Maintaining Iron Balance Research Articles

Casein phosphopeptide interferes the interactions between ferritin and ion irons

Ferritin, a vital protein required to store iron in a cage-like structure, is critical for maintaining iron balance. Ferritin can be attacked by free radicals during iron reduction and release, thereby leading to oxidative damage. Whether other biomacromolecules such as casein phosphopeptides (CPP) could influence the ferritin's function in iron oxidation and release and affect the ferritin stability remains unclear. This study aims to investigate the effect of CPP on the ferritin‑iron ion interaction, thereby focusing on role of CPP on ferritin stability. Results showed that CPP weakened the iron oxidation activity of ferritin but promoted iron release. Moreover, CPP could effectively chelate iron, capture hydroxyl radicals, and reduce the degradation of ferritin. This study highlights the role of CPP in the ferritin‑iron relationship, and lays a foundation for understanding the interaction between ferritin, peptides, and metal ions.

Comprehensive spectroscopic and computational insight into the binding of vanillin with human transferrin: targeting neuroinflammation in Alzheimer's disease therapeutics.

In present times, vanillin stands out as a promising therapeutic molecule that can be implicated in the treatment of neurodegenerative disorders (NDs), notably Alzheimer's disease (AD). This can be attributed to the highly potent scavenging activity of vanillin against reactive oxygen species (ROS). Oxidative stress leads to generation of ROS that serves a critical role in AD's pathological progression. It is apparent from various studies that diets rich in polyphenols prevent oxidative stress associated with AD development, implying the crucial role of vanillin in AD therapeutics. It is crucial to maintain iron balance to manage AD associated oxidative stress, unveiling the significance of human transferrin (hTf) that maintains iron homeostasis. Here, we have performed an integrated study of spectroscopic and computational approaches to get insight into the binding mechanism of vanillin with hTf. In the preliminary study, molecular docking deciphered that vanillin primarily occupies the hTf binding pocket, forming multiple interactions with its key residues. Moreover, the binding mechanism was evaluated at an atomistic level employing comprehensive molecular dynamic (MD) simulation. MD analysis demonstrated that binding of vanillin to hTf stabilizes its structure, without inducing any significant alterations in its native conformation. The docked complex was maintained throughout the simulations without changing its original conformation. Essential dynamics analysis further confirms that hTf achieved a stable conformation with vanillin. The outcomes were further supplemented by fluorescence spectroscopy which confirms the formation of stable hTf-vanillin complex. Taken together, the current study unveils the interaction mechanism of vanillin with hTf and providing a platform to use vanillin in AD therapeutics in the context of iron homeostasis.

Iron Absorption: Molecular and Pathophysiological Aspects.

Iron is an essential nutrient for growth among all branches of life, but while iron is among the most common elements, bioavailable iron is a relatively scarce nutrient. Since iron is fundamental for several biological processes, iron deficiency can be deleterious. On the other hand, excess iron may lead to cell and tissue damage. Consequently, iron balance is strictly regulated. As iron excretion is not physiologically controlled, systemic iron homeostasis is maintained at the level of absorption, which is mainly influenced by the amount of iron stores and the level of erythropoietic activity, the major iron consumer. Here, we outline recent advances that increased our understanding of the molecular aspects of iron absorption. Moreover, we examine the impact of these recent insights on dietary strategies for maintaining iron balance.

Ferroptosis in Cardiovascular Disease and Cardiomyopathies: Therapeutic Implications of Glutathione and Iron Chelating Agents.

This review explores ferroptosis, a form of regulated cell death reliant on iron-induced phospholipid peroxidation, in diverse physiological and pathological contexts, including neurodegenerative disorders, and ischemia-reperfusion. In the realm of cardiovascular diseases, it significantly contributes to cardiomyopathies, including dilated cardiomyopathy, hypertrophic cardiomyopathy, and restrictive cardiomyopathy. Ferroptosis involves intricate interactions within cellular iron metabolism, lipid peroxidation, and the balance between polyunsaturated and monounsaturated fatty acids. Molecularly, factors like p53 and NRF2 impact cellular susceptibility to ferroptosis under oxidative stress. Understanding ferroptosis is vital in cardiomyopathies, where cardiac myocytes heavily depend on aerobic respiration, with iron playing a pivotal role. Dysregulation of the antioxidant enzyme GPX4 is linked to cardiomyopathies, emphasizing its significance. Ferroptosis's role in myocardial ischemia-reperfusion injury, exacerbated in diabetes, underscores its relevance in cardiovascular conditions. This review explores the connection between ferroptosis, the NRF2 pathway, and atherosclerosis, emphasizing their roles in protecting cells from oxidative stress and maintaining iron balance. It discusses the use of iron chelating agents in managing iron overload conditions, with associated benefits and challenges. Finally, it highlights the importance of exploring therapeutic strategies that enhance the glutathione (GSH) system and the potential of natural compounds like quercetin, terpenoids, and phenolic acids in reducing oxidative stress.

