Regulator Of Systemic Iron Homeostasis Research Articles

Social defeat stress impairs systemic iron metabolism by activating the hepcidin-ferroportin axis.

Chronic psychological stress has been reported to decrease circulating iron concentrations and impair hematopoiesis. However, the underlying mechanisms remain unclear. This study aimed to investigate the effects of psychological stress on biological iron metabolism by using the social defeat stress (SDS) model, a widely used model of depression. Compared with control mice, mice subjected to SDS (SDS mice) had lower social interaction (SI) behavior. The SDS mice also showed impaired hematopoiesis, as evidenced by reduced circulating red blood cell counts, elevated reticulocyte counts, and decreased plasma iron levels. In the SDS mice, the iron contents in the bone marrow decreased, whereas those in the spleen increased, suggesting dysregulation in systemic iron metabolism. The concentrations of plasma hepcidin, an important regulator of systemic iron homeostasis, increased in the SDS mice. Meanwhile, the concentrations of ferroportin, an iron transport protein negatively regulated by hepcidin, were lower in the spleen and duodenum of the SDS mice than in those of the control mice. Treatment with dalteparin, a hepcidin inhibitor, prevented the decrease in plasma iron levels in the SDS mice. The gene expression and enzyme activity of furin, which converts the precursor hepcidin to active hepcidin, were high and positively correlated with plasma hepcidin concentration. Thus, furin activation might be responsible for the increased plasma hepcidin concentration. This study is the first to show that psychological stress disrupts systemic iron homeostasis by activating the hepcidin-ferroportin axis. Consideration of psychological stressors might be beneficial in the treatment of diseases with iron-refractory anemia.

Understanding iron homeostasis in MDS: the role of erythroferrone.

Myelodysplastic neoplasms (MDS) are a heterogenous group of clonal stem cell disorders characterized by dysplasia and cytopenia in one or more cell lineages. Anemia is a very common symptom that is often treated with blood transfusions and/or erythropoiesis stimulating factors. Iron overload results from a combination of these factors together with the disease-associated ineffective erythropoiesis, that is seen especially in MDS cases with SF3B1 mutations. A growing body of research has shown that erythroferrone is an important regulator of hepcidin, the master regulator of systemic iron homeostasis. Consequently, it is of interest to understand how this molecule contributes to regulating the iron balance in MDS patients. This short review evaluates our current understanding of erythroferrone in general, but more specifically in MDS and seeks to place in context how the current knowledge could be utilized for prognostication and therapy.

Fibroblast growth factor 23 is pumping iron: C-terminal-fibroblast growth factor 23 cleaved peptide and its function in iron metabolism.

Iron deficiency regulates the production of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23) but also its cleavage, to generate both intact (iFGF23) and C-terminal (Cter)-FGF23 peptides. Novel studies demonstrate that independently of the phosphaturic effects of iFGF23, Cter-FGF23 peptides play an important role in the regulation of systemic iron homeostasis. This review describes the complex interplay between iron metabolism and FGF23 biology. C-terminal (Cter) FGF23 peptides antagonize inflammation-induced hypoferremia to maintain a pool of bioavailable iron in the circulation. A key mechanism proposed is the down-regulation of the iron-regulating hormone hepcidin by Cter-FGF23. In this manuscript, we discuss how FGF23 is produced and cleaved in response to iron deficiency, and the principal functions of cleaved C-terminal FGF23 peptides. We also review possible implications anemia of chronic kidney disease (CKD).

The effect of blood transfusion on serum hepcidin levels in chronically transfused patients of β-thalassemia major: An observational study in a tertiary care centre in Western Maharashtra.

