Inherited metabolic disease of the liver

Cell therapy for liver disorders: past, present and future

The liver fulfils a plethora of vital functions and, due to their importance, liver dysfunction has life-threatening consequences. Liver disorders currently account for more than two million deaths annually worldwide and can be classified broadly into three groups, considering their onset and aetiology, as acute liver diseases, inherited metabolic disorders and chronic liver diseases. In the most advanced and severe forms leading to liver failure, liver transplantation is the only treatment available, which has many associated drawbacks, including a shortage of organ donors. Cell therapy via fully mature cell transplantation is an advantageous alternative that may be able to restore a damaged organ's functionality or serve as a bridge until regeneration can occur. Pioneering work has shown that transplanting adult hepatocytes can support liver recovery. However, primary hepatocytes cannot be grown extensively in vitro as they rapidly lose their metabolic activity. Therefore, different cell sources are currently being tested as alternatives to primary cells. Human pluripotent stem cell-derived cells, chemically induced liver progenitors, or 'liver' organoids, hold great promise for developing new cell therapies for acute and chronic liver diseases. This Review focuses on the advantages and drawbacks of distinct cell sources and the relative strategies to address different therapeutic needs in distinct liver diseases.

Cure of Congenital Purpura Fulminans via Expression of Engineered Protein C Through Neonatal Genome Editing in Mice

BACKGROUND

PC (protein C) is a plasma anticoagulant encoded by PROC; mutation in both PROC alleles results in neonatal purpura fulminans-a fatal systemic thrombotic disorder. In the present study, we aimed to develop a genome editing treatment to cure congenital PC deficiency.

METHODS

We generated an engineered APC (activated PC) to insert a furin-cleaving peptide sequence between light and heavy chains. The engineered PC was expressed in the liver of mice using an adeno-associated virus vector or CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9)-mediated genome editing using an adeno-associated virus vector in vivo.

RESULTS

The engineered PC could be released in its activated form and significantly prolonged the plasma coagulation time independent of the cofactor activity of PS (protein S) in vitro. The adeno-associated virus vector-mediated expression of the engineered PC, but not wild-type PC, prolonged coagulation time owing to the inhibition of activated coagulation FV (factor V) in a dose-dependent manner and abolished pathological thrombus formation in vivo in C57BL/6J mice. The insertion of EGFP (enhanced green fluorescent protein) sequence conjugated with self-cleaving peptide sequence at Alb locus via neonatal in vivo genome editing using adeno-associated virus vector resulted in the expression of EGFP in 7% of liver cells, mainly via homology-directed repair, in mice. Finally, we succeeded in improving the survival of PC-deficient mice by expressing the engineered PC via neonatal genome editing in vivo.

CONCLUSIONS

These results suggest that the expression of engineered PC via neonatal genome editing is a potential cure for severe congenital PC deficiency.

Disrupting Poly(ADP-ribosyl)ating Pathway Creates Premalignant Conditions in Mammalian Liver

Hepatocellular carcinoma (HCC) is a major global health concern, representing one of the leading causes of cancer-related deaths. Despite various treatment options, the prognosis for HCC patients remains poor, emphasizing the need for a deeper understanding of the factors contributing to HCC development. This study investigates the role of poly(ADP-ribosyl)ation in hepatocyte maturation and its impact on hepatobiliary carcinogenesis. A conditional Parg knockout mouse model was employed, utilizing Cre recombinase under the albumin promoter to target Parg depletion specifically in hepatocytes. The disruption of the poly(ADP-ribosyl)ating pathway in hepatocytes affects the early postnatal liver development. The inability of hepatocytes to finish the late maturation step that occurs early after birth causes intensive apoptosis and acute inflammation, resulting in hypertrophic liver tissue with enlarged hepatocytes. Regeneration nodes with proliferative hepatocytes eventually replace the liver tissue and successfully fulfill the liver function. However, early developmental changes predispose these types of liver to develop pathologies, including with a malignant nature, later in life. In a chemically induced liver cancer model, Parg-depleted livers displayed a higher tendency for hepatocellular carcinoma development. This study underscores the critical role of the poly(ADP-ribosyl)ating pathway in hepatocyte maturation and highlights its involvement in liver pathologies and hepatobiliary carcinogenesis. Understanding these processes may provide valuable insights into liver biology and liver-related diseases, including cancer.

Successful Treatment of Refractory Anemia in a Patient With Glycogen Storage Disease Type Ia Undergoing Hemodialysis

Glycogen storage disease type Ⅰa (GSDIa), also known as von Gierke disease, is a rare inherited metabolic disorder caused by defective glucose 6-phosphatase (G6Pase) activity. Although anemia, renal failure, and hepatic adenoma are the major clinical manifestations of GSDIa, there has been no report of refractory anemia in GSDIa patients on maintenance hemodialysis (HD) concomitant with multiple liver adenomas. Herein, we present a case of refractory anemia in a patient with GSDIa undergoing HD with multiple hepatic adenomas, successfully managed through aggressive treatment for renal anemia and intravenous iron therapy (IIT).

