Hereditary Hemochromatosis and Risk of Ischemic Heart Disease

Hereditary hemochromatosis with homozygous C282Y HFE mutation: possible clinical model to assess effects of elevated reactive oxygen species on the development of cardiovascular disease

Hereditary hemochromatosis with the homozygous C282Y HFE mutation (HH-282H) is a genetic condition which causes iron overload (IO) and elevated reactive oxygen species (ROS) secondary to the IO. Interestingly, even after successful iron removal therapy, HH-282H subjects demonstrate chronically elevated ROS. Raised ROS are also associated with the development of multiple cardiovascular diseases and HH-282H subjects may be at risk to develop these complications. In this narrative review, we consider HH-282H subjects as a clinical model for assessing the contribution of elevated ROS to the development of cardiovascular diseases in subjects with fewer confounding clinical risk factors as compared to other disease conditions with high ROS. We identify HH-282H subjects as a potentially unique clinical model to assess the impact of chronically elevated ROS on the development of cardiovascular disease and to serve as a clinical model to detect effective interventions for anti-ROS therapy.

Non-Transferrin-Bound Iron in the Spotlight: Novel Mechanistic Insights into the Vasculotoxic and Atherosclerotic Effect of Iron

Significance: While atherosclerosis is an almost inevitable consequence of aging, food preferences, lack of exercise, and other aspects of the lifestyle in many countries, the identification of new risk factors is of increasing importance to tackle a disease, which has become a major health burden for billions of people. Iron has long been suspected to promote the development of atherosclerosis, but data have been conflicting, and the contribution of iron is still debated controversially. Recent Advances: Several experimental and clinical studies have been recently published about this longstanding controversial problem, highlighting the critical need to unravel the complexity behind this topic. Critical Issues: The aim of the current review is to provide an overview of the current knowledge about the proatherosclerotic impact of iron, and discuss the emerging role of non-transferrin-bound iron (NTBI) as driver of vasculotoxicity and atherosclerosis. Finally, I will provide detailed mechanistic insights on the cellular processes and molecular pathways underlying iron-exacerbated atherosclerosis. Overall, this review highlights a complex framework where NTBI acts at multiple levels in atherosclerosis by altering the serum and vascular microenvironment in a proatherogenic and proinflammatory manner, affecting the functionality and survival of vascular cells, promoting foam cell formation and inducing angiogenesis, calcification, and plaque destabilization. Future Directions: The use of additional iron markers (e.g., NTBI) may help adequately predict predisposition to cardiovascular disease. Clinical studies are needed in the aging population to address the atherogenic role of iron fluctuations within physiological limits and the therapeutic value of iron restriction approaches. Antioxid. Redox Signal. 35, 387-414.

Red Blood Cells and Hemoglobin in Human Atherosclerosis and Related Arterial Diseases

As the main particulate component of the circulating blood, RBCs play major roles in physiological hemodynamics and impact all arterial wall pathologies. RBCs are the main determinant of blood viscosity, defining the frictional forces exerted by the blood on the arterial wall. This function is used in phylogeny and ontogeny of the cardiovascular (CV) system, allowing the acquisition of vasomotricity adapted to local metabolic demands, and systemic arterial pressure after birth. In pathology, RBCs collide with the arterial wall, inducing both local retention of their membranous lipids and local hemolysis, releasing heme-Fe⁺⁺ with a high toxicity for arterial cells: endothelial and smooth muscle cells (SMCs) cardiomyocytes, neurons, etc. Specifically, overloading of cells by Fe⁺⁺ promotes cell death. This local hemolysis is an event associated with early and advanced stages of human atherosclerosis. Similarly, the permanent renewal of mural RBC clotting is the major support of oxidation in abdominal aortic aneurysm. In parallel, calcifications promote intramural hemorrhages, and hemorrhages promote an osteoblastic phenotypic shift of arterial wall cells. Different plasma or tissue systems are able, at least in part, to limit this injury by acting at the different levels of this system.

