Effects of alcohol consumption on iron metabolism in mice with hemochromatosis mutations

Emerging Therapies for Alcoholic Hepatitis

The incidence of alcoholic hepatitis is increasing while the mortality rate remains high. The single current available therapy for severe alcoholic hepatitis is administration of corticosteroids for patients with severe alcoholic hepatitis, which has demonstrated limited benefits, providing a short-term mortality benefit with a marginal response rate. There is a need for developing safe and effective therapies. This article reviews novel therapies targeting various mechanisms in the pathogenesis of alcoholic hepatitis, such as the gut-liver axis, inflammatory cascade, oxidative stress, and hepatic regeneration. Current ongoing clinical trials for alcoholic hepatitis also are described.

Hepcidin and Iron Metabolism in Experimental Liver Injury

The liver plays a pivotal role in the regulation of iron metabolism through its ability to sense and respond to iron stores by release of the hormone hepcidin. Under physiologic conditions, regulation of hepcidin expression in response to iron status maintains iron homeostasis. In response to tissue injury, hepcidin expression can be modulated by other factors, such as inflammation and oxidative stress. The resulting dysregulation of hepcidin is proposed to account for alterations in iron homeostasis that are sometimes observed in patients with liver disease. This review describes the effects of experimental forms of liver injury on iron metabolism and hepcidin expression. In general, models of acute liver injury demonstrate increases in hepcidin mRNA and hypoferremia, consistent with hepcidin's role as an acute-phase reactant. Conversely, diverse models of chronic liver injury are associated with decreased hepcidin mRNA but with variable effects on iron status. Elucidating the reasons for the disparate impact of different chronic injuries on iron metabolism is an important research priority, as is a deeper understanding of the interplay among various stimuli, both positive and negative, on hepcidin regulation. Future studies should provide a clearer picture of how dysregulation of hepcidin expression and altered iron homeostasis impact the progression of liver diseases and whether they are a cause or consequence of these pathologies.

Effects of long-term ethanol ingestion on hepatic iron metabolism in two mouse strains

The mechanisms responsible for dysregulation of iron metabolism in response to ethanol ingestion are poorly understood. Relatively brief ethanol exposures in rodents are associated with reduced hepatic hepcidin expression without increases in hepatic iron content. This study evaluated the effects of long-term ethanol treatment on hepatic iron metabolism in two mouse strains. Ethanol was administered in the drinking water to C57BL/6 and BALB/c mice for up to 11 months. Hepatic histology and iron concentrations (HIC) were assessed, along with expression of relevant genes and proteins by real-time RT-PCR and western blot, respectively. The livers of ethanol-consuming mice of both strains showed mild steatosis without inflammation or fibrosis. Stainable hepatocyte iron was modestly increased in both strains ingesting ethanol, although hepatic iron concentrations were significantly higher only in C57BL/6 mice. Long-term ethanol did not affect hepcidin mRNA (Hamp1 or Hamp2) in either strain, nor was the expression of several oxidative stress-responsive genes (glutamate cysteine ligase, gamma-glutamyl transpeptidase, heme oxygenase-1 and growth differentiation factor 15) altered in response to ethanol, suggesting that oxidative stress and suppression of hepcidin expression in short-term ethanol feeding models may be transient phenomena that resolve as mice adapt to ethanol exposure. This murine model of chronic ethanol ingestion demonstrates modest increases in hepatic iron without changes in hepcidin expression, markers of oxidative stress or significant histologic liver injury. Further investigations are needed to characterize the mechanisms of dysregulated iron metabolism resulting from chronic ethanol ingestion.

GNPAT p.D519G is independently associated with markedly increased iron stores in HFE p.C282Y homozygotes

BACKGROUND

GNPAT p.D519G positivity is significantly increased in HFE p.C282Y homozygotes with markedly increased iron stores. We sought to determine associations of p.D519G and iron-related variables with iron stores in p.C282Y homozygotes.

