New role of bile acid metabolism in intestinal bacteria translocation

摘要

Bile acids are endogenous molecules synthesized in the liver as endproducts of cholesterol catabolism. Secreted in bile, stored in the gallbladder in the interprandial period, bile acids are released in the intestine mainly in response to food intake. After active uptake in the ileum, bile acids return back to the liver through the portal vein, thus completing their enterohepatic circulation. Classical physiological functions of bile acids include promotion of hepatic homeostasis and bile flow, support of the smooth progression of lipid digestion and absorption, absorption of lipophilic vitamins, cholesterol solubilization and disposal. Moreover, bile acids are directly involved in preserving the physiological commensal host-intestinal bacteria relationship. The gut microbiota hosted in the intestinal lumen is precious since it solves key metabolic roles for nutrient processing, as well as correct development and tuning of the immune system . The delicate host-intestinal bacteria balance is regulated to maintain a fixed composition of microbial species, while preventing their excessive proliferation. In pathophysiological conditions the expansion of intestinal microflora leads to migration of bacteria through the intestinal mucosa, up to mesenteric lymph nodes and extra-intestinal tissues. Bacterial overgrowth and translocation play major pathophysiological roles, especially in cirrhotic patients, potentially leading to portal hypertension, ascites, spontaneous bacterial peritonitis, and hepatorenal syndrome.