Is severe progressive liver disease caused by alpha-1-antitrypsin deficiency more common in children or adults?

UK guideline on the transition and management of childhood liver diseases in adulthood

INTRODUCTION

Improved outcomes of liver disease in childhood and young adulthood have resulted in an increasing number of young adults (YA) entering adult liver services. The adult hepatologist therefore requires a working knowledge in diseases that arise almost exclusively in children and their complications in adulthood.

AIMS

To provide adult hepatologists with succinct guidelines on aspects of transitional care in YA relevant to key disease aetiologies encountered in clinical practice.

METHODS

A systematic literature search was undertaken using the Pubmed, Medline, Web of Knowledge and Cochrane database from 1980 to 2023. MeSH search terms relating to liver diseases ('cholestatic liver diseases', 'biliary atresia', 'metabolic', 'paediatric liver diseases', 'autoimmune liver diseases'), transition to adult care ('transition services', 'young adult services') and adolescent care were used. The quality of evidence and the grading of recommendations were appraised using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system.

RESULTS

These guidelines deal with the transition of YA and address key aetiologies for the adult hepatologist under the following headings: (1) Models and provision of care; (2) screening and management of mental health disorders; (3) aetiologies; (4) timing and role of liver transplantation; and (5) sexual health and fertility.

CONCLUSIONS

These are the first nationally developed guidelines on the transition and management of childhood liver diseases in adulthood. They provide a framework upon which to base clinical care, which we envisage will lead to improved outcomes for YA with chronic liver disease.

Variants in autophagy genes MTMR12 and FAM134A are putative modifiers of the hepatic phenotype in α1-antitrypsin deficiency

BACKGROUND AND AIMS

In the classical form of α1-antitrypsin deficiency, a misfolded variant α1-antitrypsin Z accumulates in the endoplasmic reticulum of liver cells and causes liver cell injury by gain-of-function proteotoxicity in a sub-group of affected homozygotes but relatively little is known about putative modifiers. Here, we carried out genomic sequencing in a uniquely affected family with an index case of liver failure and 2 homozygous siblings with minimal or no liver disease. Their sequences were compared to sequences in well-characterized cohorts of homozygotes with or without liver disease, and then candidate sequence variants were tested for changes in the kinetics of α1-antitrypsin variant Z degradation in iPS-derived hepatocyte-like cells derived from the affected siblings themselves.

APPROACH AND RESULTS

Specific variants in autophagy genes MTMR12 and FAM134A could each accelerate the degradation of α1-antitrypsin variant Z in cells from the index patient, but both MTMR12 and FAM134A variants were needed to slow the degradation of α1-antitrypsin variant Z in cells from a protected sib, indicating that inheritance of both variants is needed to mediate the pathogenic effects of hepatic proteotoxicity at the cellular level. Analysis of homozygote cohorts showed that multiple patient-specific variants in proteostasis genes are likely to explain liver disease susceptibility at the population level.

CONCLUSIONS

These results validate the concept that genetic variation in autophagy function can determine susceptibility to liver disease in α1-antitrypsin deficiency and provide evidence that polygenic mechanisms and multiple patient-specific variants are likely needed for proteotoxic pathology.

CLINICAL, LABORATORIAL AND EVOLUTIONARY ASPECTS OF PEDIATRIC PATIENTS WITH LIVER DISEASE DUE TO ALPHA 1-ANTITRYPSIN DEFICIENCY

BACKGROUND

Alpha 1-antitrypsin deficiency (AATD) is a hereditary codominant autosomal disease. This liver disease ranges from asymptomatic cases to terminal illness, which makes early recognition and diagnosis challenging. It is the main cause of pediatric liver transplantation after biliary atresia.

OBJECTIVE

To describe the clinical characteristics, as well as those of histologic and laboratory tests, phenotypic and/or genetic evaluation and evolution of a cohort of pediatric patients with AATD.

METHODS

This is a retrospective observational study of 39 patients with confirmed or probable AATD (without phenotyping or genotyping, but with suggestive clinical features, low serum alpha 1-antitrypsin (AAT) level and liver biopsy with PAS granules, resistant diastasis). Clinical, laboratory and histological varia-bles, presence of portal hypertension (PH) and survival with native liver have been analyzed.

RESULTS

A total of 66.7% of 39 patients were male (26/39). The initial manifestation was cholestatic jaundice in 79.5% (31/39). Liver transplantation was performed in 28.2% (11/39) of patients. Diagnosis occurred at an average of 3.1 years old and liver transplantation at 4.1 years of age. 89.2% (25/28) of the patients with confirmed AATD were PI*ZZ or ZZ. The average AAT value on admission for PI*ZZ or ZZ patients was 41.6 mg/dL. All transplanted patients with phenotyping or genotyping were PI*ZZ (or ZZ). Those who were jaundiced on admission were earlier referred to the specialized service and had higher levels of GGT and platelets on admission. There was no significant difference in the survival curve when comparing cholestatic jaundiced to non-cholestatic jaundiced patients on admission. Comparing patients who did or did not progress to PH, higher levels of AST and APRI score at diagnosis (P=0.011 and P=0.026, respectively) were observed and in the survival curves patients with PH showed impairment, with 20.2% survival with native liver in 15 years.

