Diagnosis and clinical evaluation of iron overload

Screening of superior anti-osteoporotic flavonoids from Epimedii Folium with dual effects of reversing iron overload and promoting osteogenesis

Iron overload is a risk factor for postmenopausal osteoporosis (PMOP) and lowering iron levels to regulate the labile plasma iron is the preferred therapy. Icariin (ICA), baohuoside I (BHS) and icaritin (ICT) are three flavonoids obtained from Epimedii Folium that are efficient in facilitating osteogenesis. In this study, an active flavonoid with dual effects of reversing iron overload and promoting osteogenesis was screened based on pharmacokinetics, iron complexation properties and the potential to downregulate iron overload, reversing PMOP. As a result, the in vivo absorption of three compounds was ICA > ICT > BHS, while the exposure in muscle and bone was BHS > ICT > ICA. In vitro complexation showed that only ICT complexed with Fe (III) at a 1:1 ratio on 3-OH and the ICT-Fe (III) complex (m/z 424.3750) was identified by UPLC-Q-TOF-MS. In vivo dynamic detection also showed that the concentration of ICT-Fe (III) complexes varied with the concentration of ICT in plasma. The behavioral blunting and bone loss in zebrafish induced by Fe (III) were significantly reversed by ICT in a dose-dependent manner. Pharmacokinetic-pharmacodynamic analysis showed that ICT was negatively correlated with serum ferritin and positively correlated with osteogenic markers including alkaline phosphatase, osteocalcin and osteoprotegerin. Bone loss in ovariectomized rats was significantly altered after ICT intervention, with reduced serum ferritin levels and improved osteogenic marker levels. These results demonstrated that ICT had favorable musculoskeletal penetration and iron complexation capability to shrink labile plasma iron, showing superior performance in anti-PMOP through the dual effects of reversing iron overload and promoting osteogenesis.

Epidemiological associations between iron and cardiovascular disease and diabetes

Disruptions in iron homeostasis are linked to a broad spectrum of chronic conditions including cardiovascular, malignant, metabolic, and neurodegenerative disease. Evidence supporting this contention derives from a variety of analytical approaches, ranging from molecular to population-based studies. This review focuses on key epidemiological studies that assess the relationship between body iron status and chronic diseases, with particular emphasis on atherosclerosis ,metabolic syndrome and diabetes. Multiple surrogates have been used to measure body iron status, including serum ferritin, transferrin saturation, serum iron, and dietary iron intake. The lack of a uniform and standardized means of assessing body iron status has limited the precision of epidemiological associations. Intervention studies using depletion of iron to alter risk have been conducted. Genetic and molecular techniques have helped to explicate the biochemistry of iron metabolism at the molecular level. Plausible explanations for how iron contributes to the pathogenesis of these chronic diseases are beginning to be elucidated. Most evidence supports the hypothesis that excess iron contributes to chronic disease by fostering excess production of free radicals. Overall, epidemiological studies, reinforced by basic science experiments, provide a strong line of evidence supporting the association between iron and elevated risk of cardiovascular disease and diabetes. In this narrative review we attempt to condense the information from existing literature on this topic.

Iron overload in children undergoing cancer treatments

BACKGROUND

Iron overload is responsible for severe morbidity and mortality in polytransfused patients. Although repeated blood transfusions are needed during the treatment of most cancers, pediatric patients are not routinely screened for subsequent iron overload.

PROCEDURE

Seventy-five patients were identified as candidates for cancer treatment and enrolled prospectively in a yearly protocol including a cardiac and liver magnetic resonance imaging coupled with ferritin level measurements. Patients were divided into four groups using the intensity of treatment rating (ITR-3).

RESULTS

Fifty-nine patients reached 1-year of follow-up and liver iron overload was found in up to 66% of them. Such overload correlated with the total volume of red blood cells transfused and persisted at least 2 years after the initiation of therapy. Moderate myocardial overload was also, but less frequently (14%), observed in these patients.

CONCLUSIONS

Our study demonstrated that severe liver iron overload as well as moderate myocardial iron overload can be found 1 year after cancer treatment and that this overload persists overtime. The patients with higher ITR and those who have received more than a liter of blood red cells per square meter, regardless of their diagnosis or ITR, are at risk of iron overload and should be screened carefully.

Novel cardiovascular risk factors in the elderly and their correlation with the Framingham risk score

OBJECTIVES

The aim of this study was to investigate the link between the risk of developing coronary heart disease as determined by Framingham risk score (FRS) and the novel cardiac risk factors including serum levels of ferritin, C reactive protein (CRP), homocysteine, creatinine, and uric acid.

