Lactoferrin: A Promising New Player in Treatment of Iron Deficiency Anemia in Patients on Regular Hemodialysis: A Randomized Controlled Trial

Hepcidin is secreted in inflammatory states as in patients on regular hemodialysis (HD). Therefore, novel agents modulating hepcidin secretion may have the potential to effectively reverse anemia in HD patients. Bovine milk derivative lactoferrin (BLF) is a glycoprotein that was found to decrease serum interleukin-6, therefore, having anti-inflammatory properties. Thus, it can downregulate hepcidin secretion in various inflammatory states including patients on regular HD, so improving iron absorption and utilization in those patients. In addition, BLF is a source of iron as each BLF molecule chelates two ferric ions. We started an interventional study. Seventy patients on regular HD with iron deficiency anemia received 100 mg of 20%-30% iron-saturated BLF (corresponding to 70-84 μg of elemental iron) orally b.i.d for 6 months. We compared those patients with another 70 patients on regular HD with iron deficiency anemia who were given 576 mg of ferrous glycine sulfate (corresponding to 100 mg of elemental iron) orally b.i.d for 6 months. BLF significantly decreased serum hepcidin level (from 340-350 ng/mL to 101-112 ng/mL), P <0.0001 and significantly increased hemoglobin (Hb) concentration (from 7.5-8.1 g/dL to 9.3-10 g/dL), P <0.0001, and transferrin saturation (TSAT) (from 5%-9% to 26%-31%), P <0.0001. Furthermore, ferrous glycine sulfate significantly decreased serum hepcidin level (from 335-350 ng/mL to 330--341 ng/mL), P <0.0001, and significantly increased Hb (from 7.5-8.1 to 7.6-8.5 g/dL), P <0.0001, and TSAT (from 5%-9% to 7%-12%), P <0.0001. However, the magnitude of decrease in serum hepcidin level and rise in Hb and TSAT in the BLF group was significantly higher than in the ferrous glycine sulfate group, P <0.0001. Oral BLF can be considered a promising novel agent in treatment of iron deficiency anemia in patients on regular HD.

Hepcidin and GDF-15 are potential biomarkers of iron deficiency anaemia in chronic kidney disease patients in South Africa

BACKGROUND

Anaemia is a common presenting feature among patients with chronic kidney disease (CKD) and it is associated with poor clinical outcomes and quality of life. It is not clear if growth differentiation factor-15 (GDF-15) or hepcidin are useful as early markers of iron deficiency anaemia (IDA) among non-dialysis CKD patients. We therefore evaluated the diagnostic validity of GDF-15 and hepcidin as biomarkers of IDA among non-dialysis CKD patients in Johannesburg, South Africa.

METHOD

An analytic cross-sectional study was conducted among non-dialysis CKD patients (n = 312) and apparently healthy controls (n = 184) from June to December 2016 at an Academic Hospital, in Johannesburg, South Africa. An interviewer administered proforma was used to obtain the socio-biological and clinical characteristics of the participants. Serum levels of GDF-15 and hepcidin were determined. Predictive logistic regression models were built and post estimation receiver operator characteristics were determined to evaluate diagnostic validity of hepcidin and GDF-15 for absolute and functional iron deficiency anaemia.

RESULTS

About half (50.6%) of the participants were female while the participants' mean age was 49.7 ± 15.8 years. The predictive value of diagnosing absolute IDA among CKD patients using GDF-15 was 74.02% (95% CI: 67.62-80.42%) while the predictive value of diagnosing functional IDA among CKD patients using hepcidin was 70.1% (95% CI: 62.79-77.49%).There was a weak negative correlation between hepcidin levels and GFR (r = - 0.19, p = 0.04) in anaemic CKD patients, and between serum GDF-15 and haemoglobin (r = - 0.34, p = 0.001). Serum ferritin (β = 0.00389, P-value< 0.001), was a predictor of log hepcidin. MCHC (β = - 0.0220, P-value 0.005) and CKD stage (β = 0.4761, P-value < 0.001), race (β = 0.3429, P-value = 0.018) were predictors of log GDF-15. Both GDF-15 (adj OR: 1.0003, 95%CI: 1.0001-1.0005, P = 0.017) and hepcidin (adj OR: 1.003, 95%CI: 1.0004-1.0055, P = 0.023) were associated with iron deficiency anaemia after multiple linear regression modelling.

CONCLUSION

Serum GDF-15 is a potential biomarker of absolute IDA, while hepcidin levels can predict functional IDA among CKD patients.

Hepcidin, an overview of biochemical and clinical properties

Hepcidin is a peptide hormone which helps in regulating iron homeostasis in the human body. Iron obtained from daily diet is passed through the intestinal enterocyte apical membrane via divalent metal transporter 1 (DMT1), which is either stored as ferritin or moved into the plasma by hepcidin-ferroportin (Fpn) as an exporter. Hepcidin (hepatic bactericidal protein) is a cysteine rich peptide, was initially identified as a urinary antimicrobial peptide. It contains 25 amino acids and four disulfide bridges. It has significant role in regulation of iron in the body. Stimulation of iron in plasma and further its storage is linked with the production of hepcidin. This enhancement of iron hampers the absorption of iron from the diet. The cause of hereditary recessive anemia also known as Iron-refractory iron deficiency anemia (IRIDA) is characterized by increased hepcidin production due to a gene mutation in the suppressor matriptase-2/TMPRSS6. During infection, hepcidin plays a defensive role against various infections by depleting the extracellular iron from the body. Moreover, hepcidin lowers the concentrations of iron from the duodenal enterocytes, macrophages and also decrease its transport across the placenta.This review highlights the significant role of hepcidin in the iron homeostasis and as an antimicrobial agent.

Hepcidin as a therapeutic target for anemia and inflammation associated with chronic kidney disease

INTRODUCTION

Anemia is a common manifestation of chronic kidney disease (CKD). The pathogenesis of CKD-associated anemia is multifactorial. Our understanding of the molecular control of iron metabolism has improved dramatically because of the discovery of hepcidin and attempts to introduce new drugs to stimulate erythropoiesis or affect the hepcidin-ferroportin pathway have recently emerged. Areas covered: We examine the possible role of hepcidin in iron metabolism and regulation and the potential therapeutic options involving hepcidin and hepcidin-ferroportin axis in renal anemia treatment. We focus on therapeutic targeting of hepcidin, the hepcidin-ferroportin axis and key molecules such as anti-hepcidin antibodies, spigelmers, and anticalins. We also discuss compounds affecting the bone morphogenetic protein receptor [BMP/BMPR] complex and molecules that influence hepcidin, such as hypoxia-inducible factor 1 stabilizers. Expert opinion: Hepcidin is a key regulator of iron availability and is a potential future therapeutic target for managing anemia that is associated with CKD. There are potential risks and benefits associated with novel sophisticated therapies and there are several novel options on the horizon; however, clinical data are currently limited and need development. Inhibition of hepcidin via various pathways might be a viable adjunctive therapeutic option in other clinical situations.

