ABSTRACT
The present study examined the effect of diet supplementation of oxaloacetate precursors (aspartate and asparagine) and carnitine on muscle metabolism and exercise endurance. The results suggest that the diet supplementation increased the capacity of the muscle to utilize FFA and spare glycogen. Time to exhaustion was about 40% longer in the experimental group compared to the control, which received commercial diet only. These findings suggest that oxaloacetate may be important to determine the time to exhaustion during a prolonged and moderate exercise.
Subject(s)
Asparagine/pharmacology , Aspartic Acid/pharmacology , Carnitine/pharmacology , Muscle, Skeletal/metabolism , Physical Exertion/physiology , Animals , Asparagine/blood , Aspartic Acid/blood , Blood Glucose/metabolism , Carnitine/blood , Citrate (si)-Synthase/metabolism , Diet , Fatty Acids/metabolism , Glycogen/metabolism , Liver Glycogen/metabolism , Male , Muscle, Skeletal/drug effects , Muscle, Skeletal/enzymology , Oxaloacetates/metabolism , Oxidation-Reduction , Physical Conditioning, Animal , Rats , Rats, Wistar , SwimmingABSTRACT
The mitochondrial pyruvate carboxylase catalyses the ATP-dependent carboxylation of pyruvate to oxaloacetate. Since pyruvate carboxylase generates oxaloacetate for Krebs cycle function, it is proposed that the enzyme activity may be enhanced by exercise. To investigate this proposition, pyruvate carboxylase activity was determined in the heart, soleus and gastrocnemius (white portion) muscles of sedentary and swimming-trained adult rats (1 hour per day, 5 days a week, during 5 weeks) under the following conditions: rest, one hour of exercise and exhaustion. The results show that the pyruvate carboxylase activity is increased during exercise in both the sedentary and trained groups of rats. The stimulatory mechanism is unknown but it is possibly related to the generation of pyruvate from the breakdown of glycogen and acetyl CoA during fatty acid oxidation.
