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.

The pathogenesis of primary biliary cholangitis (PBC) is particularly complicated as both intrinsic and extrinsic factors are implicated. Several forms of cellular death, both programmable and non-programmable, operate leading biliary epithelial cells (BECs) to elimination. The precise role of critical pathways like autophagy, apoptosis, senescence, and their interplay has not been fully clarified. Therefore, in this review, data on these important mechanisms are presented and their implication in PBC is discussed. The interplay of the three mechanisms is examined and the factors that drive them are analyzed. Moreover, the upstream drivers of autophagy, apoptosis, and senescence are presented. They include the loss of the protective bicarbonate umbrella in BECs due to the reduction of activity of the anion exchanger 2 (AE2) with the resultant activation of the intracellular soluble adenylyl cyclase (sAC). The role of toxic bile acids is also presented. A sequence of events is proposed including involvement of the gut-liver axis and the possible role of ferroptosis. Finally, a brief account of the initial trigger of the disease is given.

Drug-induced liver injury (DILI) is an adverse reaction to drugs and other xenobiotics that can have serious consequences and jeopardise progress in pharmacological therapy. While DILI is predominantly hepatocellular, a non-negligible percentage of patients who present with cholestatic damage. Mixed damage is typically lumped together with cholestatic damage in the literature. Drug-induced cholestasis is often caused by the use of some non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics (i.e., amoxicillin-clavulanic acid), statins, and anabolic agents, among others. Drug-associated cholestasis tends to have a more chronic course and mostly affects older population. There is also a genetic predisposition to toxic cholestasis caused by some drugs (amoxicillin-clavulanic acid, statins, etc.). Recently, anatomical alterations of the biliary tract induced by drugs (especially immunotherapy drugs) have been described. Bile duct injury is one of the histopathological findings that have prognostic significance in DILI. A correct differential diagnosis with other causes of cholestasis is mandatory to reach an accurate diagnosis. Ursodexycholic acid, corticosteroids, and replacement therapies have been used as a therapeutic arsenal, although more evidence is needed to establish them as a routine therapeutic management in clinical practice. The breakthrough and validation of biomarkers of cholestasis and bile duct injury is an urgent need for drug development and post-marketing phase.

Nonalcoholic fatty liver disease (NAFLD) is an umbrella definition that describes the ectopic deposition of fat within the liver that occurs in the absence of inciting factors other than the metabolic syndrome and its individual features. NAFLD has a multi-factorial pathogenesis which determines heterogeneous clinical phenotypes and variable natural course spanning from liver-related (steatohepatitis, fibrosis, cirrhosis, hepatocellular carcinoma) to extrahepatic outcomes (cardio-metabolic and cancer). This narrative review article leverages the key aspects of disease natural history as the background information to discuss studies that may inform strategies to risk-stratify NAFLD patients. Evaluation of hepatic fibrosis with non-invasive tools, including blood-based biomarkers and imaging-based elastometry techniques, seemingly retains the core information useful to predict the heterogeneous outcomes listed above. Additionally, genetic testing and metabolomic profiles may also be utilized to this end. In conclusion, a comprehensive understanding of the variable hepatic, cardio-metabolic and cancer outcomes of NAFLD may enable physicians and researchers to risk-stratify and accurately identify the multilayered prognosis of NAFLD individuals while also defining homogeneous patient subsets to enroll in clinical trials.

Primary biliary cholangitis (PBC), previously known as primary biliary cirrhosis, is a rare chronic autoimmune cholestatic liver disease, affecting mostly females. With PBС develops chronic cholangiopathy, this is accompanied by the development of gradually progressive liver fibrosis, which leads to intrahepatic cholestasis. Defects in autoimmune tolerance are critical factors in the emergence of the disease. Biochemical signs in PBС appear already in the asymptomatic stage of the disease and they are associated with a disturbance of the secretion of bile acids. Understanding the pathophysiological mechanisms of these signs is essential to both the early diagnosis and treatment of PBC. Early diagnosis of the disease contributes to its more effective treatment. There are many scientifically based modern data on the pathophysiology of clinical and laboratory signs developing in PBС. The purpose of this review is to summarize the data available in the literature and those obtained by the authors on the mechanisms for the development of biochemical criteria for PBC and their diagnostic significance. The opportunity to present the pathophysiological mechanisms of the development of biochemical signs in patients with PBC is associated with the success in the development of modern research methods in biochemistry, molecular biology, and genetics.

