Hepcidin, a 25 amino-acid liver hormone, has recently emerged as the key regulator of iron homeostasis. Proteomic studies in limited number of subjects have shown that biological fluids can also contain truncated isoforms, whose role remains to be elucidated. We report, for the first time, data about serum levels of the hepcidin-20 isoform (hep-20) in a general population, taking advantage of the Val Borbera (VB) study where hepcidin-25 (hep-25) was measured by SELDI-TOF-MS. Detectable amount of hep-20 were found in sera from 854 out of 1577 subjects (54.2%), and its levels were about 14% of hep-25 levels. A small fraction of subjects (n = 30, 1.9%) had detectable hep-20 but undetectable hep-25. In multivariate regression models, significant predictors of hep-20 were hep-25 and age in males, and hep-25, age, serum ferritin and body mass index in females. Of note, the hep-25:hep-20 ratio was not constant in the VB population, but increased progressively with increasing ferritin levels. This is not consistent with the simplistic view of hep-20 as a mere catabolic byproduct of hep-25. Although a possible active regulation of hep-20 production needs further confirmation, our results may also have implications for immunoassays for serum hepcidin based on antibodies lacking specificity for hep-25.
This article is part of a Special Issue entitled: Integrated omics.
► Hepcidin, a 25 amino acid hormone, is the key regulator of iron metabolism. ► We measured, for the first time, serum hepcidin-20 at population level by SELDI-TOF-MS. ► Detectable amount of hepcidin 20 were found in more than half of 1577 individuals. ► The Hep25:hep20 ratio was not constant but increased with increasing iron stores. ► Our results point toward a possible active regulation of hepcidin-20 production.
BMI, body mass index; CRP, C-reactive protein; Hep-20, Hepcidin-20; Hep-24, Hepcidin-24; Hep-25, Hepcidin-25; PTH, parathyroid hormone; VB, Val Borbera; Iron metabolism; Hepcidin; Ferritin; SELDI-TOF-MS
Mass spectrometry (MS)-based assays for the quantification of the iron regulatory hormone hepcidin are pivotal to discriminate between the bioactive 25-amino acid form that can effectively block the sole iron transporter ferroportin and other naturally occurring smaller isoforms without a known role in iron metabolism. Here we describe the design, validation and use of a novel stable hepcidin-25+40 isotope as internal standard for quantification. Importantly, the relative large mass shift of 40 Da makes this isotope also suitable for easy-to-use medium resolution linear time-of-flight (TOF) platforms. As expected, implementation of hepcidin-25+40 as internal standard in our weak cation exchange (WCX) TOF MS method yielded very low inter/intra run coefficients of variation. Surprisingly, however, in samples from kidney disease patients, we detected a novel peak (m/z 2673.9) with low intensity that could be identified as hepcidin-24 and had previously remained unnoticed due to peak interference with the formerly used internal standard. Using a cell-based bioassay it was shown that synthetic hepcidin-24 was, like the -22 and -20 isoforms, a significantly less potent inducer of ferroportin degradation than hepcidin-25. During prolonged storage of plasma at room temperature, we observed that a decrease in plasma hepcidin-25 was paralleled by an increase in the levels of the hepcidin-24, -22 and -20 isoforms. This provides first evidence that all determinants for the conversion of hepcidin-25 to smaller inactive isoforms are present in the circulation, which may contribute to the functional suppression of hepcidin-25, that is significantly elevated in patients with renal impairment. The present update of our hepcidin TOF MS assay together with improved insights in the source and preparation of the internal standard, and sample stability will further improve our understanding of circulating hepcidin and pave the way towards further optimization and standardization of plasma hepcidin assays.
Assays for the detection of the iron regulatory hormone hepcidin in plasma or urine have not yet been widely available, whereas quantitative comparisons between hepcidin levels in these different matrices were thus far even impossible due to technical restrictions. To circumvent these limitations, we here describe several advances in time-of flight mass spectrometry (TOF MS), the most important of which concerned spiking of a synthetic hepcidin analogue as internal standard into serum and urine samples. This serves both as a control for experimental variation, such as recovery and matrix-dependent ionization and ion suppression, and at the same time allows value assignment to the measured hepcidin peak intensities. The assay improvements were clinically evaluated using samples from various patients groups and its relevance was further underscored by the significant correlation of serum hepcidin levels with serum iron indices in healthy individuals. Most importantly, this approach allowed kinetic studies as illustrated by the paired analyses of serum and urine samples, showing that more than 97% of the freely filtered serum hepcidin can be reabsorbed in the kidney. Thus, the here reported advances in TOF MS-based hepcidin measurements represent critical steps in the accurate quantification of hepcidin in various body fluids and pave the way for clinical studies on the kinetic behavior of hepcidin in both healthy and diseased states.
