1Dietetic Department,Birmingham Children's Hospital,Steelhouse Lane,Birmingham B74 4XN,UK.
2Department of Human Genetics,Emory University School of Medicine,Nutrition Health Sciences Program,Emory University,Atlanta,GA,USA.
Nutr Res Rev. 2019 Jun;32(1):70-78. doi: 10.1017/S0954422418000173. Epub 2018 Oct 4.
It has been nearly 70 years since the discovery that strict adherence to a diet low in phenylalanine prevents severe neurological sequelae in patients with phenylalanine hydroxylase deficiency (phenylketonuria; PKU). Today, dietary treatment with restricted phenylalanine intake supplemented with non-phenylalanine amino acids to support growth and maintain a healthy body composition remains the mainstay of therapy. However, a better understanding is needed of the factors that influence N balance in the context of amino acid supplementation. The aim of the present paper is to summarise considerations for improving N balance in patients with PKU, with a focus on gaining greater understanding of amino acid absorption, disposition and utilisation. In addition, the impact of phenylalanine-free amino acids on 24 h blood phenylalanine/tyrosine circadian rhythm is evaluated. We compare the effects of administering intact protein v. free amino acid on protein metabolism and discuss the possibility of improving outcomes by administering amino acid mixtures so that their absorption profile mimics that of intact protein. Protein substitutes with the ability to delay absorption of phenylalanine and tyrosine, mimicking physiological absorption kinetics, are expected to improve the rate of assimilation into protein and minimise fluctuations in quantitative plasma amino acid levels. They may also help maintain normal glycaemia and satiety sensation. This is likely to play an important role in improving the management of patients with PKU.
自发现严格遵循低苯丙氨酸饮食可预防苯丙氨酸羟化酶缺乏症（苯丙酮尿症；PKU）患者的严重神经后遗症以来，已经过去了近 70 年。如今，限制苯丙氨酸摄入并补充非苯丙氨酸氨基酸以支持生长和维持健康的身体成分的饮食治疗仍然是治疗的基础。然而，需要更好地了解在氨基酸补充的背景下影响氮平衡的因素。本文的目的是总结改善 PKU 患者氮平衡的注意事项，重点是更深入地了解氨基酸的吸收、分布和利用。此外，还评估了无苯丙氨酸氨基酸对 24 小时血苯丙氨酸/酪氨酸昼夜节律的影响。我们比较了给予完整蛋白质与游离氨基酸对蛋白质代谢的影响，并讨论了通过给予氨基酸混合物来改善结果的可能性，使它们的吸收模式模拟完整蛋白质。具有延迟苯丙氨酸和酪氨酸吸收能力、模拟生理吸收动力学的蛋白质替代品有望提高蛋白质同化率，并最大限度地减少定量血浆氨基酸水平的波动。它们还可能有助于维持正常的血糖水平和饱腹感。这可能在改善 PKU 患者的管理方面发挥重要作用。
