Farnesoid X Receptor Knockout Research Articles

Farnesoid X Receptor: Effective alleviation of rifampicin -induced liver injury

Antituberculosis drugs induce pharmacologic cholestatic liver injury with long-term administration. Liver injury resulting from rifampicin is potentially related to the bile acid nuclear receptor Farnesoid X Receptor (FXR). To investigate this, cholestasis was induced in both wild-type (C57BL/6N) mice and FXR knockout (FXR-null) mice through administration of rifampicin (200 mg/kg) via gavage for 7 consecutive days. Compared with C57BL/6N mice, FXR-null mice exhibited more severe liver injury after rifampicin administration, characterized by enlarged liver size, elevated transaminases, and increased inflammation. Moreover, under rifampicin treatment, FXR knockout impairs lipid secretion and exacerbates hepatic steatosis. Significantly, the expression of metabolism molecules BSEP increased, while NTCP and CYP7A1 decreased following rifampicin administration in C57BL/6N mice, whereas these changes were absent in FXR knockout mice. Furthermore, rifampicin treatment in both C57BL/6N and FXR-null mice was associated with elevated c-Jun N-terminal kinase phosphorylation (p-JNK) levels, with a more pronounced elevation in FXR-null mice. Our study suggests that rifampicin-induced liver injury, steatosis, and cholestasis are associated with FXR dysfunction and altered bile acid metabolism, and that the JNK signaling pathway is partially implicated in this injury. Based on these results, we propose that FXR might be a novel therapeutic target for addressing drug-induced liver injury.

Microbiota metabolized Bile Acids accelerate Gastroesophageal Adenocarcinoma via FXR inhibition.

The incidence of Barrett esophagus (BE) and Gastroesophageal Adenocarcinoma (GEAC) correlates with obesity and a diet rich in fat. Bile acids (BA) support fat digestion and undergo microbial metabolization in the gut. The farnesoid X receptor (FXR) is an important modulator of the BA homeostasis. The capacity of inhibiting cancer-related processes when activated, make FXR an appealing therapeutic target. In this work, we assess the role of diet on the microbiota-BA axis and evaluate the role of FXR in disease progression. Here we show that high fat diet (HFD) accelerated tumorigenesis in L2-IL1B mice (BE- and GEAC- mouse model) while increasing BA levels and enriching gut microbiota that convert primary to secondary BA. While upregulated in BE, expression of FXR was downregulated in GEAC in mice and humans. In L2-IL1B mice, FXR knockout enhanced the dysplastic phenotype and increased Lgr5 progenitor cell numbers. Treatment of murine organoids and L2-IL1B mice with the FXR agonist obeticholic acid (OCA) deacelerated GEAC progression. We provide a novel concept of GEAC carcinogenesis being accelerated via the diet-microbiome-metabolome axis and FXR inhibition on progenitor cells. Further, FXR activation protected with OCA ameliorated the phenotype in vitro and in vivo, suggesting that FXR agonists have potential as differentiation therapy in GEAC prevention. If its inhibition is linked to disease progression and its activation to cancer prevention, exploring the potential of FXR as a therapeutic target has great clinical relevance in GEAC context.

FXR deletion attenuates intestinal barrier dysfunction in murine acute intestinal inflammation.

Accumulating literature suggests that the farnesoid-X receptor (FXR), a nuclear bile acid receptor best known for its role in bile acid homeostasis, is also a potent context-dependent regulator of inflammation. FXR may thus be relevant to several intestinal disease states including inflammatory bowel disease, necrotizing enterocolitis, and sepsis. In this study, we tested the effects of FXR deletion on acute murine intestinal inflammation. We found that FXR knockout (KO) mice were protected from intestinal injury and barrier dysfunction induced by lipopolysaccharide (LPS) injection, dithizone (DI)/Klebsiella, and cecal ligation/puncture models. In the LPS model, RNA sequencing and qPCR analysis showed that this protection correlated with substantial reduction in LPS-induced proinflammatory gene expression, including lower tissue levels of Il1a, Il1b, and Tnf. Examining functional effects on the epithelium, we found that LPS-induced tight junctional disruption as assessed by internalization of ZO-1 and occludin was ameliorated in FXR KO animals. Taken together, these data suggest a role for FXR in the intestinal barrier during inflammatory injury.NEW & NOTEWORTHY Intestinal barrier failure is a hallmark in gut-origin sepsis. We demonstrate that the intestinal barriers of farnesoid-X receptor (FXR) knockout (KO) animals are protected from inflammatory insult using multiple models of acute intestinal inflammation. This protection is due to decreased inflammatory cytokine production and maintenance of tight junctional architecture seen within the KO animals. This is the first report of FXR deletion being protective to the intestinal barrier.

