Differential effects of selective- and pan-PPAR agonists on experimental steatohepatitis and hepatic macrophages☆

Insights into Clinical Trials for Drugs Targeting MASLD: Progress, Challenges, and Future Directions

The transition in terminology from fatty liver disease to metabolic dysfunction-associated steatotic liver disease (MASLD) marks a considerable evolution in diagnostic standards. This new definition focuses on liver fat accumulation in the context of overweight/obesity, type 2 diabetes, or metabolic dysfunction, without requiring the exclusion of other concurrent liver diseases. The new definition also provides clear guidelines for defining alcohol consumption in relation to the disease. MASLD is currently acknowledged as the most widespread liver disorder globally, affecting ~25% of the population. Despite the extensive array of clinical trials conducted in recent years, the number of approved treatments for metabolic dysfunction-associated fatty liver disease is very limited. In the review critically evaluates the results of clinical trials of related drugs and assesses the future directions for drug development trials. The renaming of MASLD presents new challenges and opportunities for the design of clinical trials and the selection of target populations for drug development.

Pan-PPAR agonist lanifibranor improves insulin resistance and hepatic steatosis in patients with T2D and MASLD

BACKGROUND & AIMS

Lanifibranor is a pan-PPAR agonist that improves glucose/lipid metabolism and reverses steatohepatitis and fibrosis in adults with metabolic dysfunction-associated steatohepatitis (MASH). We tested its effect on insulin resistance (IR) at the level of different target tissues in relation to changes in intrahepatic triglyceride (IHTG) content.

METHODS

In this single-center phase II study, 38 patients with type 2 diabetes and MASLD were randomized 1:1 to receive lanifibranor 800 mg or placebo for 24 weeks. The primary endpoint was the change in IHTG (1H-MRS). The main prespecified secondary endpoint was the change in hepatic, muscle and adipose tissue insulin sensitivity using the gold-standard euglycemic hyperinsulinemic clamp technique to measure glucose turnover. Other secondary endpoints included changes in cardiometabolic parameters (i.e., HbA1c, lipid profile, adiponectin).

RESULTS

Lanifibranor significantly lowered IHTG compared to placebo (full analysis set [FAS] -44% vs. -12%, respectively; least squares mean difference -31%, 95% CI -51 to -12%; in completers -50% vs. -16%; both p <0.01). More patients in the lanifibranor group (vs. the placebo group) achieved a ≥30% IHTG reduction (FAS 65% vs. 22%; completers 79% vs. 29%; both p <0.01) and steatosis resolution (FAS 25% vs. 0%; p <0.05). Lanifibranor significantly improved hepatic and peripheral IR (i.e. fasting endogenous [primarily hepatic] glucose production, hepatic IR, and insulin-stimulated muscle glucose disposal or Rd). Secondary metabolic endpoints also improved (fasting glucose, insulin, HOMA-IR, HbA1c, HDL-C), and adiponectin increased 2.4-fold (all p <0.001). Lanifibranor caused modest weight gain (+2.7%). Adverse events were mild (gastrointestinal side effects, hemoglobin decrease) and drug-related treatment-emergent adverse events leading to study discontinuation were balanced between groups.

CONCLUSIONS

Lanifibranor significantly improves hepatic, muscle and adipose tissue IR. Lanifibranor treatment was safe and effective in reducing hepatic steatosis and cardiometabolic risk factors associated with metabolic dysfunction.

IMPACT AND IMPLICATIONS

No prior studies have evaluated the effect of lanifibranor on insulin sensitivity at the level of muscle, liver and adipose tissue and its relationship to changes in intrahepatic triglyceride (IHTG) content in insulin-resistant individuals with metabolic dysfunction-associated steatotic liver disease (MASLD) and type 2 diabetes. We observed a significant decrease in IHTG after 24 weeks of treatment (by ∼50%, p <0.001 vs. placebo) that was associated with a major improvement in hepatic and peripheral (Rd) insulin sensitivity, restoration of adipose tissue function and improvement in cardiometabolic risk factors. This study has important clinical implications because it offers proof-of-concept that targeting the key underlying metabolic defects in MASLD (i.e. insulin resistance, lipotoxicity and hyperglycemia) can restore cardiometabolic health. It offers a compelling rationale for lanifibranor treatment in individuals with MASLD, either alone or in combination with weight loss and other treatment strategies.

CLINICALTRIALS

GOV IDENTIFIER

NCT03459079.

Reviewing the function of macrophages in liver disease

INTRODUCTION

The liver is a central metabolic organ, but is also hosting a unique immune microenvironment to sustain homeostasis and proper defense measures against injury threats in healthy individuals. Liver macrophages, mostly represented by the tissue-resident Kupffer cells and bone marrow- or monocyte-derived macrophages, are intricately involved in various aspects of liver homeostasis and disease, including tissue injury, inflammation, fibrogenesis and repair mechanisms.

AREAS COVERED

We review recent findings on defining the liver macrophage landscape and their functions in liver diseases with the aim of highlighting potential targets for therapeutic interventions. A comprehensive literature search in PubMed and Google Scholar was conducted to identify relevant literature up to date.

EXPERT OPINION

Liver macrophages orchestrate key homeostatic and pathogenic processes in the liver. Thus, targeting liver macrophages represents an attractive strategy for drug development, e.g. to ameliorate liver inflammation, steatohepatitis or fibrosis. However, translation from fundamental research to therapies remains challenging due to the versatile nature of the liver macrophage compartment. Recent and major technical advances such as single-cell and spatially-resolved omics approaches deepened our understanding of macrophage biology at a molecular level. Yet, further studies are needed to identify suitable, etiology- and stage-dependent strategies for the treatment of liver diseases.

TMEM132C and LIPE protein molecules drive synovial hyperplasia via the PPARγ signaling axis: Mechanistic insights into core pathogenic proteins in rheumatoid arthritis

The pathogenesis of rheumatoid arthritis (RA) involves a variety of cellular and molecular signaling pathways. TMEM132C and LIPE, as potential key protein molecules, may play an important role in synovial hyperplasia of RA. The main objective of this study was to reveal the function of TMEM132C and LIPE in the proliferation of RA synovial cells, and to explore the mechanism of their regulation through the PPARγ signaling axis. In this study, differential expression genes (DEGs) were screened through data acquisition and preprocessing. Then, principal component analysis (PCA) and functional enrichment analysis were used to clarify the importance of PPARγ signal axis in RA. Then, machine learning technology was used to identify key proteins, and SHAP-driven analysis was used to interpret the results of Logistic regression model. The expression and signaling activities of TMEM132C and LIPE were verified by cell culture, transfection, proliferation detection, RNA extraction, real-time quantitative fluorescence PCR (qPCR) and Western blot experiments. A series of significant DEGs were identified, and functional enrichment analysis showed that the PPARγ signal axis plays a key role in RA. TMEM132C and LIPE were identified as key genes mainly enriched in the PPAR signaling pathway, suggesting that they play an important role in the pathogenesis of RA.

Pemafibrate Reduced Liver Stiffness in Patients with Metabolic Dysfunction-associated Steatotic Liver Disease Complicated with Hyperlipidemia and Liver Fibrosis with a Fibrosis-4 Index Above 1.3

Objective To evaluate the effect of pemafibrate (PEM) on metabolic dysfunction-associated steatotic liver disease (MASLD). Methods We retrospectively evaluated 43 patients with hyperlipidemia and MASLD to determine changes in clinical factors between the start of PEM treatment and 0.5 years later. Using FibroScan, 39 of 43 patients were evaluated for liver stiffness (LS; kPa) and controlled attenuation parameter (CAP; dB/m). None of the patients had decompensated cirrhosis. Results Thirty patients were women, the median age was 66 years old, the median fibrosis-4 (FIB-4) score was 2.52, the median LS was 8.05 kPa, and the median CAP was 280.5 dB/m at the start of PEM treatment. AST, ALT, ALP, γGTP, and triglyceride levels decreased 0.5 years after starting PEM treatment, but FIB-4, LS, and CAP values did not decrease. However, LS decreased in patients with a FIB-4 index ≥1.3 at the start of PEM treatment, whereas it did not change in patients with a FIB-4 index <1.3. Similarly, LS decreased in patients with a value ≥8 kPa at the start of treatment and did not change in those with <8 kPa. The decreased LS group had higher baseline ALT and LS levels and lower ALT levels during 0.5 years of follow-up than the increased LS group. Conclusion At the initiation of PEM treatment, the LS decreased in patients with MASLD complicated by hyperlipidemia and moderate LS (FIB-4>1.3 or LS >8 kPa). Although there is currently no approved treatment for MASLD, PEM may be a viable treatment option for MASLD with mild LS.

