The role of the immune system in the pathogenesis of NAFLD and potential therapeutic impacts of mesenchymal stem cell-derived extracellular vesicles

Immunology and treatments of fatty liver disease

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are two major chronic liver diseases worldwide. The triggers for fatty liver can be derived from external sources such as adipose tissue, the gut, personal diet, and genetics, or internal sources, including immune cell responses, lipotoxicity, hepatocyte death, mitochondrial dysfunction, and extracellular vesicles. However, their pathogenesis varies to some extent. This review summarizes various immune mechanisms and therapeutic targets associated with these two types of fatty liver disease. It describes the gut-liver axis and adipose tissue-liver crosstalk, as well as the roles of different immune cells (both innate and adaptive immune cells) in fatty liver disease. Additionally, mitochondrial dysfunction, extracellular vesicles, microRNAs (miRNAs), and gastrointestinal hormones are also related to the pathogenesis of fatty liver. Understanding the pathogenesis of fatty liver and corresponding therapeutic strategies provides a new perspective for developing novel treatments for fatty liver disease.

Immunological dynamics in MASH: from landscape analysis to therapeutic intervention

Metabolic dysfunction-associated steatohepatitis (MASH), previously known as nonalcoholic steatohepatitis (NASH), is a multifaceted liver disease characterized by inflammation and fibrosis that develops from simple steatosis. Immune and inflammatory pathways have a central role in the pathogenesis of MASH, yet, how to target immune pathways to treat MASH remains perplexed. This review emphasizes the intricate role that immune cells play in the etiology and pathophysiology of MASH and highlights their significance as targets for therapeutic approaches. It discusses both current strategies and novel therapies aimed at modulating the immune response in MASH. It also highlights challenges in liver-specific drug delivery, potential off-target effects, and difficulties in targeting diverse immune cell populations within the liver. This review is a comprehensive resource that integrates current knowledge with future perspectives in the evolving field of MASH, with the goal of driving forward progress in medical therapies designed to treat this complex liver disease.

Causal relationship between key genes and metabolic dysfunction-associated fatty liver disease risk mediated by immune cells: A Mendelian randomization and mediation analysis

AIM

Non-invasive diagnostics for metabolic dysfunction-associated fatty liver disease (MAFLD) remain challenging. We aimed to identify novel key genes as non-invasive biomarkers for MAFLD, elucidate causal relationships between biomarkers and MAFLD and determine the role of immune cells as potential mediators.

MATERIALS AND METHODS

Utilizing published transcriptome data of patients with biopsy-proven MAFLD, we applied linear models for microarray data, least absolute shrinkage and selector operation (LASSO) regressions and receiver operating characteristic (ROC) curve analyses to identify and validate biomarkers for MAFLD. Using the expression quantitative trait loci database and a cohort of 778 614 Europeans, we used Mendelian randomization to analyse the causal relationships between key biomarkers and MAFLD. Additionally, mediation analysis was performed to examine the involvement of 731 immunophenotypes in these relationships.

RESULTS

We identified 31 differentially expressed genes, and LASSO regression showed three hub genes, IGFBP2, PEG10, and P4HA1, with area under the receiver operating characteristic (AUROC) curve of 0.807, 0.772 and 0.791, respectively, for identifying MAFLD. The model of these three genes had an AUROC of 0.959 and 0.800 in the development and validation data sets, respectively. This model was also validated using serum-based enzyme-linked immunosorbent assay data from MAFLD patients and control subjects (AUROC: 0.819, 95% confidence interval: 0.736-0.902). PEG10 was associated with an increased MAFLD risk (odds ratio = 1.106, p = 0.032) via inverse variance-weighted analysis, and about 30% of this risk was mediated by the percentage of CD11c + CD62L- monocytes.

CONCLUSIONS

The MAFLD panels have good diagnostic accuracy, and the causal link between PEG10 and MAFLD was mediated by the percentage of CD11c + CD62L- monocytes.

