Obeticholic acid ameliorates sepsis-induced renal mitochondrial damage by inhibiting the NF-κb signaling pathway.

Acute kidney injury (AKI), a common complication of sepsis, might be caused by overactivated inflammation, mitochondrial damage, and oxidative stress. However, the mechanisms underlying sepsis-induced AKI (SAKI) have not been fully elucidated, and there is a lack of effective therapies for AKI. To this end, this study aimed to investigate whether obeticholic acid (OCA) has a renoprotective effect on SAKI and to explore its mechanism of action. Through bioinformatics analysis, our study confirmed that the mitochondria might be a critical target for the treatment of SAKI. Thus, a septic rat model was established by cecal ligation puncture (CLP) surgery. Our results showed an evoked inflammatory response via the NF-κB signaling pathway and NLRP3 inflammasome activation in septic rats, which led to mitochondrial damage and oxidative stress. OCA, an Farnesoid X Receptor (FXR) agonist, has shown anti-inflammatory effects in numerous studies. However, the effects of OCA on SAKI remain unclear. In this study, we revealed that pretreatment with OCA can inhibit the inflammatory response by reducing the synthesis of proinflammatory factors (such as IL-1ß and NLRP3) via blocking NF-κB and alleviating mitochondrial damage and oxidative stress in the septic rat model. Overall, this study provides insight into the excessive inflammation-induced SAKI caused by mitochondrial damage and evidence for the potential use of OCA in SAKI treatment.

Computational study of novel natural agonists targeting farnesoid X receptor.

The farnesoid X receptor (FXR) is a crucial therapeutic target for treating non-alcoholic steatohepatitis (NASH). Although obeticholic acid (OCA) as a FXR agonist presents good efficacy, the safety data such as severe pruritus should be carefully considered. To discover new medications, we screen and choose the optimal compounds from ZINC15 database that may agonistically interact with FXR. We utilized the DS19 software to assist us in conducting the computer-aided structure based virtual screening to discover potential FXR agonists. After LibDock scores were determined by screening, their absorption, distribution, metabolism, excretion and toxicity predictions were examined. To determine the binding affinity between the chosen drugs and FXR, molecule docking was utilized. Molecular dynamics simulation was utilized to evaluate the stabilization of the ligand-FXR complex in its native environment. Higher binding affinity and stability with FXR were observed for ZINC000013374322 and ZINC000006036327, as two novel natural compounds, with lower rodent carcinogenicity, Ames mutagenicity, no hepatotoxicity and non-inhibitors of CYP2D6. They could stably exist in the environment, possess favorable potential energy and exert pharmacological effects at lower doses. Furthermore, ZINC000006036327 had lower skin irritancy and sensitization potential compared to OCA, also suggest the possibility of improved skin itching occurrence. ZINC000013374322 and ZINC000006036327 were found to be the best leading compounds to be FXR agonists. They are chosen as safe candidates for FXR target medicine, which play comparable pharmacological effects at lower doses.

Obeticholic acid attenuates the intestinal barrier disruption in a rat model of short bowel syndrome.

BACKGROUND: Short bowel syndrome (SBS) features nutrients malabsorption and impaired intestinal barrier. Patients with SBS are prone to sepsis, intestinal flora dysbiosis and intestinal failure associated liver disease. Protecting intestinal barrier and preventing complications are potential strategies for SBS treatment. This study aims to investigate the effects of farnesoid X receptor (FXR) agonist, obeticholic acid (OCA), have on intestinal barrier and ecological environment in SBS. METHODS AND RESULTS: Through testing the small intestine and serum samples of patients with SBS, impaired intestinal barrier was verified, as evidenced by reduced expressions of intestinal tight junction proteins (TJPs), increased levels of apoptosis and epithelial cell damage. The intestinal expressions of FXR and related downstream molecules were decreased in SBS patients. Then, global FXR activator OCA was used to further dissect the potential role of the FXR in a rat model of SBS. Low expressions of FXR-related molecules were observed on the small intestine of SBS rats, along with increased proinflammatory factors and damaged barrier function. Furthermore, SBS rats possessed significantly decreased body weight and elevated death rate. Supplementation with OCA mitigated the damaged intestinal barrier and increased proinflammatory factors in SBS rats, accompanied by activated FXR-related molecules. Using 16S rDNA sequencing, the regulatory role of OCA on gut microbiota in SBS rats was witnessed. LPS stimulation to Caco-2 cells induced apoptosis and overexpression of proinflammatory factors in vitro. OCA incubation of LPS-pretreated Caco-2 cells activated FXR-related molecules, increased the expressions of TJPs, ameliorated apoptosis and inhibited overexpression of proinflammatory factors. CONCLUSIONS: OCA supplementation could effectively ameliorate the intestinal barrier disruption and inhibit overexpression of proinflammatory factors in a rat model of SBS and LPS-pretreated Caco-2 cells. As a selective activator of FXR, OCA might realize its protective function through FXR activation.