A high consumption of ultra-processed food (UPF) is a hallmark of Western diets that has been related to increased risk of non-communicable diseases. As an underlying mechanism, UPF may promote non-alcoholic fatty liver disease (NAFLD) which is a key driver of metabolic impairment with extra-hepatic manifestations like type 2 diabetes, cardiovascular disease, chronic kidney disease, and osteoporosis among others. The present review provides an overview of UPF properties that may promote NAFLD and are thus potential targets for reformulation of UPF. Such approaches should address improvements in the quality of carbohydrates and fat, changes in food texture that lower eating rate as well as ingredients that prevent excess caloric intake or avoid dysbiosis and leaky gut syndrome. Promising strategies are enrichment with fiber, prebiotics, phytochemicals, and protein with a concurrent reduction in glycemic load, energy density, saturated fatty acids (FA; SFA), emulsifiers, fructose, and non-caloric sweeteners. Future studies are needed to examine the interactive and protective effects of such modifications in the composition of UPF on prevention and treatment of NAFLD.

Excessive alcohol intake is still among the leading causes of chronic liver diseases. Epidemiological studies suggest that per capita consumption of alcohol from various alcohol beverages e.g., beer, wine, or spirits, differs markedly between different areas of the world. Studies further suggest that different alcoholic beverages may impact the development of alcohol-related liver diseases (ALD) differentially. Specifically, results of several more recent epidemiological studies suggest that consumption of wine and herein especially of red wine may be less harmful in relation to the development of liver diseases than the intake of hard spirits. Results of studies evaluating the effects of beer on the development of ALD in humans are rather contradictory. Here, results of studies assessing the impact of wine, beer, and spirits on the development of ALD as well as possible underlying mechanisms are summarized and discussed.

The pathogenesis of drug-induced liver injury (DILI) is still in an early stage of research. However, investigators have shown that both oxidative stress and endoplasmic reticulum (ER) stress play a significant role in the pathological mechanism. However, there is little in-depth literature about these two mechanisms. In order to prevent and improve the clinical symptoms of DILI, it is particularly important to study its pathogenesis. In this review article, the role of ER and oxidative stress in DILI is thoroughly discussed.

The word “Kampo medicine” means the traditional Japanese herbal medicine. Even “natural herb” can cause drug-induced liver injury (DILI). In this review, the characteristics of Kampo medicine-induced liver injury (KMILI) are reported. The main causative herb involved in Kampo medicine is Scutellariae Radix. KMILI is based on certain hypersensitivity reactions. A small amount of Kampo medicine can cause liver injury, and KMILI can develop after a short latency period. The incidence of liver injury related to Scutellariae Radix is about 1%. KMILI is usually mild and not fatal. The latency period usually lasts 4 weeks to 24 weeks. Fatigue and loss of appetite are sometimes observed. Eosinophilia is not frequently observed. All three types of liver injuries are observed in KMILI: cholestatic, hepatocellular, and mixed types. In Japan, lymphocyte transformation test (LTT) has been generally used for the diagnosis of DILI; however, LTT is likely to yield false-positive result for Kampo medicines, and thus often leads to misdiagnosis in many cases. Recently, researchers reported that a specific human leukocyte antigen (HLA) genotype is possibly associated with KMILI. This hypothesis needs to be examined further. Although Kampo medicine is based on rich knowledge and experience that occurred over a period of thousands of years, much is still unknown about KMILI.

