title: Associations between vascular health indices and serum total, free and bioavailable 25-hydroxyvitamin D in adolescents.
abstract: OBJECTIVE
  The role of vitamin D in cardiovascular health remains debated as results have been inconsistent. Previous studies have not considered the bioavailability of 25-hydroxy vitamin D [25(OH)D]. Objectives of our study were to investigate the association between serum concentrations of total, free and bioavailable 25(OH)D and independent predictors of cardiovascular risk such as flow mediated dilatation (FMD) and augmentation index (AIx).
  
  
  METHODS
  This cross-sectional study included 47 post-menarchal, adolescent females [31 African American (AA) and 16 European American (EA)].
  
  
  METHODS
  AIx was standardized to a heart rate of 75 beats/min (AIx75). Free and bioavailable 25(OH)D concentrations were calculated from standard formulas.
  
  
  CONCLUSIONS
  Mean age of the participants was 15.8 ± 1.4 years and mean body mass index was 23.1 ± 4.0 kg/m2. Serum total 25(OH)D was not associated with FMD, but was positively associated with AIx75 in the adjusted model (rho = 0.4, P = 0.03). AIx75 was positively associated with bioavailable 25(OH)D (rho = 0.4, P = 0.004) and free 25(OH)D (rho = 0.4, P = 0.009) and the associations persisted after adjusting for covariates. In race-specific analyses, total, free and bioavailable 25(OH)D were strongly positively associated with AIx75 in AA (rho = 0.5, 0.4, 0.4, respectively), which persisted even after adjusting for covariates. Whereas in EA there was an inverse association between total 25(OH)D and AIx75 in EA (rho = -0.6), which attenuated after adjusting for covariates.
  
  
  CONCLUSIONS
  Circulating total, free and bioavailable 25(OH)D were associated with arterial stiffness in adolescent girls, and these associations were race dependent. Notwithstanding, the implications of associations between vascular function indices and 25(OH)D remains unclear.
authors.affiliation: Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Ambika P
authors.initials: AP
authors.lastname: Ashraf
authors.affiliation: Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Alvarez
authors.affiliation: Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Tanja
authors.initials: T
authors.lastname: Dudenbostel
authors.affiliation: Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Calhoun
authors.affiliation: Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Russell
authors.initials: R
authors.lastname: Griffin
authors.affiliation: Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Xudong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Lynae J
authors.initials: LJ
authors.lastname: Hanks
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Gower
mesh_terms: D000293:Adolescent; D001741:Black or African American; D001682:Biological Availability; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D044465:White People
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D