Hepcidin is the key regulator of systemic iron homeostasis. In iron-loading anemias, hepcidin levels are regulated by opposite forces of erythropoiesis and iron overload. In β-thalassemia major patients, transfusions are the predominant cause of iron overload; in such chronically transfused patients, hepcidin concentrations are significantly higher than nontransfused patients, due to both increased iron load of transfusions and the suppression of ineffective erythropoiesis. This study aims to evaluate the effect of blood transfusions on serum hepcidin levels in chronically transfused patients of β-thalassemia major and correlate with hemoglobin and serum ferritin levels of pre- and posttransfusion. Thirty-three β-thalassemia major patients requiring monthly transfusions were included in the study. Blood samples, collected pretransfusion and 7 days posttransfusion, were evaluated for hemoglobin, serum ferritin, and serum hepcidin using enzyme immunoassay. Data were statistically analyzed through SPSS software and P < 0.05 is considered statically significant. Posttransfusion levels of hemoglobin, serum ferritin, and serum hepcidin increased. Posttransfusion levels of hepcidin were near normal levels. Pre- and posttransfusion hepcidin concentrations were significantly associated with hemoglobin levels. Serum hepcidin concentrations vary depending on the degree of erythropoiesis drive and level of anemia. We found that the serum hepcidin levels decrease over the inter-transfusion interval and transfusions cause suppression of ineffective erythropoiesis by the increase in hemoglobin. Posttransfusion values of hepcidin in our study were closer to normal levels which may be due to lower erythropoietic drive posttransfusion. We suggest that the measurement of serum hepcidin in chronically transfused β-thalassemia patients can be used as a follow-up investigation for better management of these patients.

BMP5 contributes to hepcidin regulation and systemic iron homeostasis in mice

AbstractHepcidin is the master regulator of systemic iron homeostasis. The bone morphogenetic protein (BMP) signaling pathway is a critical regulator of hepcidin expression in response to iron and erythropoietic drive. Although endothelial-derived BMP6 and BMP2 ligands have key functional roles as endogenous hepcidin regulators, both iron and erythropoietic drives still regulate hepcidin in mice lacking either or both ligands. Here, we used mice with an inactivating Bmp5 mutation (Bmp5se), either alone or together with a global or endothelial Bmp6 knockout, to investigate the functional role of BMP5 in hepcidin and systemic iron homeostasis regulation. We showed that Bmp5se-mutant mice exhibit hepcidin deficiency at age 10 days, blunted hepcidin induction in response to oral iron gavage, and mild liver iron loading when fed on a low- or high-iron diet. Loss of 1 or 2 functional Bmp5 alleles also leads to increased iron loading in Bmp6-heterozygous mice and more profound hemochromatosis in global or endothelial Bmp6-knockout mice. Moreover, double Bmp5- and Bmp6-mutant mice fail to induce hepcidin in response to long-term dietary iron loading. Finally, erythroferrone binds directly to BMP5 and inhibits BMP5 induction of hepcidin in vitro. Although erythropoietin suppresses hepcidin in Bmp5se-mutant mice, it fails to suppress hepcidin in double Bmp5- and Bmp6-mutant males. Together, these data demonstrate that BMP5 plays a functional role in hepcidin and iron homeostasis regulation, particularly under conditions in which BMP6 is limited.

Iron homeostasis governs erythroid phenotype in polycythemia vera

AbstractPolycythemia vera (PV) is a myeloproliferative neoplasm driven by activating mutations in JAK2 that result in unrestrained erythrocyte production, increasing patients’ hematocrit and hemoglobin concentrations, placing them at risk of life-threatening thrombotic events. Our genome-wide association study of 440 PV cases and 403 351 controls using UK Biobank data showed that single nucleotide polymorphisms in HFE known to cause hemochromatosis are highly associated with PV diagnosis, linking iron regulation to PV. Analysis of the FinnGen dataset independently confirmed overrepresentation of homozygous HFE variants in patients with PV. HFE influences the expression of hepcidin, the master regulator of systemic iron homeostasis. Through genetic dissection of mouse models of PV, we show that the PV erythroid phenotype is directly linked to hepcidin expression: endogenous hepcidin upregulation alleviates erythroid disease whereas hepcidin ablation worsens it. Furthermore, we demonstrate that in PV, hepcidin is not regulated by expanded erythropoiesis but is likely governed by inflammatory cytokines signaling via GP130-coupled receptors. These findings have important implications for understanding the pathophysiology of PV and offer new therapeutic strategies for this disease.

