Biologic and clinical significance of red cell ferritin

Red cell ferritin was measured in normal subjects and patients with disorders of iron metabolism, inflammation, liver dysfunction, impaired hemoglobin synthesis, and increased red cell turnover by means of radioimmunoassays with antibodies to liver (basic) and heart (acidic) ferritins. The normal mean values for basic and acidic ferritin were 8.9 and 22.7 altogram (ag)/cell, respectively. The red cell ferritin content reflected changes occurring in tissues both in iron deficiency and iron overload. Basic ferritin was more closely related to the body iron status than acidic ferritin, and the acidic/basic ferritin ratio was increased in iron deficiency and decreased in iron overload. The major factor determining the red cell ferritin content appeared to be the transferrin saturation, that is, the distribution of iron between monoferric and diferric transferrin. This is in keeping with recent data indicating a competitive advantage of diferric transferrin in delivering iron to erythroid cells. In addition, the red cell ferritin content was increased in thalassemic patients with normal iron status, appearing to be inversely related to the rate of hemoglobin synthesis. The determination of red cell ferritin, based on a commercially available basic ferritin assay, can have clinical application. It can be used for evaluating the adequacy of the iron supply to the erythroid marrow, particularly in patients with increased red cell turnover. Moreover, it may be useful in evaluating the body iron status in patients with hemochromatosis and liver disease.     

Ferritin in the red cells of normal subjects and patients with iron deficiency and iron overload

S ummary . Red cell ferritin was measured in normal subjects and patients with iron deficiency and iron overload by means of radioimmunoassays with antibodies to liver (basic) and heart (acidic) ferritins. In most of the subjects examined, red cells were found to contain greater amounts of heart-type than liver-type ferritin. The basic ferritin content reflected the abnormal body iron status both in iron deficiency and iron overload while the acidic ferritin content was less closely related to the iron status. The two immunologically different red-cell ferritins probably represent distinct ferritin molecules and may have different metabolic functions within haem-synthesizing erythroid cells.     

Clinical significance of erythrocyte ferritin

Quantitative and qualitative evaluations of erythrocyte ferritin in 161 patients with RA and RAEB in MDS, AML, CML, PV, PA, HS, IDA, chronic liver disease and alcoholic liver disease were carried out. Mean erythrocyte ferritin levels of patients with RA, AML, PA, HS and alcoholic liver disease were increased compared with normal subjects. On isoelectric focusing analyses (IEF), erythrocyte ferritin in normal subjects were detected between pI 5.1 and 5.7. In the cases of RA, pI ranges of erythrocyte ferritin may be divided into three groups, acidic, neutral, basic shift on IEF respectively. In these groups, the more acidic the ferritin shift, the higher the proportion of morphological abnormalities of the erythroid precursors in the bone marrow was observed. In patients with AML (M2, M3, M4), little difference was found among these three subtypes, and all of the cases showed similar pattern with normal subjects on IEF. The ferritin from IDA showed low levels and slight basic shift compared with normal subjects on IEF, and these features were also found in patients with CML (chronic phase) and PV. After iron supplementation, marked increase of acidic ferritin was detected on IEF indicating an intermediate store for iron destined for haem synthesis. It was clear that the stainable iron in liver parenchymal cells were found at erythrocyte ferritin concentration 20 ag/cell or over in patients with chronic liver disease. Measurement of erythrocyte ferritin concentration is a helpful method for evaluating iron deposition in hepatocyte non-invasively. From these results it is considered that quantitative and qualitative analyses of erythrocyte ferritin are very useful for evaluating erythropoiesis as well as iron metabolism.     