Loss of the DNA-binding domain of the farnesoid X receptor gene causes severe liver and kidney injuries

Farnesoid X receptor (FXR) regulates bile acid synthesis, lipid metabolism, and glucose homeostasis in metabolic organs. FXR-knockout (FXR-KO) mice lacking the last exon of the FXR gene develop normally and display no prenatal and early postnatal lethality, whereas human patients with mutations in the DNA-binding domain of the FXR gene develop severe hepatic dysfunction. In this study, we generated novel FXR-KO mice lacking the DNA-binding domain of the FXR gene using CRISPR–Cas9 technology and evaluated their phenotypes. Similar to the aforementioned FXR-KO mice, our novel mice showed elevated serum levels of total bile acids and total cholesterol. However, they were obviously short-lived, showing severe liver and renal pathologies at an early age. These results indicate that FXR, including its unknown isoforms, has more significant functions in multiple organs than previously reported. Thus, the novel FXR-KO mice could lead to a new aspect that requires reworking of previous knowledge of FXR in the liver and renal function.

Puerarin Modulates Hepatic Farnesoid X Receptor and Gut Microbiota in High-Fat Diet-Induced Obese Mice.

Obesity is associated with alterations in lipid metabolism and gut microbiota dysbiosis. This study investigated the effects of puerarin, a bioactive isoflavone, on lipid metabolism disorders and gut microbiota in high-fat diet (HFD)-induced obese mice. Supplementation with puerarin reduced plasma alanine aminotransferase, liver triglyceride, liver free fatty acid (FFA), and improved gut microbiota dysbiosis in obese mice. Puerarin's beneficial metabolic effects were attenuated when farnesoid X receptor (FXR) was antagonized, suggesting FXR-mediated mechanisms. In hepatocytes, puerarin ameliorated high FFA-induced sterol regulatory element-binding protein (SREBP) 1 signaling, inflammation, and mitochondrial dysfunction in an FXR-dependent manner. In obese mice, puerarin reduced liver damage, regulated hepatic lipogenesis, decreased inflammation, improved mitochondrial function, and modulated mitophagy and ubiquitin-proteasome pathways, but was less effective in FXR knockout mice. Puerarin upregulated hepatic expression of FXR, bile salt export pump (BSEP), and downregulated cytochrome P450 7A1 (CYP7A1) and sodium taurocholate transporter (NTCP), indicating modulation of bile acid synthesis and transport. Puerarin also restored gut microbial diversity, the Firmicutes/Bacteroidetes ratio, and the abundance of Clostridium celatum and Akkermansia muciniphila. This study demonstrates that puerarin effectively ameliorates metabolic disturbances and gut microbiota dysbiosis in obese mice, predominantly through FXR-dependent pathways. These findings underscore puerarin's potential as a therapeutic agent for managing obesity and enhancing gut health, highlighting its dual role in improving metabolic functions and modulating microbial communities.

Aspirin Caused Intestinal Damage through FXR and ET-1 Signaling Pathways.