Experimental and Computational Insights into the Molecular Interactions between Human Transferrin and Apigenin: Implications of Natural Compounds in Targeting Neuroinflammation.

Neuroinflammation plays a vital role in Alzheimer's disease (AD) pathogenesis and other neurodegenerative disorders (NDs). Presently, only symptomatic treatments are available and no disease-modifying drugs are available for AD and other NDs. Thus, targeting AD-associated neuroinflammation with anti-inflammatory compounds and antioxidants has recently been given much focus. Now, flavonoids are being increasingly investigated as therapeutic agents to treat inflammation; apigenin has a neuroprotective effect. Iron dyshomeostasis plays a key role in sustaining the neuroinflammatory phenotype, highlighting the importance of maintaining iron balance, in which human transferrin (HTF) plays a vital role in this aspect. Herein, we explored the binding and dynamics of the HTF-apigenin complex using multifaceted computational and experimental approaches. Molecular docking revealed that apigenin occupies the iron-binding pocket of HTF, forming hydrogen bonds with critical residues Arg475 and Thr686. Molecular dynamics simulations deciphered a dynamic view of the HTF-apigenin complex's behavior (300 ns) and suggested that the complex maintained a relatively stable conformation. The results of spectroscopic observations delineated significant binding of apigenin with HTF and stable HTF-apigenin complex formation. The observed binding mechanism and conformational stability could pave the way for developing novel therapeutic strategies to target neuroinflammation by apigenin in the context of iron homeostasis.

Thyroid dysfunction alters gene expression of proteins related to iron homeostasis and metabolomics in male rats

Thyroid hormones (THs) are crucial in bodily functions, while iron is essential for processes like oxygen transport. Specialized proteins maintain iron balance, including ferritin, transferrin, ferroportin, and hepcidin. Research suggests that THs can influence iron homeostasis by affecting mRNA and protein expression, such as ferritin and transferrin. Our study focused on male rats to assess mRNA expression of iron homeostasis-related proteins and metabolomics in thyroid dysfunction. We found altered gene expression across various tissues (liver, duodenum, spleen, and kidney) and identified disrupted metabolite patterns in thyroid dysfunction. These findings highlight tissue-specific effects of thyroid dysfunction on essential iron homeostasis proteins and provide insights into associated metabolic changes. Our research contributes to understanding the intricate interplay between thyroid hormones and iron balance. By unveiling tissue-specific gene expression alterations and metabolic disruptions caused by thyroid dysfunction, our work lays a foundation for future investigations to explore underlying mechanisms and develop targeted strategies for managing iron-related complications in thyroid disorders.

