Indeed, a downregulation of the expression of cystathionine-γ lyase (CSE) and cystathionine-β synthase (CBS), the main enzymes involved in H2S synthesis, and a reduced vasodilatory effect of an H2S donor, NaHS, are closely related to eNOS impairment and therefore to ED associated with MetS [38,40]. This evidence concerns the gene NOS3 and metabolic syndrome.