FXR activation reverses insulin resistance and lipid abnormalities and protects against liver steatosis in Zucker (fa/fa) obese rats

Recent advances on FXR-targeting therapeutics

The bile acid receptor FXR has emerged as a bona fide drug target for chronic cholestatic and metabolic liver diseases, ahead of all non-alcoholic fatty liver disease (NAFLD). FXR is highly expressed in the liver and intestine and activation at both sites differentially contributes to its desired metabolic effects. Unrestricted FXR activation, however, also comes along with undesired effects such as a pro-atherogenic lipid profile, pruritus and hepatocellular toxicity under certain conditions. Several pre-clinical studies have confirmed the potency of FXR activation for cholestatic and metabolic liver diseases, but overall it remains still open whether selective activation of intestinal FXR is advantageous over pan-FXR activation and whether restricted or modulated FXR activation can limit some of the side effects. Even more, FXR antagonist also bear the potential as intestinal-selective drugs in NAFLD models. In this review we will discuss the molecular prerequisites for FXR activation, pan-FXR activation and intestinal FXR in/activation from a therapeutic point of view, different steroidal and non-steroidal FXR agonists, ways to restrict FXR activation and finally what we have learned from pre-clinical models and clinical trials with different FXR therapeutics.

Obeticholic acid inhibits hepatic fatty acid uptake independent of FXR in mouse

OBJECTIVE

Obeticholic acid (OCA), a farnesoid X receptor (FXR) agonist, is believed to alleviate nonalcoholic fatty liver disease (NAFLD) by decreasing hepatic lipogenesis in an FXR-dependent manner. Here, we revealed a novel mechanism by which OCA improves NAFLD by affecting hepatic long-chain fatty acids (LCFAs) uptake.

METHODS

Stably transfected HEK-293 cells expressing fatty acid transport protein 5 (FATP5) were established to examine fatty acid uptake; FXR^-/-, human (h) FATP5, and FXR^-/-/hFATP5 mouse models were incorporated to explore the effects of OCA on FATP5 ex vivo and in vivo.

RESULTS

OCA inhibited hFATP5 (IC₅₀ =0.07 μM) more than murine (m) FATP5 (IC₅₀ =1.04 μM) as measured by LCFAs uptake in FATP5 expressing HEK-293. OCA also inhibited LCFA uptake in primary hepatocytes from hFATP5 mice, FXR^-/-/hFATP5 mice more than that from FXR^-/- mice, ex vivo. Moreover, OCA inhibited LCFAs uptake by livers in hFATP5 mice and FXR^-/-/hFATP5 mice, but not in FXR^-/- mice, in vivo. Long-term administration of 0.04% OCA markedly reduced hepatic triglyceride (TG) accumulation in hFATP5 mice and FXR^-/-/hFATP5 mice by 63% and 53%, respectively, but not in FXR^-/- mice.

CONCLUSIONS

OCA ameliorated high-fat diet-induced NAFLD independent of FXR by inhibiting hepatic hFATP5-mediated LCFAs uptake. This suggests that the therapeutic effects of OCA on NAFLD in vivo are mediated by a novel, hFATP5 dependent mechanism.

Obeticholic Acid Induces Hepatoxicity Via FXR in the NAFLD Mice

Objective: Obeticholic acid (OCA), a potent farnesoid X receptor (FXR) agonist, is a promising drug for nonalcoholic fatty liver disease (NAFLD); however, it can cause liver injury, especially at high doses. Here, we investigated the role of FXR in the high-dose OCA-induced hepatoxicity in the condition of the NAFLD mouse model.

Methods: Wild-type (WT) mice and FXR^−/− mice were administered with over-dose OCA (0.40%) and high-dose OCA (0.16%), in a high-fat diet. RNA-seq on liver samples of mice fed with high-dose OCA was performed to dig out the prominent biological events contributing to hepatic fibrosis.

Results: Over-dose OCA induced liver injury and shortened survival in WT mice, but not FXR^−/− mice. High-dose OCA caused hepatic stellate cell activation and liver fibrosis in the presence of FXR. Furthermore, high-dose OCA induced cholesterol accumulation in livers via the upregulation of genes involved in cholesterol acquisition and downregulation of genes regulating cholesterol degradation in liver, leading to the production of interleukin -1β and an FXR-mediated inflammatory response.

Conclusion: The high-dose OCA induced FXR-dependent hepatic injury via cholesterol accumulation and interleukin -1β pathway in the NAFLD mice.

The RNA binding protein human antigen R is a gatekeeper of liver homeostasis

BACKGROUND AND AIMS

NAFLD is initiated by steatosis and can progress through fibrosis and cirrhosis to HCC. The RNA binding protein human antigen R (HuR) controls RNAs at the posttranscriptional level; hepatocyte HuR has been implicated in the regulation of diet-induced hepatic steatosis. The present study aimed to understand the role of hepatocyte HuR in NAFLD development and progression to fibrosis and HCC.

APPROACH AND RESULTS

Hepatocyte-specific, HuR-deficient mice and control HuR-sufficient mice were fed either a normal diet or an NAFLD-inducing diet. Hepatic lipid accumulation, inflammation, fibrosis, and HCC development were studied by histology, flow cytometry, quantitative PCR, and RNA sequencing. The liver lipidome was characterized by lipidomics analysis, and the HuR-RNA interactions in the liver were mapped by RNA immunoprecipitation sequencing. Hepatocyte-specific, HuR-deficient mice displayed spontaneous hepatic steatosis and fibrosis predisposition compared to control HuR-sufficient mice. On an NAFLD-inducing diet, hepatocyte-specific HuR deficiency resulted in exacerbated inflammation, fibrosis, and HCC-like tumor development. A multi-omic approach, including lipidomics, transcriptomics, and RNA immunoprecipitation sequencing revealed that HuR orchestrates a protective network of hepatic-metabolic and lipid homeostasis-maintaining pathways. Consistently, HuR-deficient livers accumulated, already at steady state, a triglyceride signature resembling that of NAFLD livers. Moreover, up-regulation of secreted phosphoprotein 1 expression mediated, at least partially, fibrosis development in hepatocyte-specific HuR deficiency on an NAFLD-inducing diet, as shown by experiments using antibody blockade of osteopontin.

CONCLUSIONS

HuR is a gatekeeper of liver homeostasis, preventing NAFLD-related fibrosis and HCC, suggesting that the HuR-dependent network could be exploited therapeutically.

In Silico Development of Combinatorial Therapeutic Approaches Targeting Key Signaling Pathways in Metabolic Syndrome

PURPOSE

Dysregulations of key signaling pathways in metabolic syndrome are multifactorial, eventually leading to cardiovascular events. Hyperglycemia in conjunction with dyslipidemia induces insulin resistance and provokes release of proinflammatory cytokines resulting in chronic inflammation, accelerated lipid peroxidation with further development of atherosclerotic alterations and diabetes. We have proposed a novel combinatorial approach using FDA approved compounds targeting IL-17a and DPP4 to ameliorate a significant portion of the clustered clinical risks in patients with metabolic syndrome. In our current research we have modeled the outcomes of metabolic syndrome treatment using two distinct drug classes.

METHODS

Targets were chosen based on the clustered clinical risks in metabolic syndrome: dyslipidemia, insulin resistance, impaired glucose control, and chronic inflammation. Drug development platform, BIOiSIM™, was used to narrow down two different drug classes with distinct modes of action and modalities. Pharmacokinetic and pharmacodynamic profiles of the most promising drugs were modeling showing predicted outcomes of combinatorial therapeutic interventions.