METHODS

We defined markedly increased iron stores as serum ferritin >2247pmol/L (>1000μg/L) and either hepatic iron >236μmol/g dry weight or iron >10g by induction phlebotomy (men and women). We defined normal or mildly elevated iron stores as serum ferritin <674.1pmol/L (<300μg/L) or either age≥40y with iron ≤2.5g iron by induction phlebotomy or age≥50y with ≤3.0g iron by induction phlebotomy (men only). We compared participant subgroups using univariate methods. Using multivariable logistic regression, we evaluated associations of markedly increased iron stores with these variables: age; iron supplement use (dichotomous); whole blood units donated; erythrocyte units received as transfusion; daily alcohol consumption, g; and p.D519G positivity (heterozygosity or homozygosity).

RESULTS

The mean age of 56 participants (94.6% men) was 55±10 (SD) y; 41 had markedly increased iron stores. Prevalences of swollen/tender 2nd/3rd metacarpophalangeal joints and elevated aspartate or alanine aminotransferase were significantly greater in participants with markedly increased iron stores. Only participants with markedly increased iron stores had cirrhosis. In multivariable analyses, p.D519G positivity was the only exposure variable significantly associated with markedly increased iron stores (odds ratio 9.9, 95% CI [1.6, 60.3], p=0.0126).

CONCLUSIONS

GNPAT p.D519G is strongly associated with markedly increased iron stores in p.C282Y homozygotes after correction for age, iron-related variables, and alcohol consumption.

Effect of alcohol exposure on hepatic superoxide generation and hepcidin expression

AIM: To understand the role of mitochondrial-produced superoxide (O₂^•-) in the regulation of iron-regulatory hormone, hepcidin by alcohol in the liver.

METHODS: For alcohol experiments, manganese superoxide dismutase knockout mice heterozygous for Sod2 gene expression (Sod2^+/-) and age-matched littermate control mice (LMC), expressing Sod2 gene on both alleles, were exposed to either 10% (w/v) ethanol in the drinking water or plain water (control) for 7 d. Total cellular O₂^•- levels in hepatocytes isolated from the livers of mice were measured by electron paramagnetic resonance spectroscopy. The mitochondrial-targeted, O₂^•--sensitive fluorogenic probe, MitoSOX Red and flow cytometry were utilized to measure O₂^•- in mitochondria. Gene and protein expression were determined by Taqman Real-time quantitative PCR and Western blotting, respectively.

RESULTS: Sod2^+/- mice expressed 40% less MnSOD protein (SOD2) in hepatocytes compared to LMC mice. The deletion of Sod2 allele did not alter the basal expression level of hepcidin in the liver. 10% ethanol exposure for 1 wk inhibited hepatic hepcidin mRNA expression three-fold both in Sod2^+/- and LMC mice. O₂^•- levels in hepatocytes of untreated Sod2^+/- mice were three-fold higher than in untreated LMC mice, as observed by electron paramagnetic resonance spectroscopy. O₂^•- levels in mitochondria of Sod2^+/ mice were four-fold higher than in mitochondria of untreated LMC mice, as measured by MitoSOX Red fluorescence and flow cytometry. Alcohol induced a two-fold higher increase in O₂^•- levels in hepatocytes of LMC mice than in Sod2^+/- mice compared to respective untreated counterparts. In contrast, 1 wk alcohol exposure did not alter mitochondrial O₂^•- levels in both Sod2^+/- and control mice.

CONCLUSION: Mitochondrial O₂^•- is not involved in the inhibition of liver hepcidin transcription and thereby regulation of iron metabolism by alcohol. These findings also suggest that short-term alcohol consumption significantly elevates O₂^•- levels in hepatocytes, which appears not to originate from mitochondria.

Sex-specific differences in the development of acute alcohol-induced liver steatosis in mice

AIMS

Results of several animal studies suggest that similar to humans, female rodents are more susceptible to chronic alcohol-induced liver disease (ALD). The aim of the present study was to determine whether female mice are more susceptible to acute alcohol-induced steatosis than male mice and to investigate possible mechanisms involved.

