Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, P.O. Box 61 6200 MD Maastricht, The Netherlands.
Department of Human Nutrition, Wageningen University, P.O. Box 17 6700 AA Wageningen, The Netherlands.
Nutrients. 2018 May 17;10(5):635. doi: 10.3390/nu10050635.
Short successive periods of physical inactivity occur throughout life and contribute considerably to the age-related loss of skeletal muscle mass. The maintenance of muscle mass during brief periods of disuse is required to prevent functional decline and maintain metabolic health.
To assess whether daily leucine supplementation during a short period of disuse can attenuate subsequent muscle loss in vivo in humans.
Thirty healthy (22 ± 1 y) young males were exposed to a 7-day unilateral knee immobilization intervention by means of a full leg cast with (LEU, = 15) or without (CON, = 15) daily leucine supplementation (2.5 g leucine, three times daily). Prior to and directly after immobilization, quadriceps muscle cross-sectional area (computed tomography (CT) scan) and leg strength (one-repetition maximum (1-RM)) were assessed. Furthermore, muscle biopsies were taken in both groups before and after immobilization to assess changes in type I and type II muscle fiber CSA.
Quadriceps muscle cross-sectional area (CSA) declined in the CON and LEU groups ( < 0.01), with no differences between the two groups (from 7712 ± 324 to 7287 ± 305 mm² and from 7643 ± 317 to 7164 ± 328 mm²; = 0.61, respectively). Leg muscle strength decreased from 56 ± 4 to 53 ± 4 kg in the CON group and from 63 ± 3 to 55 ± 2 kg in the LEU group (main effect of time < 0.01), with no differences between the groups ( = 0.052). Type I and II muscle fiber size did not change significantly over time, in both groups ( > 0.05).
Free leucine supplementation with each of the three main meals (7.5 g/d) does not attenuate the decline of muscle mass and strength during a 7-day limb immobilization intervention.
短暂连续的身体不活动贯穿人的一生，对与年龄相关的骨骼肌质量损失有很大影响。在短暂的停用期间保持肌肉质量对于防止功能下降和维持代谢健康是必要的。
评估在短暂停用期间每天补充亮氨酸是否可以减轻人体随后的肌肉损失。
30 名健康（22 ± 1 岁）的年轻男性通过全腿石膏进行了为期 7 天的单侧膝关节固定干预，其中（LEU，n = 15）或不补充亮氨酸（CON，n = 15）（每天 2.5 克亮氨酸，分 3 次服用）。在固定之前和直接固定后，评估股四头肌横截面积（计算机断层扫描（CT）扫描）和腿部力量（一次重复最大（1-RM））。此外，在两组中均在固定前后进行肌肉活检，以评估 I 型和 II 型肌纤维 CSA 的变化。
CON 和 LEU 组的股四头肌横截面积（CSA）均下降（<0.01），两组之间无差异（从 7712 ± 324 降至 7287 ± 305 mm²和从 7643 ± 317 降至 7164 ± 328 mm²；= 0.61）。CON 组的腿部肌肉力量从 56 ± 4 降至 53 ± 4 kg，LEU 组从 63 ± 3 降至 55 ± 2 kg（时间的主要影响<0.01），两组之间无差异（= 0.052）。在两组中，I 型和 II 型肌纤维大小在时间上均无明显变化（>0.05）。
在 7 天的肢体固定干预期间，每餐（7.5 g/d）补充游离亮氨酸并不能减轻肌肉质量和力量的下降。