Hepcidin is a 25-residue peptide hormone crucial to iron homeostasis. It is essential to measure the concentration of hepcidin in cells, tissues and body fluids to understand its mechanisms and roles in physiology and pathophysiology. With a mass of 2791 Da hepcidin is readily detectable by mass spectrometry and LC-ESI, MALDI and SELDI have been used to estimate systemic hepcidin concentrations by analysing serum or urine. However, peak heights in mass spectra may not always reflect concentrations in samples due to competition during binding steps and variations in ionisation efficiency. Thus the purpose of this study was to develop a robust assay for measuring hepcidin using a stable isotope labelled hepcidin spiking approach in conjunction with SELDI-TOF-MS.
We synthesised and re-folded hepcidin labelled with 13C/15N phenylalanine at position 9 to generate an internal standard for mass spectrometry experiments. This labelled hepcidin is 10 Daltons heavier than the endogenous peptides and does not overlap with the isotopic envelope of the endogenous hepcidin or other common peaks in human serum or urine mass spectra and can be distinguished in low resolution mass spectrometers. We report the validation of adding labelled hepcidin into serum followed by SELDI analysis to generate an improved assay for hepcidin.
We demonstrate that without utilising a spiking approach the hepcidin peak height in SELDI spectra gives a good indication of hepcidin concentration. However, a stable isotope labelled hepcidin spiking approach provides a more robust assay, measures the absolute concentration of hepcidin and should facilitate inter-laboratory hepcidin comparisons.
Anemia is a frequently encountered problem during inflammation. Hepcidin is an interleukin-6 (IL-6)-induced key modulator of inflammation-associated anemia. Human sepsis is a prototypical inflammatory syndrome, often complicated by the development of anemia. However, the association between inflammation, hepcidin release and anemia has not been demonstrated in this group of patients. Therefore, we explored the association between hepcidin and sepsis-associated anemia.
92 consecutive patients were enrolled after presentation on the emergency ward of a university hospital with sepsis, indicated by the presence of a proven or suspected infection and ≥ 2 extended systemic inflammatory response syndrome (SIRS) criteria. Blood was drawn at day 1, 2 and 3 after admission for the measurement of IL-6 and hepcidin-25. IL-6 levels were correlated with hepcidin concentrations. Hemoglobin levels and data of blood transfusions during 14 days after hospitalisation were retrieved and the rate of hemoglobin decrease was correlated to hepcidin levels.
53 men and 39 women with a mean age of 53.3 ± 1.8 yrs were included. Hepcidin levels were highest at admission (median[IQR]): 17.9[10.1 to 28.4]nmol/l and decreased to normal levels in most patients within 3 days (9.5[3.4 to 17.9]nmol/l). Hepcidin levels increased with the number of extended SIRS criteria (P = 0.0005). Highest IL-6 levels were measured at admission (125.0[46.3 to 330.0]pg/ml) and log-transformed IL-6 levels significantly correlated with hepcidin levels at admission (r = 0.28, P = 0.015), day 2 (r = 0.51, P < 0.0001) and day 3 (r = 0.46, P < 0.0001). Twelve patients received one or more blood transfusions during the first 2 weeks of admission, not related to active bleeding. These patients had borderline significant higher hepcidin level at admission compared to non-transfused patients (26.9[17.2 to 53.9] vs 17.9[9.9 to 28.8]nmol/l, P = 0.052). IL-6 concentrations did not differ between both groups. Correlation analyses showed significant associations between hepcidin levels on day 2 and 3 and the rate of decrease in hemoglobin (Spearman's r ranging from -0.32, P = 0.03 to -0.37, P = 0.016, respectively).
These data suggest that hepcidin-25 may be an important modulator of anemia in septic patients with systemic inflammation.
Lupus nephritis is a frequent and serious complication of systemic lupus erythematosus (SLE). Treatment often requires the use of immunosuppression, and may be associated with severe side effects. The ability to predict relapse, relapse severity, and recovery could be used to more effectively implement therapy and reduce toxicity. We postulated that a proteomic analysis of the low-molecular weight urine proteome using serial urine samples obtained before, during, and after SLE nephritis flares would demonstrate potential biomarkers of SLE renal flare. This study was undertaken to test our hypothesis.
Urine from 25 flare cycles of 19 WHO Class III, IV, and V SLE nephritis patients was used. Urine samples included a baseline, and pre-flare, flare, and post-flare specimens. The urines were fractionated to remove proteins larger than 30 kDa, and spotted onto weak cation exchanger (CM10) protein chips for analysis by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS).
SELDI-TOF MS screening showed 176 protein ions between 2-20 kDa of which 27 were found to be differentially-expressed between specific flare intervals. On-chip peptide sequencing by integrated tandem mass spectrometry was used to positively identify selected differentially-expressed protein ions. The identified proteins included the 20 and 25 amino acid isoforms of hepcidin, a fragment of α1-antitrypsin, and an albumin fragment. Hepcidin 20 increased 4 months pre-flare and returned to baseline at renal flare, whereas hepcidin 25 decreased at renal flare and returned to baseline 4 months post-flare.