Deficiency of β-arrestin2 ameliorates MASLD in mice by promoting the activation of TAK1/AMPK signaling

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a liver manifestation of metabolic syndrome characterized by excessive hepatic lipid accumulation and lipid metabolism disorders. It has become the most common chronic liver disease worldwide. β-arrestin2 is a multifunctional scaffold protein that is among the most important regulatory molecules, and it exerts key roles in regulating various cellular processes, such as immune response, cellular collagen production, and inflammation. In the current study, we aimed to explore the function of β-arrestin2 in the development and progression of MASLD. Firstly, we observed that the expression of β-arrestin2 was upregulated in liver samples from patients with MASLD. Then, the western diet (WD) combined with CCl4 injection-induced MASLD was established in wild-type mice, and showed that liver β-arrestin2 expression was also gradually increased, and positively correlated with the degree of lipid metabolism disorder during MASLD progression. Ulteriorly, β-arrestin2 knockout (Arrb2 KO) mice were utilized to induce the MASLD model and found that β-arrestin2 deficiency significantly ameliorated lipid accumulation and inflammatory response in the liver of MASLD mice. Furthermore, the in vitro depletion and overexpression experiments showed that increased β-arrestin2 aggravated lipid accumulation via inhibiting the activation of the TAK1/AMPK pathway, which may be mediated by competitively binding to TAB1 with TAK1. These findings suggest that β-arrestin2 is essential to regulate intrahepatic lipid metabolism. Here, we provide a novel insight in understanding of the expression and function of β-arrestin2 in MASLD, demonstrating that it may be a potential therapeutic target for MASLD treatment.

MST1/2 DKO abates salvianolic acid B's therapeutic effect on CCl4-induced liver injury mice

MST1 and MST2 (MST1/2) are core kinases of the Hippo/YAP signaling pathway in mammals and play key roles in various liver diseases. Deep molecular profiling has shown that the Hippo/YAP pathway interacts synergistically with TGF-β1/Smad2 signaling. Salvianolic acid B (SAB) is an ingredient extracted from Salvia miltiorrhiza that can be used to treat liver diseases. Previous studies have confirmed that SAB hold commendable efficacy against liver injury by inhibition of inflammatory response and Smad2C/2L phosphorylation. However, scientific evidence involving how mutations in the Hippo/YAP pathway are related to the hepatoprotective function of SAB in MST1/2 double knockout (MST1/2 DKO) mice remains vague. Nowadays, the MST1-/- MST2fl/fl Alb-Cre mice were generated to establish a CCl4-induced liver injury model to investigate the potential effects of MST1/2 gene knockout on inflammatory reactions and pSmad2C/pSmad2L signal transduction with the intervention of SAB. As it turns out, genotype identification and western blot assays confirmed that we have successfully obtained MST1-/- MST2fl/fl Alb-Cre mice. General observation, HE staining, and biochemical assays promulgated that genetic deletion of MST1/2 could diminish SAB's hepatoprotective effect on liver injury by promoting the phosphorylation of smad2C/2L and boosting the expression of the inflammatory factors IL- 6 and TNF-α. In summary, these results suggest that MST1/2 play a key role in mediating SAB's effects on liver injury.

Unraveling the molecular mechanisms of Fufangduzhong formula in alleviating high-fat diet-induced non-alcoholic fatty liver disease in mice

Background

Non-alcoholic fatty liver disease (NAFLD) is a common chronic liver disease, characterized by hepatic lipid accumulation. The Fufangduzhong formula (FFDZ) is a traditional Chinese medicine (TCM) formulation composed of Eucommia ulmoides Oliv., Leonurus artemisia (Lour.) S. Y. Hu, Prunella vulgaris Linn, Uncariarhynchophylla (Miq.) Miq. ex Havil., and Scutellaria baicalensis Georgi. It has demonstrated hepatoprotective effects and the ability to reduce lipid accumulation. However, its mechanisms against NAFLD remain unclear.

Methods

UPLC-MS/MS was used to identify FFDZ metabolites. C57BL/6J mice were fed a high-fat diet (HFD) supplemented with or without FFDZ (HFD+L, 0.45 g/kg/d; HFD+H, 0.9 g/kg/d) for 12 weeks. Biochemical indicators and histopathological observations were utilized to assess the extent of metabolic homeostasis disorder and hepatic steatosis. An analysis of differentially expressed genes and regulated signaling pathways was conducted using hepatic transcriptomics. Metabolomics analysis was performed to investigate the significantly changed endogenous metabolites associated with NAFLD in mice serum using UPLC-Q-TOF/MS. Western blot was employed to detect proteins involved in the lipid metabolism-related signaling pathways. Oleic acid-induced hepatic steatosis was used to examine the lipid-lowering effect of FFDZ-containing serum in vitro.

Results

A total of eight active metabolites were identified from the FFDZ formula and FFDZ-containing serum through UPLC-MS/MS analysis. FFDZ reduced body weight, liver weight, and levels of inflammatory cytokines, and it ameliorated hepatic steatosis, serum lipid profiles, insulin sensitivity, and glucose tolerance in mice with HFD-induced NAFLD. Transcriptomics revealed that FFDZ modulated the lipid metabolism-related pathways, including the PPAR signaling pathway, Fatty acid metabolism, and AMPK signaling pathway. Meanwhile, Western blot analysis indicated that FFDZ downregulated the expression of lipid synthesis-related proteins (Srebp-1c, Acly, Scd-1, Fasn, Acaca, and Cd36) and upregulated the fatty acid oxidation-related proteins (p-Ampk, Ppar-α, and Cpt-1). Furthermore, metabolomics identified FFDZ-mediated reversal of phospholipid dysregulation (PC, PE, LPC, LPE). Additionally, FFDZ-containing serum remarkedly reduced OA-induced lipid accumulation in HepG2 cells.

Conclusion

The present results demonstrate that FFDZ exerts anti-NAFLD effects by enhancing glucose tolerance and insulin sensitivity, as well as regulating the Ampk signaling pathway to ameliorate lipid metabolism disorder, lipotoxicity, hepatic steatosis, and inflammatory responses.

Macronutrient Modulation in Metabolic Dysfunction-Associated Steatotic Liver Disease-the Molecular Role of Fatty Acids compared with Sugars in Human Metabolism and Disease Progression

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a significant public health concern, with its progression to metabolic dysfunction-associated steatohepatitis (MASH) and fibrosis leading to severe outcomes including cirrhosis, hepatocellular carcinoma, and liver failure. Whereas obesity and excess energy intake are well-established contributors to the development and progression of MASLD, the distinct role of specific macronutrients is less clear. This review examines the mechanistic pathways through which dietary fatty acids and sugars contribute to the development of hepatic inflammation and fibrosis, offering a nuanced understanding of their respective roles in MASLD progression. In terms of addressing potential therapeutic options, human intervention studies that investigate whether modifying the intake of dietary fats and carbohydrates affects MASLD progression are reviewed. By integrating this evidence, this review seeks to bridge the gap in the understanding between the mechanisms of macronutrient-driven MASLD progression and the effect of altering the intake of these nutrients in the clinical setting and presents a foundation for future research into targeted dietary strategies for the treatment of the disease.

Treating metabolic dysfunction-associated steatohepatitis: The fat-trimming FGF21 approach

Metabolic dysfunction-associated steatohepatitis (MASH) is a condition characterized by hepatosteatosis, inflammation, and tissue damage, with steatosis as the initial stage, which involves chronic, excess deposition of lipids in hepatic lipid droplets. Despite the growing prevalence and serious risks it poses, including liver decompensation, the need for transplantation, and increased patient mortality, MASH currently faces no approved pharmacotherapy. Several promising treatment candidates have emerged from recent clinical trials, including analogs of FGF21 and agonists of the associated FGFR1-KLB complex. These agents were well-tolerated in trials and have demonstrated significant improvements in both histological and biochemical markers of liver fat content, inflammation, injury, and fibrosis in patients with MASH. Endocrine FGF21 plays a vital role in maintaining homeostasis of lipid, glucose, and energy metabolism. It achieves this through pathways that target lipids or lipid droplets in adipocytes and hepatocytes. Mechanistically, pharmacological FGF21 acts as a potent catabolic factor to promote lipid or lipid droplet lipolysis, fatty acid oxidation, mitochondrial catabolic flux, and heat-dissipating energy expenditure, leading to effective clearance of hepatic and systemic gluco-lipotoxicity and inflammatory stress, thereby preventing obesity, diabetes, and MASH pathologies. In this review, we aim to provide an update on the outcomes of clinical trials for several FGF21 mimetics. We compare these outcomes with preclinical studies and offer a lipid-centric perspective on the mechanisms underlying the clinical benefits of these agents for MASH.

