HFE mutations in alpha-1-antitrypsin deficiency: an examination of cirrhotic explants

Living with the enemy: from protein-misfolding pathologies we know, to those we want to know

Conformational diseases are caused by the aggregation of misfolded proteins. The risk for such pathologies develops years before clinical symptoms appear, and is higher in people with alpha-1 antitrypsin (AAT) polymorphisms. Thousands of people with alpha-1 antitrypsin deficiency (AATD) are underdiagnosed. Enemy-aggregating proteins may reside in these underdiagnosed AATD patients for many years before a pathology for AATD fully develops. In this perspective review, we hypothesize that the AAT protein could exert a new and previously unconsidered biological effect as an endogenous metal ion chelator that plays a significant role in essential metal ion homeostasis. In this respect, AAT polymorphism may cause an imbalance of metal ions, which could be correlated with the aggregation of amylin, tau, amyloid beta, and alpha synuclein proteins in type 2 diabetes mellitus (T2DM), Alzheimer's and Parkinson's diseases, respectively.

National trends and outcomes of genetically inherited non-alcoholic chronic liver disease in the USA: estimates from the National Inpatient Sample (NIS) database

Background

Medical literature on the prevalence of genetic liver disease is lacking. In this study, we investigated the in-hospital healthcare and economic burden from genetic causes of non-alcoholic chronic liver disease (NACLD) and non-alcoholic liver cirrhosis (NALC) in the USA.

Methods

Data were abstracted from the National Inpatient Sample database between 2002 and 2014 using ICD9 codes for patients discharged with NACLD and NALC secondary to genetic diseases including alpha-1 antitrypsin deficiency (A1ATd), cystic fibrosis (CF), Wilson disease (WD), hereditary hemochromatosis (HHC), glycogen storage disease, and disorders of aromatic amino-acid metabolism (DAAAM).

Results

Throughout the study period, there were 19,332 discharges for NACLD associated with the six genetic diseases including 14,368 for NALC. There were $1.09 billion in hospital charges, 790 in-hospital deaths, and 955 liver transplants performed. Overall, A1ATd was associated with 8,983 (62.52%) hospitalizations for NALC followed by WD, CF, and HHC. The highest in-hospital mortality was seen with HHC. The greatest frequency of liver transplants was seen with DAAAM.

Conclusion

The number of hospitalizations for genetic liver diseases continues to increase. With increased funding and directed research efforts, we can aim to improve medical treatments and the quality of life for patients at risk for liver deterioration.

Mild Iron Overload as Seen in Individuals Homozygous for the Alpha-1 Antitrypsin Pi*Z Variant Does Not Promote Liver Fibrogenesis in HFE Knockout Mice

The presence of the homozygous 'Pi*Z' variant of alpha-1 antitrypsin (AAT) ('Pi*ZZ' genotype) predisposes to liver fibrosis development, but the role of iron metabolism in this process remains unknown. Therefore, we assessed iron metabolism and variants in the Homeostatic Iron Regulator gene (HFE) as the major cause of hereditary iron overload in a large cohort of Pi*ZZ subjects without liver comorbidities. The human cohort comprised of 409 Pi*ZZ individuals and 254 subjects without evidence of an AAT mutation who were recruited from ten European countries. All underwent a comprehensive work-up and transient elastography to determine liver stiffness measurements (LSM). The corresponding mouse models (Pi*Z overexpressors, HFE knockouts, and double transgenic [DTg] mice) were used to evaluate the impact of mild iron overload on Pi*Z-induced liver injury. Compared to Pi*Z non-carriers, Pi*ZZ individuals had elevated serum iron, transferrin saturation, and ferritin levels, but relevant iron overload was rare. All these parameters were higher in individuals with signs of significant liver fibrosis (LSM ≥ 7.1 kPa) compared to those without signs of significant liver fibrosis. HFE knockout and DTg mice displayed similar extent of iron overload and of fibrosis. Loss of HFE did not alter the extent of AAT accumulation. In Pi*ZZ individuals, presence of HFE mutations was not associated with more severe liver fibrosis. Taken together, Pi*ZZ individuals display minor alterations in serum iron parameters. Neither mild iron overload seen in these individuals nor the presence of HFE mutations (C282Y and H63D) constitute a major contributor to liver fibrosis development.

