Emerging drugs for the treatment of non-alcoholic steatohepatitis: a focused review of farnesoid X receptor agonists

Key role of macrophages in the progression of hepatic fibrosis

Liver fibrosis is a pathological change characterized by excessive deposition of extracellular matrix caused by chronic liver injury, and the mechanisms underlying its development are associated with endothelial cell injury, inflammatory immune cell activation, and HSC activation. Furthermore, hepatic macrophages exhibit remarkable heterogeneity and hold central functions in the evolution of liver fibrosis, with different subgroups exerting dual effects of promotion and regression. Currently, targeted macrophage therapy for reversing hepatic fibrosis has been extensively studied and has shown promising prospects. In this review, we will discuss the dual role of macrophages in liver fibrosis and provide new insights into reversing liver fibrosis based on macrophages.

Regulation of bile acids and their receptor FXR in metabolic diseases

High sugar, high-fat diets and unhealthy lifestyles have led to an epidemic of obesity and obesity-related metabolic diseases, seriously placing a huge burden on socio-economic development. A deeper understanding and elucidation of the specific molecular biological mechanisms underlying the onset and development of obesity has become a key to the treatment of metabolic diseases. Recent studies have shown that the changes of bile acid composition are closely linked to the development of metabolic diseases. Bile acids can not only emulsify lipids in the intestine and promote lipid absorption, but also act as signaling molecules that play an indispensable role in regulating bile acid homeostasis, energy expenditure, glucose and lipid metabolism, immunity. Disorders of bile acid metabolism are therefore important risk factors for metabolic diseases. The farnesol X receptor, a member of the nuclear receptor family, is abundantly expressed in liver and intestinal tissues. Bile acids act as endogenous ligands for the farnesol X receptor, and erroneous FXR signaling triggered by bile acid dysregulation contributes to metabolic diseases, including obesity, non-alcoholic fatty liver disease and diabetes. Activation of FXR signaling can reduce lipogenesis and inhibit gluconeogenesis to alleviate metabolic diseases. It has been found that intestinal FXR can regulate hepatic FXR in an organ-wide manner. The crosstalk between intestinal FXR and hepatic FXR provides a new idea for the treatment of metabolic diseases. This review focuses on the relationship between bile acids and metabolic diseases and the current research progress to provide a theoretical basis for further research and clinical applications.

Hepatic DDAH1 mitigates hepatic steatosis and insulin resistance in obese mice: Involvement of reduced S100A11 expression

Dimethylarginine dimethylaminohydrolase 1 (DDAH1) is an important regulator of plasma asymmetric dimethylarginine (ADMA) levels, which are associated with insulin resistance in patients with nonalcoholic fatty liver disease (NAFLD). To elucidate the role of hepatic DDAH1 in the pathogenesis of NAFLD, we used hepatocyte-specific Ddah1-knockout mice (Ddah1HKO) to examine the progress of high-fat diet (HFD)-induced NAFLD. Compared to diet-matched flox/flox littermates (Ddah1f/f), Ddah1HKO mice exhibited higher serum ADMA levels. After HFD feeding for 16 weeks, Ddah1HKO mice developed more severe liver steatosis and worse insulin resistance than Ddah1f/f mice. On the contrary, overexpression of DDAH1 attenuated the NAFLD-like phenotype in HFD-fed mice and ob/ob mice. RNA-seq analysis showed that DDAH1 affects NF-κB signaling, lipid metabolic processes, and immune system processes in fatty livers. Furthermore, DDAH1 reduces S100 calcium-binding protein A11 (S100A11) possibly via NF-κB, JNK and oxidative stress-dependent manner in fatty livers. Knockdown of hepatic S100a11 by an AAV8-shS100a11 vector alleviated hepatic steatosis and insulin resistance in HFD-fed Ddah1HKO mice. In summary, our results suggested that the liver DDAH1/S100A11 axis has a marked effect on liver lipid metabolism in obese mice. Strategies to increase liver DDAH1 activity or decrease S100A11 expression could be a valuable approach for NAFLD therapy.

Design, synthesis, and biological studies of novel sulfonamide derivatives as farnesoid X receptor agonists

Farnesoid X receptor (FXR) is considered as a promising target for the treatment of NASH. Although many non-steroidal FXR agonists have been reported, the structure types are quite scarce and mainly limited to the isoxazole scaffold derived from GW4064. Therefore, it is crucial to expand the structure types of FXR agonist to explore wider chemical space. In this study, the structure-based scaffold hopping strategy was performed by hybrid FXR agonist 1 and T0901317, which resulted in the discovery of sulfonamide FXR agonist 19. Molecular docking study reasonably explained the SAR in this series, and compound 19 fitted well with the binding pocket in a similar mode to the co-crystal ligand. In addition, compound 19 exhibited considerable selectivity against other nuclear receptors. In NASH model, compound 19 alleviated the typical histological features of fatty liver, including steatosis, lobular inflammation, ballooning, and fibrosis. Moreover, compound 19 exhibited acceptable safety profiles with no acute toxicity to major organ. These results suggested that the novel sulfonamide FXR agonist 19 might be a promising agent for the treatment of NASH.

