Therapeutic opportunities for the treatment of NASH with genetically validated targets

[Risk of metabolic dysfunction-associated fatty liver disease in 44,939 Spanish healthcare workers: associated variables]

OBJECTIVE

To assess the association between sociodemographic variables and lifestyle habits with the risk of metabolic dysfunction-associated fatty liver disease (MASLD) in Spanish healthcare workers.

METHODS

A cross-sectional study including 44,939 healthcare workers. Sociodemographic variables (age, sex, occupation) and lifestyle habits (smoking, physical activity, adherence to the Mediterranean diet) were analyzed in relation to MASLD risk scores (FLI, HSI, LAP, ZJU, and FLD). Multinomial logistic regression models were used to identify significant associations.

RESULTS

Higher risk score values were more prevalent in men and increased with age. Nursing assistants and orderlies had a higher risk compared to physicians. Physical inactivity (OR=2.65; 95% CI: 2.47-2.84) and low adherence to the Mediterranean diet (OR=1.89; 95% CI: 1.69-2.10) were associated with an increased risk of MASLD. Smoking was significantly related to higher risk scores (OR=1.17; 95% CI: 1.13-1.21).

CONCLUSIONS

Age, sex, occupation, smoking, physical activity, and adherence to the Mediterranean diet influence MASLD risk. Preventive strategies should focus on promoting physical activity, improving dietary habits, and reducing smoking among healthcare workers.

Identification of NUV-244 as a PNPLA3 I148M degrading small molecule

The PNPLA3 I148M variant is a key genetic determinant of metabolic dysfunction-associated steatotic liver disease (MASLD) and related conditions, contributing to lipid metabolism dysregulation and disease progression. To identify small molecules that modulate PNPLA3 I148M, we conducted a high-content screen of over 820,000 compounds and identified NUV-244, a potent degrader of PNPLA3 I148M in liver-derived cells. NUV-244 reduces PNPLA3 I148M levels on lipid droplets via the ubiquitin-proteasome system, involving the E3 ligase BFAR, without affecting PNPLA2. It restores lipid droplet morphology and improves cellular fitness in PNPLA3 I148M-expressing cells. These findings provide a tool to investigate PNPLA3 I148M function and offer a potential strategy for developing targeted therapies for MASLD and related diseases. By enabling selective degradation of PNPLA3 I148M, this approach expands therapeutic possibilities beyond genetic manipulation, addressing a critical need in metabolic liver disease research.

Camellia Japonica Radix modulates gut microbiota and 9(S)-HpODE-mediated ferroptosis to alleviate oxidative stress against MASLD

BACKGROUND

Camellia japonica radix (CJR), derived from the root of Camellia japonica L., has the potential to function as an herbal tea substitute for the prevention and intervention of metabolic dysfunction-associated steatotic liver disease (MASLD). It can provide systemic therapeutic benefits, boast a favorable safety profile, facilitate convenient consumption, and support long-term applicability. Despite its potential, research on CJR remains limited.

PURPOSE

The aim of this study aims is to elucidate the therapeutic mechanisms of CJR in MASLD, thereby providing evidence to support its clinical application.

METHODS

The therapeutic effects of CJR were evaluated using a water-supplementation model in MASLD mice. Integrated microbiome, transcriptome, proteome, and metabolome analyses were employed to comprehensively explore the mechanisms involved. A drug-target pull-down assay was performed to identify specific protein targets of small molecule metabolites in vitro. Fecal microbiota transplantation in antibiotic-treated ABX mice was conducted to confirm the critical role of gut microbiota and its metabolites. Furthermore, customized medicated feed supplemented with linoleic acid was used to explore the intervention effect of its metabolite, 9(S)-HpODE, as well as to evaluate its dietary intervention potential.

RESULTS

This present study explicitly elucidates the efficacy of CJR extract in alleviating hepatic inflammation and steatosis in a MASLD model mice, with its pharmacological mechanism associated with gut microbiota, linoleic acid metabolism, and GPX4-mediated ferroptosis. Notably, 9(S)-HpODE was discovered to be a key metabolite of linoleic acid, which could target both KEAP1 and SLC7A11, bidirectionally regulating GPX4-mediated ferroptosis, while acting as a signaling molecule at low doses to induce redox adaptation via oxidative preconditioning, thus ameliorating oxidative stress in MASLD.

CONCLUSION

Our findings indicate that both CJR and linoleic acid exhibit significant potential as dietary interventions for the management of MASLD, offering promising avenues for future research and clinical application.

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 d without any changes in total liver cholesterol content. Treating mice with antisense oligonucleotides against Coenzyme A synthase (Coasy) 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 Coenzyme A synthase knockdown and bempedoic acid are therapeutic approaches to reduce liver lipid droplet cholesterol content and thereby prevent the development of MASH and liver fibrosis.

Global Epidemiology and Implications of PNPLA3 I148M Variant in Metabolic Dysfunction-Associated Steatotic Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

PNPLA3 rs738409 variant is a risk factor for onset and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). We aimed to assess its global prevalence, clinical and histological characteristics, and long-term outcomes in patients with MASLD.

METHODS

PubMed and Embase databases were searched until December 30, 2023, for observational studies on PNPLA3 genotyped adults with MASLD. Proportions were pooled using a generalized linear mixed model with Clopper-Pearson intervals. Continuous and dichotomous variables were analyzed using the DerSimonian-Laird method. International Prospective Register of Systematic Reviews registration number: CRD42023449838.

RESULTS

A total of 109 studies involving 118,302 individuals with MASLD were identified. The overall minor allele frequency of the G allele [MAF(G)] at PNPLA3 was 0.45 (95% confidence interval [CI]: 0.43; 0.48) with high heterogeneity (I2 = 98%). The highest MAF(G) was found in Latin America (0.63) and the lowest in Europe (0.38). No African countries were identified. Carriers of the PNPLA3 variant had reduced adiposity, altered fat metabolism, and worse liver damage/histology than noncarriers. There was significant heterogeneity in the clinical/histological analyses (I2 > 50%). Only the PNPLA3 GG genotype was associated with higher mortality and liver-related events with no heterogeneity (I2 = 0%). Metaregressions showed the influence of adiposity, age, diabetes mellitus, and glucose on some PNPLA3 expression parameters. Overall, there was a moderate risk of bias in the included studies.

CONCLUSIONS

This study reveals the global pattern of PNPLA3 and its clinical, histological, and outcome implications in MASLD. Patients with MASLD and PNPLA3 variant have different clinical features and worse liver severity, and only PNPLA3 GG has a higher risk of mortality and liver outcomes. Our findings highlight the importance of PNPLA3 genotyping in clinical trials and advocate for personalized medicine approaches.

Revisiting the causal impact of lipid traits on metabolic dysfunction-associated fatty liver disease: Insights from a multidimensional plasma lipid profile

AIMS

Recent advancements in plasma lipidomes genome-wide association studies data have enhanced our understanding of lipid categories, significantly improving risk assessments for metabolic dysfunction-associated fatty liver disease (MAFLD) beyond traditional lipid biomarkers.

MATERIALS AND METHODS

This study utilized Mendelian randomization (MR) to assess the causal relationships between 179 lipid species across 13 subclasses and MAFLD, primarily using the Wald ratio and IVW methods. Corrections were made using false discovery rate (FDR), supplemented by Bayesian colocalization analysis.

RESULTS

Elevated levels of genetically predicted phosphatidylcholine (16:0_16:1) [ORWald ratio = 2.638, 95% CI 1.557-4.469, P = 3.11 × 10-4], phosphatidylcholine (16:1_18:0) (ORWald ratio = 2.644, 95% CI 1.559-4.486, P = 3.11 × 10-4), triacylglycerol (46:2) (ORWald ratio = 2.515, 95% CI 1.524-4.153, P = 3.11 × 10-4), and triacylglycerol (48:2) (ORIVW = 1.863, 95% CI 1.300-2.669, P = 6.95 × 10-4) were significantly associated with increased MAFLD risk, with rs1260326 within the GCKR gene playing a crucial role. Colocalization analysis indicated that in significant evidences, the posterior probability for hypothesis 4 was over 80%, identifying rs780093 as a shared causal variant. Additionally, 16 suggestive evidences were identified.

