Aoki T T
Prog Clin Biol Res. 1981;67:161-77.
The metabolic adaptation in man to starvation, semistarvation, and carbohydrate restriction is complex and involves a number of hormones, substrates, and tissues. In particular, however, the need for the ketoacids beta-hydroxybutyric acid and acetoacetic acid to replace glucose as the primary fuel for the brain of fasting man appears to be the key to maximum protein conservation. That is, ketogenesis is necessary to provide the brain with a fat-derived, water-soluble, insulin-independent, glucose-equivalent fuel. This adaptation is associated with a small loss of the ketoacids into the urine (100-150 mM/day or 40-60 calories/day). The ketonuria, in turn, necessitates increased renal utilization of muscle-derived glutamine. Synthesis of glutamine by muscle requires muscle proteolysis. Administration of glucose in amounts needed to meet the requirements of the brain results in suppression of ketogenesis in fasting man and a significant diminution in nitrogen mobilization and utilization as well.
人类对饥饿、半饥饿和碳水化合物限制的代谢适应是复杂的，涉及多种激素、底物和组织。然而，特别需要指出的是，酮酸β-羟基丁酸和乙酰乙酸取代葡萄糖作为禁食者大脑的主要燃料，这似乎是最大程度保存蛋白质的关键。也就是说，酮体生成对于为大脑提供一种源自脂肪的、水溶性的、不依赖胰岛素的、等同于葡萄糖的燃料是必要的。这种适应伴随着少量酮酸经尿液排出（每天100 - 150毫摩尔或每天40 - 60卡路里）。反过来，酮尿症使得肾脏对源自肌肉的谷氨酰胺的利用增加。肌肉合成谷氨酰胺需要肌肉蛋白水解。给予满足大脑需求所需量的葡萄糖会导致禁食者的酮体生成受到抑制，同时氮的动员和利用也显著减少。
