Relationships between IL-6 gene polymorphism, low BMD and periodontitis in postmenopausal women

IL-6 plays critical roles in bone resorption and the pathogenesis of periodontitis in both inflammation and alveolar bone loss. A negative correlation was observed between periodontitis and truncal bone mineral density (BMD) in postmenopausal women. The C allele carriers of a genetic polymorphism IL-6-572G/C have higher levels of serum IL-6 compared to G allele carriers. We investigated the possible effect of IL-6-572G/C polymorphism on the relationship between low BMD and periodontitis in postmenopausal women.

A total of 300 postmenopausal Japanese women who lived in Yokogoshi area of Niigata City, Japan, participated in this study. Genomic DNA was extracted from peripheral blood. The IL-6-572G/C genotypes were determined by the restriction fragment length polymorphism method. Bone mineral density (BMD) of right femoral neck and serum bone metabolism markers were measured. Low BMD was defined to have the BMD<80% of the mean for young adults. Periodontal parameters at two sites per tooth were measured.

Serum osteocalcin levels were significantly lower in the IL-6-572G/G genotype (p=0.025). In the -572G allele non-carriers, percentages of PPD≥4mm sites were significantly higher in low BMD group compared with the healthy control group (p=0.021). Logistic regression analysis revealed low BMD to be associated with periodontitis (Odds ratio=1.736, p=0.027) after adjusted with IL-6-572G carriage, age, serum albumin level.

IL-6-572G/C polymorphism was not an independent risk factor of low BMD or periodontitis, but may affect the relationship between the two diseases in postmenopausal Japanese women.