Extracellular Vesicles: A New Frontier in Biomarker Discovery for Non-Alcoholic Fatty Liver Disease. Int J Mol Sci. 2016;17:376. [PMID: 26985892 PMCID: PMC4813235 DOI: 10.3390/ijms17030376]

Extracellular Vesicles in Viral Liver Diseases

Extracellular vesicles (EVs) are bilayer vesicles released by cells in the microenvironment of the liver including parenchymal and non-parenchymal cells. They are the third important mechanism in the communications between cells, besides the secretion of cytokines and chemokines and the direct cell-to-cell contact. The aim of this review is to discuss the important role of EVs in viral liver disease, as there is increasing evidence that the transportation of viral proteins, all types of RNA, and viral particles including complete virions is implicated in the pathogenesis of both viral cirrhosis and viral-related hepatocellular carcinoma. The biogenesis of EVs is discussed and their role in the pathogenesis of viral liver diseases is presented. Their use as diagnostic and prognostic biomarkers is also analyzed. Most importantly, the significance of possible novel treatment strategies for liver fibrosis and hepatocellular carcinoma is presented, although available data are based on experimental evidence and clinical trials have not been reported.

Exosome prospects in the diagnosis and treatment of non-alcoholic fatty liver disease

The growing prevalence of NAFLD and its global health burden have provoked considerable research on possible diagnostic and therapeutic options for NAFLD. Although various pathophysiological mechanisms and genetic factors have been identified to be associated with NAFLD, its treatment remains challenging. In recent years, exosomes have attracted widespread attention for their role in metabolic dysfunctions and their efficacy as pathological biomarkers. Exosomes have also shown tremendous potential in treating a variety of disorders. With increasing evidence supporting the significant role of exosomes in NAFLD pathogenesis, their theragnostic potential has become a point of interest in NAFLD. Expectedly, exosome-based treatment strategies have shown promise in the prevention and amelioration of NAFLD in preclinical studies. However, there are still serious challenges in preparing, standardizing, and applying exosome-based therapies as a routine clinical option that should be overcome. Due to the great potential of this novel theragnostic agent in NAFLD, further investigations on their safety, clinical efficacy, and application standardization are highly recommended.

Extracellular vesicles-derived ferritin from lipid-induced hepatocytes regulates activation of hepatic stellate cells

Introduction

and objectives: Extracellular vesicles (EVs) have emerged as key players in intercellular communication within the context of non-alcoholic fatty liver disease (NAFLD). This study aims to explore the intricate crosstalk between hepatocytes and hepatic stellate cells (HSCs) mediated by EVs in NAFLD.

Materials and methods

EVs ferritin was detected in hepatocytes stimulated with free fatty acids (FFA) as well as in NAFLD mice. Deferoxamine (DFO) was employed to reduce ferritin levels, while GW4869 was utilized to inhibit EVs. The impact of EVs ferritin on the HSCs activation was evaluated both in vitro and in vivo. Additionally, serum EVs ferritin levels were compared between NAFLD patients and controls.

Results

FFA treatment induces the formation and secretion of EVs and facilitates the release of ferritin from hepatocytes via EVs. Subsequently, EVs ferritin is hijacked by HSCs, prompting accelerated HSCs activation. Silencing ferritin with DFO and inhibiting EVs formation and secretion with GW4869 can reverse the effects of FFA treatment and disrupt the communication between hepatocytes and HSCs. Accumulation of ferritin leads to excessive reactive oxygen species (ROS) production, promoting HSCs fibrogenesis. Conversely, depleting EVs ferritin cargo restores liver function, concurrently mitigating NAFLD-associated fibrosis. Notably, NAFLD patients exhibit significantly elevated levels of serum EVs ferritin.

Conclusions

This study unveils a previously underestimated role of ferritin in HSCs upon its release from hepatocytes, emphasizing DFO as a promising compound to impede NAFLD advancement.

Extracellular vesicles as modulators of glioblastoma progression and tumor microenvironment

Glioblastoma is the most aggressive brain tumor with extremely poor prognosis in adults. Routine treatments include surgery, chemotherapy, and radiotherapy; however, these may lead to rapid relapse and development of therapy-resistant tumor. Glioblastoma cells are known to communicate with macrophages, microglia, endothelial cells, astrocytes, and immune cells in the tumor microenvironment (TME) to promote tumor preservation. It was recently demonstrated that Glioblastoma-derived extracellular vesicles (EVs) participate in bidirectional intercellular communication in the TME. Apart from promoting glioblastoma cell proliferation, migration, and angiogenesis, EVs and their cargos (primarily proteins and miRNAs) can act as biomarkers for tumor diagnosis and prognosis. Furthermore, they can be used as therapeutic tools. In this review, the mechanisms of Glioblastoma-EVs biogenesis and intercellular communication with TME have been summarized. Moreover, there is discussion surrounding EVs as novel diagnostic structures and therapeutic tools for glioblastoma. Finally, unclear questions that require future investigation have been reviewed.

Extracellular microvesicles: biologic properties, biogenesis, and applications in leukemia

Microvesicles are cellular membrane vesicles of which size is limited to 30-1000 nm. Almost all cells release them in response to activation signals and apoptosis. Their ability for intercellular communication and enhancement of potential for information exchange (between them) has attracted much interest. Their content is affected by the content of the mother cell, which can help identify their origin. Furthermore, these particles can change the physiology of the target cells by transferring a set of molecules to them and changing the epigenetics of the cells by transferring DNA and RNA. These changes can be induced in cells close to the mother and distant cells. Significant activities of these microvesicles are known both in physiological and pathologic conditions. In this regard, we have reviewed these small particle elements, their contents, and the way of synthesis. Finally, we discussed their current known roles to reveal more potential applications in leukemia.

Hepatoprotective efficacy and interventional mechanism of the panaxadiol saponin component in high-fat diet-induced NAFLD mice

Dietary administration is a promising strategy for intervention in non-alcoholic fatty liver disease (NAFLD). Our research team has identified a biologically active component, the panaxadiol saponin component (PDS-C) isolated from total saponins of panax ginseng, which has various pharmacological and therapeutic functions. However, the efficacy and mechanism of PDS-C in NAFLD were unclear. This study aimed to elucidate the hepatoprotective effects and underlying action mechanism of PDS-C in NAFLD. Mice were fed a high-fat diet (HFD) for 8 weeks to induce NAFLD and treated with PDS-C and metformin as the positive control for 12 weeks. PDS-C significantly alleviated liver function, hepatic steatosis and blood lipid levels, reduced oxidative stress and inflammation in NAFLD mice. In vitro, PDS-C has been shown to reduce lipotoxicity and ROS levels while enhancing the antioxidant and anti-inflammatory capabilities in HepG2 cells induced by palmitic acid. PDS-C induced AMPK phosphorylation, leading to upregulation of the Nrf2/HO1 pathway expression and downregulation of the NFκB protein level. Furthermore, our observations indicate that PDS-C supplementation improves insulin resistance and glucose homeostasis in NAFLD mice, although its efficacy is not as pronounced as metformin. In conclusion, these results demonstrate the hepatoprotective efficacy of PDS-C in NAFLD and provide potential opportunities for developing functional products containing PDS-C.

LPS-induced macrophage exosomes promote the activation of hepatic stellate cells and the intervention study of total astragalus saponins combined with glycyrrhizic acid

Huangqi decoction, also known as Huangqi Liuyi decoction, was first recorded in the prescriptions of the Bureau of Taiping People's Welfare Pharmacy. It comprises astragalus and licorice, which is a commonly used prescription in traditional Chinese medicine for the clinical treatment of chronic liver disease, especially liver cirrhosis. Total astragalus saponins (AST) is the main component of astragalus, and glycyrrhizic acid (GA) is the main component of licorice. In this study, normal macrophage exosomes were extracted, and the exosomes incubated with lipopolysaccharides (LPS) and those incubated with LPS + AST + GA were co-cultured with JS1 cells (hepatic stellate cell line). The survival rate and the activation of key signaling pathways of JS1 cells in each group were detected and compared. We found that the co-culture of LPS-induced macrophage exosomes with JS1 cells could significantly increase the expression levels of Collagen-1 (Col-1) and Alpha smooth muscle actin (α-SMA)in JS1 cells. However, a significant reversal effect was observed after pretreatment with AST combined with GA. Further evaluation found that the expression levels of phospho (p)-Smad2 and p-Smad3 in the JS1 cells were significantly increased after macrophages were induced with LPS, whereas pretreatment with AST + GA could significantly decrease the expression levels of p-Smad2 and p-Smad3. Preliminary results of this study indicated that LPS-induced macrophage exosomes can promote the activation of hepatic stellate cells, and the pretreatment of AST combined with GA can exert a significant intervention effect. In this study, the new mechanism of anti-hepatic fibrosis effect of traditional Chinese medicine components of Huangqi Decoction was analyzed from the perspective of exosomes.