Biotransformation of chenodeoxycholic acid by human intestinal fungi and the agonistic effects on FXR.

Bile acids play a vital role in modulating host metabolism, with chenodeoxycholic acid (CDCA) standing out as a primary bile acid that naturally activates farnesoid X receptor (FXR). In this study, we investigated the microbial transformations of CDCA by seven human intestinal fungal species. Our findings revealed that hydroxylation and dehydrogenation were the most prevalent metabolic pathways. Incubation of CDCA with Rhizopus microspores (PT2906) afforded eight undescribed compounds (6-13) alongside five known analogs (1-5) which were elucidated by HRESI-MS and NMR data. Notably, compounds 8, 12 and 13 exhibited an inhibitory effect on FXR in contrast to the FXR activation observed with CDCA in vitro assays. This study shone a light on the diverse transformations of CDCA by intestinal fungi, unveiling potential modulators of FXR activity with implications for host metabolism.

A Short Review on Obeticholic Acid: An Effective Modulator of Farnesoid X Receptor.

Farnesoid X receptor (FXR) was identified as an orphan nuclear receptor resembling the steroid receptor in the late '90s. Activation of FXR is a crucial step in many physiological functions of the liver. A vital role of FXR is impacting the amount of bile acids in the hepatocytes, which it performs by reducing bile acid synthesis, stimulating the bile salt export pump, and inhibiting its enterohepatic circulation, thus protecting the hepatocytes against the toxic accumulation of bile acids. Furthermore, FXR mediates bile acid biotransformation in the intestine, liver regeneration, glucose hemostasis, and lipid metabolism. In this review, we first discuss the mechanisms of the disparate pleiotropic actions of FXR agonists. We then delve into the pharmacokinetics of Obeticholic acid (OCA), the first-in-class selective, potent FXR agonist. We additionally discuss the clinical journey of OCA in humans, its current evidence in various human diseases, and its plausible roles in the future.

Obeticholic Acid Inhibit Mitochondria Dysfunction Via Regulating ERK1/2-DRP Pathway to Exert Protective Effect on Lipopolysaccharide-Induced Myocardial Injury.

Farnesoid X receptor (FXR) plays critical regulatory roles in cardiovascular physiology/pathology. However, the role of FXR agonist obeticholic acid (OCA) in sepsis-associated myocardial injury and underlying mechanisms remain unclear. C57BL/6J mice are treated with OCA before lipopolysaccharide (LPS) administration. The histopathology of the heart and assessment of FXR expression and mitochondria function are performed. To explore the underlying mechanisms, H9c2 cells, and primary cardiomyocytes are pre-treated with OCA before LPS treatment, and extracellular signal-regulated protein kinase (ERK) inhibitor PD98059 is used. LPS-induced myocardial injury in mice is significantly improved by OCA pretreatment. Mechanistically, OCA pretreatment decreased reactive oxygen species (ROS) levels and blocked the loss of mitochondrial membrane potential (ΔΨm) in cardiomyocytes. The expression of glutathione peroxidase 1 (GPX1), superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), and nuclear factor erythroid 2-related factor 2 (NRF-2) increased in the case of OCA pretreatment. In addition, OCA improved mitochondria respiratory chain with increasing Complex I expression and decreasing cytochrome C (Cyt-C) diffusion. Moreover, OCA pretreatment inhibited LPS-induced mitochondria dysfunction via suppressing ERK1/2-DRP signaling pathway. FXR agonist OCA inhibits LPS-induced mitochondria dysfunction via suppressing ERK1/2-DRP signaling pathway to protect mice against LPS-induced myocardial injury.

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.

