Iron therapy, advanced oxidation protein products, and carotid artery intima-media thickness in end-stage renal disease

Safety of intravenous iron in hemodialysis patients

Among end-stage renal disease patients maintained by hemodialysis, anemia has been managed primarily through erythropoiesis-stimulating agents (ESAs) and intravenous (IV) iron. Following concerns about the cardiovascular (CV) safety of ESAs and changes in the reimbursement policies in Medicare's ESRD program, the use of IV iron has increased. IV iron supplementation promotes hemoglobin production and reduces ESA requirements, yet there exists relatively little evidence on the long-term safety of iron supplementation in hemodialysis patients. Labile iron can induce oxidative stress and is also essential in bacterial growth, leading to concerns about IV iron use and risk of CV events and infections in hemodialysis patients. Existing randomized controlled trials provide little evidence about safety due to insufficient power and short follow-up; recent observational studies have been inconsistent, but some have associated iron exposure with increased risk of infections and CV events. Given the widespread use and potential safety concerns related to IV iron, well-designed large prospective studies are needed to assess to identify optimal strategies for iron administration that maximize its benefits while avoiding potential risks.

Diagnosing and preventing iron overload

Absolute or functional iron (Fe) deficiency is an important determinant of anemia in hemodialysis patients and parenteral Fe is routinely used to treat this condition in conjunction with erythropoiesis stimulating agents. While restoration of hemoglobin toward the target range is a good outcome of Fe replacement, it is well known that Fe overload and toxicity may be adverse consequences of this therapy. Dialysis clinical practice guidelines recommend tailoring Fe therapy based on transferrin saturation and serum ferritin levels. Unfortunately, serum Fe markers may not accurately reflect the amount of Fe in the body, because factors such as infections, inflammation, or malignancy can alter serum ferritin levels. Some recent trials in dialysis patients receiving high intravenous Fe doses have shown increased cardiovascular morbidity and mortality and studies using magnetic resonance imaging (MRI) in this population have shown excessive tissue liver iron content (LIC) suggesting Fe overload. While LIC measured by MRI correlates well with LIC quantitated by liver biopsy, it only represents a surrogate marker for total body Fe and its clinical relevance in dialysis patients in terms of mortality and morbidity remains to be demonstrated. Nevertheless, these recent findings challenge the use of current serum Fe markers recommended by clinical guidelines to guide safe Fe therapy in dialysis patients. While not yet established for the routine screening of dialysis patients for Fe overload, MRI should be considered in patients who have received a high cumulative dose of intravenous Fe, or have long cumulative dialysis vintage. Further studies are needed to assess how MRI will alter management.

HFE mutations and iron in hemodialysis patients

In chronic hemodialysis patients, a disruption in iron metabolism ranging from absolute to functional deficiency, with compartmentalization of this metal into macrophages, is often observed. Chronic inflammation indeed often causes an upregulation of the iron hormone hepcidin, thereby reducing iron absorption and availability to the erythron. We systematically reviewed the literature on the role of genetic risk factors on iron metabolism in hemodialysis. In this setting, mutations in the HFE gene of hereditary hemochromatosis may confer an adaptive benefit by decreasing hepcidin release, thus improving iron availability to erythropoiesis, anemia control, and the response to erythropoiesis stimulating agents and iron itself, and reducing the side effects of these therapies. The HFE protein together with Transferrin receptor-2 may also have a direct role on erythroid differentiation and iron uptake in erythroid cells. In addition, other genetic determinants of iron status, such as variants in Matriptase-2 (TMPRSS6), have been shown to influence iron metabolism in chronic hemodialysis patients, most likely acting through hepcidin regulation. Although data must be confirmed in larger prospective studies, this favorable shift in iron metabolism balance possibly results in reduced mortality, in particular because of cardiovascular and infective diseases. Further genetic studies may offer a valuable tool to test these hypotheses and guide personalized clinical management and the research of new therapies.

Iatrogenic Iron Overload in Dialysis Patients at the Beginning of the 21st Century

Iron overload used to be considered rare in hemodialysis patients but its clinical frequency is now increasingly realized. The liver is the main site of iron storage and the liver iron concentration (LIC) is closely correlated with total iron stores in patients with secondary hemosideroses and genetic hemochromatosis. Magnetic resonance imaging is now the gold standard method for LIC estimation and monitoring in non-renal patients. Studies of LIC in hemodialysis patients by quantitative magnetic resonance imaging and magnetic susceptometry have demonstrated a strong relation between the risk of iron overload and the use of intravenous (IV) iron products prescribed at doses determined by the iron biomarker cutoffs contained in current anemia management guidelines. These findings have challenged the validity of both iron biomarker cutoffs and current clinical guidelines, especially with respect to recommended IV iron doses. Three long-term observational studies have recently suggested that excessive IV iron doses may be associated with an increased risk of cardiovascular events and death in hemodialysis patients. We postulate that iatrogenic iron overload in the era of erythropoiesis-stimulating agents may silently increase complications in dialysis patients without creating frank clinical signs and symptoms. High hepcidin-25 levels were recently linked to fatal and nonfatal cardiovascular events in dialysis patients. It is therefore tempting to postulate that the main pathophysiological pathway leading to these events may involve the pleiotropic master hormone hepcidin (synergized by fibroblast growth factor 23), which regulates iron metabolism. Oxidative stress as a result of IV iron infusions and iron overload, by releasing labile non-transferrin-bound iron, might represent a ‘second hit’ on the vascular bed. Finally, iron deposition in the myocardium of patients with severe iron overload might also play a role in the pathogenesis of sudden death in some patients.

Effect of a Ferric Citrate Formulation, a Phosphate Binder, on Oxidative Stress in Chronic Kidney Diseases-Mineral and Bone Disorder Patients Receiving Hemodialysis: A Pilot Study

A ferric citrate formulation for treating hyperphosphatemia is a new therapeutic that not only suppresses the accumulation of phosphorus in patients with chronic kidney disease-mineral bone disorders (CKD-MBD), but also ameliorates anemia caused by iron deficiency. In contrast, it has been demonstrated that intravenous iron injection markedly increases oxidative stress. This study was designed to investigate the effect of a ferric citrate formulation on oxidative stress in CKD-MBD patients receiving hemodialysis therapy. Fifteen CKD-MBD patients undergoing dialysis were enrolled in this study. The patients were orally administered a ferric citrate formulation for 6 months. Their plasma phosphorus concentrations remained unchanged with the switch from other phosphorus adsorbents to the ferric citrate formulation. In addition, the ferric citrate formulation generally allowed for dose reduction of an erythropoiesis stimulating agent with an increased hematopoietic effect. The average values of plasma ferritin level increased after the introduction of a ferric citrate formulation, but did not exceed 100 (ng/mL). Interestingly, oxidative stress markers did not increase significantly, and anti-oxidative capacity was not significantly decreased at 6 months after the drug administration. Similarly, no change was observed in any inflammation markers. The ferric citrate formulation induces negligible oxidative stress in CKD-MBD patients receiving dialysis under the present clinical condition.

