Mechanism of tissue-specific farnesoid X receptor in suppressing the expression of genes in bile-acid synthesis in mice

Perfluorooctanoic acid (PFOA) and its alternative perfluorobutanoic acid (PFBA) alter hepatic bile acid profiles via different pathways

The disruption of per- and polyfluoroalkyl substances (PFASs) on bile acid (BA) homeostasis has raised public concerns, making the evaluation of their effects and underlying mechanisms a high priority. Although the use of perfluorooctanoic acid (PFOA) has been restricted, it remains a widespread legacy PFAS in the environment. Concurrently, the use of its prevalent short-chain alternative, perfluorobutanoic acid (PFBA), is increasing, yet the toxicity assessment of PFBA remains inadequate. In this study, C57BL/6N mice were exposed to PFOA and PFBA (0.4 or 10 mg/kg body weight) by gavage for 28 days. The results showed that both PFOA and PFBA significantly increased hepatic weight, although PFBA exhibited lower bioaccumulation than PFOA in the liver. Targeted metabolomics revealed that PFOA significantly decreased total BA levels and altered their composition. Conversely, PFBA, without significantly altering total BA levels, notably changed their composition, such as increasing the proportion of cholic acid. Further investigations using in vivo and in vitro assays suggested that PFOA inhibited the expression of Cyp7A1, a key BA synthetase, potentially via PPARα activation, thereby reducing BA levels. In contrast, PFBA enhanced Cyp7A1 expression, associated with the inhibition of intestinal Farnesoid X receptor-fibroblast growth factor 15 (FXR-FGF15) pathway. This study evaluated the differences in the BA-interfering effects of PFOA and PFBA and shed light on the potential mechanisms, which will provide new insights into the health risks of legacy PFASs and their alternatives.

How bile acids and the microbiota interact to shape host immunity

Bile acids are increasingly appearing in the spotlight owing to their novel impacts on various host processes. Similarly, there is growing attention on members of the microbiota that are responsible for bile acid modifications. With recent advances in technology enabling the discovery and continued identification of microbially conjugated bile acids, the chemical complexity of the bile acid landscape in the body is increasing at a rapid pace. In this Review, we summarize our current understanding of how bile acids and the gut microbiota interact to modulate immune responses during homeostasis and disease, with a particular focus on the gut.

Bile Acid Signaling in Metabolic and Inflammatory Diseases and Drug Development

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates biliary secretion of lipids, endogenous metabolites, and xenobiotics. In intestine, bile acids facilitate the digestion and absorption of dietary lipids and fat-soluble vitamins. Through activation of nuclear receptors and G protein-coupled receptors and interaction with gut microbiome, bile acids critically regulate host metabolism and innate and adaptive immunity and are involved in the pathogenesis of cholestasis, metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, type-2 diabetes, and inflammatory bowel diseases. Bile acids and their derivatives have been developed as potential therapeutic agents for treating chronic metabolic and inflammatory liver diseases and gastrointestinal disorders. SIGNIFICANCE STATEMENT: Bile acids facilitate biliary cholesterol solubilization and dietary lipid absorption, regulate host metabolism and immunity, and modulate gut microbiome. Targeting bile acid metabolism and signaling holds promise for treating metabolic and inflammatory diseases.

Nogo-B inhibition facilitates cholesterol metabolism to reduce hypercholesterolemia

The strategy of lowering cholesterol levels by promoting cholesterol excretion is still lacking, and few molecular targets act on multiple cholesterol metabolic processes. In this study, we find that Nogo-B deficiency/inhibition simultaneously promotes hepatic uptake of cholesterol and cholesterol excretion. Nogo-B deficiency decreases cholesterol levels by activating ATP-binding cassette transporters (ABCs), apolipoprotein E (ApoE), and low-density lipoprotein receptor (LDLR) expression. We discover that Nogo-B interacts with liver X receptor α (LXRα), and Nogo-B deficiency inhibits ubiquitination degradation of LXRα, thereby enhancing its function on cholesterol excretion. Decreased cellular cholesterol levels further activate SREBP2 and LDLR expression, thereby promoting hepatic uptake of cholesterol. Nogo-B inhibition decreases atherosclerotic plaques and cholesterol levels in mice, and Nogo-B levels are correlated to cholesterol levels in human plasma. In this study, Nogo-B deficiency/inhibition not only promotes hepatic uptake of blood cholesterol but also facilitates cholesterol excretion. This study reports a strategy to lower cholesterol levels by inhibiting Nogo-B expression to promote hepatic cholesterol uptake and cholesterol excretion.

Farnesoid X receptor modulator 12β-(m-methyl-benzoyl)-11,12-dihydro oleanolic acid represses liver fibrosis by inhibiting ERK/p38 signaling pathways

Liver fibrosis is a common pathological process in the progression of several chronic liver diseases to cirrhosis and hepatocellular carcinoma. Therefore, the development of medications that can repress the progress of liver fibrosis is essential. We discovered that initially, 12β-(m-methyl-benzoyl)-11,12-dihydro oleanolic acid (12d-OA), a farnesoid X receptor (FXR) modulator, possessed potential anti-fibrotic properties. Through an in-depth study, we revealed that 12d-OA not only inhibited the expression of fibrogenic markers in the LX-2 cells and HSC-T6 cells but also exhibited significant protective effects against liver injury and liver fibrosis in bile duct ligation (BDL) rats. Further exploration of its molecular mechanism indicated that 12d-OA exerted antifibrotic activity by inhibiting the extracellular signal-regulated kinase (ERK)/stress-activated protein kinase (p38) signaling pathways. Consequently, the great effects of 12d-OA in vitro and in vivo suggest that it may be a good candidate for liver fibrosis.

Abcb4-defect cholangitis mouse model with hydrophobic bile acid composition by in vivo liver-specific gene deletion

Progressive familial intrahepatic cholestasis (PFIC) is a liver disease that occurs during childhood and requires liver transplantation. ABCB4 is localized along the canalicular membranes of hepatocytes, transports phosphatidylcholine into bile, and its mutation causes PFIC3. Abcb4 gene-deficient mice established as animal models of PFIC3 exhibit cholestasis-induced liver injury. However, their phenotypes are often milder than those of human PFIC3, partly because of the existence of large amounts of less toxic hydrophilic bile acids synthesized by the rodent-specific enzymes Cyp2c70 and Cyp2a12. Mice with double deletions of Cyp2c70/Cyp2a12 (CYPDKO mice) have a human-like hydrophobic bile acid composition. PFIC-related gene mutations were induced in CYPDKO mice to determine whether these triple-gene-deficient mice are a better model for PFIC. To establish a PFIC3 mouse model using CYPDKO mice, we induced abcb4 gene deletion in vivo using adeno-associated viruses expressing SaCas9 under the control of a liver-specific promoter and abcb4-target gRNAs. Compared to Abcb4-deficient wild-type mice, Abcb4-deficient CYPDKO mice showed more pronounced liver injury along with an elevation of inflammatory and fibrotic markers. The proliferation of intrahepatic bile ductal cells and hematopoietic cell infiltration were also observed. CYPDKO/abcb4-deficient mice show a predominance of taurine-conjugated chenodeoxycholic acid and lithocholic acid in the liver. In addition, phospholipid levels in the gallbladder bile were barely detectable. Mice with both human-like bile acid composition and Abcb4-defect exhibit severe cholestatic liver injury and are useful for studying human cholestatic diseases and developing new treatments.

Gypensapogenin A-Liposomes Efficiently Ameliorates Hepatocellular Lipid Accumulation via Activation of FXR Receptor

Non-alcoholic fatty liver disease (NAFLD) is one of the most common metabolic diseases encountered in clinical practice, which is characterized by the excessive accumulation of triglycerides (steatosis), and a variety of metabolic abnormalities including lipid metabolism and bile acid metabolism are closely related to NAFLD. In China, Gynostemma pentaphyllum is used as functional food and Chinese medicine to treat various diseases, especially NAFLD, for a long time. However, the active components that exert the main therapeutic effects and their mechanisms remain unclear. In this study, Gypensapogenin A was isolated from the total saponins of G. pentaphyllum and prepared as a liposomal delivery system. Gypensapogenin A liposomes could activate FXR, inhibit the expression of CYP7A1 and CYP8B1, increase the expression of CYP27A1, modulate the ratio of CA and CDCA, decrease the content of CA, and increase the content of CDCA, thus forming a virtuous cycle of activating FXR to play a role in lowering blood lipid levels.