The role of hepcidin and iron homeostasis in atherosclerosis

Atherosclerotic cardiovascular disease is a major burden on global health and a leading cause of death worldwide. The pathophysiology of this chronic disease is complex, involving inflammation, lipoprotein oxidation and accumulation, plaque formation, and calcification. In 1981, Dr. Jerome Sullivan formulated the 'Iron Hypothesis', suggesting that higher levels of stored iron promote cardiovascular diseases, whereas iron deficiency may have an atheroprotective effect. This hypothesis has stimulated research focused on clarifying the role of iron in the development of atherosclerosis. However, preclinical and clinical studies have produced contradictory results and the observation that patients with hemochromatosis do not appear to have an increased risk of atherosclerosis seemed incongruous with Sullivan's initial hypothesis. The 'paradox' of systemic iron overload not being accompanied by an increased risk for atherosclerosis led to a refinement of the iron hypothesis focusing on intracellular macrophage iron. More recent in vitro and animal studies have elucidated the complex signaling pathways regulating iron, with a particular focus on hepcidin, the master regulator of body iron homeostasis. Bone morphogenetic protein (BMP) signaling is the major pathway that is required for induction of hepcidin expression in response to increasing levels of iron. Strong links between iron homeostasis, BMP signaling, inflammation and atherosclerosis have been established in both mechanistic and human studies. This review summarizes the current understanding of the role of iron homeostasis and hepcidin in the development of atherosclerosis and discusses the BMP-hepcidin-ferroportin axis as a novel therapeutic target for the treatment of cardiovascular disease.

The role of iron in the pathogenesis of atherosclerosis

Ferritin and increased iron stores first appeared on the list of cardiovascular risk factors more than 30 years ago and their causal role in the pathogenesis of atherosclerosis has been heavily discussed since the early 1990s. It seems that besides traditional factors such as hyperlipoproteinemia, hypertension, diabetes mellitus, obesity, physical inactivity, smoking and family history, high iron stores represent an additional parameter that could modify individual cardiovascular risk. The role of iron in the pathogenesis of atherosclerosis was originally primarily associated with its ability to catalyze the formation of highly reactive free oxygen radicals and the oxidation of atherogenic lipoproteins. Later, it became clear that the mechanism is more complex. Atherosclerosis is a chronic fibroproliferative inflammatory process and iron, through increased oxidation stress as well as directly, can control both native and adaptive immune responses. Within the arterial wall, iron affects all of the cell types that participate in the atherosclerotic process (monocytes/macrophages, endothelial cells, vascular smooth muscle cells and platelets). Most intracellular iron is bound in ferritin, whereas redox-active iron forms labile iron pool. Pro-inflammatory and anti-inflammatory macrophages within arterial plaque differ with regard to the amount of intracellular iron and most probably with regard to their labile iron pool. Yet, the relation between plasma ferritin and intracellular labile iron pool has not been fully clarified. Data from population studies document that the consumption of meat and lack of physical activity contribute to increased iron stores. Patients with hereditary hemochromatosis, despite extreme iron storage, do not show increased manifestation of atherosclerosis probably due to the low expression of hepcidin in macrophages.

Clinical outcomes of cryptogenic compared with non-cryptogenic cirrhosis: A retrospective cohort study

BACKGROUND AND AIM

The consequences of the association between the metabolic syndrome and cryptogenic cirrhosis are uncertain. We aimed to compare the differences in clinical outcomes between cryptogenic and non-cryptogenic cirrhosis.

METHODS

A retrospective cohort study was conducted in a large, single academic center, over a 5-year duration.

RESULTS

Complete data were available in 301 patients with cirrhosis (cryptogenic n = 94, non-cryptogenic n = 207). Compared with non-cryptogenic cirrhosis, patients with cryptogenic cirrhosis were older (mean age 66.4 ± 12.5 vs 60.7 ± 11.3 years, P < 0.0001), had more females (43.6% vs 26.6%, P = 0.003), had less disease severity (Child-Pugh C 8.5% vs 15.9%, P = 0.042), and had a higher prevalence of the metabolic syndrome (83% vs 51.2%, P < 0.0001). During the 5-year period, adults with cryptogenic Child-Pugh A cirrhosis had a longer total hospital admission duration compared with non-cryptogenic cirrhosis (median 7.0 vs 3.0 days, P = 0.035), but this was less evident in patients with more advanced disease. This difference was due to a longer duration of hospitalization for non-liver-related morbidity (median 14.0 days vs 8.0 days, P = 0.04), rather than liver-related morbidity (median 10.5 days vs 8.0 days, P = 0.34), in patients with cryptogenic compared with non-cryptogenic cirrhosis. Kaplan-Meier survival analysis showed no significant differences in survival between both types of cirrhosis for all grades of severity.