CONCLUSION

Jaundice is an important clinical sign that motivates referral to a specialist, but it does not seem to compromise survival with native liver. Patients progressing to PH had higher AST, APRi score on admission and significantly impaired survival with native liver. It is important to pay attention to these signs in the follow-up of patients with AATD.

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.

Resolution of hepatic fibrosis after ZFN-mediated gene editing in the PiZ mouse model of human α1-antitrypsin deficiency

BACKGROUND

α1-antitrypsin deficiency is most commonly caused by a mutation in exon-7 of SERPINA1 (SA1-ATZ), resulting in hepatocellular accumulation of a misfolded variant (ATZ). Human SA1-ATZ-transgenic (PiZ) mice exhibit hepatocellular ATZ accumulation and liver fibrosis. We hypothesized that disrupting the SA1-ATZ transgene in PiZ mice by in vivo genome editing would confer a proliferative advantage to the genome-edited hepatocytes, enabling them to repopulate the liver.

METHODS

To create a targeted DNA break in exon-7 of the SA1-ATZ transgene, we generated 2 recombinant adeno-associated viruses (rAAV) expressing a zinc-finger nuclease pair (rAAV-ZFN), and another rAAV for gene correction by targeted insertion (rAAV-TI). PiZ mice were injected i.v. with rAAV-TI alone or the rAAV-ZFNs at a low (7.5×1010vg/mouse, LD) or a high dose (1.5×1011vg/mouse, HD), with or without rAAV-TI. Two weeks and 6 months after treatment, livers were harvested for molecular, histological, and biochemical analyses.

RESULTS

Two weeks after treatment, deep sequencing of the hepatic SA1-ATZ transgene pool showed 6%±3% or 15%±4% nonhomologous end joining in mice receiving LD or HD rAAV-ZFN, respectively, which increased to 36%±12% and 36%±12%, respectively, 6 months after treatment. Two weeks postinjection of rAAV-TI with LD or HD of rAAV-ZFN, repair by targeted insertion occurred in 0.10%±0.09% and 0.25%±0.14% of SA1-ATZ transgenes, respectively, which increased to 5.2%±5.0% and 33%±13%, respectively, 6 months after treatment. Six months after rAAV-ZFN administration, there was a marked clearance of ATZ globules from hepatocytes, and resolution of liver fibrosis, along with reduction of hepatic TAZ/WWTR1, hedgehog ligands, Gli2, a TIMP, and collagen content.

CONCLUSIONS

ZFN-mediated SA1-ATZ transgene disruption provides a proliferative advantage to ATZ-depleted hepatocytes, enabling them to repopulate the liver and reverse hepatic fibrosis.

Quantitative measurement of the histological features of alpha-1 antitrypsin deficiency-associated liver disease in biopsy specimens

Background

Pathological mutations in Alpha-1 Antitrypsin (AAT) protein cause retention of toxic polymers in the hepatocyte endoplasmic reticulum. The risk for cirrhosis in AAT deficiency is likely directly related to retention of these polymers within the liver. Polymers are classically identified on liver biopsy as inclusion bodies by periodic acid schiff staining after diastase treatment and immunohistochemistry. However, characterization of the polymer burden within a biopsy sample is limited to a semi-quantitative scale as described by a pathologist. Better methods to quantify polymer are needed to advance our understanding of pathogenesis of disease. Therefore, we developed a method to quantify polymer aggregation from standard histologic specimens. In addition, we sought to understand the relationship of polymer burden and other histologic findings to the presence of liver fibrosis.

Methods

Liver samples from a well-categorized AATD cohort were used to develop histo-morphometric tools to measure protein aggregation.

Results

Whole-slide morphometry reliably quantifies aggregates in AATD individuals. Despite very low levels of inclusions present (0–0.41%), accumulation of globules is not linear and is associated with higher fibrosis stages. Immunohistochemistry demonstrates that fibrosis is associated with polymer accumulation and not total AAT. A proportion of patients were found to be “heavy accumulators” with a polymer burden above the upper 25% of normal distribution. Males had significantly more liver inclusions and polymer than females. These measurements also highlight interrelated phenotypes of hepatocellular degeneration and autophagy in AATD liver disease.

Conclusion

Quantitative inclusion analysis measures AAT accumulation in liver biopsy specimens. Quantification of polymer may identify individuals at risk for progressive disease and candidates for therapeutic interventions. Furthermore, these methods may be useful for evaluating efficacy of drugs targeting accumulation of AAT.