Investigational farnesoid X receptor agonists for the treatment of primary biliary cholangitis.

INTRODUCTION: Up to 40% of Primary biliary cholangitis (PBC) patients have a suboptimal response to Ursodeoxycholic acid (UDCA). Close to half of such patients show a remarkable improvement when additionally treated with Obeticholic acid (OCA) but have a dose-dependent increase of pruritus. This relative success of OCA, a first-in-class Farnesoid receptor (FXR) agonist, has positioned FXR as an attractive target for drug development. Novel candidates have since emerged, providing hope for this subgroup of patients who lack effective and safe treatments. AREAS COVERED: We discussed the role of bile acids in PBC pathogenesis and how the FXR agonists provide therapeutic value by affecting bile acid synthesis and transport. Novel FXR agonists undergoing pre-clinical and clinical trials for PBC were enlisted via literature search by including the terms 'FXR agonists,' 'FXR PBC,' 'PBC clinical trials' on PubMed, MEDLINE via Ovid, and Clinicaltrials.gov. EXPERT OPINION: Novel FXR agonists currently under investigation for PBC improve the disease surrogate markers in early trials. However, as with OCA, pruritus remains a concern with the newer drugs despite targeted chemical modifications to increase FXR specificity. Directing future resources toward studying the molecular mechanisms behind pruritus may lead to better drug design and efficacious yet safer drugs.

The function of the gut microbiota-bile acid-TGR5 axis in diarrhea-predominant irritable bowel syndrome.

Imbalanced gut microbiota (GM) and abnormal fecal bile acid (BA) are thought to be the key factors for diarrhea-predominant irritable bowel syndrome (IBS-D), but the underlying mechanism remains unclear. Herein, we explore the influence of the GM-BA-Takeda G-protein-coupled receptor 5 (TGR5) axis on IBS-D. Twenty-five IBS-D patients and fifteen healthy controls were recruited to perform BA-related metabolic and metagenomic analyses. Further, the microbiota-humanized IBS-D rat model was established by fecal microbial transplantation (FMT) to investigate the GM-BA-TGR5 axis effects on the colonic barrier and visceral hypersensitivity (VH) in IBS-D. Finally, we used chenodeoxycholic acid (CDCA), an important BA screened out by metabolome, to evaluate whether it affected diarrhea and VH via the TGR5 pathway. Clinical research showed that GM associated with bile salt hydrolase (BSH) activity such as Bacteroides ovatus was markedly reduced in the GM of IBS-D, accompanied by elevated total and primary BA levels. Moreover, we found that CDCA not only was increased as the most important primary BA in IBS-D patients but also could induce VH through upregulating TGR5 in the colon and ileum of normal rats. TGR5 inhibitor could reverse the phenotype, depression-like behaviors, pathological change, and level of fecal BSH in a microbiota-humanized IBS-D rat model. Our findings proved that human-associated FMT could successfully induce the IBS-D rat model, and the imbalanced GM-BA-TGR5 axis may promote colonic mucosal barrier dysfunction and enhance VH in IBS-D. IMPORTANCE: Visceral hypersensitivity and intestinal mucosal barrier damage are important factors that cause abnormal brain-gut interaction in diarrhea-predominant irritable bowel syndrome (IBS-D). Recently, it was found that the imbalance of the gut microbiota-bile acid axis is closely related to them. Therefore, understanding the structure and function of the gut microbiota and bile acids and the underlying mechanisms by which they shape visceral hypersensitivity and mucosal barrier damage in IBS-D is critical. An examination of intestinal feces from IBS-D patients revealed that alterations in gut microbiota and bile acid metabolism underlie IBS-D and symptom onset. We also expanded beyond existing knowledge of well-studied gut microbiota and bile acid and found that Bacteroides ovatus and chenodeoxycholic acid may be potential bacteria and bile acid involved in the pathogenesis of IBS-D. Moreover, our data integration reveals the influence of the microbiota-bile acid-TGR5 axis on barrier function and visceral hypersensitivity.

Edaravone and obeticholic acid protect against cisplatin-induced heart toxicity by suppressing oxidative stress and inflammation and modulating Nrf2, TLR4/p38MAPK, and JAK1/STAT3/NF-κB signals.

