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

OBJECTIVE

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).

METHODS

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.

RESULTS

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).

CONCLUSION

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