Zhao Lan-Juan, Liu Yong-Jun, Liu Peng-Yuan, Hamilton James, Recker Robert R, Deng Hong-Wen
Department of Orthopedic Surgery, School of Medicine, University of Missouri-Kansas City, 2411 Holmes Street, Kansas City, MO 64108, USA.
J Clin Endocrinol Metab. 2007 May;92(5):1640-6. doi: 10.1210/jc.2006-0572. Epub 2007 Feb 13.
The relationship between obesity and osteoporosis has been widely studied, and epidemiological evidence shows that obesity is correlated with increased bone mass. Previous analyses, however, did not control for the mechanical loading effects of total body weight on bone mass and may have generated a confounded or even biased relationship between obesity and osteoporosis.
The objective of this study was to reevaluate the relationship between obesity and osteoporosis by accounting for the mechanical loading effects of total body weight on bone mass.
We measured whole body fat mass, lean mass, percentage fat mass, body mass index, and bone mass in two large samples of different ethnicity: 1988 unrelated Chinese subjects and 4489 Caucasian subjects from 512 pedigrees. We first evaluated the Pearson correlations among different phenotypes. We then dissected the phenotypic correlations into genetic and environmental components with bone mass unadjusted or adjusted for body weight. This allowed us to compare the results with and without controlling for mechanical loading effects of body weight on bone mass.
In both Chinese and Caucasian subjects, when the mechanical loading effect of body weight on bone mass was adjusted for, the phenotypic correlation (including its genetic and environmental components) between fat mass (or percentage fat mass) and bone mass was negative. Further multivariate analyses in subjects stratified by body weight confirmed the inverse relationship between bone mass and fat mass, after mechanical loading effects due to total body weight were controlled.
Increasing fat mass may not have a beneficial effect on bone mass.
肥胖与骨质疏松症之间的关系已得到广泛研究，流行病学证据表明肥胖与骨量增加相关。然而，以往的分析未对总体重对骨量的机械负荷效应进行控制，可能在肥胖与骨质疏松症之间产生了混淆甚至有偏差的关系。
本研究的目的是通过考虑总体重对骨量的机械负荷效应，重新评估肥胖与骨质疏松症之间的关系。
我们在两个不同种族的大样本中测量了全身脂肪量、去脂体重、体脂百分比、体重指数和骨量：1988名无亲缘关系的中国受试者和来自512个家系的4489名白种人受试者。我们首先评估了不同表型之间的皮尔逊相关性。然后，我们将表型相关性分解为遗传和环境成分，对骨量进行未调整或根据体重调整。这使我们能够比较在控制和未控制体重对骨量的机械负荷效应的情况下的结果。
在中国受试者和白种人受试者中，当对体重对骨量的机械负荷效应进行调整后，脂肪量（或体脂百分比）与骨量之间的表型相关性（包括其遗传和环境成分）为负。在按体重分层的受试者中进行的进一步多变量分析证实，在控制了总体重引起的机械负荷效应后，骨量与脂肪量之间呈负相关。
脂肪量增加可能对骨量没有有益影响。
