Author(s): AUSSIEKER, T., HERMANS, W.J.H., KAISER, J., HENDRIKS, F.K., HOLWERDA, A.M., SENDEN, J.M., VAN KRANENBURG, J.M.X., GOESSENS, J.P.B., SNIJDERS, T., VAN LOON, L.J.C., Institution: MAASTRICHT UNIVERSITY, Country: NETHERLANDS, Abstract-ID: 611

INTRODUCTION:
Ingestion of whey protein has been reported to increase myofibrillar but not muscle connective protein synthesis rates both at rest as well as during recovery from exercise. It has been speculated that the inability of whey protein ingestion to increase muscle connective protein synthesis rates is attributed to an insufficient provision of glycine as a precursor for de novo collagen synthesis. Recently, we defined a whey and collagen protein blend (5:1 ratio) to improve post-prandial plasma glycine availability following protein ingestion. The present study assessed the ability of such a whey and collagen protein blend to increase both myofibrillar and muscle connective protein synthesis rates both at rest and during recovery from exercise.
METHODS:
In a randomized, double-blind, parallel design, 28 young men (age: 25±5 y; BMI: 23.6±2.3 kg/m2) were randomly allocated to receive either 30 g of protein (25 g whey and 5 g collagen protein; BLEND, n=14) or a non-caloric placebo (PLA, n=14). Subjects received primed continuous intravenous infusions with L-[ring-13C6]-phenylalanine. Following a single session of unilateral leg resistance type exercise (leg press and leg extension), subjects ingested either BLEND or PLA. Blood and muscle biopsy (both legs) samples were collected in post-absorptive state, immediately after ingestion and over a subsequent 5 h recovery period to assess both myofibrillar and muscle connective protein synthesis rates. Time-dependent variables were analyzed by a two-factor repeated-measures ANOVA. Non-time-dependent variables were compared between treatment groups using an independent t-test. A statistical level of P<0.05 was accepted. All data are expressed as mean±SD.
RESULTS:
Protein ingestion strongly increased plasma amino acid concentrations, including plasma leucine, glycine, and proline concentrations (P<0.001), whilst placebo ingestion showed no changes (P>0.05). There were no differences in post-absorptive myofibrillar and muscle connective protein synthesis rates between treatments (P>0.05). Post-prandial myofibrillar and muscle connective protein synthesis rates were higher in the exercised compared with the rested leg (P<0.001). In addition, myofibrillar protein synthesis rates were higher in BLEND compared to PLA in both the rested (0.038±0.008 and 0.031±0.006%/h, respectively; P<0.05) and exercised (0.052±0.011 and 0.039±0.009%/h, respectively; P<0.01) leg. Muscle connective protein synthesis rates were higher in BLEND compared to PLA in the rested (0.062±0.013 and 0.051±0.010%/h, respectively; P<0.05), but not the exercised (0.090±0.021 and 0.079±0.016%/h, respectively; P=0.11) leg.
CONCLUSION:
Ingestion of a blend containing whey (25 g) plus collagen (5 g) protein increases both myofibrillar and muscle connective protein synthesis rates at rest and further increases myofibrillar but not muscle connective protein synthesis rates during recovery from exercise in recreationally active, young men.