CONCLUSION

The study confirmed the significant role of specific lipid molecules in influencing MAFLD risk, providing new scientific bases and potential therapeutic targets for future treatment strategies.

PNPLA3(148M) is a gain-of-function mutation that promotes hepatic steatosis by inhibiting ATGL-mediated triglyceride hydrolysis

BACKGROUND & AIMS

PNPLA3(148M) (patatin-like phospholipase domain-containing protein 3) is the most impactful genetic risk factor for steatotic liver disease. A key unresolved issue is whether PNPLA3(148M) confers a loss- or gain-of-function. Here we test the hypothesis that PNPLA3 causes steatosis by sequestering ABHD5 (α/β hydrolase domain-containing protein 5), the cofactor of ATGL (adipose TG lipase), thus limiting mobilization of hepatic triglyceride (TG).

METHODS

We quantified and compared the physical interactions between ABHD5 and PNPLA3/ATGL in cultured hepatocytes using NanoBiT complementation assays and immunocytochemistry. Recombinant proteins purified from human cells were used to compare TG hydrolytic activities of PNPLA3 and ATGL in the presence or absence of ABHD5. Adenoviruses and adeno-associated viruses were used to express PNPLA3 in liver-specific Atgl-/- mice and to express ABHD5 in livers of Pnpla3M/M mice, respectively.

RESULTS

ABHD5 interacted preferentially with PNPLA3 relative to ATGL in cultured hepatocytes. No differences were seen in the strength of the interactions between ABHD5 with PNPLA3(WT) and PNPLA3(148M). In contrast to prior findings, we found that PNPLA3, like ATGL, is activated by ABHD5 in in vitro assays using purified proteins. PNPLA3(148M)-associated inhibition of TG hydrolysis required that ATGL be expressed and that PNPLA3 be located on lipid droplets. Finally, overexpression of ABHD5 reversed the hepatic steatosis in Pnpla3M/M mice.

CONCLUSIONS

These findings support the premise that PNPLA3(148M) is a gain-of-function mutation that promotes hepatic steatosis by accumulating on lipid droplets and inhibiting ATGL-mediated lipolysis in an ABHD5-dependent manner. Our results predict that reducing, rather than increasing, PNPLA3 expression will be the best strategy to treat PNPLA3(148M)-associated steatotic liver disease.

IMPACT AND IMPLICATIONS

Steatotic liver disease (SLD) is a common complex disorder associated with both environmental and genetic risk factors. PNPLA3(148M) is the most impactful genetic risk factor for SLD and yet its pathogenic mechanism remains controversial. Herein, we provide evidence that PNPLA3(148M) promotes triglyceride (TG) accumulation by sequestering ABHD5, thus limiting its availability to activate ATGL. Although the substitution of methionine for isoleucine reduces the TG hydrolase activity of PNPLA3, the loss of enzymatic function is not directly related to the steatotic effect of the variant. It is the resulting accumulation of PNPLA3 on LDs that confers a gain-of-function by interfering with ATGL-mediated TG hydrolysis. These findings have implications for the design of potential PNPLA3(148M)-based therapies. Reducing, rather than increasing, PNPLA3 levels is predicted to reverse steatosis in susceptible individuals.

Targeting PNPLA3 to Treat MASH and MASH Related Fibrosis and Cirrhosis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by metabolic triggers and genetic predisposition. Among the genetic MASLD risk variants identified today, the common PNPLA3 148M variant exerts the largest effect size of MASLD heritability. The PNPLA3 148M protein is causatively linked to the development of liver steatosis, inflammation and fibrosis in experimental studies and is therefore an appealing target for therapeutic approaches to treat this disease. Several PNPLA3 targeted approaches are currently being evaluated in clinical trials for the treatment of metabolic dysfunction-associated steatohepatitis (MASH), the most severe form of MASLD and promising proof of principle data with reduced liver fat content in homozygous PNPLA3 148M risk allele carriers has been reported from phase 1 trials following hepatic silencing of PNPLA3. Thus, targeting PNPLA3, the strongest genetic determinant of MASH may hold promise as the first precision medicine for the treatment of this disease. A histological endpoint-based phase 2b study has been initiated and several more are expected to be initiated to evaluate treatment effects on histological MASH and liver fibrosis in participants being homozygous for the PNPLA3 148M risk allele variant. The scope of this mini-review is to briefly describe the PNPLA3 148M genetics, function and preclinical experimental evidence with therapeutic approaches targeting PNPLA3 as well as to summarise the PNPLA3 based therapies currently in clinical development.

Liver-specific inactivation of Cideb improves metabolic profiles and ameliorates steatohepatitis and fibrosis in animal models for MASH

Germline mutations of CIDEB, a lipid droplets (LDs)-associated protein, confer protection against various liver diseases in humans. It remains to be determined whether liver-specific inhibition of CIDEB will bring clinical benefits. We aim to establish pharmacological proof of concept by testing GalNAc-conjugated Cideb surrogate siRNAs in respective animal models of obesity and MASH and to develop siRNA drug candidates for clinical investigations. Surrogate siRNAs targeting mouse Cideb were designed and evaluated via a panel of assays. Concurrently, humanized CIDEB knock-in mice were generated as a research tool to facilitate human therapeutic siRNA discovery. In vivo administration of the surrogate siRNAs was conducted in the diet-induced obesity (DIO) model and CDAA-HFD model of MASH. In the DIO model, Cideb knockdown led to significant reductions of serum total cholesterol (TC) and triglyceride (TG) levels, a significant decrease in hepatic macro-steatosis and notable weight loss. In the CDAA-HFD model, Cideb siRNA treatment significantly reduced liver TC and TG levels. Furthermore, remarkable reductions of hepatic steatosis and the composite NAS score were observed with a concomitant amelioration of liver fibrosis. Transcriptome analyses revealed that integrin pathways may contribute to the major pharmacological activities upon Cideb inactivation beyond lipid metabolism. CIDEB exhibits significant potential as a therapeutic target for the treatment of MASH. Liver-targeting siRNA candidates are under development for therapeutic hypothesis testing in humans.

Genetic Evidence for GLP-1 and GIP Receptors as Targets for Treatment and Prevention of MASLD/MASH

BACKGROUND AND AIMS

Glucagon-like peptide-1 receptor (GLP1R) agonists and glucose-dependent insulinotropic polypeptide receptor (GIPR) agonists may help treat metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). However, their definitive effects are still unclear. Our study aims to clarify this uncertainty.

METHODS

We utilised conventional Mendelian randomisation (MR) analysis to explore potential causal links between plasma GLP-1/GIP concentrations and MASLD and its related traits. Next, we conducted drug-target MR analysis using highly expressed tissue data to assess the effects of corresponding drug perturbation on these traits. Finally, mediation analysis was performed to ascertain whether the potential causal effect is direct or mediated by other MASLD-related traits.

RESULTS

Circulating 2-h GLP-1 and GIP concentrations measured during an oral glucose tolerance test showed hepatoprotective effects on MASLD risk (ORGLP-1 = 0.168 [95% CI 0.033-0.839], p = 0.030; ORGIP = 0.331 [95% CI 0.222-0.494], p = 6.31 × 10-8). GLP1R expression in the blood had a minimal causal effect on MASLD risk, whereas GIPR expression significantly affected MASLD risk (OR = 0.671 [95% CI 0.531-0.849], p = 9.07 × 10-4). Expression levels of GLP1R or GIPR in the blood significantly influenced MASLD-related clinical traits. Mediation analysis revealed that GIPR expression protected against MASLD, even after adjusting for type 2 diabetes or body mass index.

CONCLUSIONS

GLP-1/GIP receptor agonists offer promise in lowering MASLD/MASH risk. GIP receptor agonists can exert direct and indirect effects on MASLD mediated by weight reduction or glycemic control improvement.

