Femoral neck response to exercise and subsequent deconditioning in young and adult rats
Femoral neck response to exercise and subsequent deconditioning in young and adult rats
复制标题
DOI：
10.1359/jbmr.2003.18.7.1292
复制
发表时间：
2003-07-01
影响因子：
6.2
通讯作者：
Kannus, P
中科院分区：
文献类型：
--
作者：
Järvinen, TLN;Pajamäki, I;Kannus, P
人们认为老化的骨骼响应事件载荷变化的能力降低。通过使幼年和成年大鼠承受增加的负荷和随后的去适应，我们观察到这两组中骨骼的定量相似的适应性反应，但幼年骨骼主要通过几何变化来适应，而成年骨骼则通过增加体积密度来适应。运动引起的骨骼益处的丧失并不取决于年龄。简介：衰老已被证明会降低骨骼的机械感觉细胞对负荷引起的刺激的敏感性，可能不仅导致能力下降，而且导致老年骨骼对负荷改变的不同适应机制，以及保留运动引起的骨骼益处的能力较差。材料和方法：50 名年轻人（5 周龄）和 50 只成年（33 周龄）雄性大鼠被随机分为对照组和运动（+去适应）组。经过 14 周的逐步强化跑步计划后，一半的运动大鼠（幼年和成年）被处死，其余大鼠随后接受为期 14 周的去适应期（自由笼内活动）。使用外周定量计算机断层扫描和机械测试对股骨颈进行全面分析。结果：与对照组相比，年轻和成年运动大鼠几乎所有测量参数均显着增加：横截面积+25％（p <0.001）和+10％（不显着[NS]）；骨矿物质含量 +28% (p < 0.001) 和 +18% (p < 0.001)；骨矿物质密度增加 11% (p < 0.05) 和 +23% (p < 0.001)；断裂载荷分别为 +30% (p < 0.01) 和 +28% (p < 0.01)。幼年和成年大鼠的骨骼反应没有统计学差异。 14周的去适应期后，相应的运动与对照差异分别为+17%（p < 0.05）和+10%（NS）、+18%（p < 0.05）和+13%（p < 0.05）、+2%（NS）和+2%（NS）以及+11%（NS）和+6%（NS）。同样，不同年龄组之间的反应差异并不显着。 结论：从数量上看，年轻和成人骨骼适应增加负荷的能力相似，但适应机制似乎不同：生长中的骨骼似乎主要表现出几何变化（骨骼尺寸增加），而成人骨骼主要通过密度增加做出反应。尽管适应机制存在明显差异，但衰老并没有调节骨骼保留运动引起的骨增益的能力，因为停止训练后幼年和成年大鼠的骨丢失相似。
Aged bones have been considered to have reduced capacity to respond to changes in incident loading. By subjecting young and adult rats to increased loading and subsequent deconditioning, we observed quantitatively similar adaptive responses of bone in these two groups, but young skeletons adapted primarily through geometric changes and adult bones through increased volumetric density. Loss of the exercise-induced bone benefits did not depend on age.Introduction: Aging has been shown to decrease the sensitivity of the mechanosensory cells of bones to loading-induced stimuli, presumably resulting in not only reduced capacity but also different adaptive mechanism of the aged skeleton to altered loading, as well as poorer capacity to preserve exercise-induced bone benefits.Materials and Methods: Fifty young (5-week-old) and 50 adult (33-week-old) male rats were randomized into control and exercise (+deconditioning) groups. After a 14-week progressively intensified running program, one-half of the exercised rats (both young and adult) were killed, and the remaining rats underwent subsequent 14-week period of deconditioning (free cage activity). A comprehensive analysis of the femoral neck was performed using peripheral quantitative computed tomography and mechanical testing.Results: In comparison with the controls, both young and adult exercised rats had significant increases in almost all measured parameters: +25% (p < 0.001) and +10% (not significant [NS]) in the cross-sectional area; +28% (p < 0.001) and +18% (p < 0.001) in bone mineral content; +11% (p < 0.05) and +23% (p < 0.001) in bone mineral density; and +30% (p < 0.01) and +28% (p < 0.01) in the breaking load, respectively. The skeletal responses were not statistically different between the young and adult rats. After the 14-week period of deconditioning, the corresponding exercised-to-controls differences were +17% (p < 0.05) and +10% (NS), +18% (p < 0.05) and +13% (p < 0.05), +2% (NS) and +2% (NS), and +11% (NS) and +6% (NS), respectively. Again, the response differences were not significant between the age groups.Conclusion: Quantitatively, the capacity of the young and adult skeleton to adapt to increased loading was similar, but the adaptive mechanisms appeared different: growing bones seemed to primarily display geometric changes (increase in bone size), whereas the adult skeleton responded mainly through an increase in density. Despite this apparent difference in the adaptive mechanism, aging did not modulate the ability of the skeleton to preserve the exercise-induced bone gain, because the bone loss was similar in the young and adult rats after cessation of training.