Dysregulation of iron and copper homeostasis in nonalcoholic fatty liver

Review article: iron disturbances in chronic liver diseases other than haemochromatosis - pathogenic, prognostic, and therapeutic implications

BACKGROUND

Disturbances in iron regulation have been described in diverse chronic liver diseases other than hereditary haemochromatosis, and iron toxicity may worsen liver injury and outcome.

AIMS

To describe manifestations and consequences of iron dysregulation in chronic liver diseases apart from hereditary haemochromatosis and to encourage investigations that clarify pathogenic mechanisms, define risk thresholds for iron toxicity, and direct management METHODS: English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

Hyperferritinemia is present in 4%-65% of patients with non-alcoholic fatty liver disease, autoimmune hepatitis, chronic viral hepatitis, or alcoholic liver disease, and hepatic iron content is increased in 11%-52%. Heterozygosity for the C282Y mutation is present in 17%-48%, but this has not uniformly distinguished patients with adverse outcomes. An inappropriately low serum hepcidin level has characterised most chronic liver diseases with the exception of non-alcoholic fatty liver disease, and the finding has been associated mainly with suppression of transcriptional activity of the hepcidin gene. Iron overload has been associated with oxidative stress, advanced fibrosis and decreased survival, and promising therapies beyond phlebotomy and oral iron chelation have included hepcidin agonists.

CONCLUSIONS

Iron dysregulation is common in chronic liver diseases other than hereditary haemochromatosis, and has been associated with liver toxicity and poor prognosis. Further evaluation of iron overload as a co-morbid factor should identify the key pathogenic disturbances, establish the risk threshold for iron toxicity, and promote molecular interventions.

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.

Low hair copper concentration is related to a high risk of nonalcoholic fatty liver disease in adults

Copper, an essential micronutrient, is required for lipid metabolism, mitochondrial function, iron metabolism, and antioxidant defense. Copper deficiency has been linked to alterations in lipid metabolism and various metabolic processes of the liver, including nonalcoholic fatty liver disease (NAFLD); however, most of these studies relied on copper measurements in the blood or tissues. In this study, we investigated the association between hair copper concentration and NAFLD in Korean adults, independent of metabolic syndrome status. Clinical and laboratory parameters, including factors of metabolic syndrome, were analyzed in 751 Korean adults divided into quintiles, according to hair copper concentration. Lower hair copper concentration was significantly correlated with higher body mass index, waist circumference, blood pressure, and lower levels of high-density lipoprotein cholesterol. Subjects with NAFLD showed significantly lower hair copper concentrations, and the risk of NAFLD was significantly higher for the lower hair copper quintile groups even after adjusting for metabolic syndrome-related factors. Overall, this study suggests that lower hair copper concentration could be associated with NAFLD, independent of metabolic syndrome factors.

Carnosine modulates the Sp1-Slc31a1/Ctr1 copper-sensing system and influences copper homeostasis in murine CNS-derived cells

Carnosine (CAR) is an endogenous dipeptide physiologically present in excitable tissues, such as central nervous system (CNS) and muscle. CAR is acknowledged as a substrate involved in many homeostatic pathways and mechanisms and, due to its biochemical properties, as a molecule intertwined with the homeostasis of heavy metals such as copper (Cu). In CNS, Cu excess and dysregulation imply oxidative stress, free-radical production, and functional impairment leading to neurodegeneration. Here, we report that CAR intercepts the regulatory routes of Cu homeostasis in nervous cells and tissues. Specifically, in a murine neuron-derived cell model, i.e., the B104 neuroblastoma cells, extracellular CAR exposure up to 24 h influenced intracellular Cu entry and affected (downregulated) the key Cu-sensing system, consisting of the gene coding for the Slc31a1 transmembrane Cu importer (alias Ctr1), and the gene coding for the Cu-responsive transcription factor Sp1 ( Sp1). Also, CAR exposure upregulated CAR biosynthesis ( Carns1), extracellular degradation ( Cndp1), and transport ( Slc15a4, alias Pht1) genes and elicited CAR intracellular accumulation, contributing to the outline of functional association between CAR and Cu within the cell. Interestingly, the same gene modulation scheme acting in vitro operates in vivo in brains of mice undergoing dietary administration of CAR in drinking water for 2 wk. Overall, our findings describe for the first time a regulatory interaction between CAR and Cu pathways in CNS and indicate CAR as a novel active molecule within the network of ligands and chaperones that physiologically regulate Cu homeostasis.

