Galectin-3 inhibition as a potential therapeutic target in non-alcoholic steatohepatitis liver fibrosis

Atrial Translocation of Porphyromonas gingivalis Exacerbates Atrial Fibrosis and Atrial Fibrillation

BACKGROUND

Recent studies have indicated an association between periodontitis and atrial fibrillation (AF), although the underlying mechanisms remain unclear. Porphyromonas gingivalis is a causative agent of periodontal disease and is highly pathogenic. This study focused on P gingivalis and aimed to investigate the relationship among periodontitis, atrial translocation of P gingivalis, and atrial fibrosis and AF.

METHODS

An experiment was conducted using P gingivalis-infected C57BL/6J mice, in which P gingivalis was inoculated into the pulp of the molars. Immunohistochemistry was used to visualize the localization of P gingivalis, and loop-mediated isothermal amplification was employed to detect P gingivalis DNA in the left atrium. AF inducibility was examined by intracardiac stimulation. Moreover, left atrial appendage specimens were obtained from 68 patients with AF. A periodontal examination was conducted before the surgery, and the periodontal epithelial surface area and periodontal inflamed surface area, which are quantitative indices used to determine the clinical severity of periodontitis, were measured. The bacterial number of P gingivalis in human atrial tissue was analyzed via quantitative polymerase chain reaction. Atrial fibrosis was assessed using Azan-Mallory staining.

RESULTS

The translocation path of P gingivalis from the dental granuloma to the left atrium via the circulatory system was demonstrated by immunohistochemistry and loop-mediated isothermal amplification in P gingivalis-infected mice, which showed a higher degree of atrial fibrosis (21.9% versus 16.3%; P=0.0003) and a higher AF inducibility (30.0% versus 5.0%; P=0.04) than the control mice. Upregulation of GAL3 (galectin 3) and transforming growth factor-beta 1 in the left atrium was observed in P gingivalis-infected mice. Moreover, immunohistochemistry revealed that P gingivalis was also present in human atrial tissue. The number of P gingivalis in the human atrial tissue was positively correlated with periodontal epithelial surface area (ρ=0.35; P=0.004), periodontal inflamed surface area (ρ=0.52, P<0.0001), and the degree of atrial fibrosis (ρ=0.38; P=0.002).

CONCLUSIONS

P gingivalis translocation to the left atrium correlates with the clinical severity of periodontitis, which may exacerbate atrial fibrosis and AF. Atrial translocation of P gingivalis is a potential pathway explaining the causal relationship between periodontitis and AF.

Comparative Analysis of the Total Proteome in Nonalcoholic Steatohepatitis: Identification of Potential Biomarkers

Nonalcoholic fatty liver disease is a hepatic condition characterized by excessive fat accumulation in the liver with advanced stage nonalcoholic steatohepatitis (NASH), potentially leading to liver fibrosis, cirrhosis, and cancer. Currently, the identification and classification of NASH require invasive liver biopsy, which has certain limitations. Mass spectrometry-based proteomics can detect crucial proteins and pathways implicated in NASH development and progression. We collected the liver and serum samples from choline-deficient, L-amino acid-defined high-fat diet fed NASH C57BL/6J mice and human serum samples to examine proteomic alterations and identify early biomarkers for NASH diagnosis. In-depth targeted multiple reaction monitoring scanning and immunoblotting assays were used to verify the biomarker candidates from mouse liver and serum samples, and enzyme-linked immunosorbent assay (ELISA) was employed to analyze human serum samples. The multiple reaction monitoring analysis of NASH liver revealed 50 proteins with altered expression (21 upregulated and 29 downregulated) that are involved in biological processes such as detoxification, fibrosis, inflammation, and fatty acid metabolism. Ingenuity pathway analysis identified impaired protein synthesis, cellular stress and defense, cellular processes and communication, and metabolism in NASH mouse liver. Immunoblotting analysis confirmed that the expression of proteins associated with fatty acid metabolism (Aldo B and Fasn) and urea cycle (Arg1, Cps1, and Otc) was altered in the mouse liver and serum. Further analysis on human serum samples using ELISA confirmed the increased expression of multiple proteins, including Aldo B, Asl, and Lgals3, demonstrating values of 0.917, 0.979, and 0.965 of area under the curve in NASH diagnosis. These findings offer valuable insights into the molecular mechanisms of NASH and possible diagnostic biomarkers for early detection.

