galzuren

Galzuren, or bile acids, are steroid acids derived from cholesterol that are synthesized in the liver and secreted into the digestive system. In humans the primary bile acids are cholic acid (CA) and chenodeoxycholic acid (CDCA). These acids are typically conjugated with glycine or taurine to form bile salts, which are stored in the gallbladder and released into the small intestine in response to a meal.

Function: They emulsify dietary fats, promoting the formation of mixed micelles and enabling intestinal absorption of fat-soluble vitamins. Beyond digestion, bile acids regulate cholesterol homeostasis and act as signaling molecules by activating receptors such as FXR and TGR5, influencing glucose metabolism, lipid processing, and energy expenditure.

Biosynthesis and circulation: The classic bile acid synthesis pathway begins with cholesterol and the enzyme cholesterol 7α-hydroxylase (CYP7A1); an alternative pathway uses CYP27A1. The products CA and CDCA are commonly conjugated and secreted into bile. After aiding digestion, most bile acids are reabsorbed in the ileum and transported back to the liver in the enterohepatic circulation, creating a tight turnover. The gut microbiota deconjugates and 7α-dehydroxylates primary bile acids to form secondary bile acids, notably deoxycholic acid (DCA) and lithocholic acid (LCA). Ursodeoxycholic acid (UDCA) is a clinically important secondary bile acid used therapeutically.

Clinical and research relevance: Abnormal bile acid pools or impaired circulation can contribute to gallstone disease, cholestasis, bile acid malabsorption, and liver injury. Bile acid composition and concentration are used diagnostically in liver disease and metabolic studies, and therapies modulate bile acids or their signaling pathways, including FXR agonists and UDCA treatment.