Modern therapeutic approaches to liver-related disorders

Navigating liver health with metabolomics: A comprehensive review

Non-alcoholic fatty liver disease (NAFLD) is the main cause of chronic liver disease worldwide, affecting one-fourth of the world's population. With more than half of the world's population, the Asia-Pacific region contributed 62.6 % of liver-related fatal incidents in 2015. Currently, liver imaging techniques such as computed tomography (CT), nuclear magnetic resonance (NMR) spectroscopy, and ultrasound are non-invasive imaging methods to diagnose the disease. A liver biopsy is the gold standard test for establishing the definite diagnosis of non-alcoholic steatohepatitis (NASH). However, there are still significant problems with sample variability and the procedure's invasiveness. Numerous studies have indicated various non-invasive biomarkers for both fibrosis and steatosis to counter the invasiveness of diagnostic procedures. Metabolomics could be a promising method for detecting early liver diseases, investigating pathophysiology, and developing drugs. Metabolomics, when utilized with other omics technologies, can result in a deeper understanding of biological systems. Metabolomics has emerged as a prominent research topic, offering extensive opportunities to investigate biomarkers for liver diseases that are both sensitive and specific. In this review, we have described the recent studies involving the use of a metabolomics approach in the diagnosis of liver diseases, which would be beneficial for the early detection and treatment of liver diseases.

Current Treatment Regimens and Promising Molecular Therapies for Chronic Hepatobiliary Diseases

Chronic hepatobiliary damage progressively leads to fibrosis, which may evolve into cirrhosis and/or hepatocellular carcinoma. The fight against the increasing incidence of liver-related morbidity and mortality is challenged by a lack of clinically validated early-stage biomarkers and the limited availability of effective anti-fibrotic therapies. Current research is focused on uncovering the pathogenetic mechanisms that drive liver fibrosis. Drugs targeting molecular pathways involved in chronic hepatobiliary diseases, such as inflammation, hepatic stellate cell activation and proliferation, and extracellular matrix production, are being developed. Etiology-specific treatments, such as those for hepatitis B and C viruses, are already in clinical use, and efforts to develop new, targeted therapies for other chronic hepatobiliary diseases are ongoing. In this review, we highlight the major molecular changes occurring in patients affected by metabolic dysfunction-associated steatotic liver disease, viral hepatitis (Delta virus), and autoimmune chronic liver diseases (autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis). Further, we describe how this knowledge is linked to current molecular therapies as well as ongoing preclinical and clinical research on novel targeting strategies, including nucleic acid-, mesenchymal stromal/stem cell-, and extracellular vesicle-based options. Much clinical development is obviously still missing, but the plethora of promising potential treatment strategies in chronic hepatobiliary diseases holds promise for a future reversal of the current increase in morbidity and mortality in this group of patients.

Microfluidics for Nanomedicine Delivery

Nanomedicine is revolutionizing precision medicine, providing targeted, personalized treatment options. Lipid-based nanomedicines offer distinct benefits including high potency, targeted delivery, extended retention in the body, reduced toxicity, and lower required doses. These characteristics make lipid-based nanoparticles ideal for drug delivery in areas such as gene therapy, cancer treatment, and mRNA vaccines. However, traditional bulk synthesis methods for LNPs often produce larger particle sizes, significant polydispersity, and low encapsulation efficiency, which can reduce the therapeutic effectiveness. These issues primarily result from uneven mixing and limited control over particle formation during the synthesis. Microfluidic technology has emerged as a solution, providing precise control over particle size, uniformity, and encapsulation efficiency. In this mini review, we introduce the state-of-the-art microfluidic systems for lipid-based nanoparticle synthesis and functionalization. We include the working principles of different types of microfluidic systems, the use of microfluidic systems for LNP synthesis, cargo encapsulation, and nanomedicine delivery. In the end, we briefly discuss the clinical use of LNPs enabled by microfluidic devices.