A 26-year-old man with GSDIa who had been on HD for a year suffered from refractory anemia. He had experienced hypoglycemia and hyperlactic acidemia repeatedly and unusual hypertriglyceridemia had been observed for a long time. In addition, multiple hepatic adenomas developed and his renal function gradually declined, eventually progressing to end-stage kidney disease, and HD was started. Despite 120 µg/week of darbepoetin alfa (DA), 200 mg/day of oral sodium ferrous citrate, and 600 mg/week of roxadustat, the anemia persisted and iron deficiency gradually progressed. We considered that renal anemia, blood loss by each HD session, and decreased intestinal iron absorption due to inappropriately increased hepcidin from hepatic adenomas were the main etiology of the anemia; hence, we changed oral sodium ferrous citrate to intravenous saccharated ferric oxide along with continuous aggressive treatment of renal anemia, and the anemia resolved quickly within three months.

We believe that refractory anemia was mainly induced by renal anemia and chronic iron deficiency due to blood loss during HD and inappropriately elevated hepcidin levels in hepatic adenomas. Aggressive treatment of renal anemia, along with IIT, may be a promising treatment option. Strict monitoring of iron overload is essential for safe treatment.

Bamboo Stems (Phyllostachys nigra variety henosis) Containing Polyphenol Mixtures Activate Nrf2 and Attenuate Phenylhydrazine-Induced Oxidative Stress and Liver Injury

This study was designed to investigate the hepatoprotective effect of bamboo stems using in vitro and in vivo experimental liver damage models. Ethyl acetate fraction of 80% ethanol extract of Phyllostachys nigra stem (PN3) containing polyphenols had a higher NQO1-ARE reporter gene activity as monitored by the activity of the NF-E2-related factor (Nrf2) antioxidant pathway in cells in comparison to extracts from other species and under other conditions. The Nrf2 was translocated from the cytosol to the nucleus in response to PN3, followed by induction of the Nrf2 target gene expression, including HO-1, GCL, and NQO-1 in HepG2 cells. Phosphorylation of Nrf2 in HepG2 cells was enhanced in PN3, which was mediated by PKCδ, ERK, and p38 MAPK. Consequently, PN3 inhibited arachidonic acid (AA) + iron-induced reactive oxygen species generation and glutathione depletion, and, thus, highlighted their role in cytotoxicity. Treatment with major polyphenols of PN3, including catechin, chlorogenic acid, caffeic acid, and p-coumaric acid, also improved AA + iron-mediated oxidative stress and, thus, improved cell viability. Treatment with phenylhydrazine in mice, i.e., the iron overload liver injury model, increased plasma alanine aminotransferase and aspartate aminotransferase levels and changed histological features in mice—a response that was almost completely blocked by PN3 administration. Moreover, PN3 extract mitigated phenylhydrazine-induced oxidative stress and inflammatory responses. Conclusively, PN3 can exert a hepatoprotective effect against iron overload-induced acute liver damage due to its antioxidant properties.

Non-HFE mutations in haemochromatosis in China: combination of heterozygous mutations involving HJV signal peptide variants

INTRODUCTION

Hereditary haemochromatosis (HH) caused by a homozygous p.C282Y mutation in haemochromatosis (HFE) gene has been well documented. However, less is known about the causative non-HFE mutation. We aimed to assess mutation patterns of haemochromatosis-related genes in Chinese patients with primary iron overload.

METHODS

Patients were preanalysed for mutations in the classic HH-related genes: HFE, HJV, HAMP, TFR2 and SLC40A1. Whole exome sequencing was conducted for cases with variants in HJV signal peptide region. Representative variants were analysed for biological function.

RESULTS

None of the cases analysed harboured the HFE p.C282Y; however, 21 of 22 primary iron-overload cases harboured at least one non-synonymous variant in the non-HFE genes. Specifically, p.E3D or p.Q6H variants in the HJV signal peptide region were identified in nine cases (40.9%). In two of three probands with the HJV p.E3D, exome sequencing identified accompanying variants in BMP/SMAD pathway genes, including TMPRSS6 p.T331M and BMP4 p.R269Q, and interestingly, SUGP2 p.R639Q was identified in all the three cases. Pedigree analysis showed a similar pattern of combination of heterozygous mutations in cases with HJV p.E3D or p.Q6H, with SUGP2 p.R639Q or HJV p.C321X being common mutation. In vitro siRNA interference of SUGP2 showed a novel role of downregulating the BMP/SMAD pathway. Site-directed mutagenesis of HJV p.Q6H/p.C321X in cell lines resulted in loss of membrane localisation of mutant HJV, and downregulation of p-SMAD1/5 and HAMP.

