Retinoic acid leads to cytoskeletal rearrangement through AMPK-Rac1 and stimulates glucose uptake through AMPK-p38 MAPK in skeletal muscle cells

Retinoic acid (RA) is one of the major components of vitamin A. In the present study, we found that retinoic acid activated AMP-activated protein kinase (AMPK). RA induced Rac1-GTP formation and phosphorylation of its downstream target, p21-activated kinase (PAK), whereas the inhibition of AMPK blocked RA-induced Rac1 activation. Moreover, cofilin, an actin polymerization regulator, was activated when incubated with RA. We then showed that inhibition of AMPK by compound C, a selective inhibitor of AMPK, or small interfering RNA of AMPK alpha1 blocked RA-induced cofilin phosphorylation. Additionally, we found that retinoic acid-stimulated glucose uptake in differentiated C2C12 myoblast cells and activated p38 mitogen-activated protein kinase (MAPK). Finally, the inhibition of AMPK and p38 MAPK blocked retinoic acid-induced glucose uptake. In summary, our results suggest that retinoic acid may have cytoskeletal roles in skeletal muscle cells via stimulation of the AMPK-Rac1-PAK-cofillin pathway and may also have beneficial roles in glucose metabolism via stimulation of the AMPK-p38 MAPK pathway.