IRON Science Library
Welcome to our Iron Science Library. In this section we will demonstrate how moderately elevated to high levels of iron contribute to disease process by catalyzing oxidative stress causing cell damage, lipid peroxidation, and DNA mutagenisis. This is the underlying damage process that can lead to multiple life-threatening disease that can affect your body’s vital organs.
As in our GGT Science Library, we will not present a lengthy narrative on each affected body system or disease; but rather will briefly summarize or quote the most relevant take-home points and/or research conclusions from each study. Nearly all article titles are linked to abstracts archived at the U.S. National Library of Science. Many articles also have Full free text PDF links . Our Iron Science Library pages include:
- IRON: Your Heart, Cardiovascular System, Oxidative Stress and Mortality (below)
- IRON: Cancer, Oxidative Stress and Mortality
- IRON: Diabetes, Metabolic Syndrome, Liver Diseases, Oxidative Stress and Mortality
- IRON: Oxidative Stress; Neurodegeneration; Parkinson’s, Alzheimer’s Diseases and Others
- IRON: Bacterial, Fungal, Viral, Protozoan Infections and infectious Processes
IRON: Your Heart, Cardiovascular System, Oxidative Stress and Mortality
In this 2010 case control design study of “apparently healthy” middle-age men and women from Southwest France, “a total of 124 age- and sex-matched pairs (124 cases and 124 controls; 73.2% men and 26.8% women) were drawn from the initial sample (n = 972). Researchers found that in models adjusted for traditional cardiovascular risk factors in subjects free from inflammation, each increase of 10 ng/mL of ferritin related to a 3% increased risk for atherosclerosis. The researchers concluded, “…carotid atherosclerosis was positively associated with serum ferritin in individuals free from subclinical inflammation.” [Health-e-Iron note: Table 3 from this study appears below]
In this 2004 German study of 2,443 participant ages 45-79, the investigators observed a significant association between increased serum ferritin and carotid plaque in men (~ 29% increased odds), but only a strong trend in women. “However, both men and women showed a dose-response relation between serum ferritin levels and carotid atherosclerosis in which higher serum ferritin levels were associated with greater odds ratios for carotid plaque prevalence. Additionally, there was an interaction of serum ferritin levels with low-density lipoprotein (LDL) cholesterol (P=0.039) among men in which the association of serum ferritin levels with carotid plaque prevalence became stronger with increasing LDL cholesterol levels.” They reported that “…both men and women showed a dose-response relation between serum ferritin levels and carotid atherosclerosis in which higher serum ferritin levels were associated with greater odds ratios for carotid plaque prevalence.” The researchers concluded, “Our study identified a relationship between serum ferritin levels and carotid atherosclerosis that was potentiated by LDL cholesterol. This relationship adds support to the hypothesis of a link between iron and cardiovascular disease.” [Health-e-Iron note: Figures 1 and 2 from the study above appear below]
In this 2007 review the author summarized the evidence leading to his statement, “It is clear that oxidant damage contributes to many of the diseases of aging, such as atherosclerosis, Alzheimer’s disease, Parkinson’s diseases, diabetes, diseases of inflammation, diseases of fibrosis, diseases of autoimmunity, and so on. It is equally clear that both iron and copper can contribute to excess production of damaging reactive oxygen species through Fenton chemistry. Here, we examine the evidence that ‘normal’ levels of iron and copper contribute to various diseases of aging.”
In this 1994 study of this large cohort in Austria, the risk of carotid atherosclerosis risk increased in a dose-response manner with increasing ferritin. In an analysis adjusting for age, sex, and all major vascular risk markers, “ferritin emerged as one of the strongest indicators of carotid artery disease in both sexes (40 to 59 years; odds ratio, 1.54 per 100 ng/mL; P < .001).” “Notably, no significantly increased was found among those older than age 60. The investigators concluded, “The current study suggests a possible role of body iron in early atherogenesis.” [Health-e-Iron note: Tables 2 and 3 from the study above appear below]
“Odds ratios for increase in 1 SD (standard deviation) unit of given variables, logistic regression coefficients (LRC), and 95% confidence intervals (95% Cl) were derived from multjvariate logistic regression analysis. BP indicates Wood pressure; GOF P, probability value for Hosmer-Lemeshow goodness of fit test.”
Body iron stores and the risk of carotid atherosclerosis: prospective results from the Bruneck study (5), charts and teaching slides
In a 1997 report from the from the above-described Austrian cohort, researchers quantified the association of atherosclerosis and lipid peroxidation. The researchers reported, “Changes in iron stores during the follow-up period modified atherosclerosis risk, in that a lowering was beneficial and further iron accumulation exerted unfavorable effects.” And they concluded, “The present study provided strong epidemiological evidence for a role of iron stores in early atherogenesis and suggests promotion of lipid peroxidation as the main underlying pathomechanism.” [Health-e-Iron note: Figures 1 & 3 from the study above appear below]
Figure 1. Crude and regression-standardized risks of incident atherosclerosis (1990 to 1995) according to ferritin quintiles. Figure documents dose-response relation between ferritin measurements and risk of early atherogenesis. n=476.
Figure 3. Incidence of carotid atherosclerosis in population 40 to 59 years old by sex, menopausal status, and ferritin concentrations. Age-specific incidence rates were calculated for 5-year strata on assumption of equal rates across this limited age range. For comparison purposes, rates presented were standardized to age structure of men (40 to 59 years) in our survey and expressed as events per 100 person-years (incidence density). Cutoff for ferritin (50 µg/L) corresponds to 33rd percentile in men.