CONCLUSIONS

Cryptogenic cirrhosis is associated with a longer duration of hospitalization compared with non-cryptogenic cirrhosis at an early stage of the disease. This difference is due to a greater burden of non-liver-related complications in the former.

Metabolic alterations, HFE gene mutations and atherogenic lipoprotein modifications in patients with primary iron overload

HFE gene mutations contributed to a decrease of insulin secretion, an atherogenic LDL subfraction distribution and altered LDL and HDL particles in patients with iron overload. It remains to be determined whether these alterations contribute to cardiovascular risk.

The role of iron metabolism as a mediator of macrophage inflammation and lipid handling in atherosclerosis

Iron is an essential mineral needed for normal physiologic processes. While its function in oxygen transport and other important physiologic processes is well known, less is understood about its role in inflammatory diseases such as atherosclerosis. Existing paradigms suggest iron as a driver of atherosclerosis through its actions as a pro-oxidant capable of causing lipid oxidation and tissue damage. Recently we and others have identified hemoglobin (Hb) derived iron as an important factor in determining macrophage differentiation and function in areas of intraplaque hemorrhage within human atherosclerosis. Hb associated macrophages, M(Hb), are distinct from traditional macrophage foam cells because they do not contain large amounts of lipid or inflammatory cytokines, are characterized by high levels of expression of mannose receptor (CD206) and CD163 in addition to producing anti-inflammatory cytokines such as IL-10. Despite the well-known role of iron as an catalyst capable of producing lipid peroxidation through generation of reactive oxygen species (ROS) such as hydroxyl radical, we and others have shown that macrophages in areas of intraplaque hemorrhage demonstrate reduced intracellular iron and ROS which triggers production of anti-inflammatory cytokines as well as genes involved in cholesterol efflux. These data suggest that manipulation of macrophage iron itself may be a promising pharmacologic target for atherosclerosis prevention through its effects on macrophage inflammation and lipid metabolism. In this review we will summarize the current understanding of iron as it relates to plaque inflammation and discuss how further exploration of this subject may lead to new therapies for atherosclerosis.

Iron, oxidative stress, and redox signaling in the cardiovascular system

The redox state of the cell is predominantly dependent on an iron redox couple and is maintained within strict physiological limits. Iron is an essential metal for hemoglobin synthesis in erythrocytes, for oxidation-reduction reactions, and for cellular proliferation. The maintenance of stable iron concentrations requires the coordinated regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages, and from storage in hepatocytes. The absorption of dietary iron, which is present in heme or nonheme form, is carried out by mature villus enterocytes of the duodenum and proximal jejunum. Multiple physiological processes are involved in maintaining iron homeostasis. These include its storage at the intracellular and extracellular level. Control of iron balance in the whole organism requires communication between sites of uptake, utilization, and storage. Key protein transporters and the molecules that regulate their activities have been identified. In this field, ferritins and hepcidin are the major regulator proteins. A variety of transcription factors may be activated depending on the level of oxidative stress, leading to the expression of different genes. Major preclinical and clinical trials have shown advances in iron-chelation therapy for the treatment of iron-overload disease as well as cardiovascular and chronic inflammatory diseases.

Hereditary hemochromatosis, iron, hepcidin, and coronary heart disease

Mounting evidence suggests that a state of sustained iron depletion may exert a primary protective action against coronary heart disease. A persistent criticism of the iron hypothesis has been that atherosclerosis may not be a prominent feature of hereditary hemochromatosis. The essence of this criticism is that iron cannot be a significant factor in atherogenesis in those unaffected by inherited iron overload unless an increase in atherosclerosis is observed in hereditary hemochromatosis. However, the emerging details of the physiology of hepcidin, the key hormone in iron recycling, suggest a resolution of the apparent paradox of an important role for iron in atherogenesis in the possible absence of increased plaque burden in most types of hereditary hemochromatosis.

Meta-analyses of HFE variants in coronary heart disease

AIM

HFE gene variants can cause hereditary hemochromatosis (HH) that often comes along with an increased risk of coronary heart disease (CHD). The goal of our study is to assess the contribution of four HFE gene variants to the risk of CHD.

