XDH and diabetes mellitus: Indeed, activation of xanthine oxidase (XO), enzymes of the mitochondrial respiratory chain, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX), cyclooxygenase and uncoupled endothelial nitric oxide synthase (eNOS) as well as modulation of ROS-redox-sensitive factors such as protein kinase C (PKC) and a metabolic gene implicated in redox balance, thioredoxin-interacting protein (TXNIP) have been reported to be relevant in the pathogenesis of atherosclerosis in diabetes [36,37,38].