Association of a G2014A transition in exon 8 of the estrogen receptor-α gene with postmenopausal osteoporosis

Abstract

We report the association of a newly identified synonymous G2014A single nucleotide polymorphism (SNP) which does not alter the amino acid sequence in exon 8 of the estrogen receptor-α (ERα) gene with osteoporosis in Thai postmenopausal women. Subjects consisted of 228 postmenopausal women aged more than 55 years divided into two groups - with vertebral or femoral osteoporosis (n = 106) or without osteoporosis (n = 122) - according to bone mineral density (BMD) criteria. The exon 8 G2014A SNP, which is 6 nucleotides upstream from the end of the stop codon, was identified by PCR-RFLP. Data are expressed as the mean and 95% CI. The allele frequency of the G2014A polymorphism was 26.4% in osteoporotic subjects and was significantly higher than that in non-osteoporotic women (15.2%) (p < 0.05). By stepwise logistic regression analysis, it was found that the G2014A polymorphism was related to the presence of osteoporosis (odds ratio 2.7 per A allele, 95% CI 1.49-4.76) independently of body weight (odds ratio 0.93 per kg, 95% CI 0.89-0.96) and years since menopause (odds ratio 1.12 per year, 95% CI 1.08-1.19). In a multiple linear regression model, L2-L4 BMD of osteoporotic subjects was associated with body weight (p < 0.05), endogenous estradiol levels (p < 0.05) and the G2014A genotype (p < 0.001), while it was related only to body weight (p < 0.05) and estradiol levels in non-osteoporotic women (p < 0.05). We conclude that a G2014A SNP in exon 8 of ERα is associated with the presence and severity of postmenopausal osteoporosis. Linkage disequilibrium between this polymorphism and the 3′-untranslated region of the ERα gene which may participate in the regulation of ERα gene expression remains to be determined.