This was a 2012-reported study undertaken in India. The objective of the investigators was “to study the relationship of serum ferritin with acute myocardial infarction (AMI) in univariate and multivariate analysis and to assess the relationship of high serum ferritin with established conventional risk factors.” This was a “hospital based case-control study of 75 cases of AMI, and 75 age and equal number of age, and gender-matched controls without having AMI in the age group of 30-70 years.” “Median serum ferritin levels were significantly higher in cases (220 μg/L) than controls(155 μg/L) (P ≤ 0.0001. In univariate analysis in addition to ferritin > 200 μg/L (odds ratio [OR] 6.71, 95% confidence interval [CI] = 3.22-12.89, P<0.05), diabetes (OR=7.68, 95% CI=2.95-19.13, P<0.05), hypertension (HTN) (OR=2.36, 95% CI=1.02-5.14, P<0.05) high-density lipoprotein (HDL) < 35 mg/dL (OR = 11.9, 95% CI = 2.66-52.57, P<0.05) and smoking (OR=2.17, 95% CI = 1.12-3.87, P< 0.05) were found to be significantly associated with AMI. After controlling for all conventional risk factors, in multiple logistic regression analysis, high ferritin was significantly associated with AMI. (adjusted OR=5.72, 95% CI=2.16-15.17, P < 0.001). Serum ferritin was significantly higher in diabetics than non-diabetics (P < 0.01).” The researchers concluded, “High serum ferritin is strongly and independently associated with AMI.” [Health-e-Iron note: Figure 1 from this study appears below]
This is a large study of primarily men preformed in Korea and reported in 2012. The researchers noted, “Ferritin concentrations are often increased in patients with metabolic syndrome and type 2 diabetes mellitus, but few reports have examined the associations between ferritin and atherosclerosis. We investigated whether any relationship between ferritin and coronary artery calcium score (CACS) >0 (as a marker of atherosclerosis) was independent of potential confounders, such as iron-binding capacity (transferrin), low-grade inflammation, and cardiovascular risk factors.” “Data were analyzed from a South Korean occupational cohort of 12,033 men who underwent a cardiac computed tomography estimation of CACS and measurements of multiple cardiovascular risk factors. One-thousand three- hundred-fifteen of 12,033 (11.2%) subjects had a CACS >0. For people with a CACS >0, median (interquartile range) ferritin concentration was 196.8 (136.3-291.9) compared with 182.2 (128.1-253.6) in people with a CACS=0; P<0.001. In the highest ferritin quartile, 14.7% (442/3008) of subjects had a CACS >0 compared with 9.7% (292/3010) in the lowest quartile (P<0.0001). With increasing ferritin quartiles, there were also higher proportions of people with diabetes mellitus (P<0.0001), hypertension (P<0.0001), coronary heart disease (P=0.003), and a Framingham Risk Score >10% (P<0.0001). In logistic regression modeling with CACS >0 as the outcome, ferritin but not transferrin was independently associated with CACS >0 (odds ratio for highest quartile versus lowest quartile, 1.66 [95% CI, 1.3-1.98]; P=0.0001).” The researchers concluded, “Increased ferritin concentrations are associated with the presence of a marker of early coronary artery atherosclerosis, independently of traditional cardiovascular risk factors including Framingham risk score, transferrin, preexisting vascular disease, diabetes mellitus, metabolic syndrome factors, and low-grade inflammation.”
In a sub-group study of a large randomized trial that tested iron reduction by phlebotomy in a total of 1,227 (mainly male) patients with peripheral arterial disease (PAD), the investigators analyzed the results of iron reduction in the context of a series of inflammatory markers in the 100 patient Nevada cohort. The reported results showed, “Mean follow-up average ferritin levels were higher in 23 participants who died (132.5 ng/mL…) vs 77 survivors (83.6 ng/mL…). Ferritin levels correlated (Pearson) with average IL-6 levels … and hsCRP levels … during the study.” The researchers concluded, “These data demonstrate statistical correlations between levels of ferritin, inflammatory biomarkers, and mortality in this subset of patients with PAD.”
The researchers in this 2010 laboratory study investigated the molecular process involving the interaction between hemoglobin and artheromatous lesions and reported, “Oxidative scission of heme leads to release of iron and a feed-forward process of iron-driven plaque lipid oxidation.” The researchers concluded, “The interior of advanced atheromatous lesions is a prooxidant environment in which erythrocytes lyse, hemoglobin is oxidized to ferri- and ferrylhemoglobin, and released heme and iron promote further oxidation of lipids.” [Health-e-Iron note: the below image is one of several pictured in Figure 3 from this article]
“Figure 3. Heme with atheroma lipids augments lipid peroxidation and subsequent endothelial cell reactions. Lipids from atheromatous lesions (n = 9) or controls (n = 9) were treated with heme…”
Health-e-Iron note: the processes described above are further described in papers10-13 below
Pro-oxidant and cytotoxic effects of circulating heme (10)
Heme, heme oxygenase, and ferritin: how the vascular endothelium survives (and dies) in an iron-rich environment (12)
The researchers in this 2002 paper describe how the findings of their group and others, “showed that GGT-catalysed extracellular metabolism of GSH (glutathione) leads, in the presence of iron, to the generation of reactive oxygen species (ROS).” And that “The results obtained demonstrate that the GGT/GSH/iron system oxidises isolated erythrocyte membranes.” The researchers concluded that, “GGT-mediated ROS production is able to oxidise erythrocytes and thus disturbs their functions.” [also see our library page on GGT Heart]
Based on a study of 437 consecutive coronary heart disease patients (CHD in France, the researchers found there was a significant relationship between alcohol/ethanol intake and serum levels of iron, ferritin and GGT in patients with CHD. The research team concluded, “The available data showing positive relationships between wine ethanol intake and serum concentrations of both ferritin and iron in patients with CHD tend to disprove the hypothesis that wine ethanol consumption could decrease iron stores and thereby the risk of CHD.”
