Is iron sufficiency a risk factor in ischemic heart disease?

Relationship Between Hemoglobin Concentration and Cardiovascular Disease Mortality in a 25-Year Follow-up Study of a Japanese General Population - NIPPON DATA90

BACKGROUND

Deviations of hemoglobin from normal levels may be a factor in cardiovascular disease (CVD) risk; however, conclusive evidence is lacking. In addition, preclinical conditions may influence hemoglobin concentrations, but studies focusing on reverse causation are limited. Thus, we examined the relationship between hemoglobin concentrations and CVD mortality risk, considering reverse causation.

METHODS AND RESULTS

In a prospective cohort representative of the general Japanese population (1990-2015), we studied 7,217 individuals (mean age 52.3 years; 4,219 women) without clinical CVD at baseline. Participants were categorized into sex-specific hemoglobin quintiles (Q1-Q5) and data were analyzed using the Cox proportional hazards model adjusted for possible confounders. During a 25-year follow-up, 272 men and 334 women died from CVD. Adjusted hazard ratios for CVD mortality across sex-specific quintiles, using Q3 as the reference, were significantly higher for Q1 (1.40; 95% confidence interval [CI] 1.08-1.82) and Q5 (1.49; 95% CI 1.14-1.96), and remained significant after excluding deaths within the first 5 years of follow-up to consider reverse causation (1.35 [95% CI 1.02-1.79] and 1.45 [95% CI 1.09-1.94], respectively). A similar U-shaped association was seen between transferrin saturation levels and CVD mortality, but after excluding deaths within the first 5 years the association was significant only for Q1.

CONCLUSIONS

Low and high hemoglobin concentrations were associated with an increased risk of CVD mortality.

Nrf2 Activator PB125® as a Potential Therapeutic Agent against COVID-19

Nrf2 is a transcription factor that regulates cellular redox balance and the expression of a wide array of genes involved in immunity and inflammation, including antiviral actions. Nrf2 activity declines with age, making the elderly more susceptible to oxidative stress-mediated diseases, which include type 2 diabetes, chronic inflammation, and viral infections. Published evidence suggests that Nrf2 activity may regulate important mechanisms affecting viral susceptibility and replication. We examined gene expression levels by GeneChip microarray and by RNA-seq assays. We found that the potent Nrf2-activating composition PB125® downregulates ACE2 and TMPRSS2 mRNA expression in human liver-derived HepG2 cells. ACE2 is a surface receptor and TMPRSS2 activates the spike protein for SARS-CoV-2 entry into host cells. Furthermore, in endotoxin-stimulated primary human pulmonary artery endothelial cells, we report the marked downregulation by PB125 of 36 genes encoding cytokines. These include IL-1-beta, IL-6, TNF-α, the cell adhesion molecules ICAM-1, VCAM-1, and E-selectin, and a group of IFN-γ-induced genes. Many of these cytokines have been specifically identified in the "cytokine storm" observed in fatal cases of COVID-19, suggesting that Nrf2 activation may significantly decrease the intensity of the storm.

Nrf2 Activator PB125® as a Potential Therapeutic Agent Against COVID-19

Nrf2 is a transcription factor that regulates cellular redox balance and the expression of a wide array of genes involved in immunity and inflammation, including antiviral actions. Nrf2 activity declines with age, making the elderly more susceptible to oxidative stress-mediated diseases, which include type 2 diabetes, chronic inflammation, and viral infections. Published evidence suggests that Nrf2 activity may regulate important mechanisms affecting viral susceptibility and replication. We examined gene expression levels by GeneChip microarray and by RNA-seq assays. We found that the potent Nrf2 activating composition PB125® downregulates ACE2 and TMPRSS2 mRNA expression in human liver-derived HepG2 cells. ACE2 is a surface receptor and TMPRSS2 activates the spike protein for SARS-Cov-2 entry into host cells. Furthermore, in endotoxin-stimulated primary human pulmonary artery endothelial cells we report the marked downregulation by PB125 of 36 genes encoding cytokines. These include IL1-beta, IL6, TNF-α the cell adhesion molecules ICAM1, VCAM1, and E-selectin, and a group of IFN-γ-induced genes. Many of these cytokines have been specifically identified in the “cytokine storm” observed in fatal cases of COVID-19, suggesting that Nrf2 activation may significantly decrease the intensity of the storm.

Iron Profile and Glycaemic Control in Patients with Type 2 Diabetes Mellitus

Iron overload is increasingly being connected to insulin resistance in Type 2 Diabetes Mellitus (T2DM) patients. Free iron causes the assembly of reactive oxygen species that invariably steer the body’s homeostasis towards oxidative stress-mediated diabetic complications. This study aims to assess the serum iron, total iron binding capacity (TIBC), and percentage transferrin saturation (Tsat) of 150 subjects divided into three groups (I,II,III) of 50. Healthy individuals (controls) constituted Group I. Group II consisted of T2DM patients with optimal glycaemic control. T2DM patients with suboptimal glycaemic control formed group III. Mean serum free iron concentration was 105.34 ± 3.5, 107.33 ± 3.45, and 125.58 ± 3.45 μg/dL in Group I, Group II, and Group III, respectively. Mean serum TIBC concentration in Group I, Group II, and Group III was 311.39 ± 5.47, 309.63 ± 6.1, and 284.2 ± 3.18μg/dL, respectively. Mean serum transferrin saturation (%) in Group I, Group II, and Group III was 34.17 ± 1.21, 35.02 ± 1.2, and 44.39 ± 1.07, respectively. The difference between TIBC, mean serum free iron concentration, and transferrin saturation between Group I and Group III (for all, p values <0.001), as well as between Group II and Group III (p values 0.0012, 0.0015, and <0.0001, respectively) was statistically significant. The fasting plasma glucose values of Groups II and III were significantly higher than those of Group I, (p < 0.0001). Glycated haemoglobin (HbA1c) values were also shown to increase from Group I to II and then III, and the increase was highly significant (all p values <0.0001). Thus, decreased glycaemic control and an increase in the glycation of haemoglobin was the key to elevation in serum iron values and alterations in other parameters. However, a significant correlation was absent between serum iron and HbA1c (r = 0.05) and transferrin saturation (r = 0.0496) in Group III.

