Body iron stores are associated with serum insulin and blood glucose concentrations. Population study in 1,013 eastern Finnish men

Serum ferritin levels and polycystic ovary syndrome in obese and nonobese women

OBJECTIVE

The aim of this study is to evaluate serum ferritin levels and polycystic ovary syndrome (PCOS)-related complications in obese and nonobese women.

MATERIALS AND METHODS

This retrospective study included 539 (286 with PCOS and 253 without PCOS).

RESULTS

Serum ferritin correlated with menstrual cycle length, sex hormone-binding globulin, total testosterone, androstenedione, triglyceride, and total cholesterol in both obese and nonobese women. Obese women with high ferritin levels exhibited higher insulin resistance, impaired glucose tolerance, and liver enzymes (glutamic oxaloacetic transaminase, glutamic pyruvic transaminase) than obese women with low ferritin levels. However, among nonobese women, insulin resistance and risk of diabetes were not significantly different between the high and low ferritin groups. Independent of obesity, hypertriglyceridemia was the major metabolic disturbance observed in women with elevated serum ferritin levels.

CONCLUSION

Elevated serum ferritin levels are associated with increased insulin resistance and risk of diabetes in obese women but not in nonobese women. However, higher serum ferritin levels were correlated with a greater risk of hyperglyceridemia in both obese and nonobese women. Therefore, hypertriglyceridemia in women with PCOS might be associated with iron metabolism.

GDF-15 and Hepcidin Levels in Nonanemic Patients with Impaired Glucose Tolerance

Aims. Growth Differentiation Factor-15 (GDF-15) has been suggested as one of the regulators of hepcidin, an important regulatory peptide for iron deposition. Current data is conflicting about the relationship between hepcidin and disorders of glucose metabolism. We aimed to investigate serum hepcidin and GDF-15 concentrations and their associations with each other, in nonanemic subjects with impaired glucose tolerance (IGT) in comparison with the nonanemic subjects with normal glucose tolerance (NGT). Methods. Thirty-seven subjects with IGT and 32 control subjects with NGT, who were age-, gender-, and body mass index- (BMI-) matched, were included in the study. Results. Serum GDF-15 levels were significantly higher in IGT compared to NGT. There were no differences in hepcidin, interleukin-6, and high sensitive C-reactive protein levels between the groups. We found a positive correlation between GDF-15 and hepcidin levels. There were also positive correlations between GDF-15 and age, uric acid, creatinine, and area under the curve for glucose (AUC-G). Hepcidin was correlated positively with ferritin levels. In the multiple regression analysis, GDF-15 concentrations were independently associated with age, uric acid, and AUC-G. Conclusions. Impaired glucose tolerance is associated with increased GDF-15 levels even in the absence of anemia, but the levels of hepcidin are not significantly altered in prediabetic state.

Association of insulin resistance with serum ferritin and aminotransferases-iron hypothesis

AIM: To investigate the relationship of iron indices with diabetes mellitus (DM) in those without hemochromatosis.

METHODS: This cross-sectional study examined data collected during the Third National Health and Nutrition Examination Survey (NHANES III). Only those who fasted properly and were not anemic with transferrin saturation < 45% were included (n = 6849). Insulin sensitivity and beta cell function were calculated from fasting glucose and insulin concentrations. Indices of iron metabolism were examined in the presence or absence of DM. We examined the relationship of insulin sensitivity and beta cell function with serum ferritin concentration. The influence of C-reactive protein and liver enzymes was also investigated.

RESULTS: Serum ferritin concentration was significantly higher in diabetic subjects (P = 0.0001 to < 0.000001). The difference remained significant after adjustment for age, body mass index, alcohol consumption, and mineral/iron supplement (P = 0.03 to < 0.000001). In those who did not take insulin, serum ferritin concentration was negatively associated with insulin sensitivity (P = 0.05 to 0.00001), but not with beta cell function. The alanine aminotransferase was correlated with serum ferritin concentration (P = 0.02 to < 0.000001) but not with insulin sensitivity, suggesting the role of the liver in iron-associated insulin resistance.

CONCLUSION: As most of diabetes is type 2 diabetes and insulin resistance is a cardinal feature of type 2 diabetes, disordered iron metabolism could play a role in the pathogenesis of insulin resistance and type 2 diabetes through its effect on liver function.

Beta Cell Function and the Nutritional State: Dietary Factors that Influence Insulin Secretion

Approximately 366 million people worldwide have been diagnosed with type-2 diabetes (T2D). Chronic insulin resistance, decreased functional β-cell mass, and elevated blood glucose are defining characteristics of T2D. Great advances have been made in understanding the pathogenesis of T2D with respect to the effects of dietary macronutrient composition and energy intake on β-cell physiology and glucose homeostasis. It has been further established that obesity is a leading pathogenic factor for developing insulin resistance. However, insulin resistance may not progress to T2D unless β-cells are unable to secret an adequate amount of insulin to compensate for decreased insulin sensitivity. Therefore, pancreatic β-cell dysfunction plays an important role in the development of overt diabetes. This paper reviews recent research findings on the effects of several micronutrients (zinc, vitamin D, iron, vitamin A), leucine, and the phytochemical, genistein on pancreatic β-cell physiology with emphasis on their effects on insulin secretion, specifically in the context of T2D.

Association of Serum Ferritin Levels with Metabolic Syndrome and Insulin Resistance

INTRODUCTION

The impact of CVDs and Type II DM is increasing over the last decade. It has been estimated that by 2025 their incidence will double. Ferritin is one of the key proteins regulating iron homeostasis and is a widely available clinical biomarker of iron status. Some studies suggest that prevalence of atherosclerosis and insulin resistance increases significantly with increasing serum ferritin. Metabolic syndrome is known to be associated with increased risk of atherosclerosis as well as insulin resistance.

AIM

The present study was designed to explore the association of serum ferritin levels with metabolic syndrome and insulin resistance.

MATERIALS AND METHODS

The present study was prospective, cross sectional. The study protocol was approved by IEC. The study group consisted of 90 participants (50 cases of metabolic syndrome and 40 age and sex matched controls). Diagnosis of metabolic syndrome was done as per NCEP ATP III criteria. Estimation of serum Ferritin and Insulin was done by Chemiluminescence Immunoassay (CLIA) while Glucose by Glucose Oxidase and Peroxidase (GOD-POD) method. Insulin Resistance was calculated by HOMA IR score.

STATISTICAL ANALYSIS

Data obtained was statistically analysed by using student t-test.

RESULTS

We found statistically significant rise in the levels of serum ferritin (p=<0.001), glucose (p=<0.001), insulin (p=<0.001) and HOMA IR score (p=<0.0001) in cases of metabolic syndrome as compared with controls.

CONCLUSION

High serum ferritin levels though within normal range are significantly associated with both metabolic syndrome and insulin resistance.

Serum ferritin is associated with carotid atherosclerotic plaques but not intima-media Thickness in patients with abnormal glucose metabolism

BACKGROUND

We investigated the association between serum ferritin and carotid artery lesions in populations with abnormal glucose metabolism.

METHODS

We included 70 participants with abnormal glucose metabolism and 170 participants with normal glucose metabolism and measured their baseline serum ferritin levels. During follow-up carotid intima-media thickness and carotid plaque were evaluated.

RESULTS

Serum ferritin levels were higher in the participants with abnormal glucose metabolism (p<0.01). We further divided the patients with abnormal glucose metabolism into subgroups with and without intima-media proliferation, and found that ferritin was excluded from the final equation in the logistic regression. Furthermore, age, waist circumference, ferritin, 2h-PG, and total cholesterol were significantly different between the subgroups with and without carotid plaque. When the above data were included in a logistic regression model, the p values obtained for age, ferritin, and 2h-PG were 0.004, 0.032, and 0.011, respectively.

CONCLUSIONS

In the Chinese population, serum ferritin levels are significantly increased in patients with abnormal glucose metabolism. The carotid intima-media thickness showed no independent relationship with serum ferritin in patients with abnormal glucose metabolism. However, high serum ferritin is an important risk factor for carotid atherosclerosis in these patients.