METHODS AND RESULTS

We conducted four meta-analyses of the studies examining the association between four HFE gene variants and the risk of CHD. A systematic search was conducted using MEDLINE, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI), Wanfang Chinese Periodical.

RESULTS

Meta-analyses showed that HFE rs1799945-G allele was associated with a 6% increased risk of CHD (P=0.02, odds ratio (OR)=1.06, 95% confidence interval (CI)=1.01-1.11). However, no association between the other three HFE gene variants (rs1800562, rs1800730, and rs9366637) and CHD risk was observed by the meta-analyses (all P values>0.05). In addition, the results of our case-control study indicated that rs1800562 and rs1800730 were monomorphic, and that rs1799945 and rs9366637 were not associated with CHD in Han Chinese.

CONCLUSIONS

Our meta-analysis suggested that a significant association existed between rs1799945 mutation and CHD, although this mutation was rare in Han Chinese.

Exploring the relationship between maternal iron status and offspring's blood pressure and adiposity: a Mendelian randomization study

Background

Iron deficiency is the most common micronutrient deficiency worldwide. Experimental animal studies suggest that mothers deficient in iron during pregnancy are more likely to have offspring who become obese with high blood pressure. C282Y mutation carriers are more likely to have higher iron stores.

Methods

We undertook an instrumental variable (IV) analysis, using maternal C282Y as an indicator for the mother’s iron status, to examine its association with offspring blood pressure (BP), waist circumference (WC), and body mass index (BMI), and compared the results to that of ordinary least squares (OLS) regression. Offspring of a sub-cohort of mothers from the UK Women’s Cohort Study (UKWCS) were recruited in 2009–2010 (n = 348, mean age = 41 years). Their blood pressure, height, and weight were measured at their local general medical practice, and they were asked to self-measure their waist circumference. About half were offspring of C282Y carriers. Maternal ferritin was used as a biomarker of maternal iron status.

Results

Maternal C282Y was strongly associated with maternal ferritin (mean difference per allele = 84 g/L, 95% confidence interval: 31–137, P = 0.002). Using IV analyses, maternal ferritin was not linked to offspring’s BP, BMI, or WC. The first stage F-statistic for the strength of the instrument was 10 (Kleibergen–Paap rk LM P = 0.009). Maternal ferritin was linked to offspring diastolic BP, WC, and BMI in univariable, but not in multivariable OLS analysis. There was no difference between the OLS and the IV models coefficients for any of the outcomes considered.

Conclusion

We found no association between maternal iron status and adult offspring’s BP and adiposity using both multivariable OLS and IV modeling. To our knowledge, this is the first study examining this relationship. Further exploration in larger studies that have genetic variation assessed in both mother and offspring should be considered.

Elevated transferrin saturation and risk of diabetes: three population-based studies

OBJECTIVE

We tested the hypothesis that elevated transferrin saturation is associated with an increased risk of any form of diabetes, as well as type 1 or type 2 diabetes separately.

RESEARCH DESIGN AND METHODS

We used two general population studies, The Copenhagen City Heart Study (CCHS, N = 9,121) and The Copenhagen General Population Study (CGPS, N = 24,195), as well as a 1:1 age- and sex-matched population-based case-control study with 6,129 patients with diabetes from the Steno Diabetes Centre and 6,129 control subjects, totaling 8,535 patients with diabetes and 37,039 control subjects.

RESULTS

In the combined studies, odds ratios in those with transferrin saturation ≥50% vs. <50% were 2.1 (95% CI 1.3-3.4; P = 0.003) for any form of diabetes; 2.6 (1.2-5.6; P = 0.01) for type 1 diabetes; and 1.7 (1.4-2.1; P = 0.001) for type 2 diabetes.

CONCLUSIONS

Elevated transferrin saturation confers a two- to threefold increased risk of developing any form of diabetes, as well as type 1 and type 2 diabetes separately.

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.

