Relation between iron stores and non-insulin dependent diabetes in men: case-control study

Iron status in women with and without gestational diabetes mellitus

OBJECTIVE

Gestational diabetes mellitus (GDM) affects approximately 7% of all pregnancies. Pregnancy, mostly because of the mitochondria-rich placenta, is a condition that favors oxidative stress. A transitional metal, especially iron, which is particularly abundant in the placenta, is important in the production of free radicals. Also, studies have shown that free radicals have a role in GDM. As there are little data about iron status in GDM, this study was performed to compare iron status in GDM and control group.

RESEARCH DESIGN AND METHODS

In this case-control study, 34 women with diagnosed GDM were compared with 34 non-GDM women in the control group at 24-28 weeks of pregnancy in terms of iron status, including ferritin, serum iron, total iron-binding capacity (TIBC), hemoglobin (Hb), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH).

RESULTS

In this study, concentration of serum ferritin, iron, transferrin saturation and hemoglobin, MCV, and MCH was significantly higher in the GDM group and TIBC was significantly lower in this group (P<.05). No significant association was observed with the other variables including familial history of diabetes and GDM.

CONCLUSION

Our findings indicate an association between increased iron status and GDM. The role of iron excess from iron supplementation in the pathogenesis of GDM needs to be examined.

Effects of Cardiorespiratory Fitness on Serum Ferritin Concentration and Incidence of Type 2 Diabetes: Evidence from the Aerobics Center Longitudinal Study (ACLS)

BACKGROUND

Cardiorespiratory fitness (CRF) and physical activity (PA) are inversely related to the occurrence of type 2 diabetes (T2D). Both play an important role in reducing serum ferritin (SF) concentration. Increased SF concentration is considered a contributing factor for developing T2D.

METHODS

The present cohort study investigated 5,512 adult participants enrolled in the Aerobics Center Longitudinal Study (ACLS) between 1995 and 2001. The subjects completed a comprehensive medical examination and a SF evaluation, and had been followed up until either diabetes onset, death, or the cut-off date of November 2007. Three CRF levels were categorized. SF quartile levels were defined by gender and menopausal status. The incidence of T2D was calculated for 10,000 person-years, and hazard ratios (HR) were computed to predict the incidence of T2D based on SF quartiles and CRF levels.

RESULTS

SF concentration was significantly higher in males than in females (148.5 +/- 104.7 ng/ml vs. 52.2 +/- 45.9 ng/ml) and was inversely associated with CRF levels. In the high CRF group, 32.7% of participants had a low SF concentration whereas only 16.8% of participants had a high SF concentration level. After adjusting for potential confounders, male participants in the highest SF quartile level had a 1.7 times (HR: 1.67, 95% CI: 1.05, 2.66; p-trend = 0.027) increased risk for developing T2D compared with those in the lowest SF quartile group.

CONCLUSION

Lower SF concentration was associated with lower risk of developing T2D in those regularly participating in CRF. The findings from this study suggest that SF concentration could be used as a diabetic predictor. Based on these results clinicians and public health professionals should promote regular physical activity or fitness to reduce the incidence of T2D.

Iron overload is associated with hepatic oxidative damage to DNA in nonalcoholic steatohepatitis

Several lines of evidence have suggested that oxidative stress plays an important role for the pathogenesis of nonalcoholic steatohepatitis (NASH). Therefore, by using immunohistochemical staining of liver biopsy samples, we measured hepatic 7,8-dihydro-8-oxo-2' deoxyguanosine (8-oxodG), a DNA base-modified product generated by hydroxyl radicals, of 38 NASH patients and compared with 24 simple steatosis and 10 healthy subjects. Relation of hepatic 8-oxodG with clinical, biochemical, and histologic variables and changes after iron reduction therapy (phlebotomy plus iron-restricted diet) were also examined. Hepatic 8-oxodG levels were significantly higher in NASH compared with simple steatosis (17.5 versus 2.0 8-oxodG-positive cells/10(5) microm(2); P < 0.0001). 8-oxodG was significantly related to iron overload condition, glucose-insulin metabolic abnormality, and severities of hepatic steatosis in NASH patients. Logistic regression analysis also showed that hepatic iron deposit and insulin resistance were independent variables associated with elevated hepatic 8-oxodG. After the iron reduction therapy, hepatic 8-oxodG levels were significantly decreased (from 20.7 to 13.8 positive cells/10(5) microm(2); P < 0.01) with concomitant reductions of serum transaminase levels in NASH patients. In conclusion, iron overload may play an important role in the pathogenesis of NASH by generating oxidative DNA damage and iron reduction therapy may reduce hepatocellular carcinoma incidence in patients with NASH.

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

BACKGROUND

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

REVIEW

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

CONCLUSION

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

Ferritin concentrations, metabolic syndrome, and type 2 diabetes in middle-aged and elderly chinese

CONTEXT

Elevated ferritin concentrations frequently cluster with well-established risk factors of diabetes including obesity, metabolic syndrome, chronic inflammation, and altered circulating adipokines. Few studies, however, have systematically evaluated the effect of these risk factors on ferritin-diabetes association, particularly in Chinese populations.

OBJECTIVE

We aimed to investigate, in a middle-aged and elderly Chinese population, whether elevated ferritin concentrations are associated with higher risk of metabolic syndrome and type 2 diabetes and to what extent the associations were influenced by obesity, inflammation, and adipokines.

DESIGN AND METHODS

We conducted a population-based, cross-sectional survey of 3,289 participants aged 50-70 yr in Beijing and Shanghai in 2005. Fasting plasma ferritin, glucose, insulin, lipid profile, glycohemoglobin, inflammatory markers, adipokines, and dietary profile were measured.

RESULTS

Median ferritin concentrations were 155.7 ng/ml for men and 111.9 ng/ml for women. After multiple adjustment, the odds ratios (ORs) were substantially higher for type 2 diabetes (OR 3.26, 95% confidence interval 2.36-4.51) and metabolic syndrome [OR 2.80 (95% confidence interval 2.24-3.49)] in the highest ferritin quartile compared with those in the lowest quartile. These associations remained significant after further adjustment for dietary factors, body mass index, inflammatory markers, and adipokines.

CONCLUSIONS

Elevated circulating ferritin concentrations were associated with higher risk of type 2 diabetes and metabolic syndrome in middle-aged and elderly Chinese independent of obesity, inflammation, adipokines, and other risk factors. Our data support the crucial role of iron overload for metabolic diseases, even in a country with relatively high prevalence of iron deficiency.

Body iron stores in relation to the metabolic syndrome, glycemic control and complications in female patients with type 2 diabetes

BACKGROUND AND AIM

Studies suggest that iron plays a significant role in the development of diabetes and its complications. This study evaluates the associations of iron metabolism parameters with the metabolic syndrome (MS), control and complications in female patients with type 2 diabetes mellitus (T2DM).

METHODS AND RESULTS

Ferritin, soluble Transferrin Receptor (sTfR), sTfR/Log ferritin ratio (sTfR-F index), iron, full blood count and high-sensitivity C-reactive protein (hs-CRP) were determined in 110 female patients with T2DM. Steady state beta cell function (%B), insulin sensitivity (%S) and insulin resistance were assessed with homeostasis model. Patients were divided into tertiles of ferritin and sTfR-F index and according to the presence or absence of the MS and diabetic complications. Patients within the lowest tertile of the sTfR-F index had significantly higher fasting insulin, percent B, low-density lipoprotein cholesterol and Apolipoprotein B than those in the highest tertile. Ferritin showed significant correlations with insulin, percent B and inverse correlations with adiponectin and percent S. The sTfR-F index was significantly correlated with insulin, percent B and lipid parameters. Correcting for hs-CRP abolished the correlations with ferritin but not the sTfR-F index. Higher indices of body iron were significantly associated with diabetes complications but no associations were found with MS, glucose or glycemic control. Multiple regression analysis with confounding variables showed ferritin and the sTfR-F index were not independently associated with diabetes complications.