Fibrosis: cross-organ biology and pathways to development of innovative drugs

Fibrosis is a pathophysiological mechanism involved in chronic and progressive diseases that results in excessive tissue scarring. Diseases associated with fibrosis include metabolic dysfunction-associated steatohepatitis (MASH), inflammatory bowel diseases (IBDs), chronic kidney disease (CKD), idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc), which are collectively responsible for substantial morbidity and mortality. Although a few drugs with direct antifibrotic activity are approved for pulmonary fibrosis and considerable progress has been made in the understanding of mechanisms of fibrosis, translation of this knowledge into effective therapies continues to be limited and challenging. With the aim of assisting developers of novel antifibrotic drugs, this Review integrates viewpoints of biologists and physician-scientists on core pathways involved in fibrosis across organs, as well as on specific characteristics and approaches to assess therapeutic interventions for fibrotic diseases of the lung, gut, kidney, skin and liver. This discussion is used as a basis to propose strategies to improve the translation of potential antifibrotic therapies.

A Comprehensive Review of Metabolic Dysfunction-Associated Steatotic Liver Disease: Its Mechanistic Development Focusing on Methylglyoxal and Counterbalancing Treatment Strategies

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a multifactorial disorder characterized by excessive lipid accumulation in the liver which dysregulates the organ's function. The key contributor to MASLD development is insulin resistance (IR) which affects many organs (including adipose tissue, skeletal muscles, and the liver), whereas the molecular background is associated with oxidative, nitrosative, and carbonyl stress. Among molecules responsible for carbonyl stress effects, methylglyoxal (MGO) seems to play a major pathological function. MGO-a by-product of glycolysis, fructolysis, and lipolysis (from glycerol and fatty acids-derived ketone bodies)-is implicated in hyperglycemia, hyperlipidemia, obesity, type 2 diabetes, hypertension, and cardiovascular diseases. Its causative effect in the stimulation of prooxidative and proinflammatory pathways has been well documented. Since metabolic dysregulation leading to these pathologies promotes MASLD, the role of MGO in MASLD is addressed in this review. Potential MGO participation in the mechanism of MASLD development is discussed in regard to its role in different signaling routes leading to pathological events accelerating the disorder. Moreover, treatment strategies including approved and potential therapies in MASLD are overviewed and discussed in this review. Among them, medications aimed at attenuating MGO-induced pathological processes are addressed.

Therapeutic landscape of metabolic dysfunction-associated steatohepatitis (MASH)

Metabolic dysfunction-associated steatotic liver disease (MASLD) and its severe subgroup metabolic dysfunction-associated steatohepatitis (MASH) have become a global epidemic and are driven by chronic overnutrition and multiple genetic susceptibility factors. The physiological outcomes include hepatocyte death, liver inflammation and cirrhosis. The first therapeutic for MASLD and MASH, resmetirom, has recently been approved for clinical use and has energized this therapeutic space. However, there is still much to learn in clinical studies of MASH, such as the scale of placebo responses, optimal trial end points, the time required for fibrosis reversal and side effect profiles. This Review introduces aspects of disease pathogenesis related to drug development and discusses two main therapeutic approaches. Thyroid hormone receptor-β agonists, such as resmetirom, as well as fatty acid synthase inhibitors, target the liver and enable it to function within a toxic metabolic environment. In parallel, incretin analogues such as semaglutide improve metabolism, allowing the liver to self-regulate and reversing many aspects of MASH. We also discuss how combinations of therapeutics could potentially be used to treat patients.

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.

Precision medicine and nucleotide-based therapeutics to treat steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a complex multifactorial disease and becoming the leading cause of liver-related morbidity and mortality. MASLD spans from isolated steatosis to metabolic dysfunction-associated steatohepatitis (MASH), that may progress to cirrhosis and hepatocellular carcinoma (HCC). Genetic, metabolic, and environmental factors strongly contribute to the heterogeneity of MASLD. Lifestyle intervention and weight loss represent a viable treatment for MASLD. Moreover, Resmetirom, a thyroid hormone beta receptor agonist, has recently been approved for MASLD treatment. However, most individuals treated did not respond to this therapeutic, suggesting the need for a more tailored approach to treat MASLD. Oligonucleotide-based therapies, namely small-interfering RNA (siRNA) and antisense oligonucleotide (ASO), have been recently developed to tackle MASLD by reducing the expression of genes influencing MASH progression, such as PNPLA3 and HSD17B13. Here, we review the latest progress made in the synthesis and development of oligonucleotide-based agents targeting genetic determinants of MASH.

FLAME: Training and Validating a Newly Conceived Model Incorporating Alpha-Glutathione-S-Transferase Serum Levels for Predicting Advanced Hepatic Fibrosis and Acute Cardiovascular Events in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Alpha-Glutathione-S-transferase (alphaGST) is a liver enzyme whose serum levels increase with the worsening of fibrosis in alcoholic and viral chronic hepatitis. Its usefulness in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) remains unexplored. From January 2016 to December 2017, 200 patients with MASLD and 30 controls were enrolled. AlphaGST serum levels were measured. Variables related to advanced fibrosis (AF) were selected via Principal Component Analysis (PCA), and the best cut-off (BCO) was estimated using ROC analysis. Liver stiffness measurement (LSM), NAFLD fibrosis (NFS), Fibrosis-4 (FIB-4), and BMI-AST/ALT Ratio-Diabetes (BARD) scores were determined. The first acute cardiovascular events (ACE) in ACE-naïve subjects were recorded over five years. A validation cohort of 60 MASLD patients was enrolled from January 2018 to May 2019 and followed for five years. AlphaGST levels increased with fibrosis stage (p < 0.0001) in both cohorts, showing high accuracy in predicting AF (TrC: AUC 0.89, VlC: AUC 0.89). PCA-selected variables were HbA1c, HDL, and alphaGST, forming the "FLAME" model. FLAME showed superior predictive performance for AF and ACEs compared to other models and scores. FLAME represents a novel tool that accurately predicts AF and ACEs in MASLD.

Genetic Risk Factors for Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD), is the most common cause of liver disease, and its burden on health systems worldwide continues to rise at an alarming rate. MASLD is a complex disease in which the interactions between susceptible genes and the environment influence the disease phenotype and severity. Advances in human genetics over the past few decades have provided new opportunities to improve our understanding of the multiple pathways involved in the pathogenesis of MASLD. Notably, the PNPLA3, TM6SF2, GCKR, MBOAT7 and HSD17B13 single nucleotide polymorphisms have been demonstrated to be robustly associated with MASLD development and disease progression. These genetic variants play crucial roles in lipid droplet remodeling, secretion of hepatic very low-density lipoprotein and lipogenesis, and understanding the biology has brought new insights to this field. This review discusses the current body of knowledge regarding these genetic drivers and how they can lead to development of MASLD, the complex interplay with metabolic factors such as obesity, and how this information has translated clinically into the development of risk prediction models and possible treatment targets.

AZD2693, a PNPLA3 antisense oligonucleotide, for the treatment of MASH in 148M homozygous participants: Two randomized phase I trials

BACKGROUND & AIMS

A common genetic variant (rs738409) encoding an isoleucine to methionine substitution at position 148 in the PNPLA3 protein is a determinant of hepatic steatosis, inflammation, fibrosis, cirrhosis, and liver-related mortality. AZD2693 is a liver-targeted antisense oligonucleotide against PNPLA3 mRNA. We evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics in single and multiple ascending dose studies.

METHODS

AZD2693 was assessed in 3D cultures of homozygous PNPLA3 148M primary human hepatocytes and mice expressing human PNPLA3. The single ascending dose study investigated 2-110 mg doses in overweight/mildly obese but otherwise healthy volunteers. The multiple ascending dose study investigated three monthly doses (25 mg, 50 mg and 80 mg) in participants with MRI-proton density fat fraction (MRI-PDFF) ≥7%. Changes in liver fat content were assessed at baseline, weeks 8 and 12 by MRI-PDFF. PNPLA3 mRNA and protein knockdown levels were evaluated for the 80 mg dose.