RESULTS

Preliminary studies demonstrated that the most promising drugs belong to DPP-4 inhibitors and IL-17A inhibitors. Evogliptin was chosen to be a candidate for regulating glucose control with long term collateral benefit of weight loss and improved lipid profiles. Secukinumab, an IL-17A sequestering agent used in treating psoriasis, was selected as a repurposed candidate to address the sequential inflammatory disorders that follow the first metabolic insult.

CONCLUSIONS

Our analysis suggests this novel combinatorial therapeutic approach inducing DPP4 and Il-17a suppression has a high likelihood of ameliorating a significant portion of the clustered clinical risk in metabolic syndrome.

Nuclear Receptors Linking Metabolism, Inflammation, and Fibrosis in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) and its progressive form nonalcoholic steatohepatitis (NASH) comprise a spectrum of chronic liver diseases in the global population that can lead to end-stage liver disease and hepatocellular carcinoma (HCC). NAFLD is closely linked to the metabolic syndrome, and comorbidities such as type 2 diabetes, obesity and insulin resistance aggravate liver disease, while NAFLD promotes cardiovascular risk in affected patients. The pathomechanisms of NAFLD are multifaceted, combining hepatic factors including lipotoxicity, mechanisms of cell death and liver inflammation with extrahepatic factors including metabolic disturbance and dysbiosis. Nuclear receptors (NRs) are a family of ligand-controlled transcription factors that regulate glucose, fat and cholesterol homeostasis and modulate innate immune cell functions, including liver macrophages. In parallel with metabolic derangement in NAFLD, altered NR signaling is frequently observed and might be involved in the pathogenesis. Therapeutically, clinical data indicate that single drug targets thus far have been insufficient for reaching patient-relevant endpoints. Therefore, combinatorial treatment strategies with multiple drug targets or drugs with multiple mechanisms of actions could possibly bring advantages, by providing a more holistic therapeutic approach. In this context, peroxisome proliferator-activated receptors (PPARs) and other NRs are of great interest as they are involved in wide-ranging and multi-organ activities associated with NASH progression or regression. In this review, we summarize recent advances in understanding the pathogenesis of NAFLD, focusing on mechanisms of cell death, immunometabolism and the role of NRs. We outline novel therapeutic strategies and discuss remaining challenges.

Pharmacological Dose-Effect Profiles of Various Concentrations of Humanised Primary Bile Acid in Encapsulated Cells

Bile acids (BA)s are known surfactants and well-documented to play a major role in food digestion and absorption. Recently, potential endocrinological and formulation-stabilisation effects of BAs have been explored and their pharmacological effects on supporting cell survival and functions have gained wide interest. Hence, this study aimed to explore the hyper-glycaemic dependent dose-effect of the BA chenodeoxycholic acid (CDCA) when encapsulated with pancreatic β-cells, allowing assessment of CDCA's impacts when encapsulated. Four different concentrations of the BA were prepared, and viable cells were encapsulated and incubated for 2 days. Multiple analyses were carried out including confocal imaging, glucose-induced cellular mitochondrial viability indices, insulin production, inflammatory biomarker analyses and cellular bioenergetics measurements. There was a significant dose-effect with different concentrations of the BA, affecting cellular viability and antioxidant activities, cell functions and insulin release, inflammatory biomarkers, and cellular-bioenergetics at different oxidative stress levels. The results demonstrate that, when encapsulated, the BA CDCA exerts positive pharmacological effects at the cellular level, and such effects are concentration dependent.

Proglumide Reverses Nonalcoholic Steatohepatitis by Interaction with the Farnesoid X Receptor and Altering the Microbiome

Nonalcoholic steatohepatitis (NASH) is associated with obesity, metabolic syndrome, and dysbiosis of the gut microbiome. Cholecystokinin (CCK) is released by saturated fats and plays an important role in bile acid secretion. CCK receptors are expressed on cholangiocytes, and CCK-B receptor expression increases in the livers of mice with NASH. The farnesoid X receptor (FXR) is involved in bile acid transport and is a target for novel therapeutics for NASH. The aim of this study was to examine the role of proglumide, a CCK receptor inhibitor, in a murine model of NASH and its interaction at FXR. Mice were fed a choline deficient ethionine (CDE) diet to induce NASH. Some CDE-fed mice received proglumide-treated drinking water. Blood was collected and liver tissues were examined histologically. Proglumide's interaction at FXR was evaluated by computer modeling, a luciferase reporter assay, and tissue FXR expression. Stool microbiome was analyzed by RNA-Sequencing. CDE-fed mice developed NASH and the effect was prevented by proglumide. Computer modeling demonstrated specific binding of proglumide to FXR. Proglumide binding in the reporter assay was consistent with a partial agonist at the FXR with a mean binding affinity of 215 nM. FXR expression was significantly decreased in livers of CDE-fed mice compared to control livers, and proglumide restored FXR expression to normal levels. Proglumide therapy altered the microbiome signature by increasing beneficial and decreasing harmful bacteria. These data highlight the potential novel mechanisms by which proglumide therapy may improve NASH through interaction with the FXR and consequent alteration of the gut microbiome.

Horizon scanning of therapeutic modalities for nonalcoholic steatohepatitis

Many interventions have been investigated for the treatment of nonalcoholic steatohepatitis (NASH). This study aims to summarize all investigated options to date and review the use of specific endpoints at different stages of ongoing trials of noncirrhotic NASH treatments. Using a horizon scanning approach, evidence were identified including meta-analyses of randomized controlled trials (RCTs) in PubMed, EMBASE, Cochrane, and AMED (up to February 2020), recently published RCTs in PubMed (2015-April 2020), RCTs presented at conferences (AASL and EASL, 2015-2020), and ongoing RCTs in ClincalTrials.gov (2015-November 2020). We included 6 meta-analyses of RCTs, 30 published RCTs, 11 conference abstracts, and 62 ongoing RCTs. An evidence map was created to demonstrate the treatment effects of 49 therapeutic modalities for NASH. Only six interventions (6/49, 12.24%) met the histological surrogate endpoints for potential conditional FDA approval. Obeticholic acid is the only therapy demonstrating positive benefits in ≥1-point improvement in fibrosis with no worsening of NASH in a phase 3 trial. The other therapies were all phase 2 studies. ≥1-point improvement in fibrosis with no worsening of NASH was shown in patients treated with cenicriviroc. NASH resolution with no worsening of fibrosis was shown in patients treated with liraglutide, semaglutide and resmetirom. Lanifibranor achieved both surrogate histological endpoints. Five ongoing RCTs (5/62, 8.06%) will investigate histological progression to cirrhosis, death, or liver-related clinical outcomes. In conclusion, some therapeutic modalities showed promising benefits, but further studies are warranted to find a definite treatment of NASH which prevents progression to cirrhosis and adverse liver outcomes.