A Modular Ionophore Platform for Liver-Directed Copper Supplementation in Cells and Animals

Copper deficiency is implicated in a variety of genetic, neurological, cardiovascular, and metabolic diseases. Current approaches for addressing copper deficiency rely on generic copper supplementation, which can potentially lead to detrimental off-target metal accumulation in unwanted tissues and subsequently trigger oxidative stress and damage cascades. Here we present a new modular platform for delivering metal ions in a tissue-specific manner and demonstrate liver-targeted copper supplementation as a proof of concept of this strategy. Specifically, we designed and synthesized an N-acetylgalactosamine-functionalized ionophore, Gal-Cu(gtsm), to serve as a copper-carrying "Trojan Horse" that targets liver-localized asialoglycoprotein receptors (ASGPRs) and releases copper only after being taken up by cells, where the reducing intracellular environment triggers copper release from the ionophore. We utilized a combination of bioluminescence imaging and inductively coupled plasma mass spectrometry assays to establish ASGPR-dependent copper accumulation with this reagent in both liver cell culture and mouse models with minimal toxicity. The modular nature of our synthetic approach presages that this platform can be expanded to deliver a broader range of metals to specific cells, tissues, and organs in a more directed manner to treat metal deficiency in disease.

Hepatic R2* is more strongly associated with proton density fat fraction than histologic liver iron scores in patients with nonalcoholic fatty liver disease

BACKGROUND

The liver R2* value is widely used as a measure of liver iron but may be confounded by the presence of hepatic steatosis and other covariates.

PURPOSE

To identify the most influential covariates for liver R2* values in patients with nonalcoholic fatty liver disease (NAFLD).

STUDY TYPE

Retrospective analysis of prospectively acquired data.

POPULATION

Baseline data from 204 subjects enrolled in NAFLD/NASH (nonalcoholic steatohepatitis) treatment trials.

FIELD STRENGTH

1.5T and 3T; chemical-shift encoded multiecho gradient echo.

ASSESSMENT

Correlation between liver proton density fat fraction and R2*; assessment for demographic, metabolic, laboratory, MRI-derived, and histological covariates of liver R2*.

STATISTICAL TESTS

Pearson's and Spearman's correlations; univariate analysis; gradient boosting machines (GBM) multivariable machine-learning method.

RESULTS

Hepatic proton density fat fraction (PDFF) was the most strongly correlated covariate for R2* at both 1.5T (r = 0.652, P < 0.0001) and at 3T (r = 0.586, P < 0.0001). In the GBM analysis, hepatic PDFF was the most influential covariate for hepatic R2*, with relative influences (RIs) of 61.3% at 1.5T and 47.5% at 3T; less influential covariates had RIs of up to 11.5% at 1.5T and 16.7% at 3T. Nonhepatocellular iron was weakly associated with R2* at 3T only (RI 6.7%), and hepatocellular iron was not associated with R2* at either field strength.

DATA CONCLUSION

Hepatic PDFF is the most influential covariate for R2* at both 1.5T and 3T; nonhepatocellular iron deposition is weakly associated with liver R2* at 3T only.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1456-1466.

Hepcidin levels correlate to liver iron content, but not steatohepatitis, in non-alcoholic fatty liver disease

Background

One-third of patients with non-alcoholic fatty liver disease (NAFLD) develop dysmetabolic iron overload syndrome (DIOS), the pathogenesis of which is unknown. Altered production of the iron-regulatory peptide hepcidin has been reported in NAFLD, but it is unclear if this is related to iron accumulation, lipid status or steatohepatitis.

Methods

Eighty-four patients with liver disease, 54 of which had iron overload, underwent liver biopsy (n = 66) and/or magnetic resonance imaging (n = 35) for liver iron content determination. Thirty-eight of the patients had NAFLD, 29 had chronic liver disease other than NAFLD, and 17 had untreated genetic hemochromatosis. Serum hepcidin was measured with ELISA in all patients and in 34 controls. Hepcidin antimicrobial peptide (HAMP) mRNA in liver tissue was determined with real-time-quantitative PCR in 36 patients.

