Effects of exercise training and antioxidant R-ALA on glucose transport in insulin-sensitive rat skeletal muscle.

Saengsirisuwan V, Perez FR, Kinnick TR, Henriksen EJ.

Muscle Metabolism Laboratory, Department of Physiology, University of Arizona, College of Medicine, Tucson, Arizona 85721-0093, USA.

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 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.

POST BY: Kevin Jones

Comments: First off, I'm not sure if I am doing this correctly. Please let me know if this is OK. Second, I wanted to post an article about ALA but I could not find any relevant studies on humans and glucose uptake. All I could find was studies on rats...

But after reading a few of these reports on ALA, it makes me wonder if I am just wasting my time and money on ALA supplements. From what I've gathered, ALA is only effective in insulin resistant obese individuals. I was under the impression that ALA mimicked insulin and helped increase glucose uptake, therefore increasing glycogen stores. But I am neither diabetic nor obese, so does the ALA do anything at all for me? I also believed that it is a powerful free radical scavenger and would be smart to use after exercise as an anti-oxidant to protect against all the metabolic by-products created during the workout.