Amino acid kinetics of GMP-AA in healthy human volunteers
Research type
Research Study
Full title
Amino acid kinetics of GMP-AA vs. Phenylalanine-free amino acids compared with natural protein in healthy adults volunteers
IRAS ID
281421
Contact name
Anita MacDonald
Contact email
Sponsor organisation
Birmingham Women and Childrens Hospital NHS Foundation
Clinicaltrials.gov Identifier
Duration of Study in the UK
1 years, 7 months, 31 days
Research summary
Research Summary: Children with phenylketonuria (PKU) are treated with a special diet supplemented with a synthetic protein based on amino acids. These have a poor taste and are inefficiently used by the body. A different type of synthetic protein, called glycomacropeptide is being tried in PKU. It tastes better than amino acids but it requires the addition of some extra amino acids which may worsen how well it is absorbed compared with traditional amino acid supplements. We will perform a 3-part trial in healthy adult volunteers to compare amino acids vs glycomacropeptide protein with a ‘normal protein’ (casein) to examine the absorption properties of these proteins. Volunteers will take one dose of each of the protein sources on 3 different days. Blood and urine samples will be collected examining the rate of absorption of amino acids over 5 hours on each study day.
Summary of Results:
In metabolic disorders such as phenylketonuria known as PKU, the diet is limited in protein. Children and adults cannot eat meat, fish, normal bread, pasta and have a very small measured amount of phenylalanine as potatoes, cereals and vegetables such as sweetcorn. To prevent protein deficiency and allow normal growth they need to take a protein substitute three times a day. These contain amino acids (AA) vitamins and minerals.We know AA are very quickly absorbed in the body and this might limit growth potential as muscles need AA to grow. Good quality protein like milk, eggs and meat provide AAs but these are slowly absorbed allowing maximum growth potential
A new protein substitute known as glycomacropeptide (GMP) is made up of a mixture of a macro peptide - this is a smaller protein and some free AAs. We wanted to test if the AAs in GMP was absorbed the same or more slowly than the current protein substitutes based only on free AAs. To do this we recruited healthy volunteers and gave thenm free AAs , GMP and casein (milk powder). We know that the AAs in casein are very slowly absosred.
This was a three-way randomised, controlled, crossover study comparing the AA absorption profile of free AA, GMP and casein
Methods: All subjects took each test product (AA, GMP and casein) as a drink. Fasted blood samples were collected from healthy volunteers at 30, 60, 90, 120, 150, 180 and 240 minutes post-test. Insulin, blood urea nitrogen, glucose and total (TAAs), essential (EAAs), large neutral (LNAAs) and branch chain (BCAAs) amino acids were measured at each time point.
Results: A total of 20 subjects (11 females), median age 43 y (range 23–49), with a median BMI 24.2 (20–30.5) were recruited. Absorption curves were compared across groups. Statistically sig-nificant differences were noted for: TAAs and BCAAs between GMP and L-AAs vs. casein
There were no differences between AAs and CGMP. Absorption was largest for free AAs, then GMP and finally casein. For LNAAs, EAAs, insulin, glucose and urea, there were no statistically significant differences.
There was a consistent delivery of AAs for casein demonstrated by a sustained and slow absorption curve, but the absorption curves for AAs and GMP were transient, rising rapidly and falling, with the exception of tyrosine with GMP which showed a gradual increase over time
Conclusion: Amino acids from GMP and AAs were absorbed more rapidly than casein, inferring GMP did not slow down the absorption of AAs
REC name
West Midlands - South Birmingham Research Ethics Committee
REC reference
20/WM/0266
Date of REC Opinion
16 Nov 2020
REC opinion
Further Information Favourable Opinion