School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UNITED KINGDOM.
Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, THE NETHERLANDS.
Med Sci Sports Exerc. 2019 Oct;51(10):2125-2134. doi: 10.1249/MSS.0000000000002034.
Across the lifespan, physical activity levels decrease and time spent sedentary typically increases. However, little is known about the impact that these behavioral changes have on skeletal muscle mass regulation. The primary aim of this study was to use a step reduction model to determine the impact of reduced physical activity and increased sedentary time on daily myofibrillar protein synthesis rates in healthy young men.
Eleven men (22 ± 2 yr) completed 7 d of habitual physical activity (HPA) followed by 7 d of step reduction (SR). Myofibrillar protein synthesis rates were determined during HPA and SR using the deuterated water (H2O) method combined with the collection of skeletal muscle biopsies and daily saliva samples. Gene expression of selected proteins related to muscle mass regulation and oxidative metabolism were determined via real time reverse transcription-quantitative polymerase chain reaction (RT-qPCR).
Daily step count was reduced by approximately 91% during SR (from 13,054 ± 2763 steps per day to 1192 ± 330 steps per day; P < 0.001) and this led to an increased contribution of sedentary time to daily activity (73% ± 6% to 90% ± 3%; P < 0.001). Daily myofibrillar protein synthesis decreased by approximately 27% from 1.39 ± 0.32%·d during HPA to 1.01 ± 0.38%·d during SR (P < 0.05). Muscle atrophy F-box and myostatin mRNA expression were upregulated, whereas mechanistic target of rapamycin, p53, and PDK4 mRNA expression were downregulated after SR (P < 0.05).
One week of reduced physical activity and increased sedentary time substantially lowers daily myofibrillar protein synthesis rates in healthy young men.
在整个生命周期中，身体活动水平下降，久坐时间通常增加。然而，人们对这些行为变化对骨骼肌质量调节的影响知之甚少。本研究的主要目的是使用减少活动量模型来确定减少体力活动和增加久坐时间对健康年轻男性日常肌原纤维蛋白合成率的影响。
11 名男性（22 ± 2 岁）完成了 7 天的习惯性体力活动（HPA），随后进行了 7 天的减少活动量（SR）。使用氘水（H2O）法结合骨骼肌活检和每日唾液样本采集，在 HPA 和 SR 期间确定肌原纤维蛋白合成率。通过实时逆转录定量聚合酶链反应（RT-qPCR）测定与肌肉质量调节和氧化代谢相关的选定蛋白质的基因表达。
SR 期间每天的步数减少了约 91%（从每天 13054 ± 2763 步减少到每天 1192 ± 330 步；P < 0.001），这导致久坐时间在日常活动中的占比增加（从 73% ± 6%增加到 90% ± 3%；P < 0.001）。从 HPA 期间的 1.39 ± 0.32%·d 到 SR 期间的 1.01 ± 0.38%·d，每日肌原纤维蛋白合成减少了约 27%（P < 0.05）。SR 后肌肉萎缩 F-box 和肌肉生长抑制素 mRNA 表达上调，而雷帕霉素靶蛋白、p53 和 PDK4 mRNA 表达下调（P < 0.05）。
一周的体力活动减少和久坐时间增加会显著降低健康年轻男性的日常肌原纤维蛋白合成率。
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