TMPRSS6 rs855791 polymorphism is associated with iron deficiency in a cohort of Sri Lankan pregnant women

BackgroundHepcidin is the key regulator of systemic iron homeostasis and is downregulated by matriptase 2 (MT2), a protease encoded by TMPRSS6 gene. In the presence of low iron levels, MT2 cleaves membrane-bound hemojuvelin (HJV), causing a negative regulation of hepcidin at the gene level, and restores iron balance. rs855791T > C, a missense variant in the catalytic domain of MT2, causes valine to alanine change at 736 position. The current study aimed to investigate the association of TMPRSS6 rs855791 on iron status among a cohort of pregnant women in Sri Lanka and to predict the possible molecular mechanisms.MethodsThe study was conducted among 73 pregnant women at ≤ 12 weeks of gestation. Iron deficiency was defined as serum ferritin < 30 μg/L after adjusting for inflammation. rs855791 was genotyped with a PCR–RFLP, and its association with iron deficiency was analyzed using binary logistic regression. Docking of HJV with MT2 protein encoded by the two rs855791 alleles was undertaken in silico to predict the molecular mechanism of the observed associations.ResultsThe majority of the study population (70%) were iron deficient. Among the subjects, T allele was prevalent in the iron deficient group with a frequency of 61.8%, with a nearly twofold enhanced risk for iron deficiency (OR = 2.566, 95%CI; P = 0.011). For TT genotype, the risk of iron deficiency was nearly sixfold (OR = 5.867; 95%CI; P = 0.023). According to the in silico analysis, MT2 736A and HJV complex is more stable with an interface energy of − 7.934 kJ/mol compared to the MT2 736 V and HJV complex which generates an interface energy of − 4.689 kJ/mol.ConclusionThe current study suggests that the iron regulatory effect of rs855791 of TMPRSS6 is brought about by the differences in thermodynamic stability of the two protein complexes made by MT2 and HJV proteins. The prevalence of iron deficiency observed among Sri Lankan pregnant women may be an interplay between the prevalence of rs855791 T allele and the low dietary iron intake.

BMP Signaling and Iron Homeostasis

Iron is an essential nutrient that is critical for fundamental cellular and organismal processes including oxygen transport and energy generation. However, excess iron can catalyze the formation of toxic free oxygen radicals. Cellular and systemic iron homeostasis are therefore tightly regulated to titrate the iron supply to match iron needs. The master regulator of systemic iron homeostasis is the liver hormone hepcidin, which binds and degrades the iron exporter ferroportin to limit iron release from dietary sources and body stores. To maintain normal systemic iron homeostasis, liver hepcidin production is coordinated by a number of signals that communicate body iron needs. Iron deficiency and anemia suppress hepcidin production to increase iron availability for red blood cell production and other essential functions. Conversely, increases in serum or tissue iron stimulate hepcidin production to prevent iron overload. Inflammation also stimulates hepcidin production to restrict iron availability to infectious microorganisms. Abnormal regulation of the hepcidin‐ferroportin axis has a pathogenic role in most disorders of systemic iron homeostasis including the anemia of inflammation, the iron overload disorder hereditary hemochromatosis, and iron‐loading anemias such as beta‐thalassemia. We have discovered a key role for the bone morphogenetic protein (BMP)‐SMAD signaling pathway in controlling liver hepcidin transcription. This talk will present recent insights into how BMP‐SMAD signaling coordinates liver hepcidin transcription in response to body iron levels and the iron demand of red blood cell production to maintain systemic iron homeostasis.

SLN124, a GalNAc Conjugated 19-Mer Double-Stranded SiRNA Reduces Iron and Increases Hepcidin Levels of Healthy Volunteers in a Phase 1 Clinical Study

