Inserm UMR1048, Institute of Metabolic and Cardiovascular Diseases, Obesity Research Laboratory, CHU Rangueil, 1 Avenue Jean Poulhès, BP84225, 31432, Toulouse Cedex 4, France,
J Physiol Biochem. 2014 Jun;70(2):583-91. doi: 10.1007/s13105-013-0306-z. Epub 2013 Dec 15.
The aim of the present study was to investigate the influence of substrate availability on fuel selection during exercise. Eight endurance-trained male cyclists performed 90-min exercise at 70% of their maximal oxygen uptake in a cross-over design, either in rested condition (CON) or the day after 2-h exercise practised at 70% of maximal oxygen uptake (EX). Subjects were given a sucrose load (0.75 g kg(-1) body weight) 45 min after the beginning of the 90-min exercise test. Lipolysis was measured in subcutaneous abdominal adipose tissue (SCAT) by microdialysis and substrate oxidation by indirect calorimetry. Lipid oxidation increased during exercise and tended to decrease during sucrose ingestion in both conditions. Lipid oxidation was higher during the whole experimental period in the EX group (p = 0.004). Interestingly, fuel selection, assessed by the change in respiratory exchange ratio (RER), was increased in the EX session (p = 0.002). This was paralleled by a higher rate of SCAT lipolysis reflected by dialysate glycerol, plasma glycerol, and fatty acids (FA) levels (p < 0.001). Of note, we observed a significant relationship between whole-body fat oxidation and dialysate glycerol in both sessions (r (2) = 0.33, p = 0.02). In conclusion, this study highlights the limiting role of lipolysis and plasma FA availability to whole-body fat oxidation during exercise in endurance-trained subjects. This study shows that adipose tissue lipolysis is a determinant of fuel selection during exercise in healthy subjects.
本研究旨在探讨运动时底物可用性对燃料选择的影响。8 名耐力训练有素的男性自行车运动员以交叉设计的方式在休息状态（CON）或在以 70%最大摄氧量进行 2 小时运动后的第二天（EX）进行 90 分钟的 70%最大摄氧量运动。受试者在 90 分钟运动测试开始后 45 分钟给予蔗糖负荷（0.75 g kg(-1)体重）。通过微透析测量皮下腹部脂肪组织（SCAT）中的脂肪分解，通过间接测热法测量底物氧化。在两种情况下，脂肪氧化在运动过程中增加，并在摄入蔗糖时趋于减少。在 EX 组中，整个实验期间的脂肪氧化率更高（p = 0.004）。有趣的是，在 EX 期间，通过呼吸交换比（RER）的变化评估的燃料选择增加（p = 0.002）。这与通过透析液甘油、血浆甘油和脂肪酸（FA）水平反映的 SCAT 脂肪分解率增加（p < 0.001）相平行。值得注意的是，我们在两个阶段都观察到全身脂肪氧化与透析液甘油之间存在显著的关系（r (2) = 0.33，p = 0.02）。总之，本研究强调了在耐力训练受试者运动期间脂肪分解和血浆 FA 可用性对全身脂肪氧化的限制作用。本研究表明，脂肪组织脂肪分解是健康受试者运动期间燃料选择的决定因素。
