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Skeletal muscle bioenergetics in myotonic dystrophy
D J Taylor1, G J Kemp, C G Woods
1MRC Biochemical and Clinical Magnetic Resonance Unit, John Radcliffe Hospital, Oxford, UK.
Journal of the Neurological Sciences
|June 1, 1993
Summary
Skeletal muscle bioenergetics in myotonic dystrophy (DM) patients show altered energy stores but normal oxidative capacity. Muscle acidification during exercise is reduced, suggesting rapid proton efflux, not impaired mitochondrial function.
Area of Science:
- Biochemistry
- Physiology
- Neuromuscular Disorders
Background:
- Myotonic dystrophy (DM) is a genetic disorder affecting muscle function.
- The role of mitochondrial metabolism in DM muscle dysfunction is not fully understood.
Purpose of the Study:
- To investigate skeletal muscle bioenergetics and intracellular pH in DM patients.
- To compare DM patients with normal controls and mitochondrial myopathy patients.
Main Methods:
- 31P magnetic resonance spectroscopy was used to assess muscle function.
- Intracellular pH, energy metabolites (ATP, Pi, phosphocreatine), and recovery kinetics were measured at rest, during exercise, and during recovery.
Main Results:
- Resting DM muscle showed elevated Pi/ATP, phosphomonoesters/ATP, and phosphodiesters/ATP ratios.
- Exercise led to rapid energy store depletion in DM, similar to mitochondrial myopathy.
- DM muscles acidified less during exercise than normal muscle, with faster pH recovery.
- Oxidative capacity in DM muscles was not decreased, as indicated by normal phosphocreatine repletion rates.
Conclusions:
- DM muscle dysfunction is not primarily due to impaired mitochondrial oxidative capacity.
- Reduced acidification during exercise in DM may result from rapid proton efflux.
- Potential minor abnormalities in glycogenolysis cannot be excluded.