Alpha-1 Antitrypsin Inclusions Sequester GRP78 in a Bile Acid-Inducible Manner

BACKGROUND AND AIMS

The homozygous PiZ mutation (PIZZ genotype) constitutes the predominant cause of severe alpha-1 antitrypsin (AAT) deficiency and leads to liver disease via hepatocellular AAT aggregation. We systematically analysed the composition of AAT aggregates and studied the impact of bile acids.

METHODS

AAT inclusions were isolated from livers of PiZ overexpressing mice and PIZZ humans via fluorescence-activated and immunomagnetic sorting (FACS/MACS), while insoluble proteins were obtained via Triton-X extraction. Inclusion composition was evaluated through mass-spectrometry (MS), immunoblotting and immunostaining. Hepatocytes with versus without AAT aggregates were obtained via microdissection. Serum bile acids were assessed in 57 PIZZ subjects and 19 controls. Mice were administered 2% cholic acid (CA)-supplemented chow for 7 days.

RESULTS

MS identified the key endoplasmic reticulum chaperone 78 kDa glucose-regulated protein (GRP78) in FACS/MACS pulldowns. GRP78 was also enriched in insoluble fractions from PiZ mice versus wild types and detected in insoluble fractions/MACS isolates from PIZZ liver explants. In cultured cells/primary hepatocytes, PiZ overexpression was associated with increased GRP78 mRNA/protein levels. In human livers, hepatocytes with AAT aggregates had higher GRP78 levels than hepatocytes without. PIZZ subjects displayed higher serum bile acid levels than controls and the highest levels were seen in individuals with liver injury/fibrosis. In PiZ mice, CA-mediated bile acid challenge resulted in increased liver injury and translocation of GRP78 into the aggregates.

CONCLUSIONS

Our results demonstrate that GRP78 is sequestered within AAT inclusions. Bile acid accumulation, as seen in PIZZ subjects with liver disease, may promote GRP78 segregation and thereby augment liver damage.

TRIAL REGISTRATION

NCT02929940.

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.

The Liver and Lysosomal Storage Diseases: From Pathophysiology to Clinical Presentation, Diagnostics, and Treatment

The liver, given its role as the central metabolic organ, is involved in many inherited metabolic disorders, including lysosomal storage diseases (LSDs). The aim of this manuscript was to provide a comprehensive overview on liver involvement in LSDs, focusing on clinical manifestation and its pathomechanisms. Gaucher disease, acid sphingomyelinase deficiency, and lysosomal acid lipase deficiency were thoroughly reviewed, with hepatic manifestation being a dominant clinical phenotype. The natural history of liver disease in the above-mentioned lysosomal disorders was delineated. The importance of Niemann-Pick type C disease as a cause of cholestatic jaundice, preceding neurological manifestation, was also highlighted. Diagnostic methods and current therapeutic management of LSDs were also discussed in the context of liver involvement.

The Coming Age of Antisense Oligos for the Treatment of Hepatic Ischemia/Reperfusion (IRI) and Other Liver Disorders: Role of Oxidative Stress and Potential Antioxidant Effect

Imbalances in the redox state of the liver arise during metabolic processes, inflammatory injuries, and proliferative liver disorders. Acute exposure to intracellular reactive oxygen species (ROS) results from high levels of oxidative stress (OxS) that occur in response to hepatic ischemia/reperfusion injury (IRI) and metabolic diseases of the liver. Antisense oligonucleotides (ASOs) are an emerging class of gene expression modulators that target RNA molecules by Watson-Crick binding specificity, leading to RNA degradation, splicing modulation, and/or translation interference. Here, we review ASO inhibitor/activator strategies to modulate transcription and translation that control the expression of enzymes, transcription factors, and intracellular sensors of DNA damage. Several small-interfering RNA (siRNA) drugs with N-acetyl galactosamine moieties for the liver have recently been approved. Preclinical studies using short-activating RNAs (saRNAs), phosphorodiamidate morpholino oligomers (PMOs), and locked nucleic acids (LNAs) are at the forefront of proof-in-concept therapeutics. Future research targeting intracellular OxS-related pathways in the liver may help realize the promise of precision medicine, revolutionizing the customary approach to caring for and treating individuals afflicted with liver-specific conditions.

