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.

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.

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.

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.

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.

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.

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.

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.

Drug-induced liver injury (DILI) poses a complex and heterogeneous clinical challenge, which often resembles non-drug related acute or chronic liver diseases, such as metabolic dysfunction-associated steatotic liver disease (MASLD). Furthermore, certain drugs can induce hepatic steatosis, which is considered a rare variant of hepatotoxicity. Additionally, the detection and diagnosis of DILI in patients with non-alcoholic liver disease present additional challenges that require attention. The importance of achieving an accurate diagnosis is highlighted by the different therapeutic approaches needed for each of these diseases. Nonetheless, as definitive diagnostic tests and distinct biomarkers often remain elusive, the differential diagnosis must rely on a combination of clinical, biochemical, histological, and immunophenotypic profiling. The diagnosis of hepatotoxicity is predicated upon the temporal nexus between the administration of a potentially hepatotoxic drug and the onset of hepatic injury, concomitantly excluding alternative hepatic pathologies. More frequently, this condition presents an acute course, with a more pronounced elevation of cytolytic and cholestatic parameters as compared to fatty liver disease. Advances in elucidating the underlying mechanisms hold promise for bolstering the diagnosis and management of these conditions. This article aims to thoroughly examine and emphasize the currently available scientific evidence to provide valuable insights into the diagnostic strategies for DILI, metabolic-associated liver disease, and drug-induced steatosis (DIS).

Hunting for tumoral material in body fluids, traditionally in blood, the so-called liquid biopsy is set to revolutionize the diagnosis and management of oncological patients. However, other biofluids can also be considered as alternative sources of biomarkers to provide clinically valuable information for multiple diseases. This is the case of bile, a fluid produced in the liver, stored in the gallbladder, and excreted to the duodenum, which complex composition is known to change in different pathological conditions. Remarkably, different works have demonstrated that the identification of mutations in bile cell-free DNA (cfDNA) can outperform blood analysis for the early diagnosis of biliopancreatic tumors causing biliary strictures. Here, the literature in which bile has been tested as a liquid biopsy matrix where lipids, metabolites, proteins, and cfDNA among other analytes were measured is reviewed. Moreover, the clinical situations and procedures where bile can be available, discussing the possible applications and limitations of bile analysis are summarized. The scientific relevance and clinical potential of bile harvesting, biobanking, and analysis are put forward. All this evidence supports the value of bile as a liquid biopsy matrix for the management of patients beyond cancer, and perhaps also beyond “blood, sweat, and tears”.

Chronic liver diseases (CLDs), which are typically characterized by fibrogenic progression towards liver cirrhosis and related complications eventually leading to organ failure and can also lead to the development of primary liver cancers, represent a major burden for human health on a worldwide basis. Although the present knowledge on the pathogenesis of CLDs progression and primary liver cancers development has remarkably increased in the last decades, critical molecular mediators remain incompletely understood, and approved antifibrotic therapies to efficiently counteract CLDs progression and liver cancer are lacking. In the present review, this study will specifically analyse the putative contribution of SERPINB3, a member of the superfamily of serine-protease inhibitors (SERPINs), which has been shown to exert significant pro-inflammatory and pro-fibrogenic roles in progressive CLDs as well as to be involved in the development of primary liver cancers, including hepatocellular carcinoma (HCC), cholangiocarcinoma, and hepatoblastoma.

Mitochondria are present in all mammalian cells except matured red blood cells. Mitochondria consist of several metabolic pathways for glucose, fatty acids, amino acids, and bioenergetic pathways for ATP synthesis, membrane potential, and reactive oxygen production. In the liver, hepatic mitochondria play a key role in hepatic steatosis because mitochondrial metabolism produces acetyl-CoA which is the building block for synthesis of lipids and cholesterol. Mitochondria inner membrane is impermeable of metabolites, reducing equivalents, and small molecules such as phosphate, and sulfate. Thus, mitochondrial shuttles and carriers function as the routes of influx and efflux of these metabolites and molecules across the inner membrane. The signal regulation of these shuttles and mitochondrial enzymes could play a key role in coordinating the mitochondrial metabolism to adapt the cytosolic part of metabolic pathways in liver metabolic stress. Intriguingly, the interaction of mitochondria protein SH3 domain-binding protein 5 (SAB/SH3BP5) and c-Jun N-terminal kinase (JNK) was found as a pivotal role in sustained activation of JNK and phosphorylated-JNK (P-JNK) mediated activation of lipogenic pathway in nutritional excess. Knockout or knockdown of SAB prevented or reversed the hepatic steatosis, inflammation, and fibrosis, and improved metabolic intolerance and energy expenditure. Moreover, blocking the SAB peptide prevents palmitic acid-induced P-JNK interaction with SAB and inhibition of mitochondrial bioenergetics, implying the P-JNK effect on mitochondrial metabolism. This review focuses on the flow of mitochondrial metabolites in metabolic stress conditions and the contribution of mitochondria and mitochondrial stress signals in hepatic steatosis.

The liver, characterized by a unique metabolic and immunosuppressive environment, is also the organ to which invasive malignant cells of many different cancer types most frequently metastasize. The reasons for this organ-specific metastatic process have been investigated for decades. This review first provides an overview of recent breakthroughs in this field, introducing intercellular communication between circulating tumor cells and the heterogeneous cell populations of the liver, and modifications to the extracellular matrix (ECM). Subsequently, to improve the understanding of the molecular mechanisms involved in the metastasis of colorectal cancer to the liver, the second leading cause of cancer-related mortality, the recent literature on this question was analyzed. Among the various parameters involved, the mechanisms behind the activation of hepatic stellate cells, proteins inducing ECM remodeling, specific genomic features of liver metastases, metabolic rewiring, and characteristics of stromal-enriched microenvironments were discussed. To provide more insights into the molecular determinants of liver metastatic colonization, important findings reported on a set of mitochondrial proteins were addressed, the relative abundance of which changed in the liver during the progression stage of an aggressive experimental model of peritoneal malignant mesothelioma in immunocompetent rats. Based on previous studies cross-comparing the liver proteomes from curcumin-treated tumor-bearing rats/untreated tumor-bearing rats/normal rats, data from the literature were reviewed for 25 mitochondrial proteins of interest. Their role in lipid metabolism, heme biosynthesis, the electron transport chain, small molecule transport, mitochondrial dynamics, the tricarboxylic acid cycle, and protection against oxidative stress were analyzed in the context of both cancer and non-malignant liver diseases.