Association between body iron stores and the risk of acute myocardial infarction in men

Disordered vascular compliance in haemochromatosis

BACKGROUND

A relationship may exist between body iron stores, endothelial dysfunction and overall cardiovascular risk.

AIMS

To compare vascular compliance, biochemical endothelial function and antioxidant status between patients with homozygous hereditary haemochromatosis and healthy controls.

METHODS

Haemochromatosis patients and healthy controls were recruited. Measures of vascular compliance were assessed by applanation tonometry. Serological markers of endothelial function (plasma lipid hydroperoxides, cell adhesion molecules), antioxidant levels (ascorbate, lipid soluble antioxidants) and high-sensitivity C-reactive protein (CRP) were also measured.

RESULTS

Thirty-five hereditary haemochromatosis patients (ten females, mean age 54.6) and 36 controls (27 female, mean age 54.0) were recruited. Haemochromatosis patients had significantly higher systolic and diastolic blood pressures. Pulse wave velocity (PWV) was significantly higher in male haemochromatosis patients (9.90 vs. 8.65 m/s, p = 0.048). Following adjustment for age and blood pressure, male haemochromatosis patients continued to have a trend for higher PWVs (+1.37 m/s, p = 0.058). Haemochromatosis patients had significantly lower levels of ascorbate (46.11 vs. 72.68 μmol/L, p = 0.011), retinol (1.17 vs. 1.81 μmol/L, p = 0.001) and g-tocopherol (2.51 vs. 3.14 μmol/L, p = 0.011). However, there was no difference in lipid hydroperoxides (0.46 vs. 0.47 nmol/L, p = 0.94), cell adhesion molecule levels (ICAM: 348.12 vs. 308.03 ng/mL, p = 0.32 and VCAM: 472.78 vs. 461.31 ng/mL, p = 0.79) or high-sensitivity CRP (225.01 vs. 207.13 mg/L, p = 0.32).

CONCLUSIONS

Haemochromatosis is associated with higher PWVs in males and diminished antioxidants across the sexes but no evidence of endothelial dysfunction or increased lipid peroxidation.

Body iron stores and the risk of type 2 diabetes in middle-aged men

OBJECTIVE

We investigated the risk of type 2 diabetes mellitus (T2DM) over a wide range of body iron stores.

METHODS

Prospective cohort of 1613 men in the Kuopio Ischemic Heart Disease Risk Factor study, aged 42-60 years, free of T2DM and hereditary hemochromatosis at baseline in 1984-1989. Baseline serum ferritin (sF) and serum-soluble transferrin receptor (sTfR) concentrations were used to predict incident T2DM. T2DM was assessed by questionnaires, blood glucose measurements, and medication reimbursement register.

RESULTS

There were 331 cases of incident T2DM during the mean follow-up of 16.8 years (27,098 person-years). At baseline, subjects who later developed T2DM had average sF concentrations of 191 μg/l (S.D. 155) vs 151 μg/l (S.D. 119) among those who remained healthy, P<0.001. In a multivariate-adjusted logistic regression, each 100 μg/l increase in sF corresponded to an average of 14% increased (odds ratio=1.14, 95% CI 1.03-1.26, P=0.009) risk of developing T2DM. In a Cox regression, a markedly increased risk of developing T2DM was observed from the fourth sF quintile (185 μg/l, the median) upward (hazard ratio (HR) first vs fifth quintile=1.5, 95% CI 1.0-2.2, P-trend=0.05). In a corresponding Cox model in sTfR, the subjects in the third quintile (1840 μg/l, the median) had the least risk (HR=0.63, 95% CI 0.42-0.97, P=0.04).

CONCLUSIONS

Body iron within the sF reference range is not an important determinant of T2DM risk, whereas high normal and above is associated with markedly increased risk. Iron depletion toward iron deficiency as assessed by sTfR is not protective against T2DM. A rule of thumb safe range could be 30-200 μg/l of sF.

Iron: protector or risk factor for cardiovascular disease? Still controversial

Iron is the second most abundant metal in the Earth’s crust. Despite being present in trace amounts, it is an essential trace element for the human body, although it can also be toxic due to oxidative stress generation by the Fenton reaction, causing organic biomolecule oxidation. This process is the basis of numerous pathologies, including cardiovascular diseases (CVD). The relationship between iron and cardiovascular disease was proposed in 1981 by Jerome Sullivan. Since then, numerous epidemiological studies have been conducted to test this hypothesis. The aim of this review is to present the main findings of the chief epidemiological studies published during the last 32 years, since Sullivan formulated his iron hypothesis, suggesting that this element might act as a risk factor for cardiovascular disease. We have analyzed 55 studies, of which 27 supported the iron hypothesis, 20 found no evidence to support it and eight were contrary to the iron hypothesis. Our results suggest that there is not a high level of evidence which supports the hypothesis that the iron may be associated with CVD. Despite the large number of studies published to date, the role of iron in cardiovascular disease still generates a fair amount of debate, due to a marked disparity in results.

Association of body iron status with the risk of premature acute myocardial infarction in a Pakistani population

Background

Coronary artery disease is very common in Pakistani population. Some of the studies carried out on Western populations have shown a relationship between body iron status as determined by the ratio of concentrations of serum soluble transferrin receptor (sTfR) to ferritin and the risk of acute myocardial infarction (AMI). In order to investigate whether increased body iron status has any relationship with the risk of premature AMI in Pakistani population, a case-control study was carried out.

Methodology/Principal findings

In this case-control study, 203 consecutive AMI patients [146 males and 57 females; age range 18–45 years] admitted to the National Institute for Cardiovascular Diseases, Karachi, were enrolled with informed consent. In addition, 205 healthy controls whose gender and age (within 3 years) matched the patients, and who had a similar socio-economic background were recruited. Fasting venous blood was obtained and assessed for plasma/serum folate, vitamin B12, homocysteine, total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, sTfR and ferritin and blood lead. It was found that serum concentration of ferritin and blood lead levels were significantly higher in AMI patients compared to their age and gender-matched healthy controls (p value <0.05), while the concentrations of vitamin B12 and HDL-cholesterol were significantly lower in AMI patients compared to controls (p value <0.01). The ratio of sTfR to ferritin was significantly lower in AMI patients compared to controls [mean±SD/median (IQR) values 84.7±295/28.9 (38.4) vs 255±836/49.4 (83.8), respectively; p value <0.001]. Compared with the highest quartile of sTfR/ferritin (low body iron status), the OR for the risk of AMI was 3.29(95% CI, 1.54–7.03) for the lowest quartile (quartile 1) when the model was adjusted for vitamin B12 and HDL-cholesterol (p value for trend <0.01).