In this 2009 review by a noted expert in the field of iron homeostasis in humans, the role of retention of iron within macrophages and the association of arterial plaque and ferritin with the risk of disease development and cardiovascular events. The author describes findings that iron reduction reduces lesion size and plaque instability. The author concludes, “The reviewed findings support the concept that arterial plaque iron is a modifiable risk factor for atherogenesis.”
This 2011 study from Tulane University was based on the observation that, “Catalytic iron, which has been associated with these chronic diseases, may be one of the links between obesity and these multifactorial diverse disorders.” The investigators in this research demonstrate that obesity and waist-to-hip ratio contribute to oxidative stress that can be measured in urinary catalytic iron. The researchers team reported that, “Our study results demonstrate that obesity and waist-to-hip ratio are associated with increased urinary catalytic iron, which may be a useful marker of oxidative stress.” [Health-e-Iron note: the below table from this paper demonstrates findings consistent with the correlation of excess iron with obesity and obesity-related risk factors. Note also that the relationships are also consistent with well-established ethnic, gender and menopausal status health risk differences]
In this study from the Czech Republic, the researchers evaluated the ratio of transferrin receptors, plasma ferritin, carotid artery media thickness (measured by ultrasound) in 72 healthy men. The research team concluded, “Our study showed a clear association of body iron stores expressed by the the plasma-circulating transferrin receptor concentration to plasma ferritin concentration ratio with asymptomatic carotid atherosclerosis.”
The researchers in this 1992 study, “…tested the hypothesis that high serum ferritin concentration and high dietary iron intake are associated with an excess risk of acute myocardial infarction.” In a randomly selected group of 1,931 Finnish men of ages 42, 48, 54 or 60 years old, with no symptoms of coronary heart disease, who were studied over a period of three years, researchers found that, “… men with serum ferritin greater than or equal to 200ng/mL 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.” The researchers concluded,.”Our data suggest that a high stored iron level, as assessed by elevated serum ferritin concentration, is a risk factor for coronary heart disease.” [Health-e-Iron note: Figure 2 & 3 from the study above appear below]
The investigators of this 2009 study in Pakistan was based on previous findings that demonstrated, “oxidative stress is characterized by an increased concentration of oxygen free radicals which can cause a critical, or even an irreversible, cell injury.” The researchers measured serum iron, iron binding capacity, transferrin saturation, ferritin and oxidative stress in 140 coronary heart disease patients and compared the results to those measures in 100 healthy control subjects. “…iron, transferrin saturation and ferritin were observed to be significantly increased … in Coronary Heart Disease patients when compared with normal healthy controls.” The researchers concluded, “…it is suggested by this study that levels of malondialdehyde and biochemical markers of body iron stores can be used as an early investigative tool for assessing the oxidative stress in coronary heart disease.”
This 2009 study was reported in the U.S. The researchers noted, “Centralized adiposity, insulin resistance, excess iron, and elevated oxidative stress place postmenopausal women at risk for atherosclerotic cardiovascular disease (CVD). The objective of this study was to determine the relationship among excess iron, oxidative stress, and centralized fat mass in healthy postmenopausal women.” “Multiple regression analysis was used to determine the CVD risk factors that contributed to oxidative stress and centralized fat mass (waist + hip/thigh = AndGynFM ratio).” The researchers analyzed daily nutrient intakes and numerous blood chemistry markers relating to known CVD risk and oxidative stress, including serum ferritin.”Multiple regression analysis with backward selection was used to determine the CVD risk factors that contributed to oxidative stress and centralized fat mass in these healthy postmenopausal women.” Following their analysis or the data, the researchers concluded, “We demonstrated an association among oxidative stress, iron status, lipids, insulin resistance, and centralized adiposity. Iron status was positively associated with centralized adiposity, possibly mediating insulin resistance or oxidative stress in these postmenopausal women.”
In this study from India, “One hundred seventy-five consecutive subjects below 60 years of age were examined; they were then divided into three groups: one with coronary artery disease, another without coronary artery disease and a healthy control group.“ And they reported, “Oxidative stress was highest in smokers with coronary artery disease (3.11+/-0.79 mmol/ml) as compared to hypertensives (2.69+/-0.20 mmol/nl) and non-insulin dependent diabetics (2.78+/-0.19 mmol/ml).” The researchers found that, “Serum iron and total iron binding capacity were not significantly different in risk prone subjects. However, among all risk prone subjects, smokers with coronary artery disease showed highest serum iron levels and decreased iron binding capacity.”
In this 2007 Serbian study conducted among 188 coronary heart disease subjects and 197 controls, oxidative stress status parameters, inflammation markers and lipid status parameters were measured. Relative to controls, higher pro-oxidant measures and lower antioxidant measures were noted in patients with coronary heart disease. The researchers concluded, “The relationship between oxidative stress parameters and inflammatory species suggest their strong mutual involvement in atherosclerosis development that leads to coronary artery disease progression.”
