Abstract

BACKGROUND
Oxidative stress is induced under diabetic conditions and causes various forms of tissue damages in the patients with diabetes. Recently, pancreatic beta cells are regarded as a putative target of oxidative stress-induced tissue damage, and this seems to explain in part the progressive deterioration of beta cell function in type 2 diabetes. The aim of this study was to examine the potential of Quercetin (QE) to protect INS-1 cells from the H2O2-induced oxidative stress and the effects of QE on the glucose-stimulated insulin secretion in INS-1 cells. METHODS: To study the cell viability, cells were incubated with H2O2 and/or QE at the various concentrations. To confirm the protective effect by QE in response to H2O2, the levels of antioxidant enzymes were assessed by RT-PCR and Western blot, and glutathione peroxidase activities were quantified by spectrophotometrical method. Glucose-stimulated insulin secretion (GSIS) was measured by ELISA. RESULTS: Cell incubations were performed with 80 microM of H2O2 for 5 hours to induce 40 - 50% of cell death. QE gradually showed protective effect (IC50 = 50 microM) in dose-dependent manner. Superoxide dismutase (SOD) mRNA level in H2O2 + QE group was increased as compared to H2O2 group, but catalase did not changed. And the QE recruited glutathione peroxidase activity against H2O2-induced oxidative injuries in INS-1 cells. CONCLUSION: In conclusion, these findings suggest that QE might have protective effect on beta cells by ameliorating oxidative stress and preserving insulin secretory function.

• Keywords: Antioxidant effect;Diabetes mellitus;INS-1 cell;Oxidative stress;Quercetin