TY - JOUR

T1 - Postprandial muscle protein synthesis rate is unaffected by 20-day habituation to a high protein intake

T2 - a randomized controlled, crossover trial

AU - Højfeldt, Grith

AU - Bülow, Jacob

AU - Agergaard, Jakob

AU - Simonsen, Lene R.

AU - Bülow, Jens

AU - Schjerling, Peter

AU - van Hall, Gerrit

AU - Holm, Lars

N1 - Publisher Copyright: © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.

PY - 2021

Y1 - 2021

N2 - Purpose: During the last decade more researchers have argued in favor of an increased protein intake for older adults. However, there is a lack of knowledge on the long-term effects of conforming to such a high protein intake with regards to the basal and postprandial muscle protein turnover. The purpose of this study was to compare the postprandial synthesis response in muscle proteins, and the abundance of directly incorporated food-derived amino acids following habituation to high vs. recommended level of protein intake. Methods: In a double blinded crossover intervention 11 older male participants (66.6 ± 1.7 years of age) were habituated for 20 days to a recommended protein (RP) intake (1.1 g protein/kg lean body mass (LBM)/day) and a high protein (HP) intake (> 2.1 g protein/kg LBM/day). Following each habituation period, intrinsically labelled proteins were ingested as part of a mixed meal to determine the incorporation of meal protein-derived amino acids into myofibrillar proteins. Furthermore, the myofibrillar fractional synthesis rate (FSR) and amino acid kinetics across the leg were determined using gold standard stable isotope tracer methodologies. RT qPCR was used to assess the expression of markers related to muscle proteinsynthesis and breakdown. Results: No impact of habituation was observed on skeletal muscle amino acid or protein kinetics. However, the shunting of amino acids directly from artery to vein was on average 2.9 μ mol/min higher following habituation to HP compared to RP. Conclusions: In older males, habituation to a higher than the currently recommended protein intake did not demonstrate any adaptions in the muscle protein turnover or markers hereof when subjected to an intake of an identical mixed meal. Clinical Trial Registry: Journal number NCT02587156, Clinicaltrials.org. Date of registration: October 27th, 2015.

AB - Purpose: During the last decade more researchers have argued in favor of an increased protein intake for older adults. However, there is a lack of knowledge on the long-term effects of conforming to such a high protein intake with regards to the basal and postprandial muscle protein turnover. The purpose of this study was to compare the postprandial synthesis response in muscle proteins, and the abundance of directly incorporated food-derived amino acids following habituation to high vs. recommended level of protein intake. Methods: In a double blinded crossover intervention 11 older male participants (66.6 ± 1.7 years of age) were habituated for 20 days to a recommended protein (RP) intake (1.1 g protein/kg lean body mass (LBM)/day) and a high protein (HP) intake (> 2.1 g protein/kg LBM/day). Following each habituation period, intrinsically labelled proteins were ingested as part of a mixed meal to determine the incorporation of meal protein-derived amino acids into myofibrillar proteins. Furthermore, the myofibrillar fractional synthesis rate (FSR) and amino acid kinetics across the leg were determined using gold standard stable isotope tracer methodologies. RT qPCR was used to assess the expression of markers related to muscle proteinsynthesis and breakdown. Results: No impact of habituation was observed on skeletal muscle amino acid or protein kinetics. However, the shunting of amino acids directly from artery to vein was on average 2.9 μ mol/min higher following habituation to HP compared to RP. Conclusions: In older males, habituation to a higher than the currently recommended protein intake did not demonstrate any adaptions in the muscle protein turnover or markers hereof when subjected to an intake of an identical mixed meal. Clinical Trial Registry: Journal number NCT02587156, Clinicaltrials.org. Date of registration: October 27th, 2015.

KW - Fractional synthesis rate

KW - Habituated protein intake

KW - High protein intake

KW - Intrinsically labelled proteins

KW - Protein breakdown

KW - Protein synthesis

KW - Recommended protein intake

U2 - 10.1007/s00394-021-02590-4

DO - 10.1007/s00394-021-02590-4

M3 - Journal article

C2 - 34032900

AN - SCOPUS:85106477940

VL - 60

SP - 4307

EP - 4319

JO - European Journal of Nutrition

JF - European Journal of Nutrition

SN - 1436-6207

ER -