Natural Products in the Modulation of Farnesoid X Receptor Against Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is a global health concern with a high prevalence and increasing economic burden, but official medicine remains unavailable. Farnesoid X receptor (FXR), a nuclear receptor member, is one of the most promising drug targets for NAFLD therapy that plays a crucial role in modulating bile acid, glucose, and lipid homeostasis, as well as inhibits hepatic inflammation and fibrosis. However, the rejection of the FXR agonist, obecholic acid, by the Food and Drug Administration for treating hepatic fibrosis raises a question about the functions of FXR in NAFLD progression and the therapeutic strategy to be used. Natural products, such as FXR modulators, have become the focus of attention for NAFLD therapy with fewer adverse reactions. The anti-NAFLD mechanisms seem to act as FXR agonists and antagonists or are involved in the FXR signaling pathway activation, indicating a promising target of FXR therapeutic prospects using natural products. This review discusses the effective mechanisms of FXR in NAFLD alleviation, and summarizes currently available natural products such as silymarin, glycyrrhizin, cycloastragenol, berberine, and gypenosides, for targeting FXR, which can facilitate development of naturally targeted drug by medicinal specialists for effective treatment of NAFLD.

Farnesoid X receptor in chronic liver diseases: an immunohistochemical study.

Chronic hepatitis C virus (HCV) related liver diseases are still an ongoing cause of hepatic failure despite the effective role of direct-acting anti-viral agents. Farnesoid X receptor (FXR) agonists have a potential therapeutic effect on the management of chronic liver diseases (CLD). However, data regarding FXR protein expression in human CLDs are limited and conflicting. We aimed to assess the immunohistochemical expression of FXR in HCV-related chronic hepatitis and cirrhosis in comparison with metabolic-associated fatty liver disease (MAFLD) and normal liver tissue. The expression of FXR was low both in hepatocytes and bile ducts of HCV-related chronic hepatitis and cirrhosis (p = .001, respectively). In addition, a significantly low expression of FXR was observed in HCV-related hepatitis and cirrhosis groups compared to MAFLD in hepatocytes (p < .001, for both) and bile ducts (p = .004 and p = .018). FXR expression in HCV-related cirrhosis was significantly associated with compensated liver function (p = .032) and low inflammatory activity (p = .022). FXR expression decreases in HCV-related CLDs. There was some evidence that FXR expression could protect against post-hepatitis cirrhosis.

ELK4 Promotes Cell Cycle Progression and Stem Cell-like Characteristics in HPV-associated Cervical Cancer by Regulating the FBXO22/PTEN Axis

Background: Cervical cancer (CC) is a prevalent gynecological carcinoma, and patients infected with human papillomavirus (HPV) have a higher morbidity rate. Aims: To explore the effects of ETS-like transcription factor 4 (ELK4) in patients with HPV+ CC. Study design: In vitro cell lines and human-sample study. Methods: The ELK4 levels in human tissue (65 HPV+ CC tissue and 25 HPV− normal cervical tissue) and cell lines (human cervical epithelial immortalized cell line H8 and CC cell lines HeLa [HPV18], CaSki [HPV16], and SiHa [HPV−]) were quantified using qRT-PCR and western blot assay. ELK4 knockdown transfection was effective and confirmed by western blotting. The MTT and EDU assays were used to evaluate cell viability and proliferation, respectively. Flow cytometry was used to detect the CC cell cycle stage. Stem cell markers, such as cluster of differentiation 133 (CD133), CD44, and aldehyde dehydrogenase 1, and the cervicospheres formed were measured. ChIP-qPCR and luciferase activity experiments were used to assess the bond between ELK4 and F-box protein 22 (FBXO22). Results: ELK4 was highly expressed in the HPV+ CC tissue. CC cells with ELK4 knockdown had lower viability and proliferation than the control cells. ELK4 knockdown blocked the progression of the cell cycle from G1 to S phase. ELK4 knockdown suppressed the stem cell-like characteristics of the HPV+ CC cells. ELK4 bonded with the FBXO22 promoter, inhibiting the levels of phosphatase and tensin homolog (PTEN). Conclusion: ELK4 facilitated cell cycle progression and stem cell-like characteristics by regulating the FBXO22/PTEN axis. Thus, ELK4 could be a potential therapeutic target to arrest the progress of HPV-associated CC.

