Iron, oxidative stress, and clinical outcomes

Iron metabolism biomarkers and mortality risk in U.S. patients with congestive heart failure: NHANES 1999-2018 analysis

BACKGROUND AND AIMS

Iron deficiency is a major public health concern. We aimed to assess the predictive capability of 4 iron metabolism biomarkers for all-cause and cardiovascular disease-specific mortality in U.S. patients with congestive heart failure (CHF).

METHODS AND RESULTS

1904 CHF patients aged ≥20 years were enrolled from NHANES, 1999-2000 to 2017-2018. All analyses were weighted to provide nationally representative estimates. Among 1905 CHF patients, mean age was 71 years, and 1024 (53.8%), 459 (24.1%), 206 (10.8%), and 216 (11.3%) were Non-Hispanic Black, Non-Hispanic White, Hispanic-Mexican American, and Hispanic-Other Hispanic, respectively. During follow-ups, 1080 deaths occurred. Median follow-up time was 5.08 years. Per-unit increase in natural-logarithmic-transformed iron and transferrin saturation decreased all-cause mortality risk separately by 33.0% (adjusted hazard ratio: 0.670, 95% confidence interval: 0.563 to 0.797, P < 0.001) and 32.6% (0.674, 0.495 to 0.917, 0.013), and per-unit increase in transferrin receptor increased mortality risk by 33.7% (1.337, 1.104 to 1.618, 0.004). Two derivates from 3 significant iron biomarkers were generated - transferrin receptor to natural-logarithmic-transformed iron ratio (TRI) and transferrin receptor to natural-logarithmic-transformed transferrin saturation ratio (TRTS), which were significantly associated with all-cause mortality, with per-unit increase corresponding to 2.692- and 1.655-fold increased all-cause mortality risk (P: 0.003 and 0.023). Only iron and TRTS were associated with the significant risk of cardiovascular disease-specific mortality (P: 0.004 and 0.017).

CONCLUSIONS

Our findings identified 3 iron metabolism biomarkers that were individually, significantly, and independently associated with all-cause mortality in patients with CHF, and importantly 2 derivates generated exhibited stronger predictive capability.

Erythropoiesis-independent effects of iron in chronic kidney disease

Chronic kidney disease (CKD) leads to alterations of iron metabolism, which contribute to the development of anemia and necessitates iron supplementation in patients with CKD. Elevated hepcidin accounts for a significant iron redistribution in CKD. Recent data indicate that these alterations in iron homeostasis coupled with therapeutic iron supplementation have pleiotropic effects on many organ systems in patients with CKD, far beyond the traditional hematologic effects of iron; these include effects of iron on inflammation, oxidative stress, kidney fibrosis, cardiovascular disease, CKD-mineral and bone disorder, and skeletal growth in children. The effects of iron supplementation appear to be largely dependent on the route of administration and on the specific iron preparation. Iron-based phosphate binders exemplify the opportunity for using iron for both traditional (anemia) and novel (hyperphosphatemia) indications. Further optimization of iron therapy in patients with CKD may inform new approaches to the treatment of CKD complications and potentially allow modification of disease progression.

Discerning the antioxidant mechanism of rapanone: A naturally occurring benzoquinone with iron complexing and radical scavenging activities

Oxidative stress resulting from iron and reactive oxygen species (ROS) homeostasis breakdown has been implicated in several diseases. Therefore, molecules capable of binding iron and/or scavenging ROS may be reasonable strategies for protecting cells. Rapanone is a naturally occurring hydroxyl-benzoquinone with a privileged chelating structure. In this work, we addressed the antioxidant properties of rapanone concerning its iron-chelating and scavenging activities, and its protective potential against iron and tert-butyl hydroperoxide-induced damage to mitochondria. Experimental determinations revealed the formation of rapanone-Fe(II)/Fe(III) complexes. Additionally, the electrochemical assays indicated that rapanone oxidized Fe(II) and O₂^-, thus inhibiting Fenton-Haber-Weiss reactions. Furthermore, rapanone displayed an increased 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability in the presence of Fe(II). The above results explained the capacity of rapanone to provide near-full protection against iron and tert-butyl hydroperoxide induced mitochondrial lipid peroxidation in energized organelles, which fail under non-energized condition. We postulate that rapanone affords protection against iron and reactive oxygen species by means of both iron chelating and iron-stimulated free radical scavenging activity.