Systemic and local hepcidin as emerging and important peptides in renal homeostasis and pathology

Recent data suggest that the importance of hepcidin goes beyond its classical role in controlling systemic iron metabolism. Local hepcidins are emerging as important peptides for organ homeostasis in the brain, heart, blood vessels, and in cancer as well. Similarly, accumulating data indicate that hepcidin does seem to be an important factor in renal homeostasis. This review encompasses present knowledge concerning the role of hepcidin in renoprotection and its use as a biomarker of kidney diseases. Understanding the role of hepcidin in kidneys is important due to its relevance for kidney physiology and its potential therapeutic application in kidney pathologies. © 2018 BioFactors, 45(2):118-134, 2019.

Effect of atorvastatin on iron metabolism regulation in patients with chronic kidney disease - a randomized double blind crossover study

INTRODUCTION

To determine the effect of 6-month administration of atorvastatin on hepcidin and hemojuvelin levels, inflammatory parameters and iron metabolism in patients with chronic kidney disease (CKD) stages 3 and 4.

METHODS

Thirty six statin- and erythropoiesis-stimulating agent-naive patients with CKD stages 3 and 4 and LDL cholesterol ≥100 mg/dl received atorvastatin or placebo for two 6-month periods in a double blind, randomized crossover study. Hepcidin, hemojuvelin, hsCRP, IL-6, hemoglobin, red blood cell distribution width, iron, total iron binding capacity (TIBC), and unsaturated iron binding capacity (UIBC) were measured before and after each treatment period.

RESULTS

Hepcidin decreased (from 102 [307] to 63 [170] pg/ml (p > .001)) in the course of statin therapy but remained unchanged after placebo administration (173 [256] to 153 [204] pg/ml, respectively). Hemojuvelin did not change after either part of the study. Both IL-6 and hsCRP decreased following statin therapy (from 8.7 [12.0] to 8.1 [13.9] pg/ml; p = .04 and from 4.7 [4.0] to 4.0 [3.6] mg/l; p = .4, respectively), but did not change after placebo administration. Blood hemoglobin increased slightly but significantly after 6-month statin therapy (from 11.6 ± 1.6 to 11.9 ± 1.5 g/dl, p = .002), and was unchanged after placebo treatment. TIBC and UIBC increased significantly after 6-month statin therapy, and serum iron also tended to increase. The change of eGFR during the study did not differ between the two treatment periods.

CONCLUSIONS

Statin may have a small but potentially beneficial effect on serum hepcidin, which may lead to improvement of anemia control in CKD patients.

Role of HAMP Genetic Variants on Pathophysiology of Iron Deficiency Anemia

Hepcidin is a 25-amino acid peptide hormone produced by hepatocytes and plays a key role in body iron metabolism. Hepcidin deficiency is the cause of iron overload in hereditary hemochromatosis, iron-loading anemia, and its excess is associated with anemia of inflammation, chronic disease and iron deficiency anemia (IDA). The aims of this study was to evaluate HAMP gene mutation, namely IVS2 + 1(-G) (c.148-150 + 1del) and Gly71 Asp (c.212G > A (rs104894696) association with iron status in IDA conditions. Our study participants were 500 IDA patients and 550 age and sex-matched healthy controls. Hepcidin, ferritin and CRP analysis was done by ELISA method while ESR analysis was done according to Wintrobe method. CBC analysis was done by auto-analyzer. Two mutations in the HAMP genes were analysed by PCR RFLP method. Among the IDA patients, 7 were heterozygous for Met50del IVS2 + 1(-G) mutation. Nine IDA patients were heterozygous for G71D G-A mutation and homozygous were not identified in both mutations.Controls were showing heterozygous frequency 1.8 and 2.1% of Met50del IVS2 + 1(-G) and G71D G-A mutations respectively. Mutation of HAMP (Met50del IVS2 + 1(-G) and G71D G-A) were clinically associated with IDA and act as modulator of disease.

Changes in Hepcidin and Hemoglobin After Anti-TNF-alpha Therapy in Children and Adolescents With Crohn Disease

OBJECTIVES

Anemia is the most common systemic complication of inflammatory bowel disease, is more common in affected children than in adults, and is mediated in large part by chronic inflammation. Inflammation increases levels of the iron-regulatory protein hepcidin, which have been elevated in adults with Crohn disease.

METHODS

We measured serum hepcidin-25 and hemoglobin (Hgb) in 40 children and adolescents with Crohn disease at baseline and 10 weeks after initiation of anti-tumor necrosis factor (TNF)-α therapy. Measures of disease activity, inflammatory markers, and cytokines were obtained in all subjects. Anemia was defined by World Health Organization criteria.

RESULTS

At baseline hepcidin and C-reactive protein levels were correlated, and 95% of subjects were anemic. After anti-TNF-α therapy, median (interquartile range) hepcidin concentrations decreased significantly and the distribution narrowed (27.9 [16.2, 52.9] vs 23.2 [11.1, 37.7] ng/mL, P = 0.01). Mean (standard deviation) Hgb also increased significantly (10.6 ± 1.2 to 10.9 ± 1.1 g/dL, P = 0.02), and the increase was sustained at 12 months, although 90% of participants continued to meet anemia criteria at 10 weeks. Disease activity and markers of inflammation also decreased and albumin levels increased. In generalized estimating equation analyses, higher TNF-α, interleukin 6, erythrocyte sedimentation rate, and C-reactive protein were associated with higher hepcidin concentrations (P = 0.04, P = 0.03, P = 0.003, and P < 0.001, respectively), and increased levels of disease activity were associated with higher hepcidin.

CONCLUSIONS

In children with Crohn disease, anti-TNF-α therapy is associated with decreased levels of hepcidin and increased Hgb 10 weeks after induction. Improvement in anemia may be a secondary benefit for children who receive this therapy.

Serum Ferritin Variations and Mortality in Incident Hemodialysis Patients

BACKGROUND

Higher serum ferritin levels may be influenced by iron use and inflammation, and are associated with higher mortality in hemodialysis (HD) patients. We hypothesized that a major rise in serum ferritin is associated with a higher risk of mortality, irrespective of baseline serum ferritin in incident HD patients.

METHODS

In a cohort of 93,979 incident HD patients between 2007 and 2011, we examined the association of change in serum ferritin from the baseline patient quarter (first 91 days from dialysis start) to the subsequent quarter with mortality. Multivariable adjustments were done for case-mix and markers of the malnutrition, and inflammation complex and intravenous iron dose. Change in serum ferritin was stratified into 5 groups: <-400, -400 to <-100, -100 to <100, 100 to <400, and ≥400 ng/mL/quarter.