Chinese herbal formula in the treatment of metabolic dysfunction-associated steatotic liver disease: current evidence and practice

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease, continues to rise with rapid economic development and poses significant challenges to human health. No effective drugs are clinically approved. MASLD is regarded as a multifaceted pathological process encompassing aberrant lipid metabolism, insulin resistance, inflammation, gut microbiota imbalance, apoptosis, fibrosis, and cirrhosis. In recent decades, herbal medicines have gained increasing attention as potential therapeutic agents for the prevention and treatment of MASLD, due to their good tolerance, high efficacy, and low toxicity. In this review, we summarize the pathological mechanisms of MASLD; emphasis is placed on the anti-MASLD mechanisms of Chinese herbal formula (CHF), especially their effects on improving lipid metabolism, inflammation, intestinal flora, and fibrosis. Our goal is to better understand the pharmacological mechanisms of CHF to inform research on the development of new drugs for the treatment of MASLD.

Immunological mechanisms in steatotic liver diseases: An overview and clinical perspectives

Steatotic liver diseases (SLD) are the principal worldwide cause of cirrhosis and end-stage liver cancer, affecting nearly a quarter of the global population. SLD includes metabolic dysfunction-associated alcoholic liver disease (MetALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), resulting in asymptomatic liver steatosis, fibrosis, cirrhosis and associated complications. The immune processes include gut dysbiosis, adiposeliver organ crosstalk, hepatocyte death and immune cell-mediated inflammatory processes. Notably, various immune cells such as B cells, plasma cells, dendritic cells, conventional CD4+ and CD8+ T cells, innate-like T cells, platelets, neutrophils and macrophages play vital roles in the development of MetALD and MASLD. Immunological modulations targeting hepatocyte death, inflammatory reactions and gut microbiome include N-acetylcysteine, selonsertib, F-652, prednisone, pentoxifylline, anakinra, JKB-121, HA35, obeticholic acid, probiotics, prebiotics, antibiotics and fecal microbiota transplantation. Understanding the immunological mechanisms underlying SLD is crucial for advancing clinical therapeutic strategies.

Mesenchymal Stem Cell-Derived Exosomes Attenuate Hepatic Steatosis and Insulin Resistance in Diet-Induced Obese Mice by Activating the FGF21-Adiponectin Axis

Exosomes derived from mesenchymal stem cells have shown promise in treating metabolic disorders, yet their specific mechanisms remain largely unclear. This study investigates the protective effects of exosomes from human umbilical cord Wharton's jelly mesenchymal stem cells (hWJMSCs) against adiposity and insulin resistance in high-fat diet (HFD)-induced obese mice. HFD-fed mice treated with hWJMSC-derived exosomes demonstrated improved gut barrier integrity, which restored immune balance in the liver and adipose tissues by reducing macrophage infiltration and pro-inflammatory cytokine expression. Furthermore, these exosomes normalized lipid metabolism including lipid oxidation and lipogenesis, which alleviate lipotoxicity-induced endoplasmic reticulum (ER) stress, thereby decreasing fat accumulation and chronic tissue inflammation in hepatic and adipose tissues. Notably, hWJMSC-derived exosomes also promoted browning and thermogenic capacity of adipose tissues, which was linked to reduced fibroblast growth factor 21 (FGF21) resistance and increased adiponectin production. This process activated the AMPK-SIRT1-PGC-1α pathway, highlighting the role of the FGF21-adiponectin axis. Our findings elucidate the molecular mechanisms through which hWJMSC-derived exosomes counteract HFD-induced metabolic dysfunctions, supporting their potential as therapeutic agents for metabolic disorders.

Targeting hepatic macrophages for non-alcoholic fatty liver disease therapy

Non-alcoholic fatty liver disease (NAFLD) and its more advanced form, non-alcoholic steatohepatitis (NASH), have become global health challenges with significant morbidity and mortality rates. NAFLD encompasses several liver diseases, ranging from simple steatosis to more severe inflammatory and fibrotic forms. Ultimately, this can lead to liver cirrhosis and hepatocellular carcinoma. The intricate role of hepatic macrophages, particularly Kupffer cells (KCs) and monocyte-derived macrophages (MoMFs), in the pathogenesis of NAFLD and NASH, has received increasing attention. Hepatic macrophages can interact with hepatocytes, hepatic stellate cells, and endothelial cells, playing a crucial role in maintaining homeostasis. Paradoxically, they also participate in the pathogenesis of some liver diseases. This review highlights the fundamental role of hepatic macrophages in the pathogenesis of NAFLD and NASH, emphasizing their plasticity and contribution to inflammation and fibrosis, and hopes to provide ideas for subsequent experimental research and clinical treatment.

