Ahcy Acts as an Effector of Hnf4a-Driven Super-Enhancer Activation to Alleviate MASLD During Intermittent Fasting.

Intermittent fasting (IF) ameliorates metabolic dysfunction-associated steatotic liver disease (MASLD), but the underlying mechanism remains unclear. Combined CUT&Run and transcriptomic analysis shows that hepatic Ahcy is controlled by the super‑enhancer (SE) and acts as a key mediator of IF's benefit. Liver‑specific Ahcy knockout worsens high‑fat diet (HFD)‑induced hepatic steatosis and blunts the protective effect of IF. Furthermore, inhibition of Brd4 or deletion of the core SE region reduces Ahcy expression and exacerbates lipid accumulation in vivo or in vitro. Hnf4a is identified as the transcription factor driving the Ahcy-SE. In vitro and in vivo experiments demonstrate that IF-activated Hnf4a directly binds to and activates the Ahcy-SE. Ahcy knockdown attenuates the lipid-deposition-reducing effect of Hnf4a overexpression in mice fed a HFD. In AhcyLKO mice, the liver SAM/SAH ratio is reduced, and Reduced Representation Bisulfite Sequencing (RRBS) and transcriptome sequencing reveal liver-specific methylation remodeling. One manifestation of this remodeling is hypermethylation of metabolic gene promoters, including the Acot12 promoter, where aberrant recruitment of Dnmt3b leads to silencing of the gene and impaired lipid hydrolysis. Therefore, these findings define an IF-Hnf4a-Ahcy pathway that activates SE-driven Ahcy to orchestrate protective epigenetic reprogramming in MASLD.