Inhibition of Nuclear Receptor Related Orphan Receptor γ Ameliorates Mechanical Hypersensitivity Through the Suppression of Spinal Microglial Activation.

Microglia are crucial in induction of central sensitization under a chronic pain state. Therefore, control of microglial activity is important to ameliorate nociceptive hypersensitivity. The nuclear receptor retinoic acid related orphan receptor γ (RORγ) contributes to the regulation of inflammation-related gene transcription in some immune cells, including T cells and macrophages. Their role and function in regulation of microglial activity and nociceptive transduction have yet to be elaborated. Treatment of cultured microglia with specific RORγ inverse agonists, SR2211 or GSK2981278, significantly suppressed lipopolysaccharide (LPS)-induced mRNA expression of pronociceptive molecules interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor (TNF). Intrathecal treatment of naïve male mice with LPS markedly induced mechanical hypersensitivity and upregulation of ionized calcium-biding adaptor molecule (Iba1) in the spinal dorsal horn, indicating microglial activation. In addition, intrathecal treatment with LPS significantly induced mRNA upregulation of IL-1ß and IL-6 in the spinal dorsal horn. These responses were prevented by intrathecal pretreatment with SR2211. In addition, intrathecal administration of SR2211 significantly ameliorated established mechanical hypersensitivity and upregulation of Iba1 immunoreactivity in the spinal dorsal horn of male mice following peripheral sciatic nerve injury. The current findings demonstrate that blockade of RORγ in spinal microglia exerts anti-inflammatory effects, and that RORγ may be an appropriate target for the treatment of chronic pain.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia.

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

Baohuoside I inhibits FXR signaling pathway to interfere with bile acid homeostasis via targeting ER α degradation.

Epimedii folium (EF) is an effective herbal medicine in osteoporosis treatment, but the clinical utilization of EF has been limited due to potential hepatotoxicity. The previous studies identified that baohuoside I (BI), the main active component of EF, was relevant to EF-induced liver injury. However, the mechanisms of BI causing direct injury to hepatocytes remain unclear. Here, we reveal that BI inhibits FXR-mediated signaling pathway via targeting estrogen receptor α (ER α), leading to the accumulation of bile acids (BAs). Targeted bile acid analyses show BI alters the BA composition and distribution, resulting in impaired BA homeostasis. Mechanistically, BI induces FXR-dependent hepatotoxicity at transcriptional level. Additionally, ER α is predicted to bind to the FXR promoter region based on transcription factor binding sites databases and we further demonstrate that ER α positively regulates FXR promoter activity and affects the expression of target genes involved in BA metabolism. Importantly, we discover that ER α and its mediated FXR transcription regulation might be involved in BI-induced liver injury via ligand-dependent ER α degradation. Collectively, our findings indicate that FXR is a newly discovered target gene of ER α mediated BI-induced liver injury, and suggest BI may be responsible for EF-induced liver injury.

A microfluidic thyroid-liver platform to assess chemical safety in humans.