Plasma protein-bound di-tyrosines as biomarkers of oxidative stress in end stage renal disease patients on maintenance haemodialysis

Background

Patients with end-stage renal disease (ESRD) undergoing haemodialysis (HD) experience enhanced oxidative stress and systemic inflammation, which are risk factors for cardiovascular disease, the most common cause of excess morbidity and mortality for these patients. Different pathways producing different types of oxidative stress occur in ESRD. The purpose of our study was to determine the effect of HD on plasma levels of protein-bound dityrosine (di-Tyr), a biomarker of protein oxidation.

Methods

Protein-bound di-Tyr formation was measured by size exclusion HPLC coupled to fluorescence detector. Clinical laboratory parameters were measured by standardized methods.

Results

In most ESRD patients, a single HD session decreased significantly the plasma protein-bound di-Tyr level, although the mean post-HD level remained significantly greater than the one in healthy people. Furthermore, pre-HD plasma protein-bound di-Tyr level was positively correlated with pre-HD serum creatinine and albumin concentrations. No significant correlation was found between plasma protein-bound di-Tyr level and serum concentration of C-reactive protein, a biomarker of systemic inflammation.

Conclusions

This study demonstrates that a single HD session does not increase, rather partially decreases, oxidative pathways producing di-Tyr in the haemodialyzed patient.

General significance

The choice of the most pertinent biomarkers of oxidative stress is critical for the development of novel treatments for ESRD. However, the relative importance of oxidative stress and inflammation in ESRD remains largely undetermined, and several questions concerning oxidative stress and inflammation remain poorly defined. These results could stimulate further studies on the use of plasma protein-bound di-Tyr as a long-lasting oxidative stress biomarker in ESRD.

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Haemodialyzed patients experience oxidative stress and systemic inflammation.

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We assessed haemodialysis (HD) effect on plasma protein-bound dityrosine (di-Tyr).

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In most patients, a single HD session decreased significantly the di-Tyr level.

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Pre-HD di-Tyr level was positively correlated with those of creatinine and albumin.

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No correlation was found between di-Tyr level and C-reactive protein concentration.

Advanced oxidation protein products sensitized the transient receptor potential vanilloid 1 via NADPH oxidase 1 and 4 to cause mechanical hyperalgesia

Oxidative stress is a possible pathogenesis of hyperalgesia. Advanced oxidation protein products (AOPPs), a new family of oxidized protein compounds, have been considered as a novel marker of oxidative stress. However, the role of AOPPs in the mechanism of hyperalgesia remains unknown. Our study aims to investigate whether AOPPs have an effect on hyperalgesia and the possible underlying mechanisms. To identify the AOPPs involved, we induced hyperalgesia in rats by injecting complete Freund's adjuvant (CFA) in hindpaw. The level of plasma AOPPs in CFA-induced rats was 1.6-fold in comparison with what in normal rats (P<0.05). After intravenous injection of AOPPs-modified rat serum albumin (AOPPs-RSA) in Sprague-Dawley rats, the paw mechanical thresholds, measured by the electronic von Frey system, significantly declined. Immunofluorescence staining indicated that AOPPs increased expressions of NADPH oxidase 1 (Nox1), NADPH oxidase 4 (Nox4), transient receptor potential vanilloid 1 (TRPV1) and calcitonin gene-related peptide (CGRP) in the dorsal root ganglia (DRG) tissues. In-vitro studies were performed on primary DRG neurons which were obtained from both thoracic and lumbar DRG of rats. Results indicated that AOPPs triggered reactive oxygen species (ROS) production in DRG neurons, which were significantly abolished by ROS scavenger N-acetyl-l-cysteine (NAC) and small-interfering RNA (siRNA) silencing of Nox1 or Nox4. The expressions of Nox1, Nox4, TRPV1 and CGRP were significantly increased in AOPPs-induced DRG neurons. And relevant siRNA or inhibitors notably suppressed the expressions of these proteins and the calcium influxes in AOPPs-induced DRG neurons. In conclusion, AOPPs increased significantly in CFA-induced hyperalgesia rats and they activated Nox1/Nox4-ROS to sensitize TRPV1-dependent Ca2+ influx and CGRP release which led to inducing mechanical hyperalgesia.

Iron and peripheral arterial disease: revisiting the iron hypothesis in a different light

The relationship between iron status and atherosclerosis has long been a topic of debate in the literature. Despite more than 25 years of research, there is no consensus regarding a causal relationship. To date, the vast majority of studies have focused on iron burden with respect to a hypothesized role in the onset and progression of coronary artery disease. However, the effect of iron in the coronary arterial system may differ mechanistically and therefore clinically from its effect in the peripheral arterial system. This review will summarize the biochemical, pathologic, animal, and clinical research data with respect to iron and atherosclerosis. This background will be expanded upon to provide insights into ongoing studies and paths for future investigations into the role of iron and peripheral arterial disease.

Systemic Redox Imbalance in Chronic Kidney Disease: A Systematic Review

Patients with chronic kidney disease (CKD) experience imbalance between oxygen reactive species (ROS) production and antioxidant defenses leading to cell and tissue damage. However, it remains unclear at which stage of renal insufficiency the redox imbalance becomes more profound. The aim of this systematic review was to provide an update on recent advances in our understanding of how the redox status changes in the progression of renal disease from predialysis stages 1 to 4 to end stage 5 and whether the various treatments and dialysis modalities influence the redox balance. A systematic review was conducted searching PubMed and Scopus by using the Cochrane and PRISMA guidelines. In total, thirty-nine studies met the inclusion criteria and were reviewed. Even from an early stage, imbalance in redox status is evident and as the kidney function worsens it becomes more profound. Hemodialysis therapy per se seems to negatively influence the redox status by the elevation of lipid peroxidation markers, protein carbonylation, and impairing erythrocyte antioxidant defense. However, other dialysis modalities do not so far appear to confer advantages. Supplementation with antioxidants might assist and should be considered as an early intervention to halt premature atherogenesis development at an early stage of CKD.

Comparison of serum paraoxonase and arylesterase activities between iron deficiency anemia patients and chronic kidney disease patients with anemia

OBJECTIVE

Altered paraoxonase (PON) and arylesterase (ARE) activities have been shown in anemic chronic kidney disease (CKD) patients and in iron deficiency anemia (IDA) patients. Whether accompanying anemia alone is responsible for this diminished PON and ARE activities in CKD patients or an additive factor for this is not well studied. Therefore, we tried to clarify this issue here.

METHODS

A total of 82 subjects that consisted of 19 patients with IDA (group 1), 23 anemic CKD patients (group 2), and 40 age and sex matched healthy subjects (group 3) were enrolled. Carotid intima media thickness (CIMT), serum total thiol (-SH), PON, and ARE activities of the participants were analyzed.

RESULTS

Group 2 patients had significantly lowest serum levels of Total -SH, PON and ARE. Further comparison showed that total -SH, PON and ARE levels were lower in group 1 than group 3 (p = 0.0001 in both). Regarding comparison of group 1 and 2, only serum ARE levels were significantly lower in group 2 (p = 0.001). PON activity was not different between group 1 and group 2 whereas ARE activity was lower in group 2 than groups 1 and 3. In addition, correlation analysis showed that CIMT was negatively correlated with PON and ARE.

