Howarth Krista R, Phillips Stuart M, MacDonald Maureen J, Richards Douglas, Moreau Natalie A, Gibala Martin J
Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
J Appl Physiol (1985). 2010 Aug;109(2):431-8. doi: 10.1152/japplphysiol.00108.2009. Epub 2010 May 20.
We examined the effect of carbohydrate (CHO) availability on whole body and skeletal muscle protein utilization at rest, during exercise, and during recovery in humans. Six men cycled at approximately 75% peak O(2) uptake (Vo(2peak)) to exhaustion to reduce body CHO stores and then consumed either a high-CHO (H-CHO; 71 + or - 3% CHO) or low-CHO (L-CHO; 11 + or - 1% CHO) diet for 2 days before the trial in random order. After each dietary intervention, subjects received a primed constant infusion of [1-(13)C]leucine and l-[ring-(2)H(5)]phenylalanine for measurements of the whole body net protein balance and skeletal muscle protein turnover. Muscle, breath, and arterial and venous blood samples were obtained at rest, during 2 h of two-legged kicking exercise at approximately 45% of kicking Vo(2peak), and during 1 h of recovery. Biopsy samples confirmed that the muscle glycogen concentration was lower in the L-CHO group versus the H-CHO group at rest, after exercise, and after recovery. The net leg protein balance was decreased in the L-CHO group compared with at rest and compared with the H-CHO condition, which was primarily due to an increase in protein degradation (area under the curve of the phenylalanine rate of appearance: 1,331 + or - 162 micromol in the L-CHO group vs. 786 + or - 51 micromol in the H-CHO group, P < 0.05) but also due to a decrease in protein synthesis late in exercise. There were no changes during exercise in the rate of appearance compared with rest in the H-CHO group. Whole body leucine oxidation increased above rest in the L-CHO group only and was higher than in the H-CHO group. The whole body net protein balance was reduced in the L-CHO group, largely due to a decrease in whole body protein synthesis. These data extend previous findings by others and demonstrate, using contemporary stable isotope methodology, that CHO availability influences the rates of skeletal muscle and whole body protein synthesis, degradation, and net balance during prolonged exercise in humans.
我们研究了碳水化合物（CHO）可利用性对人体在静息、运动及恢复期间全身和骨骼肌蛋白质利用的影响。六名男性以约75%的峰值摄氧量（Vo₂peak）进行骑行直至力竭，以减少体内CHO储备，然后在试验前随机顺序食用高CHO（H - CHO；71±3% CHO）或低CHO（L - CHO；11±1% CHO）饮食2天。每次饮食干预后，受试者接受[1 - ¹³C]亮氨酸和L - [环 - ²H₅]苯丙氨酸的单次静脉推注和持续输注，以测量全身净蛋白质平衡和骨骼肌蛋白质周转。在静息状态、以约45%踢腿Vo₂peak进行双腿踢腿运动的2小时期间以及恢复的1小时期间采集肌肉、呼出气体以及动脉和静脉血样本。活检样本证实，在静息、运动后及恢复后，L - CHO组的肌肉糖原浓度低于H - CHO组。与静息时相比以及与H - CHO组相比，L - CHO组的腿部净蛋白质平衡降低，这主要是由于蛋白质降解增加（苯丙氨酸出现率曲线下面积：L - CHO组为1331±162 μmol，H - CHO组为786±51 μmol，P < 0.05），但也是由于运动后期蛋白质合成减少。与静息时相比，H - CHO组在运动期间出现率没有变化。仅L - CHO组的全身亮氨酸氧化高于静息时，且高于H - CHO组。L - CHO组的全身净蛋白质平衡降低，主要是由于全身蛋白质合成减少。这些数据扩展了其他人之前的研究结果，并使用当代稳定同位素方法证明，CHO可利用性会影响人体长时间运动期间骨骼肌和全身蛋白质的合成、降解及净平衡率。