Urinary excretion of biomarkers of oxidatively damaged DNA and RNA in hereditary hemochromatosis

Oxidatively generated damage to nucleic acids is considered to play a significant role in carcinogenesis, and it has been shown that people with hereditary hemochromatosis are at increased risk of cancer. In this study we used a new refined liquid chromatography-tandem mass spectrometry method to measure the urinary excretion of oxidatively generated 8-oxo-7,8-dihydroguanine and related 2'-deoxyribonucleoside and ribonucleoside derivatives in hereditary hemochromatosis patients, and we investigated the effect of treatment on the levels of these modifications. The study was carried out as a classical case-control study of 21 newly diagnosed, never treated hereditary hemochromatosis patients and 21 matched controls. We found that at baseline the urinary excretion of the RNA oxidation product 8-oxo-7,8-dihydroguanosine (8-oxoGuo) was 2.5-fold increased in patients compared with controls, and after phlebotomy treatment the excretion of the RNA oxidation product 8-oxoGuo returned to control values and the excretion of the DNA product 8-oxo-7,8-dihydro-2'-deoxyguanosine was reduced by 30%. In patients with hereditary hemochromatosis oxidative stress on nucleic acids is an important feature of the iron overload seen in this disease. By this mechanism cellular damage resulting in end organ damage, typically seen in the liver of such patients, may be mediated.

HFE C282Y Homozygosity Is Associated With Lower Total and Low-Density Lipoprotein Cholesterol

Background— Previous studies have suggested a positive association of coronary heart disease risk and both serum ferritin concentrations and C282Y heterozygosity. Relationships between serum lipids, C282Y homozygosity, and serum ferritin have not been well established.

Methods and Results— The Hemochromatosis and Iron Overload Screening study screened 101 168 participants in primary care from 5 field centers in the United States and Canada with serum ferritin, transferrin saturation, and HFE genotyping for C282Y and H63D mutations. Serum lipids were measured in a subset of 176 C282Y homozygotes (63 male, 113 female whites) without a prior diagnosis of, family history, or treatment for hemochromatosis and a matched sample of participants with normal transferrin saturation and serum ferritin without C282Y or H63D mutations (wild-type, 123 male, 189 female whites). The proportion of subjects who reported using prescription cholesterol-lowering medications was ≈3 times higher in HFE wild-type subjects than C282Y homozygotes among men (22% versus 7%; P =0.02) and, in women, 2 times higher (16% versus 8%; P =0.07). After excluding subjects taking cholesterol medications, C282Y homozygotes had significantly lower mean total and low-density lipoprotein cholesterol concentrations than wild-type subjects, with larger genotypic differences for low-density lipoprotein in men (−0.62 mmol/L; 95% CI, −0.93 to −0.33) than in women (−0.28 mmol/L; 95%, CI −0.52 to −0.08).

Conclusions— Total mean serum cholesterol and low-density lipoprotein levels were lower in C282Y homozygotes than in HFE wild-type participants. Further studies are required to determine whether this is related to iron overload, HFE alleles, or other factors on C282Y-positive chromosome 6p haplotypes.

The epidemiology of haemochromatosis: a population-based study

BACKGROUND

The discovery of the HFE genotype has revolutionized the diagnosis of haemochromatosis, changing the associated mortality and morbidity.

AIM

To investigate the clinical significance of a diagnosis of haemochromatosis.

METHODS

In a cohort study, we identified 501 people with haemochromatosis and 4950 age- and gender-matched controls from the UK General Practice Research Database between 1987 and 2002.

RESULTS

The incidence of a diagnosis of haemochromatosis increased approximately 2-fold over the study period and was associated with a 2.2-fold increase in mortality [hazard ratio, 95% confidence interval (95% CI), 1.6-3.0]. There was no increase in extra hepatic malignancy, but an absolute risk excess of liver cancer of 0.89% per year. Diabetes, impotence, osteoarthritis and crystal arthritis were associated with haemochromatosis with odds ratios of 5.4 (95% CI, 4.1-7.0), 2.7(95% CI, 1.8-4.0), 1.9(95% CI, 1.5-2.4) and 2.1(95% CI, 1.4-3.1) respectively.

CONCLUSION

Increasing numbers of people are being diagnosed with haemochromatosis, and the mortality associated with this disease remains high. However, people are living with considerably lower levels of morbidity than previously reported. This encouragingly suggests earlier diagnoses are being made, prior to the development of complications.

Mutations in the HFE Gene and Cardiovascular Disease Risk

Background— Whether mutations in the hemochromatosis (HFE) gene increase cardiovascular disease risk is still undetermined. The main reason is the low frequency of the mutations, in particular of the compound C282Y/H63D genotype. We combined the data of 11 observational studies for an individual patient data meta-analysis.