New insights into the molecular basis of alcohol abstinence and relapse in alcohol-associated liver disease

Alcohol use disorder remains a significant public health concern, affecting around 5% of adults worldwide. Novel pathways of damage have been described during the last years, providing insight into the mechanism of injury due to alcohol misuse beyond the direct effect of ethanol byproducts on the liver parenchyma and neurobehavioral mechanisms. Thus, the gut-liver-brain axis and immune system involvement could be therapeutic targets for alcohol use disorder. In particular, changes in gut microbiota composition and function, and bile acid homeostasis, have been shown with alcohol consumption and cessation. Alcohol can also directly disrupt intestinal and blood-brain barriers. Activation of the immune system can be triggered by intestinal barrier dysfunction and translocation of bacteria, pathogen-associated molecular patterns (such as lipopolysaccharide), cytokines, and damage-associated molecular patterns. These factors, in turn, promote liver and brain inflammation and the progression of liver fibrosis. Other involved mechanisms include oxidative stress, apoptosis, autophagy, and the release of extracellular vesicles and miRNA from hepatocytes. Potential therapeutic targets include gut microbiota (probiotics and fecal microbiota transplantation), neuroinflammatory pathways, as well as neuroendocrine pathways, for example, the ghrelin system (ghrelin receptor blockade), incretin mimetics (glucagon-like peptide-1 analogs), and the mineralocorticoid receptor system (spironolactone). In addition, support with psychological and behavioral treatments is essential to address the multiple dimensions of alcohol use disorder. In the future, a personalized approach considering these novel targets can contribute to significantly decreasing the alcohol-associated burden of disease.

Role of extracellular vesicles in nonalcoholic fatty liver disease

Background

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease that affects approximately one-quarter of the global population and is becoming increasingly prevalent worldwide. The lack of current noninvasive tools and efficient treatment is recognized as a significant barrier to the clinical management of these conditions. Extracellular vesicles (EVs) are nanoscale vesicles released by various cells and deliver bioactive molecules to target cells, thereby mediating various processes, including the development of NAFLD.

Scope of review

There is still a long way to actualize the application of EVs in NAFLD diagnosis and treatment. Herein, we summarize the roles of EVs in NAFLD and highlight their prospects for clinical application as a novel noninvasive diagnostic tool as well as a promising therapy for NAFLD, owing to their unique physiochemical characteristics. We summarize the literatures on the mechanisms by which EVs act as mediators of intercellular communication by regulating metabolism, insulin resistance, inflammation, immune response, intestinal microecology, and fibrosis in NAFLD. We also discuss future challenges that must be resolved to improve the therapeutic potential of EVs.

Major conclusions

The levels and contents of EVs change dynamically at different stages of diseases and this phenomenon may be exploited for establishing sensitive stage-specific markers. EVs also have high application potential as drug delivery systems with low immunogenicity and high biocompatibility and can be easily engineered. Research on the mechanisms and clinical applications of EVs in NAFLD is in its initial phase and the applicability of EVs in NAFLD diagnosis and treatment is expected to grow with technological progress.

MicroRNAs as Biomarkers and Therapeutic Targets for Nonalcoholic Fatty Liver Disease: A Narrative Review

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. However, biomarkers for NAFLD diagnosis and liver-specific drugs for treatment are lacking. This article reviews the possibility of circulating miRNAs in the diagnosis and treatment of NAFLD diseases and focuses on several well-studied miRNAs to provide preclinical data for subsequent related studies.

METHODS

Related articles were identified through searches of the PubMed database for literature published from 2010 to December 2022. Search terms included NAFLD, microRNA, biomarker, diagnosis, and therapy.

FINDINGS

Current research data indicate that some key circulating miRNAs may be used as diagnostic biomarkers of NAFLD and the combination of several miRNAs improves diagnostic performance. In addition, some preclinical trials using cell and mouse models provide a basis for some miRNAs as potential therapeutic targets.

IMPLICATIONS

Current evidence suggests that circulating miRNAs are potential noninvasive biomarkers for clinical diagnosis of NAFLD, which needs to be validated in more heterogeneous and larger cohorts. In addition, several miRNAs regulate multiple downstream pathways related to the pathophysiology of NAFLD in a cell- and tissue-specific manner, making them attractive drug therapeutic targets for NAFLD. However, more preclinical and clinical trials are needed for these miRNAs to become therapeutic targets of NAFLD.

Emerging Links between Nonalcoholic Fatty Liver Disease and Neurodegeneration

The association between liver and brain health has gained attention as biomarkers of liver function have been revealed to predict neurodegeneration. The liver is a central regulator in metabolic homeostasis. However, in nonalcoholic fatty liver disease (NAFLD), homeostasis is disrupted which can result in extrahepatic organ pathologies. Emerging literature provides insight into the mechanisms behind the liver-brain health axis. These include the increased production of liver-derived factors that promote insulin resistance and loss of neuroprotective factors under conditions of NAFLD that increase insulin resistance in the central nervous system. In addition, elevated proinflammatory cytokines linked to NAFLD negatively impact the blood-brain barrier and increase neuroinflammation. Furthermore, exacerbated dyslipidemia associated with NAFLD and hepatic dysfunction can promote altered brain bioenergetics and oxidative stress. In this review, we summarize the current knowledge of the crosstalk between liver and brain as it relates to the pathophysiology between NAFLD and neurodegeneration, with an emphasis on Alzheimer's disease. We also highlight knowledge gaps and future areas for investigation to strengthen the potential link between NAFLD and neurodegeneration.

Extracellular Vesicles and Fatty Liver

Fatty liver is a complex pathological process caused by multiple etiologies. In recent years, the incidence of fatty liver has been increasing year by year, and it has developed into a common chronic disease that seriously affects people's health around the world. It is an important risk factor for liver cirrhosis, liver cancer, and a variety of extrahepatic chronic diseases. Therefore, the early diagnosis and early therapy of fatty liver are important. Except for invasive liver biopsy, there is still a lack of reliable diagnosis and staging methods. Extracellular vesicles are small double-layer lipid membrane vesicles derived from most types of cells. They play an important role in intercellular communication and participate in the occurrence and development of many diseases. Since extracellular vesicles can carry a variety of biologically active substances after they are released by cells, they have received widespread attention. The occurrence and development of fatty liver are also closely related to extracellular vesicles. In addition, extracellular vesicles are expected to provide a new direction for the diagnosis of fatty liver. This article reviews the relationship between extracellular vesicles and fatty liver, laying a theoretical foundation for the development of new strategies for the diagnosis and therapy of fatty liver.

Transcriptional level evaluation of osteopontin/miRNA-181a axis in hepatocellular carcinoma cell line-secreted extracellular vesicles

Recent evidence suggested the role of secreted extracellular vesicles (EVs) in the intracellular signalling within the liver becoming a promising candidate as biomarker in hepatocellular carcinoma (HCC). Osteopontin (OPN) seems to play a relevant role both for early diagnosis of HCC than on the mechanisms that drive oncogenesis but, to date, information on the expression levels of OPN in EVs secreted by HCC tumor cell line are missing. The study aimed to verify, by transcriptional and proteomic study, the presence of OPN in EVs secreted by tumorigenic (HepG2) and non-tumorigenic hepatocyte cell line (WRL68), and to analyse the expression variations of OPN, its isoforms and miRNA-181a in both these EVs. "In silico analysis" was also performed via the Gene expression Profiling Interactive analysis (GEPIA) and Hepatocellular Carcinoma Database (HCCDB). An up-regulation of OPN in EVs secreted by HepG2 with respect to WRL68 was found in line with the results obtained by the "in silico analysis". The study demonstrates, for the first time, the OPN isoforms and its modulator miRNA-181a expression in EVs secreted by both cell lines, highlighting high levels of OPN isoforms in EVs secreted by HepG2 and identifying OPN as a promising biomarker for HCC diagnosis.

