Late-breaking abstract: Possible association between vitamin D receptor SNP FokI and treatment response in asthmatic children

Introduction: An association between poor asthma control and low 25OH Vitamin D (25OHD) has been shown. Single nucleotide polymorphisms (SNP) in the gene encoding 25OHD receptor (VDR) have been associated with asthma. Hypothesis: asthma control is associated with 25OHD levels and VDR SNP. Aims: To compare 25OHD levels in controlled and uncontrolled asthmatic children and healthy controls; to genotype, in asthmatics, 2 SNP in the VDR gene. Methods: 25OHD values in healthy children were obtained from a sample of a previous study. Asthmatics treated with at least 3 months of inhaled steroids were enrolled in outpatient clinics. A clinical questionnaire of asthma severity was applied and blood was drawn. 25OHD levels were measured with Radioinmunoasay and SNP were analyzed by a standar PCR-RFLP assay. Results: 75 asthmatics (9.6+2.5 ys) and 226 healthy children (10.2+4.8 ys), were studied. 25OHD levels were 23.9+10.7 and 22.2+7.6 ng/ml respectively (p=0.122). No significant differences were found between controlled and uncontrolled asthmatics (24.96+11.1 and 21.55+7.3 ng/ml respectively). Analysis of FokI (rs10735810) SNP revealed that all patients (16/16) requiring GINA step 4 of treatment were heterozygous for the C allele. The presence of the C allele was less frequent in patients in step 2 (30/33) and 3 (16/24) (p=0.007). No significant differences in the other SNP (rs731236) and no association of neither SNP with asthma control status, were found. Conclusions: This pilot study established a possible association between FokI C allele and need of higher steroid doses for asthma control. VDR might play a role in asthma treatment response. Further research is required to validate it.