The pan-PPAR agonist lanifibranor reduces portal pressure independent of fibrosis reduction through the splanchnic vasculature

Portal hypertension (PH) can cause severe complications in patients with advanced chronic liver disease (aCLD). The pan-peroxisome proliferator-activated receptor (pan-PPAR) agonist lanifibranor reduces portal pressure in preclinical models of aCLD. Since the effect on PH might be secondary to fibrosis improvement, we investigated the effect of lanifibranor on PH, hepatic and splanchnic angiogenesis in mouse models of fibrotic and prehepatic non-fibrotic PH. Mice with fibrotic PH (common bile duct ligation; CBDL) and prehepatic PH (partial portal vein ligation; PPVL) received daily lanifibranor/vehicle for 14 or 7 days, respectively. Hemodynamics, serum, hepatic and mesenteric histology, and hepatic, mesenteric and liver sinusoidal endothelial cells (LSEC) gene expression levels were analyzed. Vascular corrosion casts of the venous mesenteric and hepatic vasculature were analyzed using scanning electron microscopy and µCT. Portal pressure was increased in CBDL mice. Lanifibranor treatment demonstrated a dose-dependent trend towards decreasing the elevated portal pressure, and reduced fibrosis. Hepatic mRNA levels of inflammatory, fibrotic and angiogenic markers were significantly downregulated in lanifibranor-treated CBDL mice. LSEC dysfunction was improved by lanifibranor. Compared to CBDL mice, portal pressure was more extensively elevated in PPVL mice, which was significantly reduced by lanifibranor. Superior mesenteric artery blood flow, which was increased in vehicle-treated PPVL mice, tended to decrease by lanifibranor. The expansion of the mesenteric vasculature and mesenteric protein level of angiogenetic markers in PPVL mice were reduced after lanifibranor. In conclusion, lanifibranor improves PH, independently from fibrosis reduction, potentially through reducing the venous mesenteric vasculature expansion and intrahepatic angiogenesis, and ameliorating LSEC function.

MASH as an emerging cause of hepatocellular carcinoma: current knowledge and future perspectives

Hepatocellular carcinoma is one of the deadliest and fastest-growing cancers. Among HCC etiologies, metabolic dysfunction-associated fatty liver disease (MAFLD) has served as a major HCC driver due to its great potential for increasing cirrhosis. The obesogenic environment fosters a positive energy balance and results in a continuous rise of obesity and metabolic syndrome. However, it is difficult to understand how metabolic complications lead to the poor prognosis of liver diseases and which molecular mechanisms are underpinning MAFLD-driven HCC development. Thus, suitable preclinical models that recapitulate human etiologies are essentially required. Numerous preclinical models have been created but not many mimicked anthropometric measures and the course of disease progression shown in the patients. Here we review the literature on adipose tissues, liver-related HCC etiologies and recently discovered genetic mutation signatures found in MAFLD-driven HCC patients. We also critically review current rodent models suggested for MAFLD-driven HCC study.

Renal Protection of HWL-088and ZLY-032, Two Dual GPR40/PPARδ Agonists, in Adenine-Induced Renal Fibrosis Model

This research examined the potential of novel GPR40/PPARδ dual agonists, HWL-088 and ZLY-032, to protect the kidneys in a mouse model of adenine-induced renal fibrosis. Mice were given a diet containing 0.25 % adenine to develop renal fibrosis and then received different dosages of HWL-088 or ZLY-032. After being euthanized, tissue and serum samples were collected for morphological, histological, and molecular examination. Compared to the control group, mice fed adenine showed an increase in kidney-to-body weight ratio, serum creatinine, and urea levels. Hematoxylin and eosin staining revealed alleviated glomerulosclerosis, tubular dilation, and inflammatory cell infiltration in mice treated with HWL-088 or ZLY-032. Furthermore, Masson staining and immunohistochemistry demonstrated that these dual agonists protected against renal interstitial fibrosis and inflammation, corroborated by decreased expression levels of fibrosis-related proteins (TGF-β, Collα1, TIMP-1) and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6). Accordingly, it can be inferred that GPR40/PPARδ dual agonists HWL-088 and ZLY-032 could yield significant renoprotective effects by inhibiting inflammation and fibrosis. Overall, these results may contribute to the development of novel therapeutic strategies for renal fibrosis.

MAP17 is a Novel NASH Progression Biomarker Associated with Macrophage Infiltration, Immunotherapy Response, and Oxidative Stress

Background

Nonalcoholic steatohepatitis (NASH) has recently garnered increased attention due to immune infiltration. However, the role of membrane-associated protein 17 (MAP17) in NASH remains unclear, which prompted this study to explore its relationship with immune infiltration and its regulatory mechanisms.

Methods

We employed weighted correlation network analysis (WGCNA) to construct a gene co-expression network aimed at identifying key genes associated with NASH progression. Our further analyses included differential expression evaluation, protein-protein interaction (PPI) network analysis, and Venn diagram analysis to discover novel targets. The CIBERSORT algorithm assessed the correlation between MAP17 and immune cell infiltration within the tumor microenvironment (TME), while the TIDE algorithm predicted responses to immunotherapy. Additionally, we conducted gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) to elucidate the mechanisms by which MAP17 operates. The expression of MAP17 was validated using liver tissues obtained from NASH patients and mice with diet-induced NASH or CCl4-induced liver fibrosis.

Results

Our findings identified MAP17 as a novel target in the progression of NASH. Correlation analyses demonstrated a positive association between MAP17 and M1 macrophage infiltration, as well as a negative association with M2 infiltration. TIDE results positioned MAP17 as a potential biomarker for predicting responses to immune checkpoint blockade. Mechanistic studies revealed that MAP17 induced oxidative stress, which subsequently activated the p53, PI3K-AKT, and Wnt signaling pathways. Validation analyses confirmed that MAP17 levels significantly increased in liver tissues of mice with diet-induced NASH or CCl4-induced liver fibrosis, as well as in NASH patients.

Conclusion

MAP17 is a novel biomarker linked to macrophage infiltration and immunotherapy responses in NASH patients. The oxidative stress induced by MAP17 activates the p53, PI3K-AKT, and Wnt pathways, all of which contribute to the progression of NASH.

Modern-Day Therapeutics and Ongoing Clinical Trials against Type 2 Diabetes Mellitus: A Narrative Review

OBJECTIVES

Diabetes Mellitus (DM) is a global health concern that affects millions of people globally. The present review aims to narrate the clinical guidelines and therapeutic interventions for Type 2 Diabetes Mellitus (T2DM) patients. Furthermore, the present work summarizes the ongoing phase 1/2/3 and clinical trials against T2DM.

METHODS

A meticulous and comprehensive literature review was performed using various databases, such as PubMed, MEDLINE, Clinical trials database (https://clinicaltrials.gov/), and Google Scholar, to include various clinical trials and therapeutic interventions against T2DM.

RESULTS

Based on our findings, we concluded that most T2DM-associated clinical trials are interventional. Anti-diabetic therapeutics, including insulin, metformin, Dipeptidyl Peptidase-4 (DPP-4) inhibitors, Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs), and Sodium- Glucose cotransporter-2 (SGLT-2) inhibitors are frontline therapeutics being clinically investigated. Currently, the therapeutics in phase IV clinical trials are mostly SGLT-2 inhibitors, implicating their critical contribution to the clinical management of T2DM.

CONCLUSION

Despite the success of T2DM treatments, a surge in innovative treatment options to reduce diabetic consequences and improve glycemic control is currently ongoing. More emphasis needs to be on exploring novel targeted drug candidates that can offer more sustained glycemic control.

