Iron overload and cofactors with special reference to alcohol, hepatitis C virus infection and steatosis/insulin resistance

Vitamin C protective role for alcoholic liver disease in mice through regulating iron metabolism

Alcoholic liver disease (ALD) is a major medical complication of drinking alcohol, and commonly accompanied with hepatic iron overload and liver injuries. Oxidative stress plays an important role in pathogenesis of ALD and also leads to iron-metabolic disorders. In this study, the effects of vitamin C (Vc) on iron metabolism-related genes expression and liver protection from drinking in mice were investigated. Twenty-four male kunming mice were divided into four groups (six mice per group): control (water drinking); alcohol group (20% alcohol drinking), alcohol + low Vc group (adding 50 mg/kg Vc daily) and alcohol + high Vc group (adding 100 mg/kg Vc daily). All these mice were sacrificed after 7 days. Vc can ameliorate the increase of sera alanine aminotransferase (ALT) activity and hepatic iron overload of drinking alcohol in mice. Vc increases the expression of the iron-regulated hormone hepcidin and decreases transferrin receptor 1 (TfR1) expression in liver. Vc also down-regulates the expression of ferroportin 1 (Fpn1) in the intestine and decreases the iron release to blood. In conclusion, Vc ameliorated the alcoholic liver injuries through regulating the iron metabolism-related genes expression.

Measurement of serum hepcidin-25 levels as a potential test for diagnosing hemochromatosis and related disorders

BACKGROUND

Iron overload syndromes include a wide spectrum of genetic and acquired conditions. Recent studies suggest suppressed hepcidin synthesis in the liver to be the molecular basis of hemochromatosis. However, a liver with acquired iron overload synthesizes an adequate amount of hepcidin. Thus, hepcidin could function as a biochemical marker for differential diagnosis of iron overload syndromes.

METHODS

We measured serum iron parameters and hepcidin-25 levels followed by sequencing HFE, HJV, HAMP, TFR2, and SLC40A1 genes in 13 Japanese patients with iron overload syndromes. In addition, we performed direct measurement of serum hepcidin-25 levels using liquid chromatography-tandem mass spectrometry in 3 Japanese patients with aceruloplasminemia and 4 Italians with HFE hemochromatosis.

RESULTS

One patient with HJV hemochromatosis, 2 with TFR2 hemochromatosis, and 3 with ferroportin disease were found among the 13 Japanese patients. The remaining 7 Japanese patients showed no evidence for genetic basis of iron overload syndrome. As far as the serum hepcidin-25 was concerned, seven patients with hemochromatosis and 3 with aceruloplasminemia showed markedly decreased serum hepcidin-25 levels. In contrast, 3 patients with ferroportin disease and 7 with secondary iron overload syndromes showed serum hepcidin levels parallel to their hyperferritinemia. Patients with iron overload syndromes were divided into 2 phenotypes presenting as low and high hepcidinemia. These were then associated with their genotypes.

CONCLUSION

Determining serum hepcidin-25 levels may aid differential diagnosis of iron overload syndromes prior to genetic analysis.

Combination therapy with andrographolide and d-penicillamine enhanced therapeutic advantage over monotherapy with d-penicillamine in attenuating fibrogenic response and cell death in the periportal zone of liver in rats during copper toxicosis

Long treatment regime with d-penicillamine is needed before it can exert clinically meaningful benefits in the treatment of copper toxicosis. The consequence of long-term d-penicillamine treatment is associated with numerous side effects. The limitations of d-penicillamine monotherapy prompted us to search for more effective treatment strategies that could decrease the duration of d-penicillamine therapy. The present study was designed to evaluate the therapeutic potential of d-penicillamine in combination with another hepatoprotective drug, andrographolide in treatment of copper toxicosis in rats. d-penicillamine treatment led to the excretion of copper through urine. Addition of andrographolide to d-penicillamine regime appeared to increase protection of liver by increasing the biliary excretion of copper and reduction in cholestatic injury. The early removal of the causative agent copper during combination treatment was the most effective therapeutic intervention that contributed to the early rectification of fibrosis in liver. Combination treatment reduced Kupffer cells accumulation and TNFα production in liver of copper exposed rats. In particular, andrographolide mediated the anti-inflammatory effect by inhibiting the cytokine production. However, another possible mechanism of cytoprotection of andrographolide was decreasing mitochondrial production of superoxide anions that resulted in better restoration of mitochondrial dysfunction during combination therapy than monotherapy. Furthermore, ROS inhibition by combination regimen resulted in significant decline in activation of caspase cascade. Inhibition of caspases attenuated apoptosis of hepatocytes, induced by chronic copper exposure. In summary, this study suggested that added benefit of combination treatment over use of either agent alone in alleviating the hepatotoxicity and fibrosis associated with copper toxicosis.

