Wetzsteon Rachel J, Petit Moira A, Macdonald Heather M, Hughes Julie M, Beck Thomas J, McKay Heather A
Department of Pediatrics, Division of Nephrology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
J Bone Miner Res. 2008 Dec;23(12):1946-53. doi: 10.1359/jbmr.080810.
The effect of excess body fat on bone strength accrual is not well understood. Therefore, we assessed bone measures in healthy weight (HW) and overweight (OW) children. Children (9-11 yr) were classified as HW (n = 302) or OW (n = 143) based on body mass index. We assessed total (ToD) and cortical (CoD) volumetric BMD and bone area, estimates of bone strength (bone strength index [BSI]; stress-strain index [SSIp]), and muscle cross-sectional area (CSA) at the distal (8%), midshaft (50%), and proximal (66%) tibia by pQCT. We used analysis of covariance to compare bone outcomes at baseline and change over 16 mo. At baseline, all bone measures were significantly greater in OW compared with HW children (+4-15%; p <or= 0.001), with the exception of CoD at the 50% and 66% sites. Over 16 mo, ToA increased more in the OW children, whereas there was no difference for change in BSI or ToD between groups at the distal tibia. At the tibial midshaft, SSIp was similar between groups at baseline when adjusted for muscle CSA, but low when adjusted for body fat in the OW group. At both sites, bone strength increased more in OW because of a greater increase in bone area. Changes in SSIp were associated with changes in lean mass (r = 0.70, p < 0.001) but not fat mass. In conclusion, although OW children seem to be at an advantage in terms of absolute bone strength, bone strength did not adapt to excess body fat. Rather, bone strength was adapted to the greater muscle area in OW children.
过多体脂对骨强度积累的影响尚未完全明确。因此，我们评估了健康体重（HW）和超重（OW）儿童的骨指标。根据体重指数将9至11岁儿童分为HW组（n = 302）或OW组（n = 143）。我们通过外周定量计算机断层扫描（pQCT）评估了胫骨远端（8%）、骨干中部（50%）和近端（66%）的总骨密度（ToD）、皮质骨密度（CoD）、骨面积、骨强度估计值（骨强度指数[BSI]；应力应变指数[SSIp]）以及肌肉横截面积（CSA）。我们使用协方差分析比较了基线时的骨指标以及16个月内的变化情况。基线时，除了50%和66%部位的CoD外，OW儿童的所有骨指标均显著高于HW儿童（+4 - 15%；p≤0.001）。在16个月期间，OW儿童的总骨面积（ToA）增加更多，而在胫骨远端两组之间的BSI或ToD变化没有差异。在胫骨骨干中部，调整肌肉CSA后，两组在基线时的SSIp相似，但OW组调整体脂后SSIp较低。在这两个部位，由于骨面积增加更多，OW组的骨强度增加更多。SSIp的变化与去脂体重的变化相关（r = 0.70，p < 0.001），但与脂肪量无关。总之，尽管OW儿童在绝对骨强度方面似乎具有优势，但骨强度并未适应过多的体脂。相反，骨强度适应了OW儿童更大的肌肉面积。
