Asymmetrical Dimethylarginine Is Increased in Plasma and Decreased in Cerebrospinal Fluid of Patients with Alzheimer’s Disease

Asymmetrical dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase and may alter NO production during pathological conditions. Concerning Alzheimer's disease (AD), there are reports on altered cerebral NO metabolism, but only few studies on ADMA concentrations in plasma and cerebrospinal fluid (CSF).We assessed plasma ADMA in 80 AD patients and 80 age- and gender-matched controls and CSF ADMA in a subgroup of 53 AD patients and 20 controls.ADMA plasma concentrations were increased, while CSF ADMA concentrations were decreased in AD patients. There was a significant association between decreasing CSF ADMA levels and the severity of cognitive impairment.Elevated ADMA in plasma might be a contributing factor for AD through alterations of NO metabolism, for example decreased cerebral microperfusion, while decreased levels of CSF ADMA might lead to a cerebral increase of NO, peroxynitrite production and oxidative protein damage. Our study reveals different mechanisms of plasma and CSF ADMA regulation, both potentially contributing to AD pathology.