Increase in Fatty Acid Oxidation by AICAR: the Role of p38 MAPK

Lee, Woo Je; Kim, Jin Yob; Bae, Sung Jin; Koh, Eun Hee; Han, Sung Min; Park, Hye Sun; Kim, Hyun Sik; Kim, Min Seon; Park, Joong Yeol; Lee, Ki Up

Abstract

BACKGROUND: AMPK is an enzyme that increases glucose transport and fatty acid oxidation in skeletal muscle. The activation of AMPK stimulates fatty acid oxidation by decreasing the acetyl CoA carboxylase (ACC) activity and the concentration of malonyl-CoA. However, a recent study has reported a dissociation of AMPK activity and ACC phosphorylation in skeletal muscle during periods of prolonged exercise. This suggested that there is an additional mechanism for AMPK-induced fatty acid oxidation in skeletal muscle.
METHODS
Plamitate oxidation was measured via the generation of [3H]-water generation from 9,10[3H]-palmitate after treating various concentrations of AICAR on the C2C12 mouse skeletal muscle cell line. Western analysis was used to test for the possible activation of p38 MAPK by AICAR. Involvement of p38 MAPK in the AICAR-induced increase in fatty acid oxidation was tested for by using SB203580, a p38 MAPK inhibitor.
RESULTS
C2C12 cell treated with AICAR exhibited a dose-dependent increase in fatty acid oxidation compared to the cells that were not treated with AICAR. Western blot analysis revealed that phosphorylation of p38 MAPK was increased 2.5 folds after AICAR treatment. The increase of fatty acid oxidation with AICAR treatment was significantly inhibited by a treatment of SB203580; this indicated the involvement of p38 MAPK on the AICAR-induced increase in fatty acid oxidation.
CONCLUSION
AICAR stimulated the fatty acid oxidation by activating p38 MAPK. This is a novel pathway by which AMPK activation in skeletal muscle increases the fatty acid oxidation