1Department of Health and Kinesiology, Texas A&M University, College Station, TX; 2Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN; 3Department of Biomedical Engineering, Texas A&M University, College Station, TX; 4Department of Mechanical Engineering, Texas A&M University, College Station, TX; and 5Department of Nutrition and Food Science, Texas A&M University, College Station, TX.
Med Sci Sports Exerc. 2013 Nov;45(11):2052-60. doi: 10.1249/MSS.0b013e318299c614.
The purpose of this study was to investigate whether partial weight-bearing activity, at either one-sixth or one-third of body mass, blunts the deleterious effects of simulated microgravity (0G) after 21 d on muscle mass and quantitative/qualitative measures of bone.
Using a novel, previously validated partial weight-bearing suspension device, mice were subjected to 16% (G/3, i.e., simulated lunar gravity) or 33% (G/6, i.e., simulated Martian gravity) weight bearing for 21 d. One gravity control (1G, i.e., Earth gravity) and tail-suspended mice (0G, i.e., simulated microgravity) served as controls to compare the effects of simulated lunar and Martian gravity to both Earth and microgravity.
Simulated microgravity (0G) resulted in an 8% reduction in body mass and a 28% lower total plantarflexor muscle mass (for both, P < 0.01) as compared with 1G controls, but one-sixth and one-third partial weight-bearing activity attenuated losses. Relative to 1G controls, trabecular bone volume fraction (-9% to -13%) and trabecular thickness (-10% to -14%) were significantly lower in all groups (P < 0.01). In addition, cancellous and cortical bone formation rates (BFR) were lower in all reduced weight-bearing groups compared with 1G controls (-46% to -57%, trabecular BFR; -73% to -85%, cortical BFR; P < 0.001). Animals experiencing one-third but not one-sixth weight bearing exhibited attenuated deficits in femoral neck mechanical strength associated with 0G.
These results suggest that partial weight bearing (up to 33% of body mass) is not sufficient to protect against bone loss observed with simulated 0 g but does mitigate reductions in soleus mass in skeletally mature female mice.
本研究旨在探讨模拟微重力（0G）21 天后，六分之一或三分之一体重的部分负重活动是否会减轻对肌肉质量和骨定量/定性测量的有害影响。
使用一种新的、经过验证的部分负重悬吊装置，使小鼠承受 16%（G/3，即模拟月球重力）或 33%（G/6，即模拟火星重力）的负重 21 天。1 个重力对照（1G，即地球重力）和尾部悬吊小鼠（0G，即模拟微重力）作为对照，以比较模拟月球和火星重力对地球和微重力的影响。
与 1G 对照组相比，模拟微重力（0G）导致体重下降 8%，足底屈肌总质量下降 28%（均 P < 0.01），但六分之一和三分之一的部分负重活动减轻了损失。与 1G 对照组相比，所有组的小梁骨体积分数（-9%至-13%）和小梁厚度（-10%至-14%）均显著降低（P < 0.01）。此外，与 1G 对照组相比，所有负重减轻组的松质骨和皮质骨形成率（BFR）均降低（小梁 BFR：-46%至-57%；皮质 BFR：-73%至-85%；P < 0.001）。承受三分之一体重但不承受六分之一体重的动物表现出与 0G 相关的股骨颈机械强度降低的情况有所减轻。
这些结果表明，部分负重（高达体重的 33%）不足以防止模拟 0G 引起的骨丢失，但可减轻成熟雌性小鼠比目鱼肌质量的减少。
