2018 Volume 39 Pages 131-138
Proportions of muscle fiber types are responsible for a variety of properties of skeletal muscle, including contractile, metabolic, and sensory (differential tasting-component contents and fat deposition)．Therefore mechanisms that regulate these properties, and their manipulation are hot targets of research for human sports and health sciences and animal production. We recently found that resident myogenic stem satellite cells secrete semaphorin 3A (Sema3A) protein which exclusively impacts the formation of fatigue-resistant fibers (also called slow-twitch fibers) through a cell-membrane receptor (neuropilin2-plexinA3 complex) → myogenin/MEF2D/HDAC7 → slow-myosin signaling pathway 5)．Here we report that an 8-week intake of chlorogenic-acid rich materials (APP; polyphenol mixture prepared from unriped apples) in the diet, may stimulate the Sema3A-dependent pathway concerned. Results demonstrated improvement of lower hind-limb muscle endurance based on increased proportions of fatigue-resistant myofibers (types IIa and I) by the 0.5% APP-feeding to young-adult rats. There was no significant difference in the animal body-phenotypes or locomotor activity shown as total moving distance in light and dark periods. The result indicates that the shift in myosin heavy chain (MyHC) isoforms from fast-to-slow did not include a bias due to greater exercise behavior by the treated rats. Notably, a subsequent in vitro study showed that supplementation of APP (500 ng/ml) or the major component chlorogenic acid (10 ng/ml) also up-regulated the expression of slow MyHC and the up-stream signaling molecules, myogenin and MEF2D, in primary cultures of differentiating myoblasts. Other major polyphenols found in APP (procyanidin B1, B2, phloridzin, and catechin) in a range of 10-1000 ng/ml did not induce these effects. Therefore, the present study highlights a possible contribution of dietary chlorogenic acid intake to antagonizing the Sema3A-signaling pathway responsible for fatigue-resistant fiber formation. The finding may help in developing a novel strategy for application in human sports and age-related health sciences.
