The effect of hepcidin on components of metabolic syndrome in chronic kidney disease: a cross-sectional study

BACKGROUND

Hepcidin is an important regulator of iron homeostasis.

OBJECTIVES

This cross-sectional study was conducted to evaluate the association between hepcidin and components of metabolic syndrome in patients with chronic kidney disease (CKD).

DESIGN AND SETTING

103 CKD patients and 59 healthy volunteers were included in the study from the University Hospital.

METHODS

Serum hepcidin levels were measured by enyzme-linked immunosorbent assay (ELISA) test. As for the study parameters, age, sex, body mass index, renal diseases, serum biochemistry, complete blood count, iron and total iron-binding capacity, ferritin, high-sensitive C-reactive protein (hsCRP), C- reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were evaluated.

RESULTS

The mean age of the patients was 58.63 ± 11.8 years. Hepcidin level was significantly associated with hypertension and higher uric acid levels (P < 0.05). There was a positive correlation between hepcidin and urea, uric acid, creatinine, ferritin, CRP, ESR, phosphorus, triglyceride, low-density lipoprotein (LDL), proteinuria and albuminuria in 24-hour urine collection. A negative correlation was found between hepcidin and estimated glomerular filtration rate (eGFR), hemoglobin, hematocrit, calcium, 25 OH vitamin D, pH, and bicarbonate levels.

CONCLUSION

Hepcidin, a well-known hormone regulator of iron metabolism, may play an important role in the pathogenesis of metabolic syndrome in patients with CKD, and further studies might delineate in-depth its potential as a promising early marker in these patients.

Trace minerals intake: Risks and benefits for cardiovascular health

Minerals play a major role in regulating cardiovascular function. Imbalances in electrolyte minerals are frequent and potentially hazardous occurrences that may lead to the development of cardiovascular diseases (CVDs). Transition metals, such as iron, zinc, copper and selenium, play a major role in cell metabolism. However, there is controversy over the effects of dietary and supplemental intake of these metals on cardiovascular risk factors and events. Since their pro-oxidant or antioxidant functions can have different effects on cardiovascular health. While deficiency of these trace elements can cause cardiovascular dysfunction, several studies have also shown a positive association between metal serum levels and cardiovascular risk factors and events. Thus, a J- or U-shaped relationship between the transition minerals and cardiovascular events has been proposed. Given the existing controversies, large, well-designed, long-term, randomized clinical trials are required to better examine the effects of trace mineral intake on cardiovascular events and all-cause mortality in the general population. In this review, we discuss the role of dietary and/or supplemental iron, copper, zinc, and selenium on cardiovascular health. We will also clarify their clinical applications, benefits, and harms in CVDs prevention.

High Consumption of Iron Exacerbates Hyperlipidemia, Atherosclerosis, and Female Sterility in Zebrafish via Acceleration of Glycation and Degradation of Serum Lipoproteins

Elevated serum iron level is linked with an increased risk of diabetes and atherosclerosis. However, the pathological mechanism by which iron affects serum lipoprotein levels is unknown. To elucidate the mechanism, a high dose of ferrous ion was applied (final 60 µM, 120 µM) to human serum lipoproteins, macrophages, and human dermal fibroblast (HDF) cells. Iron-treated lipoproteins showed loss of antioxidant ability along with protein degradation and multimerization, especially co-treatment with fructose (final 10 mM). In the presence of fructose, HDF cells showed 3.5-fold more severe cellular senescence, as compared to the control, dependent on the dosage of fructose. In macrophages, phagocytosis of acetylated low-density lipoprotein (acLDL) was more accelerated by ferrous ion, occurring at a rate that was up to 1.8-fold higher, than acLDL alone. After 24 weeks supplementation with 0.05% and 0.1% ferrous ion in the diet (wt/wt), serum total cholesterol (TC) level was elevated 3.7- and 2.1-fold, respectively, under normal diet (ND). Serum triglyceride (TG) was elevated 1.4- and 1.7-fold, respectively, under ND upon 0.05% and 0.1% ferrous ion supplementation. Serum glucose level was elevated 2.4- and 1.2-fold under ND and high cholesterol diet (HCD), respectively. However, body weight was decreased by the Fe²⁺ consumption. Iron consumption caused severe reduction of embryo laying and reproduction ability, especially in female zebrafish via impairment of follicular development. In conclusion, ferrous ion treatment caused more pro-atherogenic, and pro-senescence processes in human macrophages and dermal cells. High consumption of iron exacerbated hyperlipidemia and hyperglycemia as well as induced fatty liver changes and sterility along with reduction of female fertility.