Diammonium Glycyrrhizinate Ameliorates Obesity Through Modulation of Gut Microbiota-Conjugated BAs-FXR Signaling

Obesity is a worldwide epidemic metabolic disease. Gut microbiota dysbiosis and bile acids (BAs) metabolism disorder are closely related to obesity. Farnesoid X-activated receptor (FXR), served as a link between gut microbiota and BAs, is involved in maintaining metabolic homeostasis and regulating glucose and lipid metabolism. We previously reported that diammonium glycyrrhizinate (DG) could alter gut microbiota and prevent non-alcoholic fatty liver disease. However, it remains ambiguous how DG affects the gut microbiota to regulate host metabolism. In this present study, 16S rRNA Illumina NovaSeq and metabolomic analysis revealed that DG treatment suppressed microbes associated with bile-salt hydrolase (BSH) activity, which, in turn, increased the levels of taurine-conjugated BAs accompanied by inhibition of ileal FXR-FGF15 signaling. As a result, several obesity-related metabolism were improved, like lower serum glucose and insulin levels, increased insulin sensitivity, few hepatic steatosis and resistance to weight gain. Additionally, decreased level of serum lipopolysaccharide was observed, which contributed to a strengthened intestinal barrier. The effect of DG on weight loss was slightly enhanced in the antibiotics-treated obese mice. Collectively, the efficacy of DG in the treatment of obesity might depend on gut microbiota-conjugated BAs-FXR axis. Hence, it will provide a potential novel approach for the treatment of obesity.

Membrane polarization in non-neuronal cells as a potential mechanism of metabolic disruption by depolarizing insecticides

A significant rise in the incidence of obesity and type 2 diabetes has occurred worldwide in the last two decades. Concurrently, a growing body of evidence suggests a connection between exposure to environmental pollutants, particularly insecticides, and the development of obesity and type 2 diabetes. This review summarizes key evidence of (1) the presence of different types of neuronal receptors - target sites for neurotoxic insecticides - in non-neuronal cells, (2) the activation of these receptors in non-neuronal cells by membrane-depolarizing insecticides, and (3) changes in metabolic functions, including lipid and glucose accumulation, associated with changes in membrane potential. Based on these findings, we propose that changes in membrane potential (V_mem) by certain insecticides serve as a novel regulator of lipid and glucose metabolism in non-excitable cells associated with obesity and type 2 diabetes.

Targeting gut microbial bile salt hydrolase (BSH) by diet supplements: new insights into dietary modulation of human health

Dietary supplements could modulate the abundance of BSH-producing bacteria to regulate the BSH enzyme activity, thereby change the BAs composition to regulate FXR signaling, which then regulate human health.

Deoxycholic Acid and Risks of Cardiovascular Events, ESKD, and Mortality in CKD: The CRIC Study

Rationale & Objective

Elevated levels of deoxycholic acid (DCA) are associated with adverse outcomes and may contribute to vascular calcification in patients with chronic kidney disease (CKD). We tested the hypothesis that elevated levels of DCA were associated with increased risks of cardiovascular disease, CKD progression, and death in patients with CKD.

Study Design

Prospective observational cohort study.

Setting & Participants

We included 3,147 Chronic Renal Insufficiency Cohort study participants who had fasting DCA levels. The average age was 59 ± 11 years, 45.3% were women, 40.6% were African American, and the mean estimated glomerular filtration rate was 42.5 ± 16.0 mL/min/1.73 m².

Predictor

Fasting DCA levels in Chronic Renal Insufficiency Cohort study participants.

Outcomes

Risks of atherosclerotic and heart failure events, end-stage kidney disease (ESKD), and all-cause mortality.

Analytical Approach

We used Tobit regression to identify predictors of DCA levels. We used Cox regression to examine the association between fasting DCA levels and clinical outcomes.

Results

The strongest predictors of elevated DCA levels in adjusted models were increased age and nonuse of statins. The associations between log-transformed DCA levels and clinical outcomes were nonlinear. After adjustment, DCA levels above the median were independently associated with higher risks of ESKD (HR, 2.67; 95% CI, 1.51-4.74) and all-cause mortality (HR, 2.13; 95% CI, 1.25-3.64). DCA levels above the median were not associated with atherosclerotic and heart failure events, and DCA levels below the median were not associated with clinical outcomes.

Limitations

We were unable to measure DCA longitudinally or in urinary or fecal samples, and we were unable to measure other bile acids. We also could not measure many factors that affect DCA levels.

Conclusions

In 3,147 participants with CKD stages 2-4, DCA levels above the median were independently associated with ESKD and all-cause mortality.

Discovery of a tricyclic farnesoid X receptor agonist HEC96719, a clinical candidate for treatment of non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is becoming the most predominant burden of chronic liver disease worldwide. Non-alcoholic steatohepatitis (NASH), the progressive form of NAFLD, can develop into cirrhosis and hepatocellular cancer. Unfortunately, current options for therapeutic treatment of NASH are very limited. Among multiple pathways in NASH, farnesoid X receptor (FXR), a nuclear bile acid receptor, is well-recognized as an important effective target. Here we report the synthesis and characterization of compound HEC96719 a novel tricyclic FXR agonist based on a prior high-affinity nonsteroidal molecule GW4064. HEC96719 exhibits excellent potency superior to GW4064 and obeticholic acid in in vitro and in vivo assays of FXR activation. It also shows higher FXR selectivity and more favorable tissue distribution dominantly in liver and intestine. Preclinical data on pharmacokinetic properties, efficacy, and safety profiles overall indicate that HEC96719 is a promising drug candidate for NASH treatment.

Discovery of a novel and orally active Farnesoid X receptor agonist for the protection of acetaminophen-induced hepatotoxicity

Acetaminophen (APAP) overdose is a leading cause of acute hepatic failure and liver transplantation, while the existing treatments are poorly effective. Therefore, it is necessary to develop effective therapeutic drugs for APAP-induced hepatotoxicity. Farnesoid X receptor (FXR) is a potential target for the treatment of liver disease, and the activation of FXR protects mice against APAP-induced hepatotoxicity. Compound 5, a glycine-conjugated derivative of FXR agonist 4, was designed to extend the chemical space of existing FXR agonists. Molecular modeling study indicated that compound 5 formed hydrogen bond network with key residues of FXR. Moreover, compound 5 (10 mg/kg) revealed better protective effects against APAP-induced hepatotoxicity than parent compound 4 (30 mg/kg). Further mechanical research indicated that compound 5 regulated the expressions of genes related to FXR and oxidative stress. These findings suggest that compound 5 is a promising FXR agonist suitable for further research, and it is the first time to verify that the glycine-conjugated derivative five exerted better protective effects than its parent compound.

Atorvastatin protects against liver and vascular damage in a model of diet induced steatohepatitis by resetting FXR and GPBAR1 signaling

Farnesoid-x-receptor (FXR) agonists, currently trialed in patients with non-alcoholic steatosis (NAFLD), worsen the pro-atherogenic lipid profile and might require a comedication with statin. Here we report that mice feed a high fat/high cholesterol diet (HFD) are protected from developing a pro-atherogenic lipid profile because their ability to dispose cholesterol through bile acids. This protective mechanism is mediated by suppression of FXR signaling in the liver by muricholic acids (MCAs) generated in mice from chenodeoxycholic acid (CDCA). In contrast to CDCA, MCAs are FXR antagonists and promote a CYP7A1-dependent increase of bile acids synthesis. In mice feed a HFD, the treatment with obeticholic acid, a clinical stage FXR agonist, failed to improve the liver histopathology while reduced Cyp7a1 and Cyp8b1 genes expression and bile acids synthesis and excretion. In contrast, treating mice with atorvastatin mitigated liver and vascular injury caused by the HFD while increased the bile acids synthesis and excretion. Atorvastatin increased the percentage of 7α-dehydroxylase expressing bacteria in the intestine promoting the formation of deoxycholic acid and litocholic acid, two GPBAR1 agonists, along with the expression of GPBAR1-regulated genes in the white adipose tissue and colon. In conclusion, present results highlight the central role of bile acids in regulating lipid and cholesterol metabolism in response to atorvastatin and provide explanations for limited efficacy of FXR agonists in the treatment of NAFLD.