The late event onset of a fraction of idiosyncratic drug-induced liver injury (DILI) cases and the link observed by genome-wide association studies (GWASs) of certain human leucocyte antigen (HLA) alleles with DILI due to specific drugs support the crucial role of the immune system (both innate and adaptive) in the pathogenesis of DILI. Recent advances in both flow and mass cytometry have allowed the profiling of all major immune cell types in a given sample. Therefore, determining the lymphocyte populations in samples from patients with DILI would facilitate the development of specific biomarkers for DILI diagnosis and prognosis. To date, a few studies have explored the immune landscape in DILI. In a recent study of leukocyte immunophenotyping using flow cytometry from the Spanish DILI Registry, an important role of adaptive immune response in DILI is suggested. DILI patients had significantly higher levels of T helper 1 (Th1) cells and activated helper and cytotoxic T cells than healthy controls. Furthermore, the increased expression of negative immune checkpoints and ligands in DILI patients could reflect a restoration of the immune homeostasis. Differences in the profile of cytokines in DILI patients from the Drug-Induced Liver Injury Network (DILIN) also suggest an involvement of both innate and adaptive immune systems in DILI development and prognosis. Moreover, several studies based on immunophenotyping of liver infiltrates showed a distinctive pattern of cellular infiltrates in patients with immune checkpoint inhibitors (ICIs)-DILI, with lower levels of plasma cells, CD20⁺ B cells and CD4⁺ T cells than in autoimmune hepatitis (AIH) patients. These pioneering studies highlight the importance of immunophenotyping for the mechanistic understanding of DILI. In this review, available data on immunophenotyping in DILI are gathered, and the potential clinical applications of cutting-edge, novel immunophenotyping techniques are discussed.

Zebrafish as a preclinical drug induced liver injury (DILI) model provides multiple advantages ranging from ease of breeding and maintenance, availability of different strains and transgenic fish amenable to study liver function, and highly conserved liver structure and function with the human liver. In this review, the authors have aimed to provide an account of the metabolic enzymes that take roles in drug detoxification in both human and zebrafish in a comparative manner and exemplify several recent models in studying liver functionality. Moreover, the authors emphasize the difficulties associated with studying idiosyncratic DILI in preclinical models and propose that zebrafish could be an important complement to mice in testing functions of genes that are associated with DILI with respect to different drugs in human genome-wide association studies (GWAS) Catalog. Finally, this review highlights the state-of-the-art in the development of novel transgenic reporter strains that can be used to study degree and molecular mechanisms of hepatotoxicity caused by drugs in zebrafish. All of these will help researchers to use effectively the available resources in the zebrafish DILI models, while advocating potential leads that can be taken to provide advancements in a better understanding and treatment of DILI.

Hereditary cholestasis comprises a broad spectrum of clinical phenotypes of varying severity. Severe forms such as progressive familial intrahepatic cholestasis (PFIC) mostly affect children with disease onset within their first years. Nevertheless, late-onset PFIC forms are increasingly diagnosed. Most adults present with less severe forms of hereditary cholestasis, often suffering from pruritus, gallstone disease, jaundice, or elevated liver enzymes. To identify the underlying genetic background and to rule out potential differential diagnoses, a broad genetic analysis like whole exome sequencing (WES) is recommended. Knowledge of the affected gene may have an impact not only on patient surveillance due to risk for disease progression or tumor development but also on potential therapeutic strategies. This case of the adult patient illustrates the importance of broad genetic analysis, which brought up the potentially relevant rare multidrug resistance protein 3 (MDR3) missense variant p.(Asn489Tyr) underlying the patient’s clinical phenotype of low phospholipid-associated cholelithiasis (LPAC). Patients with MDR3 disease may have an increased risk for cholangiocarcinoma (CCA) development and therefore need an individualized surveillance strategy. Most MDR3-affected patients benefit from life-long therapy with ursodeoxycholic acid (UDCA), which is well tolerated. Bezafibrate treatment can reduce pruritus, one of the main symptoms affecting the quality of life. Whether the administration of ileal bile acid transporter (IBAT) inhibitors is beneficial in adult patients with MDR3 disease is so far unknown.

Evaluation of the hepatobiliary function is critical for the clinicians, not only for the diagnosis of a large variety of liver diseases but also in the follow-up and management of some patients, for instance, those with different degrees of cholestasis suffering from a drug-induced liver injury (DILI) or scheduled for liver resection. Currently, the determination of global liver function mainly relies on laboratory tests, clinical scores, and data from images obtained with ultrasonography, computed tomography (CT), or magnetic resonance. Nuclear medicine scanning, displaying either planar or three-dimensional spatial distribution of liver function, is enhanced when using hepatotropic tracers based on classical radioisotopes such as technetium-99m (^99mTc) and with higher resolution using metabolized probes such as those based on monosaccharide derivatives labeled with ¹⁸F. Other cholephilic compounds, and hence selectively secreted into bile, have been proposed to visualize the correct function of the liver parenchyma and the associated secretory machinery. This review aims to summarize the state-of-the-art regarding the techniques and chemical probes available to monitor liver and gallbladder function, in some cases based on imaging techniques reflecting the dynamic of labeled cholephilic compounds.

