Swings and roundabouts for muscle gain and loss: differences between sexes?
Swings and roundabouts for muscle gain and loss: differences between sexes?
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秋千和回旋对肌肉的增加和减少：性别之间的差异？
DOI：
10.1152/japplphysiol.01289.2005
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Rennie,MichaelJ
中科院分区：
文献类型：
--
作者：
Mittendorfer,Bettina;Rennie,MichaelJ
MAINTENANCE OF MUSCLE MASS results from a balance between muscle protein synthesis and breakdown, with a greater amplitude of changes in synthesis (2-fold) than breakdown (0.25-fold) during the diurnal cycle. Furthermore, adaptive changes in human muscle mass also seem to be largely the result of modulations in the rate of muscle protein synthesis. Contractile activity increases synthesis by two-to threefold for up to 2 days, and protein breakdown rises too but to a lesser extent. Consequently, net muscle protein balance becomes positive. In starvation and many situations of slow wasting associated with chronic diseases such as heart failure, there appear to be adaptive falls in synthesis and to a lesser extent breakdown, so the net balance is negative. Excessive rates of protein breakdown are only observed in cases of extreme muscle wasting, such as sepsis and burn injury. Long-term immobilization of human muscle is not associated with rapid breakdown (2–4); however, in the early stages, components of the ubiquitin-dependent proteasome proteolytic pathway are upregulated (6). An important distinction between studies of muscle in humans and rats, which have a much higher protein turnover rate, is that the responses may be more extreme in the latter. In fact, 28 days of complete bed rest resulted in a loss of only 5% leg muscle mass (8), whereas 28 days of hindlimb unloading caused a 30% loss of rat gastrocnemius in the study by Sitnick et al. reported in the January issue of Journal of
