Farnesoid X receptor (FXR): Structures and ligands

Alpha-aminobutyric acid ameliorates diet-induced metabolic dysfunction-associated steatotic liver disease (MASLD) progression in mice via enhancing AMPK/SIRT1 pathway and modulating the gut-liver axis

Alpha-aminobutyric acid (ABA) is a nonproteinogenic amino acid, a metabolite which could be generated from the metabolism of methionine, threonine, serine and glycine or as a gut-microbiome-derived metabolite. Changes in ABA levels have been embroiled in metabolic dysfunction-associated steatotic liver disease (MASLD) intervention studies, but their relation to MASLD pathogenesis remains unclear. Hence, this present study aimed to investigate the effect of oral ABA supplementation on the progression of a high fat/high cholesterol diet (HFD) induced MASLD mice model. ABA was found to remodel the gut microbiome composition and ameliorate MASLD parameters in HFD-fed mice. ABA mitigated HFD-induced gain in liver weight, hepatic steatosis, insulin resistance, serum and hepatic triglyceride levels, and liver cholesterol levels. Modulation of lipid metabolism was observed in the liver, in which expression of proteins and/or genes involved in de novo lipogenesis were suppressed, while those involved in fatty acid oxidation and autophagy were upregulated together with cellular antioxidant capacity, in addition to the enhancement of the AMPK/SIRT1 pathway. ABA reshaped the gut composition by enriching nine bacterial species, including Helicobacter hepaticus, Desulfovibrio sp. G11, Parabacteroides distasonis, and Bacteroides fragilis, while diminishing the abundance of 16 species, which included four Helicobacter species. KEGG pathway analysis of microbial functions found that ABA impeded secondary bile acid biosynthesis - which was reflected in the faecal BA composition analysis. Notably, ABA also inhibited ileal FXR-Fgf15 signaling, allowing for increased hepatic Cyp7a1 expression to eliminate cholesterol buildup in the liver. Overall, our findings indicate that ABA could be used as a promising therapeutic approach for the intervention of MASLD.

New advances in novel pharmacotherapeutic candidates for the treatment of metabolic dysfunction-associated steatohepatitis (MASH) between 2022 and 2024

Metabolic dysfunction-associated steatotic liver disease (MASLD) covers a broad spectrum of profile from simple fatty liver, evolving to metabolic dysfunction-associated steatohepatitis (MASH), to hepatic fibrosis, further progressing to cirrhosis and hepatocellular carcinoma (HCC). MASLD has become a prevalent disease with 25% in average over the world. MASH is an active stage, and requires pharmacological intervention when there is necroptotic damage with fibrotic progression. Although there is an increased understanding of MASH pathogenesis and newly approved resmetirom, given its complexity and heterogeneous pathophysiology, there is a strong necessity to develop more drug candidates with better therapeutic efficacy and well-tolerated safety profile. With an increased list of pharmaceutical candidates in the pipeline, it is anticipated to witness successful approval of more potential candidates in this fast-evolving field, thereby offering different categories of medications for selective patient populations. In this review, we update the advances in MASH pharmacotherapeutics that have completed phase II or III clinical trials with potential application in clinical practice during the latest 2 years, focusing on effectiveness and safety issues. The overview of fast-evolving status of pharmacotherapeutic candidates for MASH treatment confers deep insights into the key issues, such as molecular targets, endpoint selection and validation, clinical trial design and execution, interaction with drug administration authority, real-world data feedback and further adjustment in clinical application.

Integrating deep learning and molecular dynamics simulations for FXR antagonist discovery

Farnesoid X receptor (FXR) is a key regulator of bile acid, lipid, and glucose homeostasis, making it a promising target for treating metabolic diseases. FXR antagonists have shown therapeutic potential in cholestasis, metabolic disorders, and certain cancers, while clinically approved FXR antagonists remain unavailable and underrepresented in current treatment strategies. To address this, we developed deep learning models for predicting FXR antagonistic activity (ANTCL) and toxicity (TOXCL). Screening 217,345 compounds from the HMDB database identified eleven human metabolite candidates with significant FXR binding potential. Molecular dynamics simulations and binding free energy calculations revealed five more stable complexes compared to the reference compound Gly-MCA, with HMDB0253354 (Fulvestrant) and HMDB0242367 (ZM 189154) standing out for their binding free energies. Hydrophobic interactions, particularly involving residues MET328, PHE329, and ALA291, contributed to their stability. These results demonstrate the effectiveness of deep learning in FXR antagonist discovery and highlight the potential of HMDB0253354 and HMDB0242367 as promising candidates for metabolic disease treatment.

Geniposidic Acid Targeting FXR "S332 and H447" Mediated Conformational Change to Upregulate CYPs and miR-19a-3p to Ameliorate Drug-Induced Liver Injury

Drug-induced liver injury (DILI), caused by chemical drugs and traditional Chinese medicine, often leads to severe outcomes like liver failure due to a lack of early detection markers. Farnesoid X receptor (FXR), a key regulator of bile acid (BA) and cholesterol metabolism, is a potential therapeutic target. This study investigates the pathogenesis, markers, and treatment strategies for DILI, focusing on the hepatoprotective effects of geniposidic acid (GPA) from Gardenia jasminoides J. Ellis. Using cellular and animal models of acute and chronic DILI induced by acetaminophen and triptolide, we explored GPA's mechanisms in BA and cholesterol metabolism. Lipidomic and BA analyses revealed that GPA alleviates DILI by enhancing bile acid synthesis and transport via FXR activation. Experiments using AAV-shFXR, Fxr- / - mice and molecular assays demonstrated that GPA targets Ser332 and His447 on FXR ligand-binding domain, promoting FXR nuclear translocation and initiating cytochrome P450 proteins (CYPs) transcriptional activation for BA metabolism. Additionally, miRNA sequencing and RNA-pulldown assays showed that GPA-activated FXR upregulates miR-19a-3p, binding to LXR 3'UTR to inhibit cholesterol production. These findings reveal the GPA-FXR "structure-target" relationship, highlighting a dual mechanism in which GPA promotes CYPs-mediated bile acid metabolism and miR-19a-3p-mediated cholesterol synthesis inhibition, providing a basis for FXR-targeted DILI therapies.

Alterations in intestinal bile acid transport provide a therapeutic target in patients with post-bariatric hypoglycaemia

While Roux-en-Y gastric bypass is an effective treatment for obesity and type 2 diabetes, up to one-third of patients develop post-bariatric hypoglycaemia (PBH). Individuals with PBH exhibit increased postprandial secretion of the intestinal hormone fibroblast growth factor 19 (FGF19, Fgf15 in mice). However, the underlying mechanisms contributing to PBH remain uncertain. Here we demonstrate that faecal and plasma bile acid (BA) profiles are significantly altered in postoperative individuals with PBH versus those without hypoglycaemia. Furthermore, altered BAs in PBH induce FGF19 secretion in intestinal cells in a manner dependent on the apical sodium-dependent BA transporter (ASBT). We demonstrate that ASBT inhibition reduces Fgf15 expression and increases postprandial glucose in hypoglycaemic mice. Our data suggest that dysregulation of luminal BA profiles and transport may contribute to PBH and provide proof of concept that ASBT inhibition could be developed as a new therapeutic strategy for PBH.

Human liver cell-based assays for the prediction of hepatic bile acid efflux transporter inhibition by drugs

INTRODUCTION

Drug-mediated inhibition of bile salt efflux transporters may cause liver injury. In vitro prediction of drug effects toward canalicular and/or sinusoidal efflux of bile salts from human hepatocytes is therefore a major issue, which can be addressed using liver cell-based assays.

AREA COVERED

This review, based on a thorough literature search in the scientific databases PubMed and Web of Science, provides key information about hepatic transporters implicated in bile salt efflux, the human liver cell models available for investigating functional inhibition of bile salt efflux, the different methodologies used for this purpose, and the modes of expression of the results. Applications of the assays to drugs are summarized, with special emphasis to the performance values of some assays for predicting hepatotoxicity/cholestatic effects of drugs.

EXPERT OPINION

Human liver cell-based assays for evaluating drug-mediated inhibition of bile acid efflux transporters face various limitations, such as the lack of method standardization and validation, the present poor adaptability to high throughput approaches, and some pitfalls with respect to interpretation of bile acid biliary excretion indexes. Hepatotoxicity of drugs is additionally likely multifactorial, highlighting that inhibition of hepatic bile salt efflux by drugs provides important, but not full, information about potential drug hepatotoxicity.

