Natural and synthetic PPAR-γ ligands. PPAR-γ ligands include the synthetic agonist BRL49653, the endogenous agonists 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), 15S-hydroxy-5Z,8Z,11Z,13E-eicosatetraenoic acid (15-HETE), and 15-keto-prostaglandin E2, and the endogenous antagonist 1-acyl-2,3-cyclic-glycerophosphate.