Results

Serum hepcidin was increased similarly in NAFLD with DIOS as in the other chronic liver diseases with iron overload, except for genetic hemochromatosis. HAMP mRNA in liver tissue, and serum hepcidin, both correlated to liver iron content in NAFLD patients (r² = 0.45, p < 0.05 and r² = 0.27, p < 0.05 respectively) but not to body mass index, NAFLD activity score or serum lipids. There was a good correlation between HAMP mRNA in liver tissue and serum hepcidin (r² = 0.39, p < 0.01).

Conclusions

In NAFLD with or without dysmetabolic iron overload, serum hepcidin and HAMP mRNA in liver correlate to body iron content but not to the degree of steatohepatitis or lipid status. Thus, the dysmetabolic iron overload syndrome seen in NAFLD is not caused by an altered hepcidin synthesis.

Triggering and resolution of inflammation in NASH

Nonalcoholic steatohepatitis (NASH) is considered the progressive form of nonalcoholic fatty liver disease (NAFLD) and is characterized by liver steatosis, inflammation, hepatocellular injury and different degrees of fibrosis. A central issue in this field relates to the identification of those factors that trigger inflammation, thus fuelling the transition from nonalcoholic fatty liver to NASH. These triggers of liver inflammation might have their origins outside the liver (such as in adipose tissue or the gut) as well as inside the organ (for instance, lipotoxicity, innate immune responses, cell death pathways, mitochondrial dysfunction and endoplasmic reticulum stress), both of which contribute to NASH development. In this Review, we summarize the currently available information on the key upstream triggers of inflammation in NASH. We further delineate the mechanisms by which liver inflammation is resolved and the implications of a defective pro-resolution process. A better knowledge of these mechanisms should help to design targeted therapies able to halt or reverse disease progression.

Copper/MYC/CTR1 interplay: a dangerous relationship in hepatocellular carcinoma

Free serum copper correlates with tumor incidence and progression of human cancers, including hepatocellular carcinoma (HCC). Copper extracellular uptake is provided by the transporter CTR1, whose expression is regulated to avoid excessive intracellular copper entry. Inadequate copper serum concentration is involved in the pathogenesis of Non Alcoholic Fatty Liver Disease (NAFLD), which is becoming a major cause of liver damage progression and HCC incidence. Finally, MYC is over-expressed in most of HCCs and is a critical regulator of cellular growth, tumor invasion and metastasis.

The purpose of our study was to understand if higher serum copper concentrations might be involved in the progression of NAFLD-cirrhosis toward-HCC. We investigated whether high exogenous copper levels sensitize liver cells to transformation and if it exists an interplay between copper-related proteins and MYC oncogene.

NAFLD-cirrhotic patients were characterized by a statistical significant enhancement of serum copper levels, even more evident in HCC patients. We demonstrated that high extracellular copper concentrations increase cell growth, migration, and invasion of liver cancer cells by modulating MYC/CTR1 axis. We highlighted that MYC binds a specific region of the CTR1 promoter, regulating its transcription. Accordingly, CTR1 and MYC proteins expression were progressively up-regulated in liver tissues from NAFLD-cirrhotic to HCC patients.

This work provides novel insights on the molecular mechanisms by which copper may favor the progression from cirrhosis to cancer. The Cu/MYC/CTR1 interplay opens a window to refine HCC diagnosis and design new combined therapies.

Is copper a new target to counteract the progression of chronic diseases?

In this review, we highlight the importance of a Cu imbalance in the pathogenesis of several chronic inflammatory diseases.

Interplay of adipocyte and hepatocyte: Leptin upregulates hepcidin

Conflicting evidence concerning leptin, an adipocyte-derived hormone, in atherogenesis and non-alcoholic fatty liver disease (NAFLD) has been reported. Iron metabolism and iron-mediated oxidative stress should be taken into consideration for the clarification of the pathogenesis of these diseases. In this study, we demonstrate that leptin receptor activation directly affects iron metabolism by the finding that serum levels of hepcidin, the master regulator of iron in the whole body, were significantly lower in leptin-deficient (ob/ob) and leptin receptor-deficient (db/db) mice. The administration of recombinant leptin to ob/ob mice for two weeks showed a significant increase in serum hepcidin and hepatic Hamp mRNA levels. Hamp mRNA levels were significantly correlated with hepatic iron content and BMP6 mRNA levels. Hepatic iron content was associated with the increase in mRNA levels of divalent metal transporter 1 and transferrin receptor. Our data provide evidence that the interplay of these two hormones could help improve the understanding of the pathogenesis of atherosclerosis and NAFLD.

