Mechanism Underlying Polydatin Improving Myocardial Injury And Insulin Resistance Through SIRT1/PGC-1? Pathway In Diabetic Rats

Objective:Based on the preliminary work,this study is to investigate whether polydatin(PD)can improve myocardial injury and insulin resistance(IR)in diabetic rats and the possible mechanism of action.It is mainly clear that polydatin plays a role in glucose and lipid metabolism,myocardial fibrosis,oxidative stress and mitochondria in diabetic rats.Whether functional metabolic abnormalities have a regulatory role,and whether to exert antimyocardial damage and improve insulin resistance by regulating silencing information regulator 2-related enzyme 1 / peroxisome proliferator-activated receptor gamma-assisted activator-1 alpha(SIRT1/PGC-1?)signaling pathway.Methods:Seventy SPF clean male Sprague-Dawley rats were randomly selected from 10 rats for normal feeding(CON),and the other 60 were fed with high-fat diet for 6 weeks to form insulin resistance.Single intraperitoneal injection of streptozotocin(STZ)35 mg/kg was used to establish a rat model of type 2 diabetes mellitus(T2DM).Rats were tested for fasting blood glucose after 72 hours and 7 days of intraperitoneal injection of STZ.Two fasting blood glucose ? 11.1 mmol/L was successful in diabetes model.Rats were randomly divided into model group(MOD),metformin group(50 mg/kg,MET),low dose of polydatin group(30 mg/kg,L-PD),and high dose of polydatin group(90 mg/kg,H-PD).The general state of the rats was recorded weekly,including the mental state,body weight,survival rate,etc.of the experimental rats,and blood glucose concentration was measured by tail blood stasis.After 4 weeks of drug treatment,the abdominal aorta blood was collected and the heart was separated.The serum triglyceride(TG)and total cholesterol(TC)were detected by automatic biochemical analyzer.The serum free fatty acid(FFA)content was determined by enzymatic method.The content of serum insulin(FINS)was determined by immunoassay(ELISA).The changes of myocardial morphology were observed by HE staining.The deposition of myocardial interstitial and perivascular collagen was observed by Sirius red staining.The positive expression of myocardial protein SIRT1,PGC-1? and IRS1 were detected by immunohistochemistry.The expression levels of TGF-?1,CTGF,3-NT,4-HNE,IRS1,NRF-1,SIRT1 and PGC-1? were detected by Western blot.Results:1.PD improves blood lipid metabolism and insulin resistance index in diabetic rats.After successful modeling,the body weight of rats in MOD group decreased continuously.The intervention of polydatin and metformin significantly slowed down the trend of weight loss.At the end of the experiment,the fasting blood glucose level of MET group,L-PD group and H-PD group was lower than that of MOD group.Rats were reduced to varying degrees but still above normal levels.Serum index test results showed: triglyceride(TG),total cholesterol(TC),free fatty acid(FFA),insulin(FINS)and insulin resistance index(HOMAIR)were significantly higher in the MOD group than in the CON group(P<0.01),insulin sensitivity index(ISI)was significantly lower than CON group(P<0.01);The treatment groups significantly decreased the levels of TG,TC,FFA,FINS and HOMA-IR in diabetic rats,and improved the insulin sensitivity.Among them,the serum lipids levels and HOMAIR of H-PD group were the most significant in the rats(P<0.01).2.PD improves myocardial morphology in diabetic rats.The results of HE staining showed that the myocardial fibers in the MOD group were disordered,multiple fractures or disappeared,and a large number of inflammatory cells infiltrated.After drug intervention,the myocardial fibers in the L-PD group had different degrees of swelling and inflammatory cell infiltration;The myocardial fibers in the H-PD group and the MET group were arranged neatly,without obvious edema,and inflammatory cells were rare.3.PD improves myocardial fibrosis in diabetic rats.Sirius red staining showed that myocardial interstitial and perivascular collagen deposition was significantly increased in MOD rats compared with CON group(P<0.01).Compared with the MOD group,metformin and high and low doses of polydatin can significantly improve the deposition of collagen in myocardial tissue,and the decrease in the H-PD group is the most significant(P<0.01).The results of Western blot showed that the levels of CTGF and TGF-?1 in the H-PD group were significantly lower than those in the model group(P<0.01).4.PD reduces myocardial oxidative stress in diabetic rats.The expression of 3-NT and 4-HNE protein in myocardial tissue was detected by Western blot.The results showed that the level of 4-HNE protein in different treatment groups was lower than that in MOD group(P<0.01,P<0.05).The levels of 3-NT protein in myocardium of H-PD group and MET group decreased(P<0.01,P<0.05),and the effect of high dose of polydatin on the levels of 3-NT and 4-HNE protein was better than metformin.5.PD increases IRS1 expression in diabetic rats.The results of immunohistochemistry showed that the expression of IRS1 protein in the MOD group was significantly lower than that in the CON group(P<0.01).Compared with the MOD group,the L-PD protein expression was increased(P<0.05),and the protein expression in the H-PD group and the MET group was significantly higher than that of the MOD group(P<0.01).Western blot results showed that the IRS1 protein levels in each treatment group were significantly higher than those in the MOD group,and the difference was statistically significant(P<0.05,P<0.01).6.PD promotes the expression of nuclear respiratory factor-1(NRF-1).The expression of NRF-1 protein was detected by Western blot.The results showed that the expression of NRF-1 protein in each treatment group was significantly higher than that in MOD group(P<0.01),but there was no significant difference between the treatment groups(P>0.05).The increase in NRF-1 protein expression after PD intervention indicates its regulation of myocardial mitochondrial function in T2 DM rats.7.PD activates the SIRT1/PGC-1? signaling pathway.Immunohistochemistry and Western blot showed that the expression of SIRT1 and PGC-1? in L-PD group,H-PD group and MET group were significantly higher than those in the MOD group(P<0.05,P< 0.01).Conclusion:1.Polydatin can improve diabetes-induced myocardial injury and insulin resistance,and regulate lipid metabolism,myocardial fibrosis,oxidative stress and mitochondrial dysfunction in diabetic rats.2.Polydatin may activate mitochondrial dysfunction by activating the SIRT1/PGC-1? signaling pathway,further exerting anti-oxidation and regulating insulin signaling.