Dirks Marlou L, Wall Benjamin T, Nilwik Rachel, Weerts Daniëlle H J M, Verdijk Lex B, van Loon Luc J C
NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University, Maastricht, The Netherlands; and.
NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University, Maastricht, The Netherlands; and
J Nutr. 2014 Aug;144(8):1196-203. doi: 10.3945/jn.114.194217. Epub 2014 Jun 11.
Short successive periods of muscle disuse, due to injury or illness, can contribute significantly to the loss of muscle mass with aging (sarcopenia). It has been suggested that increasing the protein content of the diet may be an effective dietary strategy to attenuate muscle disuse atrophy. We hypothesized that protein supplementation twice daily would preserve muscle mass during a short period of limb immobilization. Twenty-three healthy older (69 ± 1 y) men were subjected to 5 d of one-legged knee immobilization by means of a full-leg cast with (PRO group; n = 11) or without (CON group; n = 12) administration of a dietary protein supplement (20.7 g of protein, 9.3 g of carbohydrate, and 3.0 g of fat) twice daily. Two d prior to and immediately after the immobilization period, single-slice computed tomography scans of the quadriceps and single-leg 1 repetition maximum strength tests were performed to assess muscle cross-sectional area (CSA) and leg muscle strength, respectively. Additionally, muscle biopsies were collected to assess muscle fiber characteristics as well as mRNA and protein expression of selected genes. Immobilization decreased quadriceps' CSAs by 1.5 ± 0.7% (P < 0.05) and 2.0 ± 0.6% (P < 0.05), and muscle strength by 8.3 ± 3.3% (P < 0.05) and 9.3 ± 1.6% (P < 0.05) in the CON and PRO groups, respectively, without differences between groups. Skeletal muscle myostatin, myogenin, and muscle RING-finger protein-1 (MuRF1) mRNA expression increased following immobilization in both groups (P < 0.05), whereas muscle atrophy F-box/atrogen-1 (MAFBx) mRNA expression increased in the PRO group only (P < 0.05). In conclusion, dietary protein supplementation (∼20 g twice daily) does not attenuate muscle loss during short-term muscle disuse in healthy older men. This trial was registered at clinicaltrials.gov as NCT01588808.
由于受伤或患病导致的短期连续肌肉不活动,会显著加剧衰老过程中的肌肉量流失(肌肉减少症)。有人提出,增加饮食中的蛋白质含量可能是减轻肌肉不活动萎缩的一种有效饮食策略。我们假设,每天补充两次蛋白质可在短期肢体固定期间维持肌肉量。23名健康的老年男性(69±1岁),通过全腿石膏固定单腿膝关节5天,其中11名给予饮食蛋白质补充剂(每天两次,含20.7克蛋白质、9.3克碳水化合物和3.0克脂肪)(PRO组),12名不给予(CON组)。在固定期前2天和固定期结束后立即进行股四头肌单层计算机断层扫描以及单腿1次重复最大力量测试,分别评估肌肉横截面积(CSA)和腿部肌肉力量。此外,采集肌肉活检样本以评估肌纤维特征以及选定基因的mRNA和蛋白质表达。固定后,CON组和PRO组的股四头肌CSA分别减少了1.5±0.7%(P<0.05)和2.0±0.6%(P<0.05),肌肉力量分别下降了8.3±3.3%(P<0.05)和9.3±1.6%(P<)0.05),两组之间无差异。两组固定后骨骼肌肌生长抑制素、肌细胞生成素和肌肉环指蛋白-1(MuRF1)的mRNA表达均增加(P<0.05),而肌肉萎缩F盒/atrogin-1(MAFBx)的mRNA表达仅在PRO组增加(P<0.05)。总之,对于健康老年男性,饮食补充蛋白质(每天两次,约20克)并不能减轻短期肌肉不活动期间的肌肉流失。该试验已在clinicaltrials.gov上注册,注册号为NCT01588808。