Advance of Serum Biomarkers and Combined Diagnostic Panels in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) affects approximately 25-30% population worldwide, which progresses from simple steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma, and has complications such as cardiovascular events. Liver biopsy is still the gold standard for the diagnosis of NAFLD, with some limitations, such as invasive, sampling deviation, and empirical judgment. Therefore, it is urgent to develop noninvasive diagnostic biomarkers. Currently, a large number of NAFLD-related serum biomarkers have been identified, including apoptosis, inflammation, fibrosis, adipokines, hepatokines, and omics biomarkers, which could effectively diagnose NASH and exclude patients with progressive fibrosis. We summarized serum biomarkers and combined diagnostic panels of NAFLD, to provide some guidance for the noninvasive diagnosis and further clinical studies.

Extracellular Vesicles in Pathogenesis and Treatment of Metabolic Associated Fatty Liver Disease

Metabolic associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide due to the sedentary and overeating lifestyle. Yet, the pathophysiology of MAFLD is still unclear and no drug has been approved for MAFLD treatment. Extracellular vesicles (EVs) are heterogenous membrane-bound particles released from almost all types of cells. These nano-sized particles mediate intercellular communication through their bioactive cargos including nucleic acids, proteins, and lipids. The EVs modulate metabolic homeostasis via communication between adipose tissue and liver. The dysregulation of lipid metabolism leads to inflammation in liver and the number and compounds of EVs are changed during MAFLD. The injured hepatocytes secrete EVs to induce the migration of bone marrow-derived monocytes and the activation of macrophages in liver. The EVs secreted by different cells regulate the alteration of hepatic stellate cell (HSC) phenotypes and HSC activation gives rise to liver fibrosis. Based on the participation of EVs in MAFLD progression, we discuss the prospects of EVs as a therapeutic target and their application in drug delivery.

Role of Exosomes in Chronic Liver Disease Development and Their Potential Clinical Applications

Extracellular vesicles (EVs) are vesicular bodies (40-1000 nm) with double-layer membrane structures released by different cell types into extracellular environments, including apoptosis bodies, microvesicles, and exosomes. Exosomes (30-100 nm) are vesicles enclosed by extracellular membrane and contain effective molecules of secretory cells. They are derived from intracellular multivesicular bodies (MVBs) that fuse with the plasma membrane and release their intracellular vesicles by exocytosis. Research has shown that almost all human cells could secrete exosomes, which have a certain relationship with corresponding diseases. In chronic liver diseases, exosomes release a variety of bioactive components into extracellular spaces, mediating intercellular signal transduction and materials transport. Moreover, exosomes play a role in the diagnosis, treatment, and prognosis of various chronic liver diseases as potential biomarkers and therapeutic targets. Previous studies have found that mesenchymal stem cell-derived exosomes (MSC-ex) could alleviate acute and chronic liver injury and have the advantages of high biocompatibility and low immunogenicity. In this paper, we briefly summarize the role of exosomes in the pathogenesis of different chronic liver diseases and the latest research progresses of MSC-ex as the clinical therapeutic targets.

Autophagy and Exosomes: Cross-Regulated Pathways Playing Major Roles in Hepatic Stellate Cells Activation and Liver Fibrosis

Chronic liver injury, regardless of the underlying disease, results in gradual alteration of the physiological hepatic architecture and in excessive production of extracellular matrix, eventually leading to cirrhosis Liver cellular architecture consists of different cell populations, among which hepatic stellate cells (HSCs) have been found to play a major role in the fibrotic process. Under normal conditions, HSCs serve as the main storage site for vitamin A, however, pathological stimuli lead to their transdifferentiation into myofibroblast cells, with autophagy being the key regulator of their activation, through lipophagy of their lipid droplets. Nevertheless, the role of autophagy in liver fibrosis is multifaceted, as increased autophagic levels have been associated with alleviation of the fibrotic process. In addition, it has been found that HSCs receive paracrine stimuli from neighboring cells, such as injured hepatocytes, Kupffer cells, sinusoidal endothelial cells, which promote liver fibrosis. These stimuli have been found to be transmitted via exosomes, which are incorporated by HSCs and can either be degraded through lysosomes or be secreted back into the extracellular space via fusion with the plasma membrane. Furthermore, it has been demonstrated that autophagy and exosomes may be concomitantly or reciprocally regulated, depending on the cellular conditions. Given that increased levels of autophagy are required to activate HSCs, it is important to investigate whether autophagy levels decrease at later stages of hepatic stellate cell activation, leading to increased release of exosomes and further propagation of hepatic fibrosis.

Oxidative Stress in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease caused by multiple factors, which may partly explain why it still remains an orphan of adequate therapies. This review highlights the interaction between oxidative stress (OS) and disturbed lipid metabolism. Several reactive oxygen species generators, including those produced in the gastrointestinal tract, contribute to the lipotoxic hepatic (and extrahepatic) damage by fatty acids and a great variety of their biologically active metabolites in a “multiple parallel-hit model”. This leads to inflammation and fibrogenesis and contributes to NAFLD progression. The alterations of the oxidant/antioxidant balance affect also metabolism-related organelles, leading to lipid peroxidation, mitochondrial dysfunction, and endoplasmic reticulum stress. This OS-induced damage is at least partially counteracted by the physiological antioxidant response. Therefore, modulation of this defense system emerges as an interesting target to prevent NAFLD development and progression. For instance, probiotics, prebiotics, diet, and fecal microbiota transplantation represent new therapeutic approaches targeting the gut microbiota dysbiosis. The OS and its counter-regulation are under the influence of individual genetic and epigenetic factors as well. In the near future, precision medicine taking into consideration genetic or environmental epigenetic risk factors, coupled with new OS biomarkers, will likely assist in noninvasive diagnosis and monitoring of NAFLD progression and in further personalizing treatments.

The Role of Exosomes in Viral Hepatitis and Its Associated Liver Diseases

Exosomes, the important carriers between cells, can carry proteins, micro ribonucleic acids (miRNAs), long non-coding RNAs (lncRNAs) and other molecules to mediate cellular information transduction. They also play an important role in the pathogenesis, prognosis and treatment of viral hepatitis and its associated liver diseases. Several studies have reported that viral hepatitis and its associated liver diseases, including hepatitis A, B, C and E; hepatic fibrosis and hepatocellular carcinoma, were closely associated with exosomes. Exploring the role of exosomes in viral hepatitis and associated liver diseases will enhance our understanding of these diseases. Therefore, this review mainly summarised the role of exosomes in viral hepatitis and its associated liver diseases to identify new strategies for liver diseases in clinical practise.

Prognostic value of plasma exosomal levels of histone H3 protein in patients with heat stroke

Heat stroke (HS) is a condition that can lead to multiple organ dysfunction syndrome and death; however, there is no reliable method for stratifying mortality risk in HS. The abundance of exosomes in the circulation and their contents may be used as potential biomarkers of HS. The present study aimed to examine whether histone H3 levels in plasma exosomes could be used to determine HS prognosis. Blood samples were collected from patients with HS (36 survivors and 8 non-survivors) at admission to the intensive care unit and 4 days after admission. Blood samples were additionally collected from 15 healthy volunteers. Plasma exosomes were isolated using high-speed differential centrifugation. Correlation between histone H3 level and organ function and disease severity was examined. The results suggested differential expression and enrichment of histone H3 in the plasma exosomes of patients with HS (survivors, 249.3±04.6; non-survivors, 500.4±216.8; healthy controls, 161.1±52.49 pg/100 µg; P<0.05). The increased expression of histone H3 was associated with increased disease severity and duration. Plasma exosomal levels of histone H3 were significantly correlated with both organ dysfunction and disease severity (P<0.0001) and were significantly different between non-survivors and survivors (area under the receiver operating characteristic curve, 0.9668). A cutoff value of 307 pg/100 µg demonstrated optimized sensitivity (95%) and specificity (91.67%) for predicting mortality risk, suggesting that histone H3 levels in plasma exosomes may be a reliable biomarker for HS prognosis.

Identification of genes in hepatocellular carcinoma induced by non-alcoholic fatty liver disease

BACKGROUND:

Hepatocellular carcinoma (HCC) is the leading cause of mortality worldwide. In recent years, the incidence of HCC induced by NAFLD is growing rapidly.

OBJECTIVE:

To screen for new pathogenic genes and related pathways both in NAFLD and HCC, and to explore the pathogenesis of progression from NAFLD to HCC.

METHODS:

Gene expression microarrays (GSE74656, GSE62232) were used for identifying differentially expressed genes (DEGs). Functional enrichment and pathway enrichment analyses indicated that these DEGs were related to cell cycle and extracellular exosome, which were closely related to NAFLD and HCC development. We then used the Search Tool for the Retrieval of Interacting Genes (STRING) to establish the protein-protein interaction (PPI) network and visualized them in Cytoscape. And the overall survival (OS) analysis and gene expression validation in TCGA of hub genes was performed.

