Postexercise essential amino acid supplementation amplifies skeletal muscle satellite cell proliferation in older men 24 hours postexercise

Physiol Rep. 2017 Jun;5(11):e13269. doi: 10.14814/phy2.13269.

Abstract

Aged skeletal muscle has an attenuated and delayed ability to proliferate satellite cells in response to resistance exercise. The mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway is a focal point for cell growth, however, the effect of postexercise mTORC1 activation on human skeletal muscle satellite cell (SC) proliferation is unknown. To test the proliferative capacity of skeletal muscle SC in aging muscle to a potent mTORC1 activator (i.e., EAA; essential amino acids) we recruited older (~72y) men to conduct leg resistance exercise (8setsx10reps) without (-EAA; n = 8) and with (+EAA: n = 11) ingestion of 10 g of EAA 1 h postexercise. Muscle biopsies were taken before exercise (Pre) and 24 h postexercise (Post) for assessment of expression and fiber type-specific Pax7+ SC, Ki67+Pax7+ SC and MyoD+ SC -EAA did not show an increase in Pax7+ satellite cells at Post(P > 0.82). Although statistical significance for an increase in Pax7 + SC at 24 h post-RE was not observed in +EAA versus -EAA, we observed trends for a treatment difference (P < 0.1). When examining the change from Pre to Post trends were demonstrated (#/myofiber: P = 0.076; and %/myonuclei: P = 0.065) for a greater increase in +EAA versus -EAA Notably, we found an increase SC proliferation in +EAA, but not -EAA with increase in Ki67+ SC and MyoD+ cells (P < 0.05). Ki67+ SC also exhibited a significant group difference Post (P < 0.010). Pax7+ SC in fast twitch myofibers did not change and were not different between groups (P > 0.10). CDK2, MEF2C, RB1 mRNA only increased in +EAA (P < 0.05). Acute muscle satellite cell proliferative capacity may be partially rescued with postexercise EAA ingestion in older men.

Keywords: Stem cell activation; strength training.

MeSH terms

  • Aged
  • Amino Acids, Essential / administration & dosage
  • Amino Acids, Essential / pharmacology*
  • Case-Control Studies
  • Cell Proliferation*
  • Cyclin-Dependent Kinase 2 / genetics
  • Cyclin-Dependent Kinase 2 / metabolism
  • Dietary Supplements
  • Humans
  • Ki-67 Antigen / genetics
  • Ki-67 Antigen / metabolism
  • Male
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / physiology
  • MyoD Protein / genetics
  • MyoD Protein / metabolism
  • PAX7 Transcription Factor / genetics
  • PAX7 Transcription Factor / metabolism
  • Resistance Training*
  • Retinoblastoma Binding Proteins / genetics
  • Retinoblastoma Binding Proteins / metabolism
  • Satellite Cells, Skeletal Muscle / drug effects*
  • Satellite Cells, Skeletal Muscle / metabolism
  • Satellite Cells, Skeletal Muscle / physiology
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism

Substances

  • Amino Acids, Essential
  • Ki-67 Antigen
  • MyoD Protein
  • MyoD1 myogenic differentiation protein
  • PAX7 Transcription Factor
  • PAX7 protein, human
  • RB1 protein, human
  • Retinoblastoma Binding Proteins
  • Ubiquitin-Protein Ligases
  • CDK2 protein, human
  • Cyclin-Dependent Kinase 2