Multiple anti-non-alcoholic steatohepatitis (NASH) efficacies of isopropylidenyl anemosapogenin via farnesoid X receptor activation and TFEB-mediated autophagy

BACKGROUND

Non-alcoholic steatohepatitis (NASH) can develop into cirrhosis, liver failure, or hepatocellular carcinoma without effective treatment. However, there are currently no drugs for NASH treatment, and the development of new therapeutics has remained a major challenge in NASH research. Advances in traditional Chinese medicine to treat liver disease inspired us to search for new NASH candidates from Chi-Shao, a widely used traditional Chinese medicine.

PURPOSE

In this research, we aimed to clarify the anti-NASH effect and the underlying mechanism of isopropylidenyl anemosapogenin (IA, 1), which was a new lead compound isolated from Chi-Shao.

STUDY DESIGN AND METHODS

Isopropylidenyl anemosapogenin (IA, 1) was first discovered by collagen type I α 1 promoter luciferase bioassay-guided isolation and then characterized by single crystal X-ray diffraction analysis and enriched by semi-synthesis. Using various molecular biology techniques, the multiple anti-NASH efficacies and mechanisms of IA were clarified based on in vitro LX-2 and Huh7 cell models, along with the in vivo choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced mouse model and bile duct ligation (BDL)-induced rat model. The UPLC-MS/MS method was used to assess the plasma concentration of IA.

RESULTS

A new lead compound IA was isolated from the traditional Chinese medicine Chi-Shao, which showed significant anti-liver fibrosis activity in TGF-β1-treated LX-2 cells and anti-liver steatosis activity in oleic acid-treated Huh7 cells. Furthermore, IA could significantly ameliorate in vivo CDAHFD-induced liver injury by activating the farnesoid X receptor pathway, including its targets Nr0b2, Abcb11, and Slc10a2. Simultaneously, IA activated the autophagy pathway by activating the TFEB factor, thereby promoting lipid degradation. Its liver-protective and anti-fibrosis activities were verified by the BDL-induced rat model. Finally, with an oral administration of 100 mg/kg, IA achieved the maximum plasma concentration of 1.23 ± 0.18 μg/ml at 2.67 ± 0.58 h.

CONCLUSION

IA, an unreported lupine-type triterpenoid isolated from Chi-shao, can significantly alleviate liver injury and fibrosis via farnesoid X receptor activation and TFEB-mediated autophagy, which indicates that IA could serve as a novel therapeutic candidate against NASH.

FXR: structures, biology, and drug development for NASH and fibrosis diseases

The nuclear receptor farnesoid-X-receptor (FXR) plays an essential role in bile acid, glucose, and lipid homeostasis. In the last two decades, several diseases, such as obesity, type 2 diabetes, nonalcoholic fatty liver disease, cholestasis, and chronic inflammatory diseases of the liver and intestine, have been revealed to be associated with alterations in FXR functions. FXR has become a promising therapeutic drug target, particularly for enterohepatic diseases. Despite the large number of FXR modulators reported, only obeticholic acid (OCA) has been approved for primary biliary cholangitis (PBC) therapy as FXR modulator. In this review, we summarize the structure and function of FXR, the development of FXR modulators, and the structure-activity relationships of FXR modulators. Based on the structural analysis, we discuss potential strategies for developing future therapeutic FXR modulators to overcome current limitations, providing new perspectives for enterohepatic and metabolic diseases treatment.

Effective, disease-modifying, clinical approaches to patients with mild-to-moderate hypertriglyceridaemia

Plasma triglyceride concentration is easily, inexpensively, and accurately measured, and when elevated is a highly informative disease marker that identifies individuals who frequently have a host of underlying metabolic, inflammatory, and atherogenic risk factors. Although this concept aligns with much that has been discussed regarding the metabolic syndrome, individuals identified with mild-to-moderate hypertriglyceridaemia on a screening lipid profile are not necessarily recognised as having features of the metabolic syndrome and frequently do not receive definitive, meaningful, disease-modifying therapy. This treatment would include (1) lifestyle modification; (2) LDL-lowering therapies to aggressively treat elevated apolipoprotein B-containing particles; (3) antihypertensive therapies that have optimal therapeutic profiles for those individuals with metabolic syndrome; (4) icosapent ethyl for those individuals at high risk, particularly patients with established atherosclerotic cardiovascular disease who have residual hypertriglyceridaemia despite treatment with appropriate LDL-lowering therapies; (5) preferential use of cardiovascular protective diabetes therapies, in individuals with diabetes; and (6) antithrombotic therapies for secondary prevention of atherosclerotic cardiovascular disease in the context of high vascular disease risk and diabetes. Several emerging therapies, such as novel weight reducing, anti-inflammatory, lipid-modifying therapies, and therapies targeting the progression of non-alcoholic fatty liver disease, could also soon enter the clinical arena for patients with mild-to-moderate hypertriglyceridaemia and associated metabolic syndrome.