Long term results of liver transplantation for alpha-1 antitrypsin deficiency

INTRODUCTION

Liver transplantation (LT) is the therapeutic option for end-stage liver disease associated with alpha1 antitrypsin (A1AT) deficiency. The aim of the present retrospective study was to report on long-term outcomes following LT for A1AT deficiency.

METHODS

The medical records of 90 pediatric and adult patients transplanted between 1982 and 2017 in France and Geneva (Switzerland) were reviewed.

RESULTS

The study population consisted of 32 adults and 58 children; median age at transplant was 13.0 years (range: 0.2-65.1), and 65 were male (72.2%). Eighty-two patients (94.8% of children and 84.4% of adults) had the PI*ZZ genotype/phenotype and eight patients (8.9%) had the Pi*SZ genotype/phenotype. Eighty-four patients (93.3%) were transplanted for end-stage liver disease and six (all Pi*ZZ adults) for HCC. Median follow-up after LT was 13.6 years (0.1-31.7). The overall cumulative patient survival rates post-transplant were 97.8% at 1 year, and 95.5%, 95.5%, 92.0%, 89.1% at 5, 10, 15, 20 years respectively. The overall cumulative graft survival rates were 92.2% at 1 year, and 89.9%, 89.9%, 84.4%, 81.5% at 5, 10, 15 and 20 years, respectively.

CONCLUSIONS

In a representative cohort of patients having presented with end-stage-liver disease or HCC secondary to A1AT, liver transplantation offered very good patient and graft survival rates.

Hepatocyte proteomes reveal the role of protein disulfide isomerase 4 in alpha 1-antitrypsin deficiency

Background & Aims

A single point mutation in the Z-variant of alpha 1-antitrypsin (Z-AAT) alone can lead to both a protein folding and trafficking defect, preventing its exit from the endoplasmic reticulum (ER), and the formation of aggregates that are retained as inclusions within the ER of hepatocytes. These defects result in a systemic AAT deficiency (AATD) that causes lung disease, whereas the ER-retained aggregates can induce severe liver injury in patients with ZZ-AATD. Unfortunately, therapeutic approaches are still limited and liver transplantation represents the only curative treatment option. To overcome this limitation, a better understanding of the molecular basis of ER aggregate formation could provide new strategies for therapeutic intervention.

Methods

Our functional and omics approaches here based on human hepatocytes from patients with ZZ-AATD have enabled the identification and characterisation of the role of the protein disulfide isomerase (PDI) A4/ERP72 in features of AATD-mediated liver disease.

Results

We report that 4 members of the PDI family (PDIA4, PDIA3, P4HB, and TXNDC5) are specifically upregulated in ZZ-AATD liver samples from adult patients. Furthermore, we show that only PDIA4 knockdown or alteration of its activity by cysteamine treatment can promote Z-AAT secretion and lead to a marked decrease in Z aggregates. Finally, detailed analysis of the Z-AAT interactome shows that PDIA4 silencing provides a more conducive environment for folding of the Z mutant, accompanied by reduction of Z-AAT-mediated oxidative stress, a feature of AATD-mediated liver disease.

Conclusions

PDIA4 is involved in AATD-mediated liver disease and thus represents a therapeutic target for inhibition by drugs such as cysteamine. PDI inhibition therefore represents a potential therapeutic approach for treatment of AATD.

Lay summary

Protein disulfide isomerase (PDI) family members, and particularly PDIA4, are upregulated and involved in alpha 1-antitrypsin deficiency (AATD)-mediated liver disease in adults. PDI inhibition upon cysteamine treatment leads to improvements in features of AATD and hence represents a therapeutic approach for treatment of AATD-mediated liver disease.

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PDIA4 is upregulated and involved in alpha 1-antitrypsin deficiency (AATD)-mediated liver disease in adults.

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Knockdown of PDIA4 by siRNA or inhibition upon cysteamine treatment leads to improvements in features of AATD.

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RNA interference against PDIA4 or cysteamine represent approaches for treatment of AATD-mediated liver disease.