Structural insights into molecular and cellular level FXR binding potentials of GW4064 and LY2562175 hybrids by multi in silico modelling analyses

CONTEXT

Non-alcoholic fatty liver disease (NAFLD) has become a significant health concern. Existing farnesoid X receptor (FXR) agonists like GW4064 and LYS2562175 show poor pharmacokinetics, prompting researchers to develop alternative molecules. This study aims to pinpoint the structural features responsible for exhibiting FXR agonism of a series of hybrid structures of GW4064 and LYS2562175 with improved pharmacokinetic properties which supersede the existing parent ligands. Electronegative components were found to critically influence biological activity on the molecular level, supported by 2D- and 3D-Quantitative Structure Activity Relationship (2D- and 3D-QSAR) analyses. Quantitative Activity-Activity Relationship (QAAR) highlighted key descriptors impacting cellular level FXR binding potential. Molecular dynamics (MD) simulations identified pivotal interactions, such as π-π and H-bond interactions with key residues. Furthermore, binding free energy calculated with Molecular Mechanics with Generalised Born and Surface Area solvation (MM-GBSA) analyses with selected compounds reflected the variations in their binding potential towards FXR protein.

METHODS

The study began by curating ligand SMILES and preparing a dataset with molecular and cellular activity as dependent variables. AlvaDesc descriptors and interpretable descriptors were calculated using the OCHEM webserver. QSAR analyses were performed using Sequential Forward Selection (SFS) and Genetic Algorithm (GA) methods, while QAAR analysis used 50% effective concentration at the molecular level as an independent variable with the same algorithms. 3D QSAR analysis was performed with the Open3DQSAR tool. Docking studies in AutoDock 4.2 with FXR protein identified optimal ligand poses, and 500 ns MD simulations were performed with Amber 20. The use of open-access tools ensures reproducibility and accessibility for future research.

Crosstalk between bile acids and gut microbiota: a potential target for precancerous lesions of gastric cancer

As a critical juncture in the pathological continuum from gastritis to gastric cancer, precancerous lesions of gastric cancer (PLGC) are increasingly prevalent, significantly undermining the health of the global population. The primary constituents of bile, specifically bile acids (BAs), disrupt the equilibrium of gastric hormone secretion and compromise the structural integrity of the gastric mucosa, thereby facilitating gastric oncogenesis. Moreover, gut microbiota modulate host physiological and pathological processes through immune response regulation, metabolic pathway interference, and direct interaction with gastric tumor cells. Extensive research has elucidated that the metabolic dysregulation of BAs and gut microbiota, in concert with the resultant impairment of the gastric mucosa, are central to the pathogenesis of PLGC. In anticipation of future clinical preventive and therapeutic strategies, this review collates recent insights into the roles of BAs and gut bacteria in PLGC, examining their interplay and significance in the pathogenic mechanism of PLGC.

Targeting regulation of lipid metabolism with polysaccharide of traditional Chinese medicine for the treatment of non-alcoholic fatty liver disease: A review

Non-alcoholic fatty liver disease (NAFLD) has become one of the most common chronic diseases in the world, and the effective treatment of NAFLD has been listed as a key problem to be solved urgently in contemporary medicine. Polysaccharides in traditional Chinese medicine (TCM) have a wide range of pharmacological activities. A large number of preclinical studies have confirmed that TCM polysaccharides can interfere with the occurrence and development of NAFLD at multiple interrelated levels, such as improving lipid metabolism and insulin resistance, regulating oxidative stress, alleviating immune inflammatory response, and regulating intestinal microbiota, thus showing great potential as a new anti-NAFLD drug. This paper summarizes the prevention and treatment effect and mechanism of TCM polysaccharides on NAFLD, which provides a basis for the application of TCM polysaccharides in plant medicine and modern medicines, and provides a reference for promoting the development and utilization of TCM polysaccharide resources and the research and development of new drugs for NAFLD.

Insights into Clinical Trials for Drugs Targeting MASLD: Progress, Challenges, and Future Directions

The transition in terminology from fatty liver disease to metabolic dysfunction-associated steatotic liver disease (MASLD) marks a considerable evolution in diagnostic standards. This new definition focuses on liver fat accumulation in the context of overweight/obesity, type 2 diabetes, or metabolic dysfunction, without requiring the exclusion of other concurrent liver diseases. The new definition also provides clear guidelines for defining alcohol consumption in relation to the disease. MASLD is currently acknowledged as the most widespread liver disorder globally, affecting ~25% of the population. Despite the extensive array of clinical trials conducted in recent years, the number of approved treatments for metabolic dysfunction-associated fatty liver disease is very limited. In the review critically evaluates the results of clinical trials of related drugs and assesses the future directions for drug development trials. The renaming of MASLD presents new challenges and opportunities for the design of clinical trials and the selection of target populations for drug development.

SLC10A5 deficiency causes hypercholanemia

BACKGROUND AND AIMS

Solute Carrier Family 10 Member 5 (SLC10A5) is a member of SLC10, comprising transporters of bile acids, steroidal hormones, and other substrates, but its function remains unclear. The aim of the current investigation was to clarify its function in the metabolism of bile acid and hypercholanemia.

APPROACH AND RESULTS

Whole-exome sequencing and Sanger sequencing were used to identify and confirm the variant in the subjects of hypercholanemia. CRISPR/Cas9-mediated genome engineering was used to establish the knockout and point mutation mice. Primary mouse hepatocytes were isolated, and cell lines were cultured. SLC10A5 was silenced by siRNA and overexpressed by wild-type and mutant plasmids. The fluorescent bile acid derivative was used for the bile acid uptake assay. Bile acids were assessed with ultra-performance liquid chromatography tandem mass spectrometry. A heterozygous variant SLC10A5 : c.994_995del (p.D332X) was identified in subjects with elevated total bile acid or altered bile acid profiles. Bile acids were increased in the serum and liver of knockout and point mutation mice. The expressions of FXR and SHP, regulators involved in the negative feedback of bile acid synthesis, were downregulated, while the bile acid synthesis genes CYP7A1 and CYP8B1 were upregulated in both gene-edited mice. Both the wild and mutant SLC10A5 proteins were localized on the plasma membrane. Knockdown, knockout, or targeted mutation of SLC10A5 led to the inhibition of bile acid uptake by cell lines and primary mouse hepatocytes.

CONCLUSION

SLC10A5 is involved in the uptake of bile acid, and its deficiency causes hypercholanemia.

Host metabolism balances microbial regulation of bile acid signalling

Metabolites derived from the intestinal microbiota, including bile acids (BA), extensively modulate vertebrate physiology, including development1, metabolism2-4, immune responses5-7 and cognitive function8. However, to what extent host responses balance the physiological effects of microbiota-derived metabolites remains unclear9,10. Here, using untargeted metabolomics of mouse tissues, we identified a family of BA-methylcysteamine (BA-MCY) conjugates that are abundant in the intestine and dependent on vanin 1 (VNN1), a pantetheinase highly expressed in intestinal tissues. This host-dependent MCY conjugation inverts BA function in the hepatobiliary system. Whereas microbiota-derived free BAs function as agonists of the farnesoid X receptor (FXR) and negatively regulate BA production, BA-MCYs act as potent antagonists of FXR and promote expression of BA biosynthesis genes in vivo. Supplementation with stable-isotope-labelled BA-MCY increased BA production in an FXR-dependent manner, and BA-MCY supplementation in a mouse model of hypercholesteraemia decreased lipid accumulation in the liver, consistent with BA-MCYs acting as intestinal FXR antagonists. The levels of BA-MCY were reduced in microbiota-deficient mice and restored by transplantation of human faecal microbiota. Dietary intervention with inulin fibre further increased levels of both free BAs and BA-MCY levels, indicating that BA-MCY production by the host is regulated by levels of microbiota-derived free BAs. We further show that diverse BA-MCYs are also present in human serum. Together, our results indicate that BA-MCY conjugation by the host balances host-dependent and microbiota-dependent metabolic pathways that regulate FXR-dependent physiology.

Obeticholic acid aggravates liver fibrosis by activating hepatic farnesoid X receptor-induced apoptosis in cholestatic mice

Obeticholic acid (OCA) was approved for the treatment of primary biliary cholangitis (PBC) patients. However, it can cause severe drug-induced liver injury (DILI), which may put PBC patients at risk of acute-on-chronic liver failure (ACLF) and even death. Farnesoid X receptor (FXR) is considered as the target of OCA for cholestasis, but there is still a lack of research on whether hepatic and ileal FXR have different effects after OCA treatment. The aim of this study was to investigate the mechanism of OCA aggravating liver fibrosis in cholestasis. The results showed that 40 mg/kg OCA elevated serum AST, ALT, ALP and γ-GT levels in bile duct ligation (BDL) mice. Besides, severe fibrosis and necrosis were observed in the OCA-treated BDL mice, which was related to hepatic apoptosis pathway activation. Both hepatic and ileal FXR signaling could be significantly activated by OCA. However, ileum-specific knockout of Fxr aggravated OCA-induced liver injury in BDL mice. On the contrary, hepatic-specific knockout of Fxr structurally and functionally ameliorated liver pathological processes in the OCA-treated BDL mice, which was due to the blockade of hepatic FXR-induced apoptosis. In conclusion, the mechanism of OCA aggravating liver fibrosis in cholestasis was based on the activation of hepatic FXR-induced apoptosis. It was also indicated ileal FXR might be a safer pharmacological target for bile acids regulation.