FGL2 improves experimental colitis related to gut microbiota structure and bile acid metabolism by regulating macrophage autophagy and apoptosis

Inflammatory bowel disease (IBD) is a refractory disease with immune abnormalities and pathological changes. Intestinal macrophages are considered to be the main factor in establishing and maintaining intestinal homeostasis. The immunoregulatory and anti-inflammatory activity of fibrinogen-like protein 2 (FGL2) can regulate macrophage polarization. However, its function in IBD is unclear. In this study, we explored the effect of FGL2 on macrophage polarization, autophagy, and apoptosis in bone marrow-derived macrophages (BMDMs) treated with lipopolysaccharide (LPS) and further investigated changes in the intestinal barrier, flora, and bile acid in dextran sodium sulfate (DSS)-treated mice. Our results demonstrated that FGL2-/- weakened ERK signaling to promote M1 polarization and upregulate inflammation, autophagy, and apoptosis in LPS-stimulated BMDMs. rFGL2 treatment reversed these effects. FGL2-/- mice exhibited higher sensitivity to DSS exposure, with faster body weight loss, shorter colon lengths, and higher disease activity index (DAI) values. rFGL2 treatment protected against experimental ulcerative colitis (UC), restrained excessive autophagy, apoptosis, and improved gut barrier impairment. Gut microbiota structure and bile acid homeostasis were more unbalanced in FGL2-/- DSS mice than in wild-type (WT) DSS mice. rFGL2 treatment improved gut microbiota structure and bile acid homeostasis. Altogether, our results established that FGL2 is a potential therapeutic target for IBD.

The crosstalk between cell death and pregnancy related diseases: A narrative review

Programmed cell death is intricately linked to various physiological phenomena such as growth, development, and metabolism, as well as the proper function of the pancreatic β cell and the migration and invasion of trophoblast cells in the placenta during pregnancy. Traditional and recently identified programmed cell death include apoptosis, autophagy, pyroptosis, necroptosis, and ferroptosis. In addition to cancer and degenerative diseases, abnormal activation of cell death has also been implicated in pregnancy related diseases like preeclampsia, gestational diabetes mellitus, intrahepatic cholestasis of pregnancy, fetal growth restriction, and recurrent miscarriage. Excessive or insufficient cell death and pregnancy related diseases may be mutually determined, ultimately resulting in adverse pregnancy outcomes. In this review, we systematically describe the characteristics and mechanisms underlying several types of cell death and their roles in pregnancy related diseases. Moreover, we discuss potential therapeutic strategies that target cell death signaling pathways for pregnancy related diseases, hoping that more meaningful treatments will be applied in clinical practice in the future.

Regulating bile acids signaling for NAFLD: molecular insights and novel therapeutic interventions

Nonalcoholic fatty liver disease (NAFLD) emerges as the most predominant cause of liver disease, tightly linked to metabolic dysfunction. Bile acids (BAs), initially synthesized from cholesterol in the liver, undergo further metabolism by gut bacteria. Increasingly acknowledged as critical modulators of metabolic processes, BAs have been implicated as important signaling molecules. In this review, we will focus on the mechanism of BAs signaling involved in glucose homeostasis, lipid metabolism, energy expenditure, and immune regulation and summarize their roles in the pathogenesis of NAFLD. Furthermore, gut microbiota dysbiosis plays a key role in the development of NAFLD, and the interactions between BAs and intestinal microbiota is elucidated. In addition, we also discuss potential therapeutic strategies for NAFLD, including drugs targeting BA receptors, modulation of intestinal microbiota, and metabolic surgery.

Effects of intestine-specific deletion of FGF15 on the development of fatty liver disease with vertical sleeve gastrectomy

BACKGROUND

Vertical sleeve gastrectomy (SGx) is a type of bariatric surgery to treat morbid obesity and metabolic dysfunction-associated steatotic liver disease (MASLD). The molecular mechanisms of SGx to improve MASLD are unclear, but increased bile acids (BAs) and FGF19 (mouse FGF15) were observed. FGF15/19 is expressed in the ileum in response to BAs and is critical in not only suppressing BA synthesis in the liver but also promoting energy expenditure. We hypothesized the reduction of obesity and resolution of MASLD by SGx may be mediated by FGF15/19.

METHODS

First, we conducted hepatic gene expression analysis in obese patients undergoing SGx, with the results showing increased expression of FGF19 in obese patients' livers. Next, we used wild-type and intestine-specific Fgf15 knockout mice (Fgf15ile-/-) to determine the effects of FGF15 deficiency on improving the metabolic effects.

RESULTS

SGx improved metabolic endpoints in both genotypes, evidenced by decreased obesity, improved glucose tolerance, and reduced MASLD progression. However, Fgf15ile-/- mice showed better improvement compared to wild-type mice after SGx, suggesting that other mediators than FGF15 are also responsible for the beneficial effects of FGF15 deficiency. Further gene expression analysis in brown adipose tissue suggests increased thermogenesis.

CONCLUSIONS

FGF15 deficiency, the larger BA pool and higher levels of secondary BAs may increase energy expenditure in extrahepatic tissues, which may be responsible for improved metabolic functions following SGx.

Partial liver resection alters the bile salt-FGF19 axis in patients with perihilar cholangiocarcinoma: Implications for liver regeneration

BACKGROUND

Extended liver resection is the only treatment option for perihilar cholangiocarcinoma (pCCA). Bile salts and the gut hormone FGF19, both promoters of liver regeneration (LR), have not been investigated in patients undergoing resection for pCCA. We aimed to evaluate the bile salt-FGF19 axis perioperatively in pCCA and study its effects on LR.

METHODS

Plasma bile salts, FGF19, and C4 (bile salt synthesis marker) were assessed in patients with pCCA and controls (colorectal liver metastases), before and after resection on postoperative days (PODs) 1, 3, and 7. Hepatic bile salts were determined in intraoperative liver biopsies.

RESULTS

Partial liver resection in pCCA elicited a sharp decline in bile salt and FGF19 plasma levels on POD 1 and remained low thereafter, unlike in controls, where bile salts rose gradually. Preoperatively, suppressed C4 in pCCA normalized postoperatively to levels similar to those in the controls. The remnant liver volume and postoperative bilirubin levels were negatively associated with postoperative C4 levels. Furthermore, patients who developed postoperative liver failure had nearly undetectable C4 levels on POD 7. Hepatic bile salts strongly predicted hyperbilirubinemia on POD 7 in both groups. Finally, postoperative bile salt levels on day 7 were an independent predictor of LR.

CONCLUSIONS

Partial liver resection alters the bile salt-FGF19 axis, but its derailment is unrelated to LR in pCCA. Postoperative monitoring of circulating bile salts and their production may be useful for monitoring LR.

Characterization of individual bile acids in vivo utilizing a novel low bile acid mouse model

Bile acids (BAs) are signaling molecules synthesized in the liver initially by CYP7A1 and CYP27A1 in the classical and alternative pathways, respectively. BAs are essential for cholesterol clearance, intestinal absorption of lipids, and endogenous modulators of farnesoid x receptor (FXR). FXR is critical in maintaining BA homeostasis and gut-liver crosstalk. Complex reactions in vivo and the lack of suitable animal models impede our understanding of the functions of individual BAs. In this study, we characterized the in vivo effects of three-day feeding of cholic acid (CA), deoxycholic acid (DCA), or ursodeoxycholic acid (UDCA) at physiological/non-hepatotoxic concentrations in a novel low-BA mouse model (Cyp7a1-/-/Cyp27a1-/-, DKO). Liver injury, BA levels and composition and BA signaling by the FXR-fibroblast growth factor 15 (FGF15) axis were determined. Overall, higher basal inflammation and altered lipid metabolism in DKO mice might be associated with low BAs. CA, DCA, and UDCA feeding activated FXR signals with tissue specificity. Dietary CA and DCA similarly altered tissue BA profiles to be less hydrophobic, while UDCA promoted a more hydrophobic tissue BA pool with the profiles shifted toward non-12α-OH BAs and secondary BAs. However, UDCA did not offer any overt protective effects as expected. These findings allow us to determine the precise effects of individual BAs in vivo on BA-FXR signaling and overall BA homeostasis in liver physiology and pathologies.

Bile acid signaling in the regulation of whole body metabolic and immunological homeostasis

Bile acids (BAs) play a crucial role in nutrient absorption and act as key regulators of lipid and glucose metabolism and immune homeostasis. Through the enterohepatic circulation, BAs are synthesized, metabolized, and reabsorbed, with a portion entering the vascular circulation and distributing systemically. This allows BAs to interact with receptors in all major organs, leading to organ-organ interactions that regulate both local and global metabolic processes, as well as the immune system. This review focuses on the whole-body effects of BA-mediated metabolic and immunological regulation, including in the brain, heart, liver, intestine, eyes, skin, adipose tissue, and muscle. Targeting BA synthesis and receptor signaling is a promising strategy for the development of novel therapies for various diseases throughout the body.

The Effect of Coenzyme Q10 Supplementation on Bile Acid Metabolism: Insights from Network Pharmacology, Molecular Docking, and Experimental Validation

SCOPE

Bile acids play a crucial role in lipid absorption and the regulation of lipid, glucose, and energy homeostasis. Coenzyme Q10 (CoQ10), a lipophilic antioxidant, has been recognized for its positive effects on obesity and related glycolipid metabolic disorders. However, the relationship between CoQ10 and bile acids has not yet been evaluated.

METHODS AND RESULTS

This study assesses the impact of CoQ10 treatment on bile acid metabolism in mice on a high-fat diet using Ultra-Performance Liquid Chromatography-tandem Mass Spectrometry. CoQ10 reverses the reduction in serum and colonic total bile acid levels and alters the bile acid profile in mice that are caused by a high-fat diet. Seventeen potential targets of CoQ10 in bile acid metabolism are identified by network pharmacology, with six being central to the mechanism. Molecular docking shows a high binding affinity of CoQ10 to five of these key targets. Further analyses indicate that farnesoid X (FXR) receptor and Takeda G-protein coupled receptor 5 (TGR5) may be crucial targets for CoQ10 to regulate bile acid metabolism and exert beneficial effects.