CONCLUSIONS

This markedly decreased ARE activity in CKD patients, which could not be explained by the anemia alone, may have a role in the pathogenesis of increased atherosclerosis in such patients. Still further studies are needed to certain this.

Oxidative Stress Biomarkers and Left Ventricular Hypertrophy in Children with Chronic Kidney Disease

Cardiovascular diseases remain the most frequent cause of morbidity and mortality in patients with chronic kidney disease (CKD). The aim of the study was to assess the association between oxidative stress biomarkers and cardiovascular risk factors and left ventricular hypertrophy in children with CKD. Material and Methods. The studied group consisted of 65 patients aged 1.4-18.6 (mean 11.2) years with stages 1 to 5 CKD. Serum oxidized low-density lipoprotein (oxLDL), protein carbonyl group, creatinine, cystatin C, albumin, lipids, high-sensitivity C-reactive protein, intercellular adhesion molecule-1, insulin, plasma renin activity, and aldosterone levels were measured. Patients were divided into groups depending on CKD stage. Anthropometric measurements, ambulatory blood pressure (BP) measurements, and echocardiography with left ventricular mass (LVM) calculation were performed. Results. Serum oxLDL strongly correlated with creatinine (R = 0.246; p = 0.048), cystatin C (R = 0.346; p = 0.006), total cholesterol (R = 0.500; p < 0.001), triglycerides (R = 0.524; p < 0.001), low-density lipoprotein concentrations (R = 0.456; p < 0.001), and 24 hour BP values of systolic (R = 0.492; p = 0.002), diastolic (R = 0.515; p < 0.001), and mean arterial pressure (R = 0.537; p < 0.001). A significant correlation between oxLDL levels and LVM z-scores (R = 0.299; p = 0.016) was found. Conclusions. Hypertension and dyslipidemia correlated with lipid oxidation in children with CKD. oxLDLs seem to be valuable markers of oxidative stress in CKD patients, correlating with left ventricular hypertrophy.

Safety concerns about intravenous iron therapy in patients with chronic kidney disease

Anaemia in chronic kidney disease (CKD) is managed primarily with erythropoiesis-stimulating agents (ESAs) and iron therapy. Following concerns around ESA therapy, intravenous (IV) iron is being administered more and more worldwide. However, it is still unclear whether this approach is safe at very high doses or in the presence of very high ferritin levels. Some observational studies have shown a relationship between either high ferritin level or high iron dose and increased risk of death, cardiovascular events, hospitalization or infection. Others have not been able to confirm these findings. However, they suffer from indication biases. On the other hand, the majority of randomized clinical trials have only a very short follow-up (and thus drug exposure) and are inadequate to assess the mortality risk. None of them have tested the role of different iron doses on hard end points. With the lack of clear evidence coming from well-designed and large-scale studies, several data suggest that excessive iron therapy may be toxic in several aspects, ranging from iron overload to tissue damage from labile iron. A number of experimental and clinical data suggest that either excessive iron therapy or iron overload may be a possible culprit of atherogenesis. The process seems to be mediated by oxidative stress. Iron therapy should also be used cautiously in the presence of active infections, since iron is essential for bacterial growth. Recently, the European Medicines Agency officially raised concerns about rare hypersensitivity reactions following IV iron administration. The balance has been in favour of benefits. In several European countries, this has created a lot of confusion and somewhat slowed the run towards excessive use. Altogether, IV iron remains a mainstay of anaemia treatment in CKD patients. However, in our opinion, its excessive use should be avoided, especially in patients with high ferritin levels and when ESA agents are not contraindicated.

New Options for Iron Supplementation in Maintenance Hemodialysis Patients

End-stage renal disease results in anemia caused by shortened erythrocyte survival, erythropoietin deficiency, hepcidin-mediated impairment of intestinal absorption and iron release, recurrent blood loss, and impaired responsiveness to erythropoiesis-stimulating agents (ESAs). Iron malabsorption renders oral iron products generally ineffective, and intravenous (IV) iron supplementation is required in most patients receiving maintenance hemodialysis (HD). IV iron is administered at doses far exceeding normal intestinal iron absorption. Moreover, by bypassing physiologic safeguards, indiscriminate use of IV iron overwhelms transferrin, imposing stress on the reticuloendothelial system that can have long-term adverse consequences. Unlike conventional oral iron preparations, ferric citrate has recently been shown to be effective in increasing serum ferritin, hemoglobin, and transferrin saturation values while significantly reducing IV iron and ESA requirements in patients treated with HD. Ferric pyrophosphate citrate is a novel iron salt delivered by dialysate; by directly reaching transferrin, its obviates the need for storing administered iron and increases transferrin saturation without increasing serum ferritin levels. Ferric pyrophosphate citrate trials have demonstrated effective iron delivery and stable hemoglobin levels with significant reductions in ESA and IV iron requirements. To date, the long-term safety of using these routes of iron administration in patients receiving HD has not been compared to IV iron and therefore awaits future investigations.

How the Target Hemoglobin of Renal Anemia Should Be

Renal anemia is caused by the deficiency of endogenous erythropoietin (Epo) due to renal dysfunction. We think that it is possible to slow the progression of chronic kidney disease (CKD) in case we initiate Epo early in pre-dialysis patients, especially in the non-diabetic population. Erythropoiesis stimulating agent (ESA) treatments targeting mild anemia (10-12 g/dl) can decrease the risk of occurrence of cardiovascular disease (CVD) in patients with hypertension, diabetes mellitus and congestive heart failure. As the large randomized controlled trials such as Cardiovascular Risk Reduction by Early Anemia Treatment with Epoetin Beta, Correction of Hemoglobin and Outcomes in Renal Insufficiency and Trial to Reduce Cardiovascular Events with Aranesp Thearpy in the Western countries suggested, we do not recommend high doses of ESA to achieve the target hemoglobin (Hb) level. The target Hb of >13 g/dl might lead to increase in the risk of CVD although maintaining a high Hb of >12 g/dl without ESA is not harmful for CKD patients. It is desirable to determine the target Hb in dialysis patients depending on their ages. Renal anemia should be monitored constantly to start ESA and iron replacement therapy at an appropriate time, while avoiding their excess in order to minimize the occurrence of CVD and other complications. Taken all the international guidelines and our clinical experiences together, we should consider administration of ESA when the Hb level becomes <11 g/dl in pre-dialysis patients and <10 g/dl in dialysis patients.

Is hepcidin-25 a predictor of atherosclerosis in hemodialysis patients?