METHODS

Male and female C57BL/6J mice received one single dose of ethanol (6 g/kg bodyweight) or isocaloric maltose-dextrin solution intragastrically. Plasma alcohol concentration, markers of hepatic steatosis, activation of the TLR-4 signaling cascade and triglyceride export as well as lipid peroxidation and of iron metabolism were measured 12 h after acute alcohol intake.

RESULTS

In male and female ethanol-treated mice, plasma alcohol concentrations were still markedly increased 12 h after the alcohol challenge, which was associated with a significant accumulation of lipids in the liver and increase of transaminases in plasma; however, lipid accumulation was ∼3-fold higher in females in comparison with male animals. Expression of MyD88 was only found to be significantly induced in livers of female alcohol-exposed mice, whereas protein levels of ApoB were found to be significantly lower only in livers of female mice exposed to ethanol. Levels of 4-HNE protein adducts and ferritin were induced in livers of male and female ethanol-treated mice.

CONCLUSION

Taken together, these data suggest that female mice are also more susceptible to acute alcohol-induced liver steatosis and that this involves an increased activation of TLR-4-dependent signaling pathways in the liver.

Diagnosis and treatment of hereditary hemochromatosis: an update

Hereditary hemochromatosis is an inherited iron overload disorder caused by inappropriately low hepcidin secretion leading to increased duodenal absorption of dietary iron, most commonly in C282Y homozygous individuals. This can result in elevated serum ferritin, iron deposition in various organs and ultimately end-organ damage, although there is incomplete biochemical and clinical penetrance and variable phenotypic expression of the HFE mutation in hereditary hemochromatosis. An elevated SF >1000 mg/l [corrected] is associated with an increased risk of cirrhosis and mortality in C282Y homozygotes.Conversely, a SF <1000 µg/l is associated with a very low likelihood of cirrhosis, making liver biopsy unnecessary among C282Y homozygotes in the absence of concomitant risk factors for liver disease. Phlebotomy remains the mainstay of treatment and new treatments being studied include erythrocytapheresis and 'mini-hepcidins'. Iron overload is being recognized to play a carcinogenic role in hepatocellular carcinoma and other cancers, possibly supporting iron depletion in these patients.

A corn oil-based diet protects against combined ethanol and iron-induced liver injury in a mouse model of hemochromatosis

BACKGROUND

Combined iron overload and alcohol may promote synergistic chronic liver injury and toxicity. The role of specific dietary fats in influencing the development of co-toxic alcoholic liver disease needs further evaluation and is investigated in this study.

METHODS

Wild-type (WT) and the iron-loaded Hfe-null (Hfe(-/-) ) mice were fed chow (CC), a AIN-93G standard control (SC), or a corn oil-modified, AIN-93G-based (CO) diet with or without the addition of 20% ethanol (EtOH) in the drinking water for 8 weeks and assessed for liver injury.

RESULTS

WT mice on CC, SC, and CO diets had no liver injury, although mild steatosis developed in the SC and CO groups. The addition of EtOH resulted in mild steatohepatitis in WT mice fed SC but not those on a CO diet. EtOH administration in Hfe(-/-) animals on the CC and SC diets caused marked oxidative stress, inflammatory activity, and subsinusoidal and portal-portal tract linkage fibrosis with significant up-regulation of genes involved in cellular stress signaling and fibrogenic pathways. These effects were abrogated in the CO-fed mice, despite elevated serum EtOH levels and hepatic iron concentrations, reduced hepatic glutathione and mitochondrial superoxide dismutase activities. Feeding with the CO diet led to increased hepatic glutathione peroxidase and catalase activities and attenuated alcohol-induced hepatic steatosis in the Hfe(-/-) animals. Iron and EtOH feeding markedly reduced p-STAT3 and p-AMPK protein levels, but this effect was significantly attenuated when a CO diet was consumed.

CONCLUSIONS

A CO-based diet is protective against combined EtOH- and iron-induced liver toxicity, likely via attenuation of hepatic steatosis and oxidative stress and may have a role in the prevention of fibrosis development in chronic liver disease.

