Suppression of pancreatic beta cell apoptosis by Danzhi Jiangtang capsule contributes to the attenuation of type 1 diabetes in rats

Background: Danzhi Jiangtang Capsule (DJC), a Chinese medicinal formula, has been clinically used for treatment of diabetes for many years. Previous studies have demonstrated that DJC was able to improve pancreatic islet function in diabetes, but the underlying mechanisms remained unclear. Methods: Streptozotocin (STZ) induced type 1 diabetic rats were treated with DJC for 6 weeks. Fasting plasma insulin and fasting plasma glucose were determined at the end of experiment. Antioxidant status was evaluated by measuring total antioxidant capacity, superoxide dismutase activity and malondialdehyde content in plasma and pancreas. Paraffin sections of pancreas were subjected to H& E staining, TUNEL staining and immunohistochemical examination. Protein levels of Bcl-2, Bax and pancreatic duodenal homeobox-1 (PDX-1) were measured by western blot analysis. Activities of Caspase-3 and Caspase-9 were determined with commercially available kits. Results: Supplementation with DJC resulted in a significant amelioration of type 1 diabetes as manifested by reduced blood glucose, increased fasting plasma insulin and improved body weight gains. The atrophy and reduction of pancreatic islets were also alleviated in DJC supplemented groups. DJC markedly reduced pancreatic beta cell apoptosis, with Bax protein down-regulated and Bcl-2 protein up-regulated significantly. The activities of caspase-3 and caspase-9 in pancreas were decreased evidently by DJC treatment. DJC effectively ameliorated oxidative stress in type 1 diabetic rats, with the expression of PDX-1 protein increased markedly. Conclusions: DJC was capable of attenuating STZ induced type 1 diabetes in rats, which might be attributed to the suppression of pancreatic beta cell apoptosis. This study would provide further evidence for clinical use of DJC in the management of diabetes.