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The Effect of Glycomacropeptide versus Amino Acids on Phenylalanine and Tyrosine Variability over 24 Hours in Children with PKU: A Randomized Controlled Trial

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Birmingham Women’s and Children’s Hospital, Steelhouse Lane, Birmingham B4 6 NH, UK
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Nottingham Queen’s Medical Centre, University Hospital, Derby Road, Nottingham NG7 2UH, UK
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Centro de Genética Médica, Centro Hospitalar Universitário do Porto (CHUP), 4099-028 Porto, Portugal
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Centro de Referência na área de Doenças Hereditárias do Metabolismo, Centro Hospitalar Universitário do Porto-CHUP, 4099-001 Porto, Portugal
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Center for Health Technology and Services Research (CINTESIS), 4200-450 Porto, Portugal
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Beatrix Children’s Hospital, University Medical Centre of Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
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Liverpool University, Brownlow Hill, Liverpool L69 7ZX, UK
*
Author to whom correspondence should be addressed.
Nutrients 2019, 11(3), 520; https://doi.org/10.3390/nu11030520
Received: 16 December 2018 / Revised: 18 February 2019 / Accepted: 20 February 2019 / Published: 28 February 2019
Introduction: In phenylketonuria (PKU), evidence suggests that casein glycomacropeptide supplemented with rate-limiting amino acids (CGMP-AA) is associated with better protein utilisation and less blood phenylalanine (Phe) variability. Aim: To study the impact of CGMP-AA on blood Phe variability using 3 different dietary regimens in children with PKU. Methods: This was a 6-week randomised controlled cross-over study comparing CGMP-AA vs. Phe-free l-amino acids (l-AA) assessing blood Phe and tyrosine (Tyr) variability over 24 h in 19 children (7 boys) with PKU, with a median age of 10 years (6–16). Subjects were randomised to 3 dietary regimens: (1) R1, CGMP-AA and usual dietary Phe (CGMP + Phe); (2) R2, CGMP-AA − Phe content of CGMP-AA from usual diet (CGMP − Phe); and (3) R3, l-AA and usual dietary Phe. Each regimen was administered for 14 days. Over the last 48 h on days 13 and 14, blood spots were collected every 4 h at 08 h, 12 h, 16 h, 20 h, 24 h, and 04 h. Isocaloric intake and the same meal plan and protein substitute dosage at standardised times were maintained when blood spots were collected. Results: Eighteen children completed the study. Median Phe concentrations over 24 h for each group were (range) R1, 290 (30–580), R2, 220 (10–670), R3, 165 (10–640) μmol/L. R1 vs. R2 and R1 vs. R3 p < 0.0001; R2 vs. R3 p = 0.0009. There was a significant difference in median Phe at each time point between R1 vs. R2, p = 0.0027 and R1 vs. R3, p < 0.0001, but not between any time points for R2 vs. R3. Tyr was significantly higher in both R1 and R2 [70 (20–240 μmol/L] compared to R3 [60 (10–200) μmol/L]. In children < 12 years, blood Phe remained in the target range (120–360 μmol/L), over 24 h, for 75% of the time in R1, 72% in R2 and 64% in R3; for children aged ≥ 12 years, blood Phe was in target range (120–600 μmol/L) in R1 and R2 for 100% of the time, but 64% in R3. Conclusions: The residual Phe in CGMP-AA increased blood Phe concentration in children. CGMP-AA appears to give less blood Phe variability compared to l-AA, but this effect may be masked by the increased blood Phe concentrations associated with its Phe contribution. Reducing dietary Phe intake to compensate for CGMP-AA Phe content may help. View Full-Text
Keywords: glycomacropeptide; phenylalanine; phenylketonuria; phenylalanine variability; amino acids; tyrosine glycomacropeptide; phenylalanine; phenylketonuria; phenylalanine variability; amino acids; tyrosine
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MDPI and ACS Style

Daly, A.; Evans, S.; Chahal, S.; Santra, S.; Pinto, A.; Gingell, C.; Rocha, J.C.; van Spronsen, F.; Jackson, R.; MacDonald, A. The Effect of Glycomacropeptide versus Amino Acids on Phenylalanine and Tyrosine Variability over 24 Hours in Children with PKU: A Randomized Controlled Trial. Nutrients 2019, 11, 520. https://doi.org/10.3390/nu11030520

AMA Style

Daly A, Evans S, Chahal S, Santra S, Pinto A, Gingell C, Rocha JC, van Spronsen F, Jackson R, MacDonald A. The Effect of Glycomacropeptide versus Amino Acids on Phenylalanine and Tyrosine Variability over 24 Hours in Children with PKU: A Randomized Controlled Trial. Nutrients. 2019; 11(3):520. https://doi.org/10.3390/nu11030520

Chicago/Turabian Style

Daly, Anne; Evans, Sharon; Chahal, Satnam; Santra, Saikat; Pinto, Alex; Gingell, Cerys; Rocha, Júlio C.; van Spronsen, Francjan; Jackson, Richard; MacDonald, Anita. 2019. "The Effect of Glycomacropeptide versus Amino Acids on Phenylalanine and Tyrosine Variability over 24 Hours in Children with PKU: A Randomized Controlled Trial" Nutrients 11, no. 3: 520. https://doi.org/10.3390/nu11030520

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