Mammalian iron metabolism

ABSTRACT Iron is an essential transition metal for mammalian cellular and tissue viability. It is critical to supplying oxygen through heme, the mitochondrial respiratory chain, and enzymes such as ribonucleotide reductase. Mammalian organisms have evolved with the means of regulating the metabolism of iron, because if left unregulated, the resulting excess amounts of iron may induce chronic toxicities affecting multiple organ systems. Several homeostatic mechanisms exist to control the amount of intestinal dietary iron uptake, cellular iron uptake, distribution, and export. Within these processes, numerous molecular participants have been identified because of advancements in basic cell biology and efforts in disease-based research of iron storage abnormalities. For example, dietary iron uptake across the intestinal duodenal mucosa is mediated by an intramembrane divalent metal transporter 1 (DMT1), and cellular iron efflux involves ferroportin, the only known iron exporter. In addition to duodenal enterocytes, ferroportin is present in other cell types, and exports iron into plasma. Ferroportin was recently discovered to be regulated by the expression of the circulating hormone hepcidin, a small peptide synthesized in hepatocytes. These recent studies on the role of hepcidin in the regulation of dietary, cellular, and extracellular iron have led to a better understanding of the pathways by which iron balance in humans is influenced, especially its involvement in human genetic diseases of iron overload. Other important molecular pathways include iron binding to transferrin in the bloodstream for cellular delivery through the plasma membrane transferrin receptor (TfR1). In the cytosol, iron regulatory proteins 1 and 2 (IRP1 and IRP2) play a prominent role in sensing the presence of iron in order to posttranscriptionally regulate the expression of TfR1 and ferritin, two important participants in iron metabolism. From a toxicological standpoint, posttranscriptional regulation of these genes aids in the sequestration, control, and hence prevention of cytotoxic effects from free-floating nontransferrin-bound iron. Given the importance of dietary iron in normal physiology, its potential to induce chronic toxicity, and recent discoveries in the regulation of human iron metabolism by hepcidin, this review will address the regulatory mechanisms of normal iron metabolism in mammals with emphasis on dietary exposure. It is the goal of this review that this information may provide in a concise format our current understanding of major pathways and mechanisms involved in mammalian iron metabolism, which is a basis for control of iron toxicity. Such a discussion is intended to facilitate the identification of deficiencies so that future metabolic or toxicological studies may be appropriately focused. A better knowledge of iron metabolism from normal to pathophysiological conditions will ultimately broaden the spectrum of the usefulness of this information in biomedical and toxicological sciences for improving and protecting human health.

Alcohol Activates TGF-Beta but Inhibits BMP Receptor-Mediated Smad Signaling and Smad4 Binding to Hepcidin Promoter in the Liver

Hepcidin, a key regulator of iron metabolism, is activated by bone morphogenetic proteins (BMPs). Mice pair-fed with regular and ethanol-containing L. De Carli diets were employed to study the effect of alcohol on BMP signaling and hepcidin transcription in the liver. Alcohol induced steatosis and TGF-beta expression. Liver BMP2, but not BMP4 or BMP6, expression was significantly elevated. Despite increased BMP expression, the BMP receptor, and transcription factors, Smad1 and Smad5, were not activated. In contrast, alcohol stimulated Smad2 phosphorylation. However, Smad4 DNA-binding activity and the binding of Smad4 to hepcidin promoter were attenuated. In summary, alcohol stimulates TGF-beta and BMP2 expression, and Smad2 phosphorylation but inhibits BMP receptor, and Smad1 and Smad5 activation. Smad signaling pathway in the liver may therefore be involved in the regulation of hepcidin transcription and iron metabolism by alcohol. These findings may help to further understand the mechanisms of alcohol and iron-induced liver injury.

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.