Hepcidin in morbidly obese women with non-alcoholic fatty liver disease

Background

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in Western countries. Both iron and lipid metabolism seem to be involved in its pathogenesis. We aimed to assess the relationship between levels of hepcidin, the master iron-regulatory protein, in plasma and the presence of NAFLD in morbidly obese (MO) patients, and to investigate the association between the hepatic expression of the main iron and lipid metabolism -related genes.

Materials and methods

Enzyme-linked immunosorbent assay was used to measure plasma hepcidin levels in 49 normal-weight control women, 23 MO women with normal liver (NL) histology and 46 MO women with NAFLD. The mRNA expression of hepcidin, the main iron metabolism-related genes, and the main lipid-metabolism genes was quantified by qRT-PCR in liver biopsies from members of the MO group undergoing bariatric surgery.

Results

Circulating hepcidin levels were significantly greater in MO than in normal-weight control women. However, there were no significant differences between MO women with NL and those with NAFLD. PCR analysis showed increased expression of hepcidin, FPN1, TfR1 and TfR2 in the liver of MO NAFLD women compared to those with NL. Moreover, a positive association of hepatic hepcidin mRNA expression and the iron metabolism-related genes was found with some key genes involved in the lipid metabolism.

Conclusion

These findings suggest that circulating hepcidin levels are associated with obesity but not with the presence of NAFLD. However, the hepatic expression of hepcidin and the iron metabolism-related genes seem to play a role in regulating lipid metabolism pathways in liver, which has implications for NAFLD pathogenesis.

Hyperferritinemia in patients with nonalcoholic fatty liver disease

Objective:

In liver diseases, hyperferritinemia (HYF) is related to injured cells in acquired and genetic conditions with or without iron overload. It is frequent in patients with nonalcoholic fatty liver disease (NAFLD), in which it is necessary to define the mean of HYF to establish the better approach for them. The present study evaluated the significance of elevated ferritin in patients with NAFLD and steatohepatitis (NASH).

Method:

The review was performed using search instruments of indexed scientific material, including MEDLINE (by PubMed), Web of Science, IBECS and LILACS, to identify articles published in Portuguese, English and Spanish, from 2005 to May, 2016. Studies eligible included place and year of publication, diagnose criteria to NAFLD, specifications of serum ferritin measurements and/or liver histopathologic study. Exclusion criteria included studies with patients with alcohol consumption ≥ 20 g/day and other liver diseases.

Results:

A total of 11 from 30 articles were selected. It included 3,564 patients and they were cross-sectional, retrospective, case series and case-control. The result's analyses showed in 10 of these studies a relationship between ferritin elevated serum levels and NAFLD/NASH with and without fibrosis and insulin resistance.

Conclusion:

Hyperferritinemia in patients with NAFLD/NASH is associated more frequently with hepatocellular injury than hemochromatosis. These data suggest the relevance to evaluate carefully HYF in patients with NAFLD/NASH to establish appropriate clinical approach.

Circulating copper and zinc levels and risk of hepatobiliary cancers in Europeans

BACKGROUND

Copper and zinc are essential micronutrients and cofactors of many enzymatic reactions that may be involved in liver-cancer development. We aimed to assess pre-diagnostic circulating levels of copper, zinc and their ratio (Cu/Zn) in relation to hepatocellular carcinoma (HCC), intrahepatic bile duct (IHBD) and gall bladder and biliary tract (GBTC) cancers.

METHODS

A nested case-control study was conducted within the European Prospective Investigation into Cancer and Nutrition cohort. Serum zinc and copper levels were measured in baseline blood samples by total reflection X-ray fluorescence in cancer cases (HCC n=106, IHDB n=34, GBTC n=96) and their matched controls (1:1). The Cu/Zn ratio, an indicator of the balance between the micronutrients, was computed. Multivariable adjusted odds ratios and 95% confidence intervals (OR; 95% CI) were used to estimate cancer risk.

RESULTS

For HCC, the highest vs lowest tertile showed a strong inverse association for zinc (OR=0.36; 95% CI: 0.13-0.98, Ptrend=0.0123), but no association for copper (OR=1.06; 95% CI: 0.45-2.46, Ptrend=0.8878) in multivariable models. The calculated Cu/Zn ratio showed a positive association for HCC (OR=4.63; 95% CI: 1.41-15.27, Ptrend=0.0135). For IHBC and GBTC, no significant associations were observed.

