Effect of systemic hypoxia on GLUT4 protein expression in exercised rat heart.
Altitude training is a common method used to enhance endurance performance in athletes. We have examined the interactive effect of exercise training and chronic hypoxic on glycogen storage and GLUT4 protein expression in cardiac muscles. Thirty-two male Sprague-Dawley rats were weight balanced and assigned to one of the following four groups: control, exercise, hypoxia, and hypoxia-exercise. Rats with hypoxic treatment (breathing 14% O(2) for 12 hr/d) were exposed under normobaric conditions. The training protocol consisted of swimming for two 3-hr periods per day for 4 weeks. Glycogen content, GLUT4 protein, and mRNA of all rats were determined 16 hr after treatments. Four-week exercise training without hypoxia significantly elevated myocardial glycogen level by 45%. The chronic hypoxic-exercise training elevated the myocardial glycogen level by 67% above control level, significantly greater than the exercise group. Chronic hypoxia, exercise training, and hypoxia-exercise training significantly elevated GLUT4 protein by 40-70% in cardiac muscles. Chronic hypoxia significantly elevates the GLUT1 protein level independent of exercise training. The new finding in this study was that GLUT4 gene expression in cardiac muscle can be stimulated by exercise training with hypoxia treatments. This molecular adaptation appears to be associated with the observed increase in glycogen storage of the muscle.
Chou
Shih-Wei
SW
Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Taipei, Taiwan, ROC.
Chiu
Li-Ling
LL
Cho
Yu-Min
YM
Ho
Hsin-Yi
HY
Ivy
John L
JL
Ho
Chung-Fong
CF
Kuo
Chia-Hua
CH
D000531:Altitude; D000818:Animals; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism; D006321:Heart / Q000502:physiology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D009124:Muscle Proteins / Q000096:biosynthesis*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D006003:Glycogen