Training cessation does not alter GLUT-4 protein levels in human skeletal muscle.
The purpose of this study was to determine whether short-term training cessation resulted in reduced GLUT-4 protein levels. Endurance- (n = 12, ET) and strength-trained (n = 12) individuals (ST) were examined before and after 14 days of training withdrawal. GLUT-4 content was determined from muscle biopsy samples of the gastrocnemius in ET and the vastus lateralis in ST. Insulin sensitivity (oral glucose tolerance test) was significantly (P < 0.05) reduced in ET and ST with training cessation. GLUT-4 content was unaltered (P > 0.05) in both groups (92 and 100% of trained values for ET and ST, respectively). In ET, citrate synthase activity decreased significantly (P < 0.05) with training withdrawal (41.0 +/- 3.6 vs. 30.6 +/- 2.8 mumol.g-1.min-1); in ST no change was evident. The decrement in insulin sensitivity with the cessation of endurance- or resistance-oriented activity is therefore not associated with a reduction in GLUT-4 protein content. Muscle oxidative capacity and GLUT-4 content do not coincide with the removal of endurance training.
Houmard
J A
JA
Human Performance Laboratory, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
Hortobágyi
T
T
Neufer
P D
PD
Johns
R A
RA
Fraser
D D
DD
Israel
R G
RG
Dohm
G L
GL
D000328:Adult; D001823:Body Composition; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005260:Female; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009132:Muscles / Q000033:anatomy & histology / Q000737:chemistry / Q000378:metabolism*; D010806:Physical Education and Training; D010807:Physical Endurance; D005082:Physical Exertion; D010809:Physical Fitness; D012420:Running; D014891:Weight Lifting
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; D002950:Citrate (si)-Synthase