Alkaptonuria

Alkaptonuria is a rare inborn error of metabolism caused by the deficiency of homogentisate 1,2-dioxygenase activity. The consequent homogentisic acid (HGA) accumulation in body fluids and tissues leads to a multisystemic and highly debilitating disease whose main features are dark urine, ochronosis (HGA-derived pigment in collagen-rich connective tissues), and a painful and severe form of osteoarthropathy. Other clinical manifestations are extremely variable and include kidney and prostate stones, aortic stenosis, bone fractures, and tendon, ligament and/or muscle ruptures. As an autosomal recessive disorder, alkaptonuria affects men and women equally. Debilitating symptoms appear around the third decade of life, but a proper and timely diagnosis is often delayed due to their non-specific nature and a lack of knowledge among physicians. In later stages, patients' quality of life might be seriously compromised and further complicated by comorbidities. Thus, appropriate management of alkaptonuria requires a multidisciplinary approach, and periodic clinical evaluation is advised to monitor disease progression, complications and/or comorbidities, and to enable prompt intervention. Treatment options are patient-tailored and include a combination of medications, physical therapy and surgery. Current basic and clinical research focuses on improving patient management and developing innovative therapies and implementing precision medicine strategies.

Jagged-mediated development and disease: Mechanistic insights and therapeutic implications for Alagille syndrome

Notch signaling controls multiple aspects of embryonic development and adult homeostasis. Alagille syndrome is usually caused by a single mutation in the jagged canonical Notch ligand 1 (JAG1), and manifests with liver disease and cardiovascular symptoms that are a direct consequence of JAG1 haploinsufficiency. Recent insights into Jag1/Notch-controlled developmental and homeostatic processes explain how pathology develops in the hepatic and cardiovascular systems and, together with recent elucidation of mechanisms modulating liver regeneration, provide a basis for therapeutic efforts. Importantly, disease presentation can be regulated by genetic modifiers, that may also be therapeutically leverageable. Here, we summarize recent insights into how Jag1 controls processes of relevance to Alagille syndrome, focused on Jag1/Notch functions in hepatic and cardiovascular development and homeostasis.

A functional mini-GDE transgene corrects impairment in models of glycogen storage disease type III

Glycogen storage disease type III (GSDIII) is a rare inborn error of metabolism affecting liver, skeletal muscle, and heart due to mutations of the AGL gene encoding for the glycogen debranching enzyme (GDE). No curative treatment exists for GSDIII. The 4.6 kb GDE cDNA represents the major technical challenge toward the development of a single recombinant adeno-associated virus-derived (rAAV-derived) vector gene therapy strategy. Using information on GDE structure and molecular modeling, we generated multiple truncated GDEs. Among them, an N-terminal-truncated mutant, ΔNter2-GDE, had a similar efficacy in vivo compared with the full-size enzyme. A rAAV vector expressing ΔNter2-GDE allowed significant glycogen reduction in heart and muscle of Agl-/- mice 3 months after i.v. injection, as well as normalization of histology features and restoration of muscle strength. Similarly, glycogen accumulation and histological features were corrected in a recently generated Agl-/- rat model. Finally, transduction with rAAV vectors encoding ΔNter2-GDE corrected glycogen accumulation in an in vitro human skeletal muscle cellular model of GSDIII. In conclusion, our results demonstrated the ability of a single rAAV vector expressing a functional mini-GDE transgene to correct the muscle and heart phenotype in multiple models of GSDIII, supporting its clinical translation to patients with GSDIII.

Hepatocyte-targeted siTAZ therapy lowers liver fibrosis in NASH diet-fed chimeric mice with hepatocyte-humanized livers

