Ca2+ dependency of limb muscle fiber contractile mechanics in young and older adults.
Ca2+ dependency of limb muscle fiber contractile mechanics in young and older adults.
复制标题
年轻人和老年人肢体肌纤维收缩力学的 Ca2 依赖性。
DOI：
10.1152/ajpcell.00575.2019
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Fitts,RobertH
中科院分区：
文献类型：
--
作者：
Teigen,LauraE;Sundberg,ChristopherW;Kelly,LaurenJ;Hunter,SandraK;Fitts,RobertH
骨骼肌收缩功能的下降归因于多种细胞因素，包括较低的峰值力（Po），Ca 2+敏感性降低，缩短速度（Vo）降低。然而，这些细胞特性随年龄的变化仍未得到解决，特别是在老年妇女中，次最大Ca 2+对收缩功能的影响尚不清楚。因此，我们比较了19名年轻人（24 ± 3岁; 8名女性）和21名老年人（77 ± 7岁; 7名女性）在最大和次大Ca 2+下的肌纤维收缩特性，并评估了被认为影响Ca 2+敏感性的三种蛋白质的丰度。年轻人的快纤维横截面积（6，479 ± 2，487 µm2）比老年人（4，503 ± 2，071 µm2，P< 0.001）大约44%，这对应于更大的绝对Po（年轻人= 1.12 ± 0.43 mN;老年人= 0.79 ± 0.33 mN，P< 0.001）。特定于纤维尺寸的快纤维Po没有差异，这表明与年龄相关的力下降可以通过纤维尺寸的差异来解释。除了快速纤维的大小和绝对Po，没有年龄或性别差异观察到的Ca 2+敏感性，力的发展速度（ktr），或Voin无论是慢或快的纤维。次最大Ca 2+抑郁ktrand Vo，但在任何性别的影响并没有改变年龄。与啮齿动物研究相反，调节轻链（RLC）和肌球蛋白结合蛋白-C丰度和RLC磷酸化不受年龄或性别的影响。这些数据表明，与年龄相关的收缩功能下降主要是由于快纤维的萎缩，在将啮齿动物研究的结果扩展到人类时需要谨慎。
Age-induced declines in skeletal muscle contractile function have been attributed to multiple cellular factors, including lower peak force (Po), decreased Ca2+sensitivity, and reduced shortening velocity (Vo). However, changes in these cellular properties with aging remain unresolved, especially in older women, and the effect of submaximal Ca2+on contractile function is unknown. Thus, we compared contractile properties of muscle fibers from 19 young (24 ± 3 yr; 8 women) and 21 older adults (77 ± 7 yr; 7 women) under maximal and submaximal Ca2+and assessed the abundance of three proteins thought to influence Ca2+sensitivity. Fast fiber cross-sectional area was ~44% larger in young (6,479 ± 2,487 µm2) compared with older adults (4,503 ± 2,071 µm2,P< 0.001), which corresponded with a greater absolute Po(young = 1.12 ± 0.43 mN; old = 0.79 ± 0.33 mN,P< 0.001). There were no differences in fast fiber size-specific Po, indicating the age-related decline in force was explained by differences in fiber size. Except for fast fiber size and absolute Po, no age or sex differences were observed in Ca2+sensitivity, rate of force development (ktr), or Voin either slow or fast fibers. Submaximal Ca2+depressed ktrand Vo, but the effects were not altered by age in either sex. Contrary to rodent studies, regulatory light chain (RLC) and myosin binding protein-C abundance and RLC phosphorylation were unaltered by age or sex. These data suggest the age-associated reductions in contractile function are primarily due to the atrophy of fast fibers and that caution is warranted when extending results from rodent studies to humans.