METHODS

A total of 1698 patients aged 65 years or more were examined. Plasma concentrations of lipids, CRP, ferritin, homocysteine, uric acid, and creatinine were measured in all the patients. The FRS was calculated for each patient who were divided into three groups according to their FRSs: score 0-9, score 10-19, and score 20 or more group.

RESULTS

Levels of creatinine, uric acid, CRP, triglyceride, high-density lipoprotein, folate, ferritin, and homocysteine were significantly different between the three groups. Homocysteine, ferritin, triglyceride, uric acid, and creatinine significantly increased the risk of passing from score 0-9 group to 10-19 group. Triglyceride and creatinine also increased the risk of passing from score 10-19 group to 20 or more group.

CONCLUSION

An increase in homocysteine, uric acid, ferritin, creatinine, and triglyceride levels is associated with an increase in FRS in elderly people. The current findings support the use of these novel risk factors for diagnosis of coronary heart disease in elderly patients.

Diagnosis and management of iron-related anemias in critical illness

OBJECTIVE

To review of the prevalence, pathogenesis, diagnosis, and management of iron (Fe)-related anemias in critical illness.

DATA SOURCE

A MEDLINE/PubMed search from 1966 to October 2005 was conducted. References from relevant articles were manually cross-referenced with additional original articles, review articles, correspondence, and chapters from selected textbooks.

DATA EXTRACTION AND SYNTHESIS

Both Fe metabolism and erythropoiesis are affected by the inflammatory response that accompanies critical illness. As a result, many critically ill patients develop the anemia of inflammation, which may be compounded by an underlying Fe deficiency. Most commonly available markers of total body Fe detect Fe deficiency unreliably in the setting of inflammation. Among these tests, the serum transferrin receptor assay is relatively accurate in reflecting total body Fe, regardless of inflammation. Treatment options for Fe-related anemias in critical illness include Fe replacement and recombinant human erythropoietin therapy. The decision to implement these therapies is complex and centers on a critical evaluation of ability to affect anemia, morbidity, and mortality in critical illness and on the potential risks of therapy.

CONCLUSIONS

Fe deficiency anemia and the anemia of inflammation may co-exist in critical illness. Diagnosis of and differentiation between these two anemias involves careful interpretation of multiple markers of total body Fe stores. The utility of treatment with both Fe and recombinant human erythropoietin for these disorders during critical illness requires further investigation.

Genes that modify the hemochromatosis phenotype in mice

Hereditary hemochromatosis (HH) is a prevalent human disease caused by a mutation in HFE, which encodes an atypical HLA class I protein involved in regulation of intestinal iron absorption. To gain insight into the pathogenesis of hemochromatosis, we have bred Hfe knockout mice to strains carrying other mutations that impair normal iron metabolism. Compound mutant mice lacking both Hfe and its interacting protein, beta-2 microglobulin (B2m), deposit more tissue iron than mice lacking Hfe only, suggesting that another B2m-interacting protein may be involved in iron regulation. Hfe knockout mice carrying mutations in the iron transporter DMT1 fail to load iron, indicating that hemochromatosis involves iron flux through DMT1. Similarly, compound mutants deficient in both Hfe and hephaestin (Heph) show less iron loading than do Hfe knockout mice, indicating that iron absorption in hemochromatosis involves the function of Heph as well. Finally, compound mutants lacking Hfe and the transferrin receptor accumulate more tissue iron than do mice lacking Hfe alone, consistent with the idea that interaction between these two proteins contributes to the control of normal iron absorption. In addition to providing insight into the pathogenesis of HH, our results suggest that each of these genes might be a candidate modifier of the human hemochromatosis phenotype.

Total iron-binding capacity and serum transferrin determination under the influence of several clinical conditions

In this study TIBC and serum-transferrin concentrations were determined by immunochemical turbidimetry, immunochemical nephelometry and radial immunodiffusion under normal and pathological clinical conditions. A total of 246 (123 male/123 female) patients were included [iron deficiency: 60 (18/42), iron overload: 56 (39/17), chronic inflammation: 47 (23/24), undefined diseases: 35 (16/19), healthy volunteers 48 (27/21)]. The data show that determination of TIBC from conversion of transferrin values using a constant factor results in significantly higher values compared to conversion with a function of first degree. For clinical practice the influence of different diseases is negligible. This study indicates that it is not possible to develop a universal algorithm for the conversion of transferrin values into TIBC.

