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Exercise and glucocorticoid-induced diaphragmatic myopathy
F K Lieu1, S K Powers, R A Herb
1Department of Exercise and Sport Sciences, University of Florida, Gainesville 32611.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1993
Summary
Glucocorticoids cause more severe muscle atrophy in less active muscles like the plantaris than in the diaphragm. Endurance exercise did not prevent this glucocorticoid-induced myopathy in either muscle type.
Area of Science:
- Muscle physiology
- Endocrinology
- Exercise science
Background:
- Glucocorticoids are potent regulators of muscle metabolism.
- Glucocorticoid-induced myopathy is a significant clinical concern, leading to muscle atrophy and weakness.
- The diaphragm, a chronically active muscle, may exhibit different responses to glucocorticoids compared to limb muscles.
Purpose of the Study:
- To investigate the differential susceptibility of the rat diaphragm and plantaris muscle to glucocorticoid-induced myopathy.
- To determine if endurance exercise training can attenuate glucocorticoid-induced muscle atrophy in these muscles.
- To examine the effects of prednisolone on muscle bioenergetic enzyme activities in relation to muscle type and exercise.
Main Methods:
- Rats were administered varying doses of prednisolone acetate or a sham solution over 10 days.
- Experimental groups included sedentary and endurance-trained rats.
- Muscle atrophy was assessed, and the activities of key bioenergetic enzymes (phosphofructokinase, 3-hydroxyacyl-CoA dehydrogenase, citrate synthase) were measured.
Main Results:
- Prednisolone-induced muscle atrophy was more pronounced in the plantaris compared to the diaphragm.
- High-dose prednisolone significantly altered enzyme activities in the plantaris (reduced phosphofructokinase, increased 3-hydroxyacyl-CoA dehydrogenase).
- In the diaphragm, high-dose prednisolone decreased citrate synthase activity but did not affect phosphofructokinase activity.
- Endurance exercise training did not antagonize prednisolone-induced myopathy in either muscle.
Conclusions:
- The diaphragm exhibits greater resistance to glucocorticoid-induced myopathy than the plantaris muscle.
- Endurance exercise does not protect against glucocorticoid-induced muscle atrophy in the diaphragm or plantaris.
- Differential effects on muscle bioenergetic enzymes suggest distinct mechanisms underlying glucocorticoid myopathy in different muscle types.