It has been shown in both preclinical and clinical studies that during the development of hypertension, the production of superoxide anion (O2−) derived from NAD(P)H oxidase could be increased with age, which may counteract the enhanced nitric oxide (NO) production derived from inducible NO synthase and generate vasoconstrictor responses on aorta [17]. This evidence concerns the gene FMO5 and hypertensive disorder.