CONCLUSION

This study sheds light on the impact of CoQ10 in bile acids metabolism and offers a new perspective on the application of CoQ10 in metabolic health.

Exploring Advanced Therapies for Primary Biliary Cholangitis: Insights from the Gut Microbiota-Bile Acid-Immunity Network

Primary biliary cholangitis (PBC) is a cholestatic liver disease characterized by immune-mediated injury to small bile ducts. Although PBC is an autoimmune disease, the effectiveness of conventional immunosuppressive therapy is disappointing. Nearly 40% of PBC patients do not respond to the first-line drug UDCA. Without appropriate intervention, PBC patients eventually progress to liver cirrhosis and even death. There is an urgent need to develop new therapies. The gut-liver axis emphasizes the interconnection between the gut and the liver, and evidence is increasing that gut microbiota and bile acids play an important role in the pathogenesis of cholestatic diseases. Dysbiosis of gut microbiota, imbalance of bile acids, and immune-mediated bile duct injury constitute the triad of pathophysiology in PBC. Autoimmune cholangitis has the potential to be improved through immune system modulation. Considering the failure of conventional immunotherapies and the involvement of gut microbiota and bile acids in the pathogenesis, targeting immune factors associated with them, such as bile acid receptors, microbial-derived molecules, and related specific immune cells, may offer breakthroughs. Understanding the gut microbiota-bile acid network and related immune dysfunctions in PBC provides a new perspective on therapeutic strategies. Therefore, we summarize the latest advances in research of gut microbiota and bile acids in PBC and, for the first time, explore the possibility of related immune factors as novel immunotherapy targets. This article discusses potential therapeutic approaches focusing on regulating gut microbiota, maintaining bile acid homeostasis, their interactions, and related immune factors.

Discovery of novel and selective farnesoid X receptor antagonists through structure-based virtual screening, preliminary structure-activity relationship study, and biological evaluation

Farnesoid X receptor (FXR) is a bile acids receptor and plays a crucial role in regulating bile acids, lipids, and glucose metabolism. Previous research suggests that inhibiting FXR activation can be beneficial in reducing cholesterol and low-density lipoprotein cholesterol (LDL-C) levels, offering potential treatment options for metabolic syndrome with lipid disorders. Herein, we report p-acetylaminobenzene sulfonate derivatives as a novel scaffold of FXR antagonists by multistage screening. Among these derivatives, compound F44-A13 exhibited a half-maximal inhibitory concentration of 1.1 μM. Furthermore, compound F44-A13 demonstrated effective inhibition of FXR activation in cellular assays and exhibited high selectivity over eleven other nuclear receptors. Besides, compound F44-A13 significantly suppressed the regulation of FXR target genes Shp, Besp, and Cyp7a1, while reducing cholesterol levels in human hepatoma HepG2 cells. Pharmacological studies conducted on C57BL/6 mice further confirmed that compound F44-A13 had beneficial effects in reducing cholesterol, triglycerides, and LDL-C levels. These findings highlight that F44-A13 is a highly selective FXR antagonist that might serve as a useful molecule for further FXR studies as well as the development of FXR antagonists for the potential treatment of metabolic diseases with lipid disorders.

Bile acids regulation of cellular stress responses in liver physiology and diseases

Bile acids are physiological detergents and signalling molecules that are critically implicated in liver health and diseases. Dysregulation of bile acid homeostasis alters cell function and causes cell injury in chronic liver diseases. Therapeutic agents targeting bile acid synthesis, transport and signalling hold great potential for treatment of chronic liver diseases. The broad cellular and physiological impacts of pharmacological manipulations of bile acid metabolism are still incompletely understood. Recent research has discovered new links of bile acid signalling to the regulation of autophagy and lysosome biology, redox homeostasis and endoplasmic reticulum stress. These are well-conserved mechanisms that allow cells to adapt to nutrient and organelle stresses and play critical roles in maintaining cellular integrity and promoting survival. However, dysregulation of these cellular pathways is often observed in chronic liver diseases, which exacerbates cellular dysfunction to contribute to disease pathogenesis. Therefore, identification of these novel links has significantly advanced our knowledge of bile acid biology and physiology, which is needed to understand the contributions of bile acid dysregulation in disease pathogenesis, establish bile acids as diagnostic markers and develop bile acid-based pharmacological interventions. In this review, we will first discuss the roles of bile acid dysregulation in the pathogenesis of chronic liver diseases, and then discuss the recent findings on the crosstalk of bile acid signalling and cellular stress responses. Future investigations are needed to better define the roles of these crosstalks in regulating cellular function and disease processes.

Barley consumption under a high-fat diet suppresses lipogenic genes through altered intestinal bile acid composition

We evaluated whether barley flour consumption in a high-fat environment affects lipid metabolism through signals mediated by bile acids. Four-week-old mice were fed a high-fat diet supplemented with cellulose (HC) or β-glucan-rich barley flour (HB) for 12 weeks. Bile acid composition in the intestinal tract and feces was measured by GC/MS. Gene expression levels involved in bile acid metabolism in the liver and intestinal tract were determined by RT-PCR. Similar parameters were measured in mice treated with antibiotics (antibiotics-cellulose [AC] and antibiotics-barley [AB]) to reduce the activity of intestinal bacteria. The Results showed that the HB group had lower liver blood cholesterol and triglyceride levels than the HC group. The HB group showed a significant decrease in primary bile acids in the gastrointestinal tract compared to the HC group. On the other hand, the concentration of secondary bile acids relatively increased in the cecum and feces. In the liver, Fxr activation suppressed gene expression levels in synthesizing bile acids and lipids. Furthermore, in the gastrointestinal tract, Tgr5 was activated by increased secondary bile acids. Correspondingly, AMP levels were increased in the HB group compared to the HC group, AMPK was phosphorylated in the liver, and gene expression involved in lipid synthesis was downregulated. A comparison of the AC and AB groups treated with antibiotics did not confirm these effects of barley intake. In summary, our results suggest that the prevention of lipid accumulation by barley consumption involves signaling through changes in bile acid composition in the intestinal tract.

Involvement of Bile Acid Metabolism and Gut Microbiota in the Amelioration of Experimental Metabolism-Associated Fatty Liver Disease by Nobiletin

Metabolism-associated fatty liver disease (MAFLD), a growing health problem worldwide, is one of the major risks for the development of cirrhosis and liver cancer. Oral administration of nobiletin (NOB), a natural citrus flavonoid, modulates the gut microbes and their metabolites in mice. In the present study, we established a mouse model of MAFLD by subjecting mice to a high-fat diet (HFD) for 12 weeks. Throughout this timeframe, NOB was administered to investigate its potential benefits on gut microbial balance and bile acid (BA) metabolism using various techniques, including 16S rRNA sequencing, targeted metabolomics of BA, and biological assays. NOB effectively slowed the progression of MAFLD by reducing serum lipid levels, blood glucose levels, LPS levels, and hepatic IL-1β and TNF-α levels. Furthermore, NOB reinstated diversity within the gut microbial community, increasing the population of bacteria that produce bile salt hydrolase (BSH) to enhance BA excretion. By exploring further, we found NOB downregulated hepatic expression of the farnesoid X receptor (FXR) and its associated small heterodimer partner (SHP), and it increased the expression of downstream enzymes, including cholesterol 7α-hydroxylase (CYP7A1) and cytochrome P450 27A1 (CYP27A1). This acceleration in cholesterol conversion within the liver contributes to mitigating MAFLD. The present findings underscore the significant role of NOB in regulating gut microbial balance and BA metabolism, revealing that long-term intake of NOB plays beneficial roles in the prevention or intervention of MAFLD.

Predictive value of serum fibroblast growth factor 19 and liver stiffness for intestinal failure associated liver disease-cholestasis

BACKGROUND

Intestinal failure associated liver disease (IFALD)-cholestasis is a common complication of long-term parenteral nutrition (PN) in patients with intestinal failure (IF). The lack of effective early identification indicators often results in poor clinical outcomes. The objective of this study was to evaluate the predictive value of serum FGF19 and liver stiffness in IFALD-cholestasis.

METHODS

Eligible adults diagnosed with IF were identified from Jinling Hospital in China. Diagnostic criteria for IFALD-cholestasis: total bilirubin >1 mg/dL and conjugated bilirubin >0.3 mg/dL for ≥6 months. Fasting blood specimens were prospectively collected and serum FGF19 concentrations were determined using ELISA and liver stiffness was measured by Two-dimensional shear wave elastography. Binary logistic regression analysis identified predictors of IFALD-cholestasis. Receiver operating characteristic (ROC) curves and areas under the ROC curves (AUROC) were used to evaluate the accuracy of serum FGF19 and liver stiffness in identifying IFALD-cholestasis.

