Role of FXR in Bile Acid and Metabolic Homeostasis in NASH: Pathogenetic Concepts and Therapeutic Opportunities

Oligonucleotide therapies for nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) represents a severe disease subtype of nonalcoholic fatty liver disease (NAFLD) that is thought to be highly associated with systemic metabolic abnormalities. It is characterized by a series of substantial liver damage, including hepatocellular steatosis, inflammation, and fibrosis. The end stage of NASH, in some cases, may result in cirrhosis and hepatocellular carcinoma (HCC). Nowadays a large number of investigations are actively under way to test various therapeutic strategies, including emerging oligonucleotide drugs (e.g., antisense oligonucleotide, small interfering RNA, microRNA, mimic/inhibitor RNA, and small activating RNA) that have shown high potential in treating this fatal liver disease. This article systematically reviews the pathogenesis of NASH/NAFLD, the promising druggable targets proven by current studies in chemical compounds or biological drug development, and the feasibility and limitations of oligonucleotide-based therapeutic approaches under clinical or pre-clinical studies.

Probiotics, gut microbiome, and cardiovascular diseases: An update

Cardiovascular diseases (CVD) are one of the most challenging diseases and many factors have been demonstrated to affect their pathogenesis. One of the major factors that affect CVDs, especially atherosclerosis, is the gut microbiota (GM). Genetics play a key role in linking CVDs with GM, in addition to some environmental factors which can be either beneficial or harmful. The interplay between GM and CVDs is complex due to the numerous mechanisms through which microbial components and their metabolites can influence CVDs. Within this interplay, the immune system plays a major role, mainly based on the immunomodulatory effects of microbial dysbiosis and its resulting metabolites. The resulting modulation of chronic inflammatory processes was found to reduce the severity of CVDs and to maintain cardiovascular health. To better understand the specific roles of GM-related metabolites in this interplay, this review presents an updated perspective on gut metabolites related effects on the cardiovascular system, highlighting the possible benefits of probiotics in therapeutic strategies.

Gut liver brain axis in diseases: the implications for therapeutic interventions

Gut-liver-brain axis is a three-way highway of information interaction system among the gastrointestinal tract, liver, and nervous systems. In the past few decades, breakthrough progress has been made in the gut liver brain axis, mainly through understanding its formation mechanism and increasing treatment strategies. In this review, we discuss various complex networks including barrier permeability, gut hormones, gut microbial metabolites, vagus nerve, neurotransmitters, immunity, brain toxic metabolites, β-amyloid (Aβ) metabolism, and epigenetic regulation in the gut-liver-brain axis. Some therapies containing antibiotics, probiotics, prebiotics, synbiotics, fecal microbiota transplantation (FMT), polyphenols, low FODMAP diet and nanotechnology application regulate the gut liver brain axis. Besides, some special treatments targeting gut-liver axis include farnesoid X receptor (FXR) agonists, takeda G protein-coupled receptor 5 (TGR5) agonists, glucagon-like peptide-1 (GLP-1) receptor antagonists and fibroblast growth factor 19 (FGF19) analogs. Targeting gut-brain axis embraces cognitive behavioral therapy (CBT), antidepressants and tryptophan metabolism-related therapies. Targeting liver-brain axis contains epigenetic regulation and Aβ metabolism-related therapies. In the future, a better understanding of gut-liver-brain axis interactions will promote the development of novel preventative strategies and the discovery of precise therapeutic targets in multiple diseases.

Non-alcoholic fatty liver disease and gut microbial dysbiosis- underlying mechanisms and gut microbiota mediated treatment strategies

Non-alcoholic fatty liver disease (NAFLD) is by far the most prevalent form of liver disease worldwide. It's also the leading cause of liver-related hospitalizations and deaths. Furthermore, there is a link between obesity and NAFLD risk. A projected 25% of the world's population grieves from NAFLD, making it the most common chronic liver disorder. Several factors, such as obesity, oxidative stress, and insulin resistance, typically accompany NAFLD. Weight loss, lipid-lowering agents, thiazolidinediones, and metformin help prominently control NAFLD. Interestingly, pre-clinical studies demonstrate gut microbiota's potential causal role in NAFLD. Increased intestinal permeability and unhindered transport of microbial metabolites into the liver are the major disruptions due to gut microbiome dysbiosis, contributing to the development of NAFLD by dysregulating the gut-liver axis. Hence, altering the pathogenic bacterial population using probiotics, prebiotics, synbiotics, and fecal microbiota transplantation (FMT) could benefit patients with NAFLD. Therefore, it is crucial to acknowledge the importance of microbiota-mediated therapeutic approaches for NAFLD and comprehend the underlying mechanisms that establish a connection between NAFLD and gut microbiota. This review provides a comprehensive overview of the affiliation between dysbiosis of gut microbiota and the progress of NAFLD, as well as the potential benefits of prebiotic, probiotic, synbiotic supplementation, and FMT in obese individuals with NAFLD.

