Department of Physiological Sciences, The University of Arizona, 1713 E. University Blvd. #93, Tucson, AZ 85721, USA.
Bone. 2010 Apr;46(4):977-84. doi: 10.1016/j.bone.2009.12.033. Epub 2010 Jan 6.
Understanding the influence of total body fat mass (TBFM) on bone during the peri-pubertal years is critical for the development of future interventions aimed at improving bone strength and reducing fracture risk. Thus, we evaluated the relationship of TBFM to volumetric bone mineral density (vBMD), geometry, and strength at metaphyseal and diaphyseal sites of the femur and tibia of young girls. Data from 396 girls aged 8-13 years from the "Jump-In: Building Better Bones" study were analyzed. Bone parameters were assessed using peripheral quantitative computed tomography (pQCT) at the 4% and 20% distal femur and 4% and 66% distal tibia of the non-dominant leg. Bone parameters at the 4% sites included trabecular vBMD, periosteal circumference, and bone strength index (BSI), while at the 20% femur and 66% tibia, parameters included cortical vBMD, periosteal circumference, and strength-strain index (SSI). Multiple linear regression analyses were used to assess associations between bone parameters and TBFM, controlling for muscle cross-sectional area (MCSA). Regression analyses were then repeated with maturity, bone length, physical activity, and ethnicity as additional covariates. Analysis of covariance (ANCOVA) was used to compare bone parameters among tertiles of TBFM. In regression models with TBFM and MCSA, associations between TBFM and bone parameters at all sites were not significant. TBFM explained very little variance in all bone parameters (0.2-2.3%). In contrast, MCSA was strongly related (p<0.001) to all bone parameters, except cortical vBMD. The addition of maturity, bone length, physical activity, and ethnicity did not alter the relationship between TBFM and bone parameters. With bone parameters expressed relative to total body mass, ANCOVA showed that all outcomes were significantly (p<0.001) greater in the lowest compared to the middle and highest tertiles of TBFM. Although TBFM is correlated with femur and tibia vBMD, periosteal circumference, and strength in young girls, this relationship is significantly attenuated after adjustment for MCSA. Nevertheless, girls with higher TBFM relative to body mass have markedly diminished vBMD, geometry, and bone strength at metaphyseal and diaphyseal sites of the femur and tibia.
了解全身脂肪量（TBFM）对青春期骨骼的影响对于开发旨在提高骨强度和降低骨折风险的未来干预措施至关重要。因此，我们评估了 TBFM 与股骨和胫骨骨干和干骺端部位的体积骨密度（vBMD）、几何形状和强度之间的关系，该研究的数据来自于年龄在 8-13 岁的“Jump-In：Building Better Bones”研究中的 396 名女孩。使用外周定量计算机断层扫描（pQCT）在非优势侧腿的 4%和 20%远端股骨和 4%和 66%远端胫骨处评估骨骼参数。4%部位的骨骼参数包括小梁 vBMD、骨皮质周长和骨强度指数（BSI），而在 20%股骨和 66%胫骨处，参数包括皮质 vBMD、骨皮质周长和强度应变指数（SSI）。使用多元线性回归分析评估了骨骼参数与 TBFM 之间的关联，同时控制了肌肉横截面积（MCSA）。然后，使用成熟度、骨长度、身体活动和种族作为额外的协变量重复回归分析。使用协方差分析（ANCOVA）比较 TBFM 三分位组之间的骨骼参数。在 TBFM 和 MCSA 的回归模型中，TBFM 与所有部位的骨骼参数之间的关联不显著。TBFM 仅能解释所有骨骼参数的很小一部分变异（0.2-2.3%）。相比之下，MCSA 与除皮质 vBMD 之外的所有骨骼参数均密切相关（p<0.001）。添加成熟度、骨长度、身体活动和种族并没有改变 TBFM 与骨骼参数之间的关系。将骨骼参数表示为相对于总体重的比值，ANCOVA 显示，与中间和最高 TBFM 三分位组相比，所有结果在最低 TBFM 三分位组中均显著（p<0.001）更高。尽管 TBFM 与年轻女孩的股骨和胫骨 vBMD、骨皮质周长和强度相关，但在调整 MCSA 后，这种关系显著减弱。然而，与体重相比，TBFM 较高的女孩在股骨和胫骨骨干和干骺端部位的 vBMD、几何形状和骨强度明显降低。