CONCLUSIONS

Association of ferritin with metabolic derangements and complications in diabetes is partly dependent on association with inflammation. Iron status, estimated with the sTfR-F index, is associated with metabolic derangements and complications but the associations are dependent on other risk factors. Prospective studies that use the sTfR-F index as a marker of iron status are required to confirm the role of iron in the etiopathogenesis of T2DM and its complications.

Factors accounting for high ferritin levels in obesity

Ferritin is a widely used marker of iron status. A relationship between iron stores, obesity and metabolic syndrome (METs) has been proposed.

OBJECTIVE

To compare serum ferritin between obese women with and without METs, and to evaluate the main factors accounting for ferritin levels.

DESIGN

Prospective study.

SUBJECTS

A total of 239 consecutive postmenopausal women with body mass index (BMI) > or =30 kg/m(2) were included. Exclusion criteria were conditions that could influence body iron stores. In addition to ferritin, serum iron, transferrin, transferrin saturation index and the soluble transferrin receptor were measured. METs was defined according to the International Diabetes Federation guidelines. Multiple regression analyses were performed taking into account ferritin as the dependent variable.

RESULTS

Serum ferritin levels were significantly higher in obese women with METs (n=169) in comparison with obese women without METs (n=70): 81.00 (17-648) vs 48.50 (11-149) ng ml(-1), P<0.001. No differences in the other markers of iron status were observed. Diabetic patients (n=82) had higher ferritin levels than non-diabetic patients (P<0.001). Non-diabetic patients with METs (n=95) also showed higher ferritin levels than non-diabetic patients without METs (P=0.001). Among the components of METs only diabetes was independently associated with serum ferritin levels in both the whole group (P=0.02) and in patients with METs (P=0.005).

CONCLUSION

Metabolic syndrome and in particular type 2 diabetes is the main contributor to the high ferritin levels reported in obesity. Our findings suggest that ferritin should not be used as a reliable index of iron overload in obese patients with diabetes.

Circulating retinol-binding protein-4 concentration might reflect insulin resistance-associated iron overload

OBJECTIVES

The mechanisms behind the association between retinol-binding protein-4 (RBP4) and insulin resistance are not well understood. An interaction between iron and vitamin A status, of which RBP4 is a surrogate, has long been recognized. We hypothesized that iron-associated insulin resistance could be behind the impaired insulin action caused by RBP4.

RESEARCH DESIGN AND METHODS

Serum ferritin and RBP4 concentration and insulin resistance were evaluated in a sample of middle-aged men (n = 132) and in a replication independent study. Serum RBP4 was also studied before and after iron depletion in patients with type 2 diabetes. Finally, the effect of iron on RBP4 release was evaluated in vitro in adipose tissue.

RESULTS

A positive correlation between circulating RBP4 and log serum ferritin (r = 0.35 and r = 0.61, respectively; P < 0.0001) was observed in both independent studies. Serum RBP4 concentration was higher in men than women in parallel to increased ferritin levels. On multiple regression analyses to predict serum RBP4, log serum ferritin contributed significantly to RBP4 variance after controlling for BMI, age, and homeostasis model assessment value. Serum RBP4 concentration decreased after iron depletion in type 2 diabetic patients (percent mean difference -13.7 [95% CI -25.4 to -2.04]; P = 0.024). The iron donor lactoferrin led to increased dose-dependent adipose tissue release of RBP4 (2.4-fold, P = 0.005) and increased RBP4 expression, while apotransferrin and deferoxamine led to decreased RBP4 release.

CONCLUSIONS

The relationship between circulating RBP4 and iron stores, both cross-sectional and after iron depletion, and in vitro findings suggest that iron could play a role in the RBP4-insulin resistance relationship.

Novel biochemical risk factors for type 2 diabetes: pathogenic insights or prediction possibilities?

This review critically appraises studies examining the association of novel factors with diabetes. We show that many of the most studied novel and apparently 'independent' risk factors are correlated with each other by virtue of their common origins or pathways, and that residual confounding is likely. Available studies also have other limitations, including differences in methodology or inadequate statistical analyses. Furthermore, although most relevant work in this area has focused on improving our understanding of the pathogenesis of diabetes, association studies in isolation cannot prove causality; intervention studies with specific agents (if available) are required, and genetic studies may help. With respect to the potential value of novel risk factors for diabetes risk prediction, we illustrate why this work is very much in its infancy and currently not guaranteed to reach clinical utility. Indeed, the existence of several more easily measured powerful predictors of diabetes, suggests that the additional value of novel markers may be limited. Nevertheless, several suggestions to improve relevant research are given. Finally, we show that several risk factors for diabetes are only weakly associated with the risk of incident vascular events, an observation that highlights the limitations of attempting to devise unified criteria (e.g. metabolic syndrome) to identify individuals at risk of both CHD and diabetes.

[Serum ferritin and risk of the metabolic syndrome in some Korean rural residents]

OBJECTIVES

The purpose of this study was to examine the relationship between serum ferritin and the metabolic syndrome (MS).

METHODS

We conducted a cross-sectional study of 1,444 adults over age 40 and under age 70 that lived in a rural area and participated in a survey conducted as part of the Korean Rural Genomic Cohort Study (KRGCS). The MS was defined as the presence of at least three of the followings: elevated blood pressure, low high density lipoprotein cholesterol, elevated serum triglycerides, elevated plasma glucose, or abdominal obesity. After adjustment for age, alcohol intake, menopausal status, body mass index (BMI), high sensitivity C-reactive protein (hs-CRP), and alanine aminotransferase (ALT), odds ratios (ORs) for the prevalence of the MS by sex were calculated for quartiles of serum ferritin using logistic regression analysis.

RESULTS

The MS was more common in those persons with the highest levels of serum ferritin, compared to persons with the lowest levels, in men (37.1% vs. 22.4%, p=0.006) and women (58.8% vs. 34.8, p<0.001). In both sexes, the greater the number of MS components presents, the greater the serum ferritin levels. After adjustment for age, alcohol intake, and menopausal status, the OR for metabolic syndrome, comparing the fourth quartile of ferritin with the first quartile, was 2.21 (95% confidence interval; CI=1.26-3.87; p-trend=0.024) in men and 2.10 (95% CI=1.40-3.17; p-trend=0.001) in women. However, after further adjustment for BMI, hs-CRP, and ALT, the ORs were statistically attenuated in both sexes.

CONCLUSIONS

Moderately elevated serum ferritin levels were not independently associated with the prevalence of the MS after adjusting for other risk factors. Further studies are needed to obtain evidence concerning the association between serum ferritin levels and the MS.

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.

Elevated serum ferritin concentrations in prediabetic subjects

BACKGROUND

Few data are available on the association of variables of the insulin resistance syndrome and serum ferritin, an indicator of body iron stores. We examined the relationship between serum ferritin levels and impaired fasting glucose, a pre-diabetes stage associated with insulin resistance, in this study.