The ameliorating effect of intermittent fasting on intestinal glucagon-like peptide 1 in rats fed a high-fat diet via the Farnesoid X receptor and the Melanocortin-4 receptor

Obesity and its associated intestinal inflammatory responses represent a significant global challenge. (IF) is a dietary intervention demonstrating various health benefits, including weight loss, enhanced metabolic health, and increased longevity. However, its effect on the intestinal inflammation induced by high-fat diet (HFD) is still not fully comprehended. Thirty-four male Sprague-Dawley rats were randomized into three groups: Control (fed standard chow diet for 24 weeks); the HFD group (fed HFD for 24 weeks); and the HFD + IF group (fed HFD for 12 weeks, followed by an alternate day regimen of fasting and HFD for 12 weeks). The results revealed that IF significantly reduced body weight, food intake, and blood glucose levels compared to the HFD group. Furthermore, rats undergoing the intermittent fasting regimen exhibited a significant reduction in resting time, along with increased durations of grooming and exploration when compared to those on HFD. IF significantly reduced HFD-induced intestinal oxidative stress by lowering malondialdehyde levels and substantially increasing intestinal total antioxidant capacity, consistent with histopathological findings of gastric and intestinal tissues. The investigation of the underlying mechanisms revealed that IF significantly increased the intestinal expression of Farnesoid X receptor (FXR), glucagon-like peptide 1 (GLP-1), and melanocortin-4 receptors (MC4R), with a significant decrease in gastrointestinal peroxisome proliferator-activated receptor-γ (PPAR-γ) compared to the HFD group. The findings indicate that IF can mitigate HFD-induced intestinal inflammation via the FXR/GLP-1/MC4R/ PPAR-γ pathway. This highlights the need for further research to elucidate these mechanisms.

NAFLD and NAFLD Related HCC: Emerging Treatments and Clinical Trials

Nonalcoholic fatty liver disease (NAFLD), recently renamed metabolic-associated fatty liver disease (MAFLD), is the most prevalent liver disease worldwide. It is associated with an increased risk of developing hepatocellular carcinoma (HCC) in the background of cirrhosis or without cirrhosis. The prevalence of NAFLD-related HCC is increasing all over the globe, and HCC surveillance in NAFLD cases is not that common. In the present review, we attempt to summarize promising treatments and clinical trials focused on NAFLD, nonalcoholic steatohepatitis (NASH), and HCC in the past five to seven years. We categorized the trials based on the type of intervention. Most of the trials are still running, with only a few completed and with conclusive results. In clinical trial NCT03942822, 25 mg/day of milled chia seeds improved NAFLD condition. Completed trial NCT03524365 concluded that Rouxen-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) results in histological resolution of NASH without worsening of fibrosis, while NCT04677101 validated sensitivity/accuracy of blood biomarkers in predicting NASH and fibrosis stage. Moreover, trials with empagliflozin (NCT05694923), curcuvail (NCT06256926), and obeticholic acid (NCT03439254) were completed but did not provide conclusive results. However, trial NCT03900429 reported effective improvement in fibrosis by at least one stage, without worsening of NAFLD activity score (NAS), as well as improvement in lipid profile of the NASH patients by 80 or 100 mg MGL-3196 (resmetirom). Funded by Madrigal Pharmaceuticals, Rezdiffra (resmetirom), used in the clinical trial NCT03900429, is the first FDA-approved drug for the treatment of NAFLD/NASH.

FXR Activation Accelerates Early Phase of Osteoblast Differentiation Through COX-2-PGE2-EP4 Axis in BMP-2-Induced Mouse Mesenchymal Stem Cells

Farnesoid X receptor (FXR), a nuclear receptor, is expressed in calvaria and bone marrow stromal cells and plays a role in bone homeostasis. However, the mechanism of FXR-activated osteoblast differentiation remains unclear. In this study, we investigated the regulatory mechanism underlying FXR-activated osteoblast differentiation using bone morphogenetic protein-2 (BMP-2)-induced mouse ST-2 mesenchymal stem cells. We also synthesized a novel FXR agonist, FLG390, and compared its biological effects in osteoblast differentiation with a known FXR agonist, chenodeoxycholic acid (CDCA). As an FXR agonist, FLG390 accelerated osteoblast differentiation to a comparable extent with CDCA, enhancing alkaline phosphatase (ALP) activity and the expression of osteoblast differentiated-related genes such as ALP, collagen type 1 α1 chain (COL1A1), and runt-related transcription factor 2 (RUNX2). FXR activation elevated the expression of cyclooxygenase (COX)-2 and the production of prostaglandin (PG) E2 in the early phase of osteoblast differentiation. A selective COX-2 inhibitor and an antagonist of EP4 receptors, one of PGE2 receptors, partially suppressed FXR-activated osteoblast differentiation. Moreover, treatment with either inhibitor during the first 6 h after initiating osteoblast differentiation repressed FXR-activated osteoblast differentiation to the same extent as did the treatment for 6 d. Therefore, a novel FXR agonist, FLG390, exhibited potency comparable to CDCA. FXR activation promoted the early phase of osteoblast differentiation via the COX-2-PGE2-EP4 axis, representing a potential target for control of bone metabolism.

Pharmacological Mechanisms of Bile Acids Targeting the Farnesoid X Receptor

Bile acids (BAs), a category of amphiphilic metabolites synthesized by liver cells and released into the intestine via the bile duct, serve a vital role in the emulsification of ingested fats during the digestive process. Beyond their conventional emulsifying function, BAs, with their diverse structures, also act as significant hormones within the body. They are pivotal in facilitating nutrient absorption by interacting with the farnesoid X receptor (FXR), and they serve as key regulators of lipid and glucose metabolism, as well as immune system balance. Consequently, BAs contribute to the metabolism of glucose and lipids, enhance the digestion and absorption of lipids, and maintain the equilibrium of the bile pool. Their actions are instrumental in addressing obesity, managing cholestasis, and treating diabetes, and are involved in the onset and progression of cancer. This paper presents an updated systematic review of the pharmacological mechanisms by which BAs target the FXR, incorporating recent findings and discussing their signaling pathways in the context of novel research, including their distinct roles in various disease states and populations. The aim is to provide a theoretical foundation for the continued research and clinical application of BAs.

Advances in the treatment of liver injury based on mesenchymal stem cell-derived exosomes

Mesenchymal stem cells (MSCs) have shown a great potential role in treating liver injury. MSCs can promote liver regeneration by differentiating into hepatocytes, and can also secrete exosomes to participate in the repair of liver injury. Increasing evidence has shown that mesenchymal stem cell-derived exosomes (MSC-EXOs) play an important role in treating liver injury. In this review, the biogenesis and function of exosomes and the characteristics of MSC-EXOs were analyzed based on recent research results. MSC-EXOs are significant in liver injuries such as liver fibrosis, liver failure, hepatocellular carcinoma, oxidative stress, and lipid steatosis, and participate in the process of liver regeneration.

Tryptophan Ameliorates Metabolic Syndrome by Inhibiting Intestinal Farnesoid X Receptor Signaling: The Role of Gut Microbiota-Bile Acid Crosstalk

Background and Aims: Metabolic syndrome (MS) is a progressive metabolic disease characterized by obesity and multiple metabolic disorders. Tryptophan (Trp) is an essential amino acid, and its metabolism is linked to numerous physiological functions and diseases. However, the mechanisms by which Trp affects MS are not fully understood. Methods and Results: In this study, experiments involving a high-fat diet (HFD) and fecal microbiota transplantation (FMT) were conducted to investigate the role of Trp in regulating metabolic disorders. In a mouse model, Trp supplementation inhibited intestinal farnesoid X receptor (FXR) signaling and promoted hepatic bile acid (BA) synthesis and excretion, accompanied by elevated levels of conjugated BAs and the ratio of non-12-OH to 12-OH BAs in hepatic and fecal BA profiles. As Trp alters the gut microbiota and the abundance of bile salt hydrolase (BSH)-enriched microbes, we collected fresh feces from Trp-supplemented mice and performed FMT and sterile fecal filtrate (SFF) inoculations in HFD-treated mice. FMT and SFF not only displayed lipid-lowering properties but also inhibited intestinal FXR signaling and increased hepatic BA synthesis. This suggests that the gut microbiota play a beneficial role in improving BA metabolism through Trp. Furthermore, fexaramine (a gut-specific FXR agonist) reversed the therapeutic effects of Trp, suggesting that Trp acts through the FXR signaling pathway. Finally, validation in a finishing pig model revealed that Trp improved lipid metabolism, enlarged the hepatic BA pool, and altered numerous glycerophospholipid molecules in the hepatic lipid profile. Conclusion: Our studies suggest that Trp inhibits intestinal FXR signaling mediated by the gut microbiota-BA crosstalk, which in turn promotes hepatic BA synthesis, thereby ameliorating MS.

