A possible role of IL-1RN gene polymorphism in the outcome of gastrointestinal diseases associated with H. pylori infection

OBJECTIVE To verify whether the variable number of tandem repeat (VNTR) polymorphism in the IL-1RN gene that encodes the interleukin (IL)-1 receptor antagonist (IL-1Ra) plays a role in the outcome of gastrointestinal diseases associated with Helicobacter pylori (H. pylori) infection. METHODS Patients with normal endoscopy (n = 71), inflammation of the upper gastrointestinal tract only (n = 196), gastric ulcer (n = 28), duodenal ulcer (n = 76), and gastric cancer (n = 19) were studied. H. pylori infection was diagnosed by the urease test, histological examination, and polymerase chain reaction. The IL-1 receptor antagonist gene (IL-1RN intron 2 VNTR) was analyzed by polymerase chain reaction. Gastritis was scored according to the updated Sydney system of classification. RESULTS H. pylori infection was an independent risk factor for mild (odds ratio [OR] = 5.53 [95% confidence interval [CI] = 2.63-11.64; P < 0.05]), moderate (OR = 83.93 [95% CI = 29.7-237.18; P < 0.05]) and marked (OR = 47.47 [95% CI = 5.39-418.05; P < 0.05]) gastritis. The carriage of IL-1RN*2/*2 had a significant protective effect of H. pylori infection (OR = 0.31 [95% CI = 0.17-0.57; P < 0.05]). H. pylori infection was identified as an independent risk of inflammation, duodenal ulcer, and gastric ulcer. The carriage of IL-1RN*2/*2 was an independent risk factor for gastric cancer (OR = 5.81 [95% CI = 1.06-31.98; P < 0.05]); nonetheless, the carriage of allele 2 (IL-1RN*2/*2 plus IL-1RN*L/*2) had an independent protective effect on duodenal ulcer (OR = 0.45 [95% CI = 0.22-0.91; P < 0.05]). CONCLUSIONS Allele 2 of the VNTR IL-1RN polymorphism had a protective effect against duodenal ulcer and H. pylori infection; however, it increased the risk of gastric cancer.