Endurance capacity in maturing mdx mice is markedly enhanced by combined voluntary wheel running and green tea extract.

Duchenne muscular dystrophy is characterized by the absence of dystrophin from muscle cells. Dystrophic muscle cells are susceptible to oxidative stress. We tested the hypothesis that 3 wk of endurance exercise starting at age 21 days in young male mdx mice would blunt oxidative stress and improve dystrophic skeletal muscle function, and these effects would be enhanced by the antioxidant green tea extract (GTE). In mice fed normal diet, average daily running distance increased 300% from week 1 to week 3, and total distance over 3 wk was improved by 128% in mice fed GTE. Running, independent of diet, increased serum antioxidant capacity, extensor digitorum longus tetanic stress, and total contractile protein content, heart citrate synthase, and heart and quadriceps beta-hydroxyacyl-CoA dehydrogenase activities. GTE, independent of running, decreased serum creatine kinase and heart and gastrocnemius lipid peroxidation and increased gastrocnemius citrate synthase activity. These data suggest that both endurance exercise and GTE may be beneficial as therapeutic strategies to improve muscle function in mdx mice.

Passive mechanical properties of maturing extensor digitorum longus are not affected by lack of dystrophin.

Mechanical weakness of skeletal muscle is thought to contribute to onset and early progression of Duchenne muscular dystrophy, but this has not been systematically assessed. The purpose of this study was to determine in mice: (1) whether the passive mechanical properties of maturing dystrophic (mdx) muscles were different from control; and (2) if different, the time during maturation when these properties change. Prior to and following the overt onset of the dystrophic process (14-35 days), control and dystrophic extensor digitorum longus (EDL) muscles were subjected to two passive stretch protocols in vitro (5% strain at instantaneous and 1.5 L(0)/s strain rates). Force profiles were fit to a viscoelastic muscle model to determine stiffness and damping. The mdx and control EDL muscles exhibited similar passive mechanical properties at each age, suggesting a functional threshold for dystrophic muscle below which damage may be minimized. Determining this threshold may have important clinical implications for treatments of muscular dystrophy involving physical activity.