Effects And Mechanisms Of EGCG From Tea On Alleivating Nonalcoholic Fatty Liver Through Gut-liver Axis Pathway

With the increase in the intake of high calorie foods such as high-fat and high-sugar,the phenomenon of national overnutrition is widespread,and the incidence of nonalcoholic fatty liver disease(NAFLD)is high.NAFLD is a liver manifestation of metabolic syndrome,characterized by fat accumulation and fatty degeneration(oxidative stress and inflammation)of liver parenchymal cells and is closely related to obesity,impaired glucose tolerance and insulin resistance.Recent studies have showed that the imbalance of intestinal homeostasis,especially the dysfunction of intestinal mucosal barrier,is closely related to the occurrence and development of NAFLD.The proposed "gut-liver axis" theory provides a basis for studying the relationship between the intestine and NAFLD.The search for plant resources and effective ingredients that can repair the imbalance of intestinal homeostasis has gradually become a hot spot for scientists.Epigallocatechin gallate(EGCG),as the main active monomer component of green tea,is the primary component of many health and pharmacological functions of tea.It has been reported that EGCG from tea has a significant effect of regulating lipid and protecting the liver,but its mechanism of action is still not clear enough.In particular,little research has been done on maintaining intestinal homeostasis.Based on these,the effects of tea EGCG on intestinal homeostasis imbalance,especially intestinal mucosal barrier dysfunction,induced by high-fat diet in rats with NAFLD were studied,and the intervention mechanism of tea EGCG on NAFLD was explored in this paper,which provides scientific basis for promoting the highvalue utilization of tea resources and the development of efficient and safe drugs for the prevention of fatty liver injury.The research results of this paper are as follows:EGCG form tea can effectively reduce the body weight,body fat rate and blood lipid levels,improve glucose metabolism and insulin resistance of NAFLD rats induced by highfat diet.Furthermore,EGCG can reduce liver lipid aggregation,down-regulate the expression of liver TLR4/MYD88/NF-?B signaling pathway proteins and proinflammatory cytokines,and rely on its strong antioxidant capacity to reduce liver oxidative stress in NAFLD rats.1.EGCG can reduce systemic endotoxin and diamine oxidase levels,increase intestinal V/C value,reduce the expression of intestinal proinflammatory cytokines and the number of intestinal epithelial cells,protect the intestinal mucosal barrier in NAFLD rats.Meanwhile,EGCG can inhibit the expression of TLR4/MYD88/NF-?B inflammation signaling pathway proteins,increase the expression of intestinal tight junction proteins(ZO-1 and occludin)in the colon of NAFLD rats,regulate the expression of colon oxidative stress related genes,and relieve the intestine oxidative damage and increase the contents of fecal short-chain fatty acids.3.EGCG can also change the composition of intestinal microbes and increase the diversity of intestinal microbes in NAFLD rats.100 mg/kg EGCG was able to make the intestinal microbial composition of NAFLD rats on a high-fat diet close to that of rats on a normal diet.At the phylum level,EGCG can effectively inhibit the relative abundance of Proteobacteria in the intestinal microbes of NAFLD rats.At the genus level,EGCG can significantly reverse 16 genus changes due to a high-fat diet(p < 0.05),and 25 species showed a reversal trend.EGCG can also increase the relative abundance of short-chain fatty acid(SCFAs)producing bacteria and reduce the relative abundance of Gram-negative bacteria.At the OTU level,68 OTUs were changed by high-fat diet,32 of 68 were reversed by EGCG.In addition,24 OTUs were significantly reversed by EGCG and showed significant correlation with NAFLD parameters.In summary,this paper explores the mechanism of EGCG form tea to improve nonalcoholic fatty liver in rats based on the "gut-liver axis" pathway.The results show that EGCG can improve NAFLD and related metabolic diseases by regulating intestinal flora disorders,maintaining intestinal barrier function,and inhibiting intestinal oxidative stress and inflammatory pathways.