Gallensalze

Gallensalze, or bile salts, are amphipathic steroid molecules derived from cholesterol that are secreted into bile. In humans they are formed in the liver when primary bile acids, cholic acid and chenodeoxycholic acid, are conjugated with the amino acids glycine or taurine to produce glyco- and tauro-conjugates such as glycocholate and taurocholate. Conjugation increases their water solubility and facilitates their secretion into bile via canalicular transporters.

After storage in the gallbladder, bile is released into the small intestine in response to a meal. Bile salts emulsify dietary fats, forming micelles that solubilize lipids and fat-soluble vitamins, which enables digestion and absorption. They are then largely reabsorbed in the ileum and returned to the liver through the enterohepatic circulation, maintaining a circulating pool of bile salts.

The gut microbiota further modifies bile salts, producing secondary bile acids such as deoxycholic acid and lithocholic acid. These transformations influence digestion, microbial ecology, and the overall pool of signaling molecules. Bile salts also act as hormones, activating receptors such as FXR and TGR5 that regulate lipid and glucose metabolism and inflammatory processes.

Clinical aspects include disorders of bile salt homeostasis. Reduced bile flow in cholestasis impairs fat absorption, while excessive cholesterol saturation of bile can promote cholesterol gallstone formation. Therapeutically, ursodeoxycholic acid is used to alter bile composition and dissolution of certain cholesterol gallstones and to treat some cholestatic liver diseases.