This 2011 review notes, “Loss of reduction-oxidation (redox) homeostasis and generation of excess free oxygen radicals play an important role in the pathogenesis of diabetes, hypertension, and consequent cardiovascular disease. Reactive oxygen species are integral in routine in physiologic mechanisms. However, loss of redox homeostasis contributes to proinflammatory and profibrotic pathways that promote impairments in insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. Redox control of metabolic function is a dynamic process with reversible pro- and anti-free radical processes. Labile iron is necessary for the catalysis of superoxide anion, hydrogen peroxide, and the generation of the damaging hydroxyl radical. Acute hypoxia and cellular damage in cardiovascular tissue liberate larger amounts of cytosolic and extracellular iron that is poorly liganded; thus, large increases in the generation of oxygen free radicals are possible, causing tissue damage. The understanding of iron and the imbalance of redox homeostasis within the vasculature is integral in hypertension and progression of metabolic dysregulation that contributes to insulin resistance, endothelial dysfunction, and cardiovascular and kidney disease.”
This 2012 review by two of the authors of the paper described directly above noted, “Excess visceral adiposity contributes to inappropriate activation of the renin-angiotensin-aldosterone system despite a state of volume expansion and of salt retention that contributes to subclinical elevations of pro-oxidant mechanisms. These adverse effects are mediated by excess generation of reactive oxygen species (ROS) and diminished antioxidant defense mechanisms. Excess tissue (i.e., skeletal muscle, liver, heart) free oxygen radicals contribute to impairments in the insulin-dependent metabolic signaling pathways that regulate glucose utilization/disposal and systemic insulin sensitivity. The generation of ROS is required for normal cell signaling and physiological responses. It is a loss of redox homeostasis that results in a proinflammatory/profibrotic milieu that promotes impairments in insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. These maladaptive processes are increasingly recognized as important in the progression of hypertension in the cardiorenal metabolic phenotype. There is increasing evidence to support a critical role for Ang II signaling through the AT(1)R and aldosterone actions through the MR in conjunction with an altered redox-mediating impaired endothelial, cardiac and renal function in this metabolic phenotype. There are emerging clinical data that indicate that therapies that target the renin angiotensin-aldosterone system (RAAS) also attenuate oxidative stress, and improve endothelial, cardiac and renal functions, which collectively contribute to reductions in hypertension.
This 2006 published paper was based on research done in Spain. The authors noted that, “High levels of the acute phase reactants C-reactive protein (CRP) and ferritin have been reported to correlate with various components of MS (metabolic syndrome).” Serum markers and anthropometric measures were collected from 598 obese or overweight patients. “CRP levels were higher among patients with central obesity than in those without (5.8 vs 3.9 mg/l; P=0.003), and higher among those with fasting plasma glucose concentrations >or=110 mg/dl than in those with lower concentrations (7.4 vs 4.1 mg/l; P=0.01). Serum ferritin levels were higher among patients with triglyceride concentrations >or=150 mg/dl than in those with lower levels (76.8 vs 40.1 ng/ml; P<0.001), and higher among those with fasting plasma glucose concentrations >or=110 mg/dl than in those with lower concentrations (75.7 vs 41.7 ng/ml; P=0.005). The number of MS criteria that were satisfied increased with CRP and ferritin levels. Patients with insulin resistance also had higher CRP and ferritin levels than those without, 7.3 vs 4.3 mg/l for CRP (P=0.032) and 124.5 vs 80.1 ng/ml for ferritin (P<0.001).” The authors concluded, “MS and insulin resistance are associated with elevated serum CRP and ferritin. Evaluation of subclinical chronic inflammation in patients with MS and/or insulin resistance by determination of these markers might aid in their evaluation as candidates for aggressive intervention against cardiovascular risk factors.” [Health-e-Iron note: Table 2 from this study is below]
The researchers of this 2012 published research undertaken in Korea “we carried out a prospective study to evaluate the longitudinal effects of baseline serum ferritin levels on the development of MetS. RESEARCH DESIGN AND METHODS A MetS-free cohort of 18,022 healthy Korean men, who had participated in a medical health checkup program in 2005, was followed until 2010. MetS was defined according to the joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention. Cox proportional hazards models were performed. RESULTS During 45,919.3 person-years of follow-up, 2,127 incident cases of MetS developed between 2006 and 2010. After adjusting for multiple covariates, the hazard ratios (95% CI) for incident MetS comparing the second quintile to the fifth quintile of serum ferritin levels versus the first quintile were 1.19 (0.98-1.45), 1.17 (0.96-1.43), 1.36 (1.12-1.65), and 1.66 (1.38-2.01), respectively (P for trend <0.001). These associations were apparent in the clinically relevant subgroup analyses. CONCLUSIONS Elevated serum ferritin levels were independently associated with future development of MetS during the 5-year follow-up period.”