RESULTS

The median change in serum ferritin was 89 ng/mL/quarter (interquartile range -55 to 266 ng/mL/quarter). Compared to stable serum ferritin (-100 to <100 ng/mL/quarter), a major rise (≥400 ng/mL/quarter) was associated with higher all-cause mortality (hazard ratio [95% CI] 1.07 [0.99-1.15], 1.17 [1.09-1.24], 1.26 [1.12-1.41], and 1.49 [1.27-1.76] according to baseline serum ferritin: <200, 200 to <500, 500 to <800, and ≥800 ng/mL in adjusted models, respectively. The mortality risk associated with a rise in serum ferritin was robust, irrespective of intravenous iron use.

CONCLUSIONS

During the first 6-months after HD initiation, a major rise in serum ferritin in those with a baseline ferritin ≥200 ng/mL and even a slight rise in serum ferritin in those with a baseline ferritin ≥800 ng/mL are associated with higher mortality.

Hepcidin serum levels and resistance to recombinant human erythropoietin therapy in hemodialysis patients

OBJECTIVE

The aim of this study was to analyze the factors that are associated with the response to erythropoiesis-stimulating agents (ESAs) and its association with hospitalization and mortality rates; to evaluate the serum hepcidin level and its associations with iron profile, inflammatory markers, ESA responsiveness, and mortality; and to determine independent factors affecting ERI and hepcidin.

MATERIALS AND METHODS

To evaluate a dose-response effect of ESAs we used the erythropoietin resistance index (ERI). Patients were stratified in two groups: nonresponders and responders (ERI>15, n=20, and ERI ≤15U/kg/week/g per 100mL, n=153, respectively). Hematological data, hepcidin levels, iron parameters, inflammatory markers, hospitalization and mortality rates were compared between the groups. Multiple regression analysis was used to determine independent factors affecting ERI and hepcidin.

RESULTS

C-reactive protein (CRP) (β=0.078, P=0.007), albumin (β=-0.436, P=0.004), body mass index (β=-0.374, P<0.001), and hospitalization rate per year (β=3.017, P<0.001) were found to be significant determinants of ERI in maintenance hemodialysis (MHD) patients. Inadequate dialysis was associated with higher ERI. Patients with concomitant oncological diseases had higher ERI (31.2±12.4 vs 9.7±8.1U/kg/week/g per 100mL, P=0.002). The hepcidin level was 158.51±162.57 and 120.65±67.28ng/mL in nonresponders and responders, respectively (P=0.33). Hepcidin correlated directly with ERI, dose of ESAs, ferritin and inversely with Hb, transferrin saturation, and albumin. ERI (β=4.869, P=0.002) and ferritin (β=0.242, P=0.003) were found to be significant determinants of hepcidin in MHD patients. The hospitalization rate per year was 2.35±1.8 and 1.04±1.04 in nonresponders and responders, respectively (P=0.011). The mean length of one hospitalization was 25.12±21.26 and 10.82±17.25 days, respectively (P=0.012). Death occurred in 30% of the patients from the responders' group and in 50% from the nonresponders' group (P=0.289). The mean hepcidin concentration of patients who died was 141.9±129.62ng/mL and who survived, 132.98±109.27ng/mL (P=0.797).

CONCLUSIONS

CRP, albumin, BMI, and hospitalization rate per year were found to be significant determinants of ERI in MHD patients. Inadequate dialysis was associated with higher epoetin requirements. There were no difference in patient mortality by ERI, but a significant difference in hospitalization rates and mean length of one hospitalization was revealed. A significant positive relation between hepcidin and ERI was revealed. ERI and ferritin were found to be significant determinants of hepcidin in MHD patients. Hepcidin was not related to mortality.

Laboratory use of hepcidin in renal transplant recipients

Hepcidin is a small peptide with a critical role in cellular iron homeostasis, as it regulates utilization of stored iron and antimicrobial defense in inflammation (bacterial and fungal). Since it was isolated in 2000, and especially in the last decade, numerous studies aimed to evaluate the clinical use of plasma and urine hepcidin as a marker of anemia, especially anemia of chronic disease and post-transplant anemia (PTA). Hepcidin regulation is delicately tuned by two inflammatory pathways activated by interleukin-6 (IL-6) and bone morphogenic proteins (BMPs) and iron regulated pathway sensitive to circulating transferin-iron (TR-Fe) complex. BMP-mediated pathway and TR-Fe sensitive pathway seem to be connected by hemojuveline, a BMP co-factor that interacts with transferine receptor 2 (TRF2) in cases of high TR-Fe circulatory concentration. In addition to these regulatory mechanisms other regulators and signaling pathways are being extensively researched.
Hepcidin has been identified as an important contributor to morbidity and mortality in end stage renal disease (ESRD) but no such association has jet been found in case of PTA. However, there is an association between higher doses of erythropoiesis-stimulating agents (ESA) and mortality in the posttransplant period and the assumption that hepcidin might play a role in ESA resistance in PTA. Thus the review’s main goal was to summarize papers published on the association of hepcidin with PTA, give up-to-date information on hepcidin regulation and on potential therapeutics that optimize hepcidin regulation. We also compared the performances of tests for hepcidin determination and reviewed research on immunosuppressants’ (IS) effect on hepcidin concentration.

C-reactive protein but not hepcidin, NGAL and transferrin determines the ESA resistance in hemodialysis patients

BACKGROUND

Erythropoiesis-stimulating agents (ESA) are commonly used for the treatment of anemia in hemodialysis (HD) patients, however, 5-10% of these patients have resistance to ESA treatment. Hepcidin and neutrophil-gelatinase associated lipocalin (NGAL) are induced by inflammation and these proteins may take role in ESA resistance. Herein, we aimed to investigate the effects of serum hepcidin, NGAL, transferrin and C-reactive protein (CRP) levels on ESA resistance in HD patients.

METHODS

A total of 63 chronic HD patients (6.0 ± 17 years, M/F:44/19) and 20 healthy controls (6.0 ± 4 years, M/F:14/6) were enrolled. ESA resistance index (ERI) was calculated as weekly ESA dose (IU)/body weight (kg)/hemoglobin level (g/dL). Patients on ESA treatment were divided into two groups depending on the median ERI value as low and high ERI groups.

RESULTS

Serum ferritin, hepcidin and NGAL levels were significantly higher in HD patients compared with controls. Serum transferrin levels were lower in high ESA index group compared with patients without ESA treatment and healthy controls. ERI was significantly correlated with serum CRP levels (r = 0.55, p < 0.001). In HD patients, serum hepcidin levels were associated with ferritin (r = 0.55, p < 0.01) and creatinine (r = 0.27, p = 0.03). Dose of ESA was significantly associated with serum CRP (r = 0.34, p = 0.02), total protein (r = -0.34, p = 0.01), transferrin (r = -0.28, p = 0.04) and ferritin (r = 0.31, p = 0.02). In linear regression analysis to predict ERI, age, gender, serum CRP, hepcidin, NGAL, albumin, ferritin and BMI were included (Model R = 0.62, R(2) =0 .38, p = 0.02). Serum CRP was the only significant factor predicting ERI.