Cardiotoxicity is a significant adverse effect of cisplatin (CIS) that necessitates extensive medical care. The current study examines the cardioprotective effects of edaravone (EDV), obeticholic acid (OCA), and their combinations on CIS-induced cardiac damage. Rats were allocated into five groups: the normal control group, the remaining four groups received CIS (7.5 mg/kg, i.p.) as a single dose on the fifth day and were assigned to CIS, OCA (10 mg/kg/day) + CIS, EDV (20 mg/kg/day) + CIS, and the (EDV + OCA) + CIS group. Compared to the CIS-treated group, co-treating rats with EDV, OCA, or their combinations significantly decreased ALP, AST, LDH, CK-MB, and troponin-I serum levels and alleviated histopathological heart abnormalities. Biochemically, EDV, OCA, and EDV plus OCA administration mitigated cardiac oxidative stress as indicated by a marked decrease in heart MDA content with a rise in cardiac antioxidants SOD and GSH associated with upregulating Nrf2, PPARγ, and SIRT1 expression. Besides, it dampened inflammation by decreasing cardiac levels of TNF-α, IL-1ß, and IL-6, mediated by suppressing NF-κB, JAK1/STAT3, and TLR4/p38MAPK signal activation. Notably, rats co-administered with EDV plus OCA showed noticeable protection that exceeded that of EDV and OCA alone. In conclusion, our study provided that EDV, OCA, and their combinations effectively attenuated CIS-induced cardiac intoxication by activating Nrf2, PPARγ, and SIRT1 signals and downregulating NF-κB, JAK1/STAT3, and TLR4/p38MAPK signals.

FXR agonists for MASH therapy: Lessons and perspectives from obeticholic acid.

Nonalcoholic fatty liver disease, also called metabolic dysfunction-associated steatotic liver disease, is the most common liver disease worldwide and has no approved pharmacotherapy. Due to its beneficial effects on metabolic regulation, inflammation suppression, cell death prevention, and fibrogenesis inhibition, farnesoid X receptor (FXR) is widely accepted as a promising therapeutic target for nonalcoholic steatosis (NASH) or called metabolic dysfunction-associated steatohepatitis (MASH). Many FXR agonists have been developed for NASH/MASH therapy. Obeticholic acid (OCA) is the pioneering frontrunner FXR agonist and the first demonstrating success in clinical trials. Unfortunately, OCA did not receive regulatory approval as a NASH pharmacotherapy because its moderate benefits did not outweigh its safety risks, which may cast a shadow over FXR-based drug development for NASH/MASH. This review summarizes the milestones in the development of OCA for NASH/MASH and discuss its limitations, including moderate hepatoprotection and the undesirable side effects of dyslipidemia, pruritus, cholelithiasis, and liver toxicity risk, in depth. More importantly, we provide perspectives on FXR-based therapy for NASH/MASH, hoping to support a successful bench-to-clinic transition.

Dietary chenodeoxycholic acid attenuates high-fat diet-induced growth retardation, lipid accumulation and bile acid metabolism disorder in the liver of yellow catfish Pelteobagrus fulvidraco.

This experiment was conducted to investigate whether dietary chenodeoxycholic acid (CDCA) could attenuate high-fat (HF) diet-induced growth retardation, lipid accumulation and bile acid (BA) metabolism disorder in the liver of yellow catfish Pelteobagrus fulvidraco. Yellow catfish (initial weight: 4·40 (sem 0·08) g) were fed four diets: the control (105·8 g/kg lipid), HF diet (HF group, 159·6 g/kg lipid), the control supplemented with 0·9 g/kg CDCA (CDCA group) and HF diet supplemented with 0·9 g/kg CDCA (HF + CDCA group). CDCA supplemented in the HF diet significantly improved growth performance and feed utilisation of yellow catfish (P < 0·05). CDCA alleviated HF-induced increment of hepatic lipid and cholesterol contents by down-regulating the expressions of lipogenesis-related genes and proteins and up-regulating the expressions of lipololysis-related genes and proteins. Compared with the control group, CDCA group significantly reduced cholesterol level (P < 0·05). CDCA significantly inhibited BA biosynthesis and changed BA profile by activating farnesoid X receptor (P < 0·05). The contents of CDCA, taurochenodeoxycholic acid and glycochenodeoxycholic acid were significantly increased with the supplementation of CDCA (P < 0·05). HF-induced elevation of cholic acid content was significantly attenuated by the supplementation of CDCA (P < 0·05). Supplementation of CDCA in the control and HF groups could improve the liver antioxidant capacity. This study proved that CDCA could improve growth retardation, lipid accumulation and BA metabolism disorder induced by HF diet, which provided new insight into understanding the physiological functions of BA in fish.