Molecular basis of iron-loading disorders

Iron-loading disorders (haemochromatosis) represent an important class of human diseases. Primary iron loading results from inherited disturbances in the mechanisms regulating intestinal iron absorption, such that excess iron is taken up from the diet. Body iron load can also be increased by repeated blood transfusions (secondary iron loading), usually as part of the treatment for various haematological disorders. In these syndromes, an element of enhanced iron absorption is also often involved. The central regulator of body iron trafficking is the liver-derived peptide hepcidin. Hepcidin limits iron entry into the plasma from macrophages, intestinal enterocytes and other cells by binding to the sole iron-export protein ferroportin, and facilitating its removal from the plasma membrane. Mutations in hepcidin or its upstream regulators (HFE, TFR2, HFE2 and BMP6) lead to reduced or absent hepcidin expression and a concomitant increase in iron absorption. Mutations in ferroportin that prevent hepcidin binding produce a similar result. Increased ineffective erythropoiesis, which often characterises erythrocyte disorders, also leads to reduced hepcidin expression and increased absorption. Recent advances in our understanding of hepcidin and body iron homeostasis provide the potential for a range of new diagnostic and therapeutic tools for haemochromatosis and related conditions.

How I treat hemochromatosis

Hemochromatosis is a common genetic disorder in which iron may progressively accumulate in the liver, heart, and other organs. The primary goal of therapy is iron depletion to normalize body iron stores and to prevent or decrease organ dysfunction. The primary therapy to normalize iron stores is phlebotomy. In this opinion article, we discuss the indications for and monitoring of phlebotomy therapy to achieve iron depletion, maintenance therapy, dietary and pharmacologic maneuvers that could reduce iron absorption, and the role of voluntary blood donation.

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.

Hepcidin regulation in wild-type and Hfe knockout mice in response to alcohol consumption: evidence for an alcohol-induced hypoxic response

BACKGROUND/AIMS

Expression of Hamp1, the gene encoding the iron regulatory peptide hepcidin, is inappropriately low in HFE-associated hereditary hemochromatosis and Hfe knockout mice (Hfe(-/-)). Since chronic alcohol consumption is also associated with disturbances in iron metabolism, we investigated the effects of alcohol consumption on hepcidin mRNA expression in Hfe(-/-) mice.

METHODS

Hfe(-/-) and C57BL/6 (wild-type) mice were pair-fed either an alcohol liquid diet or control diet for up to 8 weeks. The mRNA levels of hepcidin and ferroportin were measured at the mRNA level by RT-PCR and protein expression of hypoxia inducible factor-1 alpha (HIF-1alpha) was measured by western blot.

RESULTS

Hamp1 mRNA expression was significantly decreased and duodenal ferroportin expression was increased in alcohol-fed wild-type mice at 8 weeks. Time course experiments showed that the decrease in hepcidin mRNA was not immediate, but was significant by 4 weeks. Consistent with the genetic defect, Hamp1 mRNA was decreased and duodenal ferroportin mRNA expression was increased in Hfe(-/-) mice fed on the control diet compared with wild-type animals and alcohol further exacerbated these effects. HIF-1alpha protein levels were elevated in alcohol-fed wild-type animals compared with controls.

CONCLUSION

Alcohol may decrease Hamp1 gene expression independently of the HFE pathway possibly via alcohol-induced hypoxia.

Is the iron regulatory hormone hepcidin a risk factor for alcoholic liver disease?

Despite heavy consumption over a long period of time, only a small number of alcoholics develop alcoholic liver disease. This alludes to the possibility that other factors, besides alcohol, may be involved in the progression of the disease. Over the years, many such factors have indeed been identified, including iron. Despite being crucial for various important biological processes, iron can also be harmful due to its ability to catalyze Fenton chemistry. Alcohol and iron have been shown to interact synergistically to cause liver injury. Iron-mediated cell signaling has been reported to be involved in the pathogenesis of experimental alcoholic liver disease. Hepcidin is an iron-regulatory hormone synthesized by the liver, which plays a pivotal role in iron homeostasis. Both acute and chronic alcohol exposure suppress hepcidin expression in the liver. The sera of patients with alcoholic liver disease, particularly those exhibiting higher serum iron indices, have also been reported to display reduced prohepcidin levels. Alcohol-mediated oxidative stress is involved in the inhibition of hepcidin promoter activity and transcription in the liver. This in turn leads to an increase in intestinal iron transport and liver iron storage. Hepcidin is expressed primarily in hepatocytes. It is noteworthy that both hepatocytes and Kupffer cells are involved in the progression of alcoholic liver disease. However, the activation of Kupffer cells and TNF-α signaling has been reported not to be involved in the down-regulation of hepcidin expression by alcohol in the liver. Alcohol acts within the parenchymal cells of the liver to suppress the synthesis of hepcidin. Due to its crucial role in the regulation of body iron stores, hepcidin may act as a secondary risk factor in the progression of alcoholic liver disease. The clarification of the mechanisms by which alcohol disrupts iron homeostasis will allow for further understanding of the pathogenesis of alcoholic liver disease.