RESULTS

Of 203 study patients with IF, 70 (34.5%) were diagnosed with IFALD-cholestasis. The serum FGF19 levels in those with IFALD-cholestasis were significantly decreased compared with those in patients without, and liver stiffness was significantly increased (p < 0.001). Multivariate logistic regression analyses suggested that intestinal discontinuity, dependence on PN, liver stiffness >6.5 kPa, and serum FGF19 ≤107 pg/mL were independent risk factors for IFALD-cholestasis. The AUROC for serum FGF19 and liver stiffness, which indicate the occurrence of IFALD-cholestasis, were 0.810 and 0.714, respectively. Serum FGF19 had a superior predictive performance than liver stiffness (p < 0.05).

CONCLUSION

Both low circulating serum FGF19 concentration and increased liver stiffness are excellent predictors of IFALD-cholestasis, but serum FGF19 is superior to increased liver stiffness in predicting IFALD-cholestasis.

Energy and macronutrient restriction regulate bile acid homeostasis

As we reported previously, caloric restriction (CR) results in an increased concentration of bile acids (BA) in the intestinal mucosa. We now investigated the background of this phenotype, trying to identify nutrition-related factors modulating BA levels. Male mice were submitted to various types of restrictive diets and BA levels and expression of associated factors were measured. We found that BA concentration is increased in the liver of CR mice, which corresponds to reduced expression of the Shp gene and elevated mRNA levels of Cyp27a1, Bal, and Ntcp, as well as CYP7A1 protein and gene expression. Correlation between decreased concentration of BAs in the feces, increased BAs levels in plasma, and elevated gene expression of BAs transporters in the ileum mucosa suggests enhanced BA uptake in the intestine of CR mice. Corresponding to CR upregulation of liver and ileum mucosa, BA concentration was found in animals submitted to other types of prolonged energy-restricting dietary protocols, including intermittent fasting and fasting-mimicking diet. While over-night fasting had negligible impact on BAs levels. Manipulation of macronutrient levels partly affected BA balance. Low-carbohydrate and ketogenic diet increased BAs in the liver but not in the intestine. Carbohydrate restriction stimulates BA synthesis in the liver, but energy restriction is required for the increase in BA levels in the intestine and its uptake.

Environmentally Relevant Concentrations of Microplastic Exposure Cause Cholestasis and Bile Acid Metabolism Dysregulation through a Gut-Liver Loop in Mice

The massive production of plastics causes the ubiquitous existence of microplastics (MPs) in the biota, therefore, posing exposure risks and potential health concerns to human beings. However, the exact mechanisms of MPs-induced toxicities and abnormalities are largely unknown. In this study, we developed a mouse model of gavage polystyrene microplastics (PS MPs) for 30 days. We found that PS MPs can damage the intestinal barrier, accumulate in the liver tissue, and cause injury. The liver and intestine are both highly associated with bile acid (BA) metabolism. Indeed, we found that PS MPs dysregulate BA synthesis and efflux-related gene expression in the liver, causing cholestasis. Tandemly, PS MPs alter the ratio of primary to secondary BA in the feces by affecting the composition of the intestinal flora. At last, PS MPs alter mice's fecal BA profile, which affects normal BA metabolism. Taken together, the present study provides robust data on the mechanism of toxicity of MPs causing the disturbance of BA metabolism via a 4-step gut-liver loop.

Gardenia extract protects against intrahepatic cholestasis by regulating bile acid enterohepatic circulation

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestasis is the main manifestation of cholestatic liver disease, which has a risk of progression to end-stage liver disease. Gardeniae Fructus is the dried fruit of Gardeniae jasminoides Ellis, a plant of the Rubiaceae family. Gardeniae Fructus has shown therapeutic potential in cholestasis-related liver diseases and it is generally believed that Gardeniae Fructus ameliorates cholestasis, which could be related to its influence on bile acids (BAs) metabolism. However, the specific targets of Gardeniae Fructus and its impact on enterohepatic circulation of BAs have not yet been fully elucidated.

AIM OF THE STUDY

To systematically elucidate the mechanism by which Gardenia extract (GE, total iridoids in Gardeniae Fructus, which contains the predominant and characteristic phytoconstituents of Gardeniae Fructus) ameliorates alpha-naphthylisothiocyanate (ANIT)-induced cholestatic liver injury.

MATERIALS AND METHODS

Sprague-Dawley rats were orally administered water, obeticholic acid (OCA, 2 mg/kg), or GE (21 and 42 mg/kg) once daily for five days. On the third day, the model was established by administration of a single dose of ANIT (40 mg/kg) by oral gavage. Biochemical and pathological analyses, BA metabolomics, transcriptomics, and qRT-PCR were performed.

RESULTS

The profile of BAs in serum and liver confirmed that GE attenuated ANIT-induced acute cholestasis by affecting BA metabolism in a dose-dependent manner. Liver transcriptomic analysis indicated that GE mainly influenced the primary bile acid (PBA) biosynthesis and bile secretion pathways. GE mainly affected PBA biosynthesis in liver by upregulating Cyp8b1 gene expression, thereby significantly reducing the level of total bile acids (TBA). GE mainly promoted PBA excretion from liver into duodenum by upregulating Fxr and Oatp1 gene expression, thereby increasing the excretion of PBA in feces, and inhibiting PBA in liver entering the blood by alternative routes to reduce TBA levels in serum and urine and improve the enterohepatic circulation of BAs.

CONCLUSION

GE attenuated ANIT-induced hepatotoxicity and cholestasis in rats by upregulating Cyp8b1 expression to inhibit BA synthesis in the liver, while also promoting BA excretion via the intestinal-fecal route, and improving enterohepatic circulation of BAs.

Ganoderma lucidum polysaccharide ameliorates cholesterol gallstone formation by modulating cholesterol and bile acid metabolism in an FXR-dependent manner

BACKGROUND

Cholesterol gallstone (CG) disease is a worldwide common disease characterized by cholesterol supersaturation in gallbladder bile. Ganoderma lucidum polysaccharide (GLP) has been shown to possess various beneficial effects against metabolic disorders. However, the role and underlying mechanism of GLP in CG formation are still unknown. This study aimed to determine the role of GLP in ameliorating lithogenic diet (LD)-induced CG formation.

METHODS

Mice were fed either a normal chow diet, a LD, or LD supplemented with GLP. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to detect the expression of genes involved in cholesterol and bile acid (BA) metabolism. The BA concentrations in the ileum were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The microbiota in cecal contents were characterized using 16S ribosomal RNA (16S rRNA) gene sequencing.

RESULTS

GLP effectively alleviated CG formation induced by LD. Specifically, GLP reduced the total cholesterol (TC) levels, increased the total BA levels, and decreased the cholesterol saturation index (CSI) in gallbladder bile. The protective effect of GLP was attributed to the inhibition of farnesoid X receptor (FXR) signaling, increased hepatic BA synthesis and decreased hepatic cholesterol synthesis and secretion. GLP also altered the BA composition in the ileum, reducing FXR-agonistic BAs and increasing FXR-antagonistic BAs, which may contribute to the inhibition of intestinal FXR signaling. Additionally, GLP improved dysbiosis of the intestinal flora and reduced the serum levels of hydrogen sulfide (H2S), a bacterial metabolite that can induce hepatic FXR, thereby inhibiting hepatic FXR signaling. Moreover, the protective effect of GLP against CG formation could be reversed by both the global and gut-restricted FXR agonists.

CONCLUSIONS

Taken together, GLP ameliorates CG formation by regulating cholesterol and BA metabolism in an FXR-dependent manner. Our study demonstrates that GLP may be a potential strategy for the prevention against CG disease.

Giardia Antagonizes Beneficial Functions of Indigenous and Therapeutic Intestinal Bacteria during Malnutrition

Undernutrition in children commonly disrupts the structure and function of the small intestinal microbial community, leading to enteropathies, compromised metabolic health, and impaired growth and development. The mechanisms by which diet and microbes mediate the balance between commensal and pathogenic intestinal flora remain elusive. In a murine model of undernutrition, we investigated the direct interactions Giardia lamblia, a prevalent small intestinal pathogen, on indigenous microbiota and specifically on Lactobacillus strains known for their mucosal and growth homeostatic properties. Our research reveals that Giardia colonization shifts the balance of lactic acid bacteria, causing a relative decrease in Lactobacillus spp . and an increase in Bifidobacterium spp . This alteration corresponds with a decrease in multiple indicators of mucosal and nutritional homeostasis. Additionally, protein-deficient conditions coupled with Giardia infection exacerbate the rise of primary bile acids and susceptibility to bile acid-induced intestinal barrier damage. In epithelial cell monolayers, Lactobacillus spp . mitigated bile acid-induced permeability, showing strain-dependent protective effects. In vivo, L. plantarum, either alone or within a Lactobacillus spp consortium, facilitated growth in protein-deficient mice, an effect attenuated by Giardia , despite not inhibiting Lactobacillus colonization. These results highlight Giardia's potential role as a disruptor of probiotic functional activity, underscoring the imperative for further research into the complex interactions between parasites and bacteria under conditions of nutritional deficiency.

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

BACKGROUND & AIMS

Hepatocellular 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.

