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PubMed1998

Iron regulatory proteins, iron responsive elements and iron homeostasis.

The discovery of iron regulatory proteins (IRPs) has provided a molecular framework from which to more fully understand the coordinate regulation of vertebrate iron metabolism. IRPs bind to iron responsive elements (IREs) in specific mRNAs and regulate their utilization. The targets of IRP action now appear to extend beyond proteins that function in the storage (ferritin) or cellular uptake (transferrin receptor) of iron to include those involved in other aspects of iron metabolism as well as in the tricarboxylic acid cycle. To date, it appears that IRPs modulate the utilization of six mammalian mRNAs. Current studies are aimed at defining the mechanisms responsible for the hierarchical regulation of these mRNAs by IRPs. In addition, much interest continues to focus on the signaling pathways through which IRP function is regulated. Multiple factors modulate the RNA binding activity of IRP1 and/or IRP2 including iron, nitric oxide, phosphorylation by protein kinase C, oxidative stress and hypoxia/reoxygenation. Because IRPs are key modulators of the uptake and metabolic fate of iron in cells, they are focal points for the modulation of cellular iron homeostasis in response to a variety of agents and circumstances.

Animals↗
PubMed1994

New advances in iron metabolism, iron deficiency, and iron overload.

Rapid advances were made in understanding the molecular and cellular bases of iron metabolism and its disorders. Molecular mechanisms for the cellular uptake, storage, and utilization of iron were clarified in investigations of the structure and functions of transferrin, transferrin receptor, ferritin, erythroid delta-aminolevulinic acid synthase, and the RNA-binding protein termed the iron responsive-element binding protein. Evidence was obtained that a nuclear DNA-binding protein, NF-E2, may be involved in the regulation of both hemoglobin synthesis in erythroid cells and of iron absorption in the intestine. Clinically, progress was made in improving the diagnosis and management of both iron deficiency and iron overload, with studies of the usefulness of serum transferrin receptor measurements, of a new therapeutic preparation of iron using a "gastric delivery system," and of the development of new orally active iron-chelating agents.

Anemia, Iron-Deficiency↗
PubMed1991

Absorption of low and therapeutic doses of ferric maltol, a novel ferric iron compound, in iron deficient subjects using a single dose iron absorption test.

Ferric maltol is a novel ferric iron compound with potential use as an oral therapy for iron deficiency anaemia. Using a single, low dose iron absorption test we compared absorption of ferric maltol with absorption of ferrous sulphate in 21 iron deficient subjects. Absorption of 10 mg of ferric maltol as either aqueous solution or a single tablet compared favourably with that of an equivalent dose of ferrous sulphate. At a higher, more therapeutic dose of 60 mg elemental iron as tablets, absorption of ferric maltol appeared to be both more rapid and total absorption greater, than that seen with ferrous sulphate. We conclude that iron from ferric maltol, both at low dose and higher, more therapeutic doses, is at least as well absorbed as from ferrous sulphate. Ferric maltol is the first ferric iron formulation to be absorbed to a degree equivalent to that of ferrous iron salts and may represent a viable form of administration for ferric iron in the treatment of iron deficiency anaemia.

Adult↗
PubMed2002

Iron plus folate is more effective than iron alone in the treatment of iron deficiency anaemia in pregnancy: a randomised, double blind clinical trial.