The purpose of this 2012 reported study from Korea study was “to investigate the relationship between serum ferritin levels and metabolic risk factors in nonobese Korean young adults.” “We analysed the fourth annual Korea National Health and Nutrition Examination Survey (KNHANES) in young adults (aged 19-39 years), conducted between 2007 and 2008. A total of 1542 nonobese [body mass index (BMI) <25 kg/m(2) ] young adults (684 men and 858 women) were enrolled. Using blood pressure and levels of serum triglycerides, plasma glucose and high-density lipoprotein (HDL) cholesterol, the Asian criteria for abdominal obesity (Waist circumference ≥90 cm in men or ≥80 cm in women) was used to identify individuals with metabolic syndrome.” …”The prevalence of metabolic syndrome was 4·1% for men and 2·7% for women. High fasting glucose and the prevalence of metabolic syndrome increased progressively across three different tertiles of ferritin levels in men. However, high ferritin levels were associated with high triglycerides, low HDL cholesterol and metabolic syndrome in women. After adjustment for age, smoking, alcohol consumption, BMI and ALT levels, low HDL cholesterol (OR 1·66, 95% confidence interval (CI) 1·16-2·36) and the presence of metabolic syndrome (OR 3·87, 95% CI 1·34-11·2) were independently associated with high serum ferritin levels in Korean nonobese young women.” The researchers concluded, “Our results suggest that elevated serum ferritin levels may be employed as a marker of metabolic syndrome in nonobese young adult women.”
This research team investigator 52 atherosclerotic carotid tissue samples and found that highly expressed transferrin receptors (iron import markers) in macrophages were significantly associated with development and severity of human carotid plaques, smoking, and patient’s symptoms. The researchers suggested that, “… pathologic macrophage iron metabolism may contribute to vulnerability of human atheroma, established risk factors, and their clinical symptoms.” [Health-e-Iron note: below Figure 3 from this paper demonstrates TfR1 and ferritin in macrophages in relationship to human carotid atherosclerotic plaques]
Figure 3.“Both TfR1 and ferritin in macrophages were significantly related to development of human carotid atherosclerotic plaques. (A–C) Localization of TfR1 expression in type 1 (A), type 2 (B), and type 3 (C) lesions. (D–F) Quantitative immunohistochemical analysis of TfR1 (D), ferritin (E), and CD68 (F) showed that compared to type 1 plaques (n ¼ 8), type 2 (n ¼ 9), and type 3 (n ¼ 19) plaques contain higher levels of TfR1, ferritin, and macrophages. *P , 0.05, and **P , 0.01 versus type 1 plaques (Bars¼100 lm)..”
[Health-e-Iron note: Similar to the above article relating to iron import markers, this article and the below images describe and depict increased GGT activity in atherosclerotic plaque. GGT activity has been shown to be integral in the formation of iron-catalyzed reactive oxygen species and lipid peroxidation.] “During the last decade, growing evidence has shown that serum gamma-glutamyl transpeptidase (GGT) is an independent prognostic marker for cardiac death and reinfarction, both in unselected populations and in patients with coronary artery disease. Clinical and epidemiological evidence indicates that the prognostic value of GGT is largely independent of other risk factors for cardiovascular disease and alcohol consumption. The catalytic activity of GGT, which is present on the surface of cell membranes and in serum, is responsible for the extracellular catabolism of the antioxidant glutathione. Cysteinyl glycine deriving from the hydrolysis of glutathione performed by GGT has been found to trigger iron-dependent production of reactive oxygen species as well as low-density lipoprotein oxidation in vitro. The localization of GGT within the coronary plaque (Figure) provides a pathological basis for the hypothesis of a direct participation of GGT in low-density lipoprotein oxidation within the plaque and in atherogenesis and coronary artery disease progression.
Histochemical and immunohistochemical demonstration of GGT enzyme activity within a frozen section of coronary atheroma from endoarteriectomy in vivo. … A strong GGT activity (the red stain) is selectively present in correspondence of the core of the atheroma, while the fibrous cap stains negative (A, magnification 20). The identification of the enzyme was confirmed immunohistochemically using a polyclonal antibody directed against the heavy chain of human GGT, which marked the same part of the atheroma (B and C, magnification 40 and 10, respectively). The homogeneous immunostaining of oxidized lipid-containing foam cells by the antibody is evident at higher magnification (B). For the sake of confirming the localization of GGT activity, another section of the same specimen was immunostained with an antibody directed against CD 68 cells (ie, macrophages), selectively identifying foam cells (D and E, magnification 10 and 40, respectively).
As in the study directly above, in 2007 this group of Italian investigators studied 38 atherosclerotic lesions. The researchers found serum ferritin was directly related to plaque. They also observed a significant relation between a catalytic form of iron markers of oxidation. The research conclusion stated, “These data suggest a role for catalytic iron in atherosclerotic plaque oxidation and in the severity of atherosclerosis, which appears indeed associated with plaque oxidant burden.”
