Increase in interleukin-6 following arterial injury is related to insulin resistance, the -174G→C polymorphism and complex plaque morphology

Interleukin-6 (IL-6) is associated with many disease states in humans. We prospectively sought to determine whether IL-6 levels increased following percutaneous coronary intervention (PCI) in the absence of myonecrosis. Additionally, we systematically assessed other clinical and anatomic factors associated with IL-6 levels in a population of patients with coronary atherosclerosis undergoing PCI. Blood samples were collected from 117 patients at baseline, 8 and 16 h following PCI. Samples were assayed for IL-6, creatine kinase-myocardial band (CK-MB), troponin-I (Tn-I), high sensitivity C-reactive protein, glucose, haemoglobin A1c, and a lipid profile. Genotyping of the -174G→C polymorphism of the IL-6 gene was performed. IL-6 levels increased following PCI among the study group (slope = 0.4 pg/mL/h, P = 0.001). IL-6 levels increased to a similar degree in the absence of myonecrosis. Patients with the XC genotype (either having the GC or the CC allele) had higher IL-6-values at baseline compared to GG genotype patients (4.9 ± 6.4 vs. 2.6 ± 1.8 pg/mL, P = 0.02). Multivariable predictors of detectable baseline IL-6 levels included XC genotype (odds ratio [OR]: 4.14, 95% CI 1.58-10.82, P = 0.004), ACC/AHA type C lesion classification (OR: 4.08, 95% CI 1.54-10.84, P = 0.005), elevated baseline Tn-I (OR: 3.31, 95% CI 1.16-9.43, P = 0.025), diabetes (OR: 3.00, 95% CI 1.11-8.09, P = 0.030), and waist circumference (OR: 1.49, 95% CI 1.08-2.06, P = 0.015). Predictors of peak IL-6 following PCI included the XC genotype (estimate 1.4, 95% CI 1.06-1.87, P = 0.019), homeostasis model assessment (estimate 0.99, 95% 0.982-0.999, P = 0.042) and baseline Tn-I > upper limit of normal (estimate 0.7, 95% CI 0.50-0.96, P = 0.039). Lastly, IL-6 increased following PCI even in the absence of myonecrosis as measured by Tn-I elevation. IL-6 levels are also related to the -174G→C polymorphism, arterial injury, lesion complexity, and insulin resistance.