title: Distribution of asymmetric dimethylarginine among 980 healthy, older adults of different ethnicities.
abstract: BACKGROUND
  Endothelium-derived nitric oxide plays a crucial role in the regulation of vascular tone and the development of cardiovascular disease. The endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) has emerged as a novel cardiovascular risk factor. ADMA appears to be an independent predictor for cardiovascular and overall mortality. However, the majority of studies investigating the clinical role of ADMA were performed in European study populations with few individuals of other ethnicities.
  
  
  METHODS
  We performed a cross-sectional study of 980 healthy, older (age 60-72 years) individuals of different ethnicities living in the San Francisco Bay area and analyzed ADMA plasma concentrations and their relationship to other cardiovascular risk factors. Plasma ADMA concentrations were measured using a recently developed, highly sensitive ELISA.
  
  
  RESULTS
  In our entire sample, we were able to define a reference interval for ADMA plasma concentrations of 0.47 (90% CI 0.46-0.48) mumol/L to 0.85 (0.84-0.89) mumol/L. The mean ADMA concentration was 0.63 (SD 0.11) mumol/L (median 0.61 mumol/L). Mean ADMA concentrations were significantly lower in African Americans (0.60 mumol/L; P < 0.01) and mixed non-Hispanics (0.60 mumol/L; P < 0.05) compared with whites (0.63 mumol/L). ADMA was positively correlated with cystatin-C in both men (rho = 0.29) and women (rho = 0.37), and median plasma ADMA concentrations increased across cystatin-C quintiles.
  
  
  CONCLUSIONS
  ADMA varies nearly 2-fold across a healthy sample of older men and women, correlates with age, body mass index, and renal function, and is different across ethnic groups. Additional studies in a wider age range and including larger ethnic subgroups would be useful.
authors.affiliation: Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA 94305-5406, USA.
authors.forename: Karsten
authors.initials: K
authors.lastname: Sydow
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Fortmann
authors.forename: Joan M
authors.initials: JM
authors.lastname: Fair
authors.forename: Ann
authors.initials: A
authors.lastname: Varady
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hlatky
authors.forename: Alan S
authors.initials: AS
authors.lastname: Go
authors.forename: Carlos
authors.initials: C
authors.lastname: Iribarren
authors.forename: Philip S
authors.initials: PS
authors.lastname: Tsao
mesh_terms: D000368:Aged; D001120:Arginine / Q000031:analogs & derivatives* / Q000097:blood; D044466:Asian People; D044383:Black People; D002318:Cardiovascular Diseases / Q000209:etiology; D055316:Cystatin C / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005919:Glomerular Filtration Rate; D006630:Hispanic or Latino; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012307:Risk Factors; D044465:White People; D001741:Black or African American
chemical_list: D055316:Cystatin C; C018524:N,N-dimethylarginine; D001120:Arginine