Lysosomal hydrolases were once considered effectors of the waste disposal system of the cell, the endo-lysosomal system. However, they are now recognized as highly selective enzymes, which can modulate the function of several substrates, contributing to essential homeostatic and pathological cellular processes. There are more than 50 different lysosomal hydrolases that display optimal activity in the pH present in the acidic cellular compartment but can also be found in other cellular locations. They can work alone or in cooperation with other proteases building signaling pathways or amplification cascades. In the context of liver fibrosis lysosomal hydrolases, especially cysteine cathepsins have been described to participate in several fundamental cellular events contributing to the development, progression, perpetuation, and resolution of liver fibrosis. This paper comprehensively reviews the current knowledge on the contribution of lysosomal hydrolases to liver fibrosis.

Metabolic zonation in the liver carries out the maintenance of organ and body homeostasis. Hypoxia is an inherent physiological feature of the liver and contributes to the zonal properties of the hepatic parenchyma. As a master regulator of hypoxia, the transcription factor hypoxia-inducing factor (HIF) is stabilized primarily by oxygen availability, and it is thought to contribute to steatohepatitis due to alcohol-related (ASH) and non-alcohol-related liver disease (NASH). Cholesterol has emerged as an important player in both diseases, and hypoxia increases hepatic cholesterol levels. Steroidogenic acute regulatory protein 1 (STARD1) is a mitochondrial outer membrane protein that transfers cholesterol to mitochondrial inner membrane for metabolic processing and acts as the rate-limiting step in the alternative pathway of bile acid synthesis in hepatocytes. STARD1 expression increases in ASH and NASH and determines the accumulation of cholesterol in mitochondria, which impacts the physico-chemical mitochondrial membranes properties and as a consequence impairs the activity of specific mitochondrial solute carriers, such as the 2-oxoglutarate carrier (2-OGC), limiting the exchange between cytosolic glutathione and mitochondrial 2-oxoglutarate (2-OG). Although HIF-1 is stabilized in hypoxia largely due to the requirement of prolylhydroxylases (PHDs) for oxygen to signal HIF degradation, PHDs are also dependent on 2-OG, and therefore it is conceivable that impairment of 2-OGC by STARD1-mediated cholesterol accumulation may contribute to HIF-1 stabilization due in part to decreased availability of cytosolic 2-OG. In this perspective, this review explores the interplay between HIF-1 stabilization and STARD1 induction and the potential contribution of this functional relationship to ASH and NASH.

During liver injury and cholestasis, the mechanisms allowing the organ to protect itself with the aim of maintaining biliary homeostasis are not completely understood. Central to their biological roles, bile acids (BAs) and their receptors constitute a signaling network with multiple molecular and cellular impacts on both liver repair and protection from BA overload. BA signal through nuclear [mainly farnesoid X receptor (FXR)] and membrane [mainly G protein-coupled BA receptor 1 (GPBAR-1), aka Takeda G protein-coupled receptor 5 (TGR5)] receptors, in which activation elicits a wide array of biological responses. So far, most of the studies have been focused on FXR signaling as hepato-protective, TGR5 being less explored to this regard. While the liver faces massive and potentially harmful BA overload during cholestasis, it is crucial to understand that BAs induce also protective responses contributing not only to reduce the inflammatory burden, but also to spare liver cells and their repair capacities. Based on the available literature, the TGR5 BA receptor protects the liver in the cholestatic context and counteracts BA overload with the aim of restoring biliary homeostasis mainly through the control of inflammatory processes, biliary epithelial barrier permeability, and BA pool composition. Mouse experimental models of cholestasis reveal that the lack of TGR5 was associated with exacerbated inflammation and necrosis, leaky biliary epithelium, and excessive BA pool hydrophobicity, resulting in biliary cell and parenchymal insult, and compromising optimal restoration of biliary homeostasis and liver repair. There are thus widely opened translational perspectives with the aim of targeting TGR5-related signaling or biological responses to trigger protection of the cholestatic liver.

