Harper A E, Peters J C
Experientia Suppl. 1983;44:107-34. doi: 10.1007/978-3-0348-6540-1_8.
Depressed food consumption is an early response of experimental, animals to: 1) a dietary deficiency of either protein or an individual indispensable amino acid; 2) a distortion of the dietary pattern of amino acids when protein intake is low; and 3) a substantial elevation in the protein content of the diet. In each of these conditions the change in feeding behaviour is associated with alterations in concentrations of amino acids in blood but in none of them has the biochemical basis for the depressed food intake been established. The depressed food intake of rats consuming a low protein diet in which an imbalance of amino acids has been created by adding quantities of amino acids other than the one most limiting for growth, is associated with elevations in the plasma concentrations of amino acids added to create the imbalance and usually with a depression in the plasma concentration of the growth-limiting amino acid. These changes, in turn, are associated with depression of the concentration of the growth-limiting amino acid in the brain free amino acid pool. Studies in which uptake of amino acids into brain slices has been examined support the conclusion that various distortions of the plasma amino acid pattern, as the result of dietary imbalances of amino acids, can lead to depletion of the brain pool of a specific amino acid through competition between it and other amino acids in surplus in plasma for uptake into brain. The results of studies with rats in vivo of the effects on brain amino acid pools of ingestion of diets containing supplements of amino acids that compete with the growth-limiting amino acid for uptake into brain also support this conclusion. Depletion of the brain pool of the limiting amino acid as the result of feeding a diet with an amino acid imbalance can be related to overall body protein metabolism. In the young growing animal, protein synthesis is stimulated after a meal. Thus, when the diet is limiting in a single amino acid, that amino acid will be depleted from the circulating body pool. At the same time, the activities of amino acid degrading enzymes are low in animals fed a low protein diet; hence, such animals have limited capacity to degrade surpluses of amino acids. These conditions, depletion of the blood pool of the limiting amino acid and slow removal of surpluses of competing amino acids from the blood, will increase the extent of competition between other amino acids and the limiting amino acid for uptake into brain.(ABSTRACT TRUNCATED AT 400 WORDS)
1）蛋白质或某一种必需氨基酸的饮食缺乏；2）蛋白质摄入量低时氨基酸饮食模式的扭曲；3）饮食中蛋白质含量大幅升高。在上述每种情况下，摄食行为的变化都与血液中氨基酸浓度的改变相关，但其中任何一种情况中食物摄入量降低的生化基础都尚未明确。给大鼠喂食低蛋白饮食，通过添加除对生长最具限制作用的氨基酸之外的其他氨基酸来造成氨基酸失衡，这种情况下大鼠食物摄入量降低与添加以造成失衡的氨基酸的血浆浓度升高相关，并且通常与对生长具有限制作用的氨基酸的血浆浓度降低相关。这些变化进而与大脑游离氨基酸池中对生长具有限制作用的氨基酸浓度降低相关。对脑切片中氨基酸摄取情况进行检测的研究支持了这样的结论，即由于氨基酸饮食失衡导致的血浆氨基酸模式的各种扭曲，可通过血浆中过剩的其他氨基酸与特定氨基酸竞争摄取进入大脑，从而导致大脑中该特定氨基酸池的枯竭。对大鼠进行体内研究，观察摄入含有与对生长具有限制作用的氨基酸竞争摄取进入大脑的氨基酸补充剂的饮食对大脑氨基酸池的影响，其结果也支持这一结论。因喂食氨基酸失衡的饮食而导致大脑中限制氨基酸池的枯竭可能与整体身体蛋白质代谢有关。在幼年生长动物中，进食后蛋白质合成会受到刺激。因此，当饮食中某一种氨基酸缺乏时，该氨基酸会从循环的身体池中耗尽。同时，喂食低蛋白饮食的动物体内氨基酸降解酶的活性较低；因此，这类动物降解过剩氨基酸的能力有限。这些情况，即限制氨基酸的血池枯竭以及血液中竞争氨基酸过剩的缓慢清除，会增加其他氨基酸与限制氨基酸竞争摄取进入大脑的程度。（摘要截选至400词）
