Cocoa flavonoid epicatechin protects pancreatic beta cell viability and function against oxidative stress

[Scope] 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 such as epicatechin (EC) constitute an important part of the human diet; they can be found in green tea, grapes, and cocoa and possess multiple biological activities. This study investigates the chemo-protective effect of EC against oxidative stress induced by tert-butylhydroperoxide (t-BOOH) on Ins-1E pancreatic beta cells.[Methods and Results] Cell viability, oxidative status, phosphorylated Jun kinase (p-JNK) expression, and insulin secretion were evaluated. Ins-1E cells treatment with 5-20 μM EC for 20 h evoked no cell damage and enhanced antioxidant enzymes and insulin secretion. Addition of 50 μM t-BOOH for 2 h induced reactive oxygen species, p-JNK, and carbonyl groups and decreased GSH and insulin secretion. Pretreatment of cells with EC prevented the t-BOOH-induced reactive oxygen species, carbonyl groups, p-JNK expression and cell death, and recovered insulin secretion.[Conclusion] Ins-1E cells treated with EC showed a remarkable recovery of cell viability and insulin secretion damaged by t-BOOH, indicating that integrity of secreting and surviving machineries in the EC-treated cells was notably protected against the oxidative insult.This work was supported by grants AGL2010–17579 and project CSD2007–00063 from Programa Consolider-Ingenio from the Spanish Ministry of Economy and Competitivity