SUBJECTS & METHODS

One hundred and eighty seven people, including 91 subjects with impaired fasting glucose (IFG) and 96 healthy people who were well matched for age and sex, were enrolled. Body mass index (BMI) and blood pressure of the participants were measured and serum cholesterol, triglyceride, white blood cells (WBC) count, C-reactive protein (CRP) and ferritin were evaluated. All the data were analysed by t-test, chi2 test and analysis of variance.

RESULTS

The IFG group had higher serum ferritin concentrations (85.5+/-6.6 microg/L vs. 49.4+/-3.7 microg/L, p=0.001). A positive correlation was found between fasting plasma glucose and serum ferritin (r=0.29, p=0.001). Using multiple regression analysis, we found an association between serum ferritin and blood pressure (0.15, p=0.01), FPG (0.29, p=0.001), triglyceride (0.08, p=0.01) and cholesterol (0.07, p=0.03). The odds ratio for the association of IFG in male subjects with a high serum ferritin level was 8.3 (95% CI: 1.2-11.9, p=0.01) and for females was 3.06 (95% CI: 0.58-15, p=0.1).

CONCLUSION

Based on the data from our study, aelevation in serum ferritin can be seen in pre-diabetes stage, before the occurrence of an overt diabetes mellitus.

Paraoxonase 1 phenotype distribution and activity differs in subjects with newly diagnosed Type 2 diabetes (the CODAM Study)

AIMS

Paraoxonase 1 (PON1) is an antioxidant high-density lipoprotein-bound enzyme, which was recently found to be expressed in the islets of Langerhans. A substitution (Q/R) at position 192 results in enzymes with different activity. Oxidation has been implicated in the onset of diabetes, and it can be hypothesized that PON1 may have a protective effect on diabetes. Our aim was to compare PON1 activities and PON1 Q/R phenotypes in subjects with different degrees of glucose intolerance.

METHODS

We examined 566 members of the Cohort study of Diabetes and Atherosclerosis Maastricht (CoDAM), including subjects with normal glucose tolerance (NGT, n = 298), impaired glucose regulation (IGR, n = 128), newly diagnosed Type 2 diabetes (nDM, n = 78) and treated, that is to say known, Type 2 diabetes (kDM, n = 64). PON1 activity was measured in serum using paraoxon and diazoxon as substrates. The PON1 phenotype was determined using two-dimensional enzyme analysis.

RESULTS

The RR-phenotype was significantly more frequent in nDM compared with NGT subjects (14.1 vs. 6.0%, P = 0.05). Adjusted for the PON1 phenotype, subjects with nDM had significant lower PON1 activity towards paraoxon and diazoxon than subjects with NGT. Adjusted odds ratios comparing the RR-variant with the QQ-variant were 2.17 [95% confidence interval (CI): 0.90-5.24] for impaired glucose tolerance, 2.84 (95% CI: 1.03-7.83) for nDM, 2.13 (95% CI; 0.61-7.42) for kDM and 2.65 (95% CI: 1.10-6.40) for total diabetes mellitus.

CONCLUSIONS

An aberrant PON1 phenotype distribution and PON1 activity were observed in early diabetes. In addition, the higher state of oxidative stress may affect the future development of complications.

Microsatellite polymorphism in the heme oxygenase-1 gene promoter is associated with iron status in persons with type 2 diabetes mellitus

BACKGROUND

High iron stores are known to cause type 2 diabetes mellitus in persons with hemochromatosis. However, it is not clear whether moderately elevated iron stores predict the risk of type 2 diabetes in healthy persons. Heme oxygenase (HO) 1 expression is increased when intracellular iron increases. Furthermore, HO shows a microsatellite polymorphism in its gene promoter that could be related to its expression and activity.

OBJECTIVES

We aimed to determine the length of (GT)(n) repeats in the HO1 gene promoter by using capillary electrophoresis and HO enzymatic activity in mononuclear cells (MNCs) from adult diabetes patients. We also aimed to assess the relation between these results and iron stores.

DESIGN

We studied 99 patients with type 2 diabetes mellitus and 90 nondiabetic (control) subjects. We determined iron status (serum iron, ferritin, and transferrin receptor), HO activity, and micropolymorphism.

RESULTS

One diabetes patient and 5 control subjects had iron deficiency anemia. No iron overload was detected in either group. Diabetes patients had significantly greater iron stores (P < 0.0001), total body iron (P < 0.001), and HO activity (P < 0.001) than did control subjects. A positive association between serum iron and HO activity was seen in the diabetes patients (P < 0.0001). Allelic frequency did not differ significantly between diabetes patients and control subjects; however, the frequency of the SM genotype was significantly higher and that of the SS and MM genotypes was significantly lower in the diabetes patients than in control subjects (P < 0.001 for all).

CONCLUSIONS

Type 2 diabetes patients carrying short (GT)(n) repeats may have higher ferritin values and greater HO enzymatic activity and may have greater susceptibility to diabetes than may those with long (GT)(n) repeats.

Multivariate optimization of solid-phase extraction applied to iron determination in finished waters

In this work, Amberlite XAD-4 resin functionalized with salicylic acid was synthetized, characterized and applied as a new packing material for an on-line system to iron determination in aqueous samples. The detection method is based on the sorption of Fe(III) ions in a minicolumn containing the synthesized resin, followed by a desorption step using an acid solution and measurement of iron by vis-spectrophotometry (CAS method). The optimization of the solid-phase extraction system was performed using factorial design and Doehlert matrix considering six variables: sample percolation rate (0.5-9 ml min(-1)), sample metal concentration (20-200 microg l(-1)), flow-through sample volume (0-5 ml) (all three directly linked to the extraction step), elution flow-rate (0.5-9 ml min(-1)), concentration and volume of eluent (HCl 0.1-0.5M) (all three directly linked to the elution step). The aim of this study was to obtain a set of operating ranges for the six variables tested in order to obtain--by means of a mathematical function allowing maximisation of each response (desirability function)--at least 90% of iron recovery rates. Using the experimental conditions defined in the optimization, the method allowed iron determination with achieved detection limit of 2.3 microgl(-1) and precision (assessed as the relative standard deviation) of 9.3-2.8% for iron solutions of 10.0-150 microgl(-1). Real samples (coming from a water treatment unit) were used successfully when evaluating potentialities of the developed SPE procedure coupled to a spectrophotometric determination.

Study of iron metabolism disturbances in an animal model of insulin resistance

The relationship between iron and insulin-resistance (IR) is documented by the positive correlation between iron stores and IR. Moreover, some patients exhibited a hepatic iron overload associated with IR (HIO-IR) but the mechanism involved in this overload is not known. Thus, we studied the iron metabolism disturbances in an animal model of IR and the influence of provoked hyperglycemia/hyperinsulinemia on plasma iron parameters. Wistar rats were fed a control or a high-fat/high-energy (HF/HE) diet. Plasma glucose, insulin, iron, transferrin and transferrin saturation (TS) were measured during intra-peritoneal glucose test tolerance (IPGTT) compared to saline. Hemogram, tissue iron concentrations and hepatic hepcidin mRNA expression were determined at the end of experiment. HF/HE rats exhibited higher body and liver weights, increased IR-index and hemoglobin concentration. Iron content was lower in the spleen of HF/HE rats and tended to decrease in the liver as compared to controls. Transferrin values were higher and these of TS lower in HF/HE group. The hepcidin mRNA was 3.5-fold lower in HF/HE rats than in controls. IPGTT had no effect on iron status parameters in both groups. As reflected by higher hemoglobin concentration, IR could increase erythropoïesis which enhances iron requirement. Iron stores and TS value decreased leading to a down-regulation of hepcidin expression which increased iron absorption. Hepcidin expression should be investigated in metabolic syndrome and hepatic iron overload associated with IR.

