Elango Rajavel, Humayun Mohammad A, Ball Ronald O, Pencharz Paul B
The Research Institute, The Hospital for Sick Children, Toronto M5G 1X8, Canada.
J Nutr. 2009 Jun;139(6):1082-7. doi: 10.3945/jn.108.101147. Epub 2009 Apr 15.
The number of days of adaptation to a specific amino acid intake required prior to the determination of amino acid requirements using the indicator amino acid oxidation method (IAAO) is still in debate. In this study, our objective was to determine whether adaptation for 8 h, 3 d, and 7 d to a wide range of lysine intakes had any effect on the oxidation of the indicator amino acid, l-[1-(13)C]phenylalanine, to (13)CO(2) (F(13)CO(2)). Five healthy young men randomly received each of 4 levels of lysine (5, 20, 35, and 70 mg x kg(-1) x d(-1)) along with an amino acid mixture to achieve a protein intake of 1.0 g x kg(-1) x d(-1) and energy intake of 1.5x resting energy expenditure during 4 separate 7-d study periods. IAAO studies were conducted on d 1, 3, and 7. During each study day, oral consumption of l-[1-(13)C]phenylalanine was followed by collection of breath for F(13)CO(2) and plasma for measurement of phenylalanine enrichment. F(13)CO(2) was affected by lysine intake but did not differ among adaptation periods of 8 h, 3 d, or 7 d. Phenylalanine flux was not significantly affected by period of adaptation. These results suggest that the minimally invasive IAAO model, where participants are adapted prior to protein intake for 2 d followed by study day adaptation to the test amino acid intake for 8 h, may be sufficient to estimate individual amino acid requirements in healthy young men.
在使用指示氨基酸氧化法（IAAO）确定氨基酸需求之前，适应特定氨基酸摄入量所需的天数仍存在争议。在本研究中，我们的目的是确定对广泛的赖氨酸摄入量分别适应8小时、3天和7天是否会对指示氨基酸L-[1-（13）C]苯丙氨酸氧化为（13）CO₂（F（13）CO₂）产生任何影响。五名健康的年轻男性在四个独立的7天研究期间，随机接受4种赖氨酸水平（5、20、35和70mg·kg⁻¹·d⁻¹）中的每一种，同时摄入氨基酸混合物，以使蛋白质摄入量达到1.0g·kg⁻¹·d⁻¹，能量摄入量达到静息能量消耗的1.5倍。在第1天、第3天和第7天进行IAAO研究。在每个研究日，口服L-[1-（13）C]苯丙氨酸后，收集呼出气体用于检测F（13）CO₂，并采集血浆用于测量苯丙氨酸富集情况。F（13）CO₂受赖氨酸摄入量的影响，但在8小时、3天或7天的适应期之间没有差异。苯丙氨酸通量不受适应期的显著影响。这些结果表明，对于健康的年轻男性，采用微创IAAO模型，即参与者在蛋白质摄入前先适应2天，然后在研究日适应测试氨基酸摄入量8小时，可能足以估计个体氨基酸需求。