Nonalcoholic steatohepatitis (NASH) is emerging as the most common cause of liver disease. Although many studies in mouse NASH models have suggested therapies, translation to humans is poor, with no approved drugs for NASH. One explanation may lie in differences between mouse and human hepatocytes. We used NASH diet-fed chimeric mice reconstituted with human hepatocytes (hu-liver mice) to test a mechanism-based hepatocyte-targeted small interfering RNA (siRNA), GalNAc-siTaz, shown previously to block the progression to fibrotic NASH in mice. Following ablation of endogenous hepatocytes, male mice were reconstituted with human hepatocytes from a single donor with the rs738409-C/G PNPLA3 risk variant, resulting in ∼95% human hepatocyte reconstitution. The mice were then fed a high-fat choline-deficient l-amino acid-defined diet for 6 weeks to induce NASH, followed by six weekly injections of GalNAc-siTAZ to silence hepatocyte-TAZ or control GalNAc-siRNA (GalNAc-control) while still on the NASH diet. GalNAc-siTAZ lowered human hepatic TAZ and IHH, a TAZ target that promotes NASH fibrosis. Most important, GalNAc-siTAZ decreased liver inflammation, hepatocellular injury, hepatic fibrosis, and profibrogenic mediator expression versus GalNAc-control, indicating that GalNAc-siTAZ decreased the progression of NASH in mice reconstituted with human hepatocytes. In conclusion, silencing TAZ in human hepatocytes suppresses liver fibrosis in a hu-liver model of NASH.

Current limitations of gene therapy for rare pediatric diseases: Lessons learned from clinical experience with AAV vectors

Gene therapy using adeno-associated viral (AAV) vectors is a promising therapeutic strategy for multiple inherited diseases. Following intravenous injection, AAV vectors carrying a copy of the missing gene or the genome-editing machinery reach their target cells and deliver the genetic material. Several clinical trials are currently ongoing and significant success has already been achieved with at least six AAV gene therapy products with market approval in Europe and the United States. Nonetheless, clinical trials and preclinical studies have uncovered several limitations of AAV gene transfer, which need to be addressed in order to improve the safety and enable the treatment of the largest patient population. Limitations include the occurrence of immune-mediated toxicities, the potential loss of correction in the long run, and the development of neutralizing antibodies against AAV vectors preventing re-administration. In this review, we summarize these limitations and discuss the potential technological developments to overcome them. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.

Targeting N6-methyladenosine reader YTHDF1 with siRNA boosts antitumor immunity in NASH-HCC by inhibiting EZH2-IL-6 axis

BACKGROUND & AIMS

RNA N6-methyladenosine (m6A) reader protein YTHDF1 has been implicated in cancer; however, its role in hepatocellular carcinoma (HCC), especially in non-alcoholic steatohepatitis-associated HCC (NASH-HCC), remains unknown. Here, we investigated the functional role of YTHDF1 in NASH-HCC and its interplay with the tumor immune microenvironment.

METHODS

Hepatocyte-specific Ythdf1-overexpressing mice were subjected to a NASH-HCC-inducing diet. Tumor-infiltrating immune cells were profiled with single-cell RNA-sequencing, flow cytometry, and immunostaining. The molecular target of YTHDF1 was elucidated with RNA-sequencing, m6A-sequencing, YTHDF1 RNA immunoprecipitation-sequencing, proteomics, and ribosome-profiling. Ythdf1 in NASH-HCC models was targeted by lipid nanoparticle (LNP)-encapsulated small-interfering Ythdf1.

RESULTS

YTHDF1 is overexpressed in tumor tissues compared to adjacent peri-tumor tissues from patients with NASH-HCC. Liver-specific Ythdf1 overexpression drives tumorigenesis in dietary models of spontaneous NASH-HCC. Single-cell RNA-sequencing and flow cytometry revealed that Ythdf1 induced accumulation of myeloid-derived suppressor cells (MDSCs) and suppressed cytotoxic CD8+ T-cell function. Mechanistically, Ythdf1 expression in NASH-HCC cells induced the secretion of IL-6, which mediated MDSC recruitment and activation, leading to CD8+ T-cell dysfunction. EZH2 mRNA was identified as a key YTHDF1 target. YTHDF1 binds to m6A-modified EZH2 mRNA and promotes EZH2 translation. EZH2 in turn increased expression and secretion of IL-6. Ythdf1 knockout synergized with anti-PD-1 treatment to suppress tumor growth in NASH-HCC allografts. Furthermore, therapeutic targeting of Ythdf1 using LNP-encapsulated small-interfering RNA significantly increased the efficacy of anti-PD-1 blockade in NASH-HCC allografts.