SU5, a new Auraptene analog with improved metabolic stability, ameliorates nonalcoholic fatty liver disease in methionine- and choline-deficient diet-fed db/db mice

Farnesoid X receptor (FXR) has been considered as a promising target for non-alcoholic steatohepatitis (NASH), while existing FXR agonists suffer from serious side effects. Thus, it is very necessary to identify novel FXR agonists with good safety. Auraptene (AUR) is a new FXR agonist with excellent safety and extensive pharmacological activities, while the lactone of AUR is vulnerable to esterolysis. In this study, the lactone of AUR was converted to metabolically stable amide moiety, and the obtained analog SU5 revealed comparable activity and better metabolic stability than that of AUR. In NASH model, SU5 showed stronger efficacy than AUR on fatty liver by up-regulating gene expressions related to FXR in vivo. Moreover, SU5 improved lipid metabolism by down-regulating the gene expressions of lipid synthesis, while up-regulating the gene expressions of fatty acid β-oxidation and triglyceride metabolism. Besides, the inflammation-related genes were significantly decreased in SU5 treated group. These positive results highlighted the pharmacological potential of SU5 for the treatment of NASH.

Discovery of BMS-986318, a Potent Nonbile Acid FXR Agonist for the Treatment of Nonalcoholic Steatohepatitis

Herein we report the discovery and preclinical biological evaluation of 6-(2-(5-cyclopropyl-3-(3,5-dichloropyridin-4-yl)isoxazol-4-yl)-7-azaspiro[3.5]non-1-en-7-yl)-4-(trifluoromethyl)quinoline-2-carboxylic acid, compound 1 (BMS-986318), a nonbile acid farnesoid X receptor (FXR) agonist. Compound 1 exhibits potent in vitro and in vivo activation of FXR, has a suitable ADME profile, and demonstrates efficacy in the mouse bile duct ligation model of liver cholestasis and fibrosis. The overall profile of compound 1 supports its continued evaluation.

Emerging synthetic drugs for the treatment of liver cirrhosis

Introduction: The number of deaths and prevalent cases of cirrhosis are increasing worldwide, but there are no licensed antifibrotic or pro-regenerative medicines and liver transplantation is a limited resource. Cirrhosis is characterized by extreme liver fibrosis, organ dysfunction, and complications related to portal hypertension. Advances in our understanding of liver fibrosis progression and regression following successful etiological therapy betray vulnerabilities in common and disease-specific mechanisms that could be targeted pharmacologically.Area covered: This review summarizes the cellular and molecular pathogenesis of cirrhosis as a preface to discussion of the current drug development landscape. The dominant indication for global pharma R&D pipelines is cirrhosis related to nonalcoholic steatohepatitis (NASH). We searched Clinicaltrials.gov, GlobalData, Pharmaprojects and PubMed for pertinent information on emerging synthetic drugs for cirrhosis, with a focus on compounds listed in phase 2 and phase 3 trials.Expert opinion: Although cirrhosis can regress following successful etiological treatment, there are no specific antifibrotic or pro-regenerative drugs approved for this condition. Obstacles to drug development in cirrhosis include intrinsic biological factors, a heterogeneous patient population, and lack of acceptable surrogate endpoints. Nevertheless, several synthetic drugs are being evaluated in clinical trials and the NASH field is rapidly embracing a drug combination approach.

Regulation of autophagy by bile acids and in cholestasis - CholestoPHAGY or CholeSTOPagy

Autophagy is a lysosomal degradation pathway in which the cell self-digests its own components to provide nutrients in harsh environmental conditions. It also represents an opportunity to rid the cell of superfluous and damaged organelles, misfolded proteins or invaded microorganisms. Liver autophagy contributes to basic hepatic functions such as lipid, glycogen and protein turnover. Deregulated hepatic autophagy has been linked to many liver diseases including alpha-1-antitrypsin deficiency, alcoholic and non-alcoholic fatty liver diseases, hepatitis B and C infections, liver fibrosis as well as liver cancer. Recently, bile acids and the bile acid receptor FXR have been implicated in the regulation of hepatic autophagy, which implies a role of autophagy also for cholestatic liver diseases. This review summarizes the current evidence of bile acid mediated effects on autophagy and how this affects cholestatic liver diseases. Although detailed studies are lacking, we suggest a concept that the activity of autophagy in cholestasis depends on the disease stage, where autophagy may be induced at early stages ("cholestophagy") but may be impaired in prolonged cholestatic states ("cholestopagy").