Does IV Iron Induce Plasma Oxidative Stress in Critically Ill Patients? A Comparison With Healthy Volunteers

OBJECTIVE

To compare the oxidative stress induced by IV iron infusion in critically ill patients and in healthy volunteers.

DESIGN

Multicenter, interventional study.

SETTING

Two ICUs and one clinical research center.

SUBJECTS

Anemic critically ill patients treated with IV iron and healthy volunteers.

INTERVENTIONS

IV infusion of 100 mg of iron sucrose.

MEASUREMENTS AND MAIN RESULTS

Thirty-eight anemic patients (hemoglobin, median [interquartile range] = 8.4 g/dL [7.7-9.2]) (men, 25 [66%]; aged 68 yr [48-77]; Simplified Acute Physiology Score II, 48.5 [39-59]) and 39 healthy volunteers (men, 18 [46%]; aged 42.1 yr [29-50]) were included. Blood samples were drawn before (H0) and 2, 6, and 24 hours (H2, H6, and H24) after a 60-minute iron infusion for the determination of nontransferrin bound iron, markers of lipid peroxidation-8α-isoprostanes, protein oxidation-advanced oxidized protein product, and glutathione reduced/oxidized. Iron infusion had no effect on hemodynamic parameter in patients and volunteers. At baseline, patients had much higher interleukin-6, C-reactive protein, and hepcidin levels. 8α-isoprostanes was also higher in patients at baseline (8.5 pmol/L [6.5-12.9] vs 4.6 pmol/L [3.5-5.5]), but the area under the curve above baseline from H0 to H6 was not different (p = 0.38). Neither was it for advanced oxidized protein product and nontransferrin bound iron. The area under the curve above baseline from H0 to H6 (glutathione reduced/oxidized) was lower in volunteers (p = 0.009). Eight patients had a second set of dosages (after the fourth iron infusion), showing higher increase in 8α-isoprostanes.

CONCLUSIONS

In our observation, IV iron infusion does not induce more nontransferrin bound iron, lipid, or protein oxidation in patients compared with volunteers, despite higher inflammation, oxidative stress, and hepcidin levels and lower antioxidant at baseline. In contrary, iron induces a greater decrease in antioxidant, compatible with higher oxidative stress in volunteers than in critically ill patients.

Subclinical cardiovascular disease and its association with risk factors in children with steroid-resistant nephrotic syndrome

BACKGROUND

The aim of this study was to evaluate the presence of subclinical cardiovascular disease (CVD) and its relation to risk factors in pediatric patients with steroid-resistant nephrotic syndrome (NS).

METHODS

Thirty-seven patients with normal renal function were compared with 22 healthy controls regarding the presence of subclinical CVD. Measurements included aortic pulse wave velocity (PWV), carotid intima media thickness (IMT), and left ventricular mass (LVM). Patients were additionally assessed for blood pressure (BP) pattern and the presence of hypertension by 24-h ambulatory blood pressure monitoring.

RESULTS

Compared with the controls, patients had significantly higher mean aortic PWV-standard deviation scores (SDS), mean carotid IMT-SDS, and LVM index (p < 0.001 for all). Increased aortic PWV was noted in 5 % of patients, increased carotid IMT in 22 %, and increased LVM index in 19 %. Five patients (14 %) were hypertensive, and mean BP indexes, SDS, and BP loads during nighttime were significantly higher than those during daytime (p < 0.001 for all). Multivariate analysis revealed a significant relationship between PWV-SDS and ferritin (R(2) = 0.269, p = 0.006) and between carotid IMT-SDS and proteinuria (R(2) = 0.141, p = 0.022). The LVM index was independently associated only with higher body mass index SDS (R(2) = 0.317, p < 0.001). In addition, six patients (16 %) had multiple abnormal subclinical CVD markers, and increased subclinical CVD risk was independently associated only with higher low-density lipoprotein cholesterol (R(2) = 0.292, p = 0.044).