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

OBJECTIVE

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

RESEARCH DESIGN AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Elevated serum ferritin levels predict new-onset type 2 diabetes: results from the EPIC-Norfolk prospective study

AIMS/HYPOTHESIS

The aim of this study was to examine the association between baseline body iron stores and new-onset diabetes.

SUBJECTS AND METHODS

We studied the association between baseline serum ferritin concentration and type 2 diabetes in 360 clinically incident diabetes cases and 758 controls nested within the EPIC (European Prospective Investigation of Cancer)-Norfolk Cohort Study. Serum ferritin levels were categorised into five groups: sex-specific quartiles of the normal range of ferritin and a group with clinically raised ferritin below levels indicative of haemochromatosis.

RESULTS

Baseline serum ferritin was higher among cases than control participants (geometric mean: men 96.6 vs 67.8 ng/ml, respectively, p < 0.001; women 45.9 vs 34.8 ng/ml, respectively, p = 0.005). In analyses adjusted for known risk factors (age, BMI, sex, family history, physical activity, smoking habit) and dietary factors measured by 7-day food diary, the risk of diabetes was markedly elevated in participants with clinically raised ferritin compared with the lowest quartile (odds ratio [OR] 7.4, 95% CI 3.5-15.4). Further adjustment for potential confounding by inflammation (C-reactive protein, IL-6 and fibrinogen) had no material impact on the observed association, while adjustment for hepatic enzymes (alanine aminotransferase and gamma glutamyl transferase) and adiponectin attenuated the magnitude of association, but it remained statistically significant (OR 3.2 [1.3-7.6]).

CONCLUSIONS/INTERPRETATION

Serum ferritin is an important and independent predictor of the development of diabetes. This finding may have important implications for understanding the aetiology of diabetes.

Endocrinopathy of HFE-related hemochromatosis

Hereditary hemochromatosis is a condition affecting many organs, as reflected by the fact that it is managed variably by hematologists, gastroenterologists, rheumatologists and endocrinologists, depending on local preferences. A potential pitfall of this approach is that certain aspects of diagnosis and management may be overlooked, particularly if they fall beyond the normal scope of practice of the specialist physician concerned. The purpose of this article is to review the nature of the endocrine complications of hereditary hemochromatosis, which have changed dramatically since the condition was first described over 100 years ago.

Serum measures of iron status and HFE gene mutations in patients with hepatitis B virus infection

AIM

We tested associations between HFE mutations and hepatitis B virus (HBV) infection. We also explored measures of total body iron status and their association with chronic HBV infection.

METHODS

Serum measures of iron status and HFE mutations (C282Y, H63D, and S65C) were assessed in 344 Iranian patients with chronic HBV infection (214 asymptomatic carriers, 130 patients with chronic progressive liver disease [CPLD]) and 302 controls.

RESULTS

Frequencies of HFE mutations did not differ between patients with chronic HBV infection and controls (C282Y: P=0.9, H63D: P= 0.8, S65C: P=0.9). By logistic regression, advanced hepatic fibrosis was associated with HFE H63D mutation (OR=13.1, P=0.006; 95% CI=2.0-84.1). Higher levels of serum ferritin and transferrin saturation were observed in patients with CPLD than in healthy controls (P=0.0001 and 0.01, respectively, adjusted for age and sex). None of the serum iron measures was related to liver fibrosis stage or necroinflammatory grade.

CONCLUSION

Serum iron measures are associated with chronic progressive hepatitis B. Carriage of HFE mutations is not associated with the presence of chronic HBV infection or values of serum iron measures in this population, although HFE H63D is associated with more advanced hepatic fibrosis.

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

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

Impact of diabetes mellitus on the relationships between iron-, inflammatory- and oxidative stress status

BACKGROUND

Diabetes is an inflammatory condition associated with iron abnormalities and increased oxidative damage. We aimed to investigate how diabetes affects the interrelationships between these pathogenic mechanisms.

METHODS

Glycaemic control, serum iron, proteins involved in iron homeostasis, global antioxidant capacity and levels of antioxidants and peroxidation products were measured in 39 type 1 and 67 type 2 diabetic patients and 100 control subjects.

RESULTS

Although serum iron was lower in diabetes, serum ferritin was elevated in type 2 diabetes (p = 0.02). This increase was not related to inflammation (C-reactive protein) but inversely correlated with soluble transferrin receptors (r = - 0.38, p = 0.002). Haptoglobin was higher in both type 1 and type 2 diabetes (p < 0.001) and haemopexin was higher in type 2 diabetes (p < 0.001). The relation between C-reactive protein and haemopexin was lost in type 2 diabetes (r = 0.15, p = 0.27 vs r = 0.63, p < 0.001 in type 1 diabetes and r = 0.36, p = 0.001 in controls). Haemopexin levels were independently determined by triacylglycerol (R(2) = 0.43) and the diabetic state (R(2) = 0.13). Regarding oxidative stress status, lower antioxidant concentrations were found for retinol and uric acid in type 1 diabetes, alpha-tocopherol and ascorbate in type 2 diabetes and protein thiols in both types. These decreases were partially explained by metabolic-, inflammatory- and iron alterations. An additional independent effect of the diabetic state on the oxidative stress status could be identified (R(2) = 0.5-0.14).

CONCLUSIONS

Circulating proteins, body iron stores, inflammation, oxidative stress and their interrelationships are abnormal in patients with diabetes and differ between type 1 and type 2 diabetes.

Relationships of serum ferritin, transferrin saturation, and HFE mutations and self-reported diabetes in the Hemochromatosis and Iron Overload Screening (HEIRS) study

OBJECTIVE

We evaluated the associations of self-reported diabetes with serum ferritin concentration, transferrin saturation (TfSat), and HFE C282Y and H63D mutations in six racial/ethnic groups recruited at five field centers in the Hemochromatosis and Iron Overload Screening (HEIRS) study.

RESEARCH DESIGN AND METHODS

Analyses were conducted on 97,470 participants. Participants who reported a previous diagnosis of diabetes and/or hemochromatosis or iron overload were compared with participants who did not report a previous diagnosis.

RESULTS

The overall prevalence of diabetes was 13.8%; the highest prevalence was in Pacific Islanders (20.1%). Of all participants with diabetes, 2.0% reported that they also had hemochromatosis or iron overload. The mean serum ferritin concentration was significantly greater in women with diabetes in all racial/ethnic groups and in Native-American men with diabetes than in those without diabetes. The mean serum ferritin concentration was significantly lower in Asian men with diabetes than in those without diabetes. Mean TfSat was lower in participants with diabetes from all racial/ethnic groups except Native-American women than in those without diabetes. There was no significant association of diabetes with HFE genotype. The mean serum ferritin concentration was greater (P < 0.0001) in women with diabetes than in those without diabetes for HFE genotypes except C282Y/C282Y and C282Y/H63D. Log serum ferritin concentration was significantly associated with diabetes in a logistic regression analysis after adjusting for age, sex, racial/ethnic group, HFE genotype, and field center.

CONCLUSIONS

Serum ferritin concentration is associated with diabetes, even at levels below those typically associated with hemochromatosis or iron overload.

Association between serum ferritin, hemoglobin, iron intake, and diabetes in adults in Jiangsu, China

OBJECTIVE

To investigate the association between iron status, iron intake, and diabetes among Chinese adults.