Using SELDI-TOF urine protein profiling in lupus nephritis, several candidate biomarkers of renal flare were found. To verify these candidates as true biomarkers, further identification and validation are needed in an independent SLE cohort.
lupus nephritis; biomarker; SELDI
Aim of this study was to evaluate whether the A736V TMPRSS6 polymorphism, a major genetic determinant of iron metabolism in healthy subjects, influences serum levels of hepcidin, the hormone regulating iron metabolism, and erythropoiesis in chronic hemodialysis (CHD).
To this end, we considered 199 CHD patients from Northern Italy (157 with hepcidin evaluation), and 188 healthy controls without iron deficiency, matched for age and gender. Genetic polymorphisms were evaluated by allele specific polymerase chain reaction assays, and hepcidin quantified by mass spectrometry.
Serum hepcidin levels were not different between the whole CHD population and controls (median 7.1, interquartile range (IQR) 0.55-17.1 vs. 7.4, 4.5-17.9 nM, respectively), but were higher in the CHD subgroup after exclusion of subjects with relative iron deficiency (p = 0.04). In CHD patients, the A736V TMPRSS6 polymorphism influenced serum hepcidin levels in individuals positive for mutations in the HFE gene of hereditary hemochromatosis (p < 0.0001). In particular, the TMPRSS6 736 V variant was associated with higher hepcidin levels (p = 0.017). At multivariate analysis, HFE and A736V TMPRSS6 genotypes predicted serum hepcidin independently of ferritin and C reactive protein (p = 0.048). In patients without acute inflammation and overt iron deficiency (C reactive protein <1 mg/dl and ferritin >30 ng/ml; n = 86), hepcidin was associated with lower mean corpuscular volume (p = 0.002), suggesting that it contributed to iron-restricted erythropoiesis. In line with previous results, in patients without acute inflammation and severe iron deficiency the “high hepcidin” 736 V TMPRSS6 variant was associated with higher erythropoietin maintenance dose (p = 0.016), independently of subclinical inflammation (p = 0.02).
The A736V TMPRSS6 genotype influences hepcidin levels, erythropoiesis, and anemia management in CHD patients. Evaluation of the effect of TMPRSS6 genotype on clinical outcomes in prospective studies in CHD may be useful to predict the outcomes of hepcidin manipulation, and to guide treatment personalization by optimizing anemia management.
Anemia; Chronic kidney disease; Erythropoietin; Genetics; Inflammation; Iron; Hemodialysis; Hepcidin; Hfe gene; Matriptase-2; Tmprss6
The mouse is a valuable model for unravelling the role of hepcidin in iron homeostasis, however, such studies still report hepcidin mRNA levels as a surrogate marker for bioactive hepcidin in its pivotal function to block ferroportin-mediated iron transport. Here, we aimed to assess bioactive mouse Hepcidin-1 (Hep-1) and its paralogue Hepcidin-2 (Hep-2) at the peptide level. To this purpose, fourier transform ion cyclotron resonance (FTICR) and tandem-MS was used for hepcidin identification, after which a time-of-flight (TOF) MS-based methodology was exploited to routinely determine Hep-1 and -2 levels in mouse serum and urine. This method was biologically validated by hepcidin assessment in: i) 3 mouse strains (C57Bl/6; DBA/2 and BABL/c) upon stimulation with intravenous iron and LPS, ii) homozygous Hfe knock out, homozygous transferrin receptor 2 (Y245X) mutated mice and double affected mice, and iii) mice treated with a sublethal hepatotoxic dose of paracetamol. The results showed that detection of Hep-1 was restricted to serum, whereas Hep-2 and its presumed isoforms were predominantly present in urine. Elevations in serum Hep-1 and urine Hep-2 upon intravenous iron or LPS were only moderate and varied considerably between mouse strains. Serum Hep-1 was decreased in all three hemochromatosis models, being lowest in the double affected mice. Serum Hep-1 levels correlated with liver hepcidin-1 gene expression, while acute liver damage by paracetamol depleted Hep-1 from serum. Furthermore, serum Hep-1 appeared to be an excellent indicator of splenic iron accumulation. In conclusion, Hep-1 and Hep-2 peptide responses in experimental mouse agree with the known biology of hepcidin mRNA regulators, and their measurement can now be implemented in experimental mouse models to provide novel insights in post-transcriptional regulation, hepcidin function, and kinetics.
