Protein turnover and cellular stress in mildly and severely affected muscles from patients with limb girdle muscular dystrophy type 2I

PLoS One. 2013 Jun 28;8(6):e66929. doi: 10.1371/journal.pone.0066929. Print 2013.

Abstract

Patients with Limb girdle muscular dystrophy type 2I (LGMD2I) are characterized by progressive muscle weakness and wasting primarily in the proximal muscles, while distal muscles often are spared. Our aim was to investigate if wasting could be caused by impaired regeneration in the proximal compared to distal muscles. Biopsies were simultaneously obtained from proximal and distal muscles of the same patients with LGMD2I (n = 4) and healthy subjects (n = 4). The level of past muscle regeneration was evaluated by counting internally nucleated fibers and determining actively regenerating fibers by using the developmental markers embryonic myosin heavy chain (eMHC) and neural cell adhesion molecule (NCAM) and also assessing satellite cell activation status by myogenin positivity. Severe muscle histopathology was occasionally observed in the proximal muscles of patients with LGMD2I whereas distal muscles were always relatively spared. No difference was found in the regeneration markers internally nucleated fibers, actively regenerating fibers or activation status of satellite cells between proximal and distal muscles. Protein turnover, both synthesis and breakdown, as well as cellular stress were highly increased in severely affected muscles compared to mildly affected muscles. Our results indicate that alterations in the protein turnover and myostatin levels could progressively impair the muscle mass maintenance and/or regeneration resulting in gradual muscular atrophy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Case-Control Studies
  • Humans
  • Middle Aged
  • Muscle Development
  • Muscle Strength
  • Muscle, Skeletal / pathology*
  • Muscle, Skeletal / physiopathology
  • Muscular Dystrophies, Limb-Girdle / metabolism*
  • Muscular Dystrophies, Limb-Girdle / pathology
  • Protein Biosynthesis*
  • Regeneration
  • Stress, Physiological*

Supplementary concepts

  • Muscular Dystrophy, Limb-Girdle, Type 2I

Grants and funding

This work was supported by grants from the Danish Medical Research Council, the University of Copenhagen, the Novo Nordisk Foundation and the Lundbeck Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.