Iron in red meat-friend or foe

In developed countries, due to high content and bioavailability, red and processed meats are the main sources of iron in the diet. Adequate intake of this nutrient is essential for the proper development and functioning of the human body, and its deficiencies are associated mainly with the occurrence of anemia, which is one of the most widespread nutritional problems in the world. However, excessive intake of iron can be detrimental to health. Studies have shown that high consumption of red meat and its products, and thereby iron, particularly in the form of heme, increases the risk of non-communicable diseases, including cancers, type II diabetes and cardiovascular disease. Due to the high nutritional value, the presence of red meat in the diet is preferable, but according to World Cancer Research Fund International its consumption should not exceed 500g per week. Furthermore, there are several potential ways to suppress the toxic effects of heme iron in the diet.

Parameters influencing in-hospital mortality in patients hospitalized in intensive cardiac care unit: is there an influence of anemia and iron deficiency?

We investigated the incidence and prognostic value of anemia as well as of the iron status in non-selected patients admitted to an intensive cardiac care unit (ICCU). 392 patients (mean age 70 ± 13.8 years, 43% women), 168 with acute coronary syndromes (ACS), 122 with acute decompensated heart failure, and 102 with other acute cardiac disorders were consecutively, prospectively assessed. The biomarkers of iron status-serum iron concentration (SIC), total iron binding capacity (TIBC), and transferrin saturation (TSAT) together with standard clinical, biochemical and echocardiographic variables-were analyzed. In-hospital mortality was 3.8% (15 patients). The prevalences of anemia (according to WHO criteria), and iron deficiency (ID) were 64 and 63%, respectively. The level of biomarkers of iron status, but not anemia, was lower in patients who died (p < 0.05). Anemia was less frequent in patients with ACS as compared to the remaining ICCU population (p = 0.019). The analysis by logistic regression indicated the highest risk of death for age [odds ratio (OD) 1.38, 95% CI 1.27-1.55], SIC (OR 0.85, 95% CI 0.78-0.94), TIBC (OR 0.95, 95% CI 0.91-0.98), left ventricle ejection fraction (OR 0.85, 95% CI 0.77-0.93), as well as hospitalization for non-ACS (OR 0.25, 95% CI 0.14-0.46), (p < 0.05). The risk of death during hospitalization tended to increase with decreasing levels of TIBC (p = 0.49), as well as with the absence of ACS (p = 0.54). The incidence of anemia and ID in heterogeneous ICCU patients is high. Parameters of the iron status, but not anemia per se, independently influence in-hospital mortality. The prevalence of anemia is higher in non-ACS patients, and tends to worsen the prognosis.

Elevated serum ferritin level is associated with the incident type 2 diabetes in healthy Korean men: a 4 year longitudinal study

Background

Elevated ferritin concentration has been implicated in the etiology of type 2 diabetes. Accumulating evidence, mostly from studies conducted on western populations, has demonstrated a strong association between the elevated ferritin concentrations and incident type 2 diabetes. In Asian populations, however, the longitudinal studies investigating the association of elevated serum ferritin levels and type 2 diabetes are lacking. In present study, we aimed to determine whether elevated serum ferritin levels are related to the incident type 2 diabetes in healthy Korean men.

Methodology/Principal Findings

This 4 year longitudinal observational study was conducted at the Asan Medical Center, Seoul, Republic of Korea. The study population consisted of 2,029 men without type 2 diabetes who underwent routine health examination in 2007 (baseline) and 2011 (follow-up). Baseline serum ferritin concentrations were measured by chemiluminescent two-site sandwich immunoassay. In multiple-adjusted model, the relative risk (RR) for incident type 2 diabetes was significantly higher in highest compared with the lowest ferritin quartile category, even after adjusting for confounding variables including homeostasis model assessment of insulin resistance (RR = 2.17, 95% confidence interval 1.27–3.72, P for trend = 0.013).

Conclusions/Significance

These results demonstrated that elevated level of serum ferritin at baseline was associated with incident type 2 diabetes in an Asian population.