Ferritin synthesis by monocyte-derived macrophages in thalassemic patients with intrinsic iron overload

Macrophage ferritin content was determined following culture of peripheral blood monocytes for a period of 8 d in 40% autologous plasma to render them mature macrophages. Ferritin content was measured prior to and following culture using the radioimmunoassay. The normal range of values was established in a group of 22 healthy volunteer blood donors. A significant increase in the ratio of macrophage/monocyte ferritin was observed in every donor studied (range 1.2 - 1.8, p less than 0.001). Also, a further significant increase was observed when these macrophages were additionally incubated for 6 h with heterologous antibody-coated sheep red blood cells (range 1.2 - 1.57, p less than 0.001). Finally, the same studies were performed on a group of thalassemic patients with and without intrinsic iron overload. Again there were significant increases in monocyte ferritin content following culture as well as ingestion of heterologous sheep red cells, with magnitudes similar to those obtained with normal donor monocytes. Therefore we could not demonstrate the presence of a cellular ferritin synthesis defect in macrophages of thalassemic patients with intrinsic iron overload to explain the uncontrolled absorption of dietary iron from their gut.     

Ferritin excretion and iron balance in humans

Summary. Under normal circumstances, most of the lumenal iron taken into the intestinal mucosal cell is stored within the cell as ferritin and subsequently is lost in the faeces when the cell exfoliates at the end of its lifespan. To evaluate whether faecal iron proteins reflect mucosal cell iron as well as whole body iron and to examine further the kinetics of gastrointestinal iron transport, faecal H-rich and L-rich ferritin were measured in normal subjects and patients with iron deficiency and genetic haemochromatosis. In normal and iron-deficient subjects, the concentration of L-rich but not H-rich faecal ferritin correlated closely with body iron status. In genetic haemochromatosis, the faecal L-rich and H-rich ferritin concentrations were lower than expected for their body iron status. The administration of oral iron to normal subjects led to a rise in L-rich ferritin. Administration of oral or parenteral iron to patients with iron deficiency led to a prompt rise in both forms of faecal ferritin, although the relative increase of L-rich ferritin was greater than that of H-rich ferritin with oral iron administration. Faecal ferritin correlated closely with iron stores in normals and patients with iron deficiency but faecal ferritin levels were lower than expected in genetic haemochromatosis, similar to that previously noted in the duodenal mucosal cells of these patients.     

Serum ferritin is a major determinant of lipid phenotype in familial combined hyperlipidemia and familial hypertriglyceridemia

Familial combined hyperlipidemia (FCH) and familial hypertriglyceridemia (FHTG) share pathogenic mechanisms and a high interaction with components of the metabolic syndrome. The metabolic syndrome associates increased serum ferritin concentration and high cardiovascular risk. The objective was to describe the frequency of iron overload and the relationship between serum ferritin and the phenotype in patients with FCH and FHTG. The study was composed of 211 consecutive unrelated patients aged at least 18 years with primary hypertriglyceridemia, 149 with FCH, and 62 with FHTG. The prevalence of the metabolic syndrome and hyperferritinemia was very high in both hypertriglyceridemic groups (51.7% and 20.1% in FCH and 62.9% and 16.1% in FHTG, respectively), without significant statistical differences between them. Serum ferritin concentration did not show any significant association with the number of metabolic syndrome criteria. Subjects in the highest tertile of ferritin concentration (ferritin >200 μg/L) presented higher concentrations of triglycerides and liver enzymes than subjects in the first tertile of ferritin concentration (ferritin <90 μg/L). The highest positive correlation coefficient for triglycerides was found with ferritin in FCH and in FHTG subjects (R = 0.317 [P < .001] when combined). Ferritin was also the covariate that showed the highest independent association with triglycerides in FCH and FHTG. In contrast, ferritin was not associated with carotid intima-media thickness. In summary, serum ferritin is commonly increased in FCH and in FHTG, it is not related with the presence of metabolic syndrome, and it is highly correlated with liver enzymes.     