FXR agonists in NASH treatment

The farnesoid X receptor (FXR), a bile acid (BA)-activated nuclear receptor highly expressed in the liver and intestine, regulates the expression of genes involved in cholesterol and bile acid homeostasis, hepatic gluconeogenesis, lipogenesis, inflammation and fibrosis, in addition to controlling intestinal barrier integrity, preventing bacterial translocation and maintaining gut microbiota eubiosis. Non-alcoholic steatohepatitis (NASH), an advanced stage of non-alcoholic fatty liver disease, is characterized by hepatic steatosis, hepatocyte damage (ballooning) and inflammation, leading to fibrosis, cirrhosis and hepatocellular carcinoma. NASH represents a major unmet medical need, but no pharmacological treatments have yet been approved. The pleiotropic mechanisms involved in NASH development offer a range of therapeutic opportunities and among them FXR activation has emerged as an established pharmacological target. Various FXR agonists with different physicochemical properties, which can be broadly classified as BA derivatives, non-BA-derived steroidal FXR agonists, non-steroidal FXR agonists, and partial FXR agonists, are in advanced clinical development. In this review we will summarize key preclinical and clinical features of the most advanced FXR agonists and critically evaluate their potential in NASH treatment.

NASH drug treatment development: challenges and lessons

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. Although NAFLD is tightly linked to obesity and type 2 diabetes, this liver disease also affects individuals who do not have obesity. NAFLD increases the risk of developing cardiovascular disease, chronic kidney disease, and certain extrahepatic cancers. There is currently no licensed pharmacotherapy for NAFLD, despite numerous clinical trials in the past two decades. Currently, the reason so few drugs have been successful in the treatment of NAFLD in a trial setting is not fully understood. As cardiovascular disease is the predominant cause of mortality in people with NAFLD, future pharmacotherapies for NAFLD must consider associated cardiometabolic risk factors. The successful use of glucose-lowering drugs in the treatment of type 2 diabetes in patients with NAFLD indicates that this strategy is important, and worth developing further. Greater public awareness of NAFLD is needed because collaboration between all stakeholders is vital to enable a holistic approach to successful treatment.

Lactiplantibacillus plantarum LPJZ-658 Improves Non-Alcoholic Steatohepatitis by Modulating Bile Acid Metabolism and Gut Microbiota in Mice

Non-alcoholic steatohepatitis (NASH) is one of the most prevalent diseases worldwide; it is characterized by hepatic lipid accumulation, inflammation, and progressive fibrosis. Here, a Western diet combined with low-dose weekly carbon tetrachloride was fed to C57BL/6J mice for 12 weeks to build a NASH model to investigate the attenuating effects and possible mechanisms of Lactiplantibacillus plantarum LPJZ-658. Hepatic pathology, lipid profiles, and gene expression were assessed. The metabolomic profiling of the serum was performed. The composition structure of gut microbiota was profiled using 16s rRNA sequencing. The results show that LPJZ-658 treatment significantly attenuated liver injury, steatosis, fibrosis, and inflammation in NASH mice. Metabolic pathway analysis revealed that several pathways, such as purine metabolism, glycerophospholipid metabolism, linoleic acid metabolism, and primary bile acid biosynthesis, were associated with NASH. Notably, we found that treatment with LPJZ-658 regulated the levels of bile acids (BAs) in the serum. Moreover, LPJZ-658 restored NASH-induced gut microbiota dysbiosis. The correlation analysis deduced obvious interactions between BAs and gut microbiota. The current study indicates that LPJZ-658 supplementation protects against NASH progression, which is accompanied by alternating BA metabolic and modulating gut microbiota.