RESULTS

AZD2693 potently reduced PNPLA3 expression in human hepatocytes and livers of mice. Clinically, AZD2693 was generally well tolerated (no adverse events leading to discontinuation or treatment-related serious adverse events). Half-life was 14-33 days across investigated doses. A least-square mean liver PNPLA3 mRNA knockdown of 89% and reduction of protein levels demonstrated target engagement. Changes in hepatic steatosis at week 12 were -7.6% and -12.2% (placebo-corrected least-square means) for the 25 mg and 50 mg doses, respectively. There was a dose-dependent increase of polyunsaturated fatty acids in serum triglycerides and decreases vs. placebo in high-sensitivity C-reactive protein and interleukin 6.

CONCLUSIONS

AZD2693 reduced liver PNPLA3 with an acceptable safety and tolerability profile. These findings support the continued development of AZD2693.

IMPACT AND IMPLICATIONS

Clinical treatment options for metabolic dysfunction-associated steatohepatitis (MASH) are limited. The genetic risk factor with the largest effect size for progressing to poor liver-related outcomes in MASH is a single-nucleotide polymorphism in the gene PNPLA3 (p.I148M). In phase I single and multiple ascending dose studies, AZD2693, a liver-targeted antisense oligonucleotide, was well tolerated, reduced liver PNPLA3 mRNA and protein levels, and dose-dependently reduced liver fat content in homozygous PNPLA3 148M risk allele carriers. These data support continued development of AZD2693 as a potential precision medicine treatment for MASH. The phase IIb FORTUNA study is now ongoing.

CLINICAL TRIAL NUMBER

NCT04142424, NCT04483947.

Statin-associated regulation of hepatic PNPLA3 in patients without known liver disease

BACKGROUND AND OBJECTIVES

Statins are used for metabolic dysfunction-associated steatotic liver disease (MASLD) (NAFLD) treatment, but their role in this context is unclear. Genetic variants of patatin-like phospholipase domain containing 3 (PNPLA3) are associated with MASLD susceptibility and statin treatment efficacy. Access to liver biopsies before established MASLD is limited, and statins and PNPLA3 in early liver steatosis are thus difficult to study.

METHODS

Liver biopsies were collected from 261 patients without known liver disease at surgery and stratified based on statin use and criteria for the metabolic syndrome (MS). Genotypes and transcript levels were measured using Illumina and Affymetrix arrays, and metabolic and lipoprotein profiles by clinical assays. Statin effects on PNPLA3, de novo lipogenesis (DNL), and lipid accumulation were further studied in vitro.

RESULTS

The PNPLA3I148M genetic variant was associated with significantly lower hepatic levels of cholesterol synthesis-associated transcripts. Patients with MS had significantly higher hepatic levels of MASLD and lipogenesis-associated transcripts than non-MS patients. Patients with MS on statin therapy had significantly higher hepatic levels of PNPLA3, acetyl-CoA carboxylase alpha, and ATP citrate lyase, and statin use was associated with higher plasma fasting glucose, insulin, and HbA1c. Exposure of hepatocyte-like HepG2 cells to atorvastatin promoted intracellular accumulation of triglycerides and lipogenesis-associated transcripts. Atorvastatin-exposure of HepG2, sterol O-acyltransferase (SOAT) 2-only-HepG2, primary human hepatic stellate, and hepatic stellate cell-like LX2 cells significantly increased levels of PNPLA3 and SREBF2-target genes, whereas knockdown of SREBF2 attenuated this effect.

CONCLUSIONS

Collectively, these observations suggest statin-associated regulation of PNPLA3 and DNL in liver. The potential interaction between PNPLA3 genotype and metabolic status should be considered in future studies in the context of statin therapy for MASLD.

Lipotoxicity-driven metabolic dysfunction-associated steatotic liver disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a spectrum of liver lesions, ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), that may further progress to cirrhosis. MASLD is estimated to affect more than one third of the general population and it represents a risk factor for end-stage liver failure and liver cancer, substantially contributing to liver-related morbidity and mortality. Although the pathogenesis of MASLD is incompletely understood, it is known to consist of a multifactorial process influenced by extrinsic and intrinsic factors such as metabolic, environmental and demographic features, gut microbiota and genetics. Dysregulation of both extracellular and intracellular lipid composition is known to promote the generation of toxic lipid species, thereby triggering lipotoxicity and cellular stress. These events ultimately lead to the activation of distinct cell death pathways, resulting in inflammation, fibrogenesis and, eventually, carcinogenesis. In this manuscript, we provide a comprehensive review of the role of lipotoxicity during MASLD pathogenesis, discussing the most relevant lipid species and related molecular mechanisms, summarizing the cell type-specific effects and highlighting the most promising putative therapeutic strategies for modulating lipotoxicity and lipid metabolism in MASLD.

PNPLA3 in Alcohol-Related Liver Disease

The discovery of PNPLA3 as a genetic risk factor for liver disease has transformed our understanding of the pathogenesis of alcohol-related liver disease (ALD). The recent reclassification of fatty liver disease as steatotic liver disease (SLD), introducing metabolic dysfunction and alcohol-related liver disease (MetALD), has highlighted how genetic and environmental factors synergistically drive liver damage. The PNPLA3 rs738409 variant stands as a paradigmatic example of gene-environment interaction, where its effect on liver disease is dramatically amplified by alcohol consumption, obesity and type 2 diabetes. Understanding these interactions has revealed novel pathogenic mechanisms. The robust genetic evidence and a growing understanding of molecular mechanisms have made PNPLA3 an attractive therapeutic target. Several compounds targeting PNPLA3 are now in clinical development. While initial trials have focused on metabolic dysfunction-associated SLD, the recognition that almost all individuals with excessive alcohol consumption have metabolic comorbidities provides an unprecedented opportunity to evaluate these genetically informed therapies in MetALD. In this review, we examine the role of PNPLA3 in ALD, focusing on gene-environment interactions and therapeutic implications in the context of the new disease classification framework.

Rab2A-mediated Golgi-lipid droplet interactions support very-low-density lipoprotein secretion in hepatocytes

Lipid droplets (LDs) serve as crucial hubs for lipid trafficking and metabolic regulation through their numerous interactions with various organelles. While the interplay between LDs and the Golgi apparatus has been recognized, their roles and underlying mechanisms remain poorly understood. Here, we reveal the role of Ras-related protein Rab-2A (Rab2A) in mediating LD-Golgi interactions, thereby contributing to very-low-density lipoprotein (VLDL) lipidation and secretion in hepatocytes. Mechanistically, our findings identify a selective interaction between Golgi-localized Rab2A and 17-beta-hydroxysteroid dehydrogenase 13 (HSD17B13) protein residing on LDs. This complex facilitates dynamic organelle communication between the Golgi apparatus and LDs, thus contributing to lipid transfer from LDs to the Golgi apparatus for VLDL2 lipidation and secretion. Attenuation of Rab2A activity via AMP-activated protein kinase (AMPK) suppresses the Rab2A-HSD17B13 complex formation, impairing LD-Golgi interactions and subsequent VLDL secretion. Furthermore, genetic inhibition of Rab2A and HSD17B13 in the liver reduces the serum triglyceride and cholesterol levels. Collectively, this study provides a new perspective on the interactions between the Golgi apparatus and LDs.

Establishing the capacity to monitor proteins relevant to the study of drug exposure and response using liver-derived extracellular vesicles

AIMS

Drug exposure and response is determined by pharmacokinetic (PK) and pharmacodynamic (PD) profiles. Interindividual differences in abundance of drug metabolizing enzymes (DMEs) and drug target proteins underpin PK and PD variability and impact treatment efficacy and tolerability. Extracellular vesicles (EVs) carry protein cargo inherited from originating cells and may be useful for defining differences in key proteins related to hepatic drug metabolism and the treatment of metabolic-associated fatty liver disease (MAFLD). We sought to quantify these proteins in liver-derived EVs and establish the profile relative to paired tissue.

