Comparison of Glycomacropeptide with Phenylalanine Free-Synthetic Amino Acids in Test Meals to PKU Patients: No Significant Differences in Biomarkers, Including Plasma Phe Levels

Abstract

Introduction Management of phenylketonuria (PKU) is achieved through low-phenylalanine (Phe) diet, supplemented with low-protein food and mixture of free-synthetic (FS) amino acid (AA). Casein glycomacropeptide (CGMP) is a natural peptide released in whey during cheese-making and does not contain Phe. Lacprodan® CGMP-20 used in this study contained a small amount of Phe due to minor presence of other proteins/peptides. Objective The purpose of this study was to compare absorption of CGMP-20 to FSAA with the aim of evaluating short-term effects on plasma AAs as well as biomarkers related to food intake. Methods This study included 8 patients, who had four visits and tested four drink mixtures (DM1–4), consisting of CGMP, FSAA, or a combination. Plasma blood samples were collected at baseline, 15, 30, 60, 120, and 240 minutes (min) after the meal. AA profiles and ghrelin were determined 6 times, while surrogate biomarkers were determined at baseline and 240 min. A visual analogue scale (VAS) was used for evaluation of taste and satiety. Results The surrogate biomarker concentrations and VAS scores for satiety and taste were nonsignificant between the four DMs, and there were only few significant results for AA profiles (not Phe). Conclusion CGMP and FSAA had the overall same nonsignificant short-term effect on biomarkers, including Phe. This combination of FSAA and CGMP is a suitable supplement for PKU patients.

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

“…In the retrospective study conducted by Pinto et al [ 24 ] with 11 subjects, GMP-AAs partially or fully substituted AAs. In the study performed by Ahring et al [ 18 ], subjects tested four DMs (1–4) in a random order at each visit (DM1 = GMP; DM2 = AAs (equivalent amino acid profile to DM1); DM3 = GMP + AAs; DM4 = AAs (equivalent amino acid profile to DM3 but without Phe).…”

“…Blood Tyr was measured in all studies, with exception of the studies of Lim et al [ 10 ] and Zaki et al [ 21 ]. BUN was measured in the studies of van Calcar et al [ 17 ], Ney et al [ 22 ], and Ahring et al [ 18 ]. In the studies of Zaki et al [ 21 ] and Pinto et al [ 24 ], only the values of urea were available.…”

“…In the studies of Zaki et al [ 21 ] and Pinto et al [ 24 ], only the values of urea were available. Glucose was measured in the studies of van Calcar et al [ 17 ], Ney et al [ 22 ], Pinto et al [ 24 ], and Ahring et al [ 18 ]. Acceptability was assessed by all apart from Pinto et al [ 24 ].…”

“…In two RCTs with sufficient methodological similarity [ 18 , 22 ], a meta-analysis was carried out. The study of Ahring et al [ 18 ] tested four drink mixtures (DMs 1–4), consisting of GMP or AAs or a combination. For the purposes of analysis, we only considered DM3 and DM4.…”

“…However, scientific evidence from clinical studies that support the use of GMP-AAs as a major source of protein in PKU patients is less robust. Doubts still persist regarding the potential effect on patients of the residual Phe provided by GMP-AAs as well as how the nutritional biomarkers are influenced by GMP-AAs intake [ 10 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ].…”