Independent and interactive associations of season, dietary vitamin D, and vitamin D-related genetic variants with serum 25(OH)D in Korean adults aged 40 years or older

Abstract

Only limited information is available on the inter-relationships between genetic and non-genetic factors such as diet and sunlight exposure with serum 25-hydroxyvitamin D [25(OH)D] concentration. This cross-sectional study aimed to examine the independent and interactive associations of season, dietary vitamin D intake, and SNPs of 11 vitamin D-related candidate genes with serum 25(OH)D concentration among 2,721 adults aged ˃= 40 years at baseline from the Yangpyeong cohort, a part of the Korean Genome Epidemiology Study (KoGES). The interactions between season or dietary vitamin D and 556 SNPs were evaluated using 2-degree of freedom joint tests. Season was strongly (p(difference) = 1.00 x 10(-12)) and dietary vitamin D intake was slightly but significantly associated with serum 25(OH)D concentration (p(difference) = 0.0119). Among five SNPs (rs11723621-GC, rs7041-GC, rs10500804-CYP2R/, rs7129781-C YP2R1, and rs2852853-DIXR7) identified in the screening steps, only one, rs10500804-CYP2R1, significantly interacted with season (p(interaction) = 8.01 x 10(-5)). The inverse association between number of minor alleles of rs10500804-CYP2R/and concentration of 25(OH)D was significant only in summer/fall. Conversely, dietary vitamin D intake was positively associated only in winter/spring. in conclusion, season, dietary vitamin D intake, and four SNPs in GC, CYP2R1, and DHCR7 are independently and rs10500804-CYP2R/ is interactively associated with serum 25(OH)D concentration. Serum 25(OH)D is influenced by genotype of rs10500804-CIP2R1 in summerlfall when sunlight exposure is high, while dietary vitamin D intake is an important determinant of serum 25(OH)D during the seasons with low cutaneous vitamin D synthesis.