METHODS & RESULTS

We used the farnesoid X receptor knockout (FxrKO) mouse model to study bile acid-dependent HCC. Temporal tracking of circulating bile acids determined more than 80% of FxrKO females developed spontaneous cholemia (ie, serum total bile acids ≥40 μmol/L) as early as 8 weeks old. Opposingly, FxrKO males were highly resistant to cholemia, with ∼23% incidence even when 26 weeks old. However, FxrKO males demonstrated higher levels of deoxycholate than females. Compared with 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 with 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.

CONCLUSIONS

Our study highlights bile acids as sex-dimorphic metabolites in HCC except in the case of portosystemic shunt.

Astragalus saponins protect against extrahepatic and intrahepatic cholestatic liver fibrosis models by activation of farnesoid X receptor

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestatic Liver Fibrosis (CLF) is a hepatobiliary disease that typically arises as a late-stage complication of cholestasis, which can have multiple underlying causes. There are no satisfactory chemical or biological drugs for CLF. Total Astragalus saponins (TAS) are considered to be the main active constituents of the traditional Chinese herb Astragali Radix (AR), which has the obvious improvement effects for treating CLF. However, the mechanism of anti-CLF effects of TAS is still unclear.

AIM OF THE STUDY

The present study was undertaken to investigate the therapeutic effects of TAS against bile duct ligation (BDL) and 3, 5-diethoxycarbonyl-1,4-dihydroxychollidine (DDC) -induced CLF models and to reveal the potential mechanism to support its clinic use with scientific evidence.

MATERIALS AND METHODS

In this study, BDL-induced CLF rats were treated with TAS (20 mg/kg, 40 mg/kg) and DDC-induced CLF mice were treated with 56 mg/kg TAS. The therapeutic effects of TAS on extrahepatic and intrahepatic CLF models were evaluated by serum biochemical analysis, liver histopathology and hydroxyproline (Hyp). Thirty-nine individual bile acids (BAs) in serum and liver were quantified by using UHPLC-Q-Exactive Orbitrap HRMS. qRT-PCR, Western blot and immunohistochemistry analysis were used to measure the expression of liver fibrosis and ductular reaction markers, inflammatory factors and BAs related metabolic transporters, along with nuclear receptor farnesoid X receptor (FXR).

RESULTS

The serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total bilirubin (TBiL), direct bilirubin (DBiL) and contents of liver Hyp were dose-dependently improved after treatment for TAS in BDL and DDC- induced CLF models. And the increased levels of ALT and AST were significantly improved by total extract from Astragali radix (ASE) in BDL model. The liver fibrosis and ductular reaction markers, α-smooth muscle actin (α-SMA) and cytokeratin 19 (CK19), were significantly ameliorated in TAS group. And the liver expression of inflammatory factors: interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β) were significantly decreased after TAS treatment. In addition, TAS significantly ameliorated taurine-conjugated BAs (tau-BAs) levels, particularly α-TMCA, β-TMCA and TCA contents in serum and liver, which correlated with induced expressions of hepatic FXR and BAs secretion transporters. Furthermore, TAS significantly improved short heterodimer partner (SHP), cholesterol 7α-hydroxylase (Cyp7a1), Na+ taurocholate cotransport peptide (NTCP) and bile-salt export pump (BSEP) mRNA and protein expression.

CONCLUSIONS

TAS exerted a hepatoprotective effect against CLF by ameliorating liver injury, inflammation and restoring the altered tau-BAs metabolism to produce a positive regulatory effect on FXR-related receptors and transporters.

Fibroblast growth factor 21 ameliorates cholestatic liver injury via a hepatic FGFR4-JNK pathway

Cholestasis is characterized by hepatic accumulation of cytotoxic bile acids (BAs), which often subsequently leads to liver injury, inflammation, fibrosis, and liver cirrhosis. Fibroblast growth factor 21 (FGF21) is a liver-secreted hormone with pleiotropic effects on the homeostasis of glucose, lipid, and energy metabolism. However, whether hepatic FGF21 plays a role in cholestatic liver injury remains elusive. We found that serum and hepatic FGF21 levels were significantly increased in response to cholestatic liver injury. Hepatocyte-specific deletion of Fgf21 exacerbated hepatic accumulation of BAs, further accentuating liver injury. Consistently, administration of rFGF21 ameliorated cholestatic liver injury caused by α-naphthylisothiocyanate (ANIT) treatment and Mdr2 deficiency. Mechanically, FGF21 activated a hepatic FGFR4-JNK signaling pathway to decrease Cyp7a1 expression, thereby reducing hepatic BAs pool. Our study demonstrates that hepatic FGF21 functions as an adaptive stress-responsive signal to downregulate BA biosynthesis, thereby ameliorating cholestatic liver injury, and FGF21 analogs may represent a candidate therapy for cholestatic liver diseases.

Vancomycin relieves tacrolimus-induced hyperglycemia by eliminating gut bacterial beta-glucuronidase enzyme activity

Up to 40% of transplant recipients treated long-term with tacrolimus (TAC) develop post-transplant diabetes mellitus (PTDM). TAC is an important risk factor for PTDM, but is also essential for immunosuppression after transplantation. Long-term TAC treatment alters the gut microbiome, but the mechanisms of TAC-induced gut microbiota in the pathogenesis of PTDM are poorly characterized. Here, we showed that vancomycin, an inhibitor of bacterial beta-glucuronidase (GUS), prevents TAC-induced glucose disorder and insulin resistance in mice. Metagenomics shows that GUS-producing bacteria are predominant and flourish in the TAC-induced hyperglycemia mouse model, with upregulation of intestinal GUS activity. Targeted metabolomics analysis revealed that in the presence of high GUS activity, the hydrolysis of bile acid (BAs)-glucuronic conjugates is increased and most BAs are overproduced in the serum and liver, which, in turn, activates the ileal farnesoid X receptor (FXR) and suppresses GLP-1 secretion by L-cells. The GUS inhibitor vancomycin significantly eliminated GUS-producing bacteria and inhibited bacterial GUS activity and BAs levels, thereby enhancing L-cell GLP-1 secretion and preventing hyperglycemia. Our results propose a novel clinical strategy for inhibiting the bacterial GUS enzyme to prevent hyperglycemia without requiring withdrawal of TAC treatment. This strategy exerted its effect through the ileal bile acid-FXR-GLP-1 pathway.

Therapeutic Potential of Danyankang Capsule in High-Fat Diet-Induced Cholelithiasis and Its Impact on Liver FXR Signaling and Gut Microbiota

Cholelithiasis, commonly known as gallstones, represents a prevalent hepatobiliary disorder. This study aimed to elucidate the therapeutic role and mechanism of Danyankang capsulein treating cholelithiasis induced by a high-fat diet in C57BL/6 mice. The therapeutical potential of Danyankang was assessed through biochemical analyses, histopathological examinations, protein detection, and 16S rDNA sequencing. A high-fat diet resulted in cholelithiasis manifestation in mice, with discernable abnormal serum biochemical indices and disrupted biliary cholesterol homeostasis. Danyankang treatment notably ameliorated liver inflammation symptoms and rectified serum and liver biochemical abnormalities. Concurrently, it addressed biliary imbalances. Elevated expressions of toll-like receptor 4 (TLR4), nuclear factor-kappaB (NF-κB)/pNF-κB, HMGCR, CYP7A1, and CYP8B1 observed at the inception of cholelithiasis, were notably reduced upon Danyankang administration. Furthermore, 16S rDNA analysis revealed a decline in species number and diversity of the intestinal flora in cholelithiasis-treated mice, while the decline was reversed with Danyankang treatment. Danyankang capsules reduced the abundance of Verrucomicrobiota and increased the abundance of Actinobacteriota and Proteobacteria. In conclusion, the present study demonstrates that Danyankang exerts potent therapeutic efficacy against high-fat diet-induced cholelithiasis. This beneficial outcome is potentially linked to the inhibition of the TLR4/pNF-κB and SHP/CYP7A1/CYP8B1 signaling pathways, as well as the enhancement of intestinal flora species abundance.

Roseburia intestinalis relieves intrahepatic cholestasis of pregnancy through bile acid/FXR-FGF15 in rats

Previous research has demonstrated significant differences in intestinal flora between pregnant women with intrahepatic cholestasis of pregnancy (ICP) and healthy pregnant women. The objective of our study is to identify the key bacteria involved in ICP rats and explore the underlying mechanism. We established an ICP rat model and collected rat feces for metagenomic sequencing and found that Roseburia intestinalis (R.I) is the key bacteria in ICP. Transplantation of R.I improved phenotypes associated with ICP through the bile acid/farnesoid X receptor-fibroblast growth factor 15 (FXR-FGF15) signaling pathway. We used the FXR antagonist Z-Guggulsterone (Z-Gu) to verify the key role of FXR in ICP and found that Z-Gu reversed the benefits of R.I on ICP rats. Our research highlights the important role of intestinal flora in the pathogenesis of ICP and provides a novel approach for its treatment.