Preventive and therapeutic effects of natural products and herbal extracts on nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a common condition that is prevalent in patients who consume little or no alcohol, and is characterized by excessive fat accumulation in the liver. The disease is becoming increasingly common with the rapid economic development of countries. Long-term accumulation of excess fat can lead to NAFLD, which represents a global health problem with no effective therapeutic approach. NAFLD is a complex, multifaceted pathological process that has been the subject of extensive research over the past few decades. Herbal medicines have gained attention as potential therapeutic agents to prevent and treat NAFLD due to their high efficacy and low risk of side effects. Our overview is based on a PubMed and Web of Science database search as of Dec 22 with the keywords: NAFLD/NASH Natural products and NAFLD/NASH Herbal extract. In this review, we evaluate the use of herbal medicines in the treatment of NAFLD. These natural resources have the potential to inform innovative drug research and the development of treatments for NAFLD in the future.

Integration of Metabolomics, Lipidomics, and Proteomics Reveals the Metabolic Characterization of Nonalcoholic Steatohepatitis

Metabolic dysfunction is associated with nonalcoholic steatohepatitis (NASH) development. However, omics studies investigating metabolic changes in NASH patients are limited. In this study, metabolomics and lipidomics in plasma, as well as proteomics in the liver, were performed to characterize the metabolic profiles of NASH patients. Moreover, the accumulation of bile acids (BAs) in NASH patients prompted us to investigate the protective effect of cholestyramine on NASH. The liver expression of essential proteins involved in FA transport and lipid droplets was significantly elevated in patients with NASH. Furthermore, we observed a distinct lipidomic remodeling in patients with NASH. We also report a novel finding suggesting an increase in the expression of critical proteins responsible for glycolysis and the level of glycolytic output (pyruvic acid) in patients with NASH. Furthermore, the accumulation of branched chain amino acids, aromatic amino acids, purines, and BAs was observed in NASH patients. Similarly, a dramatic metabolic disorder was also observed in a NASH mouse model. Cholestyramine not only significantly alleviated liver steatosis and fibrosis but also reversed NASH-induced accumulation of BAs and steroid hormones. In conclusion, NASH patients were characterized by perturbations in FA uptake, lipid droplet formation, glycolysis, and accumulation of BAs and other metabolites.

Stigmasterol Protects Against Steatohepatitis Induced by High-Fat and High-Cholesterol Diet in Mice by Enhancing the Alternative Bile Acid Synthesis Pathway

BACKGROUND

Hepatic cholesterol accumulation is a significant risk factor in the progression of nonalcoholic fatty liver disease (NAFLD) to steatohepatitis. However, the precise mechanism by which stigmasterol (STG) mitigates this process remains unclear.

OBJECTIVES

This study aimed to investigate the potential mechanism underlying the protective effect of STG in mice with NAFLD progressing to steatohepatitis while being fed a high-fat and high-cholesterol (HFHC) diet.

METHODS

Male C57BL/6 mice were fed an HFHC diet for 16 wk to establish the NAFLD model. Subsequently, the mice received STG or a vehicle via oral gavage while continuing the HFHC diet for an additional 10 wk. The study evaluated hepatic lipid deposition and inflammation as well as the expression of key rate-limiting enzymes involved in the bile acid (BA) synthesis pathways. BAs in the colonic contents were quantified using ultra-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Compared with the vehicle control group, STG significantly reduced hepatic cholesterol accumulation (P < 0.01) and suppressed the gene expression of NLRP3 inflammasome and interleukin-18 (P < 0.05) in the livers of HFHC diet-fed mice. The total fecal BA content in the STG group was nearly double that of the vehicle control group. Additionally, the administration of STG increased the concentrations of representative hydrophilic BAs in the colonic contents (P < 0.05) along with the upregulation of gene and protein expression of CYP7B1 (P < 0.01). Furthermore, STG enhanced the α-diversity of the gut microbiota and partially reversed the alterations in the relative abundance of the gut microbiota induced by the HFHC diet.

CONCLUSIONS

STG mitigates steatohepatitis by enhancing the alternative pathway for BA synthesis.

L-Theanine regulates lipid metabolism by modulating gut microbiota and bile acid metabolism

BACKGROUND

l-Theanine (LTA) is a biologically active ingredient in tea that shows great potential for regulating lipid metabolism. Bile acids (BA), an important end-product of cholesterol catabolism, participate in the regulation of lipid metabolism and gut microbiota. Here, we investigated the effect of LTA on lipid metabolism and the mechanism by which it regulates BA metabolism and gut microbiota. Male BALB/c mice were treated with LTA for 28 days.

