Purpose: Associations between Helicobacter pylori (HP) infection and lifestyle factors have been demonstrated by several studies, but there are very few reports on links with host factors, especially concerning genetic polymorphisms for inhabitants of large city. The present investigation was conducted to determine the HP infection rate with reference to the Interleukin-1 beta gene (IL-1B) polymorphism and assess the interactions with smoking reported for outpatients.
Method: The subjects were 468 participants in a health-check-up program of law of health for aged conducted by Nagoya Nishi Health Center. The participants were asked to permit use of their residual blood drawn during a health-check-up program and written informed consent was obtained for gene polymorphism tests. Data on smoking habit were obtained by self-administered questionnaire. The IL-1B C-to-T polymorphism at -31 was genotyped by PCR-CTPP (polymerase chain reaction with confronting two-pair primers) and an anti-HP IgG antibody test was used for detecting HP infection. Differences in values were assessed by a chi 2 test. An unconditional logistic model was applied for estimating odds ratios with the computer program STATA Version 6. This study was approved by the Ethical Committee at Aichi Cancer Center in 2000 before it was commenced (Ethical Committee Approval Number 11-12)
Results: The HP infection rate was 52.6% (61/116) for the C/C genotype of IL-1B-31, 48.6% (89/183) for the C/T, and 63.2% (103/163) for T/T; the difference were not statistically significant. However, when non-current smokers were excluded, the rate were 47.8% (11/23), 52.9% (18/34), and 72.7% (16/22), respectively, indicating the T/T genotype to have a higher infection rate. The age-sex-smoking adjusted odds ratio (OR) relative to the C/C genotype were 0.97 (95% confidence interval, 0.59-1.57) for the T/C genotype and 1.73 (1.04-2.87) for the T/T genotype. Among current and former smokers the age-sex adjusted OR were 1.68 (0.50-5.71) for the T/C genotype and 5.29 (1.11-25.1) for the T/T genotype, suggesting a effect of this polymorphism prominent in smokers.
Conclusion: An association between the IL-1B-31 polymorphism and persistent HP infection was observed for inhabitants with a smoking habit, indicating that this polymorphism is one genetic trait conferring an increased likelihood of persistent HP infection.