OBJECTIVE: To evaluate whether folate supplementation to iron is able to accelerate solving of iron deficiency anaemia in pregnancy. DESIGN: Multicentre, double blind, randomised clinical trial. SETTING: Nine hospital gynaecologic units located in Mexico. POPULATION: Three hundred seventy-one women with iron deficiency anaemia between 14 and 27 weeks of pregnancy. METHODS: Random allocation of the study population to receive 80 mg iron proteinsuccinylate, with or without 0.370 mg folinic acid daily for 60 days. MAIN OUTCOME MEASURE: Haemoglobin concentration increase. RESULTS: Combined iron and folate therapy showed a better therapeutic response: the increase in haemoglobin levels from baseline was 1.42 (0.14) g/dL for women treated with both compounds vs 0.80 (0.125) g/dL for those given iron only (P < 0.001). A multivariable regression analysis showed that this effect was independent of basal levels of blood iron, ferritine and serum folate and was more evident in women with more severe anaemia. In the 64 women belonging to the subgroup defined by the per-protocol (PP) population and the lowest quartile of baseline haemoglobin values (mean 8.96, range 5.9-9.8 g/dL), the increase at day 60 was estimated 2.3 (0.53) g/dL for the combined therapy vs 0.5 (0.5) g/dL for iron only (P = 0.07). No significant differences in tolerability were observed between the two groups. CONCLUSION: Folate supplementation is recommendedin pregnant women with iron deficiency anaemia irrespective of the serum levels of folate.

Adult↗
PubMed2004

Genetic ablations of iron regulatory proteins 1 and 2 reveal why iron regulatory protein 2 dominates iron homeostasis.

The two iron regulatory proteins IRP1 and IRP2 bind to transcripts of ferritin, transferrin receptor and other target genes to control the expression of iron metabolism proteins at the post-transcriptional level. Here we compare the effects of genetic ablation of IRP1 to IRP2 in mice. IRP1-/- mice misregulate iron metabolism only in the kidney and brown fat, two tissues in which the endogenous expression level of IRP1 greatly exceeds that of IRP2, whereas IRP2-/- mice misregulate the expression of target proteins in all tissues. Surprisingly, the RNA-binding activity of IRP1 does not increase in animals on a low-iron diet that is sufficient to activate IRP2. In animal tissues, most of the bifunctional IRP1 is in the form of cytosolic aconitase rather than an RNA-binding protein. Our findings indicate that the small RNA-binding fraction of IRP1, which is insensitive to cellular iron status, contributes to basal mammalian iron homeostasis, whereas IRP2 is sensitive to iron status and can compensate for the loss of IRP1 by increasing its binding activity. Thus, IRP2 dominates post-transcriptional regulation of iron metabolism in mammals.

Animals↗
PubMed1994

Increased serum iron and iron saturation without liver iron accumulation distinguish chronic hepatitis C from other chronic liver diseases.

One hundred twenty-three patients with chronic liver diseases of various etiologies were evaluated for their iron status. The patients were divided into four distinct groups: chronic hepatitis C (63), chronic hepatitis B (14), B + C (3) and nonviral chronic liver diseases (43). In 107 patients (87%) the chronic liver disease was confirmed by biopsy. Mean serum iron (+/- SD) levels in the above four groups were: 166 +/- 62, 103 +/- 52, 142 +/- 48, and 115 micrograms/dl; iron-binding capacity was 346 +/- 80, 325 +/- 72, 297 +/- 27, and 374 +/- 75 micrograms/dl, and iron saturation 50 +/- 18, 32 +/- 16, 48 +/- 16, and 28 +/- 10%, respectively. Serum ferritin, increased in all four groups, was highest in HCV; however, no evidence of hepatic iron accumulation could be found in any of the patients. There were no significant differences in liver function parameters measured in the four groups. We conclude that serum iron, iron saturation, and ferritin are increased in patients with hepatitis C in comparison to hepatitis B or other nonviral, nonhemochromatotic liver diseases. The increased iron status in hepatitis C patients is not manifested by increased liver iron. Awareness of these distinct features of chronic hepatitis C is essential in the diagnosis and treatment of chronic liver diseases.

Biopsy↗
PubMed1979

Preparation and partial characterization of iron-sulfur, iron-selenium, and iron-tellurium complexes of bovine serum albumin.

