Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Illinois.
Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois.
J Appl Physiol (1985). 2021 Sep 1;131(3):1111-1122. doi: 10.1152/japplphysiol.00295.2021. Epub 2021 Jul 29.
Leucine is regarded as an anabolic trigger for the mTORC1 pathway and the stimulation muscle protein synthesis rates. More recently, there has been an interest in underpinning the relevance of branched-chain amino acid (BCAA)-containing dipeptides and their intact absorption into circulation to regulate muscle anabolic responses. We investigated the effects of dileucine and leucine ingestion on postprandial muscle protein turnover. Ten healthy young men (age: 23 ± 3 yr) consumed either 2 g of leucine (LEU) or 2 g of dileucine (DILEU) in a randomized crossover design. The participants underwent repeated blood and muscle biopsy sampling during primed continuous infusions of l-[-C]phenylalanine and l-[N]phenylalanine to determine myofibrillar protein synthesis (MPS) and mixed muscle protein breakdown rates (MPB), respectively. LEU and DILEU similarly increased plasma leucine net area under the curve (AUC; = 0.396). DILEU increased plasma dileucine AUC to a greater extent than LEU ( = 0.013). Phosphorylation of Akt ( = 0.002), rpS6 ( < 0.001), and p70S6K ( < 0.001) increased over time under both LEU and DILEU conditions. Phosphorylation of 4E-BP1 ( = 0.229) and eEF2 ( = 0.999) did not change over time irrespective of condition. Cumulative (0-180 min) MPS increased in DILEU (0.075 ± 0.032%·h), but not in LEU (0.047 ± 0.029%·h; = 0.023). MPB did not differ between LEU (0.043 ± 0.030%·h) and DILEU conditions (0.051 ± 0.027%·h; = 0.659). Our results showed that dileucine ingestion elevated plasma dileucine concentrations and muscle protein turnover by stimulating MPS in young men. The role of dipeptides as anabolic agents remains unresolved in humans. We show that the ingestion of 2 g dileucine increased plasma dileucine concentrations and resulted in an enhancement of muscle protein turnover by stimulating an increase in muscle protein synthesis rates in healthy young males. The ingestion of 2 g leucine, however, did not stimulate an increase in muscle protein turnover. Our work provides the first insights into the effects of dipeptides on human protein metabolism.
亮氨酸被认为是 mTORC1 途径的合成代谢触发物，能刺激肌肉蛋白质合成率。最近，人们对支链氨基酸（BCAA）- 含有二肽及其完整吸收到循环中以调节肌肉合成代谢反应的相关性产生了兴趣。我们研究了二亮氨酸和亮氨酸摄入对餐后肌肉蛋白质周转的影响。10 名健康年轻男性（年龄：23 ± 3 岁）以随机交叉设计的方式分别摄入 2g 亮氨酸（LEU）或 2g 二亮氨酸（DILEU）。参与者在连续输注 l-[-C]苯丙氨酸和 l-[N]苯丙氨酸的基础上进行重复的血液和肌肉活检采样，以分别确定肌原纤维蛋白合成（MPS）和混合肌肉蛋白分解率（MPB）。LEU 和 DILEU 同样增加了血浆亮氨酸净 AUC（ = 0.396）。DILEU 增加血浆二亮氨酸 AUC 的程度大于 LEU（ = 0.013）。在 LEU 和 DILEU 条件下，Akt 的磷酸化（ = 0.002）、rpS6（ < 0.001）和 p70S6K（ < 0.001）随时间增加。4E-BP1 的磷酸化（ = 0.229）和 eEF2 的磷酸化（ = 0.999）无论条件如何均未随时间变化。DILEU 中累积（0-180 分钟）MPS 增加（0.075 ± 0.032%·h），但 LEU 中无变化（0.047 ± 0.029%·h； = 0.023）。LEU（0.043 ± 0.030%·h）和 DILEU 条件（0.051 ± 0.027%·h； = 0.659）下的 MPB 无差异。我们的结果表明，二亮氨酸通过刺激年轻男性的 MPS 来增加血浆二亮氨酸浓度和肌肉蛋白质周转。二肽作为合成代谢剂的作用在人类中仍未得到解决。我们表明，在健康年轻男性中，摄入 2g 二亮氨酸可增加血浆二亮氨酸浓度并通过刺激肌肉蛋白合成率的增加来增强肌肉蛋白质周转。然而，摄入 2g 亮氨酸不会刺激肌肉蛋白质周转的增加。我们的工作首次提供了关于二肽对人体蛋白质代谢影响的见解。
