查看肌少症的来源

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您请求的操作仅限于组中的用户:危险因素肌肉减少症被大多数人认为是衰老不可避免的一部分。然而，肌肉减少症的程度是高度可变的，并取决于某些危险因素的存在。[[文件:whf - cap-global - target -Physical-Inactivity- -][[不运动]]:#*缺乏运动被认为是肌肉减少症的首要危险因素。肌肉细胞(Myocyte)| Myocyte)的数量在50岁左右开始逐渐减少。与经常运动的患者相比，久坐生活方式的患者肌肉纤维和力量的下降更为明显。即使是专业运动员，如马拉松运动员和举重运动员，随着年龄的增长，他们的速度和力量也会逐渐(更缓慢)下降。#[[激素]]和[[细胞因子]]失衡:#*年龄相关的激素浓度下降(如睾酮、甲状腺激素和[[胰岛素样生长因子-1]])导致肌肉质量和力量的损失。极端的肌肉损失通常是由激素合成代谢信号的减少和促炎细胞因子介导的分解代谢信号的促进共同造成的。[[文件:染色体- dna -基因拷贝.jpg|右|无边框]][[蛋白质|蛋白质]]合成和再生:#*人体合成蛋白质的能力下降，再加上摄入的热量和/或蛋白质不足以维持肌肉质量，这在肌肉减少症中很常见。随着年龄的增长，骨骼肌中的氧化蛋白增加，并导致脂褐素(黄褐色，色素，不溶性颗粒)的积累。Terman A, Brunk UT。(https://linkinghub.elsevier.com/retrieve/pii/S1357272503002991脂褐质)。 The International Journal of Biochemistry & Cell Biology. 2004 Aug 1;36(8):1400-4. The age-related increase in amounts of oxidized protein may reflect the age-dependent accumulation of unrepaired DNA damage that affects the concentrations or activities of numerous factors that govern the rates of protein [[Free Radicals|oxidation]] and the degradation of oxidized proteinStadtman ER. [https://science.sciencemag.org/content/257/5074/1220 Protein oxidation and aging]. Science. 1992 Aug 28;257(5074):1220-4.. This accumulation of non-contractile dysfunctional protein in skeletal muscles is part of the reason muscle strength decreases severely in sarcopenia. # Motor Unit Remodelling: #* Age-related reduction in [[Motor Neurone|motor nerve cells]] responsible for sending signals from the brain to the muscles to initiate movement also occurs. Satellite cells are small mononuclear cells that abut muscle fibers and are normally activated upon injury or exercise. In response to these signals, satellite cells differentiate and fuse into the muscle fiber, helping to maintain muscle function. One current hypothesis is that sarcopenia is caused, in part, by a failure in satellite cell activation.

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