The Molecular Mechanism Study Of Arid1a Deletion-Induced Nonalcoholic Steatohepatitis

BACKGROUNDS AND OBJECTIVE:Nonalcoholic fatty liver disease?NAFLD?is characterized by the accumulation of fat in the liver without any history of chronic alcohol consumption or other liver injury factor exposure.With the improvement of living standards and the spread of unhealthy lifestyle,the prevalence of NAFLD is set to rise and shows a younger trend.If further accompanied by cell damage,inflammation or fibrosis,NAFLD may lead to more cases of severe end-stage liver disease,including Non-alcoholic steatohepatitis?NASH?,liver fibrosis,cirrhosis and even hepatocellular carcinoma.There are compelling evidences showing that NASH is strongly associated with insulin resistance,diabetes mellitus and obesity,however,the underlying mechanisms for this process are poorly defined,which hinder the exploration of effective treatments.Therefore,understanding its specific regulatory factors is of great significance for elucidating its pathogenesis and finding promising therapeutic approach in clinic.ARID1A,a subunit of SWI/SNF chromatin remodeling complex,may facilitate the access of transcription factors and regulatory proteins to genomic DNA.Loss of ARID1A may result in the structural and functional alterations of SWI/SNF complex,which leads to transcriptional dysfunction through disruption of nucleosome sliding activity,assembly of variant SWI/SNF complexes,targeting to specific genomic loci,and recruitment of coactivator/corepressor activities.So far,most previous studies of SWI/SNF complex are focused on cell proliferation,stem cell differentiation,genomic stability,DNA damage and repair,and the effects of SWI/SNF complex members on nutrient metabolism remain unclear.Our group previously demonstrated that hepatocyte-specific Arid1a deficiency initiated spontaneous HCC,suggesting that Arid1a might participate in lipid mechanism,however,the exact pathological process and the underlying molecular mechanism were unclear.In this project,we aim to explore the role of Arid1a in maintaining the glucose and lipid homeostasis in NAFLD disease.METHODS:Firstly,we established a NAFLD model by employing a high fat diet?HFD?for 12 weeks,and measured the fasting blood glucose and insulin levels of mice.Then the insulin sensitivity of mice was further tested by glucose tolerance test?GTT?and insulin tolerance test?ITT?.In addition,the metabolism-related indicators were determined by utilizing a variety of biological methods,including histology,real-time PCR and enzyme-linked immunosorbent assay?ELISA?.In the subsequent mechanism exploration,we used Western blot analysis?WB?,chromatin immunoprecipitation?ChIP?,RNA sequencing?RNA-seq?and Transposase-Accessible Chromatin with high-throughput sequencing?ATAC-seq?to prove that Arid1a deficiency may lead to the blockage of fatty acid oxidation process,inducing lipid accumulation and insulin resistance.RESULTS:In this report,we showed that hepatic Arid1a deletion mice(Arid1a^LKO)gained much more body weights than control(Arid1a^F/F)mice when placed on a high-fat diet?HFD?.In parallel,Arid1a^LKO mice showed significantly elevated levels of fasting blood glucose and insulin,as well as the markedly decreased insulin sensitivity.Blood lipid testing revealed that liver cholesterol?TCHO?and triglyceride?TG?were much higher in Arid1a^LKO animals,compared to Arid1a^F/F littermates,and Arid1a deletion also aggravated inflammatory response,suggesting that Arid1a deficiency may aggravate fatty hepatitis induced by high-fat diet.In vitro,Arid1a deletion in hepatocytes directly leads to free fatty acid-induced lipid accumulation and insulin resistance.Mechanically,Arid1a deficiency leads to the reduction of chromatin modification characteristic of transcriptional activation on multiple metabolic genes,especially Cpt1a and Acox1,two rate-limiting enzyme genes for fatty acid oxidation.Furthermore,our data indicated that Arid1a loss promotes hepatic steatosis by downregulating PPAR?,thereby impairing fatty acid oxidation which leads to lipid accumulation and insulin resistance.These findings reveal that targeting ARID1a might be a promising therapeutic strategy for liver steatosis and insulin resistance.