RESEARCH DESIGN AND METHODS

This cross-sectional household survey was carried out in 2002 in Jiangsu Province, China. The sample contained 2,849 men and women aged > or =20 years with a response rate of 89.0%. Iron intake was assessed by food weighing plus consecutive individual 3-day food records. Fasting plasma glucose (FPG), serum ferritin, and hemoglobin were measured.

RESULTS

The prevalence of anemia was 18.3% in men and 31.5% in women. Mean hemoglobin and serum ferritin increased across groups with increasing FPG. The prevalence of anemia among women was 15.0% in individuals with FPG >7.0 mmol/l compared with 32.6% in individuals with FPG <5.6 mmol/l. There was a similar, however not significant, trend among men. In women, after adjusting for known risk factors, the odds ratio (OR) of diabetes was 2.15 (95% CI 1.03-4.51) for subjects in the upper quartile of hemoglobin compared with the rest, and the corresponding OR for the upper quartile of serum ferritin was 3.79 (1.72-8.36). Iron intake was positively associated with diabetes in women; fourth quartile intake of iron yielded an OR of 5.53 (1.47-20.44) compared with the first quartile in the multivariate analyses. In men, similar trends were suggested, although they were not statistically significant.

CONCLUSIONS

Iron status and iron intake was independently associated with risk of diabetes in Chinese women but not in men.

Multiple polymorphic loci determine basal hepatic and splenic iron status in mice

Polymorphisms of genes linked to iron metabolism may account for individual variability in hemochromatosis and iron status connected with liver and cardiovascular diseases, cancers, toxicity, and infection. Mouse strains exhibit marked differences in levels of non-heme iron, with C57BL/6J and SWR showing low and high levels, respectively. The genetic basis for this variability was examined using quantitative trait loci (QTL) analysis together with expression profiling and chromosomal positions of known iron-related genes. Non-heme iron levels in liver and spleen of C57BL/6J x SWR F2 mice were poorly correlated, indicating independent regulation. Highly significant (P < .01) polymorphic loci were found on chromosomes 2 and 16 for liver and on chromosomes 8 and 9 for spleen. With sex as a covariate, additional significant or suggestive (P < 0.1) QTL were detected on chromosomes 7, 8, 11, and 19 for liver and on chromosome 2 for spleen. A gene array showed no clear association between most loci and differential iron-related gene expression. The gene for transferrin and a transferrin-like gene map close to the QTL on chromosome 9. Transferrin saturation was significantly lower in C57BL/6J mice than in SWR mice, but there was no significant difference in the serum level of transferrin, hepatic expression, or functional change in cDNA sequence. beta2-Microglobulin, which, unlike other loci, was associated with C57BL/6J alleles, is a candidate for the chromosome 2 QTL for higher iron. In conclusion, the findings show the location of polymorphic genes that determine basal iron status in wild-type mice. Human equivalents may be pertinent in predisposition to hepatic and other disorders.

Iron intake and the risk of type 2 diabetes in women: a prospective cohort study

OBJECTIVE

Epidemiological studies suggest that high body iron stores are associated with insulin resistance and type 2 diabetes. The aim of this study was to evaluate the association between dietary intake of iron and the risk of type 2 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort study within the Nurses' Health Study. We followed 85,031 healthy women aged 34-59 years from 1980 to 2000. Dietary data were collected every 4 years, and data on medical history and lifestyle factors were updated biennially.

RESULTS

During the 20 years of follow-up, we documented 4,599 incident cases of type 2 diabetes. We found no association between total, dietary, supplemental, or nonheme iron and the risk of type 2 diabetes. However, heme iron intake (derived from animal products) was positively associated with risk; relative risks (RRs) across increasing quintiles of cumulative intake were 1.00, 1.08 (95% CI 0.97-1.19), 1.20 (1.09-1.33), 1.27 (1.14-1.41), and 1.28 (1.14-1.45) (P(trend) < 0.0001) after controlling for age, BMI, and other nondietary and dietary risk factors. In addition, when we modeled heme iron in seven categories, the multivariate RR comparing women who consumed > or =2.25 mg/day and those with intake <0.75 mg/day was 1.52 (1.22-1.88). The association between heme iron and the risk of diabetes was significant in both overweight and lean women.

CONCLUSIONS

This large cohort study suggests that higher heme iron intake is associated with a significantly increased risk of type 2 diabetes.

Association of elevated serum ferritin levels and the risk of gestational diabetes mellitus in pregnant women: The Camden study

OBJECTIVE- We examined the influence of a moderately elevated serum ferritin level at entry to care on the risk of gestational diabetes mellitus (GDM) and a possible mechanism (increased iron stores versus inflammation). RESEARCH DESIGN AND METHODS- In a prospective observational study with 1,456 healthy pregnant women in Camden, New Jersey, serum ferritin and anthropometric measurements were determined. Serum C-reactive protein (CRP) concentration was measured in a nested case-control study of 172 subjects. RESULTS- Women who developed GDM had a higher concentration of serum ferritin than women who did not develop GDM (P < 0.001). Elevated serum ferritin level (highest quintile) was significantly and positively correlated with prepregnant BMI and skinfold measurements. Women in the highest quintile of serum ferritin had a twofold increased risk of developing GDM adjusted for several known risk factors (adjusted odds ratio, 2.02 [95% CI 1.04-3.92], P < 0.05). Similar results were obtained with a nested case-control study, in which women in the highest tertile of serum ferritin (2.35 [1.06-5.22], P < 0.05) or CRP (2.67 [1.16-6.17], P < 0.001) had a greater than twofold increased risk of GDM. However, these effects were modified and became nonstatistically significant after additional adjustment for prepregnant BMI. CONCLUSIONS- Elevated serum ferritin concentrations early in gestation are associated with an increased risk of GDM. The association, at least in part, is mediated by the maternal fat mass and obesity. These data suggest a possible link between elevated serum ferritin and low-grade inflammation.

DNA Damage by Free Radical Production by Aminoguanidine

Aminoguanidine (AG), a prototype therapeutic dicarbonyl scavenger, is the most potent drug available today to inhibit the formation of advanced glycation endproducts (AGEs) and to reverse glycation-mediated damage in normal aging. This paper examines the ability of AG to cause damage to supercoiled plasmid DNA in the presence of the transition metal, Fe(+3). Damage to DNA was dependent on the concentrations of both the transition metal and AG. We could detect hydroxyl radical as well as hydrogen peroxide during the incubation of AG with Fe(+3). Thus this finding further cautions against the indiscriminate use of AG in clinical prophylaxis in diabetes and questions its use as a therapeutic agent.

Metabolic syndrome, insulin resistance and the inflammation markers C-reactive protein and ferritin

BACKGROUND

Patients with metabolic syndrome (MS) have above-average risk of developing atherosclerosis and cardiovascular disease. Inflammation plays a key role in the development of atherosclerosis. High levels of the acute phase reactants C-reactive protein (CRP) and ferritin have been reported to correlate with various components of MS.

PATIENTS AND METHODS

The serum CRP, ferritin, glucose, insulin, triglycerides, HDL-cholesterol and total cholesterol concentrations of 598 obese or overweight patients were determined, together with relevant anthropometric parameters. Insulin resistance was evaluated by the HOMA method. MS was diagnosed using the ATP III criteria.