Lipid nanoparticle-mediated hepatocyte delivery of siRNA and silibinin in metabolic dysfunction-associated steatotic liver disease

Lipid nanoparticle-mediated co-delivery of siRNA and small molecule holds a great potential to treat metabolic dysfunction-associated steatotic liver disease (MASLD). However, targeted delivery of therapeutics to hepatocytes remains challenging. Taking the advantage of rising low density lipoprotein receptor/very-low density lipoprotein receptor (LDLR/VLDR) levels in MASLD, the biological fate of dinonylamine-ethylene glycol chlorophosphate-1-nonanol (DNNA-COP-NA) based lipid nanoparticles (LNPs) was oriented to liver tissues via apolipoprotein E (ApoE)-LDLR/VLDLR pathway. We then adopted a three-round screening strategy to optimize the formulation with both high potency and selectivity to deliver siRNA-HIF-1α (siHIF1α) and silibinin (SLB) payloads to hepatocytes. The optimized SLB/siHIF1α-LNPs mediates great siRNA delivery and transfection of hepatocytes. In high fat diet (HFD)- and carbon tetrachloride (CCl4)-induced mouse models of MASLD, SLB/siHIF1α-LNPs enabled the silencing of hypoxia inducible factor-1α (HIF-1α), a therapeutic target primarily expressed by hepatocytes, leading to significantly reduced inflammation and liver fibrosis synergized with SLB. Moreover, it is demonstrated the hepatocyte-targeting delivery of SLB/siHIF1α-LNPs has the potential to restore the immune homeostasis by modulating the population of Tregs and cytotoxic T cells in spleen. This proof-of-concept study enable siRNA and small molecule co-delivery to hepatocytes through intrinsic variation of targeting receptors for MASLD therapy.

A comprehensive framework for managing metabolic dysfunction-associated steatotic liver disease: analyzing novel risk factors and advances in nanotechnology-based treatments and diagnosis

Metabolic dysfunction-associated steatotic liver disease (MASLD) presents a growing global health challenge requiring innovative approaches for effective management. This comprehensive review examines novel risk factors, including environmental pollutants like heavy metals, and underscores the complexity of personalized medicine tailored to individual patient profiles, influenced by gender and sex differences. Traditional treatments for MASLD, such as glucose- and lipid-lowering agents, show mixed results, highlighting the necessity for larger, long-term studies to establish safety and efficacy. Alternative therapies, including antioxidants, stem cells, and antiplatelets, although promising, demand extensive clinical trials for validation. This review highlights the importance of personalized medicine, considering individual variations and specific factors such as gender and sex, to optimize treatment responses. The shift from metabolic-associated fatty liver disease (MAFLD) to MASLD terminology underscores the metabolic components of the disease, aligning with the multiple-hit theory and highlighting the necessity for comprehensive risk factor management. Our vision advocates for an integrated approach to MASLD, encompassing extensive risk factor analysis and the development of safer, more effective treatments. Primary prevention and awareness initiatives are crucial in addressing the rising prevalence of MASLD. Future research must prioritize larger, long-term studies and personalized medicine principles to ensure the effective use of emerging therapies and technologies. The review underscores the need for continuous exploration and innovation, balancing the benefits and challenges of nanotechnology, to combat MASLD and improve patient outcomes comprehensively.

From NAFLD to NASH: Understanding the spectrum of non-alcoholic liver diseases and their consequences

Non-alcoholic fatty liver disease (NAFLD) has become one of the most frequent chronic liver diseases worldwide in recent decades. Metabolic diseases like excessive blood glucose, central obesity, dyslipidemia, hypertension, and liver function abnormalities cause NAFLD. NAFLD significantly increases the likelihood of liver cancer, heart disease, and mortality, making it a leading cause of liver transplants. Non-alcoholic steatohepatitis (NASH) is a more advanced form of the disease that causes scarring and inflammation of the liver over time and can ultimately result in cirrhosis and hepatocellular carcinoma. In this review, we briefly discuss NAFLD's pathogenic mechanisms, their progression into NASH and afterward to NASH-related cirrhosis. It also covers disease epidemiology, metabolic mechanisms, glucose and lipid metabolism in the liver, macrophage dysfunction, bile acid toxicity, and liver stellate cell stimulation. Additionally, we consider the contribution of intestinal microbiota, genetics, epigenetics, and ecological factors to fibrosis progression and hepatocellular carcinoma risk in NAFLD and NASH patients.

