Ursodeoxycholic acid: unique properties and clinical applications

Abstract

Ursodeoxycholic acid (UDCA) is a natural hydrophilic bile acid, which is present in humans as a small fraction of the total amount of bile acids (5%). Its unique properties underlie its use in a number of liver diseases as a first-line therapy. The ability of UDCA to reduce the secretion of cholesterol into bile, form mixed micelles (liquid crystals) with cholesterol molecules and interact with multifunctional nuclear receptors, are actively used in the treatment and prevention of cholelithiasis. UDCA has the ability to stimulate hepatobiliary secretion, promotes the secretion of bicarbonate by cholangiocytes, which is relevant for patients with primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). UDCA activates transporter proteins such as bile acid export pump (BSEP), multiresistance protein 2 (MRP2) – conjugates transporter, type 2 anion exchanger (AE2), and promotes their movement to the canalicular membrane of cells. UDCA acts as a pleiotropic agent that plays a unique role in modulating the classical mitochondrial pathway of apoptosis in various cell types. Double molecular bonds of UDCA serve as a trap for free radicals, which suppresses the processes of lipid peroxidation. The ability of UDCA to penetrate into mitochondrial membranes leads to suppression of the activity of mitochondrial oxidase enzymes responsible for the production of superoxide anion. UDCA activates autophagy and promotes the elimination of toxic fatty acids from hepatocytes, reducing liver steatosis, UDCA has anti-inflammatory, antifibrotic, immunomodulatory and anticarcinogenic effects. UDCA is included in international and Russian clinical guidelines for the treatment of patients with various liver diseases (PBC, PSC, intrahepatic cholestasis of pregnancy, drug-induced cholestasis, alcoholic liver disease with cholestatic component), cholelithiasis, cystic fibrosis. In the pharmacotherapy of non-alcoholic fatty liver disease, UDCA is the only drug that has a bi-directional effect on the liver and cardiovascular system.