Distribution of serum transferrin, and its associations with metabolic disorders among Chinese: A nation-wide, health and nutrition survey

SCOPE

This study examined the associations of serum transferrin and metabolic disorders among Chinese population.

METHODS AND RESULTS

This study is based on nation-wide, population-based China Health and Nutrition survey including 8564 men and women aged 18 years or older. Anthropometric and fasting blood glucose, insulin, lipids, and transferrin data were collected. Elevated transferrin concentrations associated with higher body mass index, waist circumference, lipids, insulin, glucose (all p < 0.0001). Serum transferrin concentrations increased gradually with increasing numbers of metabolic syndrome (MetS) components among men and women (p = 0.0003). Elevated concentrations of transferrin were significantly related with higher risk of MetS (p = 0.0006), obesity (p = 0.0089), overweight (p < 0.0001). No associations between transferrin concentrations and risk of diabetes and high blood pressure were observed in both men and women.

CONCLUSION

Elevated transferrin concentrations were positively associated with risk of MetS and obesity, but not with risk of diabetes among Chinese.

A review of potential metabolic etiologies of the observed association between red meat consumption and development of type 2 diabetes mellitus

Epidemiological studies suggest that red and processed meat consumption is related to an increased risk of type 2 diabetes. However, it is not clearly understood which components of red and processed meat contribute to this increased risk. This review examines potential mechanisms addressing the role of saturated fatty acid, sodium, advanced glycation end products (AGEs), nitrates/nitrites, heme iron, trimethylamine N-oxide (TMAO), branched amino acids (BCAAs) and endocrine disruptor chemicals (EDCs) in the development of type 2 diabetes based on data from published clinical trials and animal models. TMAO which is derived from dietary carnitine and choline by the action of bacterial enzymes followed by oxidation in the liver may be a strong candidate molecule mediating the risk of type 2 diabetes. BCAAs may induce insulin resistance via the mammalian target of rapamycin complex 1 (mTORC1) and ribosomal protein S6 kinase β 1 (S6k1)-associated pathways. The increased risk associated with processed meat compared with red meat suggests that there are interactions between the saturated fat, salt, and nitrates in processed meat and iron, AGEs and TMAO. Intervention studies are required to clarify potential mechanisms and explore interactions among components, in order to make firm recommendations on red and processed meat consumption.

Serum ferritin and glucose homeostasis: change in the association by glycaemic state

BACKGROUND

Data on the association between body iron and glucose homeostasis by the three glycaemic states are scarce. Thus, we investigated the association between body iron as assessed by a serum ferritin concentration and glucose homeostasis using homeostasis model assessment (HOMA) of insulin resistance (HOMA-IR) and beta cell function (HOMA-BcF) in different glycaemic states.

METHODS

A cross-sectional analysis was conducted in 2541 men aged 42-60 years in 1984-1989 in the Kuopio Ischemic Heart Disease Risk Factor Study. Subjects were classified into the three glycaemic states, normoglycaemia, prediabetes and type 2 diabetes (T2D), by fasting plasma glucose measurements and the information collected at study visit. The association between serum ferritin quartiles and HOMA-IR and HOMA-BcF for each glycaemic state was examined by analysis of covariance and linear regression analysis.

RESULTS

The mean age and serum ferritin concentrations were 53.1 years (standard deviation = 5.7, range = 42.0-61.3 years) and 166.2 µg/L (standard deviation = 141.7, range = 11-960 µg/L), respectively. After multivariable adjustments, a weak and direct association was observed between serum ferritin quartiles and HOMA-IR in normoglycaemia (P-trend = 0.001) but a direct association in prediabetes (P-trend = 0.007) and in T2D (P-trend = 0.078). In HOMA-BcF, the association was weak and direct in normoglycaemia (P-trend = 0.003), direct in prediabetes (P-trend = 0.005) and inverse in T2D (P-trend = 0.105). Strongest associations were observed in prediabetes (β = 0.25, 95% confidence interval = 0.14-0.36 and P = 0.004 in HOMA-IR; β = 0.23, 95% confidence interval = 0.15-0.31 and P = 0.008 in HOMA-BcF) after a 100-µg/L increase in serum ferritin (log-transformed).

CONCLUSIONS

These data suggest that both the strength and the direction of the association between body iron stores and glucose homeostasis are dependent on the glycaemic state of the population.

Increased inflammation and decreased insulin sensitivity indicate metabolic disturbances in zoo-managed compared to free-ranging black rhinoceros (Diceros bicornis)

Black rhinoceros (rhinos) living in zoos express a host of unusual disease syndromes that are associated with increased morbidity and mortality, including hemolytic anemia, rhabdomyolysis, hepatopathy and ulcerative skin disease, hypophosphatemia and iron overload. We hypothesized that iron overload is a consequence and indicator of disturbances related to inflammation and insulin/glucose metabolism. The objectives of this study were to: (1) generate the first baseline information on biomarkers of inflammation (tumor necrosis factor alpha [TNFα], serum amyloid A [SAA]), insulin sensitivity (insulin, glucose and proxy calculations of insulin sensitivity), phosphate and iron stores (ferritin) using banked serum from free-ranging black rhinos; and (2) then compare serum biomarkers between zoo-managed (n=86 individuals) and free-ranging (n=120) animals. Enzyme immunoassays were validated for serum and then biomarker levels analyzed using mixed models while controlling for sex, age and year of sample collection. Concentrations of TNFα, SAA, insulin and insulin-to glucose ratio were higher (P<0.05) in black rhinos managed in ex situ conditions compared to free-living counterparts. Findings indicate that the captive environment is contributing to increased inflammation and decreased insulin sensitivity in this endangered species.

Higher ferritin levels, but not serum iron or transferrin saturation, are associated with Type 2 diabetes mellitus in adult men and women free of genetic haemochromatosis

CONTEXT

Iron overload predisposes to diabetes and higher ferritin levels have been associated with diabetes. However, it is unclear whether ferritin reflects differences in iron-related parameters between diabetic and nondiabetic persons. We examined associations of serum ferritin, iron and transferrin saturation with Type 2 diabetes in adults without genetic predisposition to iron overload.

DESIGN, PARTICIPANTS AND MEASUREMENTS

Cross-sectional analysis of community-dwelling men and women aged 17-97 years from the Busselton Health Survey, Western Australia. Men and women carrying genotypes associated with haemochromatosis (C282Y/C282Y or C282Y/H63D) were excluded. Serum ferritin, iron and transferrin saturation were assayed.

RESULTS

There were 1834 men (122 with diabetes, 6·6%) and 2351 women (141 with diabetes, 6%). In men, higher serum ferritin was associated with diabetes after adjusting for age, smoking, alcohol, cardiovascular history, body mass index (BMI), waist, blood pressure, lipids, C-reactive protein (CRP), adiponectin, alanine transaminase (ALT) and gamma-glutamyl transpeptidase (GGT) [odds ratio (OR): 1·29 per 1 unit increase log ferritin, 95% confidence interval (CI) = 1·01-1·65, P = 0·043]. In women, higher serum ferritin was associated with diabetes [fully adjusted OR: 1·31 per 1 unit increase log ferritin, 95% CI = 1·04-1·63, P = 0·020; 1·84 for tertile (T) 3 vs T1, 95% CI = 1·09-3·11]. Neither iron levels nor transferrin saturation were associated with diabetes risk in men or women. Higher ferritin was not associated with insulin resistance in nondiabetic adults.

CONCLUSIONS

In adults, higher ferritin levels are independently associated with prevalent diabetes while iron and transferrin saturation are not. Ferritin is a robust biomarker for diabetes risk, but further investigation is needed to clarify whether this relationship is mediated via iron metabolism.

Fasting serum levels of ferritin are associated with impaired pancreatic beta cell function and decreased insulin sensitivity: a population-based study

AIMS/HYPOTHESIS

Elevated serum ferritin levels are associated with an increased risk of type 2 diabetes, but the nature of this association remains elusive. The aim of this study was to test the hypothesis that an elevated fasting serum ferritin level is associated with an increased risk of type 2 diabetes due to its association with impaired beta cell function and decreased insulin sensitivity.

METHODS

We investigated 6,392 individuals from the Danish general population. Surrogate measures of beta cell function and insulin sensitivity were calculated for approximately 6,100 individuals based on OGTT examinations.