Regulation of bile acids and their receptor FXR in metabolic diseases

High sugar, high-fat diets and unhealthy lifestyles have led to an epidemic of obesity and obesity-related metabolic diseases, seriously placing a huge burden on socio-economic development. A deeper understanding and elucidation of the specific molecular biological mechanisms underlying the onset and development of obesity has become a key to the treatment of metabolic diseases. Recent studies have shown that the changes of bile acid composition are closely linked to the development of metabolic diseases. Bile acids can not only emulsify lipids in the intestine and promote lipid absorption, but also act as signaling molecules that play an indispensable role in regulating bile acid homeostasis, energy expenditure, glucose and lipid metabolism, immunity. Disorders of bile acid metabolism are therefore important risk factors for metabolic diseases. The farnesol X receptor, a member of the nuclear receptor family, is abundantly expressed in liver and intestinal tissues. Bile acids act as endogenous ligands for the farnesol X receptor, and erroneous FXR signaling triggered by bile acid dysregulation contributes to metabolic diseases, including obesity, non-alcoholic fatty liver disease and diabetes. Activation of FXR signaling can reduce lipogenesis and inhibit gluconeogenesis to alleviate metabolic diseases. It has been found that intestinal FXR can regulate hepatic FXR in an organ-wide manner. The crosstalk between intestinal FXR and hepatic FXR provides a new idea for the treatment of metabolic diseases. This review focuses on the relationship between bile acids and metabolic diseases and the current research progress to provide a theoretical basis for further research and clinical applications.

Brown and Beige Adipose Tissue: One or Different Targets for Treatment of Obesity and Obesity-Related Metabolic Disorders?

The failure of the fight against obesity makes us turn to new goals in its treatment. Now, brown adipose tissue has attracted attention as a promising target for the treatment of obesity and associated metabolic disorders such as insulin resistance, dyslipidemia, and glucose tolerance disorders. Meanwhile, the expansion of our knowledge has led to awareness about two rather different subtypes: classic brown and beige (inducible brown) adipose tissue. These subtypes have different origin, differences in the expression of individual genes but also a lot in common. Both tissues are thermogenic, which means that, by increasing energy consumption, they can improve their balance with excess intake. Both tissues are activated in response to specific inducers (cold, beta-adrenergic receptor activation, certain food and drugs), but beige adipose tissue transdifferentiates back into white adipose tissue after the cessation of inducing action, while classic brown adipose tissue persists, but its activity decreases. In this review, we attempted to understand whether there are differences in the effects of different groups of thermogenesis-affecting drugs on these tissues. The analysis showed that this area of research is rather sparse and requires close attention in further studies.

Effects of therapeutically approved individual bile acids on the development of metabolic dysfunction-associated steatohepatitis a low bile acid mouse model

Bile acid (BA) signaling dysregulation is an important etiology for the development of metabolic dysfunction-associated steatotic liver disease (MASLD). As diverse signaling molecules synthesized in the liver by pathways initiated with CYP7A1 and CYP27A1, BAs are endogenous modulators of farnesoid x receptor (FXR). FXR activation is crucial in maintaining BA homeostasis, regulating lipid metabolism, and suppressing inflammation. Additionally, BAs interact with membrane receptors and gut microbiota to regulate energy expenditure and intestinal health. Complex modulation of BAs in vivo and the lack of suitable animal models impede our understanding of the functions of individual BAs, especially during MASLD development. Previously, we determined that acute feeding of individual BAs differentially affects lipid, inflammation, and oxidative stress pathways in a low-BA mouse model, Cyp7a1/Cyp27a1 double knockout (DKO) mice. Currently, we investigated to what degree cholic acid (CA), deoxycholic acid (DCA), or ursodeoxycholic acid (UDCA) at physiological concentrations impact MASLD development in DKO mice. The results showed that these 3 BAs varied in the ability to activate hepatic and intestinal FXR, disrupt lipid homeostasis, and modulate inflammation and fibrosis. Additionally, UDCA activated intestinal FXR in these low-BA mice. Significant alterations in lipid uptake and metabolism in DKO mice following CA and DCA feeding indicate differences in cholesterol and lipid handling across genotypes. Overall, the DKO were less susceptible to weight gain, but more susceptible to MASH diet induced inflammation and fibrosis on CA and DCA supplements, whereas WT mice were more vulnerable to CA-induced fibrosis on the control diet.

Nuclear Receptor Interdomain Communication is Mediated by the Hinge with Ligand Specificity

Nuclear receptors are ligand-induced transcription factors that bind directly to target genes and regulate their expression. Ligand binding initiates conformational changes that propagate to other domains, allosterically regulating their activity. The nature of this interdomain communication in nuclear receptors is poorly understood, largely owing to the difficulty of experimentally characterizing full-length structures. We have applied computational modeling approaches to describe and study the structure of the full-length farnesoid X receptor (FXR), approximated by the DNA binding domain (DBD) and ligand binding domain (LBD) connected by the flexible hinge region. Using extended molecular dynamics simulations (>10 microseconds) and enhanced sampling simulations, we provide evidence that ligands selectively induce domain rearrangement, leading to interdomain contact. We use protein-protein interaction assays to provide experimental evidence of these interactions, identifying a critical role of the hinge in mediating interdomain contact. Our results illuminate previously unknown aspects of interdomain communication in FXR and provide a framework to enable characterization of other full-length nuclear receptors.

Role of Bile Acid Receptors in the Development and Function of Diabetic Nephropathy

Diabetic nephropathy (DN) is a prevalent microvascular complication that occurs often in individuals with diabetes. It significantly raises the mortality rate of affected patients. Therefore, there is an urgent need to identify therapeutic targets for controlling and preventing the occurrence and development of DN. Bile acids (BAs) are now recognized as intricate metabolic integrators and signaling molecules. The activation of BAs has great promise as a therapeutic approach for preventing DN, renal damage caused by obesity, and nephrosclerosis. The nuclear receptors (NRs), farnesoid X receptor (FXR), pregnane X receptor (PXR), vitamin D receptor (VDR); and the G protein-coupled BA receptor, Takeda G-protein-coupled receptor 5 (TGR5) have important functions in controlling lipid, glucose, and energy metabolism, inflammation, as well as drug metabolism and detoxification. Over the past 10 years, there has been advancement in comprehending the biology and processes of BA receptors in the kidney, as well as in the creation of targeted BA receptor agonists. In this review, we discuss the role of BA receptors, FXR, PXR, VDR, and TGR5 in DN and their role in renal physiology, as well as the development and application of agonists that activate BA receptors for the treatment of kidney diseases.

Tailoring obeticholic acid activity by iridium(III) complex conjugation to develop a farnesoid X receptor probe

INTRODUCTION

The farnesoid X receptor (FXR) is a crucial regulator in the intestine, maintaining bile acid homeostasis. Inhibiting intestinal FXR shows promise in managing inflammatory bowel and liver diseases by reducing bile acid accumulation. Additionally, changes in FXR expression could serve as a potential biomarker for intestinal diseases. Therefore, developing an imaging probe for FXR holds significant potential for the early detection, simultaneous treatment, and monitoring of FXR-related diseases.

OBJECTIVES

The study aimed to develop a bioimaging probe for FXR by conjugating obeticholic acid (OCA), an FXR agonist, to an iridium(III) complex, and to investigate its application for targeting FXR in intestinal cells.

METHODS

OCA was conjugated to an iridium(III) complex to generate the novel complex 1. The effect of complex 1 on FXR activity, nuclear translocation, and downstream targets was investigated in intestinal epithelial cells using various biochemical and cellular assays. Additionally, the photophysical properties of complex 1 were assessed for FXR imaging.

