Association of vitamin D genetic pathway with asthma susceptibility in the Kurdish population

Vitamin D (Vit D) function in asthma progression has been studied well. The effects of genetic variations in Vit D pathway molecules have been also studied, although the results are contradicted. In the present study, for the first time we examined the Vit D pathway molecules included serum Vit D and vitamin D-binding protein (VDBP) and also genetic variations in the vitamin D receptor (VDR) and VDBP in a Kurdish population with asthma.

An enzyme-linked immunosorbent assay (ELISA) method was used to measure the serum Vit D and VDBP. VDR rs1544410 and rs2228570 and VDBP rs7041 were assessed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

The serum level of Vit D significantly decreased in asthmatic patients versus controls (16.26 ± 6.76 vs 23.05 ± 10.57 ng/mL, P value = .001). We observed an indirect correlation between Vit D and clinical findings. We also found an increased level of serum VDBP in patients as compared to the controls (1044.6 ± 310.82 vs 545.95 ± 121.73 µg/mL, P value < .0001). Besides, the risk of asthma progression was increased in patients with the VDR rs2228570 CC and VDBP rs7041 GG genotypes (OR = 3.56, P = .0382 and OR = 2.58, P = .01, respectively).

In summary, our results explain the influence of the genetic variations in VDR and VDBP in addition to Vit D and VDBP serum concentrations on asthma susceptibility in the Kurdish population.