Methods and Results— Individual patient data were obtained from published as well as unpublished studies that had information available on the C282Y mutation as well as the H63D mutation in relation to coronary heart disease risk. Individual records were provided on each of the 53 880 participants in 11 studies. In total, 10 541 patients with coronary events were documented, of whom 5724 had an acute myocardial infarction. The crude and adjusted association between HFE genotypes and coronary events was examined by logistic regression analysis. We explored potential effect modification of the association between traditional cardiovascular risk factors and coronary events by HFE genotypes. After full adjustment, the odds ratio for coronary heart disease was 1.12 (95% CI, 0.92 to 1.37) for subjects with the compound heterozygous (C282Y/H63D) genotype relative to those with the wild-type/wild-type genotype. The odds ratios for C282Y/C282Y, C282Y/wild-type, H63D/H63D, and H63D/wild-type were 0.78 (95% CI, 0.49 to 1.26), 0.98 (95% CI, 0.90 to 1.07), 1.16 (95% CI, 0.97 to 1.38), and 1.07 (95% CI, 1.00 to 1.14), respectively. There was no evidence for effect modification.

Conclusions— The results of this large individual patient data meta-analysis do not support the view that HFE gene mutations are associated with an increased risk of coronary heart disease or acute myocardial infarction.

Sudden cardiac death in infiltrative cardiomyopathies: sarcoidosis, scleroderma, amyloidosis, hemachromatosis

Sarcoidosis, scleroderma, amyloidosis, and hemachromatosis are systemic infiltrative disorders that commonly affect the heart. Owing to their potential for diffuse organ involvement, these diseases may present with myriad clinical manifestations. Conduction system abnormalities are common, and each of these disorders has been associated with sudden cardiac death. In this review, we summarize the epidemiology, clinical features, diagnosis, and treatment of each of these entities. We place special emphasis on existing literature as it pertains to risk stratification and therapy aimed at the prevention of sudden cardiac death in these infiltrative cardiomyopathies.

HFE C282Y homozygotes have reduced low-density lipoprotein cholesterol: the Atherosclerosis Risk in Communities (ARIC) Study

Recent studies have raised questions about the long-term health risks for individuals with mutations in the HFE gene, although previous studies may have been plagued by selection bias or lack of population-based comparison groups. We examined cardiovascular disease risk factors and iron and liver biomarkers, as well as morbidity and mortality associated with the C282Y and H63D variants of HFE in the Atherosclerosis Risk in Communities (ARIC) study, which is a population-based cohort of nearly 16,000 U.S. white and black men and women who were 45-64 years old at baseline. Subjects were followed for an average of 15 years for death, incident coronary heart disease, stroke, and heart failure, and an average of 8 years for incident diabetes. The prevalence of C282Y homozygosity was 0.42% (45/10,800) in whites, which is similar to other North American population-based studies. C282Y homozygotes had significantly lower mean low-density lipoprotein (LDL) cholesterol and fibrinogen as well as higher mean levels of iron (ferritin, transferrin saturation) and liver biomarkers (alanine aminotransferase, Hepascore) compared with HFE wild-type subjects. Rates of all-cause mortality, cardiovascular disease, and diabetes were similar across HFE genotypes. These prospective, population-based data indicate higher serum iron indices and possible mild liver dysfunction or disease in some C282Y homozygotes, but they provide little evidence that HFE C282Y or H63D mutations are related to all-cause mortality, cardiovascular disease, or diabetes. Reduced LDL in C282Y homozygotes may be because of effects of excess iron on cholesterol metabolism and lipoprotein formation in the liver.

Iron and thrombosis

Although essential for cell physiology, an increase or depletion of body iron has harmful effects on health. Apart from iron deficiency anemia and iron overload-related organ tissue damage, there are increasing evidences that body iron status is implicated in atherosclerotic cardiovascular diseases. The hypothesis formulated in 1981 that iron depletion may protect against cardiovascular events is intriguing and has generated a significant debate in the last two decades. Indeed, to study this phenomenon, several investigators have tried to design appropriate experimental and clinical studies and to identify useful biochemical and genetic markers of iron status. The results of the literature on the effect of iron deficiency and overload on vascular health are critically reviewed in this study from a pathogenic and clinical point of view.