METHODS

EVs were recovered from human liver tissue samples (LT-EV, n = 11). Targeted liquid chromatography with tandem mass spectrometry (LC-MS/MS) assays were employed for absolute quantification of proteins in EV isolates and matched liver tissue.

RESULTS

DMEs and MAFLD drug targets were readily detected and quantified in LT-EVs. Twelve of 15 DMEs exhibited moderate to strong correlation (Spearman ⍴ = 0.618-0.973) between tissue and EVs. Correlation in protein abundance was influenced by the extent of extra-hepatic expression of the target.

CONCLUSIONS

This study provides evidence that key proteins related to PK and PD profiles can be measured in liver-derived EVs and abundance of liver-enriched DMEs are robustly correlated between paired tissue and EVs. The robust detection of protein markers related to drug PD profile in MAFLD opens the possibility to track within-subject changes in MAFLD and lays the foundation for future development of a liver-derived EV liquid biopsy to assess markers of drug exposure and response in vivo.

Design, synthesis and FXR partial agonistic activity of anthranilic acid derivatives bearing aryloxy moiety as therapeutic agents for metabolic dysfunction-associated steatohepatitis

Farnesoid X receptor (FXR) is considered a promising therapeutic target for the treatment of metabolic dysfunction-associated steatohepatitis (MASH). Increasing evidence suggests that targeting FXR with full agonists may lead to side effects. FXR partial agonists, which moderately activate FXR signaling, are emerging as a feasible approach to mitigate side effects and address MASH. Herein, a series of novel anthranilic acid derivatives bearing aryloxy moiety were designed and synthesized using a hybrid strategy from the previously identified FXR partial agonists DM175 and AIV-25. Particularly, compound 26 exhibited potent FXR partial agonistic activity in a dual-luciferase reporter gene assay with an EC50 value of 0.09 ± 0.02 µM (75.13 % maximum efficacy relative to OCA). In the MASH mice model, compound 26 significantly ameliorated the pathological features of the liver, including steatosis, inflammation, and fibrosis. In addition, compound 26 displayed high selectivity, good oral bioavailability, high liver distribution, as well as an acceptable safety profile. Molecular simulation studies showed that compound 26 fitted well with the binding site of FXR. Collectively, these findings demonstrated that compound 26 might serve as a promising candidate targeting FXR for MASH treatment.

Genetics of Metabolic Dysfunction-associated Steatotic Liver Disease: The State of the Art Update

Recent advances in the genetics of metabolic dysfunction-associated steatotic liver disease (MASLD) are gradually revealing the mechanisms underlying the heterogeneity of the disease and have shown promising results in patient stratification. Genetic characterization of the disease has been rapidly developed using genome-wide association studies, exome-wide association studies, phenome-wide association studies, and whole exome sequencing. These advances have been powered by the increase in computational power, the development of new analytical algorithms, including some based on artificial intelligence, and the recruitment of large and well-phenotyped cohorts. This review presents an update on genetic studies that emphasize new biological insights from next-generation sequencing approaches. Additionally, we discuss innovative methods for discovering new genetic loci for MASLD, including rare variants. To comprehensively manage MASLD, it is important to stratify risks. Therefore, we present an update on phenome-wide association study associations, including extreme phenotypes. Additionally, we discuss whether polygenic risk scores and targeted sequencing are ready for clinical use. With particular focus on precision medicine, we introduce concepts such as the interplay between genetics and the environment in modulating genetic risk with lifestyle or standard therapies. A special chapter is dedicated to gene-based therapeutics. The limitations of approved pharmacological approaches are discussed, and the potential of gene-related mechanisms in therapeutic development is reviewed, including the decision to perform genetic testing in patients with MASLD.

GSDME promotes MASLD by regulating pyroptosis, Drp1 citrullination-dependent mitochondrial dynamic, and energy balance in intestine and liver

Dysregulated metabolism, cell death, and inflammation contribute to the development of metabolic dysfunction-associated steatohepatitis (MASH). Pyroptosis, a recently identified form of programmed cell death, is closely linked to inflammation. However, the precise role of pyroptosis, particularly gasdermin-E (GSDME), in MASH development remains unknown. In this study, we observed GSDME cleavage and GSDME-associated interleukin-1β (IL-1β)/IL-18 induction in liver tissues of MASH patients and MASH mouse models induced by a choline-deficient high-fat diet (CDHFD) or a high-fat/high-cholesterol diet (HFHC). Compared with wild-type mice, global GSDME knockout mice exhibited reduced liver steatosis, steatohepatitis, fibrosis, endoplasmic reticulum stress, lipotoxicity and mitochondrial dysfunction in CDHFD- or HFHC-induced MASH models. Moreover, GSDME knockout resulted in increased energy expenditure, inhibited intestinal nutrient absorption, and reduced body weight. In the mice with GSDME deficiency, reintroduction of GSDME in myeloid cells-rather than hepatocytes-mimicked the MASH pathologies and metabolic dysfunctions, as well as the changes in the formation of neutrophil extracellular traps and hepatic macrophage/monocyte subclusters. These subclusters included shifts in Tim4+ or CD163+ resident Kupffer cells, Ly6Chi pro-inflammatory monocytes, and Ly6CloCCR2loCX3CR1hi patrolling monocytes. Integrated analyses of RNA sequencing and quantitative proteomics revealed a significant GSDME-dependent reduction in citrullination at the arginine-114 (R114) site of dynamin-related protein 1 (Drp1) during MASH. Mutation of Drp1 at R114 reduced its stability, impaired its ability to redistribute to mitochondria and regulate mitophagy, and ultimately promoted its degradation under MASH stress. GSDME deficiency reversed the de-citrullination of Drp1R114, preserved Drp1 stability, and enhanced mitochondrial function. Our study highlights the role of GSDME in promoting MASH through regulating pyroptosis, Drp1 citrullination-dependent mitochondrial function, and energy balance in the intestine and liver, and suggests that GSDME may be a potential therapeutic target for managing MASH.

GCKIII kinases control hepatocellular lipid homeostasis via shared mode of action

Metabolic dysfunction-associated steatotic liver disease has emerged as a leading global cause of chronic liver disease. Our recent translational investigations have shown that the STE20-type kinases comprising the GCKIII subfamily-MST3, STK25, and MST4-associate with hepatic lipid droplets and regulate ectopic fat storage in the liver; however, the mode of action of these proteins remains to be resolved. By comparing different combinations of the silencing of MST3, STK25, and/or MST4 in immortalized human hepatocytes, we found that their single knockdown results in a similar reduction in hepatocellular lipid content and metabolic stress, without any additive or synergistic effects observed when all three kinases are simultaneously depleted. A genome-wide yeast two-hybrid screen of the human hepatocyte library identified several interaction partners contributing to the GCKIII-mediated regulation of liver lipid homeostasis, that is, PDCD10 that protects MST3, STK25, and MST4 from degradation, MAP4K4 that regulates their activity via phosphorylation, and HSD17B11 that controls their action via a conformational change. Finally, using in vitro kinase assays on microfluidic microarrays, we pinpointed various downstream targets that are phosphorylated by the GCKIII kinases, with known functions in lipogenesis, lipolysis, and lipid secretion, as well as glucose uptake, glycolysis, hexosamine synthesis, and ubiquitination. Together, this study demonstrates that the members of the GCKIII kinase subfamily regulate hepatocyte lipid metabolism via common pathways. The results shed new light on the role of MST3, STK25, and MST4, as well as their interactions with PDCD10, MAP4K4, and HSD17B11, in the control of liver lipid homeostasis and metabolic dysfunction-associated steatotic liver disease susceptibility.

