Enterohepatic circulation is responsible for the capture of bile acids and other steroids produced or metabolized in the liver and secreted to the intestine, for reabsorption back into the circulation and transport back to the liver. Bile acids are secreted from the liver in the form of mixed micelles that also contain phosphatidylcholines and cholesterol that facilitate the uptake of fats and vitamins from the diet due to the surfactant properties of bile acids and lipids. Bile acids are synthesized in the liver from cholesterol by a cascade of enzymes that carry out oxidation and conjugation reactions, and transported to the bile duct and gall bladder where they are stored before being released into the intestine. Bile flow from the gall bladder to the small intestine is triggered by food intake in accordance with its role in lipid and vitamin absorption from the diet. Bile acids are further metabolized by gut bacteria and are transported back to the circulation. Metabolites produced in the liver are termed primary bile acids or primary conjugated bile salts, while the metabolites generated by bacterial are called secondary bile acids. About 95% of bile acids are reabsorbed in the proximal and distal ileum into the hepatic portal vein and then into the liver sinusoids, where they are efficiently transported into the liver with little remaining in circulation. Each bile acid is reabsorbed about 20 times on average before being eliminated. Enterohepatic circulation is under tight regulation by nuclear receptor signaling, notably by the farnesoid X receptor (FXR).
肠肝循环负责捕获在肝脏中产生或代谢并分泌到肠道的胆汁酸和其他类固醇，以便重新吸收回循环并运输回肝脏。胆汁酸以混合胶束的形式从肝脏分泌，其中还含有磷脂酰胆碱和胆固醇，由于胆汁酸和脂质的表面活性剂特性，有助于从饮食中摄取脂肪和维生素。。胆汁酸在肝脏中由胆固醇通过一系列酶合成，这些酶进行氧化和结合反应, 并被运送到胆管和胆囊，在它们被释放到肠道之前储存在那里。胆汁从胆囊流向小肠是由食物摄入触发的，这与其从饮食中吸收脂质和维生素的作用相一致。胆汁酸被肠道细菌进一步代谢，并被运回循环。在肝脏中产生的代谢产物称为初级胆汁酸或初级结合胆汁盐，而细菌产生的代谢产物称为次级胆汁酸。大约 95% 的胆汁酸在近端和远端回肠中被重新吸收，进入肝门脉，然后进入肝窦，在那里它们被有效地运输到肝脏中，很少残留在循环中。每种胆汁酸在被消除之前平均被重新吸收 20 次。肠肝循环受到核受体信号的严格调节，特别是法尼醇 X 受体 (FXR)。
Nuclear receptor control of enterohepatic circulation.
释 义 adj. 肠肝的
例 句 Hypercholic acidemia is caused by the interruption of enterohepatic circulation and deterioration of hepatic function after portasystemic shunt. 高胆酸血症主要为门体分流术后肝肠循环阻断和肝功能恶化所致。
circulation 英/sɜːkjʊ'leɪʃ(ə)n/ 美/,sɝkjə'leʃən/
释 义 n. 流通，传播；循环；发行量；（图书的）借出
例 句 Hemoglobin was the carrier of oxygen in blood circulation. 血红蛋白是血液循环中输送氧的载体。