This is a comprehensive review of the scientific literature on the topic of iron, oxidative stress and degenerative diseases. The author concluded: “Overall we argue, by synthesizing 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.” [Health-e-Iron note: Figures 5 and 6 from this article appear below]
The purpose of this 2009 study was “… to examine the association of ferritin and transferrin saturation with PAD.” In this large nationally representative sample of men and postmenopausal women participating in the 1999-2002 National Health and Nutrition Examination Survey (NHANES), the investigators determined,”The multivariable adjusted odds ratios… for PAD associated with a two-fold increase in serum ferritin and transferrin saturation were 1.18 … and 1.45 …, respectively, for men and 1.04… and 1.55 …, respectively, for women.” The researchers concluded, “…we found a modest association of ferritin and transferrin saturation with peripheral arterial disease, particularly among those with high cholesterol levels.” [Health-e-Iron note: Table 2 from this study appears below]
In 2011 study two Danish populations totaling 45,159 individuals, subjects with transferrin saturation equal to or above 50% were compared to subject with lower transferrin saturation. “Multifactorially adjusted hazard ratios for total mortality for TS≥50% vs <50% were 1.4 (95% CI 1.2-1.6; P<0.001) overall, 1.3 (1.1-1.6; P=0.003) in men, and 1.5 (1.1-2.0; P=0.005) in women.Results were similar if the 2 studies were considered separately. A stepwise increased risk of total mortality was observed for stepwise increasing levels of TS (log-rank P<0.0001), with the highest risk conferred by TS≥80% vs TS<20% with a hazard ratio of 2.2 (1.4-3.3; P<0.001). The population-attributable risk for total mortality in the combined studies in individuals with TS≥50% vs <50% was 0.8%. In metaanalysis, the odds ratio for total mortality for TS≥50% vs <50% was 1.3 (1.2-1.5; P<0.001) under the fixed-effects model.” The researchers concluded, “Individuals in the general population with TS≥50% vs <50% have an increased risk of premature death.” [Health-e-Iron note: Figures 2 & 3 from the study above appear below]
In this 2012 Korean study 752 consecutive patients with acute ischaemic stroke within 24 hours after a vascular event were enrolled. “After adjustment for confounding variables, multivariate analysis showed that a high ferritin level remained an independent predictor of HT (hemorrhagic transformation) in the patients with acute ischaemic stroke (P < 0.001).” The researchers concluded, “This study suggests that a high ferritin level is an important predictor of (HT) parenchymal hematoma, and symptomatic hematoma in patients with acute ischaemic stroke.Lowering the ferritin level with iron-modifying agents or using free radical scavengers could be helpful to prevent HT in ischaemic stroke.”
In a 2007 study in Germany, a total of 134 consecutive patients treated with intravenous tissue plasminogen activator were prospectively studied in four centers. “Serum ferritin levels were determined at baseline, 24 and 72 hours after treatment.” The investigators concluded, “Increased body iron stores are associated with poor outcome, symptomatic hemorrhagic transformation, and severe edema in patients treated with tissue plasminogen activator after ischemic stroke. These findings suggest that iron overload may offset the beneficial effect of thrombolytic therapies.” [Health-e-Iron note; Figure 2 & 3 and Table 2 from this paper appear below]
Figure 1. Distribution of mRS scores at day 90 by serum ferritin levels categorized in quartiles. The size of the color bars indicates the proportion of patients with a particular score for each ferritin quartile (Q). Ferritin levels for the first Q, 17 ng/mL; second Q, 18 to 79 ng/mL; third Q, 80 to 208 ng/mL, fourth Q 208 ng/mL.
Reference categories are: serum ferritin levels ≤79 ng/mL, no early signs of brain infarction, and vertebrobasilar arterial territory. Age, time from onset of treatment, and baseline NIHSS are continuous. There were no patients with missing data.
Figure 2. Median values and interquartile range (bars) of serum ferritin concentrations at baseline and at 24 and 72 hours after intravenous t-PA bolus by outcome groups at day 90 ( [black diamond] = poor outcome; ● good outcome). Numbers indicate patients studied at each time.
In this 1998 Finnish study, Transferrin receptors (TfR) and ferritin assays were carried out for 99 men who had an acute myocardial infarction (AMI) during an average 6.4 years of follow-up and 98 control men. The researchers calculated the ration of transferrin receptors to ferritin following adjustment for the strongest AMI risk factors, indications of inflammation and alcohol intake. “…men in the lowest and second lowest thirds of the TfR/ferritin ratio had a 2.9-fold…and 2.0-fold…risk of AMI compared with men in the highest third (P=.010 for trend). “These data show an association between increased body iron stores and excess risk of AMI, confirming previous epidemiological findings.” [Health-e-Iron note: the chart from this study appears below]
In this 1994 Finnish study of an Icelandic population, “a randomly selected group (n = 2,036), men and women aged 25 to 74 years, were examined between June and September 1983.” “Total Iron Binding Capacity (TIBC) was found to be a strong independent negative risk factor in men …, whereas ferritin…or other iron parameters had no significant predictive power.” And, the researchers concluded, “Each increase in TIBC of 1 mumol/L was associated with a 5.1% decrease in the risk of myocardial infarction.” In this study, “higher iron binding capacity, which generally translates to decreased transferrin saturation, was a ‘strong negative risk factor’ for myocardial infarction.”
High iron stores and risk of ischemic stroke in persons with metabolic syndrome (39)
In this “letter to the editor,” the authors suggested that the role of elevated iron stores was not considered in the outcome of metabolic syndrome/ischemic stroke study reported in this journal. After citing several references, the authors concluding statement was, “Therefore, high iron stores might be considered as an adjunctive risk factor for the development of ischemic stroke in persons with metabolic syndrome.”
This 2005 review by researchers from the Cleveland Clinic Foundation, suggests that, in line with many epidemiological studies, “…recent proteomics and molecular biology studies have shown that ferritin levels in arteries are increased in diseased tissues, which further supports the link of ferritin to coronary artery disease and myocardial infarction.”
