Objectives: Although the relationship between atherosclerosis and inflammatory cells has been recognized in recent years, the effect of interleukin-6 (IL-6) genetic variants associated with atherosclerosis is still controversial. Therefore, we investigated the association between IL-6 polymorphism and levels of IL-6 in patients with coronary artery disease (CAD).
Methods: We conducted a case-control study on 294 unrelated participants who were referred to the cardiology department of the university hospital for coronary angiography because of suspected ischemic heart disease. Group I comprised patients with clinically acute coronary syndrome, and group II comprised patients (individuals matched for age and sex) with clinically stable angina pectoris; both groups were categorized, based on their angiographic findings, as either having angiographically documented less extensive CAD (1 vessel narrowed) or extensive CAD (> or =2 vessels narrowed). They were studied to examine effect of the IL-6 gene variants in CAD. Genotyping was determined by polymerase chain reaction.
Results: The IL-6 G/C-174 polymorphism was found in 19 of 106 (18%) in group I and in four of 188 (2%) in group II (P<0.001). Median IL-6 levels were significantly higher in group I (6.7+/-13.6 pg/ml) than in group II (4.1+/-3.8 pg/ml) (P<0.05). In addition, high sensitivity C-reactive protein levels were significantly higher in group I (8.2+/-6.2 mg/dl) than in group II (4.6+/-3.4 mg/dl) (P<0.001).
Conclusion: These results demonstrated that the presence of the IL-6 G/C-174 polymorphism and increased IL-6 and high sensitivity C-reactive protein levels are strongly associated with the inflammatory system and the course of clinical and hemodynamically significant CAD.