Hereditary hemochromatosis genotypes and risk of ischemic stroke

OBJECTIVE

We tested the hypothesis that the HFE genotypes H63D/H63D, H63D/wild type, C282Y/H63D, C282Y/C282Y, and C282Y/wild type are risk factors for symptomatic carotid atherosclerosis, ischemic cerebrovascular disease (ICVD), and ischemic stroke.

METHODS

We performed an age- and gender-matched case-control study of 701 cases with symptomatic carotid atherosclerosis vs 2,777 controls, and a prospective study of 9,178 individuals from the Danish general population followed for 24 years, during which 504 developed ICVD, of whom 393 had ischemic stroke.

RESULTS

Genotype was not consistently associated with symptomatic carotid atherosclerosis. The cumulative incidences of ICVD and ischemic stroke by age were increased for H63D/H63D vs wild type/wild type (log-rank: p = 0.003 and p < 0.001). H63D/H63D vs wild type/wild type had an age- and multifactorially adjusted hazard ratio of 2.0 (95% CI: 1.2 to 3.2; p = 0.007) and 2.1 (1.3 to 3.5; p = 0.004) for ICVD and of 2.4 (1.4 to 4.0; p = 0.001) and 2.8 (1.7 to 4.6; p < 0.001) for ischemic stroke; these remained significant after correction for multiple comparisons. Other hereditary hemochromatosis genotypes were not associated with ICVD or ischemic stroke.

CONCLUSIONS

Hereditary hemochromatosis H63D homozygosity predicts a two- to threefold risk of ICVD and ischemic stroke.

HFE gene mutations and oxidative stress influence serum ferritin, associated with vascular damage, in hemodialysis patients

BACKGROUND/AIMS

Hyperferritinemia has been associated with cardiovascular mortality in hemodialysis patients. The aim of this study was to evaluate whether serum ferritin was affected by iron and oxidative status and by genetic factors (HFE mutations and the Ala9Val MnSOD polymorphism), and to assess the association between ferritin and cardiovascular damage evaluated by ecocolor-Doppler.

METHODS

63 hemodialysis patients were tested for HFE and MnSOD genotype by restriction analysis and oxidative status; vascular damage was assessed by measuring intima-media thickness, and by detecting plaques at carotid and femoral arteries.

RESULTS

Ferritin was correlated with transferrin saturation (p = 0.003), decreased iron-specific serum antioxidant activity (p = 0.01), age (p = 0.03), and C282Y and H63D HFE mutations (p = 0.05), but not with the MnSOD polymorphism. Ferritin was associated with advanced vascular damage, as evaluated by the presence of plaques, both at carotid (p = 0.03) and femoral arteries (p = 0.001), the other risk factors being age and low albumin. Low iron-specific antioxidant activity was associated with carotid plaques (p = 0.03).

CONCLUSION

In hemodialysis patients, hyperferritinemia reflects a relative increase in iron availability and a decrease in iron-specific antioxidant activity, is favored by HFE mutations, and represents a risk factor for advanced cardiovascular damage.

HFE mutations and risk of coronary heart disease in middle-aged women

BACKGROUND

Although heterozygosity for the C282Y mutation in the HFE gene has been associated with an increased risk of cardiovascular events, epidemiological studies remain inconclusive. The aim of the present study was to obtain further evidence as to whether HFE mutations are associated with risk of coronary heart disease (CHD) in middle-aged women. We used data of a cohort of 15 236 Dutch middle-aged women to investigate whether C282Y carriers and H63D carriers are at increased risk of coronary heart disease compared with non-carriers.

MATERIALS AND METHODS

Women were included in the study between 1993 and 1997 and were followed until 1 January 2000 for cardiovascular events. HFE genotyping was performed on all 211 coronary heart disease cases and a randomly selected sample from the baseline cohort (n = 1526). A weighted Cox proportional hazards model was used to estimate crude, age-adjusted and multivariate adjusted hazard ratios for C282Y and H63D carriership in relation to coronary heart disease.

RESULTS

Compared with non-carriers, those that carried the C282Y allele were not at increased risk for CHD (HR = 1.25, 95% CI = 0.74-2.09). Neither did we find an association between the H63D mutation and CHD risk (HR = 0.73, 95% CI = 0.43-1.24).

CONCLUSIONS

Our results are in accordance with similar studies to date, for which we present a meta-analysis. HFE mutations appear not to affect the risk of coronary heart disease.