(26-11-10) Exercising before protein intake allows for greater use of dietary protein-derived amino acids for

Exercising before protein intake allows for greater use of dietary protein-derived amino acids for de novo muscle protein synthesis in both young and elderly men.
Pennings B, Koopman R, Beelen M, Senden JM, Saris WH, van Loon LJ.

Top Institute Food & Nutrition, Wageningen, Netherlands.
Abstract
BACKGROUND: Sarcopenia seems to be attributed to a blunted muscle protein
synthetic response to food intake and exercise. This blunted response could be
the result of impaired protein digestion and absorption kinetics and lead to
lower postprandial plasma amino acid availability.

OBJECTIVE: The objective was to compare in vivo dietary protein digestion and
absorption kinetics and subsequent postprandial muscle protein synthesis rates
at rest and after exercise between young and elderly men.

DESIGN: Young and elderly men consumed a 20-g bolus of intrinsically l-[1-(13)
C]phenylalanine-labeled protein at rest or after exercise. Continuous infusions
with l-[ring-(2)H(5)]phenylalanine were applied, and blood and muscle samples
were collected to assess in vivo protein digestion and absorption kinetics and
subsequent postprandial muscle protein synthesis rates.

RESULTS: Exogenous phenylalanine appearance rates expressed over time did not
differ between groups. No differences were observed in plasma phenylalanine
availability between the young (51 ? 2%) and elderly (51 ? 1%) men or between
the rest (52 ? 1%) and exercise (49 ? 1%) conditions. Muscle protein synthesis
rates calculated from the oral tracer were 0.0620 ? 0.0065%/h and 0.0560 ?
0.0039%/h for the rest condition and 0.0719 ? 0.0057%/h and 0.0727 ? 0.0040%/h
for the exercise condition in young and elderly men, respectively (age effect:
P = 0.62; exercise effect: P < 0.05; interaction of age and exercise: P =
0.52).

CONCLUSIONS: Dietary protein digestion and absorption kinetics are not
impaired after exercise or at an older age. Exercising before protein intake
allows for a greater use of dietary protein-derived amino acids for de novo
muscle protein synthesis in both young and elderly men. This trial was
registered at clinicaltrials.gov as NCT00557388.

Source . Am J Clin Nutr. 2010 Nov 17. [Epub ahead of print]

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