Serum vitamin D, vitamin D receptor and binding protein genes polymorphisms in restless legs syndrome.

BACKGROUND/OBJECTIVES Several studies showed lower serum 25-hydroxyvitamin D levels in patients with idiopathic restless legs syndrome (RLS) compared with matched controls, and a single study showed an association between the rs731236 single nucleotide polymorphism (SNP) in the vitamin D receptor (VDR) gene and the risk for RLS. We aimed to study the relationship between the serum 25-hydroxyvitamin D levels and to confirm previous findings related to SNPs in the VDR and the GC vitamin D binding protein (GC) gene, with the risk for RLS in the Spanish Caucasian population. METHODS We genotyped 285 idiopathic RLS patients and 325 age and sex-matched controls for VDRrs2228750, VDRrs7975232, VDRrs739837, VDRrs78783628, GCrs7041 and GCrs4588 SNPs using TaqMan assays, and determined serum 25-hydroxyvitamin D levels in 111 idiopathic RLS patients and 167 controls using an ELISA commercial kit. RESULTS Serum 25-hydroxyvitamin D levels were significantly higher in RLS patients than in controls but were unrelated with the 7 SNPs studied. None of the 7 SNPs analyzed was associated with the risk for idiopathic RLS or with a positive family history of RLS. However, RLS patients carrying the rs7975232CC genotype or the rs7975232C allele, had a higher frequency of response to GABAergic drugs. Associations between the age at onset and the severity of RLS with SNPs were inconsistent. CONCLUSIONS This study shows an association between increased serum concentrations of 25-hydroxyvitamin D and a lack of association between 7 SNPs in the VDR and in the GC genes with RLS in the Spanish Caucasian population.