Does serum ferritin correlate with coronary angiography findings?

BACKGROUND

A number of epidemiological studies have described a positive relationship between serum ferritin levels and coronary heart disease. In this prospective study, we evaluated the association between serum ferritin levels and the angiographic extent of coronary atherosclerosis.

METHOD

We studied 307 consecutive patients (60.9% male, age 60.1+/-11.0 years) referred for diagnostic coronary angiography. Risk factors for coronary artery disease, lipids and ferritin levels, as well clinical characteristics were recorded from all patients. Two experienced cardiologists blinded for clinical and laboratory data reviewed the cinefilms. Angiographic significant coronary artery disease (CAD) was defined as any more than a 50% diameter stenosis.

RESULTS

From the 307 patients, 196 (63.8%) were found to have angiographic significant CAD. The presence of significant CAD was associated with ferritin levels (P=0.015) as well as patient age (P<0.001), male sex (P<0.001), smoking (P<0.002), and cholesterol levels (P=0.028). By multivariate analysis, however, ferritin level was not an independent risk factor for CAD (P=0.27), while the association with all the other factors remained significant.

CONCLUSION

In patients referred for coronary angiography no independent relationship was found between angiographic significant coronary artery disease and serum ferritin levels.

Lack of a relationship between serum ferritin levels and coronary atherosclerosis evaluated by coronary arteriography

Many clinical and epidemiological studies have demonstrated the relationship between serum ferritin and ischemic heart disease. In the present study we evaluated the relationship between coronary heart disease (CHD) and serum ferritin levels in patients submitted to coronary arteriography. We evaluated 307 patients (210 (68.7%) males; median age: 60 years) who were submitted to coronary angiography, measurement of serum ferritin and identification of clinical events of ischemic heart disease. Serum ferritin is reported as quartiles. Ninety-six patients (31.27%) had normal coronary angiography (group 1) and 211 (68.73%) had coronary heart disease (group 2). Of the patients with CHD, 61 (28.9%) had serum ferritin levels higher than 194 ng/ml (4th quartile), as opposed to only 14 (14.58%) of those without CHD (P = 0.0067). In the 2nd quartile, 39 patients (18.48%) had CHD, while 35 patients (36.46%) had normal coronary arteries (P = 0.00064). Multivariate analysis of the data showed that the difference between groups was not statistically significant (P = 0.33). We conclude that there is no independent relationship between coronary heart disease and increased levels of serum ferritin.

Logarithmic quantitation model using serum ferritin to estimate iron overload in secondary haemochromatosis

Nineteen children and adolescents receiving repeated transfusions and subcutaneous desferrioxamine treatment were investigated in an attempt to quantitate iron overload non-invasively. Before patients were started on desferrioxamine individual relationships were correlated for 12 to 36 months between transfused iron, absorbed iron estimated gastrointestinally, and increasing serum ferritin concentrations. Patients with inflammation, increased liver enzymes, or haemolysis were excluded from analysis. The relationship between the variables could be described by a logarithmic regression curve (y = transfused iron [plus eventually gastrointestinally absorbed iron] = iron overload = a+b log [x = serum ferritin]) for each individual patient. All patients showed close correlation (R2) between x and y (median R2 of 0.909, 0.98, and 0.92 in thalassaemia, aplastic anaemia, and sickle cell anaemia patients, respectively). When started on desferrioxamine, current serum ferritin concentrations were used to derive the iron overload from each individual regression curve. The derived estimated iron overload ranged from 0.6 g to 31 g. Left ventricular dilatation was observed in three patients with beta thalassaemia and in one patient with aplastic anaemia with median iron overload of 20.7 (14.1-31.3) g and 24.0 g respectively. Hypothyroidism was found in four patients with beta thalassaemia and one patient with aplastic anaemia with iron overload between 14.7 (6.8 and 26.1) g and 15.1 g respectively. Human growth hormone deficiency was detected in three patients with beta thalassaemia with an iron overload of 4.2 (3.5-6.8) g; all three patients had excellent desferrioxamine compliance.

