Effects Of Astragalus Polysaccharides On Expressions Of AMPK And UCP2in Type2Diabetic Rats

Background As the most endocrine metabolic disease, in recent years, the incidence of type2diabetes mellitus (T2DM) is rising year by year. The main cause for type2diabetes mellitus is insulin resistance, which has abnormal signal transduction as one of its important mechanisms. Research shows that, astragalus polysaccharides (APS) can improve insulin resistance, raise insulin sensitivity, regulating sugar, fat metabolism. Studies on influences of APS to T2DM and the mechanism are not yet understood.Objective To investigate the effects of Astragalus Polysaccharide (APS) on the insulin resistance in type2diabetic model rats.and observe the index of AMPK α (AMP-activated protein kinase)in liver and UCP2(Uncoupling Protein2) in pancreas from gene translational level and protein synthetic level. The mechanism of APS that improve type2diabetes mellitus (T2DM) was discussed in this study, so as to provide evidence for the treatment of T2DM.Methods (1)60healthy male Sprague-Dawley rats weighting210-230g. after one week adaptive feeding,were randomly divided into two groups:the normal control group(NC group.n=10) given normal feed, high fat-diet-induced model group (HFM group.n=50). After six weeks, the average weight of rats in HFM group was significantly increased by20%higher than that in NC group. The obesity rat model was made successfully.(2) The HFM group rats were intraperitoneal injected with Streptozotocin (STZ.25mg/kg). After72h the rats with random blood glucose over16.7mmol/L were identified as diabetes mellitus models. Then detect the random blood glucose after intraperitoneal injection with STZ on the14th day, and excluded the rats with the random blood glucose under16.7mmol/L. Then the type2diabetic model rats were again divided randomly into four groups:diabetic model control group (DMC group. n=12), pioglitazone group (Pio group,20mg/kg·d pioglitazone gavage n=11), APS group (APS group,400mg/kg·d Astragalus n=11), APS+Pio group (APP group,20mg/kg·d pioglitazone+400mg/kg·d Astragalus. n=11). And the rats in NC group and DMC group had been saline gavage.(3) After intervention for four weeks, the blood sample was collected after given intraperitoneal anesthesia with cardiac puncture for biochemical analysis. And the liver and pancreas tissue were collected in liquid nitrogen.The insulin were measured by enzyme linked immunosorbent assay (ELISA). The AMPKa mRNA and UCP2mRNA expression was examined by reverse transcription-polymerase chain reaction (RT-PCR). The AMPKα、p-AMPKa and UCP2protein were examined by Western-Blotting(WB). The parastastal fat pad. perinephric fat pad. omentum fat were collected to evaluate the index of visceral fat and weight (VF/W). Then analyse the correlation of these data.Results (1) after6weeks of high fat-diet. The body weight of rats in HFM group were significantly increased about20%higher than that in NC group (P<0.01). The random blood glucose of high fat model group rats lasted to the end of the experiment was higher than that of the NC group, but there was no significant statistic difference between the two groups (P>0.05). The random blood glucose level of high fat model group rats increased after injection of STZ with significant statistic difference (P<0.01).(2). After feeding12weeks, compared with NC group, the levels of FBG. TG,TC,FINS and VF/W in DMC group. Pio group, APS group and APP group were significantly increased (P<0.05) and ISI were significantly decreased (P<0.05). Compared with the DMC group, the levels of FBG, TG.TCFINS and VF/W in Pio group, APS group and APP group were significantly decreased (P<0.05) and ISI increased significant (P<0.05). The levels of these data in APS group was higher than that of Pio group, but there was no statistic difference between the two groups (P>0.05). (3). RT-PCR:Compared with normal control group, the mRNA expression of AMPKa in DMC group, Pio group、APS group and APP group were significantly elevated (P<0.05), UCP2in DMC group, Pio group, APS group and APP group were higher than the NC group. Compared with the DMC group, the levels of AMPKa in Pio group,APS group and in APP group were significantly increased (P<0.05).The levels of UCP2were significantly decreased(P<0.05),Compared with the APP group,the levels of AMPKa in Pio and APS groups were not significantly decreased(P>0.05),the levels of UCP2in the two groups were significantly increased(P<0.05).There was no significant difference in the levels of AMPKa mRNA and UCP2mRNA between Pio and APS groups(P>0.05).(4). Western-blotting:Compared with NC group, the protein expressions of AMPKa; p-AMPKa in liver of DMC group, Pio group and APS group were significantly decreased (P<0.05). While the levels of and UCP2were significantly increased (P<0.05):Compared with the DMC group, the levels of UCP2in Pio group, APS group and APP group were significantly increased (P<0.05). while the levels of AMPKa:p-AMPKa were significantly decreased (P<0.05). Compared with the APP group, levels of AMPKa; p-AMPKa were decreased in Pio group, APS group,but without significantly differences, the levels of UCP2were significantly increased(P<0.05), in Pio and APS groups, levels of AMPKα, pAMPKa and UCP2have no significantly difference(P>0.05).Conclusion:(1)APS could elevate the insulin resistence of type2diabetic model rats.(2)The mechanisms of APS to reduce the insulin resistanec of type2diabetic model rats might be achieved by increasing the levels of AMPKα。p-AMPKα and reducing the level of UCP2.