Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1.
Br J Nutr. 2012 Nov 28;108(10):1780-8. doi: 10.1017/S0007114511007422. Epub 2012 Feb 7.
Feeding stimulates robust increases in muscle protein synthesis (MPS); however, ageing may alter the anabolic response to protein ingestion and the subsequent aminoacidaemia. With this as background, we aimed to determine in the present study the dose-response of MPS with the ingestion of isolated whey protein, with and without prior resistance exercise, in the elderly. For the purpose of this study, thirty-seven elderly men (age 71 (sd 4) years) completed a bout of unilateral leg-based resistance exercise before ingesting 0, 10, 20 or 40 g of whey protein isolate (W0-W40, respectively). Infusion of l-[1-13C]leucine and l-[ring-13C6]phenylalanine with bilateral vastus lateralis muscle biopsies were used to ascertain whole-body leucine oxidation and 4 h post-protein consumption of MPS in the fed-state of non-exercised and exercised leg muscles. It was determined that whole-body leucine oxidation increased in a stepwise, dose-dependent manner. MPS increased above basal, fasting values by approximately 65 and 90 % for W20 and W40, respectively (P < 0·05), but not with lower doses of whey. While resistance exercise was generally effective at stimulating MPS, W20 and W40 ingestion post-exercise increased MPS above W0 and W10 exercised values (P < 0·05) and W40 was greater than W20 (P < 0·05). Based on the study, the following conclusions were drawn. At rest, the optimal whey protein dose for non-frail older adults to consume, to increase myofibrillar MPS above fasting rates, was 20 g. Resistance exercise increases MPS in the elderly at all protein doses, but to a greater extent with 40 g of whey ingestion. These data suggest that, in contrast to younger adults, in whom post-exercise rates of MPS are saturated with 20 g of protein, exercised muscles of older adults respond to higher protein doses.
进食可刺激肌肉蛋白质合成（MPS）大量增加；然而，随着年龄的增长，蛋白质摄入的合成代谢反应以及随后的氨基酸血症可能会发生改变。有鉴于此，本研究旨在确定在老年人中，单独摄入乳清蛋白以及在摄入乳清蛋白之前进行抗阻运动，其 MPS 的剂量反应。为此，37 名老年男性（年龄 71（标准差 4）岁）在摄入 0、10、20 或 40 g 乳清蛋白（分别为 W0-W40）之前进行了一次单侧腿部抗阻运动。通过双侧股外侧肌活检，输注 l-[1-13C]亮氨酸和 l-[环-13C6]苯丙氨酸，以确定非运动和运动腿部肌肉在进食状态下的全身亮氨酸氧化和 4 小时的 MPS。结果表明，全身亮氨酸氧化呈逐步、剂量依赖性增加。W20 和 W40 的 MPS 分别比基础值和空腹值增加了约 65%和 90%（P＜0.05），但 W20 和 W40 的剂量低于 W20 和 W40。虽然抗阻运动通常能有效地刺激 MPS，但 W20 和 W40 在运动后摄入可使 MPS 高于 W0 和 W10 运动后的水平（P＜0.05），并且 W40 高于 W20（P＜0.05）。基于该研究，得出以下结论。在休息状态下，非虚弱的老年成年人摄入乳清蛋白以增加肌原纤维 MPS 高于空腹水平的最佳剂量为 20 g。抗阻运动可增加老年人的 MPS，所有蛋白剂量均有效，但 40 g 乳清蛋白摄入的效果更大。这些数据表明，与年轻人不同，年轻人的 MPS 后率在 20 g 蛋白时达到饱和，而老年人大腿肌肉对更高蛋白剂量有反应。