CONCLUSION

CRP was the only predictor of ESA resistance index in HD patients. Hepcidin, NGAL and transferrin were not found to be markers of ESA resistance.

The Growth Attainment, Hematological, Iron Status and Inflammatory Profile of Guatemalan Juvenile End-Stage Renal Disease Patients

Background

Stunting, anemia and inflammation are frequently observed in children with end-stage renal disease (ESRD).

Objectives

To assess anthropometric, hematological and inflammatory data and to study their potential interrelationship in Guatemalan juveniles undergoing hemodialysis (HD) and peritoneal dialysis (PD).

Methods

54 juveniles 7–20 years of age were recruited in FUNDANIER, Guatemala City: 27 on HD and 27 PD. Hemoglobin, serum iron, transferrin, serum transferrin receptor (sTfR), serum ferritin, transferrin saturation and iron-binding capacity, white blood cell count (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), as well as IL-6, IL-1 and TNF-α, weight and height were determined by standard methods. Hepcidin–25 (Hep-25) was assessed by weak cation exchange time-of-flight mass-spectrometry.

Results

92% and 55% of HD and PD children, respectively, were stunted and 95% and 85% were anemic. Among iron status biomarkers, serum ferritin was massively increased and significantly higher in the HD group compared to the PD group. Hep-25 was also greatly elevated in both groups. 41% of HD patients showed increments in three or more inflammatory biomarkers, while it was 2 or less in all PD subjects.

Conclusions

The degree of stunting, the prevalence and severity of anemia in Guatemalan juvenile ESRD far exceed the national statistics for this low-income Central American country. Ferritin and Hep-25 concentrations were elevated, with the latter to an extraordinary magnitude. Additional biomarkers of inflammation not directly related to iron status were elevated as well. The role of both disease- and environment-related factors in combination best explains the magnitude of the biomarker abnormalities.

Effects of additional iron doses on hepcidin-25 level in hemodialysis patients without evident iron deficiency

BACKGROUND

Serum hepcidin-25 is not only a marker of iron stores, but also an acute phase reactant, and it could fluctuate in response to erythropoietic activity.

STUDY DESIGN

Prospective interventional, 3-months duration, investigating the influence of additional intravenous (IV) iron on hepcidin-25 in hemodialysis (HD) patients without obvious iron deficiency (ID).

SETTINGS AND PARTICIPANTS

Single HD unit, 41 patients.

MEASUREMENTS

Hepcidin-25 (ELISA method), ferritin, transferrin, transferrin saturation (TSAT), C-reactive protein and serum albumin--at baseline and assessment; hemoglobin, iron and darbepoetin doses--monthly.

INTERVENTION

Additional IV iron doses were administered, driven by hemoglobin trend: iron dose increased by 25 % for each 0.5 g/dL hemoglobin drop for baseline ferritin of 200-800 ng/mL. Iron was discontinued for stable hemoglobin or >13 g/dL. Darbepoetin doses were adjusted for 11 g/dL target hemoglobin.

RESULTS

At baseline, 21 % of patients had "optimal" iron status; none had "absolute" or "functional" ID, while 15 % had iron "overload." Hepcidin levels were 112.8 (95 % CI 105.3-121.8) ng/mL. Hemoglobin was within the target range. After 75 % augmentation in iron doses, hepcidin-25 decreased by 70 %. Transferrin increased, and TSAT and ferritin decreased. Prevalence of "functional" ID rose to 24 % and of iron "overload" declined to 0 %. Reversal of iron-restricted erythropoiesis was further sustained by unchanging hemoglobin and decrease in darbepoetin doses and darbepoetin resistance index. Reasonable associations between assessment versus baseline ratios for hepcidin-25 and transferrin (inverse), TSAT and ferritin (direct) were found. Despite the increased inflammation, decrease in transferrin and increase in ferritin ratios were independent predictors of hepcidin variability (model of logistic regression r (2) 0.34; p < 0.0001).

LIMITATIONS

Low number of participants, less diabetic nephropathy/vascular diseases than general dialyzed population, uncontrolled design, use of hepcidin-25 ELISA assay.

CONCLUSIONS

Activation of erythropoiesis by additional IV iron administration overcomes moderate inflammation in suppressing hepcidin-25. Thus, hepcidin-25 could be clinically useful to evaluate iron status in patients with renal anemia.

Potential effects of omega-3 fatty acids on anemia and inflammatory markers in maintenance hemodialysis patients

BACKGROUND

Anemia is a common complication among hemodialysis (HD) patients. Although intravenous iron and erythropoiesis-stimulating agents revolutionized anemia treatment, about 10% of HD patients show suboptimal response to these agents. Systemic inflammation and increased serum hepcidin level may contribute to this hyporesponsiveness. Considering the anti-inflammatory properties of omega-3 fatty acids, this study aimed to evaluate potential role of these fatty acids in improving anemia and inflammation of chronic HD patients.

METHODS

In this randomized, placebo-controlled trial, 54 adult patients with HD duration of at least 3 months were randomized to ingest 1800 mg of either omega-3 fatty acids or matching placebo per day for 4 months. Anemia parameters including blood hemoglobin, serum iron, transferrin saturation (TSAT), erythropoietin resistance index, and required dose of intravenous iron and erythropoietin, and serum concentrations of inflammatory/anti-inflammatory markers including interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-10, C-reactive protein (CRP), hepcidin, ferritin, intact parathyroid hormone (iPTH), and ratios of IL-10 to IL-6 and IL-10 to TNF-α were measured at baseline and after 4 months of the intervention.

RESULTS

45 subjects (25 in the omega-3 and 20 in the placebo group) completed the study. No significant changes were observed in blood hemoglobin, serum iron, TSAT, and required dose of intravenous iron in either within or between group comparisons. Additionally, erythropoietin resistance index as well as required dose of intravenous erythropoietin showed no significant change in the omega-3 group compared to the placebo group. Although a relative alleviation in inflammatory state appeared in the omega-3 group, the mean differences of inflammatory and anti-inflammatory markers between the two groups did not reach statistically significant level except for IL-10-to-IL-6 ratio and serum ferritin level which showed significant changes in favor of omega-3 treatment (P <0.001 and P = 0.003, respectively).

CONCLUSION

Omega-3 fatty acids relatively improved systemic inflammation of chronic HD patients without any prominent benefits on anemia. However, future well-designed studies on larger number of patients may determine utility of omega-3 fatty acids in HD patients with respect to inflammation and anemia.

Applications of nanoparticles in the detection and treatment of kidney diseases

Nanoparticles have emerged in the medical field as a technology well suited for the diagnosis and treatment of various disease states. They have been heralded as efficacious in terms of improved therapeutic efficacy and reduction of treatment side effects in some cases. Various nanomaterials have been developed that can be tagged with targeting moieties as well as with drug delivery and imaging capability or a combination of both as a theranostic agent. These nanomaterials have been investigated for treatment and detection of various pathological conditions. The emphasis of this review is to demonstrate current research and clinical applications for nanoparticles in the diagnosis and treatment of kidney diseases.