Atherosclerotic cardiovascular disease is an important cause of mortality and morbidity in hemodialysis patients. Iron accumulation in arterial wall macrophages is increased in atherosclerotic lesions. Hepcidin is a key hepatic hormone regulating iron balance. It inhibits iron release from macrophages and iron absorption from enterocytes by binding and inactivating the cellular iron exporter ferroportin. The aim of this study is to investigate the relation of hepcidin-25, iron parameters, and atherosclerosis measured by carotid intima media thickness (CIMT) in hemodialysis patients. Eighty-two hemodialysis patients were enrolled in this cross-sectional study. Predialysis blood samples were centrifuged at 1500 g and 4°C for 10 minutes and stored at -80°C for the measurement of hepcidin-25. DRG hepcidin enzyme-linked immunosorbent assay kit was used for the measurement of hepcidin-25. Ultrasonographical B-mode imaging of bilateral carotid arteries was performed with a high-resolution real-time ultrasonography (Mindray DC7). Mean age of the study population was 57.90 ± 16.08 years and 43.9% were men. Total study population was grouped into two according to median value of hepcidin-25. There was no difference between groups with respect to age, dialysis vintage, and C-reactive protein. CIMT was found to be statistically significantly higher in low hepcidin-25 group. In correlation analysis, CIMT was found to be correlated with age (P < 0.01, R = 0.33) and hepcidin-25 (P < 0.01, R = 0.46). In linear regression analysis, age (β = 0.31) and hepcidin-25 (β = 0.44) were found to be the determinants of CIMT in hemodialysis patients. Our results implicate that hepcidin may take part in pathophysiology of atherosclerosis and cardiovascular disease in hemodialysis patients.

Serum ferritin is associated with arterial stiffness in hemodialysis patients: results of a 3-year follow-up study

BACKGROUND

Iron may contribute to vascular injury through reactive oxygen species. Hemodialysis patients frequently receive iron supply for correction of anemia and are at a high risk of cardiovascular disease. We tested the relationship between iron status and change in arterial stiffness in hemodialysis patients.

PATIENTS AND METHODS

We measured iron status in 53 hemodialysis patients and studied the association with clinical, biochemical, and arterial stiffness measured by brachial-ankle pulse wave velocity (baPWV) over 3 years. The blood pressure was controlled to below 140/90 mmHg by anti-hypertensive drugs.

RESULTS

Median and interquartile range of baseline baPWV, baPWV at 3 years, and ΔbaPWV (difference between 3-year baPWV and baseline baPWV) were following: 17.6 (14.8-18.9), 16.9 (15.3-19.9), and 0.2 (-1.2 to 2.7) m/s. At baseline, baPWV was positively correlated with age, serum ferritin, and systolic blood pressure in univariate analysis. However, in multivariate analysis, only age and serum ferritin remained the significant determinants of baseline baPWV. After 3 years, ΔbaPWV was negatively correlated with age and positively with 3-year averaged serum ferritin in univariate analysis. Then, in multivariate analysis, only 3-year averaged serum ferritin was the important determinant of ΔbaPWV. ΔbaPWV was significantly increased in patients with 3-year averaged serum ferritin >500 ng/mL compared to patients with 3-year averaged serum ferritin ≤500 ng/mL.

CONCLUSIONS

In hemodialysis patients, serum ferritin associates with the progressive arterial stiffness, especially when serum ferritin >500 ng/mL.

Serum ferritin is associated with carotid atherosclerotic plaques but not intima-media Thickness in patients with abnormal glucose metabolism

BACKGROUND

We investigated the association between serum ferritin and carotid artery lesions in populations with abnormal glucose metabolism.

METHODS

We included 70 participants with abnormal glucose metabolism and 170 participants with normal glucose metabolism and measured their baseline serum ferritin levels. During follow-up carotid intima-media thickness and carotid plaque were evaluated.

RESULTS

Serum ferritin levels were higher in the participants with abnormal glucose metabolism (p<0.01). We further divided the patients with abnormal glucose metabolism into subgroups with and without intima-media proliferation, and found that ferritin was excluded from the final equation in the logistic regression. Furthermore, age, waist circumference, ferritin, 2h-PG, and total cholesterol were significantly different between the subgroups with and without carotid plaque. When the above data were included in a logistic regression model, the p values obtained for age, ferritin, and 2h-PG were 0.004, 0.032, and 0.011, respectively.

CONCLUSIONS

In the Chinese population, serum ferritin levels are significantly increased in patients with abnormal glucose metabolism. The carotid intima-media thickness showed no independent relationship with serum ferritin in patients with abnormal glucose metabolism. However, high serum ferritin is an important risk factor for carotid atherosclerosis in these patients.

Effects of carnitine on oxidative stress response to intravenous iron administration to patients with CKD: impact of haptoglobin phenotype

BACKGROUND

Anemia is a common disorder in CKD patients. It is largely attributed to decreased erythropoietin (EPO) production and iron deficiency. Therefore, besides EPO, therapy includes iron replenishment. However, the latter induces oxidative stress. Haptoglobin (Hp) protein is the main line of defense against the oxidative effects of Hemoglobin/Iron. There are 3 genotypes: 1-1, 2-1 and 2-2. Hp 2-2 protein is inferior to Hp 1-1 as antioxidant. So far, there is no evidence whether haptoglobin phenotype affects iron-induced oxidative stress in CKD patients. Therefore, the present study examines the influence of carnitine treatment on the intravenous iron administration (IVIR)-induced oxidative stress in CKD patients, and whether Hp phenotype affects this response.

METHODS

TRIAL REGISTRATION

Current Controlled Trials ISRCTN5700858. This study included 26 anemic (Hb = 10.23 ± 0.28) CKD patients (stages 3-4) that were given a weekly IVIR (Sodium ferric gluconate, [125 mg/100 ml] for 8 weeks, and during weeks 5-8 also received Carnitine (20 mg/kg, IV) prior to IVIR. Weekly blood samples were drawn before and after each IVIR for Hp phenotype, C-reactive protein (CRP), advanced oxidative protein products (AOPP), neutrophil gelatinase-associated lipocalin (NGAL), besides complete blood count and biochemical analyses.

RESULTS

Eight percent of CKD patients were Hp1-1, 19 % Hp2-1, and 73 % Hp2-2. IVIR for 4 weeks did not increase hemoglobin levels, yet worsened the oxidative burden as was evident by elevated plasma levels of AOPP. The highest increase in AOPP was observed in Hp2-2 patients. Simultaneous administration of Carnitine with IVIR abolished the IVIR-induced oxidative stress as evident by preventing the elevations in AOPP and NGAL, preferentially in patients with Hp2-2 phenotype.

CONCLUSIONS

This study demonstrates that Hp2-2 is a significant risk factor for IVIR-induced oxidative stress in CKD patients. Our finding, that co-administration of Carnitine with IVIR preferentially attenuates the adverse consequences of IVIR, suggests a role for Carnitine therapy in these patients.

Anaemia management in patients with chronic kidney disease: Taiwan practice guidelines

The introduction of erythropoiesis-stimulating agents (ESAs) markedly improved the lives of many anaemic patients with chronic kidney disease (CKD). In Taiwan, the strategy of management of anaemia in patients with CKD was different from many other parts of the world. In 1996, the National Health Insurance Administration of Taiwan applied a more restrictive reimbursement criteria for ESA use in patients with CKD. ESA is to be initiated when non-dialysis CKD patients have a serum creatinine >6 mg/dL and a hematocrit <28% to maintain a hematocrit level not exceeding 30%. The maximal dose of epoetin-α or β was 20 000 U per month. The target haemoglobin range and dose limitation for ESAs were the same for dialysis CKD patients. Thus, long before randomized controlled trials showing an increased risk for cardiovascular events at nearly normal haemoglobin concentrations and higher ESA doses in CKD, nephrologists in Taiwan had avoided the use of disproportionately high dosages of ESAs to achieve a haemoglobin level of 10-11 g/dL. Moreover, intravenous iron supplementation was encouraged earlier in Taiwan in 1996, when we reached consensus on the diagnostic criteria for iron deficiency (serum ferritin <300 ng/mL and/or transferrin saturation <30%). The experience of CKD anaemia management in Taiwan demonstrated that a reasonable haemoglobin target can be achieved by using the lowest possible ESA dose and intravenous iron supplementation.