Mechanisms coupling lipid droplets to MASLD pathophysiology

Hepatic steatosis, the buildup of neutral lipids in lipid droplets (LDs), is commonly referred to as metabolic dysfunction-associated steatotic liver disease when alcohol or viral infections are not involved. Metabolic dysfunction-associated steatotic liver disease encompasses simple steatosis and the more severe metabolic dysfunction-associated steatohepatitis, characterized by inflammation, hepatocyte injury, and fibrosis. Previously viewed as inert markers of disease, LDs are now understood to play active roles in disease etiology and have significant nonpathological and pathological functions in cell signaling and function. These dynamic properties of LDs are tightly regulated by hundreds of proteins that coat the LD surface, controlling lipid metabolism, trafficking, and signaling. The following review highlights various facets of LD biology with the primary goal of discussing key mechanisms through which LDs promote the development of advanced liver diseases, including metabolic dysfunction-associated steatohepatitis.

TM6SF2 -rs58542926 Genotype Has Opposing Effects on Incidence of Hepatic and Cardiac Events in a Community Cohort

INTRODUCTION

TM6SF2 -rs58542926-T is associated with increased cirrhosis and modestly decreased coronary artery disease prevalence. However, relative effects of TM6SF2 genotype on major adverse cardiovascular events (MACE) vs liver-related events (LRE) are not known.

METHODS

We used the UK Biobank, a prospective cohort with genetic and inpatient diagnosis data. The primary predictor was TM6SF2 -rs58542926 genotype, and the primary outcomes were MACE and LRE. Effects were reported as subhazard ratios (sHRs) and 10-year cumulative incidence by Fine-Gray competing risk analyses.

RESULTS

More than 430,000 individuals met inclusion criteria. TM6SF2 -rs58542926-TT genotype (vs CC) was associated with higher incidence of LRE (adjusted sHR 3.16, 95% confidence interval 1.86-5.37) and lower incidence of MACE (adjusted sHR for TT vs CC genotype 0.76, 95% confidence interval 0.63-0.91). In individuals with fibrosis-4 (FIB4) < 1.3, 1.3-2.67, and > 2.67, 10-year LRE incidence in TM6SF2 -rs58542926-TT vs CC individuals was 0.08% vs 0.06% ( P > 0.05), 0.81% vs 0.20% ( P < 0.0001), and 10.5% vs 3.4% ( P = 0.00094), respectively. The corresponding values for MACE were 3.8% vs 5.1% ( P = 0.032), 6.4% vs 8.2% ( P = 0.040), and 17.1% vs 12.4% ( P > 0.05). The absolute decrease in MACE with rs58542926-TT (vs CC) genotype exceeded the absolute increase in LRE in all groups but FIB4 > 2.67. Associations of TM6SF2 genotype with LRE/MACE were significant in men but not women. TM6SF2 -rs58542926-T allele was also associated with increased hepatic steatosis and corrected T1 time by magnetic resonance imaging, with greater effect sizes in men than women.

DISCUSSION

TM6SF2 genotype has opposite effects on LRE vs MACE incidence, and absolute effects on MACE were greater except in those with highest FIB4 scores. Effects were strongest in men. These findings clarify implications of TM6SF2 genotype based on personalized clinical risk.

Interaction Between PNPLA3 and SIRT5 Genetic Variants in Association with Liver Fibrosis Severity in Patients with Metabolic Dysfunction-Associated Steatotic Liver Disease

BACKGROUND/OBJECTIVES

This study evaluated the association between polymorphisms in the PNPLA3, TM6SF2, HSD17B13, and SIRT5 genes and the severity of fibrosis and steatosis in metabolic dysfunction-associated steatotic liver disease (MASLD).

METHODS

Fibrosis and steatosis were assessed by MRE and MRI-PDFF, respectively. The polymorphisms were determined by allelic discrimination in blood samples.

RESULTS

204 patients aged 57.0 ± 13.5 years were included. Sixty-two (30.4%) patients had significant fibrosis (≥F2). Among F2-F4 fibrosis, the PNPLA3 rs738409 GG genotype was significantly higher than the CC + CG genotypes (44.9% vs. 21.4%, p = 0.001). The SIRT5 rs12216101 GG vs. TT + TG genotypes also exhibited a similar trend (64.3% vs. 27.9%, p = 0.012). In multivariate analysis, the PNPLA3 GG genotype (OR = 3.48, 95%CI: 1.50-8.06; p = 0.004) and SIRT5 rs12216101 GG genotype (OR = 5.43, 95%CI: 1.32-22.33; p = 0.019) were independently associated with F2-F4 fibrosis. Additionally, the proportion of patients with F2-F4 fibrosis significantly increased with the number of combined risk genotypes. Among S2-S3 steatosis, the prevalence of HSD17B13 AG + GG genotypes was higher than that of the AA genotype (37.5% vs. 23.9%, p = 0.048) and independently associated with moderate/severe steatosis in multivariate analysis (OR = 2.26, 95%CI: 1.14-4.49; p = 0.020).

CONCLUSIONS

Our data indicate that the PNPLA3 and SIRT5 polymorphisms were independently and additively linked to significant fibrosis, while the HSD17B13 polymorphism was associated with increased steatosis in Thai populations. These data might emphasize the importance of genetic variants in progressive MASLD.

mARC1 Is the Main Contributor to Metabolic Reduction of N-Hydroxyurea

N-Hydroxyurea has been known since the 1960s as an antiproliferative drug and is used both in oncology and for treatment of hematological disorders such as sickle cell anemia where very high daily doses are administered. It is assumed that the cellular effect of N-hydroxyurea is caused by inhibition of ribonucleotide reductase, while alternative mechanisms, e.g., generation of nitric oxide, have also been proposed. Despite its many therapeutic applications, the metabolism of hydroxyurea is largely unexplored. The major elimination pathway of N-hydroxyurea is the reduction to urea. Since the mitochondrial amidoxime reducing component (mARC) is known for its N-reductive activity, we investigated the reduction of NHU by this enzyme system. This study presents in vitro and in vivo evidence that this reductive biotransformation is specifically mediated by the mARC1. Inactivation by mARC1 is a possible explanation for the high doses of NHU required for treatment.

A suite of genome-engineered hepatic cells provides novel insights into the spatiotemporal metabolism of apolipoprotein B and apolipoprotein B-containing lipoprotein secretion

AIMS

Apolipoprotein B (APOB)-containing very LDL (VLDL) production, secretion, and clearance by hepatocytes is a central determinant of hepatic and circulating lipid levels. Impairment of any of the aforementioned processes is associated with the development of multiple diseases. Despite the discovery of genes and processes that govern hepatic VLDL metabolism, our understanding of the different mechanistic steps involved is far from complete. An impediment to these studies is the lack of tractable hepatocyte-based systems to interrogate and follow APOB in cells, which the current study addresses.

METHODS AND RESULTS

To facilitate the cellular study of VLDL metabolism, we generated human hepatic HepG2 and Huh-7 cell lines in which CRISPR/Cas9-based genome engineering was used to introduce the fluorescent protein mNeonGreen into the APOB gene locus. This results in the production of APOB100-mNeon that localizes predominantly to the endoplasmic reticulum (ER) and Golgi by immunofluorescence and electron microscopy imaging. The production and secretion of APOB100-mNeon can be quantitatively followed in medium over time and results in the production of lipoproteins that are taken up via the LDL receptor pathway. Importantly, the production and secretion of APOB-mNeon is sensitive to established pharmacological and physiological treatments and to genetic modifiers known to influence VLDL production in humans. As a showcase, we used HepG2-APOBmNeon cells to interrogate ER-associated degradation of APOB. The use of a dedicated sgRNA library targeting all established membrane-associated ER-resident E3 ubiquitin ligases led to the identification of SYNV1 as the E3 responsible for the degradation of poorly lipidated APOB in HepG2 cells.

CONCLUSIONS

In summary, the engineered cells reported here allow the study of hepatic VLDL assembly and secretion and facilitate spatiotemporal interrogation induced by pharmacologic and genetic perturbations.