Liver lipid droplet cholesterol content is a key determinant of metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) represents a progressive form of steatotic liver disease which increases the risk for fibrosis and advanced liver disease. The accumulation of discrete species of bioactive lipids has been postulated to activate signaling pathways that promote inflammation and fibrosis. However, the key pathogenic lipid species is a matter of debate. We explored candidates using various dietary, molecular, and genetic models. Mice fed a choline-deficient L-amino acid-defined high-fat diet (CDAHFD) developed steatohepatitis and manifested early markers of liver fibrosis associated with increased cholesterol content in liver lipid droplets within 5 days without any changes in total liver cholesterol content. Treating mice with antisense oligonucleotides (ASOs) against Coenzyme A synthase (Cosay) or treatment with bempedoic acid or atorvastatin decreased liver lipid droplet cholesterol content and prevented CDAHFD-induced MASH and the fibrotic response. All these salutary effects were abrogated with dietary cholesterol supplementation. Analysis of human liver samples demonstrated that cholesterol in liver lipid droplets was increased in humans with MASH and liver fibrosis and was higher in PNPLA3 I148M (variants rs738409) than in HSD17B13 variants (rs72613567). Together, these data identify cholesterol in liver lipid droplets as a critical mediator of MASH and demonstrate that COASY knockdown and bempedoic acid are novel therapeutic approaches to reduce liver lipid droplet cholesterol content and thereby prevent the development of MASH and liver fibrosis.

Significance Statement

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive liver disease linked to fibrosis. The role of specific lipid species in its pathogenesis remains debated. Using dietary, molecular, and genetic models, we found that mice on a choline-deficient, high-fat diet (CDAHFD) developed steatohepatitis and early fibrosis, marked by increased cholesterol in liver lipid droplets within five days. Targeting COASY with antisense oligonucleotides or treating with bempedoic acid or atorvastatin reduced lipid droplet cholesterol and prevented MASH. However, dietary cholesterol supplementation negated these effects. Human liver samples confirmed elevated lipid droplet cholesterol in MASH and fibrosis, especially in PNPLA3 I148M carriers. These findings highlight cholesterol reduction as a potential MASH therapy.

Current Therapeutic Landscape for Metabolic Dysfunction-Associated Steatohepatitis

In recent years, "metabolic dysfunction-associated steatotic liver disease" (MASLD) has been proposed to better connect liver disease to metabolic dysfunction, which is the most common chronic liver disease worldwide. MASLD affects more than 30% of individuals globally, and it is diagnosed by the combination of hepatic steatosis and obesity, type 2 diabetes, or two metabolic risk factors. MASLD begins with the buildup of extra fat, often greater than 5%, within the liver, causing liver hepatocytes to become stressed. This can proceed to a more severe form, metabolic dysfunction-associated steatohepatitis (MASH), in 20-30% of people, where inflammation in the liver causes tissue fibrosis, which limits blood flow over time. As fibrosis worsens, MASH may lead to cirrhosis, liver failure, or even liver cancer. While the pathophysiology of MASLD is not fully known, the current "multiple-hits" concept proposes that dietary and lifestyle factors, metabolic factors, and genetic or epigenetic factors contribute to elevated oxidative stress and inflammation, causing liver fibrosis. This review article provides an overview of the pathogenesis of MASLD and evaluates existing therapies as well as pharmacological drugs that are currently being studied in clinical trials for MASLD or MASH.

Galectins and Liver Diseases

Galectins are widely distributed throughout the animal kingdom, from marine sponges to mammals. Galectins are a family of soluble lectins that specifically recognize β-galactoside-containing glycans and are categorized into three subgroups based on the number and function of their carbohydrate recognition domains (CRDs). The interaction of galectins with specific ligands mediates a wide range of biological activities, depending on the cell type, tissue context, expression levels of individual galectin, and receptor involvement. Galectins affect various immune cell processes through both intracellular and extracellular mechanisms and play roles in processes, such as apoptosis, angiogenesis, and fibrosis. Their importance has increased in recent years because they are recognized as biomarkers, therapeutic agents, and drug targets, with many other applications in conditions such as cardiovascular diseases and cancer. However, little is known about the involvement of galectins in liver diseases. Here, we review the functions of various galectins and evaluate their roles in liver diseases.

