Fatty acid synthase coordinates mTOR signaling and histone crotonylation during cardiomyocyte hypertrophy

Background: Epigenetic modifications are central to the regulation of cardiac gene expression during disease. Among these, histone crotonylation (Kcr) has recently emerged as a key modulator of chromatin structure and transcriptional activity. Here, we identify a novel signaling axis linking fatty acid synthase (FASN) to mTOR activation and hypertrophic gene expression through histone crotonylation. Methods: FASN expression, mTOR activation, and histone crotonylation were assessed in mouse hearts and isolated cardiomyocytes using immunoblotting. FASN was silenced by siRNA or inhibited pharmacologically using TVB-2640. Hypertrophic gene expression was quantified by RT-qPCR. Cardiomyocyte hypertrophy was evaluated by immunofluorescence-based cell size analysis. p300 acetylation and crotonylation were assessed by immunoprecipitation and immunoblotting. CUT&RUN-seq and RNA-seq were performed to identify FASN- and Histone H3K18cr-regulated genes during hypertrophic stimulation. Bioinformatic analyses of human RNA-seq and genome-wide association study (GWAS) data were conducted to investigate the clinical relevance of these findings. Results: Histone crotonylation was markedly elevated in hypertrophic myocardium and cardiomyocytes. This increase was driven by upregulated FASN expression in response to hypertrophic stimuli. Genetic or pharmacological inhibition of FASN suppressed histone crotonylation, hypertrophic gene expression, and cardiomyocyte enlargement. Mechanistic studies suggested that FASN regulates histone crotonylation through mTOR-associated signaling and changes in p300 activity. Transcriptomic analyses further revealed that FASN enhances the expression of hypertrophy-associated genes enriched for histone crotonylation marks. Analysis of human sequencing datasets demonstrated a positive association between FASN expression and molecular markers of hypertrophy in patients with hypertrophic cardiomyopathy (HCM). Furthermore, GWAS analysis identified a variant at the FASN locus associated with heart failure as the underlying cause of death and increased FASN expression in cardiomyocytes. Conclusions: Our findings identify FASN as an important regulator of mTOR signalling and histone crotonylation during cardiomyocyte hypertrophy. These results support a potential mechanism linking altered lipid metabolism to epigenetic regulation and pathological cardiac remodelling.