McIntosh Mason C, Michel J Max, Godwin Joshua S, Plotkin Daniel L, Anglin Derick A, Mattingly Madison L, Agyin-Birikorang Anthony, Kontos Nicholas J, Baweja Harsimran S, Stock Matt S, Mobley C Brooks, Roberts Michael D
bioRxiv. 2024 Nov 26:2024.11.24.625075. doi: 10.1101/2024.11.24.625075.
We recently reported that resistance trained (T, n=10) and untrained (UT, n=11) young adults experience vastus lateralis (VL) muscle atrophy following two weeks of disuse, and 8 weeks of recovery resistance training (RT) promotes VL hypertrophy in both participant cohorts. However, angiogenesis targets and muscle capillary number were not examined and currently no human studies that have sought to determine if disuse followed by recovery RT affects these outcomes. Thus, we examined whether disuse and/or recovery RT affected these outcomes. All participants underwent two weeks of left leg immobilization using locking leg braces and crutches followed by eight weeks (3d/week) of knee extensor focused progressive RT. VL biopsies were obtained at baseline (PRE), immediately after disuse (MID), and after RT (POST). Western blotting was used to assay angiogenesis markers and immunohistochemistry was performed in 16/21 participants to determine type I and II muscle fiber capillary number. Significant main effects of time (p<0.05) were observed for protein levels of VEGF (MID<POST), VEGFR2 (PRE&MID<POST), TSP-1 (PRE<POST), TIMP1 (MID<POST), phosphorylated/pan eNOS (Ser1177) (POST<PRE), and pan eNOS (PRE<POST). VEGFR2 exhibited a training status*time (p=0.018), but no differences existed between T and UT at any time point. A significant main effect of time was observed for type II fiber capillary number (PRE<POST), and type II fiber cross-sectional area (fCSA) increased from MID to POST (+25%, p<0.001) and PRE to POST (+20%, p=0.019). No significant correlations exist for percentage changes in type II fiber capillary number and type II fCSA from PRE-to-MID (r= 0.020), MID-to-POST (r= 0.392), or PRE-to-POST (r= -0.120) across all participants (p>0.100). Although disuse and recovery RT affect skeletal muscle angiogenesis-related protein targets, prior training history does not differentially affect these outcomes.
This is the first study to examine how limb immobilization and recovery resistance training affect molecular outcomes related to angiogenesis in younger adults with or without a prior training history. Regardless of resistance training history, the molecular responses are largely similar between participant cohorts and is suggestive of a reduced (pre-mid) and increased (mid-post) angiogenic response, with disuse and subsequent recovery resistance training.
我们最近报告称，经过抗阻训练的年轻人（T组，n = 10）和未经训练的年轻人（UT组，n = 11）在两周废用后出现股外侧肌（VL）萎缩，而8周的恢复性抗阻训练（RT）可促进两组参与者的VL肥大。然而，未对血管生成靶点和肌肉毛细血管数量进行检测，目前也没有人体研究试图确定废用后进行恢复性RT是否会影响这些结果。因此，我们研究了废用和/或恢复性RT是否会影响这些结果。所有参与者使用锁定腿托和拐杖对左腿进行了两周固定，随后进行了为期八周（每周3天）的以伸膝为主的渐进性RT。在基线（PRE）、废用后即刻（MID）和RT后（POST）获取VL活检样本。采用蛋白质免疫印迹法检测血管生成标志物，对21名参与者中的16名进行免疫组织化学检测以确定I型和II型肌纤维的毛细血管数量。观察到时间对VEGF蛋白水平（MID < POST）、VEGFR2（PRE和MID < POST）、TSP - 1（PRE < POST）、TIMP1（MID < POST）、磷酸化/总eNOS（Ser1177）（POST < PRE）和总eNOS（PRE < POST）有显著的主效应（p < 0.05）。VEGFR2呈现训练状态*时间效应（p = 0.018），但在任何时间点T组和UT组之间均无差异。观察到时间对II型纤维毛细血管数量有显著的主效应（PRE < POST），II型纤维横截面积（fCSA）从MID到POST增加（+25%，p < 0.001），从PRE到POST增加（+20%，p = 0.019）。在所有参与者中，II型纤维毛细血管数量和II型fCSA从PRE到MID、MID到POST或PRE到POST的百分比变化之间均无显著相关性（r = 0.020、r = 0.392、r = -0.120，p > 0.100）。尽管废用和恢复性RT会影响骨骼肌血管生成相关蛋白靶点，但既往训练史并不会对这些结果产生差异影响。
这是第一项研究肢体固定和恢复性抗阻训练如何影响有或无既往训练史的年轻成年人中与血管生成相关的分子结果的研究。无论抗阻训练史如何，参与者队列之间的分子反应在很大程度上相似，这表明在废用和随后的恢复性抗阻训练过程中，血管生成反应先降低（PRE - MID）后增加（MID - POST）。
