INRA, UMR, Unité de Nutrition Humaine, Clermont-Ferrand, France.
Br J Nutr. 2011 Dec;106(11):1683-90. doi: 10.1017/S0007114511002182. Epub 2011 Jun 21.
Sarcopenia is defined as age-related loss of muscle mass and strength. Energy restriction (ER) delays fibre loss by limiting the accumulated deleterious effects of reactive oxygen species on muscle. However, insufficient protein intake during ER might affect muscle mass and function. We hypothesised that ingestion of fast-digested proteins such as whey protein (WP) improves muscle protein synthesis and muscle strength in aged ER rats. The effect of WP or casein (CAS, slow protein) on muscle mass, protein synthesis and strength was evaluated in 21-month-old rats fed for 5 months either ad libitum (AL) or a 40 % protein and energy-restricted (PER) or 40 % AL-isonitrogenous ER diet. The nitrogen balance was reduced in PER-CAS rats only ( - 48 % v. AL-CAS). WP stimulated muscle protein synthesis rates compared with CAS in all groups (+21,+37 and +34 % in AL, PER and ER conditions, respectively). Muscle strength was higher in ER rats than in AL rats (+23 and +12 % for WP or CAS, respectively). Muscle performance tended to be greater in ER rats fed WP than in ER-CAS rats (P < 0·09). In conclusion, we observed that long-term ER combined with maintained protein intake had a beneficial impact on muscle protein synthesis rate and function during ageing.
肌肉减少症是指与年龄相关的肌肉质量和力量损失。能量限制（ER）通过限制活性氧对肌肉的累积有害影响来延缓纤维损失。然而，ER 期间蛋白质摄入不足可能会影响肌肉质量和功能。我们假设，摄入快速消化的蛋白质，如乳清蛋白（WP），可以改善老年 ER 大鼠的肌肉蛋白质合成和肌肉力量。在 21 个月大的大鼠中，评估 WP 或酪蛋白（CAS，慢蛋白）对肌肉质量、蛋白质合成和力量的影响，这些大鼠在 5 个月内分别自由进食（AL）或 40%蛋白质和能量限制（PER）或 40%AL-同氮 ER 饮食。只有 PER-CAS 大鼠的氮平衡降低（-48%比 AL-CAS）。与 CAS 相比，WP 刺激所有组的肌肉蛋白质合成率增加（AL、PER 和 ER 条件下分别增加 21%、37%和 34%）。ER 大鼠的肌肉力量高于 AL 大鼠（WP 或 CAS 分别增加 23%和 12%）。与 ER-CAS 大鼠相比，ER 大鼠喂养 WP 时肌肉性能趋于更高（P<0.09）。总之，我们观察到长期 ER 结合维持蛋白质摄入对衰老过程中的肌肉蛋白质合成率和功能有有益影响。
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