健康孕妇妊娠早、晚期的膳食苯丙氨酸需要量。
Dietary phenylalanine requirements during early and late gestation in healthy pregnant women.
机构信息
BC Children's Hospital Research Institute, BC Children's Hospital, Vancouver, British Columbia, Canada.
Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.
出版信息
Am J Clin Nutr. 2020 Feb 1;111(2):351-359. doi: 10.1093/ajcn/nqz288.
BACKGROUND
Phenylalanine is an indispensable amino acid and, via tyrosine, is the precursor for the neurotransmitters dopamine, norepinephrine, and epinephrine. Currently, dietary requirements for phenylalanine during pregnancy are unknown.
OBJECTIVES
This study's aim was to determine phenylalanine requirements (in the presence of excess tyrosine) during early and late gestation using direct amino acid oxidation (DAAO; with l-[1-13C]phenylalanine) and indicator amino acid oxidation (IAAO; with l-[1-13C]leucine).
METHODS
Twenty-three healthy women (age: 30.4 ± 3.1 y, mean ± SD) were studied at a range of phenylalanine intakes (5.5-30.5 mg · kg-1 · d-1 in early and late pregnancy using DAAO, and 2.5-30.5 mg · kg-1 · d-1 in late pregnancy using IAAO) for a total of 76 study days. Test intakes were provided as 8 isocaloric and isonitrogenous meals with 1.5 g · kg-1 · d-1 protein and energy at 1.7 times the measured resting energy expenditure. Breath samples were analyzed on an isotope ratio mass spectrometer for 13C enrichment. Phenylalanine requirement was determined using a 2-phase linear regression crossover model to identify a breakpoint in 13CO2 production (representing the mean requirement) in response to phenylalanine intakes.
RESULTS
Phenylalanine requirement during early pregnancy was determined to be 15 mg · kg-1 · d-1 (95% CI: 10.4, 19.9 mg · kg-1 · d-1); during late pregnancy, it was determined to be 21 mg · kg-1 · d-1 by DAAO (95% CI: 17.4, 24.7 mg · kg-1 · d-1) and IAAO (95% CI: 10.5, 32.2 mg · kg-1 · d-1).
CONCLUSIONS
Our results suggest a higher requirement (40%) for phenylalanine during late pregnancy than during early pregnancy. Moreover, the early pregnancy requirements are higher than the previous adult male requirement (9.1 mg · kg-1 · d-1; 95% CI: 4.6, 13.6 mg · kg-1 · d-1), although the 95% CIs overlap. Both DAAO and IAAO methods provided similar breakpoints in late pregnancy, showing that the DAAO method was appropriate even though low phenylalanine intakes could not be tested. These results have potential implications for gestation stage-specific dietary phenylalanine recommendations in future.This trial was registered at clinicaltrials.gov as NCT02669381.
背景
苯丙氨酸是一种必需氨基酸，通过酪氨酸可以转化为神经递质多巴胺、去甲肾上腺素和肾上腺素。目前，孕期苯丙氨酸的膳食需求尚不清楚。
目的
本研究旨在通过直接氨基酸氧化（DAAO；用 l-[1-13C]苯丙氨酸）和指示剂氨基酸氧化（IAAO；用 l-[1-13C]亮氨酸）来确定妊娠早、晚期苯丙氨酸的需求量（在酪氨酸过量的情况下）。
方法
23 名健康女性（年龄：30.4 ± 3.1 岁，均数 ± 标准差）在不同的苯丙氨酸摄入量下（妊娠早期和晚期为 5.5-30.5 mg·kg-1·d-1，使用 DAAO；妊娠晚期为 2.5-30.5 mg·kg-1·d-1，使用 IAAO）进行了研究，总共进行了 76 天的研究。测试摄入量以 8 种等热量和等氮的膳食提供，每公斤体重 1.5 g·d-1 的蛋白质和能量，是测量静息能量消耗的 1.7 倍。呼吸样本在同位素质谱仪上进行分析，以检测 13C 的丰度。使用 2 相线性回归交叉模型确定 13CO2 生成的转折点（代表平均需求），以确定苯丙氨酸的需求量。
结果
妊娠早期的苯丙氨酸需求量为 15 mg·kg-1·d-1（95%CI：10.4，19.9 mg·kg-1·d-1）；妊娠晚期，DAAO（95%CI：17.4，24.7 mg·kg-1·d-1）和 IAAO（95%CI：10.5，32.2 mg·kg-1·d-1）分别确定为 21 mg·kg-1·d-1。
结论
我们的结果表明，妊娠晚期的苯丙氨酸需求量（40%）比妊娠早期更高。此外，虽然 95%CI 存在重叠，但妊娠早期的需求高于先前的成年男性需求（9.1 mg·kg-1·d-1；95%CI：4.6，13.6 mg·kg-1·d-1）。DAAO 和 IAAO 方法在妊娠晚期均提供了相似的转折点，表明即使不能检测到低苯丙氨酸摄入量，DAAO 方法也是合适的。这些结果对未来妊娠特定阶段的饮食苯丙氨酸推荐具有潜在意义。本试验在 clinicaltrials.gov 注册为 NCT02669381。
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