Soy-Dairy Protein Blend and Whey Protein Ingestion After Resistance Exercise Increases Amino Acid Transport and Transporter Expression in Human Skeletal Muscle

Paul T. Reidy, Dillon K. Walker, Jared M. Dickinson, David M. Gundermann, Micah J. Drummond, Kyle L. Timmerman, Mark B. Cope, Ratna Mukherjea, Kris Jennings, Elena Volpi, Blake B. Rasmussen


Increasing amino acid availability (via infusion or ingestion) at rest or post-exercise enhances amino acid transport into human skeletal muscle. It is unknown whether alterations in amino acid availability, from ingesting different dietary proteins, can enhance amino acid transport rates and amino acid transporter (AAT) mRNA expression. We hypothesized that the prolonged hyperaminoacidemia from ingesting a blend of proteins with different digestion rates post-exercise would enhance amino acid transport into muscle and AAT expression as compared to the ingestion of a rapidly digested protein. In a double-blind, randomized clinical trial we studied 16 young adults at rest and after acute resistance exercise coupled with post-exercise (1h) ingestion of either a (soy-dairy) protein blend or whey protein. Phenylalanine net balance and transport rate into skeletal muscle were measured using stable isotopic methods in combination with femoral A-V blood sampling and muscle biopsies obtained at rest, 3 and 5h post-exercise. Phenylalanine transport into muscle and mRNA expression of select amino acid transporters (LAT1/SLC7A5, CD98/SLC3A2 SNAT2/SLC38A2, PAT1/SLC36A1, CAT1/SLC7A1) increased to a similar extent in both groups (P<0.05). However, the ingestion of the protein blend resulted in a prolonged and positive net phenylalanine balance during post-exercise recovery as compared to whey protein (P<0.05). Post-exercise myofibrillar protein synthesis increased similarly between groups. We conclude that while both protein sources enhanced post-exercise AAT expression, transport into muscle and myofibrillar protein synthesis, post-exercise ingestion of a protein blend results in a slightly prolonged net amino acid balance across the leg as compared to whey protein.

  • Protein Metabolism
  • Muscle Protein Synthesis
  • Leucine
  • mTORC1
  • Protein Anabolism