Effects of chronic AICAR administration on fiber composition, glycolytic and oxidative enzyme activities and UCP3 and PGC-1 protein content in rat muscles

This study was designed to determine the histological and metabolic effects of the administration of 5’-AMP activated protein kinase (AMPK) activator 5aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside (AICAR) for 14 successive days. AICAR-treatment caused a significant decrease in the percentage of type IIB fibers and the concomitant increase in the percentage of type IIX fibers in EDL muscle. The capillary density or the capillary to fiber ratio were not altered by AICAR. AICARtreatment increased the glycolytic and oxidative enzyme activities but not the antioxidant enzyme activities. The AICAR-treatment increased the uncoupling protein 3 (UCP3) level in EDL and the peroxisome proliferator activated receptor co-activator 1 (PGC-1) protein level in the soleus and EDL muscles whereas the myogenin level was not altered by AICAR. These results seem to imply that the chronic activation of AMPK alters such muscle histochemical and metabolic characteristics.