Several metabolic pathways are involved in the biotransformation of C27 neutral cholesterol to C24 primary bile acids (BAs), mainly cholic acid (CA) and chenodeoxycholic acid (CDCA), which are then conjugated with glycine or taurine. This process can start with the modification of the steroid ring or the shortening of the side chain and involves enzymes present in different subcellular compartments. Inborn errors affecting the biogenesis of organelles, such as peroxisomes, or the expression or function of specific enzymes of these convergent routes result in: i) the lack of mature C24-BAs, with the subsequent impairment in digestion and absorption of dietary fat and liposoluble vitamins, such as vitamin K, which may account for a deficient hepatic synthesis of several coagulation factors; ii) the accumulation of intermediate metabolites, which may affect hepatocyte physiology, causing cholestasis as a commonly shared alteration besides other deleterious hepatic events; and iii) extrahepatic clinical manifestations due to accumulation of toxic metabolites in other territories, such as the nervous system, causing neurological disorders. In general, diseases whose primary alteration is a genetic defect in BA synthesis are diagnosed in children or young individuals with a very low incidence. The symptomatology can markedly vary among individuals, ranging from mild to severe conditions. Oral therapy, based on the enrichment of the BA pool with natural C24-BAs, such as CA, CDCA, glyco-CA, or ursodeoxycholic acid (UDCA), depending on the exact deficiency causing the disease, may be beneficial in preventing life-threatening situations. In contrast, in other cases, a liver transplant is the only option for these patients. This review describes the updated information on the genetic and molecular bases of these diseases and the current approaches to achieve a selective diagnosis and specific treatment.

Normal hepatobiliary function depends on an adequate bile flow from the liver through the biliary tree to the gallbladder, where bile is stored and concentrated, and from the gallbladder to the duodenum when it is required for the digestive process. Interruption of this secretory function results in partial or complete cholestasis, which is accompanied by important repercussions due to the lack of bile acids in the intestine and their regurgitation from hepatocytes to blood together with potentially toxic compounds that are normally eliminated in bile. The presence of active and selective transporter proteins located at both poles of the plasma membrane of hepatocytes, cholangiocytes, and epithelial cells of the ileal mucosa, together with the ability of hepatocytes to synthesize bile acids from cholesterol, enables the so-called bile acid enterohepatic circulation, which is essential in liver and gastrointestinal tract physiology. The presence in the ducts of the biliary tree of agents reducing their luminal diameter by external compression or space-occupying obstacles, either in the duct wall or its lumen, can result in total or partial obstructive cholestasis. The clinical impact and management of cholestasis are different depending on the intrahepatic or extrahepatic location of the obstacle. Thus, surgical interventions can often be helpful in removing extrahepatic obstructions and restoring normal bile flow to the duodenum. In contrast, hepatocyte or cholangiocyte damage, either global, restricted to subcellular compartments, or more specifically affecting the elements of the canalicular secretory machinery, may result in hepatocellular cholestasis or cholangiopathies. In these cases, bile flow interruption is usually partial and, except for extremely severe cases when liver transplantation is required, these patients often treated with pharmacological agents, such as ursodeoxycholic acid (UDCA) and rifampicin. The present review gathers updated information on the etiopathogenesis and pathophysiological aspects of different types of cholestasis.

Caspases are key factors in the regulation of the apoptotic and/or inflammatory responses, both crucial in the pathogenesis of diverse diseases. Caspase-2 is the most evolutionary conserved albeit functionally poorly defined member of the caspase family. The precise role of caspase-2 as an initiator or effector caspase is still unknown, but it has been involved in a wide variety of functions, from apoptosis to genomic stability, oxidative stress, metabolism, and cancer. However, many conflicting results render the exact function of this protease still unresolved. Although caspase-2 has several hundred substrates, the activation, processing, and activity on specific substrates remain poorly described. Recent evidence indicates that caspase-2 has a role in metabolic homeostasis and is required for lipotoxicity-induced apoptosis in hepatocytes, contributing to non-alcoholic steatohepatitis (NASH) progression towards hepatocellular carcinoma (HCC). Caspase-2 protein expression strongly localizes to injured/ballooned hepatocytes, correlating with NASH severity. Also, mice lacking caspase-2 showed protection from western diet-induced obesity, dyslipidemia, and insulin resistance. Although there are no effective therapies for NASH and HCC, the evaluation of a pan-caspase inhibitor has reached a phase I/II in clinical trials for advanced liver disease. Nevertheless, a better understanding of caspase functions with the identification of specific proteolytic substrates is essential for future therapeutic developments. Bearing in mind the pressing need to identify new targets for NASH-HCC and its metabolic-related comorbidities, and the favorable effect of caspase-2 genetic inhibition in animal models, pharmacological caspase-2 inhibition arises as a promising strategy that should be further investigated.