RESULTS:

Seven hub genes, including CDK1, HSP90AA1, MAD2L1, PRKCD, ITGB3BP, CEP192, and RHOB were identified. Finally, we verified the expression level of ITGB3BP and CEP192 by quantitative real-time PCR in vitro.

CONCLUSIONS:

The present study implied possible DEGs, especially the new gene CEP192, in the progression of NAFLD developing to HCC. Further rigorous experiments are required to verify the above results.

Nonalcoholic Fatty Liver Disease: Focus on New Biomarkers and Lifestyle Interventions

Nonalcoholic fatty liver disease (NAFLD) is considered a hepatic manifestation of metabolic syndrome, characterized from pathological changes in lipid and carbohydrate metabolism. Its main characteristics are excessive lipid accumulation and oxidative stress, which create a lipotoxic environment in hepatocytes leading to liver injury. Recently, many studies have focused on the identification of the genetic and epigenetic modifications that also contribute to NAFLD pathogenesis and their prognostic implications. The present review is aimed to discuss on cellular and metabolic alterations associated with NAFLD, which can be helpful to identify new noninvasive biomarkers. The identification of accumulated lipids in the cell membranes, as well as circulating cytokeratins and exosomes, provides new insights in understanding of NAFLD. This review also suggests that lifestyle modifications remain the main prevention and/or treatment for NAFLD.

Bacterial and eukaryotic extracellular vesicles and nonalcoholic fatty liver disease: new players in the gut-liver axis?

The liver and intestine communicate in a bidirectional way through the biliary tract, portal vein, and other components of the gut-liver axis. The gut microbiota is one of the major contributors to the production of several proteins and bile acids. Imbalance in the gut bacterial community, called dysbiosis, participates in the development and progression of several chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD). NAFLD is currently considered the main chronic liver disease worldwide. Dysbiosis contributes to NAFLD development and progression, notably by a greater translocation of pathogen-associated molecular patterns (PAMPs) in the blood. Lipopolysaccharide (LPS) is a PAMP that activates Toll-like receptor 4 (TLR4), induces liver inflammation, and participates in the development of fibrogenesis. LPS can be transported by bacterial extracellular vesicles (EVs). EVs are spherical structures produced by eukaryotic and prokaryotic cells that transfer information to distant cells and may represent new players in NAFLD development and progression. The present review summarizes the role of eukaryotic EVs, either circulating or tissue-derived, in NAFLD features, such as liver inflammation, angiogenesis, and fibrosis. Circulating EV levels are dynamic and correlate with disease stage and severity. However, scarce information is available concerning the involvement of bacterial EVs in liver disease. The present review highlights a potential role of bacterial EVs in insulin resistance and liver inflammation, although the mechanism involved has not been elucidated. In addition, because of their distinct signatures, eukaryotic and prokaryotic EVs may also represent a promising NAFLD diagnostic tool as a "liquid biopsy" in the future.

Exosomes: A new frontier under the spotlight for diagnosis and treatment of gastrointestinal diseases

Exosomes are small plasma membrane-bound multivesicular bodies ranging in size from 20-100 nm. Exosomes are degraded fragments of mRNA, microRNA, and enriched in proteins, lipids, and nucleic acid. They are produced in the endosomes of most eukaryotic cells and once secreted, exosomes are involved in cell to cell communication and remodeling of the matrix in the extracellular compartment. Exosome biogenesis plays a crucial role in cellular development, inflammation, immunity, hemostasis, carcinogenesis, and degeneration. Due to their unique biochemical and biophysical properties, exosomes serve a variety of functions including biomarkers of diagnostic and prognostic significance. Besides, there is an increasing level of evidence to expand our understanding of the exosomes as novel therapeutic agents. Inflammatory bowel disease (IBD) such as Crohn's disease and ulcerative colitis, hepatic fibrosis, and gastrointestinal malignancies such as colorectal cancer are the potential avenues where exosomes can be applied as cell therapy and immunotherapy and have shown promising results in several in-vitro and animal models. The purpose of this review article is to highlight the emerging role of exosomes as the diagnostic and therapeutic tool in various diseases involving the gastrointestinal tract like IBD, hepatocellular carcinoma, and colon cancer. A thorough literature search was performed on databases such as PubMed, Ovid Medline, and EMBASE to achieve the objectives of this review article.

Extracellular Vesicles as Inflammatory Drivers in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver disease in most parts of the world affecting one-third of the western population and a growing cause for end-stage liver diseases such as hepatocellular carcinoma (HCC). Majorly driven by obesity and diabetes mellitus, NAFLD is more of a multifactorial disease affected by extra-hepatic organ crosstalk. Non-alcoholic fatty liver (NAFL) progressed to non-alcoholic steatohepatitis (NASH) predisposes multiple complications such as fibrosis, cirrhosis, and HCC. Although the complete pathogenic mechanisms of this disease are not understood, inflammation is considered as a key driver to the onset of NASH. Lipotoxicity, inflammatory cytokines, chemokines, and intestinal dysbiosis trigger both hepatic and systemic inflammatory cascades simultaneously activating immune responses. Over a few years, extracellular vesicles studied extensively concerning the pathobiology of NAFLD indicated it as a key modulator in the setting of immune-mediated inflammation. Exosomes and microvesicles, the two main types of extracellular vesicles are secreted by an array of most mammalian cells, which are involved mainly in cell-cell communication that are unique to cell type. Various bioactive cargoes containing extracellular vesicles derived from both hepatic and extrahepatic milieu showed critical implications in driving steatosis to NASH reaffirming inflammation as the primary contributor to the whole process. In this mini-review, we provide brief insights into the inflammatory mediators of NASH with special emphasis on extracellular vesicles that acts as drivers of inflammation in NAFLD.

A High-Fat Diet Attenuates AMPK α1 in Adipocytes to Induce Exosome Shedding and Nonalcoholic Fatty Liver Development In Vivo

Exosomes are important for intercellular communication, but the role of exosomes in the communication between adipose tissue (AT) and the liver remains unknown. The aim of this study is to determine the contribution of AT-derived exosomes in nonalcoholic fatty liver disease (NAFLD). Exosome components, liver fat content, and liver function were monitored in AT in mice fed a high-fat diet (HFD) or treated with metformin or GW4869 and with AMPKα1-floxed (Prkaα1 ^fl/fl/wild-type [WT]), Prkaα1 ^-/-, liver tissue-specific Prkaα1 ^-/-, or AT-specific Prkaα1 ^-/- modification. In cultured adipocytes and white AT, the absence of AMPKα1 increased exosome release and exosomal proteins by elevating tumor susceptibility gene 101 (TSG101)-mediated exosome biogenesis. In adipocytes treated with palmitic acid, TSG101 facilitated scavenger receptor class B (CD36) sorting into exosomes. CD36-containing exosomes were then endocytosed by hepatocytes to induce lipid accumulation and inflammation. Consistently, an HFD induced more severe lipid accumulation and cell death in Prkaα1 ^-/- and AT-specific Prkaα1 ^-/- mice than in WT and liver-specific Prkaα1 ^-/- mice. AMPK activation by metformin reduced adipocyte-mediated exosome release and mitigated fatty liver development in WT and liver-specific Prkaα1 ^-/- mice. Moreover, administration of the exosome inhibitor GW4869 blocked exosome secretion and alleviated HFD-induced fatty livers in Prkaα1 ^-/- and adipocyte-specific Prkaα1 ^-/- mice. We conclude that HFD-mediated AMPKα1 inhibition promotes NAFLD by increasing numbers of AT CD36-containing exosomes.

Hepatocellular carcinoma and other complications of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis in Japan: A structured review of published works

AIMS

Hepatocellular carcinoma (HCC) is a significant cause of morbidity and mortality in Japan. As the treatment of viral hepatitis improves, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are rapidly becoming leading causes of HCC in Japan. This structured review aims to characterize the morbidity and mortality of HCC and other malignant and non-malignant complications among Japanese NAFLD and NASH patients.

METHODS

An English and Japanese structured search of published works was undertaken in PubMed, Embase, and Ichushi Web databases, identifying 6553 studies, 34 of which met predefined inclusion criteria.