Iron dextran increases hepatic oxidative stress and alters expression of genes related to lipid metabolism contributing to hyperlipidaemia in murine model

The objective of this study was to investigate the effects of iron dextran on lipid metabolism and to determine the involvement of oxidative stress. Fischer rats were divided into two groups: the standard group (S), which was fed the AIN-93M diet, and the standard plus iron group (SI), which was fed the same diet but also received iron dextran injections. Serum cholesterol and triacylglycerol levels were higher in the SI group than in the S group. Iron dextran was associated with decreased mRNA levels of pparα, and its downstream gene cpt1a, which is involved in lipid oxidation. Iron dextran also increased mRNA levels of apoB-100, MTP, and L-FABP indicating alterations in lipid secretion. Carbonyl protein and TBARS were consistently higher in the liver of the iron-treated rats. Moreover, a significant positive correlation was found between oxidative stress products, lfabp expression, and iron stores. In addition, a negative correlation was found between pparα expression, TBARS, carbonyl protein, and iron stores. In conclusion, our results suggest that the increase observed in the transport of lipids in the bloodstream and the decreased fatty acid oxidation in rats, which was promoted by iron dextran, might be attributed to increased oxidative stress.

Epidemiological associations between iron and cardiovascular disease and diabetes

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

Association of low serum iron levels with low-grade inflammation and hyperadiponectinemia in community-living elderly women

AIM

There have been inconsistent reports regarding the relationship between the iron status and coronary vascular diseases (CVD). Recently, low serum iron levels have been shown to be associated with mortality from CVD in women.

METHODS

The relationships between the serum iron levels and traditional and nontraditional risk factors for CVD were examined in 202 community-living elderly Japanese women.

RESULTS

The women in the lowest iron tertile had higher high-sensitivity C-reactive protein (hsCRP) and tumor necrosis factor-α (TNF-α) levels than the women in the top iron tertile (p<0.01 or less for both). In addition, the women in the lowest tertile had higher serum levels of adiponectin and copper and ratios of serum copper to zinc and lower serum levels of albumin, hemoglobin and hematocrit. Furthermore, the women in the lowest tertile had higher creatinine levels and lower eGFR values, although there were no significant differences in the prevalence of chronic kidney disease between the three tertile groups. In a multiple regression analysis including the levels of hsCRP, TNF-α, adiponectin and serum creatinine and the ratio of serum copper to zinc as independent variables, the levels of hsCRP, TNF-α and adiponectin emerged as independent determinants of the serum iron level (R(2)= 0.106). In the model to which the hemoglobin level was added as an independent variable, the levels of hemoglobin, hsCRP and TNF-α emerged as independent determinants of the serum iron level (R(2)= 0.192).

CONCLUSIONS

The present study demonstrated that community-living elderly Japanese women with low serum iron levels have nontraditional risk factors for CVD, including low-grade inflammation and higher levels of serum adiponectin.

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.

Dietary factors related to higher plasma fibrinogen levels of Japanese-americans in hawaii compared with Japanese in Japan

OBJECTIVE

We investigated whether dietary factors explain higher plasma fibrinogen levels in Japanese emigrants living a Western lifestyle in Hawaii compared with Japanese in Japan.

METHODS AND RESULTS

Plasma fibrinogen and nutrient intakes were examined by standardized methods in men and women 40 to 59 years of age from a Japanese-American sample in Hawaii (100 men and 106 women) and 4 population samples in Japan (569 men and 567 women). Multiple linear regression models were used to examine the relationship between dietary factors and the plasma fibrinogen difference between Hawaii and Japan. Average plasma fibrinogen was significantly higher in Hawaii compared with Japan (P<0.001 in both genders). In multiple linear regression analyses with each dietary variable considered separately, body mass index reduced the plasma fibrinogen difference between Hawaii and Japan by 20.4%; iron intake (mg/1000 kcal) and estimated total sugar intake (%kcal) reduced this difference by 30.0% and 14.4%, respectively. In a model that included body mass index, iron, estimated total sugars, and caffeine (also age and gender), this difference was reduced by 61.3% (from 42.2 to 16.3 mg/dL).

CONCLUSIONS

Higher intake of iron, sugar, and caffeine, in addition to obesity, account largely for higher fibrinogen levels with Westernized lifestyle.