In this 2003 study a significant correlation was found between ferritin expression and diseased coronary arteries. The authors concluded, “Our results provide in situ proteomic evidence consistent with the ‘iron hypothesis,‘ which proposes an association between excessive iron storage and a high risk of coronary artery disease (CAD). However, it is also possible that the increased ferritin expression in diseased coronary arteries is a consequence, rather than a cause, of CAD.”[Health-e-Iron note: we believe substantial research published since the date of this report (2003) have refuted the investigator’s alternative interpretation of their finding. Figure 2 from this study appears below]
“Fig. 2. A: Western blot analysis of the ferritin light chain. The protein extracts used for 2-D gel analysis were analyzed using Western blot for ferritin and -actin expression. Normal coronary arteries are in lanes 1 to 7 (QW1 to QW7) and CAD coronary arteries are in lanes 8 to 17 (QW8 to QW17). CAD coronary arteries expressed high levels of ferritin compared with normal ones. B: significant association of increased expression of the ferritin light chain with CAD. The expression level of the ferritin light chain was calibrated by the corresponding -actin value from the same tissue. CAD coronary arteries expressed about 2-fold greater ferritin light chain than the normal ones (P = 0.01). C: mRNA expression of ferritin light chain in CAD (n 8) and normal (n = 7) coronary arteries. The vertical axis (y-axis) shows the mean fold change in ferritin light chain mRNA expression (mean ± SD). A repeated measures ANOVA F test yielded a P value of 0.013 on null hypothesis of no difference in gene expression between CAD and normal tissues, suggesting that CAD coronary arteries expressed less ferritin light chain mRNA than the normal ones.”
In this Turkish study CAD (coronary artery disease study) of 68 male patients with high cholesterol (HCL or hypercholesterolemia) and a control cohort of 52 individuals with normal cholesterol, who underwent coronary angiography, the researchers concluded that, “Our data suggest that increased iron stores are closely associated with a greater extent and severity of perfusion and functional abnormalities but not with the angiographic extent of CAD in patients with HCL. Enhanced iron-mediated oxidative stress and LDL peroxidation may contribute to the hypercholesterolemia-related endothelial dysfunction and cause further impairment of myocardial perfusion and wall motion.”
Iron status and its relationship with lipid peroxidation in patients with acute myocardial infarction (43)
The researchers in this 2001 study set out to “investigate iron status and its relationships with lipid peroxidation in patients with acute myocardial infarction (MI). Based on an analysis of the information gathered, the researchers concluded, “There was an association of higher iron status with increased lipid peroxidation in patients with myocardial infarction.”
This was a 2003-reported study undertaken in India. The researchers noted that, “The relation of ferritin status to risk of AMI in Indian men, along with other established major risk factors like serum total cholesterol, HDL cholesterol, LDL cholesterol, VLDL cholesterol and triglycerides has not been documented previously. The hypothesis that increased serum ferritin was related to increased chances of AMI along with the risk factors was tested.” This was a “case control study involving 145 men (100 cases and 45 healthy control subjects) in the age group of 30-70 years. Serum ferritin levels were estimated by using ELISA, and other risk factors by enzymatic methods.” “Increased serum ferritin levels significantly (p < 0.001) correlated with an increase of other risk factors in Indian male patients with AMI.” The researchers concluded, “Significant direct correlation between serum ferritin levels and risk of AMI was observed.”
This 1999 research was conducted through as “a nested, case-control study of 60 patients who had their first MI (myocardial infarction) and 112 age- and sex-matched control subjects embedded in the population-based cohort of the Rotterdam Study. The researchers determined that subjects with serum ferritin of 200 ng/mL, or greater, had an age and sex adjusted relative risk of 1.82 compared to that of those with lower serum ferritin. Risks in the highest third of the cohort were also significantly elevated for current and former smokers and those with high cholesterol. The researchers concluded, “In the presence of other risk factors, serum ferritin may adversely affect ischemic heart disease risk in the elderly.” [Health-e-Iron note: Figure 1 from the study above appears below]
This 2012-reported study is part of a 20-year investigation by the NIH, U.S. Department of Agriculture Food Surveys Research Group and others to measure health and nutrition in a low-income, inner-city Baltimore population. The stated objective of this study was to examine “the association of serum ferritin with CHD risk using the Framingham Heart Study’s 10-year risk algorithm.” “Ordinal logistic regression modelling was used to interpret risk. Proportional odds modelling assessed four divisions of ranked CHD risk (4, high; 3, increased; 2, slight; 1, minimal), separately by sex.” The subjects were “African-American and white participants (n 1823) from baseline of the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study, aged 30-64 years.” The results were: “For men, there was a 0·5 % increase in risk for every 10-unit rise in serum ferritin (pmol/l). Other significant predictors included increased BMI, white race, unemployment and C-reactive protein ≥9·5 mg/l. For women, there was a 5·1 % increase in risk per 10-unit rise in serum ferritin (pmol/l). Other significant predictors included increased BMI, lower education, unemployment and C-reactive protein ≥9·5 mg/l.” The investigators concluded, “Serum ferritin is a significant predictor of 10-year hard CHD risk for HANDLS study participants, a low-income, urban population. Serum ferritin, independent of elevated C-reactive protein, was associated with increased 10-year CHD risk for HANDLS participants…”
U.S. investigators analyzed data collected from the National Health and Nutrition Examination Survey 1999-2002 to examine the relation between elevated ferritin and Cardio Vascular (CVF) Fitness in relatively healthy young adult men aged 20 to 49 years. The investigators found evidence of a trend to decreased cardio vascular fitness in participants with ferritin above 100 ng/mL that became significant, and increasingly so, for each 50ng/mL ferritin increment to and above 300 ng/mL. The investigators concluded, “…elevated ferritin levels, even those much lower than what is normally considered to be elevated, were associated with a decreased likelihood of having high cardiovascular fitness in young adult men.”
