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Strength, skeletal muscle composition, and enzyme activity in multiple sclerosis
J A Kent-Braun1, A V Ng, M Castro
1Department of Radiology, University of California, San Francisco 94121, California 94115, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 14, 1998
Summary
Skeletal muscle in multiple sclerosis (MS) patients shows reduced fiber size and aerobic energy capacity, suggesting disuse. These muscle changes may contribute to the excessive fatigue experienced by individuals with MS.
Area of Science:
- Neurology
- Skeletal Muscle Physiology
- Biochemistry
Background:
- Multiple sclerosis (MS) is a chronic neurological disease often associated with significant patient fatigue.
- The underlying causes of MS-related fatigue are not fully understood, with potential contributions from central nervous system and peripheral factors.
- Skeletal muscle adaptations may play a role in the functional impairments and fatigue observed in MS.
Purpose of the Study:
- To investigate whether specific intramuscular adaptations in skeletal muscle contribute to excessive fatigue in multiple sclerosis patients.
- To compare the functional, biochemical, and morphological characteristics of skeletal muscle between MS patients and healthy controls.
- To explore the relationship between skeletal muscle characteristics, physical activity, and symptomatic fatigue in MS.
Main Methods:
- Biopsies of the tibialis anterior muscle were analyzed from nine MS patients and eight healthy controls.
- Muscle fiber type distribution, cross-sectional area, and enzyme activities (succinic dehydrogenase [SDH] and alpha-glycerol-phosphate dehydrogenase [GPDH]) were assessed.
- Maximal voluntary isometric force, magnetic resonance imaging (MRI) for muscle cross-sectional area, and accelerometer-based physical activity were measured.
Main Results:
- MS patients exhibited fewer type I muscle fibers, smaller fiber sizes, and reduced SDH activity compared to controls.
- Skeletal muscle in MS patients showed a greater reliance on anaerobic energy supply.
- Muscle force production was significantly correlated with fiber size and muscle cross-sectional area; physical activity correlated with aerobic enzyme activity.
Conclusions:
- Skeletal muscle in MS patients demonstrates characteristics indicative of disuse, including smaller fiber size and reduced oxidative capacity.
- These intrinsic alterations in skeletal muscle structure and function are likely contributors to the impaired physical performance and excessive fatigue seen in MS.
- The findings highlight the importance of considering peripheral skeletal muscle changes in the management of MS-related functional deficits and fatigue.