CONCLUSIONS

Based on these results, steroid-resistant NS children generally are at high risk of cardiovascular complications, but the increased risk is likely to be multifactorial.

Kidney Disease: Improving Global Outcomes guidelines on anaemia management in chronic kidney disease: a European Renal Best Practice position statement

Recently, the Kidney Disease: Improving Global Outcomes (KDIGO) group has produced comprehensive clinical practice guidelines for the management of anaemia in CKD patients. These guidelines addressed all of the important points related to anaemia management in CKD patients, including therapy with erythropoieis stimulating agents (ESA), iron therapy, ESA resistance and blood transfusion use. Because most guidelines were 'soft' rather than 'strong', and because global guidelines need to be adapted and implemented into the regional context where they are used, on behalf of the European Renal Best Practice Advisory Board some of its members, and other external experts in this field, who were not participants in the KDIGO guidelines group, were invited to participate in this anaemia working group to examine and comment on the KDIGO documents in this position paper. In this article, the group concentrated only on those guidelines which we considered worth amending or adapting. All guidelines not specifically mentioned are fully endorsed.

Comparative efficacy and safety of intravenous ferric carboxymaltose (Ferinject) and iron(III) hydroxide dextran (Cosmofer) in pregnancy

BACKGROUND

Iron-deficiency anaemia is common in pregnancy, with well-described maternal morbidities. When oral iron therapy has failed, intravenous (IV) preparations are considered. Ferric carboxymaltose (ferinject) is a new IV preparation which can be given quickly. There are no published data on Ferinject use in pregnancy. This study analyses historical data from women given Cosmofer, compared with those given Ferinject in pregnancy, to assess comparative efficacy and safety.

METHODS

Pregnant women treated with Cosmofer and Ferinject, were identified from pharmacy records. Records for all cases were reviewed and those which fulfilled inclusion criteria selected. The inclusion criteria included: symptomatic iron-deficient anaemia unresponsive to oral iron; age ≥18; second to third trimester; full blood count taken at least once at two, four and/or six weeks post-infusion. Data were collected on the pre-treatment Hb, ferritin, and same data collected at two, four and six weeks after the infusion. Side-effects or adverse reactions were noted for both the Cosmofer and Ferinject patients.

RESULTS

Results were obtained for 92 women (44 received Ferinject and 48 Cosmofer). Pre-infusion Hb and ferritin levels were comparable in the two groups. At two weeks, the mean Hb rise in the Ferinject group was 1.73 g/dL and 1.34 g/dL in the Cosmofer group. At four weeks, the total rise in Hb was 2.57 g/dL Ferinject, 2.34 g/dL Cosmofer. At six weeks the rise was 3.01 g/dL and 3.2 g/dL respectively. No serious adverse events were reported in either group.

CONCLUSION

Both preparations appear effective and safe, with low risk of serious adverse effects and side-effects.

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.

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.

Anemia in chronic kidney disease: new advances

Anemia resulting from iron and erythropoietin deficiencies is a common complication of advanced chronic kidney disease (CKD). This article covers major advances in our understanding of anemia in patients with CKD, including newly discovered regulatory molecules, such as hepcidin, to innovative intravenous iron therapies. The use of erythropoiesis-stimulating agents (ESA) in the treatment of anemia has undergone seismic shift in the past 3 years as a result of adverse outcomes associated with targeting higher hemoglobin levels with these agents. Potential mechanisms for adverse outcomes, such as higher mortality, are discussed. Despite the disappointing experience with ESAs, there is a tremendous interest in other novel agents to treat anemia in CKD. Lastly, while awaiting updated guidelines, the authors outline their recommendations on how to best manage patients who are anemic and have CKD.