CONCLUSIONS

Zinc may have a role in preventing liver-cancer development, but this finding requires further investigation in other settings.

Convergence of hepcidin deficiency, systemic iron overloading, heme accumulation, and REV-ERBα/β activation in aryl hydrocarbon receptor-elicited hepatotoxicity

Persistent aryl hydrocarbon receptor (AhR) agonists elicit dose-dependent hepatic lipid accumulation, oxidative stress, inflammation, and fibrosis in mice. Iron (Fe) promotes AhR-mediated oxidative stress by catalyzing reactive oxygen species (ROS) production. To further characterize the role of Fe in AhR-mediated hepatotoxicity, male C57BL/6 mice were orally gavaged with sesame oil vehicle or 0.01-30μg/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) every 4days for 28days. Duodenal epithelial and hepatic RNA-Seq data were integrated with hepatic AhR ChIP-Seq, capillary electrophoresis protein measurements, and clinical chemistry analyses. TCDD dose-dependently repressed hepatic expression of hepcidin (Hamp and Hamp2), the master regulator of systemic Fe homeostasis, resulting in a 2.6-fold increase in serum Fe with accumulating Fe spilling into urine. Total hepatic Fe levels were negligibly increased while transferrin saturation remained unchanged. Furthermore, TCDD elicited dose-dependent gene expression changes in heme biosynthesis including the induction of aminolevulinic acid synthase 1 (Alas1) and repression of uroporphyrinogen decarboxylase (Urod), leading to a 50% increase in hepatic hemin and a 13.2-fold increase in total urinary porphyrins. Consistent with this heme accumulation, differential gene expression suggests that heme activated BACH1 and REV-ERBα/β, causing induction of heme oxygenase 1 (Hmox1) and repression of fatty acid biosynthesis, respectively. Collectively, these results suggest that Hamp repression, Fe accumulation, and increased heme levels converge to promote oxidative stress and the progression of TCDD-elicited hepatotoxicity.

Evaluation of tissue metal and trace element content in a rat model of non-alcoholic fatty liver disease using ICP-DRC-MS

The primary objective of the study was to assess the level of metals and trace elements in liver, serum, and hair of rats with diet-induced non-alcoholic fatty liver disease (NAFLD) using inductively coupled plasma dynamic reaction cell mass spectrometer (ICP-DRC-MS). 56 female 3-months-old Wistar rats divided into two equal groups were fed either standard (10% calories from fat) or high-fat high-carbohydrate diet (60% calories from fat in chow and 10% sucrose solution) for 6 weeks. Serum was examined for insulin resistance markers, lipid profile, and alanine aminotransferase (ALT) activity. Liver histology was assessed after hematoxylin and eosin staining. Metal and trace element concentrations were assessed by means of ICP-DRC-MS. Overfed animals were characterized by higher values of morphometric parameters. Liver examination revealed large and small droplet steatosis, hepatocyte ballooning and necrosis, being characteristic for NAFLD. Animals with NAFLD were characterized by insulin resistance, atherogenic changes of lipid profile and increased ALT activity. Significantly decreased hepatic Co, Cu, I, Li, Mn, Se, Zn levels were observed in rats with NAFLD. At the same time, only hepatic Mn and Se levels remained decreased after adjustment for total protein. Overfed animals were characterized by significantly lower I, Li, and Mn levels in blood serum, whereas concentration of Co, Se, V, and Sr exceeded the control values. In general, the results of the study demonstrate that NAFLD significantly affects metal and trace element status in experimental animals.

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

Copper is a required metal nutrient for life, but global or local alterations in its homeostasis are linked to diseases spanning genetic and metabolic disorders to cancer and neurodegeneration. Technologies that enable longitudinal in vivo monitoring of dynamic copper pools can help meet the need to study the complex interplay between copper status, health, and disease in the same living organism over time. Here, we present the synthesis, characterization, and in vivo imaging applications of Copper-Caged Luciferin-1 (CCL-1), a bioluminescent reporter for tissue-specific copper visualization in living animals. CCL-1 uses a selective copper(I)-dependent oxidative cleavage reaction to release d-luciferin for subsequent bioluminescent reaction with firefly luciferase. The probe can detect physiological changes in labile Cu+ levels in live cells and mice under situations of copper deficiency or overload. Application of CCL-1 to mice with liver-specific luciferase expression in a diet-induced model of nonalcoholic fatty liver disease reveals onset of hepatic copper deficiency and altered expression levels of central copper trafficking proteins that accompany symptoms of glucose intolerance and weight gain. The data connect copper dysregulation to metabolic liver disease and provide a starting point for expanding the toolbox of reactivity-based chemical reporters for cell- and tissue-specific in vivo imaging.