RESULTS

Hepatocellular carcinoma was the most common incident malignancy among NAFLD/NASH patients, with higher incidence in patients with advanced/severe fibrosis (F3/F4) of 10.5%-20.0%. Although NASH results in a lower HCC cumulative incidence than hepatitis C virus (HCV) (11.3% vs. 30.5%), they have similar impacts on health outcomes, including overall mortality. Among Japanese NASH patients, HCC was found to be the main driver of mortality (40.0% in 2.7 years in NASH-HCC). With longer follow-up, higher mortality rates are observed in F3/4 patients: 25.0% in NASH F3/F4 versus 0.0% in NASH F0/2 over 7.7 years. The NASH-HCC patients also have a higher post-operative mortality than HCV-HCC patients. Additionally, NAFLD/NASH patients had higher rates of cardiovascular disease than non-NAFLD/NASH controls, and slightly higher rates of gastric cancer than HCV patients.

CONCLUSION

Hepatocellular carcinoma is the most common malignancy and cause of death among NAFLD/NASH patients in Japan, with higher mortality observed among those with advanced disease and complications. Early identification and effective treatments are needed.

Mesenchymal stem cell-derived extracellular vesicle-based therapies protect against coupled degeneration of the central nervous and vascular systems in stroke

Stem cell-based treatments have been suggested as promising candidates for stroke. Recently, mesenchymal stem cells (MSCs) have been reported as potential therapeutics for a wide range of diseases. In particular, clinical trial studies have suggested MSCs for stroke therapy. The focus of MSC treatments has been directed towards cell replacement. However, recent research has lately highlighted their paracrine actions. The secretion of extracellular vesicles (EVs) is offered to be the main therapeutic mechanism of MSC therapy. However, EV-based treatments may provide a wider therapeutic window compared to tissue plasminogen activator (tPA), the traditional treatment for stroke. Exosomes are nano-sized EVs secreted by most cell types, and can be isolated from conditioned cell media or body fluids such as plasma, urine, and cerebrospinal fluid (CSF). Exosomes apply their effects through targeting their cargos such as microRNAs (miRs), DNAs, messenger RNAs, and proteins at the host cells, which leads to a shift in the behavior of the recipient cells. It has been indicated that exosomes, in particular their functional cargoes, play a significant role in the coupled pathogenesis and recovery of stroke through affecting the neurovascular unit (NVU). Therefore, it seems that exosomes could be utilized as diagnostic and therapeutic tools in stroke treatment. The miRs are small endogenous non-coding RNA molecules which serve as the main functional cargo of exosomes, and apply their effects as epigenetic regulators. These versatile non-coding RNA molecules are involved in various stages of stroke and affect stroke-related factors. Moreover, the involvement of aging-induced changes to specific miRs profile in stroke further highlights the role of miRs. Thus, miRs could be utilized as diagnostic, prognostic, and therapeutic tools in stroke. In this review, we discuss the roles of stem cells, exosomes, and their application in stroke therapy. We also highlight the usage of miRs as a therapeutic choice in stroke therapy.

A preliminary study: proteomic analysis of exosomes derived from thyroid-stimulating hormone-stimulated HepG2 cells

BACKGROUND

Thyroid-stimulating hormone (TSH) plays an important role in the regulation of lipid metabolism. However, little is known about the role that exosomes play in the process of TSH-induced lipotoxicity in non-alcoholic fatty liver disease (NAFLD). As a preliminary step, the present study set out to investigate alterations in protein expression in exosomes derived from TSH-stimulated HepG2 cells.

METHODS

HepG2 cells were treated with TSH, exosomes were collected, and proteins were identified by mass spectrometry (MS). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) pathway analysis were performed to analyze the identified proteins.

RESULTS

TSH treatment significantly increased exosomal production and changed the exosomal proteomic profile in HepG2 cells. Among the 1728 proteins, 140 identified proteins were upregulated and seven proteins were downregulated. GO analysis and KEGG analysis revealed that these proteins were involved in multiple processes including metabolism, apoptosis, and inflammation.

CONCLUSION

Our preliminary study demonstrated that exosomes derived from TSH-stimulated hepatocytes were increased and showed a specific altered spectrum of proteins, many of which were involved in metabolism, signal transduction, apoptosis, and inflammation. This study offers new insights into the pathogenesis of TSH-induced lipotoxicity in NAFLD.

Insights Into Extracellular Vesicles as Biomarker of NAFLD Pathogenesis

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease around the world estimated to affect up to one-third of the adult population and is expected to continue rising in the coming years. Nonalcoholic fatty liver disease is considered as the hepatic manifestation of the metabolic syndrome because it is strongly associated with obesity, insulin resistance, type 2 diabetes mellitus, and cardiovascular complications. Despite its high prevalence, factors leading to NAFLD progression from simple steatosis to nonalcoholic steatohepatitis, cirrhosis, and, ultimately hepatocellular carcinoma remain poorly understood. To date, no treatment has proven efficacy, and also no reliable method is currently available for diagnosis or staging of NAFLD beyond the highly invasive liver biopsy. Recently, extracellular vesicles (EVs) have emerged as potential candidate biomarkers for the diagnosis of NAFLD. Extracellular vesicles are circulating, cell-derived vesicles containing proteins and nucleic acids, among other components, that interact with and trigger a plethora of responses in neighbor or distant target cells. Several mechanisms implicated in NAFLD progression, such as inflammation, fibrosis, and angiogenesis, all related to metabolic syndrome–associated lipotoxicity, trigger EV production and release by liver cells. As hepatocytes represent ~80% of the liver volume, in this review we will focus on hepatocyte-derived EVs as drivers of the interactome between different liver cell types in NAFLD pathogenesis, as well as in their role as noninvasive biomarkers for NAFLD diagnosis and progression. Based on that, we will highlight the research that is currently available on EVs in this topic, the current limitations, and future directions for implementation in a clinical setting as biomarkers or targets of liver disease.

Lipotoxic Hepatocyte-Derived Exosomal MicroRNA 192-5p Activates Macrophages Through Rictor/Akt/Forkhead Box Transcription Factor O1 Signaling in Nonalcoholic Fatty Liver Disease

BACKGROUND AND AIMS

Hepatic macrophages can be activated by many factors such as gut-derived bacterial components and factors released from damaged hepatocytes. Macrophage polarization toward a proinflammatory phenotype (M1) represents an important event in the disease progression of nonalcoholic fatty liver disease (NAFLD). However, the underlying molecular mechanisms remain incompletely understood. Exosomes have been identified as important mediators for cell-cell communication by transferring various biological components such as microRNAs (miRs), proteins, and lipids. The role of exosomes in crosstalk between hepatocytes and macrophages in disease progression of NAFLD is yet to be explored.

APPROACH AND RESULTS

In the present study, we reported that lipotoxic injury-induced release of hepatocyte exosomes enriched with miR-192-5p played a critical role in the activation of M1 macrophages and hepatic inflammation. Serum miR-192-5p levels in patients with NAFLD positively correlated with hepatic inflammatory activity score and disease progression. Similarly, the serum miR-192-5p level and the number of M1 macrophages, as well as the expression levels of the hepatic proinflammatory mediators, were correlated with disease progression in high-fat high-cholesterol diet-fed rat models. Lipotoxic hepatocytes released more miR-192-5p-enriched exosomes than controls, which induced M1 macrophage (cluster of differentiation 11b-positive [CD11b+ ]/CD86+ ) activation and increase of inducible nitric oxide synthase, interleukin 6, and tumor necrosis factor alpha expression. Furthermore, hepatocyte-derived exosomal miR-192-5p inhibited the protein expression of the rapamycin-insensitive companion of mammalian target of rapamycin (Rictor), which further inhibited the phosphorylation levels of Akt and forkhead box transcription factor O1 (FoxO1) and resulted in activation of FoxO1 and subsequent induction of the inflammatory response.

CONCLUSIONS

Hepatocyte-derived exosomal miR-192-5p plays a critical role in the activation of proinflammatory macrophages and disease progression of NAFLD through modulating Rictor/Akt/FoxO1 signaling. Serum exosomal miR-192-5p represents a potential noninvasive biomarker and therapeutic target for nonalcoholic steatohepatitis.