FXR agonists INT-787 and OCA increase RECK and inhibit liver steatosis and inflammation in diet-induced ob/ob mouse model of NASH.

BACKGROUND AND AIMS: We have previously shown in a model of hepatic ischaemia/reperfusion injury that the farnesoid X receptor (FXR) agonist obeticholic acid (OCA) restores reversion-inducing-cysteine-rich protein with Kazal motifs (RECK), an inverse modulator of metalloproteases (MMPs) and inhibitor of the sheddases ADAM10 and ADAM17 involved in inflammation and fibrogenesis. Here, the effects of FXR agonists OCA and INT-787 on hepatic levels of RECK, MMPs, ADAM10 and ADAM17 were compared in a diet-induced ob/ob mouse model of non-alcoholic steatohepatitis (NASH). METHODS: Lep ob/ob NASH mice fed a high-fat diet (HFD) or control diet (CD) for 9 weeks (wks) were treated with OCA or INT-787 0.05% dosed via HFD admixture (30 mg/kg/day) or HFD for further 12 wks. Serum alanine transaminase (ALT) and inflammatory cytokines, liver RECK, MMP-2 and MMP-9 activity as well as ADAM10, ADAM17, collagen deposition (Sirius red), hepatic stellate cell activation (α-SMA) and pCK+ reactive biliary cells were quantified. RESULTS: Only INT-787 significantly reduced serum ALT, IL-1ß and TGF-ß. A downregulation of RECK expression and protein levels observed in HFD groups (at 9 and 21 wks) was counteracted by both OCA and INT-787. HFD induced a significant increase in liver MMP-2 and MMP-9; OCA administration reduced both MMP-2 and MMP-9 while INT-787 markedly reduced MMP-2 expression. OCA and INT-787 reduced both ADAM10 and ADAM17 expression and number of pCK+ cells. INT-787 was superior to OCA in decreasing collagen deposition and α-SMA levels. CONCLUSION: INT-787 is superior to OCA in controlling specific cell types and clinically relevant anti-inflammatory and antifibrotic molecular mechanisms in NASH.

Bile acid metabolomics identifies chenodeoxycholic acid as a therapeutic agent for pancreatic necrosis.

Bile acids are altered and associated with prognosis in patients with acute pancreatitis (AP). Here, we conduct targeted metabolomic analyses to detect bile acids changes in patients during the acute (n = 326) and the recovery (n = 133) phases of AP, as well as in healthy controls (n = 60). Chenodeoxycholic acid (CDCA) decreases in the acute phase, increases in the recovery phase, and is associated with pancreatic necrosis. CDCA and its derivative obeticholic acid exhibit a protective effect against acinar cell injury in vitro and pancreatic necrosis in murine models, and RNA sequencing reveals that the oxidative phosphorylation pathway is mainly involved. Moreover, we find that overexpression of farnesoid X receptor (FXR, CDCA receptor) inhibits pancreatic necrosis, and interfering expression of FXR exhibits an opposite phenotype in mice. Our results possibly suggest that targeting CDCA is a potential strategy for the treatment of acinar cell necrosis in AP, but further verification is needed.

The implication of LPS/TLR4 and FXR receptors in hepatoprotective efficacy of indole-3-acetic acid and chenodeoxycholic acid.