Characterization of six clinical drugs and dietary intervention in the nonobese CDAA-HFD mouse model of MASH and progressive fibrosis

The choline-deficient l-amino acid defined-high-fat diet (CDAA-HFD) mouse model is widely used in preclinical metabolic dysfunction-associated steatohepatitis (MASH) research. To validate the CDAA-HFD mouse, we evaluated disease progression and responsiveness to dietary and pharmacological interventions with semaglutide, lanifibranor, elafibranor, obeticholic acid (OCA), firsocostat, and resmetirom. Disease phenotyping was performed in C57BL/6J mice fed CDAA-HFD for 3-20 wk and ranked using the MASLD Human Proximity Score (MHPS). Semaglutide, lanifibranor, elafibranor, OCA, firsocostat, or resmetirom were profiled as treatment intervention for 8 wk, starting after 6 wk of CDAA-HFD feeding. Semaglutide and lanifibranor were further evaluated as early (preventive) therapy for 9 wk, starting 3 wk after CDAA-HFD diet feeding. In addition, benefits of dietary intervention (chow reversal) for 8 wk were characterized following 6 wk of CDAA-HFD feeding. CDAA-HFD mice demonstrated a nonobese phenotype with fast onset and progression of MASH and fibrosis, high similarity to human MASH-fibrosis, and tumor development after 20 wk of diet-induction. Semaglutide and lanifibranor partially reversed fibrosis when administered as prevention but not as treatment intervention. Elafibranor was the only interventional drug therapy to improve fibrosis. In comparison, chow-reversal resulted in complete regression of steatosis with improved liver inflammation and fibrosis in CDAA-HFD mice. CDAA-HFD mice recapitulate histological hallmarks of advanced MASH with progressive severe fibrosis, however, in the absence of a clinical translational obese dysmetabolic phenotype. CDAA-HFD mice are suitable for profiling drug candidates directly targeting hepatic lipid metabolism, inflammation, and fibrosis. The timing of pharmacological intervention is critical for determining antifibrotic drug efficacy in the model.NEW & NOTEWORTHY The CDAA-HFD mouse model is widely used in preclinical MASH research, but validation of the model is lacking. This study presents the longitudinal characterization of disease progression. Furthermore, late-stage clinical compounds and dietary intervention (chow reversal) display distinct hepatoprotective effects in the model. Collectively, the study provides critical information guiding the use of the CDAA-HFD mouse model in preclinical drug discovery for MASH and fibrosis.

Citrus aurantium 'Changshan-huyou' physiological premature fruit drop: A promising prebiotic to tackle obesity

BACKGROUND

Presently, the mitigation and governance of obesity have surfaced as significant public health dilemmas on a global scale. A wealth of studies indicated that the host gut microbiota is instrumental in regulating the interplay between high-fat diet (HFD) intake and the pathogenesis of obesity. Physiological premature fruit drop, a major byproduct of citrus, is rich in a variety of bioactive constituents, yet its potential has remained underutilized for an extended period.

PURPOSE

The objective of this investigation is to examine the chemical constituents of Citrus aurantium'Changshan-huyou' premature fruit drop (HYFD) and investigate its anti-obesity effects, elucidating its potential pathways.

METHODS

Volatile compounds and flavonoids in HYFD were analyzed using chromatographic and mass spectrometric techniques. Furthermore, this study utilized biochemical assays and histopathological examinations to evaluate the effects of HYFD on HFD-fed mice. The impact of HYFD on the gut microbiota of the mice was examined through 16S rRNA gene sequencing, and fecal microbiota transplantation was employed to validate the role of the gut microbial community in host obesity prevention. Concurrently, transcriptome was employed to identify differentially expressed genes, providing further insights into the molecular mechanisms through which HYFD manifests its anti-obesity effects.

RESULTS

Our findings demonstrated that HYFD supplementation significantly alleviated adiposity and ameliorated the dysbiosis of gut microbiota in HFD-induced mice. HYFD rectified the HFD-induced gut microbiota dysregulation, enhanced the presence of beneficial microbial taxa linked to lipid metabolism, including Parabacteroides and Alistipes, and elevated concentrations of the anti-obesity short-chain fatty acids, comprising caproic acid and isocaproic acid. Additionally, transcriptomic analyses confirmed that HYFD prevented obesity in mice by enhancing fatty acid catabolism via the activation of the AMPK/PPARα/CPT1a signaling pathway.

CONCLUSION

Our results provided novel insights into the mechanism of citrus physiological premature fruit drop and its potential role in preventing obesity, while sparking greater interest in leveraging more biomass waste.

PPARα agonist ameliorates cholestatic liver injury by regulating hepatic macrophage homeostasis

Inflammatory response plays an essential role in the pathogenesis of cholestatic liver injury. PPARα agonists have been shown to regulate bile acid homeostasis and hepatic inflammation. However, the immunoregulatory mechanisms through which PPARα agonists ameliorate cholestatic liver injury remain unclear. In this study, surgical bile duct ligation was performed to establish a mouse model of cholestasis. Our study revealed that PPARα agonist alleviated cholestatic liver injury in mice by suppressing inflammatory response, reducing neutrophil infiltration, and promoting M2-like macrophage polarization. CyTOF analysis showed that PPARα agonist increased the proportion of anti-inflammatory F4/80hiCD44+MHCII- M2-like macrophages while decreasing the proportion of pro-inflammatory CD64+CX3CR1+CCR2hiVISTAhiCD172a+CD44hi M1-like MoMFs. Additionally, scRNA-seq indicated that PPARα agonist regulated the developmental trajectory and homeostasis of hepatic macrophages. Mechanistically, PPARα agonist may influence the expression of immune regulators in heterogeneous macrophages to exert protective effects against cholestasis. In addition, the CCL and MIF signaling pathways may participate in the communication among hepatic immune cells, including macrophages, neutrophils, natural killer cells, and dendritic cells, in response to the PPARα agonist. In conclusions, PPARα agonist alleviated cholestatic liver injury by attenuating the inflammatory response and restoring hepatic macrophage homeostasis. This study might enhance the understanding of the immunoregulatory mechanisms of PPARα agonists, providing promising therapeutic targets for cholestatic liver diseases.

Cell metabolism-based therapy for liver fibrosis, repair, and hepatocellular carcinoma

Progression of chronic liver injury to fibrosis, abnormal liver regeneration, and HCC is driven by a dysregulated dialog between epithelial cells and their microenvironment, in particular immune, fibroblasts, and endothelial cells. There is currently no antifibrogenic therapy, and drug treatment of HCC is limited to tyrosine kinase inhibitors and immunotherapy targeting the tumor microenvironment. Metabolic reprogramming of epithelial and nonparenchymal cells is critical at each stage of disease progression, suggesting that targeting specific metabolic pathways could constitute an interesting therapeutic approach. In this review, we discuss how modulating intrinsic metabolism of key effector liver cells might disrupt the pathogenic sequence from chronic liver injury to fibrosis/cirrhosis, regeneration, and HCC.

Immunologic role of macrophages in sepsis-induced acute liver injury

Sepsis-induced acute liver injury (SALI), a manifestation of sepsis multi-organ dysfunction syndrome, is associated with poor prognosis and high mortality. The diversity and plasticity of liver macrophage subpopulations explain their different functional responses in different liver diseases. Kupffer macrophages, liver capsular macrophages, and monocyte-derived macrophages are involved in pathogen recognition and clearance and in the regulation of inflammatory responses, exacerbating the progression of SALI through different pathways of pyroptosis, ferroptosis, and autophagy. Concurrently, they play an important role in maintaining hepatic homeostasis and in the injury and repair processes of SALI. Other macrophages are recruited to diseased tissues under pathological conditions and are polarized into various phenotypes (mainly M1 and M2 types) under the influence of signaling molecules, transcription factors, and metabolic reprogramming, thereby exerting different roles and functions. This review provides an overview of the immune role of macrophages in SALI and discusses the multiple roles of macrophages in liver injury and repair to provide a reference for future studies.

Metabolic disorders, inter-organ crosstalk, and inflammation in the progression of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a global health concern, affecting over 30 % of adults. It is a principal driver in the development of cirrhosis and hepatocellular carcinoma. The complex pathogenesis of MASLD involves an excessive accumulation of lipids, subsequently disrupting lipid metabolism and prompting inflammation within the liver. This review synthesizes the recent research progress in understanding the mechanisms contributing to MASLD progression, with particular emphasis on metabolic disorders and interorgan crosstalk. We highlight the molecular mechanisms linked to these factors and explore their potential as novel targets for pharmacological intervention. The insights gleaned from this article have important implications for both the prevention and therapeutic management of MASLD.

LDT409 (pan-PPAR partial agonist) mitigates metabolic dysfunction-associated steatotic liver disease in high-fructose-fed mice

AIM

This study sought to evaluate the effects of LDT409, a pan-PPAR partial agonist obtained from the main industrial waste from cashew nut processing, on hepatic remodeling, highlighting energy metabolism and endoplasmic reticulum (ER) stress in high-fructose-fed mice.

METHODS

Male C57BL/6 mice received a control diet (C) or a high-fructose diet (HFRU) for ten weeks. Then, a five-week treatment started: C, C-LDT409, HFRU, and HFRU-LDT409. The LDT409 (40 mg/kg of body weight) was mixed with the diets.

RESULTS

The HFRU diet caused insulin resistance and endoplasmic reticulum (ER) stress. High Pparg and decreased Ppara expression increased steatosis and pro-fibrogenic gene expression in livers of HFRU-fed mice. Suppressed lipogenic factors, orchestrated by PPAR-gamma, and mitigated ER stress concomitant with the increase in beta-oxidation driven by PPAR-alpha mediated the LDT409 beneficial effects.

CONCLUSIONS

LDT409 may represent a potential low-cost approach to treat metabolic dysfunction-associated steatotic liver disease, which does not currently have a specific treatment.

