title: Improved contractile function of the mdx dystrophic mouse diaphragm muscle after insulin-like growth factor-I administration.
abstract: Limited knowledge exists regarding the efficacy of insulin-like growth factor I (IGF-I) administration as a therapeutic intervention for muscular dystrophies, although findings from other muscle pathology models suggest clinical potential. The diaphragm muscles of mdx mice (a model for Duchenne muscular dystrophy) were examined after 8 weeks of IGF-I administration (1 mg/kg s.c.) to test the hypothesis that IGF-I would improve the functional properties of dystrophic skeletal muscles. Force per cross-sectional area was approximately 49% greater in the muscles of treated mdx mice (149.6 +/- 9.6 kN/m(2)) compared with untreated mice (100.1 +/- 4.6 kN/m(2), P < 0.05), and maintenance of force over repeated maximal contraction was enhanced approximately 30% in muscles of treated mice (P < 0.05). Diaphragm muscles from treated mice comprised fibers with approximately 36% elevated activity of the oxidative enzyme succinate dehydrogenase, and approximately 23% reduction in the proportion of fast IId/x muscle fibers with concomitant increase in the proportion of type IIa fibers compared with untreated mice (P < 0.05). The data demonstrate that IGF-I administration can enhance the fatigue resistance of respiratory muscles in an animal model of dystrophin deficiency, in conjunction with enhancing energenic enzyme activity. As respiratory function is a mortality predictor in Duchenne muscular dystrophy patients, further evaluation of IGF-I intervention is recommended.
authors.affiliation: Department of Physiology, The University of Melbourne, Victoria, Australia 3010.
authors.forename: Paul
authors.initials: P
authors.lastname: Gregorevic
authors.forename: David R
authors.initials: DR
authors.lastname: Plant
authors.forename: Kerri S
authors.initials: KS
authors.lastname: Leeding
authors.forename: Leon A
authors.initials: LA
authors.lastname: Bach
authors.forename: Gordon S
authors.initials: GS
authors.lastname: Lynch
mesh_terms: D000818:Animals; D003964:Diaphragm / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000502:physiology*; D009137:Muscular Dystrophy, Animal / Q000503:physiopathology; D020388:Muscular Dystrophy, Duchenne / Q000503:physiopathology*; D011897:Random Allocation; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D007334:Insulin-Like Growth Factor I; D013385:Succinate Dehydrogenase