| Summary: | <p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>Twenty-four healthy older men (75±1 y) were randomly assigned to ingest 20 g intrinsically L-[1-<sup>13</sup>C] phenylalanine-labeled casein protein with (PRO-CHO) or without (PRO) 40 g carbohydrate. Ingestion of specifically produced intrinsically L-[1-<sup>13</sup>C] 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.</p> <p>Results</p> <p>Plasma glucose and insulin concentrations showed a greater increase in PRO-CHO compared with PRO (<it>P</it><0.001). Muscle protein-bound L-[1-<sup>13</sup>C] 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; <it>P</it>=0.13). However, 6 h after protein ingestion, differences in muscle protein-bound L-[1-<sup>13</sup>C] phenylalanine enrichments were no longer observed between experiments (0.0213±0.0024 vs 0.0185±0.0010 MPE, respectively; <it>P</it>=0.30).</p> <p>Conclusions</p> <p>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.</p>
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