The role of macrophages in liver fibrosis: composition, heterogeneity, and therapeutic strategies

Macrophages, the predominant immune cells in the liver, are essential for maintaining hepatic homeostasis and responding to liver injury caused by external stressors. The hepatic macrophage population is highly heterogeneous and plastic, mainly comprised of hepatic resident kuffer cells (KCs), monocyte-derived macrophages (MoMφs), lipid-associated macrophages (LAMs), and liver capsular macrophages (LCMs). KCs, a population of resident macrophages, are localized in the liver and can self-renew through in situ proliferation. However, MoMφs in the liver are recruited from the periphery circulation. LAMs are a self-renewing subgroup of liver macrophages near the bile duct. While LCMs are located in the liver capsule and derived from peripheral monocytes. LAMs and LCMs are also involved in liver damage induced by various factors. Hepatic macrophages exhibit distinct phenotypes and functions depending on the specific microenvironment in the liver. KCs are critical for initiating inflammatory responses after sensing tissue damage, while the MoMφs infiltrated in the liver are implicated in both the progression and resolution of chronic hepatic inflammation and fibrosis. The regulatory function of liver macrophages in hepatic fibrosis has attracted significant interest in current research. Numerous literatures have documented that the MoMφs in the liver have a dual impact on the progression and resolution of liver fibrosis. The MoMφs in the liver can be categorized into two subtypes based on their Ly-6C expression level: inflammatory macrophages with high Ly-6C expression (referred to as Ly-6Chi subgroup macrophages) and reparative macrophages with low Ly-6C expression (referred to as Ly-6Clo subgroup macrophages). Ly-6Chi subgroup macrophages are conducive to the occurrence and progression of liver fibrosis, while Ly-6Clo subgroup macrophages are associated with the degradation of extracellular matrix (ECM) and regression of liver fibrosis. Given this, liver macrophages play a pivotal role in the occurrence, progression, and regression of liver fibrosis. Based on these studies, treatment therapies targeting liver macrophages are also being studied gradually. This review aims to summarize researches on the composition and origin of liver macrophages, the macrophage heterogeneity in the progression and regression of liver fibrosis, and anti-fibrosis therapeutic strategies targeting macrophages in the liver.

Exploring PPAR Gamma and PPAR Alpha's Regulation Role in Metabolism via Epigenetics Mechanism

Peroxisome proliferator-activated receptors (PPARs) belong to a family of nuclear receptors. To date, three types of PPARs, namely PPARα, PPARδ, and PPARγ, have been identified, demonstrating co-expression across numerous tissues. PPARγ is primarily distributed in adipose tissue, the colon, the immune system, and the retina, while PPARα is predominantly expressed in metabolic tissues such as brown adipose tissue, the liver, and the kidneys. Both PPARγ and PPARα play crucial roles in various cellular processes. Recent data suggest that the PPAR family, among other mechanisms, might also be regulated by epigenetic mechanisms. Our recent studies, alongside numerous others, have highlighted the pivotal roles of DNA methylation and histone modifications in the regulation of PPARγ and PPARα, implicating them in the deterioration of metabolic disorders via epigenetic mechanisms. This still not fully understood mechanism of regulation in the nuclear receptors family has been summarized and described in the present paper. The present review summarizes the available data on PPARγ and PPARα regulation via epigenetic mechanisms, elucidating the link between the development of metabolic disorders and the dysregulation of PPARγ and PPARα resulting from these mechanisms.

A roadmap for clinical trials in MASH-related compensated cirrhosis

Although metabolic dysfunction-associated steatohepatitis (MASH) is rapidly becoming a leading cause of cirrhosis worldwide, therapeutic options are limited and the number of clinical trials in MASH-related compensated cirrhosis is low as compared to those conducted in earlier disease stages. Moreover, designing clinical trials in MASH cirrhosis presents a series of challenges regarding the understanding and conceptualization of the natural history, regulatory considerations, inclusion criteria, recruitment, end points and trial duration, among others. The first international workshop on the state of the art and future direction of clinical trials in MASH-related compensated cirrhosis was held in April 2023 at Vall d'Hebron University Hospital in Barcelona (Spain) and was attended by a group of international experts on clinical trials from academia, regulatory agencies and industry, encompassing expertise in MASH, cirrhosis, portal hypertension, and regulatory affairs. The presented Roadmap summarizes important content of the workshop on current status, regulatory requirements and end points in MASH-related compensated cirrhosis clinical trials, exploring alternative study designs and highlighting the challenges that should be considered for upcoming studies on MASH cirrhosis.

Chiglitazar attenuates high-fat diet-induced nonalcoholic fatty liver disease by modulating multiple pathways in mice

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide; however, effective intervention strategies for NAFLD are still unavailable. The present study sought to investigate the efficacy of chiglitazar, a pan-PPAR agonist, in protecting against NAFLD in mice and its underlying molecular mechanism. Male C57BL/6 J mice were fed a high-fat diet (HFD) for 8 weeks to generate NAFLD and the HFD was continued for an additional 10 weeks in the absence or presence of 5 mg/kg/d or 10 mg/kg/d chiglitazar by gavage. Chiglitazar significantly improved dyslipidemia and insulin resistance, ameliorated hepatic steatosis and reduced liver inflammation and oxidative stress in NAFLD mice. RNA-seq revealed that chiglitazar alleviated HFD-induced NAFLD in mice through multiple pathways, including fatty acid metabolism regulation, insulin signaling pathway, and AMPK signaling pathway. This study demonstrated the potential therapeutic effect of chiglitazar on NAFLD. Chiglitazar ameliorated NAFLD by modulating multiple pathways.

Evaluation of Gremlin-1 as a therapeutic target in metabolic dysfunction-associated steatohepatitis

Gremlin-1 has been implicated in liver fibrosis in metabolic dysfunction-associated steatohepatitis (MASH) via inhibition of bone morphogenetic protein (BMP) signalling and has thereby been identified as a potential therapeutic target. Using rat in vivo and human in vitro and ex vivo model systems of MASH fibrosis, we show that neutralisation of Gremlin-1 activity with monoclonal therapeutic antibodies does not reduce liver inflammation or liver fibrosis. Still, Gremlin-1 was upregulated in human and rat MASH fibrosis, but expression was restricted to a small subpopulation of COL3A1/THY1+ myofibroblasts. Lentiviral overexpression of Gremlin-1 in LX-2 cells and primary hepatic stellate cells led to changes in BMP-related gene expression, which did not translate to increased fibrogenesis. Furthermore, we show that Gremlin-1 binds to heparin with high affinity, which prevents Gremlin-1 from entering systemic circulation, prohibiting Gremlin-1-mediated organ crosstalk. Overall, our findings suggest a redundant role for Gremlin-1 in the pathogenesis of liver fibrosis, which is unamenable to therapeutic targeting.

Potential therapeutic strategies for MASH: from preclinical to clinical development

Current treatment paradigms for metabolic dysfunction-associated steatohepatitis (MASH) are based primarily on dietary restrictions and the use of existing drugs, including anti-diabetic and anti-obesity medications. Given the limited number of approved drugs specifically for MASH, recent efforts have focused on promising strategies that specifically target hepatic lipid metabolism, inflammation, fibrosis, or a combination of these processes. In this review, we examined the pathophysiology underlying the development of MASH in relation to recent advances in effective MASH therapy. Particularly, we analyzed the effects of lipogenesis inhibitors, nuclear receptor agonists, glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists, fibroblast growth factor mimetics, and combinatorial therapeutic approaches. We summarize these targets along with their preclinical and clinical candidates with the ultimate goal of optimizing the therapeutic prospects for MASH.

Pioglitazone alleviates lacrimal gland impairments induced by high-fat diet by suppressing M1 polarization

A high-fat diet (HFD) contributes to the pathogenesis of various inflammatory and metabolic diseases. Previous research confirms that under HFD conditions, the extraorbital lacrimal glands (ELGs) can be impaired, with significant infiltration of pro-inflammatory macrophages (Mps). However, the relationship between HFD and Mps polarization in the ELGs remains unexplored. We first identified and validated the differential expression of PPAR-γ in murine ELGs fed ND and HFD through RNA sequencing. Tear secretion was measured using the Schirmer test. Lipid droplet deposition within the ELGs was observed through Oil Red O staining and transmission electron microscopy. Mps phenotypes were determined through quantitative RT-PCR, immunofluorescence, and flow cytometric analysis. An in vitro high-fat culture system for Mps was established using palmitic acid (PA), with supernatants collected for co-culture with lacrimal gland acinar cells. Gene expression was determined through ELISA, immunofluorescence, immunohistochemistry, quantitative RT-PCR, and Western blot analysis. Pioglitazone reduced M1-predominant infiltration induced by HFD by increasing PPAR-γ levels in ELGs, thereby alleviating lipid deposition and enhancing tear secretion. In vitro tests indicated that PPAR-γ agonist shifted Mps from M1-predominant to M2-predominant phenotype in PA-induced Mps, reducing lipid synthesis in LGACs and promoting lipid catabolism, thus alleviating lipid metabolic disorders within ELGs. Conversely, the PPAR-γ antagonist induced opposite effects. In summary, the lacrimal gland is highly sensitive to high-fat and lipid metabolic disorders. Downregulation of PPAR-γ expression in ELGs induces Mps polarization toward predominantly M1 phenotype, leading to lipid metabolic disorder and inflammatory responses via the NF-κb/ERK/JNK/P38 pathway.

