The effect of young and old ex vivo human serum on cellular protein synthesis and growth in an in vitro model of aging

Sophie L Allen, Ryan N Marshall, Sophie J Edwards, Janet M Lord, Gareth G Lavery, Leigh Breen

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In vitro models of muscle aging are useful for understanding mechanisms of age-related muscle loss and aiding the development of targeted therapies. To investigate mechanisms of age-related muscle loss in vitro utilizing ex vivo human serum, fasted blood samples were obtained from four old (72 ± 1 yr) and four young (26 ± 3 yr) men. Older individuals had elevated levels of plasma CRP, IL-6, HOMA-IR, and lower concentric peak torque and work-per-repetition compared with young participants ( P < 0.05). C2C12 myotubes were serum and amino acid starved for 1 h and conditioned with human serum (10%) for 4 h or 24 h. After 4 h, C2C12 cells were treated with 5 mM leucine for 30 min. Muscle protein synthesis (MPS) was determined through the surface sensing of translation (SUnSET) technique and regulatory signaling pathways were measured via Western blot. Myotube diameter was significantly reduced in myotubes treated with serum from old, in comparison to young donors (84%, P < 0.001). MPS was reduced in myotubes treated with old donor serum, compared with young serum before leucine treatment (32%, P < 0.01). MPS and the phosphorylation of Akt, p70S6K, and eEF2 were increased in myotubes treated with young serum in response to leucine treatment, with a blunted response identified in cells treated with old serum ( P < 0.05). Muscle protein breakdown signaling pathways did not differ between groups. In summary, we show that myotubes conditioned with serum from older individuals had decreased myotube diameter and MPS compared with younger individuals, potentially driven by low-grade systemic inflammation.

Original languageEnglish
Pages (from-to)C26-C37
Number of pages12
JournalAJP: Cell Physiology
Issue number1
Early online date28 Jun 2021
Publication statusPublished - 1 Jul 2021

Bibliographical note

Funding Information:
The study was funded by the National Institute for Health Research (NIHR) Birmingham Biomedical Research Centre Grant BRC-1215-20009.

Publisher Copyright:
Copyright © 2021 The Authors.


  • Anabolic resistance
  • Leucine
  • Muscle protein synthesis
  • Serum
  • Skeletal muscle cells

ASJC Scopus subject areas

  • Physiology
  • Cell Biology


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