Glutathione synthesis inhibitor butathione sulfoximine regulates ceruloplasmin by dual but opposite mechanism: Implication in hepatic iron overload

Glutathione (GSH) depletion is often detected in chronic pathological conditions like hepatitis C infection, alcohol consumption or xenobiotic assault with simultaneous reactive oxygen species (ROS) generation and hepatic iron overload. However, relation between GSH depletion and regulators of iron homeostasis is not clear so far. To determine that hepatic HepG2 cells were treated with GSH synthesis inhibitor butathione sulfoximine (BSO) and a dual regulation of ceruloplasmin (Cp) that involves in hepatic iron release was detected unlike other iron homeostasis regulators. BSO treatment that caused marginal GSH deficiency increased Cp synthesis due to increased transcription mediated by activator protein (AP)-1-binding site. In higher GSH deficiency (> 40 %) with increased ROS generation, Cp expression was decreased due to promotion of Cp mRNA decay mediated by 3'untranslated region (3'UTR) as found by transfecting chimera of chloramphenicol acetyl transferase (CAT) gene with Cp 3'UTR. RNA gel shift assay showed significant reduction in 3'UTR binding protein complex in similar condition. Decreased CAT expression and RNA-protein complex binding are reversed by pretreatment with antioxidant N-acetyl cysteine suggesting 3'UTR binding protein complex is redox-sensitive. This unique and opposite regulation of Cp provides a mechanism of hepatic iron-deposition during glutathione deficiency detected in chronic pathological conditions.

Liver iron content determination by magnetic resonance imaging

Accurate evaluation of iron overload is necessary to establish the diagnosis of hemochromatosis and guide chelation treatment in transfusion-dependent anemia. The liver is the primary site for iron storage in patients with hemochromatosis or transfusion-dependent anemia, therefore, liver iron concentration (LIC) accurately reflects total body iron stores. In the past 20 years, magnetic resonance imaging (MRI) has emerged as a promising method for measuring LIC in a variety of diseases. We review the potential role of MRI in LIC determination in the most important disorders that are characterized by iron overload, that is, thalassemia major, other hemoglobinopathies, acquired anemia, and hemochromatosis. Most studies have been performed in thalassemia major and MRI is currently a widely accepted method for guiding chelation treatment in these patients. However, the lack of correlation between liver and cardiac iron stores suggests that both organs should be evaluated with MRI, since cardiac disease is the leading cause of death in this population. It is also unclear which MRI method is the most accurate since there are no large studies that have directly compared the different available techniques. The role of MRI in the era of genetic diagnosis of hemochromatosis is also debated, whereas data on the accuracy of the method in other hematological and liver diseases are rather limited. However, MRI is a fast, non-invasive and relatively accurate diagnostic tool for assessing LIC, and its use is expected to increase as the role of iron in the pathogenesis of liver disease becomes clearer.

Plasma prohepcidin levels in patients with chronic viral hepatitis: relationship with liver fibrosis

OBJECTIVES

Iron is deemed to play a crucial role in the pathophysiology of liver damage in patients with chronic viral hepatitis. Hepcidin has recently emerged as the key hormone in the regulation of iron balance and recycling. We assessed plasma prohepcidin levels in patients with chronic viral hepatitis and investigated the association of this molecule with iron parameters, histologic activity index, and liver fibrosis scores.

METHODS

We enrolled 35 patients with chronic hepatitis C, 27 with chronic hepatitis B, and 21 healthy controls. Plasma levels of prohepcidin were measured by enzyme-linked immunosorbent assay.