Macrophage-derived exosomal miR-155 regulating hepatocyte pyroptosis in MAFLD

Background

Previous studies have shown that pyroptosis in hepatocyte is essential for the development of MAFLD. Growing evidence has shown that exosomal miRNAs-mediated communication between inflammatory cells and hepatocyte is an important link in MAFLD. In the present study, we aim to elucidate whether macrophage-derived exosomal miRNAs contribute to the hepatocyte pyroptosis in the pathophysiological process of MAFLD.

Methods

The effects of hepatocyte pyroptosis were investigated in an HFD-induced MAFLD mouse model and in the liver tissues from patients with MAFLD using immunohistochemistry, real-time PCR, Western blotting, and luciferase reporter assay, among other techniques. MiR-155 inhibitor tail injections and AAV-FoxO3a-GFP were also administered to respectively inhibit or overexpress its expression in an HFD-induced MAFLD mouse model.

Results

Hepatocyte pyroptosis was heightened in the liver tissue of patients with MAFLD or HFD-induced MAFLD mouse. Importantly, treatment with a caspase-1 inhibitor or overexpression of FoxO3a reversed this trend. Our study also demonstrated that miR-155 expression and the number of infiltrated macrophages were increased, and knockdown of miR-155 attenuated hepotocyte pyroptosis and liver fibrosis in HFD-induced mouse. In addition, we demonstrated that macrophage-derived exosomal miR-155 was transferred to hepatocytes, leading to hepatocyte pyroptosis in MAFLD mouse. Furthermore, blockade of exosome secretion improved hepotocyte pyroptosis and liver fibrosis in HFD-induced mouse. On the contrary, macrophage-derived exosomal miR-155 worsened hepotocyte pyroptosis. Moreover, we found that miR-155 promoted hepatocyte pyroptosis in MAFLD by down-regulating FoxO3a.

Conclusions

Taken together, our results demonstrated that macrophage-derived exosomal miR-155 promotes hepatocyte pyroptosis and liver fibrosis in MAFLD.

Pathophysiological Relationship between Type 2 Diabetes Mellitus and Metabolic Dysfunction-Associated Steatotic Liver Disease: Novel Therapeutic Approaches

Type 2 diabetes mellitus (T2DM), often featuring hyperglycemia or insulin resistance, is a global health concern that is increasing in prevalence in the United States and worldwide. A common complication is metabolic dysfunction-associated steatotic liver disease (MASLD), the hepatic manifestation of metabolic syndrome that is also rapidly increasing in prevalence. The majority of patients with T2DM will experience MASLD, and likewise, individuals with MASLD are at an increased risk for developing T2DM. These two disorders may act synergistically, in part due to increased lipotoxicity and inflammation within the liver, among other causes. However, the pathophysiological mechanisms by which this occurs are unclear, as is how the improvement of one disorder can ameliorate the other. This review aims to discuss the pathogenic interactions between T2D and MASLD, and will highlight novel therapeutic targets and ongoing clinical trials for the treatment of these diseases.

Nuclear receptors: pathophysiological mechanisms and drug targets in liver disease

Nuclear receptors (NRs) are ligand-dependent transcription factors required for liver development and function. As a consequence, NRs have emerged as attractive drug targets in a wide range of liver diseases. However, liver dysfunction and failure are linked to loss of hepatocyte identity characterised by deficient NR expression and activities. This might at least partly explain why several pharmacological NR modulators have proven insufficiently efficient to improve liver functionality in advanced stages of diseases such as metabolic dysfunction-associated steatotic liver disease (MASLD). In this perspective, we review the most recent advances in the hepatic NR field and discuss the contribution of multiomic approaches to our understanding of their role in the molecular organisation of an intricated transcriptional regulatory network, as well as in liver intercellular dialogues and interorgan cross-talks. We discuss the potential benefit of novel therapeutic approaches simultaneously targeting multiple NRs, which would not only reactivate the hepatic NR network and restore hepatocyte identity but also impact intercellular and interorgan interplays whose importance to control liver functions is further defined. Finally, we highlight the need of considering individual parameters such as sex and disease stage in the development of NR-based clinical strategies.

Immune system dysregulation in the pathogenesis of non-alcoholic steatohepatitis: unveiling the critical role of T and B lymphocytes

Non-alcoholic fatty liver disease (NAFLD), characterized by the excessive accumulation of fat within the cytoplasm of hepatocytes (exceeding 5% of liver weight) in individuals without significant alcohol consumption, has rapidly evolved into a pressing global health issue, affecting approximately 25% of the world population. This condition, closely associated with obesity, type 2 diabetes, and the metabolic syndrome, encompasses a spectrum of liver disorders ranging from simple steatosis without inflammation to non-alcoholic steatohepatitis (NASH) and cirrhotic liver disease. Recent research has illuminated the complex interplay between metabolic and immune responses in the pathogenesis of NASH, underscoring the critical role played by T and B lymphocytes. These immune cells not only contribute to necroinflammatory changes in hepatic lobules but may also drive the onset and progression of liver fibrosis. This narrative review aims to provide a comprehensive exploration of the effector mechanisms employed by T cells, B cells, and their respective subpopulations in the pathogenesis of NASH. Understanding the immunological complexity of NASH holds profound implications for the development of targeted immunotherapeutic strategies to combat this increasingly prevalent and burdensome metabolic liver disease.

Dissecting Acute Drug-Induced Hepatotoxicity and Therapeutic Responses of Steatotic Liver Disease Using Primary Mouse Liver and Blood Cells in a Liver-On-A-Chip Model

Metabolic dysfunction-associated steatotic liver disease (MASLD) is hallmarked by hepatic steatosis, cell injury, inflammation, and fibrosis. This study elaborates on a multicellular biochip-based liver sinusoid model to mimic MASLD pathomechanisms and investigate the therapeutic effects of drug candidates lanifibranor and resmetirom. Mouse liver primary hepatocytes, hepatic stellate cells, Kupffer cells, and endothelial cells are seeded in a dual-chamber biocompatible liver-on-a-chip (LoC). The LoC is then perfused with circulating immune cells (CICs). Acetaminophen (APAP) and free fatty acids (FFAs) treatment recapitulate acute drug-induced liver injury and MASLD, respectively. As a benchmark for the LoC, multiplex immunofluorescence on livers from APAP-injected and dietary MASLD-induced mice reveals characteristic changes on parenchymal and immune cell populations. APAP exposure induces cell death in the LoC, and increased inflammatory cytokine levels in the circulating perfusate. Under FFA stimulation, lipid accumulation, cellular damage, inflammatory secretome, and fibrogenesis are increased in the LoC, reflecting MASLD. Both injury conditions potentiate CIC migration from the perfusate to the LoC cellular layers. Lanifibranor prevents the onset of inflammation, while resmetirom decreases lipid accumulation in hepatocytes and increases the generation of FFA metabolites in the LoC. This study demonstrates the LoC potential for functional and molecular evaluation of liver disease drug candidates.

New advances in drug development for metabolic dysfunction-associated diseases and alcohol-associated liver disease

Metabolic disorders are currently threatening public health worldwide. Discovering new targets and developing promising drugs will reduce the global metabolic-related disease burden. Metabolic disorders primarily consist of lipid and glucose metabolic disorders. Specifically, metabolic dysfunction-associated steatosis liver disease (MASLD) and alcohol-associated liver disease (ALD) are two representative lipid metabolism disorders, while diabetes mellitus is a typical glucose metabolism disorder. In this review, we aimed to summarize the new drug candidates with promising efficacy identified in clinical trials for these diseases. These drug candidates may provide alternatives for patients with metabolic disorders and advance the progress of drug discovery for the large disease burden.