Hepcidin-minireview

Iron related disorders are encountered in daily clinical settings. Maintenance of stable extracellular iron concentrations requires the coordinate regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages and from storage in hepatocytes. Hepcidin acts as a systemic iron-regulatory hormone. Many human diseases are associated with alterations in hepcidin concentrations. This review has focused on hepcidin structure, kinetics and function, its correlation with iron metabolism disorders, the therapeutic potential for modulating hepcidin expression and the diagnostic potential of hepcidin measurements in clinical practice.

Hepcidin-25 is related to cardiovascular events in chronic haemodialysis patients

BACKGROUND

The development of atherosclerosis may be enhanced by iron accumulation in macrophages. Hepcidin-25 is a key regulator of iron homeostasis, which downregulates the cellular iron exporter ferroportin. In haemodialysis (HD) patients, hepcidin-25 levels are increased. Therefore, it is conceivable that hepcidin-25 is associated with all-cause mortality and/or fatal and non-fatal cardiovascular (CV) events in this patient group. The aim of the current analysis was to study the relationship between hepcidin-25 and all-cause mortality and both fatal and non-fatal CV events in chronic HD patients.

METHODS

Data from 405 chronic HD patients included in the CONvective TRAnsport STudy (NCT00205556) were studied (62% men, age 63.7 ± 13.9 years [mean ± SD]). The median (range) follow-up was 3.0 (0.8-6.6) years. Hepcidin-25 was measured with mass spectrometry. The relationship between hepcidin-25 and all-cause mortality or fatal and non-fatal CV events was investigated with multivariate Cox proportional hazard models.

RESULTS

Median (interquartile range) hepcidin-25 level was 13.8 (6.6-22.5) nmol/L. During follow-up, 158 (39%) patients died from any cause and 131 (32%) had a CV event. Hepcidin-25 was associated with all-cause mortality in an unadjusted model [hazard ratio (HR) 1.14 per 10 nmol/L, 95% CI 1.03-1.26; P = 0.01], but not after adjustment for all confounders including high-sensitive C-reactive protein (HR 1.02 per 10 nmol/L, 95% CI 0.87-1.20; P = 0.80). At the same time, hepcidin-25 was significantly related to fatal and non-fatal CV events in a fully adjusted model (HR 1.24 per 10 nmol/L, 95% CI 1.05-1.46, P = 0.01).

CONCLUSION

Hepcidin-25 was associated with fatal and non-fatal CV events, even after adjustment for inflammation. Furthermore, inflammation appears to be a significant confounder in the relation between hepcidin-25 and all-cause mortality. These findings suggest that hepcidin-25 might be a novel determinant of CV disease in chronic HD patients.

Hepcidin-25 in chronic hemodialysis patients is related to residual kidney function and not to treatment with erythropoiesis stimulating agents

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.

Serum hepcidin in haemodialysis patients: associations with iron status and microinflammation

Hepcidin plays a key role in iron homeostasis. This cross-sectional study measured the serum hepcidin levels of 48 maintenance haemodialysis patients and 20 age-matched healthy control subjects using a competitive enzyme-linked immunosorbent assay (C-ELISA). Serum hepcidin, interleukin (IL)-6 and high-sensitivity C-reactive protein levels were significantly higher in maintenance haemodialysis patients compared with control subjects. In all patients, there was a positive correlation between serum hepcidin levels and ferritin, transferrin saturation and IL-6, and an inverse correlation between serum hepcidin and unsaturated iron-binding capacity, total iron-binding capacity (TIBC) and transferrin. Linear regression analyses showed that ferritin and TIBC were independently associated with serum hepcidin levels. In conclusion, serum hepcidin levels are associated with iron status and microinflammation (defined as hsCRP < 15 mg/l, without clinical manifestation of inflammation) in maintenance haemodialysis patients. The C-ELISA method for measuring serum hepcidin should facilitate the routine measurement of hepcidin in clinical practice.

Serum hemojuvelin and hepcidin levels in chronic kidney disease

BACKGROUND

Hemojuvelin (HJV) has recently emerged as one of a number of significant regulators of iron homeostasis and hepcidin expression. Recently, an immunoassay has been developed to measure circulating levels of soluble HJV (sHJV). The aim of this study was to measure serum hepcidin and sHJV levels in a chronic kidney disease (CKD) population.

METHODS

A total of 93 patients participated in the study (31 hemodialysis, 31 non-dialysis, 31 transplant recipients), and were matched for age and gender. Serum samples were taken for measurement of hepcidin-25 and sHJV, along with standard hematological, biochemical and inflammatory markers, and univariate/multivariate analyses were performed.

RESULTS

Serum sHJV levels were markedly elevated in the hemodialysis patients (2,619 ± 1,445 ng/ml) compared to the CKD (590 ± 344 ng/ml) and transplant recipients (870 ± 638 ng/ml) (p < 0.001), normal range 370-890 ng/ml. There was a strong correlation between serum ferritin and sHJV, which remained after adjustment for potential confounders (beta 0.92, p < 0.001). In the univariate analysis, sHJV levels correlated with serum hepcidin but this was not evident in the multivariate analysis. No associations were seen between sHJV and markers of inflammation or eGFR.

CONCLUSIONS

sHJV is elevated in hemodialysis patients compared to non-dialysis CKD patients. There was no association between sHJV and eGFR (in the non-dialysis groups), suggesting that factors other than decreased renal clearance are responsible for the high sHJV levels. The strong association between sHJV and ferritin suggests an interdependent relationship, although further studies are required to elucidate the possible mechanism(s) for this.

Hepcidin in anemia of chronic kidney disease: review for the pediatric nephrologist

Anemia coincident with hyporesponsiveness to erythropoiesis-stimulating agents is an ongoing and prevalent problem in children with chronic kidney disease (CKD). The recently identified iron-regulatory protein hepcidin appears likely to play a significant role in this problem. Hepcidin up-regulation in the setting of CKD, with subsequent increased serum levels, results in impaired iron absorption from the intestine and decreased iron release from body storage sites. Ultimately, in the setting of such elevated levels, a state of functional iron deficiency may develop and lead to anemia due to iron-restricted erythropoiesis. Elevated hepcidin levels are expected in the face of decreased glomerular filtration rate and inflammation. Based on current evidence, it seems likely that hepcidin represents a potentially modifiable mediator of anemia of CKD and is thus a potential target for future anemia therapy. Currently, increased removal via intensified dialysis and-/or blockade of the inflammatory pathway appear to be two viable generic strategies for reducing hepcidin levels. Goals of directly manipulating the hepcidin pathway should offer the pediatric clinician new options for treating the complex anemia associated with CKD.

