Adiponectin Increases Fatty Acid Oxidation in Skeletal Muscle Cells by Sequential Activation of AMP-Activated Protein Kinase, p38 Mitogen-Activated Protein Kinase, and Peroxisome Proliferator–Activated Receptor α

Adiponectin Increases Fatty Acid Oxidation in Skeletal Muscle Cells by Sequential Activation of AMP-Activated Protein Kinase, p38 Mitogen-Activated Protein Kinase, and Peroxisome Proliferator–Activated Receptor α Myeong Jin Yoon 1 , Gha Young Lee 1 , Jun-Jae Chung 1 , Young Ho Ahn 2 , Seung Hwan Hong 2 and Jae Bum Kim 1 1 Laboratory of Adipocyte and Metabolism Research, Research Center for Functional Cellulomics, Department of Biological Sciences, Seoul National University, Seoul, Korea 2 Laboratory of Cell Biology, Department of Biological Sciences, Seoul National University, Seoul, Korea Address correspondence and reprint requests to Jae Bum Kim, PhD, Department of Biological Sciences, Seoul National University, San 56-1, Sillim-Dong, Gwanak-Gu, Seoul 151-742, Korea. E-mail: jaebkim{at}snu.ac.kr Abstract Adiponectin has recently received a great deal of attention due to its beneficial effects on insulin resistance and metabolic disorders. One of the mechanisms through which adiponectin exerts such effects involves an increase in fatty acid oxidation in muscle and liver. In the present study, we demonstrate that 5′–AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK) are involved in the activation of peroxisome proliferator–activated receptor (PPAR)α by adiponectin in muscle cells. Adiponectin increases the transcriptional activity of PPARα and the expression of its target genes, including ACO , CPT1 , and FABP3 in C2C12 myotubes. These effects were suppressed by the overexpression of a dominant-negative form of AMPK. Moreover, chemical inhibitors of AMPK and p38 MAPK potently repressed fatty acid oxidation and the induction of PPARα target gene expression by adiponectin. Interestingly, araA, an AMPK inhibitor, prevented the activation of p38 MAPK, whereas SB203580, a p38 MAPK inhibitor, did not affect AMPK activation, suggesting that p38 MAPK is a downstream signaling factor of AMPK. Taken together, these results suggest that adiponectin stimulates fatty acid oxidation in muscle cells by the sequential activation of AMPK, p38 MAPK, and PPARα. ACC, acetyl-CoA carboxylase ACO, acyl-CoA oxidase AICAR, 5-aminoimidazole-4-caroxamide-1-β-d-ribofuranoside AMPK, AMP-activated protein kinase CPT1, carnitine palmitoyl transferase 1 DMEM, Dulbecco’s modified Eagle’s medium HMW, high molecular weight LMW, low molecular weight MAPK, mitogen-activated protein kinase PPAR, peroxisome proliferator–activated receptor Footnotes Additional in