Conclusions/Significance

This study shows a positive association between total body iron status and risk of premature AMI in a Pakistani population.

Intravenous ferric chloride hexahydrate supplementation induced endothelial dysfunction and increased cardiovascular risk among hemodialysis patients

Background

The association between intravenous (IV) iron administration and outcomes in hemodialysis (HD) patients is still debated. Therefore, this study was aimed to assess the relationship between the IV administration of ferric chloride hexahydrate (Atofen®) and cardiovascular (CV) outcome and the interaction between iron-induced oxidative stress and endothelial dysfunction in chronic HD patients.

Methodology/Principal Findings

A cohort of 1239 chronic HD patients was recruited. In a follow-up of 12 months, Kaplan-Meier survival curves showed that higher doses of IV Atofen associated with higher risks for CV events and deaths in HD patients. In multivariate Cox models, compared to no iron supplementation, IV Atofen administration was an independent predictor for CV events and overall mortality. However, the nature of the observational cohort study possibly bears selection bias. We further found that IV Atofen enhanced the superoxide production of mononuclear cells (MNCs), the levels of circulating soluble adhesion molecules, and the adhesion of MNCs to human aortic endothelial cells (HAECs). In vitro experiments showed that Atofen increased the expression of intracellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 in HAECs and aggravated the endothelial adhesiveness in a dose-dependent manner. These iron-induced changes were significantly attenuated by the co-treatment of HAECs with N-acetylcysteine and inhibitors of NADPH oxidase, nuclear factor κB, and activator protein-1.

Conclusion

A cumulative dose of IV Atofen >800 mg within 6 months was associated with an adverse CV outcome and a higher mortality among chronic HD patients. The detrimental effects of IV iron supplementation were partly due to the increased oxidative stress and induction of MNC adhesion to endothelial cells, a pivotal index of early atherogenesis.

Long-term consequences of iron-fortified flour consumption in nonanemic men

BACKGROUND/AIMS

Despite the advantages of fortifying flour with iron, there are still special concerns regarding the possible adverse effects of the extra iron consumed by nonanemic individuals. This study aimed to investigate the oxidative stress and iron status following 8 and 16 months of consumption of iron-fortified flour in nonanemic men.

METHODS

In a before-and-after intervention study, 78 nonanemic apparently healthy 40- to 65-year-old men were randomly selected from Semnan, in the northeast of Iran. Data were collected at three time points. Evaluation of oxidative stress biomarkers as well as the assessment of iron status was performed in all three stages. After baseline data collection, the flour fortification program was started with 30 mg/kg iron as ferrous sulfate.

RESULTS

After 16 months, serum iron levels had significantly increased from 102.9 ± 31.5 μg/dl (baseline) to 117.2 ± 29.8 μg/dl (p < 0.001). The mean total antioxidant capacity (1.71 ± 0.10 μM) was significantly lower than that at baseline (1.83 ± 0.17 μM; p < 0.01). Among other oxidative stress biomarkers, only superoxide dismutase and glutathione peroxidase activity increased significantly compared to the beginning of the study (p < 0.001 and p < 0.001, respectively). The results of this study did not show any symptoms of iron overload after 8 and 16 months.

CONCLUSIONS

Our data did not support the safety of flour fortification with 30 mg/kg iron as ferrous sulfate as a community-based approach to control iron deficiency in nonanemic healthy men.

Impaired iron status in aging research

Aging is associated with disturbances in iron metabolism and storage. During the last decade, remarkable progress has been made toward understanding their cellular and molecular mechanisms in aging and age-associated diseases using both cultured cells and animal models. The field has moved beyond descriptive studies to potential intervention studies focusing on iron chelation and removal. However, some findings remain controversial and inconsistent. This review summarizes important features of iron dyshomeostasis in aging research with a particular emphasis on current knowledge of the mechanisms underlying age-associated disorders in rodent models.

Association between Serum Ferritin and Circulating Oxidized Low-density Lipoprotein Levels in Patients with Coronary Artery Disease

INTRODUCTION

Oxidation of low-density lipoprotein (LDL) is believed to be a key factor in the development of atherosclerosis. Oxidative modification of LDL is associated with increased uptake of these particles by the macrophage receptors located in the arterial wall which in turns would lead to accumulation of lipids within the cytoplasm of the cell and formation of the foam cells, a perquisite step in the development of the atherosclerotic plaque. The aim of the present study was to evaluate the association between serum Ferritin and oxidized low-density lipoprotein in coronary artery disease (CAD) patients.

METHODS

The study group consisted of 160 males [mean age (47±7) years] with suspected CAD and no history of renal, liver and diabetic disorders undergoing coronary angiography. Oxidized LDL and Ferritin levels were measured by ELISA methods.

RESULTS

Results obtained from the study revealed that the mean serum Ferritin concentration in our study population was 149.77+119.93 ng/ml and that of OX-LDL was 8.86+5.67 IU/L. Serum Ferritin levels were significantly correlated with both OX-LDL concentrations (p=0.001, r=0.24) and CAD SCORE (p=0.005, r=0.208) in study patients group; however no correlation was detected between OX-LDL and CAD SCORE (p>0.9).

CONCLUSION

The present study is the first to report serum Ferritin levels is associated with circulating OX-LDL level in patients with CAD. The correlation of CAD SCORE with Ferritin levels in these patients is indicative of the importance of this parameter in predicating CAD. These results suggest that measurement of OX- LDL and Ferritin could be of great assistance in predicating premature CHD.

Iron stores are associated with asymptomatic atherosclerosis in healthy men of primary prevention

BACKGROUND

The aim of our study was to assess the impact of increased iron stores on the presence of asymptomatic atherosclerosis in a cohort of healthy men. We anticipated that higher iron stores would be associated with higher soluble cluster of differentiation 163 (sCD163) concentrations, elevated markers of oxidative stress, inflammation and higher common carotid intima-media thickness, independently of traditional risk factors of atherosclerosis.

