pparδ is activated in the cell by various fatty acids and fatty acid derivatives. examples of naturally occurring fatty acids that bind with and activate ppar delta include arachidonic acid and certain members of the 15-hydroxyicosatetraenoic acid family of arachidonic acid metabolites including 15("s")-hete, 15("r")-hete, and 15-hpete. several synthetic ligands have been identified that selectively bind pparδ.