Glycomacropeptide in children with phenylketonuria: does its phenylalanine content affect blood phenylalanine control?. Issue 4 (22nd January 2017)

• Record Type: Journal Article
• Authors: Daly, A.; Evans, S.; Chahal, S.; Santra, S.; MacDonald, A.
• Is Part Of: Journal of human nutrition and dietetics. Volume 30:Issue 4(2017)
• Page Start: 515
• Page End: 523
• Publication Date: 2017-01-22
• Subjects: amino acid -- glycomacropeptide -- phenylalanine -- phenylketonuria -- protein substitute; Dietetics -- Periodicals; Nutrition -- Periodicals; 613.205
• DOI: 10.1111/jhn.12438
• Languages: English
• ISSNs: 0952-3871

Abstract

Abstract: Background: In phenylketonuria (PKU), there are no data available for children with respect to evaluating casein glycomacropeptide (CGMP) as an alternative to phenylalanine‐free protein substitutes [Phe‐free L‐amino acid (AA)]. CGMP contains a residual amount of phenylalanine, which may alter blood phenylalanine control. Methods: In a prospective 6‐month pilot study, we investigated the effect on blood phenylalanine control of CGMP‐amino acid (CGMP‐AA) protein substitute in 22 PKU subjects (13 boys, nine girls), median age (range) 11 years (6–16 years). Twelve received CGMP‐AA and nine received Phe‐free L‐AA, (1 CGMP‐AA withdrawal). Subjects partially or wholly replaced Phe‐free L‐AA with CGMP‐AA. If blood phenylalanine exceeded the target range, the CGMP‐AA dose was reduced and replaced with Phe‐free L‐amino acids. The control group remained on Phe‐free L‐AAs. Phenylalanine, tyrosine and Phe : Tyr ratio concentrations were compared with the results for the previous year. Results: In the CGMP‐AA group, there was a significant increase in blood phenylalanine concentrations (pre‐study, 275 μmol L −1 ; CGMP‐AA, 317 μmol L −1 ; P = 0.02), a decrease in tyrosine concentrations (pre‐study, 50 μmol L −1 ; CGMP‐AA, 40 μmol L −1 ; P = 0.03) and an increase in Phe : Tyr ratios (pre‐study, Phe : Tyr 4.9:1; CGMP‐AA, Phe : Tyr 8:1; P = 0.02). In the control group there was a non‐significant fall in phenylalanine concentrations (pre‐study 325μmol/L: study 280μmol/L [p = 0.9], and no significant changes for tyrosine or phe/tyr ratios [p = 0.9]. Children taking the CGMP‐AA found it more acceptable to L‐AA. Conclusions: Blood phenylalanine control declined with CGMP‐AA but, by titrating the dose of CGMP‐AA, blood phenylalanine control remained within target range. The additional intake of phenylalanine may have contributed to the change in blood phenylalanine concentration. CGMP‐AA use requires careful monitoring in children.