METHODS

In this cross-sectional study that included 72 healthy men, we measured the ultrasonography of common carotid intima-media thickness (IACC), the ratio of plasma-circulating transferrin receptors concentration to plasma ferritin concentration, certain inflammatory and oxidative stress markers, insulin sensitivity, plasma lipids and markers of endothelial dysfunction.

RESULTS

The plasma-circulating transferrin receptor concentration to plasma ferritin concentration ratio (TfR/F) showed significant association with IACC (r=-0·310, P=0·008 vs. r=0·295, P=0·012). Multivariate analysis confirmed that the correlation of TfR/F with IACC is independent of traditional risk factors of atherosclerosis. The TfR/F ratio correlated with other indicators of atherosclerotic process fibrinogen (r=-0·292, P=0·013), von Willebrand factor (vWf; r=0·284, P=0·017), sCD163 (r=0·239, P=0·043) and IL-8 (r=0·233, P=0·049). In multivariate analysis, TfR/F independently correlated with haemoglobin (β=-0·220, P=0·047), fibrinogen (β=-0·290, P=0·009), IL-8 (β=0·227, P=0·039) and sCD163 (β=0·244, P=0·025); however, when vWf was added, significant independent correlation was seen only with fibrinogen (β=-0·301, P=0·007) and IL-8 (β=0·219, P=0·047). In addition, we demonstrated the independent correlation of sCD163 with vWf (β=0·240, P=0·040).

CONCLUSIONS

Our study showed a clear association of body iron stores expressed by the TfR/F ratio with asymptomatic carotid atherosclerosis. TfR/F further exhibited an independent positive correlation with fibrinogen and a negative correlation with sCD163 and IL-8.

Atrial and vascular oxidative stress in patients with heart failure

Heart failure is characterized by a great number of metabolic and histological defects, however, previous studies did not provide strong evidence of a correlation between the antioxidant status of myocardial tissue itself and cardiac function. The goal of our study was to assess, in patients with heart failure consecutive to dilated cardiomyopathy (DCM), alterations in norepinephrine (NE), lipid peroxidation (malonedialdehyde: MDA) and iron levels in different parts of the myocardium and aorta, in relation to functional parameters. Biopsied heart samples were obtained from 12 DCM patients and from 4 brain-dead organ donors (Controls). The left ventricular ejection fraction (LVEF) was reduced to 19.1±2.6% in DCM. For all patients, the distribution of NE in the atria, ventricles and vessels was different, but NE content in control hearts was systematically higher than in cardiomyopathy patients. MDA levels tended to be higher in the different samples from the DCM group in comparison with the values obtained in the C group; the values were significantly decreased (p<0.05) in endocardium and the aortic samples. In the right atrium there was a significant correlation between NE content and LVEF and between MDA and iron concentrations. These findings could give further insights into the relationship between iron metabolism disturbances and the severity of cardiovascular diseases.

The diagnostic accuracy of the percentage of hypochromic red blood cells (%HYPOm) and cellular hemoglobin in reticulocytes (CHr) in differentiating iron deficiency anemia and anemia of chronic diseases

BACKGROUND

The percentages of hypochromic red blood cells (%HYPOm) and cellular hemoglobin in reticulocytes (CHr) are suggested to be useful screening markers of iron deficiency. The aim of this study was to investigate the diagnostic accuracy of %HYPOm and CHr in differentiating iron deficiency anemia (IDA) and anemia of chronic disease (ACD).

METHODS

The retrospective population consisted of 58 IDA patients, 129 ACD patients and 63 controls, on whom bone marrow examination and blood count with %HYPOm and CHr had been performed. Receiver operating characteristic (ROC) analyses with area under the ROC curves (AUC) were used as statistical tests.

RESULTS

AUCs for differentiating the groups using %HYPOm were as follows: IDA vs. controls 0.99, ACD vs. controls 0.85 and IDA vs. ACD 0.88. AUCs for CHr in distinguishing the groups were as follows: IDA vs. controls 0.95, ACD vs. controls 0.65 and IDA vs. ACD 0.83.

CONCLUSIONS

IDA and ACD patients were efficiently differentiated by using %HYPOm and CHr. Additionally, %HYPOm was higher and CHr was lower in IDA patients and in ACD patients than in controls. Thus, %HYPOm is higher and CHr is lower not only in absolute iron deficiency, but also when iron availability for erythropoiesis is restricted.

Plasma ferritin levels, genetic variations in HFE gene, and coronary heart disease in Chinese: a case-control study

BACKGROUND

The association between body iron stores and coronary heart disease (CHD) was inconsistent. We sought to explore this association in Chinese Han population and further examine the association of the variations in hemochromatosis (HFE) gene and CHD risk.

METHODS

We conducted a case-control study including 1334 CHD patients and 1334 age- and sex-frequency matched controls. The plasma ferritin levels were measured by enzyme linked immunosorbent assay. Genotypes of the tagging single nucleotide polymorphisms (tagSNPs) were determined by TaqMan SNP allelic discrimination.

RESULTS

The plasma ferritin levels in CHD cases (197.9μg/L [2.7-932.9μg/L]) were higher than those in controls (179.9μg/L [21.1-878.2μg/L]; P=0.028). The odds ratios (ORs) across the tertiles of plasma ferritin levels were 1.0 (reference), 0.93 (0.76-1.13), and 1.23 (1.02-1.48; P for trend=0.028). Adjustment for the traditional risk factors attenuated the associations to null (P for trend=0.22). Compared with the TT genotype of tagSNP rs9366637, subjects with C allele had higher risk of CHD (OR=1.35 for TC and 1.76 for CC; P=0.001 and <0.001 respectively). After adjustment for the conventional risk factors the results remained unchanged. We did not find significantly different plasma ferritin levels among different genotypes of rs9366637 (P=0.52).

CONCLUSIONS

The plasma ferritin levels were not significantly associated with CHD risk. However, the SNP rs9366637 in HFE gene was associated with higher CHD risk in Chinese Han population. The underlie mechanism remained to be elucidated in further studies.

Iron load and liver enzymes in 10- and 13-year-olds

OBJECTIVES

Iron plays a pivotal role in adult steatosis, but its role in child and adolescent steatosis is unclear. We investigated the effect of dietary iron, serum iron, and ferritin on serum transaminases and γ-glutamyltransferase in 10- and 13-year-olds.

