Genetic polymorphisms in vitamin D pathway influence 25(OH)D levels and are associated with atopy and asthma

Vitamin D deficiency or insufficiency, has been associated with atopy and lack of asthma control. Our objective was to investigate associations between variants in genes of vitamin D pathway with serum levels of 25-hydroxyvitamin D (25(OH)D), atopy, asthma and asthma severity in teenagers from Northeast Brazil.

This is a cross sectional study nested in a cohort population of asthma. 25(OH)D was quantified from 968 of 11-17 years old individuals by ELISA. Asthma diagnosis was obtained by using the ISAAC Phase III questionnaire. Specific IgE was determined by ImmunoCAP; genotyping was performed using the 2.5 HumanOmni Biochip from Illumina. Statistical analyses were performed in PLINK 1.07 and SPSS 22.1.

After quality control, 104 Single Nucleotides Variants (SNVs) in vitamin D pathway genes, typed in 792 individuals, were included in the analysis. The allele A of rs10875694 on VDR was positively associated with atopy (OR = 1.35; 95% CI 1.01-1.81). The allele C of rs9279 on VDR, was negatively associated with asthma risk (OR = 0.66; 95% CI 0.45-0.97), vitamin D insufficiency (OR = 0.78; 95% CI 0.70-0.96) and higher VDR expression. Two variants in VDR were associated with asthma severity, the allele A of rs2189480 (OR = 0.34; 95% CI 0.13-0.89) and the allele G of rs4328262 (OR = 3.18; 95% CI 1.09-9.28). The combination of variants in CYP2R1 and CYP24A1 (GAC, to rs10500804, rs12794714 and rs3886163, respectively) was negatively associated with vitamin D production (β = - 1.24; 95% CI - 2.42 to - 0.06).

Genetic variants in the vitamin D pathway affect vitamin D serum levels and, thus, atopy and asthma.