Vitamin D Receptor rs2228570 Gene Polymorphism Is Associated with Asthma Severity and Exacerbations

Abstract

Vitamin D plays a crucial role in immune system function. Several studies have indicated that genetic variations in the vitamin D receptor (VDR) and vitamin D binding protein (VDBP, encoded by GC gene) increase the risk of developing asthma. However, the effect of these variations on the prognosis and clinical outcomes of asthma remains unclear. This study, involving 152 adult patients with asthma, aimed to assess the influence of VDR and GC polymorphisms on asthma severity and its exacerbation. Gene polymorphisms previously associated with asthma risk were analyzed, and VDR mRNA expression levels were evaluated in peripheral blood mononuclear cells. The AA genotype of the VDR rs2228570 polymorphism was associated with an elevated risk of severe asthma compared to the AG/GG genotype (odds ratio, 3.20; 95% confidence interval [CI], 1.24–8.28). Furthermore, patients with the rs2228570 AA genotype showed an elevated risk of exacerbation during the 1-year follow-up period (hazard ratio, 4.01; 95% CI, 1.75–9.15). VDR mRNA expression was significantly reduced in patients with the AA genotype. Furthermore, the mRNA expression levels of GLCCI1, HDAC2, NR3C1, and NFE2L2, which are associated with steroid response, were reduced in patients with the AA genotype. Our findings indicate that patients with the AA genotype of VDR rs2228570 are more likely to experience severe asthma and exacerbations. This polymorphism has the potential to reduce vitamin D efficacy by altering VDR function and expression, potentially resulting in increased inflammation and reduced steroid responsiveness in patients with asthma.