Exercise-induced Gene Expression Of Angiogenesis-regulated Transcriptional Factors Differs Between Fiber Types In The Skeletal Muscle

Abstract

Exercise training promotes many adaptations in skeletal muscle, including the development of new capillaries, known as angiogenesis. Acute exercise induces a greater expression of genes known to promote angiogenesis, such as vascular endothelial growth factor (VEGF). The exercise-induced alteration of VEGF gene expression differs between muscle fiber types (i.e., slow-twitch oxidative muscle fibers and fast-twitch glycolytic muscle fibers). PURPOSE To gain insight into the molecular mechanism underlying the difference of exercise-induced angiogenesis between slow fiber type and fast fiber type, we investigated whether the basal and exercise-induced gene expression of angiogenesis-regulated transcriptional factors in muscle differ between these two fiber types. METHODS We determined a difference of level in gene expression of angiogenesis-regulated transcriptional factors (transforming growth factor [TGF]-beta1, c-Jun and c-Fos) between the muscle of slow fiber type (soleus) and fast fiber type (plantaris) at rest and the end of a single bout of exercise (running on a treadmill for 30-min) using male Sprague-Dawley rats (10 wk old). RESULTS The mRNA expression of TGF-beta1, c-Jun and c-Fos at resting condition was significantly higher in the soleus than the plantaris. On the other hand, the mRNA expressions of TGF-beta1 and c-Jun in the plantaris, but not in the soleus, were significantly increased by exercise. The exercise-induced increase in c-Fos mRNA expression was higher in the plantaris than the soleus, although the mRNA expressions of c-Fos in both muscles were significantly increased by exercise. Thus, slow type fiber constitutively activates transcriptional regulation of angiogenesis at resting condition, whereas the exercise-induced increase in gene expression of angiogenesis-regulated transcriptional factors mainly occurs in fast fiber type of muscle. CONCLUSION The present study suggests that 1) the difference of constitutive gene expression of angiogenesis-regulated transcriptional factors between fast and slow fiber types of muscle may be one of the causal factors for the difference in homeostatic angiogenesis to the muscle capillary and 2) the exercise-induced different manner of gene expression of angiogenesis-regulated transcriptional factors between fast and slow fiber types of muscle may participate in molecular mechanism underlying exercise-enhanced angiogenesis. Supported by grants from the Ministry of Education, Science, Sports and Culture of Japan (15650130, 16500391).