RESULTS

The ORs for type 2 diabetes were 4.2 (95% CI 2.4, 7.2) for the highest vs the lowest quintile of serum ferritin, and 17 (95% CI 8.9, 33) for serum ferritin levels ≥97.5th percentile vs <20th percentile. Elevated serum ferritin levels were associated with elevated plasma glucose levels at 0, 30 and 120 min (p < 0.001), elevated serum insulin levels at 0 and 120 min (p = 0.02 and p < 0.001), decreased beta cell function estimated as the insulinogenic index and corrected insulin response (p < 0.001), and decreased insulin sensitivity estimated by the Matsuda index of insulin sensitivity and HOMA-IR (p < 0.001). Whereas the association with impaired beta cell function was present in both men and women, the association with decreased insulin sensitivity was observed among men and older women but not among younger women.

CONCLUSIONS/INTERPRETATION

Elevated fasting serum ferritin levels are associated with surrogate measures of both impaired beta cell function and decreased insulin sensitivity. Menopause seems to modify the association with insulin sensitivity.

Serum ferritin, insulin resistance, and metabolic syndrome: clinical and laboratory associations in 769 non-hispanic whites without diabetes mellitus in the HEIRS study

BACKGROUND

In some reports, serum ferritin (SF) has been associated with insulin resistance and metabolic syndrome.

METHODS

We studied non-Hispanic whites without diabetes mellitus in a postscreening examination. Participants included cases [HFE C282Y homozygosity; and transferrin saturation (TS) >50% and SF >300 μg/L (males) and TS >45% and SF >200 μg/dL (females), regardless of HFE genotype] and controls [HFE wild-type (wt/wt) and TS/SF 25th-75th percentiles]. We excluded participants with overnight fasts <8 hr, cirrhosis, hepatitis B or C, pregnancy, or missing data. Observations were age, sex, C282Y homozygosity, body mass index (BMI), systolic and diastolic blood pressures (SBP, DBP), lymphocytes, alanine aminotransferase (ALT), aspartate aminotransferase (AST), C-reactive protein (CRP), TS, SF, and glucose/insulin. Insulin resistance was defined as homeostasis model assessment of insulin resistance (HOMA-IR) 4th quartile (≥2.70).

RESULTS

A total of 407 women and 362 men (mean age 54 years) included 188 C282Y homozygotes and 371 wt/wt. Significant trends across HOMA-IR quartiles included age, male sex, BMI, SBP, DBP, lymphocytes, ALT, CRP >0.5 mg/dL (positive), and TS (negative). Multiple regression on HOMA-IR revealed significant associations with male sex, BMI, SBP, lymphocytes, ALT, CRP>0.5 mg/dL (positive), and DBP and SF (negative). Logistic regression on HOMA-IR 4th quartile revealed significant positive associations with age, male sex, BMI, and lymphocytes. Metabolic syndrome occurred in 53 participants (6.9%). Logistic regression on metabolic syndrome revealed these odds ratios: HOMA-IR 4th quartile [9.1 (4.8, 17.3)] and CRP >0.5 mg/dL [2.9 (1.6, 5.4)].

CONCLUSIONS

Age, male sex, BMI, and lymphocytes were positively associated with HOMA-IR after correction for other factors. HOMA-IR 4th quartile and CRP >0.5 mg/dL predicted metabolic syndrome.

Gender differences in associations of serum ferritin and diabetes, metabolic syndrome, and obesity in the China Health and Nutrition Survey

SCOPE

This study examines gender differences in associations of serum ferritin and diabetes, metabolic syndrome (MetS), and obesity in Chinese.

METHODS AND RESULTS

Based on a nationwide, population-based China Health and Nutrition survey this study included 8564 men and women aged 18 years or older. Anthropometric and fasting blood glucose, insulin, lipids, ferritin, and transferrin data were collected. Ferritin concentrations were higher in men than women (201.55 ± 3.6 versus 80.46 ± 1.64 ng/mL, p < 0.0001). The prevalences of MetS, diabetes, obesity, and overweight were 8.05, 8.97, 4.67, 25.88% among men and 14.23, 6.58, 5.81, 26.82% among women, respectively. Elevated ferritin concentrations were associated with higher body mass index, waist circumference, lipids, insulin, glucose (all p < 0.0001). Serum ferritin concentrations increased gradually with aging among women. The inverted U-shaped association between serum ferritin and age was observed among men. Elevated concentration of ferritins were significantly related with higher risk of MetS (p < 0.0001), obesity (p = 0.010), overweight (p < 0.0001), and diabetes (p < 0.0001) among men, but not among women.

CONCLUSION

There was a gender difference in associations between ferritin and MetS, obesity, and diabetes in Chinese adults. Further evaluations of the variation in gender on these associations are warranted to understand the mechanisms behind gender differences.

Iron increases diabetes-induced kidney injury and oxidative stress in rats

Diabetic nephropathy is both a common and a severe complication of diabetes mellitus. Iron is an essential trace element. However, excess iron is toxic, playing a role in the pathogenesis of diabetic nephropathy. The present study aimed to determine the extent of the interaction between iron and type 2 diabetes in the kidney. Male rats were randomly assigned into four groups: control, iron (300-mg/kg iron dextran), diabetes (a single dose of intraperitoneal streptozotocin), and iron + diabetes group. Iron supplementation resulted in a higher liver iron content, and diabetic rats showed higher serum glucose compared with control rats, which confirmed the model as iron overload and diabetic. It was found that iron + diabetes group showed a greater degree of kidney pathological changes, a remarkable reduction in body weight, and a significant increase in relative kidney weight and iron accumulation in rat kidneys compared with iron or diabetes group. Moreover, malondialdehyde values in the kidney were higher in iron + diabetes group than in iron or diabetes group, sulfhydryl concentration and glutathione peroxidase activity were decreased by the diabetes and iron + diabetes groups, and protein oxidation and nitration levels were higher in the kidney of iron + diabetes group as compared to iron or diabetes group. However, iron supplementation did not elevate the glucose level of a diabetic further. These results suggested that iron increased the diabetic renal injury probably through increased oxidative/nitrative stress and reduced antioxidant capacity instead of promoting a rise in blood sugar levels; iron might be a potential cofactor of diabetic nephropathy, and strict control of iron would be important under diabetic state.

Variation in macro and trace elements in progression of type 2 diabetes

Macro elements are the minerals of which the body needs more amounts and are more important than any other elements. Trace elements constitute a minute part of the living tissues and have various metabolic characteristics and functions. Trace elements participate in tissue and cellular and subcellular functions; these include immune regulation by humoral and cellular mechanisms, nerve conduction, muscle contractions, membrane potential regulations, and mitochondrial activity and enzyme reactions. The status of micronutrients such as iron and vanadium is higher in type 2 diabetes. The calcium, magnesium, sodium, chromium, cobalt, iodine, iron, selenium, manganese, and zinc seem to be low in type 2 diabetes while elements such as potassium and copper have no effect. In this review, we emphasized the status of macro and trace elements in type 2 diabetes and its advantages or disadvantages; this helps to understand the mechanism, progression, and prevention of type 2 diabetes due to the lack and deficiency of different macro and trace elements.

Effects of acute dietary iron overload in pigs (Sus scrofa) with induced type 2 diabetes mellitus

Epidemiological studies have reported an association between high iron (Fe) levels and elevated risk of developing type 2 diabetes mellitus (T2D). It is believed that the formation of Fe-catalyzed hydroxyl radicals may contribute to the development of diabetes. Our goal was to determine the effect of a diet with a high Fe content on type 2 diabetic pigs. Four groups of piglets were studied: (1) control group, basal diet; (2) Fe group, basal diet with 3,000 ppm ferrous sulfate; (3) diabetic group (streptozotocin-induced type 2 diabetes) with basal diet; (4) diabetic/Fe group, diabetic animals/3,000 ppm ferrous sulfate. For 2 months, biochemical and hematological parameters were evaluated. Tissue samples of liver and duodenum were obtained to determine mRNA relative abundance of DMT1, ferroportin (Fpn), ferritin (Fn), hepcidin (Hpc), and transferrin receptor by qRT-PCR. Fe group presented increased levels of hematological (erythrocytes, hematocrit, and hemoglobin) and iron parameters. Diabetic/Fe group showed similar behavior as Fe group but in lesser extent. The relative abundance of different genes in the four study groups yielded a different expression pattern. DMT1 showed a lower expression in the two iron groups compared with control and diabetic animals, and Hpc showed an increased on its expression in Fe and diabetic/Fe groups. Diabetic/Fe group presents greater expression of Fn and Fpn. These results suggest that there is an interaction between Fe nutrition, inflammation, and oxidative stress in the diabetes development.

