Associations between Vascular Health Indices and Serum Total, Free and Bioavailable 25-Hydroxyvitamin D in Adolescents

• Authors: Ambika P. Ashraf, University of Alabama Birmingham; Jessica Alvarez, Emory University; Tanja Dudenbostel, University of Alabama Birmingham; David Calhoun, University of Alabama Birmingham; Russell Griffin, University of Alabama Birmingham; Xudong Wang, University of Alabama Birmingham; Lynae Hanks, University of Alabama Birmingham; Barbara A. Gower, University of Alabama Birmingham
• Journal Title: PLoS ONE
• Volume: Volume 9, Number 12
• Publisher: Public Library of Science | 2014-12-05, Pages e114689-e114689
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pone.0114689
• Subjects: Health Sciences, Medicine and Surgery; Health Sciences, Epidemiology; Biology, Molecular
• Keywords: Science & Technology; Multidisciplinary Sciences; Science & Technology - Other Topics; VITAMIN-D STATUS; FLOW-MEDIATED VASODILATION; EXPERT CONSENSUS DOCUMENT; PULSE-WAVE VELOCITY; D-BINDING PROTEIN; ARTERIAL STIFFNESS; BLOOD-PRESSURE; INSULIN-RESISTANCE; RACIAL-DIFFERENCES; SUPPLEMENTATION

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). Design 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. Results and 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. Conclusion 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.