Introduction

Phenylketonuria (PKU) is an inborn error of metabolism, which is caused by a deficiency in the enzyme phenylalanine hydroxylase (PAH). Life-long Phe-free diet impairs quality of life, especially in adolescents and young adults which take responsibility over their diet and therapy from their parents, but expect freedom in daily routine.

Methods and results

105 patients with PKU were screened for eligibility for participating in this study. Data of 21 patients with genetic predictive value (GPV) ≤5 and age between 14 and 30 years were included in the analysis. Mean age of the study population was 22.6 ± 7.5 years, 8 patients (38%) were female. At baseline, structured counselling by a professional nutrionist was performed.

Mean Phe-level at baseline was 926 ± 432 μmol/l, after six months Phe-levels were significantly reduced to 709 ± 314 μmol/l (p = .039), in total 4 additional patients (38% of the population) reached values within the therapeutic goal. After 12, 18 and 24 months, mean Phe-level elevated significantly to initial level (869 ± 427 μmol/l; p = .311). Mean daily intake of natural protein at baseline was 32.3 ± 24.3 g per day. There was a significant decrease after 6 months (26.9 ± 18.8 g/day; p = .049) and 12 months (25.9 ± 16.2 g/day; p = .30) compared to baseline. Values at 18 months (27.5 ± 9.2 g/day; p = .26) and 24 months (35.0 ± 22.3 g/day; p = .87) did not differ. Mean daily supplementation of Phe-free amino acids was 26.2 ± 19.2 g per day. In all follow-up examinations a significant increase compared to baseline values was calculated (42.4 ± 17.6 g/day after 6 moths (p = .028), 52.1 ± 29.9 g/day after 12 months (p ≤.01), 38.7 ± 20.3 g/day after 18 months (p < .01) and 39.3 ± 21.9 g/day after 24 months (p = .014)). At baseline, mean total protein intake (natural protein plus supplements) was 0.97 ± 0.42 g per kg body weight (g/kgBW). After 24 months the protein intake was within recommended levels. (1.23 ± 0.33 g/kgKB; p = .013). After 24 months, plasma Vitamin B12 increased to 424.8 ± 176.9 pg/ml (baseline 368.6 ± 205.6 pg/ml; p = .049) and Vitamin D increased to 30.4 ± 9.9 ng/ml (baseline 24.5 ± 10.1 ng/ml; p = .06).

Conclusion

Counselling by a professional nutrionist in young adults with PKU has clear short-term effects on plasma Phe-levels. Easy applicable therapeutic recommendations, as additional intake of amino acid supplement, are well tolerated and result in strict therapy adherence up to 24 months. Apart from that, the effects on Phe-levels seem only to sustain for about 6 months. More frequent nutritional counselling, i.e. at least two times per year, is recommended to preserve positive effects on Phe-levels. Lack of Vitamin B12 and Vitamin D still are common in PKU patients, but not necessarily need to be substituted. They can effectively be equalized by a well-balanced diet within 24 months.

中文翻译：

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营养治疗对患有苯丙酮尿症的年轻人的持续益处 - 一项为期 2 年的前瞻性研究。

介绍

苯丙酮尿症 (PKU) 是一种先天性代谢错误，由苯丙氨酸羟化酶 (PAH) 缺乏引起。终生无 Phe 饮食会损害生活质量，尤其是在青少年和年轻人中，他们从父母那里对饮食和治疗负责，但在日常生活中期望自由。

方法和结果

筛选了 105 名 PKU 患者参加本研究的资格。分析包括21名遗传预测值（GPV）≤5且年龄在14至30岁之间的患者的数据。研究人群的平均年龄为 22.6 ± 7.5 岁，8 名患者 (38%) 为女性。在基线时，由专业营养师进行结构化咨询。

基线时的平均 Phe 水平为 926 ± 432 μmol/l，六个月后 Phe 水平显着降低至 709 ± 314 μ​​mol/l ( p  = .039)，总共有 4 名患者（占人口的 38%）达到治疗目标内的价值。12、18 和 24 个月后，平均 Phe 水平显着升高至初始水平（869 ± 427 μmol/l；p  = .311）。基线时天然蛋白质的平均每日摄入量为每天 32.3 ± 24.3 克。与基线相比，6 个月（26.9 ± 18.8 g/天； p  = .049）和 12 个月（25.9 ± 16.2 g/天；p  = .30）后显着下降。18 个月（27.5 ± 9.2 g/天；p  = .26）和 24 个月（35.0 ± 22.3 g/天；p = .87) 没有差异。无 Phe 氨基酸的平均每日补充量为每天 26.2 ± 19.2 克。在所有后续检查中，计算出与基线值相比显着增加（6 个月后 42.4 ± 17.6 g/天（p  = .028），12 个月后 52.1 ± 29.9 g/天（p  ≤.01），38.7 ± 18 个月后 20.3 克/天（p  < .01）和 24 个月后 39.3 ± 21.9 克/天（p  = .014））。在基线时，平均总蛋白质摄入量（天然蛋白质加补充剂）为 0.97 ± 0.42 g/kg 体重 (g/kgBW)。24 个月后，蛋白质摄入量在推荐水平之内。(1.23 ± 0.33 g/kgKB；p  = .013)。24 个月后，血浆维生素 B12 增加到 424.8 ± 176.9 pg/ml（基线 368.6 ± 205.6 pg/ml；p = .049）和维生素 D 增加到 30.4 ± 9.9 ng/ml（基线 24.5 ± 10.1 ng/ml；p  = .06）。

结论

由专业营养师对患有 PKU 的年轻人进行咨询对血浆 Phe 水平有明显的短期影响。简单适用的治疗建议，如额外摄入氨基酸补充剂，耐受性良好，并导致严格的治疗依从性长达 24 个月。除此之外，对 Phe 水平的影响似乎只持续了大约 6 个月。建议更频繁地进行营养咨询，即每年至少两次，以保持对 Phe 水平的积极影响。缺乏维生素 B12 和维生素 D 在 PKU 患者中仍然很常见，但不一定需要替代。他们可以在 24 个月内通过均衡的饮食有效地平衡。