Micronutrient status in type 2 diabetes: a review

Type 2 diabetes is characterized by significant losses of important micronutrients due to metabolic basis of the disease and its complications. Evidence of changes in trace mineral and vitamin metabolism as a consequence of type 2 diabetes is reviewed in this chapter. This review is not a meta-analysis but an overview of the micronutrient status, metabolic needs, and potential micronutrient requirements in type 2 diabetics. This chapter will not concentrate on vitamin D and type 2 diabetes as this is a topic that has been extensively reviewed before. The less well-known micronutrients notably zinc, magnesium, chromium, copper, manganese, iron, selenium, vanadium, B-group vitamins, and certain antioxidants are assessed. While some evidence is available to demonstrate the positive influence of micronutrient supplementation on glycemic control, much remains to be investigated. Additional research is necessary to characterize better biomarkers of micronutrient status and requirements in type 2 diabetics. The optimal level of micronutrient supplementation to achieve glucose homeostasis in type 2 diabetics remains a challenge.

Serum ferritin level is higher in poorly controlled patients with type 2 diabetes and people without diabetes, aged over 55 years

AIMS

Diabetes mellitus has been increasing in Mongolia. There is also growing concern about the relationship between iron stores and the severity of type 2 diabetes. In this study, we aimed to evaluate serum ferritin level among Mongolian individuals with and without diabetes.

METHODS

Of 254 participants, a total of 99 previously diagnosed patients with type 2 diabetes and the same numbers of subjects without diabetes were enrolled and invited to a physical examination (BMI, central obesity, blood pressure) and fasting blood tests (fasting blood glucose, HbA1c , serum ferritin, C-reactive protein, aspartate aminotransferase, alanine transferase).

RESULTS

Serum ferritin was higher in the patients with type 2 diabetes compared with the control group without diabetes, with a significant difference in the female groups (341.6 ± 67.2 and 159.1 ± 36.8 ng/ml respectively, P = 0.019). Of the patients with type 2 diabetes, 43.4% had hyperferritinaemia, and 21.2% of the individuals without diabetes had hyperferritinaemia. In the group with type 2 diabetes, serum ferritin level was significantly higher in the group of women whose HbA1c was ≥ 53 mmol/mol (7.0%) compared with the other group of women whose HbA1c was < 53 mmol/mol (7.0%) (562.1 ± 122.1 and 220.5 ± 78.7 ng/ml respectively, P = 0.025). We also found that the subjects without diabetes, aged over 55 years, are at risk of increased serum ferritin.

CONCLUSION

Poorly controlled patients with type 2 diabetes and people without diabetes of over 55 years of age are likely to be at a higher risk of developing hyperferritinaemia. Thus, regular assessments of serum ferritin might be important for those who are at risk of hyperferritnaemia for prevention and an early intervention.

The impact of obesity and insulin resistance on iron and red blood cell parameters: a single center, cross-sectional study

Objective: Obesity and iron deficiency (ID) are the 2 most common nutritional disorders worldwide causing significant public health implications. Obesity is characterized by the presence of low-grade inflammation, which may lead to a number of diseases including insulin resistance (IR) and type 2 diabetes. Increased levels of acute-phase proteins such as C-reactive protein (CRP) have been reported in obesity-related inflammation. The aim of this study was to investigate the impact of obesity/IR on iron and red blood cell related parameters.

Materials and Methods: A total of 206 patients and 45 control subjects of normal weight were included in this cross-sectional study. Venous blood samples were taken from each patient to measure hemoglobin (Hb), serum iron (Fe), iron-binding capacity (IBC), ferritin, CRP, fasting blood glucose, and fasting insulin. Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated for each patient. IR was determined using the HOMA-IR formula.

Results: Subjects were divided into 3 groups according to BMI. There were 152 severely obese (BMI: 42.6±10.1), 54 mildly obese (BMI: 32.4±2.1), and 45 normal-weight (BMI: 24.3±1.3) patients. Hb levels in severely obese patients and normal controls were 12.8±1.3 g/dL and 13.6±1.8 g/dL, respectively. We found decreasing Fe levels with increasing weight (14.9±6.9 µmol/L, 13.6±6.3 µmol/L, and 10.9±4.6 µmol/L for normal controls and mildly and severely obese patients, respectively). Hb levels were slightly lower in patients with higher HOMA-IR values (13.1±1.5 g/dL vs. 13.2±1.2 g/dL; p=0.36). Serum iron levels were significantly higher in the group with low HOMA-IR values (13.6±5.9 µmol/L vs. 11.6±4.9 µmol/L; p=0.008). IBC was found to be similar in both groups (60.2±11.4 µmol/L vs. 61.9±10.7 µmol/L; p=0.23). Ferritin was slightly higher in patients with higher HOMA-IR values (156.1±209.5 pmol/L vs. 145.3±131.5 pmol/L; p=0.62).

Conclusion: Elevated BMI and IR are associated with lower Fe and hemoglobin levels. These findings may be explained by the chronic inflammation of obesity and may contribute to obesity-related co-morbidities. People with IR may present with ID without anemia.

Relationship between serum ferritin levels and sarcopenia in Korean females aged 60 years and older using the fourth Korea National Health and Nutrition Examination Survey (KNHANES IV-2, 3), 2008-2009

Context

It has been suggested that elevated serum ferritin is associated with several metabolic disorders. However, there is no reported study assessing any association between serum ferritin and sarcopenia despite the close relationship between sarcopenia and metabolic disorders.

Objective

We investigated whether serum ferritin was associated with sarcopenia in older Koreans.

Design and Setting

We conducted a cross-sectional study based on data acquired in the second and third years (2008–9) of the fourth Korean National Health and Nutrition Examination Survey.

Participants

In total, 952 men (mean age 69.0 years) and 1,380 women (mean age 69.3 years) aged 60 years and older completed a body composition study using dual energy X-ray absorptiometry.

Measurements

Serum ferritin levels were measured. Sarcopenia was defined as an appendicular skeletal mass as a percentage of body weight that was less than two standard deviations below the gender-specific mean for young adults.

Results

Serum ferritin levels were lower in women than in men. Women with sarcopenia showed a higher level of serum ferritin than women without sarcopenia (men: without sarcopenia 115.7 ng/mL and with sarcopenia 134.4 ng/mL vs. women: without sarcopenia 70.7 ng/mL and with sarcopenia 85.4 ng/mL). The prevalence of sarcopenia increased as the tertile of serum ferritin increased. However, statistical significance was only seen in elderly women (1^st tertile 6.3%, 2^nd tertile 8.0%, 3^rd tertile 12.0%; p = 0.008). Without adjustment, compared with those in the lowest tertile of serum ferritin level, participants in the highest tertile had an odds ratio of 2.02 (95% confidence interval = 1.26–3.23) for sarcopenia in women. After adjusting for known risk factors, the OR for sarcopenia was 1.74 (95% CI = 1.02–2.97) in women. There was no statistically significant association between sarcopenia and serum ferritin tertiles in men.

Conclusions

Elevated serum ferritin levels were associated with an increased prevalence of sarcopenia in women but not in men from a representative sample of elderly Koreans.

5-aminolevulinic acid, a precursor of heme, reduces both fasting and postprandial glucose levels in mildly hyperglycemic subjects

OBJECTIVE

The aim of this study was to evaluate the combined effects of 5-aminolevulinic acid phosphate (ALA-P) and iron on the glycemic index in mildly hyperglycemic adults.

