Robert J J, Bier D, Schoeller D, Wolfe R, Matthews D E, Munro H N, Young V R
J Gerontol. 1984 Nov;39(6):673-81. doi: 10.1093/geronj/39.6.673.
We examined whole body leucine metabolism in healthy young and elderly adults while in the postabsorptive state and during an intravenous glucose administration at two rates. Leucine flux, incorporation into whole body protein, and oxidation were estimated from a continuous intravenous infusion of L-[1-13C]leucine and determination of 13C enrichment in plasma leucine and expired air. Per unit of body weight, leucine flux and rates of incorporation into protein were similar in young and old men. Old women showed lower rates compared with young women. Rates were similar for both age groups when expressed per unit of total body water and/or of muscle protein mass. Intravenous glucose infusion (4 mg . kg-1 . min-1) reduced plasma leucine levels and flux similarly in both age groups. Thus, age-related differences in muscle mass and sensitivity of peripheral tissues to insulin-mediated glucose uptake and metabolism are not paralleled by alterations in whole body leucine kinetics in the postabsorptive state.
我们研究了健康年轻人和老年人在空腹状态下以及以两种速率静脉输注葡萄糖期间的全身亮氨酸代谢情况。通过持续静脉输注L-[1-13C]亮氨酸并测定血浆亮氨酸和呼出气体中的13C富集情况，来估算亮氨酸通量、掺入全身蛋白质的量以及氧化量。按单位体重计算，年轻男性和老年男性的亮氨酸通量以及掺入蛋白质的速率相似。老年女性的速率低于年轻女性。当按单位总体水和/或肌肉蛋白质量表示时，两个年龄组的速率相似。静脉输注葡萄糖（4 mg·kg-1·min-1）在两个年龄组中同样降低了血浆亮氨酸水平和通量。因此，在空腹状态下，肌肉质量以及外周组织对胰岛素介导的葡萄糖摄取和代谢的敏感性方面与年龄相关的差异，并未伴随着全身亮氨酸动力学的改变。