The relationship between trace elements and cardiac markers in acute coronary syndromes

Previous studies have demonstrated increased serum copper and iron levels and decreased selenium and zinc levels in patients with myocardial infarction. Furthermore, the prognostic value of the levels of trace elements in myocardial infarction has been stressed. We examined serum levels of Cu, Fe, Zn and Se, as well as glutathione peroxidase (GPx), a selenoenzyme with antioxidant properties, and C-reactive protein (CRP), a marker of inflammation, in acute coronary syndromes (ACS) regarding their relationship to cardiac troponins and creatine kinase-MB mass (CK-MBm), important prognostic markers. Serum trace elements, GPx activity and CRP were determined in 70 patients with ACS who were admitted within 12 h after the onset. Differences in these parameters were evaluated in three groups of patients divided according to the levels of cardiac markers: group III consisted of patients with high increases in cTnT, cTnI and CK-MBm (> or =0.9 ng/mL, > or =1.0 ng/mL, > or =30 ng/mL, respectively), patients with milder increases in these markers were included in groups II and I consisted of patients with values just above the upper reference limits. Serum Fe levels increased significantly in group II and even more prominently in group III compared to group I (p = 0.04, 0.002, respectively). There was no significant difference between groups II and III. The increase in serum Cu was significant in group III compared to both groups II and I (p = 0.04, 0.001, respectively). There was no significant difference between groups I and II regarding Cu and Zn. The decrease in serum Se and GPx levels was significant only between groups III and I (p = 0.004 for Se and p = 0.0001 for GPx). CRP levels showed a significant increase in group III compared to groups II and I (p = 0.03 and 0.001). CRP showed a significant positive and GPx a significant negative correlation to the cardiac markers cTnT, cTnI and CK-MBm. Cu was positively correlated to all cardiac markers, while the positive correlation between Fe and cardiac markers was significant only for cTnI. Both Zn and Se were negatively correlated to cTnT, and Se was also to cTnI. In conclusion, the increase in serum levels of Cu and Fe and the decrease in serum levels of Zn and Se in patients with higher levels of troponins and CK-MBm imply that trace element levels are related to the degree of myocardial damage and thus may play a role in the pathogenesis of ischemic heart disease. The strong correlations between cardiac markers and both CRP and GPx suggest that these parameters are promising prognostic factors in acute coronary syndromes.

New and emerging theories of cardiovascular disease: infection and elevated iron

Heart disease is the leading cause of death in both men and women in industrialized countries. Despite the tremendous gains made in decreasing the number of deaths due to cardiovascular disease, it still is health care's greatest challenge. Traditional risk factors account for only 50% of the incidence of cardiac disease. In fact, many individuals who develop heart disease have normal cholesterol and blood pressure levels. This suggests that other less well-studied risk factors may also play a role. The purpose of this report is to examine the role that recently suggested risk factors may play in the development of heart disease: coronary artery infection, specifically from Chlamydia pneumoniae, and elevated iron levels. Both initiate an inflammatory response, which might explain the elevated C-reactive protein levels frequently found in those who suffer from cardiac disease.

Is blood donation induced low iron status associated with favourable levels of OxLDL, s-ICAM-1, sVCAM-1 and vWF-antigen in healthy men

The potential effect of iron depletion by blood donation and its relevance to cardiovascular diseases are still under debate. Markers of vascular integrity are increasingly applied in investigations of atherothrombotic diseases. In this study, we investigated whether a lower iron status through blood donation was associated with markers of vascular integrity (circulating oxidised LDL, sICAM-1, sVCAM-1 and vWF-antigen) by comparing healthy male voluntary donors to non-donors, taking into account differences in baseline characteristics. Two fasting blood samples were collected within 1 week from 41 donors and 39 non-donors. The iron status was estimated by measuring the concentration of plasma iron, ferritin, haemoglobin and hematocrit. The markers of iron status were all significantly lower in donors compared to non-donors, especially for ferritin concentrations. However, the lower iron status by blood donation was not reflected in the concentrations of OxLDL, sICAM-1, sVCAM-1 and vWF-antigen in men after adjustment for BMI and ratio total/HDL cholesterol. In order to avoid possible selection-bias related to donorship, we have additionally investigated the difference in marker concentrations within the non-donors, comparing low- and high-ferritin concentrations. This analysis suggests that ferritin concentration is not associated with in vivo LDL oxidation.

Iron status in association with cardiovascular disease risk in 3 controlled feeding studies

BACKGROUND

The role of body iron stores in free radical-induced peroxidation and cardiovascular disease risk has been debated, but controlled feeding studies using measurements of non-transferrin-bound iron (NTBI) and LDL oxidation have not been conducted.

OBJECTIVE

We tested the hypothesis that NTBI and other measures of iron status do not affect oxidative susceptibility in healthy subjects with normal iron status.

DESIGN

Plasma samples were analyzed from 77 healthy men and women aged 20-65 y who participated in 3 controlled feeding studies in which the type and amount of dietary fat were controlled. Iron status and in vitro LDL oxidation were assessed at baseline and at the end of each feeding period (4-8 wk).

RESULTS

No significant relations were found between any measure of iron status (ferritin: 83 +/- 8.9 micro g/L; iron: 20.9 +/- 5.4 micro mol/L; TIBC: 74.4 +/- 11.0 micro mol/L; NTBI: 0.184 +/- 0.15 micro mol/L) and the in vitro measures of LDL oxidation (total dienes: 485 +/- 55 micro mol/mg LDL protein; lag time: 51.7 +/- 15.9 min; and rate of oxidation: 25.4 +/- 6.8 micro mol dienes.min(-1).g LDL protein(-1)). Equal-iron peanut butter-based diets were associated with higher plasma iron in men (22.4 +/- 3.8 micro mol/L) than was the olive oil diet (17.7 +/- 4.5 micro mol/L) (P = 0.02), but this slight elevation did not alter LDL oxidation.

CONCLUSIONS

Diet composition may affect plasma iron in men, but LDL oxidative susceptibility is unaffected by the subtle variation in iron status. Thus, the results do not support a relation between iron status and LDL oxidative susceptibility, a possible risk factor for cardiovascular disease.