CHOP and c-JUN up-regulate the mutant Z α1-antitrypsin, exacerbating its aggregation and liver proteotoxicity

α₁-Antitrypsin (AAT) encoded by the SERPINA1 gene is an acute-phase protein synthesized in the liver and secreted into the circulation. Its primary role is to protect lung tissue by inhibiting neutrophil elastase. The Z allele of SERPINA1 encodes a mutant AAT, named ATZ, that changes the protein structure and leads to its misfolding and polymerization, which cause endoplasmic reticulum (ER) stress and liver disease through a gain-of-function toxic mechanism. Hepatic retention of ATZ results in deficiency of one of the most important circulating proteinase inhibitors and predisposes to early-onset emphysema through a loss-of-function mechanism. The pathogenetic mechanisms underlying the liver disease are not completely understood. C/EBP-homologous protein (CHOP), a transcription factor induced by ER stress, was found among the most up-regulated genes in livers of PiZ mice that express ATZ and in human livers of patients homozygous for the Z allele. Compared with controls, juvenile PiZ/Chop ^-/- mice showed reduced hepatic ATZ and a transcriptional response indicative of decreased ER stress by RNA-Seq analysis. Livers of PiZ/Chop ^-/- mice also showed reduced SERPINA1 mRNA levels. By chromatin immunoprecipitations and luciferase reporter-based transfection assays, CHOP was found to up-regulate SERPINA1 cooperating with c-JUN, which was previously shown to up-regulate SERPINA1, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. In summary, CHOP and c-JUN up-regulate SERPINA1 transcription and play an important role in hepatic disease by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.

Alpha-1 Antitrypsin Deficiency-Mediated Liver Toxicity: Why Do Some Patients Do Poorly? What Do We Know So Far?

Alpha-1 antitrypsin deficiency (AATD) is a rare genetic disease caused by mutations in the SERPINA1 gene and is associated with a decreased level of circulating alpha-1 antitrypsin (AAT). Among all the known mutations in the SERPINA1 gene, homozygous for the Z allele is well-known to result in both lung and liver disease. Unlike the lung injury that occurs in adulthood with the environment (notably, tobacco) as a co-factor, the hepatic damage is more complicated. Despite a common underlying gene mutation, the liver disease associated with AATD presents a considerable variability in the age-of-onset and severity, ranging from transient neonatal cholestasis (in early childhood) to cirrhosis and liver cancer (in childhood and adulthood). Given that all the cofactors- genetics and/or environmental- have not been fully identified, it is still impossible to predict which individuals with AATD may develop severe liver disease. The discovery of these modifiers represents the major challenge for the detection, diagnosis, and development of new therapies to provide alternative options to liver transplantation. The aim of this current review is to provide an updated overview of our knowledge on why some AATD patients associated with liver damage progress poorly.

Development of an RNAi therapeutic for alpha-1-antitrypsin liver disease

The autosomal codominant genetic disorder alpha-1 antitrypsin (AAT) deficiency (AATD) causes pulmonary and liver disease. Individuals homozygous for the mutant Z allele accumulate polymers of Z-AAT protein in hepatocytes, where AAT is primarily produced. This accumulation causes endoplasmic reticulum (ER) stress, oxidative stress, damage to mitochondria, and inflammation, leading to fibrosis, cirrhosis, and hepatocellular carcinoma. The magnitude of AAT reduction and duration of response from first-generation intravenously administered RNA interference (RNAi) therapeutic ARC-AAT and then with next-generation subcutaneously administered ARO-AAT were assessed by measuring AAT protein in serum of the PiZ transgenic mouse model and human volunteers. The impact of Z-AAT reduction by RNAi on liver disease phenotypes was evaluated in PiZ mice by measuring polymeric Z-AAT in the liver; expression of genes associated with fibrosis, autophagy, apoptosis, and redox regulation; inflammation; Z-AAT globule parameters; and tumor formation. Ultrastructure of the ER, mitochondria, and autophagosomes in hepatocytes was evaluated by electron microscopy. In mice, sustained RNAi treatment reduced hepatic Z-AAT polymer, restored ER and mitochondrial health, normalized expression of disease-associated genes, reduced inflammation, and prevented tumor formation. RNAi therapy holds promise for the treatment of patients with AATD-associated liver disease. ARO-AAT is currently in phase II/III clinical trials.

Alpha 1-Antitrypsin Deficiency: A Disorder of Proteostasis-Mediated Protein Folding and Trafficking Pathways

Human cells express large amounts of different proteins continuously that must fold into well-defined structures that need to remain correctly folded and assemble in order to ensure their cellular and biological functions. The integrity of this protein balance/homeostasis, also named proteostasis, is maintained by the proteostasis network (PN). This integrated biological system, which comprises about 2000 proteins (chaperones, folding enzymes, degradation components), control and coordinate protein synthesis folding and localization, conformational maintenance, and degradation. This network is particularly challenged by mutations such as those found in genetic diseases, because of the inability of an altered peptide sequence to properly engage PN components that trigger misfolding and loss of function. Thus, deletions found in the ΔF508 variant of the Cystic Fibrosis (CF) transmembrane regulator (CFTR) triggering CF or missense mutations found in the Z variant of Alpha 1-Antitrypsin deficiency (AATD), leading to lung and liver diseases, can accelerate misfolding and/or generate aggregates. Conversely to CF variants, for which three correctors are already approved (ivacaftor, lumacaftor/ivacaftor, and most recently tezacaftor/ivacaftor), there are limited therapeutic options for AATD. Therefore, a more detailed understanding of the PN components governing AAT variant biogenesis and their manipulation by pharmacological intervention could delay, or even better, avoid the onset of AATD-related pathologies.

