PSC is a rare disease with a poor prognosis and can lead to cirrhosis of the liver or bile duct cancer. It affects 0.01% of the population but, even though it is rare, PSC is responsible for more than 10% of all liver transplants, making it the third commonest indication for liver transplant in Europe.
Although the recent studies led by Michael Trauner demonstrated initial positive effects of a synthetically produced bile acid (norUDCA) and bile acid receptor agonists (cilofexor), there is not yet any approved pharmacological treatment for PSC. In the present study, aimed at gaining a better understanding of the mechanisms of PSC, the research team focused on the action mechanism of monoacylglycerol lipase (MAGL). This enzyme plays a key role in the breakdown of fat, but little is yet known about how it behaves in liver disease. Trauner's hypothesis was that fatty acid metabolism might play a greater role than previously thought in the epithelium of the biliary tract, the innermost layer of cells of the biliary tract. In this process, MAGL regulates the breakdown of fat into individual fatty acids, which can cause cell damage and inflammation, if their release is uncontrolled. Hitherto, researchers have focused on this enzyme in connection with fatty liver; so far, little has been known about its role in bile duct disease.
The question posed in the mouse model was whether inhibition of the enzyme MAGL can reduce the extent of liver damage. In the model, cholestasis, impaired bile secretion, was induced in mice that lacked MAGL or in which it had been pharmacologically inhibited. A pharmacological MAGL-inhibitor was also tested in a mouse model for PSC. It appeared that those mice without any MAGL activity were protected against damage and displayed less fibrosis (accumulation of connective tissue) and inflammation in the liver. A further positive effect that was observed was an anti-inflammatory effect in the bowel, with normalisation of the microbiome. This is important, since in around 70% of cases, PSC is associated with chronic inflammatory bowel disease and anti-inflammatory effects in the bowel are also beneficial for the liver.
The result points to a potential immunometabolic treatment approach through targeted inhibition of MAGL. These approaches would subsequently need to undergo pharmacological testing. MAGL-inhibitors are already being clinically developed, primarily for neurological diseases and cancer. Trauner and his team are also planning clinical pilot studies for PSC. For example, MAGL inhibitors could be used in the treatment of PSC or other cholestatic liver diseases as a combination therapy, together with other bile-acid-based treatments.
The project was funded via an international Austrian Science Fund (FWF) project (I2661) and FWF specialist research area 73 (lipid hydrolysis).
MedUni Vienna’s Division of Gastroenterology and Hepatology is regarded as one of the world’s leading centres for research into primary sclerosing cholangitis (PSC), non-alcoholic fatty liver disease (NAFLD) and other liver and bile duct disorders. One of MedUni Vienna's main research interests within the Immunology Research Cluster is immunometabolism, which is concerned with the interaction between immunologic and metabolic processes. Additionally, MedUni Vienna and the Medical University of Graz have been collaborating on lipid metabolism for decades, within the framework of FWF specialist research areas.
Monoacylglycerol Lipase Inhibition Protects from Liver Injury in Mouse Models of Sclerosing Cholangitis. Tardelli M, Bruschi FV, Fuchs CD, Claudel T, Auer N, Kunczer V, Baumgartner M, A H O Ronda O, Verkade HJ, Stojakovic T, Scharnagl H, Habib A, Zimmermann R, Lotersztajn S, Trauner M. doi: 10.1002/hep.30929.