Hypoglycemic effects of Trichosanthes kirilowii and its protein constituent in diabetic mice: the involvement of insulin receptor pathway

BACKGROUND Diabetes is a serious chronic metabolic disorder. Trichosanthes kirilowii Maxim. (TK) is traditionally used for the treatment of diabetes in traditional Chinese medicine (TCM). However, the clinical application of TK on diabetic patients and the hypoglycemic efficacies of TK are still unclear. METHODS A retrospective cohort study was conducted to analyze the usage of Chinese herbs in patients with type 2 diabetes in Taiwan. Glucose tolerance test was performed to analyze the hypoglycemic effect of TK. Proteomic approach was performed to identify the protein constituents of TK. Insulin receptor (IR) kinase activity assay and glucose tolerance tests in diabetic mice were further used to elucidate the hypoglycemic mechanisms and efficacies of TK. RESULTS By a retrospective cohort study, we found that TK was the most frequently used Chinese medicinal herb in type 2 diabetic patients in Taiwan. Oral administration of aqueous extract of TK displayed hypoglycemic effects in a dose-dependent manner in mice. An abundant novel TK protein (TKP) was further identified by proteomic approach. TKP interacted with IR by docking analysis and activated the kinase activity of IR. In addition, TKP enhanced the clearance of glucose in diabetic mice in a dose-dependent manner. CONCLUSIONS In conclusion, this study applied a bed-to-bench approach to elucidate the hypoglycemic efficacies and mechanisms of TK on clinical usage. In addition, we newly identified a hypoglycemic protein TKP from TK. Our findings might provide a reasonable explanation of TK on the treatment of diabetes in TCM.