The Effect on Vitamin D Levels and VDR Gene Polymorphism on Clinical Outcomes in Asthma

Objective: This study aimed to investigate the relationship between vitamin D receptor gene polymorphism and vitamin D levels with asthma severity, control level and exacerbation status in asthmatic patients. Subjects and Methods: Over a six-month period, 162 patients diagnosed with asthma and 85 healthy volunteers were prospectively evaluated. Blood samples were analyzed for Vitamin D receptor gene polymorphism by PCR and periostin by ELISA. Results: Among the study participants, 163 were females and 84 were males. The median value of Vitamin D in the patient group was significantly lower at 13.95 (3.5-33) compared to 17 (6.1-39.9) in the control group (p = 0.003). A significant positive correlation was found between Vitamin D and Asthma Control Test (ACT), eosinophil count, Peak Expiratory Flow (PEF, %) (r:0.18 to 0.25 p < 0.05). When VDR gene polymorphism Fok1 and Apa1 alleles in the patient and control groups were examined, they were found to be similar (p > 0.05). However, when VDR gene polymorphism genotypes were analyzed in terms of vitamin D levels, no significant difference was found between Apa1 genotypes (CC, CT, TT). Regression analysis of variables which are considered to influence Vitamin D levels showed that gender and PEF are independent determinants. Conclusions: In our study, a significant relationship was found between Vitamin D levels and asthma severity, asthma control level, and respiratory functions. However, no significant effect of VDR gene polymorphism was detected on the vitamin D levels and asthma.