Iron administration and clinical outcomes in hemodialysis patients

To evaluate the impact of parenteral iron administration on the survival and rate of hospitalization of US hemodialysis patients, a nonconcurrent cohort study of 10,169 hemodialysis patients in the United States in 1994 was conducted. The main outcome measures were patient survival and rate of hospitalization. After adjusting for 23 demographic and comorbidity characteristics among 5833 patients included in multivariable analysis, bills for <or=10 vials of iron over 6 mo showed no adverse effect on survival (adjusted relative risk [RR] = 0.93; 95% confidence interval [CI], 0.84 to 1.02; P = 0.14) when compared with none, but bills for >10 vials showed a statistically significant elevated rate of death (adjusted RR = 1.11; 95% CI, 1.00 to 1.24; P = 0.05). Bills for <or=10 vials of iron over 6 mo also showed no significant association with hospitalization (adjusted RR = 0.92; 95% CI, 0.83 to 1.03; P = 0.15), but bills for >10 vials showed statistically significant elevated risk (adjusted RR = 1.12; 95% CI, 1.01 to 1.25; P = 0.03). Prescribing iron in quantities of <or=10 vials over 6 mo had no association with an elevated risk of death or rate of hospitalization. More intensive dosing was associated with diminished survival and higher rates of hospitalization, even after extensive adjustment for baseline comorbidity. Although these potential risks may be offset by the known elevations in morbidity and mortality associated with anemia, these findings indicate that caution is warranted when prescribing >10 vials (1000 mg) of iron dextran over a period of 6 mo.

Impact of body iron status on myocardial perfusion, left ventricular function, and angiographic morphologic features in patients with hypercholesterolemia

BACKGROUND

Previous studies have shown that the effects of iron stores on atherogenesis through promotion of free radical formation and low-density lipoprotein (LDL) oxidation largely depend on the state of hypercholesterolemia (HCL) in animal models. A synergistic association of serum ferritin and LDL cholesterol with the risk of myocardial infarction has also been observed in humans.

METHODS

We sought to assess the relationship of serum iron parameters to myocardial perfusion and wall motion abnormalities and to the extent of angiographic coronary artery disease (CAD) in patients with HCL. Sixty-eight male patients (mean age 58 +/- 9 years) with hypercholesterolemia (LDL cholesterol >130 mg/dL) who had never been treated and 52 normocholesterolemic male subjects of similar age underwent coronary angiography and exercise technetium-99m sestamibi gated single-photon emission computed tomography imaging within 10 days.

RESULTS

Serum ferritin had a significant correlation with the perfusion index (r = 0.70, P <.001), the reversibility index (r = 0.68, P <.01), and the wall motion index (r = 0.54, P <.05), whereas a relatively weak correlation was observed between total iron binding capacity and perfusion index (inversely) (r = -0.59, P <.01) in patients with HCL. Iron parameters were not associated with either perfusion or wall motion indices in the normocholesterolemic group. Stepwise multiple regression analysis confirmed these results. Ferritin was a strong determinant of perfusion in patients with HCL only (beta =.55, P =.002). Iron parameters were not related to the angiographic extent of CAD as defined by angiographic vessel or extent score in either group.

CONCLUSIONS

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.

Adaptations to iron deficiency: cardiac functional responsiveness to norepinephrine, arterial remodeling, and the effect of beta-blockade on cardiac hypertrophy

BACKGROUND

Iron deficiency (ID) results in ventricular hypertrophy, believed to involve sympathetic stimulation. We hypothesized that with ID 1) intravenous norepinephrine would alter heart rate (HR) and contractility, 2) abdominal aorta would be larger and more distensible, and 3) the beta-blocker propanolol would reduce hypertrophy.

METHODS

1) 30 CD rats were fed an ID or replete diet for 1 week or 1 month. Norepinephrine was infused via jugular vein; pressure was monitored at carotid artery. Saline infusions were used as a control. The pressure trace was analyzed for HR, contractility, systolic and diastolic pressures. 2) Abdominal aorta catheters inflated the aorta, while digital microscopic images were recorded at stepwise pressures to measure arterial diameter and distensibility. 3) An additional 10 rats (5 ID, 5 control) were given a daily injection of propanolol or saline. After 1 month, the hearts were excised and weighed.

RESULTS

Enhanced contractility, but not HR, was associated with ID hypertrophic hearts. Systolic and diastolic blood pressures were consistent with an increase in arterial diameter associated with ID. Aortic diameter at 100 mmHg and distensibility were increased with ID. Propanolol was associated with an increase in heart to body mass ratio.

CONCLUSIONS

ID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine. Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content. The failure of propanolol to prevent hypertrophy suggests that ID hypertrophy is not mediated via beta-adrenergic neurotransmission.

Hemochromatosis gene variants in patients with cardiomyopathy

Iron depletion was suggested to be protective against the development of ischemic heart disease. Population studies have led to conflicting results, and such an association has not been addressed in patients with heart failure due to cardiomyopathy. We studied the distribution of hemochromatosis-related mutations in 319 patients with heart failure due to cardiomyopathy of different etiologies. The genotypic distribution showed a significantly higher prevalence of heterozygotes for the C282Y mutation in patients with ischemic cardiomyopathy than in patients with cardiomyopathy of nonischemic etiologies (p = 0.0036). The frequency of the D63 mutation was not significantly different between ischemic versus nonischemic groups. In multiple logistic regression models adjusted for age, sex, ethnicity, and different degrees of disease progression, there was a strong and significant association of the C282Y mutation with ischemic cardiomyopathy compared with the nonischemic group (odds ratio 6.64, 95% confidence interval 1.71 to 25.73, after adjustment). In our sample, genetic variation in the HFE gene was associated with ischemic cardiomyopathy. Such association merits further study regarding its value as a prognostic marker in patients with ischemic heart disease.