Aspirin is a non-steroidal, anti-inflammatory drug often used long term. However, long-term or large doses will cause gastrointestinal adverse reactions. To explore the mechanism of intestinal damage, we used non-targeted metabolomics; farnesoid X receptor (FXR) knockout mice, which were compared with wild-type mice; FXR agonists obeticholic acid (OCA) and chenodeoxycholic acid (CDCA); and endothelin-producing inhibitor estradiol to explore the mechanisms of acute and chronic intestinal injuries induced by aspirin from the perspective of molecular biology. Changes were found in the bile acids taurocholate acid (TCA) and tauro-β-muricholic acid (T-β-MCA) in the duodenum, and we detected a significant inhibition of FXR target genes. After additional administration of the FXR agonists OCA and CDCA, duodenal villus damage and inflammation were effectively improved. The results in the FXR knockout mice and wild-type mice showed that the overexpression of endothelin 1 (ET-1) was independent of FXR regulation after aspirin exposure, whereas CDCA was able to restore the activation of ET-1, which was induced by aspirin in wild-type mice in an FXR-dependent manner. The inhibition of ET-1 production could also effectively protect against small bowel damage. Therefore, the study revealed the key roles of the FXR and ET-1 pathways in acute and chronic aspirin-induced intestinal injuries, as well as strategies on alleviating aspirin-induced gastrointestinal injury by activating FXR and inhibiting ET-1 overexpression.

Sex Dimorphic Effects of Bile Acid Metabolism in Liver Cancer in Mice

Background & AimsHepatocellular carcinoma (HCC) is a male-dominant disease, but targeted sex hormone therapies have not been successful. Bile acids are a potential liver carcinogen and are biomolecules with hormone-like effects. A few studies highlight their potential sex dimorphism in physiology and disease. We hypothesized that bile acids could be a potential molecular signature that explains sex disparity in HCC. Approach & ResultsWe employed the farnesoid X receptor knockout (FxrKO) mouse model to study bile acid-dependent HCC. Temporal tracking of circulating bile acids determined over 80% of FxrKO females developed spontaneous cholemia (i.e., serum total bile acids ≥40 μM) as early as 8 weeks old. Opposingly, FxrKO males were highly resistant to cholemia with ∼23% incidence even when 26 weeks old. Yet, FxrKO males demonstrated higher levels of deoxycholate than females. Compared to males, FxrKO females had more severe cholestatic liver injury and further aberrancies in bile acid metabolism. Yet, FxrKO females expressed more detoxification transcripts and had greater renal excretion of bile acids. Intervention with CYP7A1 (rate limiting enzyme for bile acid biosynthesis) deficiency or taurine supplementation either completely or partially normalized bile acid levels and liver injury in FxrKO females. Despite higher cholemia prevalence in FxrKO females, their tumor burden was less compared to FxrKO males. An exception to this sex-dimorphic pattern was found in a subset of male and female FxrKO mice born with congenital cholemia due to portosystemic shunt, where both sexes had comparable robust HCC. ConclusionsOur study highlights bile acids as sex-dimorphic metabolites in HCC except in the case of portosystemic shunt.

FXR controls insulin content by regulating Foxa2-mediated insulin transcription

Farnesoid X receptor (FXR) is a nuclear ligand-activated receptor of bile acids that plays a role in the modulation of insulin content. However, the underlying molecular mechanisms remain unclear. Forkhead box a2 (Foxa2) is an important nuclear transcription factor in pancreatic β-cells and is involved in β-cell function. We aimed to explore the signaling mechanism downstream of FXR to regulate insulin content and underscore its association with Foxa2 and insulin gene (Ins) transcription. All experiments were conducted on FXR transgenic mice, INS-1 823/13 cells, and diabetic Goto-Kakizaki (GK) rats undergoing sham or Roux-en-Y gastric bypass (RYGB) surgery. Islets from FXR knockout mice and INS-1823/13 cells with FXR knockdown exhibited substantially lower insulin levels than that of controls. This was accompanied by decreased Foxa2 expression and Ins transcription. Conversely, FXR overexpression increased insulin content, concomitant with enhanced Foxa2 expression and Ins transcription in INS-1 823/13 cells. Moreover, FXR knockdown reduced FXR recruitment and H3K27 trimethylation in the Foxa2 promoter. Importantly, Foxa2 overexpression abrogated the adverse effects of FXR knockdown on Ins transcription and insulin content in INS-1 823/13 cells. Notably, RYGB surgery led to improved insulin content in diabetic GK rats, which was accompanied by upregulated FXR and Foxa2 expression and Ins transcription. Collectively, these data suggest that Foxa2 serves as the target gene of FXR in β-cells and mediates FXR-enhanced Ins transcription. Additionally, the upregulated FXR/Foxa2 signaling cascade could contribute to the enhanced insulin content in diabetic GK rats after RYGB.