RESULTS

Daily LTA doses of 100 and 300 mg kg^-1  d^-1 altered the gut microbiota in mice, predominantly by decreasing Lactobacillus, Streptococcus, Bacteroides, Clostridium and Enterorhabdus microbes associated with bile-salt hydrolase (BSH) activity, thereby decreasing the activity of BSH and increasing the levels of ileum conjugated BA (such as glycocholic acid (GCA) and lithocholic acid), thereby inhibiting the intestinal farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) signaling pathway. Inhibition of FXR-FGF15 signaling was accompanied by upregulation of cholesterol 7α-hydroxylase (CYP7A1) mRNA and protein expression and increased hepatic production of cholic acid, deoxycholic acid, GCA, glycine cholic acid and glycine ursodeoxycholic acid. Meanwhile, increasing hepatic unconjugated BA upregulated the mRNA and protein expression of liver 3-hydroxy-3-methylglutaryl-CoA reductase and downregulated the mRNA and protein expression of stearoyl-CoA desaturase-1, liver low-density lipoprotein receptor and type B scavenger receptor. Therefore, the serum levels of cholesterol and triglycerides decreased.

CONCLUSION

Our findings indicate that LTA regulates lipid metabolism by modulating the gut microbiota and BA metabolism via the FXR-FGF15-CYP7A1 pathway. © 2022 Society of Chemical Industry.

Deciphering the Structural Determinants Critical in Attaining the FXR Partial Agonism

Elucidation of structural determinants is pivotal for structure-based drug discovery. The Farnesoid X receptor (FXR) is a proven target for NASH; however, its full agonism causes certain clinical complications. Therefore, partial agonism (PA) appears as a viable alternative for improved therapeutics. Since the agonist and PA both share the same binding site, i.e., ligand-binding pocket (LBP), which is highly dynamic and has synergy with the substrate binding site, the selective designing of PA is challenging. The identification of structural and conformational determinants is critical for PA compared with an agonist. Furthermore, the mechanism by which PA modulates the structural dynamics of FXR at the residue level, a prerequisite for PA designing, is still elusive. Here, by using ∼4.5 μs of MD simulations and residue-wise communication network analysis, we identified the structural regions which are flexible with PA but frozen with an agonist. Also, the network analysis identified the considerable changes between an agonist and PA in biologically essential zones of FXR such as helix H10/H11 and loop L:H11/H12, which lead to the modulation of synergy between LBP and the substrate binding site. Furthermore, the thermodynamic profiling suggested the methionine residues, mainly M³²⁸, M³⁶⁵, and M⁴⁵⁰, seem to be responsible for the recruitment of PA. The other residues I³⁵⁷, Y³⁶¹, L⁴⁶⁵, F³⁰⁸, Q³¹⁶, and K³²¹ are also identified, exclusively interacting with PA. This study offers novel structural and mechanistic insights that are critical for FXR targeted drug discovery for PA designing.

Stimulation of the farnesoid X receptor promotes M2 macrophage polarization

FXR is a key molecule that modulates anti-inflammatory activity in the intestinal-liver axis. Although FXR has pleiotropic functions including regulation of liver inflammation and activation of macrophages, it remains unclear whether it is involved in macrophage polarization. In this paper we demonstrated that stimulation of macrophages derived from the bone marrow using an FXR agonist activated polarization toward M2 but not M1 macrophages. The treatment of mice with chitin skewed macrophage polarization towards M2 macrophages, while co-treatment with an FXR agonist further promoted the polarization toward M2 macrophages in vivo. This skewed polarization towards M2 macrophages by an FXR agonist was accompanied by increased expression of signaling molecules related to the retinoic acid receptor. Inhibition of the retinoic acid receptor suppressed FXR agonist-mediated M2 macrophage polarization, indicating that this polarization was, at least, partly dependent on the retinoic acid receptor pathway. These data demonstrate that FXR has a role in polarization toward M2 macrophages and suggest a possible therapeutic potential of FXR agonists in M2 macrophage-related conditions.

Celastrol-regulated gut microbiota and bile acid metabolism alleviate hepatocellular carcinoma proliferation by regulating the interaction between FXR and RXRα in vivo and in vitro