Role of Extracellular Vesicles in the Pathophysiology, Diagnosis and Tracking of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, affecting approximately one-third of the global population. Most affected individuals experience only simple steatosis—an accumulation of fat in the liver—but a proportion of these patients will progress to the more severe form of the disease, non-alcoholic steatohepatitis (NASH), which enhances the risk of cirrhosis and hepatocellular carcinoma. Diagnostic approaches to NAFLD are currently limited in accuracy and efficiency; and liver biopsy remains the only reliable way to confirm NASH. This technique, however, is highly invasive and poses risks to patients. Hence, there is an increasing demand for improved minimally invasive diagnostic tools for screening at-risk individuals and identifying patients with more severe disease as well as those likely to progress to such stages. Recently, extracellular vesicles (EVs)—small membrane-bound particles released by virtually all cell types into circulation—have emerged as a rich potential source of biomarkers that can reflect liver function and pathological processes in NAFLD. Of particular interest to the diagnosis and tracking of NAFLD is the potential to extract microRNAs miR-122 and miR-192 from EVs circulating in blood, particularly when using an isolation technique that selectively captures hepatocyte-derived EVs.

Exosomes: Carriers of Pro-Fibrotic Signals and Therapeutic Targets in Fibrosis

Exosomes are nano-sized extracellular vesicles that are released by a variety of cells. Exosomes contain cargo from cells they derived, including lipids, proteins and nucleic acids. The bilayer lipid membrane structure of exosomes protects these contents from degradation, allowing them for intercellular communication. The role of exosomes in fibrotic diseases is increasingly being valued. Exosomes, as carriers of profibrotic signals, are involved in the development of fibrotic diseases, and also regulate fibrosis by transmitting signals that inhibit fibrosis or inflammation. Exosomes mobilize and activate a range of effector cells by targeted delivery of bioactive information. Exosomes can also reflect the condition of cells, tissues and organisms, and thus become potential biomarkers of fibrotic diseases. Exosomes from bone marrow stem cells support biological signaling that regulates and inhibits fibrosis and thus initially used in the treatment of fibrotic diseases. This article briefly summarizes the role of exosomes in the pathogenesis and treatment of fibrotic diseases and raises some issues that remain to be resolved.

Current understanding of the role of Adipose-derived Extracellular Vesicles in Metabolic Homeostasis and Diseases: Communication from the distance between cells/tissues

Extracellular vesicles (EVs) including exosomes, microvesicles (MVs), and apoptotic bodies, are small membrane vesicular structures that are released during cell activation, senescence, or programmed cell death, including apoptosis, necroptosis, and pyroptosis. EVs serve as novel mediators for long-distance cell-to-cell communications and can transfer various bioactive molecules, such as encapsulated cytokines and genetic information from their parental cells to distant target cells. In the context of obesity, adipocyte-derived EVs are implicated in metabolic homeostasis serving as novel adipokines. In particular, EVs released from brown adipose tissue or adipose-derived stem cells may help control the remolding of white adipose tissue towards browning and maintaining metabolic homeostasis. Interestingly, EVs may even serve as mediators for the transmission of metabolic dysfunction across generations. Also, EVs have been recognized as novel modulators in various metabolic disorders, including insulin resistance, diabetes mellitus, and non-alcoholic fatty liver disease. In this review, we summarize the latest progress from basic and translational studies regarding the novel effects of EVs on metabolic diseases. We also discuss EV-mediated cross-talk between adipose tissue and other organs/tissues that are relevant to obesity and metabolic diseases, as well as the relevant mechanisms, providing insight into the development of new therapeutic strategies in obesity and metabolic diseases.

Chinese herbal medicine mixture 919 syrup alleviates nonalcoholic fatty liver disease in rats by inhibiting the NF-κB pathway

BACKGROUND

In many countries, nonalcoholic fatty liver disease (NAFLD) has risen to be the leading cause of liver disease, seriously threatening public health, while effective medical treatments are currently limited. 919 syrup (919 T J) is a Chinese herbal medicine, and both clinical and experimental studies have revealed that it can improve liver function.

OBJECTIVE

To study whether 919 T J shows a protective effect in a NAFLD rat model and explore its underlying mechanism, with a focus on the NF-κB pathway.

METHODS

Rats were randomly divided into three groups, including a control group, NAFLD group, and 919 T J group (n = 10 each). The control group received a standard diet, and the other two groups were fed a high-fat diet to establish the NAFLD model. From week 10, rats in the 919 T J group were intragastrically administered 919 T J for 4 weeks, and the NAFLD group was administered the same amount of saline. All rats were anesthetized at the beginning of week 14 to collect blood and liver specimens. Serum lipid levels, serum biochemical markers of liver function, and the gene expression levels of IL-1β, TNF-α, CXCL6, CXCR1, SREBP-1c, PPARγ, and NF-κB in the liver were measured. Oil Red O and hematoxylin and eosin staining of the liver was performed to observe pathological changes in the liver.

RESULTS

Significant abnormalities in serum lipid levels and serum biochemical markers of liver function were found in the NAFLD group relative to those in the control group. In addition, serious abnormalities were noted in the expression levels of liver inflammatory factors and lipid metabolism-related genes. Treatment of NAFLD rats with 919 T J reduced body weight and food intake and ameliorated the abnormal blood lipid levels and liver function markers. By regulating the NF-κB pathway, 919 T J downregulated the NF-κB-related proinflammatory signals, ameliorating the expression of inflammatory (IL-1β, TNF-α, CXCL6, and CXCR1) and lipid metabolism-related (SREBP-1c) factors in the liver and improving the NAFLD-induced pathological changes in the liver.

CONCLUSION

919 T J reduces the liver injury, steatosis, and inflammation caused by NAFLD, thus reversing the disease process.

Extracellular Vesicles in NAFLD/ALD: From Pathobiology to Therapy

In recent years, knowledge on the biology and pathobiology of extracellular vesicles (EVs) has exploded. EVs are submicron membrane-bound structures secreted from different cell types containing a wide variety of bioactive molecules (e.g., proteins, lipids, and nucleic acids (coding and non-coding RNA) and mitochondrial DNA). EVs have important functions in cell-to-cell communication and are found in a wide variety of tissues and body fluids. Better delineation of EV structures and advances in the isolation and characterization of their cargo have allowed the diagnostic and therapeutic implications of these particles to be explored. In the field of liver diseases, EVs are emerging as key players in the pathogenesis of both nonalcoholic liver disease (NAFLD) and alcoholic liver disease (ALD), the most prevalent liver diseases worldwide, and their complications, including development of hepatocellular carcinoma. In these diseases, stressed/damaged hepatocytes release large quantities of EVs that contribute to the occurrence of inflammation, fibrogenesis, and angiogenesis, which are key pathobiological processes in liver disease progression. Moreover, the specific molecular signatures of released EVs in biofluids have allowed EVs to be considered as promising candidates to serve as disease biomarkers. Additionally, different experimental studies have shown that EVs may have potential for therapeutic use as a liver-specific delivery method of different agents, taking advantage of their hepatocellular uptake through interactions with specific receptors. In this review, we focused on the most recent findings concerning the role of EVs as new structures mediating autocrine and paracrine intercellular communication in both ALD and NAFLD, as well as their potential use as biomarkers of disease severity and progression. Emerging therapeutic applications of EVs in these liver diseases were also examined, along with the potential for successful transition from bench to clinic.

Effect of circulating exosomes derived from normal-weight and obese women on gluconeogenesis, glycogenesis, lipogenesis and secretion of FGF21 and fetuin A in HepG2 cells

BACKGROUND

It is generally accepted that obesity can lead to metabolic disorders such as NAFLD and insulin resistance. However, the underlying mechanism has been poorly understood. Moreover, there is evidence to support the possible role of exosomes in the metabolic homeostasis regulation. Accordingly, we aimed to determine the effect of plasma circulating exosomes derived from obese and normal-weight women on insulin signaling and the secretion of hepatokines in human liver cells.

METHODS

Plasma exosomes isolated from four obese (O-Exo) women and four normal-weight (N-Exo) female candidates were characterized for size, zeta potential, and CD63 protein expression and were used for stimulation of HepG2 cells. Then, cell viability, as well as levels of glycogen and triglyceride (TG), were evaluated. Levels of fetuin-A and FGF21 were measured using the ELISA kit. Expression of glucose 6-phosphatase (G6pase) and phosphoenolpyruvate carboxykinase (PEPCK) genes were determined using qRT-PCR. Western blot analysis was carried out to evaluating the phosphorylation of GSK3β.

RESULTS

The TG levels increased significantly in the cells treated with O-Exo than the control (vehicle) group (P = 0.005) and normal-weight group (P = 0.018). Levels of p-GSK3β and glycogen were significantly reduced by O-Exo in comparison with control (P = 0.002, P = 0.018, respectively). The mRNA expression of G6pase and PEPCK enzymes increased in the cells treated with O-Exo in comparison with the vehicle group (P = 0.017, P = 0.010, respectively). The levels of FGF21 in the supernatant of cells treated with O-Exo and N-Exo were significantly lower than the control group (P = 0.007).