A randomized trial of intravenous and oral iron in chronic kidney disease

Although iron is commonly used to correct iron deficiency anemia (IDA) in chronic kidney disease (CKD) its effect on kidney function is unclear. To assess this, we randomly assigned patients with Stage 3 and 4 CKD and IDA to either open-label oral ferrous sulfate (69 patients to 325 mg three times daily for 8 weeks) or intravenous iron sucrose (67 patients to 200 mg every 2 weeks, total 1 gram). The primary outcome was the between group difference in slope of measured glomerular filtration rate (mGFR) change over two years. The trial was terminated early on the recommendation of an independent Data and Safety Monitoring Board based on little chance of finding differences in mGFR slopes, but a higher risk of serious adverse events in the intravenous iron treatment group. mGFR declined similarly over two years in both treatment groups (oral −3.6 mL/min/1.73m², intravenous − 4.0 mL/min/1.73m², between group difference − 0.35 mL/min/1.73m² (95% confidence interval −2.9 to 2.3). There were 36 serious cardiovascular events among 19 participants assigned to the oral iron treatment group and 55 events among 17 participants of the intravenous iron group (adjusted incidence rate ratio 2.51 (1.56−4.04). Infections resulting in hospitalizations had a significant adjusted incidence rate ratio of 2.12 (1.24−3.64). Thus, among non-dialyzed patients with CKD and IDA, intravenous iron therapy is associated with an increased risk of serious adverse events, including those from cardiovascular causes and infectious diseases.

The Labile Side of Iron Supplementation in CKD

The practice of intravenous iron supplementation has grown as nephrologists have gradually moved away from the liberal use of erythropoiesis-stimulating agents as the main treatment for the anemia of CKD. This approach, together with the introduction of large-dose iron preparations, raises the future specter of inadvertent iatrogenic iron toxicity. Concerns have been raised in original studies and reviews about cardiac complications and severe infections that result from long-term intravenous iron supplementation. Regarding the iron preparations specifically, even though all the currently available preparations appear to be relatively safe in the short term, little is known regarding their long-term safety. In this review we summarize current knowledge of iron metabolism with an emphasis on the sources and potentially harmful effects of labile iron, highlight the approaches to identifying labile iron in pharmaceutical preparations and body fluids and its potential toxic role as a pathogenic factor in the complications of CKD, and propose methods for its early detection in at-risk patients.

Iron supplementation associates with low mortality in pre-dialyzed advanced chronic kidney disease patients receiving erythropoiesis-stimulating agents: a nationwide database analysis

BACKGROUND

A risk/benefit analysis of iron supplementation in pre-dialysis advanced chronic kidney disease (CKD) patients has not been conducted. We aim to assess the effectiveness and the safety of iron supplementation in patients with CKD Stage 5 who have not yet received dialysis (CKD 5 ND).

METHODS

A prospective cohort study was conducted based on the Taiwan National Health Insurance Research Database. From 1 January 2000 to 30 June 2009, we enrolled 31 971 adult patients who had a serum creatinine >6 mg/dL and a haematocrit <28% and who were treated with erythropoiesis-stimulating agents (ESAs). All patients were further divided into two groups with or without iron supplementation within 90 days after starting ESA therapy. Patient follow-up took place until dialysis, death before initiation of dialysis or 31 December 2009. The primary outcomes were death before initiating dialysis, hospitalization before death or long-term dialysis.

RESULTS

After propensity score matching, the patients who received iron supplementation were associated with a lower risk of all-cause death [hazard ratio (HR), 0.85; 95% confidence interval (CI), 0.80-0.90] compared with non-users. The survival benefit of iron use was consistent across the majority of dosage groups, except for those who were treated with monthly IV iron >200 mg. Moreover, compared with the non-users, the iron users were associated with a lower risk of hospitalizations (HR, 0.97; 95% CI, 0.94-0.99) but with a higher risk of faster progression to end-stage renal disease (HR, 1.05; 95% CI, 1.01-1.08).

CONCLUSIONS

Iron supplementation is associated with 15% risk reduction in death among CKD 5 ND patients who received ESA treatment. Randomized studies are needed to validate this association.

The Role of the Carotid Doppler Examination in the Evaluation of Atherosclerotic Changes in β-Thalassemia Patients

BACKGROUND

Iron overload in patients with beta-thalassemia major (BTM) lead to alterations in the arterial structures and the thickness of the carotid arteries. Doppler ultrasound scanning of extra-cranial internal carotid arteries is non-invasive and relatively quick to perform and may identify children at increased risk of stroke that would otherwise be missed. Increased carotid artery intima media thickness (CIMT) is a structural marker for early atherosclerosis and correlates with the vascular risk factors and to the severity and extent of coronary artery disease.

OBJECTIVE

To evaluate the role of carotid Doppler examination and CIMT measurement as a predictor of atherosclerotic changes in BTM children with iron overload.

PATIENTS AND METHODS

Sixty two children with BTM and, thirty age and sex matched normal controls were included. Complete blood count, ferritin, serum cholesterol were done, as well as carotid Doppler ultrasonography to measure the CIMT in both patients and controls.

RESULTS

CIMT of thalassemic patients was significantly increased compared to controls (p=0.001). There was a significant positive correlation between CIMT and patient's age, the duration from first blood transfusion, serum cholesterol and, iron overload parameters as serum ferritin, frequency of blood transfusion, iron chelation. The length of the transfusion period was the highest risk factor, and an inadequate iron chelation was a further risk factor. Significant negative correlation was found between CIMT and hematocrit value while no significant correlation was found between CIMT and weight, height, BMI centiles and Hb level.

CONCLUSION

Carotid Doppler is very useful in measurement of CIMT that increased in thalassemic patients that shows a strong relationship with features of iron overload. Routine Doppler measurement of CIMT in these patients is recommended to predict early atherosclerotic changes as well as in follow-up.

Wishful Thinking: The Surprisingly Sparse Evidence for a Relationship between Oxidative Stress and Cardiovascular Disease in Hemodialysis Patients

The increased frequency of cardiovascular disease observed in hemodialysis patients is secondary to the combination of many traditional (age, male sex, hypertension, smoking, diabetes mellitus, and dyslipidemia) and novel and uremia-related (inflammation, uremic toxins, adipokine imbalance, coagulation disorders, protein-energy wasting, volume overload, endothelial dysfunction, hyperparathyroidism, and subclinical hypothyroidism) risk factors. Usually, in the latter group, oxidative stress is included. However, after decades of research, it remains essentially unknown if oxidative stress has a causative role in the development of cardiovascular disease in long-term hemodialysis patients because adequate longitudinal studies are lacking. Data deriving from cross-sectional studies suggest that biomarkers of oxidative stress are associated with cardiovascular disease prevalence. Conversely, conflicting and inconclusive results have been obtained on the association between oxidative stress and coronary artery calcification, atherosclerosis, and all-cause and cardiovascular disease-related outcome. It is desirable that further studies are conducted on this topic in the near future.

