Glucocorticoid-induced skeletal muscle atrophy is associated with upregulation of myostatin gene expression.

Abstract

The mechanisms by which excessive glucocorticoids cause muscular atrophy remain unclear. We previously demonstrated that dexamethasone increases the expression of myostatin, a negative regulator of skeletal muscle mass, in vitro. In the present study, we tested the hypothesis that dexamethasone-induced muscle loss is associated with increased myostatin expression in vivo. Daily administration (60, 600, 1,200 micro g/kg body wt) of dexamethasone for 5 days resulted in rapid, dose-dependent loss of body weight (-4.0, -13.4, -17.2%, respectively, P < 0.05 for each comparison), and muscle atrophy (6.3, 15.0, 16.6% below controls, respectively). These changes were associated with dose-dependent, marked induction of intramuscular myostatin mRNA (66.3, 450, 527.6% increase above controls, P < 0.05 for each comparison) and protein expression (0.0, 260.5, 318.4% increase above controls, P < 0.05). We found that the effect of dexamethasone on body weight and muscle loss and upregulation of intramuscular myostatin expression was time dependent. When dexamethasone treatment (600 micro g. kg-1. day-1) was extended from 5 to 10 days, the rate of body weight loss was markedly reduced to approximately 2% within this extended period. The concentrations of intramuscular myosin heavy chain type II in dexamethasone-treated rats were significantly lower (-43% after 5-day treatment, -14% after 10-day treatment) than their respective corresponding controls. The intramuscular myostatin concentration in rats treated with dexamethasone for 10 days returned to basal level. Concurrent treatment with RU-486 blocked dexamethasone-induced myostatin expression and significantly attenuated body loss and muscle atrophy. We propose that dexamethasone-induced muscle loss is mediated, at least in part, by the upregulation of myostatin expression through a glucocorticoid receptor-mediated pathway.

• Authors: Kun Ma, Con Mallidis, Shalender Bhasin, Vahid Mahabadi, Jorge Artaza, Nestor Gonzalez-Cadavid, Jose Arias, Behrouz Salehian
• Journal: American journal of physiology. Endocrinology and metabolism (Am J Physiol Endocrinol Metab) Vol. 285 Issue 2 Pg. E363-71 (Aug 2003) ISSN: 0193-1849 [Print] United States
• PMID: 12721153 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Glucocorticoids
• Mstn protein, rat
• Myostatin
• RNA, Messenger
• Receptors, Glucocorticoid
• Transforming Growth Factor beta
• Mifepristone
• Dexamethasone

Topics

• Animals
• Body Weight (drug effects)
• Dexamethasone (adverse effects, antagonists & inhibitors, pharmacology)
• Gene Expression Regulation (drug effects)
• Glucocorticoids (adverse effects)
• Kinetics
• Male
• Mifepristone (pharmacology)
• Muscle, Skeletal (chemistry, pathology)
• Muscular Atrophy (chemically induced)
• Myostatin
• Organ Size (drug effects)
• RNA, Messenger (analysis)
• Rats
• Rats, Sprague-Dawley
• Receptors, Glucocorticoid (physiology)
• Transforming Growth Factor beta (genetics)