Effects of epicatechin on rat islets of Langerhans.

Plants containing epicatechin (a flavonoid) have been used to treat diabetes mellitus in Indian medicine. The present study reports effects of this compound on isolated islets of Langerhans. The flavonoid (1 mM) was found to increase insulin secretion from isolated rat islets of Langerhans in the presence of either 2 or 20 mM glucose, in static incubations, or in perifusion. The increase in insulin secretion mediated by epicatechin was both ATP- and temperature-dependent. Ultrastructural studies showed no deleterious changes in the structure of the B-cells after 5 days of exposure to the compound. Intraperitoneal injection of 30 mg/kg body wt of epicatechin twice daily for 4 days increased the islet insulin content by 30%. Secretion of insulin from islets isolated from epicatechin-injected rats was significantly increased when exposed to 20 mM glucose in comparison with water-injected controls. Furthermore, islets of adult rats cultured with 5.5 mM glucose for 4 days showed a significant increase in DNA synthesis in the presence of 0.05 mM epicatechin. These results suggest direct effects of epicatechin on various aspects of islet function.