The Influence of Vitamin D Receptor Gene Polymorphisms in Spondyloarthritis

Abstract

Spondyloarthritis (SpA) is an inflammatory rheumatic disease related to low bone mineral density. Because vitamin D plays an important role in bone metabolism and immune system modulation, the aim of this study was to evaluate the influence of polymorphisms in vitamin D receptor genes (<i>VDR</i>) in the development of SpA. In this case-control study, a total of 244 patients with SpA and 197 individuals with no SpA were included. Among the patients, 174 had ankylosing spondylitis (AS) and 66 had psoriatic arthritis (PsA). Genotyping of <i>Fok</i>I (rs2228570 C > T), <i>Bsm</i>I (rs1544410 C > T), <i>Apa</i>I (rs7975232 A > C), and <i>Taq</i>I (rs731236 T > C) was performed using PCR-RFLP, while genotyping of <i>HLA-B∗27</i> was performed using PCR-SSP. Serum levels for hydroxy (OH) vitamin D and the clinical activity index of the disease (BASDAI) were also evaluated. SNPStats and OpenEpi software were used for statistical analysis. The <i>Apa</i>I <i>a</i> allele and <i>Apa</i>I <i>a/a</i> genotype were less frequent in PsA compared with controls. The <i>Apa</i>I <i>a/a</i> genotype was associated with a protecting factor for PsA in females, and <i>Apa</i>I <i>A/a</i> was associated with a protecting factor for the disease in <i>HLA-B∗27</i> positive patients. Notwithstanding, the <i>Apa</i>I <i>a/a</i> genotype was a risk factor for SpA and AS in males. The <i>Fok</i>I <i>f/f</i> genotype was associated with a better clinical activity in PsA. When considering the covariates, vitamin D sufficiency, and gender, the <i>Fok</i>I <i>F/F</i> genotype was associated with a risk factor in males with SpA and AS compared with females with this same genotype. In conclusion, the <i>Apa</i>I rs7975232 polymorphism was associated with PsA, and the <i>Fok</i>I rs2228570 polymorphism was associated with better clinical PsA activity. <i>Apa</i>I and <i>Fok</i>I were associated with SpA and AS when considering gender and vitamin D sufficiency.