enterohepatischen

Entrohepatic circulation, sometimes called enterohepatic circulation, refers to the recycling of bile acids and other substances between the liver and the digestive tract. In this cycle, bile acids are synthesized in hepatocytes from cholesterol, conjugated, and secreted into bile. They are stored in the gallbladder and released into the small intestine during meals to aid lipid digestion. After helping with emulsification, most bile acids are reabsorbed in the terminal ileum via the apical sodium-dependent bile acid transporter (ASBT), pass Enterocytes via OST alpha/beta, and return to the liver through the portal vein.

Hepatic uptake and resecretion of bile acids involve transporters such as NTCP (the Na+-taurocholate cotransporting polypeptide) and organic anion-transporting polypeptides (OATPs), enabling resecretion into bile and maintenance of the bile acid pool. The gut microbiota also modifies bile acids in the colon through deconjugation and dehydroxylation, producing secondary bile acids such as deoxycholic and lithocholic acids, which can be reabsorbed and contribute to signaling and pool balance. Bile acids activate receptors such as FXR and TGR5, regulating lipid, glucose, and energy metabolism and providing feedback control of bile acid synthesis.

Clinical relevance: Disruption of enterohepatic circulation can affect fat digestion and cholesterol homeostasis. Ileal diseases (e.g., Crohn’s disease) reduce reabsorption, causing bile acid loss in stool and diarrhea. Drugs that interrupt reabsorption, such as bile acid sequestrants, lower cholesterol but may cause gastrointestinal symptoms. Liver disease or cholestasis can perturb the cycle and bile acid signaling. In German, the concept is referred to as enterohepatischer Kreislauf.