Dexamethasone impairs muscle energetics, studied by (31)P NMR, in rats
J-F Dumas1, G Bielicki, J-P Renou
1Inserm EMI-U 00.18, Laboratoire de Biochimie et de Biologie Moléculaire, CHU, 4 rue Larrey, 49033 Angers Cedex, France.
Aims/Hypothesis:
Glucocorticoid treatments are associated with increased whole-body oxygen consumption. We hypothesised that an impairment of muscle energy metabolism can participate in this increased energy expenditure.
Methods:
To investigate this possibility, we have studied muscle energetics of dexamethasone-treated rats (1.5 mg kg(-1) day(-1) for 6 days), in vivo by (31)P NMR spectroscopy. Results were compared with control and pair-fed (PF) rats before and after overnight fasting.
Results:
Dexamethasone treatment resulted in decreased phosphocreatine (PCr) concentration and PCr:ATP ratio, increased ADP concentration and higher PCr to gamma-ATP flux but no change in beta-ATP to beta-ADP flux in gastrocnemius muscle. Neither 4 days of food restriction (PF rats) nor 24 h fasting affected high-energy phosphate metabolism. In dexamethasone-treated rats, there was an increase in plasma insulin and non-esterified fatty acid concentration.
Conclusions/Interpretation:
We conclude that dexamethasone treatment altered resting in vivo skeletal muscle energy metabolism, by decreasing oxidative phosphorylation, producing ATP at the expense of PCr.