PATIENTS AND METHODS

The study included 4894 fifth and eighth graders enrolled between 2006 and 2009 in all schools in Shunan City, Japan. Multiple regression analyses were performed with adjustments for grade, sex, z score of the body mass index, serum lipids, plasma glucose, frequency of sports activities, having a single parent, number of siblings, tobacco smoking behavior, passive smoking at home, resident areas, and schools, using linear mixed models. In addition, we analyzed ferritin and insulin resistance in randomly selected subset of participants.

RESULTS

Dietary iron intake was positively associated with serum alanine aminotransferase levels (standardized coefficient β = 2.35, P = 0.019). Serum iron concentrations were associated with transaminase and γ-glutamyltransferase levels (β = 3.22, and 4.05, respectively, P < 0.01). In the subset of 421 subjects with further serum analysis, serum ferritin levels were significantly associated with serum enzyme levels (β = 2.43-3.35; P < 0.05) and showed significant odds ratio for the elevated alanine aminotransferase levels (1.05 for 1 SD with 95% confidence intervals 1.02-1.08). However, iron load did not show a positive association with insulin resistance.

CONCLUSIONS

Although an effect size for iron is small in regression analyses, iron is implicated in increased transaminase levels in prepubertal and pubertal children.

Trace elements, heavy metals and vitamin levels in patients with coronary artery disease

AIM

In the present study, we aimed to assess serum concentrations of zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd), lead (Pb), manganese (Mn), vitamins A (retinol), D (cholecalciferol) and E (α-tocopherol) in patients with coronary artery disease (CAD) and to compare with healthy controls.

METHODS

A total of 30 CAD patients and 20 healthy subjects were included in this study. Atomic absorption spectrophotometry (UNICAM-929) was used to measure heavy metal and trace element concentrations. Serum α-tocopherol, retinol and cholecalciferol were measured simultaneously by high performance liquid chromatography (HPLC).

RESULTS

Demographic and baseline clinical characteristics were not statistically different between the groups. Serum concentrations of retinol (0.3521 ± 0.1319 vs. 0.4313 ± 0.0465 mmol/I, p=0.013), tocopherol (3.8630 ± 1.3117 vs. 6.9124 ± 1.0577 mmol/I, p<0.001), cholecalciferol (0.0209 ± 0.0089 vs. 0.0304±0.0059 mmol/I, p<0.001) and Fe (0.5664 ± 0.2360 vs. 1.0689 ± 0,4452 µg/dI, p<0.001) were significantly lower in CAD patients. In addition, while not statistically significant serum Cu (1.0164 ± 0.2672 vs. 1.1934 ± 0.4164 µg/dI, p=0.073) concentrations were tended to be lower in patients with CAD, whereas serum lead (0.1449 ± 0.0886 vs. 0.1019 ± 0.0644 µg/dI, p=0.069) concentrations tended to be higher.

CONCLUSIONS

Serum level of trace elements and vitamins may be changed in patients with CAD. In this relatively small study we found that serum levels of retinol, tocopherol, cholecalciferol, iron and copper may be lower whereas serum lead concentrations may be increased in patients with CAD.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Correlation of concentrations of selected trace elements with Gleason grade of prostate tissues

The causes of prostate cancer are still obscure but some evidence indicates that there is a close connection between several trace elements and processes which may lead to malignant cells. In our study the microbeam synchrotron radiation X-ray fluorescence emission (micro-SRIXE) technique was applied for quantitative analysis of selected elements. For the first time, we correlate the concentrations of Mn, Fe, Cu, and Zn with the clinical stage of the prostate cancer at the time of operation (described by Gleason grade). Serial sections of prostate tissues were collected from patients undergoing radical prostatectomy. One section, stained with hematoxylin and eosin, was prepared for histopathological analysis; a second, adjacent unstained section was used in micro-SRIXE experiments. All experiments were performed at beamline L at HASYLAB, DESY, Germany. Our results seem to be valuable in light of the determination of the changes in the concentrations of trace elements as a potential diagnostic marker and their etiological involvement in the different stages of prostate diseases.

Effects of C282Y, H63D, and S65C HFE gene mutations, diet, and life-style factors on iron status in a general Mediterranean population from Tarragona, Spain

Mutations in the HFE gene result in iron overload and can produce hereditary hemochromatosis (HH), a disorder of iron metabolism characterized by increased intestinal iron absorption. Dietary quality, alcoholism and other life-style factors can increase the risk of iron overload, especially among genetically at risk populations. Polymorphisms of the HFE gene (C282Y, H63D and S65C) were measured together with serum ferritin (SF), transferrin saturation (TS) and hemoglobin, to measure iron status, in randomly-selected healthy subjects living in the Spanish Mediterranean coast (n = 815; 425 females, 390 males), 18 to 75 years of age. The intake of dietary components that affect iron absorption was calculated from 3-day dietary records. The presence of C282Y/H63D compound heterozygote that had a prevalence of 2.8% in males and 1.2% in females was associated with an elevated TS and SF. No subject was homozygous for C282Y or S65C. The C282Y heterozygote, H63D heterozygote and homozygote and H63D/S65C compound heterozygote genotypes were associated with increased TS relative to the wild type in the general population. These genotypes together with the alcohol and iron intake increase the indicators of iron status, while calcium intake decreases them. We did not observe any affect of the S65C heterozygote genotype on these levels. All the HFE genotypes except for the S65C heterozygote together with the alcohol, iron and calcium intake affect the indicators of iron status. The C282Y/H63D compound heterozygote genotype has the higher phenotypic expression in our Spanish Mediterranean population.

