两周的低活动量可减少腿部瘦体重，并导致健康老年人的肌原纤维蛋白合成出现“合成代谢抵抗”。

Two weeks of reduced activity decreases leg lean mass and induces "anabolic resistance" of myofibrillar protein synthesis in healthy elderly.

机构信息

Department of Kinesiology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.

出版信息

J Clin Endocrinol Metab. 2013 Jun;98(6):2604-12. doi: 10.1210/jc.2013-1502. Epub 2013 Apr 15.

DOI:10.1210/jc.2013-1502

PMID:23589526

Abstract

BACKGROUND

Alterations in muscle protein metabolism underlie age-related muscle atrophy. During periods of muscle disuse, muscle protein synthesis is blunted, and muscle atrophy occurs in young and old. The impact of a short reduction in physical activity on muscle protein metabolism in older adults is unknown.

PURPOSE

The aim of this study was to investigate the impact of 14 days of reduced daily steps on fasted and fed-state rates of myofibrillar protein synthesis (MPS) to provide insight into the mechanisms for changes in muscle mass and markers of metabolic health.

METHODS

Before and after 14 days of reduced daily step-count, 10 healthy older adults (age, 72 ± 1 y) underwent measures of insulin sensitivity, muscle strength, physical function, and body composition. Using a primed constant infusion of L-[ring-(13)C6]phenylalanine with serial muscle biopsies, basal, postabsorptive, and postprandial rates of MPS were determined before and after the 14-day intervention.

RESULTS

Daily step-count was reduced by approximately 76% to 1413 ± 110 steps per day. Leg fat-free mass was reduced by approximately 3.9% (P < .001). Postabsorptive insulin resistance was increased by approximately 12%, and postprandial insulin sensitivity was reduced by approximately 43% after step reduction (P < .005). Concentrations of TNF-α and C-reactive protein were increased by approximately 12 and 25%, respectively, after step reduction (P < .05). Postprandial rates of MPS were reduced by approximately 26% after the intervention (P = .028), with no difference in postabsorptive rates.

CONCLUSION

The present study demonstrates that 14 days of reduced steps in older adults induces small but measurable reductions in muscle mass that appear to be underpinned by reductions in postprandial MPS and are accompanied by impairments in insulin sensitivity and systemic inflammatory markers and postprandial MPS.

摘要

背景

肌肉蛋白质代谢的改变是导致与年龄相关的肌肉萎缩的基础。在肌肉失用期间，肌肉蛋白质合成受到抑制，年轻人和老年人都会发生肌肉萎缩。目前尚不清楚短期减少体力活动对老年人肌肉蛋白质代谢的影响。

目的

本研究旨在探讨 14 天减少日常步数对空腹和进食状态下肌纤维蛋白合成（MPS）率的影响，以期深入了解肌肉质量变化和代谢健康标志物的变化机制。

方法

在减少日常步数 14 天前后，10 名健康老年人（年龄 72±1 岁）接受了胰岛素敏感性、肌肉力量、身体功能和身体成分的测量。使用 L-[环-（13）C6]苯丙氨酸的脉冲恒速输注和连续肌肉活检，在 14 天干预前后测定基础、餐后和进餐后 MPS 率。

结果

日常步数减少约 76%，至每天 1413±110 步。腿部去脂体重减少约 3.9%（P<0.001）。餐后胰岛素抵抗增加约 12%，餐后胰岛素敏感性降低约 43%（P<0.005）。步减少后 TNF-α和 C 反应蛋白的浓度分别增加约 12%和 25%（P<0.05）。干预后餐后 MPS 率降低约 26%（P=0.028），而餐后率无差异。