Hepcidin-25, the bioactive form of hepcidin, is a key regulator of iron homeostasis as it induces internalization and degradation of ferroportin, a cellular iron exporter on enterocytes, macrophages and hepatocytes. Hepcidin levels are increased in chronic hemodialysis (HD) patients, but as of yet, limited information on factors associated with hepcidin-25 in these patients is available. In the current cross-sectional study, potential patient-, laboratory- and treatment-related determinants of serum hepcidin-20 and -25, were assessed in a large cohort of stable, prevalent HD patients. Baseline data from 405 patients (62% male; age 63.7±13.9 [mean SD]) enrolled in the CONvective TRAnsport STudy (CONTRAST; NCT00205556) were studied. Predialysis hepcidin concentrations were measured centrally with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Patient-, laboratory- and treatment related characteristics were entered in a backward multivariable linear regression model. Hepcidin-25 levels were independently and positively associated with ferritin (p<0.001), hsCRP (p<0.001) and the presence of diabetes (p = 0.02) and inversely with the estimated glomerular filtration rate (p = 0.01), absolute reticulocyte count (p = 0.02) and soluble transferrin receptor (p<0.001). Men had lower hepcidin-25 levels as compared to women (p = 0.03). Hepcidin-25 was not associated with the maintenance dose of erythropoiesis stimulating agents (ESA) or iron therapy. In conclusion, in the currently studied cohort of chronic HD patients, hepcidin-25 was a marker for iron stores and erythropoiesis and was associated with inflammation. Furthermore, hepcidin-25 levels were influenced by residual kidney function. Hepcidin-25 did not reflect ESA or iron dose in chronic stable HD patients on maintenance therapy. These results suggest that hepcidin is involved in the pathophysiological pathway of renal anemia and iron availability in these patients, but challenges its function as a clinical parameter for ESA resistance.
AIM: To investigate whether the iron stores regulator hepcidin is implicated in colon cancer-associated anaemia and whether it might have a role in colorectal carcinogenesis.
METHODS: Mass spectrometry (MALDI-TOF MS and SELDI-TOF MS) was employed to measure hepcidin in urine collected from 56 patients with colorectal cancer. Quantitative Real Time RT-PCR was utilized to determine hepcidin mRNA expression in colorectal cancer tissue. Hepcidin cellular localization was determined using immunohistochemistry.
RESULTS: We demonstrate that whilst urinary hepcidin expression was not correlated with anaemia it was positively associated with increasing T-stage of colorectal cancer (P < 0.05). Furthermore, we report that hepcidin mRNA is expressed in 34% of colorectal cancer tissue specimens and was correlated with ferroportin repression. This was supported by hepcidin immunoreactivity in colorectal cancer tissue.
CONCLUSION: We demonstrate that systemic hepcidin expression is unlikely to be the cause of the systemic anaemia associated with colorectal cancer. However, we demonstrate for the first time that hepcidin is expressed by colorectal cancer tissue and that this may represent a novel oncogenic signalling mechanism.
Iron; Hepcidin; Colon; Cancer; Anaemia; Mass spectrometry
The aim of this study was to analyze the relationship between serum pro-hepcidin concentration and the anemia profiles of rheumatoid arthritis (RA) and to estimate the pro-hepcidin could reflect the disease activity of RA. RA disease activities were measured using Disease Activity Score 28 (DAS28), tender/swollen joint counts, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Anemia profiles such as hemoglobin, iron, total iron binding capacity (TIBC), ferritin, and transferrin levels were measured. Serum concentration of pro-hepcidin, the prohormone of hepcidin, was measured using enzyme-linked immunosorbent assay (ELISA). Mean concentration of serum pro-hepcidin was 237.6±67.9 ng/mL in 40 RA patients. The pro-hepcidin concentration was correlated with rheumatoid factor, CRP, ESR, and DAS28. There was a significant correlation between pro-hepcidin with tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. The pro-hepcidin concentration was significantly higher in the patients with active RA (DAS28>5.1) than those with inactive to moderate RA (DAS28≤5.1). However, the pro-hepcidin concentration did not correlate with the anemia profiles except hemoglobin level. There was no difference of pro-hepcidin concentration between the patients with anemia of chronic disease and those without. In conclusion, serum concentration of pro-hepcidin reflects the disease activity, regardless of the anemia states in RA patients, thus it may be another potential marker for disease activity of RA.
Arthritis, Rheumatoid; Anemia; Hepcidin; Prohepcidin
We investigated the role of hepcidin in ameliorating anemia in hemodialysis patients with hepatitis. A total of 72 hemodialysis patients with hepatitis were classified according to their requirement of erythropoietin (EPO). Anemia parameters, C-reactive protein (CRP), and biochemical measurements were recorded along with the hepcidin. The number of patients receiving no EPO was higher among patients with liver disease when compared with those without liver disease (P = 0.002). The mean hepcidin levels of the patients who did not receive EPO did not differ statistically from those of the patients who received the maximum dose (P = 0.5). The hepcidin levels of patients with liver disease who received no EPO were lower compared to those patients without liver disease who received the maximum dose (P = 0.04). There was a positive correlation between hepcidin and mean platelet levels (r = 0.26, P = 0.027) and annual intravenous iron dose (r = 0.31, P = 0.007). In hemodialysis patients with hepatitis, liver disease may be one of the factors affecting erythropiesis, related with decreased hepcidin levels and iron hemostasis. Further studies are needed to verify these associations.
Anemia; erythropoietin; hemodialysis; hepatitis B; hepatitis C; hepcidin
The measurement of serum hepcidin, a peptide hormone that regulates iron metabolism, is clinically important to the understanding of iron homeostasis in health and disease. To date, the quantification of serum hepcidin levels by conventional immunological detection methods has proven problematic due to challenges in obtaining high quality antibodies which demonstrate good reproducibility. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) has been employed recently for more sensitive quantification of hepcidin; however, this method has high background levels and therefore less than optimal specificity.
