The increased plasma C-reactive protein and interleukin-6 levels in patients undergoing coronary artery bypass grafting surgery are associated with the interleukin-6−174G > C gene polymorphism

Abstract

The interleukin-6 (IL-6) promoter -174G/C polymorphism (rs1800795) is associated with enhanced systemic inflammatory response to injury. However, data on the effect of this polymorphism on inflammatory markers in patients undergoing coronary artery bypass grafting surgery (CABG) are inconsistent. The aim of our study was to investigate whether -174G/C IL-6 polymorphism affects plasma IL-6 and C-reactive protein (CRP) concentrations in patients undergoing CABG. A total of 179 consecutive white patients (77% men, aged 65 +/- 8.6 standard deviation [SD] y) scheduled for elective isolated CABG were studied. Pre- and postoperative CRP and IL-6 levels were analysed in relation to the 174G/C IL-6 polymorphism determined by using TaqMan single-nucleotide polymorphism genotyping technique. The genotype distribution was as follows: GG -46 (26%), GC -93 (52%) and CC -40 (22%). The C allele carriers had higher baseline CRP (4.1 +/- 0.35 versus 2.4 +/- 0.59 mg/L, P = 0.02) and IL-6 levels (3.0 +/- 0.17 versus 2.2 +/- 0.3 pg/mL, P = 0.02) than GG patients. Five to seven days after CABG, CRP levels rose by 54% (P = 0.03), and IL-6 levels tended to be higher (P = 0.07) in -174C allele carriers than the non-carriers. There were no associations between -174G/C IL-6 polymorphism and any demographic-, clinical- or procedure-related variables as well as major adverse cardiovascular events. Multivariate regression analysis, including sex, age, body mass index, hypercholesterolaemia, smoking, hypertension diabetes, identified CG + CC genotype as the only independent predictor of preoperative CRP and IL-6 levels. The presence of the -174C allele determines to some extent higher plasma CRP and IL-6 concentrations pre- and postoperatively in CABG patients.