Background: Asthma is a genetically heterogeneous disease. Polymorphisms of genes encoding components of
the vitamin D pathway have been reported to associate with the risk of asthma. We have previously demonstrated
that vitamin D status was associated with lung function in Chinese asthma patients. In this study, we tested
whether polymorphisms of genes encoding for vitamin D receptor (VDR), vitamin D 25-hydroxylase (CYP2R1) and
vitamin D binding protein (GC) were associated with asthma in the Chinese Han population.
Methods: We sequenced all 8 exons of VDR and all 5 exons of CYP2R1 in a Chinese case-control cohort of asthma
consisting of 467 cases and 288 unrelated healthy controls. Two mutations were identified in these regions. These
variants were specified as rs2228570 in exon 2 of VDR and rs12794714 in exon 1 of CYP2R1. We also genotyped
two common polymorphisms in GC gene (rs4588 and rs7041) by a PCR-restriction fragment length polymorphism
(RFLP) method. We analyzed the association between these 4 polymorphisms and asthma susceptibility and
asthma-related traits.
Results: Polymorphic markers in VDR and CYP2R1 were not associated with asthma in the Chinese Han cohort.
Importantly, variants in GC gene, which give rise to the two most common electrophoretic isoforms of the vitamin
D binding protein, were associated with asthma susceptibility. Compared with isoform Gc1, Gc2 was significantly
associated with the risk of asthma (OR = 1.35, 95% CI = 1.01-1.78 p = 0.006).
Conclusions: The results provide supporting evidence for association between GC variants and asthma
susceptibility in the Chinese Han population.