An artificial Fe-S* protein was prepared by the reaction of bovine serum albumin with FeSO4 and Na2S or with a synthetic Fe-S*-1,4-butanenedithiol complex. These improved methods enabled us to characterize the derivatives from serum albumin. The Fe-S* albumin complex has about 20 iron ions and 14 labile sulfur atoms per molecule of the protein, whose absorption spectrum closely resembled that of 2Fe-2S* proteins. Its electron paramagnetic resonance spectrum exhibited signals different from those of ferredoxins. The addition of p-chloromercuriphenylsulfonate quenched the optical absorption in the visible region as well as the electron paramagnetic resonance signals. These properties of the albumin-iron complex are similar to those of iron-sulfur dithiothreitol and mercaptoethanol complexes, suggesting that the albumin-iron complex has one or more protein ligands besides sulfur lignads. Presumably, the oxygen atom of the tyrosine residue, or other hydroxyamino acids participates in the complex formation. In this context, the albumin polypeptide appears to be incapable of forming an iron-sulfur cluster identical to those of ferredoxins. Yet, from the albumin-iron derivative, the extrusion of the iron-sulfur core with benzenethiol provided products similar to those from ferredoxins. The iron-selenium and iron-tellurium derivatives of the bovine serum albumin were prepared and partially characterized by optical absorption and electron paramagnetic resonsnace spectroscopies. These results imply that both selenium and tellurium can be incorporated into the protein molecule as the respective labile components.

Chemical Phenomena↗
PubMed2007

Quantitative geometric descriptions of the belt iron atoms of the iron-molybdenum cofactor of nitrogenase and synthetic iron(II) model complexes.

Six of the seven iron atoms in the iron-molybdenum cofactor of nitrogenase display an unusual geometry, which is distorted from the tetrahedral geometry that is most common in iron-sulfur clusters. This distortion pulls the iron along one C3 axis of the tetrahedron toward a trigonal pyramid. The trigonal pyramidal coordination geometry is rare in four-coordinate transition metal complexes. In order to document this geometry in a systematic fashion in iron(II) chemistry, we have synthesized a range of four-coordinate iron(II) complexes that vary from tetrahedral to trigonal pyramidal. Continuous shape measures are used for a quantitative comparison of the stereochemistry of the Fe atoms in the iron-molybdenum cofactor with those of the presently and previously reported model complexes, as well as with those in polynuclear iron-sulfur compounds. This understanding of the iron coordination geometry is expected to assist in the design of synthetic analogues for intermediates in the nitrogenase catalytic cycle.

Iron↗
PubMed1997

Interaction of nitric oxide with non-haem iron sites of Escherichia coli bacterioferritin: reduction of nitric oxide to nitrous oxide and oxidation of iron(II) to iron(III).

The bacterioferritin (BFR) of Escherichia coli consists of 24 identical subunits, each containing a dinuclear metal-binding site consisting of two histidines and four carboxylic acid residues. Earlier studies showed that the characterization of iron binding to BFR could be aided by EPR analysis of iron-nitrosyl species resulting from the addition of NO to the protein [Le Brun, Cheesman, Andrews, Harrison, Guest, Moore and Thomson (1993) FEBS Lett. 323, 261-266]. We now report data from gas chromatographic head space analysis combined with EPR spectroscopy to show that NO is not an inert probe: iron(II)-BFR catalyses the reduction of NO to N2O, resulting in oxidation of iron(II) at the dinuclear centre and the subsequent detection of mononuclear iron(III). In the presence of excess reductant (sodium ascorbate), iron(II)-BFR also catalyses the reduction of NO to N2O, giving rise to three mononuclear iron-nitrosyl species which are detectable by EPR. One of these, a dinitrosyl-iron complex of S = 1/2, present at a maximum of one per subunit, is shown by EPR studies of site-directed variants of BFR not to be located at the dinuclear centre. This is consistent with a proposal that the diferric form of the centre is unstable and breaks down to form mononuclear iron species.

Bacterial Proteins↗
PubMedDate not supplied

Treatment of iron deficiency conditions in blood donors: controlled study of iron sulphate versus iron protein succinylate.