RESULTS

CRP levels were higher among patients with central obesity than in those without (5.8 vs 3.9 mg/l; P=0.003), and higher among those with fasting plasma glucose concentrations >or=110 mg/dl than in those with lower concentrations (7.4 vs 4.1 mg/l; P=0.01). Serum ferritin levels were higher among patients with triglyceride concentrations >or=150 mg/dl than in those with lower levels (76.8 vs 40.1 ng/ml; P<0.001), and higher among those with fasting plasma glucose concentrations >or=110 mg/dl than in those with lower concentrations (75.7 vs 41.7 ng/ml; P=0.005). The number of MS criteria that were satisfied increased with CRP and ferritin levels. Patients with insulin resistance also had higher CRP and ferritin levels than those without, 7.3 vs 4.3 mg/l for CRP (P=0.032) and 124.5 vs 80.1 ng/ml for ferritin (P<0.001).

CONCLUSIONS

MS and insulin resistance are associated with elevated serum CRP and ferritin. Evaluation of subclinical chronic inflammation in patients with MS and/or insulin resistance by determination of these markers might aid in their evaluation as candidates for aggressive intervention against cardiovascular risk factors.

Hyperglycosylated ferritin in sera of HIV-1-infected patients treated with highly active antiretroviral therapy

A study was conducted to determine the relationship between ferritin and glycosylated isoforms of ferritin and insulin resistance in 69 HIV-infected men receiving HAART. Ferritin levels were significantly correlated with aspartate aminotransferase, alanine aminotransferase, bilirubin and with insulin resistance. The ferritin isoelectric focusing patterns of five insulin-resistant HIV-infected patients under HAART showed large amounts of hyperglycosylated isoforms, which was not found in 56 control subjects and 46 untreated HIV-1-infected patients.

HFE genotypes and dietary heme iron: no evidence of strong gene-nutrient interaction on serum ferritin concentrations in middle-aged women

BACKGROUND AND AIM

Hereditary hemochromatosis (HH) is a disorder characterized by inappropriately high intestinal iron absorption. In populations of Northern European descent, HH is most commonly caused by mutations (C282Y/H63D) in the HFE gene.

METHODS AND RESULTS

We investigated the effects of dietary heme iron intake and HFE mutations on serum ferritin concentrations in a population-based random sample of 1611 women aged >50 years using analysis of covariance (ANCOVA). Higher heme iron intake was associated with significantly higher serum ferritin concentrations (P(trend) < 0.001). Also, women with the compound or C282Y homozygous genotype had significantly higher serum ferritin concentrations (geometric mean 115.2 microg/L (95% CI 81.4-162.9 microg/L) than women carrying normal alleles (geometric mean 76.6 microg/L (95% CI 72.5-80.9 microg/L). We observed the highest serum ferritin concentrations among postmenopausal women who are compound heterozygous or C282Y homozygous, and who consume relatively high amounts of heme iron (geometric mean 183.9 microg/L (95% CI 97.2-347.8 microg/L).

CONCLUSIONS

Even when there are currently no clinical signs, women with the compound or C282Y homozygous genotype may still be at risk for developing iron overload sometime after menopause.

Insulin resistance: a metabolic pathway to chronic liver disease

Insulin resistance (IR) is the pathophysiological hallmark of nonalcoholic fatty liver disease (NAFLD), one of the most common causes of chronic liver disease in Western countries. We review the definition of IR, the methods for the quantitative assessment of insulin action, the pathophysiology of IR, and the role of IR in the pathogenesis of chronic liver disease. Increased free fatty acid flux from adipose tissue to nonadipose organs, a result of abnormal fat metabolism, leads to hepatic triglyceride accumulation and contributes to impaired glucose metabolism and insulin sensitivity in muscle and in the liver. Several factors secreted or expressed in the adipocyte contribute to the onset of a proinflammatory state, which may be limited to the liver or more extensively expressed throughout the body. IR is the common characteristic of the metabolic syndrome and its related features. It is a systemic disease affecting the nervous system, muscles, pancreas, kidney, heart, and immune system, in addition to the liver. A complex interaction between genes and the environment favors or enhances IR and the phenotypic expression of NAFLD in individual patients. Advanced fibrotic liver disease is associated with multiple features of the metabolic syndrome, and the risk of progressive liver disease should not be underestimated in individuals with metabolic disorders. Finally, the ability of insulin-sensitizing, pharmacological agents to treat NAFLD by reducing IR in the liver (metformin) and in the periphery (thiazolidinediones) are discussed.

Iron stores, blood donation, and insulin sensitivity and secretion

BACKGROUND

Epidemiologists have observed that blood donation is associated with decreased risk of type 2 diabetes and cardiovascular disease.

METHODS

We investigated the relationship between iron stores and insulin sensitivity, after controlling for known confounding factors, and compared insulin sensitivity between blood donors and individuals who had never donated blood (nondonors). In 181 men, insulin sensitivity and insulin secretion were evaluated through frequently sampled intravenous glucose tolerance tests with minimal model analysis. Men who donated blood between 6 months and 5 years before inclusion (n = 21) were carefully matched with nondonors (n = 66) for age, body mass index, waist-to-hip ratio, and cardiovascular risk profile, including blood lipids, blood pressure, and smoking status.

RESULTS

Frequent blood donors (2-10 donations) had increased insulin sensitivity [3.42 (1.03) vs 2.45 (1.2) x 10(-4) x min(-1) x mIU/L; P = 0.04], decreased insulin secretion [186 (82) vs 401.7 (254) mIU/L x min; P <0.0001], and significantly lower iron stores [serum ferritin, 101.5 (74) vs 162 (100) microg/L; P = 0.017] than nondonors, but the 2 groups had similar blood hematocrits and blood hemoglobin concentrations.

CONCLUSIONS

Blood donation is simultaneously associated with increased insulin sensitivity and decreased iron stores. Stored iron seems to impact negatively on insulin action even in healthy people, and not just in classic pathologic conditions associated with iron overload (hemochromatosis and hemosiderosis). According to these observations, it is imperative that a definition of excessive iron stores in healthy people be formulated.

Soluble transferrin receptors and ferritin in Type 2 diabetic patients

AIM

To determine circulating transferrin receptor levels (sTfR) in Type 2 diabetic patients to evaluate whether serum ferritin reflects iron body stores or inflammation in diabetic population.

METHODS

A total of 84 consecutive Type 2 diabetic patients and 60 healthy subjects matched by age and gender were included in this case-control study. Ferritin concentration was measured by a turbidimetric method and sTfR concentration were determined by nephelometry.

RESULTS

Diabetic patients have higher serum ferritin levels than control subjects [114 ng/ml (12-831) vs. 74 ng/ml (11-697); P = 0.006]. However, no differences in sTfR concentrations were observed between both groups [1.27 mg/l (0.69-2.47) vs. 1.24 mg/l (0.77-2.80); P = NS]. A negative correlation between ferritin and sTfR concentration was detected in control subjects but not in diabetic patients.

CONCLUSIONS

Serum ferritin levels are increased in Type 2 diabetic patients in the absence of a reciprocal decrease of sTfR. This finding suggests that elevated ferritin levels in Type 2 diabetes are mainly as a result of inflammatory mechanisms rather than iron overload.

Diabetes is the main factor accounting for the high ferritin levels detected in chronic hepatitis C virus infection

OBJECTIVE

A high prevalence of diabetes has been reported in patients with hepatitis C virus (HCV) infection. Both diabetes and HCV infection are associated with high serum ferritin levels. Although HCV infection could be the main factor responsible for the high ferritin levels, it is also possible that diabetes rather than HCV infection might be a major contributor to the high ferritin levels observed in patients with HCV infection. The aim of this study was to investigate the contribution of diabetes to the high ferritin levels observed in HCV-infected patients with chronic hepatitis.