Celastrol, a triterpene derived from Thunder God Vine (Tripterygium wilfordii Hook f; Celastraceae), a traditional Chinese herb, has promising anticancer activity. The present study aimed to elucidate an indirect mechanism of celastrol-mediated alleviation of hepatocellular carcinoma (HCC) via gut microbiota-regulated bile acid metabolism and downstream signaling. Here, we constructed a rat model of orthotopic HCC and performed 16S rDNA sequencing and UPLC-MS analysis. The results showed that celastrol could regulate gut bacteria; suppress the abundance of Bacteroides fragilis; raise the levels of glycoursodeoxycholic acid (GUDCA), a bile acid; and alleviate HCC. We found that GUDCA suppressed cellular proliferation and induced the arrest of mTOR/S6K1 pathway-associated cell cycle G0/G1 phase in HepG2 cells. Further analyses using molecular simulations, Co-IP, and immunofluorescence assays revealed that GUDCA binds to farnesoid X receptor (FXR) and regulates the interaction of FXR with retinoid X receptor a (RXRα). Transfection experiments using the FXR mutant confirmed that FXR is essential for GUCDA-mediated suppression of HCC cellular proliferation. Finally, animal experiments showed that the treatment with the combination of celastrol/GUDCA alleviated the adverse effects of celastrol alone treatment on body weight loss and improved survival in rats with HCC. In conclusion, the findings of this study suggest that celastrol exerts an alleviating effect on HCC, in part via regulation of the B. fragilis-GUDCA-FXR/RXRα-mTOR axis.

Integrative network-based analysis on multiple Gene Expression Omnibus datasets identifies novel immune molecular markers implicated in non-alcoholic steatohepatitis

INTRODUCTION

Non-alcoholic steatohepatitis (NASH), an advanced subtype of non-alcoholic fatty liver disease (NAFLD), has becoming the most important aetiology for end-stage liver disease, such as cirrhosis and hepatocellular carcinoma. This study were designed to explore novel genes associated with NASH.

METHODS

Here, five independent Gene Expression Omnibus (GEO) datasets were combined into a single cohort and analyzed using network biology approaches.

RESULTS

11 modules identified by weighted gene co-expression network analysis (WGCNA) showed significant association with the status of NASH. Further characterization of four gene modules of interest demonstrated that molecular pathology of NASH involves the upregulation of hub genes related to immune response, cholesterol and lipid metabolic process, extracellular matrix organization, and the downregulation of hub genes related to cellular amino acid catabolic, respectively. After DEGs enrichment analysis and module preservation analysis, the Turquoise module associated with immune response displayed a remarkably correlation with NASH status. Hub genes with high degree of connectivity in the module, including CD53, LCP1, LAPTM5, NCKAP1L, C3AR1, PLEK, FCER1G, HLA-DRA and SRGN were further verified in clinical samples and mouse model of NASH. Moreover, single-cell RNA-seq analysis showed that those key genes were expressed by distinct immune cells such as microphages, natural killer, dendritic, T and B cells. Finally, the potential transcription factors of Turquoise module were characterized, including NFKB1, STAT3, RFX5, ILF3, ELF1, SPI1, ETS1 and CEBPA, the expression of which increased with NASH progression.

DISCUSSION

In conclusion, our integrative analysis will contribute to the understanding of NASH and may enable the development of potential biomarkers for NASH therapy.

Gut-liver axis: Pathophysiological concepts and clinical implications

Bidirectional crosstalk along the gut-liver axis controls gastrointestinal health and disease and exploits environmental and host mediators. Nutrients, microbial antigens, metabolites, and bile acids regulate metabolism and immune responses in the gut and liver, which reciprocally shape microbial community structure and function. Perturbation of such host-microbe interactions is observed in a variety of experimental liver diseases and is facilitated by an impaired intestinal barrier, which is fueling hepatic inflammation and disease progression. Clinical evidence describes perturbation of the gut-liver crosstalk in non-alcoholic fatty liver disease, alcoholic liver disease, and primary sclerosing cholangitis. In liver cirrhosis, a common sequela of these diseases, the intestinal microbiota and microbial pathogen-associated molecular patterns constitute liver inflammation and clinical complications, such as hepatic encephalopathy. Understanding the intricate metabolic interplay between the gut and liver in health and disease opens an avenue for targeted therapies in the future, which is probed in controlled clinical trials.

Immune mechanisms linking metabolic injury to inflammation and fibrosis in fatty liver disease - novel insights into cellular communication circuits