CONCLUSIONS

We identified that YTHDF1 promotes NASH-HCC tumorigenesis via EZH2-IL-6 signaling, which recruits and activates MDSCs to cause cytotoxic CD8+ T-cell dysfunction. YTHDF1 may be a novel therapeutic target to improve responses to anti-PD-1 immunotherapy in NASH-HCC.

IMPACT AND IMPLICATIONS

YTHDF1, a N6-methyladenosine reader, is upregulated in patients with non-alcoholic steatohepatitis (NASH)-associated hepatocellular carcinoma (HCC); however, its role in modulating the tumor immune microenvironment in NASH-HCC remains unclear. Here, we show that Ythdf1 mediates immunosuppression in NASH-HCC and that targeting YTHDF1 in combination with immune checkpoint blockade elicits robust antitumor immune responses. Our findings suggest novel therapeutic targets for potentiating the efficacy of immune checkpoint blockade in NASH-HCC and provide the rationale for developing YTHDF1 inhibitors for the treatment of NASH-HCC.

Localization of unlabeled bepirovirsen antisense oligonucleotide in murine tissues using in situ hybridization and CARS imaging

Current methods for detecting unlabeled antisense oligonucleotide (ASO) drugs rely on immunohistochemistry (IHC) and/or conjugated molecules, which lack sufficient sensitivity, specificity, and resolution to fully investigate their biodistribution. Our aim was to demonstrate the qualitative and quantitative distribution of unlabeled bepirovirsen, a clinical stage ASO, in livers and kidneys of dosed mice using novel staining and imaging technologies at subcellular resolution. ASOs were detected in formalin-fixed paraffin-embedded (FFPE) and frozen tissues using an automated chromogenic in situ hybridization (ISH) assay: miRNAscope. This was then combined with immunohistochemical detection of cell lineage markers. ASO distribution in hepatocytes versus nonparenchymal cell lineages was quantified using HALO AI image analysis. To complement this, hyperspectral coherent anti-Stokes Raman scattering (HS-CARS) imaging microscopy was used to specifically detect the unique cellular Raman spectral signatures following ASO treatment. Bepirovirsen was localized primarily in nonparenchymal liver cells and proximal renal tubules. Codetection of ASO with distinct cell lineage markers of liver and kidney populations aided target cell identity facilitating quantification. Positive liver signal was quantified using HALO AI, with 12.9% of the ASO localized to the hepatocytes and 87.1% in nonparenchymal cells. HS-CARS imaging specifically detected ASO fingerprints based on the unique vibrational signatures following unlabeled ASO treatment in a totally nonperturbative manner at subcellular resolution. Together, these novel detection and imaging modalities represent a significant increase in our ability to detect unlabeled ASOs in tissues, demonstrating improved levels of specificity and resolution. These methods help us understand their underlying mechanisms of action and ultimately improve the therapeutic potential of these important drugs for treating globally significant human diseases.

Pediatric and Adult Liver Disease in Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency (AATD) arises due to inherited variants in SERPINA1, the AAT gene that impairs the production or secretion of this hepatocellular protein and leads to a gain-of-function liver proteotoxicity. Homozygous Pi*Z pathogenic variant (Pi*ZZ genotype) is the leading cause of severe AATD. It manifests in 2 to 10% of carriers as neonatal cholestasis and 20 to 35% of adults as significant liver fibrosis. Both children and adults may develop an end-stage liver disease requiring liver transplantation. Heterozygous Pi*Z pathogenic variant (Pi*MZ genotype) constitutes an established disease modifier. Our review summarizes the natural history and management of subjects with both pediatric and adult AATD-associated liver disease. Current findings from a phase 2 clinical trial indicate that RNA silencing may constitute a viable therapeutic approach for adult AATD. In conclusion, AATD is an increasingly appreciated pediatric and adult liver disorder that is becoming an attractive target for modern pharmacologic strategies.