CONCLUSION

It appears that obesity-related circulating exosomes can impair insulin signaling pathways and associated components, increase intracellular TG content, and decrease FGF21 secretion in the hepatocytes.

Cholesterol impairs hepatocyte lysosomal function causing M1 polarization of macrophages via exosomal miR-122-5p

Nonalcoholic steatohepatitis (NASH) is a major threat to health worldwide. Lipotoxicity and macrophage-mediated inflammation play key roles in the pathogenesis of NASH. In this study, we found that individuals with higher serum LDL-C levels have a higher prevalence of nonalcoholic fatty liver disease (NAFLD) and elevated levels of glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase and alkaline phosphatase. A logistic regression analysis revealed that serum LDL-C level is an independent risk factor for the prevalence and prognosis of NAFLD. In vitro, we used ox-LDL and MβCD-cholesterol to treat Huh7 cells and found that cholesterol loading reduced lysosomal quantity and impaired lysosomal acidification, reducing the number of multivesicular bodies (MVBs) colocalizing with lysosomes. The bafilomycin A1 inhibition of lysosomal function also inhibited lysosomal MVBs degradation, promoting the release of exosomes from the Huh7 cells. Next, we found that cholesterol loading promoted exosome release from the Huh7 cells. The exosomes from the cholesterol-loaded cells increased the ratio of the THP-1 cells positive for the M1 marker (iNOS-1) without affecting the ratio of the cells positive for the M2 marker (CD206). Moreover, an elevated level of miR-122-5p was observed in exosomes derived from the Huh7 cells loaded with cholesterol. While the miR-122-5p mimics promoted THP-1 M1 polarization, downregulating miR-122-5p in the Huh7 cells inhibited the exosome-induced activation of macrophages and macrophage-related inflammation. These findings suggest that cholesterol plays an important role in the development and progression of NASH. Cholesterol-induced lysosomal dysfunction increases exosome release from hepatocytes, resulting in M1 polarization and macrophage-induced inflammation in a miR-122-5p-dependent manner.

Saturated fatty acid stimulates production of extracellular vesicles by renal tubular epithelial cells

Lipotoxicity, an accumulation of intracellular lipid metabolites, has been proposed as an important pathogenic mechanism contributing to kidney dysfunction in the context of metabolic disease. Palmitic acid, a predominant lipid derivative, can cause lipoapoptosis and the release of inflammatory extracellular vesicles (EVs) in hepatocytes, but the effect of lipids on EV production in chronic kidney disease remains vaguely explored. This study was aimed to investigate whether palmitic acid would stimulate EV release from renal proximal tubular epithelial cells. Human and rat proximal tubular epithelial cells, HK-2 and NRK-52E, were incubated with 1% bovine serum albumin (BSA), BSA-conjugated palmitic acid (PA), and BSA-conjugated oleic acid (OA) for 24-48 h. The EVs released into conditioned media were isolated by ultracentrifugation and quantified by nanoparticle-tracking analysis (NTA). According to NTA, the size distribution of EVs was 30-150 nm with similar mode sizes in all experimental groups. Moreover, BSA-induced EV release was significantly enhanced in the presence of PA, whereas EV release was not altered by the addition of OA. In NRK-52E cells, PA-enhanced EV release was associated with an induction of cell apoptosis reflected by an increase in cleaved caspase-3 protein by Western blot and Annexin V positive cells analyzed by flow cytometry. Additionally, confocal microscopy confirmed the uptake of lipid-induced EVs by recipient renal proximal tubular cells. Collectively, our results indicate that PA stimulates EV release from cultured proximal tubular epithelial cells. Thus, extended characterization of lipid-induced EVs may constitute new signaling paradigms contributing to chronic kidney disease pathology.

The potential diagnostic and prognostic role of extracellular vesicles in glioma: current status and future perspectives

Lack of appropriate diagnostic/prognostic tools for glioblastoma (GB) is considered one of the major setbacks in the early diagnosis and treatment of this deadly brain tumor. The current gold standard for its diagnosis and staging still relies on invasive biopsy followed by histological examination as well as molecular profiling. Nevertheless, noninvasive approaches are being explored and one example is through the investigation of extracellular vesicles (EVs) in the biofluids of GB patients. EVs are known to carry molecular cargoes such as DNA, mRNA, miRNA, proteins and lipids in almost every type of body fluids. Thus, molecular signature of GB may be present in the EVs derived from these patients. This review focuses on the diagnostic/prognostic potential of EVs in GB, through presenting recent studies on (i) molecular components of EVs, (ii) links between EVs and GB tumor microenvironment, and (iii) clinical potential of EV biomarkers, together with the technical shortcomings researchers need to consider for future studies.

Combatting Fibrosis: Exosome-Based Therapies in the Regression of Liver Fibrosis

Hepatic fibrosis results from chronic injury and inflammation in the liver and leads to cirrhosis, liver failure, and portal hypertension. Understanding the molecular mechanisms underlying hepatic fibrosis has advanced the prospect of developing therapies for regression of the disease. Resolution of fibrosis requires a reduction of proinflammatory and fibrogenic cytokines, a decrease in extracellular matrix (ECM) protein production, an increase in collagenase activity, and finally, a disappearance of activated myofibroblasts. Exosomes are nanovesicles of endocytic origin secreted by most cell types. They epigenetically reprogram and alter the phenotype of their recipient cells and hold great promise for the reversal of fibrosis. Recent studies have shown that exosomes function as conduits for intercellular transfer and contain all the necessary components to induce resolution of fibrosis, including the ability to (1) inhibit macrophage activation and cytokine secretion, (2) remodel ECM production and decrease fibrous scars, and (3) inactivate hepatic stellate cells, a major myofibroblast population. Here, we discuss the research involving the regression of hepatic fibrosis. We focus on the newly discovered roles of exosomes during fibrogenesis and as a therapy for fibrosis reversal. We also emphasize the novel discoveries of exosome‐based antifibrotic treatments in vitro and in vivo.

Neuronal Enriched Extracellular Vesicle Proteins as Biomarkers for Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of injury-related death throughout the world and lacks effective treatment. Surviving TBI patients often develop neuropsychiatric symptoms, and the molecular mechanisms underlying the neuronal damage and recovery following TBI are not well understood. Extracellular vesicles (EVs) are membranous nanoparticles that are divided into exosomes (originating in the endosomal/multi-vesicular body [MVB] system) and microvesicles (larger EVs produced through budding of the plasma membrane). Both types of EVs are generated by all cells and are secreted into the extracellular environment, and participate in cell-to-cell communication and protein and RNA delivery. EVs enriched for neuronal origin can be harvested from peripheral blood samples and their contents quantitatively examined as a window to follow potential changes occurring in brain. Recent studies suggest that the levels of exosomal proteins and microRNAs (miRNAs) may represent novel biomarkers to support the clinical diagnosis and potential response to treatment for neurological disorders. In this review, we focus on the biogenesis of EVs, their molecular composition, and recent advances in research of their contents as potential diagnostic tools for TBI.

Hepatoprotective Effect of Loquat Leaf Flavonoids in PM2.5-Induced Non-Alcoholic Fatty Liver Disease via Regulation of IRs-1/Akt and CYP2E1/JNK Pathways

Ambient air particulate matter (PM) represents a class of heterogeneous substances present in polluted air, which contains many harmful components. Exposure to ambient particulate matter in fine rages (PM_2.5) is associated with non-alcoholic fatty liver disease (NAFLD). Loquat Leaf possesses pharmacological actions on NAFLD. As the main biological active ingredients, the potential therapeutic role of total flavonoids (TF) isolated from Loquat Leaf in PM_2.5-induced NAFLD model remains unclear. The present study was designed to explore the hepatoprotective effect of TF in PM_2.5-induced NAFLD mice with its related mechanisms of action. Mice were exposed to PM_2.5 to induce NAFLD, and body weight, the ratio of liver to body weight, and blood lipids increased significantly compared with the control group. It was found that TF significantly reduced the above parameters in PM_2.5-induced NAFLD mice. TF treatment alleviated oxidative stress by preventing the accumulation of oxidative product malondialdehyde (MDA) and by strengthening the anti-oxidative capacity of superoxide dismutase (SOD). TF was also found to reduce the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in the PM_2.5 group. In addition, TF repaired the PM_2.5-induced decline of insulin receptor substrate-1 (IRs-1) and protein kinase B (Akt) phosphorylation. Meanwhile, the data showed TF suppressed the expression of cytochrome P450 2E1(CYP2E1) and the phosphorylation of c-jun N-terminal kinase (JNK) in PM_2.5-induced NAFLD. Taken together, these findings show that TF alleviate PM_2.5-induced NAFLD via regulation of IRs-1/Akt and CYP2E1/JNK pathways, which may have potential for further development as novel therapeutic agents for NAFLD.