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and is emerging as the leading cause of cirrhosis, liver transplantation and hepatocellular carcinoma (HCC). NAFLD is a metabolic disease that is considered the hepatic manifestation of the metabolic syndrome; however, during the evolution of NAFLD from steatosis to non-alcoholic steatohepatitis (NASH), to more advanced stages of NASH with liver fibrosis, the immune system plays an integral role. Triggers for inflammation are rooted in hepatic (lipid overload, lipotoxicity, oxidative stress) and extrahepatic (gut-liver axis, adipose tissue, skeletal muscle) systems, resulting in unique immune-mediated pathomechanisms in NAFLD. In recent years, the implementation of single-cell RNA-sequencing and high dimensional multi-omics (proteogenomics, lipidomics) and spatial transcriptomics have tremendously advanced our understanding of the complex heterogeneity of various liver immune cell subsets in health and disease. In NAFLD, several emerging inflammatory mechanisms have been uncovered, including profound macrophage heterogeneity, auto-aggressive T cells, the role of unconventional T cells and platelet-immune cell interactions, potentially yielding novel therapeutics. In this review, we will highlight the recent discoveries related to inflammation in NAFLD, discuss the role of immune cell subsets during the different stages of the disease (including disease regression) and integrate the multiple systems driving inflammation. We propose a refined concept by which the immune system contributes to all stages of NAFLD and discuss open scientific questions arising from this paradigm shift that need to be unravelled in the coming years. Finally, we discuss novel therapeutic approaches to target the multiple triggers of inflammation, including combination therapy via nuclear receptors (FXR agonists, PPAR agonists).

A new perspective on NAFLD: Focusing on the crosstalk between peroxisome proliferator-activated receptor alpha (PPARα) and farnesoid X receptor (FXR)

Nonalcoholic fatty liver disease (NAFLD) is primarily caused by abnormal lipid metabolism and the accumulation of triglycerides in the liver. NAFLD is also associated with hepatic steatosis and nutritional and energy imbalances and is a chronic liver disease associated with a number of factors. Nuclear receptors play a key role in balancing energy and nutrient metabolism, and the peroxisome proliferator-activated receptor alpha (PPARα) and farnesoid X receptor (FXR) regulate lipid metabolism genes, controlling hepatocyte lipid utilization and regulating bile acid (BA) synthesis and transport. They play an important role in lipid metabolism and BA homeostasis. At present, PPARα and FXR are the most promising targets for the treatment of NAFLD among nuclear receptors. This review focuses on the crosstalk mechanisms and transcriptional regulation of PPARα and FXR in the pathogenesis of NAFLD and summarizes PPARα and FXR drugs in clinical trials, laying a theoretical foundation for the targeted treatment of NAFLD and the development of novel therapeutic strategies.

Penthorum chinense Pursh. extract attenuates non-alcholic fatty liver disease by regulating gut microbiota and bile acid metabolism in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Penthorum chinense Pursh. (PCP) is commonly used as a Miao ethnomedicine and health food for liver protection in China. Gansukeli (WS3-B-2526-97) is made from the extract of PCP (PCPE) for the treatment of viral hepatitis. In recent years, PCPE has been reported in the treatment of non-alcoholic fatty liver disease (NAFLD), however its potential mechanism is not fully elucidated.

AIM OF THE STUDY

To investigate the ameliorating effect of PCPE on high-fat diet (HFD)-induced NAFLD mice and demonstrate whether its protective effect is gut microbiota dependent and associated with bile acid (BA) metabolism.

MATERIALS AND METHODS

The alleviating effect of PCPE on NAFLD was conducted on male C57BL/6J mice fed an HFD for 16 weeks, and this effect associated with gut microbiota dependent was demonstrated by pseudo-germfree mice treated with antibiotics and fecal microbiota transplantation (FMT). The composition of the gut microbiota in the cecum contents was analyzed by 16S rRNA sequencing, and the levels of BAs in liver and fecal samples were determined by UPLC/MS-MS.

RESULTS

The results showed that administration of PCPE for 8 weeks could potently ameliorate HFD-induced NAFLD and alleviate dyslipidemia and insulin resistance. Moreover, PCPE treatment alleviated gut dysbiosis, especially reducing the relative abundance of bile salt hydrolase (BSH)-producing bacteria. Furthermore, PCPE significantly increased the levels of taurine-conjugated BAs in feces, such as tauro-β-muricholic acid (T-βMCA), tauroursodesoxycholic acid (TUDCA), and taurochenodeoxycholic acid (TCDCA), and increased hepatic chenodeoxycholic acid (CDCA). The protein and mRNA expression of farnesoid X receptor (FXR) and fibroblast growth factor 15 (FGF15) were decreased in intestine, increased taurine-conjugated BAs inhibited the intestinal signaling pathway, which was associated with increased genes expression of enzymes in the alternative BA synthesis pathway that reduced the levels of cholesterol. The increased CDCA produced via the alternative BA synthesis pathway promoted hepatic FXR activation and BA excretion.