The Mechanism of Endotoxin-Induced Hypoferraemia

The effect of endotoxin on the processing of erythrocyte iron by reticuloendothelial cells of the liver and spleen was studied in rats using heat damaged erythrocytes labelled with ⁵⁹Fe. Endotoxin did not alter the uptake of the damaged cells but markedly inhibited the subsequent early phase of iron release from the reticuloendothelial cells. The inhibition seemed to be due to both a decreased rate of labelled haem destruction and an increased incorporation of radioiron into ferritin. Although early iron release was decreased 0–2 h after endotoxin administration, the diversion of iron into ferritin was more marked when endotoxin was given 18 h before. The block in iron release was partially overcome in animals that had been kept on an iron free diet or had been phlebotomised. In these animals the decreased rate of haem catabolism remained unaltered but less iron was diverted into ferritin.     

The mechanism of endotoxin-induced hypoferraemia.

The effect of endotoxin on the processing of erythrocyte iron by reticuloendothelial cells of the liver and spleen was studied in rats using heat damaged erythrocytes labelled with 59Fe. Endotoxin did not alter the uptake of the damaged cells but markedly inhibited the subsequent early phase of iron release from the reticuloendothelial cells. The inhibition seemed to be due to both a decreased rate of labelled haem destruction and an increased incorporation of radioiron into ferritin. Although early iron release was decreased 0--2 h after endotoxin administration, the diversion of iron into ferritin was more marked when endotoxin was given 18 h before. The block in iron release was partially overcome in animals that had been kept on an iron free diet or had been phlebotomised. In these animals the decreased rate of haem catabolism remained unaltered but less iron was diverted into ferritin.     

Red cell destruction by human monocytes — changes in intracellular ferritin concentration and phenotype

Abstract: Mononuclear cells from 5 normal men and 5 patients homozygous for hereditary haemochromatosis (HFE) have been incubated for 18 h with or without the addition of sheep red blood cells coated with antibody (SRBC). In the absence of SRBC mean H type ferritin concentrations were greater than L type (normals: mean L type 11.6 ng/10⁶ cells, H type 15.5; patients, L type 23.5 ng/10⁶ cells, H type 41.6). In the presence of SRBC, monocyte L type ferritin concentrations increased considerably (76 ng/10⁶ cells in normals and 141 ng/10⁶ cells in patients) but H type ferritin concentrations were the same or decreased compared with incubation in medium only. Incubation with additional iron (ferric ammonium citrate, 2.5 μg Fe/ml) increased both H and L type ferritin concentrations. Erythrophagocytosis thus appears to cause differential regulation of H and L ferritin subunit synthesis or breakdown. Normal subjects and patients do not differ in this response to erythrophagocytosis.     

Erythrocyte ferritin in normal subjects and patients with abnormal iron metabolism

S ummary . Erythrocyte ferritin is about 10 times more reactive with antibody to heart ferritin than to spleen ferritin. The concentration of erythrocyte ferritin reflects the abnormal body iron status both in iron deficiency and in idiopathic haemochromatosis. Increased concentrations in β-thalassaemia trait and primary sideroblastic anaemia may also reflect the intrinsic erythroid abnormality. Differences in the response of 'heart-type' and 'spleen-type' ferritin to changes of iron status suggest possible differences in metabolic function.     

Increased serum ferritin is common in men with essential hypertension

OBJECTIVES : Insulin-resistance-associated hepatic iron overload syndrome (IRHIO) is characterized by high serum ferritin and presence of metabolic alterations that are part of insulin-resistance syndrome (IRS). Thus, clinical conditions characterized by a high prevalence of IRS may also be characterized by a high prevalence of IRHIO. DESIGN AND METHODS : We studied 88 consecutive patients with essential hypertension, 62 patients with IRHIO and 102 healthy normotensive controls. Hemochromatosis, other conditions able to induce secondary iron overload or serum ferritin increase unrelated to body iron stores were excluded. Iron indices, metabolic profiles and hepatic tests in hypertensive with or without increased serum ferritin and in IRHIO with and without hypertension were studied. Metabolic variables, serum iron indices, liver function tests and hepatic ultrasound data were analysed. Data were compared by non-parametric tests. RESULTS : In men with hypertension, increased serum ferritin was more frequent than in controls (21 versus 0%, P = 0.001). Hypertensive men with increased serum ferritin had more frequent and pronounced metabolic alterations than those with normal serum ferritin, the metabolic abnormalities and serum ferritin being frequently positively correlated. In hypertensive men with increased serum ferritin, metabolic and iron data were similar to those of IRHIO patients with hypertension. CONCLUSIONS : In males, hypertension is characterized by a higher prevalence of increased iron stores and metabolic abnormalities that are part of the IRHIO syndrome. This finding may have clinical implications due to the increased risk of IRHIO patients to develop hepatic cirrhosis and also for the role of iron in early atherogenesis.     

