Liver Fat and Glucagon Resistance

One in four adults worldwide have too much fat stored in the liver which is known as metabolic associated steatotic liver disease (MASLD). This was previously known as non- alcoholic fatty liver disease (NAFLD). This can lead to liver failure and death in severe cases. Unfortunately, there are no specific drugs to treat MASLD. Glucagon is a natural hormone that controls how the body stores and uses fuel. Glucagon acts on liver cells to use protein and fat to make sugar. It decreases the amount of liver fat. The investigators think that patients with MASLD may not respond to the actions of glucagon. This could contribute to the build-up of fat in the liver. In this study the investigators will be investigating the effects of glucagon on protein breakdown and sugar production in patients with and without MASLD. Healthy volunteers and patients with MASLD will attend for one study visit each which will last for 4-5 hours. During this time they will have infusions into a vein of glucagon and other hormones, amino acids (to mimic the fed state) and 'tracers'. From another vein they will have several blood samples during this period. By analysing these blood samples the investigators will be able to measure the effects of glucagon on protein and glucose turnover (metabolism), and whether this differs between healthy volunteers and those with MASLD. If the investigators find that patients with MASLD are resistant to the actions of glucagon, this could help with the development of drugs to treat MASLD.