Biliary mixed micelles and cholesterol

Biliary mixed micelles are macromolecular aggregates composed of bile salts, phospholipids (primarily lecithin), and cholesterol, which serve as the primary vehicle for transporting cholesterol in the aqueous environment of bile [PubMed: 10411130]. The liver secretes cholesterol into bile, where it is solubilized within these micelles; however, when the concentration of cholesterol exceeds the solubilizing capacity of the bile salts and phospholipids, the bile becomes supersaturated [NIH: Gallstones]. This supersaturation leads to the nucleation and precipitation of cholesterol crystals, which eventually aggregate to form gallstones (cholelithiasis) [StatPearls: Cholelithiasis]. Therapeutic intervention often involves the use of hydrophilic bile acids, such as ursodeoxycholic acid, which decrease the cholesterol saturation index of bile by inhibiting intestinal cholesterol absorption and suppressing hepatic cholesterol secretion [PubMed: 2489113]. These drugs promote the dissolution of cholesterol gallstones by shifting the equilibrium from a crystalline state back into a soluble micellar or liquid-crystalline phase [Journal of Lipid Research: 1994]. This target is central to managing gallstone disease without surgical intervention.

Other names

Biliary micellesBile salt-phospholipid-cholesterol micellesBiliary cholesterolMixed micelles

Drugs like ursodeoxycholic acid reduce the cholesterol saturation index (CSI) of bile by suppressing hepatic cholesterol secretion and inhibiting intestinal cholesterol absorption, thereby promoting the dissolution of cholesterol from gallstones into a liquid-crystalline or micellar phase [StatPearls: Ursodeoxycholic Acid].