The association of functional polymorphisms of IL-6 gene promoter with ischemic stroke: analysis in two Chinese populations

Polymorphisms of G-572C and G-174C in the interleukin-6 (IL-6) promoter can affect both the transcription and secretion of IL-6 and may be involved in inflammation related to and the pathogenesis of ischemic stroke (IS). However, whether IL-6 polymorphisms are indeed risk factors for IS remains controversial. We recruited 748 Chinese IS patients diagnosed by magnetic resonance imaging (MRI) within 24h of symptom onset and 748 normal healthy controls from two ethnic populations and performed two case-control studies in order to assess the nature of the polymorphisms of IL-6 and any links with IS. Common polymorphic loci in the IL-6 gene promoter were determined by TaqMan SNP genotyping assays. Multivariate logistic regression analysis was used to examine the association between IL-6 genotypes and a diagnosis of IS. We found that the C allele frequency at the -174 promoter region of IL-6 was extremely low in both IS patients and controls in both ethnic groups. The G allele of the promoter single nucleotide polymorphism (SNP) G-572C was more common in IS subjects than controls (P=0.004, corrected for multiple testing) in the Han population but not in the Uyghur population. GC carriage therefore increased the risk of IS in the Han ethnic group (OR 1.45, 95% CI 1.13-1.86). In addition, the differences in GG and GC frequency between the two ethnic populations were significant. The C allele frequency at the -174 promoter region of IL-6 was rare in Chinese IS patients and controls from either ethnic group. We conclude that IL-6-572GC may be an independent risk factor for IS in the Chinese Han population.