Intake of branched-chain amino acids influences the levels of MAFbx mRNA and MuRF-1 total protein in resting and exercising human muscle

Am J Physiol Endocrinol Metab. 2012 Mar 1;302(5):E510-21. doi: 10.1152/ajpendo.00353.2011. Epub 2011 Nov 29.


Resistance exercise and amino acids are two major factors that influence muscle protein turnover. Here, we examined the effects of resistance exercise and branched-chain amino acids (BCAA), individually and in combination, on the expression of anabolic and catabolic genes in human skeletal muscle. Seven subjects performed two sessions of unilateral leg press exercise with randomized supplementation with BCAA or flavored water. Biopsies were collected from the vastus lateralis muscle of both the resting and exercising legs before and repeatedly after exercise to determine levels of mRNA, protein phosphorylation, and amino acid concentrations. Intake of BCAA reduced (P < 0.05) MAFbx mRNA by 30 and 50% in the resting and exercising legs, respectively. The level of MuRF-1 mRNA was elevated (P < 0.05) in the exercising leg two- and threefold under the placebo and BCAA conditions, respectively, whereas MuRF-1 total protein increased by 20% (P < 0.05) only in the placebo condition. Phosphorylation of p70(S6k) increased to a larger extent (∼2-fold; P < 0.05) in the early recovery period with BCAA supplementation, whereas the expression of genes regulating mTOR activity was not influenced by BCAA. Muscle levels of phenylalanine and tyrosine were reduced (13-17%) throughout recovery (P < 0.05) in the placebo condition and to a greater extent (32-43%; P < 0.05) following BCAA supplementation in both resting and exercising muscle. In conclusion, BCAA ingestion reduced MAFbx mRNA and prevented the exercise-induced increase in MuRF-1 total protein in both resting and exercising leg. Further-more, resistance exercise differently influenced MAFbx and MuRF-1 mRNA expression, suggesting both common and divergent regulation of these two ubiquitin ligases.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acids / blood
  • Amino Acids / metabolism
  • Amino Acids, Branched-Chain / administration & dosage*
  • Amino Acids, Branched-Chain / blood
  • Amino Acids, Branched-Chain / metabolism
  • Cross-Over Studies
  • Dietary Supplements*
  • Double-Blind Method
  • Female
  • Gene Expression Regulation*
  • Humans
  • Male
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism*
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Quadriceps Muscle / metabolism*
  • RNA, Messenger / metabolism
  • Resistance Training*
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • SKP Cullin F-Box Protein Ligases / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism*
  • Signal Transduction
  • TOR Serine-Threonine Kinases / metabolism
  • Tripartite Motif Proteins
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • Amino Acids
  • Amino Acids, Branched-Chain
  • Muscle Proteins
  • RNA, Messenger
  • Tripartite Motif Proteins
  • FBXO32 protein, human
  • SKP Cullin F-Box Protein Ligases
  • TRIM63 protein, human
  • Ubiquitin-Protein Ligases
  • MTOR protein, human
  • Ribosomal Protein S6 Kinases, 70-kDa
  • TOR Serine-Threonine Kinases
  • ribosomal protein S6 kinase, 70kD, polypeptide 1