In order to increase the specificity of the mass spectrometry based assay, we developed a robust, ultra-performance liquid-chromatography-tandem mass spectrometry (UPLC-MS/MS) protocol using multiple selected reaction monitoring (mSRM) for quantification of hepcidin levels in urine and serum of human subjects. With this assay, we assessed levels of hepcidin before and for up to 8 h after oral ingestion of ferrous sulfate in ten adult human subjects without known disease.
The linear response of hepcidin quantitation on each instrument was measured, and the correlation coefficients of these calibrations were r2 = 0.9512 ± 0.0202 (n=5) for urine and r2 = 0.9709 ± 0.0291 (n=5) for serum [r2= mean ± SD]. Compared to baseline, the levels of urinary hepcidin between 2-4 h and 4-8 h of both women and men showed significant increases with p < 0.05 and p < 0.001, respectively. The levels of serum hepcidin between 4 h and 8 h in both women and men showed significant increases, compared with baseline values, with both p < 0.01. Interestingly, we also observed some degree of oscillation of levels, occurring at later time points.
We have developed and validated a new method for measuring hepcidin concentrations in human serum and urine and used it to demonstrate early increases with iron supplement in both urinary and serum levels of hepcidin, which return to baseline levels, except in urine samples from men.
Hepcidin; Oral Iron; Mass Spectrometry; LC-MS/MS; Selected Reaction Monitoring
Hepcidin is the key mediator of renal anemia, and reliable measurement of serum hepcidin levels has been made possible by the ProteinChip system. We therefore investigated the iron status and serum hepcidin levels of peritoneal dialysis (PD) patients who had not received frequent doses of an erythrocytosis-stimulating agent (ESA) and had not received iron therapy. In addition to the usual iron parameters, the iron status of erythrocytes can be determined by measuring reticulocyte hemoglobin (RET-He). The mean serum hepcidin level of the PD patients (n = 52) was 80.7 ng/mL. Their serum hepcidin levels were significantly positively correlated with their serum ferritin levels and transferrin saturation (TSAT) levels, but no correlations were found between their serum hepcidin levels and RET-He levels, thereby suggesting that hepcidin has no effect on the iron dynamics of reticulocytes. Since low serum levels of CRP and IL-6, biomarkers of inflammation, were not correlated with the serum hepcidin levels, there is likely to be a threshold for induction of hepcidin expression by inflammation.
Iron deficiency (ID) and iron deficiency anemia (IDA) are common nutritional disorders in children. Hepcidin, a peptide hormone produced in the liver, is a central regulator of systemic iron metabolism. We evaluated whether serum hepcidin levels can diagnose ID in children.
Sera from 59 children (23 males and 36 females; 5 months to 17 years) were analyzed for hepcidin-25 by ELISA. Patients were classified according to hemoglobin level and iron parameters as: IDA, (N=17), ID (N=18), and control (N=24).
Serum hepcidin, ferritin, soluble transferrin receptor (sTfR), transferrin saturation, and hemoglobin levels differed significantly between groups (P<0.0001). Serum hepcidin and ferritin levels (mean±SD) were 2.01±2.30 and 7.00±7.86, 7.72±8.03 and 29.35±24.01, 16.71±14.74 and 46.40±43.57 ng/mL in the IDA, ID, and control groups, respectively. The area under the receiver operating characteristic curve for serum hepcidin as a predictor of ID was 0.852 (95% CI, 0.755-0.950). Hepcidin ≤6.895 ng/mL had a sensitivity of 79.2% and specificity of 82.8% for the diagnosis of ID. Serum hepcidin levels were significantly correlated with ferritin, transferrin saturation, and hemoglobin levels and significantly negatively correlated with sTfR level and total iron binding capacity (P<0.0001).
Serum hepcidin levels are significantly associated with iron status and can be a useful indicator of ID. Further studies are necessary to validate these findings and determine a reliable cutoff value in children.
Serum hepcidin; Iron deficiency; Children
The benefit of oral iron therapy (OIT) and factors predictive of OIT response are not established in hemodialysis (HD) patients with iron deficiency anemia (IDA). We examined the values of hepcidin-25, mean corpuscular volume (MCV), and ferritin as predictors of OIT response. Oral ferrous fumarate (50 mg/day, 8 weeks) was given to 51 HD patients with IDA (hemoglobin (Hb) < 12 g/dL, ferritin < 100 ng/mL) treated with an erythropoietin activator. Sixteen patients were responders (improvement of Hb (ΔHb) ≥ 2 g/dL) and 35 were non-responders (ΔHb < 2g/dL). Baseline Hb, MCV, serum hepcidin-25, ferritin, iron parameters, and C-reactive protein (CRP) before and ΔHb after OIT were compared between groups. Hepcidin-25, MCV, ferritin, and transferrin saturation were lower in the responders than in the non-responders. Hepcidin-25 positively correlated with ferritin. Hepcidin-25, MCV, and ferritin positively correlated with baseline Hb and negatively correlated with ΔHb. Despite normal CRP levels in all patients, CRP correlated positively with hepcidin-25 and ferritin. Stepwise multiple linear regression analysis and receiver operating characteristics curve analysis revealed that hepcidin-25, MCV, and ferritin could predict OIT response. We conclude that hepcidin-25, MCV, and ferritin could be useful markers of iron storage status and may help predict OIT response in HD patients.
