Cited by 115Muscle Physiology and DisordersMuscle metabolism and nutritionSpaceflight effects on biology

Clenbuterol induces muscle-specific attenuation of atrophy through effects on the ubiquitin-proteasome pathway

Yimlamai, Tossaporn, Dodd, Stephen L., Borst, Stephen E., Park, Sooyeon·2005·Journal of Applied Physiology

Abstract

The ubiquitin-proteasome pathway is primarily responsible for myofibrillar protein degradation during hindlimb unweighting (HU). Beta-adrenergic agonists such as clenbuterol (CB) induce muscle hypertrophy and attenuate muscle atrophy due to disuse or inactivity. However, the molecular mechanism by which CB exerts these effects remains poorly understood. The aims of this study were to investigate whether CB attenuates HU-induced muscle atrophy through an inhibition of the ubiquitin-proteasome pathway and whether insulin-like growth factor I (IGF-I) mediates this inhibition. Rats were randomized to the following groups: weight-bearing control, 14-day CB-treated, 14-day HU, and CB + HU. HU-induced atrophy was associated with increased proteolysis and upregulation of components of the ubiquitin-proteasome pathway (ubiquitin conjugates, ubiquitin conjugating enzyme E2-14 kDa, and 20S proteasome activity). Upregulation of the ubiquitin proteasome occurred in all muscles tested but was more pronounced in muscles composed primarily of slow-twitch fibers (soleus) than in fast-twitch muscles (plantaris and tibialis anterior). Although CB induced hypertrophy in all muscles, CB attenuated the HU-induced atrophy and reduced ubiquitin conjugates only in the fast plantaris and tibialis anterior and not in the slow soleus muscle. CB did not elevate IGF-I protein content in either of the muscles examined. These results suggest that CB induces hypertrophy and alleviates HU-induced atrophy, particularly in the fast muscles, at least in part through a muscle-specific inhibition of the ubiquitin-proteasome pathway and that these effects are not mediated by the local production of IGF-I in skeletal muscle.

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Crossref · 10.1152/japplphysiol.00448.2004

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Authors
Yimlamai, T., Dodd, S. L., Borst, S. E., & Park, S.
Affiliations
University of Florida (US)
Venue
Journal of Applied Physiology
Published
2005-07
Volume
99
Issue
1
Pages
71-80
ISSN
  • 0161-7567 (ISSN-L)
  • 8750-7587
  • 1522-1601
OpenAlex
W2031235555
Cited by
115
References
55
Citations by year
2026: 1 · 2024: 4 · 2023: 2 · 2022: 1 · 2021: 5 · 2020: 4 · 2019: 4 · 2018: 4 · 2017: 1 · 2016: 6 · 2015: 5 · 2014: 4 · 2013: 8 · 2012: 8
FWCI
3.87
Type
journal article
Language
en
Open access
closed
Locations
  • Journal of Applied Physiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Health Sciences › Medicine › Physiology › Spaceflight effects on biology
Keywords
clenbuterol, muscle atrophy, ubiquitin-proteasome system, hindlimb unloading, beta-adrenergic agonists, muscle hypertrophy, insulin-like growth factor I, skeletal muscle proteolysis, fast-twitch muscle, slow-twitch muscle, soleus muscle, plantaris, tibialis anterior, 20S proteasome
MeSH terms
Administration, Oral, Animals, Clenbuterol, Female, Gene Expression Regulation, Insulin-Like Growth Factor I, Muscular Atrophy, Signal Transduction, Rats, Sprague-Dawley, Muscle, Skeletal, Hindlimb Suspension, Ubiquitin, Proteasome Endopeptidase Complex, Rats

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