Whey and casein labelled with L-[1-13C]-leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion

Søren Reitelseder, Jakob Agergaard, Simon Doessing, I C Helmark, P Lund, N.B. Kristensen, Jan Frystyk, Allan Flyvbjerg, Peter Schjerling, G van Hall, Michael Kjær, Lars Holm

Research output: Contribution to journalArticlepeer-review

129 Citations (Scopus)


Muscle protein turnover following resistance exercise and amino acid availability are relatively well described. By contrast, the beneficial effects of different sources of intact proteins in relation to exercise need further investigation. Our objective was to compare muscle anabolic responses to a single bolus intake of whey or casein after performance of heavy resistance exercise. Young male individuals were randomly assigned to participate in two protein trials (n = 9) or one control trial (n = 8). Infusion of l-[1-(13)C]leucine was carried out, and either whey, casein (0.3 g/kg lean body mass), or a noncaloric control drink was ingested immediately after exercise. l-[1-(13)C]leucine-labeled whey and casein were used while muscle protein synthesis (MPS) was assessed. Blood and muscle tissue samples were collected to measure systemic hormone and amino acid concentrations, tracer enrichments, and myofibrillar protein synthesis. Western blots were used to investigate the Akt signaling pathway. Plasma insulin and branched-chain amino acid concentrations increased to a greater extent after ingestion of whey compared with casein. Myofibrillar protein synthesis was equally increased 1-6 h postexercise after whey and casein intake, both of which were higher compared with control (P <0.05). Phosphorylation of Akt and p70(S6K) was increased after exercise and protein intake (P <0.05), but no differences were observed between the types of protein except for total 4E-BP1, which was higher after whey intake than after casein intake (P <0.05). In conclusion, whey and casein intake immediately after resistance exercise results in an overall equal MPS response despite temporal differences in insulin and amino acid concentrations and 4E-BP1.
Original languageEnglish
Pages (from-to)E231-242
JournalAmerican Journal of Physiology: Endocrinology and Metabolism
Issue number1
Publication statusPublished - 1 Jan 2011


  • Adaptor Proteins, Signal Transducing
  • Adult
  • Amino Acids
  • Carbon Isotopes
  • Caseins
  • Dietary Proteins
  • Food, Formulated
  • Humans
  • Insulin
  • Leucine
  • Male
  • Milk Proteins
  • Muscle Proteins
  • Myofibrils
  • Phosphoproteins
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt
  • Resistance Training
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Signal Transduction
  • Single-Blind Method


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