RESULTS

Complex 1 retained the desirable photophysical properties for monitoring FXR in intestinal cells while reversing OCA's activity from agonistic to antagonistic. It disrupted FXR-RXR heterodimerization, inhibited FXR nuclear translocation, and downregulated downstream targets responsible for bile acid absorption, transport, and metabolism in intestinal epithelial cells.

CONCLUSION

The study successfully developed an imaging probe and modulator of FXR by conjugating OCA to an iridium(III) complex. Complex 1 retained the favorable photophysical properties of the iridium(III) complex, while reversing OCA's activity from agonistic to antagonistic. The findings highlight the exciting application of using metals to tailor the activity of nuclear receptor modulators in living systems.

Activation of Nrf2 and FXR via Natural Compounds in Liver Inflammatory Disease

Liver inflammation is frequently linked to oxidative stress and dysregulation of bile acid and fatty acid metabolism. This review focuses on the farnesoid X receptor (FXR), a critical regulator of bile acid homeostasis, and its interaction with the nuclear factor erythroid 2-related factor 2 (Nrf2), a key modulator of cellular defense against oxidative stress. The review explores the interplay between FXR and Nrf2 in liver inflammatory diseases, highlighting the potential therapeutic effects of natural FXR agonists. Specifically, compounds such as auraptene, cafestol, curcumin, fargesone A, hesperidin, lycopene, oleanolic acid, resveratrol, rutin, ursolic acid, and withaferin A are reviewed for their ability to modulate both the FXR and Nrf2 pathways. This article discusses their potential to alleviate liver inflammation, oxidative stress, and damage in diseases such as metabolic-associated fatty liver disease (MAFLD), cholestatic liver injury, and viral hepatitis. In addition, we address the molecular mechanisms driving liver inflammation, including oxidative stress, immune responses, and bile acid accumulation, while also summarizing relevant experimental models. This review emphasizes the promising therapeutic potential of targeting both the Nrf2 and FXR pathways using natural compounds, paving the way for future treatments for liver diseases. Finally, the limitations of the clinical application were indicated, and further research directions were proposed.

Strategies for enhancing non-small cell lung cancer treatment: Integrating Chinese herbal medicines with epidermal growth factor receptor-tyrosine kinase inhibitors therapy

Non-small cell lung cancer (NSCLC) poses a global health threat, and epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) such as gefitinib, afatinib, and osimertinib have achieved significant success in clinical treatment. However, the emergence of resistance limits the long-term efficacy of these treatments, necessitating urgent exploration of novel EGFR-TKIs. This review provides an in-depth summary and exploration of the resistance mechanisms associated with EGFR-TKIs, with a specific focus on representative drugs like gefitinib, afatinib, and osimertinib. Additionally, the review introduces a therapeutic strategy involving the combination of Chinese herbal medicines (CHMs) and chemotherapy drugs, highlighting the potential role of CHMs in overcoming NSCLC resistance. Through systematic analysis, we elucidate the primary resistance mechanisms of EGFR-TKIs in NSCLC treatment, emphasizing CHMs as potential treatment medicines and providing a fresh perspective for the development of next-generation EGFR-TKIs. This comprehensive review aims to guide the application of CHMs in combination therapy for NSCLC management, fostering the development of more effective and comprehensive treatment modalities to ultimately enhance patient outcomes.

Protective effects of cilostazol via the HNF1α/FXR signalling pathway and anti-apoptotic mechanisms in a rat model of estrogen-induced intrahepatic cholestasis

Currently, there is a lack of targeted medications for estrogen-induced intrahepatic cholestasis (EIC) and the primary objective in managing this condition is to safeguard liver function. Consequently, this study was conducted to examine the pharmacological efficacy of cilostazol (CTZ) in the management of EIC and explore its underlying mechanisms through the use of an animal model. Thirty female Sprague-Dawley rats were divided into five groups of six animals each: Normal group, 17-ethinylestradiol (EE)-induced intrahepatic cholestasis group, EE + ursodeoxycholic acid (UDCA)-treated group, EE + CTZ (5 mg/kg)-treated group, and EE + CTZ (10 mg/kg)-treated group. It was found that the therapeutic efficacy of UDCA and low dosage of CTZ (5 mg/kg) was comparable. Nevertheless, when CTZ was administered at a dose of 10 mg/kg, it resulted in the normalization of all liver function parameters, oxidative stress, and pro-inflammatory markers, together with improvement in the histopathological derangements and hepatocytic apoptosis. These effects were mediated through the activation of the hepatocyte nuclear factor-1 alpha (HNF1α)/Farnesoid X receptor (FXR) pathway with subsequent down-regulation of the bile acids (BAs) synthesis enzyme; cholesterol 7α-hydroxylase (CYP7A1), and up-regulation of the BAs-metabolizing enzyme; cytochrome P450 (CYP)3A1 and the bile salt export pump; BSEP. Therefore, the administration of CTZ in a dose-dependent manner can protect against EIC through regulating the HNF1α/FXR pathway and anti-apoptotic mechanisms. This implies that CTZ exhibits considerable promise as a therapeutic agent for the treatment of cholestatic liver disorders.

Modulation of PI3K/AKT/mTOR signaling pathway in the ovine liver and duodenum during early pregnancy

The liver and intestine play a critical role in nutrient absorption, storage, and metabolism. The aim of this study was to evaluate expression pattern of phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of the rapamycin (mTOR) signaling pathway that included PI3K, AKT1, mTOR, FoxO1, SREBP-1, PPARα, PTEN and FXR in the maternal liver and duodenum. Ovine livers and duodenums were sampled at day 16 of the estrous cycle, and at days 13, 16 and 25 of gestation, and RT-qPCR, western blot and immunohistochemistry analysis were used to detect mRNA and protein expression. The results showed that expression of PI3K, AKT1, p-mTOR, FoxO1, SREBP-1 and PTEN upregulated in the maternal liver, and PPARα upregulated in the duodenum. However, expression of FoxO1, SREBP-1 and PTEN in the duodenum downregulated during early pregnancy. In addition, expression levels of SREBP-1, PTEN and PPARα in the maternal liver, and PI3K in the duodenum peaked at day 13 of pregnancy. In addition, expression levels of PI3K, p-mTOR and FoxO1 in the liver, and AKT1 and p-mTOR in the duodenum peaked at day 16 of pregnancy. Nevertheless, expression levels of FXR both in the maternal liver duodenum downregulated at days 13 and 16 of pregnancy. In conclusion, early pregnancy regulated expression pattern of PI3K/AKT/mTOR signaling pathway in the ovine liver and duodenum in a pregnancy stage-specific and tissue-specific manner, which may be necessary for the adaptations in maternal hepatic nutrient metabolism and intestinal nutrient absorption early pregnancy.

Comparative analysis of bile acid composition and metabolism in the liver of Bufo gargarizans aquatic larvae and terrestrial adults

Bile acids are crucial for lipid metabolism and their composition and metabolism differ among species. However, there have been no data on the differences in the composition and metabolism of bile acids between aquatic larvae and terrestrial adults of amphibians. This study explored the differences in composition and metabolism of bile acid between Bufo gargarizans larvae and adults. The results demonstrated that adult liver had a lower total bile acid level and a higher conjugated/total bile acid ratio than larval liver. Meanwhile, histological analysis revealed that the larvae showed a larger cross-sectional area of bile canaliculi lumen compared with the adults. The transcriptomic analysis showed that B. gargarizans larvae synthesized bile acids through both the alternative and the 24-hydroxylase pathway, while adults only synthesized bile acids through the 24-hydroxylase pathway. Moreover, bile acid regulator-related genes FXR and RXRα were highly expressed in adult, whereas genes involved in bile acid synthesis (CYP27A1 and CYP46A1) were highly expressed in larvae. The present study will provide valuable insights into understanding metabolic disorders and exploring novel bile acid-based therapeutics.

Unveiling structural determinants for FXR antagonism in 1,3,4-trisubstituted-Pyrazol amide derivatives: A multi-scale in silico modelling approach

Non-alcoholic fatty liver disease (NAFLD) is a growing global health concern due to its potential to progress into severe liver diseases. Targeting the bile acid receptor FXR has emerged as a promising strategy for managing NAFLD. Building upon our previous research on FXR partial agonism, the present study investigates a series of 1,3,4-trisubstituted-pyrazol amide derivatives as FXR antagonists, aiming to delineate the structural features for antagonism. By means of 2D-QSAR (quantitative structure-activity relationships) modelling techniques, we elucidated the key structural elements responsible for the antagonistic properties of these derivatives. We then employed QPhAR, an open-access software, to identify key molecular features within the compounds that enhance their antagonistic activity. Additionally, 3D-QSAR modelling allowed us to analyse the steric and electrostatic fields of aligned 3D structures, further refining our understanding of structure-activity relationships. Subsequent molecular dynamics simulations provided insights into the binding mode interactions between the compounds and FXR, with varying potencies, confirming and complementing the findings from 2D-QSAR, pharmacophore, and 3D-QSAR modelling. Particularly, our study highlighted the significance of hydrophobic interactions in conferring potent antagonism by the 1,3,4-trisubstituted-pyrazol amide derivatives against FXR. Overall, this work underscores the potential of 1,3,4-trisubstituted-pyrazol amides as FXR antagonists for NAFLD treatment. Notably, our reliance on open-access software fosters reproducibility and broadens the accessibility of our findings.