FXR, a Key Regulator of Lipid Metabolism, Is Inhibited by ER Stress-Mediated Activation of JNK and p38 MAPK in Large Yellow Croakers (Larimichthys crocea) Fed High Fat Diets

High-fat diets induced abnormal lipid accumulation in the liver of cultured fish that caused body damage and diseases. The purpose of this research was to investigate the role and mechanism of farnesoid X receptor (FXR) in regulating lipid metabolism and to determine how high-fat diets affect FXR expression in large yellow croakers. The results showed that ligand-meditated FXR-activation could prevent abnormal lipid accumulation in the liver and hepatocytes of large yellow croakers. FXR activation increased the expression of lipid catabolism-related genes while decreasing the expression of lipogenesis-related genes. Further investigation found that the promoter activity of proliferator-activated receptor α (PPARα) could be increased by croaker FXR. Through the influence of SHP on LXR, FXR indirectly decreased the promoter activity of sterol regulatory element binding protein 1 (SREBP1) in large yellow croakers. Furthermore, the findings revealed that endoplasmic reticulum (ER)-stress-induced-activation of JNK and P38 MAPK participated in the reduction of FXR induced by high-fat diets. Then, hepatocyte nuclear factor 1α (HNF1α) was confirmed to be an FXR regulator in large yellow croaker, and it was reduced by high-fat diets and ER stress. In addition, co-expression of c-Jun with HNF1α inhibited the effect of HNF1α on FXR promoter, and suppression of P38 MAPK could relieve the HNF1α expression reduction caused by ER stress activation. In summary, the present study showed that FXR mediated lipid metabolism can prevent abnormal lipid accumulation through regulating PPARα and SREBP1 in large yellow croakers, while high-fat diets can suppress FXR expression by ER stress mediated-activation of JNK and P38 MAPK pathways. This research could benefit the study of FXR functions in vertebrate evolution and the development of therapy or preventative methods for nutrition-related disorders.

The Role and Mechanism of Oxidative Stress and Nuclear Receptors in the Development of NAFLD

The overproduction of reactive oxygen species (ROS) and consequent oxidative stress contribute to the pathogenesis of acute and chronic liver diseases. It is now acknowledged that nonalcoholic fatty liver disease (NAFLD) is characterized as a redox-centered disease due to the role of ROS in hepatic metabolism. However, the underlying mechanisms accounting for these alternations are not completely understood. Several nuclear receptors (NRs) are dysregulated in NAFLD, and have a direct influence on the expression of a set of genes relating to the progress of hepatic lipid homeostasis and ROS generation. Meanwhile, the NRs act as redox sensors in response to metabolic stress. Therefore, targeting NRs may represent a promising strategy for improving oxidation damage and treating NAFLD. This review summarizes the link between impaired lipid metabolism and oxidative stress and highlights some NRs involved in regulating oxidant/antioxidant turnover in the context of NAFLD, shedding light on potential therapies based on NR-mediated modulation of ROS generation and lipid accumulation.

Role of FXR in Bile Acid and Metabolic Homeostasis in NASH: Pathogenetic Concepts and Therapeutic Opportunities

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent cause of liver disease, increasingly contributing to the burden of liver transplantation. In search for effective treatments, novel strategies addressing metabolic dysregulation, inflammation, and fibrosis are continuously emerging. Disturbed bile acid (BA) homeostasis and microcholestasis via hepatocellular retention of potentially toxic BAs may be an underappreciated factor in the pathogenesis of NAFLD and nonalcoholic steatohepatitis (NASH) as its progressive variant. In addition to their detergent properties, BAs act as signaling molecules regulating cellular homeostasis through interaction with BA receptors such as the Farnesoid X receptor (FXR). Apart from being a key regulator of BA metabolism and enterohepatic circulation, FXR regulates metabolic homeostasis and has immune-modulatory effects, making it an attractive therapeutic target in NAFLD/NASH. In this review, the molecular basis and therapeutic potential of targeting FXR with a specific focus on restoring BA and metabolic homeostasis in NASH is summarized.

Intestinal Flora is a Key Factor in Insulin Resistance and Contributes to the Development of Polycystic Ovary Syndrome

CONTEXT

The key gut microbial biomarkers for polycystic ovarian syndrome (PCOS) and how dysbiosis causes insulin resistance and PCOS remain unclear.

OBJECTIVE

To assess the characteristics of intestinal flora in PCOS and explore whether abnormal intestinal flora can affect insulin resistance and promote PCOS and whether chenodeoxycholic acid (CDCA) can activate intestinal farnesoid X receptor (FXR), improving glucose metabolism in PCOS.

SETTING AND DESIGN

The intestinal flora of treatment-naïve PCOS patients and hormonally healthy controls was analyzed. Phenotype analysis, intestinal flora analysis, and global metabolomic profiling of caecal contents were performed on a letrozole-induced PCOS mouse model; similar analyses were conducted after 35 days of antibiotic treatment on the PCOS mouse model, and glucose tolerance testing was performed on the PCOS mouse model after a 35-day CDCA treatment. Mice receiving fecal microbiota transplants from PCOS patients or healthy controls were evaluated after 10 weeks.

RESULTS

Bacteroides was significantly enriched in treatment-naïve PCOS patients. The enrichment in Bacteroides was reproduced in the PCOS mouse model. Gut microbiota removal ameliorated the PCOS phenotype and insulin resistance and increased relative FXR mRNA levels in the ileum and serum fibroblast growth factor 15 levels. PCOS stool-transplanted mice exhibited insulin resistance at 10 weeks but not PCOS. Treating the PCOS mouse model with CDCA improved glucose metabolism.

CONCLUSIONS

Bacteroides is a key microbial biomarker in PCOS and shows diagnostic value. Gut dysbiosis can cause insulin resistance. FXR activation might play a beneficial rather than detrimental role in glucose metabolism in PCOS.

Brown Rice Inhibits Development of Nonalcoholic Fatty Liver Disease in Obese Zucker (fa/fa) Rats by Increasing Lipid Oxidation Via Activation of Retinoic Acid Synthesis

BACKGROUND

White rice and its unrefined form, brown rice, contain numerous compounds that are beneficial to human health. However, the starch content of rice can contribute to obesity, a main risk factor for nonalcoholic fatty liver disease (NAFLD).

OBJECTIVES

We investigated the effect of rice consumption on NAFLD and its underlying molecular mechanism.

METHODS

We randomly divided 7-week-old male obese Zucker (fa/fa) rats, an animal model of NAFLD, into 3 groups (n = 10 each) fed 1 of 3 diets for 10 weeks: a control diet (Cont; AIN-93G diet; 53% cornstarch), a white rice diet (WR; AIN-93G diet with cornstarch replaced with white rice powder), or a brown rice diet (BR; AIN-93G diet with cornstarch replaced with brown rice powder). Liver fat accumulation and gene expression related to lipid and vitamin A metabolisms, including retinoic acid (RA) signaling, were analyzed.