AIM: Valproic acid (VPA) belongs to the first-generation antiepileptic drugs, yet its prolonged use can cause life-threatening liver damage. The importance of our study is to investigate the protective effect of indole-3-acetic acid (IAA), chenodeoxycholic acid (CDCA) and their combination on VPA-induced liver injury focusing on lipopolysaccharides (LPS)/toll-like receptor 4 (TLR4) pathway and farnesoid X receptor (FXR). METHODS: Thirty rats were randomly assigned into five groups, normal control group, VPA group received 500 mg/kg of VPA intraperitoneally. The remaining groups were orally treated with either 40 mg/kg of IAA, 90 mg/kg of CDCA, or a combination of both, along with VPA. All treatments were administered one hour after the administration of VPA for three weeks. KEY FINDINGS: VPA group showed significant elevations in the liver weight/body weight ratio, serum aminotransferases, triglyceride, and total cholesterol levels. Hepatic glutathione (GSH) level and superoxide dismutase (SOD) activity were significantly decreased, while malondialdehyde (MDA) level, tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1ß), lipopolysaccharide (LPS) and caspase 3 were significantly increased. Likewise, immunohistochemical analysis revealed that TLR4 expression was elevated, whereas FXR expression was downregulated in hepatocytes. IAA substantially ameliorated all previously altered parameters, whereas CDCA treatment showed a partial improvement compared to IAA. Surprisingly, combination therapy of IAA with CDCA showed an additive effect only in the hepatic expression of TLR4 and FXR proteins. SIGNIFICANCE: IAA could be a promising protective agent against VPA-induced liver injury.

Farnesoid X receptor activation inhibits pancreatic carcinogenesis.

Farnesoid X receptor (FXR), a member of the nuclear receptor superfamily that controls bile acid (BA) homeostasis, has also been proposed as a tumor suppressor for breast and liver cancer. However, its role in pancreatic ductal adenocarcinoma (PDAC) tumorigenesis remains controversial. We recently found that FXR attenuates acinar cell autophagy in chronic pancreatitis resulting in reduced autophagy and promotion of pancreatic carcinogenesis. Feeding Kras-p48-Cre (KC) mice with the BA chenodeoxycholic acid (CDCA), an FXR agonist, attenuated pancreatic intraepithelial neoplasia (PanIN) progression, reduced cell proliferation, neoplastic cells and autophagic activity, and increased acinar cells, elevated pro-inflammatory cytokines and chemokines, with a compensatory increase in the anti-inflammatory response. Surprisingly, FXR-deficient KC mice did not show any response to CDCA, suggesting that CDCA attenuates PanIN progression and decelerate tumorigenesis in KC mice through activating pancreatic FXR. FXR is activated in pancreatic cancer cell lines in response to CDCA in vitro. FXR levels were highly increased in adjuvant and neoadjuvant PDAC tissue compared to healthy pancreatic tissue, indicating that FXR is expressed and potentially activated in human PDAC. These results suggest that BA exposure activates inflammation and suppresses autophagy in KC mice, resulting in reduced PanIN lesion progression. These data suggest that activation of pancreatic FXR has a protective role by reducing the growth of pre-cancerous PDAC lesions in response to CDCA and possibly other FXR agonists.

Farnesoid X receptor represses human sulfotransferase 1A3 expression through direct binding to the promoter.

Human sulfotransferases 1A3 (SULT1A3) has received particular interest, due to their functions of catalyzing the sulfonation of numerous phenolic substrates, including bioactive endogenous molecules and therapeutic agents. However, the regulation of SULT1A3 expression and the underlying mechanism remain unclear. Here, we aimed to investigate the regulation effects of bile acid-activated farnesoid X receptor (FXR) on SULT1A3 expression, and to shed light on the mechanism thereof. Our results demonstrated that FXR agonists (CDCA and GW4064) significantly inhibit the expression of SULT1A3 at mRNA and protein levels. In addition, overexpression of FXR led to decrease in SULT1A3 expression and knockdown of FXR significantly induced the expression of SULT1A3 in protein and mRNA levels, confirming that FXR expression manifestly showed negative regulatory effect on basal SULT1A3 expression. Furthermore, a combination of luciferase reporter gene and CHIP assays showed that FXR repressed SULT1A3 transcription through direct binding to the region at base pair positions -664 to -654. In conclusion, this study for the first time confirmed FXR was a negative transcriptional regulator of human SULT1A3 enzyme.

Bile salts and proinflammatory cytokines inhibit MCT1-mediated cellular uptake of butyrate and interfere with its antiproliferative properties.