Molecular pathogenesis and clinical consequences of iron overload in liver cirrhosis

BACKGROUND

The liver, as the main iron storage compartment and the place of hepcidin synthesis, is the central organ involved in maintaining iron homeostasis in the body. Excessive accumulation of iron is an important risk factor in liver disease progression to cirrhosis and hepatocellular carcinoma. Here, we review the literature on the molecular pathogenesis of iron overload and its clinical consequences in chronic liver diseases.

DATA SOURCES

PubMed was searched for English-language articles on molecular genesis of primary and secondary iron overload, as well as on their association with liver disease progression. We have also included literature on adjuvant therapeutic interventions aiming to alleviate detrimental effects of excessive body iron load in liver cirrhosis.

RESULTS

Excess of free, unbound iron induces oxidative stress, increases cell sensitivity to other detrimental factors, and can directly affect cellular signaling pathways, resulting in accelerated liver disease progression. Diagnosis of liver cirrhosis is, in turn, often associated with the identification of a pathological accumulation of iron, even in the absence of genetic background of hereditary hemochromatosis. Iron depletion and adjuvant therapy with antioxidants are shown to cause significant improvement of liver functions in patients with iron overload. Phlebotomy can have beneficial effects on liver histology in patients with excessive iron accumulation combined with compensated liver cirrhosis of different etiology.

CONCLUSION

Excessive accumulation of body iron in liver cirrhosis is an important predictor of liver failure and available data suggest that it can be considered as target for adjuvant therapy in this condition.

Relationship between iron overload and nonalcoholic fatty liver disease: An update

As a component of the multiple hits, iron overload plays an important role in the development of nonalcoholic fatty liver disease (NAFLD). Iron overload could affect glucose, lipid, energy metabolism and inflammatory reaction. This paper reviews the relationship between iron overload and nonalcoholic fatty liver disease, in order to clarify how and why iron overload influences the progression of NAFLD.

Quantification of liver fat in the presence of iron overload

PURPOSE

To evaluate the accuracy of R2* models (1/T₂ * = R2*) for chemical shift-encoded magnetic resonance imaging (CSE-MRI)-based proton density fat-fraction (PDFF) quantification in patients with fatty liver and iron overload, using MR spectroscopy (MRS) as the reference standard.

MATERIALS AND METHODS

Two Monte Carlo simulations were implemented to compare the root-mean-squared-error (RMSE) performance of single-R2* and dual-R2* correction in a theoretical liver environment with high iron. Fatty liver was defined as hepatic PDFF >5.6% based on MRS; only subjects with fatty liver were considered for analyses involving fat. From a group of 40 patients with known/suspected iron overload, nine patients were identified at 1.5T, and 13 at 3.0T with fatty liver. MRS linewidth measurements were used to estimate R2* values for water and fat peaks. PDFF was measured from CSE-MRI data using single-R2* and dual-R2* correction with magnitude and complex fitting.

RESULTS

Spectroscopy-based R2* analysis demonstrated that the R2* of water and fat remain close in value, both increasing as iron overload increases: linear regression between R2*_W and R2*_F resulted in slope = 0.95 [0.79-1.12] (95% limits of agreement) at 1.5T and slope = 0.76 [0.49-1.03] at 3.0T. MRI-PDFF using dual-R2* correction had severe artifacts. MRI-PDFF using single-R2* correction had good agreement with MRS-PDFF: Bland-Altman analysis resulted in -0.7% (bias) ± 2.9% (95% limits of agreement) for magnitude-fit and -1.3% ± 4.3% for complex-fit at 1.5T, and -1.5% ± 8.4% for magnitude-fit and -2.2% ± 9.6% for complex-fit at 3.0T.

CONCLUSION

Single-R2* modeling enables accurate PDFF quantification, even in patients with iron overload.

LEVEL OF EVIDENCE

1 J. Magn. Reson. Imaging 2017;45:428-439.

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.