Thyroid hormones (THs) are crucial regulators of human metabolism and early development. During the safety assessment of plant protection products, the human relevance of chemically induced TH perturbations observed in test animals remains uncertain. European regulatory authorities request follow-up in vitro studies to elucidate human-relevant interferences on thyroid gland function or TH catabolism through hepatic enzyme induction. However, human in vitro assays based on single molecular initiating events poorly reflect the complex TH biology and related liver-thyroid axis. To address this complexity, we present human three-dimensional thyroid and liver organoids with key functions of TH metabolism. The thyroid model resembles in vivo-like follicular architecture and a TSH-dependent triiodothyronine synthesis over 21 days, which is inhibited by methimazole. The HepaRG-based liver model, secreting the critical TH-binding proteins albumin and thyroxine-binding globulin, emulates an active TH catabolism via the formation of glucuronidated and sulfated thyroxine (gT4/sT4). Activation of the nuclear receptors PXR and AHR was demonstrated via the induction of specific CYP isoenzymes by rifampicin, pregnenolone-16α-carbonitrile, and ß-naphthoflavone. However, this nuclear receptor activation, assumed to regulate UDP-glucuronosyltransferases and sulfotransferases, appeared to have no effect on gT4 and sT4 formation in this human-derived hepatic cell line model. Finally, established single-tissue models were successfully co-cultured in a perfused two-organ chip for 21 days. In conclusion, this model presents a first step towards a complex multimodular human platform that will help to identify both direct and indirect thyroid disruptors that are relevant from a human safety perspective.

Diminished Tubule Epithelial Farnesoid X Receptor Expression Exacerbates Inflammation and Fibrosis Response in Aged Rat Kidney.

The age-associated functional decline of the kidney is accompanied by structural changes including glomerular sclerosis and interstitial fibrosis. Aging kidneys also exhibit increased vulnerability in stressful environmental conditions. In this study, we assessed the differences in responses between young and aged animals to folic acid (FA)-induced renal fibrosis. To monitor the effects of aging on FA-induced kidney fibrosis, we administered FA (250 mg/kg) to young (6-month old) and aged (20-month old) rats. The development of severe fibrosis was only detected in aged rat kidneys, which was accompanied by increased kidney injury and inflammation. Furthermore, we found that FA-treated aged rats had significantly lower farnesoid X receptor (FXR) expression in the tubular epithelial cells than the rats not treated with FA. Interestingly, the extent of inflammation was severe in the kidneys of aged rat, where the FXR expression was low. To explore the role of FXR in kidney inflammation, in vitro studies were performed using NRK52E kidney tubule epithelial cells. NF-κB activation by lipopolysaccharide treatment induces chemokine production in NRK52E cells. The activation of FXR by obeticholic acid significantly reduced the transcriptional activity of NF-κB and chemokine production. In contrast, FXR knockdown increased LPS-induced chemokine production in NRK52E cells. Finally, FXR-knockout mice that were administered FA showed increased inflammation and severe fibrosis. In summary, we demonstrated that diminished FXR expression in the epithelial cells of the renal tubules exacerbated the fibrotic response in aged rat kidneys by upregulating pro-inflammatory NF-κB activation.

Glycine-ß-muricholic acid antagonizes the intestinal farnesoid X receptor-ceramide axis and ameliorates NASH in mice.

Nonalcoholic steatohepatitis (NASH) is a rapidly developing pathology around the world, with limited treatment options available. Some farnesoid X receptor (FXR) agonists have been applied in clinical trials for NASH, but side effects such as pruritus and low-density lipoprotein elevation have been reported. Intestinal FXR is recognized as a promising therapeutic target for metabolic diseases. Glycine-ß-muricholic acid (Gly-MCA) is an intestine-specific FXR antagonist previously shown to have favorable metabolic effects on obesity and insulin resistance. Herein, we identify a role for Gly-MCA in the pathogenesis of NASH, and explore the underlying molecular mechanism. Gly-MCA improved lipid accumulation, inflammatory response, and collagen deposition in two different NASH models. Mechanistically, Gly-MCA decreased intestine-derived ceramides by suppressing ceramide synthesis-related genes via decreasing intestinal FXR signaling, leading to lower liver endoplasmic reticulum (ER) stress and proinflammatory cytokine production. The role of bile acid metabolism and adiposity was excluded in the suppression of NASH by Gly-MCA, and a correlation was found between intestine-derived ceramides and NASH severity. This study revealed that Gly-MCA, an intestine-specific FXR antagonist, has beneficial effects on NASH by reducing ceramide levels circulating to liver via lowering intestinal FXR signaling, and ceramide production, followed by decreased liver ER stress and NASH progression. Intestinal FXR is a promising drug target and Gly-MCA a novel agent for the prevention and treatment of NASH.

