Chromatin Rewiring by SETD2 Drives Lipotoxic Injury in Cardiometabolic HFpEF

BACKGROUND Cardiometabolic heart failure with preserved ejection fraction (cHFpEF) is a highly prevalent and deadly condition. Histone 3 trimethylation at lysine 36 (H3k36me3)-a chromatin signature induced by the histone methyltransferase SETD2 (SET domain containing 2)-correlates with changes in gene expression in human failing hearts; however, its role remains poorly understood. This study investigates the role of SETD2 in cHFpEF. METHODS Chromatin immunoprecipitation sequencing and RNA sequencing were used to investigate H3k36me3-related transcriptional regulation. Mice with cardiomyocyte-specific deletion of SETD2 (c-SETD2$^{-/-}$) were generated and subjected to high-fat diet feeding and L-NAME treatment for 15 weeks to induce cHFpEF. Cardiac function and exercise tolerance were assessed by echocardiography and treadmill exhaustion test. A selective pharmacological inhibitor of SETD2, EZM0414, was also tested in cHFpEF mice. Mechanistic experiments were performed in cultured cardiomyocytes exposed to palmitic acid. SETD2 signaling and the effects of EZM0414 were also investigated in cardiomyocytes from patients with cHFpEF and control donors. RESULTS SETD2 was upregulated in cHFpEF mouse hearts, and its chromatin mark H3k36me3 was involved in lipid metabolism and highly enriched on the promoter of the Srebf1 gene, encoding for SREBP1 (sterol regulatory binding protein 1). SETD2 activation in cHFpEF led to SREBP1 upregulation, triglyceride accumulation, and lipotoxic damage. Of note, cardiomyocyte-specific deletion of SETD2 in mice prevented heart failure with preserved ejection fraction-related hypertrophy, diastolic dysfunction, and lung congestion while improving exercise tolerance. SETD2 deletion blunted H3K36me3 enrichment on Srebf1 promoter, thus leading to a marked rewiring of the cardiac lipidome and restoration of autophagic flux. In vivo treatment with the SETD2 inhibitor EZM0414 recapitulated the effects of SETD2 deletion. Silencing of SETD2 in palmitic acid-treated cardiomyocytes prevented SREBP1 upregulation, whereas SETD2 overexpression mirrored lipotoxic damage. Finally, SETD2 was upregulated in left ventricle specimens from patients with cHFpEF while EZM0414 attenuated cardiomyocyte stiffness. CONCLUSIONS Targeting SETD2 might prevent lipotoxic injury in cHFpEF.