Iron protein succinylate is a new iron preparation for oral administration. In a controlled study versus iron sulphate in 40 blood donors with low levels of stored iron, treatment for 30 days with iron protein succinylate resulted in greater iron absorption compared to the reference drug. Serum iron concentration significantly increased compared with baseline values only in patients given iron protein succinylate. The amount of stored iron, evaluated by serum ferritin levels, significantly increased in both treatment groups.

Administration, Oral↗
PubMed1989

Relationship of serum ferritin and iron concentrations and serum total iron-binding capacity to nonheme iron stores in dogs.

The relationships of various iron-related analytes were evaluated in 95 dogs. Liver and spleen nonheme iron content was determined coulometrically on acid-digested tissue specimens. Serum iron concentration and total iron-binding capacity also were measured coulometrically, whereas serum ferritin concentration was measured by ELISA. Significant (P less than 0.0002) correlation was found between serum ferritin concentration and nonheme iron stores. Significant correlation was not found between nonheme iron stores and serum iron concentration or total iron-binding capacity. Serum ferritin concentration should provide a convenient and relatively noninvasive means of estimating iron stores in dogs.

Animals↗
PubMed1988

Comparison trial of iron succinylprotein complex or iron gluconate complex in the treatment of iron deficiency anemia.

Forty patients suffering from iron deficiency anemia were randomly assigned to receive iron succinylprotein complex (containing 80 mg of elemental iron daily) or iron gluconate complex (containing 125 mg of elemental iron daily) for two months. Improvement, as measured by hematological variables, was noted in both groups, iron succinylprotein complex being superior to iron gluconate complex on some measures. Side effects were reported by two of the 20 patients treated with iron succinylprotein complex and by ten of the 20 patients treated with iron gluconate complex.

Adult↗
PubMed1993

Relative bioavailability of iron from two different iron tablets used in the Indonesian Iron Supplementation Program.

The relative bioavailability of two different iron tablets which are used in the Indonesian iron supplementation program was determined, because low bioavailability of iron might decrease the impact of the program. In two studies volunteers (n = 12, n = 6) received 120 mg elemental iron either as two iron tablets, each containing 60 mg elemental iron, or as an aqueous Fe(II)-sulphate solution in a randomized cross-over design. Plasma iron concentrations were measured before, and 1, 2, 4, 6, 8 and 10 hours after dosing. For each of the tablets and solutions, the positive area under the concentration/time curve (AUC+), the peak plasma level (Cmax), the time to reach the peak plasma level (tmax) and the relative bioavailability were determined. Relative bioavailability of both tablets was high (106.9 +/- 24.3%) and 116.3 +/- 43.1%). This indicates a good therapeutical efficacy of both tablets. In case where low effectiveness of iron supplementation programs is recorded, factors other than low bioavailability of iron in the tablets must be responsible.

Adult↗
PubMed1993

Chronic feeding of carbonyl-iron and TMH-ferrocene in rats. Comparison of two iron-overload models with different iron absorption.

1. The use of carbonyl-iron and (3,5,5-trimethylhexanoyl)-ferrocene (TMH-ferrocene) as a dietary iron-overload model was studied in rats using 59Fe-labelled compounds. 2. The intestinal absorption of carbonyl-iron but not from the TMH-ferrocene-iron was dependent upon the dosage and downregulated in iron-loaded rats. 3. In both models, and similar to hereditary haemochromatosis in humans, the storage of excess iron in the liver started in hepatocytes, whereas the range of iron-loading was strikingly different. 4. Because of the fast and progressive iron-loading, the TMH-ferrocene-model is the most encouraging animal model for experimental haemochromatosis.

Administration, Oral↗
PubMed2005

Bioavailability of oral iron drugs as judged by a 59Fe-whole-body counting technique in patients with iron deficiency anaemia. Therapeutic efficacy of iron(II)-glycine sulfate.