Nuclear receptor ligand screening in an iPSC-derived in vitro blood-brain barrier model identifies new contributors to leptin transport.

BACKGROUND: The hormone leptin exerts its function in the brain to reduce food intake and increase energy expenditure to prevent obesity. However, most obese subjects reflect the resistance to leptin even with elevated serum leptin. Considering that leptin must cross the blood-brain barrier (BBB) in several regions to enter the brain parenchyma, altered leptin transport through the BBB might play an important role in leptin resistance and other biological conditions. Here, we report the use of a human induced pluripotent stem cell (iPSC)-derived BBB model to explore mechanisms that influence leptin transport. METHODS: iPSCs were differentiated into brain microvascular endothelial cell (BMEC)-like cells using standard methods. BMEC-like cells were cultured in Transwell filters, treated with ligands from a nuclear receptor agonist library, and assayed for leptin transport using an enzyme-linked immune sorbent assay. RNA sequencing was further used to identify differentially regulated genes and pathways. The role of a select hit in leptin transport was tested with the competitive substrate assay and after gene knockdown using CRISPR techniques. RESULTS: Following a screen of 73 compounds, 17ß-estradiol was identified as a compound that could significantly increase leptin transport. RNA sequencing revealed many differentially expressed transmembrane transporters after 17ß-estradiol treatment. Of these, cationic amino acid transporter-1 (CAT-1, encoded by SLC7A1) was selected for follow-up analyses due to its high and selective expression in BMECs in vivo. Treatment of BMEC-like cells with CAT-1 substrates, as well as knockdown of CAT-1 expression via CRISPR-mediated epigenome editing, yielded significant increases in leptin transport. CONCLUSIONS: A major female sex hormone, as well as an amino acid transporter, were revealed as regulators of leptin BBB transport in the iPSC-derived BBB model. Outcomes from this work provide insights into regulation of hormone transport across the BBB.

Combining selinexor with alisertib to target the p53 pathway in neuroblastoma.

Neuroblastoma accounts for 15% of cancer-related deaths in children, highlighting an unmet need for novel therapies. Selinexor is a small molecule inhibitor of XPO1. XPO1 shuffles cargo proteins with a nuclear export sequence from the nucleus to the cytosol, many of which are essential for cancer growth and cell maintenance. We systematically tested the effect of selinexor against neuroblastoma cells in vitro and in vivo and used an advanced proteomic and phosphoproteomic screening approach to interrogate unknown mechanisms of action. We found that selinexor induced its cytotoxic effects in neuroblastoma through the predominantly nuclear accumulation of p53 and global activation of apoptosis pathways. Selinexor also induced p53 phosphorylation at site S315, which is one initiating step for p53 degradation. Since this phosphorylation step is undertaken mostly by aurora kinase A (AURKA), we used the clinically available AURKA inhibitor, alisertib, and found p53-mediated lethality could be further augmented in three orthotopic xenograft mouse models. These findings suggest a potential therapeutic benefit using selinexor and alisertib to synergistically increase p53-mediated cytotoxicity of high-risk neuroblastoma.

Modulating undruggable targets to overcome cancer therapy resistance.

