of saccharides and polyol was similarly additive. Mannnoheptulose and diazoxide suppressed the stimulative action of 1,5-AG on insulin release. The secretagogue action of 1,5-AG seemed to be independent on an increase in the intracellular content of cAMP and ATP. These results suggest that 1,5-AG can stimulate insulin secretion through a mechanism that completely differs from that of glucose.