Effects of exercise training and antioxidant R-ALA on glucose transport in insulin-sensitive rat skeletal muscle.
We have recently demonstrated (Saengsirisuwan V, Kinnick TR, Schmit MB, and Henriksen EJ, J Appl Physiol 91: 145-153, 2001) that exercise training (ET) and the antioxidant R-(+)-alpha-lipoic acid (R-ALA) interact in an additive fashion to improve insulin action in insulin-resistant obese Zucker (fa/fa) rats. The purpose of the present study was to assess the interactions of ET and R-ALA on insulin action and oxidative stress in a model of normal insulin sensitivity, the lean Zucker (fa/-) rat. For 6 wk, animals either remained sedentary, received R-ALA (30 mg. kg body wt(-1). day(-1)), performed ET (treadmill running), or underwent both R-ALA treatment and ET. ET alone or in combination with R-ALA significantly increased (P < 0.05) peak oxygen consumption (28-31%) and maximum run time (52-63%). During an oral glucose tolerance test, ET alone or in combination with R-ALA resulted in a significant lowering of the glucose response (17-36%) at 15 min relative to R-ALA alone and of the insulin response (19-36%) at 15 min compared with sedentary controls. Insulin-mediated glucose transport activity was increased by ET alone in isolated epitrochlearis (30%) and soleus (50%) muscles, and this was associated with increased GLUT-4 protein levels. Insulin action was not improved by R-ALA alone, and ET-associated improvements in these variables were not further enhanced with combined ET and R-ALA. Although ET and R-ALA caused reductions in soleus protein carbonyls (an index of oxidative stress), these alterations were not significantly correlated with insulin-mediated soleus glucose transport. These results indicate that the beneficial interactive effects of ET and R-ALA on skeletal muscle insulin action observed previously in insulin-resistant obese Zucker rats are not apparent in insulin-sensitive lean Zucker rats.
Saengsirisuwan
Vitoon
V
Muscle Metabolism Laboratory, Department of Physiology, University of Arizona, College of Medicine, Tucson, Arizona 85721-0093, USA.
Perez
Felipe R
FR
Kinnick
Tyson R
TR
Henriksen
Erik J
EJ
D000818:Animals; D000963:Antimetabolites / Q000378:metabolism; D000975:Antioxidants / Q000494:pharmacology*; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D003847:Deoxyglucose / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000097:blood / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D010101:Oxygen Consumption / Q000187:drug effects; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D011924:Rats, Zucker; D008063:Thioctic Acid / Q000494:pharmacology*
D000963:Antimetabolites; D000975:Antioxidants; D001786:Blood Glucose; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D008063:Thioctic Acid; D003847:Deoxyglucose; D005947:Glucose