Many cancer patients frequently fail to respond to anti-cancer treatment due to therapy resistance which is the major obstacle towards curative cancer treatment. Therefore, identification of the molecular mechanisms underlying resistance is of paramount clinical and economic importance. The advent of targeted therapies based on a molecular understanding of cancer could serve as a model for strategies to overcome drug resistance. Accordingly, the identification and validation of proteins critically involved in resistance mechanisms represent a path towards innovative therapeutic strategies to improve the clinical outcome of cancer patients. In this review, we discuss emerging targets, small molecule therapeutics and drug delivery strategies to overcome therapy resistance. We focus on rational treatment strategies based on transcription factors, pseudokinases, nuclear export receptors and immunogenic cell death strategy. Historically, unliganded transcription factors and pseudokinases were considered undruggable while blocking the nuclear export e.g., through inhibition of the nuclear export receptor CRM1 was predicted as highly toxic. Recent success inhibiting Gli-1, HIF-1α, HIF-2α and reactivating the tumor suppressor transcription factors p53 and FOXO illustrates the feasibility and power of this targeting approach. Similarly, progress has been made in modulating the activity of pseudokinase proteins implicated in therapy resistance including members of the Tribbles protein family. On the other hand, the recent clinical approval of Selinexor, a specific inhibitor of CRM-1, a protein that mediates the transport of cargos with leucine-rich nuclear export signals and known to be a driver of drug resistance, represents the proof-of-concept for inhibiting the nuclear export as a feasible strategy to overcome therapy resistance. The ever-growing capacity to target resistance mechanisms with judiciously selected small molecules, some of which are being formulated within smart nanoparticles, will pave the way towards the improvement of the clinical outcome and realize the full potential of targeted therapies and immunotherapies.

Nuclear receptors: from molecular mechanisms to therapeutics.

Nuclear receptors are classically defined as ligand-activated transcription factors that regulate key functions in reproduction, development, and physiology. Humans have 48 nuclear receptors, which when dysregulated are often linked to diseases. Because most nuclear receptors can be selectively activated or inactivated by small molecules, they are prominent therapeutic targets. The basic understanding of this family of transcription factors was accelerated in the 1980s upon the cloning of the first hormone receptors. During the next 20 years, a deep understanding of hormone signaling was achieved that has translated to numerous clinical applications, such as the development of standard-of-care endocrine therapies for hormonally driven breast and prostate cancers. A 2004 issue of this journal reviewed progress on elucidating the structures of nuclear receptors and their mechanisms of action. In the current issue, we focus on the broad application of new knowledge in this field for therapy across diverse disease states including cancer, cardiovascular disease, various inflammatory diseases, the aging brain, and COVID-19.

Farnesoid X Receptor as a Promising Therapeutic Target for Nonalcoholic Fatty Liver Disease (NAFLD) and the Current Development of Its Agonists.

Nonalcoholic fatty liver disease (NAFLD) comprises a group of clinical syndromes characterized by excessive fat deposition in liver cells. Owing to its increasing incidence, NAFLD has becomea pertinent global health problem as well as an important contributor to the fatality rate of liver and metabolic diseases. Farnesoid X receptor (FXR) has emerged as a new target in the treatment of NAFLD, and related drugs are being reported. This review provides an overview of the structure and function of FXR, along with its important regulatory roles in bile acid metabolism and lipid metabolism. The review also highlights the clinical application of FXR and the progress on basic research related to FXR modulators in NAFLD treatment. Identifying potent FXR modulators, structure-based virtual screening strategy, and the development of new drugs to regulate the allosteric pathway of FXR activity have become effective approaches for the study of novel ligand, which can expand the therapeutic applications of novel FXR agonists. Identification of potential FXR modulators may help elucidate the physiological effects of FXR and provide new opportunities for targeting FXR for metabolic diseases.

Nuclear Receptors as Potential Therapeutic Targets for Myeloid Leukemia.

The nuclear receptor (NR) superfamily has been studied extensively in many solid tumors and some receptors have been targeted to develop therapies. However, their roles in leukemia are less clear and vary considerably among different types of leukemia. Some NRs participate in mediating the differentiation of myeloid cells, making them attractive therapeutic targets for myeloid leukemia. To date, the success of all-trans retinoic acid (ATRA) in treating acute promyelocytic leukemia (APL) remains a classical and unsurpassable example of cancer differentiation therapy. ATRA targets retinoic acid receptor (RAR) and forces differentiation and/or apoptosis of leukemic cells. In addition, ligands/agonists of vitamin D receptor (VDR) and peroxisome proliferator-activated receptor (PPAR) have also been shown to inhibit proliferation, induce differentiation, and promote apoptosis of leukemic cells. Encouragingly, combining different NR agonists or the addition of NR agonists to chemotherapies have shown some synergistic anti-leukemic effects. This review will summarize recent research findings and discuss the therapeutic potential of selected NRs in acute and chronic myeloid leukemia, focusing on RAR, VDR, PPAR, and retinoid X receptor (RXR). We believe that more mechanistic studies in this field will not only shed new lights on the roles of NRs in leukemia, but also further expand the clinical applications of existing therapeutic agents targeting NRs.