The interplay between iron regulation and ferroptosis cell death signaling

Iron is an important ion that is mainly involved in different aspects of cellular metabolism. Normally, iron homeostasis is regulated by storage and transport proteins that help stabilize and facilitate transport throughout the body. Transferrin is the main iron transport protein in the blood; it transports ferric iron (Fe3+) from absorption sites to different tissue cells via endocytosis upon interacting with the transferrin receptor. In the cell, in addition to the cytoplasm, mitochondria are heavily involved in iron metabolism. The excess of labile (free unbound) iron in the cell can undergo the Fenton reaction to further enhance ROS production inevitably leading to cell death through apoptosis and/or ferroptosis. Ferroptosis is a new type of cell death that is mediated by iron-dependent lipid peroxidation and is associated with a myriad of diseases such as cardiovascular and neurodegenerative diseases, and cancer, among others. Mitochondria are involved in ferroptotic cell death signaling, nevertheless, the exact mechanisms underlying the contribution of mitochondria to ferroptotic signaling remain unknown. This study was performed to elucidate the effects of iron on cell viability and mitochondrial function in cardiomyocytes. H9c2 cardiomyocytes were cultured in the presence/absence of ferric ammonium citrate (FAC, 200 and 400 μM), tert-butyl hydroxide (TBH, 10 and 100 μM), and deferoxamine (DFO, 200 and 400 μM) individually and in combination. Cell death was quantified by the lactate dehydrogenase (LDH) activity in the culture media whereas mitochondrial function was estimated by changes in the mitochondrial membrane potential measured by using TMRM, a potential-sensitive fluorescent dye. Our results show that TBH at low concentrations or FAC at both low and high concentrations did not induce cell death. However, FAC at high concentration (400 μM) in combination with TBH (10 μM) significantly increased cell death. Additionally, DFO alone induced cell death, demonstrating the importance of maintaining iron balance in cellular media. In conclusion, this study demonstrated that the detrimental effects of iron (FAC) on cell viability are increased in the presence of oxidative stress (TBH) in H9c2 cardiomyocytes. This study was supported by the National Institutes of Health (Grant R16GM145390). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Vegetarian Diet Rich in Soybean Products Compromises Iron Status in Young Students

The iron status of young Chinese Buddhist vegetarians (23 men and 32 women) and nonvegetarian students (20 men and 39 women from a medical college) was investigated by dietary assessment of iron intake and hematological measurement of biochemical indices including hemoglobin, plasma iron, transferrin, transferrin saturation and plasma ferritin. A characteristic of the vegetarian diet in this study was the replacement of meat by soybean products. Results of the dietary assessment showed that the average iron density of the diets ranged from 1.9 to 2.2 mg/MJ, with no difference between the vegetarian and nonvegetarian diets. Daily iron intake was similar in both vegetarian and nonvegetarian men. However, iron intake was significantly higher in female vegetarians than nonvegetarians, averaging 104 and 78% of the RDA, respectively. Results of blood analysis showed that, for both sexes, the median plasma ferritin concentration of the vegetarians (male 47 µg/L and female 12 µg/L) was about half the level of the nonvegetarians (male 91 µg/L and female 27 µg/L). Occurrence and risk of iron deficiency are more prevalent in vegetarians. Correlation between plasma ferritin concentration and years of vegetarian practice in vegetarian men was marginally significant (r = -0.38, P = 0.077). We conclude that a vegetarian diet that is rich in soybean products and restricted in animal foods is limited in bioavailable iron and is not adequate for maintaining iron balance in men and women.

Iron chelation therapy.

Iron overload is a pathological condition resulting from a congenital impairment of its regulation, increased intestinal iron absorption secondary to bone marrow erythroid hyperplasia, or a chronic transfusional regimen. In normal conditions, intracellular and systemic mechanisms contribute to maintaining iron balance. When this complex homeostatic mechanism fails, an iron overload could be present. Detecting an iron overload is not easy. The gold standard remains the liver biopsy, even if it is invasive and dangerous. Identifying iron using noninvasive techniques allowed a better understanding of the rate of iron overload in different organs, with a low risk for the patient. Estimating serum ferritin (mg/L) is the easiest and, consequently, the most employed diagnostic tool for assessing body iron stores, even if it could be a not specific method. The most common hematological causes of iron overload are myelodysplastic syndromes, sickle cell disease, and thalassemia. In all of these conditions, three drugs have been approved for the treatment of iron overload: deferiprone, deferoxamine, and deferasirox. These chelators have been demonstrated to help lower tissue iron levels and prevent iron overload complications, improving event-free survival (EFS). Nowadays, the decision to start chelation and which chelator to choose remains the joint decision of the clinician and patient.

Effect of ultramarathon running on iron metabolism.

