The Journal of clinical endocrinology and metabolism 2017 05 03() doi 10.1210/jc.2017-00296
Low 25-hydroxyvitamin D (25(OH)D) is associated with a greater risk of coronary heart disease (CHD) in individuals who are white and Chinese, but not black or Hispanic. Vitamin D binding globulin (VDBG) avidly binds 25(OH)D, reducing its bioavailability, and differs in isoform and concentration by race/ethnicity.
Evaluate associations of VDBG with CHD and whether accounting for VDBG or estimating bioavailable 25(OH)D explains the racial heterogeneity of the association of serum 25(OH)D with CHD.
Design and Setting
We conducted a case-cohort study within the Multi-Ethnic Study of Atherosclerosis. Participants with an incident CHD event over 12 years of follow-up (n=538) and a random subcohort (n=999) were included. We measured baseline 25(OH)D, VDBG and isoforms using mass spectrometry and estimated bioavailable 25(OH)D from published equations.
VDBG was associated with an increased risk of CHD (HR: 1.77 (95% CI: 1.46, 2.14) per SD increment, p<0.0001), without evidence of heterogeneity by race/ethnicity or isoform (each p-for-interaction>0.1). Low total 25(OH)D was not associated with CHD events among black or Hispanic participants, with or without adjustment for VDBG (p-for-interaction = 0.04 or 0.05, respectively). Associations of 25(OH)D with CHD were strengthened with adjustment for VDBG among participants who were white or Chinese and bioavailable 25(OH)D was only associated with CHD events among white participants.
High VDBG concentration was associated with CHD events in all racial/ethnic groups. Incorporation of VDBG strengthened associations of 25(OH)D with CHD among white and Chinese individuals, but did not explain racial heterogeneity in associations of 25(OH)D with CHD.