title: Effect of prolonged intermittent hypoxia and exercise training on glucose tolerance and muscle GLUT4 protein expression in rats.
abstract: We compared the chronic effect of intermittent hypoxia and endurance training on the glucose tolerance and GLUT4 protein expression in rat skeletal muscle. Thirty-two Sprague-Dawley rats were matched for weight and assigned to one of the following four groups: control, endurance training, hypoxia, or hypoxia followed by endurance training. Hypoxic treatment consisted of breathing 14% O2 for 12 h/day under normobaric conditions, and the training protocol consisted of making animals swim 2 times for 3 h/day. At the end of the 3rd week, an oral glucose tolerance test (OGTT) was performed 16 h after treatments. At the end of the 4th week, GLUT4 protein, mRNA, and glycogen storage in skeletal muscle were determined. Endurance training significantly improved OGTT results. Glycogen content and GLUT4 protein expression in the plantaris and red gastrocnemius, but not in the soleus or white gastrocnemius muscles, were also elevated. Chronic intermittent hypoxia also improved OGTT results, but did not alter GLUT4 protein expression. Additionally, hypoxia followed by exercise training produced significant increases in GLUT4 protein and mRNA in a greater number of muscles compared to endurance training alone. Both exercise training and hypoxia significantly reduced body mass, and an additive effect of both treatments was found. In conclusion, chronic intermittent hypoxia improved glucose tolerance in the absence of increased GLUT4 protein expression. This treatment facilitated the exercise training effect on muscle GLUT4 expression and glycogen storage. These new findings open the possibility of utilizing intermittent hypoxia, with or without exercise training, for the prevention and clinical treatment of type 2 diabetes or insulin resistance.
authors.affiliation: Laboratory of Exercise Biochemistry, Taipei Physical Education College, Taipei, Taiwan, ROC.
authors.forename: Li-Ling
authors.initials: LL
authors.lastname: Chiu
authors.forename: Shih-Wei
authors.initials: SW
authors.lastname: Chou
authors.forename: Yu-Min
authors.initials: YM
authors.lastname: Cho
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Ho
authors.forename: John L
authors.initials: JL
authors.lastname: Ivy
authors.forename: Desmond
authors.initials: D
authors.lastname: Hunt
authors.forename: Paulus S
authors.initials: PS
authors.lastname: Wang
authors.forename: Chia-Hua
authors.initials: CH
authors.lastname: Kuo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001835:Body Weight; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism; D000860:Hypoxia; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat; D006003:Glycogen