Center for Translational Research in Aging & Longevity, Dept. of Health and Kinesiology, Texas A&M University, College Station, TX, USA.
NUTRIM School for Nutrition, Toxicology and Metabolism, Dept. of Respiratory Medicine, Maastricht University Medical Centre, Maastricht, The Netherlands.
Clin Nutr. 2019 Aug;38(4):1684-1691. doi: 10.1016/j.clnu.2018.08.006. Epub 2018 Aug 16.
BACKGROUND & AIMS: Carbohydrates (CHO) and leucine (LEU) both have insulinotropic properties, and could therefore enhance the protein anabolic capacity of dietary proteins, which are important nutrients in preventing muscle loss in patients with Chronic Obstructive Pulmonary Disease (COPD). LEU is also known to activate protein anabolic signaling pathways independent of insulin. Based on our previous findings in COPD, we hypothesized that whole body protein anabolism is enhanced to a comparable extent by the separate and combined co-ingestion of CHO and LEU with protein.
To disentangle the protein anabolic effects of CHO and/or free LEU when co-ingested with a high-quality protein, we studied 10 patients with moderate to very severe COPD and dyspnea (GOLD: II-IV, mMRC dyspnea scale ≥ 2), at risk for muscle loss, and 10 healthy age- and gender-matched controls. On four occasions, in a single-blind randomized crossover design, each subject ingested a drink containing 0.6 g/kg fat-free mass (ffm) hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein + CHO), c) 0.095 g/kg ffm leucine (protein + LEU), d) both add-ons (protein + CHO + LEU). Whole body protein breakdown (PB), protein synthesis (PS), and net protein balance (= PS - PB) were measured by IV primed and continuous infusion of L-[ring-H]-phenylalanine and L-[C,N]-tyrosine. L-[N]-phenylalanine was added to the protein drinks to measure splanchnic extraction.
In both groups, whole body PS, PB and net protein balance responses were comparable between the four protein drinks, despite higher postprandial plasma LEU concentrations for the LEU supplemented drinks (P < 0.05), and higher insulin concentrations for the CHO supplemented drinks as compared to the protein only drink (P < 0.05).
Adding CHO and/or LEU to a serving of high-quality protein does not further augment whole body protein anabolism in dyspneic COPD patients at risk for muscle loss or healthy older adults.
ClinicalTrials.gov; No. NCT01734473; URL: www.clinicaltrials.gov.
碳水化合物（CHO）和亮氨酸（LEU）均具有胰岛素刺激特性，因此可以增强膳食蛋白质的蛋白质合成能力，这对于预防慢性阻塞性肺疾病（COPD）患者的肌肉损失很重要。LEU 也已知可独立于胰岛素激活蛋白质合成信号通路。基于我们在 COPD 中的先前发现，我们假设单独和联合摄入 CHO 和 LEU 与蛋白质会同等程度地增强全身蛋白质合成。
为了分解 CHO 和/或游离 LEU 与高质量蛋白质共同摄入时的蛋白质合成作用，我们研究了 10 名患有中度至非常严重 COPD 和呼吸困难（GOLD：II-IV，mMRC 呼吸困难量表≥2）的患者，他们有肌肉损失的风险，以及 10 名年龄和性别匹配的健康对照者。在一项单盲随机交叉设计中，每个对象在 4 次中分别摄入含有 0.6g/kg 去脂体重（ffm）水解酪蛋白的饮料，a）无添加物（蛋白质），b）0.3g/kg ffm CHO（蛋白质+CHO），c）0.095g/kg ffm LEU（蛋白质+LEU），d）两种添加物（蛋白质+CHO+LEU）。通过 IV 脉冲和持续输注 L-[ring-H]-苯丙氨酸和 L-[C，N]-酪氨酸测量全身蛋白质分解（PB），蛋白质合成（PS）和净蛋白质平衡（= PS-PB）。向蛋白质饮料中添加 L-[N]-苯丙氨酸以测量内脏提取。
在两组中，尽管添加 LEU 的饮料的餐后血浆 LEU 浓度较高（P<0.05），并且添加 CHO 的饮料的胰岛素浓度高于仅含蛋白质的饮料（P<0.05），但四种蛋白质饮料的全身 PS，PB 和净蛋白质平衡反应均相似。
在有肌肉损失风险的呼吸困难 COPD 患者或健康老年人中，向高质量蛋白质的一份中添加 CHO 和/或 LEU 不会进一步增强全身蛋白质合成。
ClinicalTrials.gov；编号 NCT01734473；网址：www.clinicaltrials.gov。