A prospective study of coronary heart disease and the hemochromatosis gene (HFE) C282Y mutation: the Atherosclerosis Risk in Communities (ARIC) study

Increased iron stores may play a role in the development of coronary heart disease (CHD) by increasing lipoprotein oxidation. Recently, mutations have been discovered in the gene (HFE) for hereditary hemochromatosis, an autosomal recessive condition of disordered iron metabolism, absorption, and storage. It is possible that people who carry HFE mutations have increased risk of CHD. We used a prospective case-cohort design (243 CHD cases and 535 non-cases) to determine whether the HFE C282Y mutation was associated with incident CHD in a population-based sample of middle-aged men and women. The frequencies of homozygosity and heterozygosity for the C282Y mutation in the ARIC study population were 0.2% (one homozygous person) and 6%, respectively. The C282Y mutation was associated with nonsignificantly increased risk of CHD (relative risk=1.60, 95% CI 0.9-2.9). After adjusting for other confounding risk factors (age, race, gender, ARIC community, smoking status, diabetes status, hypertension status, LDL cholesterol, HDL cholesterol, and triglycerides), the association became stronger (relative risk=2.70, 95% CI 1.2-6.1). However, a sensitivity analysis showed that this estimate of relative risk was somewhat unstable due to few subjects in some strata. Our prospective findings suggest that individuals carrying the HFE C282Y mutation may be at increased risk of CHD.

Level of dietary iron, not type of dietary fat, is hyperlipidemic in copper-deficient rats

OBJECTIVE

This study was conducted to determine whether high dietary iron will negate the protective effect of unsaturated fat against hyperlipidemia.

METHODS

Forty-eight weanling, male Sprague Dawley rats were randomly assigned to eight dietary groups differing in the levels of copper and iron and type of dietary fat (saturated or unsaturated). The diets were either deficient (0.6 microg Cu/g) or adequate (6.8 microg Cu/g) copper and either adequate (53 microg Fe/g) or high (506 microg Fe/g) iron. All diets contained starch as the sole source of dietary carbohydrate.

RESULTS

Regardless of the type of dietary fat, three copper-deficient rats fed the high levels of dietary iron died prematurely due to ruptured hearts. Surviving rats belonging to the copper deficiency and high-dietary iron regimen developed severe anemia, enlarged hearts and livers, and exhibited the highest levels of liver iron. These rats also developed hypercholesterolemia. Triglycerides were elevated by the consumption of high iron diets.

CONCLUSION

Data show that levels of dietary iron, not the type of dietary fat, are potential inducers of hypertriglyceridemia. Data also show that the combination of high iron intake and dietary copper deficiency is responsible for elevating blood cholesterol.

Does serum ferritin correlate with coronary angiography findings?

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSION

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

Relationship between serum ferritin and risk factors for ischaemic heart disease in 2235 Danes aged 30-60 years

OBJECTIVES

The aim was to examine the relationships between serum ferritin and risk factors for ischaemic heart disease (physical activity, body mass index, tobacco smoking, alcohol consumption, serum total cholesterol, serum triglycerides, serum high-density lipoprotein (HDL) cholesterol, systolic and diastolic blood pressures).

DESIGN

Epidemiological population survey performed at the Copenhagen County Centre for Prevention of Disease in 1982-84.

SUBJECTS

The participants were selected at random from the census register and comprised 2235 healthy Caucasian Danes, all non-blood-donors (1044 men and 1191 women), in cohorts of 30, 40, 50 and 60 years of age. The participants gave a detailed medical history and had a clinical examination including blood samples.

MAIN OUTCOME MEASURES

In both men and women, all risk factors displayed a significant increase with age. In men aged 40-60 years, significant positive associations were found between serum ferritin and the following risk factors: body mass index, alcohol intake, serum triglycerides, and systolic and diastolic blood pressures. There was a significant negative association between serum ferritin and tobacco smoking. There was no association between serum ferritin and physical activity, serum total cholesterol or serum HDL cholesterol. In women aged 40-60 years, significant positive associations were found between serum ferritin and the following risk factors: body mass index, alcohol intake and serum triglycerides. There was no association between serum ferritin and physical activity, tobacco smoking, serum total cholesterol, serum HDL cholesterol or blood pressure.

CONCLUSIONS

Associations were found between serum ferritin and some risk factors for ischaemic heart disease in men and women. The clinical significance of these findings remains to be clarified. One may hypothesize that the 'missing link' between serum ferritin and ischaemic heart disease in men is the relationship between serum ferritin, serum triglycerides and blood pressure.

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

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

Effect of hepatic iron on hypercholesterolemia and hypertriacylglycerolemia in copper-deficient fructose-fed rats

The purpose of this investigation was to establish whether plasma cholesterol and triacylglycerol(s) in copper deficiency can be increased or decreased by hepatic iron levels. Weanling male Sprague-Dawley rats were randomly divided into six dietary groups based on levels of dietary copper and iron. They were fed from weaning their respective diets for 6 wk. Forty percent of the copper-deficient rats fed a 15.7 mumol Fe/g diet died; 22% of those fed a diet containing 8.6 mumol Fe/g died; and there were no deaths in the 3.4 mumol Fe/g diet group. Rats belonging to the group fed the high-iron diet also exhibited the highest levels of liver iron, liver glutathione, and plasma cholesterol and triacylglycerol(s) compared with those fed either the adequate or low levels of dietary iron. There was a direct correlation (r = 0.82 and 0.77, respectively) between levels of cholesterol and triacylglycerol(s) in plasma and hepatic iron concentrations. These results provide strong evidence that points to a major involvement of iron in the lipemia of copper deficiency. These data may be important to those individuals who consume large quantities of fortified iron foods and supplement with iron but whose intake of copper is suboptimal.