The regulation of tissue-specific farnesoid X receptor on genes and diseases involved in bile acid homeostasis

Bile acids (BAs) facilitate the absorption of dietary lipids and vitamins and have also been identified as signaling molecules involved in regulating their own metabolism, glucose and lipid metabolism, as well as immunity. Disturbances in BA homeostasis are associated with various enterohepatic and metabolic diseases, such as cholestasis, nonalcoholic steatohepatitis, inflammatory bowel disease, and obesity. As a key regulator, the nuclear orphan receptor farnesoid X receptor (FXR, NR1H4) precisely regulates BA homeostasis by transcriptional regulation of genes involved in BA synthesis, metabolism, and enterohepatic circulation. FXR is widely regarded as the most potential therapeutic target. Obeticholic acid is the only FXR agonist approved to treat patients with primary biliary cholangitis, but its non-specific activation of systemic FXR also causes high-frequency side effects. In recent years, developing tissue-specific FXR-targeting drugs has become a research highlight. This article provides a comprehensive overview of the role of tissue-specific intestine/liver FXR in regulating genes involved in BA homeostasis and briefly discusses tissue-specific FXR as a therapeutic target for treating diseases. These findings provide the basis for the development of tissue-specific FXR modulators for the treatment of enterohepatic and metabolic diseases associated with BA dysfunction.

Gut microbiota-bile acid crosstalk regulates murine lipid metabolism via the intestinal FXR-FGF19 axis in diet-induced humanized dyslipidemia

BACKGROUND

Diet-induced dyslipidemia is linked to the gut microbiota, but the causality of microbiota-host interaction affecting lipid metabolism remains controversial. Here, the humanized dyslipidemia mice model was successfully built by using fecal microbiota transplantation from dyslipidemic donors (FMT-dd) to study the causal role of gut microbiota in diet-induced dyslipidemia.

RESULTS

We demonstrated that FMT-dd reshaped the gut microbiota of mice by increasing Faecalibaculum and Ruminococcaceae UCG-010, which then elevated serum cholicacid (CA), chenodeoxycholic acid (CDCA), and deoxycholic acid (DCA), reduced bile acid synthesis and increased cholesterol accumulation via the hepatic farnesoid X receptor-small heterodimer partner (FXR-SHP) axis. Nevertheless, high-fat diet led to decreased Muribaculum in the humanized dyslipidemia mice induced by FMT-dd, which resulted in reduced intestinal hyodeoxycholic acid (HDCA), raised bile acid synthesis and increased lipid absorption via the intestinal farnesoid X receptor-fibroblast growth factor 19 (FXR-FGF19) axis.

CONCLUSIONS

Our studies implicated that intestinal FXR is responsible for the regulation of lipid metabolism in diet-induced dyslipidemia mediated by gut microbiota-bile acid crosstalk. Video Abstract.

Therapeutic implications of impaired nuclear receptor function and dysregulated metabolism in Wilson's disease

Copper is an essential trace element that is required for the activity of many enzymes and cellular processes, including energy homeostasis and neurotransmitter biosynthesis; however, excess copper accumulation results in significant cellular toxicity. The liver is the major organ for maintaining copper homeostasis. Inactivating mutations of the copper-transporting P-type ATPase, ATP7B, result in Wilson's disease, an autosomal recessive disorder that requires life-long medicinal therapy or liver transplantation. Current treatment protocols are limited to either sequestration of copper via chelation or reduction of copper absorption in the gut (zinc therapy). The goal of these strategies is to reduce free copper, redox stress, and cellular toxicity. Several lines of evidence in Wilson's disease animal models and patients have revealed altered hepatic metabolism and impaired hepatic nuclear receptor activity. Nuclear receptors are transcription factors that coordinate hepatic metabolism in normal and diseased livers, and several hepatic nuclear receptors have decreased activity in Wilson's disease and Atp7b-/- models. In this review, we summarize the basic physiology that underlies Wilson's disease pathology, Wilson's disease animal models, and the possibility of targeting nuclear receptor activity in Wilson's disease patients.

Bile Acid Network and Vascular Calcification-Associated Diseases: Unraveling the Intricate Connections and Therapeutic Potential

Bile acids play a crucial role in promoting intestinal nutrient absorption and biliary cholesterol excretion, thereby protecting the liver from cholesterol accumulation and bile acid toxicity. Additionally, bile acids can bind to specific nuclear and membrane receptors to regulate energy expenditure and specific functions of particular tissues. Vascular calcification refers to the pathological process of calcium-phosphate deposition in blood vessel walls, which serves as an independent predictor for cardiovascular adverse events. In addition to aging, this pathological change is associated with aging-related diseases such as atherosclerosis, hypertension, chronic kidney disease, diabetes mellitus, and osteoporosis. Emerging evidence suggests a close association between the bile acid network and these aforementioned vascular calcification-associated conditions. Several bile acids have been proven to participate in calcium-phosphate metabolism, affecting the transdifferentiation of vascular smooth muscle cells and thus influencing vascular calcification. Targeting the bile acid network shows potential for ameliorating these diseases and their concomitant vascular calcification by regulating pathways such as energy metabolism, inflammatory response, oxidative stress, and cell differentiation. Here, we present a summary of the metabolism and functions of the bile acid network and aim to provide insights into the current research on the profound connections between the bile acid network and these vascular calcification-associated diseases, as well as the therapeutic potential.

Molecular Mechanisms Involved in MAFLD in Cholecystectomized Patients: A Cohort Study

Gallstone disease and metabolic dysfunction-associated fatty liver disease (MAFLD) share numerous common risk factors and progression determinants in that they both manifest as organ-specific consequences of metabolic dysfunction. Nevertheless, the precise molecular mechanisms underlying fibrosis development in cholecystectomized MAFLD patients remain inadequately defined. This study aimed to investigate the involvement of farnesoid X receptor 1 (FXR1) and fibroblast growth factor receptor 4 (FGFR4) in the progression of fibrosis in cholecystectomized MAFLD patients. A meticulously characterized cohort of 12 patients diagnosed with MAFLD, who had undergone liver biopsies during programmed cholecystectomies, participated in this study. All enrolled patients underwent a follow-up regimen at 1, 3, and 6 months post-cholecystectomy, during which metabolic biochemical markers were assessed, along with elastography, which served as indirect indicators of fibrosis. Additionally, the hepatic expression levels of FGFR4 and FXR1 were quantified using quantitative polymerase chain reaction (qPCR). Our findings revealed a robust correlation between hepatic FGFR4 expression and various histological features, including the steatosis degree (r = 0.779, p = 0.023), ballooning degeneration (r = 0.764, p = 0.027), interphase inflammation (r = 0.756, p = 0.030), and steatosis activity score (SAS) (r = 0.779, p = 0.023). Conversely, hepatic FXR1 expression did not exhibit any significant correlations with these histological features. In conclusion, our study highlights a substantial correlation between FGFR4 expression and histological liver damage, emphasizing its potential role in lipid and glucose metabolism. These findings suggest that FGFR4 may play a crucial role in the progression of fibrosis in cholecystectomized MAFLD patients. Further research is warranted to elucidate the exact mechanisms through which FGFR4 influences metabolic dysfunction and fibrosis in this patient population.

In vivo mouse models to study bile acid synthesis and signaling

The synthesis of bile acids (BAs) is carried out by complex pathways characterized by sequential chemical reactions in the liver through various cytochromes P450 (CYP) and other enzymes. Maintaining the integrity of these pathways is crucial for normal physiological function in mammals, encompassing hepatic and neurological processes. Studying on the deficiencies in BA synthesis genes offers valuable insights into the significance of BAs in modulating farnesoid X receptor (FXR) signaling and metabolic homeostasis. By creating mouse knockout (KO) models, researchers can manipulate deficiencies in genes involved in BA synthesis, which can be used to study human diseases with BA dysregulation. These KO mouse models allow for a more profound understanding of the functions and regulations of genes responsible for BA synthesis. Furthermore, KO mouse models shed light on the distinct characteristics of individual BA and their roles in nuclear receptor signaling. Notably, alterations of BA synthesis genes in mouse models have distinct differences when compared to human diseases caused by the same BA synthesis gene deficiencies. This review summarizes several mouse KO models used to study BA synthesis and related human diseases, including mice deficient in Cyp7a1, Cyp27a1, Cyp7a1/Cyp27a1, Cyp8b1, Cyp7b1, Cyp2c70, Cyp2a12, and Cyp2c70/Cyp2a12, as well as germ-free mice.

Fucogalactan Sulfate (FS) from Laminaria japonica Regulates Lipid Metabolism in Diet-Induced Humanized Dyslipidemia Mice via an Intestinal FXR-FGF19-CYP7A1/CYP8B1 Pathway

Our previous study found that fucogalactan sulfate (FS) from Laminaria japonica exhibited significant hypolipidemic effects. To further elucidate the mechanism, we first constructed a dyslipidemia mouse model with humanized gut microbiota and proved the main differential metabolic pathway involved bile acid metabolism. Then, we evaluated the beneficial effects of FS on dyslipidemia in this model mice, which revealed that oral FS administration reduced serum cholesterol levels and mitigated liver fat accumulation. Gut microbiota and microbiome analysis showed FS increased the abundance of Ruminococcaceae_NK4A214_group, GCA-900066755, and Eubacterium, which were positively associated with the fecal DCA, β-MCA, and HDCA. Further investigation demonstrated that FS inhibited the hepatic farnesoid X receptor (FXR), while activating the intestinal FXR-FGF19 pathway, leading to suppression of CYP7A1 and CYP8B1, as well as potentially reduced bile acid synthesis and lipid absorption. Overall, FS regulated lipid metabolism in diet-induced humanized dyslipidemia mice via the bile acid-mediated intestinal FXR-FGF19-CYP7A1/CYP8B1 pathway.

