Abstract
Summary
This study assessed independent associations and interactions of IL-6 promoter alleles (−174G/C and −634C/G), calcium intake and physical activity with bone mass among pre-menarche Chinese girls. The −634 CC carriers, greater calcium intake and physical activity were associated with better bone mass. The gene-bone association was more pronounced among girls with high physical activity or with low calcium intake.
Introduction
The association between interleukin (IL)-6 promoter polymorphisms and bone mass remains in debate. This cross-sectional study examined the association between the IL-6 promoter alleles (−174G/C and −634C/G) and bone mass, and assessed if the association could be modified by calcium intake or physical activity in pre-menarche Chinese girls.
Methods
Two-hundred and twenty-eight healthy pre-menarche girls aged 9–11 years were recruited from primary schools in Guangzhou, China by sending letters to parents. None of them had diseases or medications known to affect bone metabolism. The IL-6 promoter genotypes were determined by PCR-RFLP, and BMD and BMC at the total body, lumbar spine, total hip and femoral neck were measured by DXA. Calcium intake and physical activity were assessed by face-to-face questionnaire interview.
Results
One hundred and seventy-six subjects completed the entire study. We did not detect gene polymorphism at the IL-6 −174G/C locus, all were GG homozygotes. The IL-6 −634C/G polymorphism was significantly associated with both BMD and BMC even after adjusting for age and weight. Girls with CC genotype had higher levels of BMC and BMD than G allele carriers (+8.3% for the total body BMC, and +2.9%, +5.8%, and +5.7% for BMDs at the total body, total hip, and femoral neck, respectively; P < 0.05). The favorable effect of physical activity on BMDs at the total hip and femoral neck was much more pronounced in CC carriers than in G allele carriers, and the CC genotype associated higher BMDs at the total hip and femoral neck were observed only in girls with high level physical activity (P for interactions = 0.036 and 0.021, adjusted for age and weight). Calcium had a more benefit to the total body BMC in G allele carriers than in CC carriers, and the G allele-associated lower total body BMC was found only in subjects with low calcium intake.
Conclusion
The IL-6 −634C/G polymorphism was significantly associated with BMD and the association might be modified by calcium intake or physical activity in pre-menarche Chinese girls.
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Acknowledgements
The study was supported by Chinese National Science Foundation (CNSF, No: 30571569). We thank all the study subjects for volunteering to participate in the study.
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Li, X., He, GP., Zhang, B. et al. Interactions of interleukin-6 gene polymorphisms with calcium intake and physical activity on bone mass in pre-menarche Chinese girls. Osteoporos Int 19, 1629–1637 (2008). https://doi.org/10.1007/s00198-008-0613-3
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DOI: https://doi.org/10.1007/s00198-008-0613-3