Taveroff A, Lapin H, Hoffer L J
McGill Nutrition and Food Science Centre, McGill University, Montreal, Quebec, Canada.
Metabolism. 1994 Mar;43(3):320-7. doi: 10.1016/0026-0495(94)90100-7.
The mechanism governing short-term adaptation to dietary protein restriction was investigated in nine normal adults by measuring their metabolic response to a standard mixed meal, first while they were adapted to a conventional, high-protein diet (day 1) and then again after they had eaten two low-protein meals (day 2). Urea appearance (measured as the sum of its urinary excretion and the change in body urea pool size), body retention of 15N-alanine included in each test meal, and whole-body protein turnover were calculated over the 9 hours following meal consumption on each day. Postprandial urea nitrogen appearance was 5.05 +/- 0.26 g/9 h on day 1 and decreased to 4.16 +/- 0.31 on day 2 (P < .05). Whole-body N flux (Q), protein synthesis (S), and protein breakdown (B) all decreased significantly on day 2 as assessed using either urea or ammonium end-product enrichments; however, recovery of 15N in the test meal as 15N-urea was similar on both days, approximately 22%. It is concluded that short-term metabolic adaptation occurs within two meals of reduced protein intake. The mechanism appears not to involve selectively an increased "first-pass" retention of dietary amino acids, but rather a general reduction in fed-state whole-body protein breakdown.
通过测量9名正常成年人对标准混合餐的代谢反应，研究了短期适应蛋白质限制饮食的机制。首先在他们适应传统高蛋白饮食时（第1天）进行测量，然后在他们进食两顿低蛋白餐后（第2天）再次测量。计算了每天进食后9小时内的尿素生成量（以尿排泄量与体内尿素池大小变化之和来衡量）、每餐中所含15N-丙氨酸的身体潴留量以及全身蛋白质周转率。第1天餐后尿素氮生成量为5.05±0.26g/9小时，第2天降至4.16±0.31（P<0.05）。使用尿素或铵终产物富集评估时，第2天全身氮通量（Q）、蛋白质合成（S）和蛋白质分解（B）均显著下降；然而，两天内测试餐中15N作为15N-尿素的回收率相似，约为22%。得出的结论是，在摄入低蛋白饮食两餐后会发生短期代谢适应。其机制似乎并非选择性地涉及饮食氨基酸“首过”潴留增加，而是进食状态下全身蛋白质分解普遍减少。