ERAD defects and the HFE-H63D variant are associated with increased risk of liver damages in Alpha 1-Antitrypsin Deficiency

BACKGROUND

The most common and severe disease causing allele of Alpha 1-Antitrypsin Deficiency (1ATD) is Z-1AT. This protein aggregates in the endoplasmic reticulum, which is the main cause of liver disease in childhood. Based on recent evidences and on the frequency of liver disease occurrence in Z-1AT patients, it seems that liver disease progression is linked to still unknown genetic factors.

METHODS

We used an innovative approach combining yeast genetic screens with next generation exome sequencing to identify and functionally characterize the genes involved in 1ATD associated liver disease.

RESULTS

Using yeast genetic screens, we identified HRD1, an Endoplasmic Reticulum Associated Degradation (ERAD) associated protein, as an inducer of Z-mediated toxicity. Whole exome sequencing of 1ATD patients resulted in the identification of two variants associated with liver damages in Z-1AT homozygous cases: HFE H63D and HERPUD1 R50H. Functional characterization in Z-1AT model cell lines demonstrated that impairment of the ERAD machinery combined with the HFE H63D variant expression decreased both cell proliferation and cell viability, while Unfolded Protein Response (UPR)-mediated cell death was hyperstimulated.

CONCLUSION

This powerful experimental pipeline allowed us to identify and functionally validate two genes involved in Z-1AT-mediated severe liver toxicity. This pilot study moves forward our understanding on genetic modifiers involved in 1ATD and highlights the UPR pathway as a target for the treatment of liver diseases associated with 1ATD. Finally, these findings support a larger scale screening for HERPUD1 R50H and HFE H63D variants in the sub-group of 1ATD patients developing significant chronic hepatic injuries (hepatomegaly, chronic cholestasis, elevated liver enzymes) and at risk developing liver cirrhosis.

Signal-intensity-ratio MRI accurately estimates hepatic iron load in hemodialysis patients

Background

Iron overload, diagnosed by means of magnetic resonance imaging (MRI), is an increasingly recognized disorder in hemodialysis patients. Specific MRI protocols have been shown to provide a reliable estimation of tissue iron content in non-renal patient populations but have not been validated in dialysis patients. Such validation studies require liver biopsy for histological comparison, but this invasive and risky procedure raises ethical concerns, especially regarding frail patients with end-stage renal disease.

Materials and methods

We compared in a pilot study Scheuer’s histological classification and Deugnier and Turlin’s histological classification of iron overload (Perls staining) with signal-intensity-ratio MRI values obtained with the Rennes University algorithm in 11 hemodialysis patients in whom liver biopsy was formally indicated for their medical follow-up.

Results

For Scheuer’s histological classification, the Wilcoxon non-parametric matched-pairs test showed no significant difference in the ranking of iron overload by the two methods eg histology and MRI (sum of ranks = 1.5; p = 1). The MRI and Scheuer’s histological classifications were tightly correlated (rho = 0.866, p = 0.0035, Spearman’s coefficient), as were the absolute liver iron concentrations (LIC) at MRI (rho = 0.860, p = 0.0013, Spearman’s coefficient). The absolute liver iron concentrations at MRI were also highly correlated with Deugnier and Turlin’s histological scoring (rho = 0.841, p = 0.0033, Spearman’s coefficient).

Conclusions

This pilot study shows that liver iron determination based on signal-intensity-ratio MRI (Rennes University algorithm) very accurately identifies iron load in hemodialysis patients, by comparison with liver histology.

Impaired hepcidin expression in alpha-1-antitrypsin deficiency associated with iron overload and progressive liver disease

Liver disease due to alpha-1-antitrypsin deficiency (A1ATD) is associated with hepatic iron overload in a subgroup of patients. The underlying cause for this association is unknown. The aim of the present study was to define the genetics of this correlation and the effect of alpha-1-antitrypsin (A1AT) on the expression of the iron hormone hepcidin. Full exome and candidate gene sequencing were carried out in a family with A1ATD and hepatic iron overload. Regulation of hepcidin expression by A1AT was studied in primary murine hepatocytes. Cells co-transfected with hemojuvelin (HJV) and matriptase-2 (MT-2) were used as a model to investigate the molecular mechanism of this regulation. Observed familial clustering of hepatic iron overload with A1ATD suggests a genetic cause, but genotypes known to be associated with hemochromatosis were absent. Individuals homozygous for the A1AT Z-allele with environmental or genetic risk factors such as steatosis or heterozygosity for the HAMP non-sense mutation p.Arg59* presented with severe hepatic siderosis. In hepatocytes, A1AT induced hepcidin mRNA expression in a dose-dependent manner. Experiments in overexpressing cells show that A1AT reduces cleavage of the hepcidin inducing bone morphogenetic protein co-receptor HJV via inhibition of the membrane-bound serine protease MT-2. The acute-phase protein A1AT is an inducer of hepcidin expression. Through this mechanism, A1ATD could be a trigger of hepatic iron overload in genetically predisposed individuals or patients with environmental risk factors for hepatic siderosis.

