Carbohydrate does not augment exercise-induced protein accretion versus protein alone.
OBJECTIVE
We tested the thesis that CHO and protein coingestion would augment muscle protein synthesis (MPS) and inhibit muscle protein breakdown (MPB) at rest and after resistance exercise.


METHODS
Nine men (age=23.0±1.9 yr, body mass index=24.2±2.1 kg·m) performed two unilateral knee extension trials (four sets×8-12 repetitions to failure) followed by consumption of 25 g of whey protein (PRO) or 25 g of whey protein plus 50 g of maltodextrin (PRO+CARB). Muscle biopsies and stable isotope methodology were used to measure MPS and MPB.


RESULTS
The areas under the glucose and insulin curves were 17.5-fold (P<0.05) and 5-fold (P<0.05) greater, respectively, for PRO+CARB than for PRO. Exercise increased MPS and MPB (both P<0.05), but there were no differences between PRO and PRO+CARB in the rested or exercised legs. Phosphorylation of Akt was greater in the PRO+CARB than in the PRO trial (P<0.05); phosphorylations of Akt (P=0.05) and acetyl coA carboxylase-β (P<0.05) were greater after exercise than at rest. The concurrent ingestion of 50 g of CHO with 25 g of protein did not stimulate mixed MPS or inhibit MPB more than 25 g of protein alone either at rest or after resistance exercise.


CONCLUSIONS
Our data suggest that insulin is not additive or synergistic to rates of MPS or MPB when CHO is coingested with a dose of protein that maximally stimulates rates of MPS.
Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
Aaron W
AW
Staples
Nicholas A
NA
Burd
Daniel W D
DW
West
Katharine D
KD
Currie
Philip J
PJ
Atherton
Daniel R
DR
Moore
Michael J
MJ
Rennie
Maureen J
MJ
Macdonald
Steven K
SK
Baker
Stuart M
SM
Phillips
D000328:Adult; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism; D004435:Eating; D015444:Exercise; D006801:Humans; D007328:Insulin / Q000097:blood; D007717:Knee / Q000502:physiology; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D011134:Polysaccharides / Q000008:administration & dosage / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000067816:Whey Proteins; D055815:Young Adult
D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D007328:Insulin; D008894:Milk Proteins; D009124:Muscle Proteins; D011134:Polysaccharides; D000067816:Whey Proteins; C008315:maltodextrin; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; C033288:(acetyl-CoA carboxylase) kinase