title: Strength, skeletal muscle composition, and enzyme activity in multiple sclerosis.
abstract: This study examined functional, biochemical, and morphological characteristics of skeletal muscle in nine multiple sclerosis (MS) patients and eight healthy controls in an effort to ascertain whether intramuscular adaptations could account for excessive fatigue in this disease. Analyses of biopsies of the tibialis anterior muscle showed that there were fewer type I fibers (66 +/- 6 vs. 76 +/- 6%), and that fibers of all types were smaller (average downward arrow26%) and had lower succinic dehydrogenase (SDH; average downward arrow40%) and SDH/alpha-glycerol-phosphate dehydrogenase (GPDH) but not GPDH activities in MS vs. control subjects, suggesting that muscle in this disease is smaller and relies more on anaerobic than aerobic-oxidative energy supply than does muscle of healthy individuals. Maximal voluntary isometric force for dorsiflexion was associated with both average fiber cross-sectional area (r = 0.71, P = 0.005) and muscle fat-free cross-sectional area by magnetic resonance imaging (r = 0.80, P < 0. 001). Physical activity, assessed by accelerometer, was associated with average fiber SDH/GPDH (r = 0.78, P = 0.008). There was a tendency for symptomatic fatigue to be inversely associated with average fiber SDH activity (r = -0.57, P = 0.068). The results of this study suggest that the inherent characteristics of skeletal muscle fibers per se and of skeletal muscle as a whole are altered in the direction of disuse in MS. They also suggest that changes in skeletal muscle in MS may significantly affect function.
authors.affiliation: Department of Radiology, University of California, San Francisco 94121, California 94115, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Kent-Braun
authors.forename: A V
authors.initials: AV
authors.lastname: Ng
authors.forename: M
authors.initials: M
authors.lastname: Castro
authors.forename: M W
authors.initials: MW
authors.lastname: Weiner
authors.forename: D
authors.initials: D
authors.lastname: Gelinas
authors.forename: G A
authors.initials: GA
authors.lastname: Dudley
authors.forename: R G
authors.initials: RG
authors.lastname: Miller
mesh_terms: D000328:Adult; D001823:Body Composition / Q000502:physiology; D005260:Female; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000201:enzymology* / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000503:physiopathology*; D009412:Nerve Fibers / Q000502:physiology / Q000648:ultrastructure; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D005993:Glycerolphosphate Dehydrogenase; D013385:Succinate Dehydrogenase