Exportin 1 Inhibition Induces Nerve Growth Factor Receptor Expression to Inhibit the NF-κB Pathway in Preclinical Models of Pediatric High-Grade Glioma.

High-grade glioma (HGG) is the leading cause of cancer-related death among children. Selinexor, an orally bioavailable, reversible inhibitor of the nuclear export protein, exportin 1, is in clinical trials for a range of cancers, including HGG. It inhibits the NF-κB pathway and strongly induces the expression of nerve growth factor receptor (NGFR) in preclinical cancer models. We hypothesized that selinexor inhibits NF-κB via upregulation of NGFR. In HGG cells, sensitivity to selinexor correlated with increased induction of cell surface NGFR expression. Knocking down NGFR in HGG cells increased proliferation, anchorage-independent growth, stemness markers, and levels of transcriptionally available nuclear NF-κB not bound to IκB-α, while decreasing apoptosis and sensitivity to selinexor. Increasing IκB-α levels in NGFR knockdown cells restored sensitivity to selinexor. Overexpression of NGFR using cDNA reduced levels of free nuclear NF-κB, decreased stemness markers, and increased markers of cellular differentiation. In all HGG lines tested, selinexor decreased phosphorylation of NF-κB at serine 536 (a site associated with increased transcription of proliferative and inflammatory genes). Because resistance to selinexor monotherapy occurred in our in vivo model, we screened selinexor with a panel of FDA-approved anticancer agents. Bortezomib, a proteasome inhibitor that inhibits the NF-κB pathway through a different mechanism than selinexor, showed synergy with selinexor against HGG in vitro Our results help elucidate selinexor's mechanism of action and identify NGFR as a potential biomarker of its effect in HGG and in addition suggest a combination therapy strategy for these challenging tumors.

The Pharmacology of Bile Acids and Their Receptors.

This review provides a historical perspective of bile acids and their receptors as therapeutic targets. Bile acids are atypical steroids generated by the liver from cholesterol and have been used for almost half a century for treating liver and biliary disorders. Since the early 1970s of the last century, chenodeoxycholic acid (CDCA), a primary bile acid, and ursodeoxycholic acid (UDCA), a secondary bile acid and the 7ßepimer of CDCA, have been shown effective in promoting the dissolution of cholesterol gallstones. However, lack of activity and side effects associated with the use of CDCA, along with the advent of laparoscopic cholecystectomy, have greatly reduced the clinical relevance of this application. At the turn of the century, however, the discovery that bile acids activate specific receptors, along with the discovery that those receptors are placed at the interface of the host and intestinal microbiota regulating physiologically relevant enterohepatic and entero-pancreatic axes, has led to a "bile acid renaissance." Similarly to other steroids, bile acids bind and activate both cell surface and nuclear receptors, including the bile acid sensor farnesoid X receptor (FXR) and a G-protein-coupled bile acid receptor, known as GPBAR1 (TGR5). Both receptors have been proved druggable, and several highly potent, selective, and nonselective ligands for the two receptors have been discovered in the last two decades. Currently, in addition to obeticholic acid, a semisynthetic derivative of CDCA and the first in class of FXR ligands approved for clinical use, either selective or dual FXR and GPBAR1 ligands, have been developed, and some of them are undergoing pre-approval trials. The effects of FXR and GPBAR1 ligands in different therapeutic area are reviewed.

