Ohsumi M, Shi X, Tuchiya T, Tujioka K, Lyou S, Hayase K, Yokogoshi H
Department of Home Economics, Aichi University of Education, Kariya, Aichi, Japan.
Amino Acids. 2007 Feb;32(2):247-53. doi: 10.1007/s00726-006-0362-6. Epub 2006 Jun 7.
The purpose of the present study was to determine whether the regulation of brain protein synthesis was mediated through changes in the plasma concentrations of insulin and growth hormone (GH), and whether the concentrations of amino acids in the brain and plasma regulate the brain protein synthesis when the quantity and quality of dietary protein is manipulated. Two experiments were done on three groups of aged rats given diets containing 20% casein, 5% casein or 0% casein (Experiment 1), and 20% casein, 20% gluten, or 20% gelatin (Experiment 2) for 1 d (only one 5-h period) after all rats were fed the 20% casein diet for 10 d (only 5-h feeding per day). The aggregation of brain ribosomes, the concentration in plasma GH, and the branched chain amino acids in the plasma and cerebral cortex declined with a decrease of quantity and quality of dietary protein. The concentration of plasma insulin did not differ among groups. The results suggest that the ingestion of a higher quantity and quality of dietary protein increases the concentrations of GH and several amino acids in aged rats, and that the concentrations of GH and amino acids are at least partly related to the mechanism by which the dietary protein affects brain protein synthesis in aged rats.
本研究的目的是确定脑蛋白合成的调节是否通过胰岛素和生长激素（GH）血浆浓度的变化介导，以及当膳食蛋白质的数量和质量受到控制时，脑和血浆中的氨基酸浓度是否调节脑蛋白合成。对三组老年大鼠进行了两项实验，所有大鼠先喂食20%酪蛋白饮食10天（每天仅5小时喂食），之后分别给予含20%酪蛋白、5%酪蛋白或0%酪蛋白的饮食（实验1），以及20%酪蛋白、20%谷蛋白或20%明胶的饮食（实验2），持续1天（仅一个5小时时间段）。随着膳食蛋白质数量和质量的降低，脑核糖体聚集、血浆GH浓度以及血浆和大脑皮质中的支链氨基酸均下降。各实验组间血浆胰岛素浓度无差异。结果表明，摄入数量和质量更高的膳食蛋白质可提高老年大鼠的GH浓度和几种氨基酸浓度，且GH和氨基酸浓度至少部分与膳食蛋白质影响老年大鼠脑蛋白合成的机制有关。
