BC Children's Hospital Research Institute, BC Children's Hospital, Vancouver, British Columbia, Canada.
Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
J Nutr. 2020 Sep 1;150(9):2398-2404. doi: 10.1093/jn/nxaa180.
Nutritionally, there is a dietary requirement for indispensable amino acids (IAAs) but also a requirement for nitrogen (N) intake for the de novo synthesis of the dispensable amino acids (DAAs). It has been suggested that there might be a dietary requirement for specific DAAs.
Experiment 1 tested whether 9 of the DAAs (Ala, Arg, Asn, Asp, Gln, Glu, Gly, Pro, Ser) are ideal N sources using the indicator amino acid oxidation (IAAO) technique. Experiment 2 examined whether there is a dietary requirement for Glu in adult men.
Seven healthy men (aged 20-24 y) participated in 11 or 2 test diet intakes, in experiment 1 and 2, respectively, in a repeated measures design. In experiment 1, a base diet consisting of the IAA provided at the RDA was compared with test intakes with the base diet plus addition of individual DAAs to meet a 50:50 ratio of IAA:DAA on an N basis. In experiment 2, the diets corresponded to the amino acid pattern present in egg protein, in which all Glu and Gln was present as Glu, or removed, with Ser used to make the diets isonitrogenous. On each study day the IAAO protocol with l-[1-13C]phenylalanine was used to measure whole-body protein synthesis.
In experiment 1, repeated measures ANOVA with post hoc multiple comparisons showed that 7 of the 9 DAAs (Ala, Arg, Asn, Asp, Glu, Gly, Ser) decreased IAAO significantly (P < 0.05) compared with base IAA diet, the exceptions being Gln and Pro. In experiment 2, a paired t test did not find significant (P > 0.05) differences in the IAAO in response to removal and replacement of Glu intake.
The results suggest that in healthy men most DAAs are ideal N sources for protein synthesis, in the presence of adequate IAAs, and that endogenous synthesis of Glu is sufficient.Registered clinicaltrials.gov identifier: NCT02009917.
从营养角度来看，人体不仅需要必需氨基酸（IAAs），还需要摄入氮（N）来合成非必需氨基酸（DAAs）。有人认为，人体可能对某些 DAA 有特定的需求。
实验 1 使用指示剂氨基酸氧化（IAAO）技术测试 9 种 DAA（Ala、Arg、Asn、Asp、Gln、Glu、Gly、Pro、Ser）是否为理想的 N 源。实验 2 检验成年男性是否需要 Glu。
7 名健康男性（年龄 20-24 岁）分别参加了实验 1 和实验 2，在重复测量设计中分别进行了 11 次和 2 次试验饮食摄入。在实验 1 中，将由 RDA 提供的 IAA 组成的基础饮食与测试饮食进行比较，基础饮食中添加了各种 DAA，使 IAA 和 DAA 的 N 含量比为 50:50。在实验 2 中，膳食对应于蛋清中的氨基酸模式，其中所有的 Glu 和 Gln 都以 Glu 的形式存在，或去除，用 Ser 来使膳食达到等氮水平。在每个研究日，使用 l-[1-13C]苯丙氨酸的 IAAO 方案来测量全身蛋白质合成。
在实验 1 中，重复测量方差分析和事后多重比较显示，9 种 DAA 中的 7 种（Ala、Arg、Asn、Asp、Glu、Gly、Ser）与基础 IAA 饮食相比，显著降低了 IAAO（P<0.05），Gln 和 Pro 除外。在实验 2 中，配对 t 检验未发现 Glu 摄入的去除和替代对 IAAO 有显著（P>0.05）差异。
结果表明，在健康男性中，大多数 DAA 在有足够 IAAs 的情况下是蛋白质合成的理想 N 源，而内源性 Glu 合成足以满足需求。临床试验注册号：NCT02009917。