Iron measures in coronary angiography patients

Excess iron has been postulated as a risk factor for coronary artery disease (CAD) because of its presence in atherosclerotic lesions, its ability to oxidize low density lipoprotein cholesterol (LDLc), and its promotion of oxygen reperfusion damage after an ischemic event. Whether iron, indirectly measured by its storage protein ferritin and its transport protein transferrin, is related to CAD was examined in a consecutive series of white male (n = 457) and female (n = 114) cardiac patients. Atherosclerosis measures were analyzed in patients grouped by tertiles of ferritin. A similar analysis was done with tertiles of transferrin. Contrary to expectations, men in the third tertile of ferritin had a smaller mean number of stenoses than men in the two lower tertiles (4.9 versus 5.6 and 5.9; P = 0.027); otherwise, there were no statistically significant differences in either number of lesions or extent of arterial narrowing based on tertiles of either measure. Separate multiple logistic regression models with age, fibrinogen, LDLc and triglycerides as covariates provided no evidence that ferritin (odds ratio = 0.88 with 95% C.I. = 0.72-1.07 for men and odds ratio = 0.79 with 95% C.I. = 0.54-1.16 for women) or transferrin (odds ratio = 0.60 with 95% C.I. = 0.31-1.16 for men and odds ratio = 1.33 with 95% C.I. 0.52-3.42 for women) were important correlates of the presence of atherosclerosis in this study.

Hepatic iron overload may contribute to hypertriglyceridemia and hypercholesterolemia in copper-deficient rats

The present study was conducted in order to determine whether hepatic iron retention in rats fed a copper-deficient diet containing fructose is associated with hypertriglyceridemia and hypercholesterolemia, and whether a reduction of iron intake will prevent elevation of blood triglycerides and cholesterol. Rats were fed from weaning either a copper-deficient (0.6 microgram Cu/g) or copper-adequate (6.0 micrograms Cu/g) diet for 4 weeks. Half the rats consumed either an adequate level of iron (50 micrograms Fe/g) or a low level (17 micrograms Fe/g). Reduction of iron intake reduced blood levels of both triglycerides and cholesterol in rats fed a copper-deficient diet containing fructose. In addition, hepatic lipid peroxidation was also decreased. The combination of high iron, low copper, and fructose may be responsible for increased levels of risk-factor metabolites associated with heart disease.

Serum iron level, coronary artery disease, and all-cause mortality in older men and women

The association between iron levels and coronary artery disease (CAD) mortality is controversial. Whereas most data show no association, some have raised the possibility of a causal role, while others have suggested a protective effect of iron on CAD. To address these possibilities, we examined the association between serum iron and CAD, cardiovascular disease, and all-cause mortality in a large cohort of 3,936 persons aged > or =71 years who completed an interview, had a serum iron determination, and survived at least 1 year after baseline. The median follow-up time was 4.4 years. Serum iron levels were categorized according to sex-specific quartiles. Relative risks (RR) and 95% confidence intervals (CI) were calculated from proportional-hazards regression models adjusted for age, race, education, creatinine, serum albumin, serum lipids, use of iron supplementation, smoking, use of alcohol, blood pressure, body mass index, and presence of chronic conditions. There was a gradual decrease in the RRs of CAD, cardiovascular disease, and all-cause mortality with increasing serum iron levels (all tests for trend, p <0.05). Men in the highest iron quartile were one fifth as likely to die of CAD as men in the lowest iron quartile (RR 0.22; 95% CI 0.11 to 0.48), and women in the highest quartile had half the risk of women in the lowest quartile (RR 0.48; 95% CI 0.27 to 0.87). When compared with the lowest quartile, risk of all-cause mortality was 38% lower in men in the highest iron quartile (RR 0.62; 95% CI 0.46 to 0.85) and 28% lower in women in the highest quartile (RR 0.72; 95% CI 0.53 to 0.96). Results of similar strength and magnitude were observed for cardiovascular disease mortality and in analyses that excluded the first 3 years of follow-up. In this large cohort of persons aged > or =71 years, there was consistent evidence of increasing risk of mortality at lower serum iron levels. In fact, lower serum iron levels were associated with an increased risk of CAD, cardiovascular disease, and all-cause mortality. The results are compatible with the possibility that in an older population, there is an inverse association between serum iron levels and risk of mortality.

Iron status and risk of cardiovascular disease

Free Iron, as well as other transition metals, can catalyze free radical formation. For this reason iron is tightly bound to transport and storage proteins to prevent their involvement in free radical formation. It has been hypothesized that increased iron intake or iron stores may promote atherogenesis by increasing free radical formation and oxidative stress. While a coherent, plausible hypothesis as to how transition metals, such as iron, might accelerate the progression of atherosclerosis has been generated from basic research, iron status, measured as dietary iron intake, serum iron, serum ferritin, and transferrin saturation, has been inconsistently associated with cardiovascular disease in human epidemiologic research. In addition, limited data suggest that iron overload states do not appear to be strongly associated with increased risk of atherosclerotic disease. One real limitation of the existing data is the lack of a generally agreed upon and logistically feasible means of assessing iron status in free living humans. Further research, including basic research and large-scale epidemiologic studies, is needed to fully assess the association between iron status and the risk of CVD and other adverse outcomes. At present the currently available data do not support radical changes in dietary recommendations or screening to detect high normal levels nor do they support the need for large-scale randomized trials of dietary restriction or phlebotomy as a means of lowering iron stores.

The iron hypothesis--does iron cause atherosclerosis?