Galectin-3 in metabolic disorders: mechanisms and therapeutic potential

Galectin-3 (Gal3), a β-galactoside-binding lectin, is expressed predominantly in immunological and inflammatory cells. Gal3 expression is elevated in metabolic diseases, including obesity, diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD), and plays an important role in the progression of these diseases. In this review, we summarize the structure and post-translational modifications of Gal3 and the cellular functions of Gal3 according to its subcellular localization. We focused on the pathological functions and molecular mechanisms of Gal3 in various cell types. In particular, extracellular Gal3 and intracellular Gal3 may have different physiological and pathological functions. We also discuss promising Gal3 inhibitors or antibodies that are currently in clinical trials and outstanding questions and challenges for future pursuit.

Current and experimental pharmacotherapy for the management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease, with its incidence increasing in parallel with the global prevalence of obesity and type 2 diabetes mellitus. Despite our steadily increasing knowledge of its pathogenesis, there is as yet no available pharmacotherapy specifically tailored for NAFLD. To define the appropriate management, it is important to clarify the context in which the disease appears. In the case of concurrent metabolic comorbidities, NAFLD patients are treated by targeting these comorbidities, such as diabetes and obesity. Thus, GLP-1 analogs, PPAR, and SGLT2 inhibitors have recently become central to the treatment of NAFLD. In parallel, randomized trials are being conducted to explore new agents targeting known pathways involved in NAFLD progression. However, there is an imperative need to intensify the effort to design new, safe drugs with biopsy-proven efficacy. Of note, the main target of the pharmacotherapy should be directed to the regression of fibrotic NASH, as this histologic stage has been correlated with increased overall as well as liver-related morbidity and mortality. Herein we discuss the drugs currently at the forefront of NAFLD treatment.

Genomics of human NAFLD: Lack of data reproducibility and high interpatient variability in drug target expression as major causes of drug failures

BACKGROUND AND AIMS

NAFLD is a major disease burden and a foremost cause of chronic liver disease. Presently, nearly 300 trials evaluate the therapeutic efficacy of > 20 drugs. Remarkably, the majority of drugs fail. To better comprehend drug failures, we investigated the reproducibility of fatty liver genomic data across 418 liver biopsies and evaluated the interpatient variability of 18 drug targets.

APPROACH AND RESULTS

Apart from our own data, we retrieved NAFLD biopsy genomic data sets from public repositories and considered patient demographics. We divided the data into test and validation sets, assessed the reproducibility of differentially expressed genes and performed gene enrichment analysis. Patients were stratified by disease activity score, fibrosis grades and sex, and we investigated the regulation of 18 drug targets across 418 NAFLD biopsies of which 278 are NASH cases. We observed poor reproducibility of differentially expressed genes across 9 independent studies. On average, only 4% of differentially expressed genes are commonly regulated based on identical sex and 2% based on identical NAS disease score and fibrosis grade. Furthermore, we observed sex-specific gene regulations, and for females, we noticed induced expression of genes coding for inflammatory response, Ag presentation, and processing. Conversely, extracellular matrix receptor interactions are upregulated in males, and the data agree with clinical findings. Strikingly, and with the exception of stearoyl-CoA desaturase, most drug targets are not regulated in > 80% of patients.

CONCLUSIONS

Lack of data reproducibility, high interpatient variability, and the absence of disease-dependent drug target regulations are likely causes of NASH drug failures in clinical trials.

The galectin-3 inhibitor selvigaltin reduces liver inflammation and fibrosis in a high fat diet rabbit model of metabolic-associated steatohepatitis

Introduction

Galectin-3 is a pro-fibrotic β-galactoside binding lectin highly expressed in fibrotic liver and implicated in hepatic fibrosis. Selvigaltin (previously known as GB1211) is a novel orally active galectin-3 small molecule inhibitor that has high affinity for galectin-3 (human KD = 25 nM; rabbit KD = 12 nM) and high oral bioavailability in rabbits and man. In this study the efficacy of selvigaltin was investigated in a high fat diet (HFD) rabbit model of metabolic-associated steatohepatitis (MASH).

Methods

Male New Zealand White rabbits were individually caged under standard conditions in a temperature and humidity-controlled room on a 12 h light/darkness cycle. After 1 week of regular diet (RD), rabbits were randomly assigned for 8 or 12 weeks to different groups: RD/vehicle, RD/selvigaltin, HFD (8 weeks), HFD/vehicle and HFD/selvigaltin (0.3, 1.0, 5.0 or 30 mg/kg selvigaltin with vehicle/selvigaltin p.o. dosed therapeutically q.d. 5 days per week from week 9 or 12). Liver inflammation, steatosis, ballooning, and fibrosis was measured via blood metabolic markers, histomorphological evaluation [Oil Red O, Giemsa, Masson's trichome, picrosirius red (PSR) and second harmonic generation (SHG)], and mRNA and protein expression.