Iron is a vital trace element for energy production and oxygen transportation; importantly, it is essential to athletic performance. Maintaining iron balance is tightly controlled at systemic and cellular levels. This study aimed to determine serum iron tests, hepcidin levels, and cellular iron import and export activities in peripheral blood mononuclear cells (PBMCs) in ultramarathon runners to elucidate the association of systemic inflammation response and iron metabolism. Sixteen amateur runners were enrolled. Blood samples were taken 1 week before, immediately, and 24 h after the run. Plasma hepcidin levels were measured by enzyme-linked immunosorbent assay. The expression levels of divalent metal iron transporter 1 (DMT1), ZRT/IRT-like protein 14 (ZIP14), transferrin receptor 1 (TfR1), and ferroportin (FPN) in PBMCs were measured using real-time quantitative reverse transcription-polymerase chain reaction. Serum iron concentrations and transferrin saturation significantly decreased immediately after the race and dramatically recovered 24 h post-race. Serum ferritin levels had a statistically significant rise immediately after the race and remained high 24 h after the completion of the race. Ultramarathons were associated with increased plasma interleukin-6 concentrations corresponding to the state of severe systemic inflammation and therefore boosted plasma hepcidin levels. The expression levels of DMT1 and FPN mRNA were markedly decreased immediately and 24 h after the race. The ZIP14 and TfR1 mRNA expression in PBMCs significantly decreased immediately after the race and returned to the baseline level at 24 h post-race. Positive significant correlations were observed between plasma hepcidin and ferritin levels. Iron homeostasis and systemic inflammatory response are closely interconnected. Cellular iron import and export mRNA activities in PBMCs were acutely inhibited during an ultramarathon.

Comparative efficacy, safety, and cost of iron chelation monotherapy vs. combination therapy in pediatric beta-thalassemia major: a single-center retrospective study

Background Iron chelation therapy is used to maintain iron balance in β-thalassemia major patients who undergo repeated blood transfusions.
 Objective To compare the efficacy, safety, and cost of iron chelation combination regimens [deferiprone (DFP) + deferoxamine (DFO) or DFP + deferasirox (DFX])] vs. high-dose DFP monotherapy (≥ 90 mg/kg/day) in pediatric β-thalassemia major patients.
 Methods This cross-sectional, retrospective study was done at Cipto Mangunkusumo Hospital, Jakarta, Indonesia. Retrospective data was obtained from electronic medical records of pediatric b-thalassemia major patients with serum ferritin of ≥ 2,500 ng/mL and/or transferrin saturation of ≥ 60%, who received either combination or monotherapy iron chelation agents. Outcome effectiveness was determined by the reduction of serum ferritin level of at least 80%. Safety was analyzed descriptively. A pharmacoeconomic analysis was performed based on clinical outcomes consisting of effectiveness and direct medical costs.
 Results At the end of the study, serum ferritin was reduced in 34.7% of the combination therapy group and 27.5% of the monotherapy group, however there was no significant difference between the two treatments (P=0.391). Nine (19.5%) patients on combination therapy and 17 (21.2%) patients on monotherapy had adverse drug reaction (ADR), with the most frequently reported ADR was elevated transaminase enzyme levels. Cost minimization analysis revealed that monotherapy for 6 months was IDR 13,556,592.64 less expensive than combination therapy (IDR 44,498,732.07); whereas monotherapy for 12 months was IDR 20,162,836.10 less expensive than combination therapy (IDR 78,877,661.12).
 Conclusion Combination regimens are as effective as monotherapy regimens in reducing serum ferritin in pediatric β-thalassemia major patients. There is no differences of ADR between combination or monotherapy. The average cost per patient is less expensive with monotherapy compared to combination therapy.

Iron deficiency exacerbates aortic medial degeneration by inducing excessive mitochondrial fission.

Iron deficiency (ID) is a global nutritional deficiency that was shown to be involved in the pathogenesis of aortic aneurysm and dissection (AAD) in our previous studies. Some studies suggested that mitochondrial dynamics was involved in the apoptosis and phenotypic transformation of vascular smooth muscle cells (VSMCs). However, little is known about the role of mitochondrial dynamics in aortic medial degeneration (AMD) promoted by an iron deficient diet. The present study investigated the effect of ID on the phenotypic transformation of VSMCs, the progression of AMD, and the underlying mechanism. The expression of p-Drp1 (Ser616) and Fis1 was markedly upregulated in the aortic media of AAD patients and ApoE-/- mice with subcutaneous AngII osmotic pumps. ID facilitated the formation of mitochondria-associated endoplasmic reticulum membranes (MAMs), which triggered excessive mitochondrial fission, induced the phenotypic transformation of VSMCs, and ultimately accelerated the progression of AMD. Furthermore, the present study indicated that an inhibitor of Drp1 could partially reverse this process. Maintaining iron balance in the human body may prevent the development of AAD.