Pulmonary oxidative stress, inflammation, and dysregulated iron homeostasis in rat models of cardiovascular disease

Underlying cardiovascular disease (CVD) is a risk factor for the exacerbation of air pollution health effects. Pulmonary oxidative stress, inflammation, and altered iron (Fe) homeostasis secondary to CVD may influence mammalian susceptibility to air pollutants. Rodent models of CVD are increasingly used to examine mechanisms of variation in susceptibility. Baseline cardiac and pulmonary disease was characterized in healthy normotensive Wistar Kyoto (WKY) rats, cardiovascular compromised spontaneously hypertensive rats (SHR), and spontaneously hypertensive heart failure (SHHF) rats. Blood pressure, heart rate, and breathing frequencies were measured in rats 11 to 12 wk of age, followed by necropsy at 14 to 15 wk of age. Blood pressure and heart rate were increased in SHR and SHHF relative to WKY rats (SHR > SHHF > WKY). Increased breathing frequency in SHHF and SHR (SHR > SHHF > WKY) resulted in greater minute volume relative to WKY. Bronchoalveolar lavage fluid (BALF) protein and neutrophils were higher in SHHF and SHR relative to WKY (SHHF >> SHR > WKY). Lung ascorbate and glutathione levels were low in SHHF rats. BALF Fe-binding capacity was decreased in SHHF relative to WKY rats and was associated with increased transferrin (Trf) and ferritin. However, lung ferritin was lower and Trf was higher in SHHF relative to WKY or SHR rats. mRNA for markers of inflammation and oxidative stress (macrophage inflammatory protein [MIP]-2, interleukin [IL]-1alpha, and heme oxygenase [HO]-1) were greater in SHHF and SHR relative to WKY rats. Trf mRNA rose in SHR but not SHHF relative to WKY rats, whereas transferrin receptors 1 and 2 mRNA was lower in SHHF rats. Four of 12 WKY rats exhibited cardiac hypertrophy despite normal blood pressure, while demonstrating some of the pulmonary complications noted earlier. This study demonstrates that SHHF rats display greater underlying pulmonary complications such as oxidative stress, inflammation, and impaired Fe homeostasis than WKY or SHR rats, which may play a role in SHHF rats' increased susceptibility to air pollution.

Preventive cardiology and cardiac rehabilitation programmes in women

Cardiovascular diseases are the most common cause of death among women. Women historically under-appreciate these risks. There are key differences in terms of the relative importance of risk factors, particularly in the age of presentation. The female 'gender advantage' previously felt to be due to female sex hormones remains unexplained. The effects of post-menopausal hormone replacement also remain controversial. Risk can be reduced by sensible risk-factor control, but there is an ongoing imbalance between calculated risk and evidence of subclinical atherosclerosis and in women, in particular, a more proactive approach to risk reduction may be required. The controversy surrounding the effectiveness of statins in women is probably more due to problems with meta-analyses than from gender dimorphism. Cardiac rehabilitation reduces cardiac risk but women have previously been under-referred, although the benefits are equally great in both genders.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Excessive body iron stores are not associated with risk of coronary heart disease in women

The positive association between body iron stores and risk of coronary heart disease (CHD) initially observed among a Finnish male population has not been corroborated by studies conducted in other populations. The soluble transferrin receptor (sTfR):ferritin ratio has been suggested to be a better index than ferritin to measure body iron stores. Because sTfR is sensitive to iron deficiency, this ratio can distinguish individuals with similar ferritin levels with respect to their iron status. To evaluate this novel index in relation to CHD risk, we prospectively identified and confirmed 242 incident CHD cases and randomly selected 483 controls matched for age, smoking, and fasting status among women that provided blood samples in the Nurses' Health Study during 9 y of follow-up. In both crude and multivariate analyses, neither the sTfR:ferritin ratio nor ferritin was significantly associated with an elevated risk of CHD. After multivariate adjustment for established and potential CHD risk factors, compared with women in the lowest quartile of the sTfR:ferritin ratio, women in the 2nd to 4th quartiles had relative risks (RR) (95% CI) of 1.39 (0.82, 2.36), 1.12 (0.66, 1.91), and 1.13 (0.65, 1.97; P-trend = 0.61), respectively. The multivariate RR (95% CI) for ferritin were 1.05 (0.62, 1.77), 1.19 (0.69, 2.03), and 1.05 (0.60, 1.85; P-trend = 0.90) across quartiles. Our data do not support the hypothesis that excessive body iron stores are associated with risk of CHD.

The iron regulatory hormone hepcidin reduces ferroportin 1 content and iron release in H9C2 cardiomyocytes

Iron plays a key pathophysiological role in a number of cardiac diseases. Studies on the mechanisms of heart iron homeostasis are therefore crucial for understanding the causes of excessive heart iron. In addition to iron uptake, cellular iron balance in the heart also depends on iron export. We provided evidence for the existence of iron exporter ferroportin 1 (Fpn1) in the heart in a recent study. The presence of hepcidin, a recently discovered iron regulatory hormone, was also confirmed in the heart recently. Based on these findings and the inhibiting role of hepcidin on Fpn1 in other tissues, we speculated that hepcidin might be able to bind with, internalize and degrade Fpn1 and then decrease iron export in heart cells, leading to an abnormal increase in heart iron and iron mediated cell injury. We therefore investigated the effects of hepcidin on the contents of Fpn1 and iron release in H9C2 cardiomyocyte cell line. We demonstrated that hepcidin has the ability to reduce Fpn1 content as well as iron release in this cell. The similar regulation patterns of hepcidin on the Fpn1 and iron release suggested that the decreased iron release resulted from the decreased content of Fpn1 induced by hepcidin. We also found that hepcidin has no significant effects on ceruloplasmin (CP) and hephaestin (Heph)--two proteins required for iron release from mammalian cells. The data imply that Fpn1, rather than Heph and CP, is the limited factor in the regulation of iron release from heart cells under physiological conditions.

Iron homeostasis and eye disease

BACKGROUND

Iron is necessary for life, but excess iron can be toxic to tissues. Iron is thought to damage tissues primarily by generating oxygen free radicals through the Fenton reaction.

METHODS

We present an overview of the evidence supporting iron's potential contribution to a broad range of eye disease using an anatomical approach.

RESULTS

Iron can be visualized in the cornea as iron lines in the normal aging cornea as well as in diseases like keratoconus and pterygium. In the lens, we present the evidence for the role of oxidative damage in cataractogenesis. Also, we review the evidence that iron may play a role in the pathogenesis of the retinal disease age-related macular degeneration. Although currently there is no direct link between excess iron and development of optic neuropathies, ferrous iron's ability to form highly reactive oxygen species may play a role in optic nerve pathology. Lastly, we discuss recent advances in prevention and therapeutics for eye disease with antioxidants and iron chelators.

GENERAL SIGNIFICANCE

Iron homeostasis is important for ocular health.