Iron and vascular calcification. Is there a link?

Iron deficiency is frequently seen in patients with end-stage renal disease, particularly in those treated by dialysis, this is because of an impairment in gastrointestinal absorption and ongoing blood losses or alternatively, due to an impaired capacity to mobilize iron from its stores, called functional iron deficiency. Therefore, these patients may require intravenous iron to sustain adequate treatment with erythropoietin-stimulating agents. Aside from this, they are also prone to vascular calcification, which has been reported a major contributing factor in the development of cardiovascular disease and the increased mortality associated herewith. Several factors and mechanisms underlying the development of vascular calcification in chronic kidney diseased patients have been put forward during recent years. In view of the ability of iron to exert direct toxic effects and to induce oxidative stress on the one hand versus its essential role in various cellular processes on the other hand, the possible role of iron in the development of vascular calcification should be considered.

Proteinuria induced by parenteral iron in chronic kidney disease--a comparative randomized controlled trial

BACKGROUND AND OBJECTIVES

Among patients with chronic kidney disease (CKD), differences in proteinuria are seen between intravenous iron preparations after a single dose exposure. This study examined differences in proteinuria between two intravenous iron preparations after multiple doses.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with iron-deficiency anemia and CKD, stratified by angiotensin converting enzyme inhibitor (ACEI)/angiotensin receptor-blocker (ARB) use, were randomized to iron sucrose or ferric gluconate. Each patient at 12 centers received 100 mg of study drug weekly for 5 weeks. Urine protein/urine creatinine ratio was measured before each dose and frequently thereafter for 3 hours.

RESULTS

Postbaseline data were available from 33 patients receiving iron sucrose and 29 patients receiving ferric gluconate. Although neither preparation of intravenous iron increased the predose level of proteinuria, the proteinuric response to intravenous iron was dependent on the type of iron and ACEI/ARB use. Without ACEIs/ARBs, ferric gluconate tended to cause less proteinuria with repeated iron administration; iron sucrose did not mitigate or aggravate proteinuria. Among patients receiving ACEIs/ARBs, in contrast to ferric gluconate, which produced only mild transient proteinuria, iron sucrose produced a consistent and persistent proteinuric response that was on average 78% greater.

CONCLUSIONS

Although multiple doses of either intravenous iron did not increase basal levels of proteinuria, postdose proteinuria was greater with iron sucrose than with ferric gluconate. These data suggest that nephrotoxicity of iron may depend on type of intravenous iron and on ACEI/ARB use. The long-term effects on kidney function need to be further evaluated.

Oxidative status in iron-deficiency anemia

Oxidative stress is an imbalance between free radicals and antioxidant molecules that can play an important role in the pathogenesis of iron-deficiency anemia (IDA). The aim of this study was to investigate oxidative status in patients with IDA and alteration of oxidative status after iron treatment. Thirty-three female patients with IDA and 25 healthy controls were included in this study. Oxidant and total antioxidant capacity were determined using free oxygen radicals test and free oxygen radicals defence (Form CR 3000, Callegari, Parma, Italy). Catalase activity was measured by spectrophotometer using a commercially available kit (Bioxytech Catalase-520, OxisResearch, Portland, OR). Oxidant activity in patients with IDA was significantly higher than controls (P<0.05), while total antioxidant and catalase activity were significantly lower (P<0.05). After treatment, oxidant, antioxidant, and catalase activity reached the levels of the control group, and no significant differences were observed among groups (P>0.05). In conclusion, our data indicate that blood reactive oxygen species was lower and total antioxidant and catalase activity were higher after rather than before treatment in patients with IDA. The results of our study support the higher oxidative stress hypothesis in IDA; however, due to the limited number of cases included, more studies may be required to confirm the results.