The effect of interleukin-6 C/G-174 polymorphism and circulating interleukin-6 on fibrinogen plasma levels

Background and Objectives. C-reactive protein (C-RP) levels correlate with fibrinogen values and are predictive of coronary artery disease. Interleuki n-6 (IL-6) strongly regulates the production of C-RP. A polymorphism (C/G- 174) within the IL-6 gene has been shown to affect IL-6 gene expression and plasma concentrations. Design and Methods. In 598 asymptomatic employees of a hospital in Southern Italy, we investigated the association between IL-6 C/G-174 gene variants and plasma, fibrinogen levels. Results. Subjects with IL-6 plasma levels >2.0 pg/mL had a higher body mass index (BMI) (24.5+/-1.2) than subjects with IL-6 levels below this cut-off value (23.7+/-1.2; p =0.005). No association was found with sex, cigarette smoking, or alcohol consumption (p always>0.05). When the whole sample was analyzed according to the IL-6 C/G -174 polymorphism, there was no differe nce with respect to age, sex, alcohol consumption, cigarette smoking, total cholesterol, triglyc-erides, and body mass index. Median plasma fibrinogen levels, as well as carriers of plasma levels of IL-6 >2.0 pg/mL and C-RP > 0.33 mg/L, were similar among subjects with different IL-6 genotypes. Simil arly, no differ ence was observed when only carriers of plasma levels of IL -6 >2.0 pg/mL were analyzed, whereas in those with Ci RP >0.33 mg/L IL-6 GG carriers had significantly lower plasma fibrinogen levels. Interpretation and Conclusions. The investigation of the IL-6 C/G-174 polym orphism does not seem to be a useful tool for predicting raised plasma fibr inogen levels.