Melatonin improves cholestatic liver disease via the gut-liver axis.

Cholestatic liver disease is characterized by disturbances in the intestinal microbiota and excessive accumulation of toxic bile acids (BA) in the liver. Melatonin (MT) can improve liver diseases. However, the underlying mechanism remains unclear. This study aimed to explore the mechanism of MT on hepatic BA synthesis, liver injury, and fibrosis in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed and Mdr2-/- mice. MT significantly improved hepatic injury and fibrosis with a significant decrease in hepatic BA accumulation in DDC-fed and Mdr2-/- mice. MT reprogramed gut microbiota and augmented fecal bile salt hydrolase activity, which was related to increasing intestinal BA deconjugation and fecal BA excretion in both DDC-fed and Mdr2-/- mice. MT significantly activated the intestinal farnesoid X receptor (FXR)/fibroblast growth factor 15 (FGF-15) axis and subsequently inhibited hepatic BA synthesis in DDC-fed and Mdr2-/- mice. MT failed to improve DDC-induced liver fibrosis and BA synthesis in antibiotic-treated mice. Furthermore, MT provided protection against DDC-induced liver injury and fibrosis in fecal microbiota transplantation mice. MT did not decrease liver injury and fibrosis in DDC-fed intestinal epithelial cell-specific FXR knockout mice, suggesting that the intestinal FXR mediated the anti-fibrosis effect of MT. In conclusion, MT ameliorates cholestatic liver diseases by remodeling gut microbiota and activating intestinal FXR/FGF-15 axis-mediated inhibition of hepatic BA synthesis and promotion of BA excretion in mice.

Farnesoid X Receptor Agonist GW4064 Protects Lipopolysaccharide-Induced Intestinal Epithelial Barrier Function and Colorectal Tumorigenesis Signaling through the αKlotho/βKlotho/FGFs Pathways in Mice

The farnesoid X receptor (FXR)/βKlotho/fibroblast growth factors (FGFs) pathway is crucial for maintaining the intestinal barrier and preventing colorectal cancer (CRC). We used an FXR agonist, GW4064, and FXR-knockout (FXR-KO) mice to investigate the role of FXR/Klothos/FGFs pathways in lipopolysaccharide (LPS)-induced intestinal barrier dysfunction and colon carcinogenesis. The results showed that upregulation of FXR in enterocytes effectively ameliorated intestinal tight-junction markers (claudin1 and zonula occludens-1), inflammation, and bile acid levels, thereby protecting mice from intestinal barrier dysfunction and colon carcinogenesis. GW4064 treatment increased FXR, αKlotho, βKlotho, FGF19, FGF21, and FGF23 in wild-type mice exposed to LPS, while FXR-KO mice had decreased levels. FXR-KO mice exhibited elevated colon cancer markers (β-catenin, LGR5, CD44, CD34, and cyclin D1) under LPS, underscoring the pivotal role of FXR in inhibiting the development of colon tumorigenesis. The varying gut microbiota responses in FXR-KO mice versus wild-type mice post LPS exposure emphasize the pivotal role of FXR in preserving intestinal microbial health, involving Bacteroides thetaiotaomicron, Bacteroides acidifaciens, and Helicobacter hepaticus. Our study validates the effectiveness of GW4064 in alleviating LPS-induced disruptions to the intestinal barrier and colon carcinogenesis, emphasizing the importance of the FXR/αKlotho/βKlotho/FGFs pathway and the interplay between bile acids and gut microbiota.

