A number of reports suggests that therapeutic treatment with AT1-receptor-blockers, statins, and organic nitrates with pleiotropic antioxidant effects, improves the expression of GCH-1, and thereby normalizes BH4 levels, eNOS, and endothelial function in diabetes, hypertension, and nitrate tolerance [188,230,231,232]. Here, AGTR1 is linked to diabetes mellitus.