Ferritin levels and risk of type 2 diabetes mellitus: an updated systematic review and meta-analysis of prospective evidence

BACKGROUND

Emerging evidence suggests that a strong link that exists between elevated baseline body iron stores and high risk of incident type 2 diabetes mellitus (T2DM) in general populations, but the precise magnitude of the associations remains uncertain.

METHODS

We conducted a systematic review and meta-analysis of published prospective studies evaluating the associations of baseline ferritin (a biomarker of body iron stores) levels with risk of T2DM in general populations. A subsidiary review of dietary heme iron status and T2DM risk associations was also conducted. Studies were identified in a literature search of PubMed, EMBASE, and Web of Science up to October 2012.

RESULTS

Of the 730 studies reviewed for eligibility, 12 published studies involving 185 462 participants and 11 079 incident T2DM events were included in the analyses. Nine studies assessed associations between ferritin levels and T2DM with heterogeneous findings (I(2)  = 58%, 12-80%, p = 0.014). The pooled fully adjusted relative risk (RR) with (95% confidence interval) for T2DM was 1.73 (1.35-2.22) in a comparison of extreme fifths of baseline ferritin levels. Three studies evaluated associations between dietary heme iron status and T2DM with a corresponding RR for T2DM of 1.28 (1.16-1.41). In dose-response analyses, the pooled RRs for an increment of 5 ng/mL in ferritin levels and 5 mg/day in dietary heme iron were, respectively, 1.01 (0.99-1.02) and 3.24 (2.05-5.10).

CONCLUSION

Elevated levels of ferritin may help identify individuals at high risk of T2DM. Further research is warranted to establish causality of these associations and to ascertain which patients are likely to benefit from lifestyle or therapeutic interventions.

Do high ferritin levels confer lower cardiovascular risk in men with Type 2 diabetes?

AIMS

High ferritin levels are associated with insulin resistance and liver steatosis, both thought of as emerging cardiovascular risk factors. The association between ferritin and cardiovascular disease is poorly documented in cardiometabolic states with higher cardiovascular risk, such as diabetes and metabolic syndrome. We therefore characterized a cohort of males with Type 2 diabetes mellitus (T2DM) according to ferritin levels and prevalent macroangiopathy.

METHODS

The presence of overall macroangiopathy, peripheral and/or coronary artery disease was documented in 424 consecutive T2DM males, who were divided according to ferritin quartiles (Q) as follows: QI-III, normal ferritin (NF; n=318), mean+/-1 sd ferritin 133+/-72 ng/ml; and QIV patients, high ferritin (HF; n=106), ferritin 480+/-228 ng/ml.

RESULTS

Age, age at diabetes diagnosis, smoking, ethanol intake, body mass index, waist circumference, blood pressure and presence of metabolic syndrome did not differ between groups. However, the prevalence of macroangiopathy was unexpectedly much lower in patients with high ferritin, as follows: 25% vs. 43% for overall macroangiopathy; 7% vs. 16% for peripheral artery disease; and 16% vs. 31% for coronary artery disease (P=0.0009, P=0.0140 and P=0.0035, respectively, vs. NF patients). Insulin resistance index and prevalence of liver steatosis were higher in HF compared with NF patients as follows: 2.17% vs. 1.89% and 78% vs. 64% (P=0.0345 and P=0.0059, respectively). Liver enzymes (aspartate aminotransferase, alanine aminotransferase and gamma-glutamyl transferase) were significantly higher in HF, by 33%, 42% and 72%, respectively (all P<0.0002), suggesting a higher prevalence of steatohepatitis. Glycated haemoglobin, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglycerides, urate, high-sensitivity C-reactive protein and albuminuria were not different between groups.

CONCLUSIONS

Our results demonstrate that T2DM males with high ferritin levels exhibit a markedly decreased prevalence of macroangiopathy, despite more severe insulin resistance and higher markers of steatohepatitis. High ferritin levels and/or steatosis may thus paradoxically confer a lowered cardiovascular risk in diabetic males.

