Le Roux-Mallouf Thibault, Laurent Julien, Besset Dimitri, Marillier Mathieu, Larribaut Julie, Belaidi Elise, Corne Christelle, Doutreleau Stéphane, Verges Samuel
Laboratoire HP2 (U1042 INSERM), Université, Grenoble Alpes, Grenoble, France.
Inherited Metabolic Disease Laboratory, Department of Biochemistry, Molecular and Environmental Toxicology Biology, Biology and Pathology Institute, Hôpital Michallon, Grenoble, France.
Exp Physiol. 2019 Jul;104(7):1100-1114. doi: 10.1113/EP087493. Epub 2019 May 12.
What is the central question of this study? What is the effect of acute NO precursor intake on vascular function, muscle and cerebral oxygenation and peripheral and central neuromuscular fatigue during knee-extension exercise? What is the main finding and its importance? Acute NO precursor ingestion increases the plasma concentrations of NO precursors (nitrate, arginine and citrulline) and enhances post-ischaemic vasodilatation, but has no significant effect on muscle and cerebral oxygenation, peripheral and central mechanisms of neuromuscular fatigue and, consequently, does not improve exercise performance.
Nitric oxide (NO) plays an important role in matching blood flow to oxygen demand in the brain and contracting muscles during exercise. Previous studies have shown that increasing NO bioavailability can improve muscle function. The aim of this study was to assess the effect of acute NO precursor intake on muscle and cerebral oxygenation and on peripheral and central neuromuscular fatigue during exercise. In four experimental sessions, 15 healthy men performed a thigh ischaemia-reperfusion test followed by submaximal isometric knee extensions (5 s on-4 s off; 45% of maximal voluntary contraction) until task failure. In each session, subjects drank a nitrate-rich beetroot juice containing 520 mg nitrate (N), N and citrulline (6 g; N+C), N and arginine (6 g; N+A) or a placebo (PLA). Prefrontal cortex and quadriceps near-infrared spectroscopy parameters were monitored continuously. Transcranial magnetic stimulation and femoral nerve electrical stimulation were used to assess central and peripheral determinants of fatigue. The post-ischaemic increase in thigh blood total haemoglobin concentration was larger in N (10.1 ± 3.7 mmol) and N+C (10.9 ± 3.3 mmol) compared with PLA (8.2 ± 2.7 mmol; P < 0.05). Nitric oxide precursors had no significant effect on muscle and cerebral oxygenation or on peripheral and central mechanisms of neuromuscular fatigue during exercise. The total number of knee extensions did not differ between sessions (N, 71.9 ± 33.2; N+A, 73.3 ± 39.4; N+C, 74.6 ± 34.0; PLA, 71.8 ± 39.9; P > 0.05). In contrast to the post-ischaemic hyperaemic response, NO bioavailability in healthy subjects might not be the limiting factor for tissue perfusion and oxygenation during submaximal knee extensions to task failure.
本研究的核心问题是什么？急性摄入一氧化氮前体对膝关节伸展运动期间的血管功能、肌肉和脑氧合以及外周和中枢神经肌肉疲劳有何影响？主要发现及其重要性是什么？急性摄入一氧化氮前体可增加血浆中一氧化氮前体（硝酸盐、精氨酸和瓜氨酸）的浓度，并增强缺血后血管舒张，但对肌肉和脑氧合、神经肌肉疲劳的外周和中枢机制无显著影响，因此不会改善运动表现。
一氧化氮（NO）在运动期间使大脑和收缩肌肉的血流与氧需求相匹配方面发挥着重要作用。先前的研究表明，提高一氧化氮的生物利用度可改善肌肉功能。本研究的目的是评估急性摄入一氧化氮前体对运动期间肌肉和脑氧合以及外周和中枢神经肌肉疲劳的影响。在四个实验环节中，15名健康男性先进行了一次大腿缺血再灌注测试，随后进行次最大等长膝关节伸展（5秒收缩-4秒放松；最大自主收缩的45%），直至任务失败。在每个环节中，受试者饮用富含硝酸盐的甜菜根汁，其中含有520毫克硝酸盐（N）、N和瓜氨酸（6克；N+C）、N和精氨酸（6克；N+A）或安慰剂（PLA）。持续监测前额叶皮层和股四头肌的近红外光谱参数。采用经颅磁刺激和股神经电刺激来评估疲劳的中枢和外周决定因素。与PLA组（8.2±2.7毫摩尔）相比，N组（10.1±3.7毫摩尔）和N+C组（10.9±3.3毫摩尔）缺血后大腿血液总血红蛋白浓度的增加幅度更大（P<0.05）。一氧化氮前体对运动期间的肌肉和脑氧合或神经肌肉疲劳的外周和中枢机制无显著影响。各环节膝关节伸展的总数无差异（N组，71.9±33.2；N+A组，73.3±39.4；N+C组，74.6±34.0；PLA组，71.8±39.9；P>0.05）。与缺血后充血反应相反，在健康受试者中，一氧化氮的生物利用度可能不是次最大膝关节伸展至任务失败期间组织灌注和氧合的限制因素。