METHODS

This double-blind, randomized placebo-controlled trial comprised 212 subjects (ages 35-70 y, fasting plasma glucose 105-125 mg/dL or hemoglobin (Hb)A1c 6.1%-7.1%). These participants were randomly assigned to four groups receiving either one of three doses of ALA-P and iron as sodium ferrous citrate (5 mg and 0.6 mg, 5 mg and 1.8 mg, or 15 mg and 1.8 mg, respectively) or a placebo, administered orally once a day over a 12-wk period.

RESULTS

Fifteen mg ALA-P plus 1.8 mg iron decreased the fasting plasma glucose level (2.32 mg/dL, 95% confidence interval [CI], 0.24-4.42, P = 0.029), serum glycoalbumin (0.22%, 95% CI, 0.02-0.42; P = 0.031), and 2h-oral glucose tolerance test levels (14.2 mg/dL, 95% CI, 1.8-26.6; P = 0.025) more than the placebo. However, the levels of HbA1c, fasting insulin, serum 1,5-anhydro-d-glucitol, and Homeostasis Model of Assessment-Insulin Resistance showed no appreciable changes. The participant numbers with impaired glucose tolerance and impaired fasting glucose decreased in the highest dosage group of ALA-P plus iron compared with the placebo group.

CONCLUSION

An oral intake of ALA would be a novel approach to prevent type 2 diabetes mellitus.

Serum ferritin levels and the development of metabolic syndrome and its components: a 6.5-year follow-up study

BACKGROUND

The aim of this study was to investigate the relationship between changes in serum ferritin concentrations and the development of metabolic syndrome (MetS) and its components over a 6.5 year follow-up period in Finnish adults.

METHODS

Adults born in Pieksämäki, Finland, in 1942, 1947, 1952, 1957, and 1962 (n = 1294) were invited to health checkups between 1997 and 1998 and 2003 and 2004. All of the required variables for both checkups were available from 691 (53%) subjects (289 men and 402 women). MetS was defined by the National Cholesterol Education Program criteria.

RESULTS

During the 6.5-year follow-up period, 122 (18%) subjects developed incident cases of MetS. Increases in serum ferritin levels were significantly higher in both women and men with incident MetS compared with women and men without MetS (p = 0.04, p = 0.03). Also, serum ferritin levels increased significantly less in women in whom the criteria for MetS resolved during the follow-up period (p = 0.01). Increases in serum ferritin levels were significantly lower in women in whom the glucose criterion for MetS resolved, and higher in women for whom the waist criterion developed (p = 0.01 and p <0.001, respectively). Serum ferritin levels decreased significantly more in men in whom the triglyceride criterion for MetS resolved during the follow-up period (p = 0.01). There was a clear and significant correlation between change in serum ferritin level and change in waist circumference both in men and women (p <0.001, p <0.01). In addition, correlations between change in serum ferritin level and change in plasma triglyceride as well as glucose levels were strongly positive in men (p <0.001). There was negative correlation between change in serum ferritin and plasma high density cholesterol level both in men and women.

CONCLUSIONS

Increases in serum ferritin over a 6,5 year period are associated with development of MetS in both men and women. Whereas, lower increases in serum ferritin over the same timeframe are associated with resolution of hypertriglyceridemia in men and hyperglycemia in women. Increases in waist circumference was positively correlated with increases in serum ferritin in both men and women.

Hepcidin levels in diabetes mellitus and polycystic ovary syndrome

AIM

Increased body iron is associated with insulin resistance. Hepcidin is the key hormone that negatively regulates iron homeostasis. We hypothesized that individuals with insulin resistance have inadequate hepcidin levels for their iron load.

METHODS

Serum concentrations of the active form of hepcidin (hepcidin-25) and hepcidin:ferritin ratio were evaluated in participants with Type 2 diabetes (n = 33, control subjects matched for age, gender and BMI, n = 33) and participants with polycystic ovary syndrome (n = 27, control subjects matched for age and BMI, n = 16). To investigate whether any changes observed were associated with insulin resistance rather than insulin deficiency or hyperglycaemia per se, the same measurements were made in participants with Type 1 diabetes (n = 28, control subjects matched for age, gender and BMI, n = 30). Finally, the relationship between homeostasis model assessment of insulin resistance and serum hepcidin:ferritin ratio was explored in overweight or obese participants without diabetes (n = 16).

RESULTS

Participants with Type 2 diabetes had significantly lower hepcidin and hepcidin:ferritin ratio than control subjects (P < 0.05 and P < 0.01, respectively). Participants with polycystic ovary syndrome had a significantly lower hepcidin:ferritin ratio than control subjects (P < 0.05). There was no significant difference in hepcidin or hepcidin:ferritin ratio between participants with Type 1 diabetes and control subjects (P = 0.88 and P = 0.94). Serum hepcidin:ferritin ratio inversely correlated with homeostasis model assessment of insulin resistance (r = -0.59, P < 0.05).

CONCLUSION

Insulin resistance, but not insulin deficiency or hyperglycaemia per se, is associated with inadequate hepcidin levels. Reduced hepcidin concentrations may cause increased body iron stores in insulin-resistant states.

When less is more: novel mechanisms of iron conservation

Disorders of iron homeostasis are very common, yet the molecular mechanisms of iron regulation remain understudied. Over 20 years have passed since the first characterization of iron-regulatory proteins (IRP) as mediators of cellular iron-deficiency response in mammals through iron acquisition. However, little is known about other mechanisms necessary for adaptation to low-iron states. In this review, we present recent evidence that establishes the existence of a new iron-regulatory pathway aimed at iron conservation and optimization of iron use through suppression of nonessential iron-consuming processes. Moreover, we discuss the possible links between iron homeostasis and energy metabolism uncovered by studies of iron-deficiency response.

Association between serum ferritin levels and risk of the metabolic syndrome in Chinese adults: a population study

Ferritin is a ubiquitous intracellular protein that can store and release iron and act as a buffer against iron deficiency and iron overload. Ferritin is widely used as a clinical biomarker to evaluate iron status. Increased serum ferritin concentrations have been reported to be associated with metabolic syndrome (MetS) features. However, serum ferritin concentrations differ significantly according to sex and ethnicity, and the data concerning the relationship between serum ferritin concentrations and MetS in Asian men and women are conflicting. This study aimed to explore the relationship between serum ferritin and MetS in Chinese population. Fasting blood samples and anthropometric data collected on 8,441 adults aged 18 and older in 2009 as part of the China Health and Nutrition Survey, a large-scale longitudinal, household-based survey in China. Data was collected by trained physicians and biomarkers were measured with Hitachi Clinical Autoanalyzer 7600 D model and P model. Median levels of serum ferritin were significantly higher in men compared with women (121.9 vs. 51.0 ng/ml, P < 0.001), and significantly lower in non metabolic syndrome population with MetS population (73.2 vs. 106.0 ng/ml, P < 0.001). The difference remained significant after further adjusted for age, nationality, Body mass index (BMI), smoking status, and alcohol consumption. For both men and women, the highest prevalence of MetS occurred in the highest quartile of serum ferritin. The odds ratios increased progressively across the ferritin quartiles (P<0.001 for trend). Increased serum ferritin concentrations are associated with the metabolic syndrome among men and women in China.

Body iron stores and the risk of type 2 diabetes in middle-aged men

OBJECTIVE

We investigated the risk of type 2 diabetes mellitus (T2DM) over a wide range of body iron stores.

METHODS

Prospective cohort of 1613 men in the Kuopio Ischemic Heart Disease Risk Factor study, aged 42-60 years, free of T2DM and hereditary hemochromatosis at baseline in 1984-1989. Baseline serum ferritin (sF) and serum-soluble transferrin receptor (sTfR) concentrations were used to predict incident T2DM. T2DM was assessed by questionnaires, blood glucose measurements, and medication reimbursement register.