Farnesoid X receptor activation by bile acids suppresses lipid peroxidation and ferroptosis

Ferroptosis is a regulated cell death modality that occurs upon iron-dependent lipid peroxidation. Recent research has identified many regulators that induce or inhibit ferroptosis; yet, many regulatory processes and networks remain to be elucidated. In this study, we performed a chemical genetics screen using small molecules with known mode of action and identified two agonists of the nuclear receptor Farnesoid X Receptor (FXR) that suppress ferroptosis, but not apoptosis or necroptosis. We demonstrate that in liver cells with high FXR levels, knockout or inhibition of FXR sensitized cells to ferroptotic cell death, whereas activation of FXR by bile acids inhibited ferroptosis. Furthermore, FXR inhibited ferroptosis in ex vivo mouse hepatocytes and human hepatocytes differentiated from induced pluripotent stem cells. Activation of FXR significantly reduced lipid peroxidation by upregulating the ferroptosis gatekeepers GPX4, FSP1, PPARα, SCD1, and ACSL3. Together, we report that FXR coordinates the expression of ferroptosis-inhibitory regulators to reduce lipid peroxidation, thereby acting as a guardian of ferroptosis.

Hepatic farnesoid X receptor is necessary to facilitate ductular reaction and expression of heme biosynthetic genes.

Bile, which contains bile acids, the natural ligands for farnesoid x receptor (FXR), moves from the liver to the intestine through bile ducts. Ductular reaction often occurs during biliary obstruction. A subset of patients with erythropoietic protoporphyria, an inherited genetic mutation in heme biosynthetic enzyme ferrochelatase, accumulate porphyrin-containing bile plugs, leading to cholestasis. Here, we examined the link between FXR, bile plug formation, and how heme biosynthesis relates to this connection. We treated female and male wild-type and global and tissue-specific Fxr knockout mice with a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine, an inhibitor of ferrochelatase, and examined the expression of heme biosynthetic genes. We mined FXR mouse ChIP-Seq data, performed biochemical and histological analysis, and tested HepG2 and primary human hepatocytes after treatment with obeticholic acid, an FXR agonist. We observed that hepatic but not intestinal Fxr loss resulted in reduced bile plugs and ductular reaction in the liver. Then, we examined if FXR plays a regulatory role in heme biosynthesis and found significantly lower porphyrin accumulation in 3,5-diethoxycarbonyl-1, 4-dihydrocollidine-fed Fxr knockout mice. Gene expression and FXR mouse ChIP-Seq atlas analysis revealed that FXR orchestrates the expression of multiple heme biosynthetic enzymes. Finally, human HepG2 cells and primary human hepatocytes treated with obeticholic acid, showed increased expression of several heme biosynthetic genes. Overall, our data show that hepatic Fxr is necessary to maintain ductular reaction and accumulation of bile plugs. FXR can direct the expression of multiple heme biosynthetic genes. Thus, modulating FXR activity in EPP patients may help alleviate its associated liver disease.

The Role of the Nuclear Receptor FXR in Arsenic-Induced Glucose Intolerance in Mice.

Inorganic arsenic in drinking water is prioritized as a top environmental contaminant by the World Health Organization, with over 230 million people potentially being exposed. Arsenic toxicity has been well documented and is associated with a plethora of human diseases, including diabetes, as established in numerous animal and epidemiological studies. Our previous study revealed that arsenic exposure leads to the inhibition of nuclear receptors, including LXR/RXR. To this end, FXR is a nuclear receptor central to glucose and lipid metabolism. However, limited studies are available for understanding arsenic exposure-FXR interactions. Herein, we report that FXR knockout mice developed more profound glucose intolerance than wild-type mice upon arsenic exposure, supporting the regulatory role of FXR in arsenic-induced glucose intolerance. We further exposed mice to arsenic and tested if GW4064, a FXR agonist, could improve glucose intolerance and dysregulation of hepatic proteins and serum metabolites. Our data showed arsenic-induced glucose intolerance was remarkably diminished by GW4064, accompanied by a significant ratio of alleviation of dysregulation in hepatic proteins (83%) and annotated serum metabolites (58%). In particular, hepatic proteins "rescued" from arsenic toxicity by GW4064 featured members of glucose and lipid utilization. For instance, the expression of PCK1, a candidate gene for diabetes and obesity that facilitates gluconeogenesis, was repressed under arsenic exposure in the liver, but revived with the GW4064 supplement. Together, our comprehensive dataset indicates FXR plays a key role and may serve as a potential therapeutic for arsenic-induced metabolic disorders.