Hepcidin modulation in human diseases: From research to clinic

By modulating hepcidin production, an organism controls intestinal iron absorption, iron uptake and mobilization from stores to meet body iron need. In recent years there has been important advancement in our knowledge of hepcidin regulation that also has implications for understanding the physiopathology of some human disorders. Since the discovery of hepcidin and the demonstration of its pivotal role in iron homeostasis, there has been a substantial interest in developing a reliable assay of the hormone in biological fluids. Measurement of hepcidin in biological fluids can improve our understanding of iron diseases and be a useful tool for diagnosis and clinical management of these disorders. We reviewed the literature and our own research on hepcidin to give an updated status of the situation in this rapidly evolving field.

Regulation of liver hepcidin expression by alcohol in vivo does not involve Kupffer cell activation or TNF-alpha signaling

Alcohol downregulates hepcidin expression in the liver leading to an increase in intestinal iron transport and liver iron storage. We have previously demonstrated that alcohol-mediated oxidative stress is involved in the inhibition of hepcidin transcription by alcohol in vivo. Kupffer cells and TNF-alpha play a key role in alcohol-induced liver injury. The aim of this study was to define their involvement in the regulation of hepcidin expression by alcohol. Kupffer cells were inactivated or depleted by employing gadolinium chloride and liposomes containing clodronate, respectively. Rats pair fed with the alcohol-Lieber-DeCarli diet for 6 wk and mice fed with 20% ethanol in the drinking water for 1 wk were used as experimental models. Interestingly, alcohol downregulated hepcidin expression in the livers of rats and mice independent of gadolinium chloride or clodronate treatment. One week of alcohol treatment was sufficient to induce a significant increase in TNF-alpha levels and phosphorylation of NF-kappaB subunit p65. The neutralization of TNF-alpha by specific antibodies inhibited p65 phosphorylation. However, neither the neutralization of TNF-alpha nor the lack of TNF-alpha receptor expression reversed alcohol-induced suppression of liver hepcidin expression. The level of alcohol-induced ROS in the liver was also undiminished following Kupffer cell inactivation or depletion. Our results demonstrate that alcohol-induced Kupffer cell activation and TNF-alpha signaling are not involved in the suppression of liver hepcidin expression by alcohol-mediated oxidative stress in vivo. Therefore, these findings suggest that alcohol acts within hepatocytes to suppress hepcidin expression and thereby influences iron homeostasis.

Co-factors in liver disease: the role of HFE-related hereditary hemochromatosis and iron

The severity of liver disease and its presentation is thought to be influenced by many host factors. Prominent among these factors is the level of iron in the body. The liver plays an important role in coordinating the regulation of iron homeostasis and is involved in regulating the level of iron absorption in the duodenum and iron recycling by the macrophages. Iron homeostasis is disturbed by several metabolic and genetic disorders, including various forms of hereditary hemochromatosis. This review will focus on liver disease and how it is affected by disordered iron homeostasis, as observed in hereditary hemochromatosis and due to HFE mutations. The types of liver disease covered herein are chronic hepatitis C virus (HCV) infection, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), end-stage liver disease, hepatocellular carcinoma (HCC) and porphyria cutanea tarda (PCT).

Ferroportin Q248h, dietary iron, and serum ferritin in community African-Americans with low to high alcohol consumption

BACKGROUND

Alcohol consumption is associated with increased iron stores. In sub-Saharan Africa, high dietary ionic iron and the ferroportin Q248H allele have also been implicated in iron accumulation. We examined the associations of ferroportin Q248H, alcohol and dietary iron with serum ferritin, aspartate aminotransaminase (AST) and alanine aminotransaminase (ALT) concentrations in African-Americans.

