Case-control study of IL23R rs76418789 polymorphism, smoking, and ulcerative colitis in Japan

Background

Interleukin (IL)-23 is involved in the pathogenesis of ulcerative colitis (UC). A genome-wide significant association between IL23R p.G149R (rs76418789) and UC was previously identified in Japan and Korea. This case-control study aims to examine this association within the Japanese population.

Methods

The study included 384 cases diagnosed with UC within the past 4 years and 661 control subjects. Adjustment was made for sex, age, and smoking.

Results

The frequency of the AA genotype of rs76418789 was 0.0 % in cases and 0.5 % in control subjects. In comparison to study subjects with the GG genotype of rs76418789, those with the GA or AA genotype had a significantly reduced risk of UC, with an adjusted odds ratio of 0.67 (95 % confidence interval: 0.44–0.999). A significant multiplicative interaction was observed between rs76418789 and having ever smoked influencing UC (p for interaction = 0.03). A significant positive association was found between having ever smoked and UC in individuals with at least one A allele, while no such positive relationship was observed in those with the GG genotype.

Conclusion

IL23R SNP rs76418789 showed a significant association with UC. This study provides new evidence regarding the interaction between rs76418789 and smoking in relation to UC.