RESULTS

Hepatic lipid values were significantly decreased in the BR group compared with the Cont group, by 0.4-fold (P < 0.05). The expression of genes related to hepatic fatty acid oxidation, such as carnitine palmitoyltransferase 2, was approximately 2.1-fold higher in the BR group than the Cont group (P < 0.05). The expression of peroxisomal acyl-coenzyme A oxidase 1 and acyl-CoA dehydrogenase medium chain was also significantly increased, by 1.6-fold, in the BR group compared with the Cont group (P < 0.05). The expression of VLDL-secretion-related genes, such as microsomal triglyceride transfer protein, was also significantly higher in the BR group (2.4-fold; P < 0.05). Furthermore, aldehyde dehydrogenase 1 family member A1, an RA synthase gene, was 2-fold higher in the BR group than the Cont group (P < 0.05).

CONCLUSIONS

Brown rice prevented development of NAFLD in obese Zucker (fa/fa) rats. The beneficial effects of pregelatinized rice on NAFLD could be manifested as increased fatty acid oxidation and VLDL secretion, which are regulated by RA signaling.

Enhanced Bilosomal Properties Resulted in Optimum Pharmacological Effects by Increased Acidification Pathways

INTRODUCTION

Recent studies in our laboratory have shown that some bile acids, such as chenodeoxycholic acid (CDCA), can exert cellular protective effects when encapsulated with viable β-cells via anti-inflammatory and anti-oxidative stress mechanisms. However, to explore their full potential, formulating such bile acids (that are intrinsically lipophilic) can be challenging, particularly if larger doses are required for optimal pharmacological effects. One promising approach is the development of nano gels. Accordingly, this study aimed to examine biological effects of various concentrations of CDCA using various solubilising nano gel systems on encapsulated β-cells.

METHODS

Using our established cellular encapsulation system, the Ionic Gelation Vibrational Jet Flow technology, a wide range of CDCA β-cell capsules were produced and examined for morphological, biological, and inflammatory profiles.

RESULTS AND CONCLUSION

Capsules' morphology and topographic characteristics remained similar, regardless of CDCA or nano gel concentrations. The best pharmacological, anti-inflammatory, and cellular respiration, metabolism, and energy production effects were observed at high CDCA and nano gel concentrations, suggesting dose-dependent cellular protective and positive effects of CDCA when incorporated with high loading nano gel.

Current and Emerging Approaches for Hepatic Fibrosis Treatment

Liver fibrosis resulting from chronic liver injury is a key factor to develop liver cirrhosis and risk of hepatocellular carcinoma (HCC) which are major health burden worldwide. Therefore, it is necessary for antifibrotic therapies to prevent chronic liver disease progression and HCC development. There has been tremendous progress in understanding the mechanisms of liver fibrosis in the last decade, which has created new opportunities for the treatment of this condition. In this review, we aim to make an overview on information of different potential therapies (drug treatment, cell therapy, and liver transplantation) for the liver fibrosis and hope to provide the therapeutic options available for the treatment of liver fibrosis and discuss novel approaches.

Obeticholic acid ameliorates obesity and hepatic steatosis by activating brown fat

Obeticholic acid (OCA) is exemplified as a potent drug for treating primary biliary cirrhosis and nonalcoholic fatty liver disease by inhibiting bile acid synthesis. However, it remains unclear whether the effect of OCA is mediated by the function of brown adipose tissue (BAT). In the present study, brown adipogenesis differentiation in vitro and db/db mouse model treated with OCA were used to assess the anti-obesity function by body weight tracking, O₂ consumption, food intake, physical activity, glucose tolerance tests. In addition, uncoupling protein 1 (Ucp1) protein expression in brown adipose tissue was measured by western blotting, morphometry of brown adipose tissue was analyzed by hematoxylin and eosin staining. Hepatic steatosis was detected by Oil-Red O staining and serological analysis was performed to assess the effect of OCA on hyperlipidemia. OCA treatment enhanced brown adipocyte cell differentiation and upregulated the expression of the BAT-specific gene Ucp1) in C3H10T1/2 cells in vitro. Consistent with these findings, OCA increased whole-body energy metabolism and glucose homeostasis by enhancing BAT activity in vivo, and ultimately decreased body weight gain in db/db mice. In addition, the results demonstrated that spontaneous hepatic steatosis in db/db mice was ameliorated following OCA treatment. In summary, OCA functioned as a BAT activator to help ameliorate obesity and maintain glucose homeostasis in db/db mice. The present results may provide a novel potential therapeutic approach to activate brown fat in patients with obesity and other metabolic disorders.

Abnormal Metabolism in the Progression of Nonalcoholic Fatty Liver Disease to Hepatocellular Carcinoma: Mechanistic Insights to Chemoprevention

Nonalcoholic fatty liver disease (NAFLD) is on the rise and becoming a major contributor to the development of hepatocellular carcinoma (HCC). Reasons for this include the rise in obesity and metabolic syndrome in contrast to the marked advances in prevention and treatment strategies of viral HCC. These shifts are expected to rapidly propel this trend even further in the coming decades, with NAFLD on course to become the leading etiology of end-stage liver disease and HCC. No Food and Drug Administration (FDA)-approved medications are currently available for the treatment of NAFLD, and advances are desperately needed. Numerous medications with varying mechanisms of action targeting liver steatosis and fibrosis are being investigated including peroxisome proliferator-activated receptor (PPAR) agonists and farnesoid X receptor (FXR) agonists. Additionally, drugs targeting components of metabolic syndrome, such as antihyperglycemics, have been found to affect NAFLD progression and are now being considered in the treatment of these patients. As NAFLD drug discovery continues, special attention should be given to their relationship to HCC. Several mechanisms in the pathogenesis of NAFLD have been implicated in hepatocarcinogenesis, and therapies aimed at NAFLD may additionally harbor independent antitumorigenic potential. This approach may provide novel prevention and treatment strategies.

Targeting Farnesoid X receptor (FXR) for developing novel therapeutics against cancer

Cancer is one of the lethal diseases that arise due to the molecular alterations in the cell. One of those alterations associated with cancer corresponds to differential expression of Farnesoid X receptor (FXR), a nuclear receptor regulating bile, cholesterol homeostasis, lipid, and glucose metabolism. FXR is known to regulate several diseases, including cancer and cardiovascular diseases, the two highly reported causes of mortality globally. Recent studies have shown the association of FXR overexpression with cancer development and progression in different types of cancers of breast, lung, pancreas, and oesophagus. It has also been associated with tissue-specific and cell-specific roles in various cancers. It has been shown to modulate several cell-signalling pathways such as EGFR/ERK, NF-κB, p38/MAPK, PI3K/AKT, Wnt/β-catenin, and JAK/STAT along with their targets such as caspases, MMPs, cyclins; tumour suppressor proteins like p53, C/EBPβ, and p-Rb; various cytokines; EMT markers; and many more. Therefore, FXR has high potential as novel biomarkers for the diagnosis, prognosis, and therapy of cancer. Thus, the present review focuses on the diverse role of FXR in different cancers and its agonists and antagonists.

A review on gut microbiota: a central factor in the pathophysiology of obesity

Obesity and its complications constitute a substantial burden. Considerable published research describes the novel relationships between obesity and gut microbiota communities. It is becoming evident that microbiota behave in a pivotal role in their ability to influence homeostatic mechanisms either to the benefit or detriment of host health, the extent of which is not fully understood. A greater understanding of the contribution of gut microbiota towards host pathophysiology is revealing new therapeutic avenues to tackle the global obesity epidemic. This review focuses on causal relationships and associations with obesity, proposed central mechanisms encouraging the development of obesity and promising prospective methods for microbiota manipulation.