Metabolic reprogramming in liver fibrosis

Chronic liver diseases, primarily metabolic dysfunction-associated steatotic liver disease (MASLD), harmful use of alcohol, or viral hepatitis, may result in liver fibrosis, cirrhosis, and cancer. Hepatic fibrogenesis is a complex process with interactions between different resident and non-resident heterogeneous liver cell populations, ultimately leading to deposition of extracellular matrix and organ failure. Shifts in cell phenotypes and functions involve pronounced transcriptional and protein synthesis changes that require metabolic adaptations in cellular substrate metabolism, including glucose and lipid metabolism, resembling changes associated with the Warburg effect in cancer cells. Cell activation and metabolic changes are regulated by metabolic stress responses, including the unfolded protein response, endoplasmic reticulum stress, autophagy, ferroptosis, and nuclear receptor signaling. These metabolic adaptations are crucial for inflammatory and fibrogenic activation of macrophages, lymphoid cells, and hepatic stellate cells. Modulation of these pathways, therefore, offers opportunities for novel therapeutic approaches to halt or even reverse liver fibrosis progression.

MAFLD Pandemic: Updates in Pharmacotherapeutic Approach Development

With around one billion of the world's population affected, the era of the metabolic-associated fatty liver disease (MAFLD) pandemic has entered the global stage. MAFLD is a chronic progressive liver disease with accompanying metabolic disorders such as type 2 diabetes mellitus and obesity which can progress asymptomatically to liver cirrhosis and subsequently to hepatocellular carcinoma (HCC), and for which to date there are almost no approved pharmacologic options. Because MAFLD has a very complex etiology and it also affects extrahepatic organs, a multidisciplinary approach is required when it comes to finding an effective and safe active substance for MAFLD treatment. The optimal drug for MAFLD should diminish steatosis, fibrosis and inflammation in the liver, and the winner for MAFLD drug authorisation seems to be the one that significantly improves liver histology. Saroglitazar (Lipaglyn®) was approved for metabolic-dysfunction-associated steatohepatitis (MASH) in India in 2020; however, the drug is still being investigated in other countries. Although the pharmaceutical industry is still lagging behind in developing an approved pharmacologic therapy for MAFLD, research has recently intensified and many molecules which are in the final stages of clinical trials are expected to be approved in the coming few years. Already this year, the first drug (Rezdiffra™) in the United States was approved via accelerated procedure for treatment of MAFLD, i.e., of MASH in adults. This review underscores the most recent information related to the development of drugs for MAFLD treatment, focusing on the molecules that have come furthest towards approval.

A review of MASLD-related hepatocellular carcinoma: progress in pathogenesis, early detection, and therapeutic interventions

The incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) is continuously rising, evolving into a global health challenge. Concurrently, cases of hepatocellular carcinoma (HCC) associated with MASLD are also on the increase. Although traditional risk factors such as age, gender, and metabolic factors play significant roles in the development of HCC, it cannot be overlooked that MASLD, triggered by changes in modern lifestyle and dietary habits, may also exacerbate the risk of HCC, and this phenomenon is common even among non-obese individuals. Regrettably, MASLD often fails to receive timely diagnosis, resulting in a limited number of patients receiving HCC surveillance. Moreover, there is currently a lack of clear definition for the target population for surveillance beyond patients with cirrhosis. Consequently, MASLD-related HCC is often detected at a late stage, precluding the optimal timing for curative treatment. However, our understanding of the pathogenesis and progression of HCC remains limited. Therefore, this paper reviews relevant literature from recent years, delving into multiple dimensions such as pathogenesis, surveillance and diagnosis, prevention, and treatment, aiming to provide new ideas and directions for the prevention and treatment of MASLD-related HCC.

A 5:2 intermittent fasting regimen ameliorates NASH and fibrosis and blunts HCC development via hepatic PPARα and PCK1

The role and molecular mechanisms of intermittent fasting (IF) in non-alcoholic steatohepatitis (NASH) and its transition to hepatocellular carcinoma (HCC) are unknown. Here, we identified that an IF 5:2 regimen prevents NASH development as well as ameliorates established NASH and fibrosis without affecting total calorie intake. Furthermore, the IF 5:2 regimen blunted NASH-HCC transition when applied therapeutically. The timing, length, and number of fasting cycles as well as the type of NASH diet were critical parameters determining the benefits of fasting. Combined proteome, transcriptome, and metabolome analyses identified that peroxisome-proliferator-activated receptor alpha (PPARα) and glucocorticoid-signaling-induced PCK1 act co-operatively as hepatic executors of the fasting response. In line with this, PPARα targets and PCK1 were reduced in human NASH. Notably, only fasting initiated during the active phase of mice robustly induced glucocorticoid signaling and free-fatty-acid-induced PPARα signaling. However, hepatocyte-specific glucocorticoid receptor deletion only partially abrogated the hepatic fasting response. In contrast, the combined knockdown of Ppara and Pck1 in vivo abolished the beneficial outcomes of fasting against inflammation and fibrosis. Moreover, overexpression of Pck1 alone or together with Ppara in vivo lowered hepatic triglycerides and steatosis. Our data support the notion that the IF 5:2 regimen is a promising intervention against NASH and subsequent liver cancer.

PPARβ/δ as a promising molecular drug target for liver diseases: A focused review

Various liver diseases pose great threats to humans. Although the etiologies of these liver diseases are quite diverse, they share similar pathologic phenotypes and molecular mechanisms such as oxidative stress, lipid and glucose metabolism disturbance, hepatic Kupffer cell (KC) proinflammatory polarization and inflammation, insulin resistance, and hepatic stellate cell (HSC) activation and proliferation. Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) is expressed in various types of liver cells with relatively higher expression in KCs and HSCs. Accumulating evidence has revealed the versatile functions of PPARβ/δ such as controlling lipid homeostasis, inhibiting inflammation, regulating glucose metabolism, and restoring insulin sensitivity, suggesting that PPARβ/δ may serve as a potential molecular drug target for various liver diseases. This article aims to provide a concise review of the structure, expression pattern and biological functions of PPARβ/δ in the liver and its roles in various liver diseases, and to discuss potential future research perspectives.

MASLD/MASH and type 2 diabetes: Two sides of the same coin? From single PPAR to pan-PPAR agonists

Type 2 diabetes (T2D) and metabolic dysfunction-associated steatotic liver disease (MASLD), mainly related to nutrition and lack of physical activity, are both very common conditions, share several disease pathways and clinical manifestations, and increasingly co-occur with disease progression. Insulin resistance is an upstream node in the biology of both conditions and triggers liver parenchymal injury, inflammation and fibrosis. Peroxisome proliferator-activated receptor (PPAR) nuclear transcription factors are master regulators of energy homeostasis - insulin signaling in liver, adipose and skeletal muscle tissue - and affect immune and fibrogenesis pathways. Among distinct yet overlapping effects, PPARα regulates lipid metabolism and energy expenditure, PPARβ/δ has anti-inflammatory effects and increases glucose uptake by skeletal muscle, while PPARγ improves insulin sensitivity and exerts direct antifibrotic effects on hepatic stellate cells. Together PPARs thus represent pharmacological targets across the entire biology of MASH. Single PPAR agonists are approved for hypertriglyceridemia (PPARα) and T2D (PPARγ), but these, as well as dual PPAR agonists, have shown mixed results as anti-MASH treatments in clinical trials. Agonists of all three PPAR isoforms have the potential to improve the full disease spectrum from insulin resistance to fibrosis, and correspondingly to improve cardiometabolic and hepatic health, as has been shown (phase II data) with the pan-PPAR agonist lanifibranor.

Pharmacotherapeutic options for metabolic dysfunction-associated steatotic liver disease: where are we today?

INTRODUCTION

Metabolic dysfunction-associated steatotic liver disease (MASLD) is defined by hepatic steatosis and cardiometabolic risk factors like obesity, type 2 diabetes, and dyslipidemia. Persistent metabolic injury may promote inflammatory processes resulting in metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. Mechanistic insights helped to identify potential drug targets, thereby supporting the development of novel compounds modulating disease drivers.

AREAS COVERED

The U.S. Food and Drug Administration has recently approved the thyroid hormone receptor β-selective thyromimetic resmetirom as the first compound to treat MASH and liver fibrosis. This review provides a comprehensive overview of current and potential future pharmacotherapeutic options and their modes of action. Lessons learned from terminated clinical trials are discussed together with the first results of trials investigating novel combinational therapeutic approaches.

EXPERT OPINION

Approval of resmetirom as the first anti-MASH agent may revolutionize the therapeutic landscape. However, long-term efficacy and safety data for resmetirom are currently lacking. In addition, heterogeneity of MASLD reflects a major challenge to define effective agents. Several lead compounds demonstrated efficacy in reducing obesity and hepatic steatosis, while anti-inflammatory and antifibrotic effects of monotherapy appear less robust. Better mechanistic understanding, exploration of combination therapies, and patient stratification hold great promise for MASLD therapy.

