Peroxisome proliferator-activated receptors as therapeutic targets in inflammation.

For decades, advances in endocrinology were characterized by a process in which hormones were first identified based upon their physiologic roles and then purified, often from vast quantities of biologic material. This purified material was then used to identify the receptors through which the hormone signaled. In this classic progression, science moved from physiology to cellular signaling. More recently, technological advances have turned this process literally inside out. With the advent of rapid complementary deoxyribonucleic acid screening, multiple genes were identified whose predicted structure revealed a steroid hormone receptor. This produced a group of so-called orphan receptors, whose cognate ligands and physiologic role remained completely obscure (1).