Butyrate (BT) is important in the prevention and inhibition of colorectal cancer (CRC). Inflammatory bowel disease, a risk factor for CRC, is associated with higher levels of proinflammatory cytokines and bile acids. The aim of this work was to investigate the interaction of these compounds in inhibiting BT uptake by Caco-2 cells, as a mechanism contributing to the link between IBD and CRC. TNF-α, IFN-γ, chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) markedly reduce 14C-BT uptake. All these compounds appear to inhibit MCT1-mediated BT cellular uptake at a posttranscriptional level, and, because their effect is not additive, they are most probably inhibiting MCT1 by a similar mechanism. Correspondingly, the antiproliferative effect of BT (MCT1-dependent) and of the proinflammatory cytokines and CDCA were not additive. In contrast, the cytotoxic effect of BT (MCT1-independent) and of the proinflammatory cytokines and CDCA were additive. In conclusion, proinflammatory cytokines (TNF-α and IFN-γ) and bile acids (DCA and CDCA) inhibit MCT1-mediated BT cellular uptake. These proinflammatory cytokines and CDCA were found to interfere with the antiproliferative effect of BT, mediated by an inhibitory effect upon MCT1-mediated cellular uptake of BT.

Chenodeoxycholic acid regulates fibroblast growth factor 23 gene expression via estrogen-related receptor γ in human hepatoma Huh7 cells.

Fibroblast growth factor 23 (FGF23) is a glycoprotein that belongs to the FGF19 subfamily and participates in phosphate and vitamin D homeostasis. Chenodeoxycholic acid (CDCA), one of the primary bile acids, is reported to induce the secretion of FGF19 subfamily members, FGF21 and FGF19, in hepatocytes. However, whether and how CDCA influences FGF23 gene expression are largely unknown. Thus, we performed real-time polymerase chain reaction and Western blot analyses to determine the mRNA and protein expression levels of FGF23 in Huh7 cells. CDCA upregulated estrogen-related receptor γ (ERRγ) alongside FGF23 mRNA and protein levels, while, the knockdown of ERRγ ablated the induction effect of CDCA on FGF23 expression. Promoter studies showed that CDCA-induced FGF23 promoter activity occurred partly through ERRγ binding directly to the ERR response element (ERRE) in the human FGF23 gene promoter. Finally, the inverse agonist of ERRγ, GSK5182 inhibited the induction of FGF23 by CDCA. Overall, our results revealed the mechanism of CDCA-mediated FGF23 gene upregulation in the human hepatoma cell line. Moreover, the ability of GSK5182 to reduce CDCA-induced FGF23 gene expression might represent a therapeutic strategy to control abnormal FGF23 induction in conditions that involve elevated levels of bile acids, such as nonalcoholic fatty liver disease and biliary atresia.

Gut microbiome determines therapeutic effects of OCA on NAFLD by modulating bile acid metabolism.

Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease, had no approved pharmacological agents yet. Obeticholic acid (OCA), a novel bile acid derivative, was demonstrated to ameliorate NAFLD-related manifestations. Regarding the role of gut-liver axis in liver disease development, this study aimed to explore the potential role of gut microbiota in the treatment of OCA in NAFLD mice induced by the high-fat diet (HFD). Antibiotic-induced microbiome depletion (AIMD) and fecal microbiota transplantation (FMT) confirmed the critical role of gut microbiota in OCA treatment for NAFLD by effectively alleviating histopathological lesions and restoring liver function impaired by HFD. Metagenomic analysis indicated that OCA intervention in HFD mice remarkably increased the abundance of Akkermansia muciniphila, Bifidobacterium spp., Bacteroides spp., Alistipes spp., Lactobacillus spp., Streptococcus thermophilus, and Parasutterella excrementihominis. Targeted metabolomics analysis indicated that OCA could modulate host bile acids pool by reducing levels of serum hydrophobic cholic acid (CA) and chenodeoxycholic acid (CDCA), and increasing levels of serum-conjugated bile acids, such as taurodeoxycholic acid (TDCA) and tauroursodesoxycholic acid (TUDCA) in the HFD-fed mice. Strong correlations were observed between differentially abundant microbes and the shifted bile acids. Furthermore, bacteria enriched by OCA intervention exhibited much greater potential in encoding 7alpha-hydroxysteroid dehydrogenase (7α-HSDs) producing secondary bile acids rather than bile salt hydrolases (BSHs) mainly responsible for primary bile acid deconjugation. In conclusion, this study demonstrated that OCA intervention altered gut microbiota composition with specially enriched gut microbes modulating host bile acids, thus effectively alleviating NAFLD in the mice.