Effects of muscle activity and fiber composition on glucose transport and GLUT-4.
We examined glucose uptake and GLUT-4 in rat muscles [soleus (Sol), plantaris (PL), extensor digitorum longus (EDL), tibialis anterior, and the red and white gastrocnemius (WG)]. In the normally innervated perfused rat hindlimb muscles the proportion of oxidative fibers was highly correlated with the muscle's insulin-stimulated 3-O-methyl-D-glucose (3-MG) uptake (R2 = 0.78) and GLUT-4 content (r = 0.94). Insulin-stimulated 3-MG uptake and GLUT-4 were also highly correlated (R2 = 0.996). In 3-day denervated muscles, insulin-stimulated 3-MG uptake was reduced in all six muscles (-41 to -14.6%, P < 0.05), and GLUT-4 content was also reduced (-87.5 to -34.9%), except in the WG and EDL (P > 0.05). A very high correlation was observed between the decrements in GLUT-4 (%) and the decrements in 3-MG uptake (%; r = 0.99). The relatively greater loss in muscle activity (%) due to denervation in the Sol compared with the PL coincided with the reductions (%) in GLUT-4 and 3-MG uptake. These studies demonstrate that glucose uptake and GLUT-4 are regulated by insulin-independent means, namely the oxidative capacity of the muscle and the normal activity level of the muscle.
Megeney
L A
LA
Department of Kinesiology, University of Waterloo, Ontario, Canada.
Neufer
P D
PD
Dohm
G L
GL
Tan
M H
MH
Blewett
C A
CA
Elder
G C
GC
Bonen
A
A
D019325:3-O-Methylglucose; D000818:Animals; D003624:Darkness; D004591:Electrophoresis, Polyacrylamide Gel; D006614:Hindlimb; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008027:Light; D008297:Male; D008757:Methylglucosides / Q000378:metabolism*; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009119:Muscle Contraction; D009121:Muscle Denervation; D009132:Muscles / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009928:Organ Specificity; D005082:Physical Exertion; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values
D007328:Insulin; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D019325:3-O-Methylglucose