The oxidation of tetrahydrobiopterin, the cofactor of eNOS, is responsible for the increased formation of oxygen-derived radicals due to eNOS uncoupling, contributing to vascular dysfunction associated with T2D [28]; meanwhile, the reaction of NO with superoxide generates peroxynitrite, which is considered a mediator of cytokine-induced islet β cell destruction [29] (Table 1). Here, NOS3 is linked to type 2 diabetes mellitus.