Low levels of serum ferritin lead to adequate hemoglobin levels and good survival in hemodialysis patients

BACKGROUND

The optimal level of serum ferritin (s-ft) for anemia control and good survival in hemodialysis (HD) patients remains unclear. A 10-year survey was performed to clarify the appropriate quantities of s-ft and investigate the relationships among s-ft, transferrin saturation (TSAT), and mortality in HD patients.

METHODS

HD outpatients (n = 125) treated with erythropoiesis-stimulating agents (ESA) were followed for 10 years. The ESA and low-dose iron supplement dosages were adjusted to maintain the hemoglobin (Hb) at 10-11 g/dl, according to Japanese guidelines. The Kaplan-Meier method, log-rank tests, and the Cox proportional hazards model were used for performing the statistical analyses. The interactions among the Hb, s-ft, and TSAT were analyzed using a multiple linear regression model. Patients with TSAT ≥20% were classified according to the s-ft cutoff values: group 1 (s-ft <30 ng/ml); group 2 (s-ft 30-80 ng/ml); group 3 (s-ft >80 ng/ml); TSAT <20% was a predictor of poor outcome.

RESULTS

The survival rate in group 2 was significantly higher than that in other groups (p = 0.013), and the Cox proportional hazards model analysis showed a good effect of low levels of s-ft on patients' survival. The multiple linear regression model showed a strong effect of s-ft on the Hb (log [s-ft], β-coefficient -0.45: 95% confidence interval -0.65 to -0.26, p < 0.001).

CONCLUSION

This study revealed that low levels of s-ft have a beneficial effect on the outcome of HD patients receiving ESA. Thus, the optimal s-ft level might be lower than that established previously for these patients.

Correlations between peroxisome proliferator activator receptor γ, Cystatin C, or advanced oxidation protein product, and atherosclerosis in diabetes patients

We aimed to explore the relationship between peroxisome proliferator activator receptor γ (PPAR γ), Cystatin C or advanced oxidation protein product (AOPP) and atherosclerosis (AS), and identify their diagnostic values for AS. Eighty AS patients above the age of 75 with type 2 diabetes were screened by brachial-ankle pulse wave velocity (baPWV) and ankle brachial index (ABI). The baseline level of patients was firstly analyzed, and then the expression of PPAR γ was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Meanwhile, a double-antibody sandwich enzyme-linked immunosorbent assay was performed to analyze the concentration of AOPP, and immunonephelometry was carried out to detect the concentration of Cystatin C. The baseline level of patients was basically consistent. The expression of PPAR γ was significantly higher in severe AS than mild AS patients (P < 0.05), while no differences were found in serum Cystatin C and AOPP between severe AS and mild AS patients (P > 0.05). Thus, PPAR γ exhibited a high diagnostic value for severe AS (AUC = 0.850), but not Cystatin C and AOPP (AUC = 0.553, AUC = 0.4780). Moreover, the combination of PPAR γ, Cystatin C and AOPP exhibited a quite high diagnostic value in AS (AUC = 0.961, Sen = 0.9, Spe = 0.975), which was also higher than PPAR γ alone. In conclusion, the contents of PPAR γ, Cystatin C and AOPP were closely related to AS in diabetes, indicating a potential clinical diagnostic value of PPAR γ, Cystatin C and AOPP in diabetes with AS.

An alternative pathway through the Fenton reaction for the formation of advanced oxidation protein products, a new class of inflammatory mediators

The accumulation of advanced oxidation protein products (AOPPs) has been linked to several pathological conditions, and their levels are formed during oxidative stress as a result of reactions between plasma proteins and chlorinated oxidants produced by myeloperoxidase (MPO). However, it was suggested that the generation of this mediator of inflammation may also occur via an MPO-independent pathway. The aim of this study was to induce the formation of AOPPs in vitro through Fenton reaction and to investigate whether this generation could be counteracted by N-acetylcysteine (NAC) and fructose-1,6-bisphosphate (FBP). The complete Fenton system increased the AOPPs levels and both NAC and FBP were capable of inhibiting the formation of Fenton reaction-induced AOPPs. These data provide a new hypothesis about another pathway of AOPPs formation, as well as report that NAC and FBP may be good candidates to neutralize pro-inflammatory and pro-oxidant effects of AOPPs in several diseases.

Intravenous iron exposure and mortality in patients on hemodialysis

BACKGROUND AND OBJECTIVES

Clinical trials assessing effects of larger cumulative iron exposure with outcomes are lacking, and observational studies have been limited by assessment of short-term exposure only and/or failure to assess cause-specific mortality. The associations between short- and long-term iron exposure on all-cause and cause-specific mortality were examined.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study included 14,078 United States patients on dialysis initiating dialysis between 2003 and 2008. Intravenous iron dose accumulations over 1-, 3-, and 6-month rolling windows were related to all-cause, cardiovascular, and infection-related mortality in Cox proportional hazards models that used marginal structural modeling to control for time-dependent confounding.

RESULTS

Patients in the 1-month model cohort (n=14,078) were followed a median of 19 months, during which there were 27.6% all-cause deaths, 13.5% cardiovascular deaths, and 3% infection-related deaths. A reduced risk of all-cause mortality with receipt of >150-350 (hazard ratio, 0.78; 95% confidence interval, 0.64 to 0.95) or >350 mg (hazard ratio, 0.79; 95% confidence interval, 0.62 to 0.99) intravenous iron compared with >0-150 mg over 1 month was observed. There was no relation of 1-month intravenous iron dose with cardiovascular or infection-related mortality and no relation of 3- or 6-month cumulative intravenous iron dose with all-cause or cardiovascular mortality. There was a nonstatistically significant increase in infection-related mortality with receipt of >1050 mg intravenous iron in 3 months (hazard ratio, 1.69; 95% confidence interval, 0.87 to 3.28) and >2100 mg in 6 months (hazard ratio, 1.59; 95% confidence interval, 0.73 to 3.46).

CONCLUSIONS

Among patients on incident dialysis, receipt of ≤ 1050 mg intravenous iron in 3 months or 2100 mg in 6 months was not associated with all-cause, cardiovascular, or infection-related mortality. However, nonstatistically significant findings suggested the possibility of infection-related mortality with receipt of >1050 mg in 3 months or >2100 mg in 6 months. Randomized clinical trials are needed to assess the safety of exposure to greater cumulative intravenous iron doses.

Cumulative iron dose and resistance to erythropoietin

INTRODUCTION

Optimizing anemia treatment in hemodialysis (HD) patients remains a priority worldwide as it has significant health and financial implications. Our aim was to evaluate in a large cohort of chronic HD patients in Fresenius Medical Care centers in Spain the value of cumulative iron (Fe) dose monitoring for the management of iron therapy in erythropoiesis-stimulating agent (ESA)-treated patients, and the relationship between cumulative iron dose and risk of hospitalization.