▪BackgroundHepcidin, a peptide hormone consisting of 25-amino-acids, is the central regulator of systemic iron homeostasis. It is synthesized predominantly in hepatocytes, and dysregulation of its production leads to a variety of disorders of iron metabolism, including iron overload as well as congenital or acquired iron-loading anaemias. These conditions are a major source of morbidity and mortality. SLN124 increases hepatic hepcidin synthesis and hence plasma hepcidin by silencing its repressor, TMPRSS6. SLN124 has been shown to lower serum iron levels for at least 6 weeks after single administration in mice and has also been shown to increase haemoglobin in a mouse model of beta-thalassemia. Here we report results from a randomised, double-blind, placebo-controlled phase 1, single ascending dose study to evaluate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of subcutaneously (sc) administered SLN124 in healthy volunteers.ObjectivesThe primary objective was to evaluate the safety and tolerability of single ascending doses of SLN124 in healthy subjects. In addition, PK parameters of SLN124 and PD biomarkers of iron metabolism were evaluated.MethodsEach subject received a single dose of SLN124 or placebo given by sc injection into their abdomen. Dose levels of 1 mg/kg, 3 mg/kg and 4.5 mg/kg were evaluated. At each dose level, 6 subjects received SLN124 and 2 received matching placebo.ResultsThree cohorts of 8 subjects (6:2) were included in the study. The mean age of subjects was 31.3 years (SD 7.8) and 71% were male. There were no serious adverse events or severe treatment emergent adverse events (TEAEs) or TEAEs leading to withdrawal. The majority of TEAEs were mild, including transient mild injection site reactions, which resolved without intervention. No dose limiting toxicities were observed.Plasma hepcidin levels at baseline were (mean ± SD) 2.3±1.1, 2.5±1.8 and 2.7±2.0 nM in the three treatment groups, respectively. After a single administration of 1, 3 or 4.5 mg/kg of SLN124, levels were increased by 3.1±2.7, 5.8±2.6 and 7.8±2.9 nM on day 29 and by 2.6±2.6, 2.8±1.4 and 3.5±1.8 nM day 57 post dosing, respectively.Serum iron was reduced by mean (±SD) 32% (26), 40% (14) ,46% (21) on day 8 and by 42% (20), 48% (14) and 47% (26) on day 29 for single doses of 1, 3 and 4.5 mg/kg, respectively. Average percentage changes in all three treatment groups were also still reduced from baseline at day 57.The mean (±SD) percent transferrin saturation (TSAT) was reduced from baseline levels in all single dose administration groups with maximum decreases observed at day 29 but reductions still observed at day 57. (Table 1).The observed PK is consistent with the PK model based on preclinical data.Thus, whereas the effects of SLN124 on plasma hepcidin show clear increments across the dose range tested, the effect on lowering serum iron and transferrin saturation shows something of a plateau effect at the highest dose. In future studies in patients with raised baseline transferrin saturations, it will be of note to determine whether transferrin saturation continues to decrease at the highest SLN124 doses.Conclusion/summaryIn summary, SLN124, a GalNAc conjugated siRNA targeting TMPRSS6, effectively reduces serum iron levels and has the potential as a therapeutic for patients with alpha and beta-thalassemia, myelodysplastic syndromes, hereditary hemochromatosis and other related disorders. The effect on hepcidin levels at the end of study, day 57, suggest a prolonged duration of action. The encouraging efficacy signal on serum iron and transferrin saturation and the expected benign safety profile of SLN124 supports further development. The GEMINI II trial (NCT04718844) is currently recruiting and wil l evaluate single and multiple doses of SLN124 in patients withthalassemia and myelodysplastic syndromes. [Display omitted] DisclosuresPorter: bluebird bio, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Honoraria; Protagonism: Honoraria; La Jolla Pharmaceuticals: Honoraria; Celgene (BMS): Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Silence Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Vifor: Honoraria, Membership on an entity's Board of Directors or advisory committees. Scrimgeour: Silence Therapeutics: Current Employment, Current holder of stock options in a privately-held company. Martinez: Silence Therapeutics: Current Employment, Current holder of stock options in a privately-held company. James: Silence Therapeutics: Consultancy. Aleku: Silence Therapeutics: Current Employment, Current holder of stock options in a privately-held company. Wilson: Silence Therapeutics: Consultancy. Muckenthaler: Silence Therapeutics: Research Funding. Schaeper: Silence Therapeutics: Current Employment, Current holder of stock options in a privately-held company. Campion: Silence Therapeutics: Current Employment, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company.

Epigallocatechin-3-Gallate Suppresses BMP-6-Mediated SMAD1/5/8 Transactivation of Hepcidin Gene by Inducing SMILE in Hepatocytes.

Hepcidin, a major regulator of systemic iron homeostasis, is mainly induced in hepatocytes by activating bone morphogenetic protein 6 (BMP-6) signaling in response to changes in the iron status. Small heterodimer partner-interacting leucine zipper protein (SMILE), a polyphenol-inducible transcriptional co-repressor, regulates hepatic gluconeogenesis and lipogenesis. Here, we examine the epigallocatechin-3-gallate (EGCG) effect on BMP-6-mediated SMAD1/5/8 transactivation of the hepcidin gene. EGCG treatment significantly decreased BMP-6-induced hepcidin gene expression and secretion in hepatocytes, which, in turn, abated ferroportin degradation. SMILE overexpression significantly decreased BMP receptor-induced hepcidin promoter activity. SMILE overexpression also significantly suppressed BMP-6-mediated induction of hepcidin mRNA and its secretion in HepG2 and AML12 cells. EGCG treatment inhibited BMP-6-mediated hepcidin gene expression and secretion, which were significantly reversed by SMILE knockdown in hepatocytes. Interestingly, SMILE physically interacted with SMAD1 in the nucleus and significantly blocked DNA binding of the SMAD complex to the BMP-response element on the hepcidin gene promoter. Taken together, these findings suggest that SMILE is a novel transcriptional repressor of BMP-6-mediated hepcidin gene expression, thus contributing to the control of iron homeostasis.