Hepcidin in human iron disorders: diagnostic implications

BACKGROUND

The peptide hormone hepcidin plays a central role in regulating dietary iron absorption and body iron distribution. Many human diseases are associated with alterations in hepcidin concentrations. 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.

CONTENT

We describe hepcidin structure, kinetics, function, and regulation. We moreover explore the therapeutic potential for modulating hepcidin expression and the diagnostic potential for hepcidin measurements in clinical practice.

SUMMARY

Cell-culture, animal, and human studies have shown that hepcidin is predominantly synthesized by hepatocytes, where its expression is regulated by body iron status, erythropoietic activity, oxygen tension, and inflammatory cytokines. Hepcidin lowers serum iron concentrations by counteracting the function of ferroportin, a major cellular iron exporter present in the membrane of macrophages, hepatocytes, and the basolateral site of enterocytes. Hepcidin is detected in biologic fluids as a 25 amino acid isoform, hepcidin-25, and 2 smaller forms, i.e., hepcidin-22 and -20; however, only hepcidin-25 has been shown to participate in the regulation of iron metabolism. Reliable assays to measure hepcidin in blood and urine by use of immunochemical and mass spectrometry methods have been developed. Results of proof-of-principle studies have highlighted hepcidin as a promising diagnostic tool and therapeutic target for iron disorders. However, before hepcidin measurements can be used in routine clinical practice, efforts will be required to assess the relevance of hepcidin isoform measurements, to harmonize the different assays, to define clinical decision limits, and to increase assay availability for clinical laboratories.

Anemia in children with chronic kidney disease

Anemia is a common comorbidity in children with chronic kidney disease (CKD). This condition is associated with multiple adverse clinical consequences and its management is a core component of nephrology care. Increased morbidity and mortality, increased risk of cardiovascular disease and decreased quality of life have been associated with anemia of CKD in children. Although numerous complex factors interact in the development of this anemia, erythropoietin deficiency and iron dysregulation (including iron deficiency and iron-restricted erythropoiesis) are the primary causes. In addition to iron supplementation, erythropoietin-stimulating agents (ESAs) can effectively treat this anemia, but there are important differences in ESA dose requirements between children and adults. Also, hyporesponsiveness to ESA therapy is a common problem in children with CKD. Although escalating ESA doses to target increased hemoglobin values in adults has been associated with adverse outcomes, no studies have demonstrated this association in children. The question of appropriate target hemoglobin levels in children, and the approach by which to achieve these levels, remains under debate. Randomized, controlled studies are needed to evaluate whether normalization of hemoglobin concentrations is beneficial to children, and whether this practice is associated with increased risks.

Determinants of red cell distribution width (RDW) in cardiorenal patients: RDW is not related to erythropoietin resistance

BACKGROUND

Studies have shown that red cell distribution width (RDW) is related to outcome in chronic heart failure (CHF). The pathophysiological process is unknown. We studied the relationship between RDW and erythropoietin (EPO) resistance, and related factors such as erythropoietic activity, functional iron availability and hepcidin.

METHODS AND RESULTS

In the Mechanisms of Erythropoietin Action in the Cardiorenal Syndrome (EPOCARES) study, which investigates the role of EPO in 54 iron-supplemented anemic patients with CHF and chronic kidney disease (CKD) (n = 35 treated with 50 IU/kg/wk Epopoetin beta, n = 19 control), RDW was not associated with EPO resistance. We defined EPO resistance by EPO levels (r = 0.12, P = .42), the observed/predicted log EPO ratio (r = 0.12, P = .42), the increase in reticulocytes after 2 weeks of EPO treatment (r = -0.18, P = .31), and the increase of hemoglobin after 6 months of EPO treatment (r = 0.26, P = .35). However, RDW was negatively correlated with functional iron availability (reticulocyte hemoglobin content, r = -0.48, P < .001, and transferrin saturation, r = -0.39, P = .005) and positively with erythropoietic activity (soluble transferrin receptor, r = 0.48, P < .001, immature reticulocyte fraction, r = 0.36, P = .01) and positively with interleukin-6 (r = 0.48, P < .001). No correlation existed between hepcidin-25 and RDW.

CONCLUSIONS

EPO resistance was not associated with RDW. RDW was associated with functional iron availability, erythropoietic activity, and interleukin-6 in anemic patients with CHF and CKD.

Serum hepcidin: reference ranges and biochemical correlates in the general population

To date, concentrations of the promising biomarker hepcidin have only been assessed in serum of relatively small series of healthy volunteers and patients. We assessed age- and sex-stratified reference ranges of serum hepcidin concentration in a selected reference set and performed regression analyses to study associations between hepcidin and (biochemical) variables in a large, well-phenotyped sample of the general population (n = 2998). All participants filled out a questionnaire on lifestyle, health status, and medical history. Serum measurements of iron parameters, liver enzyme alanine aminotransferase, creatinine and C-reactive protein were available. Serum hepcidin concentrations were lower for premenopausal than for postmenopausal women (median, 4.1 nM vs 8.5 nM, respectively). Hepcidin concentrations in men were constant over age (median, 7.8 nM). Serum hepcidin was strongly associated with serum ferritin in men and women: β-coefficient of log-transformed variables (95% confidence interval): 0.78 (0.74-0.82) and 0.83 (0.78-0.88), respectively. Additional significant, though less strong, associations were observed for C-reactive protein and total iron binding capacity in men and for total iron binding capacity, alanine aminotransferase, and glomerular filtration rate in women. Our study provides age- and sex-specific reference ranges of serum hepcidin concentration and indicates ferritin as the primary correlate of serum hepcidin concentration.

Serum hepcidin as a diagnostic test of iron deficiency in premenopausal female blood donors

BACKGROUND

Currently used indicators of iron status have limitations. Hepcidin, a key regulator of iron metabolism, is reduced in iron deficiency. We sought to determine the properties of hepcidin as a diagnostic test of iron deficiency.

DESIGN AND METHODS

Sera from female, non-anemic, whole blood donors were analyzed for hepcidin (enzyme-linked immunosorbent assay), ferritin, soluble transferrin receptor and C-reactive protein. Iron deficiency was defined as (i) serum ferritin less than 15 ng/mL or (ii) soluble transferrin receptor /log(ferritin) index greater than 3.2 if the C-reactive protein concentration was less than 10 mg/L, or greater than 2.2 if the C-reactive protein concentration was greater than 10 mg/L). Receiver operating characteristic curves were plotted to determine the overall utility and identify optimal cut-points of hepcidin as a test of iron deficiency.