METHODS

Demographic, clinical and laboratory parameters from EuCliD(®) (European Clinical Dialysis Database) on 3,591 patients were recorded including ESA dose (UI/kg/week), erythropoietin resistance index (ERI) [U.I weekly/kg/gr hemoglobin (Hb)] and hospitalizations. Moreover the cumulative Fe dose (mg/kg of bodyweight) administered over the last 2 years was calculated. Univariate and multivariate analyses were performed to identify the main predictors of ESA resistance and risk of hospitalization. Patients belonging to the 4th quartile of ERI were defined as hypo-responders.

RESULTS

The 2-year iron cumulative dose was significantly higher in the 4th quartile of ERI. In hypo-responders, 2-year cumulative iron dose was the only iron marker associated with ESA resistance. At case-mix adjusted multivariate analysis, 2-year iron cumulative dose was an independent predictor of hospitalization risk.

DISCUSSION

In ESA-treated patients cumulative Fe dose could be a useful tool to monitor the appropriateness of Fe therapy and to prevent iron overload. To establish whether the associations between cumulative iron dose, ERI and hospitalization risk are causal or attributable to selection bias by indication, clinical trials are necessary.

Sevelamer revisited: pleiotropic effects on endothelial and cardiovascular risk factors in chronic kidney disease and end-stage renal disease

Endothelial dysfunction underlies multiple cardiovascular consequences of chronic kidney disease (CKD) and antecedent diabetes or hypertension. Endothelial insults in CKD or end-stage renal disease (ESRD) patients include uremic toxins, serum uric acid, hyperphosphatemia, reactive oxygen species, and advanced glycation endproducts (AGEs). Sevelamer carbonate, a calcium-free intestinally nonabsorbed polymer, is approved for hyperphosphatemic dialysis patients in the US and hyperphosphatemic stage 3-5 CKD patients in many other countries. Sevelamer has been observed investigationally to reduce absorption of AGEs, bacterial toxins, and bile acids, suggesting that it may reduce inflammatory, oxidative, and atherogenic stimuli in addition to its on-label action of lowering serum phosphate. Some studies also suggest that noncalcium binders may contribute less to vascular calcification than calcium-based binders. Exploratory sevelamer carbonate use in patients with stages 2-4 diabetic CKD significantly reduced HbA1c, AGEs, fibroblast growth factor (FGF)-23, and total and low-density lipoprotein (LDL) cholesterol versus calcium carbonate; inflammatory markers decreased and defenses against AGEs increased. Sevelamer has also been observed to reduce circulating FGF-23, potentially reducing risk of left ventricular hypertrophy. Sevelamer but not calcium-based binders in exploratory studies increases flow-mediated vasodilation, a marker of improved endothelial function, in patients with CKD. In contrast, lanthanum carbonate and calcium carbonate effects on FMV did not differ in hemodialysis recipients. The recent independent-CKD randomized trial compared sevelamer versus calcium carbonate in predialysis CKD patients (investigational in the US, on-label in European participants); sevelamer reduced 36-month mortality and the composite endpoint of mortality or dialysis inception. Similarly, independent-HD in incident dialysis patients showed improved survival with 24 months of sevelamer versus calcium-based binders. This review discusses recent exploratory evidence for pleiotropic effects of sevelamer on endothelial function in CKD or ESRD. Endothelial effects of sevelamer may contribute mechanistically to the improved survival observed in some studies of CKD and ESRD patients.

Association between hemoglobin variability, serum ferritin levels, and adverse events/mortality in maintenance hemodialysis patients

In recent times, therapy for renal anemia has changed dramatically in that iron administration has increased and doses of erythropoiesis-stimulating agents (ESAs) have decreased. Here we used a prospective, observational, multicenter design and measured the serum ferritin and hemoglobin levels every 3 months for 2 years in 1086 patients on maintenance hemodialysis therapy. The associations of adverse events with fluctuations in ferritin and hemoglobin levels and ESA and iron doses were measured using a Cox proportional hazards model for time-dependent variables. The risks of cerebrovascular and cardiovascular disease (CCVD), infection, and hospitalization were higher among patients who failed to maintain a target-range hemoglobin level and who exhibited high-amplitude fluctuations in hemoglobin compared with patients who maintained a target-range hemoglobin level. Patients with a higher compared with a lower ferritin level had an elevated risk of CCVD and infectious disease. Moreover, the risk of death was significantly higher among patients with high-amplitude ferritin fluctuations compared with those with a low ferritin level. The risks of CCVD, infection, and hospitalization were significantly higher among patients who were treated with high weekly doses of intravenous iron compared with no intravenous iron. Thus, there is a high risk of death and/or adverse events in patients with hemoglobin levels outside the target range, in those with high-amplitude hemoglobin fluctuations, in those with consistently high serum ferritin levels, and in those with high-amplitude ferritin fluctuations.

Iron sucrose accelerates early atherogenesis by increasing superoxide production and upregulating adhesion molecules in CKD

High-dose intravenous iron supplementation is associated with adverse cardiovascular outcomes in patients with CKD, but the underlying mechanism is unknown. Our study investigated the causative role of iron sucrose in leukocyte-endothelium interactions, an index of early atherogenesis, and subsequent atherosclerosis in the mouse remnant kidney model. We found that expression levels of intracellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and adhesion of U937 cells increased in iron-treated human aortic endothelial cells through upregulated NADPH oxidase (NOx) and NF-κB signaling. We then measured mononuclear-endothelial adhesion and atherosclerotic lesions of the proximal aorta in male C57BL/6 mice with subtotal nephrectomy, male apolipoprotein E-deficient (ApoE(-/-)) mice with uninephrectomy, and sham-operated mice subjected to saline or parenteral iron loading. Iron sucrose significantly increased tissue superoxide production, expression of tissue cell adhesion molecules, and endothelial adhesiveness in mice with subtotal nephrectomy. Moreover, iron sucrose exacerbated atherosclerosis in the aorta of ApoE(-/-) mice with uninephrectomy. In patients with CKD, intravenous iron sucrose increased circulating mononuclear superoxide production, expression of soluble adhesion molecules, and mononuclear-endothelial adhesion compared with healthy subjects or untreated patients. In summary, iron sucrose aggravated endothelial dysfunction through NOx/NF-κB/CAM signaling, increased mononuclear-endothelial adhesion, and exacerbated atherosclerosis in mice with remnant kidneys. These results suggest a novel causative role for therapeutic iron in cardiovascular complications in patients with CKD.

Involvement of iron-evoked oxidative stress in smoking-related endothelial dysfunction in healthy young men

Background

Oxidative stress and smoking contribute to endothelial dysfunction. Iron might also play a role in oxidative stress generation and endothelial dysfunction. However, the involvement of iron in smoking-induced endothelial dysfunction in healthy smokers remains unclear. Therefore, we examined here whether (1) intravenous iron infusion impaired endothelial function evaluated by flow-mediated vasodilatation (FMD) in non-smokers, and (2) deferoxamine, a potent iron chelator, ameliorated endothelial dysfunction in healthy smokers.

