Berberine protects against palmitate induced beta cell injury via promoting mitophagy

Background Destruction of pancreatic beta cells is the most typical characteristic of diabetes. Objective We aimed to evaluate the effect of berberine (BBR), a bioactive isoquinoline derivative alkaloid, on beta cell injury. Methods Rodent pancreatic beta cell line INS-1 was treated with 0.5 mM palmitate (PA) for 24 h to establish an in vitro beta cell injury model. Results BBR at 5 µM promoted cell viability, inhibited cell apoptosis and enhanced insulin secretion in PA-induced INS-1 cells. BBR treatment also suppressed PA-induced oxidative stress in INS-1 cells, as evidenced by the decreased ROS production and increased activities of antioxidant enzymes. In addition, suppressed ATP production and reduced mitochondrial membrane potential were restored by BBR in PA-treated INS-1 cells. It was further determined that BBR affected the expressions of mitophagy-associated proteins, suggesting that BBR promoted mitophagy in PA-exposed INS-1 cells. Meanwhile, we found that BBR facilitated nuclear expression and DNA-binding activity of Nrf2, an antioxidative protein that can regulate mitophagy. Finally, a rescue experiment was performed and the results demonstrated that the effect of BBR on cell viability, apoptosis and mitochondrial function in PA-induced INS-1 cells were cancelled by PINK1 knockdown. Conclusions BBR protects islet β cells from PA-induced injury, and this protective effect may be achieved by regulating mitophagy. The present study may provide a novel therapeutic strategy for β cell injury in diabetes mellitus.