Increased Frequency of Heterozygous Alpha-1-Antitrypsin Deficiency in Liver Explants From Nonalcoholic Steatohepatitis Patients

Cirrhotic explanted livers occasionally have unexpected periodic acid-Schiff-diastase (PASD)-positive globules within the hepatocyte cytoplasm. It is often unclear whether this finding is a nonspecific consequence of cirrhosis or is indicative of an underlying alpha-1-antitrypsin deficiency (A1ATD) contributing to the cirrhosis. In this study, explanted livers were retrospectively evaluated for histopathology (including PASD status with confirmatory alpha-1-antitrypsin [A1AT] immunohistochemistry [IHC]), and chart review provided etiology of liver failure and general clinical parameters. Real-time polymerase chain reaction was used to detect A1AT genotype (SERPINA1 S and Z alleles) by melting curve analysis on liver explant tissue from selected cases. Of 196 explanted livers, 21 (11%) had PASD+ globules, which were significantly enriched in patients with a clinical diagnosis of nonalcoholic steatohepatitis (NASH; 47%) compared with other causes (P < 0.001). IHC confirmed all PASD+ globules were A1AT+, with 20 of 21 cases demonstrating diffuse A1AT staining. In an expanded NASH cohort, 42% (14/33) of explants had PASD+ globules, 92% of which were homozygous (n = 1) or heterozygous (n = 11) for the SERPINA1 Z allele, corresponding to nearly 40% of all NASH patients. Overall, the Z allele was present in 10% of all tested liver explants, with 85% of PASD+ cases genotyping homozygous (n = 2) or heterozygous (n = 20), which is far in excess of the estimated 2% in the general population. These results indicate PASD+ A1AT globules (with confirmatory genotyping showing at least 1 Z allele) are commonly observed in NASH, suggesting a synergistic relationship toward liver fibrosis. In addition, the high frequency of SERPINA1 Z alleles in liver transplantation patients supports the utility of pretransplant genotyping.

Expression of mitochondrial membrane-linked SAB determines severity of sex-dependent acute liver injury

SH3 domain-binding protein that preferentially associates with Btk (SAB) is an outer-membrane docking protein for JNK-mediated impairment of mitochondrial function. Deletion of Sab in hepatocytes inhibits sustained JNK activation and cell death. The current study demonstrates that an increase in SAB expression enhanced the severity of acetaminophen-induced (APAP-induced) liver injury. Female mice were resistant to liver injury and exhibited markedly decreased hepatic SAB protein expression compared with male mice. The mechanism of SAB repression involved a pathway from ERα to p53 expression that induced miR34a-5p. miR34a-5p targeted the Sab mRNA coding region, thereby repressing SAB expression. Fulvestrant or p53 knockdown decreased miR34a-5p and increased SAB expression in female mice, leading to increased injury from APAP and TNF/galactosamine. In contrast, an ERα agonist increased p53 and miR34a-5p, which decreased SAB expression and hepatotoxicity in male mice. Hepatocyte-specific deletion of miR34a also increased the severity of liver injury in female mice, which was prevented by GalNAc-ASO knockdown of Sab. Similar to mice, premenopausal women expressed elevated levels of hepatic p53 and low levels of SAB, whereas age-matched men expressed low levels of p53 and high levels of SAB, but there was no difference in SAB expression between the sexes in the postmenopausal stage. In conclusion, SAB expression levels determined the severity of JNK-dependent liver injury. Female mice expressed low levels of hepatic SAB protein because of the ERα/p53/miR34a pathway, which repressed SAB expression and accounted for the resistance to liver injury seen in these females.

Genetic Causes of Liver Disease: When to Suspect a Genetic Etiology, Initial Lab Testing, and the Basics of Management

Genetic causes of liver disease lead to a wide range of presentations. This article describes hereditary hemochromatosis, Gilbert syndrome, alpha-1 antitrypsin deficiency, Wilson disease, PFIC, BRIC, and LAL-D. The most common cause of hereditary hemochromatosis is a C282Y mutation in the HFE gene. Gilbert syndrome is a benign cause of indirect hyperbilirubinemia. Alpha-1 antitrypsin deficiency causes both lung and liver disease. Wilson disease can cause neurologic disease and liver disease. Progressive familial intrahepatic cholestasis and benign recurrent intrahepatic cholestasis are rare causes of cholestasis. LAL-D is a rare disease that can appear similar to NAFLD in adults.

