Interleukin-6 receptor gene polymorphisms and periodontitis in a non-smoking Japanese population

Aim: The indispensable role of interleukin-6 receptor (IL-6R) in regulating IL-6 responses has been clearly established. We have previously reported that IL6R polymorphisms strongly influenced the serum levels of soluble IL-6R. In this study, we investigated the association between these genetic variations and periodontitis. Material and Methods: Among the seven novel IL6R single-nucleotide polymorphisms (SNPs) reported, we genotyped two important sites: the +48892 A/C in exon 9 and the -183 G/A in the promoter region. The SNP in exon 9 results in Asp -> Ala substitution in the proteolytic cleavage site of IL-6R alpha. In total, 212 periodontitis cases and 210 healthy controls were genotyped using polymerase chain reaction, restriction fragment length polymorphisms and direct sequencing methods. Results: Analysis of the genotype distribution of the +48892 A/C SNP in periodontitis patients and in controls revealed a suggestive association with aggressive (p=0.04) and chronic periodontitis (p=0.04). In addition, the carriage rate for the A allele was significantly higher in chronic periodontitis patients [p=0.02, odds ratio (OR)=2.25]. No association was found in the -183 G/A SNP. The two markers were in linkage disequilibrium (LD) (|D'|=0.53). Conclusion: The IL6R +48892 A/C polymorphism could act as a risk factor for periodontitis; however, further association and biological studies are needed.