Carbohydrate co-ingestion with protein does not further augment post-prandial muscle protein accretion in older men.
BACKGROUND
A blunted muscle protein synthetic response to protein ingestion may contribute to the age related loss of muscle tissue. We hypothesized that the greater endogenous insulin release following co-ingestion of carbohydrate facilitates post-prandial muscle protein accretion after ingesting a meal-like bolus of protein in older males.


METHODS
Twenty-four healthy older men (75±1 y) were randomly assigned to ingest 20 g intrinsically L-[1-13C] phenylalanine-labeled casein protein with (PRO-CHO) or without (PRO) 40 g carbohydrate. Ingestion of specifically produced intrinsically L-[1-13C] phenylalanine labeled protein allowed us to assess post-prandial incorporation of dietary protein derived amino acids into muscle protein. Blood samples were collected at regular intervals, with muscle biopsies being obtained prior to and 2 and 6 h after protein ingestion.


RESULTS
Plasma glucose and insulin concentrations showed a greater increase in PRO-CHO compared with PRO (P<0.001). Muscle protein-bound L-[1-13C] phenylalanine enrichments tended to increase to a greater extent in PRO-CHO compared with PRO during the first 2 h after protein ingestion (0.0072±0.0013 vs 0.0046±0.010 MPE, respectively; P=0.13). However, 6 h after protein ingestion, differences in muscle protein-bound L-[1-13C] phenylalanine enrichments were no longer observed between experiments (0.0213±0.0024 vs 0.0185±0.0010 MPE, respectively; P=0.30).


CONCLUSIONS
This study shows that carbohydrate ingestion may accelerate, but does not further augment post-prandial incorporation of dietary protein derived amino acids into muscle protein in healthy elderly men.
Department of Human Movement Sciences, Maastricht University Medical Centre, PO Box 616, Maastricht, MD, 6200, The Netherlands. l.vanloon@maastrichtuniversity.nl.
Henrike M
HM
Hamer
Benjamin T
BT
Wall
Alexandra
A
Kiskini
Anneke
A
de Lange
Bart Bl
BB
Groen
Jaap A
JA
Bakker
Annemie P
AP
Gijsen
Lex B
LB
Verdijk
Luc Jc
LJ
van Loon