Study On The Relationship Between Intestinal Microbiota And Metabolism In The Development Of NAFLD

Background:Evidence is increasingly suggesting that the role of the intestinal microbiota(IM)in the pathogenesis of Non-alcoholic fatty liver disease(NAFLD).However,the underlying mechanism of gut microbial involvement in NAFLD has not been elucidated.Previous studies focused more on the changes in the structure and function of the IM during the NAFLD,but how the microbiota affect the metabolism has not been reported.Based on the pre-experimental study,we suggested that the intestinal dysbiosis may affect the bile acids metabolism.Changed bile acids will affect the absorption and digestion of lipids,thereby promoting the development of NAFLD.In addition,IM significantly affects the metabolic phenotype of the host especially amino acid metabolism and participates in the process of metabolism.This study sought to examine the metabonomic changes especially bile acids and amino acid metabolism homeostasis in patients with NAFLD and to relate that with IM.Methods:Totally 166 subjects were recruited:93 patients with NAFLD(non-alcoholic fatty liver:NAFL(n = 53)and non-alcoholic steatohepatitis:NASH(n-40))and 73 healthy controls(HCs).The microbial community was profiled by denaturing gradient gel electrophoresis(DGGE)and examined by Illumina(?)MiSeq platform of the 16S ribosomal RNA V3 region.UPLC-MS/MS and nuclear magnetic resonance(NMR)were used to detect metabolic changes in NAFLD patients.Results:Compared with HC,NS patients had less phylum Bacteroidetes(25.78%vs.44.71%,P<0.05),but higher Proteobacteria(18.21%vs.6.52%P<0.05)and Actinobacteria(3.84%vs.2.32%P<0.05).At the family level,member of the Bacteroidaceae(24.78%vs.43.71%,P<0.05)were similar with phylum Bacteroidetes,significantly decreased in NASH group than HC.The prevalence of Enterobacteriaceae was higher in NASH patients when compared with healthy control(3.84%vs.2.32%P<0.05).At the genus level,Bacteroides significantly decreased in NASH group than HC(24.78%vs.43.71%,P<0.05);but genus Blautia was higher in NASH patients when compared with healthy control(3.84%vs.2.32%P<0.05).Through the functional metabolic analysis,we found that the functional genes involved in the metabolic pathway of the intestinal microflora in NAFLD patients were significantly changed.The fecal primary bile acids were significantly higher in the gut of patients with NASH compared with HC and NAFL.Through the method of nuclear magnetic analysis,we found that the metabolic mass spectrum in the blood were different among HC,NAFL and NASH group.Through the correlation analysis,we found that the altered IM were significantly related with liver biochemical indicators,bile acid content and plasma metabolic substances,suggesting that intestinal flora is likely to change the body metabolism to affect the occurrence and progress of NAFLD.And fecal bile acids and serum metabolites,especially amino acids,can combined with liver biochemical markers for the prediction of the severity of NAFLD.Conclusion:The structure and function of intestinal microbiota in NAFLD patients were significantly changed.And changed IM may influence the transformation of bile acids which play an important role in lipid metabolism.Intestinal dysbiosis also influence the amino acid metabolism,and changed amino acid can provide a new method to predict the progress of NAFLD.