LNCHC directly binds and regulates YBX1 stability to ameliorate metabolic dysfunction-associated steatotic liver disease progression

BACKGROUND AND AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents the foremost cause of chronic liver disease, yet its underlying mechanisms remain elusive. Our group previously discovered a novel long non-coding RNA (lncRNA) in rats, termed lncHC and its human counterpart, LNCHC. This study aimed to explore the role of LNCHC in the progression of MASLD.

METHODS

RNA-binding proteins bound to LNCHC were searched by mass spectrometry. The target genes of LNCHC and Y-Box binding protein 1 (YBX1) were identified by RNA-seq. MASLD animal models were utilised to examine the roles of LNCHC, YBX1 and patatin-like phospholipase domain containing 3 (PNPLA3) in MASLD progression.

RESULTS

Here, we identified LNCHC as a native restrainer during MASLD development. Notably, LNCHC directly binds YBX1 and prevents protein ubiquitination. Up-regulation of YBX1 then stabilises PNPLA3 mRNA to alleviate lipid accumulation in hepatocytes. Furthermore, both cell and animal studies demonstrate that LNCHC, YBX1 and PNPLA3 function to improve hepatocyte lipid accumulation and exacerbate metabolic dysfunction-associated steatohepatitis development.

CONCLUSIONS

In summary, our findings unveil a novel LNCHC functionality in regulating YBX1 and PNPLA3 mRNA stability during MASLD development, providing new avenues in MASLD treatment.

Maladaptive regeneration and metabolic dysfunction associated steatotic liver disease: Common mechanisms and potential therapeutic targets

The normal liver has an extraordinary capacity of regeneration. However, this capacity is significantly impaired in steatotic livers. Emerging evidence indicates that metabolic dysfunction associated steatotic liver disease (MASLD) and liver regeneration share several key mechanisms. Some classical liver regeneration pathways, such as HGF/c-Met, EGFR, Wnt/β-catenin and Hippo/YAP-TAZ are affected in MASLD. Some recently established therapeutic targets for MASH such as the Thyroid Hormone (TH) receptors, Glucagon-like protein 1 (GLP1), Farnesoid X receptor (FXR), Peroxisome Proliferator-Activated Receptors (PPARs) as well as Fibroblast Growth Factor 21 (FGF21) are also reported to affect hepatocyte proliferation. With this review we aim to provide insight into common molecular pathways, that may ultimately enable therapeutic strategies that synergistically ameliorate steatohepatitis and improve the regenerating capacity of steatotic livers. With the recent rise of prolonged ex-vivo normothermic liver perfusion prior to organ transplantation such treatment is no longer restricted to patients undergoing major liver resection or transplantation, but may eventually include perfused (steatotic) donor livers or even liver segments, opening hitherto unexplored therapeutic avenues.

Emerging mechanisms of non-alcoholic steatohepatitis and novel drug therapies

Non-alcoholic fatty liver disease (NAFLD) has become a leading cause of chronic liver disease globally. It initiates with simple steatosis (NAFL) and can progress to the more severe condition of non-alcoholic steatohepatitis (NASH). NASH often advances to end-stage liver diseases such as liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Notably, the transition from NASH to end-stage liver diseases is irreversible, and the precise mechanisms driving this progression are not yet fully understood. Consequently, there is a critical need for the development of effective therapies to arrest or reverse this progression. This review provides a comprehensive overview of the pathogenesis of NASH, examines the current therapeutic targets and pharmacological treatments, and offers insights for future drug discovery and development strategies for NASH therapy.

Insulin resistance is an integral feature of MASLD even in the presence of PNPLA3 variants

Background & Aims

It has been postulated that carriers of PNPLA3 I148M (CG [Ile/Met] or GG [Met/Met]) develop metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance or metabolic syndrome. However, the relationship between insulin resistance and MASLD according to the PNPLA3 allele has not been carefully assessed.

Methods

A total of 204 participants were recruited and underwent PNPLA3 genotyping, an oral glucose tolerance test, liver proton magnetic resonance spectroscopy and percutaneous liver biopsy if diagnosed with MASLD. A subgroup of patients (n = 55) had an euglycemic hyperinsulinemic clamp with glucose tracer infusion.

Results

As expected, patients with the CG/GG genotype had worse intrahepatic triglyceride content and worse liver histology. However, regardless of PNPLA3 genotype, patients with a diagnosis of MASLD had severe whole-body insulin resistance (Matsuda index, an estimation of insulin resistance in glucose metabolic pathways) and fasting and postprandial adipose tissue insulin resistance (Adipo-IR index and free fatty acid suppression during the oral glucose tolerance test, respectively, as measures of insulin resistance in lipolytic metabolic pathways) compared to patients without MASLD. Moreover, for the same amount of liver fat accumulation, insulin resistance was similar in patients with genotypes CC vs. CG/GG. In multiple regression analyses, A1c and Adipo-IR were associated with the presence of MASLD and advanced liver fibrosis, independently of PNPLA3 genotype.

Conclusions

PNPLA3 variant carriers with MASLD are equally insulin resistant as non-carriers with MASLD at the level of the liver, muscle, and adipose tissue. This calls for reframing "PNPLA3 MASLD" as an insulin-resistant condition associated with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes, wherein early identification and aggressive intervention are warranted to reverse metabolic dysfunction and prevent disease progression.

Impact and implications

It has been proposed that the PNPLA3 G allele is associated with the presence of metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance. However, our results suggest that regardless of PNPLA3 alleles, the presence of insulin resistance is necessary for the development of MASLD. This calls for reframing patients with "PNPLA3 MASLD" not as insulin sensitive, but on the contrary, as an insulin-resistant population with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes.

Blood cell parameters and risk of nonalcoholic fatty liver disease: a comprehensive Mendelian randomization study

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is on the rise globally, and past research suggests a significant association with various blood cell components. Our goal is to explore the potential correlation between whole blood cell indices and NAFLD risk using Mendelian randomization (MR).

METHODS

We analyzed data from 4,198 participants in the 2017-2018 National Health and Nutrition Examination Survey to investigate the link between blood cell indicators and NAFLD. Using various methods like weighted quantile sum and multivariate logistic regression, we assessed the association. Additionally, two-sample Mendelian randomization were employed to infer causality for 36 blood cell indicators and NAFLD.

RESULTS

Multivariate logistic regression identified 10 NAFLD risk factors. Weighted quantile sum revealed a positive correlation (p = 6.03e-07) between total blood cell indices and NAFLD, with hemoglobin and lymphocyte counts as key contributors. Restricted cubic spline analysis found five indicators with significant nonlinear correlations to NAFLD. Mendelian randomization showed a notable association between reticulocyte counts and NAFLD using the inverse-variance weighted method.

CONCLUSIONS

Hematological markers pose an independent NAFLD risk, with a positive causal link found for reticulocyte count. These results emphasize the importance of monitoring NAFLD and investigating specific underlying mechanisms further.

Genetics of liver disease in adults

Chronic liver disease stands as a significant global health problem with an estimated 2 million annual deaths across the globe. Combining the use of next-generation sequencing technologies with evolving knowledge in the interpretation of genetic variation across the human genome is propelling our understanding, diagnosis, and management of both rare and common liver diseases. Here, we review the contribution of risk and protective alleles to common forms of liver disease, the rising number of monogenic diseases affecting the liver, and the role of somatic genetic variants in the onset and progression of oncological and non-oncological liver diseases. The incorporation of genomic information in the diagnosis and management of patients with liver disease is driving the beginning of a new era of genomics-informed clinical hepatology practice, facilitating personalized medicine, and improving patient care.

