Nielsen Joachim, Farup Jean, Rahbek Stine Klejs, de Paoli Frank Vincenzo, Vissing Kristian
Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark; Department of Pathology, SDU Muscle Research Cluster (SMRC), Odense University Hospital, Odense C, Denmark.
Section of Sport Science, Department of Public Health, Aarhus University, Aarhus, Denmark.
PLoS One. 2015 May 21;10(5):e0127808. doi: 10.1371/journal.pone.0127808. eCollection 2015.
Unaccustomed eccentric exercise is accompanied by muscle damage and impaired glucose uptake and glycogen synthesis during subsequent recovery. Recently, it was shown that the role and regulation of glycogen in skeletal muscle are dependent on its subcellular localization, and that glycogen synthesis, as described by the product of glycogen particle size and number, is dependent on the time course of recovery after exercise and carbohydrate availability. In the present study, we investigated the subcellular distribution of glycogen in fibers with high (type I) and low (type II) mitochondrial content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies for analysis included time points 3, 24 and 48 h post exercise from the exercising leg, whereas biopsies corresponding to prior to and at 48 h after the exercise bout were collected from the non-exercising, control leg. Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h) enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils) of type I fibers, which was associated with an increase in the number of particles. In contrast, late in recovery (post 48 h), intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles. We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber's oxidative capacity, and the time course of recovery. The early enhanced storage of intramyofibrillar glycogen after the eccentric contractions may entail important implications for muscle function and fatigue resistance.
不习惯的离心运动伴随着肌肉损伤以及随后恢复过程中葡萄糖摄取和糖原合成受损。最近有研究表明，骨骼肌中糖原的作用和调节取决于其亚细胞定位，并且如糖原颗粒大小和数量的乘积所描述的糖原合成，取决于运动后恢复的时间进程和碳水化合物的可利用性。在本研究中，我们调查了离心收缩运动后恢复过程中，线粒体含量高（I型）和低（II型）的纤维中糖原的亚细胞分布。对五名男性受试者进行了分析，他们进行了一组由15×10次最大离心收缩组成的运动。随后在整个48小时的恢复期间摄入富含碳水化合物的饮料，用于分析的肌肉活检样本包括运动腿运动后3小时、24小时和48小时的时间点，而与运动前和运动后48小时对应的活检样本则从非运动的对照腿采集。通过透射电子显微镜进行的定量成像显示，I型纤维的肌原纤维内糖原（定义为位于肌原纤维内的糖原颗粒）在早期（3小时和24小时后）储存增加，这与颗粒数量的增加有关。相比之下，在恢复后期（48小时后），与对照腿相比，运动腿的I型和II型纤维中的肌原纤维间、肌原纤维内和肌膜下糖原均较低，这与糖原颗粒较小有关。我们得出结论，在补充碳水化合物的状态下，离心收缩对糖原代谢的影响取决于亚细胞定位、肌纤维的氧化能力和恢复的时间进程。离心收缩后肌原纤维内糖原的早期储存增加可能对肌肉功能和抗疲劳能力具有重要意义。