Intestine farnesoid X receptor agonist and the gut microbiota activate G-protein bile acid receptor-1 signaling to improve metabolism.

Bile acids activate farnesoid X receptor (FXR) and G protein-coupled bile acid receptor-1 (aka Takeda G protein-coupled receptor-5 [TGR5]) to regulate bile acid metabolism and glucose and insulin sensitivity. FXR and TGR5 are coexpressed in the enteroendocrine L cells, but their roles in integrated regulation of metabolism are not completely understood. We reported recently that activation of FXR induces TGR5 to stimulate glucagon-like peptide-1 (GLP-1) secretion to improve insulin sensitivity and hepatic metabolism. In this study, we used the intestine-restricted FXR agonist fexaramine (FEX) to study the effect of activation of intestinal FXR on the gut microbiome, bile acid metabolism, and FXR and TGR5 signaling. The current study revealed that FEX markedly increased taurolithocholic acid, increased secretion of fibroblast growth factors 15 and 21 and GLP-1, improved insulin and glucose tolerance, and promoted white adipose tissue browning in mice. Analysis of 16S ribosomal RNA sequences of the gut microbiome identified the FEX-induced and lithocholic acid-producing bacteria Acetatifactor and Bacteroides. Antibiotic treatment completely reversed the FEX-induced metabolic phenotypes and inhibited taurolithocholic acid synthesis, adipose tissue browning, and liver bile acid synthesis gene expression but further increased intestinal FXR target gene expression. FEX treatment effectively improved lipid profiles, increased GLP-1 secretion, improved glucose and insulin tolerance, and promoted adipose tissue browning, while antibiotic treatment reversed the beneficial metabolic effects of FEX in obese and diabetic mice. CONCLUSION: This study uncovered a mechanism in which activation of intestinal FXR shaped the gut microbiota to activate TGR5/GLP-1 signaling to improve hepatic glucose and insulin sensitivity and increase adipose tissue browning; the gut microbiota plays a critical role in bile acid metabolism and signaling to regulate metabolic homeostasis in health and disease. (Hepatology 2018).

Small heterodimer partner attenuates profibrogenic features of hepatitis C virus-infected cells.

BACKGROUND & AIMS: An atypical orphan nuclear receptor small heterodimer partner (SHP) is known to be regulated by AMP-activated protein kinase (AMPK). Both of them inhibit TGF-ß and Smad signalling and exhibit antifibrotic activity in the liver. However, little is known about the protective effects of SHP and AMPK against hepatitis c virus (HCV)-induced hepatic fibrosis. METHODS: Levels of SHP, p-AMPK and fibrotic markers in HCV-infected human liver and in Huh-7.5 cells infected with HCV genotype 2a (JFH-1) were investigated. The effect of adenovirus-mediated overexpression of SHP (Ad-SHP) and AMPK activation via metformin and 5-amino-1-b-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) on fibrotic gene expression was evaluated in HCV-infected cells. Finally, we examined the effect of Ad-SHP and AMPK activators on invasion and activation of LX2 human HSCs induced by conditioned media from HCV-infected hepatocyte (CM). RESULTS: In HCV-infected human livers and Huh-7.5 cells infected with HCV, SHP mRNA and protein levels were diminished compared with controls, whereas profibrotic factors were increased. Pharmacological AMPK activation recovered SHP expression, and Ad-SHP inhibited HCV-induced fibrotic gene expression. This finding was accompanied by inhibition of HCV-stimulated nuclear factor-kappa B, an inducer of TGF-ß. Moreover, CytoSelect invasion assay revealed that enhanced activity and invasiveness of hepatic stellate cells induced by CM. CONCLUSION: These results demonstrate that overexpression of SHP and activation of AMPK reverses profibrogenic features of HCV-infected cells by decreasing TGF-ß and fibrotic gene expression. These findings provide a rationale for SHP as a possible therapeutic target against HCV-induced hepatic fibrosis.