Vitamin D receptor gene mutations and Vitamin D serum levels in asthmatic children

Abstract

Objective: To verify the relationship between polymorphisms of the vitamin D receptor gene (VDR), clinical findings, and serum vitamin D (VD) levels in asthmatics. Methods: A cross sectional study of 77 children aged 7 to 14 years old, who were attended at a specialized clinic. The children were divided into 3 groups: asthmatics who had been using inhaled corticosteroids (ICS) for more than one year; asthmatics who had not been using ICS; non‑asthmatics, and children without allergies (according to the International Study of Asthma and Allergies in Childhood - ISAAC). Spirometry, skin prick tests, the presence of a VDR promoter CDX2 polymorphism from an allele‑specific polimerase chain reaction (PCR), exons 2 and 3 polymorphisms genotyping by PCR‑SSCA (single-strand conformationalanalysis), total immunoglobulin E (IgE) and specific IgE to mites and grass were evaluated in these three groups. Levels of 25‑hydroxyvitamin D were determined in asthmatics only. Results: The mean age of the children was 10.8±2.0 years old, 57% were male, 38 were asthmatic and using ICS, 22 were asthmatic and not using ICS, and 17 were non‑asthmatic. Allergic rhinitis was present in 90% of asthmatics. Homozygous CDX2 was detected in 23% of the patients and absent in the control group (p=0.03). Lower forced expiratory volume in 1 second (FEV1%) values were observed in CDX2 homozygous asthmatics (p=0.001). Variations in the exon 2 and 3 sequences were not related to asthma or the other tests. VD deficiency or insufficiency was detected in 98% of asthmatics. There was no association between VD levels and genetic polymorphisms from exons 2 and 3. Conclusions: There was a positive association between homozygous CDX2 polymorphism, asthma and lower FEV1% values. CDX2 is capable of modifying cell interaction between VDR and VD, and it could be associated with the prevalence of asthma, and the difficulty in controlling the disease.