Major components of metabolic syndrome and nutritional intakes in different genotype of UCP2 -866G/A gene polymorphisms in patients with NAFLD

Background

It has been suggested that dietary modifications in combination with genetic predisposition play an important role in the pathogenesis of NAFLD. In the current study we aimed to investigate the major components of metabolic syndrome in patients with non-alcoholic fatty liver disease (NAFLD) and nutritional intakes according to different genotype of uncoupling protein-2 (UCP2) −866G/A gene polymorphism in these patients.

Methods

In this study 151 participants including 75 patients with NAFLD and 76 healthy individuals were enrolled. Dietary intakes were assessed using a semi-quantitative food-frequency questionnaire. Physical activity was obtained by metabolic equivalent questionnaire. Anthropometric assessments were conducted by a trained researcher and body mass index and waist to hip ratio were calculated. Body composition was measured by bioelectrical impedance analysis and biochemical assays including fasting serum glucose, liver enzymes and lipid profiles were measured. Polymorphisms of −866G/A UCP2 gene was determined using polymerase chain reaction-restriction fragment length polymorphism method.

Results

Serum triglyceride concentrations in 53.3 % of NAFLD patients compared with 35.5 % of control group was more than 150 mg/dl (P = 0.034). A significantly higher prevalence of low serum high density lipoprotein cholesterol concentrations was also observed in female NAFLD patients (P < 0.001). Dietary intakes in NAFLD group were not significantly different compared with control group (P > 0.05). However, according to genotypes patients with AG genotype had significantly higher protein consumption compared with control group (P < 0.05). Significantly higher consumption of dietary iron and copper in NAFLD patients with AG genotype was only observed among patients with NAFLD. However, the comparison of macro and micronutrient intakes in control group sound for stronger differences for AA genotype although these differences did not achieve significant threshold.

Conclusions

A high prevalence of metabolic abnormalities was reported among NAFLD patients. Additionally, among NAFLD group, patients with AG genotype significantly consumed more protein, iron and copper in their usual diet.

Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a necro-inflammatory response that ensues when hepatocytes are injured by lipids (lipotoxicity). NASH is a potential outcome of nonalcoholic fatty liver (NAFL), a condition that occurs when lipids accumulate in hepatocytes. NASH may be reversible, but it can also result in cirrhosis and primary liver cancer. We are beginning to learn about the mechanisms of progression of NAFL and NASH. NAFL does not inevitably lead to NASH because NAFL is a heterogeneous condition. This heterogeneity exists because different types of lipids with different cytotoxic potential accumulate in the NAFL, and individuals with NAFL differ in their ability to defend against lipotoxicity. There are no tests that reliably predict which patients with NAFL will develop lipotoxicity. However, NASH encompasses the spectrum of wound-healing responses induced by lipotoxic hepatocytes. Differences in these wound-healing responses among individuals determine whether lipotoxic livers regenerate, leading to stabilization or resolution of NASH, or develop progressive scarring, cirrhosis, and possibly liver cancer. We review concepts that are central to the pathogenesis of NASH.

Lack of hepcidin expression attenuates steatosis and causes fibrosis in the liver

AIM: To investigate the role of key iron-regulatory protein, hepcidin in non-alcoholic fatty liver disease (NAFLD).

METHODS: Hepcidin (Hamp1) knockout and floxed control mice were administered a high fat and high sucrose (HFS) or a regular control diet for 3 or 7 mo. Steatosis, triglycerides, fibrosis, protein and gene expression in mice livers were determined by histological and biochemical techniques, western blotting and real-time polymerase chain reaction.

RESULTS: Knockout mice exhibited hepatic iron accumulation. Despite similar weight gains, HFS feeding induced hepatomegaly in floxed, but not knockout, mice. The livers of floxed mice exhibited higher levels of steatosis, triglycerides and c-Jun N-terminal kinase (JNK) phosphorylation than knockout mice. In contrast, a significant increase in fibrosis was observed in knockout mice livers within 3 mo of HFS administration. The hepatic gene expression levels of sterol regulatory element-binding protein-1c and fat-specific protein-27, but not peroxisome proliferator-activated receptor-alpha or microsomal triglyceride transfer protein, were attenuated in HFS-fed knockout mice. Knockout mice fed with regular diet displayed increased carnitine palmitoyltransferase-1a and phosphoenolpyruvate carboxykinase-1 but decreased glucose-6-phosphatase expression in the liver. In summary, attenuated steatosis correlated with decreased expression of lipogenic and lipid storage genes, and JNK phosphorylation. Deletion of Hamp1 alleles per se modulated hepatic expression of beta-oxidation and gluconeogenic genes.