CONCLUSION

Compound heterozygous mutations of HJV or combined heterozygous mutations of BMP/SMAD pathway genes, marked by HJV variants in the signal peptide region, may represent a novel aetiological factor for HH.

Recent advance in the molecular genetics of Wilson disease and hereditary hemochromatosis

Metabolic liver diseases such as Wilson disease (WD) and hereditary hemochromatosis (HH) possess complicated pathogenesis and typical hereditary characteristics with the hallmarks of a deficiency in metal metabolism. Mutations in genes encoding ATPase, Cu + transporting, beta polypeptide (ATP7B) and hemochromatosis (HFE) or several non-HFE genes are considered to be causative for WD and HH, respectively. Although the identification of novel mutations in ATP7B for WD and HFE or the non-HFE genes for HH has increased, especially with the application of whole genome sequencing technology in recent years, the biological function of the identified mutations, as well as genotype-phenotype correlations remain to be explored. Further analysis of the causative gene mutation would be critical to clarify the mechanisms underlying specific disease phenotypes. In this review, we therefore summarize the recent advances in the molecular genetics of WD and HH including the updated mutation spectrums and the correlation between genotype and phenotype, with an emphasis on biological functional studies of the individual mutations identified in WD and HH. The weakness of the current functional studies and analysis for the clinical association of the individual mutation was also discussed. These works are essential for the understanding of the association between genotypes and phenotypes of these inherited metabolic liver diseases.

The Role of Iron and Iron Overload in Chronic Liver Disease

The liver plays a major role in iron homeostasis; thus, in patients with chronic liver disease, iron regulation may be disturbed. Higher iron levels are present not only in patients with hereditary hemochromatosis, but also in those with alcoholic liver disease, nonalcoholic fatty liver disease, and hepatitis C viral infection. Chronic liver disease decreases the synthetic functions of the liver, including the production of hepcidin, a key protein in iron metabolism. Lower levels of hepcidin result in iron overload, which leads to iron deposits in the liver and higher levels of non-transferrin-bound iron in the bloodstream. Iron combined with reactive oxygen species leads to an increase in hydroxyl radicals, which are responsible for phospholipid peroxidation, oxidation of amino acid side chains, DNA strain breaks, and protein fragmentation. Iron-induced cellular damage may be prevented by regulating the production of hepcidin or by administering hepcidin agonists. Both of these methods have yielded successful results in mouse models.

Genetic diseases that predispose to early liver cirrhosis

Inherited liver diseases are a group of metabolic and genetic defects that typically cause early chronic liver involvement. Most are due to a defect of an enzyme/transport protein that alters a metabolic pathway and exerts a pathogenic role mainly in the liver. The prevalence is variable, but most are rare pathologies. We review the pathophysiology of such diseases and the diagnostic contribution of laboratory tests, focusing on the role of molecular genetics. In fact, thanks to recent advances in genetics, molecular analysis permits early and specific diagnosis for most disorders and helps to reduce the invasive approach of liver biopsy.

Gaucher disease and malignancy: a model for cancer pathogenesis in an inborn error of metabolism

Clinical observations spanning almost half a century have demonstrated a consistent association of type 1 Gaucher disease (GD1) and cancers. However, the cellular and molecular bases of the association are not understood. Gaucher disease (GD) is a lysosomal storage disorder due to an inherited deficiency of acid β-glucosidase that underlies the accumulation of glucosylceramide in lysosomes of mononuclear phagocytes and immune dysregulation. The overall cancer risk is markedly increased in GD, and the determinants of malignancy in a subset of patients with GD1 are not known. The association of GD and cancer is most striking for hematological malignancies, with the risk for multiple myeloma estimated at almost 37-fold compared to the general population; some studies have also suggested increased cancer risk for non-hematological malignancies. There is no association of overall severity of GD to risk of cancer, although there is an increased prevalence of splenectomy among patients exhibiting the GD/cancer phenotype. Moreover, there appears to be an increased incidence of multiple consecutive cancers in individual patients. Several factors could contribute to cancer development in GD, including polarization of macrophages to the alternatively activated phenotype, chronic inflammation, chronic B-cell stimulation, splenectomy, hyperferritinemia, lysosomal dysfunction, and endoplasmic reticulum stress. Recent studies have highlighted T-cell dysfunction and modifier genes contributing to an increased cancer risk in GD. Macrophage-targeted enzyme replacement therapy (ERT) reverses systemic features of GD1; while cancer risk appears to be reduced in the era of ERT, it is not known whether this is a direct effect of therapy. Delineation of the mechanisms underlying the increased cancer risk in GD will provide additional novel insights into the role of lipids and macrophages in cancer pathogenesis and, moreover, have the potential to reveal novel therapeutic targets.

