Association among genetic variants in the vitamin D pathway and circulating 25-hydroxyvitamin D levels in Korean adults: results from the Korea National Health and Nutrition Examination Survey 2011-2012.

Vitamin D deficiency affects >60% of the Korean population. Recent reports in Caucasian, African American, and Chinese populations indicate an association between vitamin D status and related single nucleotide polymorphisms (SNPs), but specific associations differ among study populations. We investigated the relationship between five SNPs involved in the vitamin D metabolic pathway (DHCR7 rs12785878, GC rs2282679, CYP2R1 rs12794714, CYP2R1 rs10741657, and CYP24A1 rs6013897) and serum 25-hydroxyvitamin D [25(OH)D] status in Koreans using the Korea National Health and Nutrition Examination Survey, a nationwide database. Whether the association was modified by demographic and lifestyle factors, including sex, body mass index (BMI), smoking status, drinking status, physical activity, and sun exposure, were also investigated. The results showed the serum level of 25(OH)D was associated with rs12785878, rs2282679, and rs12794714 genotypes, but not with rs10741657 or rs6013897. The genetic risk score (GRS) calculated by summing the number of alleles of these 5 SNPs was associated with low circulating levels of 25(OH)D. However, the negative association between 25(OH)D and GRS was modified by obesity and sun exposure. Specifically, negative associations between 25(OH)D and GRS were present in adults with lower BMI (<25 kg/m2) and longer sun exposure time (≥2 h/day). In conclusion, common variants of vitamin D-related SNPs are associated with vitamin D status in Koreans, and this genetic effect was masked when BMI ≥25 kg/m2 or sun exposure <2 h/day. Additionally, seasonal variation must be considered in future studies among Koreans.