Søren Reitelseder1, Britt Tranberg2, Jakob Agergaard3, Kasper Dideriksen4, Grith Højfeldt5, Marie Emily Merry6, Adam C Storm7, Kristian R Poulsen8, Erik T Hansen9, Gerrit van Hall10, Peter Lund11, Lars Holm12. 1. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Electronic address: s.reitelseder@gmail.com. 2. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: britt.tranberg@gmail.com. 3. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: jakobagergaard@hotmail.com. 4. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: kasperjuel@hotmail.com. 5. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: grithwh@gmail.com. 6. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: gr3v@kk.dk. 7. Department of Animal Science, Aarhus University Foulum, Aarhus University, Aarhus, Denmark. Electronic address: achs@novozymes.com. 8. Arla Foods Ingredients Group P/S, Nr. Vium, Denmark. Electronic address: kristian.raaby.poulsen@arlafoods.com. 9. DC Ingredients, Copenhagen, Denmark. Electronic address: eth@dat-schaub.dk. 10. Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Clinical Metabolomics Core Facility, Clinical Biochemistry, Rigshospitalet. Electronic address: gerrit.van.hall@regionh.dk. 11. Department of Animal Science, Aarhus University Foulum, Aarhus University, Aarhus, Denmark. Electronic address: peter.lund@anis.au.dk. 12. Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK. Electronic address: L.Holm@bham.ac.uk.
Abstract
BACKGROUND & AIMS: Availability of dietary protein-derived amino acids (AA) is an important determinant for their utilization in metabolism and for protein synthesis. Intrinsic labeling of protein is the only method to directly trace availability and utilization. The purpose of the present study was to produce labeled milk and meat proteins and investigate how dietary protein-derived AA availability is affected by the protein-meal matrix. METHODS: Four lactating cows were infused with L-[ring-d5]phenylalanine and one with L-[15N]phenylalanine for 72 h. Milk was collected, and three of the [d5]phenylalanine cows were subsequently slaughtered. Two human studies were performed to explore plasma AA availability properties utilizing the labeled proteins. One study compared the intake of whey protein either alone or together with carbohydrates-fat food-matrix. The other study compared the intake of meat hydrolysate with minced beef. Cow blood, milk, meat and human blood samples were collected and analyzed by mass spectrometry. RESULTS: Whey and caseinate acquired label to 15-20 mol percent excess (MPE), and the meat proteins reached 0.41-0.73 MPE. The [d5]phenylalanine appeared fast in plasma and peaked 30 min after whey protein alone and meat hydrolysate intake, whereas whey protein with a food-matrix and the meat minced beef postponed the [d5]phenylalanine peak until 2 and 1 h, respectively. CONCLUSIONS: Phenylalanine stable isotope-labeled milk and meat were produced and proved a valuable tool to investigate AA absorption characteristics. Dietary protein in food-matrices showed delayed postprandial plasma AA availability as compared to whey protein alone and meat hydrolysate.
BACKGROUND & AIMS: Availability of dietary protein-derived amino acids (AA) is an important determinant for their utilization in metabolism and for protein synthesis. Intrinsic labeling of protein is the only method to directly trace availability and utilization. The purpose of the present study was to produce labeled milk and meat proteins and investigate how dietary protein-derived AA availability is affected by the protein-meal matrix. METHODS: Four lactating cows were infused with L-[ring-d5]phenylalanine and one with L-[15N]phenylalanine for 72 h. Milk was collected, and three of the [d5]phenylalaninecows were subsequently slaughtered. Two human studies were performed to explore plasma AA availability properties utilizing the labeled proteins. One study compared the intake of whey protein either alone or together with carbohydrates-fat food-matrix. The other study compared the intake of meat hydrolysate with minced beef. Cow blood, milk, meat and human blood samples were collected and analyzed by mass spectrometry. RESULTS: Whey and caseinate acquired label to 15-20 mol percent excess (MPE), and the meat proteins reached 0.41-0.73 MPE. The [d5]phenylalanine appeared fast in plasma and peaked 30 min after whey protein alone and meat hydrolysate intake, whereas whey protein with a food-matrix and the meat minced beef postponed the [d5]phenylalanine peak until 2 and 1 h, respectively. CONCLUSIONS:Phenylalanine stable isotope-labeled milk and meat were produced and proved a valuable tool to investigate AA absorption characteristics. Dietary protein in food-matrices showed delayed postprandial plasma AA availability as compared to whey protein alone and meat hydrolysate.