An overview of the cholesterol metabolism and its proinflammatory role in the development of MASLD

Cholesterol is an essential lipid molecule in mammalian cells. It is not only involved in the formation of cell membranes but also serves as a raw material for the synthesis of bile acids, vitamin D, and steroid hormones. Additionally, it acts as a covalent modifier of proteins and plays a crucial role in numerous life processes. Generally, the metabolic processes of cholesterol absorption, synthesis, conversion, and efflux are strictly regulated. Excessive accumulation of cholesterol in the body is a risk factor for metabolic diseases such as cardiovascular disease, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). In this review, we first provide an overview of the discovery of cholesterol and the fundamental process of cholesterol metabolism. We then summarize the relationship between dietary cholesterol intake and the risk of developing MASLD, and also the animal models of MASLD specifically established with a cholesterol-containing diet. In the end, the role of cholesterol-induced inflammation in the initiation and development of MASLD is discussed.

(+)-Lipoic acid reduces mitochondrial unfolded protein response and attenuates oxidative stress and aging in an in vitro model of non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a liver disorder characterized by the ac-cumulation of fat in hepatocytes without alcohol consumption. Mitochondrial dysfunction and endoplasmic reticulum (ER) stress play significant roles in NAFLD pathogenesis. The unfolded protein response in mitochondria (UPRmt) is an adaptive mechanism that aims to restore mitochondrial protein homeostasis and mitigate cellular stress. This study aimed to investigate the effects of ( +)-Lipoic acid (ALA) on UPRmt, inflammation, and oxidative stress in an in vitro model of NAFLD using HepG2 cells treated with palmitic acid and oleic acid to induce steatosis.

RESULTS

Treatment with palmitic and oleic acids increased UPRmt-related proteins HSP90 and HSP60 (heat shock protein), and decreased CLPP (caseinolytic protease P), indicating ER stress activation. ALA treatment at 1 μM and 5 μM restored UPRmt-related protein levels. PA:OA (palmitic acid:oleic acid)-induced ER stress markers IRE1α (Inositol requiring enzyme-1), CHOP (C/EBP Homologous Protein), BIP (Binding Immunoglobulin Protein), and BAX (Bcl-2-associated X protein) were significantly reduced by ALA treatment. ALA also enhanced ER-mediated protein glycosylation and reduced oxidative stress, as evidenced by decreased GPX1 (Glutathione peroxidase 1), GSTP1 (glutathione S-transferase pi 1), and GSR (glutathione-disulfide reductase) expression and increased GSH (Glutathione) levels, and improved cellular senescence as shown by the markers β-galactosidase, γH2Ax and Klotho-beta.

CONCLUSIONS

In conclusion, ALA ameliorated ER stress, oxidative stress, and inflammation in HepG2 cells treated with palmitic and oleic acids, potentially offering therapeutic benefits for NAFLD providing a possible biochemical mechanism underlying ALA beneficial effects.

Mesenchymal Stem Cell-Derived Exosomes in Various Chronic Liver Diseases: Hype or Hope?

Chronic liver conditions are associated with high mortality rates and have a large adverse effect on human well-being as well as a significant financial burden. Currently, the only effective treatment available for the effects of liver failure and cirrhosis resulting from the progression of several chronic liver diseases is liver transplantation carried out at the original location. This implies that developing novel and effective treatments is imperative. Regenerative medicine has long been associated with stem cell therapy. Mesenchymal stem cells (MSCs), a type of cell with great differentiation potential, have become the preferred source for stem cell therapy. According to recent studies, MSCs' paracrine products-rather than their capacity for differentiation-play a significant therapeutic effect. MSC exosomes, a type of extracellular vesicle (MSC-EV), came into view as the paracrine substances of MSCs. According to research, MSC exosomes can maintain tissue homeostasis, which is necessary for healthy tissue function. All tissues contain them, and they take part in a variety of biological activities that support cellular activity and tissue regeneration in order to preserve tissue homeostasis. The outcomes support the use of MSCs and the exosomes they produce as a therapeutic option for a range of diseases. This review provides a brief overview of the source of MSC-EVs and outlines their physiological roles and biochemical capabilities. The elucidation of the role of MSC-EVs in the recovery and repair of hepatic tissues, as well as their contribution to maintaining tissue homeostasis, is discussed in relation to different chronic liver diseases. This review aims to provide new insights into the unique roles that MSC-EVs play in the treatment of chronic liver diseases.