Extracellular vesicles in mesenchymal stromal cells: A novel therapeutic strategy for stroke

A stroke is a focal cerebral insult that frequently causes severe neurological deficit and mortality. Recent studies have demonstrated that multipotent mesenchymal stromal cells (MSCs) hold great promise for neurovascular remodeling and neurological function recovery following a stroke. Rather than a direct replacement of parenchymal brain cells, the therapeutic mechanism of MSCs is suggested to be the secretion of soluble factors. Specifically, emerging data described MSCs as being able to release extracellular vesicles (EVs), which contain a variety of cargo including proteins, lipids, DNA and various RNA species. The released EVs can target neurocytes and vascular cells and modify the cell's functions by delivering the cargo, which are considered to mediate the neural restoration effects of MSCs. Therefore, EVs may be developed as a novel cell-free therapy for neurological disorders. In the present review, the current advances regarding the components, functions and therapeutic potential of EVs are summarized and the use of MSC-derived EVs as a promising approach in the treatment of stroke are highlighted.

Improved resolution in extracellular vesicle populations using 405 instead of 488 nm side scatter

Improvements in identification and assessment of extracellular vesicles (EVs) have fuelled a recent surge in EV publications investigating their roles as biomarkers and mediators of disease. Meaningful scientific comparisons are, however, hampered by difficulties in accurate, reproducible enumeration and characterization of EVs in biological fluids. High-sensitivity flow cytometry (FCM) is presently the most commonly applied strategy to assess EVs, yet its utility is limited by variant ability to resolve smaller EVs. Here, we propose the use of 405 nm (violet) wavelength lasers in place of 488 nm (blue) for side scatter (SSC) detection to obtain greater resolution of EVs using high-sensitivity FCM. To test this hypothesis, we modelled EV resolution by violet versus blue SSC in silico and compared resolution of reference beads and biological EVs from plasma and bronchoalveolar lavage (BAL) fluid using either violet or blue wavelength SSC EV detection. Mie scatter modelling predicted that violet as compared to blue SSC increases resolution of small (100–500 nm) spherical particles with refractive indices (1.34–1.46) similar to EVs by approximately twofold in terms of light intensity and by nearly 20% in SSC signal quantum efficiency. Resolution of reference beads was improved by violet instead of blue SSC with two- and fivefold decreases in coefficients of variation for particles of 300–500 nm and 180–240 nm size, respectively. Resolution was similarly improved for detection of EVs from plasma or BAL fluid. Violet SSC detection for high-sensitivity FCM allows for significantly greater resolution of EVs in plasma and BAL compared to conventional blue SSC and particularly improves resolution of smaller EVs. Notably, the proposed strategy is readily implementable and inexpensive for machines already equipped with 405 nm SSC or the ability to accommodate 405/10 nm bandpass filters in their violet detector arrays.

Differential metabolic effects of constant moderate versus high intensity interval training in high-fat fed mice: possible role of muscle adiponectin

Exercise regimens may have differing effects in the presence of obesity. In addition to being fat derived, adiponectin has recently been described as a myokine that regulates insulin sensitivity, which may link to exercise-related metabolic benefits in obesity. Whether skeletal muscle adiponectin varies in different exercise modalities is unclear. This study investigated the comparative effects of 10 weeks of endurance constant-moderate intensity exercise (END) with high intensity interval training (HIIT), on metabolic outcomes, including muscle adiponectin in a mouse model of diet-induced obesity. Ten-week-old male C57BL/6 mice were fed a high-fat diet (HFD) (45% FAT) or standard CHOW diet ab libitum and underwent one of three training regimes: (1) no exercise, (2) END, or (3) HIIT (8 bouts of 2.5 min with eight periods of rest of 2.5 min) for 10 weeks (3 × 40 min sessions/week). Chow-fed mice acted as controls. Compared with HFD alone, both training programs similarly protected against body weight gain (HFD = 45 ± 2; END = 37 ± 2; HIIT = 36 ± 2 g), preserved lean/fat tissue mass ratio (HFD = 0.64 ± 0.09; END = 0.34 ± 0.13; HIIT = 0.33 ± 0.13), and improved blood glucose excursion during an insulin tolerance test (HFD = 411 ± 54; END = 350 ± 57; HIIT = 320 ± 66 arbitrary units [AU]). Alterations in fasting glycemia, insulinemia, and AST/ALT ratios were prevented only by END. END, but not HIIT increased skeletal muscle adiponectin mRNA (14-fold; P < 0.05) and increased protein content of high molecular weight (HMW) adiponectin (3.3-fold), whereas HIIT induced a milder increase (2.4-fold). Compared with HFD, neither END nor HIIT altered circulating low (LMW) or high (HMW) molecular weight adiponectin forms. Furthermore, only END prevented the HFD downregulation of PGC1α (P < 0.05) mRNA levels downstream of muscle adiponectin. These data show that different training programs affect muscle adiponectin to differing degrees. Together these results suggest that END is a more effective regimen to prevent HFD-induced metabolic disturbances in mice.

Extracellular vesicles: Novel mediator for cell to cell communications in liver pathogenesis

Extracellular vesicles (EVs) are membrane derived nanometer-sized vesicles. EVs are released by normal, diseased, and transformed cells in vitro and in vivo, and carry lipids, proteins, mRNAs, non-coding RNAs, and even DNA out of cells. Transferring biological information via EVs to neighboring cells and inter-cellular communication not only maintain physiological functions, but also involve in the pathogenesis of several diseases, including cancer. The aim of this review is to discuss the emerging role of EVs in viral hepatitis, non-alcoholic or alcoholic liver disease and liver cancers. We summarize what is known about exosome biogenesis, and role in liver disease progression, and discuss the potential clinical applications of EVs as predictive biomarkers and therapeutic modalities.

NAFLD: Is There Anything New under the Sun?

Nonalcoholic fatty liver disease (NAFLD) is an "umbrella" definition that encompasses a spectrum of histological liver changes ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with/without fibrosis, "cryptogenic" cirrhosis, and hepatocellular carcinoma (HCC), occurring in a dysmetabolic milieu, though in the absence of excessive alcohol consumption and other competing etiologies of chronic liver disease [1].[...].

Extracellular Vesicles in Brain Tumors and Neurodegenerative Diseases

Extracellular vesicles (EVs) can be classified into apoptotic bodies, microvesicles (MVs), and exosomes, based on their origin or size. Exosomes are the smallest and best characterized vesicles which derived from the endosomal system. These vesicles are released from many different cell types including neuronal cells and their functions in the nervous system are investigated. They have been proposed as novel means for intercellular communication, which takes part not only to the normal neuronal physiology but also to the transmission of pathogenic proteins. Indeed, exosomes are fundamental to assemble and transport proteins during development, but they can also transfer neurotoxic misfolded proteins in pathogenesis. The present review will focus on their roles in neurological diseases, specifically brain tumors, such as glioblastoma (GBM), neuroblastoma (NB), medulloblastoma (MB), and metastatic brain tumors and chronic neurodegenerative diseases, such as Alzheimer, Parkinson, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Huntington, and Prion diseseases highlighting their involvement in spreading neurotoxicity, in therapeutics, and in pathogenesis.

Non-alcoholic fatty liver disease, to struggle with the strangle: Oxygen availability in fatty livers

Nonalcoholic fatty liver diseases (NAFLD) is one of the most common chronic liver disease in Western countries. Oxygen is a central component of the cellular microenvironment, which participate in the regulation of cell survival, differentiation, functions and energy metabolism. Accordingly, sufficient oxygen supply is an important factor for tissue durability, mainly in highly metabolic tissues, such as the liver. Accumulating evidence from the past few decades provides strong support for the existence of interruptions in oxygen availability in fatty livers. This outcome may be the consequence of both, impaired systemic microcirculation and cellular membrane modifications which occur under steatotic conditions. This review summarizes current knowledge regarding the main factors which can affect oxygen supply in fatty liver.