Blood glucose lowering effect of ophiopogonis tuber extract and mechanism of anti-insulin-resistance

Objective 　To study the hypoglycemic effect and insulin sensitization mechanism of ophiopogonis tuber extracts on the 3T3-L1-induced adipocytes, and also in rats with reproduction of type 2 diabetes mellitus (T2DM). Methods 　3T3-L1 cells were induced and differentiated into adipocytes. After the intervention with ophiopogonpolysaccharide (OPSR) and ophiopogonin (OPG), glucose consuming rate was detected for screening the extracts which may have effective hypoglycemic effects. The insulin resistance (IR) adipocyte model was established by dexamethasone induction, and then it was treated with OPSR. The protein expression levels of leptin, adiponectin and resistin were detected by Western blotting. The T2DM rat model was reproduced and then treated with OPSR for 4 weeks. Body weight (BW), triglyeride (TG), fasting blood glucose (FBG) and fasting insulin (FINs) of the rats were measured respectively. Results 　OPSR in dosage of 0.5-50mg/L promoted glucose consumption of adipocytes in a dose-dependent manner, the glucose consumption ratios were 32.27%, 75.14% and 90.47% respectively. OPG of 50mg/L showed very weak activity with glucose consumption ratio of only 8.49%. OPSR could significantly promote the protein expression of leptin and adiponectin, and showed an inhibitory effect on the protein expression of resistin (P<0.05). After treatment with OPSR for 4 weeks, the BW of rats increased obviously, while TG, FBG and HOMA-IR decreased significantly (P<0.05 or P<0.01). Conclusions 　OPSR may promote glucose transport and utilization of adipocytes, decrease the level of FBG and TG, and improve the condition of IR in T2DM rats. The mechanism of blood glucose lowering effect may be attributed to secretion of adipokines, such as leptin, adiponectin and resistin by IR adipocytes.