Anti-diabetic Activity Of Polysaccharides From Tuberous Root Of Liriope Spicata Var. Prolifera On IR Cell Model And KKAy Type2Diabetic Mice And Its Probable Mechanisms

Objective:This study was to investigate anti-diabetic activity of polysaccharides from the tuberous root of Liriope spicata (Thunb.) var. prolifera (TLSP、LSP1and LSP2)on the HepG2, proliferation of3T3-L1adipocytes and NIT-1cells and the diabetic KKAy mice and its mechanisms of anti-insulin-resistance.Method:The activity of HepG2, proliferation of3T3-L1adipocytes and NIT-1cell was estimated by MTT method and the glucose consumption of cells was mearured with glucose oxidase method (GOD). Insulin secretion of NIT-1cells was estimated by radioimmunoassay.The KKAy diabetic mice received daily administration of TLSP, LSP1and LSP2at doses of50,100and200(mg/kg/day) and rosiglitazone at a2mg/kg/day for28days. In addition, normal control and diabetic control were treated with vehicle. FBG, OGTT and FINS were measured, TC, TG, HDL and LDL were alse estimated to evaluate the anti-diabetic activity of Liriope spicata (Thunb.) var. prolifera. Immunohistochemistry and western blotting were estmited the protein expressions of InsR-a, IRS-1, PI3K and PPARy in liver tissue of KKAy diabetic mice. In addition, liver histological analysis was observed by HE stanning. The hepatic glycogen content, GK and G6Pase activities were also detected to evaluate the effects of polysaccharides on glucose metabolism.Results:In vitro study, MTT method showed that absorbance at570nm of polysaccharides-treated HepG2, proliferation of3T3-L1adipocytes and NIT-1cell was significantly decrease. Glucose oxidase method indicated that TLSP、LSP1and LSP2could enhanced the glucose consumption of cells, compared with the untreated insulin resistance cell model (P<0.05). Compared with untreated group, insulin secretion level on NIT-1cells is increased significantly in TLSP, LSP1and LSP2-treated group (P<0.05).In vivo experiment, the type2diabetic KKAy mice were received daily oral administration of the preparations for28days. TLSP, LSP1and LSP2all caused a marked decrease of fasting blood glucose (FBG) and a remarkable amelioration on insulin resistance (IR) and serum lipid condition in diabetic models, In addition, liver histological analysis shown that TLSP, LSP1and LSP2ameliorated the hepatocyte hypertrophy and significantly decreased the lipid accumulation in KKAy diabetic mice. TLSP, LSP1and LSP2, caused a remarkable lower of FBG, also had a significant amelioration on OGTT and insulin resistance in KKAy diabetic mice. As well as decreasing total cholesterol (TC), triglyceride (TG). TLSP, LSPl and LSP2were also increse the relative of HDL/LDL. The result of immunohistochemistry and western blot indicated that greater positive expression of immunoprotein for InsR-a, IRS-1, PI3K and PPARy was observed in the tubulointerstitial regions of TLSP, LSP1and LSP2group compared with diabetic group. The protein expression of these four signaling pathway of insulin were marked enhanced in liver tissues of KKAy mice. The glycogen content of TLSP, LSP1and LSP2groups were remarkable enhanced, and GK activity of TLSP, LSP1and LSP2groups was alse markedly increase, as well as the G6Pase activity was remarkably decrease.Conclusion:TLSP, LSP1and LSP2present the remarkable activities of amelioating Hypoglycemia, hypolipidemia, hypoinsulinemia and the amelioration of insulin resistance. The mechanisms of insulin resistance may be related with the improvement of insulin signaling transduction and glucose metabolism.