Interleukin 6, white blood cell count and risk of myocardial infarction

Abstract

Interleukin 6 (IL-6) is pro-inflammatory cytokine which is reported to have a positive association with total and differential white blood cell (WBC) levels. Elevated white blood cell levels have been implicated as an independent risk factor of cardiovascular disease and myocardial infarction (MI). Single nucleotide polymorphisms (SNP) located within the promoter region of the IL6 gene have been associated with elevated serum IL-6 levels. The aim of this study is to determine whether the IL-6 -597 G→A promoter polymorphism influences white blood cell count and therefore the risk of MI. The results of this study indicate that there is no increased risk of myocardial infarction (MI) associated with the IL-6 -597 G→A polymorphism when including all cases and controls [1.0 (95% CI 0.4 – 2.2) in homozygous mutants and 1.0 (95% CI 0.7 – 1.3) in heterozygotes], after adjusting for age and gender. The polymorphism shows no interaction with smoking, a wellestablished risk factor of MI. No significant differences are observed in the blood cell levels of men and women carrying the IL-6 -597A allele when compared to their wildtype counterparts. These results remain generally unaltered in males after excluding smokers and quitters from blood cell analysis and observing levels in non-smokers. Female smokers who lack the IL-6 -597A allele have significantly higher WBC levels than carriers while female non-smokers carrying the allele have higher WBC levels than homozygous wildtypes, suggesting a possible antagonistic interaction between the genotype and smoking. The IL-6 -597A allele is associated with lower BMI in both men and women, indicating a possible protective effect against adiposity and obesity.