Women experience only 30-50% of the coronary heart disease (CHD) incidence and mortality of age-matched men. Since oxidation of low-density lipoprotein (LDL) cholesterol is important in atherosclerosis, and oxidation is catalyzed by iron, it has been hypothesized that the lower iron stores of women reduce their risk of CHD through lessened lipid peroxide. The biochemistry of oxidation is well described in the literature and involves iron as a catalyst in the formation of powerful free radicals which subsequently modify LDL cholesterol. Chelating iron with desferrioxamine stops oxidation. Iron is present in atherosclerotic gruel and this gruel stimulates lipid peroxidation. Serum deficient in iron has minimal oxidative capacity which increases with iron repletion. At least seven epidemiologic studies have found a positive association between CHD and various indicators of body iron. Conversely 18 epidemiologic studies have found a negative or no association. While biochemically appealing, the iron hypothesis remains unproven.

Correlation of hematologic markers of inflammation and lung function: a comparison of asymptomatic smokers and nonsmokers

Increased inflammation of the peripheral airways has been implicated as a cause of pulmonary function impairment. However, little information is available on the correlation between subclinical decrements of pulmonary function and inflammation in asymptomatic individuals. A relationship between markers of inflammation and lung function may be useful in predicting the early onset of lung function impairment. The purpose of this study was to investigate the correlation of hematologic markers of inflammation and spirometry in asymptomatic smokers and nonsmokers. The specific objectives of this study were twofold. The first objective was to quantify and compare the spirometric measures of lung function in smokers and nonsmokers having similar demographic and lifestyle characteristics. The second objective was to define the correlation between these spirometric measurements and hematologic markers of inflammation (white blood cells, monocytes, basophils, PGE1, IgG, and IgE). Systemic blood samples and spirometric measurements were obtained from 61 age-matched (33 +/- 9 years) healthy, asymptomatic smokers and nonsmokers, with similar self reported lifestyles (i.e., food, alcohol, vitamin consumption and exercise). Both male and female smokers self reported a higher coffee consumption (P < 0.05) compared to nonsmokers. Male smokers self-reported a trend toward current blue-collar versus white-collar occupation when compared with the nonsmokers. Body weight (77.6 +/- 16.6 kg) did not differ between the smokers and nonsmokers. The male nonsmokers were taller than the male smokers (P < 0.05). All subjects were asymptomatic and had clinically normal spirometry. Compared to male nonsmokers, the male smokers had lower FEF25-75% and FEF75-45% values (P < 0.05). No additional spirometric measurements, including FEV1/FVC, FEV1 and FVC were significantly different. The female smokers did not differ from the female nonsmokers (P < 0.05) in any of the spirometric endpoints measured. Thirteen statistically significant (P < 0.05) correlations involving inflammatory (white blood cells, monocytes, basophils, and PGE1) or immunologic endpoints (IgE) and spirometric measurements were observed in female smokers, female nonsmokers and male nonsmokers. No statistically significant correlations involving immunologic or inflammatory endpoints were observed in the male smokers. A better mechanistic understanding of the observed relationship between elevated hematologic inflammatory endpoints and reduced lung function may provide valuable insight into the clinical significance of these correlations.

Coronary heart disease risk factors in older persons

In most Western nations, coronary heart disease (CHD) is the leading cause of death and one of the most important causes of physical disability in persons over 65 years of age. The importance of traditional CHD risk factors has been well documented in middle-aged populations, whereas their role in older populations is still under debate. This paper reviews the epidemiologic evidence from observational studies and randomized clinical trials that established risk factors for CHD predict level of risk of CHD, and identify high risk individuals among older men and women. Hypertension and cigarette smoking have been clearly associated with an increased risk of CHD events, and their modification has been proven to be highly effective in the primary and secondary prevention of CHD in older persons. For other highly prevalent risk factors, such as lipid abnormalities, obesity and physical inactivity, evidence of an independent association with CHD risk has been demonstrated by the majority of observational studies. However, definitive proof from controlled clinical trials of the beneficial effects of their modification is still lacking in the older population. The role of estrogen replacement therapy in the primary and secondary prevention of CHD in old women is still an open question. In evaluating the impact of these risk factors in older persons, elements such as comorbidity, frailty, and age-related changes in risk profile should also be taken into consideration. Given the complexity of the relationship between risk factors and multiple disease statuses, other important outcomes, such as osteoporosis, cancer, falls and physical disability, should be considered when evaluating the risks and benefits of risk factor modifications in older persons.

Iron and heart disease: the epidemiologic data

There has developed a general theory of chronic and degenerative disease causation--the Oxidative Stress Theory. This theory states that the production of tissue-damaging free radicals is an essential component in the pathogenesis of chronic diseases and that iron may help to catalyze the reactions producing free radicals. As a result, it has been suggested that the risk of coronary heart disease increases with increasing body iron stores. In support of that hypothesis, a prospective epidemiologic study of heart disease in Finnish men found that the risk of heart attack increased with increasing levels of serum ferritin. However, the vast majority of the epidemiologic data, including results from prospective, cross-sectional, and case-control and autopsy studies, published since that initial study have failed to support the original hypothesis that high body iron stores increase the risk of coronary heart disease.

Dual role of melanins and melanin precursors as photoprotective and phototoxic agents: inhibition of ultraviolet radiation-induced lipid peroxidation

Ultraviolet radiation (UVR) is one of the risk factors for skin cancer and the main inducer of melanin pigmentation, the major protective mechanism of mammalian skin against radiation damage. The melanin pigments, eumelanin and pheomelanin, are likely to be important in protection against UVR, but their precursors are generally considered as phototoxic. The available data suggest DNA damage as the mechanism of phototoxicity. However, the effect of melanin precursors on membrane damage through lipid peroxidation, another important and probably more relevant (from the point-of-view of the melanosomal confinement of these molecules) mechanism of phototoxicity, not known. As a model system for UVR-melanin-membrane interactions, we irradiated liposomes in the presence of eumelanin, pheomelanin and two of their major precursors, 5,6-dihydroxyindole (DHI) and 5-S-cysteinyldopa (SCD). The presence of the two melanin precursors substantially reduced the formation of lipid peroxidation products resulting from UVR exposure. The antioxidant activity of the melanin precursors was diminished under strong prooxidant conditions (presence of Fe3+). These results suggest that melanin precursors may have an important role in the protection of skin against the harmful effects of UVR including photocarcinogenesis.