anemia; ferritin; hemodialysis; hepcidin; iron; mean corpuscular volume
We examined whether regulation of hepcidin-25 by short- or long-acting recombinant human erythropoietin (rhEPO) is dependent on ferritin and predicts the response to rhEPO in hemodialysis (HD) patients.
Two studies with rhEPO were performed in 9 HD patients with a 2-year interval. Serum hepcidin-25 was measured at 0-18 h after intravenous epoetin-β (EPO) or methoxy polyethylene glycol-epoetin-β (PEG-EPO) administration and on days 3-7 after PEG-EPO. Hemoglobin (Hb), serum ferritin, transferrin, C-reactive protein (CRP), and interleukin (IL)-6 were analyzed before hepcidin measurement and 6 months after rhEPO. Based on the serum ferritin levels before hepcidin measurement, the patients in the two studies with EPO or PEG-EPO were combined into low (11; serum ferritin of <15.0 ng/ml) and high ferritin groups (7; serum ferritin of ≥15.0 ng/ml). The response of hepcidin-25 to rhEPO and the effect of rhEPO on anemia were compared between the groups.
The serum hepcidin-25 levels rose at 6-9 h and returned to the baseline at 18 h after EPO. They rose at 6-9 h, returned to the baseline at 18 h, and decreased on day 5-7 after PEG-EPO. Serum hepcidin-25 levels were low (<5.0 ng/ml) in the low ferritin group, but rose at 6-9 h after rhEPO in the high ferritin group. Serum transferrin levels were similar, and CRP and IL-6 were normal in both groups. Hb tended to increase in the low ferritin group, but it significantly decreased in the high ferritin group after rhEPO.
Regulation of hepcidin-25 by rhEPO may be dependent on ferritin, affecting the response to rhEPO in HD patients.
Anemia; Erythropoietin; Ferritin; Hemodialysis; Hepcidin; Iron deficiency
A previous urine proteomic analysis from our laboratory suggested that hepcidin may be a biomarker for lupus nephritis flare. Immunohistochemical staining of kidney biopsies from lupus patients showed that hepcidin was expressed by infiltrating renal leukocytes. Here we investigated whether inflammatory cytokines relevant to the pathogenesis of lupus nephritis and other glomerular diseases regulate hepcidin expression by human monocytes.
Human CD14+ monocytes were incubated with interferon alpha (IFNα), interferon gamma (IFNγ), interleukin-6 (IL6), interleukin-1 beta (IL1β), monocyte chemotactic factor-1 (MCP1), or tumor necrosis factor alpha (TNFα). Hepcidin expression was examined by real-time PCR and enzyme immunoassay.
Monocyte hepcidin mRNA increased during adherence to the tissue culture wells, reaching a level 150-fold higher than baseline within 12 hours of plating. After accounting for the effects of adhesion, monocytes showed time and dose-dependent up-regulation of hepcidin mRNA upon treatment with IFNα or IL6. One hour of incubation with IFNα or IL6 increased hepcidin mRNA 20 and 80-fold respectively; by 24 hours the mRNA remained 5 and 2.4-fold higher than baseline. IL1β, IFNγ, and MCP-1 did not affect monocyte hepcidin expression. TNFα inhibited hepcidin induction by IL6 in monocytes by 44%. After 24 hours of treatment with IFNα or IL6, immunoreactive hepcidin production by monocytes increased 3 and 2.6-fold respectively.
Human monocytes produce hepcidin in response to adhesion and the pro-inflammatory cytokines IFNα and IL6.
The appearance of hepcidin in the kidneys or urine during glomerular diseases may be from infiltrating monocytes induced to express hepcidin by adherence and exposure to pro-inflammatory cytokines found in the renal milieu.
Hepcidin; Interferon Alpha; Human Monocytes; Nephritis
Hepcidin, a key regulator of iron homeostasis, is increased in response to inflammation and some infections, but the in vivo role of hepcidin, particularly in children with iron deficiency anemia (IDA) is unclear. We investigated the relationships between hepcidin, cytokines and iron status in a pediatric population with a high prevalence of both anemia and co-morbid infections.