Results

Steatosis, inflammation, ballooning, and fibrosis were all increased from RD to HFD/vehicle groups. Selvigaltin demonstrated target engagement by significantly decreasing galectin-3 levels in the liver as measured via immunohistochemistry and mRNA analysis. Selvigaltin dose-dependently reduced biomarkers of liver function (AST, ALT, bilirubin), inflammation (cells foci), and fibrosis (PSR, SHG), as well as decreasing the mRNA and protein expression of several key inflammation and fibrosis biomarkers (e.g., IL6, TGFβ3, SNAI2, collagen). Doses of 1.0 or 5.0 mg/kg demonstrated consistent efficacy across most biological endpoints supporting the current clinical doses of selvigaltin being investigated in liver disease.

Discussion

Selvigaltin significantly reduced hepatic inflammation and fibrosis in an HFD rabbit model of MASH following therapeutic dosing for 4 weeks in a dose-dependent manner. These data support the human selvigaltin dose of 100 mg b.i.d. that has been shown to reduce key liver biomarkers during a clinical study in liver cirrhosis.

Steatotic Liver Disease: Pathophysiology and Emerging Pharmacotherapies

Steatotic liver disease (SLD) displays a dynamic and complex disease phenotype. Consequently, the metabolic dysfunction-associated steatotic liver disease (MASLD)/metabolic dysfunction-associated steatohepatitis (MASH) therapeutic pipeline is expanding rapidly and in multiple directions. In parallel, noninvasive tools for diagnosing and monitoring responses to therapeutic interventions are being studied, and clinically feasible findings are being explored as primary outcomes in interventional trials. The realization that distinct subgroups exist under the umbrella of SLD should guide more precise and personalized treatment recommendations and facilitate advancements in pharmacotherapeutics. This review summarizes recent updates of pathophysiology-based nomenclature and outlines both effective pharmacotherapeutics and those in the pipeline for MASLD/MASH, detailing their mode of action and the current status of phase 2 and 3 clinical trials. Of the extensive arsenal of pharmacotherapeutics in the MASLD/MASH pipeline, several have been rejected, whereas other, mainly monotherapy options, have shown only marginal benefits and are now being tested as part of combination therapies, yet others are still in development as monotherapies. Although the Food and Drug Administration (FDA) has recently approved resmetirom, additional therapeutic approaches in development will ideally target MASH and fibrosis while improving cardiometabolic risk factors. Due to the urgent need for the development of novel therapeutic strategies and the potential availability of safety and tolerability data, repurposing existing and approved drugs is an appealing option. Finally, it is essential to highlight that SLD and, by extension, MASLD should be recognized and approached as a systemic disease affecting multiple organs, with the vigorous implementation of interdisciplinary and coordinated action plans. SIGNIFICANCE STATEMENT: Steatotic liver disease (SLD), including metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis, is the most prevalent chronic liver condition, affecting more than one-fourth of the global population. This review aims to provide the most recent information regarding SLD pathophysiology, diagnosis, and management according to the latest advancements in the guidelines and clinical trials. Collectively, it is hoped that the information provided furthers the understanding of the current state of SLD with direct clinical implications and stimulates research initiatives.

Galectin-3 and Severity of Liver Fibrosis in Metabolic Dysfunction-Associated Fatty Liver Disease

Metabolic dysfunction-associated Fatty Liver Disease (MAFLD) is a chronic liver disease characterized by the accumulation of fat in the liver and hepatic steatosis, which can progress to critical conditions, including Metabolic dysfunction-associated Steatohepatitis (MASH), liver fibrosis, hepatic cirrhosis, and hepatocellular carcinoma. Galectin-3, a member of the galectin family of proteins, has been involved in cascades that are responsible for the pathogenesis and progression of liver fibrosis in MAFLD. This review summarizes the present understanding of the role of galectin-3 in the severity of MAFLD and its associated liver fibrosis. The article assesses the underlying role of galectin-3-mediated fibrogenesis, including the triggering of hepatic stellate cells, the regulation of extracellular degradation, and the modulation of immune reactions and responses. It also highlights the assessments of the potential diagnostic and therapeutic implications of galectin-3 in liver fibrosis during MAFLD. Overall, this review provides insights into the multifaceted interaction between galectin-3 and liver fibrosis in MAFLD, which could lead to the development of novel strategies for diagnosis and treatment of this prevalent liver disease.

