The role of orphan nuclear receptors in the regulation of cholesterol homeostasis

Cholesterol balance is maintained by a series of regulatory pathways that c ontrol the acquisition of cholesterol from endogenous and exogenous sources and the elimination of cholesterol, facilitated by its conversion to bile acids. Over the past decade, investigators have discovered that a family of membrane-bound transcription factors, sterol regulatory element-binding pr oteins (SREBPs), mediate the end-product repression of key enzymes of chole sterol biosynthesis. Recently orphan members of another family of transcrip tion factors, the nuclear hormone receptors, have been found to regulate ke y pathways in bile acid metabolism, thereby controlling cholesterol elimina tion. The study of these orphan nuclear receptors suggests their potential as targets for new drug therapies.