Tranilast inhibits glucose-induced insulin secretion from pancreatic beta-cells.

Tranilast, N-(3,4-demethoxycinnamoyl)-anthranilic acid, is an anti-allergic agent identified as an inhibitor of mast cell degranulation. Recently, tranilast was shown to decrease albuminuria in a rat model of diabetic nephropathy and to ameliorate vascular hypertrophy in diabetic rats, suggesting that it may be clinically useful in the treatment of diabetic complications. However, the effects of tranilast on glucose tolerance have not been elucidated. Thus, the aim of this study is to investigate the effect of tranilast on insulin secretion in pancreatic beta-cells. Treatment with tranilast significantly suppressed insulin secretion in INS-1E cells and rat islets induced by 16.7 mmol/l glucose. Furthermore, tranilast inhibited tolbutamide-induced insulin secretion. Treatment with tranilast increased (86)Rb (+) efflux from COS-1 cells in which pancreatic beta-cell-type ATP-sensitive K (+) (K (ATP)) channels were reconstructed and suppressed the cytosolic ATP/ADP ratio in INS-1E cells. Interestingly, treatment with tranilast enhanced glucose uptake in INS-1E cells. In the present study, we demonstrated that tranilast inhibited glucose- and tolbutamide-induced insulin secretion through the activation of K (ATP) channels in pancreatic beta-cells.