Effect Of High-fat Diet On The Expression Of Liver Bile Acid Regulatory Pathway Genes In C57BL/6J Mice

Objective:In order to reveal the effect of high-fat diet on the regulation of key metabolic genes in the liver bile acid pathway in mice,and to provide a theoretical basis for drug discovery and gene targeting and clinical precise drug use.Methods:After adaptive feeding for 1 week,a total of 55 male C57BL/6J mice were randomly divided into 5 groups(n=10).The mice in the model group were fed with a high-fat diet(feed calorie composition: fat 60%;carbohydrate 20%;protein 20%)and the control group was fed an ordinary diet(feed calorie composition: fat 12.1%;carbohydrate 64.7%;protein 23.2 %).After 16 weeks of feeding,the biochemical method is adopted to determine the target animal serum total cholesterol(TC),triglyceride(TG),low density lipoprotein(LDL-C),high density lipoprotein(HDL-C)and indexes of blood sugar,combined with liver pathological to determine the model was established successfully.LC-MS was used to analyze the bile acid content in the liver.Total RNA liver tissue samples was extracted from the control group and the model group with typical changes.Using principal component analysis,heat map visualization,mapping method and other methods for data mining,and find out a significant change of bile acid and differentially expressed genes.Then,the feeding time extended to 38 weeksto analyze the effects of age and duration of high-fat diet induction on this study.Results:1.After 16 weeks of free intake of high-fat diet,the body weight,serum total cholesterol,low density lipoprotein and blood glucose in C57 BL / 6J mice were significantly increased(P <0.05),and the model group in mice impaired glucose tolerance and insulin resistance,similar to human hyperlipidemia.Histopathologicalchanges of liver tissue were observed by HE staining.The edema of hepatocytes was obvious,hepatic sinusoids was disappeared or unclear,and the nuclei were squeezed to the edge by the lipid droplets vacuolization,indicating that high-fat diet caused hepatic steatosis of liver cells in mice,in line with non-alcoholic fatty liver disease pathological features.Moreover,liver cholic acid and chenodeoxycholic acid decreased significantly(P <0.05)2.For 16 weeks,heat map visualization visually demonstrated significant changes in gene expression in the bile acid pathway in the control and model groups.The overall profile of differentially expressed genes could be visualized from the volcano plot results.Using the principal component analysis method,in the case of selecting two principal components,the two groups of mice in the score map were clustered and could be significantly distinguished,and combined with the loading map information,the most significant change was seven genes by high-fat dietary.The differential gene expression folds were quantified by histograms.With the extension of feeding time,Cyp39a1,Scp2 and Hsd17b4 genes were presented in the model group with high expression at 16 weeks,and reversed at 38 weeks.The Fgfr4,Hnf4α and Nr0b2 genes were down-regulated at 16 and 38 weeks,and the degree of down-regulation was more significant at 38 weeks.3.The visualization of the heat map showed the influence of the bile acid level on the high-fat diet from the macro level,which showed the overall contour of bile acid with significant changes.Using the principal component analysis method,the data of 16 weeks and 38 weeks were analyzed under the condition of selecting two main components.The four groups of mice in the score map were clustered but could be significantly distinguished.Combined with the information in the load map,the most significant changes in bile acids were taurate chenodeoxycholic acid(TCDCA),taurine cholic acid(TCA),and taurodeoxycholic acid(TDCA).4.After the animal model was established successfully,correlation studies found that the correlation between differentially expressed genes was: Scp2 positively correlated with Hsd17b4 and Nrlh4;Nr0b2 and Hsd3b7 were positively correlated;Fgfr4 and Mapk3 were positively correlated.In addition,TC was positively correlated with body weight,LDL-C,and negatively correlated with Slc27a5 gene.Conclusion:1.Long-term high-fat diet caused significant changes in gene expression on the bile acid pathway in male C57BL/6J mice,which will directly affect the metabolism of drugs that are more affected by liver drug enzymes.2.Age changes and intervention time of high-fat diet in mice may lead to the reversal of the regulation of some key genes,which should be paid attention to in the clinical application of precision medicine.