RESULTS

There were 331 cases of incident T2DM during the mean follow-up of 16.8 years (27,098 person-years). At baseline, subjects who later developed T2DM had average sF concentrations of 191 μg/l (S.D. 155) vs 151 μg/l (S.D. 119) among those who remained healthy, P<0.001. In a multivariate-adjusted logistic regression, each 100 μg/l increase in sF corresponded to an average of 14% increased (odds ratio=1.14, 95% CI 1.03-1.26, P=0.009) risk of developing T2DM. In a Cox regression, a markedly increased risk of developing T2DM was observed from the fourth sF quintile (185 μg/l, the median) upward (hazard ratio (HR) first vs fifth quintile=1.5, 95% CI 1.0-2.2, P-trend=0.05). In a corresponding Cox model in sTfR, the subjects in the third quintile (1840 μg/l, the median) had the least risk (HR=0.63, 95% CI 0.42-0.97, P=0.04).

CONCLUSIONS

Body iron within the sF reference range is not an important determinant of T2DM risk, whereas high normal and above is associated with markedly increased risk. Iron depletion toward iron deficiency as assessed by sTfR is not protective against T2DM. A rule of thumb safe range could be 30-200 μg/l of sF.

Comparison of the serum iron, ferritin levels and total iron-binding capacity between pregnant women with and without gestational diabetes

BACKGROUND

Gestational diabetes mellitus (GDM) is the most common metabolic disorder during pregnancy. GDM causes substantial morbidity and mortality and long- term complications. GDM-related risk factors have not been completely identified yet. Some studies have found relationship between increased serum ferritin and impaired oral glucose tolerance test but the relationship between serum ferritin and risk of GDM has been controversial. The aim of the study was to determine serum iron and ferritin levels and total iron binding capacity (TIBC) in women with GDM and comparison with normal pregnant women.

MATERIALS AND METHODS

This case-control study was performed among 200 pregnant women (case = 100, control = 100) who were referred to Yahya-Nejad Hospital in the second trimester in Babol from 2008 to 2009. GDM was diagnosed by impaired OGTT based on Carpenter and Coustan criteria. The 2 groups were matched in age, gestational age and parity.

RESULTS

High serum ferritin level increased the risk of gestational diabetes to 2.4-fold [OR = 2.4 (0.83-6.9) CI = 95% (P = 0.10)], while in those with low ferritin levels, the risk of developing gestational diabetes was reduced to 82% [OR = 0.8 with (0.08-0.37) CI = 95% (P = 0.001)]. Using the logistic regression model, after adjustment for BMI, the OR was 2.37 [(0.80-7.01) CI = 95% (P = 0.11)] for low ferritin level and OR = 0.20 [(0.09-0.44) CI = 95% (P = 0.0001)] for high ferritin level, which was statistically significant.

CONCLUSION

The serum ferritin level was markedly higher in women with gestational diabetes than in normal pregnant women; therefore, high ferritin can be regarded as a significant risk factor for the development of gestational diabetes.

Glucose metabolism in the Belgrade rat, a model of iron-loading anemia

The iron-diabetes hypothesis proposes an association between iron overload and glucose metabolism that is supported by a number of epidemiological studies. The prevalence of type 2 diabetes in patients with hereditary hemochromatosis and iron-loading thalassemia supports this hypothesis. The Belgrade rat carries a mutation in the iron transporter divalent metal transporter 1 (DMT1) resulting in iron-loading anemia. In this study, we characterized the glycometabolic status of the Belgrade rat. Belgrade rats displayed normal glycemic control. Insulin signaling and secretion were not impaired, and pancreatic tissue did not incur damage despite high levels of nonheme iron. These findings suggest that loss of DMT1 protects against oxidative damage to the pancreas and helps to maintain insulin sensitivity despite iron overload. Belgrade rats had lower body weight but increased food consumption compared with heterozygous littermates. The unexpected energy balance was associated with increased urinary glucose output. Increased urinary excretion of electrolytes, including iron, was also observed. Histopathological evidence suggests that altered renal function is secondary to changes in kidney morphology, including glomerulosclerosis. Thus, loss of DMT1 appears to protect the pancreas from injury but damages the integrity of kidney structure and function.

Red meat consumption is associated with the risk of type 2 diabetes in men but not in women: a Japan Public Health Center-based Prospective Study

The relationship between different types of meat intake and the risk of type 2 diabetes remains unclear. We prospectively examined the association between total meat, total red meat, unprocessed red meat, processed meat and poultry intake and the incidence of type 2 diabetes. Subjects were 27 425 men and 36 424 women aged 45–75 years who participated in the second survey of the Japan Public Health Center-based Prospective Study, and had no history of type 2 diabetes, cancer, stroke, IHD, chronic liver disease or kidney disease. Meat intake was estimated using a validated 147-item FFQ. OR of self-reported, physician-diagnosed type 2 diabetes over 5 years were estimated using a multiple logistic regression. A total of 1178 newly diagnosed cases of type 2 diabetes were self-reported. Intakes of total meat and total red meat were associated with the increased risk of type 2 diabetes in men but not in women. The multivariate-adjusted OR for the highest quartile compared with the lowest quartile of total meat and total red meat intake were 1·36 (95% CI 1·07, 1·73; P for trend=0·006) and 1·48 (95% CI 1·15, 1·90; P for trend=0·003) for men, respectively, and 0·82 (95% CI 0·62, 1·09; P for trend=0·14) and 0·77 (95% CI 0·57, 1·02; P for trend=0·08) for women, respectively. Intakes of processed red meat and poultry were not associated with the increased risk of diabetes in either men or women. In conclusion, elevated intake of red meat is associated with the increased risk of type 2 diabetes in Japanese men but not in women.

Effects of excess dietary iron and fat on glucose and lipid metabolism

PURPOSE

Diets rich in fat and energy are associated with metabolic syndrome (MS). Increased body iron stores have been recognized as a feature of MS. High-fat diets (HFs), excess iron loading and MS are closely associated, but the mechanism linking them has not been clearly defined. We investigated the interaction between dietary fat and dietary Fe in the context of glucose and lipid metabolism in the body.

METHODS

C57BL6/J mice were divided into four groups and fed the modified AIN-93G low-fat diet (LF) and HF with adequate or excess Fe for 7 weeks. The Fe contents were increased by adding carbonyl iron (2% of diet weight) (LF+Fe and HF+Fe).

RESULTS

High iron levels increased blood glucose levels but decreased high-density lipoprotein cholesterol levels. The HF group showed increases in plasma levels of glucose and insulin and insulin resistance. HF+Fe mice showed greater changes. Representative indices of iron status, such hepatic and plasma Fe levels, were not altered further by the HF. However, both the HF and excess iron loading changed the hepatic expression of hepcidin and ferroportin. The LF+Fe, HF and HF+Fe groups showed greater hepatic fat accumulation compared with the LF group. These changes were paralleled by alterations in the levels of enzymes related to hepatic gluconeogenesis and lipid synthesis, which could be due to increases in mitochondrial dysfunction and oxidative stress.

CONCLUSIONS

High-fat diets and iron overload are associated with insulin resistance, modified hepatic lipid and iron metabolism and increased mitochondrial dysfunction and oxidative stress.

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.

Sex differences in the association between serum ferritin and fasting glucose in type 2 diabetes among South Asian Surinamese, African Surinamese, and ethnic Dutch: the population-based SUNSET study

OBJECTIVE

Moderately elevated iron stores below the levels commonly associated with hemochromatosis have been implicated in the etiology of diabetes. Studies suggest that iron status (measured by serum ferritin) differs significantly according to sex, but inconsistent findings have been reported. Our aim is to test the association between serum ferritin and the prevalence of type 2 diabetes and fasting glucose concentrations in a population-based, multiethnic, cross-sectional study including men and women of African Surinamese, South Asian Surinamese, and ethnic Dutch origin.

RESEARCH DESIGN AND METHODS

We analyzed data on 508 ethnic Dutch, 597 African Surinamese, and 339 South Asian Surinamese aged 35-60 years. Type 2 diabetes was defined as a fasting plasma glucose level ≥7.0 mmol/L or a self-reported diagnosis.

RESULTS

Serum ferritin was positively associated with type 2 diabetes and fasting glucose, but differences in the associations according to sex were observed. Serum ferritin concentration was positively associated with type 2 diabetes among women in all ethnic groups (odds ratio [OR] ethnic Dutch: 1.07 [95% CI 1.01-1.13]; OR South Asian Surinamese: 1.05 [1.00-1.10]; OR African Surinamese: 1.05 [1.01-1.10]), but not among men. Serum ferritin was also more strongly associated with fasting glucose in women than in men. Moreover, the magnitude of sex differences in the association between serum ferritin and fasting glucose, but not type 2 diabetes, was more pronounced in the African Surinamese group than in the other ethnic groups (P for interaction ≤0.0001).