In this 2002 study reported in Japan the investigators tested young healthy men and women for markers of oxidative stress. “We tested the hypothesis that oxidative stress is greater in men than in women.” Baseline markers of oxidative stress were higher in men than in women. “after a baseline measurement, a randomly selected group of study subjects received 300 mg of vitamin E and 600 mg of vitamin C daily for 4 weeks before a second measurement was taken.” “Chronic administration of antioxidant vitamins resulted in significant reduction in oxidative stress in men.” “Supplementation of antioxidant vitamins for 4 weeks in men produced a significant reduction in TBARS and 8-iso-PGF2alpha by 34% (P<0.01) and 48% (P<0.05), respectively (all markers of oxidative stress).” The investigators concluded, “…whole-body ROS production is higher in healthy young men than in premenopausal women under ambulatory conditions… ”
This study from the Cleveland Clinic was reported in 2000. The researchers set out to “determine whether particular semen characteristics in various clinical diagnoses of infertility are associated with high oxidative stress and whether any group of infertile men is more likely to have high seminal oxidative stress.” The researches noted that “reactive oxygen species (ROS) play an important role in sperm physiological functions, but elevated levels of ROS or oxidative stress are related to male infertility.” “Measurement of sperm concentration, motility, morphology, seminal ROS, and total antioxidant capacity (TAC) in patients seeking infertility treatment and controls. SETTING: Male infertility clinic of a tertiary care center. PATIENT(s): One hundred sixty-seven infertile patients and 19 controls.Intervention(s): None. MAIN OUTCOME MEASURE(s): Semen characteristics, seminal ROS, and TAC in samples from patients with various clinical diagnoses and controls. RESULT(s): Fifteen patients (9.0%) were Endtz positive and 152 (91.0%) Endtz negative. Sperm concentration, motility, and morphology were significantly reduced in all groups compared with the controls (P =.02), except in varicocele associated with infection group. Mean (+/-SD) ROS levels in patient groups ranged from 2.2 +/- 0.13 to 3.2 +/- 0.35, significantly higher than controls (1.3 +/- 0.3; P<.005). Patient groups had a significantly lower mean (+/-SD) TAC from 1014.75 +/- 79.22 to 1173.05 +/- 58.07 than controls (1653 +/- 115.28, P<.001), except in the vasectomy reversal group (1532.02 +/- 74.24). Sperm concentration was negatively correlated with ROS both overall and within all groups… ” The researchers concluded, “Irrespective of the clinical diagnosis and semen characteristics, the presence of seminal oxidative stress in infertile men suggests its role in the pathophysiology of infertility. Medical or surgical treatments for infertility in these men should include strategies to reduce oxidative stress.”
This was a study undertaken in Japan that was reported in 2012. The researchers, “investigated the relationship between dietary iron intake and mortality from cardiovascular disease (CVD) in a population-based sample of Japanese adults.Methods: The study cohort consisted of 58,615 healthy Japanese (23,083 men and 35,532 women), aged between 40 and 79 years, who had no history of stroke, coronary heart disease (CHD), or cancer at baseline.” “We documented 2690 (1343 men and 1347 women) deaths from CVD: 1227 (607 men and 620 women) deaths from total stroke, 651 from ischemic stroke (355 men and 296 women), 459 (196 men and 263 women) from hemorrhagic stroke, and 557 (311 men and 246 women) from CHD. Dietary intake of total iron was positively associated with mortality from total and ischemic stroke and total CVD in men. The multivariable hazard ratio for the highest versus the lowest quintile of total iron intake was 1.43 (95% CI, 1.02-2.00; P for trend = 0.009) for total stroke and 1.27 (1.01-1.58; 0.023) for total CVD in men. Dietary total iron intake was not associated with mortality from other endpoints in men, and was not associated with any endpoints in women.” The researchers concluded, “Dietary intake of total iron was positively associated with mortality from stroke and total CVD in Japanese men.”
In this 2012-reported study from the Czech Republic, the researchers noted, “Cardiovascular disease is a major cause of morbidity and mortality in young adults with end-stage renal disease (ESRD), but its basis is still not well understood. We therefore evaluated the determinants of atherosclerosis in children with ESRD. A total of 37 children with ESRD (with 31 who had undergone transplantation) were examined and compared to a control group comprising 22 healthy children. The common carotid intima-media thickness (CIMT) was measured by ultrasound as a marker of preclinical atherosclerosis. The association of CIMT with anthropometrical data, blood pressure, plasma lipid levels, and other biochemical parameters potentially related to cardiovascular disease was evaluated. Children with ESRD had significantly higher CIMT, blood pressure, and levels of lipoprotein (a), urea, creatinine, ferritin, homocysteine, and serum uric acid as well as significantly lower values of apolipoprotein A. The atherogenic index of plasma (log(triglycerides/HDL cholesterol)) was also higher in patients with ESRD; however, this difference reached only borderline significance. In addition, a negative correlation was found between CIMT and serum albumin and bilirubin in the ESRD group, and this correlation was independent of age and body mass index. In the control group, a significant positive correlation was observed between CIMT and ferritin levels. Factors other than traditional cardiovascular properties, such as the anti-oxidative capacity of circulating blood, may be of importance during the early stages of atherosclerosis in children with end-stage renal disease.