Genetic polymorphisms in the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which is responsible for ADMA metabolism (Figure 1), have been associated with different levels of ADMA in adult sepsis [11], diabetes mellitus [18], and pre-eclampsia [19], and co-localization of DDAH with NOS expression supports a key role for this enzyme in the regulation of NO activity [10]. The gene discussed is DDAH1; the disease is diabetes mellitus.