Association of vitamin D binding protein (VDBP) polymorphisms and serum 25(OH)D concentrations in a sample of young Canadian adults of different ancestry.

Variants of the vitamin D binding protein (VDBP) gene appear to be associated with levels of the main circulating vitamin D metabolite, 25-hydroxyvitamin D [(25(OH)D]. We examined the associations between the common variants of the VDBP (GC) gene and concentrations of 25(OH)D in a sample of young Canadian adults of East Asian, European and South Asian ancestry, taking into account the effect of vitamin D intake, skin pigmentation, sex, BMI, sun exposure and season. Three hundred and fifty-one (351) healthy young adults were genotyped for two non-synonymous single nucleotide polymorphisms (SNPs), T436K (rs4588) and D432E (rs7041), using a method that ascertains the GC diplotypes of each individual. After controlling for relevant predictor variables in multiple regression models, the number of GC-2 (436K) alleles was found to be associated with lower 25(OH)D concentrations in the East Asian sample at fall and winter visits. The number of GC-2 alleles also showed a significant negative association with fall 25(OH)D concentration in the European sample. No associations were noted between the number of GC-2 alleles and 25(OH)D in the South Asian sample at either season. Vitamin D intake was also significantly predictive of serum 25(OHD) concentrations, and similarly to what was observed for the GC polymorphisms, the relative strength of the association was influenced by ancestry and season.