Evidence of dysregulated iron homeostasis in newly diagnosed diabetics, but not in pre-diabetics.

Diabetes mellitus has been reported to be associated with increased serum levels of ferritin. The basis of this association is unclear. It is also not precisely known whether other iron-related parameters, including hepcidin (the central regulator of systemic iron homeostasis), are affected under these circumstances. This study attempted to determine this. Adult men (normoglycemic or newly diagnosed with diabetes or pre-diabetes) were recruited. Anthropometric, metabolic, and hematological and iron-related parameters in blood were measured. Indices of insulin resistance (HOMA-IR) and pancreatic beta cell function (HOMA-β) were calculated. Subjects in the 3 groups were similar in age, and anthropometric and hematological parameters. Serum ferritin and hepcidin levels were higher in diabetics, than in pre-diabetics and in control subjects. These elevations seen were not linked to the presence of inflammation. HOMA-IR was higher in diabetics, and HOMA-β lower in diabetics and pre-diabetics, than in control subjects. HOMA-IR and serum ferritin were positively correlated with one another. Elevated levels of serum ferritin and hepcidin in newly diagnosed diabetics (but not pre-diabetics) indicate dysregulated iron homeostasis, with the former positively associated with insulin resistance in these patients.

Assessment of iron status and its correlation with hepcidin in obese adults – A prospective case-control study

Obesity, broadly refers to increased body fat, which has become an important public health problem. Its prevalence continues to increase worldwide. In the World Health Survey, the prevalence of physical inactivity in India was 9.3% in men and 15.2% in women. Adipose tissue being an endocrine organ secretes several cytokines such as Interleukin-6, TNF-α and adipokines such as adiponectin, hepcidin, resistin. This study is to compare ferritin to iron and hepcidin with normal and obese men. This case-control study was conducted at a multispecialty centre in Chennai, Tamil Nadu between 2013 and 2015, including 80 subjects of South Indian population. The biochemical parameters which were measured included the levels of hepcidin, ferritin, iron, Total Iron Binding Capacity and Hemoglobin. The results were statistically analyzed. Mann whitney U test performed to check for the statistical significance for differences in mean between the groups. The mean hepcidin values for the control group was 800.55 ± 503.50 and the study group was 1106.68 ± 826.25 and was found to be statistically significant with a p-value of 0.03. There was positive correlation of hepcidin with ferritin and Transferrin Saturation. Hepcidin is recognized as the key regulator of systemic iron homeostasis. The measurement of hepcidin in biological fluids is therefore a promising tool in the diagnosis and management of medical conditions in which iron metabolism is affected.

20 years of Hepcidin: How far we have come

Twenty years ago the discovery of hepcidin deeply changed our understanding of the regulation of systemic iron homeostasis. It is now clear that hepcidin orchestrates systemic iron levels by controlling the amount of iron exported into the bloodstream through ferroportin. Hepcidin expression is increased in situations where systemic iron levels should be reduced, such as in iron overload and infection. Conversely, hepcidin is repressed during iron deficiency, hypoxia or expanded erythropoiesis, to increase systemic iron availability and sustain erythropoiesis. In this review, we will focus on molecular mechanisms of hepcidin regulation and on the pathological consequences of their disruption.

Hepcidin Signaling in Health and Disease: Ironing Out the Details.