Loss of Farnesoid X receptor (FXR) accelerates dysregulated glucose and renal injury in db/db mice.

End-stage renal disease is primarily caused by diabetic kidney disease (DKD). The Farnesoid X receptor (FXR), a member of the nuclear receptor superfamily, has anti-inflammatory, lipid-lowering and hypoglycemic properties. It also inhibits renal fibrosis. Although its physiological role is not fully understood, it also plays a role in the control of diabetic nephropathy (DN). In the present study, we examined male FXR & leptin receptor double knockout mice, in which weight, blood glucose, body fat, and other indicators were monitored. After 6 months of rearing, blood and urine samples were collected and biochemical parameters were measured. Fibrosis was assessed by Masson's stain, while the assessment of the resuscitation case's condition was performed using succinate dehydrogenase (SDHA) stain immunohistochemistry, which measures aerobic respiration. Expression of molecules such as connective tissue growth factor (CTGF), SMAD family members 3 (Smad3) and 7 (Smad7), and small heterodimer partner were detected by RT-PCR and Western blotting as part of the application. FXR knockout decreased body weight and body fat in db/db mice, but increased blood glucose, urine output, and renal fibrosis. Primary mesangial cells (P-MCs) from FXR+/+ mice stimulated with transforming growth factor β1 (TGFβ1) showed significantly higher levels of related fibrosis factors, TGFβ1 and Smad3 mRNA and protein, and significantly reduced levels of Smad7. These effects were reversed by the action of FXR agonist chenodeoxycholic acid (CDCA). P-MCs from FXR-/- mice stimulated with TGFβ1 resulted in an increase in the expression and protein levels of collagen I and TGFβ1, and the addition of CDCA had no significant effect on TGFβ1 stimulation. However, compared with FXR+/+db/db mice, the rate of oxygen consumption, the rate of carbon dioxide production, and the rate of energy conversion were increased in FXR-/-db/db mice, whereas the SDHA succinate dehydrogenase, a marker enzyme for aerobic respiration, was significantly decreased. These results provide evidence that FXR plays a critical role in the regulation of mesangial cells in DN. The likely mechanism is that aberrant FXR expression activates TGFβ1, which induces extracellular matrix accumulation through the classical Smad signaling pathway, leading to mitochondrial dysfunction.

FXR Maintains the Intestinal Barrier and Stemness by Regulating CYP11A1-Mediated Corticosterone Synthesis in Biliary Obstruction Diseases.

Biliary obstruction diseases are often complicated by an impaired intestinal barrier, which aggravates liver injury. Treatment of the intestinal barrier is often neglected. To investigate the mechanism by which intestinal bile acid deficiency mediates intestinal barrier dysfunction after biliary obstruction and identify a potential therapeutic modality, we mainly used a bile duct ligation (BDL) mouse model to simulate biliary obstruction and determine the important role of the bile acid receptor FXR in maintaining intestinal barrier function and stemness. Through RNA-seq analysis of BDL and sham mouse crypts and qRT-PCR performed on intestinal epithelial-specific Fxr knockout (FxrΔIEC) and wild-type mouse crypts, we found that FXR might maintain intestinal stemness by regulating CYP11A1 expression. Given the key role of CYP11A1 during glucocorticoid production, we also found that FXR activation could promote intestinal corticosterone (CORT) synthesis by ELISA. Intestinal organoid culture showed that an FXR agonist or corticosterone increased crypt formation and organoid growth. Further animal experiments showed that corticosterone gavage treatment could maintain intestinal barrier function and stemness, decrease LPS translocation, and attenuate liver injury in BDL mice. Our study hopefully provides a new theoretical basis for the prevention of intestinal complications and alleviation of liver injury after biliary obstruction.