African refugee children <16 years were consecutively recruited at the initial post-resettlement health check with 181 children meeting inclusion criteria. Data on hematological parameters, cytokine levels and co-morbid infections (Helicobacter pylori, helminth and malaria) were obtained and urinary hepcidin assays performed. The primary outcome measure was urinary hepcidin levels in children with and without iron deficiency (ID) and/or ID anaemia (IDA). The secondary outcome measures included were the relationship between co-morbid infections and (i) ID and IDA, (ii) urinary hepcidin levels and (iii) cytokine levels. IDA was present in 25/181 (13.8%). Children with IDA had significantly lower hepcidin levels (IDA median hepcidin 0.14 nmol/mmol Cr (interquartile range 0.05–0.061) versus non-IDA 2.96 nmol/mmol Cr, (IQR 0.95–6.72), p<0.001). Hemoglobin, log-ferritin, iron, mean cell volume (MCV) and transferrin saturation were positively associated with log-hepcidin levels (log-ferritin beta coefficient (β): 1.30, 95% CI 1.02 to 1.57) and transferrin was inversely associated (β: −0.12, 95% CI −0.15 to −0.08). Cytokine levels (including IL-6) and co-morbid infections were not associated with IDA or hepcidin levels.
This is the largest pediatric study of the in vivo associations between hepcidin, iron status and cytokines. Gastro-intestinal infections (H. pylori and helminths) did not elevate urinary hepcidin or IL-6 levels in refugee children, nor were they associated with IDA. Longitudinal and mechanistic studies of IDA will further elucidate the role of hepcidin in paediatric iron regulation.
The discovery of hepcidin clarified the basic mechanism of the control of systemic iron homeostasis. Hepcidin is mainly produced by the liver as a propeptide and processed by furin into the mature active peptide. Hepcidin binds ferroportin, the only cellular iron exporter, causing the internalization and degradation of both. Thus hepcidin blocks iron export from the key cells for dietary iron absorption (enterocytes), recycling of hemoglobin iron (the macrophages) and the release of storage iron from hepatocytes, resulting in the reduction of systemic iron availability. The BMP/HJV/SMAD pathway is the major regulator of hepcidin expression that responds to iron status. Also inflammation stimulates hepcidin via the IL6/STAT3 pathway with a support of an active BMP/HJV/SMAD pathway. In some pathological conditions hepcidin level is inadequately elevated and reduces iron availability in the body, resulting in anemia. These conditions occur in the genetic iron refractory iron deficiency anemia and the common anemia of chronic disease (ACD) or anemia of inflammation. Currently, there is no definite treatment for ACD. Erythropoiesis-stimulating agents and intravenous iron have been proposed in some cases but they are scarcely effective and may have adverse effects. Alternative approaches aimed to a pharmacological control of hepcidin expression have been attempted, targeting different regulatory steps. They include hepcidin sequestering agents (antibodies, anticalins, and aptamers), inhibitors of BMP/SMAD or of IL6/STAT3 pathway or of hepcidin transduction (siRNA/shRNA) or ferroportin stabilizers. In this review we summarized the biochemical interactions of the proteins involved in the BMP/HJV/SMAD pathway and its natural inhibitors, the murine and rat models with high hepcidin levels currently available and finally the progresses in the development of hepcidin antagonists, with particular attention to the role of heparins and heparin sulfate proteoglycans in hepcidin expression and modulation of the BMP6/SMAD pathway.
hepcidin; heparin; anemia of chronic diseases; inflammation; iron metabolism
Iron overload may represent an additional clinical problem in patients with Myelodysplastic Syndromes (MDS), with recent data suggesting prognostic implications. Beyond red blood cells transfusions, dysregulation of hepcidin, the key iron hormone, may play a role, but studies until now have been hampered by technical problems. Using a recently validated assay, we measured serum hepcidin in 113 patients with different MDS subtypes. Mean hepcidin levels were consistently heterogeneous across different MDS subtypes, with the lowest levels in refractory anemia with ringed sideroblasts (RARS, 1.43 nM) and the highest in refractory anemia with excess blasts (RAEB, 11.3 nM) or in chronic myelomonocytic leukemia (CMML, 10.04 nM) (P = 0.003 by ANOVA). MDS subtypes remained significant predictors of hepcidin in multivariate analyses adjusted for ferritin and transfusion history. Consistently with current knowledge on hepcidin action/regulation, RARS patients had the highest levels of toxic non-transferrin-bound-iron, while RAEB and CMML patients had substantial elevation of C-Reactive Protein as compared to other MDS subtypes, and showed lost of homeostatic regulation by iron. Growth differentiation factor 15 did not appear as a primary hepcidin regulator in this series. If confirmed, these results may help to calibrate future treatments with chelating agents and/or hepcidin modulators in MDS patients.
Colorectal cancer is the second most common cause of cancer related death in the developed world. To date, no blood or stool biomarkers with both high sensitivity and specificity for potentially curable early stage disease have been validated for clinical use. SELDI and MALDI profiling are being used increasingly to search for biomarkers in both blood and urine. Both techniques provide information predominantly on the low molecular weight proteome (<15 kDa). There have been several reports that colorectal cancer is associated with changes in the serum proteome that are detectable by SELDI and we hypothesised that proteomic changes would also be detectable in urine.