Non-Pharmacological Approach to Diet and Exercise in Metabolic-Associated Fatty Liver Disease: Bridging the Gap between Research and Clinical Practice

This review provides a practical and comprehensive overview of non-pharmacological interventions for metabolic-associated fatty liver disease (MASLD), focusing on dietary and exercise strategies. It highlights the effectiveness of coffee consumption, intermittent fasting, and Mediterranean and ketogenic diets in improving metabolic and liver health. The review emphasizes the importance of combining aerobic and resistance training as a critical approach to reducing liver fat and increasing insulin sensitivity. Additionally, it discusses the synergy between diet and exercise in enhancing liver parameters and the role of gut microbiota in MASLD. The paper underscores the need for a holistic, individualized approach, integrating diet, exercise, gut health, and patient motivation. It also highlights the long-term benefits and minimal risks of lifestyle interventions compared to the side effects of pharmacological and surgical options. The review calls for personalized treatment strategies, continuous patient education, and further research to optimize therapeutic outcomes in MASLD management.

Innovative preconditioning strategies for improving the therapeutic efficacy of extracellular vesicles derived from mesenchymal stem cells in gastrointestinal diseases

Gastrointestinal (GI) diseases have become a global health issue and an economic burden due to their wide distribution, late prognosis, and the inefficacy of recent available medications. Therefore, it is crucial to search for new strategies for their management. In the recent decades, mesenchymal stem cells (MSCs) therapy has attracted attention as a viable option for treating a myriad of GI disorders such as hepatic fibrosis (HF), ulcerative colitis (UC), acute liver injury (ALI), and non-alcoholic fatty liver disease (NAFLD) due to their regenerative and paracrine properties. Importantly, recent studies have shown that MSC-derived extracellular vesicles (MSC-EVs) are responsible for most of the therapeutic effects of MSCs. In addition, EVs have revealed several benefits over their parent MSCs, such as being less immunogenic, having a lower risk of tumour formation, being able to cross biological barriers, and being easier to store. MSC-EVs exhibited regenerative, anti-oxidant, anti-inflammatory, anti-apoptotic, and anti-fibrotic effects in different experimental models of GI diseases. However, a key issue with their clinical application is the maintenance of their stability and efficacy following in vivo transplantation. Preconditioning of MSC-EVs or their parent cells is one of the novel methods used to improve their effectiveness and stability. Herein, we discuss the application of MSC-EVs in several GI disorders taking into account their mechanism of action. We also summarise the challenges and restrictions that need to be overcome to promote their clinical application in the treatment of various GI diseases as well as the recent developments to improve their effectiveness. A representation of the innovative preconditioning techniques that have been suggested for improving the therapeutic efficacy of MSC-EVs in GI diseases. The pathological conditions in various GI disorders (ALI, UC, HF and NAFLD) create a harsh environment for EVs and their parents, increasing the risk of apoptosis and senescence of MSCs and thereby diminishing MSC-EVs yield and restricting their large-scale applications. Preconditioning with pharmacological agents or biological mediators can improve the therapeutic efficacy of MSC-EVs through their adaption to the lethal environment to which they are subjected. This can result in establishment of a more conducive environment and activation of numerous vital trajectories that act to improve the immunomodulatory, reparative and regenerative activities of the derived EVs, as a part of MSCs paracrine system. ALI, acute liver injury; GI diseases, gastrointestinal diseases; HF, hepatic fibrosis; HSP, heat shock protein; miRNA, microRNA; mRNA, messenger RNA; MSC-EVs, mesenchymal stem cell-derived extracellular vesicles; NAFLD, non-alcoholic fatty liver disease; UC, ulcerative colitis.

