Leucine metabolism in aging humans: effect of insulin and substrate availability.
Leucine metabolism in aging humans: effect of insulin and substrate availability.
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DOI：
10.1152/ajpendo.1989.256.2.e288
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发表时间：
1989-02
期刊：
影响因子：
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通讯作者：
N. Fukagawa;K. Minaker;V. Young;D. Matthews;D. Bier;J. Rowe
中科院分区：
文献类型：
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作者：
N. Fukagawa;K. Minaker;V. Young;D. Matthews;D. Bier;J. Rowe
为了阐明胰岛素（I）和氨基酸（AA）利用率对机体蛋白质经济性和AA动力学的相对作用，我们比较了全身亮氨酸动力学反应，使用360分钟恒定输注L-[1- 13 C]亮氨酸，在将L-AA溶液给予六名健康年轻人期间，（21-25岁）和6名健康老年（72-87岁）男性（研究1）与AA溶液与正葡萄糖I钳夹联合给药（研究2）时的结果进行比较。在研究1中，年轻（Y）和老年（O）男性的血清I分别显著增加（P <0.02）4 +/- 1和4 +/- 2 microU/ml。在研究2中，I升高至91 +/- 7（Y）和88 +/- 7（O）microU/ml; Y中维持正常的葡萄糖输注量显著大于O（8.0 +/- 0.1 vs. 6.8 +/- 1.9 mg.kg-1.min-1）。在AA给药期间，两个年龄组的亮氨酸通量和氧化显著增加。在研究1和2中，年轻人蛋白质分解释放的亮氨酸估计值分别下降了18%和20%（P <0.01），老年人分别下降了12%和44%。在两个年龄组和两项研究中，亮氨酸掺入蛋白质的速率增加（P <0.01）相似。这些发现强调了AA在刺激蛋白质合成中的重要性，并表明胰岛素在体内的主要作用是抑制全身蛋白质水解。此外，尽管有证据表明，年龄相关的葡萄糖处置下降，老年人有类似的亮氨酸动力学反应高氨基酸血症。
To elucidate the relative roles of insulin (I) and amino acid (AA) availability on body protein economy and AA kinetics, we compared whole body leucine kinetic responses, using a 360-min constant infusion of L-[1-13C]leucine, during administration of an L-AA solution to six healthy young (21-25 yr) and six healthy old (72-87 yr) men (study 1) to those when the AA solution was given in conjunction with a euglycemic I clamp (study 2). In study 1, serum I increased significantly (P less than 0.02) by 4 +/- 1 and 4 +/- 2 microU/ml in young (Y) and old (O) men, respectively. In study 2, I was raised to 91 +/- 7 (Y) and 88 +/- 7 (O) microU/ml; the glucose infusion to maintain euglycemia in the Y was significantly greater than in the O (8.0 +/- 0.1 vs. 6.8 +/- 1.9 mg.kg-1.min-1). Leucine flux and oxidation increased significantly in both age groups during the administration of AA. Estimates of leucine released from protein breakdown declined (P less than 0.01) by 18 and 20% in study 1 and 2, respectively, in the young and by 12 and 44%, respectively, in the elderly. Rates of leucine incorporation into protein increased (P less than 0.01) similarly in both age groups and in both studies. These findings emphasize the importance of AA availability in the stimulation of protein synthesis and suggest that insulin's major role in vivo is to repress whole body proteolysis. Furthermore, despite evidence of an age-related decline in glucose disposal, the elderly had similar leucine kinetic responses to hyperaminoacidemia.