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Query: UMLS:C0240066 (iron deficiency)
 7,156 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism that leads to iron overload in hereditary hemochromatosis is not yet fully understood and genes other than HFE may be involved. Nramp2 is an intestinal iron transporter, upregulated by dietary iron deficiency, which also colocalizes with transferrin in recycling endosomes. The purpose of the present study was to analyze the coding region of the Nramp2 gene in 14 hemochromatosis probands which did not carry any HFE mutations on both chromosomes. We confirmed the existence of a polymorphism (1254 T --> C), which presumably is not associated with hereditary hemochromatosis, but we did not find any mutation. On the other hand, we identified 17 splice variants of the Nramp2 mRNA. Eight corresponded to activation of cryptic splicing sequences between exons 3 and 4. They were observed in a majority of hemochromatosis probands and control subjects. This indicates the existence of an important splicing instability in this region. At this stage, the biological significance of these variants is unclear. Our study did not find evidence for the involvement of the Nramp2 gene in hereditary hemochromatosis. The remaining question is whether hemochromatosis probands in our study have iron overload because of environmental factors or due to mutation in gene(s) other than HFE and Nramp2.
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PMID:Nramp2 analysis in hemochromatosis probands. 1104 33

We describe a case of homozygosity due to the substitution of aspartic acid with histidine at position 63 of the protein encoded by the gene (known as HFE) associated with hereditary hemochromatosis. Liver biopsy did not disclose stainable iron accumulation; serum ferritin was elevated (639 ng/mL), while the transferrin saturation index was within the normal range (38.1%). As the patient was affected by chronic hepatitis C virus, the high serum ferritin could be attributed to this disease, a frequent occurrence. We also describe a case of heterozygosity for both the substitution of tyrosine with cysteine at position 282 and the substitution of histidine to aspartic acid at position 63 (so-called "compound heterozygosity"). The patient had the typical biochemical abnormalities of iron overload: transferrin saturation index of 53.1% and elevated serum ferritin (658 ng/mL). The removal of > 5 g of iron by phlebotomies did not precipitate iron deficiency. Although the patient refused to undergo liver biopsy, clinical evidence alone enabled a diagnosis of hemochromatosis. These two cases concord with the present scientific orientation, i.e.: 1) homozygosity for the major mutation is associated with the phenotypical (clinical) picture of hemochromatosis, but compound heterozygosity also determines significant iron metabolism abnormalities; 2) homozygosity for the minor mutation does not appear to determine important phenotypical abnormalities.
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PMID:[Significance of "minor" genetic mutations in hereditary hemochromatosis: 2 case reports]. 1105 64

Thirteen adults (eight men, five women) with hemochromatosis had undergone routine iron depletion therapy but while on maintenance phlebotomies developed iron deficiency which persisted for 25 +/- 13 (mean +/- 1 SD) months before diagnosis. All had symptoms and signs of iron deficiency. Levels of transferrin saturation were 10% +/- 5% (1 SD), and serum ferritin concentrations were 8 +/- 3 ng/mL. Eleven had anemia; eight had hypochromia and microcytosis. Bone marrow specimens obtained in five patients revealed no stainable iron. Medical records indicated that parameters of body iron status were infrequently or incorrectly used for adjusting the frequency of phlebotomies. Two patients developed iron deficiency due to additional blood loss from esophageal varices and bilateral hip replacement, respectively. Ten of the patients were treated with ferrous sulfate, 325 mg daily, for 2-6 weeks when anemia was corrected. In patients who were not given iron, anemia and microcytosis recovered in 8-24 months. We conclude that (i) sustained iron deficiency in hemochromatosis patients should be prevented by monitoring hemoglobin levels and serum ferritin; and (ii) hemoglobin concentrations and values of mean corpuscular hemoglobin may be higher in iron-deficient persons with hemochromatosis than in individuals without hemochromatosis. Symptomatic iron deficiency in hemochromatosis patients may be treated safely with a brief course of ferrous sulfate. Recovery is slower when iron is not given. However, iron supplementation is unnecessary and not recommended for the mild, self-limited anemia and decreased serum iron and ferritin concentrations encountered after initial iron depletion therapy for hemochromatosis.
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PMID:Iron deficiency due to excessive therapeutic phlebotomy in hemochromatosis. 1107 39