CONCLUSIONS

We found a positive association between serum ferritin and type 2 diabetes and fasting glucose in our multiethnic population, which appeared stronger among women than men. Further evaluation of the variation in sex differences between ethnic groups is warranted, particularly among the African Surinamese, to understand the mechanisms behind these sex differences.

Serum ferritin is associated with markers of insulin resistance in Japanese men but not in women

OBJECTIVE

Several epidemiological studies have reported that high concentrations of circulating ferritin, a marker of iron stores, are related to insulin resistance (IR); however, questions remain regarding inconsistent data between Asian men and women and the inadequate consideration of potential confounding effects on the relationship between ferritin and IR. Our aim was to examine the relationship between serum ferritin concentrations and IR markers in the Japanese population.

MATERIALS/METHODS

We analyzed data (n=493) from a cross-sectional survey conducted in 2009 among a Japanese working population aged 20-68years. Fasting serum ferritin and insulin levels and fasting plasma glucose levels were determined, and the homeostatic model assessment of IR (HOMA-IR) was calculated. Multiple regression analysis was performed with adjustments for demographic and lifestyle factors, body mass index and serum C-reactive protein.

RESULTS

Fasting insulin and HOMA-IR significantly increased with increasing levels of serum ferritin after adjustment for covariates in men (P for trend=.005 and .001, respectively). Compared with men in the lowest tertile of serum ferritin, those in the highest tertile had a 24% higher HOMA-IR score. Additional data suggested a positive association between iron intake and HOMA-IR (P for trend=.07) in men. Neither serum ferritin nor iron intake was related to IR markers in women, even in postmenopausal women.

CONCLUSIONS

Serum ferritin concentrations were positively associated with fasting insulin and HOMA-IR in men but not in women, suggesting an important role of iron storage in the pathogenesis of IR in Japanese men.

Iron and diabetes risk

Iron overload is a risk factor for diabetes. The link between iron and diabetes was first recognized in pathologic conditions-hereditary hemochromatosis and thalassemia-but high levels of dietary iron also impart diabetes risk. Iron plays a direct and causal role in diabetes pathogenesis mediated both by β cell failure and insulin resistance. Iron also regulates metabolism in most tissues involved in fuel homeostasis, with the adipocyte in particular serving an iron-sensing role. The underlying molecular mechanisms mediating these effects are numerous and incompletely understood but include oxidant stress and modulation of adipokines and intracellular signal transduction pathways.

Endocrinopathies in transfusion-associated iron overload

BACKGROUND

Transfusional iron overload primarily results in reticuloendothelial iron accumulation, which is considered to be less harmful than parenchymal iron accumulation. However, systematic and comprehensive data on endocrine function in transfusion-associated haemochromatosis are limited.

METHODS

We examined 25 aplastic anaemia patients (11 men and 14 women) diagnosed with transfusion-associated haemochromatosis at a single institution. Pituitary function was determined with a combined pituitary function test. On a different day, a 75-g oral glucose tolerance test was performed. The bone mineral density (BMD) of the lumbar spine and total hip was assessed with dual-energy X-ray absorptiometry.

RESULTS

Twenty-two (88%) of these 25 patients had at least one endocrine abnormality, and 12 had more than one abnormality. The most common pituitary hormonal deficiency involved the pituitary-gonadal axis; 54% of the total subjects had hypogonadotropic hypogonadism. Two patients had an insufficient cortisol response to corticotrophin-releasing hormone stimulation. No patient had a deficiency of growth hormone or thyroid-stimulating hormone. Twelve (48%) had diabetes mellitus, and these patients tended to have higher concentrations of ferritin, alanine aminotransferase and γ-glutamyl transferase. Osteoporosis (T-score <-2·5 SD) was observed in 48% of patients. The reduction in BMD was more pronounced in the lumbar spine than in the total hip. The patients with osteoporosis were accompanied by hypogonadism, which predominantly affected the trabecular bone.

CONCLUSIONS

Our observations suggest that endocrinopathies are common in transfusion-associated haemochromatosis.

Heme Iron Intake and Risk of Stroke

Background and Purpose—

Intake of iron, especially heme iron, has been associated with several diseases. However, epidemiological studies of heme iron and nonheme iron intake in relation to risk of stroke are lacking. The aim of this study was to examine the associations between heme iron and nonheme iron intake and stroke incidence in men.

Methods—

The population-based prospective Cohort of Swedish Men included 38 859 men, aged 45 to 79 years, who had no history of stroke, coronary heart disease, or cancer at baseline. Hazard ratios and 95% confidence intervals (95% CIs) were calculated using Cox proportional hazards regression models.

Results—

During an 11.7 years follow-up, 3097 incident cases of stroke, including 2482 cerebral infarctions and 450 intracerebral hemorrhages, were registered. The hazard ratios of total stroke and cerebral infarction for the highest compared with the lowest quintiles of heme iron intake were 1.16 (95% CI, 1.03–1.31; P trend=0.037) and 1.15 (95% CI, 1.00–1.31; P trend=0.089), respectively. The incidence rates of total stroke per 10 000 person-years were 72.6 in the lowest quintile and 84.4 in the highest. The association was confined to men with body mass index <25 kg/m 2 , the hazard ratios were 1.40 (95% CI, 1.17–1.68; P trend<0.001) for total stroke and 1.38 (95% CI, 1.13–1.70; P trend=0.001) for cerebral infarction; no association was observed among overweight and obese men. There was no association between nonheme iron intake and risk of total stroke and stroke types.

Conclusions—

Findings from this prospective study indicate that a high heme iron intake, particularly in normal weight individuals, may increase the risk of stroke.

High levels of iron status and oxidative stress in patients with metabolic syndrome

Studies concerning oxidative stress (OxE) parameters have increased, mainly because of its important role in cardiovascular diseases and diabetes complications. The main objective of this study was to evaluate iron nutrition status and oxidative stress parameters in subjects that had developed metabolic syndrome (MetS). Subjects from the Research Program of Risk Factors for Cardiovascular Disease (n = 155) were studied (ages ranging from 45 to 65 years old) and classified according to the Adult Treatment Panel III criterion. A blood sample was taken after a 12-h fasting period, and basal glucose, insulin, thiobarbituric acid reactive substances (TBARS), oxidized LDL (oxLDL), heme oxygenase (HO) activity, lipid profile, and iron nutrition status were determined. Eighty-five subjects were classified as MetS, and 70 non-MetS. Individuals with MetS showed higher Fe storage (high levels of ferritin, total body iron and low transferrin receptor), oxLDL, TBARS, and homeostatic model assessment for insulin resistance levels. The MetS group showed high levels of oxidative stress parameters (HO activity, oxLDL, and TBARS). The presence of MetS showed an association with LDL oxidation risk (multiple lineal regression according to sex and age, p < 0.001). High levels of triglycerides (p < 0.001) and waist circumference (p < 0.012) were associated with oxLDL levels, as well as an association between TBARS and oxLDL with ferritin levels. Through logistic regression analyses, the highest quartile of ferritin was associated with a threefold risk of developing MetS compared to the lowest quartile; also, TBARS showed a 21-fold risk for the development of MetS. Finally, elevated levels of oxidative stress parameters such us oxLDL, TBARS, HO, and Fe storage were associated to MetS.

Association of serum ferritin and the development of metabolic syndrome in middle-aged Korean men: a 5-year follow-up study

OBJECTIVE

Elevated serum ferritin has been known to be associated with the prevalence of metabolic syndrome (MetS). However, there was no research to examine whether serum ferritin levels have been actually associated with the prospective development of MetS. Accordingly, we carried out a prospective study to evaluate the longitudinal effects of baseline serum ferritin levels on the development of MetS.

RESEARCH DESIGN AND METHODS

A MetS-free cohort of 18,022 healthy Korean men, who had participated in a medical health checkup program in 2005, was followed until 2010. MetS was defined according to the joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention. Cox proportional hazards models were performed.