Bile Acids, Their Receptors, and the Gut Microbiota

Bile acids (BAs) are a family of hydroxylated steroids secreted by the liver that aid in the breakdown and absorption of dietary fats. BAs also function as nutrient and inflammatory signaling molecules, acting through cognate receptors, to coordinate host metabolism. Commensal bacteria in the gastrointestinal tract are functional modifiers of the BA pool, affecting composition and abundance. Deconjugation of host BAs creates a molecular network that inextricably links gut microtia with their host. In this review we highlight the roles of BAs in mediating this mutualistic relationship with a focus on those events that impact host physiology and metabolism.

Vertical sleeve gastrectomy confers metabolic improvements by reducing intestinal bile acids and lipid absorption in mice

Vertical sleeve gastrectomy (VSG) is one of the most effective and durable therapies for morbid obesity and its related complications. Although bile acids (BAs) have been implicated as downstream mediators of VSG, the specific mechanisms through which BA changes contribute to the metabolic effects of VSG remain poorly understood. Here, we confirm that high fat diet-fed global farnesoid X receptor (Fxr) knockout mice are resistant to the beneficial metabolic effects of VSG. However, the beneficial effects of VSG were retained in high fat diet-fed intestine- or liver-specific Fxr knockouts, and VSG did not result in Fxr activation in the liver or intestine of control mice. Instead, VSG decreased expression of positive hepatic Fxr target genes, including the bile salt export pump (Bsep) that delivers BAs to the biliary pathway. This reduced small intestine BA levels in mice, leading to lower intestinal fat absorption. These findings were verified in sterol 27-hydroxylase (Cyp27a1) knockout mice, which exhibited low intestinal BAs and fat absorption and did not show metabolic improvements following VSG. In addition, restoring small intestinal BA levels by dietary supplementation with taurocholic acid (TCA) partially blocked the beneficial effects of VSG. Altogether, these findings suggest that reductions in intestinal BAs and lipid absorption contribute to the metabolic benefits of VSG.

Combined treatment with FABP4 inhibitor ameliorates rosiglitazone-induced liver steatosis in obese diabetic db/db mice

Rosiglitazone has been reported to exert dual effects on liver steatosis, and it could exacerbate liver steatosis in obese animal models, which was suggested to be closely related to the elevated hepatic expression of FABP4. This study aimed to investigate whether combined treatment with FABP4 inhibitor I-9 could alleviate rosiglitazone-induced liver steatosis in obese diabetic db/db mice. Male C57BL/KsJ-db/db mice were orally treated with rosiglitazone, rosiglitazone combined with I-9 daily for 8 weeks. The liver steatosis was evaluated by triglyceride content and H&E staining. The expression of hepatic lipogenic genes or proteins in liver tissue or in FFA-treated hepatocytes and PMA-stimulated macrophages were determined by real-time quantitative polymerase chain reaction (RT-qPCR) or western blotting. Results showed that combined treatment with I-9 decreased rosiglitazone-induced increase in serum FABP4 level and expression of lipogenic genes in liver, especially FABP4, and ameliorated liver steatosis in db/db mice. Rosiglitazone-induced intracellular TG accumulation and increased expression of FABP4 in the cultured hepatocytes and macrophages were also suppressed by combined treatment. We concluded that combined treatment with FABP4 inhibitor I-9 could ameliorate rosiglitazone-exacerbated elevated serum FABP4 level and ectopic liver fat accumulation in obese diabetic db/db mice without affecting its anti-diabetic efficacy.

Activation of a Specific Gut Bacteroides-Folate-Liver Axis Benefits for the Alleviation of Nonalcoholic Hepatic Steatosis

A beneficial gut Bacteroides-folate-liver pathway regulating lipid metabolism is demonstrated. Oral administration of a Ganoderma meroterpene derivative (GMD) ameliorates nonalcoholic hepatic steatosis in the liver of fa/fa rats by reducing endotoxemia, enhancing lipid oxidation, decreasing de novo lipogenesis, and suppressing lipid export from the liver. An altered gut microbiota with an increase of butyrate and folate plays a causative role in the effects of GMD. The commensal bacteria Bacteroides xylanisolvens, Bacteroides thetaiotaomicron, Bacteroides dorei, and Bacteroides uniformis, which are enriched by GMD, are major contributors to the increased gut folate. Administration of live B. xylanisolvens reduces hepatic steatosis and enhances the folate-mediated signaling pathways in mice. Knockout of the folate biosynthetic folp gene in B. xylanisolvens blocks its folate production and beneficial effects. This work confirms the therapeutic potential of GMD and B. xylanisolvens in alleviating nonalcoholic hepatic steatosis and provides evidence for benefits of the gut Bacteroides-folate-liver pathway.

The identification of farnesoid X receptor modulators as treatment options for nonalcoholic fatty liver disease

INTRODUCTION

The farnesoid-x-receptor (FXR) is a ubiquitously expressed nuclear receptor selectively activated by primary bile acids.

AREA COVERED

FXR is a validated pharmacological target. Herein, the authors review preclinical and clinical data supporting the development of FXR agonists in the treatment of nonalcoholic fatty liver disease.

EXPERT OPINION

Development of systemic FXR agonists to treat the metabolic liver disease has been proven challenging because the side effects associated with these agents including increased levels of cholesterol and LDL-c and reduced HDL-c raising concerns over their long-term cardiovascular safety. Additionally, pruritus has emerged as a common, although poorly explained, dose-related side effect with all FXR ligands, but is especially common with OCA. FXR agonists that are currently undergoing phase 2/3 trials are cilofexor, tropifexor, nidufexor and MET409. Some of these agents are currently being developed as combination therapies with other agents including cenicriviroc, a CCR2/CCR5 inhibitor, or firsocostat an acetyl CoA carboxylase inhibitor. Additional investigations are needed to evaluate the beneficial effects of combination of these agents with statins. It is expected that in the coming years, FXR agonists will be developed as a combination therapy to minimize side effects and increase likelihood of success by targeting different metabolic pathways.

The role of bariatric surgery in the management of nonalcoholic steatohepatitis

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the United States and increasing globally. The progressive form of NAFLD, nonalcoholic steatohepatitis (NASH), can lead to cirrhosis and complications of end-stage liver disease. No FDA-approved therapy for NAFLD/NASH exists. Treatment of NAFLD/NASH includes effective and sustained life-style modification and weight loss. This review reports on the recent findings of bariatric surgery in the management of NASH.

RECENT FINDINGS

NAFLD, at all stages, is common in those who meet indication for bariatric surgery. Bariatric surgery resolves NAFLD/NASH and reverses early stages of fibrosis. Although randomized controlled trials of bariatric surgery in NASH are infeasible, studies defining the metabolic changes induced by bariatric surgery, and their effect on NASH, provide insight for plausible pharmacologic targets for the nonsurgical treatment of NASH.

SUMMARY

Resolution of NASH and fibrosis regression can occur after bariatric surgery. Although the exact mechanism(s) underlying the improvement of NASH and hepatic fibrosis following bariatric surgery is not fully elucidated, emerging data on this topic is vitally important for lending insight into the pharmacotherapies for NASH for patients who are not otherwise suitable candidates for bariatric surgery.