Low total and nonheme iron intakes are associated with a greater risk of hypertension

The relationship between iron intake and blood pressure (BP) status has not been well established. Only 1 cross-sectional study has suggested an inverse association of dietary total iron intake and nonheme iron intake with BP. We investigated the relationship between total, heme, and nonheme iron intakes, markers of iron status, 5.4-y changes in BP, and the incidence of hypertension. A total of 2895 participants included in the Supplémentation en Vitamines et Minéraux Antioxydants cohort were followed up for 5.4 y. At least 3 repeated 24-h dietary records were performed at baseline and 5.4 y later. Hemoglobin and serum ferritin concentrations were assessed at baseline. Low nonheme iron intake at baseline was associated with a greater increase in systolic BP (SBP) and pulse pressure over time after adjustment for multiple possible confounding factors (P-trend = 0.002 and 0.0005, respectively). Conversely, participants in the 3rd tertile of nonheme iron intake at baseline had a 37% lower risk of hypertension after 5.4 y of follow-up compared with those in the first tertile (P-trend = 0.04). Heme iron intake was not associated with BP changes or risk of hypertension. Meat intake was positively associated with an increase in SBP (P-trend = 0.04). However, that relation became nonsignificant after adjusting for dietary pattern scores. Baseline hemoglobin and ferritin concentrations were not associated with changes in BP or incidental hypertension. Our data support a possible role of low nonheme iron intake, independent of heme iron intake, in the development of hypertension.

Biomarkers of body iron stores and risk of developing type 2 diabetes

AIM

Iron may contribute to the pathogenesis of type 2 diabetes mellitus (DM) by inducing oxidative stress and interfering with insulin secretion. Elevated ferritin levels are associated with increased DM risk among healthy individuals. However, it is yet unknown if ferritin predicts DM incidence among high-risk individuals with impaired glucose tolerance (IGT). Furthermore, the association between soluble transferrin receptors (sTfR), a novel marker of iron status, and DM risk has not yet been prospectively investigated in these individuals. We conducted this study to evaluate the association between baseline levels of ferritin and sTfR and the risk of developing DM among overweight and obese individuals at high risk of DM.

METHODS

This nested case-control study (280 cases and 280 matched controls) was conducted within the placebo arm of the Diabetes Prevention Program, is a clinical trial conducted among overweight/obese individuals with IGT. Ferritin and sTfR levels were measured by immunoturbidimetric assays. Incident DM was ascertained by annual 75-g oral glucose tolerance test and semi-annual fasting glucose.

RESULTS

Compared with controls, cases had higher sTfR levels (3.50 +/- 0.07 vs. 3.30 +/- 0.06 mg/l; p = 0.03), but ferritin levels were not statistically different. The multivariable odds ratios (OR) and 95% confidence intervals (95% CI) for DM incidence comparing highest with the lowest quartiles of sTfR was 2.26 (1.37-4.01) (p-trend: 0.008).

CONCLUSIONS

Modestly elevated sTfR levels are associated with increased DM risk among overweight and obese individuals with IGT. Future studies should evaluate factors determining sTfR levels and examine if interventions that lower body iron stores reduce DM incidence.

The role of iron in type 2 diabetes in humans

The role of micronutrients in the etiology of type 2 diabetes is not well established. Several lines of evidence suggest that iron play may a role in the pathogenesis of type 2 diabetes. Iron is a strong pro-oxidant and high body iron levels are associated with increased level of oxidative stress that may elevate the risk of type 2 diabetes. Several epidemiological studies have reported a positive association between high body iron stores, as measured by circulating ferritin level, and the risk of type 2 diabetes and of other insulin resistant states such as the metabolic syndrome, gestational diabetes and polycystic ovarian syndrome. In addition, increased dietary intake of iron, especially that of heme iron, is associated with risk of type 2 diabetes in apparently healthy populations. Results from studies that have evaluated the association between genetic mutations related to iron metabolism have been inconsistent. Further, several clinical trials have suggested that phlebotomy induced reduction in body iron levels may improve insulin sensitivity in humans. However, no interventional studies have yet directly evaluated the effect of reducing iron intake or body iron levels on the risk of developing type 2 diabetes. Such studies are required to prove the causal relationship between moderate iron overload and diabetes risk.

