The (-174) G/C polymorphism in the interleukin-6 gene is associated with the severity of acute cerebrovascular events

Abstract

Background and purpose: Elevated plasma levels of interleukin-6 (IL-6) are associated with an increased risk and worse outcome of acute vascular events. A common G/C promoter polymorphism at nt (-174) of the IL-6 gene has been shown to affect basal IL-6 levels. Consequently, the IL-6 genotype may be associated with risk and outcome of ischemic stroke (IS). We investigated the statistical association between this polymorphism and cerebrovascular events, as well as the clinical outcome in patients with symptoms before the age of 60.

Methods: We examined 214 patients of 60 years or less with acute ischemic stroke or transient ischemic attack (TIA) and 214 age- and sex-matched healthy control subjects for the (-174) IL-6 G/C polymorphism by mutagenic separated polymerase chain reaction (MS PCR). Clinical severity of the vascular event was evaluated by validated scales at predefined points of time.

Results: In the total group of patients, the genotype and allele frequencies in the patient group (38% GG, 45% GC, 17% CC; allelic frequency: 60% G, 40% C) did not differ significantly from the control group. However, individuals homozygous for the (-174)G variant had significantly worse scores on the NIH Stroke Scale (NIHSS) already on admission and 1 week after the event. Also, patients with severe disability 1 week and 3 months after the event (Rankin Scale (RS) 4 or 5; NIH Stroke Scale> or =6) were significantly more often carriers of the GG genotype. In a multivariate analysis, the IL-6 (-174)GG genotype was significantly associated with severe disability after 1 week (RS 4-5; odds ratio (OR)=3.2, 95% CI: 1.5-6.6; p=0.002; NIHSS> or =6; OR=4.2, 95% CI: 1.6-11.1).

Conclusions: The (-174)GG-genotype of the IL-6 gene is associated with severe stroke in young patients with acute cerebrovascular events. Further studies with larger patient groups are warranted to confirm these findings.