The bioavailability of the oral iron compound iron(II)-glycine sulfate (ferro sanol duodenal, FSD, 1 x 100 mg Fe/d) was studied in 56 patients with iron deficiency anaemia using a 59Fe-labelling technique and 59Fe-whole-body counting. This technique measures the individual iron loss and allows in patients with substantial blood loss under iron medication a reliable information on the bioavailability of the drug. In all patients, the increased loss of iron (mean 5.8 +/- 4.4 mg/d) was clearly compensated by the iron utilisation (mean: 11.1 +/- 5.6 mg/d) from a daily dosage of 100 mg iron from FSD. A significant increase in the haemoglobin concentration was observed within the monitored treatment period of 6-10 weeks (mean Hb increase from 10.7 +/- 1.7 to 12.1 +/- 1.8 g/dl). FSD has therefore documented a bioavailability of at least 11% from a single daily dose of 100 mg Fe and was effective in the treatment of the anaemia in almost all patients under study.

Adult↗
PubMed1999

Anaemia and iron deficiency screening in adolescence: a pilot study of iron stores and haemoglobin response to iron treatment in a population of 14-15-year-olds in Norway.

Screening for haemoglobin (Hb) and s-ferritin, in 176 of all 189 (93%) pupils at 8th grade (14-15-years-old) in one Norwegian community was performed in order to map the prevalence of anaemia and depleted iron stores. In order to determine the clinical significance of the findings, a questionnaire aimed at detecting symptoms or risk factors for iron deficiency was completed by all participants, and a 3 mo therapeutic trial with iron was offered to subjects with s-ferritin values below 15 microg/l. Four percent of girls and 8% of boys were anaemic according to WHO cut-off levels. S-ferritin <15 microg/l was found in 25% of girls and 30% of boys. Forty-four of 48 pupils with s-ferritin <15 microg/l completed the therapeutic trial. Only three pupils had a clinically significant increase in Hb, representing less than 2% of the population. The questionnaire gave no clues that could identify subjects with depleted iron stores. To increase Hb in one 14-15-y-old with depleted iron stores, 59 (95% CHI: 20-285) had to be screened and 16 (6-76) had to be given iron treatment. This pilot study suggests that functional iron deficiency is rare in Norwegian adolescents despite a high frequency of low iron stores. A double blind, placebo controlled study covering the entire span of pubescence is needed to confirm these results.

Adolescent↗
PubMed2000

Iron metabolism: iron deficiency and iron overload.

Iron is an essential cofactor in a variety of cellular processes. Except for a few unusual bacterial species, iron is indispensable for living organisms. However, free iron is toxic because of its propensity to induce the formation of dangerous free radicals. Consequently, iron balance is tightly regulated. Disorders of iron homeostasis are among the most common afflictions of humans. This review discusses inherited iron deficiency and iron overload disorders and recent insights into their pathophysiology.

Anemia, Iron-Deficiency↗
PubMed1994

Potentiation of iron accumulation in cardiac myocytes during the treatment of iron overload in gerbils with the hydroxypyridinone iron chelator CP94.

Gerbils administered iron dextran are the only animal species which have been shown to develop hemochromatosis of the liver and heart in the same manner as transfusion dependent homozygous thalassemics. The iron chelating hydroxypyridinone, CP94, has been administered prophylactically to iron overloaded gerbils in a dosing regime which favors the formation of bidentate chelated iron, to examine the possibility of additional toxicity being caused to the liver and heart by the bidentate chelated iron complex. Hepatic iron accumulation was inhibited by CP94 administration for up to 6 weeks, but not after 20 weeks. Iron accumulation in the heart was increased significantly after 6 and 20 weeks of chelator treatment. Pathological changes in both organs were markedly more severe after 20 weeks in chelator treated animals. There was a higher incidence of cardiofibrosis and more extensive liver fibrosis in iron overloaded, chelator treated animals after 20 weeks.

Animals↗