The surface of intestinal epithelial cells is covered by the brush border, which consists of densely packed cellular extrusions called microvilli. Until recently, microvilli have not been known to be interconnected. In 2014, a protein complex, called the intermicrovillar adhesion complex (IMAC) which is located at the tips of the microvilli and responsible for the regular spatial organization of the brush border, was identified. Deletion of IMAC components such as cadherin-related family member-2 (CDHR2) in mice resulted in microvillus disorganization and fanning, a structural aberration that is also found in the brush border of patients with inflammatory bowel disease. The etiology of inflammatory bowel disease has been primarily associated with dysfunctional mucosal immunity, but the discovery of the IMAC may encourage theories of an epithelial origin. Here, possible effects of the brush border on the gut barrier function and intestinal inflammation are discussed proposing that the IMAC protects against inflammation through its microvillus cross-linking function.

Worldwide the number of individuals being overweight or obese has dramatically increased during the last decades, which is also associated with a similar dramatic increase of individuals afflicted with metabolic disorders like dyslipidemia, hypertension, and non-alcoholic fatty liver disease (NAFLD). Genetic predisposition may account for some of the increases in body weight and the development of metabolic disorders; however, much is probably also related to the changes in physical activity and dietary pattern. Indeed, results of epidemiological studies suggest that a ‘western-type dietary pattern’ composed of highly processed foods, sweetened foods, and beverages, all adding to a low fiber but high sugar and saturated fat intake, may increase the odd of developing overweight and metabolic disorders. Consumption of sugar, and especially, fructose has repeatedly been discussed to be a key contributor to the development of health disturbances including hypertension, dyslipidemia, insulin resistance as well as NAFLD. However, despite intense research effort, the question if and how (high) dietary fructose intake interferes with human health has not yet been fully answered also as findings are sometimes contradictory. In the present narrative review, results of recent studies assessing the effect of fructose consumption on the development of metabolic disorders including hypertension, dyslipidemia, cardiovascular diseases (CVDs), hyperinsulinemia, and NAFLD as well as underlying molecular mechanisms are reviewed, thereby, aiming to further address the question if (high) fructose intake is a trigger of metabolic diseases.

Hepatocellular carcinoma (HCC) is considered one of the most aggressive tumors worldwide. The consumption of lipid-enriched diets, mainly high cholesterol, induces oxidative stress and chronic inflammation, leading to HCC progression. Moreover, fatty acids and cholesterol could display differential responses on immune cells inside the tumor immune microenvironment (TIME). Tumor-associated macrophages (TAMs) represent one of the most critical leukocytes in the tumor microenvironment (TME) displaying pro-tumoral responses and one of the mainly cholesterol donors to cancer cells. Immunotherapy or cholesterol regulators, alone or combined, would represent an effective strategy for HCC treatment. Nonetheless, steatotic etiology from non-alcoholic fatty liver disease (NAFLD)-HCC tumors has been unexpectedly resulting in highly aggressive behavior.

The prevalence of metabolic dysfunction-associated fatty liver disease (MAFLD) is increasing rapidly worldwide due to the obesity epidemic. Advanced stages of the MAFLD, such as non-alcoholic steatohepatitis (NASH) with advanced fibrosis or cirrhosis are affecting global health. Extracellular vesicles (EVs) are released by all cell types and are important in cell-to-cell communication and maintaining homeostasis, but they also play a role in the pathogenesis of various diseases. EVs contain biological information such as lipids, proteins, messenger RNAs (mRNAs), small RNAs, and DNA, and they act on (distant) target cells. The cargo of EVs is dependent on the type and the state of the releasing cell. EVs have been proposed as biomarkers, prognostic, and even therapeutic agents, also in the context of liver diseases. This review aims to give an overview of the current knowledge on EVs in MAFLD, including the role and interaction of EVs with different cell types in the liver. Several aspects of EVs, including their origin, characteristics, cargo, and functions are reviewed. Moreover, the potential of EVs as targets for the treatment of MAFLD is discussed.