Phosphoethanolamine reverses aberrant DNA methylation in non-alcoholic steatohepatitis caused by Pcyt2 deficiency

Abstract

Abstract Background Accumulating evidence links disruptions in phospholipid homeostasis to obesity, type 2 diabetes, and fatty liver diseases. Mice with a heterozygous ablation of the phosphatidylethanolamine (PE) synthesizing enzyme Pcyt2+/− show reduced PE synthesis and turnover and develop an age-dependent metabolic syndrome that is characterized by impaired fatty acid and glucose metabolism, hypertriglyceridemia, insulin resistance, obesity, and all characteristics of NASH. Aberrant DNA methylation can lead to the onset of pathological phenotypes and is increasingly being implicated in age-related metabolic diseases, including NASH. The methylation of PE to phosphatidylcholine (PC) is a major consumer of liver S-adenosyl methionine (SAM) and thus, alterations in PE metabolism have the potential to influence DNA methylation by modulating SAM availability. Here, we hypothesize that abnormal DNA methylation patterns underly the development of Pcyt2+/− NASH. We conduct an epigenome-wide methylation analysis to determine differential methylation and investigate whether treatment with the Pcyt2 substrate phosphoethanolamine (PEtn) for 8 weeks can reverse aberrant DNA methylation through the stimulation PE synthesis. Results Pcyt2 +/− NASH liver experiences significant alterations in DNA hypo- and hypermethylation relative to Pcyt2+/+. Differentially methylated genes belong to pathways including PI3K-Akt signalling pathway, Foxo signalling pathway, oxidative phosphorylation and insulin signalling/secretion indicating that epigenetic regulation underlies many of our previously established pathological mechanisms of Pcyt2+/− NASH. Previously unidentified pathways during Pcyt2 deficiency are highlighted such as cell cycle regulation and cellular senescence that may contribute to NASH development. Treatment with PEtn dramatically reverses aberrant total and protein-coding DNA methylation patterns by 96%. PEtn treatment restored the methylation status of key genes involved in epigenetic modifications and induced differential methylation of genes associated with obesity and T2DM such as Adyc3, Celsr2, Fam63b. Conclusion The Pcyt2+/− liver methylome and transcriptome is altered and likely underlies much of the pathology in Pcyt2+/− NASH phenotype. PEtn significantly attenuates aberrant DNA methylation in Pcyt2+/− liver by stimulating the CDP:Ethanolamine Kennedy pathway and corrects the epigenetic regulation of genes involved in the pathogenesis of NASH, showing its therapeutic potential. This analysis provides critical insight into the epigenetic basis of NASH pathophysiology and suggests diagnostic markers and therapeutic targets.