Interleukin-6 gene -174 promoter polymorphism is associated with endothelial dysfunction but not with disease susceptibility in patients with rheumatoid arthritis.

OBJECTIVE

To determine whether the interleukin (IL)6 -174 gene polymorphism may influence the development of subclinical atherosclerosis manifested by the presence of endothelial dysfunction in RA patients.

PATIENTS AND METHODS

311 patients (228 [73.3%] women; 243 [78.1%] rheumatoid factor positive) who fulfilled the 1987 ACR classification criteria for RA seen at the Rheumatology outpatient clinic of Hospital Xeral-Calde, Lugo between March 1996 and December 2006 and 226 matched controls were included in this study. Between March and December 2007, a subgroup of 98 patients randomly selected was assessed for the presence of endothelial dysfunction. Patients and controls were genotyped for a single biallelic (G/C) nucleotide polymorphism (rs1800795) in the promoter region at the position -174 of the IL6 gene using a TaqMan 5' allele discrimination assay.

RESULTS

No significant differences in the IL6 -174 allele or genotype frequency between RA patients and controls were found. However, RA patients homozygous for the IL6 -174 GG genotype had more severe endothelial dysfunction (flow-mediated endothelium-dependent vasodilatation-FMD%: 4.2 + or - 6.6) than those carrying the IL6 -174 GC (FMD%: 6.3 + or - 8.1) or IL6 -174 CC (FMD%: 6.0 + or - 3.3) genotypes. In this regard, significant differences were observed when FMD% values in RA patients carrying the IL6 -174 GG genotype were compared with that observed in those carrying the IL6 -174 GC and the IL6 -174 CC genotypes (FMD%: 6.3 + or - 4.6) (p=0.02).

CONCLUSIONS

Our results support a role of IL6 -174 gene polymorphism in the development of subclinical atherosclerosis in patients with RA.