Model of reticuloendothelial iron metabolism in humans: abnormal behavior in idiopathic hemochromatosis and in inflammation

Iron transport in the reticuloendothelial (RE) system plays a central role in iron metabolism, but its regulation has not been characterized physiologically in vivo in humans. In particular, why serum iron is elevated and RE cells are much less iron-loaded than parenchymal cells in idiopathic hemochromatosis is not known. The processing of erythrocyte iron by the RE system was studied after intravenous (IV) injection of 59Fe heat-damaged RBCs (HDRBCs) and 55Fe transferrin in normal subjects and in patients with iron deficiency, idiopathic hemochromatosis, inflammation, marrow aplasia, or hyperplastic erythropoiesis. Early release of 59Fe by the RE system was calculated from the plasma iron turnover and the 59Fe plasma reappearance curve. Late release was calculated from the ratio of 59Fe/55Fe RBC utilization in 2 weeks. The partitioning of iron between the early (release from heme catabolism) and late (release from RE stores) phases depended on the size of RE iron stores, as illustrated by the inverse relationship observed between early release and plasma ferritin (P less than .001). There was a strong correlation between early release and the rate of change of serum iron levels during the first three hours in normal subjects (r = .85, P less than .001). Inflammation produced a blockade of the early release phase, whereas in idiopathic hemochromatosis early release was considerably increased as compared with subjects with similar iron stores. Based on these results, we describe a model of RE iron metabolism in humans. We conclude that the RE system appears to determine the diurnal fluctuations in serum iron levels through variations in the immediate output of heme iron. In idiopathic hemochromatosis, a defect of the RE cell in withholding iron freed from hemoglobin could be responsible for the high serum iron levels and low RE iron stores.     

Erythrocyte ferritin in human neonates: maternofetal iron kinetics revisited

Serum and erythrocyte ferritin concentrations were measured in 369 healthy term neonates and their mothers, with a view to understanding maternofetal iron kinetics. Erythrocyte ferritin concentrations in the neonates were on average 100 times higher than maternal values, while those of serum ferritin were about 10 times higher. Maternal and fetal iron status were correlated in the overall study population. Serum and erythrocyte ferritin values were also correlated with each other in both the mothers and neonates. To study the influence of iron status on these conditions, we formed three groups of mother–child pairs of equal size, based on maternal iron status (serum ferritin). The correlations found in the overall population were not always present in each subgroup. In the infants born to mothers with adequate tissue iron reserves (serum ferritin >12 μg/l), a statistical link was found between serum and erythrocyte ferritin levels. When the mothers had optimal iron status (serum ferritin ≥22 μg/l), there was a correlation between the neonatal and maternal erythrocyte ferritin levels. No such links were found when the mothers had low tissue iron stores (serum ferritin <12 mg/l). These data point to special iron kinetics during fetal life and the influence of maternal iron status.     