RESULTS

In 261 blood donors the prevalence of iron deficiency defined by ferritin concentration was 59/261 [22.6% (17.5, 27.7)], whereas defined by soluble transferrin receptor/log(ferritin) index it was 53/261 [20.4% (15.4, 25.2)]. The 95% reference range of hepcidin concentration in the iron-replete population was 8.2-199.7 ng/mL. The area under the receiver operating characteristic curve for hepcidin compared with ferritin concentration less than 15 ng/mL was 0.87 (0.82, 0.92), while that compared with the soluble transferrin receptor /log(ferritin) index was 0.89 (95% CI 0.84, 0.93). For a diagnosis of iron deficiency defined by the soluble transferrin receptor/log(ferritin) index, hepcidin less than 8 ng/mL had a sensitivity of 41.5% and a specificity of 97.6%, while hepcidin less than 18 ng/mL had a sensitivity of 79.2% and a specificity of 85.6%.

CONCLUSIONS

Serum hepcidin concentration may be a useful indicator of deficient iron stores. Further studies are required to evaluate the role of hepcidin in the diagnosis of iron deficiency in other groups of patients.

Hepcidin: a novel peptide hormone regulating iron metabolism

BACKGROUND

Hepcidin is a low-molecular weight hepatic peptide regulating iron homeostasis. Hepcidin inhibits the cellular efflux of iron by binding to, and inducing the internalization and degradation of, ferroportin, the exclusive iron exporter in iron-transporting cells. It has been recently recognized as a main hormone behind anemia of chronic disease.

METHOD

A comprehensive literature search was conducted from the websites of Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/) and the National Library of Medicine (http://www.ncbl.nlm.nih.gov). The data was also assessed from journals and books that published relevant articles in this field.

RESULT

Hepcidin regulates iron uptake constantly on a daily basis, to maintain sufficient iron stores for erythropoiesis. Hepcidin, by its iron regulatory action on iron metabolism may be expected to have an important role in immune regulation, inflammatory diseases and malignancies. Hepcidin is the underlying cause of anemia in these clinical settings.

CONCLUSION

Hepcidin analysis may prove to be a novel tool for differential diagnosis and monitoring of disorders of iron metabolism, and establishment of therapeutic measures in various disease conditions like hereditary hemochromatosis, anemia associated with chronic kidney disease, rheumatoid arthritis and cancers.

Hepcidin-25 is a marker of the response rather than resistance to exogenous erythropoietin in chronic kidney disease/chronic heart failure patients

AIMS

Erythropoietin (EPO) resistance, an important cause of anaemia in patients with heart and renal failure, is associated with increased mortality. The hypothesis of the present study was that exogenous EPO decreases hepcidin levels and that the decrease in hepcidin levels upon EPO treatment is related to the bone marrow response.

METHODS AND RESULTS

In the EPOCARES trial, patients with renal failure (glomerular filtration rate 20-70 mL/min), heart failure, and anaemia were randomized to receive 50 IU/kg/week EPO (n = 20) or not (n = 13). Haemoglobin (Hb), hepcidin-25, ferritin, reticulocytes, serum transferrin receptor (sTfR), IL-6, and high-sensitivity C-reactive protein were measured at baseline and during treatment. Hepcidin-25 was measured by weak cation exchange chromatography/matrix assisted laser desorption ionization time-of-flight mass spectrometry. Baseline hepcidin levels were increased compared with a healthy reference population and were inversely correlated with Hb (r(2) = 0.18, P = 0.02), and positively with ferritin (r(2) = 0.51, P < 0.001), but not with renal function, high-sensitivity C-reactive protein or IL-6. Erythropoietin treatment increased reticulocytes (P < 0.001) and sTfR (P < 0.001), and decreased hepcidin (P < 0.001). Baseline hepcidin levels and the magnitude of the decrease in hepcidin correlated with the increase in reticulocytes (r(2) = 0.23, P = 0.03) and sTfR (r(2) = 0.23, P = 0.03) and also with the Hb response after 6 months (r(2) = 0.49, P = 0.001).

CONCLUSION

In this group of patients with combined heart and renal failure and anaemia, increased hepcidin levels were associated with markers of iron load and not with markers of inflammation. The (change in) hepcidin levels predicted early and long-term bone marrow response to exogenous EPO. In our group hepcidin seems to reflect iron load and response to EPO rather than inflammation and EPO resistance.

Ferumoxytol: a new intravenous iron preparation for the treatment of iron deficiency anemia in patients with chronic kidney disease

Ferumoxytol is an intravenous iron preparation for treatment of the anemia of chronic kidney disease (CKD). It is a carbohydrate-coated, superparamagnetic iron oxide nanoparticle. Because little free iron is present in the preparation, doses of 510 mg have been administered safely in as little as 17 seconds. Two prospective, randomized studies compared two doses of ferumoxytol 510 mg given in 5 +/- 3 days with 3 weeks of oral iron 200 mg/day (as ferrous fumarate) in anemic patients with CKD. One study enrolled 304 patients with stages 1-5 CKD (predialysis), and the other study enrolled 230 patients with stage 5D CKD (undergoing hemodialysis). In both studies, a greater increase in hemoglobin level from baseline to end of study (day 35) was noted in patients who received ferumoxytol compared with those who received oral iron (mean +/- SD 0.82 +/- 1.24 vs 0.16 +/- 1.02 g/dl in patients with stages 1-5 CKD and 1.02 +/- 1.13 vs 0.46 +/- 1.06 g/dl in patients with stage 5D CKD, p<0.001). A greater proportion of both predialysis and hemodialysis patients who received ferumoxytol had hemoglobin level increases from baseline of 1 g/dl or more compared with those who received oral iron (p<0.001). In a prospective, double-blind, crossover study of more than 700 patients with CKD stages 1-5D that compared the safety of ferumoxytol with normal saline injection, the rates of treatment-related adverse events were 5.2% and 4.5%, respectively. Serious treatment-related adverse events were seen in one patient in each treatment group. The most common adverse events with ferumoxytol occurred at the injection site (bruising, pain, swelling, erythema). Dizziness, nausea, pruritus, headache, and fatigue occurred in less than 2% of patients receiving ferumoxytol, with a similar frequency noted after administration of normal saline. In short-term studies, intravenous ferumoxytol was safely and rapidly administered, and was more effective than oral iron therapy in increasing hemoglobin levels in anemic patients with CKD. Long-term clinical trials with clinical outcomes and studies comparing ferumoxytol with other parenteral iron agents will help define the role of ferumoxytol in treating the anemia of CKD.

Molecular mechanisms of hepcidin regulation: implications for the anemia of CKD

Anemia is prevalent in patients with chronic kidney disease (CKD) and is associated with lower quality of life and higher risk of adverse outcomes, including cardiovascular disease and death. Anemia management in patients with CKD currently revolves around the use of erythropoiesis-stimulating agents and supplemental iron. However, many patients do not respond adequately and/or require high doses of these medications. Furthermore, recent clinical trials have shown that targeting higher hemoglobin levels with conventional therapies leads to increased cardiovascular morbidity and mortality, particularly when higher doses of erythropoiesis-stimulating agents are used and in patients who are poorly responsive to therapy. One explanation for the poor response to conventional therapies in some patients is that these treatments do not fully address the underlying cause of the anemia. In many patients with CKD, as with patients with other chronic inflammatory diseases, poor absorption of dietary iron and the inability to use the body's iron stores contribute to the anemia. Recent research suggests that these abnormalities in iron balance may be caused by increased levels of the key iron regulatory hormone hepcidin. This article reviews the pathogenesis of anemia in CKD, the role and regulation of hepcidin in systemic iron homeostasis and the anemia of CKD, and the potential diagnostic and therapeutic implications of these findings.

