BET Inhibition with apabetalone restores cardiometabolic HFpEF through suppression of myocardial and systemic inflammation

Background Limited therapeutic options are available for cardiometabolic heart failure with preserved ejection fraction (cHFpEF). Bromodomain (BRD) and extraterminal containing protein family (BET) proteins bind acetylated histone motif to initiate gene transcription. Apabetalone (APA), an FDA approved BET inhibitor, has recently shown to reduce cardiovascular events and heart failure hospitalization in patients with diabetes and coronary artery disease. Purpose The present study investigates the molecular mechanisms and therapeutic effects of APA in cHFpEF. Methods Mice were subjected to high fat diet feeding and L-NAME treatment for 15 weeks to induce cHFpEF and were treated with the BET inhibitor APA (150mg/kg/day) or vehicle for 14 days. Histology, echocardiography, and Treadmill exhaustion test were performed. Unbiased gene expression profiling via PCR array and proteomic analysis (Olink) were conducted on left ventricular (LV) myocardial specimens obtained from HFpEF and control mice. Chromatin immunoprecipitation sequencing (ChIPseq) was employed to study the genome-wide distribution of H3K27ac, while ChIP assays were employed to investigate BRD4 enrichment on genes showing the highest H3K27ac enrichment. The role of BET proteins was validated in cultured cardiomyocytes (CMs) exposed to metabolic stress (palmitic acid, PA). Finally, passive stiffness of skinned CMs isolated from cHFpEF patients was assessed ex vivo before and after APA treatment. Results cHFpEF mice displayed LV hypertrophy, diastolic dysfunction, lung congestion and impaired exercise tolerance as compared to controls. ChiP-seq showed a genome wide increase of histone acetylation (H3K27ac) in HFpEF as compared to control hearts, suggesting the potential of BET-modulating strategies in this setting. Of interest, treatment with the BET inhibitor APA rescued diastolic dysfunction, lung congestion and exercise intolerance in HFpEF mice. cHFpEF mice showed myocardial upregulation of inflammatory genes, namely IL-6, TNF-alpha, and IL-1beta, whereas APA suppressed their levels, with a pronounced effect on IL-6 expression. ChIP assays confirmed a strong enrichment of BRD4 and H3K27ac on target inflammatory genes in HFpEF vs control hearts. Notably, APA also exerted systemic anti-inflammatory effects with suppression of several chemokines, as assessed by proteomic profiling in plasma from HFpEF vs control mice. At the mechanistic level, the beneficial effects of APA were mainly explained by the modulation of IL-6/CaMKII/STAT3 pathway both in cHFpEF hearts and PA-treated CMs. Of clinical relevance, treatment with APA attenuated passive stiffness in skinned CMs from cHFpEF patients. Conclusions In mice and patients, we show for the first time that the FDA approved BET inhibitor APA exerts significant beneficial effects in cHFpEF. Our results set the stage for validation in large preclinical models and clinical trials testing APA in patients with cHFpEF.