Lipid metabolism in MASLD and MASH: From mechanism to the clinic

Metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH) is recognised as a metabolic disease characterised by excess intrahepatic lipid accumulation due to lipid overflow and synthesis, alongside impaired oxidation and/or export of these lipids. But where do these lipids come from? The main pathways related to hepatic lipid accumulation are de novo lipogenesis and excess fatty acid transport to the liver (due to increased lipolysis, adipose tissue insulin resistance, as well as excess dietary fatty acid intake, in particular of saturated fatty acids). Not only triglycerides but also other lipids are secreted by the liver and are associated with a worse histological profile in MASH, as shown by lipidomics. Herein, we review the role of lipid metabolism in MASLD/MASH and discuss the impact of weight loss (diet, bariatric surgery, GLP-1RAs) or other pharmacological treatments (PPAR or THRβ agonists) on hepatic lipid metabolism, lipidomics, and the resolution of MASH.