Blood donation, body iron status and carotid intima-media thickness

Iron could promote free radical formation, which may lead to injury of the arterial wall and atherosclerosis. Blood donation may reduce cardiovascular risk by lowering body iron status. We collected data on blood donation history and intima-media thickness of the common carotid artery (CIMT) in 819 subjects (50-70 years), who were recruited from municipal and blood bank registries in The Netherlands. Serum iron parameters were assessed, including non-transferrin bound iron (NTBI) that has recently been found in conditions of iron overload. Serum ferritin was lower in current donors (n=443; 44 microg/L) than in ex-donors (n=120; 114 microg/L) and never-donors (n=256; 124 microg/L, P for trend <0.001). For NTBI, values were 2.33, 2.54, and 2.51 micromol/L, respectively (P<0.05). CIMT was slightly reduced in frequent donors (i.e., > or =49 times during life or > or =2 times per year), although not statistically significant. CIMT was not significantly related to NTBI. Frequent blood donation, resulting in lowered body iron, might give some protection against accelerated atherosclerosis.

Diabetes and the heart: could the diabetic myocardium be protected by preconditioning?

Both type 1 and type 2 diabetes (insulin-dependent and non-insulin dependent diabetes, respectively) are associated with increased risk for microvascular and macrovascular complications including retinopathy, neuropathy, nephropathy and atherosclerosis. Type 2 diabetes markedly increases the risk for cardiovascular morbidity and mortality, which has major public health implications. In this review, molecular mechanisms pertaining to diabetes-induced heart pathology are addressed.

Ferritin and transferrin are associated with metabolic syndrome abnormalities and their change over time in a general population: Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR)

OBJECTIVE

The aim of this work was to study cross-sectional and longitudinal relations between iron stocks (ferritin) and the iron transport protein (transferrin) with the metabolic syndrome and its abnormalities.

RESEARCH DESIGN AND METHODS

A total of 469 men and 278 premenopausal and 197 postmenopausal women from the French Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) cohort, aged 30-65 years, were followed over 6 years.

RESULTS

Higher concentrations of both ferritin and transferrin were associated with the International Diabetes Federation (IDF) and the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults Adult Treatment Panel III original and revised definitions of the metabolic syndrome at baseline: for the IDF definition of the metabolic syndrome, the standardized, age-adjusted odds ratios (95% CI) for log(ferritin) were 1.49 (1.14-1.94) for men, 2.10 (1.27-3.48) for premenopausal women, and 1.80 (1.21-2.68) for postmenopausal women; for transferrin they were, respectively, 1.94 (1.53-2.47), 2.22 (1.32-3.75), and 2.14 (1.47-3.10). After 6 years of follow-up, the change in the presence of the metabolic syndrome was associated with higher baseline values in all three groups: log(ferritin), 1.46 (1.13-1.89), 1.28 (0.85-1.94), and 1.62 (1.10-2.38); and transferrin, 1.41 (1.10-1.81), 1.63 (1.05-2.52), and 1.51 (1.02-2.22). Among syndrome components, hypertriglyceridemia at 6 years was the component most strongly associated with baseline ferritin and transferrin. The odds of an incident IDF-defined metabolic syndrome after 6 years was more than fourfold higher when ferritin and transferrin values were both above the group-specific top tertile, in comparison with participants with both parameters below these thresholds.

CONCLUSIONS

This is the first prospective study associating ferritin and transferrin with the metabolic syndrome and its components. When both markers of the iron metabolism are elevated, the incidence of the metabolic syndrome is increased in men and both pre- and postmenopausal women.

Expression of ferroportin1, hephaestin and ceruloplasmin in rat heart

Iron-mediated injury plays an important role in a number of heart disorders. Studies on heart iron are therefore crucial for understanding the causes of excessive heart iron. Heart cells have the ability to accumulate transferrin-bound-iron via the transferrin receptor and non-transferrin-bound-iron probably via the L-type Ca2+ channel and the divalent metal transporter1. However, little is known about the mechanisms of iron export in the heart cells. Here, we investigated expression of iron exporters including ferroportin 1 (Fpn1), ceruloplasmin (CP) and hephaestin (Heph) and provided evidence for their existence in the heart. We demonstrated that iron has a significant effect on expression of Fpn1 and CP, but not Heph. Treatment of a high-iron diet induced a significant increase in Fpn1, a decrease in CP but no change in Heph mRNA and protein. The control of Fpn1 and CP protein expression by iron was parallel to that of their mRNA expression, suggesting a transcriptional regulation of Fpn1 and CP by iron. The existence of these proteins in the heart implies that they might have a role in heart iron homeostasis.

Poor iron status is more prevalent in Hispanic than in non-Hispanic white older adults in Massachusetts

Iron status and dietary correlates of iron status have not been well described in Hispanic older adults of Caribbean origin. The aim of this study was to evaluate iron status and describe dietary components and correlates of iron status in Hispanic older adults and in a neighborhood-based comparison group of non-Hispanic white older adults. Six hundred four Hispanic and non-Hispanic white adults (59-91 y of age) from the Massachusetts Hispanic Elders Study were included in the analysis. We examined physiological markers of iron status as well as dietary factors in relation to iron status. Dietary intake was assessed by FFQ. Our results revealed that Hispanics had significantly lower geometric mean serum ferritin (74.1 microg/L vs. 100 microg/L; P<0.001), lower hemoglobin concentrations (137+/-13 vs. 140+/-12 g/L; P<0.01), higher prevalence of anemia (11.5 vs. 7.3%; P<0.05), and suboptimal hemoglobin concentrations (<125 g/L) for this age group (21.4 vs. 13.3%; P<0.05). Iron deficiency anemia was higher (7.2% vs. 2.3%; P<0.05) in Hispanic women. Hispanics had lower mean intakes of total iron, vitamin C, supplemental vitamin C, and total calcium than did non-Hispanic whites. After adjusting for age, sex, BMI, alcohol use, smoking, total energy intake, inflammation, diabetes, and liver disease, intake of heme iron from red meat was positively associated and dietary calcium was negatively associated with serum ferritin. This population of Hispanic older adults was significantly more likely than their non-Hispanic white neighbors to suffer from anemia and poor iron status, particularly among women. Cultural variation in dietary patterns may influence iron availability and body iron stores and contribute to an increased risk for iron deficiency anemia among some Hispanic older adults.