Bone marrow iron, iron indices, and the response to intravenous iron in patients with non-dialysis-dependent CKD

BACKGROUND

Information about iron stores and their relationship with transferrin saturation (TSAT), serum ferritin, and the erythropoietic response to iron therapy is scarce in anemic non-dialysis-dependent patients with chronic kidney disease (CKD). We examined the diagnostic utility of peripheral-iron indices and the erythropoietic response to intravenous iron as indices of iron store depletion using bone marrow iron as a reference test in anemic non-dialysis-dependent patients with CKD.

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

100 anemic (hemoglobin <11 g/dL) patients with CKD stages 3-5, not receiving epoetin and iron.

INDEX TESTS

TSAT index and serum ferritin level at baseline and increase in hemoglobin level 1 month after 200 mg of iron sucrose daily for 5 days.

REFERENCE TEST

Bone marrow iron (assessed using aspiration and Perls' stain), depleted versus replete, at baseline.

MEASUREMENTS

Area under the receiver operating characteristic curve (AUROC), sensitivity, and specificity of peripheral-iron indices and erythropoietic response to describe bone marrow iron stores.

RESULTS

Bone marrow iron stores were depleted in 48% of patients at baseline. In iron-depleted versus -replete subjects, mean hemoglobin level, median TSAT index, median serum ferritin level, and hemoglobin level increase after iron sucrose administration were 8.74 +/- 1.1 (SD) versus 9.22 +/- 0.9 g/dL (P = 0.02), 19% (interquartile range [IQR], 15%) versus 28% (IQR, 12%; P < 0.001), 100 (IQR, 131) versus 220 ng/mL (IQR, 213; P < 0.001), and 1.2 +/- 0.4 versus 0.8 +/- 0.3 g/dL (P < 0.001), respectively. TSAT, ferritin level, and increase in hemoglobin level AUROCs were similar: 0.75 (95% CI, 0.66-0.85), 0.76 (95% CI, 0.66-0.85), and 0.74 (95% CI, 0.65-0.84), respectively.

LIMITATIONS

Bone marrow iron as the index of iron stores.

CONCLUSIONS

Half the anemic patients with CKD stages 3-5 had depleted iron stores. Peripheral-iron indices and erythropoietic response had equivalent, but limited, utility in identifying depletion of bone marrow iron stores. Use of these indices to indicate depletion of iron stores should be reconsidered.

Multiple loci influence erythrocyte phenotypes in the CHARGE Consortium

Measurements of erythrocytes within the blood are important clinical traits and can indicate various hematological disorders. We report here genome-wide association studies (GWAS) for six erythrocyte traits, including hemoglobin concentration (Hb), hematocrit (Hct), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) and red blood cell count (RBC). We performed an initial GWAS in cohorts of the CHARGE Consortium totaling 24,167 individuals of European ancestry and replication in additional independent cohorts of the HaemGen Consortium totaling 9,456 individuals. We identified 23 loci significantly associated with these traits in a meta-analysis of the discovery and replication cohorts (combined P values ranging from 5 x 10(-8) to 7 x 10(-86)). Our findings include loci previously associated with these traits (HBS1L-MYB, HFE, TMPRSS6, TFR2, SPTA1) as well as new associations (EPO, TFRC, SH2B3 and 15 other loci). This study has identified new determinants of erythrocyte traits, offering insight into common variants underlying variation in erythrocyte measures.

Plasma hepcidin levels are elevated but responsive to erythropoietin therapy in renal disease

Hepcidin is a critical inhibitor of iron export from macrophages, enterocytes, and hepatocytes. Given that it is filtered and degraded by the kidney, its elevated levels in renal failure have been suggested to play a role in the disordered iron metabolism of uremia, including erythropoietin resistance. Here, we used a novel radioimmunoassay for hepcidin-25, the active form of the hormone, to measure its levels in renal disease. There was a significant diurnal variation of hepcidin and a strong correlation to ferritin levels in normal volunteers. In 44 patients with mild to moderate kidney disease, hepcidin levels were significantly elevated, positively correlated with ferritin but inversely correlated with the estimated glomerular filtration rate. In 94 stable hemodialysis patients, hepcidin levels were also significantly elevated, but this did not correlate with interleukin-6 levels, suggesting that increased hepcidin was not due to a general inflammatory state. Elevated hepcidin was associated with anemia, but, intriguingly, the erythropoietin dose was negatively correlated with hepcidin, suggesting that erythropoietin suppresses hepcidin levels. This was confirmed in 7 patients when hepcidin levels significantly decreased after initiation of erythropoietin treatment. Our results show that hepcidin is elevated in renal disease and suggest that higher hepcidin levels do not predict increased erythropoietin requirements.

Hepcidin--a potential novel biomarker for iron status in chronic kidney disease

BACKGROUND AND OBJECTIVES

Hepcidin is a key regulator of iron homeostasis, but its study in the setting of chronic kidney disease (CKD) has been hampered by the lack of validated serum assays.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study reports the first measurements of bioactive serum hepcidin using a novel competitive ELISA in 48 pediatric (PCKD2-4) and 32 adult (ACKD2-4) patients with stages 2 to 4 CKD along with 26 pediatric patients with stage 5 CKD (PCKD5D) on peritoneal dialysis.

RESULTS

When compared with their respective controls (pediatric median = 25.3 ng/ml, adult = 72.9 ng/ml), hepcidin was significantly increased in PCKD2-4 (127.3 ng/ml), ACKD2-4 (269.9 ng/ml), and PCKD5D (652.4 ng/ml). Multivariate regression analysis was used to assess the relationship between hepcidin and indicators of anemia, iron status, inflammation, and renal function. In PCKD2-4 (R(2) = 0.57), only ferritin correlated with hepcidin. In ACKD2-4 (R(2) = 0.78), ferritin and soluble transferrin receptor were associated with hepcidin, whereas GFR was inversely correlated. In PCKD5D (R(2) = 0.52), percent iron saturation and ferritin were predictors of hepcidin. In a multivariate analysis that incorporated all three groups (R(2) = 0.6), hepcidin was predicted by ferritin, C-reactive protein, and whether the patient had stage 5D versus stages 2 to 4 CKD.

CONCLUSIONS

These findings suggest that increased hepcidin across the spectrum of CKD may contribute to abnormal iron regulation and erythropoiesis and may be a novel biomarker of iron status and erythropoietin resistance.