Faculty of Kinesiology & Physical Education, University of Toronto, Ontario, Canada.
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
J Gerontol A Biol Sci Med Sci. 2015 Jan;70(1):57-62. doi: 10.1093/gerona/glu103. Epub 2014 Jul 23.
Adequate protein ingestion-mediated stimulation of myofibrillar protein synthesis (MPS) is required to maintain skeletal muscle mass. It is currently unknown what per meal protein intake is required to maximally stimulate the response in older men and whether it differs from that of younger men.
We retrospectively analyzed data from our laboratories that measured MPS in healthy older (71 years) and younger (22 years) men by primed constant infusion of l-ring-[(13)C6]phenylalanine after ingestion of varying amounts (0-40 g) of high-quality dietary protein as a single bolus and normalized to body mass and, where available, lean body mass (LBM).
There was no difference (p = .53) in basal MPS rates between older (0.027±0.04%/h; means ± 95% CI) and young (0.028 ± 0.03%/h) men. Biphase linear regression and breakpoint analysis revealed the slope of first line segment was lower (p < .05) in older men and that MPS reached a plateau after ingestion of 0.40 ± 0.19 and 0.24 ± 0.06 g/kg body mass (p = .055) and 0.60 ± 0.29 and 0.25 ± 0.13 g/kg lean body mass (p < .01) in older and younger men, respectively.
This is the first report of the relative (to body weight) protein ingested dose response of MPS in younger and older men. Our data suggest that healthy older men are less sensitive to low protein intakes and require a greater relative protein intake, in a single meal, than young men to maximally stimulate postprandial rates of MPS. These results should be considered when developing nutritional solutions to maximize MPS for the maintenance or enhancement of muscle mass with advancing age.
摄入足够的蛋白质以刺激肌原纤维蛋白合成（MPS）是维持骨骼肌质量的必要条件。目前尚不清楚每餐需要摄入多少蛋白质才能最大限度地刺激老年人的反应，以及与年轻人相比是否有所不同。
我们回顾性分析了我们实验室的数据，这些数据通过在摄入不同量（0-40 克）的高质量膳食蛋白质作为单一弹丸后，用 l-环-[(13)C6]苯丙氨酸脉冲恒速输注来测量健康的老年人（71 岁）和年轻人（22 岁）的 MPS，并将其标准化为体重，在有条件的情况下，还标准化为去脂体重（LBM）。
老年人（0.027 ± 0.04%/h；平均值 ± 95%置信区间）和年轻人（0.028 ± 0.03%/h）之间的基础 MPS 率没有差异（p =.53）。双相线性回归和断点分析显示，老年人的第一段斜率较低（p <.05），并且在摄入 0.40 ± 0.19 和 0.24 ± 0.06 g/kg 体重（p =.055）和 0.60 ± 0.29 和 0.25 ± 0.13 g/kg 去脂体重（p <.01）后，MPS 达到平台。
这是首次报道年轻人和老年人的 MPS 相对（与体重相比）蛋白质摄入剂量反应。我们的数据表明，健康的老年人对低蛋白质摄入的敏感性较低，并且需要比年轻人在一顿饭中摄入更大的相对蛋白质摄入量，以最大限度地刺激餐后 MPS 率。在制定营养解决方案以最大限度地提高 MPS 以维持或增强随着年龄增长的肌肉质量时，应考虑这些结果。
