Vitamin D receptor variants and uncontrolled asthma

Abstract

Background. Asthma is a common childhood respiratory disease, affecting around 20% of Irish children. In other populations, vitamin D receptor (VDR) polymorphisms have been associated with asthma risk. We aimed to investigate the association between 2 VDR polymorphisms and uncontrolled paediatric asthma. Methods. 44 asthmatic children and 57 healthy volunteers were studied. The VDR TaqI gene variant in exon 9 (T/C) (rs731236) and ApaI (rs7975232) in intron 8 (C/T) were determined, using TaqMan® Assays. The lung function, serum 25-hydroxyvitamin D (25OHD) levels and other biomarkers of allergy, immunity, airway and systemic inflammation were assessed. Results. The distribution of T and C alleles and genotype frequencies differed significantly between asthmatics and controls for both polymorphisms (p < 0.05). A significant association was found between both TaqI (OR = 2.37, 95% CI (1.27 - 4.45), p = 0.007) and ApaI polymorphisms, and asthma risk (OR = 2.93, 95% CI (1.62 - 5.3), p = 0.0004). No association was observed between genotypes and 25OHD levels, lung function and other biomarkers, with the exception of Interleukin-10 (IL-10) and white blood cells count (WBC). IL-10 levels were lower in asthmatics with TC genotype for TaqI polymorphism (p < 0.01) and were higher in patients with TT genotype for ApaI (p < 0.01). WBC were higher in patients with TC and CC genotypes for TaqI (p < 0.05) and lower in TT genotype for ApaI (p < 0.05). Conclusion. TaqI and ApaI polymorphisms are associated with asthma in Irish children. Further studies are warranted to investigate the importance of decreased IL-10 levels in paediatric asthmatics with specific genotypes.