Pathophysiological Relationship between Type 2 Diabetes Mellitus and Metabolic Dysfunction-Associated Steatotic Liver Disease: Novel Therapeutic Approaches

Type 2 diabetes mellitus (T2DM), often featuring hyperglycemia or insulin resistance, is a global health concern that is increasing in prevalence in the United States and worldwide. A common complication is metabolic dysfunction-associated steatotic liver disease (MASLD), the hepatic manifestation of metabolic syndrome that is also rapidly increasing in prevalence. The majority of patients with T2DM will experience MASLD, and likewise, individuals with MASLD are at an increased risk for developing T2DM. These two disorders may act synergistically, in part due to increased lipotoxicity and inflammation within the liver, among other causes. However, the pathophysiological mechanisms by which this occurs are unclear, as is how the improvement of one disorder can ameliorate the other. This review aims to discuss the pathogenic interactions between T2D and MASLD, and will highlight novel therapeutic targets and ongoing clinical trials for the treatment of these diseases.

Recent advances in COVID-19-induced liver injury: causes, diagnosis, and management

Since the start of the pandemic, considerable advancements have been made in our understanding of the effects of SARS-CoV-2 infection and the associated COVID-19 on the hepatic system. There is a broad range of clinical symptoms for COVID-19. It affects multiple systems and has a dominant lung illness depending on complications. The progression of COVID-19 in people with pre-existing chronic liver disease (CLD) has also been studied in large multinational groups. Notably, SARS-CoV-2 infection is associated with a higher risk of hepatic decompensation and death in patients with cirrhosis. In this review, the source, composition, mechanisms, transmission characteristics, clinical characteristics, therapy, and prevention of SARS-CoV-2 were clarified and discussed, as well as the evolution and variations of the virus. This review briefly discusses the causes and effects of SARS-CoV-2 infection in patients with CLD. As part of COVID-19, In addition, we assess the potential of liver biochemistry as a diagnostic tool examine the data on direct viral infection of liver cells, and investigate potential pathways driving SARS-CoV-2-related liver damage. Finally, we explore how the pandemic has had a significant impact on patient behaviors and hepatology services, which may increase the prevalence and severity of liver disease in the future. The topics encompassed in this review encompass the intricate relationships between SARS-CoV-2, liver health, and broader health management strategies, providing valuable insights for both current clinical practice and future research directions.

Butylparaben induces glycolipid metabolic disorders in mice via disruption of gut microbiota and FXR signaling

Butylparaben, a common preservative, is widely used in food, pharmaceuticals and personal care products. Epidemiological studies have revealed the close relationship between butylparaben and diabetes; however the mechanisms of action remain unclear. In this study, we administered butylparaben orally to mice and observed that exposure to butylparaben induced glucose intolerance and hyperlipidemia. RNA sequencing results demonstrated that the enrichment of differentially expressed genes was associated with lipid metabolism, bile acid metabolism, and inflammatory response. Western blot results further validated that butylparaben promoted hepatic lipogenesis, inflammation, gluconeogenesis, and insulin resistance through the inhibition of the farnesoid X receptor (FXR) pathway. The FXR agonists alleviated the butylparaben-induced metabolic disorders. Moreover, 16 S rRNA sequencing showed that butylparaben reduced the abundance of Bacteroidetes, S24-7, Lactobacillus, and Streptococcus, and elevated the Firmicutes/Bacteroidetes ratio. The gut microbiota dysbiosis caused by butylparaben led to decreased bile acids (BAs) production and increased inflammatory response, which further induced hepatic glycolipid metabolic disorders. Our results also demonstrated that probiotics attenuated butylparaben-induced disturbances of the gut microbiota and hepatic metabolism. Taken collectively, the findings reveal that butylparaben induced gut microbiota dysbiosis and decreased BAs production, which further inhibited FXR signaling, ultimately contributing to glycolipid metabolic disorders in the liver.

Multiomics to Characterize the Molecular Events Underlying Impaired Glucose Tolerance in FXR-Knockout Mice

The prevalence of different metabolic syndromes has grown globally, and the farnesoid X receptor (FXR), a metabolic homeostat for glucose, lipid, and bile acid metabolisms, may serve an important role in the progression of metabolic disorders. Glucose intolerance by FXR deficiency was previously reported and observed in our study, but the underlying biology remained unclear. To investigate the ambiguity, we collected the nontargeted profiles of the fecal metaproteome, serum metabolome, and liver proteome in Fxr-null (Fxr-/-) and wild-type (WT) mice with LC-HRMS. FXR deficiency showed a global impact on the different molecular levels we monitored, suggesting its serious disruption in the gut microbiota, hepatic metabolism, and circulating biomolecules. The network and enrichment analyses of the dysregulated metabolites and proteins suggested the perturbation of carbohydrate and lipid metabolism by FXR deficiency. Fxr-/- mice presented lower levels of hepatic proteins involved in glycogenesis. The impairment of glycogenesis by an FXR deficiency may leave glucose to accumulate in the circulation, which may deteriorate glucose tolerance. Lipid metabolism was dysregulated by FXR deficiency in a structural-dependent manner. Fatty acid β-oxidations were alleviated, but cholesterol metabolism was promoted by an FXR deficiency. Together, we explored the molecular events associated with glucose intolerance by impaired FXR with integrated novel multiomic data.

The role of botanical triterpenoids and steroids in bile acid metabolism, transport, and signaling: Pharmacological and toxicological implications

Bile acids (BAs) are synthesized by the host liver from cholesterol and are delivered to the intestine, where they undergo further metabolism by gut microbes and circulate between the liver and intestines through various transporters. They serve to emulsify dietary lipids and act as signaling molecules, regulating the host's metabolism and immune homeostasis through specific receptors. Therefore, disruptions in BA metabolism, transport, and signaling are closely associated with cholestasis, metabolic disorders, autoimmune diseases, and others. Botanical triterpenoids and steroids share structural similarities with BAs, and they have been found to modulate BA metabolism, transport, and signaling, potentially exerting pharmacological or toxicological effects. Here, we have updated the research progress on BA, with a particular emphasis on new-found microbial BAs. Additionally, the latest advancements in targeting BA metabolism and signaling for disease treatment are highlighted. Subsequently, the roles of botanical triterpenoids in BA metabolism, transport, and signaling are examined, analyzing their potential pharmacological, toxicological, or drug interaction effects through these mechanisms. Finally, a research paradigm is proposed that utilizes the gut microbiota as a link to interpret the role of these important natural products in BA signaling.

Microbial metabolite trimethylamine-N-oxide induces intestinal carcinogenesis through inhibiting farnesoid X receptor signaling

PURPOSE

Microbial dysbiosis is considered as a hallmark of colorectal cancer (CRC). Trimethylamine-N-oxide (TMAO) as a gut microbiota-dependent metabolite has recently been implicated in CRC development. Nevertheless, evidence relating TMAO to intestinal carcinogenesis remains largely unexplored. Herein, we aimed to examine the crucial role of TMAO in CRC progression.

METHODS

Apcmin/+ mice were treated with TMAO or sterile PBS for 14 weeks. Intestinal tissues were isolated to evaluate the effects of TMAO on the malignant transformation of intestinal adenoma. The gut microbiota of mouse feces was detected by 16S rRNA sequencing analysis. HCT-116 cells were used to provide further evidence of TMAO on the progression of CRC.

RESULTS

TMAO administration increased tumor cell and stem cell proliferation, and decreased apoptosis, accompanied by DNA damage and gut barrier impairment. Gut microbiota analysis revealed that TMAO induced changes in the intestinal microbial community structure, manifested as reduced beneficial bacteria. Mechanistically, TMAO bound to farnesoid X receptor (FXR), thereby inhibiting the FXR-fibroblast growth factor 15 (FGF15) axis and activating the Wnt/β-catenin signaling pathway, whereas the FXR agonist GW4064 could blunt TMAO-induced Wnt/β-catenin pathway activation.

