A total of 105 patients was screened for participating in this study. Main exclusion criteria were the following: Age not within the inclusion range or treatment with Saproterine (n= 58), not willing to participate (n=15), no genetic information (n=5) and personal circumstances avoiding regular follow-ups (n=2). At least 25 patients were included in this study, of which 4 patients were lost to follow-up. In total, data of 21 patients were included in the analysis. Mean age of the study population was 22.6±7.5 years, 8 patients (38%) were female. Follow-up visits were performed after 6.5±3.9 months (Follow-Up 1), 11.2±3.3 months (Follow-up 2), 19.8±7.4 months (Follow-Up 3) and 25.5±5.7 months (Final Visit) after the baseline examination. The study protocol is shown in figure 1. Mean plasma Phe-level at baseline was 957±389 µmol/l, only 4 patients (19%) reached the therapeutic goal (Phe <600µmol/l). All baseline characteristics are presented in table 1.
Changes in plasma Phe-levels and daily protein-intake
Retrospective data, according to plasma Phe-level (930±414µmol/l; p=0.69), daily Phe-Intake (1530±1139 g/day; p=0.89), daily intake of natural protein (33.4±26.1 g/day; p=0.78) and supplemental intake of Phe-free amino acids (23±15g/day; p=0.85) were not different to baseline values.
Mean Phe-level at baseline was 926±432 µmol/l, only 4 patients (19%) had values within the therapeutic goal. Six months after the intervention, Phe-levels were significantly reduced to 709±314 µmol/l (p=0.039), in total 4 additional patients (38% of the population) reached values within the therapeutic goal. After 12 months, mean Phe-level elevated significantly to initial level (901±398 µmol/l, p=0.04 vs. Follow-up 1; p=0.187 vs. baseline) and henceforth remained stable after 18 months (919±306 µmol/l, p=0.267) and 24 months 869±427 µmol/l (p=0.311) (Figure 2A).
Mean daily Phe-Intake was calculated with 1542±1146 mg per day at baseline. Six months after the intervention, the mean intake remained stable at 1435±1051 mg/day (p=0.91), followed by a decline to 1237±730 mg/day after 12 months and 1316±462 mg/day after 18 months. The difference to baseline was statistically significant for 12 months (p=0.03), but not for 18 month’s value (p=0.11). At the final examination after 24 months daily Phe-Intake increased to 1725±1097 mg/day back to initial values (p=0.53) (Figure 2B).
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=0.049) and 12 months (25.9±16.2 g/day; p=0.30) compared to baseline. Values at 18 months (27.5±9.2 g/day; p=0.26) and 24 months (35.0±22.3 g/day; p=0.87) did not differ to baseline (Figure 2C).
Mean daily supplementation of Phe-free amino acids at baseline was 26.2±19.2 g per day. In all follow-up examinations a significant increase compared to baseline values was calculated. In detail 42.4±17.6 g/day after 6 moths (p=0.028), 52.1±29.9 g/day after 12 months (p=<0.01), 38.7±20.3 g/day after 18 months (p<0.01) and 39.3±21.9 g/day after 24 months (p=0.014) (Figure 2D).
At baseline, mean total protein intake (natural protein plus supplements) was 0.97±0.42 g per kg body weight (g/kgBW). After 6 months, the total protein intake increased to 1.1±0.33 g/kgBW (p=0.041), which remained stable after 12 months (1.1±0.34 g/kgBW; p=0.024) and 18 months (1.0±0.24 g/kgBW p=0.044). Even after 24 months the protein intake was significantly higher compared to baseline (1.23±0.33 g/kgKB; p=0.013) (Figure 3).
Vitamins and micronutrients
Concerning Vitamins and micronutrients, no significant changes were found after 24 months for Vitamin A (1.7±0.4 vs. 1.8±0.3 µg/ml; p=0.70), Vitamin C (15.1±5.3 vs. 12.4±4.5 mg/l; p=0.54), Vitamin E (25.8±5.7 vs 28.4±9.9 µmol/l; p=0.18), plasma iron (19.1±5.4 vs. 20.8±7.7 µmol/l; p=0.20) and zinc (10.9± 1.9 vs. 10.8±1.9 µmol/l; p=0.89).
At baseline examination 3 patients (14%) presented with lack of Vitamin B12 supply (<191pg/ml) and 7 patients (33%) with lack of Vitamin D (<20ng/ml). At the final examination after 24 months, plasma Vitamin B12 increased to 424.8±176.9 pg/ml (baseline 368.6±205.6 pg/ml; p=0.049), all patients (100%) had values upon the lower reference levels. Plasma Vitamin D increased to 30.4±9.9 ng/ml (baseline 24.5±10.1 ng/ml; p=0.06), only one patient (5%) had apparent lack of Vitamin D. All values are presented in figure 4.
Changes in body weight and BMI
Mean body weight did not significantly change during the follow-up period (65.5±22.0 vs. 66.9 ± 19.4 kg; p=0.49) as well as the body-mass index (BMI; 23.3±4.9 vs. 23.4±4.3 kg/m2; p=0.15).