An investigation into the relationship between soft tissue body composition and bone mineral density in a young adult twin sample

Authors

  • Leonie H Bogl,

    Corresponding author
    1. The Finnish Twin Cohort Study, Department of Public Health, University of Helsinki, Helsinki, Finland
    • Department of Public Health, PO Box 41, Mannerheimintie 172, University of Helsinki, FI-00014 Helsinki, Finland.
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  • Antti Latvala,

    1. Department of Mental Health and Substance Abuse Services, National Institute for Health and Welfare, Helsinki, Finland
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  • Jaakko Kaprio,

    1. The Finnish Twin Cohort Study, Department of Public Health, University of Helsinki, Helsinki, Finland
    2. Department of Mental Health and Substance Abuse Services, National Institute for Health and Welfare, Helsinki, Finland
    3. Institute for Molecular Medicine, Helsinki, Finland
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  • Olli Sovijärvi,

    1. Obesity Research Unit, Department of Psychiatry, Helsinki University Central Hospital, Helsinki, Finland
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  • Aila Rissanen,

    1. Obesity Research Unit, Department of Psychiatry, Helsinki University Central Hospital, Helsinki, Finland
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  • Kirsi H Pietiläinen

    1. The Finnish Twin Cohort Study, Department of Public Health, University of Helsinki, Helsinki, Finland
    2. Obesity Research Unit, Department of Psychiatry, Helsinki University Central Hospital, Helsinki, Finland
    3. Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland
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Abstract

The purpose of this study was to investigate the relationship of fat mass (FM) and lean mass (LM) with bone mineral density (BMD) independent of genetic effects. We also assessed the extent to which genetic and environmental influences explain the associations between these phenotypes. Body composition and BMD were measured using dual-energy X-ray absorptiometry in 57 monozygotic and 92 same-sex dizygotic twin pairs, aged 23 to 31 years, chosen to represent a wide range of intrapair differences in body mass index (BMI; 0 to 15.2 kg/m2). Heritability estimates were adjusted for height and gender. In multiple linear regression analysis, intrapair differences in both FM and LM were independently associated with intrapair differences in BMD at most skeletal sites after adjustment for gender and differences in height. Within monozygotic and dizygotic pairs, LM was a significantly stronger predictor of whole-body BMD than FM (p < .01). Additive genetic factors explained 87% [95% confidence interval (CI) 80%–91%), 81% (95% CI 70%–88%), and 61% (95% CI 41%–75%) of the variation in whole-body BMD, LM, and FM, respectively. Additive genetic factors also accounted for 69% to 88% of the covariance between LM and BMD and for 42% to 72% of the covariance between FM and BMD depending on the skeletal site. The genetic correlation between LM and whole-body BMD (rg = 0.46, 95% CI 0.32–0.58) was greater than that of FM and whole-body BMD (rg = 0.25, 95% CI 0.05–0.42). In conclusion, our data indicate that peak BMD is influenced by acquired body weight as well as genetic factors. In young adulthood, LM and BMD may have more genes in common than do FM and BMD. © 2011 American Society for Bone and Mineral Research.

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