Effect of exercise on protein metabolism in humans as explored with stable isotopes.
Effect of exercise on protein metabolism in humans as explored with stable isotopes.
复制标题
用稳定同位素探讨运动对人类蛋白质代谢的影响。
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
M. Rennie
中科院分区：
文献类型：
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作者：
D. J. Millward;C. Davies;D. Halliday;S. Wolman;D. Matthews;M. Rennie
在50%最大摄氧量状态下，在跑步机上运动3.75h后，运动后18h的氮排泄量增加了71 mg/kg。然而，对摄入的[1-13C]亮氨酸的13CO2排泄变化的时间进程的测量表明，所有这些增加的氮产生都发生在运动期间。由于尿素池的肾脏清除减少和周转缓慢，尿素的排泄滞后于尿素的生产。对重复口服15N标记甘氨酸所获得的尿氨平台标记的氮通量的测量表明，氮的损失是蛋白质降解增加和蛋白质合成减少的结果。对[1-13C]亮氨酸的进一步研究表明，2小时的跑步机运动导致氮损失从5.4毫克增加到16毫克。Kg-1。[1-13C]亮氨酸持续输注，测量H-1。这是由于全身蛋白质合成下降所致。葡萄糖以0.88g的速率给药。Kg-1。H-1抑制全身蛋白质降解率，并抑制运动诱导的氮排泄增加。在增加工作速率下测量亮氨酸氧化速率时，当亮氨酸流量的54%被氧化时，VO2_(Max)百分比与亮氨酸氧化的线性关系可达89%VO_2_(Max)。这些变化可能涉及到非肌肉组织和肌肉组织。因此，氮损失增加的来源可能是肝脏。在肌肉中，蛋白质降解实际上是通过甲基组氨酸排泄来判断的，而在肝脏中，蛋白质降解可能会增加。此外，全身蛋白质合成的下降可能反映了非肌肉组织的变化，因为在跑步大鼠中，肌肉中的蛋白质合成保持不变。就亮氨酸代谢而言，由于亮氨酸及其酮酸浓度下降时，亮氨酸氧化增加，运动必须特异性地激活2-氧酸脱氢酶。
Exercising for 3.75 h on a treadmill at 50% VO2 max in the fed state induced an increased excretion of 71 mg nitrogen/kg over the 18 h after exercise. However, measurements of the time course of changes in 13CO2 excretion from ingested [1-13C]leucine indicated that all of this increased nitrogen production occurs during the exercise period. Because of the reduced renal clearance and slow turnover of the urea pool, urea excretion lags behind urea production. Measurements of nitrogen flux from the plateau labeling of urinary ammonia achieved by repeated oral doses of 15N-labeled glycine indicated that the nitrogen loss resulted from an increase in protein degradation and a decrease in protein synthesis. Further studies with [1-13C]leucine indicated that a 2-h treadmill exercise induced an increase in the nitrogen loss from 5.4 to 16 mg . kg-1 . h-1 measured with a primed constant infusion of [1-13C]leucine. This resulted from a fall in whole-body protein synthesis. Glucose given at the rate of 0.88 g . kg-1 . h-1 depressed the rate of whole-body protein degradation and appeared to suppress the exercise-induced increase in nitrogen excretion. When leucine oxidation rates were measured at increasing work rates, a linear relationship between percentage of VO2 max and leucine oxidation was observed up to 89% VO2 max when 54% of the flux of leucine was oxidized. These changes may involve nonmuscle as well as muscle tissue. Thus the source of the increased nitrogen losses is probably liver. In muscle, protein degradation is actually decreased judged by methylhistidine excretion, whereas in liver, protein degradation may be increased. Also the fall in whole-body protein synthesis may reflect changes in nonmuscle tissues because in running rats protein synthesis in muscle is maintained. As far as leucine metabolism is concerned, because the increase in leucine oxidation occurs when leucine and its keto acid concentration falls, exercise must specifically activate the 2-oxoacid dehydrogenase.