NOS3 and endothelial dysfunction: Sirtuin1 (Sirt1) is a class III histone deacetylase expressed in cell types comprising the vascular wall that stimulates endothelial nitric oxide (NO) by deacetylating endothelial nitric oxide synthase (eNOS), promotes endothelium-dependent vasorelaxation, and protects against endothelial dysfunction and atherosclerosis9, 10.