RNAi therapeutics for diseases involving protein aggregation: fazirsiran for alpha-1 antitrypsin deficiency-associated liver disease

INTRODUCTION

Therapeutic agents that prevent protein misfolding or promote protein clearance are being studied to treat proteotoxic diseases. Among them, alpha-1 antitrypsin deficiency (AATD) is caused by mutations in the alpha-1 antitrypsin (SERPINA1) gene. Fazirsiran is a small interfering RNA (siRNA) that is intended to address the underlying cause of liver disease associated with AATD through the RNA interference (RNAi) mechanism.

AREAS COVERED

This article describes the role of misfolded proteins and protein aggregates in disease and options for therapeutic approaches. The RNAi mechanism is discussed, along with how the siRNA therapeutic fazirsiran for the treatment of AATD was developed. We also describe the implications of siRNA therapeutics in extrahepatic diseases.

EXPERT OPINION

Using RNAi as a therapeutic approach is well suited to treat disease in conditions where an excess of a protein or the effect of an abnormal mutated protein causes disease. The results observed for the first few siRNA therapeutics that were approved or are in development provide an important promise for the development of future drugs that can address such conditions in a specific and targeted way. Current developments should enable the use of RNAi therapeutics outside the liver, where there are many more possible diseases to address.

Cleaning up alpha-1 antitrypsin deficiency related liver disease

PURPOSE OF REVIEW

Alpha-1 antitrypsin deficiency (AATD) is one of the most common genetic disorders arising due to mutations in alpha-1 antitrypsin (AAT) gene affecting primarily the lung and the liver. This review summarizes the pathophysiology and clinical manifestation of different AATD genotypes and discusses the recent therapeutic developments. The focus is on the severe, rare homozygous Pi∗ZZ and the common heterozygous Pi∗MZ genotype.

RECENT FINDINGS

Pi∗ZZ individuals harbor an up to 20 times higher risk of liver fibrosis and cirrhosis than noncarriers and liver transplantation is currently the only available therapeutic option. AATD constitutes a proteotoxic disorder arising from hepatic AAT accumulation and the currently most promising data come from a phase 2, open-label trial of fazirsiran, a hepatocyte-targeted siRNA. Pi∗MZ subjects display an increased risk of advanced liver disease and at the latter stage, a faster deterioration than individuals without AAT mutation.

SUMMARY

Although the fazirsiran data offer a glimpse of hope to AATD patients, a consensus on appropriate study endpoint, a careful patient selection as well as monitoring of long-term safety will be essential for an approval.

Loss of liver function in chronic liver disease: An identity crisis

Adult hepatocyte identity is constructed throughout embryonic development and fine-tuned after birth. A multinodular network of transcription factors, along with pre-mRNA splicing regulators, define the transcriptome, which encodes the proteins needed to perform the complex metabolic and secretory functions of the mature liver. Transient hepatocellular dedifferentiation can occur as part of the regenerative mechanisms triggered in response to acute liver injury. However, persistent downregulation of key identity genes is now accepted as a strong determinant of organ dysfunction in chronic liver disease, a major global health burden. Therefore, the identification of core transcription factors and splicing regulators that preserve hepatocellular phenotype, and a thorough understanding of how these networks become disrupted in diseased hepatocytes, is of high clinical relevance. In this context, we review the key players in liver differentiation and discuss in detail critical factors, such as HNF4α, whose impairment mediates the breakdown of liver function. Moreover, we present compelling experimental evidence demonstrating that restoration of core transcription factor expression in a chronically injured liver can reset hepatocellular identity, improve function and ameliorate structural abnormalities. The possibility of correcting the phenotype of severely damaged and malfunctional livers may reveal new therapeutic opportunities for individuals with cirrhosis and advanced liver disease.