RESULTS

Mean prohepcidin levels were significantly lower in patients with chronic hepatitis B than in those with chronic hepatitis C (P<0.001) and healthy comparison controls (P<0.05). In patients with chronic hepatitis C, prohepcidin was independently associated with liver fibrosis scores (beta=-0.009, standard error=0.003, P<0.05). No association of prohepcidin with iron parameters was found.

CONCLUSION

Significantly lower prohepcidin levels are frequently found in patients with chronic hepatitis B. Levels of this molecule may represent a biochemical correlate of fibrosis in chronic hepatitis C virus infection.

Iron in obesity. An ancient micronutrient for a modern disease

Iron is a necessary constituent of several macromolecules involved in cell metabolism, but, at the same time, it could be a potentially dangerous element. For this reason iron balance must be finely regulated. At present, obesity has been recognized as a worldwide public health problem. Excess body fat is associated with increased all-cause mortality and increased risk for several medical morbidities. Many studies have shown that obesity might increase the risk of iron deficiency but, at the same time, obese subjects exhibit high serum ferritin levels. Recent studies seem to indicate that obesity is associated with iron deficiency although the aetiology appears to be multifactorial and includes (i) A decrease in iron food intake; (ii) An impairment of intestinal iron uptake and iron release from stores because of an overexpression of hepcidin and (iii) Inadequate iron bioavailability because of inflammation. In addition, abnormal ferritin concentrations can be explained by chronic inflammation rather than by iron overload. The aim of the present article is to review current knowledge of iron and obesity.

Genetic mechanisms and modifying factors in hereditary hemochromatosis

Primary iron overload is one of the most common inherited diseases worldwide. Several genetic mutations underlie the various forms of the disease, which have similar pathophysiological profiles but distinct clinical presentations. Patients with hereditary hemochromatosis absorb too much iron from the diet, which accumulates over time within parenchymal cells. This accumulation leads to eventual organ failure as a consequence of iron-mediated formation of free radicals. The mechanism underlying this excessive absorption of iron is a sensing defect caused by the reduced formation of hepcidin, the master regulator of iron homeostasis, as a consequence of mutations in the genes encoding several membrane-bound signaling molecules present on hepatocytes. A considerable number of carriers of these specific genetic mutations, however, do not develop iron overload, indicating that additional genetic and environmental factors modify the severity and clinical penetrance of disease. In affected patients, early initiation of treatment by phlebotomy can prevent organ damage. Genetic screening of first-degree relatives can be also used to identify individuals at risk. Our expanding knowledge of the regulation of iron metabolism and the role of factors that modify the severity of the disease may lead to the design of new and improved treatments.

Factors associated with hepatic fibrosis in patients with chronic hepatitis C: a retrospective study of a large cohort of U.S. patients

GOALS

To determine the risk factors for stage 3 and 4 fibrosis in a large cohort of U.S. patients with chronic hepatitis C (CHC).

BACKGROUND

Multiple host and viral factors affect the outcomes of CHC. Further defining the pathogenic roles of these factors in CHC progression will lead to improving management of this disease.

STUDY

Retrospective study of a large cohort of US patients with CHC.

RESULTS

Of the 460 patients, 331 were males and 129 were females with mean age of 48.4+/-8.0 years, and 191 (41.7%) had stage 3 and 4 fibrosis. Clinically, a multivariate analysis revealed that age of > or =60 years at presentation, the estimated duration of hepatitis C virus (HCV) infection > or =25 years, a body mass index > or =30 kg/m, and a history of diabetes mellitus were independently associated with stage 3 and 4 fibrosis, after adjusting for history of alcohol use. Laboratorially, a multivariate analysis revealed that aspartate aminotransferase (AST) > or =2 x upper limit of normal (ULN), alpha fetoprotein > or =15 microg/L, and presence of grade 2 and 3 steatosis were independently associated with stage 3 and 4 fibrosis, after adjusting for alanine aminotransferase > or =2 x upper limit of normal, AST/alanine aminotransferase ratio > or =1, HCV genotyping, transferrin saturation, and a histology activity index score > or =7.

