Interactive effect of exercise training and growth hormone administration on glucose tolerance and muscle GLUT4 protein expression in rats.
The insulin-resistance effect of growth hormone (GH) administration has been frequently reported. The present study investigated the effect of GH administration on glucose tolerance and muscle GLUT4 protein expression in exercise-trained and untrained rats. Forty-eight rats were weight-matched and assigned to the following 4 groups: control, GH, exercise training, and exercise training + GH groups. After 2 weeks of GH injections (65 microg/kg/day) and exercise training, the glucose tolerance and insulin response were measured in these rats. The GLUT4 protein level, glycogen storage, and citrate synthase activity were determined in red gastrocnemius and plantaris muscles. Daily GH administration elevated the curves of the oral glucose tolerance test and insulin response compared with those of saline-injected control rats. Furthermore, exercise training completely eliminated this GH-induced insulin resistance as determined 18 h after the last bout of exercise training. Additionally, exercise training significantly increased muscle glycogen storage and GLUT4 protein levels. GH administration did not affect the GLUT4 protein and glycogen storage increases induced by exercise training, but the citrate synthase activity in the plantaris muscle was further elevated by GH administration to a level above that induced by training. In conclusion, this is the first study that demonstrates that regular exercise training prevents GH-induced insulin-resistance side effect in rats.
Hou
Chien-Wen
CW
Laboratory of Exercise Biochemistry, Taipei Physical Education College, 5 Dun-Hua N. Road, Taipei 105, Taiwan/ROC.
Chou
Shih-Wei
SW
Ho
Hsin-Yi
HY
Lee
Wen-Chih
WC
Lin
Ching-Hung
CH
Kuo
Chia-Hua
CH
D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000502:physiology*; D001835:Body Weight; D002950:Citrate (si)-Synthase / Q000737:chemistry; D005951:Glucose Tolerance Test / Q000662:veterinary; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000737:chemistry; D013006:Growth Hormone / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D007333:Insulin Resistance / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000502:physiology*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000737:chemistry; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D013006:Growth Hormone; D006003:Glycogen; D002950:Citrate (si)-Synthase