METHODS

Inner-city African-Americans (103 men, 40 women) were recruited from the community according to reported ingestion of >4 alcoholic drinks/d or <2/wk. Typical daily heme iron, nonheme iron and alcohol were estimated using University of Hawaii's multiethnic dietary questionnaire. Based on dietary questionnaire estimates we established categories of < versus > or =56 g alcohol/d, equivalent to 4 alcoholic drinks/d assuming 14 g alcohol per drink.

RESULTS

Among 143 participants, 77% drank <56 g alcohol/d and 23%> or =56 g/d as estimated by the questionnaire. The prevalence of ferroportin Q248H was 23.3% with alcohol >56 g/d versus 7.5% with lower amounts (p = 0.014). Among subjects with no history of HIV disease, serum ferritin concentration had positive relationships with male gender (p = 0.041), alcohol consumption (p = 0.021) and ALT concentration (p = 0.0001) but not with dietary iron intake or ferroportin Q248H. Serum AST and ALT concentrations had significant positive associations with male gender and hepatitis C seropositivity but not with alcohol or dietary iron intake or ferroportin Q248H.

CONCLUSIONS

Our findings suggest a higher prevalence of ferroportin Q248H with greater alcohol consumption, and this higher prevalence raises the possibility that the allele might ameliorate the toxicity of alcohol. Our results suggest that alcohol but not dietary iron contributes to higher body iron stores in African-Americans. Studies with larger numbers of participants are needed to further clarify the relationship of ferroportin Q248H with the toxicity of alcohol consumption.

Caffeic acid alleviates the increased lipid levels of serum and tissues in alcohol-induced [hepatotoxicity in] rats

Ethanol is one of the most widely used and abused drugs that increases lipid levels in human and experimental animals. The objective of this study was to determine the effect of caffeic acid (CA) on alcohol-induced alterations of lipid levels in serum, liver and kindey of Wistar rats. The alcohol toxicity was induced by oral administration of ethanol (7.9 g/kg/bw) for 45 days through intragastric intubation. The elevation in the levels of lipids upon alcohol administration was accompanied by a significant increase in the levels of cholesterol, phospholipids (PL), free fatty acids (FFA) and triglycerides (TG) in serum, liver and kidney. Oral administration of CA (12 mg/kg/bw) to alcohol fed rats significantly decreased the serum and tissue lipid levels to near those of the control rats. In conclusion, our study suggests that oral administration of CA to alcohol fed rats markedly reduced the accumulation of cholesterol, TG, FFA and PL in circulation, liver and kidney.

Alcohol and the liver

PURPOSE OF REVIEW

To update the reader with advances in epidemiology, genetics, detection, pathogenesis and therapy of alcohol-related liver disease.

RECENT FINDINGS

Ill-health due to alcohol abuse is improving in some nations but deteriorating in others. Oxidative and nitrosative stress are key to the pathogenesis of alcoholic liver disease, and there is now greater emphasis than previously on their development and role of cytochrome P450 2E1, on mitochondrial stress and disruption, (including elucidation of mitochondrial protection mechanisms) disturbance of signaling pathways and involvement of extrahepatic mediators like adiponectin. Treatment of alcoholic liver disease has stagnated, but transplantation is still favored and debated for end-stage cirrhosis.

SUMMARY

Basic and clinical research into the mechanisms of alcoholic liver disease is making headway, but has yet to produce safe and effective therapies for alcoholic hepatitis and for reversing cirrhosis.

