Baojun Xu
Beijing Normal University, China
Title: Daphnetin protects INS-1 pancreatic β-cells from streptozotocin-induced apoptosis
Biography
Biography: Baojun Xu
Abstract
Excessive loss of pancreatic β-cell, mainly due to apoptosis is major causes in the development of diabetes hyperglycemia in both type 1 and 2 diabetes mellitus. Pancreatic β-cell apoptosis is initiated by stimuli such as inflammation and hyperglycemia. Numerous epidemiological studies have demonstrated that excessive human consumption of diet rich phytochemicals attenuates effect of diabetes. Daphnetin (7,8-dihydrocoumarin), a naturally present such as fruits, Daphne koreane Nakai and Daphne odora var. marginata, has shown significant biological effects of antioxidant and antiflammatrory activities. The objective of the present study was to evaluate the mechanism behind its antidiabetic property in streptozotocin (STZ)-induced diabetic in INS-1 cell line. The INS-1 rat insulinoma cell line was cultured. INS-1 cells were pretreated with daphetin (1, 10, 20 and 40 µM) for 24 h, cells were exposed to STZ (3 mM) for 12h. STZ induced cell damage was estimated by MTT assay, glucose stimulated insulin secretion assay, lipid peroxidation (thiobarbituric acid reactive substance and lipid hydroperoxide), antioxidant status (SOD, CAT, GPx, and GST), apoptosis stainings (DAPI, Hoechst33342, AO/EB, ROS) by fluorescence microscopy and annexin V and propidium iodide double staining by flow cytometry. The exposure to STZ for 12h significantly reduced the viability of INS-1 cells, compared to control cells in culture media, while pretreated with daphnetin for 24h resulted in a significant improve of cell viability as determined by MTT. Daphnetin was tested for its effects on insulin secretion by INS-1 cells cultured in low and high glucose medium; we found that daphnetin pretreatment improved glucose stimulated insulin secretion. STZ cause increased levels of lipid peroxidation and decreased antioxidant status of diabetic in INS-1 cells. Daphnetin pretreatment significantly reduced the levels of lipid peroxidation markers and improved antioxidant status in STZ induced INS-1 cells. STZ-induced cells showed less live cells and highly condensed chromatin in nuclei. However, daphnetin obviously decreased the apoptotic ratio in comparison with STZ-induced diabetic in INS-1 cells. The results suggest that daphnetin may be used in treating diabetes mellitus by considering its insulin stimulating property and subsequent regulation of apoptotic pathway.