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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

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@article{ecd3635e41cf470582f7d2188b198643,
title = "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",
abstract = "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.",
author = "Grith H{\o}jfeldt and Jacob B{\"u}low and Jakob Agergaard and Ali Asmar and Peter Schjerling and Lene Simonsen and Jens B{\"u}low and {van Hall}, Gerrit and Lars Holm",
note = "Copyright {\textcopyright} The Author(s) on behalf of the American Society for Nutrition 2020.",
year = "2020",
month = dec,
day = "10",
doi = "10.1093/ajcn/nqaa201",
language = "English",
volume = "112",
pages = "1468--1484",
journal = "American Journal of Clinical Nutrition",
issn = "0002-9165",
publisher = "American Society for Nutrition",
number = "6",

}

RIS

TY - JOUR

T1 - Impact of habituated dietary protein intake on fasting and postprandial whole-body protein turnover and splanchnic amino acid metabolism in elderly men

T2 - a randomized, controlled, crossover trial

AU - Højfeldt, Grith

AU - Bülow, Jacob

AU - Agergaard, Jakob

AU - Asmar, Ali

AU - Schjerling, Peter

AU - Simonsen, Lene

AU - Bülow, Jens

AU - van Hall, Gerrit

AU - Holm, Lars

N1 - Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.

PY - 2020/12/10

Y1 - 2020/12/10

N2 - 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.

AB - 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.

U2 - 10.1093/ajcn/nqaa201

DO - 10.1093/ajcn/nqaa201

M3 - Journal article

C2 - 32710741

VL - 112

SP - 1468

EP - 1484

JO - American Journal of Clinical Nutrition

JF - American Journal of Clinical Nutrition

SN - 0002-9165

IS - 6

ER -

ID: 61569102