Introduction: Ursolic Acid (UA) is a lipophilic triterpenoid compound, found in large amounts in apple peel. Anabolic effects of UA on the skeletal muscle and the role of this tissue as a key regulator of systematic aging aroused this question in mind whether UA might amend skeletal muscle performances such as myoglobin expression and also whether it switches skeletal muscle fibers from glycolytic to oxidative. Methods: In this study, 20 male C57BL/6 mice, aged 10 months, were used and divided to 2 groups. One group received UA (200 mg/kg) + corn oil as vehicle, and the other group was given only corn oil, intraperitoneally. Injection was done twice a day for 7 days, after which skeletal muscle was isolated and evaluated for myoglobin expression and fiber typing by western blotting and mATPase histochemistry techniques. Results: UA caused myoglobin over-expression (p<0/01). It also changed anaerobic glycolytic muscle fibers into fast-oxidative (~ 30%) and slow-oxidative (4%) fibers. Conclusion: It seems that UA mimics beneficial effects of exercise through up-regulation of myoglobin expression and switching of muscle fiber types into oxidative fibers. It may be proposed as a good candidate for treatment of skeletal muscle dysfunction.

Keywords: Ursolic Acid, Myoglobin, Skeletal Muscle, Slow-oxidative, Fast-oxidative.

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