Negative confounding in the evaluation of toxicity: the case of methylmercury in fish and seafood

In observational studies, the presence of confounding [corrected] can distort the true association between an exposure and a toxic-effect outcome, if the confounding variable is not controlled for in the study design or analysis phase. While confounding is often assumed to occur in the same direction as the toxicant exposure, the relationship between the benefits and risks associated with fish and seafood consumption is a classic example of negative confounding: the exposure to methylmercury occurs with fish and seafood, which are also associated with beneficial nutrients, and the signs of mercury toxicity [corrected] Mercury and nutrients may affect the same epidemiological outcomes, but most studies addressing one of them have ignored the potential for negative confounding by the other. This article reviews the existing evidence of effects of both nutrient and contaminant intakes as predictors of neurodevelopmental and cardiovascular outcomes. Substantial underestimation of the effects of mercury toxicity and of fish benefits occurs from the lack of confounder adjustment and imprecision of the exposure parameters. Given this inherent bias in observational studies, regulatory agencies should reconsider current dietary advice in order to provide better guidance to consumers in making prudent choices to maintain a nutritious diet with seafood that is low in mercury concentrations. Attention should also be paid to the occurrence of negative confounding in other connections.

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.

Immune and nutrition status in elderly Koreans with hyperLDL-cholesterolemia

Although the effects of nutrition and immune status on disease development have been investigated, little attention has been given to changes in immune function in the elderly vulnerable to coronary artery disease (CAD). Our objective was to evaluate the association between immune variables and CAD risk factors, and nutritional factors related to immune and lipid profiles in elderly Koreans (n = 90). The subjects were divided into three groups based on serum low-density lipoprotein cholesterol (LDL-cholesterol) level: risk (> or = 160 mg/dL), borderline (130-160 mg/dL), and control groups (< 130 mg/dL). Concanavalin A-induced lymphocyte proliferation rate and interleukin (IL)-2 secretion were significantly lower in the risk group than the control group. The subjects in the risk group showed the highest serum concentrations of proinflammatory mediators such as complement 3 (C3), IL-1beta, and IL-1 receptor antagonist (IL-1RA). The nutrient intake status of the subjects was generally satisfactory without differences among groups. IL-1RA concentration was negatively associated with intake of vitamin E and C3 was positively related to intake of Ca and Fe in the subjects with LDL-cholesterol > or = 130 mg/dL. This study suggests that elderly individuals with high serum LDL-cholesterol are in a mild chronic inflammation state and micronutrient status such as vitamin E, Ca, and Fe may relate to this state.

Serum ferritin, cardiovascular risk factors and ischaemic heart diseases: a prospective analysis in the SU.VI.MAX (SUpplementation en VItamines et Minéraux AntioXydants) cohort

BACKGROUND

Iron has been suggested to play a role in the development of cardiovascular disease (CVD) through its pro-oxidant properties. However, epidemiological studies on iron status and the risk of CVD have yielded conflicting results. We therefore carried out a prospective study to evaluate the relationship between iron status and CVD in a middle-aged French population.

METHODS

In total, 9917 subjects (3223 men aged 45-60 years and 6694 women aged 35-60 years) included in the SU.VI.MAX (SUpplementation en VItamines et Minéraux AntioXydants) cohort were followed prospectively for 7.5 years. All cases of ischaemic heart disease (IHD) were identified and validated. CVD risk factors, haemoglobin and serum ferritin concentrations were measured at baseline.

FINDINGS

Of men 4.3%, and of women 37.8%, presented at baseline a serum ferritin concentration <30 microg l(-1). During the follow-up, 187 subjects (148 men, 39 women) developed IHD. Serum ferritin was positively associated with total cholesterol, serum triglycerides, systolic and diastolic blood pressure, body mass index and haemoglobin. No linear association was found between serum ferritin and IHD risk in men or in women.

CONCLUSION

Our data do not support a major role of iron status in the development of IHD in a healthy general population.

Comparison of the serum ferritin and percentage of transferrin saturation as exposure markers of iron-driven oxidative stress-related disease outcomes

BACKGROUND

Iron-catalyzed oxidative stress may be the primary mechanism for the pathogenesis of diseases related to iron excess. We hypothesized previously that certain markers of iron in bound form that are commonly used in epidemiologic studies might be inappropriate for investigating iron-related adverse health effects because oxidative stress requires iron in redox-active form.

METHODS

To study aspects of this hypothesis, we examined the association between levels of serum ferritin or the percentage of transferrin saturation (%TS) and levels of serum antioxidant vitamins and C-reactive protein (CRP). This cross-sectional analysis included 11245 adults aged 20 years or older who participated in the Third National Health and Nutrition Examination Survey.