Unveiling the role of gut dysbiosis in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial complicated condition, reflected by the accumulation of extra fat in the liver. A detailed study of literature throws light on the fascinating connection between gut dysbiosis and NAFLD. The term 'gut dysbiosis' describes an imbalance in the harmony and operation of the gut microflora, which can upshoot a number of metabolic disorders. To recognize the underlying mechanisms and determine treatment options, it is essential to comprehend the connection between gut dysbiosis and NAFLD. This in-depth review discusses the normal gut microflora composition and its role in health, alterations in the gut microflora composition that leads to disease state focusing on NAFLD. The potential mechanisms influencing the advent and aggravation of NAFLD suggested disturbance of microbial metabolites, changes in gut barrier integrity, and imbalances in the composition of the gut microflora. Furthermore, it was discovered that gut dysbiosis affected immune responses, liver inflammation, and metabolic pathways, aggravating NAFLD.

Immunometabolic impact of pancreastatin inhibitor PSTi8 in MCD induced mouse model of oxidative stress and steatohepatitis

AIM

Pancreastatin, a dysglycemic hormone that encourages inflammation and steatosis in a variety of metabolic disorder animal models. The purpose of this study is to determine the effect of the pancreastatin inhibitor PSTi8 on immunometabolic changes in the liver of MCD-induced NASH mice.

MAIN METHODS

Methionine and choline-deficient (MCD) diet was used for the development of NASH. Liver enzymes like SGOT, SGPT, and ALP and lipid profiles were also performed in the serum. Further, immunophenotyping study was performed in the liver through flowcytometer. Subsequently, Hematoxylin and Eosin, Picro Sirius Red and Masson's Trichrome staining were done to check the liver morphology and collagen staining, respectively. Inflammatory cytokines were measured through ELISA and gene expression through RT-PCR. The expression of α-SMA was examined using immunohistochemistry and immunofluorescence staining.

KEY FINDINGS

PSTi8 inhibited the expression of lipogenic genes in the liver and attenuated bad cholesterol, SGOT, SGPT, and ALP in the serum. PSTi8 improved the liver morphology and attenuated collagen deposition. Subsequently, PSTi8 attenuated inflammatory M1-macrophages, CD8+T, CD4+T cells and increased anti-inflammatory M2 macrophages, T-reg and eosinophil populations in the liver. It also attenuated the expression of pro-inflammatory genes like Mcp1, Tnfα, and Il6. Apart from this, PSTi8 attenuated the oxidative stress marker, like ROS, and MDA and fibrosis marker α-SMA in the liver. It also decreased the apoptosis and ROS and MDA level in the liver.

SIGNIFICANCE

Overall, these compressive studies revealed that PSTi8 exhibited beneficial effect on the liver of MCD-induced NASH mice by attenuating inflammation and oxidative stress.

Molecular mechanisms of metabolic disease-associated hepatic inflammation in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

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

Non-alcoholic fatty liver disease: Immunological mechanisms and current treatments

Non-alcoholic fatty liver disease (NAFLD) causes significant global disease burden and is a leading cause of mortality. NAFLD induces a myriad of aberrant changes in hepatocytes at both the cellular and molecular level. Although the disease spectrum of NAFLD is widely recognised, the precise triggers for disease progression are still to be fully elucidated. Furthermore, the propagation to cirrhosis is poorly understood. Whilst some progress in terms of treatment options have been explored, an incomplete understanding of the hepatic cellular and molecular alterations limits their clinical utility. We have therefore reviewed some of the key pathways responsible for the pathogenesis of NAFLD such as innate and adaptative immunity, lipotoxicity and fibrogenesis, and highlighted current trials and treatment options for NAFLD patients.

Customized liver organoids as an advanced in vitro modeling and drug discovery platform for non-alcoholic fatty liver diseases

Non-alcoholic fatty liver disease (NAFLD) and its progressive form non-alcoholic steatohepatitis (NASH) have presented a major and common health concern worldwide due to their increasing prevalence and progressive development of severe pathological conditions such as cirrhosis and liver cancer. Although a large number of drug candidates for the treatment of NASH have entered clinical trial testing, all have not been released to market due to their limited efficacy, and there remains no approved treatment for NASH available to this day. Recently, organoid technology that produces 3D multicellular aggregates with a liver tissue-like cytoarchitecture and improved functionality has been suggested as a novel platform for modeling the human-specific complex pathophysiology of NAFLD and NASH. In this review, we describe the cellular crosstalk between each cellular compartment in the liver during the pathogenesis of NAFLD and NASH. We also summarize the current state of liver organoid technology, describing the cellular diversity that could be recapitulated in liver organoids and proposing a future direction for liver organoid technology as an in vitro platform for disease modeling and drug discovery for NAFLD and NASH.