Lanifibranor Reduces Inflammation and Improves Dyslipidemia in Lysosomal Acid Lipase-Deficient Mice

Background and Aims

Recent studies showed that patients suffering from lysosomal acid lipase deficiency (LAL-D) benefit from enzyme replacement therapy; however, liver histopathology improved in some but not all patients. We hypothesized that the pan-peroxisome proliferator-activated receptor agonist lanifibranor may have beneficial effects on liver inflammation in LAL knockout (Lal-/-) mice based on its promising results in alleviating liver inflammation in patients with metabolic dysfunction-associated steatohepatitis.

Methods

Female Lal-/- mice were daily gavaged with lanifibranor or vehicle for 21 days. The effects of the treatment were assessed by measuring body and organ weights, plasma lipids and lipoproteins, as well as hematological parameters, followed by liver proteomics and metabolomics.

Results

Lanifibranor treatment slightly altered organ weights without affecting the total body weight of Lal-/- mice. We observed major changes in the proteome, with multiple proteins related to lipid metabolism, peroxisomal, and mitochondrial activities being upregulated and inflammation-related proteins being downregulated in the livers of treated mice. Hepatic lipid levels and histology remained unaltered, whereas plasma triacylglycerol and total cholesterol levels were decreased and the lipoprotein profile of lanifibranor-treated Lal-/- mice improved.

Conclusion

Lanifibranor treatment positively affected liver inflammation and dyslipidemia in Lal-/- mice. These findings suggest the necessity of a further combined study of lanifibranor with enzyme replacement therapy in Lal-/- mice to improve the phenotype. Moreover, there is a compelling rationale for conducting clinical trials to assess the efficacy of lanifibranor as a potential treatment option for LAL-D in humans.

Activation of Nrf2/HO-1 signaling pathway exacerbates cholestatic liver injury

Nuclear factor erythroid 2-related factor-2 (Nrf2) antioxidant signaling is involved in liver protection, but this generalization overlooks conflicting studies indicating that Nrf2 effects are not necessarily hepatoprotective. The role of Nrf2/heme oxygenase-1 (HO-1) in cholestatic liver injury (CLI) remains poorly defined. Here, we report that Nrf2/HO-1 activation exacerbates liver injury rather than exerting a protective effect in CLI. Inhibiting HO-1 or ameliorating bilirubin transport alleviates liver injury in CLI models. Nrf2 knockout confers hepatoprotection in CLI mice, whereas in non-CLI mice, Nrf2 knockout aggravates liver damage. In the CLI setting, oxidative stress activates Nrf2/HO-1, leads to bilirubin accumulation, and impairs mitochondrial function. High levels of bilirubin reciprocally upregulate the activation of Nrf2 and HO-1, while antioxidant and mitochondrial-targeted SOD2 overexpression attenuate bilirubin toxicity. The expression of Nrf2 and HO-1 is elevated in serum of patients with CLI. These results reveal an unrecognized function of Nrf2 signaling in exacerbating liver injury in cholestatic disease.

A Systematic Review of Statins for the Treatment of Nonalcoholic Steatohepatitis: Safety, Efficacy, and Mechanism of Action

Nonalcoholic fatty liver disease (NAFLD) is the liver component of a cluster of conditions, while its subtype, nonalcoholic steatohepatitis (NASH), emerges as a potentially progressive liver disorder that harbors the risk of evolving into cirrhosis and culminating in hepatocellular carcinoma (HCC). NASH and cardiovascular disease (CVD) have common risk factors, but compared to liver-related causes, the most common cause of death in NASH patients is CVD. Within the pharmacological armamentarium, statins, celebrated for their lipid-modulating prowess, have now garnered attention for their expansive therapeutic potential in NASH. Evidence from a plethora of studies suggests that statins not only manifest anti-inflammatory and antifibrotic properties but also impart a multifaceted beneficial impact on hepatic health. In this review, we used "statin", "NAFLD", "NASH", and "CVD" as the major keywords and conducted a literature search using the PubMed and Web of Science databases to determine the safety and efficacy of statins in patients and animals with NASH and NAFLD, and the mechanism of statin therapy for NASH. Simultaneously, we reviewed the important role of the intestinal microbiota in statin therapy for NASH, as it is hoped that statins will provide new insights into modulating the harmful inflammatory microbiota in the gut and reducing systemic inflammation in NASH patients.

Advances in management of metabolic dysfunction-associated steatotic liver disease: from mechanisms to therapeutics

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading cause of chronic liver disease that affects over 30% of the world's population. For decades, the heterogeneity of non-alcoholic fatty liver disease (NAFLD) has impeded our understanding of the disease mechanism and the development of effective medications. However, a recent change in the nomenclature from NAFLD to MASLD emphasizes the critical role of systemic metabolic dysfunction in the pathophysiology of this disease and therefore promotes the progress in the pharmaceutical treatment of MASLD. In this review, we focus on the mechanism underlying the abnormality of hepatic lipid metabolism in patients with MASLD, and summarize the latest progress in the therapeutic medications of MASLD that target metabolic disorders.

Imbalance of mitochondrial fusion in peripheral blood mononuclear cells is associated with liver fibrosis in patients with metabolic dysfunction-associated steatohepatitis

Mitochondrial dysfunction and inflammation contribute to the pathophysiology of metabolic dysfunction-associated steatohepatitis (MASH). This study aims to evaluate the potential association between mitochondrial dynamics and cell death markers from peripheral blood mononuclear cells (PBMCs) and the presence of MASH with significant liver fibrosis among metabolic dysfunction-associated steatotic liver disease (MASLD) patients. Consecutive patients undergoing bariatric surgery from January to December 2022 were included. Patients with histologic steatosis were classified into MASH with significant fibrosis (F2-4) group or MASLD/MASH without significant fibrosis group (F0-1). Mitochondrial dynamic proteins and cell death markers were extracted from PBMCs. A total of 23 MASLD/MASH patients were included (significant fibrosis group, n = 7; without significant fibrosis group, n = 16). Of the mitochondrial dynamics and cell death markers evaluated, OPA1 protein, a marker of mitochondrial fusion is higher in MASH patients with significant fibrosis compared to those without (0.861 ± 0.100 vs. 0.560 ± 0.260 proportional to total protein, p = 0.001). Mitochondrial fusion/fission (OPA1/DRP1) ratio is significantly higher in MASH patients with significant fibrosis (1.072 ± 0.307 vs. 0.634 ± 0.313, p = 0.009). OPA1 (per 0.01 proportional to total protein) was associated with the presence of significant liver fibrosis with an OR of 1.08 (95%CI, 1.01-1.15, p = 0.035), and adjusted OR of 1.10 (95%CI, 1.00-1.21, p = 0.042). OPA1 from PBMCs is associated with MASH and substantial fibrosis. Future studies should explore if OPA1 could serve as a novel non-invasive liver fibrosis marker.

A pan-PPAR agonist E17241 ameliorates hyperglycemia and diabetic dyslipidemia in KKAy mice via up-regulating ABCA1 in islet, liver, and white adipose tissue

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is a common chronic metabolic disease. Peroxisome proliferator-activated receptors (PPARs) play crucial roles in regulating glucolipid metabolism. Previous studies showed that E17241 could ameliorate atherosclerosis and lower fasting blood glucose levels in ApoE-/- mice. In this work, we investigated the role of E17241 in glycolipid metabolism in diabetic KKAy mice.

APPROACH AND RESULTS

We confirmed that E17241 is a powerful pan-PPAR agonist with a potent agonistic activity on PPARγ, a high activity on PPARα, and a moderate activity on PPARδ. E17241 also significantly increased the protein expression of ATP-binding cassette transporter 1 (ABCA1), a crucial downstream target gene for PPARs. E17241 clearly lowered plasma glucose levels, improved OGTT and ITT, decreased islet cholesterol content, improved β-cell function, and promoted insulin secretion in KKAy mice. Moreover, E17241 could significantly lower plasma total cholesterol and triglyceride levels, reduce liver lipid deposition, and improve the adipocyte hypertrophy and the inflammatory response in epididymal white adipose tissue. Further mechanistic studies indicated that E17241 boosts cholesterol efflux and insulin secretion in an ABCA1 dependent manner. RNA-seq and qRT-PCR analysis demonstrated that E17241 induced different expression of PPAR target genes in liver and adipose tissue differently from the PPARγ agonist rosiglitazone. In addition, E17241 treatment was also demonstrated to have an exhilarating cardiorenal benefits.

CONCLUSIONS

Our results demonstrate that E17241 regulates glucolipid metabolism in KKAy diabetic mice while having cardiorenal benefits without inducing weight gain. It is a promising drug candidate for the treatment of T2DM.