Hepcidin, a peptide hormone produced by hepatocytes, is the central regulator of systemic iron homeostasis through its interaction with ferroportin, the major cellular iron export protein. Hepcidin binding to ferroportin results in reduced iron export from macrophages and intestinal absorptive cells, leading to decreased serum iron levels. Hepcidin expression is influenced by several factors that include serum and liver iron stores, erythropoiesis, hypoxia, inflammation, and infection. Erythropoietic drive and hypoxia suppress hepcidin expression and promote red cell production. In contrast, inflammation and infection are associated with increased hepcidin production to sequester iron intracellularly as a means of depriving microorganisms of iron. Chronic inflammation may up‐regulate hepcidin expression through the interleukin‐6 (IL‐6)–Janus kinase 2 (JAK2)–signal transducer and activator of transcription 3 (STAT3) pathway. The bone morphogenetic protein (BMP)–mothers against decapentaplegic homolog (SMAD) pathway is a major positive driver of hepcidin expression in response to either increased circulating iron in the form of transferrin or iron loading in organs. Hereditary hemochromatosis (HH) consists of several inherited disorders that cause inappropriately reduced hepcidin expression in response to body iron stores, leading to increased iron absorption from a normal diet. The most common form of HH is due to a mutation in the HFE gene, which causes a failure in the hepatocyte iron–sensing mechanism, leading to reduced hepcidin expression; the clinical manifestations of HFE‐HH include increased serum transferrin–iron saturation and progressive iron loading in the liver and other tissues over time among patients who express the disease phenotype. In this article, we review the physiologic mechanisms and cellular pathways by which hepcidin expression is regulated, and the different forms of HH resulting from various mutations that cause hepcidin deficiency. We also review other drivers of hepcidin expression and the associated pathophysiologic consequences.

Decreased Serum Level of Interleukin-22 Correlates with Hepcidin in Patients with Hidradenitis Suppurativa.

Current understanding of the underlying pathophysiology of hidradenitis suppurativa (HS) links the disease with proinflammatory activation and autoimmune processes. This study investigated serum levels of interleukin (IL)-22, a cytokine critically involved in epithelial homeostasis, in the context of the broad clinical spectrum of patients with HS. The study also assessed the relationship between serum IL-22 and pro-inflammatory activation (as evidenced by serum level of IL-6) and serum hepcidin (central regulator of systemic iron homeostasis). Serum concentrations of IL-22 were assessed in 74 patients with HS and 15 healthy subjects. Compared with healthy controls, patients with HS demonstrated decreased levels of serum IL-22 (median; interquartile range (IQR): 12.4 pg/ml (9.8; 23.5) vs 34.8 pg/ml (24.8; 39.8), p < 0.001 vs controls). Disease severity (assessed both with Hurley staging and Hidradenitis Suppurativa Severity Index) did not differentiate IL-22 levels (p > 0.1 in both comparisons). Serum levels of IL-22 and IL-6 did not correlate with each other (R=–0.17, p = ns). In a subgroup of 24 patients with HS with pro-inflammatory activation, the mean level of IL-22 was similar to that of the remaining patients (median (IQR): 9.8 pg/ml (8.5; 15.0) vs 12.0 pg/ml (9.4; 16.3), p = ns). Patients with HS demonstrated a decreased level of hepcidin (mean: 31.3 ± 25.9 pg/ml), which correlated with the levels of IL-22 (R=0.36, p < 0.05). Patients with HS demonstrated significantly decreased levels of serum IL-22, which was neither correlated with pro-inflammatory status nor associated with disease severity, but correlated modestly with serum hepcidin.

Hepcidin: An emerging hormone in iron homeostasis: A review

Hepcidin, is a peptide hormone, which is a key regulator of systemic iron homeostasis and its unbalanced production contributes to iron disorders is derived from liver. Hepcidin was discovered by Krause and coworkers in the year 2000. The name ‘Hepcidin’ was given, from the place of synthesis in liver hepatocytes (hep-) and its antimicrobial activity (-cidin). The gene encoding hepcidin is expressed in various organs like liver, heart, lungs, brain, spinal cord, intestine, stomach, pancreas, adipocytes, skeletal muscles, testis and macrophages. Hepcidin is a 25 amino acid peptide hormone which inhibits entry of iron into the plasma compartment from the three main sources of iron: dietary absorption in the duodenum, the release of recycled iron from macrophages and the release of stored iron from hepatocytes. This blocking of iron flow is achieved by Hepcidin functios by causing degradation of iron receptor, via an iron transporter ferroportin. Hepcidin production is tightly regulated by (1) increased plasma and liver iron as a feedback mechanism to maintain stable body iron levels, (2) decreased by erythroid activity to ensure iron supply for erythropoiesis and (3) increased by inflammation as a host defense mechanism to limit extracellular iron availability to microbes. Hepcidin levels reflect the integration of signals involved in iron regulation and it directly controls iron absorption and bioavailability in circulation. Its measurement is a useful clinical tool for the management of iron disorders in the body. Recent evidence shows that the deficiency of hepcidin may cause iron overloading even in the much milder common form of hemochromatosis, from mutations in the HFE gene. The discovery of hepcidin and its role in iron metabolism could lead to new therapies for hemochromatosis and anemia of inflammation.