RESULTS

During 45,919.3 person-years of follow-up, 2,127 incident cases of MetS developed between 2006 and 2010. After adjusting for multiple covariates, the hazard ratios (95% CI) for incident MetS comparing the second quintile to the fifth quintile of serum ferritin levels versus the first quintile were 1.19 (0.98-1.45), 1.17 (0.96-1.43), 1.36 (1.12-1.65), and 1.66 (1.38-2.01), respectively (P for trend <0.001). These associations were apparent in the clinically relevant subgroup analyses.

CONCLUSIONS

Elevated serum ferritin levels were independently associated with future development of MetS during the 5-year follow-up period.

Dietary iron intake, body iron stores, and the risk of type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Excess iron has been shown to induce diabetes in animal models. However, the results from human epidemiologic studies linking body iron stores and iron intake to the risk of type 2 diabetes mellitus (T2DM) are conflicting. In this study, we aimed to systematically evaluate the available evidence for associations between iron intake, body iron stores, and the risk of T2DM.

METHODS

A systematic search of the PubMed/MEDLINE and EMBASE databases to the end of 22 April 2012 was performed, and reference lists of retrieved articles were screened. Two reviewers independently evaluated the eligibility of inclusion and extracted the data. Pooled relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random-effects models.

RESULTS

We reviewed 449 potentially relevant articles, and 11 prospective studies were included in the analysis. A meta-analysis of five studies gave a pooled RR for T2DM of 1.33 (95% CI 1.19 to 1.48; P<0.001) in individuals with the highest level of heme iron intake, compared with those with the lowest level. The pooled RR for T2DM for a daily increment of 1 mg of heme iron intake was 1.16 (1.09 to 1.23, P<0.001). Body iron stores, as measured by ferritin, soluble transferrin receptor (sTfR) and the sTfR:ferritin ratio, were significantly associated with the risk of T2DM. The pooled RRs for T2DM in individuals with the highest versus the lowest intake of ferritin levels was 1.70 (1.27-2.27, P<0.001) before adjustment for inflammatory markers and 1.63 (1.03-2.56, P = 0.036) after adjustment. We did not find any significant association of dietary intakes of total iron, non-heme, or supplemental iron intake with T2DM risk.

CONCLUSION

Higher heme iron intake and increased body iron stores were significantly associated with a greater risk of T2DM. Dietary total iron, non-heme iron, or supplemental iron intakes were not significantly associated with T2DM risk.

Increased serum ferritin concentrations and liver enzyme activities in patients with metabolic syndrome

Emerging scientific evidence suggests that increases in body iron represent a risk factor for the development of metabolic syndrome and diabetes. The aim of our study was to determine the body iron stores in patients with metabolic syndrome, and to evaluate the potential relationship of iron overload with specific features of the metabolic syndrome, such as fatty liver. A total of 490 individuals were enrolled. The diagnosis of metabolic syndrome was based on National Cholesterol Education Program-Adult Treatment Panel III (ATPIII) criteria. The metabolic syndrome group was consisted of 185 patients having three or more criteria, whereas individuals with less than three criteria constituted the control group. Metabolic syndrome patients displayed higher ferritin concentration as compared to control individuals. Ferritin levels were positively correlated with insulin concentration, as well as with Homeostasis Model Assessment (HOMA) index values. Multiple regression analysis revealed that ferritin was the most important independent determinant of insulin resistance indices. Patients with metabolic syndrome also exhibited increased concentrations of alanine aminotransferase and gamma-glutamyltranspeptidase compared to controls. Multiple regression analysis revealed that ferritin concentration was the most important determinant of gamma-glutamyltranspeptidase levels. Patients with the metabolic syndrome exhibit an increase in body iron stores as well as elevated concentrations of liver enzymes compared to the individuals who do not fulfill the criteria for the diagnosis of this syndrome. Our data support a direct role of increased body iron in the pathogenesis of insulin resistance, whereas iron overload may also contribute to the development of specific features of the metabolic syndrome, such as fatty liver.

Oxidative Stress in Type 2 Diabetes with Iron Deficiency in Asian Indians

A close relationship exists between iron metabolism, diabetes and oxidative stress. Both diabetes and redox active iron are individually known to enhance oxidative stress. However, the role of iron deficiency and oxidative stress in diabetes is not clear; hence, the levels of oxidative stress in type 2 diabetes with and without iron deficiency have been compared. Two groups of 30 patients each with diabetes were selected (one group with iron deficiency and the other group with normal iron levels) and compared with 30 normal healthy controls. The anthropometric parameters, fasting blood sugar, iron profile and oxidative stress parameters (malondialdehyde levels (index of lipid peroxidation) and serum uric acid levels (antioxidant)) were measured. While the diabetes group had significantly increased serum levels of ferritin (an acute phase reactant and antioxidant) in comparison with normal controls (P=0.040), the diabetic group with iron deficiency had decreased serum levels of iron (P =0.000), ferritin (P = 0.000) and uric acid (P = 0.006) and increased levels of malondialdehyde (P = 0.000) in comparison with diabetics without iron deficiency. This study shows an increase in oxidative stress in the diabetic group with iron deficiency together with reduction in antioxidant levels could further promote prooxidant levels and inflammation and in turn result in the development of complications in this high-risk Asian Indian population.

Iron intake, haemoglobin and risk of gestational diabetes: a prospective cohort study

OBJECTIVE

To investigate the possible association between total daily iron intake during pregnancy, haemoglobin in early pregnancy and the risk of gestational diabetes mellitus (GDM) in women at increased risk of GDM.

DESIGN

A prospective cohort study (based on a cluster-randomised controlled trial, where the intervention and the usual care groups were combined).

SETTING

Primary healthcare maternity clinics in 14 municipalities in south-western Finland.

PARTICIPANTS

399 Pregnant women who were at increased risk of GDM participated in a GDM prevention trial and were followed throughout pregnancy.

MAIN OUTCOME MEASUREMENTS

The main outcome was GDM diagnosed with oral glucose tolerance test at 26-28 weeks' gestation or based on a diagnosis recorded in the Finnish Medical Birth registry. Data on iron intake was collected using a 181-item food frequency questionnaire and separate questions for supplement use at 26-28 weeks' gestation.

RESULTS

GDM was diagnosed in 72 women (18.1%) in the study population. The OR for total iron intake as a continuous variable was 1.006 (95% CI 1.000 to 1.011; p=0.038) after adjustment for body mass index, age, diabetes in first-degree or second-degree relatives, GDM or macrosomia in earlier pregnancy, total energy intake, dietary fibre, saturated fatty acids and total gestational weight gain. Women in the highest fifth of total daily iron intake had an adjusted OR of 1.66 (95% CI 0.84 to 3.30; p=0.15) for GDM. After excluding participants with low haemoglobin levels (≤120 g/l) already in early pregnancy the adjusted OR was 2.35 (95% CI 1.13 to 4.92; p=0.023).

CONCLUSIONS

Our results suggest that high iron intake during pregnancy increases the risk of GDM especially in women who are not anaemic in early pregnancy and who are at increased risk of GDM. These findings suggest that routine iron supplementation should be reconsidered in this risk group of women.

Iron overload in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a major causative agent of chronic liver disease worldwide, but the actual mechanisms responsible for liver injury remain unclear. NAFLD includes a spectrum of clinical entities ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with possible evolution to cirrhosis and hepatocellular carcinoma. Iron is considered a putative element that interacts with oxygen radicals in inducing liver damage/fibrosis and insulin resistance. The role of hepatic iron in the progression of NASH remains controversial, but in some patients, iron may have a role in the pathogenesis of NASH. Though genetic factors, insulin resistance, dysregulation of iron-regulatory molecules, erythrophagocytosis by Kupffer cells may be responsible for hepatic iron accumulation in NASH, exact mechanisms involved in iron overload remain to be clarified. Iron reduction therapy such as phlebotomy or iron-restricted diet may be promising in patients with NAFLD/NASH to reduce hepatic injury as well as insulin resistance. Larger controlled trials of longer duration are warranted to assess the long-term clinical benefit of phlebotomy and/or iron-restricted diet in NAFLD/NASH.