Aqueous extract from Cirsium japonicum leaves improves glucose homeostasis in diabetic rats

An aqueous extract from Cirsium japonicum (AECJ) leaves was purified using ion exchange resin, gel filtration, and reverse-phase HPLC sequentially and analyzed to mainly be saponins using Thin Layer Chromatography. The anti-diabetic effect of the saponins was investigated in diabetic rats established by induction with streptozotocin (30 mg/kg body weight) in cold citrate buffer and feeding with high-carbohydrate / high-fat diet. The plasma glucose level in diabetic rats was significantly decreased after AECJ treatment for two weeks, accompanied by decreased total plasma cholesterol and triglycerides. The dysregulated insulin and leptin secretions were not affected by AECJ, while the plasma adiponectin level in AECJ-treated diabetic rats was obviously increased compared to that before treatment. Western-blot assay showed that AECJ has little effect on plasma membrane GLUT4 level in fat tissue. Furthermore, AECJ restored the altered enzyme activities of several metabolic enzymes in liver from diabetic rats, including phosphofructokinase, pyruvate kinase, glucose-6-phosphatase and fructose-1,6-bisphosphatase. In conclusion, our study demonstrated the anti-hyperglycemic effect of AECJ, which might involve the improved activities of metabolic enzymes in liver and expression of adiponectin playing important role in the development of diabetes, suggesting the potential benefit of the Cirsium japonicum as an alternative in treating diabetes mellitus.