Pparα and fatty acid oxidation coordinate hepatic transcriptional architecture

Fasting requires tight coordination between the metabolism and transcriptional output of hepatocytes to maintain systemic glucose and lipid homeostasis. Deficits in hepatic fatty acid oxidation result in dramatic fasting-induced hepatocyte lipid accumulation and induction of genes for oxidative metabolism that are largely driven by Pparα. While fatty acid oxidation is required for a rise in acetyl-CoA and subsequent lysine acetylation following a fast, changes in histone acetylation (total, H3K9ac, and H3K27ac) do not require fatty acid oxidation. Active enhancers in fasting mice are enriched for Pparα binding motifs. Genetically-defined inhibition of hepatic fatty acid oxidation results in higher levels of chromatin accessibility as well as elevated enhancer priming and acetylation proximal to Pparα sites largely associated with genes in lipid metabolism. Also, greater number of Pparα-associated H3K27ac signal changes occur at active enhancers compared to promoters, suggesting a mechanism for Pparα to tune target expression levels at pre-primed sites. Overall, these data show the requirement for Pparα activation in maintaining transcriptionally permissive hepatic genomic architecture particularly when fatty acid oxidation is limiting.