RESULTS

Adjusted concentrations of serum alpha-carotene, beta-carotene, beta-cryptoxanthin, and lycopene were inversely correlated with the serum ferritin concentration (P for trend < .01), even within the lower deciles of the serum ferritin. In contrast, the %TS was significantly and positively associated with beta-cryptoxanthin, vitamin C, and vitamin E. In addition, the serum ferritin was positively associated but the %TS was strongly and inversely associated with the serum CRP (P for trend < .01).

CONCLUSIONS

The serum ferritin and %TS showed contrasting associations with serum antioxidant vitamin levels and CRP although they have been used interchangeably in epidemiologic studies as markers of body iron. These results suggest that the %TS may not be a valid marker of exposure to iron-related oxidative stress. It appears that the serum ferritin is the preferred marker for assessment of clinical outcomes presumed to be caused by iron-related oxidative stress.

Non–Transferrin-Bound Iron and Risk of Coronary Heart Disease in Postmenopausal Women

Background— Epidemiological studies aimed at correlating coronary heart disease (CHD) with serum ferritin levels have thus far yielded inconsistent results. We hypothesized that a labile iron component associated with non–transferrin-bound iron (NTBI) that appears in individuals with overt or cryptic iron overload might be more suitable for establishing correlations with CHD.

Methods and Results— We investigated the relation of NTBI, serum iron, transferrin saturation, and serum ferritin with risk of CHD and acute myocardial infarction (AMI). The cohort used comprised a population-based sample of 11 471 postmenopausal women aged 49 to 70 years at enrollment in 1993 to 1997. During a median follow-up of 4.3 years (quartile limits Q1 to Q3: 3.3 to 5.4), 185 CHD events were identified, including 66 AMI events. We conducted a case-cohort study using all CHD cases and a random sample from the baseline cohort (n=1134). A weighted Cox proportional hazards model was used to estimate hazard ratios for tertiles of iron variables in relation to CHD and AMI. Adjusted hazard ratios of women in the highest NTBI tertile (range 0.38 to 3.51) compared with the lowest (range −2.06 to −0.32) were 0.84 (95% confidence interval 0.61 to 1.16) for CHD and 0.47 (95% confidence interval 0.31 to 0.71) for AMI. The results were similar for serum iron, transferrin saturation, and serum ferritin.

Conclusions— Our results show no excess risk of CHD or AMI within the highest NTBI tertile compared with the lowest but rather seem to demonstrate a decreased risk. Additional studies are warranted to confirm our findings.

Nonalcoholic Fatty Liver Disease Is Associated With Carotid Atherosclerosis

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) frequently coexists with obesity, diabetes, and dyslipidemia. We examined whether NAFLD was associated with atherosclerosis, as measured by ultrasound in the carotid arteries.

METHODS AND RESULTS

Carotid atherosclerosis and cardiovascular risk factors were assessed in 40 patients with an ultrasound diagnosis of primary NAFLD and 40 matched population controls. The metabolic syndrome and all its individual traits, including elevated C-reactive protein, were significantly (P<0.005) more frequent in NAFLD patients than in control subjects. Patients with NAFLD showed more carotid atherosclerosis than controls, with mean intima-media thickness (IMT) of 0.70+/-0.20 mm and 0.54+/-0.13 mm (P<0.0001) and plaque prevalence of 50% and 25% (P=0.021), respectively. By multivariate analysis, older age (odds ratio [OR], 2.5 per 10 years; 95% CI, 1.4 to 4.4; P=0.002), the presence of NAFLD (OR, 8.4; 95% CI, 2.49 to 29.4; P=0.001), and elevated serum ferritin (OR, 3.1; 95% CI, 1.2 to 7.9; P=0.016) were independent predictors of an increased IMT.

CONCLUSIONS

Patients with NAFLD show a cluster of risk factors of the metabolic syndrome and advanced carotid atherosclerosis. NAFLD appears to be a feature of the metabolic syndrome, and its detection on abdominal ultrasound should alert to the existence of an increased cardiovascular risk.

Iron, zinc, and alcohol consumption and mortality from cardiovascular diseases: the Iowa Women's Health Study

BACKGROUND

The relation between iron status and atherosclerosis has long been a topic of debate.

OBJECTIVE

We examined associations of cardiovascular disease (CVD) mortality with dietary intakes of iron (a possible prooxidant), zinc (a possible antioxidant), and alcohol (a disruptor of iron homeostasis).

DESIGN

Postmenopausal women (n = 34 492) aged 55-69 y at baseline, who completed a food-frequency questionnaire, were followed for CVD mortality over 15 y.