Iron overload is highly prevalent, but its molecular pathogenesis is poorly understood. Recently, DMT1 was shown to be a major apical iron transporter in absorptive cells of the duodenum. In vivo, it is the only transporter known to be important for the uptake of dietary non-heme iron from the gut lumen. The expression and subcellular localization of DMT1 protein in 3 mouse models of iron overload were examined: hypotransferrinemic (Trf(hpx)) mice, Hfe knockout mice, and B2m knockout mice. Interestingly, in Trf(hpx) homozygotes, DMT1 expression was strongly induced in the villus brush border when compared to control animals. This suggests that DMT1 expression is increased in response to iron deficiency in the erythron, even in the setting of systemic iron overload. In contrast, no increase was seen in DMT1 expression in animals with iron overload resembling human hemochromatosis. Therefore, it does not appear that changes in DMT1 levels are primarily responsible for iron loading in hemochromatosis.
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PMID:Expression of the DMT1 (NRAMP2/DCT1) iron transporter in mice with genetic iron overload disorders. 1115 49

Restless legs syndrome (RLS) occurs in some persons with iron deficiency, and some persons with RLS benefit from oral iron therapy. Approximately one in 200 persons of northern European ancestry have hemochromatosis attributable to inheritance of two common mutations of the hemochromatosis-associated HFE gene on chromosome 6. We evaluated and treated a 46-year-old man with RLS who was diagnosed as having hemochromatosis after he developed new symptoms associated with taking iron therapy for RLS. He had transferrin saturation 88%, serum ferritin 658 ng/ml, and C282Y homozygosity. Therapeutic phlebotomy of one unit of blood (450-500 ml) weekly (total 24 units) relieved his non-RLS symptoms, caused RLS symptoms to occur more frequently, and was associated with transient fatigue and mild dependent edema. His sister, who also has RLS, was subsequently diagnosed as having hemochromatosis. We conclude that serum transferrin saturation and ferritin levels should be measured before initiation of iron therapy of RLS. Patients with a history of iron deficiency or low serum iron parameters should undergo evaluation for iron deficiency; patients who have histories suggestive of hemochromatosis or iron overload or elevated pre-treatment transferrin saturation or serum ferritin levels should undergo evaluation to determine the cause of these abnormalities before they are treated with iron. In all persons with RLS treated with oral iron, serum iron parameters should be re-measured once or twice yearly during therapy.
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PMID:Hemochromatosis and iron therapy of Restless Legs Syndrome. 1131 89

During the last decades efforts regarding dietary iron supply focused mostly on the prevention of deficiencies, especially during growth and pregnancy. Correspondingly, homeostatic mechanisms increase intestinal iron absorption in iron deficiency, but its downregulation at high intake levels seems insufficient to prevent accumulation of high iron stores at high intake. There is no regulated iron excretion in overload. Excess of pharmaceutical iron may cause toxicity and therapeutic doses may cause gastrointestinal side effects. Chronic iron excess, e.g. in primary and secondary hemochromatosis, may lead to hepatic fibrosis, diabetes mellitus and cardiac failure. Chronic intake of 50-100 mg Fe/day of highly bioavailable iron with home-brewed beer in sub-Saharan Africans lead to cirrhosis and diabetes. Applying a safety factor of 2 would lead to an upper safe level of 25-50 mg Fe/day for this endpoint of conventional iron toxicity. However, beyond this kind of damage iron is known to catalyze the generation of hydroxyl radicals from superoxide anions and to increase oxidative stress which, in turn, increases free iron concentration. This self-amplifying process may cause damage to lipid membranes and proteins, which relates radical generation and organ damage after ischemia-reperfusion events to available free iron in clinical and experimental settings. Correspondingly, epidemiological studies as well as observations in heterozygotes for hereditary hemochromatosis suggest that the risk of atherosclerosis and acute myocardial infarction is related to body iron stores, though there is conflicting epidemiological evidence as well. The most recent and best controlled studies, however, support the hypothesis that iron stores are related to cardiovascular risk. Iron-amplified oxidative stress may also increase DNA damage, oxidative activation of precancerogens and support tumor cell growth. This is supported by experimental, clinical and epidemiological observations. Due to these mechanisms high iron stores may present a health hazard. Though this has not been finally proven, available evidence strongly recommends not to increase iron intake beyond physiological requirements. To avoid iron deficiency symptoms, on the other hand, care must be taken to meet recommended daily intake.
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PMID:Safety aspects of iron in food. 1142