Evolving Trends in Liver Transplant for Metabolic Liver Disease in the United States

Indications for liver transplantation (LT) in metabolic disease are evolving. We reviewed the US experience with primary LT for metabolic disease in the Scientific Registry for Transplant Recipients (October 1987 to June 2017) to determine the following: temporal changes in indications, longterm outcomes, and factors predicting survival. Patients were grouped by the presence of structural liver disease (SLD) and whether the defect was confined to the liver. There were 5996 patients who underwent LT for metabolic disease, 2354 (39.3%) being children. LT for metabolic disease increased in children but not in adults. Children experienced a 6-fold increase in LT for metabolic disease without SLD. Indications for LT remained stable in adults. Living donor liver transplantation increased between era 1 and era 3 from 5.6% to 7.6% in children and 0% to 4.5% in adults. Patient and graft survival improved with time. The latest 5-year patient survival rates were 94.5% and 81.5% in children and adults, respectively. Outcomes were worse in adults and in those with extrahepatic disease (P < 0.01), whereas SLD did not affect outcomes. Survival improved with younger age at LT until age <2 years. On multivariate analysis, diagnostic category, inpatient status, age at LT, and transplant era significantly predicted outcomes in all ages with male sex predicting survival in childhood only. Children without structural disease were less likely to die awaiting LT and had improved post-LT survival compared with children with chronic liver disease. In conclusion, LT for metabolic disease is increasingly used for phenotypic correction in children; extrahepatic manifestations significantly impact survival at all ages; where indicated, transplantation should not be unnecessarily delayed; and the development of new allocation models may be required.

Heteropolymerization of α-1-antitrypsin mutants in cell models mimicking heterozygosity

The most common genotype associated with severe α-1-antitrypsin deficiency (AATD) is the Z homozygote. The Z variant (Glu342Lys) of α-1-antitrypsin (AAT) undergoes a conformational change and is retained within the endoplasmic reticulum (ER) of hepatocytes leading to the formation of ordered polymeric chains and inclusion bodies. Accumulation of mutated protein predisposes to cirrhosis whilst plasma AAT deficiency leads to emphysema. Increased risk of liver and lung disease has also been reported in heterozygous subjects who carry Z in association with the milder S allele (Glu264Val) or even with wild-type M. However, it is unknown whether Z AAT can co-polymerize with other AAT variants in vivo. We co-expressed two AAT variants, each modified by a different tag, in cell models that replicate AAT deficiency. We used pull-down assays to investigate interactions between co-expressed variants and showed that Z AAT forms heteropolymers with S and with the rare Mmalton (Phe52del) and Mwurzburg (Pro369Ser) mutants, and to a lesser extent with the wild-type protein. Heteropolymers were recognized by the 2C1 mAb that binds to Z polymers in vivo. There was increased intracellular accumulation of AAT variants when co-expressed with Z AAT, suggesting a dominant negative effect of the Z allele. The molecular interactions between S and Z AAT were confirmed by confocal microscopy showing their colocalization within dilated ER cisternae and by positivity in Proximity Ligation Assays. These results provide the first evidence of intracellular co-polymerization of AAT mutants and contribute to understanding the risk of liver disease in SZ and MZ heterozygotes.

Hepatic-targeted RNA interference provides robust and persistent knockdown of alpha-1 antitrypsin levels in ZZ patients

BACKGROUND & AIMS

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder causing pulmonary and liver disease. The PiZ mutation in AAT (SERPINA1) results in mis-folded AAT protein (Z-AAT) accumulating in hepatocytes, leading to fibrosis and cirrhosis. RNAi-based therapeutics silencing production of hepatic Z-AAT might benefit patients with AATD-associated liver disease. This study evaluated an RNAi therapeutic to silence production of AAT.

METHODS

Part A of this double-blind first-in-human study randomized 54 healthy volunteers (HVs) into single dose cohorts (two placebo: four active), receiving escalating doses of the investigational agent ARC-AAT from 0.38 to 8.0 mg/kg or placebo. Part B randomized 11 patients with PiZZ (homozygous for Z-AAT) genotype AATD, who received up to 4.0 mg/kg of ARC-AAT or placebo. Patients with baseline FibroScan® >11 kPa or forced expiratory volume in one second (FEV1) <60% were excluded. Assessments included safety, pharmacokinetics, and change in serum AAT concentrations.

RESULTS

A total of 36 HVs received ARC-AAT and 18 received placebo (part A). Seven PiZZ individuals received ARC-AAT and four received placebo (part B). A dose response in serum AAT reduction was observed at doses ≥4 mg/kg with similar relative reductions in PiZZ patients and HVs at 4 mg/kg and a maximum reduction of 76.1% (HVs) vs. 78.8% (PiZZ) at this dose. The time it took for serum AAT to return to baseline was similar for HV and PiZZ. There were no notable differences between HV and PiZZ safety parameters. The study was terminated early because of toxicity findings related to the delivery vehicle (ARC-EX1) seen in a non-human primate study.

