Sepiapterin supplementation in diabetic or obese mice resulted in a significant increase in BH4, coupled eNOS, and NO production [4, 24–27], and diabetic mice fed sepiapterin along with L-citrulline showed inhibition of diabetic cardiomyopathy as well as beneficial effects on eNOS dimerization and NO production [28]. The gene discussed is NOS3; the disease is diabetic cardiomyopathy.