Dietary iron intake and risk of non-fatal acute myocardial infarction

Objective

The relation between several measures of body iron and atherosclerotic disease, particularly acute myocardial infarction (AMI), is debated. This is of specific interest since iron is frequently included in supplementation and fortification of foods. We assessed the relation between dietary iron intake and the risk of non-fatal AMI.

Design

Case–control study. The information was collected by interviewers using a food-frequency questionnaire tested for validity and reproducibility. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were obtained by multiple unconditional logistic regression models, including terms for energy and alcohol intakea, as well as for sociodemographic factors, tobacco and other major recognised risk factors for AMI.

Setting

Milan, Italy, between 1995 and 1999.

Subjects

Cases were 507 patients, below age 79 years, with a first episode of non-fatal AMI, and controls were 478 patients admitted to hospital for a wide spectrum of acute conditions unrelated to known or potential AMI risk factors.

Results

Compared with patients in the lowest tertile of total iron intake, the OR was 0.48 (95% CI 0.29–0.82) for those in the highest tertile. The corresponding value for haem iron was 0.71 (95% CI 0.48–1.06), for non-haem, non-alcohol iron was 0.80 (95% CI 0.51–1.24) and for iron derived from alcoholic beverages was 0.60 (95% CI 0.40–0.90). Sex-specific OR for total iron intake were not heterogeneous.

Conclusions

In this Italian population dietary iron intake was inversely related to AMI risk. This inverse association may depend on other nutrients present in the major sources of iron in the Italian diet.

On risks and benefits of iron supplementation recommendations for iron intake revisited

Iron is an essential trace element with a high prevalence of deficiency in infants and in women of reproductive age from developing countries. Iron deficiency is frequently associated with anaemia and, thus, with reduced working capacity and impaired intellectual development. Moreover, the risk for premature delivery, stillbirth and impaired host-defence is increased in iron deficiency. Iron-absorption and -distribution are homeostatically regulated to reduce the risk for deficiency and overload. These mechanisms interact, in part, with the mechanisms of oxidative stress and inflammation and with iron availability to pathogens. In the plasma, fractions of iron may not be bound to transferrin and are hypothesised to participate in atherogenesis. Repleted iron stores and preceding high iron intakes reduce intestinal iron absorption which, however, offers no reliable protection against oral iron overload. Recommendations for dietary iron intake at different life stages are given by the US Food and Nutrition Board (FNB), by FAO/WHO and by the EU Scientific Committee, among others. They are based, on estimates for iron-losses, iron-bioavailability from the diet, and iron-requirements for metabolism and growth. Differences in choice and interpretation of these estimates lead to different recommendations by the different panels which are discussed in detail. Assessment of iron-related risks is based on reports of adverse health effects which were used in the attempts to derive an upper safe level for dietary iron intake. Iron-related harm can be due to direct intestinal damage, to oxidative stress, or to stimulated growth of pathogens. Unfortunately, it is problematic to derive a reproducible cause-effect and dose-response relationship for adverse health effects that suggest a relationship to iron-intake, be they based on mechanistic or epidemiological observations. Corresponding data and interpretations are discussed for the intestinal lumen, the vascular system and for the intracellular and interstitial space, considering interference of the mechanisms of iron homoeostasis as a likely explanation for differences in epidemiological observations.

Molecular and clinical aspects of iron homeostasis: From anemia to hemochromatosis

The discovery in recent years of a plethora of new genes whose products are implicated in iron homeostasis has led to rapid expansion of our knowledge in the field of iron metabolism and its underlying complex regulation in both health and disease. Abnormalities of iron metabolism are among the most common disorders encountered in practical medicine and may have significant negative impact on physical condition and life expectancy. Basic insights into the principles of iron homeostasis and the pathophysiological and clinical consequences of iron overload, iron deficiency and misdistribution are thus of crucial importance in modern medicine. This review summarizes our current understanding of human iron metabolism and focuses on the clinically relevant features of hereditary and secondary hemochromatosis, iron deficiency anemia, anemia of chronic disease and anemia of critical illness. The interconnections between iron metabolism and immunity are also addressed, in as much as they may affect the risk and course of infections and malignancies.

Intravenous iron increases labile serum iron but does not impair forearm blood flow reactivity in dialysis patients

BACKGROUND

There are concerns about adverse vascular effects of intravenous iron by inducing oxidative stress. We therefore examined the effect of a single high dose of intravenous iron on endothelial function and biochemical markers of iron homeostasis.

METHODS

In a randomized, placebo-controlled, double-blind, parallel-group study, forearm blood flow (FBF) was assessed by strain-gauge plethysmography in 38 peritoneal dialysis patients before and after a single intravenous infusion of 300 mg iron sucrose.

RESULTS

Iron infusion increased total (Delta 601 microg/100 mL, CI 507, 696) and non-transferrin-bound iron (Delta 237.2 micromol/L, CI 173.6, 300.8) approximately 10-fold, as well as redox-active iron nearly five-fold (Delta 0.76 micromol/L, CI 0.54, 0.98). After iron infusion basal FBF was 59% higher than after placebo. FBF response to acetylcholine before and after iron infusion was 263 +/- 32% and 310 +/- 33%, corresponding to 304 +/- 43% and 373 +/- 29% in the placebo group, respectively. Before and after iron or placebo infusion, glyceryl-trinitrate increased resting FBF to 232 +/- 22% and 258 +/- 21% in the iron group, and to 234 +/- 18% and 270 +/- 30% in the placebo group. L-N-monomethyl-arginine decreased FBF to 70 +/- 4% and 72 +/- 3% before and after iron, and to 74 +/- 4% and 73 +/- 4% before and after placebo infusions, respectively. Despite higher basal FBF after iron infusion, absolute and relative FBF changes in response to vasoactive substances were not significantly different between iron and placebo groups.

CONCLUSION

Our data suggest that 300 mg intravenous iron sucrose has a vasodilatory effect, but does not impair vascular reactivity in dialysis patients, despite a significant increase in non-transferrin-bound and redox-active iron.

Iron status and clinical outcome in patients with coronary artery disease after coronary stenting

BACKGROUND AND AIM

So far, no studies have assessed whether there is an association between iron status and the incidence of major adverse cardiac events or restenosis after coronary stenting. We conducted this study to investigate whether there is an association between body iron status and clinical outcome in patients with coronary artery disease after coronary stenting.