Major roles of kupffer cells and macrophages in NAFLD development

Non-alcoholic fatty liver disease (NAFLD) is an important public health problem with growing numbers of NAFLD patients worldwide. Pathological conditions are different in each stage of NAFLD due to various factors. Preclinical and clinical studies provide evidence for a crucial role of immune cells in NAFLD progression. Liver-resident macrophages, kupffer cells (KCs), and monocytes-derived macrophages are the key cell types involved in the progression of NAFLD, non-alcoholic steatohepatitis (NASH), and hepatocellular carcinoma (HCC). Their unique polarization contributes to the progression of NAFLD. KCs are phagocytes with self-renewal abilities and play a role in regulating and maintaining homeostasis. Upon liver damage, KCs are activated and colonized at the site of the damaged tissue. The secretion of inflammatory cytokines and chemokines by KCs play a pivotal role in initiating NAFLD pathogenesis. This review briefly describes the role of immune cells in the immune system in NAFLD, and focuses on the pathological role and molecular pathways of KCs and recruited macrophages. In addition, the relationship between macrophages and insulin resistance is described. Finally, the latest therapeutics that target KCs and macrophages are summarized for the prevention and treatment of NAFLD.

Analysis of the Genetic Relationship between Atherosclerosis and Non-Alcoholic Fatty Liver Disease through Biological Interaction Networks

Non-alcoholic fatty liver disease (NAFLD) seems to have some molecular links with atherosclerosis (ATH); however, the molecular pathways which connect both pathologies remain unexplored to date. The identification of common factors is of great interest to explore some therapeutic strategies to improve the outcomes for those affected patients. Differentially expressed genes (DEGs) for NAFLD and ATH were extracted from the GSE89632 and GSE100927 datasets, and common up- and downregulated DEGs were identified. Subsequently, a protein-protein interaction (PPI) network based on the common DEGs was performed. Functional modules were identified, and the hub genes were extracted. Then, a Gene Ontology (GO) and pathway analysis of common DEGs was performed. DEGs analysis in NAFLD and ATH showed 21 genes that were regulated similarly in both pathologies. The common DEGs with high centrality scores were ADAMTS1 and CEBPA which appeared to be down- and up-regulated in both disorders, respectively. For the analysis of functional modules, two modules were identified. The first one was oriented to post-translational protein modification, where ADAMTS1 and ADAMTS4 were identified, and the second one mainly related to the immune response, where CSF3 was identified. These factors could be key proteins with an important role in the NAFLD/ATH axis.

Regulatory Effects and Molecular Mechanisms of Tea and Its Active Compounds on Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disease, is a multifactorial disease resulting from the interaction between environment, genetic background, and metabolic stress. Most treatments for NAFLD include dietary intervention and exercise show limited efficacy due to the complex mechanisms involved in NAFLD. Meanwhile, drug therapy is accompanied by serious side effects. The development of high-efficiency natural supplements is a sustainable strategy for the prevention and treatment of NAFLD. As the second most consumed beverage, tea has health benefits that have been widely recognized. Nevertheless, the intervention of tea active compounds in NAFLD has received limited attention. Tea contains abundant bioactive compounds with potential effects on NAFLD, such as catechins, flavonoids, theanine, tea pigments, and tea polysaccharides. We reviewed the intrinsic and environmental factors and pathogenic mechanisms that affect the occurrence and development of NAFLD, and summarized the influences of exercise, drugs, diet, and tea drinking on NAFLD. On this basis, we further analyzed the potential effects and molecular regulatory mechanisms of tea active compounds on NAFLD and proposed future development directions. This review hopes to provide novel insights into the development and application of tea active compounds in the prevention and treatment of NAFLD.

The Effect of Lipopolysaccharide-Stimulated Adipose-Derived Mesenchymal Stem Cells on NAFLD Treatment in High-Fat Diet-Fed Rats

Background

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are 2 common liver diseases that currently lack effective treatment options.

Objectives

This study aimed to investigate the effect of lipopolysaccharide (LPS)-stimulated adipose-derived stem cells (ADSCs) on NAFLD treatment in an animal model.

