Sustaining benefits of nutritional therapy in young adults with phenylketonuria - A 2?year prospective study

摘要

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.