Gut Microbiota and NAFLD: Pathogenetic Mechanisms, Microbiota Signatures, and Therapeutic Interventions

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Its worldwide prevalence is rapidly increasing and is currently estimated at 24%. NAFLD is highly associated with many features of the metabolic syndrome, including obesity, insulin resistance, hyperlipidaemia, and hypertension. The pathogenesis of NAFLD is complex and not fully understood, but there is increasing evidence that the gut microbiota is strongly implicated in the development of NAFLD. In this review, we discuss the major factors that induce dysbiosis of the gut microbiota and disrupt intestinal permeability, as well as possible mechanisms leading to the development of NAFLD. We also discuss the most consistent NAFLD-associated gut microbiota signatures and immunological mechanisms involved in maintaining the gut barrier and liver tolerance to gut-derived factors. Gut-derived factors, including microbial, dietary, and host-derived factors involved in NAFLD pathogenesis, are discussed in detail. Finally, we review currently available diagnostic and prognostic methods, summarise latest knowledge on promising microbiota-based biomarkers, and discuss therapeutic strategies to manipulate the microbiota, including faecal microbiota transplantation, probiotics and prebiotics, deletions of individual strains with bacteriophages, and blocking the production of harmful metabolites.

Loss of Thymine DNA Glycosylase Causes Dysregulation of Bile Acid Homeostasis and Hepatocellular Carcinoma

Thymine DNA glycosylase (TDG) is a nuclear receptor coactivator that plays an essential role in the maintenance of epigenetic stability in cells. Here, we demonstrate that the conditional deletion of TDG in adult mice results in a male-predominant onset of hepatocellular carcinoma (HCC). TDG loss leads to a prediabetic state, as well as bile acid (BA) accumulation in the liver and serum of male mice. Consistent with these data, TDG deletion led to dysregulation of the farnesoid X receptor (FXR) and small heterodimer partner (SHP) regulatory cascade in the liver. FXR and SHP are tumor suppressors of HCC and play an essential role in BA and glucose homeostasis. These results indicate that TDG functions as a tumor suppressor of HCC by regulating a transcriptional program that protects against the development of glucose intolerance and BA accumulation in the liver.

Obeticholic Acid Derivative, T-2054 Suppresses Osteoarthritis via Inhibiting NF-κB-Signaling Pathway

Osteoarthritis (OA), a degenerative joint disorder, has been reported as the most common cause of disability worldwide. The production of inflammatory cytokines is the main factor in OA. Previous studies have been reported that obeticholic acid (OCA) and OCA derivatives inhibited the release of proinflammatory cytokines in acute liver failure, but they have not been studied in the progression of OA. In our study, we screened our small synthetic library of OCA derivatives and found T-2054 had anti-inflammatory properties. Meanwhile, the proliferation of RAW 264.7 cells and ATDC5 cells were not affected by T-2054. T-2054 treatment significantly relieved the release of NO, as well as mRNA and protein expression levels of inflammatory cytokines (IL-6, IL-8 and TNF-α) in LPS-induced RAW 264.7 cells. Moreover, T-2054 promoted extracellular matrix (ECM) synthesis in TNF-α-treated ATDC5 chondrocytes. Moreover, T-2054 could relieve the infiltration of inflammatory cells and degeneration of the cartilage matrix and decrease the levels of serum IL-6, IL-8 and TNF-α in DMM-induced C57BL/6 mice models. At the same time, T-2054 showed no obvious toxicity to mice. Mechanistically, T-2054 decreased the extent of p-p65 expression in LPS-induced RAW 264.7 cells and TNF-α-treated ATDC5 chondrocytes. In summary, we showed for the first time that T-2054 effectively reduced the release of inflammatory mediators, as well as promoted extracellular matrix (ECM) synthesis via the NF-κB-signaling pathway. Our findings support the potential use of T-2054 as an effective therapeutic agent for the treatment of OA.

Modeling Diet-Induced NAFLD and NASH in Rats: A Comprehensive Review

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, characterized by hepatic steatosis without any alcohol abuse. As the prevalence of NAFLD is rapidly increasing worldwide, important research activity is being dedicated to deciphering the underlying molecular mechanisms in order to define new therapeutic targets. To investigate these pathways and validate preclinical study, reliable, simple and reproducible tools are needed. For that purpose, animal models, more precisely, diet-induced NAFLD and nonalcoholic steatohepatitis (NASH) models, were developed to mimic the human disease. In this review, we focus on rat models, especially in the current investigation of the establishment of the dietary model of NAFLD and NASH in this species, compiling the different dietary compositions and their impact on histological outcomes and metabolic injuries, as well as external factors influencing the course of liver pathogenesis.

Elafibranor improves diet-induced nonalcoholic steatohepatitis associated with heart failure with preserved ejection fraction in Golden Syrian hamsters

BACKGROUND

Cardiovascular disease is the leading cause of deaths in nonalcoholic steatohepatitis (NASH) patients. Mouse models, while widely used for drug development, do not fully replicate human NASH nor integrate the associated cardiac dysfunction, i.e. heart failure with preserved ejection fraction (HFpEF). To overcome these limitations, we established a nutritional hamster model developing both NASH and HFpEF. We then evaluated the effects of the dual peroxisome proliferator activated receptor alpha/delta agonist elafibranor developed for the treatment of NASH patients.

METHODS

Male Golden Syrian hamsters were fed for 10 to 20 weeks with a free choice diet, which presents hamsters with a choice between control chow diet with normal drinking water or a high fat/high cholesterol diet with 10% fructose enriched drinking water. Biochemistry, histology and echocardiography analysis were performed to characterize NASH and HFpEF. Once the model was validated, elafibranor was evaluated at 15 mg/kg/day orally QD for 5 weeks.

RESULTS

Hamsters fed a free choice diet for up to 20 weeks developed NASH, including hepatocyte ballooning (as confirmed with cytokeratin-18 immunostaining), bridging fibrosis, and a severe diastolic dysfunction with restrictive profile, but preserved ejection fraction. Elafibranor resolved NASH, with significant reduction in ballooning and fibrosis scores, and improved diastolic dysfunction with significant reduction in E/A and E/E' ratios.

CONCLUSION

Our data demonstrate that the free choice diet induced NASH hamster model replicates the human phenotype and will be useful for validating novel drug candidates for the treatment of NASH and associated HFpEF.

LXRα/β Antagonism Protects against Lipid Accumulation in the Liver but Increases Plasma Cholesterol in Rhesus Macaques

Nonalcoholic fatty liver disease (NAFLD) is characterized by lipid accumulation in the liver and associates with obesity, hyperlipidemia, and insulin resistance. NAFLD could lead to nonalcoholic steatohepatitis (NASH), hepatic fibrosis, cirrhosis, and even cancers. The development of therapy for NAFLD has been proven difficult. Emerging evidence suggests that liver X receptor (LXR) antagonist is a potential treatment for fatty liver disease. However, concerns about the cholesterol-increasing effects make it questionable for the development of LXR antagonists. Here, the overweight monkeys were fed with LXRβ-selective antagonist sophoricoside or LXRα/β dual-antagonist morin for 3 months. The morphology of punctured liver tissues was examined by H&E staining. The liver, heart, and kidney damage indices were analyzed using plasma. The blood index was assayed using complete blood samples. We show that LXRβ-selective antagonist sophoricoside and LXRα/β dual-antagonist morin alleviated lipid accumulation in the liver in overweight monkeys. The compounds resulted in higher plasma TC or LDL-c contents, increased white blood cell and lymphocyte count, and decreased neutrophile granulocyte count in the monkeys. The compounds did not alter plasma glucose, apolipoprotein A (ApoA), ApoB, ApoE, lipoprotein (a) (LPA), nonesterified fatty acid (NEFA), aspartate transaminases (AST), creatinine (CREA), urea nitrogen (UN), and creatine kinase (CK) levels. Our data suggest that LXRβ-selective and LXRα/β dual antagonism may lead to hypercholesterolemia in nonhuman primates, which calls into question the development of LXR antagonist as a therapy for NAFLD.

