Vitis thunbergii var. Taiwaniana leaf extract reduces blood glucose levels in mice with streptozotocin-induced diabetes

Background and Objective: Vitis thunbergii var. taiwaniana (VTT) is a native folk medicinal plant in Taiwan used to treat hepatitis, jaundice, stomachaches, diarrhea and arthritis. This study aimed to investigate the antidiabetic activity of VTT extracts using a mice model of streptozotocin (STZ)-induced diabetes. Materials and Methods: The ICR male mice were received a single i.p., injection of 100 mg kg^-1 of STZ to induce type 2-like diabetes. Diabetic mice were orally administered with 100 mg kg^-1 of VTT-leaf alcohol extracts, VTT-stem alcohol extracts, VTT-leaf hot water extracts or VTT-stem hot water extracts five times per week for 4 weeks. In short-term experiments, the mice were orally received with 100 mg kg^-1 of VTT-leaf or stem hot water extracts once for 180 min. The fasting blood was collected for determining the glucose level and lipid profile. The one-way analysis of variance (ANOVA) was used to determine whether there were any statistically significant differences (p<0.05) between the means of three or four independent groups. Results: The alcohol extracts of VTT-stem and leaf were used to examine the hypoglycemic activity in STZ-induced diabetic mice. However, these two kinds of VTT alcohol extracts did not have any effects on blood glucose level of diabetic mice. Second, the hot water extracts of VTT-stem and leaf were orally administered to the STZ-induced diabetic mice for 4 weeks. Interestingly, only hot water extracts of VTT-leaf significantly (p<0.05) decreased blood glucose level, but the stem extracts did not. In the short-term experiments, the blood glucose level of diabetic mice could be quickly decreased after feeding with hot water extracts of VTT-leaf for 2-3 h. In addition, hot water extracts of VTT-leaf could protect pancreatic β-cells from STZ-induced damage by immunohistochemistry staining. On the other hand, only hot water extracts of VTT-stem could decrease triglyceride level in STZ-induced diabetic mice. Conclusion: It is concluded that hot water extracts of VTT-leaf exhibited antidiabetic activity and might be developed as functional food to treat diabetes mellitus in the future.