Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disease, and numerous recent findings suggest that several pathologic signs, including loss of muscle strength and mass, are also detected in these patients. In the present study, we evaluated muscle cross-sectional area (CSA), myonuclear number, satellite cell (SC) content, and myosin heavy chain (MyHC) types in an animal model of AD and examined the possible role of resistance training in controlling skeletal muscle size in this disease. Fifty-eight male rats were randomly divided into four groups: healthy-control (H-C), healthy-exercise (H-Ex), Alzheimer-control (A-C), and Alzheimer-exercise (A-Ex). AD was induced by the single injection of 1-42 amyloid into the CA1 region of the hippocampus (1 μl/site). The rats in H-Ex and A-Ex groups performed a 5-week resistance training period (17 sessions). The results indicated that AD induces significant skeletal muscle atrophy and reduces the myonuclear number and SC content in gastrocnemius muscle in both whole muscle cross-sections and isolated myofibers. Interestingly, we did not find any significant differences in the different MyHC distributions of AD animals compared with controls, while resistance training significantly increased the CSA of MyHC IIb fibers in both AD and healthy animals. Altogether, these observations suggest that the skeletal muscle of AD animals are more prone to atrophy and loss of myonuclear number and satellite cell content, while resistance training successfully restores these impairments.