Jiangtang Xiaozhi Recipe (降糖消脂方) prevents diabetic retinopathy in streptozotocin-induced diabetic rats

Objective To evaluate the prevention effect of diabetic retinopathy of Jiangtang Xiaozhi Recipe (降糖消脂方, JXR) in streptozotocin (STZ)-induced diabetic rats. Methods Sprague-Dawley rats were randomly divided into normal control group and diabetic group. Rats in the diabetic group were induced by intraperitoneal administration of STZ (50 mg/kg), and subdivided into 5 groups. Rats in the diabetic control group were given saline; four treatment groups were given metformin (300 mg/kg), JXR (2, 4 and 8 g/kg) respectively for 8 weeks, while rats in the normal control group were injected with citrate buffer and given the same volume of vehicle. Body weight and food intake were measured every week. The hypoglycaemic effects were determined by testing fasting blood glucose (FBG) every other week, and hemoglobin A1c (HbA1c), insulin, and glucagon at the end of the treatment. The preventive effects of JXR on STZ-induced diabetic rats were determined by histopathological examination with hematoxylin and eosin staining, and periodic acid-schiff staining. The effects were further evaluated by serum superoxide dismutase (SOD) activity and malondialdehyde (MDA). Results High-dose JXR significantly reduced FBG and HbA1c level at the 8th week of administration ( P <0.01, P <0.05). JXR significantly increased insulin level ( P <0.05), and decreased glucagon level ( P <0.05). JXR showed the antioxidant defense with increased SOD activity and decreased MDA contents in diabetic rats. Histopathological studies revealed that there were no basement membrane thickening and mild destruction in the treated groups. Morphometric measurements of retina microvascular showed that acellular capillary and capillary density decreased in treated rats while pericyte and endothelial cell increasing after the treatment. Conclusion JXR have protective effect of diabetic retinopathy and its mechanism may be associated with the obvious hypoglycemic and antioxidant effect.