Cocoa flavanols show beneficial effects in cultured pancreatic beta cells and liver cells to prevent the onset of type 2 diabetes

•Cocoa flavanols strengthen antioxidant defenses of pancreatic beta cells.•Cocoa flavanols protect beta cells against chemically-induced oxidative stress.•Cocoa flavanols increase insulin responsiveness of liver cells.•Cocoa flavanols restrain glucose production from liver cells.

Diabetes mellitus is associated with reductions in glutathione, supporting the critical role of oxidative stress in its pathogenesis. Antioxidant food components such as flavonoids have a protective role against oxidative stress-induced degenerative and age-related diseases. Flavonoids constitute an important part of the human diet; they can be found in most plant foods, including green tea, grapes or cocoa and possess multiple biological activities. This article summarizes the latest results obtained with a cocoa phenolic extract (CPE) and its main flavonoid component epicatechin (EC) in cell culture models of beta cells and hepatocytes. The effect of CPE and EC on cell integrity and redox status and their chemo-protective capacity against an oxidative stress induced by tert-butylhydroperoxide (t-BOOH) were tested on pancreatic beta cells as well as cell viability and first elements of the insulin signaling pathway were evaluated in hepatocytes. Doses of 1–20 μg/mL CPE and 1–20 μM EC, considered realistic, evoked no damage and preserved the redox status of cultured beta cells and hepatocytes. Treatment of beta cells with CPE/EC significantly prevented the t-BOOH-induced oxidative damage. Besides, treatment of hepatocytes with CPE/EC increased responsiveness to insulin and decreased glucose production. Thus, CPE and EC show favorable effects against a diabetic condition both in pancreatic and hepatic cells.