We collected urine from 67 patients with colorectal cancer and 72 non-cancer control subjects, diluted to a constant protein concentration and generated MALDI and SELDI spectra. The intensities of 19 peaks differed significantly between cancer and non-cancer patients by both t-tests and after adjusting for confounders using multiple linear regressions. Logistic regression classifiers based on peak intensities identified colorectal cancer with up to 78% sensitivity at 87% specificity. We identified and independently quantified 3 of the discriminatory peaks using synthetic stable isotope peptides (an 1885 Da fragment of fibrinogen and hepcidin-20) or ELISA (β2-microglobulin).
Changes in the urine proteome may aid in the early detection of colorectal cancer.
AIM: To study the role of hepcidin in hereditary hyperferritinemia cataract syndrome (HHCS).
METHODS: Six patients from two families with HHCS, confirmed by genetic analysis showing A to G mutation at position +40 in the L-ferritin gene, were recruited to undergo serum hepcidin and prohepcidin measurements using radioimmunoassay and enzyme linked immunoassay, respectively, and measurements were compared with levels in serum from 25 healthy volunteers (14 females), mean age 36 ± 11.9 years.
RESULTS: The serum hepcidin and prohepcidin levels in patients with HHCS were 19.1 ± 18.6 and 187 ± 120.9 ng/mL, respectively. Serum ferritin was 1716.3 ± 376 μg/L. Liver biopsy in one patient did not show any evidence of iron overload. Serum hepcidin and prohepcidin values in healthy controls (HCs) were 15.30 ± 15.71 and 236.88 ± 83.68 ng/mL, respectively, while serum ferritin was 110 ± 128.08 μg/L. There was no statistical difference in serum hepcidin level between the two cohorts (19.1 ± 18.6 ng/mL vs 15.30 ± 15.71 ng/mL, P = 0.612) using two-tailed t-test.
CONCLUSION: Serum hepcidin levels in HHCS patients is similar to that in HCs. Our study suggests that circulating ferritin is not a factor influencing hepcidin synthesis and does not have a role in the iron-sensing mechanism in hepatocytes.
Hereditary hyperferritinemia; Hereditary hyperferritinemia cataract syndrome; Hepcidin; Hepcidin assay; Iron-sensing mechanism; Iron responsive element; Ferritin
Hepcidin is an innate immune element which decreases the iron absorption from diet and iron releasing from macrophage cell. In contrast to the chemical iron chelators, there has been limited effort applied to the specific use of hepcidin as a new drug for decreasing the iron overload.
Hepcidin is produced in different biological systems. For instance, E-coli is used for human hepcidin expression, however, post-translational modification is impaired. We have used a simple baculovirus expression system (BES) to improve the hepcidin folding and activity. Hepcidin Messenger Ribonucleic acid (mRNA) was isolated from mouse liver cells and its complementary Deoxyribonucleic acid (cDNA) was produced and amplified. PFastBac HTB vector was used for recombinant bacmid production. Recombinant baculovirus was produced using SF-9 cell line. The mouse hepcidin-1 protein was expressed in a large quantity and functional tests were performed for this recombinant peptide. The yield of hepcidin in BES was 20 μg/mL and anti-histidine (anti-His) tag antibody was used for the confirmation of hepcidin on western blot nitrocellulose paper. Functional tests showed that mouse hepcidin accumulates iron in the macrophage cell line J774A.1 up to 63%. In addition, our data showed that the mouse hepcidin-1 has less toxicity compared to the synthetic human hepcidin-25 (p = 0.000).
Hepcidin; Baculovirus expression system; Functional study; J774A.1
AIM: To examine body fluids such as ascitic fluid (AF), saliva, bile and pleural effusions for the presence of hepcidin using a novel radioimmunoassay (RIA).
METHODS: Serum samples were collected from 25 healthy volunteers (mean age: 36 ± 11.9 years, 11 males, 14 females). In addition bile was obtained from 12 patients undergoing endoscopic retrograde cholangiopancreatography (mean age: 66.9 ± 16.7 years, M:F = 5:7). Saliva was collected from 17 healthy volunteers (mean age: 35 ± 9.9 years, M:F = 8:9). Pleural and AF were collected from 11 and 16 patients [(mean age: 72 ± 20.5 years, M:F = 7:4) and (mean age: 67.32 ± 15.2 years, M:F = 12:4)], respectively. All biological fluid samples (serum, exudative and transudative fluids) were tested for the presence of hepcidin-25 molecule using RIA.
RESULTS: Hepcidin-25 was detected in all biological fluids tested. The mean ± SD hepcidin-25 in serum was 15.68 ± 15.7 ng/mL, bile 7.37 ± 7.4 ng/mL, saliva 3.4 ± 2.8 ng/mL, exudative fluid 65.64 ± 96.82 ng/mL and transudative fluid 14.1 ± 17.8 ng/mL.
CONCLUSION: We provide clear evidence that hepcidin-25 is present in bile, saliva, pleural and ascitic fluids. Hepcidin is likely to play a role here in innate immunity.
Hepcidin; Hepcidin assay; Hepcidin in biological fluids; Hepcidin in ascitic fluid; Bile; Exudates; Antimicrobial peptides