Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men.
BACKGROUND
The anabolic effect of resistance exercise is enhanced by the provision of dietary protein.


OBJECTIVE
We aimed to determine the ingested protein dose response of muscle (MPS) and albumin protein synthesis (APS) after resistance exercise. In addition, we measured the phosphorylation of candidate signaling proteins thought to regulate acute changes in MPS.


METHODS
Six healthy young men reported to the laboratory on 5 separate occasions to perform an intense bout of leg-based resistance exercise. After exercise, participants consumed, in a randomized order, drinks containing 0, 5, 10, 20, or 40 g whole egg protein. Protein synthesis and whole-body leucine oxidation were measured over 4 h after exercise by a primed constant infusion of [1-(13)C]leucine.


RESULTS
MPS displayed a dose response to dietary protein ingestion and was maximally stimulated at 20 g. The phosphorylation of ribosomal protein S6 kinase (Thr(389)), ribosomal protein S6 (Ser(240/244)), and the epsilon-subunit of eukaryotic initiation factor 2B (Ser(539)) were unaffected by protein ingestion. APS increased in a dose-dependent manner and also reached a plateau at 20 g ingested protein. Leucine oxidation was significantly increased after 20 and 40 g protein were ingested.


CONCLUSIONS
Ingestion of 20 g intact protein is sufficient to maximally stimulate MPS and APS after resistance exercise. Phosphorylation of candidate signaling proteins was not enhanced with any dose of protein ingested, which suggested that the stimulation of MPS after resistance exercise may be related to amino acid availability. Finally, dietary protein consumed after exercise in excess of the rate at which it can be incorporated into tissue protein stimulates irreversible oxidation.
Moore
Daniel R
DR
Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Canada.
Robinson
Meghann J
MJ
Fry
Jessica L
JL
Tang
Jason E
JE
Glover
Elisa I
EI
Wilkinson
Sarah B
SB
Prior
Todd
T
Tarnopolsky
Mark A
MA
Phillips
Stuart M
SM
D002247:Carbon Isotopes; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D015387:Egg Proteins, Dietary / Q000008:administration & dosage*; D006801:Humans; D007930:Leucine / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010766:Phosphorylation; D012709:Serum Albumin / Q000096:biosynthesis*; D014891:Weight Lifting / Q000502:physiology*; D055815:Young Adult
D002247:Carbon Isotopes; D015387:Egg Proteins, Dietary; D009124:Muscle Proteins; D012709:Serum Albumin; D007930:Leucine