Analysis of polymorphism of the interleukin-6 gene in Thai subjects with osteoporosis.

Osteoporosis is the imbalance between bone formation by osteoblast and bone resorption by osteoclast. The genetic factors play an important role in determining bone mass and several genes probably act as regulators of this process. Interkeukin-6 (IL-6) is one of the candidate genes to regulate bone density, since IL-6 has some effect on stimulation of osteoclast resorption and has been implicated in the pathogenesis of bone loss associated with estrogen deficiency. We investigated the relationship between bone mineral density (BMD) and a polymorphic AT rich repeat in the 3' flank of the IL-6 gene in 272 Thai subjects. The subjects were classified into 3 groups i.e. normal healthy control (n=95), border-line (n=112) and osteoporotic patients (n=65). Five alleles different in sizes were identified (designated a, b, c, e and f). It was observed that c/c was the most common genotype in Thais (86.76%). The other genotype frequencies were 0.74, 3.31, 8.09, 0.74 and 0.37 for a/c, b/c, c/e, c/f and b/e genotypes, respectively. The common genotype was different from the Caucasians in a previous study. These frequencies were significantly different from the Caucasians (p<0.05). There was no significant relationship between 3' flanking AT repeat of the IL-6 genotypes and the BMD values of the distal forearm that were determined by One-way ANOVA (p>0.05). Additionally, the impact of the IL-6 genotypes on risk of osteoporosis was assessed by determination of the odds ratio. The c/e genotype may be a protective factor of osteoporosis. On the contrary, the b/c and c/c genotypes were considered to be risk factors of osteoporosis.