Association between vitamin D receptor gene polymorphisms and chronic periodontitis in Thais

Abstract

Polymorphisms of the vitamin D receptor (VDR) gene have been implicated in the susceptibility to infections and bone-related diseases. However, their relationship with periodontal disease remains unclear. This cross-sectional study investigated whether the susceptibility to chronic periodontitis in a Thai population is associated with VDR polymorphisms. Genomic DNA was obtained from 1,460 subjects, aged 39-65 years. Genotyping of VDR polymorphisms (FokI, BsmI, ApaI, and TaqI) was performed using real-time polymerase chain reaction. Subjects were categorized into three groups; no/mild, moderate, and severe periodontitis. Multinomial logistic regression analysis was used to determine the degree of association between VDR polymorphisms and periodontal status adjusted for age, gender, education, smoking, and diabetes. The CC+CT genotypes of FokI polymorphism were associated with moderate and severe periodontitis with odds ratios (OR) of 1.4 (95% CI 1.0-1.9) and 2.0 (95% CI 1.3-2.9), respectively. There was no significant relationship between the other VDR polymorphisms or BsmI-ApaI-TaqI haplotypes and periodontitis. To examine gene-smoking interaction, non-smokers with the TT genotype of FokI polymorphism were used as the reference group for all comparisons. Current smokers who had the CC+CT genotypes presented the highest risk of severe periodontitis with an OR of 10.4 (95% CI 4.9-22.1), whereas their counterparts with the TT genotype and non-smokers bearing the CC+CT genotypes had an increased risk by 2.7 (95% CI 1.1-6.7) and 2.0 folds (95% CI 1.2-3.4), respectively. The combined effect of FokI polymorphism and current smoking was 3.5 times (95% CI 1.3-9.9) greater than what would be expected from the sum of their individual effects, indicating a significant additive interaction. In conclusion, our data indicate that FokI polymorphism of VDR gene was significantly associated with periodontal disease severity in this study group. We are also the first to demonstrate that FokI polymorphism and smoking synergistically interacted in increasing the risk of chronic periodontitis.