The Relationship between Interleukin-6 Promotor Polymorphisms and Slow Coronary Flow Phenomenon

Several lines of evidence suggest that slow coronary flow (SCF) phenomenon seems to be an early form of atherosclerosis and low-grade inflammation plays a role in the development of SCF. Interleukin-6 (IL-6) is a pleiotropic cytokine, functions as a mediator of inflammatory response, and has both pro-inflammatory and anti-inflammatory properties. The aim of the present study is to investigate the relationship between IL-6 -634C/G polymorphism and SCF in Han Chinese.

250 subjects who underwent coronary angiography and had normal coronary arteries of varying coronary flow rates without any atherosclerotic lesion were enrolled in this study. 41 patients who had thrombolysis in myocardial infarction frame counts (TFC) above the normal cutoffs were considered to have SCF and 209 subjects within normal limits served as normal coronary flow (NCF) group. The PCR-based restriction fragment length polymorphism (PCR-RFLP) technique was used to assess the genotypes.

The distribution of the IL-6 -634C/G genotypes (CC, CG, and GG) was 56.94%, 37.80%, and 5.26% in the NCF subjects, and 36.59%, 48.78%, and 14.63% in the SCF group, respectively (p = 0.0173). The frequency of the G allele in the SCF (39.02%) group was significantly higher than that in the NCF (24.16%) group (p = 0.0054). Compared with the CC genotype, the G allele carriers (CG + GG genotypes) had increased risk of SCF in both unadjusted and adjusted analyses. In SCF patients, the average serum IL-6 levels (pg/mL) in CG + GG genotype (4.78 ± 0.42) were statistically higher than in CC genotype (3.93 ± 0.36) (p = 0.0000).

Our data support that IL-6 -634C/G polymorphism is associated with SCF and the G allele has increased risk for SCF in Han Chinese.