CONCLUSION

The microbial metabolite TMAO can enhance intestinal carcinogenesis by inhibiting the FXR-FGF15 pathway.

Farnesoid X receptor: From Structure to Function and Its Pharmacology in Liver Fibrosis

The farnesoid X receptor (FXR), a ligand-activated transcription factor, plays a crucial role in regulating bile acid metabolism within the enterohepatic circulation. Beyond its involvement in metabolic disorders and immune imbalances affecting various tissues, FXR is implicated in microbiota modulation, gut-to-brain communication, and liver disease. The liver, as a pivotal metabolic and detoxification organ, is susceptible to damage from factors such as alcohol, viruses, drugs, and high-fat diets. Chronic or recurrent liver injury can culminate in liver fibrosis, which, if left untreated, may progress to cirrhosis and even liver cancer, posing significant health risks. However, therapeutic options for liver fibrosis remain limited in terms of FDA-approved drugs. Recent insights into the structure of FXR, coupled with animal and clinical investigations, have shed light on its potential pharmacological role in hepatic fibrosis. Progress has been achieved in both fundamental research and clinical applications. This review critically examines recent advancements in FXR research, highlighting challenges and potential mechanisms underlying its role in liver fibrosis treatment.

Liver Fibrosis: From Basic Science towards Clinical Progress, Focusing on the Central Role of Hepatic Stellate Cells

The burden of chronic liver disease is globally increasing at an alarming rate. Chronic liver injury leads to liver inflammation and fibrosis (LF) as critical determinants of long-term outcomes such as cirrhosis, liver cancer, and mortality. LF is a wound-healing process characterized by excessive deposition of extracellular matrix (ECM) proteins due to the activation of hepatic stellate cells (HSCs). In the healthy liver, quiescent HSCs metabolize and store retinoids. Upon fibrogenic activation, quiescent HSCs transdifferentiate into myofibroblasts; lose their vitamin A; upregulate α-smooth muscle actin; and produce proinflammatory soluble mediators, collagens, and inhibitors of ECM degradation. Activated HSCs are the main effector cells during hepatic fibrogenesis. In addition, the accumulation and activation of profibrogenic macrophages in response to hepatocyte death play a critical role in the initiation of HSC activation and survival. The main source of myofibroblasts is resident HSCs. Activated HSCs migrate to the site of active fibrogenesis to initiate the formation of a fibrous scar. Single-cell technologies revealed that quiescent HSCs are highly homogenous, while activated HSCs/myofibroblasts are much more heterogeneous. The complex process of inflammation results from the response of various hepatic cells to hepatocellular death and inflammatory signals related to intrahepatic injury pathways or extrahepatic mediators. Inflammatory processes modulate fibrogenesis by activating HSCs and, in turn, drive immune mechanisms via cytokines and chemokines. Increasing evidence also suggests that cellular stress responses contribute to fibrogenesis. Recent data demonstrated that LF can revert even at advanced stages of cirrhosis if the underlying cause is eliminated, which inhibits the inflammatory and profibrogenic cells. However, despite numerous clinical studies on plausible drug candidates, an approved antifibrotic therapy still remains elusive. This state-of-the-art review presents cellular and molecular mechanisms involved in hepatic fibrogenesis and its resolution, as well as comprehensively discusses the drivers linking liver injury to chronic liver inflammation and LF.

Patented Farnesoid X receptor modulators: a review (2019 - present)

INTRODUCTION

The Farnesoid X receptor (FXR) is a key transcription factor that is involved in the bile acid signaling network. The modulation of the FXR activity influences glucose and lipid homeostasis, reduces obesity and insulin resistance, as well as it regulates the pathogenesis of inflammatory and metabolic disorders. FXR ligands have therefore emerged in drug discovery as promising therapeutic agents for the prevention and treatment of gastrointestinal and liver diseases, including cancer.

AREAS COVERED

Recent advances in the field of FXR modulators are reviewed, with a particular attention on patent applications filed in the past 5 years related to both the discovery and development of FXR targeting drugs.

EXPERT OPINION

FXR agonists have proven their efficacy and safety in humans and have shown a significant potential as clinical agents to treat metabolic and inflammatory associated conditions. However, several challenges, including adverse events such as pruritus, remain to be solved. Current studies aim to gain insights into the pathophysiological mechanisms by which FXR regulates metabolism and inflammation in terms of tissue/organ/isoform-specificity, post-translational modifications and coregulatory proteins, on the route of novel, improved FXR modulators.

Role of FXR in the development of NAFLD and intervention strategies of small molecules

Non-alcoholic fatty liver disease (NAFLD) remains a prevailing etiological agent behind hepatocyte diseases like chronic liver disease. The spectrum of processes involved in NAFLD stages includes hepatic steatosis, non-alcoholic fatty liver, and non-alcoholic steatohepatitis (NASH). Without intervention, the progression of NASH can further deteriorate into cirrhosis and ultimately, hepatocellular carcinoma. The cardinal features that characterize NAFLD are insulin resistance, lipogenesis, oxidative stress and inflammation, extracellular matrix deposition and fibrosis. Due to its complex pathogenesis, existing pharmaceutical agents fail to take a curative or ameliorative effect on NAFLD. Consequently, it is imperative to identify novel therapeutic targets and strategies for NAFLD, ideally to improve the aforementioned key features in patients. As an enterohepatic regulator of bile acid homeostasis, lipid metabolism, and inflammation, FarnesoidX receptor (FXR) is an important pharmacological target for the treatment of NAFLD. Manipulating FXR to regulate lipid metabolic signaling pathways is a potential mechanism to mitigate NAFLD. Therefore, elucidating the modulatory character of FXR in regulating lipid metabolism in NAFLD has the potential to yield groundbreaking perspectives for drug design. This review details recent advances in the regulation of lipid depletion in hepatocytes and investigates the pivotal function of FXR in the progress of NAFLD.

Gut Microbiota Metabolite Messengers in Brain Function and Pathology at a View of Cell Type-Based Receptor and Enzyme Reaction

The human gastrointestinal (GI) tract houses a diverse microbial community, known as the gut microbiome comprising bacteria, viruses, fungi, and protozoa. The gut microbiome plays a crucial role in maintaining the body's equilibrium and has recently been discovered to influence the functioning of the central nervous system (CNS). The communication between the nervous system and the GI tract occurs through a two-way network called the gut-brain axis. The nervous system and the GI tract can modulate each other through activated neuronal cells, the immune system, and metabolites produced by the gut microbiome. Extensive research both in preclinical and clinical realms, has highlighted the complex relationship between the gut and diseases associated with the CNS, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This review aims to delineate receptor and target enzymes linked with gut microbiota metabolites and explore their specific roles within the brain, particularly their impact on CNS-related diseases.

Pulsatilla decoction alleviates DSS-induced UC by activating FXR-ASBT pathways to ameliorate disordered bile acids homeostasis

Ethnopharmacological relevance: Pulsatilla decoction (PD) is a classical prescription for the treatment of ulcerative colitis. Previous studies have demonstrated that the therapeutic efficacy of PD is closely associated with the activation of Farnesoid X receptor (FXR). The activity of FXR is regulated by apical sodium-dependent bile acid transporter (ASBT), and the FXR-ASBT cascade reaction, centered around bile acid receptor FXR, plays a pivotal role in maintaining bile acid metabolic homeostasis to prevent the occurrence and progression of ulcerative colitis (UC). Aim of the study: To elucidate the underlying mechanism by which PD exerts its proteactive effects against Dextran Sulfate Sodium Salt (DSS)-induced ulcerative colitis, focusing on the modulation of FXR and ASBT. Materials and methods: To establish a model of acute ulcerative colitis, BALB/C mice were administered 3.5% DSS in their drinking water for consecutive 7 days. The disease activity index (DAI) was employed to evaluate the clinical symptoms exhibited by each group of mice. Goblet cell expression in colon tissue was assessed using glycogen schiff periodic acid-Schiff (PAS) and alcian blue staining techniques. Inflammatory cytokine expression in serum and colonic tissues was examined through enzyme-linked immunosorbent assay (ELISA). A PCR Array chip was utilized to screen 88 differential genes associated with the FXR-ASBT pathway in UC treatment with PD. Western blotting (WB) analysis was performed to detect protein expression levels of differentially expressed genes in mouse colon tissue. Results: The PD treatment effectively reduced the Disease Activity Index (DAI) score and mitigated colon histopathological damage, while also restoring weight and colon length. Furthermore, it significantly alleviated the severity of ulcerative colitis (UC), regulated inflammation, modulated goblet cell numbers, and restored bile acid balance. Additionally, a PCR Array analysis identified 21 differentially expressed genes involved in the FXR-ASBT pathway. Western blot results demonstrated significant restoration of FXR, GPBAR1, CYP7A1, and FGF15 protein expression levels following PD treatment; moreover, there was an observed tendency towards increased expression levels of ABCB11 and RXRα. Conclusion: The therapeutic efficacy of PD in UC mice is notable, potentially attributed to its modulation of bile acid homeostasis, enhancement of gut barrier function, and attenuation of intestinal inflammation.

