Holwerda Andrew M, Weijzen Michelle E G, Zorenc Antoine, Senden Joan, Jetten Guus H J, Houben Lisanne H P, Verdijk Lex B, VAN Loon Luc J C
Department of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre+, Maastricht, THE NETHERLANDS.
Med Sci Sports Exerc. 2024 Apr 1;56(4):612-622. doi: 10.1249/MSS.0000000000003342. Epub 2023 Nov 22.
Short periods of limb immobilization lower myofibrillar protein synthesis rates. Within skeletal muscle, the extracellular matrix of connective proteins is recognized as an important factor determining the capacity to transmit contractile force. Little is known regarding the impact of immobilization and subsequent recovery on muscle connective protein synthesis rates. This study examined the impact of 1 wk of leg immobilization and 2 wk of subsequent ambulant recovery on daily muscle connective protein synthesis rates.
Thirty healthy, young (24 ± 5 yr) men were subjected to 7 d of one-legged knee immobilization followed by 14 d of ambulant recovery. Deuterium oxide ingestion was applied over the entire period, and muscle biopsy samples were collected before immobilization, after immobilization, and after recovery to measure muscle connective protein synthesis rates and mRNA expression of key extracellular matrix proteins (collagen I, collagen III), glycoproteins (fibronectin, tenascin-C), and proteoglycans (fibromodulin, and decorin). A two-way repeated-measures (time-leg) ANOVA was used to compare changes in muscle connective protein synthesis rates during immobilization and recovery.
During immobilization, muscle connective protein synthesis rates were lower in the immobilized (1.07 ± 0.30%·d -1 ) compared with the nonimmobilized (1.48 ± 0.44%·d -1 ; P < 0.01) leg. When compared with the immobilization period, connective protein synthesis rates in the immobilized leg increased during subsequent recovery (1.48 ± 0.64%·d -1 ; P < 0.01). After recovery, skeletal muscle collagen I, collagen III, fibronectin, fibromodulin, and decorin mRNA expression increased when compared with the postimmobilization time point (all P < 0.001).
One week of leg immobilization lowers muscle connective protein synthesis rates. Muscle connective protein synthesis rates increase during subsequent ambulant recovery, which is accompanied by increased mRNA expression of key extracellular matrix proteins.
短期肢体固定会降低肌原纤维蛋白合成速率。在骨骼肌中，结缔蛋白的细胞外基质被认为是决定传递收缩力能力的一个重要因素。关于固定及随后恢复对肌肉结缔蛋白合成速率的影响，目前所知甚少。本研究考察了1周腿部固定及随后2周行走恢复对每日肌肉结缔蛋白合成速率的影响。
30名健康的年轻（24±5岁）男性接受单腿膝关节固定7天，随后进行14天的行走恢复。在整个期间摄入氧化氘，并在固定前、固定后及恢复后采集肌肉活检样本，以测量肌肉结缔蛋白合成速率以及关键细胞外基质蛋白（I型胶原蛋白、III型胶原蛋白）、糖蛋白（纤连蛋白、腱生蛋白-C）和蛋白聚糖（纤维调节素、核心蛋白聚糖）的mRNA表达。采用双向重复测量（时间-腿）方差分析来比较固定和恢复期间肌肉结缔蛋白合成速率的变化。
在固定期间，与未固定的腿（1.48±0.44%·d -1 ）相比，固定腿的肌肉结缔蛋白合成速率较低（1.07±0.30%·d -1 ；P<0.01）。与固定期相比，固定腿的结缔蛋白合成速率在随后的恢复期间增加（1.48±0.64%·d -1 ；P<0.01）。恢复后，与固定后时间点相比，骨骼肌I型胶原蛋白、III型胶原蛋白、纤连蛋白、纤维调节素和核心蛋白聚糖的mRNA表达增加（均P<0.001）。
1周腿部固定会降低肌肉结缔蛋白合成速率。在随后的行走恢复期间，肌肉结缔蛋白合成速率增加，同时关键细胞外基质蛋白mRNA表达增加。