Erythrocyte and plasma ferritin in normal subjects,blood donors and iron deficiency anemia patients

Summary Ferritin concentration has been determined with an immunoradiometric assay in plasma and washed sedimented erythrocytes after hypotonic lysis. There was a gradual decrease of plasma ferritin in the sequence normal males, normal females, blood donors and patients with iron deficiency anemia. Erythrocyte ferritin remained unchanged in normal males and females and in blood donors, but dropped significantly in the anemic patients. Correspondingly, the ratio of erythrocyte to plasma ferritin rose from less than 2 in healthy males up to 8 in persons with iron deficiency.Little, if any effect on plasma and erythrocyte ferritin was observed in 12 male and female volunteers when taking iron for 4 weeks. In 2 patients with iron deficiency anemia the blood counts were normalized within 2–3 months during oral iron substitution, accompanied by a drastic increase of the erythrocyte ferritin concentration to values far above normal. In contrast, the plasma ferritin concentration remained below normal.Thus, in iron deficiency erythrocyte ferritin is synthesized with priority in the presence of iron and, in addition to plasma ferritin, appears to be a useful parameter of the iron status.     

Iron deficiency in cystic fibrosis: relationship to lung disease severity and chronic Pseudomonas aeruginosa infection.

BACKGROUND: Iron deficiency (ID) is common in patients with cystic fibrosis (CF) and may be related to GI factors and chronic inflammation. Pseudomonas aeruginosa (PA) infection is predominantly responsible for chronic lung suppuration in patients with CF, but its survival is critically dependent on the availability of extracellular iron, which it obtains via highly efficient mechanisms. OBJECTIVE: To determine whether ID in CF patients is directly related to the severity of suppurative lung disease. DESIGN: We determined the iron status of 30 randomly selected adult CF patients (13 women) and assessed the relationship to lung disease severity and GI factors by determining their daily sputum volume, FEV(1) percent predicted, C-reactive protein (CRP) level, erythrocyte sedimentation rate, and degree of pancreatic supplementation. Additionally, we measured the sputum concentrations of iron and ferritin in a randomly selected subgroup of 13 of the 30 subjects. SETTING: Adult CF Service in a tertiary-care center. RESULTS: Seventy-four percent of subjects experienced ID (ie, serum iron levels < or = 12 micromol/L and/or transferrin saturation levels < or = 16%). There was no relationship found with the degree of pancreatic supplementation. The daily sputum volume was strongly associated with low serum iron levels, transferrin saturation, ferritin/CRP ratio, and FEV(1) percent predicted (p < 0.05). Serum iron levels and transferrin saturation were negatively related to CRP (r = -0.8 and r = -0.7, respectively; p < 0.01) and erythrocyte sedimentation rate (r = -0.5 and r = -0.4, respectively; p < 0.05). FEV(1) percent predicted was positively related to serum iron level (r = 0.5; p < 0.01), transferrin saturation (r = 0.4; p < 0.05), and ferritin/CRP ratio (r = 0.7; p < 0.05). Sputum iron concentration (median, 63 micromol/L; range, 17 to 134 micromol/L) and ferritin concentration (median, 5,038 microg/L; range, 894 to 6,982 microg/L) exceeded plasma levels and negatively correlated with FEV(1) percent predicted (r = -0.6 and r = -0.5, respectively; p < or = 0.05). CONCLUSION: In our CF patients, ID was directly related to the increased severity of suppurative lung disease but not to the degree of pancreatic insufficiency. Iron loss into the airway may contribute to ID and may facilitate PA infection.     

Subclinical Atherosclerosis In Young β-thalassemia Major Patients

Subclinical atherosclerosis in young β-thalassemia major (β-TM) patients and its risk factors including dyslipidemia compared to type 1 diabetic patients were assessed. Ninety subjects were included and divided into three groups: group I comprised 30 β-TM patients with a mean age of 18.4 ± 6.18 years; group II comprised of 30 type 1 diabetic patients with a mean age of 19.23 ± 4.25 years, and 30 healthy subjects served as controls in group III. Fasting lipid profiles, hemoglobin (Hb) electrophoresis, serum ferritin and high resolution ultrasound for the measurement of carotid artery intima media thickness (CIMT) were done. Serum triglycerides, total cholesterol, apoprotein A (ApoA), and CIMT were significantly elevated, while high density lipoproteins (HDL) were significantly lowered in thalassemic and diabetic patients compared to controls. In thalassemic patients, CIMT was positively correlated with age, Hb F, ferritin and cholesterol levels. Atherogenic lipid profiles in young thalassemic patients with increased CIMT highlights their importance as prognostic factors for vascular risk stratification.     