CONCLUSION

PiZZ patients and HVs responded similarly to ARC-AAT. Deep and durable knockdown of hepatic AAT production based on observed reduction in serum AAT concentrations was demonstrated.

LAY SUMMARY

Accumulation of abnormal proteins in the livers of patients with alpha-1 antitrypsin deficiency may lead to decreased liver function and potentially liver failure. Therapeutics targeting the production of these abnormal proteins may be used to prevent or treat liver disease in patients with alpha-1 antitrypsin deficiency.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02363946.

Alpha-1 antitrypsin deficiency: outstanding questions and future directions

Background

Alpha-1 antitrypsin deficiency (AATD) is a rare hereditary condition that leads to decreased circulating alpha-1 antitrypsin (AAT) levels, significantly increasing the risk of serious lung and/or liver disease in children and adults, in which some aspects remain unresolved.

Methods

In this review, we summarise and update current knowledge on alpha-1 antitrypsin deficiency in order to identify and discuss areas of controversy and formulate questions that need further research.

Results

1) AATD is a highly underdiagnosed condition. Over 120,000 European individuals are estimated to have severe AATD and more than 90% of them are underdiagnosed.

Conclusions

2) Several clinical and etiological aspects of the disease are yet to be resolved. New strategies for early detection and biomarkers for patient outcome prediction are needed to reduce morbidity and mortality in these patients; 3) Augmentation therapy is the only specific approved therapy that has shown clinical efficacy in delaying the progression of emphysema. Regrettably, some countries reject registration and reimbursement for this treatment because of the lack of larger randomised, placebo-controlled trials. 4) Alternative strategies are currently being investigated, including the use of gene therapy or induced pluripotent stem cells, and non-augmentation strategies to prevent AAT polymerisation inside hepatocytes.

Retrospective analysis of children with α-1 antitrypsin deficiency

BACKGROUND

α-1 Antitrypsin (AAT) deficiency is the most frequently occurring genetic liver disorder. The association among classical α-1 antitrypsin deficiency (AATD), chronic liver disease, and cirrhosis is common in adult patients but rare in children.

AIM

To assess the clinical characteristics of children with AATD and to compare symptoms between homozygous and heterozygous children.

MATERIALS AND METHODS

The study included 20 children who were found to have mutant Pi alleles. AAT phenotyping was conducted on patients with a low serum AAT level. The exclusion criteria included infectious, anatomic, and metabolic conditions. Symptoms on presentation, physical examination findings, laboratory values, liver biopsy results, and follow-up periods were recorded for each patient.

RESULTS

The patients included six (30%) girls and 14 (70%) boys, with a mean age of 6.3±5.1 (1-16) years. The PiZZ phenotype was present in eight (40%) and PiMZ in 12 (60%) patients. The most frequent symptom was elevated liver function test results. Three patients were referred with neonatal cholestasis and one with compensated cirrhosis. Eight patients underwent liver biopsy; all patients except one had periodic acid-Schiff-positive diastase-resistant globules in the hepatocytes. The mean follow-up period was 34±33 (12-101) months. At the end of follow-up, all patients with PiZZ were found to have chronic hepatitis, and one with cirrhosis. On the contrary, two patients with PiMZ were found to have chronic hepatitis.

CONCLUSION

Children with classical AATD commonly have chronic liver disease. In heterozygous (PiMZ) children with AATD, enzyme levels can normalize with occasional fluctuations, sometimes causing delayed diagnosis.

Heterozygosity for the alpha-1-antitrypsin Z allele in cirrhosis is associated with more advanced disease

Alpha-1-antitrypsin deficiency (A1ATD) due to homozygosity for the Z allele (ZZ) is an established risk factor for cirrhosis, but the liver disease risk in heterozygous Z allele carriers (MZ) is controversial. The aim of the present study was to determine the prevalence of the MZ genotype among patients with cirrhosis and the associated risk of decompensation and liver transplantation/mortality. An unselected cohort of 561 patients with cirrhosis and 248 deceased liver donors were genotyped for the A1ATD risk alleles Z and S using a validated allelic discrimination assay. Clinical and biochemical parameters were assessed in 488 genotype MM and 52 MZ patients at baseline when cirrhosis was diagnosed and at the last contact, before liver transplantation or death, as study endpoints. MZ prevalence was 2.8% among liver donors, 5.8%, 9.1%, 10.9%, and 19.0% in patients with cirrhosis and Model for End-Stage Liver Disease-sodium (MELD-Na) ≤10, 11-20, 21-30, and >30, respectively. Among liver transplant recipients, MZ prevalence was 9.7%. MS prevalence was not different between donors, patients with cirrhosis, or transplant recipients. At the end of follow-up, MELD-Na scores were higher among heterozygous Z risk allele carriers (16 versus 19; P = 0.03). Decompensation of cirrhosis with ascites or encephalopathy was significantly more frequent in patients with MZ than in MM patients. In the subgroup with transferrin (Tf) saturation >50% or Tf <180 mg/dL, MZ patients had a significantly higher risk of liver transplantation or death than MM patients. In conclusion, the genotype MZ is a genetic risk factor for more advanced cirrhosis and decompensation. MZ patients with cirrhosis and hypotransferrinemia or increased Tf saturation are at higher risk of death and liver transplantation. Liver Transplantation 24 744-751 2018 AASLD.

