Abstract Background Cardiometabolic heart failure with preserved ejection fraction (cHFpEF) is a prevalent disease whose mechanisms remain poorly understood. Key biological processes such as autophagy appear to be heavily involved in the pathophysiology of the disease, with epigenetic modulators acting as a bridge between environmental stressors and transcriptional changes. Within this context, bromodomain and extraterminal domain (BET) proteins, functioning as epigenetic readers of acetylated histones, have attracted considerable interest as potential therapeutic targets to modulate maladaptive gene expression. The role of BET proteins in regulating cardiac autophagy remains largely unexplored. Here, we propose that BET proteins modulate autophagy in cHFpEF, and that their pharmacological inhibition restores autophagic flux and alleviates cardiac dysfunction. Methods An established experimental mouse model of cHFpEF combining metabolic and hemodynamic stress for 15 weeks was used in our study. To investigate autophagy regulation at the cellular level, we performed single nuclei RNA sequencing (snRNAseq) using the 10x Genomics platform. Chromatin immunoprecipitation sequencing (ChIP-seq) was conducted to evaluate histone modifications at autophagy-related gene loci and gene set enrichment analysis (GSEA) was performed using Reactome gene sets with significance determined by false discovery rate (FDR). Subsequently, cHFpEF and control mice were treated with either vehicle or the selective BET inhibitor RVX-208 (Apabetalone) for 21 days. Cardiac function was assessed by echocardiography, and expression of autophagy-related genes was quantified using a custom real-time PCR array. Cardiomyocytes exposed to metabolic stress (palmitic acid, PA) were used as an in vitro model mimicking cHFpEF. Results snRNAseq revealed a significant downregulation of autophagy-related genes in hearts from HFpEF mice compared to controls. Cell clustering identified a distinct subset of ventricular cardiomyocytes (CM) characterized by impaired autophagy, driven by activation of mTOR and calcineurin signaling pathways. This maladaptive response was associated with sustained oxidative stress and mitochondrial dynamics, fostering mitochondrial damage and eventually apoptosis highlighting a potential mechanistic link between defective autophagy and cardiomyocyte dysfunction in HfpEF (Figure 1). Epigenomic profiling demonstrated strong enrichment of active chromatin marks, particularly H3K27ac, recognized by BET proteins, at gene loci involved in autophagy and stress responses (Figure 2). Importantly, pharmacological BET inhibition with RVX-208 restored autophagy-related transcriptional programs in the cHFpEF myocardium and improved both diastolic function and exercise capacity. Conclusions Our study reveals a BET-driven epigenetic block of autophagy in cHFpEF, reversible by BET inhibition, highlighting FDA-approved BET inhibitors as potential therapies of cHFpEF.snRNAseq in HFpEF vs. Control heartsFor image description, please refer to the figure legend and surrounding text. ChIP of H3K27acFor image description, please refer to the figure legend and surrounding text.
Venanzio et al. (Sun,) studied this question.