Iron-mediated regulation of liver hepcidin expression in rats and mice is abolished by alcohol

Alcohol reduces and iron increases liver hepcidin synthesis. This study investigates the interaction of alcohol and iron in the regulation of hepcidin messenger RNA (mRNA) expression in animal models. Mice were administered 10% ethanol for 7 days after an iron-overloaded diet. Rats were administered regular or ethanol-Lieber De Carli diets for 7 weeks with or without carbonyl iron. Hfe(-/-) mice were used as a model for genetic iron overload. Hepcidin mRNA expression was determined by real-time polymerase chain reaction (PCR) and northern blotting. Iron elevated and alcohol decreased liver hepcidin expression in mice and rats. Interestingly, despite iron overload, alcohol was capable of suppressing the up-regulation of hepcidin mRNA expression in both models. Liver iron and ferritin protein expression was elevated in alcohol-treated rats, but was not elevated further in rats treated with both iron and alcohol. Duodenal ferroportin protein expression was increased both in alcohol-treated mice and in mice treated with alcohol and iron. Hfe(-/-) mice treated with ethanol for 7 days exhibited a further decrease in hepcidin mRNA expression. The iron-induced increase in DNA-binding activity of the transcription factor CCAAT/enhancer binding protein alpha (C/EBP alpha) was also suppressed by alcohol.

CONCLUSION

Alcohol abolishes the iron-induced up-regulation of both liver hepcidin transcription and the DNA-binding activity of C/EBP alpha. Of note, hepcidin protects the body from the harmful effects of iron overload. Our findings therefore suggest that alcohol negates the protective effect of hepcidin, which may have implications for the liver injury observed in alcoholic liver disease and genetic hemochromatosis in combination with alcohol.

Role of alcohol in the regulation of iron metabolism

Patients with alcoholic liver disease frequently exhibit increased body iron stores, as reflected by elevated serum iron indices (transferrin saturation, ferritin) and hepatic iron concentration. Even mild to moderate alcohol consumption has been shown to increase the prevalence of iron overload. Moreover, increased hepatic iron content is associated with greater mortality from alcoholic cirrhosis, suggesting a pathogenic role for iron in alcoholic liver disease. Alcohol increases the severity of disease in patients with genetic hemochromatosis, an iron overload disorder common in the Caucasian population. Both iron and alcohol individually cause oxidative stress and lipid peroxidation, which culminates in liver injury. Despite these observations, the underlying mechanisms of iron accumulation and the source of the excess iron observed in alcoholic liver disease remain unclear. Over the last decade, several novel iron-regulatory proteins have been identified and these have greatly enhanced our understanding of iron metabolism. For example, hepcidin, a circulatory antimicrobial peptide synthesized by the hepatocytes of the liver is now known to play a central role in the regulation of iron homeostasis. This review attempts to describe the interaction of alcohol and iron-regulatory molecules. Understanding these molecular mechanisms is of considerable clinical importance because both alcoholic liver disease and genetic hemochromatosis are common diseases, in which alcohol and iron appear to act synergistically to cause liver injury.

Iron storage disease: facts, fiction and progress

There are many forms of iron storage disease, some hereditary and some acquired. The most common of the hereditary forms is HFE-associated hemochromatosis, and it is this disorder that is the main focus of this presentation. The body iron content is regulated by controlling absorption, and studies in the past decade have clarified, in part, how this regulation functions. A 25-amino-acid peptide hepcidin is up-regulated by iron and by inflammation, and it inhibits iron absorption and traps iron in macrophages by binding to and causing degradation of the iron transport protein ferroportin. Most forms of hemochromatosis results from dysregulation of hepcidin or defects of hepcidin or ferroportin themselves. Hereditary hemochromatosis was once considered to be very rare, but in the 1970s and 1980s, with the introduction of better diagnostic tests, it was considered the most common disease among Europeans. Controlled epidemiologic studies carried out in the last decade have shown, however, the disease itself actually is rare, and only its genotype and associated biochemical changes that are common. We do not understand why only a few homozygotes develop severe disease. It now seems unlikely that there are important modifying genes, and although alcohol is known to have some effect, excess drinking probably plays only a modest role in determining the hemochromatosis phenotype. Hereditary hemochromatosis is readily treated by phlebotomy. Secondary forms of the disease require chelation therapy, and the recent introduction of effective oral chelating agents is an important step forward in treating patients with disorders in which iron overload often proves to be fatal, such as thalassemia, myelodysplastic anemias, and dyserythropoietic anemias. While much has been learned about the regulation of iron homeostasis in the past decade, many mysteries remain and represent challenges that will keep us occupied for years to come.