Effect Of Tea Polyphenols On Insulin Resistance And The Relative Mechanism In Rat With Non-alcoholic Fatty Liver Disease

Objective To investigate tea polyphenol's impact on factors in NAFLD,namely,insulin resistance,adiponectin,adiponectin receptor level and its signal transduction in liver tissue and to explore tea polyphenol's possible interacting mechanism of NAFLD glucolipid metabolism and insulin resistance,the model of high-fat and high-sugar diet induced non-alcoholic fatty liver disease on rats was established and tea polyphenol's intervention effect on NAFLD was observed.Method The rat model with 20 NAFLD rats were built through gavaging high-fat and high-sugar emulsion diet.They were randomly divided into model control group(MC group,n=10)and tea polyphenols intervention group(TP group,n=10).normal control group(NC group,n=10),MC group was administered intragastrically with high fat emulsion.TP group was administered intragastrically with high fat emulsion + tea polyphenols.NC group was given the same amount of normal saline.Four weeks later,all rats were executed and the serum and liver tissues were collected to observe the pathological changes of liver tissue and the ALT,AST,TC,TG,LDL,and HDL were measured.The serum free fatty acids(FFA)in each group were measured using spectrophotometric method.FIN and ADP in each group were measured by ELISA.Then insulin resistance index was calculated and ADP?AdipoR2?AMPK ? 2?PPAR??PPAR ? mRNA levels were detected by RT-PCR.In addition,protein expression of ADP?AMPK ??P-AMPK? were determined through Western Blotting.Moreover,the ratio between P-AMPK? and AMPK ? was calculated.Finally,the level of AMPK's phosphorylation was evaluatedResults In this experiment,the rat model of NAFLD was successfully constructed by gavaging high fat and high glucose emulsion for four weeks.Compared with the NC group,NAFLD activity scores of the MC group were increased.With the intervention of tea polyphenol,the pathological changes relieved to a certain extent.The levels of ALT,AST,TC,TG,LDL,FFA,and FBG in their serum were decreased and the differences were statistically significant(p<0.05).Although the level of HDL increased,the difference was not statistically significant(p=0.17).In the meantime,tea polyphenols could reduce the levels of serum insulin and adiponectin and improve the insulin resistance evaluated by HOMA-IR and ISI.The differences were statistically significant(p<0.05).Compared with the NC group,ADP,AdipoR2,AMPKa2,PPARa,PPAR?mRNA levels in MC group were decreased remarkably,while the ADP protein expression level decreased significantly.The differences were statistically significant(p<0.05).Compared with the MC group,the liver tissues' ADP,AdipoR2,AMPKa2,PPARa,PPAR?mRNA were increased and the ADP protein expression level increased.The differences were statistically significant(p<0.05).Phosphorylation of AMPK levels in MC group decreased to 29.11%compared with NC group.With the intervention of tea polyphenol,phosphorylation of AMPK in TP group raised to 60.76%compared with NC group.The difference was statistically significant.Conclusion Tea polyphenols could be used to ameliorate the disorders of glucose and lipid metabolism in NAFLD rats.Improving insulin resistance may be one of the mechanism that conditioned the lipid metabolism of NAFLD rats.The mechanism that improve insulin resistance may be regulated by signal transduction pathway's factors,for instance,PPARs,AMPKmRNA,and protein expression level.