High-resolution DNA methylation changes reveal biomarkers of heart failure with preserved ejection fraction versus reduced ejection fraction.

Novel biomarkers are needed to better identify-and distinguish-heart failure with preserved ejection fraction (HFpEF) from other clinical phenotypes. The goal of our study was to identify epigenetic-sensitive biomarkers useful to a more accurate diagnosis of HFpEF. We performed a network-oriented genome-wide DNA methylation study of circulating CD4 T lymphocytes isolated from peripheral blood using reduced representation bisulfite sequencing (RRBS) in two cohorts (i.e., discovery/validation) each of both male and female patients with HFpEF (n = 12/10), HF with reduced EF (HFrEF; n = 7/5), and volunteers lacking clinical evidence of HF (CON; n = 7/5). RRBS is the gold-standard platform for measuring genome-wide DNA methylation changes at single-cytosine resolution in hypothesis-generating studies. We identified three hypomethylated HFpEF-specific differentially methylated positions (DMPs) associated with FOXB1, ELMOD1, and DGKH genes wherein ROC curve analysis revealed that increased expression levels had a reasonable diagnostic performance in predicting HFpEF (AUC ≥ 0.8, p < 0.05). Network analysis identified additional three genes including JUNB (p = 0.037), SETD7 (p = 0.003), and MEF2D (p = 0.0001) which were significantly higher in HFpEF vs. HFrEF patients. ROC curve analysis showed that integrating the functional HFPEF classification with the expression levels of the FOXB1, ELMOD1, and DGKH as well as the JUNB, SETD7, and MEF2D genes improved diagnostic accuracy, with AUC = 0.8 (p < 0.0001) as compared to HFPEF score alone (p > 0.05). Besides, increased expression levels of SETD7-RELA-IL6 axis significantly discriminated overweight/obese HFpEF vs. HFrEF patients (AUC = 1; p = 0.001, p = 0.006, p = 0.006, respectively). We support an emerging dogma that indirect epigenetic testing via high-resolution RRBS methylomics represents a non-invasive tool that may enable easier access to both diagnostic and mechanistic insights of HFpEF. An epigenetic-oriented dysregulation of network-derived SETD7-RELA-IL6 axis in circulating CD4 T lymphocytes may drive pro-inflammatory responses which, in turn, may lead to cardiac remodeling in overweight/obese HFpEF.