With rare exceptions, virtually all studied organisms from Archaea to man are dependent on iron for survival. Despite the ubiquitous distribution and abundance of iron in the biosphere, iron-dependent life must contend with the paradoxical hazards of iron deficiency and iron overload, each with its serious or fatal consequences. Homeostatic mechanisms regulating the absorption, transport, storage and mobilization of cellular iron are therefore of critical importance in iron metabolism, and a rich biology and chemistry underlie all of these mechanisms. A coherent understanding of that biology and chemistry is now rapidly emerging. In this review we will emphasize discoveries of the past decade, which have brought a revolution to the understanding of the molecular events in iron metabolism. Of central importance has been the discovery of new proteins carrying out functions previously suspected but not understood or, more interestingly, unsuspected and surprising. Parallel discoveries have delineated regulatory mechanisms controlling the expression of proteins long known--the transferrin receptor and ferritin--as well as proteins new to the scene of iron metabolism and its homeostatic control. These proteins include the iron regulatory proteins (IRPs 1 and 2), a variety of ferrireductases in yeast an mammalian cells, membrane transporters (DMT1 and ferroportin 1), a multicopper ferroxidase involved in iron export from cells (hephaestin), and regulators of mitochondrial iron balance (frataxin and MFT). Experimental models, making use of organisms from yeast through the zebrafish to rodents have asserted their power in elucidating normal iron metabolism, as well as its genetic disorders and their underlying molecular defects. Iron absorption, previously poorly understood, is now a fruitful subject for research and well on its way to detailed elucidation. The long-sought hemochromatosis gene has been found, and active research is underway to determine how its aberrant functioning results in disease that is easily controlled but lethal when untreated. A surprising connection between iron metabolism and Friedreich's ataxia has been uncovered. It is no exaggeration to say that the new understanding of iron metabolism in health and disease has been explosive, and that what is past is likely to be prologue to what is ahead.
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PMID:Chemistry and biology of eukaryotic iron metabolism. 1147 Feb 29

The content of body iron is regulated primarily by absorption since humans have no physiological mechanism by which excess iron is excreted. This regulation, however, is not absolute. Many factors such as the content of diets, iron doses, life styles, etc. influence iron absorption. In the past, nutrition programs for iron fortification and the ingestion of iron preparations have been widely practiced because of the seriousness of worldwide iron deficiency. Also, we now know that a significant number of asymptomatic people carry the hemochromatosis gene, HFE, indicating that these people have the potential to accumulate excess body iron in their lifetime. Excess body iron can be highly toxic. This toxicity involves many organs leading to a variety of serious diseases such as liver disease, heart disease, diabetes mellitus, hormonal abnormalities, dysfunctional immune system, etc. The tissue damage associated with iron overload is believed to result primarily from free radical reactions mediated by iron. Iron is an effective catalyst in free radical reactions. The diseases associated with iron overload can be managed effectively or prevented. Therefore, early diagnosis of iron overload and appropriate therapy are critical. By providing the necessary laboratory data, clinical chemistry laboratories can play the pivotal role in the management of these health problems.
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PMID:Chronic iron overload and toxicity: clinical chemistry perspective. 1151 32

We recently reported the hemochromatosis-like phenotype observed in our Usf2 knockout mice. In these mice, as in murine models of hemochromatosis and patients with hereditary hemochromatosis, iron accumulates in parenchymal cells (in particular, liver and pancreas), whereas the reticuloendothelial system is spared from this iron loading. We suggested that this phenotypic trait could be attributed to the absence, in the Usf2 knockout mice, of a secreted liver-specific peptide, hepcidin. We conjectured that the reverse situation, namely overexpression of hepcidin, might result in phenotypic traits of iron deficiency. This question was addressed by generating transgenic mice expressing hepcidin under the control of the liver-specific transthyretin promoter. We found that the majority of the transgenic mice were born with a pale skin and died within a few hours after birth. These transgenic animals had decreased body iron levels and presented severe microcytic hypochromic anemia. So far, three mosaic transgenic animals have survived. They were unequivocally identified by physical features, including reduced body size, pallor, hairless and crumpled skin. These pleiotropic effects were found to be associated with erythrocyte abnormalities, with marked anisocytosis, poikylocytosis and hypochromia, which are features characteristic of iron-deficiency anemia. These results strongly support the proposed role of hepcidin as a putative iron-regulatory hormone. The animal models devoid of hepcidin (the Usf2 knockout mice) or overexpressing the peptide (the transgenic mice presented in this paper) represent valuable tools for investigating iron homeostasis in vivo and for deciphering the molecular mechanisms of hepcidin action.
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PMID:Severe iron deficiency anemia in transgenic mice expressing liver hepcidin. 1193 10

