Cholestenoic acid is a naturally occurring ligand for liver X receptor alpha

Excessive cholesterol is eliminated from extrahepatic cells by reverse cholesterol transport, a process by which neutral sterols are transferred to extracellular acceptor lipoproteins for further transport to the liver. Another process independent of lipoproteins involves excretion of 3beta-hydroxy-5-cholesten-25(R)-26-carboxylic (cholestenoic) acid, a metabolite of 27-hydroxycholesterol. Physiological concentrations of cholestenoic acid activated the nuclear receptor liver X receptor alpha (LXR alpha; NR1H3), but not other oxysterol receptors. As a ligand, cholestenoic acid modulated interaction of LXR alpha with the nuclear receptor coactivator Grip-1. Cholestenoic acid, therefore, may function as a signaling molecule for regulation of lipid metabolism via LXR alpha.