Insights into the Role of Galectin-3 as a Diagnostic and Prognostic Biomarker of Atrial Fibrillation

Atrial fibrillation (AF) is an irregular atrial activity and the most prevalent type of arrhythmia. Although AF is easily diagnosed with an electrocardiogram, there is a keen interest in identifying an easy-to-dose biomarker that can predict the prognosis of AF and its recurrence. Galectin-3 (Gal-3) is a beta-galactoside binding protein from the lectin family with pro-fibrotic and -inflammatory effects and a pivotal role in a variety of biological processes, cell proliferation, and differentiation; therefore, it is implicated in the pathogenesis of many cardiovascular (e.g., heart failure (HF)) and noncardiovascular diseases. However, its specificity and sensitivity as a potential marker in AF patients remain debated and controversial. This article comprehensively reviewed the evidence regarding the interplay between Gal-3 and patients with AF. Clinical implications of measuring Gal-3 in AF patients for diagnosis and prognosis are mentioned. Moreover, the role of Gal-3 as a potential biomarker for the management of AF recurrence is investigated. The association of Gal-3 and AF in special populations (coronary artery disease, HF, metabolic syndrome, chronic kidney disease, and diabetes mellitus) has been explored in this review. Overall, although further studies are needed to enlighten the role of Gal-3 in the diagnosis and treatment of AF, our study demonstrated the high potential of this molecule to be used and focused on by researchers and clinicians.

Pancreatic Cancer-Secreted Proteins: Targeting Their Functions in Tumor Microenvironment

Pancreatic Ductal Adenocarcinoma (PDAC) is a ravaging disease with a poor prognosis, requiring a more detailed understanding of its biology to foster the development of effective therapies. The unsatisfactory results of treatments targeting cell proliferation and its related mechanisms suggest a shift in focus towards the inflammatory tumor microenvironment (TME). Here, we discuss the role of cancer-secreted proteins in the complex TME tumor-stroma crosstalk, shedding lights on druggable molecular targets for the development of innovative, safer and more efficient therapeutic strategies.

Hepatocyte-specific disruption of soluble epoxide hydrolase attenuates abdominal aortic aneurysm formation: novel role of the liver in aneurysm pathogenesis

Introduction

Inflammation is a key pathogenic feature of abdominal aortic aneurysm (AAA). Soluble epoxide hydrolase (sEH) is a pro-inflammatory enzyme that converts cytochrome P450-derived epoxides of fatty acids to the corresponding diols, and pharmacological inhibition of sEH prevented AAA formation. Both cytochrome P450 enzymes and sEH are highly expressed in the liver. Here, we investigated the role of hepatic sEH in AAA using a selective pharmacological inhibitor of sEH and hepatocyte-specific Ephx2 (which encodes sEH gene) knockout (KO) mice in two models of AAA [angiotensin II (AngII) infusion and calcium chloride (CaCl 2 ) application].

Methods and results

sEH expression and activity were strikingly higher in mouse liver compared with aorta and further increased the context of AAA, in conjunction with elevated expression of the transcription factor Sp1 and the epigenetic regulator Jarid1b, which have been reported to positively regulate sEH expression. Pharmacological sEH inhibition, or liver-specific sEH disruption, achieved by crossing sEH floxed mice with albumin-cre mice, prevented AAA formation in both models, concomitant with reduced expression of hepatic sEH as well as complement factor 3 (C3) and serum amyloid A (SAA), liver-derived factors linked to AAA formation. Moreover, sEH antagonism markedly reduced C3 and SAA protein accumulation in the aortic wall. Co-incubation of liver ex vivo with aneurysm-prone aorta resulted in induction of sEH in the liver, concomitant with upregulation of Sp1, Jarid1b, C3 and SAA gene expression, suggesting that the aneurysm-prone aorta secretes factors that activate sEH and downstream inflammatory signaling in the liver. Using an unbiased proteomic approach, we identified a number of dysregulated proteins [ e.g., plastin-2, galectin-3 (gal-3), cathepsin S] released by aneurysm-prone aorta as potential candidate mediators of hepatic sEH induction.

Conclusion

We provide the first direct evidence of the liver's role in orchestrating AAA via the enzyme sEH. These findings not only provide novel insight into AAA pathogenesis, but they have potentially important implications with regard to developing effective medical therapies for AAA.