Peroxisome proliferator-activated receptor ? (PPAR?) is a member of the ligand-activated nuclear receptor superfamily and functions as a transcriptional activator. PPAR? is preferentially expressed in adipocytes as well as in vascular smooth muscle cells and macrophage. Besides its role in mediating adipogenesis and lipid metabolism, PPAR? also modulates insulin sensitivity, cell proliferation and inflammation. PPAR? transcriptional activity is inhibited by MAP kinase phosphorylation of PPAR? at Ser84.