Liver iron stores in patients with secondary haemosiderosis under iron chelation therapy with deferoxamine or deferiprone

Total body iron stores including liver and spleen iron were assessed by non-invasive SQUID biomagnetometry. The liver iron concentration was measured in groups of patients with beta-thalassaemia major or other posttransfusional siderosis under treatment with the oral iron chelator deferiprone (n = 19) and/or with parenteral deferoxamine (n = 33). An interquartile range for liver iron concentrations of 1680-4470 micrograms/g liver was found in these patients. In both groups a poor correlation between liver iron and serum ferritin values was observed. Repeated measurements of liver and spleen iron concentrations as well as determination of liver and spleen volume by sonography were performed in six patients under continuous deferiprone treatment for 3-15 months. In this group detailed information was obtained on the whole body iron store (5-36g) and the iron excretion rates (14-34 mg/d) for each patient. As indicated by decreasing liver iron concentrations, five out of six subjects showed a negative iron balance (2-13 mg/d). Conventional measurements of both serum ferritin and urine iron excretion gave fluctuating results, thus being only of limited use in the control of iron depletion therapy. The non-invasive biomagnetic liver iron quantification is a precise and clinically verified technique which offers more direct information on the long-term efficacy of an iron depletion therapy than the hitherto used methods. This technique may be of use in the clinical evaluation of new oral iron chelators.

Body iron stores, dietary iron intake and coronary heart disease mortality

OBJECTIVES

To assess whether increased body iron stores and dietary iron intake are associated with an increased risk of coronary heart disease mortality.

DESIGN

A prospective population study with a mean mortality follow-up time of 14 years.

SETTING

Participants attending a health screening examination carried out in several localities in Finland.

SUBJECTS

All 6086 men and 6102 women aged from 45 to 64 years at the baseline examination without known heart disease, who had had serum iron and total iron binding capacity (TIBC) assessed. In a random fifth of these people, dietary iron intake was assessed by a dietary history.

INTERVENTIONS

The study was observational without any interventions.

MAIN OUTCOME MEASURES

Mortality from coronary heart disease.

RESULTS

Altogether, 739 of the men and 245 of the women died from coronary heart disease. No relationship between TIBC and coronary mortality was observed in the men; in the women, an inverse although not significant association was found. Transferrin saturation was inversely but not significantly associated with coronary mortality in men; in women, the relationship was U-formed with a higher mortality at both the lower and higher ends of the distribution. Adjustment for other risk factors did not alter the results. No association was found with dietary iron intake and coronary mortality.

CONCLUSIONS

The results do not corroborate earlier findings that excess body iron stores and increased iron intake are associated with an elevated risk of coronary heart disease.

Evaluation of transfusional iron overload before and during iron chelation by magnetic resonance imaging of the liver and determination of serum ferritin in adult non-thalassaemic patients

The ability to quantitate transfusional iron overload is crucial for determining the need for and the efficacy of chelation therapy in patients with long-standing transfusion-dependent anaemias. We evaluated the usefulness of some indirect measures of iron overload in estimating the iron concentration in the liver--the most important iron storage organ--in 26 non-chelated adult non-thalassaemic patients. Liver iron concentration was determined non-invasively by magnetic resonance imaging (MRI). The standard error of the estimated liver iron concentration was 80 mumol Fe/g dried liver tissue when using the number of transfused blood units, and 93 mumol Fe/g when using a serum ferritin assay. Follow-up in 11 patients (12-48 months) revealed that serum ferritin is a poor measure of the liver iron concentration during iron chelation. However, this discrepancy was individually different and seemed to be dependent on the erythropoietic marrow activity. By monitoring the liver iron concentration by MRI, we compared the efficacy of chelation with desferrioxamine given either by subcutaneous continuous infusions or by bolus injections. Depletion of liver iron stores could be achieved efficiently by both regimens.

Non-invasive assessment of tissue iron overload in the liver by magnetic resonance imaging

We investigated the clinical usefulness of a standard magnetic resonance imaging (MRI) system for non-invasive determination of the liver iron concentration in 38 patients with iron overload and 15 normal controls by measurement of the signal intensity ratio between liver and skeletal muscle (SIR). However, SIR was found dependent on the applied repetition time (TR) of the MRI system, which led us to investigate this relationship in autopsy material of liver and muscle tissue specimens with various iron content. Based on these results, adjustment of SIR measurements to a constant value of TR was achieved. By use of this technique we found a close correlation between MRI and chemically determined liver iron concentration (r2 = 0.98) as well as the serum ferritin concentration (r2 = 0.86). The reproducibility was sufficiently good for the use of MRI in the follow-up of iron reductive treatment. The use of iron store parameters in serum was found insufficient as indicators of endpoint for venesection therapy, if 20 mumol Fe/g dry weight was applied as the upper reference limit of the liver iron concentration. It is concluded that MRI based on SIR measurements offers a precise and reproducible non-invasive method for the determination and follow-up of iron overload within a wide range of liver iron concentrations. Our findings may increase the clinical use of MRI in haematological patients with iron overload.

