Alterations in peroxisome proliferator-activated receptor mRNA expression in skeletal muscle after acute and repeated bouts of exercise

Abstract

Peroxisome proliferator-activated receptors (PPAR) exist in three different forms, alpha (alpha), beta/delta (beta/delta), or gamma (gamma), all of which are expressed in skeletal muscle and play a critical role in the regulation of oxidative metabolism. The purpose of this investigation was to determine the mRNA expression pattern of the different PPARs and peroxisome proliferator-activated receptor alpha coactivator-1 alpha (PGC-1alpha) in muscles that largely rely on either glycolytic (plantaris) or oxidative (soleus) metabolism. Further, we also examined the alterations in the PPARs mRNA expression after one bout of endurance exercise or after 12 weeks of exercise training in the different muscles. Female Sprague-Dawley rats (5-8 months) were either run on the treadmill once or exercised trained for 12 weeks. The muscles were removed 24 h after the last bout of exercise. The results demonstrated with the exception of PPAR beta/delta, the PPAR mRNAs are expressed to a greater extent in the soleus muscle than in the plantaris muscle in sedentary animals. PPARgamma was the least abundantly expressed PPAR in either the soleus or the plantaris muscle. With respect to exercise training, only PPARgamma mRNA expression increased in the soleus muscle, while PPARbeta/delta and gamma mRNA levels increased in the plantaris muscle. Minimal changes were detected in any of the PPARs with one bout of exercise training. These results suggest that PPARgamma mRNA levels are the lowest in skeletal muscle among all of the PPARs and PPARgamma mRNA is the most responsive to changes in physical activity levels.

Fig. 1

a, b PPARγ mRNA expression is relatively lower than PPARα and PPARβ/δ in both the soleus and plantaris muscles of the rat (a). PGC-1α mRNA expression is higher in the soleus muscle compared to the plantaris muscle (b). * Significantly different than the soleus muscle, ^# different than soleus muscle in the alpha and delta group, ^$ different than the plantaris in the alpha and delta group (P < 0.05). n = 5 per group

Fig. 2

a, b PPARγ mRNA is increased in the plantaris (b) and soleus muscle (a) after 12 weeks of treadmill training compared to the sedentary animals. * Significantly different than the sedentary group (P < 0.05). n = 5 sedentary, n = 7 one bout, n = 8 trained

Fig. 3

a, b PPARβ/δ mRNA is increased in the plantaris (b), but decreased in the soleus muscle (a) after 12 weeks of treadmill training compared to the sedentary animals. * Significantly different than the sedentary group (P < 0.05). n = 5 sedentary, n = 7 one bout, n = 8 trained

Fig. 4

a, b PPARα mRNA is decreased in the soleus muscle (a) after one bout of exercise, but does not changes in the plantaris muscle (b). ^# Significant differently than the sedentary group (P < 0.05). n = 5 sedentary, n = 7 one bout, n = 8 trained

Fig. 5

PGC-1α mRNA is increased in the plantaris after one bout and with training, compared to the sedentary animals. *, ^# Significantly different than the sedentary group (P < 0.05). n = 5 sedentary, n = 7 one bout, n = 8 trained

Fig. 6

a–d UCP3 (a, b) and PDK4 (c, d) mRNA expression is increased in skeletal muscle with exercise training. *, ^# Significantly different than the sedentary group (P < 0.05). n = 5 sedentary, n = 7 one bout, n = 8 trained