Hyodeoxycholic acid attenuates cholesterol gallstone formation via modulation of bile acid metabolism and gut microbiota

BACKGROUND & AIMS

Hyodeoxycholic acid (HDCA), a hydrophilic bile acid (BA), may prevent and suppress the formation of cholesterol gallstones (CGs). However, the mechanism by which HDCA prevents CGs formation remains unclear. This study aimed to investigate the underlying mechanism of HDCA in preventing CG formation.

METHODS

C57BL/6J mice were fed either a lithogenic diet (LD), a chow diet, or LD combined with HDCA. The concentration of BAs in the liver and ileum were determined using liquid chromatography-mass spectrometry (LC-MS/MS). Genes involved in cholesterol and BAs metabolism were detected using polymerase chain reaction (PCR). The gut microbiota in the faeces was determined using 16S rRNA.

RESULTS

HDCA supplementation effectively prevented LD-induced CG formation. HDCA increased the gene expression of BA synthesis enzymes, including Cyp7a1, Cyp7b1, and Cyp8b1, and decreased the expression of the cholesterol transporter Abcg5/g8 gene in the liver. HDCA inhibited LD-induced Nuclear farnesoid X receptor (Fxr) activation and reduced the gene expression of Fgf15 and Shp in the ileum. These data indicate that HDCA could prevent CGs formation partly by promoting BA synthesis in the liver and reduced the cholesterol efflux. In addition, HDCA administration reversed the LD-induced decrease in the abundance of norank_f_Muribaculaceae, which was inversely proportional to cholesterol levels.

CONCLUSIONS

HDCA attenuated CG formation by modulating BA synthesis and gut microbiota. This study provides new insights into the mechanism by which HDCA prevents CG formation.

LAY SUMMARY

In this study, we found that HDCA supplementation suppressed LD-induced CGs in mice by inhibiting Fxr in the ileum, enhancing BA synthesis, and increasing the abundance of norank_f_Muribaculaceae in the gut microbiota. HDCA can also downregulate the level of total cholesterol in the serum, liver, and bile.

Hepatocyte-specific Sox9 knockout ameliorates acute liver injury by suppressing SHP signaling and improving mitochondrial function

BACKGROUND AND AIMS

Sex determining region Y related high-mobility group box protein 9 (Sox9) is expressed in a subset of hepatocytes, and it is important for chronic liver injury. However, the roles of Sox9+ hepatocytes in response to the acute liver injury and repair are poorly understood.

METHODS

In this study, we developed the mature hepatocyte-specific Sox9 knockout mouse line and applied three acute liver injury models including PHx, CCl4 and hepatic ischemia reperfusion (IR). Huh-7 cells were subjected to treatment with hydrogen peroxide (H2O2) in order to induce cellular damage in an in vitro setting.

RESULTS

We found the positive effect of Sox9 deletion on acute liver injury repair. Small heterodimer partner (SHP) expression was highly suppressed in hepatocyte-specific Sox9 deletion mouse liver, accompanied by less cell death and more cell proliferation. However, in mice with hepatocyte-specific Sox9 deletion and SHP overexpression, we observed an opposite phenotype. In addition, the overexpression of SOX9 in H2O2-treated Huh-7 cells resulted in an increase in cytoplasmic SHP accumulation, accompanied by a reduction of SHP in the nucleus. This led to impaired mitochondrial function and subsequent cell death. Notably, both the mitochondrial dysfunction and cell damage were reversed when SHP siRNA was employed, indicating the crucial role of SHP in mediating these effects. Furthermore, we found that Sox9, as a vital transcription factor, directly bound to SHP promoter to regulate SHP transcription.

CONCLUSIONS

Overall, our findings unravel the mechanism by which hepatocyte-specific Sox9 knockout ameliorates acute liver injury via suppressing SHP signaling and improving mitochondrial function. This study may provide a new treatment strategy for acute liver injury in future.

The polysaccharides from Auricularia auricula alleviate non-alcoholic fatty liver disease via modulating gut microbiota and bile acids metabolism

The polysaccharides from Auricularia auricula (AAPs), containing a large number of O-acetyl groups that are related to the physiological and biological properties, seem to be potential prebiotics like other edible fungus polysaccharides. In the present study, therefore, the alleviating effects of AAPs and deacetylated AAPs (DAAPs, prepared from AAPs by alkaline treatment) on nonalcoholic fatty liver disease (NAFLD) induced by high-fat and high-cholesterol diet combined with carbon tetrachloride were investigated. The results revealed that both AAPs and DAAPs could effectively relieve liver injury, inflammation and fibrosis, and maintain intestinal barrier function. Both AAPs and DAAPs could modulate the disorder of gut microbiota and altered the composition of gut microbiota with enrichment of Odoribacter, Lactobacillus, Dorea and Bifidobacterium. Further, the alteration of gut microbiota, especially enhancement of Lactobacillus and Bifidobacterium, was contributed to the changes of bile acids (BAs) profile with increased deoxycholic acid (DCA). Farnesoid X receptor could be activated by DCA and other unconjugated BAs, which participated the BAs metabolism and alleviated the cholestasis, then protected against hepatitis in NAFLD mice. Interestingly, it was found that the deacetylation of AAPs negatively affected the anti-inflammation, thereby reducing the health benefits of A. auricula-derived polysaccharides.

FXR Friend-ChIPs in the Enterohepatic System

Chronic liver diseases encompass a wide spectrum of hepatic maladies that often result in cholestasis or altered bile acid secretion and regulation. Incidence and cost of care for many chronic liver diseases are rising in the United States with few Food and Drug Administration-approved drugs available for patient treatment. Farnesoid X receptor (FXR) is the master regulator of bile acid homeostasis with an important role in lipid and glucose metabolism and inflammation. FXR has served as an attractive target for management of cholestasis and fibrosis; however, global FXR agonism results in adverse effects in liver disease patients, severely affecting quality of life. In this review, we highlight seminal studies and recent updates on the FXR proteome and identify gaps in knowledge that are essential for tissue-specific FXR modulation. In conclusion, one of the greatest unmet needs in the field is understanding the underlying mechanism of intestinal versus hepatic FXR function.

Effects of cholesterol-lowering probiotics on non-alcoholic fatty liver disease in FXR gene knockout mice

Background/aims

Some studies showed that probiotics could improve the composition and structure of gut microbiota. Changes in the gut microbiota may alter bile acid (BAs) composition and kinetics, improving non-alcoholic fatty liver disease (NAFLD). However, it still needs to be clarified how probiotics improve both the metabolism of BAs and NAFLD. This study aimed to reveal the regulatory mechanisms of cholesterol-lowering (CL) probiotics on NAFLD from aspects involved in BA metabolism in FXR gene knockout (FXR-/-) mice.

Methods

FXR-/- male mice were randomly divided into three groups based on different interventions for 16 weeks, including normal diet (ND), high-fat diet (HFD), and probiotic intervention in the HFD (HFD+P) group. 16s rDNA sequencing and ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) were utilized to analyze the changes in gut microbiota and fecal bile acids in mice.

Results

We found that the intervention of the CL probiotics improved liver lipid deposition and function in HFD-induced NAFLD mice by decreasing the levels of total cholesterol (TC; p = 0.002) and triglyceride (TG; p = 0.001) in serum, as well as suppressing liver inflammation, such as interleukin-1 beta (IL-1β; p = 0.002) and tumor necrosis factor-alpha (TNF-α; p < 0.0001). 16S rDNA sequencing and metabolomic analyses showed that probiotics effectively reduced the abundance of harmful gut microbiota, such as Firmicutes (p = 0.005), while concomitantly increasing the abundance of beneficial gut microbiota in NAFLD mice, such as Actinobacteriota (p = 0.378), to improve NAFLD. Compared with the ND group, consuming an HFD elevated the levels of total BAs (p = 0.0002), primary BAs (p = 0.017), and secondary BAs (p = 0.0001) in mice feces, while the intervention with probiotics significantly reduced the increase in the levels of fecal total bile acids (p = 0.013) and secondary bile acids (p = 0.017) induced by HFD.

Conclusion

The CL probiotics were found to improve liver function, restore microbiota balance, correct an abnormal change in the composition and content of fecal bile acids, and repair the damaged intestinal mucosal barrier in mice with NAFLD, ultimately ameliorating the condition. These results suggested that CL probiotics may be a promising and health-friendly treatment option for NAFLD.

Intermittent Fasting Alleviates Non-Alcoholic Steatohepatitis by Regulating Bile Acid Metabolism and Promoting Fecal Bile Acid Excretion in High-Fat and High-Cholesterol Diet Fed Mice

SCOPE

Intermittent fasting (IF) has a protective role across a wide range of chronic disorders, including obesity, diabetes, and cardiovascular disease, but its protection against non-alcoholic steatohepatitis (NASH) is still lacking. This study seeks to investigate how IF alleviates NASH by regulating gut microbiota and bile acids (BAs) composition.

