The Regulatory Mechanism Of Enteromorpha Polysaccharides On Hypercholesterolemia Mice Based On Gut Microbiota And Metabonomics

Object:The previous research explored the molecular mechanism of Enteromorpha polysaccharides(EP)to improve cholesterol metabolism.Most of the bioactive polysaccharides ingested by the human body cannot be directly digested or absorbed by the small intestine,but can be fermented and degraded by the intestinal flora,and then play a role in regulating metabolism.This study established a hypercholesterolemia C57BL/6 mice model induced by a high-fat and high-cholesterol diet(HFHC),and the mice were given three concentration gradients of EP,aims to study the role of gut microbiota and its metabolites in the improvement of cholesterol metabolism by EP.Method:Fifty male C57BL/6 mice were adaptively fed for 1 week and randomly divided into5 groups according to their body weight,10 in each group,which were respectively the control group(Control),the high-fat and high-cholesterol diet model group(HFHC),the high-fat and high-cholesterol diet+low-dose EP group(HFHC+LEP,100mg/kg·BW),the high-fat and high-cholesterol diet+mid-dose EP group(HFHC+MEP,200mg/kg·BW),the high-fat and high-cholesterol diet+high-dose EP group(HFHC+HEP,300mg/kg·BW).The control group was given normal diet,and the other four groups were fed with high-fat and high-cholesterol diet for 12 weeks.Observe the general conditions and record their body weight and food intake;test blood lipid index,serum transaminase content,liver lipid content,liver cholesterol metabolism-related gene expression level;16s r DNA microorganisms Diversity sequencing to detect changes in the structure of the gut microbiota of C57BL/6 mice;UHPLC-PRM-MS/MS was used to detect bile acids in the fecal intestinal flora concentration;~1H-NMR metabolomics technology was used to detect changes in the content of metabolites in the cecum of C57BL/6 mice.Result:1.EP(high dose group)can significantly reduce the relative liver weight of C57BL/6mice with hypercholesterolemia,reduce serum TC,LDL-C,increase HDL-C levels(P<0.05),reduce liver lipid deposition,and reduce liver TC content,Improve liver lipid deposition and liver damage.2.EP(high dose group)can significantly increase the expression of liver cholesterol uptake genes LDLR,bile acid synthesis-related genes CYP7A1,CYP27A1,and bile acid receptor FXR in C57BL/6 mice with hypercholesterolemia(P<0.05),and promoted the metabolism and transformation of cholesterol in the body.3.16s r DNA intestinal microbial sequencing results showed that the composition of the gut microbiota of hypercholesterolemia C57BL/6 mice has changed significantly,and EP can reverse the gut microbiota caused by high-fat and high-cholesterol diet to a certain extent.EP significantly increased the relative abundance of Bacteroidetes and its sub-categories Bacteroidales and its sub-categories Muribaculaceae,norank＿f＿Muribaculaceae,Clostridiaceae＿1 and Clostridium＿sensu＿stricto＿13 and so on.EP significantly reduced Proteobacteria and its sub-categories Escherichia-Shigella and Parasutterella.Spearman correlation analysis suggests that the abundance of Bacteroides,Proteobacteria,Clostridium＿sensu＿stricto＿13 are related to serum TC,LDL-C,HDL-C,etc.4.UHPLC-PRM-MS/MS detection results showed that EP caused substantial changes in ursodeoxycholic acid,ursolic acid and lambda murine cholic acid,significantly reduced the ratio of combined bile acids.Spearman correlation analysis reveals Bacteroides,norank＿f＿Muribaculaceae is significantly negatively correlated with conjugated bile acids and ~1H-NMR showed EP caused significant changes in 20metabolites,including Acetate,Propionate,Methionine,Nicotinate,Alanine,Ribose,etc.Spearman correlation analysis reveals short-chain fatty acids,branched-chain amino acids,and lactic acid are significantly related to Bacteroides,Muribculaceae,and Proteobacteria.Conclusion:EP can reduce the blood and liver cholesterol levels of mice by up-regulating the expression of liver cholesterol intake and bile acid synthesis-related genes.Its mechanism may be similar to that EP can improve mouse gut microbiota caused by high-fat and high-cholesterol diet and regulate the composition of gut metabolites.Specifically,EP can reduce the ratio of feces conjugated bile acids,which may inhibit the efficiency of the enterohepatic circulation of bile acids,thereby promoting the metabolic conversion of cholesterol to bile acids,and the decrease in the ratio of bound bile acids may be in contrast to increased relative abundance of the bacterial species with bile salt hydrolase activity,such as Bacteroides,Muribculaceae,etc.