DISC-a, the First in a Novel Class of Potent and Selective Matriptase-2 Inhibitors for the Treatment of Hematologic Disorders Characterized By Low Hepcidin

Hepcidin is known as the master regulator of systemic iron homeostasis with reduction in synthesis leading to the development of iron overload. Hepcidin gene expression is negatively modulated by matriptase-2 (MT-2), a liver-specific type II transmembrane serine protease. MT-2 cleaves hemojuvelin (HJV), leading to the extracellular release of soluble HJV fragments and suppression of hepcidin expression. Loss-of-function of MT-2 leads to increased hepcidin expression, as has been established by human genetics (Finberg et al., 2008) and genetic mouse models (Du et al., 2008). Therefore, inhibition of MT-2 represents a potential therapeutic strategy for diseases caused by inappropriately low hepcidin leading to iron overload or where therapeutic iron restriction may be used to control excessive erythrocytosis. Here we describe the characteristics of DISC-A, a potent (low nM Ki) small molecule MT-2 inhibitor for treatment of low hepcidin disorders, with a favorable pharmacokinetics profile in rats (Clp 6.4 ml/min/kg, and t ½ 4.6 hr) and monkeys (Clp 8.1 ml/min/kg, and t ½ 2.8 hr) and drug-like properties. DISC-A inhibits proteolytic activity of MT-2 expressed on the surface of transfected HEK293 cells and prevents shedding of MT-2 from the membrane (autocleavage). In addition, in MT-2 and HJV co-transfected HEK293A cells, DISC-A shows a dose dependent inhibition of HJV cleavage. The efficacy of DISC-A was evaluated in a rat model of low hepcidin. In this model, when Sprague-Dawley rats who are fed a standard iron diet (45 ppm) reach 8 - 9 weeks of age, they are administered erythropoietin (EPO) at 30 IU/animal/day for 4-consecutive days, before dosing with DISC-A. Under the conditions of the model, the increased erythropoiesis leads to increased iron utilization and consequently suppressed hepcidin levels. We determine hepcidin changes by measuring the changes in the expression of liver HAMP (the gene that encodes hepcidin) mRNA expression. Circulating soluble HJV is assayed as a direct measure of MT-2 activity. In this model, a single subcutaneous administration of DISC-A at 20 mg/kg resulted in a 50% reduction in soluble HJV, 14-fold increase in liver HAMP expression and &amp;gt;50% reduction in serum iron and transferrin saturation (TSAT) at 2, 4, 6, and 8 hours. The pharmacokinetics/pharmacodynamics response was robust. In summary, we have identified DISC-A, a novel, potent inhibitor of MT-2. We have demonstrated that DISC-A inhibits MT-2 proteolytic activity, prevents cleavage of HJV, and modulates hepcidin gene expression and iron homeostasis in vitro and in vivo. The favorable pharmacokinetics suggest compounds from these chemical series have the potential for clinical therapeutic benefit. Disclosures Hong: Disc Medicine: Current Employment, Current equity holder in private company. Babu:Aurigene Discovery Technologies: Current Employment. Blaustein:Disc Medicine: Current Employment, Current equity holder in private company. Nguyen:Disc Medicine: Current Employment, Current equity holder in private company. Rao:Aurigene Discovery Technologies: Current Employment. Savage:Disc Medicine: Current Employment, Current equity holder in private company. MacDonald:Disc Medicine: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Beconi:Disc Medicine: Current Employment, Current equity holder in private company. Venkatraman:Disc Medicine: Current Employment, Current equity holder in private company.

Iron metabolism and iron disorders revisited in the hepcidin era.