Alterations in the gut microbiota and serum metabolomics of spontaneous cholestasis caused by loss of FXR signal in mice.

Background: Farnesoid X receptor (FXR) is a key metabolic target of bile acids (BAs) and is also a target for drugs against several liver diseases. However, the contribution of FXR in the pathogenesis of cholestasis is still not fully understood. The purpose of this study is to provide a comprehensive insight into the metabolic properties of FXR-involved cholestasis in mice. Materials and methods: In this study, an alpha-naphthylisothiocyanate (ANIT)-induced cholestasis mouse model and FXR-/- mice were established to investigate the effect of FXR on cholestasis. The effect of FXR on liver and ileal pathology was evaluated. Simultaneously, Untargeted metabolomics combined with 16s rRNA gene sequencing analysis was applied to reveal the involvement of FXR in the pathogenesis of cholestasis. Results: The results showed that ANIT (75mg/kg) induced marked cholestasis in WT and FXR -/- mice. It is noteworthy that FXR-/- mice developed spontaneous cholestasis. Compared with WT mice, significant liver and ileal tissue damage were found. In addition, 16s rRNA gene sequencing analysis revealed gut microbiota dysbiosis in FXR-/- mice and ANIT-induced cholestasis mice. Differential biomarkers associated with the pathogenesis of cholestasis caused by FXR knockout were screened using untargeted metabolomics. Notably, Lactobacillus_ johnsonii_FI9785 has a high correlation with the differential biomarkers associated with the pathogenesis and progression of cholestasis caused by FXR knockout. Conclusion: Our results implied that the disorder of the intestinal flora caused by FXR knockout can also interfere with the metabolism. This study provides novel insights into the FXR-related mechanisms of cholestasis.

Aquaporin-8 ameliorates hepatic steatosis through farnesoid X receptor in obese mice

Aquaporin-8(AQP8), is a transmembrane channel protein that abounds in liver, which mainly promotes water transport, modulating bile acid formation. However, its role in hepatic lipid metabolism remains unclear. In this study, we found the expression of AQP8 was reduced in liver specimens of patients with NAFLD, high-fat diet (HFD)-induced mice and genetically obese db/db mice. Knockdown of AQP8 in hepatocytes exacerbated the intracellular lipid accumulation induced by free fatty acid (FFA) mixtures. In contrast, hepatic AQP8 overexpression activated farnesoid X receptor (FXR), inhibiting gene expression associated with lipogenesis, which further reduced intrahepatic triglyceride overload in obese mice. FXR knockout abrogated the ameliorating effect of AQP8 overexpression on NAFLD in mice. These findings indicate that AQP8 overexpression protects against fatty liver through activating the FXR pathway.

The essential roles of FXR in diet and age influenced metabolic changes and liver disease development: a multi-omics study

