Changes in Muscle Glycogen and PGC-1α Protein After Low-Intensity Swimming and Running Exercise in Rat

Abstract

1819 Purpose: Previously we reported that electrical stimulation of the rat epitrochlearis muscle in vitro increases peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) mRNA expression (Biochem Biophys Res Commun. 296: 350–4, 2002), suggesting that the stimuli evoked in the recruited muscle directly enhance PGC-1α expression during exercise. However, several factors, which are known to emerge during exercise (ex. β-adrenergic receptor stimulation), may possibly induce skeletal muscle PGC-1α expression. Therefore, for the purpose of confirming the relationship between the muscle recruitments during exercises and PGC-1α protein expression in skeletal muscle, we observed changes in muscle glycogen concentration and PGC-1α protein content after different modes of exercise (swimming vs. running) in which different muscles are recruited and in which the humoral effects might be virtually similar. Methods: Male Sprague-Dawley rats (5–6-wk-old, body weight: 150–170 g) were randomly assigned to low-intensity prolonged swimming exercise (SE), lowintensity running exercise (RE), and age-matched sedentary control group. Rats in the SE and RE group swam without a load and ran on the treadmill at a speed of 13 m/min, respectively, in two 3-h sessions separated by 45 min of rest. Epitrochlearis, triceps, soleus, plantaris, and red- and white-gastrocnemius muscles were dissected out immediately after and 6-h after the SE and RE for measurements of muscle glycogen concentration and PGC-1α protein expression, respectively. Results: Muscle glycogen concentrations in rat epitrochlearis, triceps and red-gastrocnemius muscles significantly decreased after SE, while RE significantly reduced muscle glycogen concentrations in the soleus, plantaris, and red-gastrocnemius muscles. Irrespectively of exercise mode, approximately 60–100 % increase in PGC-1α protein expression were observed exclusively in the muscles in which glycogen concentrations significantly decreased after the SE and RE. Conclusion: The present investigation demonstrated that acute bouts of low-intensity prolonged swimming and running exercise increased the PGC-1α protein content in the rat skeletal muscles that were recruited during each exercise.