Therapeutic management of metabolic dysfunction associated steatotic liver disease

The incidence and prevalence of non-alcoholic fatty liver disease (NAFLD) have been steadily increasing worldwide, with a huge societal and economic burden. Recently, NAFLD and non-alcoholic steatohepatitis have been renamed and redefined as metabolic dysfunction associated steatotic liver disease (MASLD) and steatohepatitis (Metabolic Dysfunction Associated Steatohepatitis (MASH)), which result from an imbalance between metabolic and inflammatory stress (mainly as a consequence of adipose tissue dysfunction and insulin resistance) and the defence and repair mechanisms of the steatotic liver. Once MASLD progresses to end-stage of liver disease, treatment efficacy becomes limited and may require liver transplantation. Early detection and intervention are crucial. Lifestyle modification is consequently the cornerstone of its management. Timely consideration of bariatric surgeries should be given to patients meeting specific criteria. A multidisciplinary approach is warranted, starting from the concept that MASLD/MASH is at the centre of the cardiovascular-liver-metabolic syndrome. In some cases, pharmacological treatment can complement lifestyle modification. Several drugs used to treat the cardiometabolic co-morbidities have some potential efficacy in slowing Down disease progression, and some have demonstrated efficacy on histological endpoints that are likely to translate into long-term clinical benefits. Optimising the use of these drugs within their licenced indications is thus paramount for patients with MASLD. Several MASH-specific drugs are on the horizon and are likely to enrich our therapeutic armamentarium in the near future, particularly in non-cirrhotic stages of the disease. Much work still needs to be done to understand the specific features of MASH cirrhosis and develop efficacious treatments for this disease stage.

Drug targets regulate systemic metabolism and provide new horizons to treat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), is the advanced stage of nonalcoholic fatty liver disease (NAFLD) with rapidly rising global prevalence. It is featured with severe hepatocyte apoptosis, inflammation and hepatic lipogenesis. The drugs directly targeting the processes of steatosis, inflammation and fibrosis are currently under clinical investigation. Nevertheless, the long-term ineffectiveness and remarkable adverse effects are well documented, and new concepts are required to tackle with the root causes of NASH progression. We critically assess the recently validated drug targets that regulate the systemic metabolism to ameliorate NASH. Thermogenesis promoted by mitochondrial uncouplers restores systemic energy expenditure. Furthermore, regulation of mitochondrial proteases and proteins that are pivotal for intracellular metabolic homeostasis normalize mitochondrial function. Secreted proteins also improve systemic metabolism, and NASH is ameliorated by agonizing receptors of secreted proteins with small molecules. We analyze the drug design, the advantages and shortcomings of these novel drug candidates. Meanwhile, the structural modification of current NASH therapeutics significantly increased their selectivity, efficacy and safety. Furthermore, the arising CRISPR-Cas9 screen strategy on liver organoids has enabled the identification of new genes that mediate lipid metabolism, which may serve as promising drug targets. In summary, this article discusses the in-depth novel mechanisms and the multidisciplinary approaches, and they provide new horizons to treat NASH.

GLP-1 receptor agonists in the treatment of diabetic non-alcoholic steatohepatitis patients

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disease affecting almost 30% of the world population. Approximately 25% of people with NAFLD develop nonalcoholic steatohepatitis (NASH), the fulminant version of the disease. Diabetes mellitus is present in 22.5% of people with NAFLD and 44.60% of individuals with NASH. This review was undertaken to examine the current contribution of glucagon-like peptide 1 (GLP-1) receptor agonists to the pharmacotherapy of diabetic nonalcoholic steatohepatitis.

AREAS COVERED

The author analyzed the current status of GLP-1 receptor agonists for pharmacotherapy of diabetic NASH. Research data and literature reports were taken from the database and or websites of Diabetes UK, American Diabetes Association, ClinicalTrials.gov, PubMed, and Scopus. The keywords utilized included type 2 diabetes, GLP-1, NASH, NAFLD, and clinical trials.

EXPERT OPINION

Since diabetic NASH is associated with obesity, diabetes mellitus, oxidative stress and inflammation, drugs capable of mitigating all of these conditions simultaneously, are most ideal for the treatment of diabetic NASH. These drugs include (in order of relevance), GLP-1 receptor agonists, GLP-1 and GIP dual receptor agonists, sodium-glucose co-transporter-2 (SGLT2) inhibitors, and pioglitazone. The future, FDA-approved drug for diabetic NASH treatment will likely be GLP-1 agonist, which could be used as monotherapy or in combination with other drugs.

Exercise training improves serum biomarkers of liver fibroinflammation in patients with metabolic dysfunction-associated steatohepatitis

BACKGROUND AND AIMS

Exercise training is recommended for all patients with metabolic dysfunction-associated steatotic liver disease and may reverse liver fibrosis. Whether exercise training improves liver fibrosis without body weight loss remains controversial. We further investigated this relationship using serum biomarkers of liver fibroinflammation in a post hoc analysis of an exercise trial where patients did not lose significant body weight.

METHODS

In the NASHFit trial, patients with metabolic dysfunction-associated steatohepatitis were randomized to receive either moderate-intensity aerobic exercise training or standard clinical care for 20 weeks. Mediterranean-informed dietary counselling was provided to each group. Change in serum biomarkers was measured and compared between the two groups.

RESULTS

Exercise training led to improvement in serum biomarkers of liver fibroinflammation, including (1) ≥17 IU/L reduction in alanine aminotransferase (ALT) in 53% of individuals in the exercise training group compared to 13% in the standard clinical care group (p < 0.001; mean reduction 24% vs. 10% respectively) and (2) improvement in CK18 (-61 vs. +71 ng/mL, p = 0.040). ALT improvement ≥17 IU/L was correlated with ≥30% relative reduction in magnetic resonance imaging-measured liver fat and PNPLA3 genotype.

CONCLUSION

Exercise training improves multiple serum biomarkers of liver fibroinflammation at clinically significant thresholds of response without body weight loss. This study provides further evidence that exercise training should be viewed as a weight-neutral intervention for which response to intervention can be readily monitored with widely available non-invasive biomarkers that can be applied at the population level.

MASLD treatment-a shift in the paradigm is imminent

MASLD prevalence is growing towards the leading cause of end-stage liver disease. Up to today, the most effective treatment is weight loss. Weight loss interventions are moving from lifestyle changes to bariatric surgery or endoscopy, and, more recently, to a new wave of anti-obesity drugs that can compete with bariatric surgery. Liver-targeted therapy is a necessity for those patients who already present liver fibrosis. The field is moving fast, and in the near future, we will testify to a disruptive change in MASLD treatment, similar to the paradigm-shift that occurred for hepatitis C almost one decade ago with direct antiviral agents.

Activation of GPBAR1 attenuates vascular inflammation and atherosclerosis in a mouse model of NAFLD-related cardiovascular disease

While patients with nonalcoholic fatty liver disease (NAFLD) are at increased risk to develop clinically meaningful cardiovascular diseases (CVD), there are no approved drug designed to target the liver and CVD component of NAFLD. GPBAR1, also known as TGR5, is a G protein coupled receptor for secondary bile acids. In this study we have investigated the effect of GPBAR1 activation by BAR501, a selective GPBAR1 agonist, in Apolipoprotein E deficient (ApoE-/-) mice fed a high fat diet and fructose (Western diet), a validated model of NAFLD-associated atherosclerosis. Using aortic samples from patients who underwent surgery for abdominal aneurism, and ex vivo experiments with endothelial cells and human macrophages, we were able to co-localize the expression of GPBAR1 in CD14+ and PECAM1+ cells. Similar findings were observed in the aortic plaques from ApoE-/- mice. Treating ApoE-/- mice with BAR501, 30 mg/kg for 14 weeks, attenuated the body weight gain while ameliorated the insulin sensitivity by increasing the plasma concentrations of GLP-1 and FGF15. Activation of GPBAR1 reduced the aorta thickness and severity of atherosclerotic lesions and decreased the amount of plaques macrophages. Treating ApoE-/- mice reshaped the aortic transcriptome promoting the expression of anti-inflammatory genes, including IL-10, as also confirmed by tSNE analysis of spleen-derived macrophages. Feeding ApoE-/- mice with BAR501 redirected the bile acid synthesis and the composition of the intestinal microbiota. In conclusion, GPBAR1 agonism attenuates systemic inflammation and improve metabolic profile in a genetic/dietetic model of atherosclerosis. BAR501 might be of utility in the treatment for NAFLD-related CVD.