RESULTS

Among women who consumed >/=10 g alcohol/d, after adjustment for CVD risk factors in a model that contained dietary heme iron, nonheme iron, and zinc intakes, dietary heme iron showed a positive association, dietary nonheme iron showed a U-shaped association, and dietary zinc showed an inverse association with CVD mortality. For example, the relative risks (RRs) for categories of dietary heme iron were 1.0, 1.46, 1.52, 1.73, and 2.47 (P for trend = 0.04); corresponding RRs for dietary nonheme iron were 1.0, 0.93, 0.63, 0.83, and 1.20 (P for quadratic term = 0.02). The corresponding RRs for dietary zinc were 1.0, 0.61, 0.59, 0.57, and 0.37 (P for trend = 0.07). In an analysis restricted to those who consumed >/=30 g alcohol/d, the risk gradients strengthened.

CONCLUSIONS

Our results suggest that a higher intake of heme iron might be harmful, whereas a higher intake of zinc might be beneficial in relation to CVD mortality in the presence of a trigger that can disturb iron homeostasis, such as alcohol consumption.

Serum markers of stored body iron are not appropriate markers of health effects of iron: a focus on serum ferritin

Experimental studies have consistently shown that iron is a critical catalyst in generating oxygen free radicals via Fenton chemistry. Nevertheless, epidemiologic studies conflict on the association between stored body iron markers and disease outcomes, including coronary heart disease. We hypothesize that stored body iron markers common in epidemiologic studies, such as serum ferritin, transferrin saturation, iron, or iron-binding capacity, are inappropriate to investigate harmful health effects related to iron overload. Oxygen free radicals are produced only by free iron, but stored body iron markers reflect iron bound to ferritin or transferrin, which are produced to sequester catalytically active free iron. Moreover, increased serum ferritin may occur as a defense mechanism in response to oxidative stress; such increase might eventually minimize oxidative stress and consequent pathology due to free iron. Therefore, though highly correlated with stored body iron, a measure of bound iron will fail to identify any harmful effect, unless it is also a marker of free iron. It is generally believed that free iron rarely exists, except in iron-overload with 100% transferrin saturation. However, some recent studies find non-transferrin bound iron (NTBI) or the intracellular labile iron pool (LIP) in the presence of triggers disturbing iron homeostasis, such as alcohol consumption. In contrast to the tight bond in ferritin or transferrin, free iron is more likely to dissociate from a looser bond. Therefore research on the relation of iron with disease outcomes should investigate NTBI or the intracellular LIP. Any positive influence of iron on coronary heart and other diseases might be observable only when a trigger is present. These factors may explain why there have been conflicting results between serum markers of stored body iron and disease outcomes in epidemiological studies.

Body iron stores and their determinants in healthy postmenopausal US women

BACKGROUND

Data on the determinants of body iron stores in middle-aged women are sparse.

OBJECTIVE

We prospectively evaluated nondietary and dietary determinants of iron stores.

DESIGN

Using blood samples collected in 1989-1990, we measured plasma ferritin concentrations in 620 healthy postmenopausal women aged 44-69 y who participated in the Nurses' Health Study. Food-frequency questionnaires completed in 1980, 1984, and 1986 were used to calculate average dietary intakes. Generalized linear regression and multiple logistic regression models were used to assess the association between plasma ferritin and its determinants.

RESULTS

Among these postmenopausal women, the median plasma ferritin concentration was 73.8 ng/mL (interquartile range: 41.6-125.8 ng/mL), 2.7% were iron depleted (ferritin concentration < 12 ng/mL), and 9.8% had an elevated ferritin concentration (> 200 ng/mL). Age, time since menopause, time since the last postmenopausal hormone (PMH) use, body mass index, iron supplement use, and alcohol and heme-iron intakes were positively associated with ferritin concentrations, whereas PMH use, physical activity, aspirin use, and gastrointestinal ulcer were inversely related. The association between heme-iron intake and ferritin was most apparent among the women who consumed > 30 g alcohol/d.

CONCLUSIONS

Our prospective data confirm that in postmenopausal women, intakes of heme iron, supplemental iron, and alcohol are dietary determinants of plasma ferritin, and age, PMH use, body mass index, physical activity, aspirin use, and gastrointestinal ulcer are nondietary determinants.