Iron is a vitally important element in mammalian metabolism because of its unsurpassed versatility as a biologic catalyst. However, when not appropriately shielded or when present in excess, iron plays a key role in the formation of extremely toxic oxygen radicals, which ultimately cause peroxidative damage to vital cell structures. Organisms are equipped with specific proteins designed for iron acquisition, export, transport, and storage as well as with sophisticated mechanisms that maintain the intracellular labile iron pool at an appropriate level. These systems normally tightly control iron homeostasis but their failure can lead to iron deficiency or iron overload and their clinical consequences. This review describes several rare iron loading conditions caused by genetic defects in some of the proteins involved in iron metabolism. A dramatic decrease in the synthesis of the plasma iron transport protein, transferrin, leads to a massive accumulation of iron in nonhematopoietic tissues but virtually no iron is available for erythropoiesis. Humans and mice with hypotransferrinemia have a remarkably similar phenotype. Homozygous defects in a recently identified gene encoding transferrin receptor 2 lead to iron overload (hemochromatosis type 3) with symptoms similar to those seen in patients with HFE-associated hereditary hemochromatosis (hemochromatosis type 1). Transferrin receptor 2 is primarily expressed in the liver but it is unclear how mutant forms cause iron overload. Mutations in the gene encoding the iron exporter, ferroportin 1, cause iron overload characterized by iron accumulation in macrophages yet normal plasma iron levels. Plasma iron, together with dominant inheritance, discriminates iron overload due to ferroportin mutations (hemochromatosis type 4) from hemochromatosis type 1. Heme oxygenase 1 is essential for the catabolism of heme and in the recycling of hemoglobin iron in macrophages. Homozygous heme oxygenase 1 deletion in mice leads to a paradoxical accumulation of nonheme iron in macrophages, hepatocytes, and many other cells and is associated with low plasma iron levels, anemia, endothelial cell damage, and decreased resistance to oxidative stress. A similar phenotype occurred in a child with severe heme oxygenase 1 deficiency. Recently, a mutation in the L-subunit of ferritin has been described that causes the formation of aberrant L-ferritin with an altered C-terminus. Individuals with this mutation in one allele of L-ferritin have abnormal aggregates of ferritin and iron in the brain, primarily in the globus pallidus. Patients with this dominantly inherited late-onset disease present with symptoms of extrapyramidal dysfunction. Mice with a targeted disruption of a gene for iron regulatory protein 2 (IRP2), a translational repressor of ferritin, misregulate iron metabolism in the intestinal mucosa and the central nervous system. Significant amounts of ferritin and iron accumulate in white matter tracts and nuclei, and adult IRP2-deficient mice develop a movement disorder consisting of ataxia, bradykinesia, and tremor. Mutations in the frataxin gene are responsible for Friedreich ataxia, the most common of the inherited ataxias. Frataxin appears to regulate mitochondrial iron (or iron-sulfur cluster) export and the neurologic and cardiac manifestations of Friedreich ataxia are due to iron-mediated mitochondrial toxicity. Finally, patients with Hallervorden-Spatz syndrome, an autosomal recessive, progressive neurodegenerative disorder, have mutations in a novel pantothenate kinase gene (PANK2). The cardinal feature of this extrapyramidal disease is pathologic iron accumulation in the globus pallidus. The defect in PANK2 is predicted to cause the accumulation of cysteine, which binds iron and causes oxidative stress in the iron-rich globus pallidus.
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PMID:Rare causes of hereditary iron overload. 1238


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