Bed rest increases the amount of mismatched fibers in human skeletal muscle
Bed rest increases the amount of mismatched fibers in human skeletal muscle
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DOI：
10.1152/jappl.1999.86.2.455
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发表时间：
1999-02-01
影响因子：
3.3
通讯作者：
Schiaffino, S
中科院分区：
文献类型：
--
作者：
Andersen, JL;Gruschy-Knudsen, T;Schiaffino, S
研究了37 d卧床休息对人骨骼肌纤维中肌球蛋白重链（myosin heavy chain， MHC） mRNA和蛋白表达的影响。对7名健康青年男性受试者在卧床休息前后进行股外侧肌活检。肌肉组织切片的原位杂交、免疫细胞化学和atp酶组织化学分析表明，卧床休息后，MHC亚型mRNA和蛋白质水平不匹配的纤维显著增加，表明处于过渡状态的肌纤维数量增加。因此，卧床休息后，MHC-1和MHC-2A mRNA和蛋白表达相匹配的纤维减少，MHC-2X mRNA和蛋白表达相匹配的纤维增加。总的来说，从表型型1 -> 2A和2A -> 2X过渡状态的纤维有所增加。此外，卧床休息后观察到许多MHC mRNA和同工蛋白组合不寻常的纤维（例如，1型纤维只有2X mRNA， 1型纤维没有MHC- β /慢速、2A和2X mRNA）。相比之下，仅在蛋白质水平检查后未发现任何变化。这些数据表明，通过卧床休息对骨骼肌施加的负重活动减少会改变MHC基因表达，导致mRNA和MHC异构体的组合，通常在承受负重活动的肌肉中没有（或很少）观察到。另一方面，目前的数据还表明，37天的卧床休息不足以在蛋白质水平上诱导类似的变化，正如在基因水平上观察到的那样。
The effects of a 37-day period of bed rest on myosin heavy chain (MHC) expression on both mRNA and protein level in human skeletal muscle fibers were studied. Muscle biopsies from vastus lateralis muscle were obtained from seven healthy young male subjects before and after the bed-rest period. Combined in situ hybridization, immunocytochemistry, and ATPase histochemistry analysis of serial sections of the muscle biopsies demonstrated that fibers showing a mismatch between MHC isoforms at the mRNA and protein level increased significantly after the bed-rest period, suggesting an increase in the amount of muscle fibers in a transitional state. Accordingly fibers showing a match in expression of MHC-1 and of MHC-2A at the mRNA and protein level decreased, whereas fibers showing a match between MHC-2X mRNA and protein increased after bed rest. Overall, there was an increase in fibers in a transitional state from phenotypic type 1 --> 2A and 2A --> 2X. Furthermore, a number of fibers with unusual MHC mRNA and isoprotein combinations were observed after bed rest (e.g., type 1 fibers with only mRNA for 2X and type 1 fibers negative for mRNA for MHC-beta/slow, 2A, and 2X). In contrast, no changes were revealed after an examination at the protein level alone. These data suggest that the reduced load-bearing activity imposed on the skeletal muscles through bed rest will alter MHC gene expression, resulting in combinations of mRNA and MHC isoforms normally not (or only rarely) observed in muscles subjected to load-bearing activity. On the other hand, the present data also show that 37 days of bed rest are not a sufficient stimulus to induce a similar change at the protein level, as was observed at the gene level.