[Combined effect of interleukin-6 and estrogen receptor gene polymorphisms on bone mass in postmenopausal women]

To examine the individual and combined effects of interleukin-6 (IL-6) and estrogen receptor (ER) gene polymorphisms on the Z score of bone mineral density (BMD).

BMD at lumbar spine (L(2 - 4)) and femoral neck (FN) were analyzed in 205 postmenopausal Chinese women by dual energy X-ray absorptiometry. Polymorphic 3'flanking region of IL-6 gene and the allelic variance in ER gene PvuII and XbaI sites were studied by polymerase chain reaction. Serum alkaline phosphatase, osteocalcin and urinary pyridinolin were also measured.

There were D/D, D/E, C/D, C/C and E/E 5 genotypes of IL-6 gene in our samples, 193 of 205 women were D/D or D/E types. No difference of BMD at L(2 - 4) or FN was found between D/D and D/E types. For the PvuII and XbaI polymorphisms in these IL-6 D/D and D/E genotypes, the FN BMD was higher in pp in comparison with Pp (P = 0.036), and lumbar spine BMD was higher in XX type, comparing with Xx and xx genotype (P = 0.005 and 0.031, respectively). Women without Px haplotype had elevated BMD at L(2 - 4) (P = 0.029) and a trend for higher BMD at FN (P = 0.056) than those with it. Combining the women with IL-6 D/D, D/E genotypes and ER gene Px haplotypes, the L(2 - 4) BMD in those of DD * without Px haplotype showed a tendency to be higher than those of DD * with Px haplotype (P = 0.057), and was significantly increased than those of DE * with Px haplotypes (P = 0.036).

The introduction of ER gene Px haplotype in the analysis of IL-6 gene might identify individuals with a reduced bone mass more precisely.