Ursodeoxycholic Acid Modulates the Interaction of miR-21 and Farnesoid X Receptor and NF-κB Signaling

(1) Background: This study investigates the effects of Ursodeoxycholic acid (UDCA) on NF-κB signaling, farnesoid X receptor (FXR) singling, and microRNA-21 in HepG2 cells. (2) Methods: HepG2 cells were treated with lipopolysaccharide (LPS) to simulate hepatic inflammation. The investigation focused on the expression of NF-κB activation, which was analyzed using Western blot, confocal microscopy, and Electrophoretic Mobility-shift Assays (EMSA). Additionally, NF-κB and farnesoid X receptor (FXR) singling expressions of micro-RNA-21, COX-2, TNF-α, IL-6, cyp7A1, and shp were assessed by RT-PCR. (3) Results: UDCA effectively downregulated LPS-induced expressions of NF-κB/65, p65 phosphorylation, and also downregulated FXR activity by Western blot. Confocal microscopy and EMSA results confirmed UDCA's role in modulating NF-κB signaling. UDCA reduced the expressions of LPS-induced COX-2, TNF-α, and IL-6, which were related to NF-κB signaling. UDCA downregulated LPS-induced cyp7A1 gene expression and upregulated shp gene expression, demonstrating selective gene regulation via FXR. UDCA also significantly decreased micro-RNA 21 levels. (4) Conclusions: This study demonstrates UDCA's potent anti-inflammatory effects on NF-κB and FXR signaling pathways, and thus its potential to modulate hepatic inflammation and carcinogenesis through interactions with NF-κB and FXR. The decrease in micro-RNA 21 expression further underscores its therapeutic potential.

Effects of Saponins on Lipid Metabolism: The Gut-Liver Axis Plays a Key Role

Unhealthy lifestyles (high-fat diet, smoking, alcohol consumption, too little exercise, etc.) in the current society are prone to cause lipid metabolism disorders affecting the health of the organism and inducing the occurrence of diseases. Saponins, as biologically active substances present in plants, have lipid-lowering, inflammation-reducing, and anti-atherosclerotic effects. Saponins are thought to be involved in the regulation of lipid metabolism in the body; it suppresses the appetite and, thus, reduces energy intake by modulating pro-opiomelanocortin/Cocaine amphetamine regulated transcript (POMC/CART) neurons and neuropeptide Y/agouti-related peptide (NPY/AGRP) neurons in the hypothalamus, the appetite control center. Saponins directly activate the AMP-activated protein kinase (AMPK) signaling pathway and related transcriptional regulators such as peroxisome-proliferator-activated-receptors (PPAR), CCAAT/enhancer-binding proteins (C/EBP), and sterol-regulatory element binding proteins (SREBP) increase fatty acid oxidation and inhibit lipid synthesis. It also modulates gut-liver interactions to improve lipid metabolism by regulating gut microbes and their metabolites and derivatives-short-chain fatty acids (SCFAs), bile acids (BAs), trimethylamine (TMA), lipopolysaccharide (LPS), et al. This paper reviews the positive effects of different saponins on lipid metabolism disorders, suggesting that the gut-liver axis plays a crucial role in improving lipid metabolism processes and may be used as a therapeutic target to provide new strategies for treating lipid metabolism disorders.

Tailoring FXR Modulators for Intestinal Specificity: Recent Progress and Insights

While FXR has shown promise in regulating bile acid synthesis and maintaining glucose and lipid homeostasis, undesired side effects have been observed in clinical trials. To address this issue, the development of intestinally restricted FXR modulators has gained attention as a new avenue for drug design with the potential for safer systematic effects. Our review examines all currently known intestinally restricted FXR ligands and provides insights into the steps taken to enhance intestinal selectivity.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Increased hepatoprotective effects of the novel farnesoid X receptor agonist INT-787 versus obeticholic acid in a mouse model of nonalcoholic steatohepatitis

The nuclear farnesoid X receptor (FXR), a master regulator of bile acid and metabolic homeostasis, is a key target for treatment of nonalcoholic steatohepatitis (NASH). This study compared efficacy of FXR agonists obeticholic acid (OCA) and INT-787 by liver histopathology, plasma biomarkers of liver damage, and hepatic gene expression profiles in the Amylin liver NASH (AMLN) diet-induced and biopsy-confirmed Lepob/ob mouse model of NASH. Lepob/ob mice were fed the AMLN diet for 12 weeks before liver biopsy and subsequent treatment with vehicle, OCA, or INT-787 for 8 weeks. Hepatic steatosis, inflammation, and fibrosis (liver lipids, galectin-3, and collagen 1a1 [Col1a1], respectively), as well as plasma alanine transaminase (ALT) and aspartate transaminase (AST) levels, were assessed. Hepatic gene expression was assessed in Lepob/ob mice that were fed the AMLN diet for 14 weeks then treated with vehicle, OCA, or INT-787 for 2 weeks. INT-787, which is equipotent to OCA but more hydrophilic, significantly reduced liver lipids, galectin-3, and Col1a1 compared with vehicle, and to a greater extent than OCA. INT-787 significantly reduced plasma ALT and AST levels, whereas OCA did not. INT-787 modulated a substantially greater number of genes associated with FXR signaling, lipid metabolism, and stellate cell activation relative to OCA in hepatic tissue. These findings demonstrate greater efficacy of INT-787 treatment compared with OCA in improving liver histopathology, decreasing liver enzyme levels, and enhancing gene regulation, suggesting superior clinical potential of INT-787 for the treatment of NASH and other chronic liver diseases.

NR1H4 disease: rapidly progressing neonatal intrahepatic cholestasis and early death

BACKGROUND

Clinical studies on progressive familial intrahepatic cholestasis (PFIC) type 5 caused by mutations in NR1H4 are limited.

METHODS

New patients with biallelic NR1H4 variants from our center and all patients from literature were retrospectively analyzed.

RESULTS

Three new patients were identified to be carrying five new variants. Liver phenotypes of our patients manifests as low-γ-glutamyl transferase cholestasis, liver failure and related complications. One patient underwent liver transplantation (LT) and survived, and two other patients died without LT. Nine other patients were collected through literature review. Twelve out of 13 patients showed neonatal jaundice, with the median age of onset being 7 days after birth. Reported clinical manifestations included cholestasis (13/13, 100%), elevated AFP (11/11, 100%), coagulopathy (11/11, 100%), hypoglycemia (9/13, 69%), failure to thrive (8/13, 62%), splenomegaly (7/13, 54%), hyperammonemia (7/13, 54%), and hepatomegaly (6/13, 46%). Six of 13 patients received LT at a median age of 6.2 months, and only one patient died of acute infection at one year after LT. Other 7 patients had no LT and died with a median age of 5 months (range 1.2-8). There were 8 patients with homozygous genotype and 5 patients with compound heterozygous genotype. In total, 13 different variants were detected, and 5 out of 12 single or multiple nucleotides variants were located in exon 5.

CONCLUSIONS

We identified three newly-diagnosed patients and five novel mutations. NR1H4-related PFIC typically cause progressive disease and early death. LT may be the only lifesaving therapy leading to cure.

Nuclear receptor interdomain communication is mediated by the hinge with ligand specificity

Nuclear receptors are ligand-induced transcription factors that bind directly to target genes and regulate their expression. Ligand binding initiates conformational changes that propagate to other domains, allosterically regulating their activity. The nature of this interdomain communication in nuclear receptors is poorly understood, largely owing to the difficulty of experimentally characterizing full-length structures. We have applied computational modeling approaches to describe and study the structure of the full length farnesoid X receptor (FXR), approximated by the DNA binding domain (DBD) and ligand binding domain (LBD) connected by the flexible hinge region. Using extended molecular dynamics simulations (> 10 microseconds) and enhanced sampling simulations, we provide evidence that ligands selectively induce domain rearrangement, leading to interdomain contact. We use protein-protein interaction assays to provide experimental evidence of these interactions, identifying a critical role of the hinge in mediating interdomain contact. Our results illuminate previously unknown aspects of interdomain communication in FXR and provide a framework to enable characterization of other full length nuclear receptors.