The STING in Non-Alcoholic Fatty Liver Diseases: Potential Therapeutic Targets in Inflammation-Carcinogenesis Pathway

Non-alcoholic fatty liver disease (NAFLD), an important chronic disease, is one of the major causes of high mortality and creates a substantial financial burden worldwide. The various immune cells in the liver, including macrophages, NK cells, dendritic cells, and the neutrophils involved in the innate immune response, trigger inflammation after recognizing the damage signaled from infection or injured cells and tissues. The stimulator of interferon genes (STING) is a critical molecule that binds to the cyclic dinucleotides (CDNs) generated by the cyclic GMP-AMP synthase (cGAS) to initiate the innate immune response against infection. Previous studies have demonstrated that the cGAS-STING pathway plays a critical role in inflammatory, auto-immune, and anti-viral immune responses. Recently, studies have focused on the role of STING in liver diseases, the results implying that alterations in its activity may be involved in the pathogenesis of liver disorders. Here, we summarize the function of STING in the development of NAFLD and present the current inhibitors and agonists targeting STING.

Noncoding RNAs in liver physiology and metabolic diseases

The liver holds central roles in detoxification, energy metabolism and whole-body homeostasis but can develop malignant phenotypes when being chronically overwhelmed with fatty acids and glucose. The global rise of metabolic-associated fatty liver disease (MAFLD) is already affecting a quarter of the global population. Pharmaceutical treatment options against different stages of MAFLD do not yet exist and several clinical trials against hepatic transcription factors and other proteins have failed. However, emerging roles of noncoding RNAs, including long (lncRNA) and short noncoding RNAs (sRNA), in various cellular processes pose exciting new avenues for treatment interventions. Actions of noncoding RNAs mostly rely on interactions with proteins, whereby the noncoding RNA fine-tunes protein function in a process termed riboregulation. The developmental stage-, disease stage- and cell type-specific nature of noncoding RNAs harbors enormous potential to precisely target certain cellular pathways in a spatio-temporally defined manner. Proteins interacting with RNAs can be categorized into canonical or non-canonical RNA binding proteins (RBPs) depending on the existence of classical RNA binding domains. Both, RNA- and RBP-centric methods have generated new knowledge of the RNA-RBP interface and added an additional regulatory layer. In this review, we summarize recent advances of how of RBP-lncRNA interactions and various sRNAs shape cellular physiology and the development of liver diseases such as MAFLD and hepatocellular carcinoma.

Fazirsiran for Liver Disease Associated with Alpha1-Antitrypsin Deficiency

BACKGROUND

Alpha₁-antitrypsin (AAT) deficiency results from carriage of a homozygous SERPINA1 "Z" mutation (proteinase inhibitor [PI] ZZ). The Z allele produces a mutant AAT protein called Z-AAT, which accumulates in hepatocytes and can lead to progressive liver disease and fibrosis. This open-label, phase 2 trial investigated the safety and efficacy of fazirsiran, an RNA interference therapeutic, in patients with liver disease associated with AAT deficiency.

METHODS

We assigned adults with the PI ZZ genotype and liver fibrosis to receive fazirsiran at a dose of 200 mg (cohorts 1 [4 patients] and 2 [8 patients]) or 100 mg (cohort 1b [4 patients]) subcutaneously on day 1 and week 4 and then every 12 weeks. The primary end point was the change from baseline to week 24 (cohorts 1 and 1b) or week 48 (cohort 2) in liver Z-AAT concentrations, which were measured by means of liquid chromatography-mass spectrometry.

RESULTS

All the patients had reduced accumulation of Z-AAT in the liver (median reduction, 83% at week 24 or 48). The nadir in serum was a reduction of approximately 90%, and treatment was also associated with a reduction in histologic globule burden (from a mean score of 7.4 [scores range from 0 to 9, with higher scores indicating a greater globule burden] at baseline to 2.3 at week 24 or 48). All cohorts had reductions in liver enzyme concentrations. Fibrosis regression was observed in 7 of 15 patients and fibrosis progression in 2 of 15 patients after 24 or 48 weeks. There were no adverse events leading to trial or drug discontinuation. Four serious adverse events (viral myocarditis, diverticulitis, dyspnea, and vestibular neuronitis) resolved.

CONCLUSIONS

In this small trial, fazirsiran was associated with a strong reduction of Z-AAT concentrations in the serum and liver and concurrent improvements in liver enzyme concentrations. (Funded by Arrowhead Pharmaceuticals; AROAAT-2002 ClinicalTrials.gov number, NCT03946449.).