METHODS AND RESULTS

Male C57BL/6 mice are fed a high-fat and high-cholesterol (HFHC) diet for 16 weeks to establish a NASH model. Mice then continued HFHC feeding and are treated with or without every other day fasting for 10 weeks. Hepatic pathology is assessed using hematoxylin-eosin staining. Gut microbiota of the cecum are profiled using 16S rDNA gene sequencing and the levels of BAs in serum, colon contents, and feces are measured using ultra-performance liquid chromatography-tandem mass spectrometry. Results indicate that IF significantly decreases murine body weight, insulin resistance, hepatic steatosis, ballooning, and lobular inflammation. IF reshapes the gut microbiota, reduces the accumulation of serum BAs, and increases total colonic and fecal BAs. Moreover, IF increases the expression of cholesterol 7α-hydroxylase 1 in liver, but decreases the expressions of both farnesoid-X-receptor and fibroblast growth factor 15 in the ileum.

CONCLUSION

IF alleviates NASH by regulating bile acid metabolism and promoting fecal bile acid excretion.

The regulatory role of bile acid microbiota in the progression of liver cirrhosis

Bile acids (BAs) are synthesized in liver tissue from cholesterol and are an important endocrine regulator and signaling molecule in the liver and intestine. It maintains BAs homeostasis, and the integrity of intestinal barrier function, and regulates enterohepatic circulation in vivo by modulating farnesoid X receptors (FXR) and membrane receptors. Cirrhosis and its associated complications can lead to changes in the composition of intestinal micro-ecosystem, resulting in dysbiosis of the intestinal microbiota. These changes may be related to the altered composition of BAs. The BAs transported to the intestinal cavity through the enterohepatic circulation are hydrolyzed and oxidized by intestinal microorganisms, resulting in changes in their physicochemical properties, which can also lead to dysbiosis of intestinal microbiota and overgrowth of pathogenic bacteria, induction of inflammation, and damage to the intestinal barrier, thus aggravating the progression of cirrhosis. In this paper, we review the discussion of BAs synthesis pathway and signal transduction, the bidirectional regulation of bile acids and intestinal microbiota, and further explore the role of reduced total bile acid concentration and dysregulated intestinal microbiota ratio in the development of cirrhosis, in order to provide a new theoretical basis for the clinical treatment of cirrhosis and its complications.

Licraside as novel potent FXR agonist for relieving cholestasis: structure-based drug discovery and biological evaluation studies

Cholestasis is a common clinical disease caused by a disorder in bile acids (BAs) homeostasis, which promotes its development. The Farnesoid X receptor (FXR) plays a critical role in regulating BAs homeostasis, making it an essential target for cholestasis treatment. Although several active FXR agonists have been identified, effective drugs for cholestasis are still lacking. To address this, a molecular docking-based virtual screening method was used to identify potential FXR agonists. A hierarchical screening strategy was employed to improve the screening accuracy, and six compounds were selected for further evaluation. Dual-luciferase reporter gene assay was used to demonstrate FXR activation by the screened compounds, and their cytotoxicity was then evaluated. Among the compounds, licraside showed the best performance and was selected for in vivo evaluation using an ANIT-induced cholestasis animal model. Results demonstrated that licraside significantly reduced biliary TBA, serum ALT, AST, GGT, ALP, TBIL, and TBA levels. Liver histopathological analysis showed that licraside also had a therapeutic effect on ANIT-induced liver injury. Overall, these findings suggest that licraside is an FXR agonist with potential therapeutic effects on cholestasis. This study provides valuable insights into the development of novel lead compounds from traditional Chinese medicine for cholestasis treatment.

Circadian PER1 controls daily fat absorption with the regulation of PER1-PKA on phosphorylation of bile acid synthetase

Several epidemiological studies suggest a correlation between eating time and obesity. Night eating syndrome characterized by a time-delayed eating pattern is positively associated with obesity in humans as well as in experimental animals. Here, we show that oil intake at night significantly makes more fat than that at day in wild-type mice, and circadian Period 1 (Per1) contributes to this day-night difference. Per1-knockout mice are protected from high-fat diet-induced obesity, which is accompanied by a reduction in the size of the bile acid pool, and the oral administration of bile acids restores fat absorption and accumulation. We identify that PER1 directly binds to the major hepatic enzymes involved in bile acid synthesis such as cholesterol 7alpha-hydroxylase and sterol 12alpha-hydroxylase. A biosynthesis rhythm of bile acids is accompanied by the activity and instability of bile acid synthases with PER1/PKA-mediated phosphorylation pathways. Both fasting and high fat stress enhance Per1 expression, increasing the fat absorption and accumulation. Our findings reveal that Per1 is an energy regulator and controls daily fat absorption and accumulation. Circadian Per1 controls daily fat absorption and accumulation, suggesting Per1 is a potential candidate of a key regulator in stress response and the relevant obesity risk.

Therapeutic mechanisms of the medicine and food homology formula Xiao-Ke-Yin on glucolipid metabolic dysfunction revealed by transcriptomics, metabolomics and microbiomics in mice

BACKGROUND

In recent decades, the prevalence of metabolic diseases, particularly diabetes, hyperlipidemia, obesity, and non-alcoholic fatty liver disease (NAFLD), has increased dramatically, causing great public health and economic burdens worldwide. Traditional Chinese medicine (TCM) serves as an effective therapeutic choice. Xiao-Ke-Yin (XKY) is a medicine and food homology TCM formula consisting of nine "medicine and food homology" herbs and is used to ameliorate metabolic diseases, such as insulin resistance, diabetes, hyperlipidemia and NAFLD. However, despite its therapeutic potential in metabolic disorders, the underlying mechanisms of this TCM remain unclear. This study aimed to evaluate the therapeutic effectiveness of XKY on glucolipid metabolism dysfunction and explore the potential mechanisms in db/db mice.

METHODS

To verify the effects of XKY, db/db mice were treated with different concentrations of XKY (5.2, 2.6 and 1.3 g/kg/d) and metformin (0.2 g/kg/d, a hypoglycemic positive control) for 6 weeks, respectively. During this study, we detected the body weight (BW) and fasting blood glucose (FBG), oral glucose tolerance test (OGTT), insulin tolerance test (ITT), daily food intake and water intake. At the end of the animal experiment, blood samples, feces, liver and intestinal tissue of mice in all groups were collected. The potential mechanisms were investigated by using hepatic RNA sequencing, 16 S rRNA sequencing of the gut microbiota and metabolomics analysis.

RESULTS

XKY efficiently mitigated hyperglycemia, IR, hyperlipidemia, inflammation and hepatic pathological injury in a dose dependent manner. Mechanistically, hepatic transcriptomic analysis showed that XKY treatment significantly reversed the upregulated cholesterol biosynthesis which was further confirmed by RT-qPCR. Additionally, XKY administration maintained intestinal epithelial homeostasis, modulated gut microbiota dysbiosis, and regulated its metabolites. In particular, XKY decreased secondary bile acid producing bacteria (Clostridia and Lachnospircaeae) and lowered fecal secondary bile acid (lithocholic acid (LCA) and deoxycholic acid (DCA)) levels to promote hepatic bile acid synthesis by inhibiting the LCA/DCA-FXR-FGF15 signalling pathway. Furthermore, XKY regulated amino acid metabolism including arginine biosynthesis, alanine, aspartate and glutamate metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, and tryptophan metabolism likely by increasing Bacilli, Lactobacillaceae and Lactobacillus, and decreasing Clostridia, Lachnospircaeae, Tannerellaceae and Parabacteroides abundances.

CONCLUSION

Taken together, our findings demonstrate that XKY is a promising "medicine food homology" formula for ameliorating glucolipid metabolism and reveal that the therapeutic effects of XKY may due to its downregulation of hepatic cholesterol biosynthesis and modulation of the dysbiosis of the gut microbiota and metabolites.

Gentamicin alleviates cholestatic liver injury by decreasing gut microbiota-associated bile salt hydrolase activity in rats

Intrahepatic cholestasis lacks effective therapeutic drugs. The gut microbiota-associated bile salt hydrolases (BSH) may be a potential therapeutic target. In this study, oral administration of gentamicin (GEN) decreased the serum and hepatic levels of total bile acid in 17α-ethynylestradiol (EE)-induced cholestatic male rats, significantly improved the serum levels of hepatic biomarkers and reversed the histopathological changes in the liver. In healthy male rats, the serum and hepatic levels of total bile acid were also decreased by GEN, the ratio of primary to secondary bile acids, and conjugated to unconjugated bile acids was significantly increased, and the urinary excretion of total bile acid was elevated. 16S rDNA sequencing of the ileal contents revealed that GEN treatment substantially reduced the abundance of Lactobacillus and Bacteroides both of which expressed BSH. Consistently, BSH activity analysis by the generation of d5-chenodeoxycholic acid from d5-taurochenodeoxycholic acid in situ showed BSH was significantly inhibited in the ileal contents of rats treated with GEN. This finding led to an increased proportion of hydrophilic conjugated bile acids and facilitated the urinary excretion of total bile acids, thereby decreasing serum and hepatic total bile acids and reversing liver injury related to cholestasis. Our results provide important evidence that BSH can be a potential drug target for treating cholestasis.