Iron deficiency in pregnancy: effects on the newborn

Iron deficiency during pregnancy affects a significant portion of women in countries with low economic wealth and is not uncommon in pregnant women in industrialized countries. Inadequate intake of iron related to diets poor in bioavailable iron is often responsible for iron deficiency before pregnancy, and metabolic adjustments (such as mobilization of iron stores and increased absorption) are insufficient to meet increasing needs during pregnancy. The effects of iron deficiency on the fetus are still controversial. Numerous measures, including the evaluation of erythrocyte ferritin, favor the hypothesis that the level of iron stores in newborns is related to maternal iron status and that the materno-fetal unit is dependent on exogenous iron, which is necessary to prevent iron deficiency in both mothers and infants. In industrialized countries, iron supplements should be prescribed for pregnant women in the third trimester, when the need for iron is prominent. In developing countries, supplementation should be initiated as soon as possible after conception because of the high prevalence of iron deficiency at the onset of pregnancy. The results of studies comparing intermittent with daily supplementation remain controversial.     

Impaired insulin-mediated erythrocyte magnesium accumulation is correlated to impaired insulin-mediated glucose diposal in aged non-diabetic obese patients

Basal erythrocyte magnesium levels were significantly lower in obese than lean subjects. In vitro incubation in the presence of 100 mU/l insulin significantly increased magnesium erythrocyte levels in both groups of subjects. However, even in the presence of 100 mU/l, the erythrocyte magnesium content of obese patients was lower than that of control subjects. The in vitro dose-response curve of the effect of insulin on magnesium erythrocyte accumulation was shifted to the right when the red cells of obese were used, with a highly significant reduction of the maximal effect. Such reduction of the maximal effect of insulin suggests that the impairment of insulin-induced erythrocyte magnesium accumulation observed in obese patients results essentially from a post-receptor defect. In obese patients, net increase in erythrocyte magnesium levels (calculated as the difference between basal and 100 mU/l insulin-induced erythrocyte magnesium levels) was negatively correlated with basal plasma insulin levels (r = 0.79 p less than 0.01), and with body mass index (r = 0.81 p less than 0.01) while it was positively correlated with the glucose disappearance rate after glucose load (r = 0.67 p less than 0.05) and glucose metabolic clearance rate (r = 0.71 p less than 0.01). These results demonstrate that insulin-induced erythrocyte magnesium accumulation is impaired in patients with obesity and that such defect is correlated to impaired -- mediated glucosal disposal in the patients.     

Red cell ferritin and iron overload in heterozygous beta-thalassemia

Red cell ferritin was evaluated in 101 individuals with heterozygous beta-thalassemia to determine its clinical utility as an index for iron deficiency or overload in these subjects. The mean red cell ferritin for the total population was elevated threefold and showed a significant correlation with transferrin saturation, plasma ferritin, and HbA2 levels. Five of six subjects with reduced red cell ferritin had associated iron deficiency; a further five had iron deficiency and normal red cell ferritin. Normal red cell ferritin occurred in 51 subjects, and 44 had increased values. In the elevated red cell ferritin group, 21 individuals had associated normal plasma ferritin, and 23 had increased plasma ferritin. Only in the latter group was red cell ferritin significantly correlated with transferrin saturation and plasma ferritin. Ten individuals had a red cell ferritin greater than or equal to 150 attogram/cell, and liver biopsy performed in four showed grades II to IV iron overload. A clinical feature of subjects with both increased red cell and plasma ferritin levels was a high incidence of inappropriate iron administration. These findings suggest that red cell ferritin, particularly when combined with plasma ferritin, is a useful parameter for determining potential iron overload in individuals with heterozygous beta-thalassemia.