Analysis of polymorphisms in the promoter region and protein levels of interleukin-6 gene among gout patients

Objective: To explore the associations between the polymorphisms and protein levels of interleukin-6 (IL-6) gene and gout disease. Methods: A total of 120 male gout patients and 184 healthy controls were enrolled. Each patient was matched with 1-2 gout-free controls by age within three years. Four polymorphisms in the promoter of IL-6 gene, including -597G/A, -572C/G, -373A(m)T(n), and -174G/C, and the IL-6 levels were analyzed. The clinical characteristics and biochemical markers in plasma were measured, including age of gout onset, duration of gout history, tophus number, gout attack frequency, uric acid, total cholesterol, triglycerides and creatinine. Results: The mean IL-6 level for gout patients was 9.80 (±11.76 pg/ml) which showed no significant difference from the controls (7.06±7.58 pg/ ml, p=0.230). When the IL-6 levels were dichotomized according to the median value (5 pg/ml), there were significantly higher proportions of the gout patients (59.66%) than controls (44%) with high IL-6 levels (OR=1.88, 95% CI=1.17-3.02, p=0.008). Unique genotype was found at polymorphisms -174G/C and -597G/A. Neither the polymorphisms -572C/G nor -373A(m)T(n) in the genotype or allele distributions showed a significant association related to clinical characteristics, biochemical markers, IL-6 levels or gout disease (all p>0.05). Conclusions: Those with gout disease have greater proportions of high IL-6 levels in plasma than controls, and there is no significant association between the four polymorphisms in the promoter region of IL-6 gene and gout disease.