Aims:Accumulation of reactive oxygen species (ROS) promotes vascular disease in obesity, but the underlying molecular mechanisms remain poorly understood. The adaptor p66Shc is emerging as a key molecule responsible for ROS generation and vascular damage. This study investigates whether epigenetic regulation of p66Shc contributes to obesity-related vascular disease. Methods and results:ROS-driven endothelial dysfunction was observed in visceral fat arteries (VFAs) isolated from obese subjects when compared with normal weight controls. Gene profiling of chromatin-modifying enzymes in VFA revealed a significant dysregulation of methyltransferase SUV39H1 (fold change, -6.9, P < 0.01), demethylase JMJD2C (fold change, 3.2, P < 0.01), and acetyltransferase SRC-1 (fold change, 5.8, P < 0.01) in obese vs. control VFA. These changes were associated with reduced di-(H3K9me2) and trimethylation (H3K9me3) as well as acetylation (H3K9ac) of histone 3 lysine 9 (H3K9) on p66Shc promoter. Reprogramming SUV39H1, JMJD2C, and SRC-1 in isolated endothelial cells as well as in aortas from obese mice (LepOb/Ob) suppressed p66Shc-derived ROS, restored nitric oxide levels, and rescued endothelial dysfunction. Consistently, in vivo editing of chromatin remodellers blunted obesity-related vascular p66Shc expression. We show that SUV39H1 is the upstream effector orchestrating JMJD2C/SRC-1 recruitment to p66Shc promoter. Indeed, SUV39H1 overexpression in obese mice erased H3K9-related changes on p66Shc promoter, while SUV39H1 genetic deletion in lean mice recapitulated obesity-induced H3K9 remodelling and p66Shc transcription. Conclusion:These results uncover a novel epigenetic mechanism underlying endothelial dysfunction in obesity. Targeting SUV39H1 may attenuate oxidative transcriptional programmes and thus prevent vascular disease in obese individuals.