The -174G>C IL-6 gene promoter polymorphism and diabetic microvascular complications

This study examined a possible association of the G>C polymorphism at nucleotide -174 in the promoter region of the interleukin-6 (IL-6) gene (rs1800795) with the prevalence of diabetic complications in 235 patients with type 1 and 498 patients with type 2 diabetes. Genotyping was performed using polymerase chain reaction (PCR) and subsequent cleavage by Nla III restriction endonuclease. Analyzing all diabetic patients together demonstrated that 301 patients (41.1%) carried the GG genotype, 114 (15.6%) the CC genotype, and 318 (43.3%) were heterozygous for the GC genotype. However, there was no correlation of any of the genotypes with the prevalence of diabetic nephropathy or diabetic neuropathy, but subjects with the CC genotype had a significantly higher prevalence of diabetic retinopathy compared to patients with the GC and GG genotype (p=0.016). This association was mainly lost when a logistic regression model was adjusted for diabetes duration (p=0.07). Consistently, a weak but not significant association of the polymorphism with diabetic retinopathy was observed when type 1 and type 2 diabetic patients were analyzed separately (patients with type 1 diabetes: p=0.12; patients with type 2 diabetes: p=0.09). Analogically, no association of the polymorphism was found for diabetic nephropathy or diabetic neuropathy in these groups. In conclusion these data suggest no major influence of the -174G>C variant in the promoter region of the IL-6 gene on the development of microvascular complications in patients with diabetes.