| Long-term excessive alcohol consumption will induce hepatic lesions,the initial symptom of which is alcoholic fatty liver,i.e.,lipid accumulation in hepatocytes,always accompanied by the occurrence of alcoholic hepatitis.Continuous alcohol consumption often leads to the further aggravation of the alcoholic liver disease and the occurrence of other diseases,including cirrhosis,diabetes and pancreatic lesions,which are often irreversible.Therefore,in the stage of alcoholic fatty liver,timely inhibition of lipid accumulation,alleviation of steatohepatitis,will help slow down the progression of alcoholic liver disease.In recent years,some biological agents especially probiotics have been widely used in the remission and treatment of a variety of diseases due to their good efficacy and less adverse reactions,etc..However,the mechanism of probiotics in alleviating liver disease is not thorough enough,hindering the application of probiotics in clinical practice.This study aims to explore the alleviating effect of L.plantarum P101 on alcoholic lipid accumulation in mice liver,and elucidate the potential mechanism of probiotics to intervene liver disease distally.The contents of each chapter are described as follows:Chapter 1: This chapter reviewed the pathogenesis and treatment status of alcoholic fatty liver,and discusses the function and the possible mechanism of probiotics on alleviating alcoholic fatty liver.Chapter 2: In order to explore the alleviating effect of L.plantarum P101 on alcoholic lipid accumulation in mice liver and the signal pathway mechanism,this chapter comprehensively evaluated the biochemical indicators of serum and liver,oxidative stress and inflammation indicators,histopathological changes and the signal pathways related to the lipid homeostasis regulated by AMPK.The results showed that mice fed with alcoholic liquid diet had obvious lipid accumulation symptoms,while after intervention by L.plantarum P101,the AMPK signal pathway in mice liver was activated,enhancing fatty acid metabolism,alleviating liver injury and reducing lipid deposition.However,after inhibiting the AMPK signal pathway,the alleviating effect of L.plantarum P101 on alcoholic lipid accumulation in mice liver was weakened.The above results indicated that L.plantarum P101 alleviated alcohol-induced liver injury and lipid accumulation in mice based on the AMPK signal pathway partially.Chapter 3: In order to explore the distal alleviating mechanism of L.plantarum P101 on alcoholic lipid accumulation in mice liver,this chapter comprehensively evaluated the diversity and composition of gut microbiota by using high-throughput sequencing technology.The results showed that the diversity of gut microbiota were recovered,the microbial composition was more similar to that of the pair-fed group,and the relative abundance of some beneficial bacteria was increased after intervention by L.plantarum P101.Some specific bacterial genera were strongly correlated with AMPK-related signal pathway and lipid accumulation.In addition,the fecal microbiota from mice fed with alcoholic liquid diet caused liver injury and lipid accumulation symptoms in the recipient mice.However,the fecal microbiota from mice intervened by L.plantarum P101 did not cause obvious liver injury in the recipient mice,and the expression of AMPK and fatty acid metabolism related genes was up-regulated.The above results indicated that the effect of L.plantarum P101 on alleviating alcoholic liver injury and lipid accumulation in mice based on the AMPK signal pathway,might be mediated by intestinal microbiota.Chapter 4: In order to further investigate the mitigation mechanism of L.plantarum P101 on alcoholic hepatic lipid accumulation based on gut microbiota,the serum metabolite composition and specific small molecules were comprehensive assessed by using the un-targeted metabolomics.The results showed that after the intervention with L.plantarum P101,the serum metabolite composition of mice was more similar to that of control group,and some anti-inflammatory metabolites derived from gut microbiota were increased.Some altered specific metabolites were strongly correlated with gut microbiota and alcoholic hepatic lipid accumulation and alleviation.In addition,the tryptophan metabolism was significantly changed by alcoholic liquid diet or L.plantarum P101 intervention in mice.The serum kynurenic acid were significantly increased in mice fed with alcoholic liquid diet,while the levels of gut microbial-dependent indoles were significantly increased in the mice with the intervention of L.plantarum P101,especially indole-3-acetamide(IAM),which might be a potential metabolic marker for the intervention effect of L.plantarum P101.The above results suggested that the attenuation effect of L.plantarum P101 on liver injury and lipid accumulation in mice might be achieved by regulating gut microbiota and its derived metabolites.Chapter 5: In order to explore the alleviating effect of gut microbiota-derived metabolic markers on the alcoholic lipid accumulation,this chapter evaluated the biochemical indicators and lipid homeostasis-related signal pathways regulated by AMPK in Hep G2 cells induced by ethanol(Et OH)and intervened by IAM.The results showed that IAM pre-intervention alleviated the cell damage,reduced intracellular lipid accumulation,and also activated the AMPK signal pathway,enhanced fatty acid metabolism.It is noteworthy that the Aryl hydrocarbon receptor(Ah R)protein and related target genes of Hep G2 cells were activated by IAM,and the Ah R protein and related target genes in the mice liver intervened by L.plantarum P101 were also significantly activated,which might be related to the content of IAM increased by L.plantarum P101.The above results indicated that the gut microbiotaderived metabolic marker IAM might trigger AMPK-regulated lipid metabolism cascade reaction by activating Ah R.To sum up,the present study demonstrated that L.plantarum P101 alleviated the alcohol-induced hepatic lipid accumulation in the mice liver,and the effect might be mediated by gut microbiota and its derived metabolites.The metabolic biomarker IAM on AMPK signal pathway through activating Ah R may be a potential mechanism. |
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