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.

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.

It is generally accepted that eradication of Helicobacter pylori (H. pylori) infection may reduce the risk of the development of gastric cancer. Recommendations for global generalized tests and treat all individuals detected positive for H. pylori infection are currently proposed. However, the bacterium is commensal and harmless for the vast majority of the infected population. Moreover, eradication may have detrimental consequences in several groups of patients. In the present review, the current epidemiological data and recommendations for eradication in connection with the possible beneficial effects of the colonization with H. pylori in diseases such as asthma and allergies or chronic gastro-intestinal disorders such as inflammatory bowel disease and Barrett’ esophagus are presented the problems with increasing antibiotic resistance were also examined. Specific groups of patients where eradication of H. pylori may be necessary and endoscopic surveillance is advised were identified. Finally, based on the paradox of high H. pylori prevalence and low gastric risk as reported for areas of Africa, Asia, South America, and Greece, alternatives that may replace the widespread eradication of H. pylori with equal if not better results and more prudent use of the available financial resources are proposed. Mediterranean diets and alcohol and smoking reduction are among the well documented alternatives.

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and its death rate is rising faster than that of any other cancer, while we still lack effective treatments. The increasing incidence of liver cancer in western countries is closely associated with the growing prevalence of metabolic dysfunction-associated steatohepatitis (MASH) linked to metabolic diseases. While the contribution of lipids in the progression of MASH pathogenesis and its progression to HCC is well recognized, the specific contribution of cholesterol is subject to controversy. The liver plays a central role in cholesterol metabolism, where the majority of its biosynthesis, storage, excretion, recycling, and conversion into bile acids occur. Moreover, cholesterol is implicated in numerous hepatocyte cellular processes, encompassing endoplasmic reticulum function, formation of lipid microdomains in the plasma membrane, metabolism of lipoproteins, and mitochondrial function and performance. Therefore, it is not surprising that cholesterol plays key roles in initiation, promotion, and survival of HCC cells and there are several lines of evidence pointing to that cancer cells are subverting cholesterol metabolism to foster their proliferation and survival through various mechanisms. This narrative review provides a concise overview of the physiological and pathological roles of cholesterol in the transition from healthy hepatocytes to HCC, in the context of MASH. Gaining further understanding of how hepatic cancer cells disrupt cholesterol homeostasis and how these perturbations impact cancer progression will facilitate the identification of novel and more effective cancer treatment strategies in this complex and devastating disease.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Lipids are intricate biomolecules responsible for the building up of biological membranes. Besides this structural function, they also display crucial roles in signaling, acting as second messengers that activate specific pathways. Mitochondria are fundamental for cells as they participate in several pivotal functions, such as ATP synthesis, cell survival, metabolic pathways, and calcium homeostasis. Thus, the lipid composition of mitochondrial membranes can affect specific proteins and impact vital functions of mitochondria, such as oxidative phosphorylation and dynamics. The liver possesses a critical function in lipid homeostasis, involving the generation, oxidation, and trafficking of free fatty acids (FFA), triglycerides (TG), cholesterol, and bile acids (BAs). Mitochondria play a key role in lipid storage regulation in hepatocytes, which can control liver function. Their diverse tasks are affected by the lipid composition of mitochondrial membranes, characterized by low cholesterol content and enrichment of specific lipids such as cardiolipin. As mitochondria determine the bioenergetic status of cells and are key regulators of cell viability, alterations of mitochondrial lipid composition can contribute to the induction and progression of chronic diseases, including alcohol-related liver disease (ARLD) and metabolic dysfunction-associated steatotic liver disease (MASLD), two of the most common forms of liver diseases characterized by steatosis, necroinflammation, and fibrosis, which can progress to hepatocellular carcinoma (HCC). Thus, the disruption of lipid metabolism and membrane composition of mitochondria are characteristic features of cancer cells, and altered mitochondrial lipid composition may be a critical player in the progression of chronic liver diseases toward HCC. This review will address the mechanisms whereby alterations of mitochondrial lipid composition lead to the onset and progression of chronic liver diseases. Thus, a better characterization of the alterations of lipid composition in mitochondria may be a crucial step to design strategies and novel therapeutic opportunities for the treatment of MASLD and ARLD.

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 formation of metabolic changes is based on many factors. In particular, the infectious theory of the development of metabolic “breakdowns” has not lost its relevance. In this regard, many scientists are investigating the role of various microorganisms in the pathogenesis of metabolic syndrome. The review provides the results of current research on the role of Helicobacter pylori (as one of the most well-known and widespread bacterial pathogens) in the pathogenesis of metabolic syndrome. However, the results of scientific work are sometimes contradictory, which dictates the need for novel further research to clarify the characteristics of the influence Helicobacter pylori on the formation of various components of the metabolic syndrome.

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.

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.