Methods

Male Wistar rats were fed a high-fat diet (HFD) to induce NAFLD for 7 weeks. The rats were then categorized into 3 groups: Mesenchymal stem cell (MSC), MSC + LPS, and fenofibrate (FENO) groups. Liver and body weight were measured, and the expression of genes involved in fatty acid biosynthesis, β-oxidation, and inflammatory responses was assessed.

Results

Lipopolysaccharide-stimulated ADSCs were more effective in regulating liver and body weight gain and reducing liver triglyceride (TG) levels compared to the other groups. Treatment with LPS-stimulated ADSCs effectively corrected liver enzymes, including alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and lipid factors, including low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) values, better than treatment with both FENO and MSCs. ADSCs + LPS treatment significantly decreased transforming growth factor β (TGF-β) and genes associated with inflammatory responses. Additionally, there was a significant reduction in reactive oxygen species (ROS) levels in the rats treated with ADSCs + LPS.

Conclusions

Lipopolysaccharide-stimulated ADSCs showed potential in alleviating NAFLD by reducing inflammatory genes and ROS levels in HFD rats, demonstrating better results than treatment with ADSCs and FENO groups alone.

Advances in Purification, Modification, and Application of Extracellular Vesicles for Novel Clinical Treatments

Extracellular vesicles (EV) are membrane vesicles surrounded by a lipid bilayer membrane and include microvesicles, apoptotic bodies, exosomes, and exomeres. Exosome-encapsulated microRNAs (miRNAs) released from cancer cells are involved in the proliferation and metastasis of tumor cells via angiogenesis. On the other hand, mesenchymal stem cell (MSC) therapy, which is being employed in regenerative medicine owing to the ability of MSCs to differentiate into various cells, is due to humoral factors, including messenger RNA (mRNA), miRNAs, proteins, and lipids, which are encapsulated in exosomes derived from transplanted cells. New treatments that advocate cell-free therapy using MSC-derived exosomes will significantly improve clinical practice. Therefore, using highly purified exosomes that perform their original functions is desirable. In this review, we summarized advances in the purification, modification, and application of EVs as novel strategies to treat some diseases.

Association of complement components with the risk and severity of NAFLD: A systematic review and meta-analysis

Background

It is generally believed that complement system is strongly associated with the risk of nonalcoholic fatty liver disease (NAFLD). However, complement system contains a variety of complement components, and the relationship between complement components and the risk and severity of NAFLD is inconsistent. The aim of this meta-analysis was to evaluate the association of complement components with the risk and severity of NAFLD.

Methods

We searched PubMed, Embase, Cochrane Library, Google Scholar, Scopus, and ZhiWang Chinese databases from inception to May 2022 for observational studies reporting the risk of NAFLD with complement components. Random-effects meta-analysis was used to obtain pooled estimates of the effect due to heterogeneity.

Results

We identified 18 studies with a total of 18560 included subjects. According to recent studies, levels of complement component 3 (C3) (mean difference (MD): 0.43, 95% confidence interval (CI) 0.26-0.60), complement component 4 (C4) (MD: 0.04, 95% CI 0.02-0.07), complement component 5(C5) (MD: 34.03, 95% CI 30.80-37.27), complement factor B (CFB) (MD: 0.22, 95% CI 0.13-0.31) and acylation stimulating protein (ASP) (standard mean difference (SMD): 5.17, 95% CI 2.57-7.77) in patients with NAFLD were significantly higher than those in the control group. However, no statistical significance was obtained in complement factor D (CFD) levels between NAFLD and non-NAFLD (MD=156.51, 95% CI -59.38-372.40). Moreover, the levels of C3, C5, CFB, and ASP in patients with moderate and severe NAFLD were significantly higher than those in patients with mild NAFLD. Except for C4 and CFD, the included studies did not explore the changes in the severity of NAFLD according to the concentration of C4 and CFD.

Conclusions

This meta-analysis demonstrates that an increase in complement components including C3, C5, CFB, and ASP is associated with an increased risk and severity of NAFLD, indicating that they may be good biomarkers and targets for the diagnosis and treatment of NAFLD.

Systematic review registration

PROSPERO [https://www.crd.york.ac.uk/PROSPERO/], identifier CRD42022348650.

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.