RESEARCH DESIGN AND METHODS

A total of 634 noncirrhotic individuals were prospectively recruited at a university hospital. According to the HCV antibody status and the presence of diabetes, the subjects were divided into four groups: group A (anti-HCV-positive diabetic patients, n = 53), group B (anti-HCV-negative diabetic patients, n = 242), group C (anti-HCV-positive nondiabetic patients, n = 191), and group D (anti-HCV-negative nondiabetic control subjects, n = 148). Multiple regression analyses were used to explore the variables independently related to ferritin levels.

RESULTS

Serum ferritin levels in group A were significantly higher than in the other groups (A > B, P < 0.01; A > C, P < 0.001; A > D, P < 0.001). Ferritin levels were higher in group B than in group D (P = 0.001). However, group C has ferritin values similar to those of group D. In multivariate analyses, diabetes but not HCV infection was independently related to serum ferritin concentrations.

CONCLUSIONS

Diabetes rather than HCV infection itself is the main factor associated with the increased ferritin levels detected in patients with HCV infection. Therefore, the presence of diabetes should be taken into account when iron metabolism is evaluated in HCV-infected patients.

Serum ferritin and risk of the metabolic syndrome in U.S. adults

OBJECTIVE

We examined the relationship among iron stores, the metabolic syndrome, and insulin resistance.

RESEARCH DESIGN AND METHODS

We conducted a cross-sectional study of 6,044 adults >20 years of age who participated in the Third National Health and Nutrition Examination Survey. Metabolic syndrome was defined as the presence of at least three of the following: elevated blood pressure, low HDL cholesterol, elevated serum triglycerides, elevated plasma glucose, and abdominal obesity. Insulin resistance was estimated using homeostasis model assessment (for insulin resistance), fasting insulin, and triglyceride-to-HDL cholesterol ratio.

RESULTS

After excluding individuals with likely hemochromatosis, mean serum ferritin values in premenopausal women, postmenopausal women, and men were 33.6, 93.4, and 139.9 microg/l, respectively. Metabolic syndrome was more common in those with the highest compared with the lowest levels of serum ferritin in premenopausal women (14.9 vs. 6.4%, P = 0.002), postmenopausal women (47.5 vs. 28.2%, P < 0.001), and men (27.3 vs. 13.8%, P < 0.001). Insulin resistance also increased across quartiles of serum ferritin for men and postmenopausal women and persisted after adjustment for age, race/ethnicity, C-reactive protein, smoking, alcohol intake, and BMI.

CONCLUSIONS

Elevated iron stores were positively associated with the prevalence of the metabolic syndrome and with insulin resistance.

Elevated iron indices in patients with diabetes

AIMS

Excess iron has been implicated in the pathogenesis of diabetes and its complications. This study documents the assessment of plasma iron indices and the correlation between transferrin saturation with biochemical and clinical parameters in a cross-sectional survey of 820 patients with diabetes in long-term follow-up in a single clinic.

METHODS

Plasma iron indices, together with the biochemical and clinical profile of all patients, were recorded over a 2-year period. Predictors of the transferrin saturation were identified using multiple and logistic regression analysis.

RESULTS

Eighty per cent of patients had Type 2 diabetes. The prevalence of elevated transferrin saturation (> 35%) was 3-4-fold higher in patients with diabetes, compared with historical prevalence described in the general population. Independent associations with elevated transferrin saturation were male gender, low C-reactive protein, and increased fasting plasma glucose (all P < 0.0001). Patients with Type 1 diabetes were also more likely to have an elevated transferrin saturation [odds ratio 3.9 (95% CI 1.9-8.0), P < 0.001]. Patients with an elevated transferrin saturation were younger, but had a similar duration of diabetes, possibly suggesting an earlier age of onset. There was no correlation between the presence of diabetic complications and the presence of elevated iron indices.

CONCLUSIONS

Elevated iron indices are more common in patients with diabetes. Excess iron may have a role in the development of diabetes and subsequently in glycaemic control. This should be balanced by the strong association between iron indices and anaemia in patients with diabetes.

The role of iron neurotoxicity in ischemic stroke

Stroke is the second leading cause of death worldwide, and its incidence is expected to rise with the projected increase in the number of aging population. Disturbances of brain iron homeostasis have been linked to acute neuronal injury following cerebral ischemia. Free iron catalyzes the conversion of superoxide and hydrogen peroxide into hydroxyl radicals, which promote oxidative stress leading to subsequent cell death/apoptosis. In recent years, considerable evidence has emerged regarding the role of iron neurotoxicity following experimental cerebral ischemia. Few clinical studies have also attempted to investigate the role of iron in stroke patients. The present review will examine the currently available evidence for iron-mediated neurotoxicity and the potential mechanisms underlying deregulation of iron homeostasis in the brain following cerebral ischemia. Understanding the changes in brain iron metabolism and its relationship to neuronal injury in ischemic stroke could provide new therapeutic targets to improve the outcome of stroke patients.

High prevalence of glucose abnormalities in patients with hepatitis C virus infection: a multivariate analysis considering the liver injury

OBJECTIVE

The aim of this study was to compare the prevalence of both impaired fasting glucose (IFG) and diabetes between hepatitis C virus (HCV)-infected patients and patients with other liver diseases but anti-HCV-, taking into account the degree of liver damage.

RESEARCH DESIGN AND METHODS

A total of 642 consecutive patients attending the outpatient liver unit of a university hospital (498 anti-HCV+ and 144 anti-HCV-) were prospectively recruited. Patients were classified as having chronic hepatitis (n = 472) or cirrhosis (n = 170) by means of the result of either a liver biopsy or by typical clinical features. A logistic regression model was used to determine independent associations of covariates (age, sex, BMI, HCV antibody status, and triglycerides) with the presence of glucose abnormalities.

RESULTS

A threefold increase in the prevalence of glucose abnormalities was observed in HCV+ patients with chronic hepatitis in comparison with HCV- subjects (32 vs. 12%; P = 0.0003). In contrast, among patients with cirrhosis, although both diabetes and IFG were more prevalent in anti-HCV+ patients (40%) than in anti-HCV- patients (36%), the differences were not statistically significant. Finally, the logistic regression analysis showed that HCV infection was independently related to glucose abnormalities in those patients with chronic hepatitis (odds ratio 4.26 [95% CI 2.03-8.93]). In contrast, HCV was not an independent predictor of glucose abnormalities in cirrhotic patients.

CONCLUSIONS

The high prevalence of IFG and diabetes found in HCV-infected patients observed in our study suggests that screening for glucose abnormalities should be indicated in these patients. In addition, we provide evidence that the genuine connection between HCV infection and diabetes is initiated at early stages of hepatic disease.

Non-alcoholic fatty liver and insulin resistance: a cause-effect relationship?

The role of insulin resistance in non-alcoholic fatty liver disease is suggested by laboratory data (hyperinsulinemia and decreased sensitivity to endogenous and exogenous insulin). The clinical association with features of the metabolic syndrome, particularly in the most aggressive stages of the disease, further confirms a causative role. Fat accumulation in the liver may stem either from genetic defects, primarily responsible for insulin resistance, or excessive calorie intake and visceral obesity, and is mediated by adipocytokines (leptin, adiponectin, tumour necrosis factor-alpha). Progression of fatty liver to steatohepatitis may be the result of an imbalance between pro-inflammatory and anti-inflammatory cytokines, triggering the formation of reactive oxygen species and intrahepatic lipid peroxidation. This process may also be promoted or accelerated by pro-oxidant xenobiotics or environmental factors. Insulin resistance provides a target for specific treatment of non-alcoholic fatty liver, and insulin-sensitising agents (metformin or thiazolidinediones) as well as lifestyle changes to reduce visceral adiposity are the most promising therapeutic options. Future trials need to be performed in order to test the long-term effectiveness of these treatments on the basis of clinically relevant histological outcomes.

