Tributyrin inhibits ethanol-induced epigenetic repression of CPT-1A and attenuates hepatic steatosis and injury

Abstract: Background & Aims Ethanol-mediated downregulation of CPT-1A gene expression plays a major role in the development of hepatic steatosis; however, the underlying mechanisms are not completely elucidated. Tributyrin, a butyrate prodrug that can inhibit HDAC activity, attenuates hepatic steatosis and injury. The present study examined the beneficial effect of tributyrin/butyrate in attenuating ethanol-induced pathogenic epigenetic mechanisms affecting CPT-1A promoter-histone modifications and gene expression and hepatic steatosis/injury. Methods Mice were fed a liquid Lieber-DeCarli diet with or without ethanol for 4 weeks. In a subset of mice, tributyrin (2g/kg) was administered orally by gavage. Primary rat hepatocytes were treated with ethanol 50 mM and/or butyrate 2 mM. Gene expression and epigenetic modifications at CPT-1A promoter were analyzed by chromatin immunoprecipitation (ChIP) analysis. Results In vivo, ethanol induced hepatic CPT-1A promoter histone H3K9 de-acetylation, indicative of repressive chromatin state, and decreased CPT-1A gene expression. Our data identified HDAC1 as the predominant HDAC causing CPT-1A promoter histone H3K9 de-acetylation and epigenetic downregulation of gene expression. Significantly, SP1 and HNF4α participated in the recruitment of HDAC1 to the proximal and distal regions of CPT-1A promoter respectively and mediated transcriptional repression. Importantly, butyrate, a dietary HDAC inhibitor, attenuated ethanol-induced recruitment of HDAC1 and facilitated p300-HAT binding by enabling SP1/p300 interaction at proximal region and HNF4α/PGC-1α/p300 interactions at distal region, leading to promoter histone acetylation and enhanced CPT-1A transcription. Conclusions Study identifies HDAC1-mediated repressive epigenetic mechanisms that underlie ethanol-mediated decrease in CPT-1A expression. Importantly, tributyrin/butyrate inhibits HDAC1, rescues CPT-1A expression and attenuates ethanol mediated hepatic steatosis and injury, suggesting its potential use in therapeutic strategies for ALD.