title: Exercise training exacerbates tourniquet ischemia-induced decreases in GLUT4 expression and muscle atrophy in rats.
abstract: The current study determined the interactive effects of ischemia and exercise training on glycogen storage and GLUT4 expression in skeletal muscle. For the first experiment, an acute 1-h tourniquet ischemia was applied to one hindlimb of both the 1-week exercise-trained and untrained rats. The contralateral hindlimb served as control. For the second experiment, 1-h ischemia was applied daily for 1 week to both trained (5 h post-exercise) and untrained rats. GLUT4 mRNA was not affected by acute ischemia, but exercise training lowered GLUT4 mRNA in the acute ischemic muscle. GLUT4 protein levels were elevated by exercise training, but not in the acute ischemic muscle. Exercise training elevated muscle glycogen above untrained levels, but this increase was reversed by chronic ischemia. GLUT4 mRNA and protein levels were dramatically reduced by chronic ischemia, regardless of whether the animals were exercise-trained or not. Chronic ischemia significantly reduced plantaris muscle mass, with a greater decrease found in the exercise-trained rats. In conclusion, the exercise training effect on muscle GLUT4 protein expression was prevented by acute ischemia. Furthermore, chronic ischemia-induced muscle atrophy was exacerbated by exercise training. This result implicates that exercise training could be detrimental to skeletal muscle with severely impaired microcirculation.
authors.affiliation: Department of Athletic Training and Health, National College of Physical Education and Sports, Taoyuan 333, Taiwan, ROC.
authors.forename: Ying-Lan
authors.initials: YL
authors.lastname: Tsai
authors.forename: Chien-Wen
authors.initials: CW
authors.lastname: Hou
authors.forename: Yi-Hung
authors.initials: YH
authors.lastname: Liao
authors.forename: Chung-Yu
authors.initials: CY
authors.lastname: Chen
authors.forename: Fang-Ching
authors.initials: FC
authors.lastname: Lin
authors.forename: Wen-Chih
authors.initials: WC
authors.lastname: Lee
authors.forename: Shih-Wei
authors.initials: SW
authors.lastname: Chou
authors.forename: Chia-Hua
authors.initials: CH
authors.lastname: Kuo
mesh_terms: D000208:Acute Disease; D000818:Animals; D015152:Blotting, Northern; D002908:Chronic Disease; D004195:Disease Models, Animal; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis*; D007511:Ischemia / Q000150:complications* / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism; D009133:Muscular Atrophy / Q000209:etiology* / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000009:adverse effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014111:Tourniquets
chemical_list: D051275:Glucose Transporter Type 4; C495694:Slc2a4 protein, rat