Impact of iron deficiency anemia on prevalence of gestational diabetes mellitus

OBJECTIVE

Increased Hb and ferritin have been associated with gestational diabetes mellitus (GDM). This study was performed to determine whether the prevalence of GDM is influenced by iron deficiency anemia.

RESEARCH DESIGN AND METHODS

In a retrospective case-control study, 242 women with iron deficiency anemia (Hb<10 g/dl with features of iron deficiency) were compared with 484 nonanemic women matched for year of birth, who were delivered within the same 24-month period in our hospital, with respect to maternal demographics, infant outcome, and the prevalence of GDM diagnosed according to the World Health Organization criteria.

RESULTS

There was no difference in the prepregnancy weight or BMI, but the anemic group had more multiparas and significantly lower gestational weight and BMI increments and prevalence of GDM (odds ratio [OR] 0.52, 95% CI 0.27-0.97), which was inversely correlated (P=0.045) with the duration of anemia. To determine the independent effect of anemia on GDM, multiple logistic regression analysis was performed adjusting for the effects of multiparity and BMI, and anemia was confirmed to be significantly associated with decreased prevalence of GDM (adjusted OR 0.46, 95% CI 0.23-0.90).

CONCLUSIONS

The prevalence of GDM is reduced in iron deficiency anemia, which probably served as a surrogate for other factors such as nutritional inadequacy and reduced gestational weight gain. Further studies on the relationship between nutritional improvement and the increasing prevalence of GDM in the developing world are warranted.

Dietary iron intake and Type 2 diabetes incidence in postmenopausal women: the Iowa Women's Health Study

AIMS/HYPOTHESIS

Recently, a clear biological link between iron metabolism and diabetes has emerged from epidemiological and experimental studies. We carried out a prospective study of dietary iron intake and incidence of Type 2 diabetes.

METHODS

35,698 postmenopausal women initially aged 55 to 69 years were followed for 11 years. Diet was assessed with a food frequency questionnaire at baseline.

RESULTS

Intake of heme iron showed a positive association with incident Type 2 diabetes; the relative risks were 1.0, 1.07, 1.12, 1.14, and 1.28 across quintiles of heme iron (p trend =0.02) after adjustment for non-dietary and dietary risk factors. Heme iron showed a weak positive association among non-drinkers, but the association appeared to be stronger among subjects who consumed more alcohol. For example, in a model restricted to those who drank alcohol at least 15 g/day, adjusted relative risks across quintiles of heme iron were 1.0, 2.26, 3.22, 1.92, and 4.42 (p trend =0.05); and consumers of 30 g/day of more of supplemental iron had an adjusted relative risk equal to 3.03 (95% CI, 1.29-7.12)], compared to those who took no iron supplement. Non-heme iron was inversely associated with incidence of Type 2 diabetes. Amongst non-drinkers adjusted relative risks were 1.0, 0.83, 0.87, 0.72, and 0.67 across quintiles (p trend <0.01). This inverse association was lost among drinkers, in whom there was no association of diabetes incidence with non-heme iron.

CONCLUSIONS/INTERPRETATION

Greater dietary heme-iron intake and/or supplemental iron were associated with an increased risk of Type 2 diabetes, especially amongst those who drink alcohol.

ALTERED TISSUE CONCENTRATION OF MINERALS IN SPONTANEOUS DIABETIC RATS (Goto-Kakizaki rats)

A relationship has been reported between trace elements and diabetes mellitus. This study examined the concentration of several trace elements (Zn, Mg, Ca, Fe, Cu, Mn, P) in each organ from spontaneous type 2 diabetic model rat (GK rat) and compared with control. Results showed that diabetic rat excreted 1.25-, 1.5-fold more zinc and magnesium, respectively, than control in the urine. Contents of zinc and magnesium in kidney and testis and fatty tissue were lowered significantly in GK rat. Zinc in liver and magnesium in lung were also lowered. Concentrations of other trace elements also changed in some organs from GK rats compared with those from control. These results demonstrate that trace element imbalances come out significantly in mild diabetes and the need to instruct a nutritionally balanced diet that takes account of trace elements in diabetes from the early stage.

Dietary iron intake and blood donations in relation to risk of type 2 diabetes in men: a prospective cohort study

BACKGROUND

Excessive iron stores may promote insulin resistance and lead to the development of type 2 diabetes. However, prospective data relating iron intake and blood donations (determinants of body iron stores) to diabetes incidence are limited.

OBJECTIVE

We examined iron intake and blood donations in relation to the incidence of type 2 diabetes.

DESIGN

We followed men aged 40-75 y who participated in the Health Professionals' Follow-up Study; were free of diabetes, cardiovascular disease, and cancer in 1986; and provided dietary data (n = 38 394). Of those participants, 33 541 also provided a history of blood donation during the past 30 y in 1992.

RESULTS

During 12 y of follow-up, we ascertained 1168 new cases of type 2 diabetes. After adjustment for age, body mass index, and other diabetes risk factors, total iron intake was not associated with the risk of type 2 diabetes. Intakes of total heme iron [multivariate relative risk (RR) for extreme quintiles: 1.28; 95% CI: 1.02, 1.61; P for trend = 0.045] and of heme iron from red meat (RR: 1.63; 1.26, 2.10; P for trend < 0.001) were associated with an increased risk. However, heme-iron intake from sources other than red meat was not associated with diabetes risk (RR: 0.99; 0.81, 1.22). No significant associations were found between blood donation and the risk of type 2 diabetes.

CONCLUSIONS

Heme-iron intake from red meat sources is positively associated with the risk of type 2 diabetes. Total iron intake, heme-iron intake from non-red meat sources, and blood donations are not related to the risk of type 2 diabetes.

Processed meat intake and incidence of Type 2 diabetes in younger and middle-aged women

AIM/HYPOTHESIS

The aim of this study was to investigate the association between processed and other meat intake and incidence of Type 2 diabetes in a large cohort of women.

METHODS

Incident cases of Type 2 diabetes were identified during 8 years of follow-up in a prospective cohort study of 91246 U.S. women aged 26 to 46 years and being free of diabetes and other major chronic diseases at baseline in 1991.

RESULTS

We identified 741 incident cases of confirmed Type 2 diabetes during 716276 person-years of follow-up. The relative risk adjusted for potential non-dietary confounders was 1.91 (95% CI: 1.42-2.57) in women consuming processed meat five times or more a week compared with those consuming processed meat less than once a week ( p<0.001 for trend). Further adjustment for intakes of magnesium, cereal fibre, glycaemic index, and caffeine or for a Western dietary pattern did not appreciably change the results and associations remained strong after further adjustment for fatty acid and cholesterol intake. Frequent consumption of bacon, hot dogs, and sausage was each associated with an increased risk of diabetes. While total red meat (beef or lamb as main dish, pork as main dish, hamburger, beef, pork or lamb as sandwich or mixed dish) intake was associated with an increased risk of diabetes, this association was attenuated after adjustment for magnesium, cereal fiber, glycaemic index, and caffeine (relative risk: 1.44; 95% CI: 0.92-2.24).

CONCLUSION/INTERPRETATION

Our data suggest that diets high in processed meats could increase the risk for developing Type 2 diabetes.