title: Green tea extract attenuates muscle loss and improves muscle function during disuse, but fails to improve muscle recovery following unloading in aged rats.
abstract: In this study we tested the hypothesis that green tea extract (GTE) would improve muscle recovery after reloading following disuse. Aged (32 mo) Fischer 344 Brown Norway rats were randomly assigned to receive either 14 days of hindlimb suspension (HLS) or 14 days of HLS followed by normal ambulatory function for 14 days (recovery). Additional animals served as cage controls. The rats were given GTE (50 mg/kg body wt) or water (vehicle) by gavage 7 days before and throughout the experimental periods. Compared with vehicle treatment, GTE significantly attenuated the loss of hindlimb plantaris muscle mass (-24.8% vs. -10.7%, P < 0.05) and tetanic force (-43.7% vs. -25.9%, P <0.05) during HLS. Although GTE failed to further improve recovery of muscle function or mass compared with vehicle treatment, animals given green tea via gavage maintained the lower losses of muscle mass that were found during HLS (-25.2% vs. -16.0%, P < 0.05) and force (-45.7 vs. -34.4%, P < 0.05) after the reloading periods. In addition, compared with vehicle treatment, GTE attenuated muscle fiber cross-sectional area loss in both plantaris (-39.9% vs. -23.9%, P < 0.05) and soleus (-37.2% vs. -17.6%) muscles after HLS. This green tea-induced difference was not transient but was maintained over the reloading period for plantaris (-45.6% vs. -21.5%, P <0.05) and soleus muscle fiber cross-sectional area (-38.7% vs. -10.9%, P <0.05). GTE increased satellite cell proliferation and differentiation in plantaris and soleus muscles during recovery from HLS compared with vehicle-treated muscles and decreased oxidative stress and abundance of the Bcl-2-associated X protein (Bax), yet this did not further improve muscle recovery in reloaded muscles. These data suggest that muscle recovery following disuse in aging is complex. Although satellite cell proliferation and differentiation are critical for muscle repair to occur, green tea-induced changes in satellite cell number is by itself insufficient to improve muscle recovery following a period of atrophy in old rats.
authors.affiliation: Laboratory of Muscle Biology and Sarcopenia, Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia; West Virginia Center for Clinical and Translational Science Institute, Morgantown, West Virginia; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, West Virginia; and salway@hsc.wvu.edu.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Alway
authors.affiliation: Laboratory of Muscle Biology and Sarcopenia, Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, West Virginia; and.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Bennett
authors.affiliation: Laboratory of Muscle Biology and Sarcopenia, Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, West Virginia; and.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Wilson
authors.affiliation: Laboratory of Muscle Biology and Sarcopenia, Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, West Virginia; and.
authors.forename: Justin
authors.initials: J
authors.lastname: Sperringer
authors.affiliation: Laboratory of Muscle Biology and Sarcopenia, Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, West Virginia; and.
authors.forename: Junaith S
authors.initials: JS
authors.lastname: Mohamed
authors.affiliation: Strategic R&D, Abbott Nutrition, Columbus, Ohio.
authors.forename: Neile K
authors.initials: NK
authors.lastname: Edens
authors.affiliation: Strategic R&D, Abbott Nutrition, Columbus, Ohio.
authors.forename: Suzette L
authors.initials: SL
authors.lastname: Pereira
mesh_terms: D000375:Aging / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019417:Hindlimb Suspension / Q000379:methods; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009133:Muscular Atrophy / Q000188:drug therapy* / Q000378:metabolism; D009142:Musculoskeletal Physiological Phenomena / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D013662:Tea / Q000737:chemistry*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D010936:Plant Extracts; D013662:Tea; D051028:bcl-2-Associated X Protein
keywords: EGCg; apoptosis; catechin; disuse; exercise; muscle atrophy; reloading; sarcopenia