Ursolic Acid-Induced Elevation of Serum Irisin Augments Muscle Strength During Resistance Training in Men
Hyun Seok Bang1,*, Dae Yun Seo2,*, Yong Min Chung3, Kyoung-Mo Oh4, Jung Jun Park5, Figueroa Arturo6, Seung-Hun Jeong2, Nari Kim2, and Jin Han2
1Division of Humanities and Social Science, POSTECH, Pohang 790-784, 2Department of Physiology, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan 614-735, 3Department of Physical Education, Tongmyong University, Busan 608-711, 4Department of Physical Education, Pukyong University, Busan 608-737, 5Division of Sport Science, Pusan National University, Busan 609-735, Korea, 6Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee FL 32306, USA
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Ursolic acid (UA), a type of pentacyclic triterpenoid carboxylic acid purified from natural plants, can promote skeletal muscle development. We measured the effect of resistance training (RT) with/without UA on skeletal muscle development and related factors in men. Sixteen healthy male participants (age, 29.37±5.14 years; body mass index=27.13±2.16 kg/m2) were randomly assigned to RT (n=7) or RT with UA (RT+UA, n=9) groups. Both groups completed 8 weeks of intervention consisting of 5 sets of 26 exercises, with 10~15 repetitions at 60~80% of 1 repetition maximum and a 60~90-s rest interval between sets, performed 6 times/week. UA or placebo was orally ingested as 1 capsule 3 times/day for 8 weeks. The following factors were measured pre-and post-intervention: body composition, insulin, insulin-like growth factor-1 (IGF-1), irisin, and skeletal muscle strength. Body fat percentage was significantly decreased (p<0.001) in the RT+UA group, despite body weight, body mass index, lean body mass, glucose, and insulin levels remaining unchanged. IGF-1 and irisin were significantly increased compared with baseline levels in the RT+UA group (p<0.05). Maximal right and left extension (p<0.01), right flexion (p<0.05), and left flexion (p<0.001) were significantly increased compared with baseline levels in the RT+UA group. These findings suggest that UA-induced elevation of serum irisin may be useful as an agent for the enhancement of skeletal muscle strength during RT.