The Use of Glycomacropeptide in Patients with Phenylketonuria: A Systematic Review and Meta-Analysis

Abstract

In phenylketonuria (PKU), synthetic protein derived from L-amino acids (AAs) is essential in a low-phenylalanine (Phe) diet. Glycomacropeptide (GMP), an intact protein, is very low in Phe in its native form. It has been modified and adapted for PKU to provide an alternative protein source through supplementation with rate-limiting amino acids (GMP-AAs), although it still contains residual Phe. This review aims to systematically evaluate published intervention studies on the use of GMP-AAs in PKU by considering its impact on blood Phe control (primary aim) and changes in tyrosine control, nutritional biomarkers, and patient acceptability or palatability (secondary aims). Four electronic databases were searched for articles published from 2007 to June 2018. Of the 274 studies identified, only eight were included. Bias risk was assessed and a quality appraisal of the body of evidence was completed. A meta-analysis was performed with two studies with adequate comparable methodology which showed no differences between GMP-AAs and AAs for any of the interventions analysed. This work underlines the scarcity and nature of studies with GMP-AAs interventions. All were short-term with small sample sizes. There is a need for better-designed studies to provide the best evidence-based recommendations.

PKU dietary handbook to accompany PKU guidelines

“…Nevertheless, children with milder forms of PKU or on sapropterin therapy with a higher natural protein tolerance should tolerate the extra phenylalanine provided by CGMP. No significant increase in blood phenylalanine has been observed in adult patients using CGMP [16], although some patients may have had suboptimal blood phenylalanine control prior to CGMP commencement or they may have received only a partial amount of their protein substitute intake from this source.…”

“…In humans, there is evidence that CGMP has a better taste, improves satiety and improves nitrogen retention. In animal (PKU mice) studies, there is suggestion that CGMP reduces blood phenylalanine in the brain, improves bone health and acts as prebiotic [16].…”

“…3 Department of PKU, Kennedy Centre, Glostrup, Denmark. 4 16 School of Life and Health Sciences, Aston University, Birmingham, UK. 17 Department of Paediatrics, University of Heidelberg, Heidelberg, Germany.…”

Protective Effect of Glycomacropeptide on Food Allergy with Gastrointestinal Manifestations in a Rat Model through Down-Regulation of Type 2 Immune Response

“…It is considered safe for human use and is not immunogenic regardless of the administration route [ 23 , 24 ]. GMP is free from phenylalanine residues, which allows it to be used as a protein-based ingredient in the formulation of food products for the nutrition of phenylketonuria patients [ 25 ]. Many different biological activities have been attributed to GMP [ 26 ].…”

La phénylcétonurie

“…que l'on récupère lors de la fabrication du fromage, sont apparus [31]. Ces GMP contiennent naturellement très peu de phénylalanine, ce qui les rend utilisables en remplacement des substituts d'acides aminés.…”