Iron is biologically essential, but also potentially toxic; as such it is tightly controlled at cell and systemic levels to prevent both deficiency and overload. Iron regulatory proteins post-transcriptionally control genes encoding proteins that modulate iron uptake, recycling and storage and are themselves regulated by iron. The master regulator of systemic iron homeostasis is the liver peptide hepcidin, which controls serum iron through degradation of ferroportin in iron-absorptive enterocytes and iron-recycling macrophages. This review emphasizes the most recent findings in iron biology, deregulation of the hepcidin-ferroportin axis in iron disorders and how research results have an impact on clinical disorders. Insufficient hepcidin production is central to iron overload while hepcidin excess leads to iron restriction. Mutations of hemochro-matosis genes result in iron excess by downregulating the liver BMP-SMAD signaling pathway or by causing hepcidin-resistance. In iron-loading anemias, such as β-thalassemia, enhanced albeit ineffective ery-thropoiesis releases erythroferrone, which sequesters BMP receptor ligands, thereby inhibiting hepcidin. In iron-refractory, iron-deficiency ane-mia mutations of the hepcidin inhibitor TMPRSS6 upregulate the BMP-SMAD pathway. Interleukin-6 in acute and chronic inflammation increases hepcidin levels, causing iron-restricted erythropoiesis and ane-mia of inflammation in the presence of iron-replete macrophages. Our improved understanding of iron homeostasis and its regulation is having an impact on the established schedules of oral iron treatment and the choice of oral versus intravenous iron in the management of iron deficiency. Moreover it is leading to the development of targeted therapies for iron overload and inflammation, mainly centered on the manipulation of the hepcidin-ferroportin axis.

Effect of regular Exercise and iron injection on iron status of anemic obese male rats.

Many animal studies have reported an association between obesity and reduced iron storage. Systemic chronic inflammation induced by obesity and higher hepcidin levels has been suggested as a reason for the iron deficiency that occurs with obesity. Hepcidin is a master regulator of systemic iron homeostasis. Hepcidin is a peptide hormone, produced mainly from the liver. It inhibits intestinal iron absorption. The hepatic production of hepcidin is up-regulated by pro-inflammatory cytokines. An exercise is an effective approach for controlling obesity. Several studies showed that exercise reduced body weight. So this study hypothesized that regular exercises may be used as an adjuvant line in treating iron deficiency associated with obesity via reducing serum hepcidin. Materials and methods: 75 young male albino rats were categorized into 5 groups. Obesity was induced by high-fat diet(HFD) for 3 months in Group II, III, IV, and V. After 12 weeks, Rats of GIII and GV were injected once every 2 days with iron-III poly-maltose 50 ml/kg for 2 weeks.,treadmill regular exercise was performed for 8 weeks for rats of GIV and GV. Measurement of body weight was done after 3 months of HFD and at the end of the experiment. Biochemical analysis was done for serum iron and serum hepcidin. Results: Measurement of body weight showed that exercise has a decreasing effect on body weight in obese rats. Exercise decreased serum hepcidin levels in obese rats and increased serum iron. Conclusion: Exercise decreases serum hepcidin level also improves the serum iron level in obese rats.

Enhanced insulin signaling and its downstream effects in iron-overloaded primary hepatocytes from hepcidin knock-out mice

BackgroundIncreased body iron stores have been implicated in the pathogenesis of diabetes mellitus. However, the molecular mechanisms involved are unclear. The liver plays a central role in homeostasis of iron and glucose in the body. Mice deficient in hepcidin (the central regulator of systemic iron homeostasis) (Hamp1−/− mice) accumulate iron in the liver in vivo. The effects of such iron loading on hepatic insulin signaling and glucose metabolism are not known. MethodsHepatocytes isolated from Hamp1−/− mice were studied for markers of insulin signaling (and its downstream effects), glucose production, expression of gluconeogenic and lipogenic enzymes, and markers of AMPK (AMP-activated protein kinase) activation and oxidative stress. These parameters were studied both in the absence and presence of insulin, and also with the use of an iron chelator. ResultsAkt in the insulin signaling pathway was found to be activated in the Hamp1−/− hepatocytes to a greater extent than wild-type (WT) cells, both under basal conditions and in response to insulin. Incubation of the Hamp1−/− hepatocytes with an iron chelator attenuated these effects. There was no evidence of oxidative stress or AMPK activation in the Hamp1−/− hepatocytes. Glucose production by these cells was similar to that by WT cells. Gene expression of key gluconeogenic enzymes was decreased in these cells. In addition, they showed evidence of increased lipogenesis. ConclusionsHepatocytes from Hamp1−/− mice showed evidence of greater sensitivity to the effects of insulin than WT hepatocytes. This may explain the insulin-sensitive phenotype that has been reported in classical hemochromatosis.