Mendelian inheritance of anemia due to disturbed iron homeostasis

Genetic disorders that affect proteins involved in maintaining iron balance may lead to Mendelian anemias. They may be classified as defects of intestinal iron absorption, iron transport in the circulation, iron uptake and utilization by maturing erythroid cells, iron recycling by macrophages and systemic regulation of iron homeostasis. All these Mendelian anemias are rare disorders, prevalently recessive, characterized by microcytic and hypochromic red blood cells. Advances in our knowledge of iron metabolism and its systemic regulation on one side have facilitated the identification of novel iron related anemias, while on the other the study of the affected patients and of the corresponding animal models have contributed to our understanding of iron trafficking and regulation.

Effect of dietary iron levels on growth, iron concentration in tissues, and blood concentration levels of transferrin and hepcidin in bighead carp (Aristichthys nobilis)

A 60‐day feeding trial was conducted to estimate the effects of dietary iron (Fe) levels on growth, Fe concentration in the liver, spleen, and blood, and transferrin and hepcidin concentrations in the blood of bighead carp (Aristichthys nobilis). The six experimental diets were formulated to contain different Fe levels (0, 43.1, 84.2, 123.3, 162.2 and 203.1 mg/kg of dry diet) using ferrous sulphate (FeSO₄) as the source. The weight gain (WG) and the specific growth ratio (SGR) of A. nobilis fed with a dietary Fe level of 123.3 mg/kg were significantly higher than that of the 0 mg/kg Fe group (p liver > whole body. When the Fe dietary content increases to 162.2 mg/kg, the blood concentrations of Fe significantly decreased and thereafter increased, hepcidin significantly decreased and thereafter decreased, and transferrin significantly increased and thereafter decreased. The results indicate that the transferrin blood content significantly increased with decreasing hepcidin of up to 264.63 μg/ml content and thereafter decreased. It could be concluded that after transferrin saturation, hepcidin functions to maintain iron balance in the blood of A. nobilis by decreasing transferrin content.

Influences of different Fe sources on Fe bioavailability and homeostasis in SD rats.

The purpose of this study was to determine whether the enteric coating process affects growth performance, Fe bioavailability, and gene expression levels that maintain iron balance in the body. The test was divided into the control group, ferrous sulfate group, ferrous fumarate group, ferrous glycinechelate(1:1) (Fe-Gly(1:1)) group, ferrous glycinechelate(2:1) (Fe-Gly(2:1)) group, enteric-coated Fe-Gly(1:1) group, and enteric-coated Fe-Gly(2:1) group. The results showed that the growth performance of the rats in each iron supplement group was no significant difference among them. The results of serum biochemical indicators showed that the antioxidant capacity of the rats in the iron supplement group after enteric coating increased. The iron supplementation effect of Fe-Gly(1:1) and Fe-Gly(2:1) was better than that of ferrous sulfate, and the effect of Fe-Gly(1:1) after enteric coating was enhanced. The expression levels of IRP1 and IRP2 in the genes of enteric-coated Fe-Gly(1:1) and enteric-coated Fe-Gly(2:1) were significantly higher than those of ferrous sulfate. The expression levels of IRP1 and IRP2 in the protein of enteric-coated Fe-Gly(1:1) group were significantly higher than those in the Fe-Gly(1:1) group. The above results show that Fe-Gly can improve the bioavailability and antioxidant capacity of iron and reduce the iron output of feces after enteric coating.

Analysis of Heme and Non-Heme Iron Intake and Iron Dietary Sources in Adolescent Menstruating Females in a National Polish Sample.

