Asymmetric dimethylarginine in somatically healthy schizophrenia patients treated with atypical antipsychotics: a case–control study

BACKGROUND Schizophrenia is associated with increased cardiovascular morbidity and mortality. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of the nitric oxide synthase, and the L-arginine:ADMA ratio are markers of endothelial dysfunction that predict mortality and adverse outcome in a range of cardiovascular disorders. Increased ADMA levels may also lead to increased oxidative stress. We hypothesized that ADMA and the L-arginine:ADMA ratio are increased in somatically healthy schizophrenia patients treated with atypical antipsychotics (AAP), and that the ADMA and the L-arginine: ADMA ratio are positively correlated to measures of oxidative stress. METHODS We included 40 schizophrenia patients treated with AAP, but without somatic disease or drug abuse, and 40 healthy controls. Plasma concentrations of ADMA and L-arginine were determined by high-performance liquid chromatography. Data were related to markers of systemic oxidative stress on DNA, RNA and lipids, as well as measures of medication load, duration of disease and current symptomatology. RESULTS Plasma ADMA and the L-arginine:ADMA ratio did not differ between schizophrenia patients and controls. Furthermore, ADMA and the L-arginine:ADMA ratio showed no correlations with oxidative stress markers, medication load, or Positive and Negative Syndrome Scale scores. CONCLUSIONS Schizophrenia and treatment with AAP was not associated with increased levels of plasma ADMA or the L-arginine:ADMA ratio. Furthermore, plasma levels of ADMA were not associated with levels of systemic oxidative stress in vivo.