BackgroundAging and diet are risks for metabolic diseases. Bile acid receptor farnesoid X receptor (FXR) knockout (KO) mice develop metabolic liver diseases that progress into cancer as they age, which is accelerated by Western diet (WD) intake. The current study uncovers the molecular signatures for diet and age-linked metabolic liver disease development in an FXR-dependent manner.MethodsWild-type (WT) and FXR KO male mice, either on a healthy control diet (CD) or a WD, were euthanized at the ages of 5, 10, or 15 months. Hepatic transcriptomics, liver, serum, and urine metabolomics as well as microbiota were profiled.ResultsWD intake facilitated hepatic aging in WT mice. In an FXR-dependent manner, increased inflammation and reduced oxidative phosphorylation were the primary pathways affected by WD and aging. FXR has a role in modulating inflammation and B cell-mediated humoral immunity which was enhanced by aging. Moreover, FXR dictated neuron differentiation, muscle contraction, and cytoskeleton organization in addition to metabolism. There were 654 transcripts commonly altered by diets, ages, and FXR KO, and 76 of them were differentially expressed in human hepatocellular carcinoma (HCC) and healthy livers. Urine metabolites differentiated dietary effects in both genotypes, and serum metabolites clearly separated ages irrespective of diets. Aging and FXR KO commonly affected amino acid metabolism and TCA cycle. Moreover, FXR is essential for colonization of age-related gut microbes. Integrated analyses uncovered metabolites and bacteria linked with hepatic transcripts affected by WD intake, aging, and FXR KO as well as related to HCC patient survival.ConclusionFXR is a target to prevent diet or age-associated metabolic disease. The uncovered metabolites and microbes can be diagnostic markers for metabolic disease.

Early Deregulation of Cholangiocyte NR0B2 During Primary Sclerosing Cholangitis.

Primary sclerosing cholangitis (PSC) is a probable autoimmune liver disease characterized by persistent and progressive biliary inflammation that leads to biliary infection, cirrhosis, or cholangiocarcinoma. Genome-wide omics data are scarce regarding this severe disease. MEDLINE database gene prioritization by text mining (biliary inflammation, biliary fibrosis, biliary stasis) was integrated in distinct omics data: (1) PSC liver transcriptome training and validation cohorts, (2) farnesoid X receptor (FXR) mice liver transcriptome subjected to an FXR agonist or FXR knockout mice; (3) liver single-cell transcriptome of the Abcb4-/- mice model of PSC. A liver molecular network highlighted the involvement of nuclear receptor subfamily 0 group B member 2 (NR0B2) and its associated nuclear receptor FXR in a metabolic cascade that may influence the immune response. NR0B2 upregulation in PSC liver was independent of gender, age, body mass index, liver fibrosis, and PSC complications. Heterogeneity of NR0B2 upregulation was found in cholangiocyte cell types in which the NR0B2-based cell fate decision revealed the involvement of several metabolic pathways for detoxification (sulfur, glutathione derivative, and monocarboxylic acid metabolisms). Genes potentially implicated in carcinogenesis were also discovered on this cholangiocyte trajectory: GSTA3, inhibitor of DNA binding 2, and above all, TMEM45A, a transmembrane molecule from the Golgi apparatus considered as oncogenic in several cancers. By revisiting PSC through PubMed data mining, we evidenced the early cholangiocyte deregulation of NR0B2, highlighting a metabolic and premalignant reprogramming of the cholangiocyte cell type. The therapeutic targeting of NR0B2 could potentiate that of FXR and enable action on early events of the disease and prevent its progression.

Regulation of Chromatin Accessibility by the Farnesoid X Receptor Is Essential for Circadian and Bile Acid Homeostasis In Vivo.

The Farnesoid X Receptor (FXR) belongs to the nuclear receptor superfamily and is an essential bile acid (BA) receptor that regulates the expression of genes involved in the metabolism of BAs. FXR protects the liver from BA overload, which is a major etiology of hepatocellular carcinoma. Herein, we investigated the changes in gene expression and chromatin accessibility in hepatocytes by performing RNA-seq in combination with the Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) using a novel FXR knockout mouse model (Fxrex5Δ: Nr1h4ex5Δ/ex5Δ) generated through CRISPR/Cas9. Consistent with previous Fxr knockout models, we found that Fxrex5Δ mice develop late-onset HCC associated with increased serum and hepatic BAs. FXR deletion was associated with a dramatic loss of chromatin accessibility, primarily at promoter-associated transcription factor binding sites. Importantly, several genes involved in BA biosynthesis and circadian rhythm were downregulated following loss of FXR, also displayed reduced chromatin accessibility at their promoter regions. Altogether, these findings suggest that FXR helps to maintain a transcriptionally active state by regulating chromatin accessibility through its binding and recruitment of transcription factors and coactivators.