Iron intake and heme/non-heme iron proportions are crucial for iron deficiency anemia prevention. Women of childbearing age are indicated by World Health Organization as the primary target group, but maintaining iron balance is particularly challenging for adolescents. The aim of the presented study was to analyze heme and non-heme iron intake and dietary sources in adolescent menstruating females in a national Polish sample. The study was conducted in a representative sample of adolescents (aged 15–20) who were recruited from all regions of Poland based on secondary school sampling (random quota sampling), with 1385 female adolescents being included in the sample. The iron intake was assessed using the previously validated IRONIC-FFQ (IRON Intake Calculation–Food Frequency Questionnaire). The intakes of iron, heme iron, non-heme iron, and iron from food product groups were assessed and compared with those of male adolescents (n = 1025) who were recruited from the same schools, as well as between sub-groups stratified by age, body mass index, anemia history, following vegetarian diet, applying iron supplementation and school type. Compared with male individuals, females were characterized by a lower intake of all forms of iron. It was stated that non-heme iron intake was highest in younger ones, overweight ones, vegetarian ones, and comprehensive school students. Female adolescents with anemia history were characterized by similar iron intake as others. For the target group, there is inadequate nutritional education and a necessity to broaden the knowledge about specific sources of iron.

Research progress on hepcidin and its related regulatory drugs

Iron is the most basic element involved in oxygen transport, cell respiration, DNA replication, and other disorders of iron metabolism associated with a variety of diseases, including anemia (iron deficiency anemia, chronic anemia) and iron overload (hemochromatosis). Hepcidin is a small molecule peptide hormone synthesized by the liver, which plays a negative role in regulating iron metabolism and is particularly important for maintaining iron balance. Hepcidin is encoded by Hamp gene, and its expression is regulated by multiple signaling pathways such as BMP and STAT. Signal molecules such as interleukin (IL)-6 and transmembrane serine protease (TMPRSS)6 also play important roles in the regulation of hepcidin. This article reviews the molecular structure and role of hepcidin, as well as the current research progress on regulatory drugs targeting hepcidin, Hamp gene and its related signaling pathways. Key words: Iron; Iron metabolism disorders; Hemochromatosis; Interleukin-6; Hepcidin; Hamp gene

MtsR, an Iron-Dependent Regulator in <i>Streptococcus iniae</i>

Streptococcus iniae (S. iniae) is a major pathogen that is capable of resulting severe economic loss to cultured fish. Steadily iron availability from micro-environment is an important virulence factor for pathogens, and S. iniae encodes the iron-transporter MtsABC to accomplish heme utilization, but very little was known about the mechanisms involved in regulating and maintaining iron balance in S. iniae. In this study, the role of a putative iron-dependent transcriptional regulator MtsR was investigated, and the results showed that MtsR regulated the expression of iron-transport mtsABC to control iron homeostasis in S. iniae.

Pharmacokinetics of Ferric Pyrophosphate Citrate, a Novel Iron Salt, Administered Intravenously to Healthy Volunteers

Ferric pyrophosphate citrate (Triferic) is a water‐soluble iron salt that is administered via dialysate to maintain iron balance and hemoglobin in hemodialysis patients. This double‐blind, randomized, placebo‐controlled, single‐, ascending‐dose study was conducted to evaluate the pharmacokinetics and safety of intravenous ferric pyrophosphate citrate in 48 healthy iron‐replete subjects (drug, n = 36; placebo, n = 12). Single doses of 2.5, 5.0, 7.5, or 10 mg of ferric pyrophosphate citrate or placebo were administered over 4 hours, and single doses of 15 or 20 mg of ferric pyrophosphate citrate or placebo were administered over 12 hours via intravenous infusion. Serum total iron (sFetot), transferrin‐bound iron (TBI), hepcidin‐25, and biomarkers of oxidative stress and inflammation were determined using validated assays. Marked diurnal variation in sFetot was observed in placebo‐treated subjects. Concentrations of sFetot and TBI increased rapidly after drug administration, with maximum serum concentrations (Cmax) reached at the end of infusion. Increases in baseline‐corrected Cmax and area under the concentration‐time curve from 0 to the time of the last quantifiable concentration (AUC0‐t) were dose proportional up to 100% transferrin saturation. Iron was rapidly cleared (apparent terminal phase half‐life 1.2‐2 hours). No significant changes from baseline in serum hepcidin‐25 concentration were observed at end of infusion for any dose. Biomarkers of oxidative stress and inflammation were unaffected. Intravenous doses of ferric pyrophosphate citrate were well tolerated. These results demonstrate that intravenous ferric pyrophosphate citrate is rapidly bound to transferrin and cleared from the circulation without increasing serum hepcidin levels or biomarkers of oxidative stress or inflammation.

Iron accelerates cardiovascular disease: The importance of maintaining iron balance

Iron accelerates cardiovascular disease: The importance of maintaining iron balance