Muscle Physiology

Pflügers Archiv - European Journal of Physiology

, 457:1121

First online:

The physiological effects of IGF-1 (class 1:Ea transgene) over-expression on exercise-induced damage and adaptation in dystrophic muscles of mdx mice

  • James A. RidgleyAffiliated withSchool of Anatomy and Human Biology (M309), The University of Western Australia
  • , Gavin J. PinnigerAffiliated withSchool of Anatomy and Human Biology (M309), The University of Western AustraliaSchool of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia
  • , Peter W. HamerAffiliated withDiscipline of Physiotherapy, The University of Notre Dame Australia
  • , Miranda D. GroundsAffiliated withSchool of Anatomy and Human Biology (M309), The University of Western Australia Email author 

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Duchenne muscular dystrophy (DMD) is a genetic disorder in which muscle weakness and fragility contribute to ongoing muscle degeneration. Although exercise-induced muscle damage is associated with adaptation that protects normal muscle from further damage, exploiting this process to protect dystrophic muscle has been avoided for fear of inducing excessive muscle degeneration. However, muscle-specific over-expression of the class 1:Ea isoform of insulin-like growth factor-1 (IGF-1) reduces myofibre necrosis in dystrophic mdx mice (a model for DMD) and, therefore, may enhance the adaptation process in response to eccentric exercise. To test this hypothesis, we evaluated the effect of transgenic class 1:Ea IGF-1 over-expression on the susceptibility to muscle damage and subsequent adaptation in 12-week-old dystrophic mdx and non-dystrophic control mice. Experiments were conducted in vivo using a custom-built isokinetic mouse dynamometer to measure the deficit in joint torque (indicating muscle damage) after 20 maximal lengthening (eccentric) contractions. Adaptation to this damaging exercise was evaluated by repeating the protocol 7 days after the initial exercise. The over-expression of IGF-1 significantly increased the normalised joint torque in non-dystrophic mice and appeared to ameliorate the muscle weakness in dystrophic mice. All mice displayed a marked reduction in the susceptibility to muscle damage on day 7; however, this adaptation was unaffected by IGF-1, showing that IGF-1 does not protect the dystrophic muscles of adult mdx mice against damage resulting from maximal lengthening contractions.


Insulin-like growth factor Eccentric muscle damage Isokinetic dynamometer Duchenne muscular dystrophy Mdx mouse Dystrophy Muscle damage Muscle adaptation Mouse