Quercetin protects islet β-cells from oxidation-induced apoptosis via Sirt3 in T2DM

Objective(s): Sirt3 may regulate ROS production and might be involved in ?-cell apoptosis, which plays an important role in the progression of type 2 diabetes mellitus (T2DM). Quercetin is a potent antioxidative bioflavonoid, but its effects on T2DM remain to be explored. This study aimed to investigate the effects of quercetin on ?-cell apoptosis and explore its mechanisms. Materials and Methods: The effects of quercetin were conducted on db/db mice and INS1 cells. Fasting blood glucose was determined by the colorimetric method, serum insulin was measured by enzyme-linked immunosorbent assay (ELISA). Meanwhile, Sirt3 in INS1 cells was knocked down by plasmid transfection. The antioxidant proteins (SOD2 and CAT), apoptosis proteins (cleaved Caspase-3, Bax, and BCL-2), and Sirt3 protein in pancreases and INS1 cells were determined by western blotting. Results: When INS1 cells and diabetic mice were treated with quercetin, the levels of SOD2, CAT, and Sirt3 proteins were increased, the levels of cleaved Caspase-3 and the ratio of Bax to BCL-2 were decreased at different degrees, along with reduced blood glucose levels and elevated insulin levels in diabetic mice. When Sirt3 was knocked down in INS1 cells, increase of two antioxidants and decrease of cell apoptosis generated by quercetin could not occur. Conclusion: Quercetin protected islet ?-cells from oxidation-induced apoptosis via Sirt3 in T2DM, which would be beneficial to develop new strategies for preventing ?-cell failure in T2DM.