The Role Of Gut Microbiota And Endogenous Ethanol’s Metabolism In NASH

Background: Nonalcoholic fatty liver disease (NAFLD) is characterizedby excessive fat accumulation in the liver, without any other evident causes ofchronic liver diseases (viral, autoimmune, genetic, etc.), and without analcohol consumption. The spectrum of NAFLD ranges from nonalcoholic fattyliver(NAFL), with benign prognosis, to a potentially progressive form,nonalcoholic steatohepatitis (NASH), which may lead to liver fibrosis andcirrhosis, liver failure, and hepatocellular carcinoma. NAFLD is generallyasymptomatic. The prevalence of NAFLD in the developed areas in China isestimated to be over30%. Most patients with NAFLD stay in simple hepaticsteatosis without progression to steatohepatitis and fibrosis. However, about20%of NAFLD can progress to NASH which can eventually causeprogressive fibrosis and lead to cirrhosis and related complications includinghepatocellular carcinoma. Though diabetes, obesity and hyperlipidemia arerecognized as risk factors for advanced liver disease, other significant factorsleading to progressive liver injury are remain to be identified. With theaccumulation of researches, a clear link between intestinal bacterialovergrowth and liver damage in NASH has recently been established.Intestinal bacterial overgrowth has been detected in NASH patients withhydrogen breath tests with lactulose and D-xilose. Similarities in the liverpathology of NASH and ethanol exposure suggest that these conditions evokecommon pathogenic mechanisms: ethanol synthesized by intestinal bacteriamight be involved in NASH pathogenesis, since obese female NAFLDpatients present higher levels of breath ethanol. However not all the alcoholicsor NAFLD patients develop into ASH/NASH. Acetaldehyde is a much morepotent toxin to rat astrocytes than ethanol, and at least a part of ethanoltoxicity is due to its first metabolite acetaldehyde. Speculate that the metabolic disorders of endogenous ethanol may play a more important role in thepathogenesis of NASH than endogenous ethanol. And gut bacterial disordermay play a incipient role in the progression of NAFLD.Alcoholdehydrogenase(ADH) and aldehyde dehydrogenase(ALDH) are the keyenzymes in the metabolism of alcohol, and AytP4502E1possess a fraction ofAHD activity(about20%). Detect the activity of serum ADH and ALDH couldinfer the metabolic situation of ethanol.Objective：1Whether there is a difference in intestinal flora quantity and types inNASH, NAFL and NORMAL groups by feces smear and culture.2Detect the activity of alcohol dehydrogenase and aldehydedehydrogenase of human serum alcohol, to determine whether there ismetabolism disorder of endogenous ethanol in NASH.3Expound the relationship between the intestinal flora and themetabolism metabolism disorder of endogenous ethanol.Methods：1Subjects and grouping：33patients with hepatic steatosis andaminotransferase Rised (ALT≥40U/L) as NASH group.27patients withhepatic steatosis and normal aminotransferas（eALT<40U/L）as NAFL group.And29healthy controls as NORMAL group from the medical examinationcentre of the second hospital of Hebei Medical University from July toSeptember of2013. All people included are free from any other evidentcauses of chronic liver diseases (virus, autoimmune, genetic, etc.), or with analcohol consumption.2Methods: stools were collected to smear, gram staining and quantitativebacterial culture,and peripheral serum with over8hours of fasting werecollected to detect the activity of alcohol dehydrogenase and aldehydedehydrogenase by ELISA. The SPSS13.0was used to analyze statistics.Results：1Stool smear counting: the abundance of gut bacteria in NASH group(162+5/view mirror) is slightly lower than that of NAFL group (404+25/ oil field lens, P <0.001), while,the two groups are significantly lower thanthat of normal control group (2573+230/oil field lens, P <0.001).2Stool culture: the numbers of Proteusbacillus and Enterococcus inNASH and NAFL groups are obviously increased than that of NOEMALgroup（9.54±0.186vs9.15±0.23vs8.69±0.21，P<0.001；7.64±0.61vs7.86±0.51，P<0.001）. And the numbers of Bifidobacterium and Bacteroidesare obviously decreased in NASH and NAFL groups compared to NORMALgroup（8.91±0.33vs8.86±0.29vs9.17±0.31，P<0.003；8.93±0.30vs8.90±0.24vs9.19±0.18，P<0.001）Except the Proteusbacillus is increased morebright in NASH than NAFL group, no statistically significant difference canbeviewed in the two groups of the rest three kinds of bacteria.3The incidence of aldehyde accumulation in NASH group is higher thanthat of NAFL and NORMAL groups (P<0.05), and is similar between NAFLand NORMAL groups(P>0.8).4Proteus increase is positively correlated with the accumulation ofacetaldehyde. Spearman correlation coefficient is0.504(P <0.001), the restthree bacterial genus has no obvious correlation with the accumulation ofacetaldehyde.5Proteus has a positive correlation with ALT. Spearman correlationcoefficient is0.755, and the other three bacterial genus has no linear relationwith ALT.Conclusions：1The abundance of gut microbiota is reduced in NASH and NAFLgroups compared to NORMAL group,and the reduction is more obvious inNASH group, indicate that the decrease of gut microbiota may promote theprevalence and progression of NAFL.2Proteus, Enterococcus increase, and Bifidobacterium, Bacteroidesdecrease, may be associated with the occurrence of NAFL. And Proteusincrease may be associated with the progression of NAFL to NASH. 3The incidence of the accumulation of acetaldehyde in NASH issignificantly higher than that in NAFL group and NORMAL group, indicatethat NASH group has ethanol metabolic disorders.4Proteus and acetaldehyde accumulation are closely related, and both arerelated to the occurrence of a NASH, speculated that Proteus can not onlyincrease the production of endogenous alcohol, but also affect the metabolismof endogenous alcohol, the two together promote the occurrence andprogression of NASH.