Meta-analyses of HFE variants in coronary heart disease

AIM

HFE gene variants can cause hereditary hemochromatosis (HH) that often comes along with an increased risk of coronary heart disease (CHD). The goal of our study is to assess the contribution of four HFE gene variants to the risk of CHD.

METHODS AND RESULTS

We conducted four meta-analyses of the studies examining the association between four HFE gene variants and the risk of CHD. A systematic search was conducted using MEDLINE, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI), Wanfang Chinese Periodical.

RESULTS

Meta-analyses showed that HFE rs1799945-G allele was associated with a 6% increased risk of CHD (P=0.02, odds ratio (OR)=1.06, 95% confidence interval (CI)=1.01-1.11). However, no association between the other three HFE gene variants (rs1800562, rs1800730, and rs9366637) and CHD risk was observed by the meta-analyses (all P values>0.05). In addition, the results of our case-control study indicated that rs1800562 and rs1800730 were monomorphic, and that rs1799945 and rs9366637 were not associated with CHD in Han Chinese.

CONCLUSIONS

Our meta-analysis suggested that a significant association existed between rs1799945 mutation and CHD, although this mutation was rare in Han Chinese.

Cryptogenic chronic hepatitis and its changing guise in adults

Cryptogenic chronic hepatitis is a disease that is unexplained by conventional clinical, laboratory and histological findings, and it can progress to cirrhosis, develop hepatocellular carcinoma, and require liver transplantation. The goals of this review are to describe the changing phenotype of cryptogenic chronic hepatitis in adults, develop a diagnostic algorithm appropriate to current practice, and suggest treatment options. The frequency of cryptogenic hepatitis is estimated at 5.4%. Cryptogenic cirrhosis is diagnosed in 5-30% of patients with cirrhosis, and it is present in 3-14% of adults awaiting liver transplantation. Nonalcoholic fatty liver disease has been implicated in 21-63% of patients, and autoimmune hepatitis is a likely diagnosis in 10-54% of individuals. Viral infections, hereditary liver diseases, celiac disease, and unsuspected alcohol or drug-induced liver injury are recognized infrequently in the current cryptogenic population. Manifestations of the metabolic syndrome heighten the suspicion of nonalcoholic fatty liver disease, and the absence of hepatic steatosis does not discount this possibility. The diagnostic scoring system of the International Autoimmune Hepatitis Group can support the diagnosis of autoimmune hepatitis in some patients. Certain genetic mutations may have disease-specificity, and they suggest that some patients may have an independent and uncharacterized disease. Corticosteroid therapy is effective in patients with autoimmune features, and life-style changes and specific therapies for manifestations of the metabolic syndrome are appropriate for all obese patients. The 1- and 5-year survivals after liver transplantation have ranged from 72-85% to 58-73%, respectively.

Advances in hepatobiliary pathology: update for 2010

Recent publications on hepatology and hepatic pathology provide a wealth of new information on wideranging topics. Morphologic aspects of liver disease associated with hepatitis B and C viruses, autoimmune hepatitis, and HIV infection were addressed, as was the prevalent problem of nonalcoholic fatty liver disease. Advances in diagnosis and pathogenesis of primary biliary cirrhosis, primary sclerosing cholangitis, and the increasingly complex spectrum of IgG4 hepatobiliary diseases were also reported. The histologic and immunohistochemical features of the rare "calcifying nested stromal-epithelial tumor" of the liver were described in a 9-case series. For benign and malignant liver tumors, immunohistochemistry plays a major diagnostic role, and several recent studies demonstrate the value of immunostains in distinguishing between liver-cell adenoma and focal nodular hyperplasia.