Oxidation of spin trap 5,5-dimethyl-1-pyrroline-1-oxide in an electron paramagnetic resonance study of the reaction of methemoglobin with hydrogen peroxide

The possibility that methemoglobin (metHb) may function as a biological Fenton reagent to produce hydroxyl radical from hydrogen peroxide is investigated by electron paramagnetic resonance (EPR) spin-trapping techniques. The spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) gives a nine-line EPR spectrum and no hydroxyl radical or superoxide spin adduct signals for the metHb/H2O2 system. From the known hyperfine splitting constants, the spectrum is assigned to 5,5-dimethylpyrrolidone-2(2)-oxyl-(1) (DMPOX), an oxidized derivative of DMPO. The likely involvement of the peroxidase activity of metHb in this reaction is suggested by the oxidation of DMPO to DMPOX by horseradish peroxidase as well. Furthermore, peroxidase inhibitors prevent the formation of DMPOX. Spectrophotometric assays confirm the peroxidase activity of metHb toward typical phenolic and nonphenolic substrates under the conditions used for the EPR experiments. The visible absorption spectra indicate the formation of a ferrylHb intermediate and its reduction by DMPO. Glutathione and ascorbic acid compete with DMPO as electron donors in the reaction to form thiyl and ascorbate radicals. Neither hydroxyl radical nor any other signal is observed when N-tert-butyl-alpha-phenylnitrone (PBN) is used as the spin trap in the metHb/H2O2 system. It is concluded that methemoglobin-bound iron may not catalyze the Fenton reaction forming hydroxyl radical, but can oxidize a variety of substrates, including DMPO, in a peroxidase-type reaction.

Exercise, oxidative stress, and antioxidants: a review

Elemental and gaseous oxygen presents a conundrum in that it is simultaneously essential for and potentially destructive to human life. Traditionally the ability to consume large volumes of oxygen has been assumed to be totally beneficial to the organism. In the past 10 years it has become clear that oxygen radicals are generated even during normal resting metabolism. Nevertheless, such radicals are usually of no appreciable threat since a wide array of protective biochemical systems exist. However, under certain circumstances aerobic exercise may increase free radical production to a level that overwhelms those defenses. A broad array of nutrients such as vitamin C, vitamin E, beta-carotene, and so forth are known to suppress such radical events. This paper reviews the status of our knowledge relative to the potential benefits of nutritional modification in augmenting the organism's normal defense against harmful radical chemistry.

The effect of a synthetic hexadentate iron chelator (CP130) and desferrioxamine on rabbit kidneys exposed to cold and warm ischaemia

The effect of CP130 (a synthetic hexadentate pyridinone iron chelator) on the formation of two markers of lipid peroxidation (TBA-reactive material and Schiff's bases) in rabbit kidneys following a 72 h period of cold (0-4 degrees C) ischaemia was investigated by either adding CP130 to the flush/storage solution (hypertonic citrate solution) or by administering the agent intravenously 15 min before removal of the organs. In both cases, CP130 blocked the adverse rises in lipid peroxidation caused by ischaemia and subsequent reoxygenation of the homogenates in vitro. Both CP130 and desferrioxamine (DFX) (administered intravenously 15 min before ischaemia and 5 min before reperfusion) were also found to significantly reduce post-ischaemic rates of in vitro lipid peroxidation in kidneys rendered warm ischaemic for 90 min followed by reperfusion for 5 or 60 min in situ. Kidneys exposed to warm ischaemia and reperfusion developed interstitial and intracellular oedema, congestion and haemorrhage. DFX administration had little effect on the histological outcome, whereas CP130 significantly reduced interstitial oedema (at 5 min reperfusion compared to the DFX-treated group), intracellular oedema (at 60 min reperfusion compared to the DFX-treated group) and congestion (at 5 min reperfusion compared with a control group not given any agent). It is concluded that while CP130 and DFX exhibited similar antioxidant properties, CP130 provided better protection from ischaemia/reperfusion injury at the histological level. Synthetic iron chelators may therefore be of benefit in clinical organ transplantation by protecting against tissue damage caused by prolonged ischaemia.

Increase in bleomycin-detectable iron in ischaemia/reperfusion injury to rat kidneys

Iron has been shown to be important in ischaemic, immune and toxic forms of tissue injury in various organs. Although it is generally accepted that iron participates in the generation of powerful oxidant species (e.g. hydroxyl radicals) there has not been any direct evidence that iron capable of catalysing free-radical reactions is increased in tissues in these models of injury. In the present study we demonstrate that ischaemia/reperfusion injury to the kidney results in no significant change in total, nonhaem or ferritin iron levels, but there is a marked and specific increase in bleomycin-detectable iron (capable of catalysing free-radical reactions) in the kidney. The increase in bleomycin-detectable iron is observed only after reperfusion but not during the ischaemic period. In a separate study we demonstrate that despite a drastic reduction in the iron content in the kidney, as a result of feeding an iron-deficient diet, there is a similar and a marked increase in the bleomycin-detectable iron in kidneys accompanied by a lack of protection against ischaemia/reperfusion injury.