Casein Ingestion Does Not Increase Muscle Connective Tissue Protein Synthesis Rates

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Abstract

Purpose This study aimed to assess the effect of dietary protein ingestion on intramuscular connective tissue protein synthesis rates during overnight recovery from a single bout of resistance exercise. Methods Thirty-six healthy, young males were randomly assigned to one of three treatments. One group ingested 30 g intrinsically L-[1-C-13]-phenylalanine-labeled casein protein before sleep (PRO,n= 12). The other two groups performed a bout of resistance exercise in the evening and ingested either placebo (EX,n= 12) or 30 g intrinsically L-[1-C-13]-phenylalanine-labeled casein protein before sleep (EX + PRO,n= 12). Continuous intravenous infusions of L-[ring-H-2(5)]-phenylalanine and L-[1-C-13]-leucine were applied, and blood and muscle tissue samples were collected to assess connective tissue protein synthesis rates and dietary protein-derived amino acid incorporation in the connective tissue protein fraction. Results Resistance exercise resulted in higher connective tissue protein synthesis rates when compared with rest (0.086 +/- 0.017%center dot h(-1)[EX] and 0.080 +/- 0.019%center dot h(-1)[EX + PRO] vs 0.059 +/- 0.016%center dot h(-1)[PRO];P<0.05). Postexercise casein protein ingestion did not result in higher connective tissue protein synthesis rates when compared with postexercise placebo ingestion (P= 1.00). Dietary protein-derived amino acids were incorporated into the connective tissue protein fraction at rest, and to a greater extent during recovery from exercise (P= 0.002). Conclusion Resistance exercise increases intramuscular connective tissue protein synthesis rates during overnight sleep, with no further effect of postexercise protein ingestion. However, dietary protein-derived amino acids are being used as precursors to supportde novoconnective tissue protein synthesis.

Original languageEnglish
Pages (from-to)1983-1991
Number of pages9
JournalMedicine and Science in Sports and Exercise
Volume52
Issue number9
DOIs
Publication statusPublished - Sep 2020

Keywords

  • COLLAGEN
  • INJURY
  • FORCE TRANSFER
  • LIGAMENT
  • TENDON
  • PROTEIN SUPPLEMENTATION
  • HUMAN SKELETAL-MUSCLE
  • ESSENTIAL AMINO-ACIDS
  • RESISTANCE EXERCISE
  • DIFFERENTIAL STIMULATION
  • LATERAL TRANSMISSION
  • YOUNG MEN
  • MYOFIBRILLAR
  • AUGMENTS
  • FORCE

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