Impact of habituated dietary protein intake on fasting and postprandial whole-body protein turnover and splanchnic amino acid metabolism in elderly men: a randomized, controlled, crossover trial.
caseinate protein
habitual protein intake
intrinsically labeled proteins
protein breakdown
protein turnover
recommended protein intake
stable-isotope tracers
whey protein
whole-body protein turnover
Journal
The American journal of clinical nutrition
ISSN: 1938-3207
Titre abrégé: Am J Clin Nutr
Pays: United States
ID NLM: 0376027
Informations de publication
Date de publication:
10 12 2020
10 12 2020
Historique:
received:
21
01
2020
accepted:
29
06
2020
pubmed:
28
7
2020
medline:
7
1
2021
entrez:
26
7
2020
Statut:
ppublish
Résumé
Efficacy of protein absorption and subsequent amino acid utilization may be reduced in the elderly. Higher protein intakes have been suggested to counteract this. We aimed to elucidate how habituated amounts of protein intake affect the fasted state of, and the stimulatory effect of a protein-rich meal on, protein absorption, whole-body protein turnover, and splanchnic amino acid metabolism. Twelve men (65-70 y) were included in a double-blinded crossover intervention study, consisting of a 20-d habituation period to a protein intake at the RDA or a high amount [1.1 g · kg lean body mass (LBM)-1 · d-1 or >2.1 g · kg LBM-1 · d-1, respectively], each followed by an experimental trial with a primed, constant infusion of D8-phenylalanine and D2-tyrosine. Arterial and hepatic venous blood samples were obtained after an overnight fast and repeatedly 4 h after a standardized meal including intrinsically labeled whey protein concentrate and calcium-caseinate proteins. Blood was analyzed for amino acid concentrations and phenylalanine and tyrosine tracer enrichments from which whole-body and splanchnic amino acid and protein kinetics were calculated. High (compared with the recommended amount of) protein intake resulted in a higher fasting whole-body protein turnover with a resultant mean ± SEM 0.03 ± 0.01 μmol · kg LBM-1 · min-1 lower net balance (P < 0.05), which was not rescued by the intake of a protein-dense meal. The mean ± SEM plasma protein fractional synthesis rate was 0.13 ± 0.06%/h lower (P < 0.05) after habituation to high protein. Furthermore, higher fasting and postprandial amino acid removal were observed after habituation to high protein, yielding higher urea excretion and increased phenylalanine oxidation rates (P < 0.01). Three weeks of habituation to high protein intake (>2.1 g protein · kg LBM-1 · d-1) led to a significantly higher net protein loss in the fasted state. This was not compensated for in the 4-h postprandial period after intake of a meal high in protein.This trial was registered at clinicaltrials.gov as NCT02587156.
Sections du résumé
BACKGROUND
Efficacy of protein absorption and subsequent amino acid utilization may be reduced in the elderly. Higher protein intakes have been suggested to counteract this.
OBJECTIVES
We aimed to elucidate how habituated amounts of protein intake affect the fasted state of, and the stimulatory effect of a protein-rich meal on, protein absorption, whole-body protein turnover, and splanchnic amino acid metabolism.
METHODS
Twelve men (65-70 y) were included in a double-blinded crossover intervention study, consisting of a 20-d habituation period to a protein intake at the RDA or a high amount [1.1 g · kg lean body mass (LBM)-1 · d-1 or >2.1 g · kg LBM-1 · d-1, respectively], each followed by an experimental trial with a primed, constant infusion of D8-phenylalanine and D2-tyrosine. Arterial and hepatic venous blood samples were obtained after an overnight fast and repeatedly 4 h after a standardized meal including intrinsically labeled whey protein concentrate and calcium-caseinate proteins. Blood was analyzed for amino acid concentrations and phenylalanine and tyrosine tracer enrichments from which whole-body and splanchnic amino acid and protein kinetics were calculated.
RESULTS
High (compared with the recommended amount of) protein intake resulted in a higher fasting whole-body protein turnover with a resultant mean ± SEM 0.03 ± 0.01 μmol · kg LBM-1 · min-1 lower net balance (P < 0.05), which was not rescued by the intake of a protein-dense meal. The mean ± SEM plasma protein fractional synthesis rate was 0.13 ± 0.06%/h lower (P < 0.05) after habituation to high protein. Furthermore, higher fasting and postprandial amino acid removal were observed after habituation to high protein, yielding higher urea excretion and increased phenylalanine oxidation rates (P < 0.01).
CONCLUSIONS
Three weeks of habituation to high protein intake (>2.1 g protein · kg LBM-1 · d-1) led to a significantly higher net protein loss in the fasted state. This was not compensated for in the 4-h postprandial period after intake of a meal high in protein.This trial was registered at clinicaltrials.gov as NCT02587156.
Identifiants
pubmed: 32710741
pii: S0002-9165(22)00926-1
doi: 10.1093/ajcn/nqaa201
doi:
Substances chimiques
Amino Acids
0
Dietary Proteins
0
Proteins
0
Nitrogen
N762921K75
Banques de données
ClinicalTrials.gov
['NCT02587156']
Types de publication
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
1468-1484Informations de copyright
Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.