High stored iron levels are associated with excess risk of myocardial infarction in eastern Finnish men

BACKGROUND

Iron can induce lipid peroxidation in vitro and in vivo in humans and has promoted ischemic myocardial injury in experimental animals. We tested the hypothesis that high serum ferritin concentration and high dietary iron intake are associated with an excess risk of acute myocardial infarction.

METHODS AND RESULTS

Randomly selected men (n = 1,931), aged 42, 48, 54, or 60 years, who had no symptomatic coronary heart disease at entry, were examined in the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD) in Eastern Finland between 1984 and 1989. Fifty-one of these men experienced an acute myocardial infarction during an average follow-up of 3 years. On the basis of a Cox proportional hazards model adjusting for age, examination year, cigarette pack-years, ischemic ECG in exercise test, maximal oxygen uptake, systolic blood pressure, blood glucose, serum copper, blood leukocyte count, and serum high density lipoprotein cholesterol, apolipoprotein B, and triglyceride concentrations, men with serum ferritin greater than or equal to 200 micrograms/l had a 2.2-fold (95% CI, 1.2-4.0; p less than 0.01) risk factor-adjusted risk of acute myocardial infarction compared with men with a lower serum ferritin. An elevated serum ferritin was a strong risk factor for acute myocardial infarction in all multivariate models. This association was stronger in men with serum low density lipoprotein cholesterol concentration of 5.0 mmol/l (193 mg/dl) or more than in others. Also, dietary iron intake had a significant association with the disease risk in a Cox model with the same covariates.

CONCLUSIONS

Our data suggest that a high stored iron level, as assessed by elevated serum ferritin concentration, is a risk factor for coronary heart disease.

Assessment of iron availability using stable 54Fe

This paper describes a method of quantitatively assaying the bioavailability of orally administered iron in order to promote haemoglobin synthesis in iron deficiency anaemia. The non-radioactive tracer substance 54Fe was employed. An experimental iron deficiency model was tested in 18 healthy male volunteers. The trial design made it possible to assess intestinal absorption and efficacy of iron substitution. The iron deficiency was experimentally induced by weekly phlebotomy. Two commercially available iron preparations with different rates of iron release were investigated at a dosage of 150 and 160 mg Fe2+ daily, respectively. In the first seven days of treatment, both preparations were administered in 54Fe-labelled form. Afterwards, iron substitution was given with the commercially available preparations. Measurements were made of erythrocyte utilization of 54Fe and plasma iron tolerance curves at the beginning of the periods in which the 54Fe-labelled product and the commercially available preparation were administered, and of haemoglobin and serum ferritin concentration curves over three months. The mean utilization of the iron administered was virtually identical for the two preparations (23 and 22%, respectively). Likewise, there was no difference with respect to the average daily increase in haemoglobin concentration in the blood (1.5 g 1-1). There was also no significant difference with respect to serum ferritin concentration curves. In contrast, the two preparations differed markedly with respect to the plasma iron tolerance curves. This suggests that evaluation of plasma iron tolerance curves alone is not suitable for comparative assessment of the therapeutic value of orally administered iron preparations.

Non-invasive quantitation of liver iron-overload by magnetic resonance imaging

A standard magnetic resonance imaging (MRI) system allowing spin echo times of 10 ms was used to quantitate liver iron concentration in nine healthy normal subjects and 13 patients with various grades of iron overload. Body iron status was estimated by measuring the serum ferritin concentration. In 11 subjects (two normal healthy controls, eight patients with HLA-related hereditary haemochromatosis and one patient with thalassaemia major) non-haem hepatic iron concentration was determined chemically in biopsy specimens (dry weight), in parallel to serum ferritin and MRI-T2 relaxation times. A moderate correlation (r = 0.79) was obtained for the correlation of the T2-relaxation rate (1/T2) and serum ferritin of the 22 subjects investigated. A much closer correlation (r = 0.98) was observed for the 1/T2 liver iron relationship in the 10 subjects analysed by liver biopsy. It is concluded from these preliminary observations, that MR-imaging may provide a useful non-invasive tool for the quantitative determination of liver iron in iron overload-syndromes.