CONCLUSION: Lack of hepcidin expression inhibits hepatic lipid accumulation and induces early development of fibrosis following high fat intake. Hepcidin and iron may play a role in the regulation of metabolic pathways in the liver, which has implications for NAFLD pathogenesis.

Ceramide Induces Human Hepcidin Gene Transcription through JAK/STAT3 Pathway

Changes in lipid metabolism and iron content are observed in the livers of patients with fatty liver disease. The expression of hepcidin, an iron-regulatory and acute phase protein synthesized by the liver, is also modulated. The potential interaction of lipid and iron metabolism is largely unknown. We investigated the role of lipid intermediate, ceramide in the regulation of human hepcidin gene, HAMP. Human hepatoma HepG2 cells were treated with cell-permeable ceramide analogs. Ceramide induced significant up-regulation of HAMP mRNA expression in HepG2 cells. The effect of ceramide on HAMP expression was mediated through transcriptional mechanisms because it was completely blocked with actinomycin D treatment. Reporter assays also confirmed the activation of 0.6 kb HAMP promoter by ceramide. HepG2 cells treated with ceramide displayed increased phosphorylation of STAT3, JNK, and NF-κB proteins. However, ceramide induced the binding of STAT3, but not NF-κB or c-Jun, to HAMP promoter, as shown by the chromatin immunoprecipitation assays. The mutation of STAT3 response element within 0.6 kb HAMP promoter region significantly inhibited the stimulatory effect of ceramide on HAMP promoter activity. Similarly, the inhibition of STAT3 with a pan-JAK kinase inhibitor and STAT3 siRNA pool also diminished the induction of both HAMP promoter activity and mRNA expression by ceramide. In conclusion, we have shown a direct role for ceramide in the activation of hepatic HAMP transcription via STAT3. Our findings suggest a crosstalk between lipid and iron metabolism in the liver, which may contribute to the pathogenesis of obesity-related fatty liver disease.

A Single Center Study Comparing the Stainable Iron Depositions in 1000 Explanted Cirrhotic Livers of Different Causes

BACKGROUND

There have been very few studies evaluating the close association between excess iron and cirrhosis; however, cirrhosis could be regarded as an iron-loading disorder.

OBJECTIVES

In this study, the goal was to show the levels of the iron content in the liver tissue in certain types of cirrhosis.

PATIENTS AND METHODS

In this 7 year study (2008 - 2014), in 1000 explanted livers, the amount of iron was scored and compared according to the cause of the cirrhosis. The amount of iron in the liver was determined via the histochemical staining of the liver tissue, using Prussian-blue staining. Additionally, in each patient, the serum iron was determined and compared according to the cause of cirrhosis.

RESULTS

The highest content of iron has been found in cirrhosis caused by chronic hepatitis (i.e. hepatitis B, C, and autoimmune hepatitis), as well as in alcoholic cirrhosis. The least amount of stainable iron has been shown in biliary cirrhosis.

CONCLUSIONS

The presence of high stainable iron in patients with cirrhosis, secondary to chronic viral hepatitis, autoimmune hepatitis, and alcoholic hepatitis, should not be considered indicative of the presence of hereditary hemochromatosis; however, in those patients with biliary cirrhosis, a high iron content is rare, and can be a sign of the presence of the high iron Fe (HFE) gene mutation, or another type of hereditary hemochromatosis.

Kupffer cells and hepatic lipid metabolism disorder

Non-alcoholic fatty liver disease (NAFLD) has become the most common liver disorder of our times in both developed and developing countries, which is associated with insulin resistance and genetic susceptibility. Simple steatosis, a seemingly innocent manifestation of early stage NAFLD, may progress into steatohepatitis and cirrhosis, which may even progress into hepatocellular carcinoma. Kupffer cells (KCs) constitute the first firewall of the liver, representing 80%-90% of all tissue macrophages in the body and taking part in various acute and chronic inflammatory reactions. It is deemed that the genesis and development of NAFLD are closely related to the chronic metabolic inflammation induced by KCs. KCs could be activated by lipids accumulated in the liver, and activated KCs participate in metabolic inflammation through releasing pro-inflammatory factors. In this review, we focus on recently uncovered aspects of the biochemical, immunological and molecular events that are responsible for the development and progression of this highly prevalent and potentially serious disease, and summarize the role of KCs in the pathogenesis of NAFLD.