CONCLUSION

Our study is the first time to demonstrate that PCPE could ameliorate NAFLD in HFD-induced mice by regulating the gut microbiota and BA metabolism, and from a novel perspective, to clarify the mechanism of PCPE in NAFLD.

Identification and validation of immune related core transcription factors GTF2I in NAFLD

Background

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide that endangers human health. Transcription factors (TFs) have gradually become hot spots for drug development in NAFLD for their impacts on metabolism. However, the specific TFs that regulate immune response in the development of NAFLD is not clear. This study aimed to investigate the TFs involved in the immune response of NAFLD and provide novel targets for drug development.

Methods

Microarray data were obtained from liver samples from 26 normal volunteers and 109 NAFLD patients using the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were analyzed by limma package. Differentially expressed transcription factors (DETFs) were obtained on DEGs combined with Cistrome Cancer database. Immune signatures and pathways hallmark were identified by ssGSSEA and GSVA. The co-regulation network was constructed by the above results. Further, quantitative Real-time Polymerase Chain Reaction (qRT-PCR), Western blot (WB) and Immunohistochemistry (IHC) were used to validate the relationship between GTF2I and NAFLD. CIBERSORT analysis was performed to identify cell types to explore the relationship between differential expression of GTF2I and immune cell surface markers.

Results

A total of 617 DEGs and six DETFs (ESR1, CHD2, GTF2I, EGR1, HCFC1, SP2) were obtained by differential analysis. Immune signatures and pathway hallmarks were identified by ssGSSEA and GSVA. GTF2I and CHD2 were screened through the co-regulatory networks of DEGs, DETFs, immune signatures and pathway hallmarks. Furthermore, qRT-PCR, WB and IHC indicated that GTF2I but not CHD2 was significantly upregulated in NAFLD. Finally, in silico, our data confirmed that GTF2I has a wide impact on the immune profile by negatively regulating the expression of the chemokine receptor family (227/261, count of significance).

Conclusion

GTF2I plays a role in NAFLD by negatively regulating the chemokine receptor family, which affects the immune profile. This study may provide a potential target for the diagnosis or therapy of NAFLD.

Multiple anti-non-alcoholic steatohepatitis (NASH) efficacies of isopropylidenyl anemosapogenin via farnesoid X receptor activation and TFEB-mediated autophagy

BACKGROUND

Non-alcoholic steatohepatitis (NASH) can develop into cirrhosis, liver failure, or hepatocellular carcinoma without effective treatment. However, there are currently no drugs for NASH treatment, and the development of new therapeutics has remained a major challenge in NASH research. Advances in traditional Chinese medicine to treat liver disease inspired us to search for new NASH candidates from Chi-Shao, a widely used traditional Chinese medicine.

PURPOSE

In this research, we aimed to clarify the anti-NASH effect and the underlying mechanism of isopropylidenyl anemosapogenin (IA, 1), which was a new lead compound isolated from Chi-Shao.

STUDY DESIGN AND METHODS

Isopropylidenyl anemosapogenin (IA, 1) was first discovered by collagen type I α 1 promoter luciferase bioassay-guided isolation and then characterized by single crystal X-ray diffraction analysis and enriched by semi-synthesis. Using various molecular biology techniques, the multiple anti-NASH efficacies and mechanisms of IA were clarified based on in vitro LX-2 and Huh7 cell models, along with the in vivo choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced mouse model and bile duct ligation (BDL)-induced rat model. The UPLC-MS/MS method was used to assess the plasma concentration of IA.

RESULTS

A new lead compound IA was isolated from the traditional Chinese medicine Chi-Shao, which showed significant anti-liver fibrosis activity in TGF-β1-treated LX-2 cells and anti-liver steatosis activity in oleic acid-treated Huh7 cells. Furthermore, IA could significantly ameliorate in vivo CDAHFD-induced liver injury by activating the farnesoid X receptor pathway, including its targets Nr0b2, Abcb11, and Slc10a2. Simultaneously, IA activated the autophagy pathway by activating the TFEB factor, thereby promoting lipid degradation. Its liver-protective and anti-fibrosis activities were verified by the BDL-induced rat model. Finally, with an oral administration of 100 mg/kg, IA achieved the maximum plasma concentration of 1.23 ± 0.18 μg/ml at 2.67 ± 0.58 h.

CONCLUSION

IA, an unreported lupine-type triterpenoid isolated from Chi-shao, can significantly alleviate liver injury and fibrosis via farnesoid X receptor activation and TFEB-mediated autophagy, which indicates that IA could serve as a novel therapeutic candidate against NASH.

