A temporal study on musculoskeletal morphology and metabolism in hibernating Daurian ground squirrels (Spermophilus dauricus)
A temporal study on musculoskeletal morphology and metabolism in hibernating Daurian ground squirrels (Spermophilus dauricus)
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冬眠达乌尔地松鼠 (Spermophilus dauricus) 肌肉骨骼形态和代谢的时间研究
DOI：
10.1016/j.bone.2020.115826
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发表时间：
2021
期刊：
影响因子：
4.1
通讯作者：
Gao Yunfang
中科院分区：
文献类型：
--
作者：
Zhang Jie;Chang Hui;Yin Rongrong;Xu Shenhui;Wang Huiping;Gao Yunfang
冬眠者提供了一个自然模型来研究预防废用引起的肌肉骨骼退化的机制。然而目前，人们对这些机制仍知之甚少。在此，我们研究了达斡尔地松鼠(Spermophilusdauricus)在不同冬眠时期后肢骨骼肌和骨骼的形态和代谢指标的变化，并进一步探讨了冬眠动物在长期不活动后肌肉骨骼维持的可能机制。结果表明，与夏季活跃组（SA）水平相比，冬眠不同时期的几乎所有骨骼肌和骨形态指标，包括肌肉质量、肌纤维横截面积、骨量、骨长度和骨力学性能均没有变化。冬眠后组（POST）中只有少数骨骼微观结构参数出现恶化，包括骨比表面积增加（+71%）、胫骨骨小梁厚度减少（-43%）和平均皮质厚度减少（-51%），以及股骨骨小梁分离增加（+60%）。此外，除了间歇性唤醒组（IBA）中的几个指标外，大多数检查的涉及肌肉蛋白周转和骨重塑的代谢指标没有变化，即股内侧肌中真核起始因子4E结合蛋白1（4E-BP1）磷酸化的增加（IBA与SA，+ 80％），股内侧肌中胰凝乳蛋白酶样活性的增加（IBA与SA，+ 62％）。胫骨前肌，胫骨中每个骨表面的成骨细胞数量（IBA 与 SA，+110%；IBA 与 torpor (TOR)，+68%）和破骨细胞数量（IBA 与 TOR，+105%）增加，以及股骨中每个骨表面的破骨细胞表面增加（IBA 与 TOR，+128%）。上述证据表明，松鼠的肌肉骨骼形态在很大程度上得到了保留，并且在长时间冬眠不活动后，肌肉骨骼代谢基本得以维持。这些发现表明，维持良好的肌肉骨骼代谢可能是冬眠期间保存肌肉骨骼系统的重要机制。 IBA期间多项代谢指标同时上调，表明该时期肌肉骨骼代谢可能相对活跃；然而，它在冬眠期间肌肉骨骼维持中的作用需要进一步阐明。
Hibernators provide a natural model to study the mechanisms underlying the prevention of disuse-induced musculoskeletal deterioration. Currently, however, these mechanisms remain poorly understood. Here, we investigated changes in morphology and metabolic indices in the hindlimb skeletal muscle and bone of Daurian ground squirrels (Spermophilusdauricus) during different periods of hibernation, and further explored the possible mechanisms involved in the musculoskeletal maintenance of hibernators after prolonged inactivity. Results showed that, compared with levels in the summer active group (SA), almost all morphological indices of skeletal muscle and bone, including muscle mass, muscle fiber cross-sectional area, bone mass, bone length, and bone mechanical properties, were unchanged in the different periods of hibernation. Only a few microstructural parameters of bone showed deterioration in the post-hibernation group (POST), including increased specific bone surface (+71%), decreased trabecular thickness (−43%), and decreased average cortical thickness (−51%) in the tibia, and increased trabecular separation (+60%) in the femur. Furthermore, most examined metabolic indices involved in muscle protein turnover and bone remodeling were unchanged, except for several indices in the inter-bout arousal group (IBA), i.e., increase in the phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1) (IBA vs. SA, +80%) in the vastus medialis muscle, increase in chymotrypsin-like activity (IBA vs. SA, +62%) in the tibialis anterior muscle, increase in osteoblast number (IBA vs. SA, +110%; IBA vs. torpor (TOR), +68%) and osteoclast number (IBA vs. TOR, +105%) per bone surface in the tibia, and increase in osteoclast surface per bone surface (IBA vs. TOR, +128%) in the femur. The above evidence demonstrates that the musculoskeletal morphology of squirrels was largely preserved, and musculoskeletal metabolism was generally maintained after prolonged hibernation inactivity. These findings suggest that the well-maintained musculoskeletal metabolism may be a vital mechanism underlying the preservation of the musculoskeletal system during hibernation. The coincident up-regulation of several metabolic indicators during IBA indicates that musculoskeletal metabolism may be relatively active during this period; however, its role in musculoskeletal maintenance during hibernation needs further clarification.