Journal de la recherche osseuse
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Bone Marrow Adipose Tissue in Adolescence- Protective or Pathogenic

Lynae J Hanks, Anna L Newton, Pranayraj Kondapally and Krista Casazza

Background: Pathogenic attributes of bone marrow adipose tissue (BMAT) described in the older population could explain the prominent sequela in osteoporosis and even type 2 diabetes in adults. However, its rapid appearance in long bones during arguably the most critical period in skeletal and metabolic programming, challenge this notion. The timing of a substantial proportion of BMAT accrual in long bones during the linear growth spurt suggest an evolutionarily conserved protective effect in which the growing skeleton must benefit from it appearance in some way. Thus, if BMAT is protective, how does induced disruption of the conversion influence differentiation at the cellular level between osteogenesis and adipogenesis and subsequently affect bone strength-structure properties. The objective of this study was to test the hypothesis that obesity accelerates the size of the marrow compartment at the expense of quality components of bone, ultimately compromising bone material properties and structural design. Further, as muscle and bone adapt in parallel we also aimed to evaluate qualitative and quantitative aspects of skeletal muscle and the relationship between bone and muscle.

Methods: Subjects were 46 overweight/obese girls age 7-12 years. Magnetic resonance imaging (MRI) was used to assess femoral BMAT and marrow area and density were assessed by peripheral quantitative computed tomography (pQCT). Bone and muscle parameters were evaluated by MRI, pQCT and dual-energy X-ray absorptiometry (DXA). Partial correlation was used to assess the degree of association between BMAT and bone parameters as well as BMAT and muscle parameters after controlling for race and age.

Results: BMAT was positively associated with quantitative aspects of bone and muscle. However, marrow density, a qualitative attribute of the marrow compartment representative of hematopoietic capacity was inversely associated with cortical density and marginally inversely associated with cortical area. Further, muscle density, reflective of muscle health was positively associated with quantitative aspects of bone and muscle, yet an association with quality was not detected.

Conclusion: Early in the life course, at a critical period for bone health, obesity may negatively influence muscle and skeletal development. Though speculative, our results support a potential mechanism by which obesity impairs bone integrity via effects on the marrow compartment. Future studies are warranted to evaluate how the protective effect of BMAT on bone and muscle health may be conserved.