Hereditary pancreatic and hepatobiliary cancers

Hereditary etiologies of pancreatic and hepatobiliary cancers are increasingly recognized. An estimated >10% of pancreatic and increasing number of hepatobiliary cancers are hereditary. The cumulative risk of hereditary pancreatic cancer ranges from measurable but negligible in cystic fibrosis to a sobering 70% in cases of hereditary pancreatitis. Candidates for pancreatic cancer surveillance are those with a risk pancreatic cancer estimated to be >10-fold that of the normal population. Screening for pancreatic cancer in high-risk individuals is typically performed by endoscopic ultrasound and should begin at least 10 years prior to the age of the youngest affected relative. Disease states known to be associated with increased risk of hepatocellular cancer include hereditary hemochromatosis, autoimmune hepatitis, porphyria, and α1-antitrypsin deficiency, with relative risks as high as 36-fold. Although much less is known about hereditary bile-duct cancers, Muir-Torre syndrome and bile salt export pump deficiency are diseases whose association with hereditary carcinogenesis is under investigation.

Inherited hepatocellular carcinoma

Inherited liver disorders that cause chronic inflammation, fibrosis, and cirrhosis can lead to the development of liver cancer. Because of the rarity and diversity of some of these syndromes, the relative risk of developing HCC in these patients and the age at which tumours typically arise cannot be accurately estimated. Among patients with hereditary hemachromatosis (HH), the annual incidence of HCC is 4% once cirrhosis has been established. Fibrosis and portal hypertension associated with HH can be partially reversed with therapeutic phlebotomy, but it is unclear whether this treatment alters the incidence of HCC in these patients. Importantly, it seems likely that coincidence of these genetic disorders with known HCC risk factors such as alcoholism and viral hepatitis would amplify their oncogenic potential. For this reason, patients with known genetic disorders of the liver should be repeatedly counselled to avoid environmental and toxic injury to the liver. Treatment of HCC in patients with inherited liver disease mirrors that of HCC associated with other etiologies. Unfortunately, there are case series which suggest these patients with inherited liver disease and HCC tend to present at more advanced stages and are therefore not eligible for curative therapies, causing overall decreased survival relative to patients with HCC of viral or other etiologies.

Hepatocellular carcinoma: prevalence and molecular pathogenesis of Helicobacter spp

Helicobacter pylori infection is one of the most common chronic bacterial infections in humans. The association of other Helicobacter spp. with extragastric diseases in animals is well established, and a role of these bacteria in human liver disease is becoming clearer. Several case-control studies have reported possible associations of Helicobacter spp. with various liver diseases, including hepatocellular carcinoma, which is the fifth most common type of carcinoma among men worldwide, and the eighth most common among women. Thus, it is important to understand molecular mechanisms that may lead to hepatotoxicity or hepatocellular dysfunction in which Helicobacter spp. may play a role in inducing malignant transformation of liver cells.

Caring for adults with pediatric liver disease

The etiology of liver disease in childhood varies significantly from its etiology in the adult population. More children with complex diseases are surviving into adulthood, providing challenges to the primary care provider. Adults with pediatric liver disease differ in management, treatment, complications, and extrahepatic considerations. To provide these patients with an optimal transition into the adult health care system, the provider needs a comprehensive knowledge of the common causes of childhood liver disease and their implications and must understand the differences in caring for these patients. This review addresses some of the most common childhood liver diseases, their causes, presentation, evaluation, management, complications, and additional concerns.

Mutation in the abcb7 gene causes abnormal iron and fatty acid metabolism in developing medaka fish

The medaka fish (Oryzias latipes) is an emerging model organism for which a variety of unique developmental mutants have now been generated. Our recent mutagenesis screening of the medaka isolated a unique mutant that develops a fatty liver at larval stages. Positional cloning identified the responsible gene as medaka abcb7. Abcb7, a mitochondrial ABC (ATP binding cassette) half-transporter, has been implicated in iron metabolism. Recently, human Abcb7 was found to be mutated in X-linked sideroblastic anemia with cerebellar ataxia (XLSA/A). The homozygous medaka mutant exhibits abnormal iron metabolism in erythrocytes and accumulation of lipid in the liver. Microarray and in situ hybridization analyses demonstrated that the expression of genes involved in iron and lipid metabolisms are both affected in the mutant liver, suggesting novel roles of Abcb7 in the development of physiologically functional liver. The medaka abcb7 mutant thus could provide insights into the pathogenesis of XLSA/A as well as the normal function of the gene.