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      Lower serum prohepcidin levels associated with lower iron and erythropoietin requirements in hemodialysis patients with chronic hepatitis C

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          Abstract

          Background

          Patients with chronic HCV infection have increased liver iron. Recently identified protein hepcidin synthesized in the liver, is thought to be a key regulator for iron homeostasis and is induced by infection and inflammation. Lower erythropoietin and iron supplementation requirements were previously reported in HD patients with HCV infection. We investigated the association of prohepcidin with inflammation and iron parameters in HD patients with and without chronic HCV infection.

          Methods

          Sixty patients (27 male, 33 female, mean age 50 ±15 years) on chronic HD were included. Parameters related to iron metabolism (ferritin, serum iron and total iron binding capacity (TIBC)), inflammation (hs-CRP, TNF-α and IL-6) and prohepcidin levels were measured. The response to treatment (erythropoiesis-stimulating agent (ESA) resistance index) was assessed from the ratio of the weekly erythropoietin (rhuEPO) dose to hemoglobin (Hb) per unit weight.

          Results

          Serum prohepcidin levels of HCV positive patients (135 ± 25 ng/mL) were significantly lower than HCV negative patients [148 ± 18 ng/mL, (p = 0.025)]. Serum IL-6 levels of HCV positive patients were also significantly lower than HCV negative patients (p = 0.016). Serum prohepcidin levels were positively correlated with ferritin (r = 0.405, p = 0.001) and IL-6 (r = 0.271, p = 0.050) levels in HD patients. In the HCV positive group, serum prohepcidin levels significantly correlated with ferritin levels (r = 0.514 p = 0.004). In the HCV negative group, serum prohepcidin levels significantly correlated with serum IL-6 levels (r = 0.418, p = 0.027). In multiple regression analysis performed to predict prohepcidin in HCV positive patients, serum ferritin was found to be an independent variable (r = 0.28, p = 0.008).

          Conclusions

          HCV positive HD patients have low levels of serum prohepcidin and IL-6 which might account for iron accumulation together with lower iron and rhuEPO requirements in these patients.

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          Most cited references 18

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          IL-6 mediates hypoferremia of inflammation by inducing the synthesis of the iron regulatory hormone hepcidin.

          Hypoferremia is a common response to systemic infections or generalized inflammatory disorders. In mouse models, the development of hypoferremia during inflammation requires hepcidin, an iron regulatory peptide hormone produced in the liver, but the inflammatory signals that regulate hepcidin are largely unknown. Our studies in human liver cell cultures, mice, and human volunteers indicate that IL-6 is the necessary and sufficient cytokine for the induction of hepcidin during inflammation and that the IL-6-hepcidin axis is responsible for the hypoferremia of inflammation.
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            Hepcidin, a putative mediator of anemia of inflammation, is a type II acute-phase protein.

            Hepcidin is a liver-made peptide proposed to be a central regulator of intestinal iron absorption and iron recycling by macrophages. In animal models, hepcidin is induced by inflammation and iron loading, but its regulation in humans has not been studied. We report that urinary excretion of hepcidin was greatly increased in patients with iron overload, infections, or inflammatory diseases. Hepcidin excretion correlated well with serum ferritin levels, which are regulated by similar pathologic stimuli. In vitro iron loading of primary human hepatocytes, however, unexpectedly down-regulated hepcidin mRNA, suggesting that in vivo regulation of hepcidin expression by iron stores involves complex indirect effects. Hepcidin mRNA was dramatically induced by interleukin-6 (IL-6) in vitro, but not by IL-1 or tumor necrosis factor alpha (TNF-alpha), demonstrating that human hepcidin is a type II acute-phase reactant. The linkage of hepcidin induction to inflammation in humans supports its proposed role as a key mediator of anemia of inflammation.
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              Hepatitis C virus-induced reactive oxygen species raise hepatic iron level in mice by reducing hepcidin transcription.

              Despite abundant clinical evidence, the mechanisms by which hepatic iron overload develops in patients with hepatitis C virus (HCV)-associated chronic liver disease remain unknown. The aim of this study was to investigate how hepatic iron overload develops in the presence of HCV proteins. Male transgenic mice expressing the HCV polyprotein and nontransgenic control mice (C57BL/6) were assessed for iron concentrations in the liver, spleen, and serum and iron regulatory molecules in vivo and ex vivo. Transgenic mice had increased hepatic and serum iron concentrations, decreased splenic iron concentration, and lower hepcidin expression in the liver accompanied by higher expression of ferroportin in the duodenum, spleen, and liver. In response to hepatocellular iron excess, transferrin receptor 1 expression decreased and ferritin expression increased in the transgenic liver. Transgenic mice showed no inflammation in the liver but preserved the ability to induce hepcidin in response to proinflammatory cytokines induced by lipopolysaccharide. Hepcidin promoter activity and the DNA binding activity of CCAAT/enhancer-binding protein alpha (C/EBP) were down-regulated concomitant with increased expression of C/EBP homology protein, an inhibitor of C/EBP DNA binding activity, and with increased levels of reactive oxygen species in transgenic mice at the ages of 8 and 14 months. HCV-induced reactive oxygen species may down-regulate hepcidin transcription through inhibition of C/EBPalpha DNA binding activity by C/EBP homology protein, which in turn leads to increased duodenal iron transport and macrophage iron release, causing hepatic iron accumulation.
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                Author and article information

                Journal
                BMC Nephrol
                BMC Nephrol
                BMC Nephrology
                BioMed Central
                1471-2369
                2012
                7 July 2012
                : 13
                : 56
                Affiliations
                [1 ]Division of Nephrology, Department of Internal Medicine, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
                [2 ]Department of Biochemistry, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
                Article
                1471-2369-13-56
                10.1186/1471-2369-13-56
                3496582
                22768976
                Copyright ©2012 Caliskan et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Categories
                Research Article

                Nephrology

                iron metabolism, inflammation, ferritin, hemodialysis, hepcidin, hepatitis c

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