Methods

Eight healthy young male non-smokers (23±4 years old) received intravenous injection of saccharated ferric oxide (0.7 mg/kg body weight), while 10 age-matched healthy male smokers received deferoxamine mesylate (8.3 mg/kg body weight). At baseline, 5 and 20 minutes after treatment with iron or deferoxamine, biochemical variables were measured, including serum iron and marondialdehyde (MDA), a marker of lipid oxidation, and endothelial function was simultaneously evaluated by FMD.

Results

Compared with non-smokers, FMD was significantly lower in smokers. Iron and MDA levels were significantly increased, whereas FMD was impaired by iron infusion in non-smokers. Conversely, deferoxamine treatment significantly decreased iron and MDA levels and restored the decreased FMD in smokers. Baseline serum iron and MDA levels in all 18 subjects (non-smokers and smokers) were correlated with each other. There was a significant inverse correlation between the changes in MDA values and FMD from baseline in 18 men. Endothelium-independent vasodilation by glyceryl trinitrate was unaltered by either treatment.

Conclusions

Our present study suggests that iron-evoked oxidative stress might play a role in endothelial dysfunction in healthy smokers.

Chronic Kidney Disease—Effect of Oxidative Stress

Chronic kidney disease (CKD) is a growing health problem with increasing incidence. The annual mortality of end-stage renal disease patients is about 9%, which is 10–20 fold higher than the general population, approximately 50% of these deaths are due to cardiovascular (CV) disease. CV risk factors, such as diabetes, hypertension, and hyperlipidemia, are strongly associated with poor outcome. Many other nontraditional risk factors such as inflammation, infection, oxidative stress, anemia, and malnutrition are also present. In this review we will focus on the role of oxidative stress in chronic kidney disease.

TSAT is a better predictor than ferritin of hemoglobin response to Epoetin alfa in US dialysis patients

Clinical guidelines recommend concurrent treatment of anemia in end-stage renal disease with erythropoiesis-stimulating agents (ESAs) and iron. However, there are mixed data about optimal iron supplementation. To help address this gap, the relationship between iron markers and hemoglobin (Hb) response to ESA (Epoetin alfa) dose was examined. Electronic medical records of 1902 US chronic hemodialysis patients were analyzed over a 12-month period between June 2009 and June 2010. The analysis included patients who had at least one Hb value during each 4-week interval for four consecutive intervals (k - 2, k - 1, k, and k + 1; k is the index interval), received at least one ESA dose during intervals k - 1 or k, had at least one transferrin saturation (TSAT) value at interval k, and at least one ferritin value during intervals k - 2, k - 1, or k. Effect modification by TSAT and ferritin on Hb response was evaluated using the generalized estimating equations approach. Patients had a mean (standard deviation) age of 62 (15) years; 41% were Caucasian, 34% African American, 65% had hypertension, and 39% diabetes. Transferrin saturation, but not ferritin, had a statistically significant (P < 0.05) modifying effect on Hb response. Maximum Hb response was achieved when TSAT was 34%, with minimal incremental effect beyond these levels. Of the two standard clinical iron markers, TSAT should be used as the primary marker of the modifying effect of iron on Hb response to ESA. Long-term safety of iron use to improve Hb response to ESA warrants further study.

High dose intravenous iron, mineral homeostasis and intact FGF23 in normal and uremic rats

BACKGROUND

High iron load might have a number of toxic effects in the organism. Recently intravenous (iv) iron has been proposed to induce elevation of fibroblast growth factor 23 (FGF23), hypophosphatemia and osteomalacia in iron deficient subjects. High levels of FGF23 are associated with increased mortality in the chronic kidney disease (CKD) population. CKD patients are often treated with iv iron therapy in order to maintain iron stores and erythropoietin responsiveness, also in the case of not being iron depleted. Therefore, the effect of a single high iv dose of two different iron preparations, iron isomaltoside 1000 (IIM) and ferric carboxymaltose (FCM), on plasma levels of FGF23 and phosphate was examined in normal and uremic iron repleted rats.

METHODS

Iron was administered iv as a single high dose of 80 mg/kg bodyweight and the effects on plasma levels of iFGF23, phosphate, Ca2+, PTH, transferrin, ferritin and iron were examined in short and long term experiments (n = 99). Blood samples were obtained at time 0, 30, 60, 180 minutes, 24 and 48 hours and in a separate study after 1 week. Uremia was induced by 5/6-nephrectomy.

RESULTS

Nephrectomized rats had significant uremia, hyperparathyroidism and elevated FGF23. Iron administration resulted in significant increases in plasma ferritin levels. No significant differences were seen in plasma levels of iFGF23, phosphate and PTH between the experimental groups at any time point within 48 hours or at 1 week after infusion of the iron compounds compared to vehicle.

CONCLUSIONS

In non-iron depleted normal and uremic rats a single high dose of either of two intravenous iron preparations, iron isomaltoside 1000, and ferric carboxymaltose, had no effect on plasma levels of iFGF23 and phosphate for up to seven days.

Intravenous iron supplementation practices and short-term risk of cardiovascular events in hemodialysis patients

Background & Objectives

Intravenous iron supplementation is widespread in the hemodialysis population, but there is uncertainty about the safest dosing strategy. We compared the safety of different intravenous iron dosing practices on the risk of adverse cardiovascular outcomes in a large population of hemodialysis patients.

Design settings, participants, & measurements

A retrospective cohort was created from the clinical database of a large dialysis provider (years 2004-2008) merged with administrative data from the United States Renal Data System. Dosing comparisons were (1) bolus (consecutive doses ≥ 100 mg exceeding 600 mg during one month) versus maintenance (all other iron doses during the month); and (2) high (> 200 mg over 1 month) versus low dose (≤ 200 mg over 1 month). We established a 6-month baseline period (to identify potential confounders and effect modifiers), a one-month iron exposure period, and a three-month follow-up period. Outcomes were myocardial infarction, stroke, and death from cardiovascular disease.

Results

117,050 patients contributed 776,203 unique iron exposure/follow-up periods. After adjustment, we found no significant associations of bolus dose versus maintenance, hazards ratio for composite outcome, 1.03 (95% C.I. 0.99, 1.07), or high dose versus low dose intravenous iron, hazards ratio for composite outcome, 0.99 (95% C.I. 0.96, 1.03). There were no consistent associations of either high or bolus dose versus low or maintenance respectively among pre-specified subgroups.

Conclusions

Strategies favoring large doses of intravenous iron were not associated with increased short-term cardiovascular morbidity and mortality. Investigation of the long-term safety of the various intravenous iron supplementation strategies may still be warranted.

Iron toxicity: relevance for dialysis patients

Iron deficiency is common among patients with advanced kidney disease, particularly those requiring hemodialysis. Intravenous iron is a convenient treatment to supplement iron and is widely used among hemodialysis patients. Its efficacy is well established that, with treatment, hemoglobin levels rise and erythropoiesis-stimulating agent dose requirements are reduced. However, the safety of intravenous iron with respect to patient-centered outcomes has not been adequately studied. A variety of studies have indicated potential safety concerns, but most have been of small numbers of patients and with end points studied that have unclear clinical relevance. In this study, issues related to iron toxicity are reviewed.