Steatotic liver disease (SLD) has been known for a long time, but our understanding of this disease has remained poor until the past decade. Despite extensive research, our ability to comprehend the etiopathogenesis and natural course of SLD is far from the desired level of comprehension. This is required to develop a universally effective novel therapeutic agent. This review aims to concisely elaborate the conceptual approach and advancement in the understanding of global disease burden and etiopathogenic process, identifying the gaps and the pathophysiologic mechanism behind developing novel therapeutic agents. We searched two major databases, PubMed and Google Scholar, to identify publications related to the abovementioned topics. All publications, including original papers, reviews, and commentaries, were reviewed. Findings: Metabolic dysfunction-associated steatotic liver disease (MASLD) is not limited to obese individuals, rather, it may develop in any individual independent of weight. Visceral adiposity is strongly associated with MASLD and subsequent risks of cirrhosis, hepatocellular carcinoma, and cardiovascular disease. MASLD is associated with diabetes mellitus independent of underlying pathogenic mechanisms, and there is a bidirectional connection between MASLD and diabetes mellitus, making the situation quite challenging. Not all patients with MASLD exhibit atherogenic dyslipidemia and thus do not have a higher risk of cardiovascular disease. The overlap of these metabolic risk factors is not straightforward. There is a differential contribution of these risk factors based on age, gender, race, ethnicity, alcohol consumption, and microbiota composition. Poor dietary habits and lifestyle directly affect the microbiota, modulators, and mediators, thereby affecting the final biochemical processes leading to steatosis, steatohepatitis, fibrosis, and oncogenesis. In conclusion, MASLD is a complex and pathogenically heterogeneous disease with significant interpatient variation in the natural course and outcome. Understanding the precise mechanism of variability is the key gap and a limiting factor in the development of a novel therapeutic agent.

Metabolic-associated steatotic liver disease (MASLD) and its pathological version, metabolic dysfunction-associated steatohepatitis (MASH), are becoming the main leading causes of chronic liver disease almost worldwide and are the fastest growing aetiology of hepatocellular carcinoma (HCC), especially in the Western countries. The combination of high incidence and morbidity with limited treatment options for both MASH and HCC highlights an urgent need for the discovery of novel therapeutic candidates to inform drug development. The importance of lysosomes and cathepsins, their most abundant hydrolases, has been overlooked for decades. They were considered organelles only involved in the recycling of macromolecules, with cathepsins simply being their effectors. Contrary to this traditional view, recent findings have shed new light on the lysosome and its enzymes as drivers of essential cellular processes, such as apoptosis and autophagy. Bringing lysosomal activity and the regulation of cathepsins into the spotlight of MASH and HCC research can open new avenues for the development of novel drugs based on targeting cathepsin-driven lysosomal activity and its associated pathological processes. This review comprehensively summarises the current knowledge on the role and contribution of lysosomal cathepsins to MASLD/MASH and HCC progression.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is one of the most common chronic liver diseases. Over time, there has been a significant increase in the prevalence of MASLD. It has become one of the leading causes of hepatocellular carcinoma (HCC) in the United States, France, and the United Kingdom. Globally, the incidence of HCC related to MASLD may further increase with the growing prevalence of obesity. Non-alcoholic steatohepatitis (NASH) is an important stage of MASLD, which is more likely to cause cirrhosis and even HCC. And patients with NASH cirrhosis have a much higher incidence of hepatocellular cancer than patients with non-cirrhotic MASLD. As a result, it is critical to investigate the targets of MASLD therapy in HCC. This article reviews therapeutic targets of MASLD, such as farnesoid X receptor (FXR), peroxisome proliferator activated receptor (PPAR), fibroblast growth factor-21 (FGF-21), etc., and introduces the drugs related to these targets and their mechanisms of action in HCC. In addition, the developmental process and pathogenesis of MASLD, as well as risk factors for HCC development, are discussed. These are of great significance for the prevention and treatment of HCC.

Non-alcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide, with a progressive form of non-alcoholic steatohepatitis (NASH). It may progress to advanced liver diseases, including liver fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD/NASH is a comorbidity of many metabolic disorders such as obesity, insulin resistance, type 2 diabetes, cardiovascular disease, and chronic kidney disease. These metabolic diseases are often accompanied by systemic or extrahepatic inflammation, which plays an important role in the pathogenesis and treatment of NAFLD or NASH. Metabolites, such as short-chain fatty acids, impact the function, inflammation, and death of hepatocytes, the primary parenchymal cells in the liver tissue. Cholangiocytes, the epithelial cells that line the bile ducts, can differentiate into proliferative hepatocytes in chronic liver injury. In addition, hepatic non-parenchymal cells, including liver sinusoidal endothelial cells, hepatic stellate cells, and innate and adaptive immune cells, are involved in liver inflammation. Proteins such as fibroblast growth factors, acetyl-coenzyme A carboxylases, and nuclear factor erythroid 2-related factor 2 are involved in liver metabolism and inflammation, which are potential targets for NASH treatment. This review focuses on the effects of metabolic disease-induced extrahepatic inflammation, liver inflammation, and the cellular and molecular mechanisms of liver metabolism on the development and progression of NAFLD and NASH, as well as the associated treatments.