METHODS AND RESULTS

The study included 664 patients with coronary artery disease who underwent coronary stent implantation. The soluble transferring receptor/ferritin ratio (sTfR/ferritin ratio) was used as an index of iron status. Patients were divided into three groups according to the tertiles of sTfR/ferritin ratio: lower tertile (<11.9; n = 221), middle tertile (11.9-27.8; n = 221) and upper tertile (>27.8; n = 222). The combined incidence of major adverse cardiac events (death, myocardial infarction and target vessel revascularization) was the primary end point of the study. Patients in the lower tertile of the sTfR/ferritin ratio presented more often with unstable angina or acute myocardial infarction and had longer lesions and higher grade of stenosis than the patients in the middle or upper tertile of the sTfR/ferritin ratio. Angiographic restenosis at 6-month angiography was also evaluated. The cumulative event rate of composite end point of death, myocardial infarction or target vessel revascularization was 27.6% in patients in the lower tertile, 24.4% in patients in the middle tertile and 28.4% in patients in the upper tertile of the sTfR/ferritin ratio (p = 0.68). Restenosis was found in 27.8% (n = 45) in the lower tertile, 25.8% (n = 42) in the middle tertile and 27.5% (n = 38) in the upper tertile of the sTfR/ferritin ratio (p = 0.90).

CONCLUSIONS

Our study showed no association between iron status and the incidence of major adverse cardiac events or angiographic coronary restenosis in patients with coronary artery disease after coronary stenting.

Iron supplement use and iron status among US adults: results from the third National Health and Nutrition Examination Survey

BACKGROUND

Patients with hemochromatosis are instructed to avoid taking supplemental iron. Whether supplemental iron intakes lead to higher iron status among healthy persons remains less clear.

OBJECTIVE

The objective was to ascertain whether supplemental iron intakes are associated with increases in iron transport (transferrin saturation) and stores (serum ferritin) among US adults aged > or = 19 y.

DESIGN

We analyzed data for 5948 adults from whom a fasting serum sample was collected during the third National Health and Nutrition Examination Survey. We used multivariable linear regression and analysis of variance to assess the association of supplemental iron intake with iron transport and stores among men (aged 19-30 y or > 30 y) and women (nonpregnant premenopausal or postmenopausal); multiple comparison tests were also performed.

RESULTS

Healthy adults who took supplements containing average daily amounts of iron at < or = 3 times the recommended dietary allowance (RDA) did not have significantly higher iron transport or stores than did those who did not take supplements. In younger men, the intake of > 32 mg Fe/d (> 4x RDA) was associated with mean transport iron concentrations that were significantly higher than those in persons who took 0 to < or = 24 mg Fe/d. In older men, the intake of > 32 mg Fe/d (> 4x RDA) was associated with mean iron stores that were significantly higher than those in persons who took 0 to < or = 24 mg Fe/d; a similar result was observed in postmenopausal women, but it was of borderline statistical significance.

CONCLUSION

Supplement users should be made aware of the amount of iron necessary to satisfy dietary requirements and informed of the possible influence that excess iron intake can have on body iron stores and health.

A safe strategy for addition of vitamins and minerals to foods

Addition of vitamins and minerals to foods must be done without health risk to any consumer group. International expert groups have aimed at establishing tolerable upper intake levels (ULs) for vitamins and minerals although lack of solid data on their safety is a major obstacle to this work. In this paper, we summarize the existing ULs and suggest the use of guidance levels (GLs) set by others and temporary guidance levels (TGLs) proposed here, whenever no consensus UL has been established for adults. We suggest the use of body surface area ratios to establish similar levels for younger age groups. The levels are applied in a model for calculation of safe fortification levels for all ages. We have estimated the upper 95(th) percentile intake of vitamins and minerals from food in various Danish age and gender groups and suggest that a daily multivitamin-mineral pill is included in the calculation of total dietary intake levels of all vitamins and minerals. By subtracting this dietary intake level from the UL, GL or TGL, we calculate the amount that can be safely used for fortification. Since safety must be assured for all age groups, the smallest difference relative to energy intake calculated for any age group is proposed as the maximal allowance (MA) for fortification with each nutrient. We suggest that the MA should be expressed in weight units per energy unit in order to distribute it equally between potentially fortifiable food groups according to their usual contribution to total energy intakes.

Hemochromatosis Gene Mutations, Body Iron Stores, Dietary Iron, and Risk of Colorectal Adenoma in Women

BACKGROUND

Some experimental evidence suggests that iron may play a role in colorectal carcinogenesis, but human data for this role have been conflicting, possibly because of problems related to study design or measurement of iron exposure. We assessed dietary iron intake and genetic and biochemical markers of iron status in a prospective, nested case-control study of women enrolled in the Nurses' Health Study.

METHODS

Among 32 826 women who provided a blood specimen, we identified 527 women with colorectal adenoma and 527 matched control subjects who underwent endoscopy but were not diagnosed with adenoma after blood collection. We assessed iron intake, mutations in the HFE gene that are associated with hereditary hemochromatosis (i.e., H63D and C282Y), and plasma biochemical measures of total body iron, including transferrin saturation and the ratio of the concentrations of transferrin receptors to ferritin. Logistic regression models were used to estimate relative risks (RR) and 95% confidence intervals (CI). All statistical tests were two-sided.

RESULTS

Women with any HFE gene mutation had higher total body iron stores, as reflected by higher transferrin saturations (P < .001) and lower levels of the ratio of transferrin receptors to ferritin (P = .02), than women with no HFE gene mutation. However, HFE gene mutations were not associated with risk of adenoma (multivariable RR = 1.08, 95% CI = 0.83 to 1.39; P = .58). Moreover, comparison of extreme categories showed no associations between adenoma and the extent of transferrin saturation (multivariable RR = 0.96, 95% CI = 0.63 to 1.47; Ptrend = .66), the ratio of transferrin receptors to ferritin (multivariable RR = 0.98, 95% CI, 0.60 to 1.60; Ptrend = .99), or dietary iron intake (multivariable RR = 1.04, 95% CI = 0.68 to 1.57; Ptrend = .94).

CONCLUSIONS

Although our study used several distinct measures of iron status (i.e., genetic mutations, biochemical markers, and dietary intake) and a nested case-control design, we did not observe a role for iron in the pathogenesis of colorectal neoplasia in women.