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Am J Physiol Regul Integr Comp Physiol. 2007 Jan;292(1):R328-36. Epub 2006 Aug 31.

Burn-induced increase in atrogin-1 and MuRF-1 in skeletal muscle is glucocorticoid independent but downregulated by IGF-I.

Author information

1
Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA. clang@psu.edu

Abstract

The present study determined whether thermal injury increases the expression of the ubiquitin (Ub) E3 ligases referred to as muscle ring finger (MuRF)-1 and muscle atrophy F-box (MAFbx; aka atrogin-1), which are muscle specific and responsible for the increased protein breakdown observed in other catabolic conditions. After 48 h of burn injury (40% total body surface area full-thickness scald burn) gastrocnemius weight was reduced, and this change was associated with an increased mRNA abundance for atrogin-1 and MuRF-1 (3.1- to 8-fold, respectively). Similarly, burn increased polyUb mRNA content in the gastrocnemius twofold. In contrast, there was no burn-induced atrophy of the soleus and no significant change in atrogin-1, MuRF-1, or polyUb mRNA. Burns also did not alter E3 ligase expression in heart. Four hours after administration of the anabolic agent insulin-like growth factor (IGF)-I to burned rats, the mRNA content of atrogin-1 and polyUb in gastrocnemius had returned to control values and the elevation in MuRF-1 was reduced 50%. In contrast, leucine did not alter E3 ligase expression. In a separate study, in vivo administration of the proteasome inhibitor Velcade prevented burn-induced loss of muscle mass determined at 48 h. Finally, administration of the glucocorticoid receptor antagonist RU-486 did not prevent burn-induced atrophy of the gastrocnemius or the associated elevation in atrogin-1, MuRF-1, or polyUb. In summary, the acute muscle wasting accompanying thermal injury is associated with a glucocorticoid-independent increase in the expression of several Ub E3 ligases that can be downregulated by IGF-I.

PMID:
16946078
DOI:
10.1152/ajpregu.00561.2006
[Indexed for MEDLINE]
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