Recent advances on FXR-targeting therapeutics

The bile acid receptor FXR has emerged as a bona fide drug target for chronic cholestatic and metabolic liver diseases, ahead of all non-alcoholic fatty liver disease (NAFLD). FXR is highly expressed in the liver and intestine and activation at both sites differentially contributes to its desired metabolic effects. Unrestricted FXR activation, however, also comes along with undesired effects such as a pro-atherogenic lipid profile, pruritus and hepatocellular toxicity under certain conditions. Several pre-clinical studies have confirmed the potency of FXR activation for cholestatic and metabolic liver diseases, but overall it remains still open whether selective activation of intestinal FXR is advantageous over pan-FXR activation and whether restricted or modulated FXR activation can limit some of the side effects. Even more, FXR antagonist also bear the potential as intestinal-selective drugs in NAFLD models. In this review we will discuss the molecular prerequisites for FXR activation, pan-FXR activation and intestinal FXR in/activation from a therapeutic point of view, different steroidal and non-steroidal FXR agonists, ways to restrict FXR activation and finally what we have learned from pre-clinical models and clinical trials with different FXR therapeutics.

Current therapies and new developments in NASH

Non-alcoholic steatohepatitis is becoming the most important aetiology for advanced liver disease. There has been important progress in the field in recent years and the complexity of the pathophysiology of NASH is better understood. Multiple non-invasive circulating and imaging biomarkers have been tested. The importance of lifestyle has been recognised and several drugs are being tested in clinical trials. This review addresses the challenges that healthcare professionals face in the management of NASH patients.

Hepatocyte nuclear factor 4α in the pathogenesis of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is emerging as the most common chronic liver disease worldwide. It refers to a range of liver conditions affecting people who drink little or no alcohol. NAFLD comprises non-alcoholic fatty liver and non-alcoholic steatohepatitis (NASH), the more aggressive form of NAFLD. NASH is featured by steatosis, lobular inflammation, hepatocyte injury, and various degrees of fibrosis. Although much progress has been made over the past decades, the pathogenic mechanism of NAFLD remains to be fully elucidated. Hepatocyte nuclear factor 4α (HNF4α) is a nuclear hormone receptor that is highly expressed in hepatocytes. Hepatic HNF4α expression is markedly reduced in NAFLD patients and mouse models of NASH. HNF4α has been shown to regulate bile acid, lipid, glucose, and drug metabolism. In this review, we summarize the recent advances in the understanding of the pathogenesis of NAFLD with a focus on the regulation of HNF4α and the role of hepatic HNF4α in NAFLD. Several lines of evidence have shown that hepatic HNF4α plays a key role in the initiation and progression of NAFLD. Recent data suggest that hepatic HNF4α may be a promising target for treatment of NAFLD.

Molecular and Cellular Mediators of the Gut-Liver Axis in the Progression of Liver Diseases

The gut-liver axis covers the bidirectional communication between the gut and the liver, and thus includes signals from liver-to-gut (e.g., bile acids, immunoglobulins) and from gut-to-liver (e.g., nutrients, microbiota-derived products, and recirculating bile acids). In a healthy individual, liver homeostasis is tightly controlled by the mostly tolerogenic liver resident macrophages, the Kupffer cells, capturing the gut-derived antigens from the blood circulation. However, disturbances of the gut-liver axis have been associated to the progression of varying chronic liver diseases, such as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, and primary sclerosing cholangitis. Notably, changes of the gut microbiome, or intestinal dysbiosis, combined with increased intestinal permeability, leads to the translocation of gut-derived bacteria or their metabolites into the portal vein. In the context of concomitant or subsequent liver inflammation, the liver is then infiltrated by responsive immune cells (e.g., monocytes, neutrophils, lymphoid, or dendritic cells), and microbiota-derived products may provoke or exacerbate innate immune responses, hence perpetuating liver inflammation and fibrosis, and potentiating the risks of developing cirrhosis. Similarly, food derived antigens, bile acids, danger-, and pathogen-associated molecular patterns are able to reshape the liver immune microenvironment. Immune cell intracellular signaling components, such as inflammasome activation, toll-like receptor or nucleotide-binding oligomerization domain-like receptors signaling, are potent targets of interest for the modulation of the immune response. This review describes the current understanding of the cellular landscape and molecular pathways involved in the gut-liver axis and implicated in chronic liver disease progression. We also provide an overview of innovative therapeutic approaches and current clinical trials aiming at targeting the gut-liver axis for the treatment of patients with chronic liver and/or intestinal diseases.