Genetic Testing in Liver Disease: What to Order, in Whom, and When

Genetic causes of liver disease lead to a wide range of presentations, from mildly abnormal liver tests to acute liver failure. This article discusses the indications for testing and what to test for hereditary hemochromatosis, progressive familial intrahepatic cholestasis, benign recurrent intrahepatic cholestasis, lysosomal acid lipase deficiency, Gilbert syndrome, alpha-1 antitrypsin deficiency, and Wilson disease.

Liver Disease in Alpha-1 Antitrypsin Deficiency: Current Approaches and Future Directions

Purpose of Review

The aim of the study is to review the liver disease caused by alpha-1 antitrypsin deficiency (A1ATD), including pathogenesis, epidemiology, diagnostic testing, and recent therapeutic developments.

Recent Findings

Therapeutic approaches target several intracellular pathways to reduce the cytotoxic effects of the misfolded mutant globular protein (ATZ) on the hepatocyte. These include promoting ATZ transport out of the endoplasmic reticulum (ER), enhancing ATZ degradation, and preventing ATZ globule-aggregation.

Summary

A1ATD is the leading genetic cause of liver disease among children. It is a protein-folding disorder in which toxic insoluble ATZ proteins aggregate in the ER of hepatocytes leading to inflammation, fibrosis, cirrhosis, and increased risk of hepatocellular carcinoma. The absence of the normal A1AT serum protein also predisposes patients to pan lobar emphysema as adults. At this time, the only approved therapy for A1ATD-associated liver disease is orthotopic liver transplantation, which is curative. However, there has been significant recent progress in the development of small molecule therapies with potential both to preserve the native liver and prevent hepatotoxicity.

Liver Transplantation in Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin (AAT) deficiency is a common inherited metabolic disorder caused by a point mutation in the SERPIN1A gene. A small portion of homozygous PI*ZZ individuals develop severe liver disease that requires liver transplantation. Posttransplant survival is excellent. The largest burden of advanced liver disease lies within the adult population rather than children. Evaluation of lung function in adults before transplant is essential because of the underlying risk for chronic obstructive pulmonary disease. Post-liver transplantation lung function should also be monitored for decline. Although uncommon, cases of simultaneous lung and liver transplant for AAT deficiency have been reported.

α1-antitrypsin Deficiency: A Misfolded Secretory Protein Variant with Unique Effects on the Endoplasmic Reticulum

In the classical form of α1-antitrypsin deficiency (ATD) a point mutation leads to accumulation of a misfolded secretory glycoprotein in the endoplasmic reticulum (ER) of liver cells and so ATD has come to be considered a prototypical ER storage disease. It is associated with two major types of clinical disorders, chronic obstructive pulmonary disease (COPD) by loss-of-function mechanisms and hepatic cirrhosis and carcinogenesis by gain-of-function mechanisms. The lung disease predominantly results from proteolytic damage to the pulmonary connective tissue matrix because of reduced levels of protease inhibitor activity of α1-anitrypsin (AT) in the circulating blood and body fluids. Cigarette smoking is a powerful disease-promoting modifier but other modifiers are known to exist because variation in the lung disease phenotype is still found in smoking and non-smoking homozygotes. The liver disease is highly likely to be caused by the proteotoxic effects of intracellular misfolded protein accumulation and a high degree of variation in the hepatic phenotype among affected homozygotes has been hypothetically attributed to genetic and environmental modifiers that alter proteostasis responses. Liver biopsies of homozygotes show intrahepatocytic inclusions with dilation and expansion of the ER and recent studies of iPS-derived hepatocyte-like cells from individuals with ATD indicate that the changes in the ER directly vary with the hepatic phenotype i.e there is much lesser alteration in the ER in cells derived from homozygotes that do not have clinically significant liver disease. From a signaling perspective, studies in mammalian cell line and animal models expressing the classical α1-antitrypsin Z variant (ATZ) have found that ER signaling is perturbed in a relatively unique way with powerful activation of autophagy and the NFκB pathway but relatively limited, if any, UPR signaling. It is still not known how much these unique structural and functional changes and the variation among affected homozygotes relate to the tendency of this variant to polymerize and aggregate and/or to the repertoire of proteostasis mechanisms that are activated.