Bile acids profile, histopathological indices and genetic variants for non-alcoholic fatty liver disease progression

OBJECTIVE

Metabolomic studies suggest plasma levels of bile acids (BAs) are elevated amongst subjects with non-alcoholic fatty liver disease (NAFLD) compared to healthy controls. However, it remains unclear whether or not specific BAs are associated with the clinically relevant transition from nonalcoholic fatty liver (i.e. simple steatosis) to non-alcoholic steatohepatitis (NASH), or enhanced progression of hepatic fibrosis, or genetic determinants of NAFLD/NASH.

METHODS

Among sequential subjects (n=102) undergoing diagnostic liver biopsy, we examined the associations of a broad panel of BAs with distinct histopathological features of NAFLD, the presence of NASH, and their associations with genetic variants linked to NAFLD and NASH.

RESULTS

Plasma BA alterations were observed through the entire spectrum of NAFLD, with several glycine conjugated forms of the BAs demonstrating significant associations with higher grades of inflammation and fibrosis. Plasma 7-Keto-DCA levels showed the strongest associations with advanced stages of hepatic fibrosis [odds ratio(95% confidence interval)], 4.2(1.2-16.4), NASH 24.5(4.1-473), and ballooning 18.7(4.8-91.9). Plasma 7-Keto-LCA levels were associated with NASH 9.4(1.5-185) and ballooning 5.9(1.4-28.8). Genetic variants at several NAFLD/NASH loci were nominally associated with increased levels of 7-Keto- and glycine-conjugated forms of BAs, and the NAFLD risk allele at the TRIB1 locus showed strong tendency toward increased plasma levels of GCA (p=0.02) and GUDCA (p=0.009).

CONCLUSIONS

Circulating bile acid levels are associated with histopathological and genetic determinants of the transition from simple hepatic steatosis into NASH. Further studies exploring the potential involvement of bile acid metabolism in the development and/or progression of distinct histopathological features of NASH are warranted.

An Update on Efficacy and Safety of Emerging Hepatic Antifibrotic Agents

Liver fibrosis represents a response to chronic liver injury. Metabolic dysfunction-associated fatty liver disease and metabolic dysfunction-associated steatohepatitis are the most common chronic liver diseases, both with increasing incidence. Therefore, there is a great impetus for development of agents targeting these conditions. Accumulating data on possible treatment options for liver fibrosis are emerging in the literature. However, despite extensive research and much effort in the field, approved agents for liver fibrosis are still lacking. In this critical review, we have summarized the main data about specific treatment options for liver fibrosis gained from ongoing clinical trials, with an emphasis on efficacy and safety of these agents.

An Update on Efficacy and Safety of Emerging Hepatic Antifibrotic Agents

Liver fibrosis represents a response to chronic liver injury. Metabolic dysfunction-associated fatty liver disease and metabolic dysfunction-associated steatohepatitis are the most common chronic liver diseases, both with increasing incidence. Therefore, there is a great impetus for development of agents targeting these conditions. Accumulating data on possible treatment options for liver fibrosis are emerging in the literature. However, despite extensive research and much effort in the field, approved agents for liver fibrosis are still lacking. In this critical review, we have summarized the main data about specific treatment options for liver fibrosis gained from ongoing clinical trials, with an emphasis on efficacy and safety of these agents.

Bile acids and their receptors in metabolic disorders

Bile acids are a large family of atypical steroids which exert their functions by binding to a family of ubiquitous cell membrane and nuclear receptors. There are two main bile acid activated receptors, FXR and GPBAR1, that are exclusively activated by bile acids, while other receptors CAR, LXRs, PXR, RORγT, S1PR2and VDR are activated by bile acids in addition to other more selective endogenous ligands. In the intestine, activation of FXR and GPBAR1 promotes the release of FGF15/19 and GLP1 which integrate their signaling with direct effects exerted by theother receptors in target tissues. This network is tuned in a time ordered manner by circadian rhythm and is critical for the regulation of metabolic process including autophagy, fast-to-feed transition, lipid and glucose metabolism, energy balance and immune responses. In the last decade FXR ligands have entered clinical trials but development of systemic FXR agonists has been proven challenging because their side effects including increased levels of cholesterol and Low Density Lipoproteins cholesterol (LDL-c) and reduced High-Density Lipoprotein cholesterol (HDL-c). In addition, pruritus has emerged as a common, dose related, side effect of FXR ligands. Intestinal-restricted FXR and GPBAR1 agonists and dual FXR/GPBAR1 agonists have been developed. Here we review the last decade in bile acids physiology and pharmacology.

The Liver under the Spotlight: Bile Acids and Oxysterols as Pivotal Actors Controlling Metabolism

Among the myriad of molecules produced by the liver, both bile acids and their precursors, the oxysterols are becoming pivotal bioactive lipids which have been underestimated for a long time. Their actions are ranging from regulation of energy homeostasis (i.e., glucose and lipid metabolism) to inflammation and immunity, thereby opening the avenue to new treatments to tackle metabolic disorders associated with obesity (e.g., type 2 diabetes and hepatic steatosis) and inflammatory diseases. Here, we review the biosynthesis of these endocrine factors including their interconnection with the gut microbiota and their impact on host homeostasis as well as their attractive potential for the development of therapeutic strategies for metabolic disorders.

Transcriptional Regulation of Metabolic Pathways via Lipid-Sensing Nuclear Receptors PPARs, FXR, and LXR in NASH

Nonalcoholic fatty liver disease comprises a wide spectrum of liver injuries from simple steatosis to steatohepatitis and cirrhosis. Nonalcoholic steatohepatitis (NASH) is defined when liver steatosis is associated with inflammation, hepatocyte damage, and fibrosis. A genetic predisposition and environmental insults (ie, dietary habits, obesity) are putatively responsible for NASH progression. Here, we present the impact of the lipid-sensing nuclear receptors in the pathogenesis and treatment of NASH. In detail, we discuss the pros and cons of the putative transcriptional action of the fatty acid sensors (peroxisome proliferator-activated receptors), the bile acid sensor (farnesoid X receptor), and the oxysterol sensor (liver X receptors) in the pathogenesis and bona fide treatment of NASH.

Enterohepatic circulation of bile acids and their emerging roles on glucolipid metabolism

Bile acids (BAs) are amphiphilic molecules with a nonpolar steroid carbon skeleton and a polar carboxylate side chain. Recently, BAs have aroused the attention of scholars due to their potential roles on metabolic diseases. As important endogenous ligands, BAs are wildly active in the enterohepatic circulation, during which microbiota play a significant role in promoting the hydrolysis and dehydroxylation of BAs. Besides, many pathways initiated by BAs including glucolipid metabolism and inflammation signaling pathways have been reported to regulate the host metabolism and maintain immune homeostasis. Herein, the characteristics on the enterohepatic circulation and metabolism of BAs are systematically summarized. Moreover, the regulation mechanism of the glucolipid metabolism by BAs is intensively discussed. Worthily, FXR and TGR5, which are involved in glucolipid metabolism, are the prime candidates for targeted therapies of chronic metabolic diseases such as diabetes and hypercholesterolemia.