For example, several polymorphisms located in NOS1, NOS2, and NOS3 genes have been identified; some of these polymorphic sites could be responsible for variations in the genetic control of plasma NOS levels, which would be a useful tool for studying the relationship between NOS and diseases including asthma [64,65], depressive disorder [66], Parkinson's disease [67], diabetic nephropathy [68], and stroke [69]. Here, NOS2 is linked to Parkinson disease.