Exercise training increases GLUT-4 protein concentration in previously sedentary middle-aged men.
The purpose of this study was to determine if 14 wk of exercise training would increase insulin-sensitive glucose transporter protein (GLUT-4) concentration in skeletal muscle of previously sedentary middle-aged men (47.2 +/- 1.3 yr; n = 13). Muscle samples (lateral gastrocnemius) and insulin action [insulin sensitivity index (ISI), minimal model] were obtained in the sedentary condition and 48 h after the final training bout. GLUT-4 protein concentration increased (P < 0.001, 2,629 +/- 331 to 4,140 +/- 391 absorbance units/100 micrograms protein) with exercise training by 1.8-fold. ISI increased by twofold (P < 0.05, 2.1 +/- 0.5 to 3.4 +/- 0.7 SI x 10(5) min/pM) with training. The percentage of GLUT-4 rich type IIa muscle fibers increased by approximately 10% (P < 0.01), which may have contributed to the elevation in transporter protein. GLUT-4 concentration and citrate synthase activity (1.7-fold, P < 0.001) also increased by similar increments. These findings indicate that GLUT-4 protein concentration is elevated in middle-aged individuals with exercise training.
Houmard
J A
JA
Department of Biochemistry, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
Shinebarger
M H
MH
Dolan
P L
PL
Leggett-Frazier
N
N
Bruner
R K
RK
McCammon
M R
MR
Israel
R G
RG
Dohm
G L
GL
D001823:Body Composition; D002149:Energy Intake; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009132:Muscles / Q000378:metabolism; D009994:Osmolar Concentration; D010806:Physical Education and Training; D010807:Physical Endurance
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human