CONCLUSIONS

The present study indicated that elderly, longer duration of HCV infection, obesity, and history of diabetes mellitus are independent clinical parameters associated with advanced fibrosis, whereas elevated AST, alpha fetoprotein, and presence of grade 2 and 3 steatosis are independent laboratorial parameters associated with stage 3 and 4 fibrosis in patients with CHC.

Use of phlebotomy treatment in Atlantic bottlenose dolphins with iron overload

CASE DESCRIPTION

3 adult (24- to 43-year-old) Atlantic bottlenose dolphins (Tursiops truncatus) with chronic episodic malaise and inappetence associated with high serum aminotransferase (alanine aminotransferase and aspartate aminotransferase) activities, high serum iron concentration, and serum transferrin saturation > 80% were evaluated.

CLINICAL FINDINGS

Results of histologic examination of liver biopsy specimens revealed hemosiderosis in all 3 dolphins. Except for chronic lymphocytosis in 1 dolphin, results of extensive diagnostic testing revealed no other abnormalities. For each dolphin, a diagnosis of iron overload of unknown origin was made.

TREATMENT AND OUTCOME

Phlebotomy treatment was implemented to reduce body stores of iron. Each phlebotomy procedure removed 7% to 17% (1 to 3 L) of estimated blood volume. Treatment consisted of an induction phase of weekly phlebotomy procedures for 22 to 30 weeks, which was complete when serum iron concentration and aminotransferase activities were within reference ranges and serum transferrin saturation was < or = 20% or Hct was < or = 30%. Total amount of iron removed from each dolphin was 53 to 111 mg/kg (24.1 to 50.5 mg/lb) of body weight. One dolphin required maintenance procedures at 8- to 12-week intervals when high serum iron concentration was detected.

CLINICAL RELEVANCE

Although the cause of the iron overload and high serum aminotransferase activities remained unknown, phlebotomy treatment successfully resolved the clinicopathologic abnormalities, supporting a role of iron overload in the hepatopathy of the 3 dolphins.

Glucose abnormalities in non-alcoholic fatty liver disease and chronic hepatitis C virus infection: the role of iron overload

Non-alcoholic fatty liver disease (NAFLD) and chronic hepatitis C virus (HCV) infection are major causes of liver disease frequently described in outpatient patients with glucose abnormalities. Hyperferritinemia, which suggests that iron overload plays a decisive role in the pathophysiology of insulin resistance and hyperglycemia, is a common finding in both disorders. However, the role of the hepatic iron deposition differs from one to the other. In NAFLD, a moderate liver iron accumulation has been observed and molecular mechanisms, including the downregulation of the liver iron exporter ferroportin-1, have been described. Iron overload will enhance intrahepatic oxidative stress that promotes hepatic fibrosis, interfere with insulin signalling at various levels and may hamper hepatic insulin extraction. Therefore, liver fibrosis, hyperglycemia and hyperinsulinemia will lead to increased levels of insulin resistance and the development of glucose abnormalities. Furthermore, iron depletion by phlebotomy removes liver iron content and reduces serum glucose and insulin resistance in NAFLD patients. Therefore, it seems that iron overload participates in those glucose abnormalities associated with NAFLD. Concerning chronic HCV infection, it has been classically assumed that iron overload contributes to insulin resistance associated with virus infection. However, recent evidence argues against the presence of iron overload in these patients and points to inflammation associated with diabetes as the main contributor to the elevated ferritin levels. Therefore, glucose abnormalities, and specially type 2 diabetes, should be taken into account when evaluating serum ferritin levels in patients with HCV infection.

Suppressive effects of retinoids on iron-induced oxidative stress in the liver

BACKGROUND & AIMS

We previously reported that impaired retinoid signaling in the liver causes steatohepatitis and hepatocellular carcinoma. Recently, oxidative stress induced by hepatic iron overload has emerged as an important factor for the progression of liver disease in patients with chronic hepatitis C, alcoholic liver disease, and nonalcoholic steatohepatitis. In this study, the relationship between retinoid signaling and iron metabolism in the liver was investigated.

