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      Circulating Hepcidin-25 Is Reduced by Endogenous Estrogen in Humans

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          Abstract

          Objective

          Hepcidin reduces iron absorption by binding to the intestinal iron transporter ferroportin, thereby causing its degradation. Although short-term administration of testosterone or growth hormone (GH) has been reported to decrease circulating hepcidin levels, little is known about how hepcidin is influenced in human endocrine conditions associated with anemia.

          Research design and methods

          We used a sensitive and specific dual–monoclonal antibody sandwich immunoassay to measure hepcidin-25 in patients (a) during initiation of in vitro fertilization when endogenous estrogens were elevated vs. suppressed, (b) with GH deficiency before and after 12 months substitution treatment, (c) with hyperthyroidism before and after normalization, and (d) with hyperprolactinemia before and after six months of treatment with a dopamine agonist.

          Results

          In response to a marked stimulation of endogenous estrogen production, median hepcidin levels decreased from 4.85 to 1.43 ng/mL (p < 0.01). Hyperthyroidism, hyperprolactinemia, or GH substitution to GH-deficient patients did not influence serum hepcidin-25 levels.

          Conclusions

          In humans, gonadotropin-stimulated endogenous estrogen markedly decreases circulating hepcidin-25 levels. No clear and stable correlation between iron biomarkers and hepcidin-25 was seen before or after treatment of hyperthyroidism, hyperprolactinemia or growth hormone deficiency.

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          Most cited references34

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          LEAP-1, a novel highly disulfide-bonded human peptide, exhibits antimicrobial activity.

          We report the isolation and characterization of a novel human peptide with antimicrobial activity, termed LEAP-1 (liver-expressed antimicrobial peptide). Using a mass spectrometric assay detecting cysteine-rich peptides, a 25-residue peptide containing four disulfide bonds was identified in human blood ultrafiltrate. LEAP-1 expression was predominantly detected in the liver, and, to a much lower extent, in the heart. In radial diffusion assays, Gram-positive Bacillus megaterium, Bacillus subtilis, Micrococcus luteus, Staphylococcus carnosus, and Gram-negative Neisseria cinerea as well as the yeast Saccharomyces cerevisiae dose-dependently exhibited sensitivity upon treatment with synthetic LEAP-1. The discovery of LEAP-1 extends the known families of mammalian peptides with antimicrobial activity by its novel disulfide motif and distinct expression pattern.
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            Hepcidin-induced endocytosis of ferroportin is dependent on ferroportin ubiquitination.

            Ferroportin exports iron into plasma from absorptive enterocytes, erythrophagocytosing macrophages, and hepatic stores. The hormone hepcidin controls cellular iron export and plasma iron concentrations by binding to ferroportin and causing its internalization and degradation. We explored the mechanism of hepcidin-induced endocytosis of ferroportin, the key molecular event in systemic iron homeostasis. Hepcidin binding caused rapid ubiquitination of ferroportin in cell lines overexpressing ferroportin and in murine bone marrow-derived macrophages. No hepcidin-dependent ubiquitination was observed in C326S ferroportin mutant which does not bind hepcidin. Substitutions of lysines between residues 229 and 269 in the third cytoplasmic loop of ferroportin prevented hepcidin-dependent ubiquitination and endocytosis of ferroportin, and promoted cellular iron export even in the presence of hepcidin. The human ferroportin mutation K240E, previously associated with clinical iron overload, caused hepcidin resistance in vitro by interfering with ferroportin ubiquitination. Our study demonstrates that ubiquitination is the functionally relevant signal for hepcidin-induced ferroportin endocytosis. Copyright © 2012 Elsevier Inc. All rights reserved.
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              17β-Estradiol inhibits iron hormone hepcidin through an estrogen responsive element half-site.

              Interaction of estrogen with iron at the systemic level is long suspected, but direct evidence linking the two is limited. In the present study, we examined the effects of 17β-estradiol (E2) on hepcidin, a key negative regulator of iron absorption from the liver. We found that transcription of hepcidin was suppressed by E2 treatment in human liver HuH7 and HepG2 cells, and this down-regulation was blocked by E2 antagonist ICI 182780. Chromatin immunoprecipitation, deletion, and EMSA detected a functional estrogen responsive element half-site that is located between -2474 and -2462 upstream from the start of transcription of the hepcidin gene. After cloning the human hepcidin promoter into the pGL3Luc-Reporter vector, luciferase activity was also down-regulated by E2 treatment in HepG2 cells. E2 reduced hepcidin mRNA in wild-type mice as well as in hemochromatosis Fe gene knockout mice. In summary, our data suggest that hepcidin inhibition by E2 is to increase iron uptake, a mechanism to compensate iron loss during menstruation. This mechanism may also contribute to increased iron stores in oral contraceptive users.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                11 February 2016
                2016
                : 11
                : 2
                : e0148802
                Affiliations
                [1 ]Department of Endocrinology, Metabolism and Diabetes, Departments of Medicine and Molecular Medicine and Surgery, Karolinska Institutet at Karolinska University Hospital, S-141 86 Stockholm, Sweden
                [2 ]Molecular Nutrition Unit, Center for Innovative Medicine, Department of Biosciences and Nutrition, Karolinska Institutet at Karolinska University Hospital, S-141 86 Stockholm, Sweden
                [3 ]Lilly Research Laboratories, Eli Lilly & Co, Indianapolis, Indiana, United States of America
                Lady Davis Institute for Medical Research/McGill University, CANADA
                Author notes

                Competing Interests: JHS and RJK are employed by Ely Lilly & Co. This does not alter the authors adherence to PLOS ONE policies on sharing data and materials.

                Conceived and designed the experiments: ML MR BA. Performed the experiments: JHS LB. Analyzed the data: ML BA YB. Contributed reagents/materials/analysis tools: JHS RK KB CH LB YB. Wrote the paper: ML BA MR.

                Article
                PONE-D-15-41511
                10.1371/journal.pone.0148802
                4750915
                26866603
                e6bf4684-88d4-464c-b31c-f34e0b7d3c68
                © 2016 Lehtihet et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 21 September 2015
                : 17 December 2015
                Page count
                Figures: 0, Tables: 5, Pages: 10
                Funding
                The authors received no specific funding for this work. Lilly Research Laboratories, Eli Lilly & Co, provided support in the form of salaries for authors JHS and RJK, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ʻauthor contributionsʼ section.
                Categories
                Research Article
                Biology and Life Sciences
                Biochemistry
                Hormones
                Estrogens
                Biology and Life Sciences
                Biochemistry
                Proteins
                Protein Complexes
                Ferritin
                Biology and Life Sciences
                Biochemistry
                Hormones
                Lipid Hormones
                Estradiol
                Biology and Life Sciences
                Biochemistry
                Hormones
                Androgens
                Testosterone
                Biology and Life Sciences
                Biochemistry
                Hormones
                Lipid Hormones
                Testosterone
                Biology and Life Sciences
                Biochemistry
                Hormones
                Peptide Hormones
                Prolactin
                Biology and Life Sciences
                Nutrition
                Nutritional Deficiencies
                Iron Deficiency
                Medicine and Health Sciences
                Nutrition
                Nutritional Deficiencies
                Iron Deficiency
                Research and Analysis Methods
                Immunologic Techniques
                Immunoassays
                Enzyme-Linked Immunoassays
                Medicine and Health Sciences
                Oncology
                Cancers and Neoplasms
                Endocrine Tumors
                Prolactinoma
                Custom metadata
                All relevant data are within the paper and its Supporting Information files.

                Uncategorized
                Uncategorized

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