METHODS

The effect of retinoids on the iron metabolism was examined in HuH7 cells treated with all-trans retinoic acid and acyclic retinoid NIK-333. In in vivo experiments, we used the mice expressing the dominant negative form of retinoic acid receptor alpha gene under the control of albumin enhancer/promoter (RAR-E Tg) and iron-overloaded wild mice fed with retinoid-deficient and retinoid-excess diets.

RESULTS

Hepatic iron accumulation and increased expression of hemojuvelin were observed in RAR-E Tg mouse liver. Retinoid treatment significantly suppressed expression of hemojuvelin and mildly suppressed expression of transferrin receptor type 2 and hepcidin, accompanied by decreased hepatic iron content and iron-induced oxidative stress in vitro and in vivo. Overexpression of hemojuvelin in HuH7 hepatoma cells led to a significant increase in cellular iron content.

CONCLUSIONS

Our results suggest that retinoids are involved in hepatic iron metabolism through transcriptional regulation of hemojuvelin. This study demonstrated a novel functional role of retinoids in preventing iron-induced oxidative stress in the liver.

Reactive oxygen species regulate ceruloplasmin by a novel mRNA decay mechanism involving its 3'-untranslated region: implications in neurodegenerative diseases

Ceruloplasmin (Cp), a copper-containing protein, plays a significant role in body iron homeostasis as aceruloplasminemia patients and Cp knock-out mice exhibit iron overload in several tissues including liver and brain. Several other functions as oxidant, as antioxidant, and in nitric oxide metabolism are also attributed to Cp. Despite its role in iron oxidation and other biological oxidation reactions the regulation of Cp by reactive oxygen species (ROS) remains unexplored. Cp is synthesized in liver as a secretory protein and predominantly as a glycosylphosphatidylinositol-anchored membrane-bound form in astroglia. In this study we demonstrated that Cp expression is decreased by an mRNA decay mechanism in response to extracellular (H2O2) or intracellular oxidative stress (by mitochondrial chain blockers rotenone or antimycin A) in both hepatic and astroglial cells. The promotion of Cp mRNA decay is conferred by its 3'-untranslated region (UTR). When chloramphenicol acetyltransferase (CAT) gene was transfected as a chimera with Cp 3'-UTR in hepatic or astroglial cells, in response to either H2O2, rotenone, or antimycin A, the expression of CAT transcript was decreased, whereas expression of a 3'-UTR-less CAT transcript remained unaffected. RNA gel shift assay showed significant reduction in 3'-UTR-binding protein complex by ROS in both cell types that was reversed by the antioxidant N-acetylcysteine suggesting that ROS affects RNA-protein complex formation to promote Cp mRNA decay. Our finding is not only the first demonstration of regulation of Cp by ROS by a novel post-transcriptional mechanism but also provides a mechanism of iron deposition in neurodegenerative diseases.

Dysregulation of systemic iron metabolism in alcoholic liver diseases

Alcoholic liver diseases (ALD) are frequently associated with iron overload. Until recently, the effects of ethanol in hepatic iron uptake and intestinal iron absorption have not been clarified in detail. Two possible mechanisms for iron overload are the uptake of iron into hepatocytes in a specific manner through the increased expression of transferrin receptor (TfR) 1; and increased intestinal iron absorption by the lowering of hepcidin. It is worthwhile to examine whether a similar mechanism is present in the development of steatosis and non-alcoholic steatohepatitis (NASH). Hepatocytes have several iron uptake pathways. Ethanol increases transferrin (Tf)-mediated uptake via a receptor-dependent manner, but downregulates the non-Tf-bound iron uptake. According to immunohistochemical study, TfR1 was increased in hepatocytes in 80% of hepatic tissues of patients with ALD, but was not detected in normal hepatic tissues. In an experimental model, ethanol exposure to the primary cultured-hepatocytes in the presence of iron increased TfR1 expression and (59)Fe-labeled Tf uptake. In patients with ALD, intestinal iron absorption is increased by oral iron uptake assay. The regulatory hormone for iron homeostasis, hepcidin is downregulated in ethanol-loaded mice liver. As well as ALD, a similar mechanism was present in the mouse model fed with a high-fat diet, a model of the initial phenomenon of steatosis. The common mechanism for hepatic iron deposition and the triggering role of iron may be present in the development of ALD and non-alcoholic fatty liver disease/NASH.