HFE gene mutations in susceptibility to childhood leukemia: HuGE review

DES-Mutation: System for Exploring Links of Mutations and Diseases

During cellular division DNA replicates and this process is the basis for passing genetic information to the next generation. However, the DNA copy process sometimes produces a copy that is not perfect, that is, one with mutations. The collection of all such mutations in the DNA copy of an organism makes it unique and determines the organism’s phenotype. However, mutations are often the cause of diseases. Thus, it is useful to have the capability to explore links between mutations and disease. We approached this problem by analyzing a vast amount of published information linking mutations to disease states. Based on such information, we developed the DES-Mutation knowledgebase which allows for exploration of not only mutation-disease links, but also links between mutations and concepts from 27 topic-specific dictionaries such as human genes/proteins, toxins, pathogens, etc. This allows for a more detailed insight into mutation-disease links and context. On a sample of 600 mutation-disease associations predicted and curated, our system achieves precision of 72.83%. To demonstrate the utility of DES-Mutation, we provide case studies related to known or potentially novel information involving disease mutations. To our knowledge, this is the first mutation-disease knowledgebase dedicated to the exploration of this topic through text-mining and data-mining of different mutation types and their associations with terms from multiple thematic dictionaries.

The relationship between iron bone marrow stores and response to treatment in pediatric acute lymphoblastic leukemia

Iron is an intracellular element whose accumulation in the body is associated with tissue damage. This study examines the effect of iron on pediatric acute lymphoblastic leukemia (ALL) and its "response to treatment." At the end of the first year of treatment, bone marrow iron store (BMIS) was evaluated in children with ALL and the relationship between iron store and minimal residual disease was investigated. Moreover, the 3-year disease-free survival (3-DFS) of patients was determined. Patients' BMIS were compared with that of subjects with normal bone marrow. The study examined 93 children, including 78 Pre-B and 15 T-cell ALL patients. BMIS did not differ between the children with ALL and those with no evidence of cancer. BMIS was increased in 26.6% of patients at the end of the first year of treatment. Drug resistance and BM relapses were more prevalent in cases with high BMIS in both Pre-B and T-cell groups. Bone marrow iron store is not considered a risk factor for childhood ALL. However, high levels of BMIS are associated with poor response to treatment and the risk of relapse. Bone marrow iron store control during treatment can therefore help achieve better outcomes and improve the chances of recovery.

Haplotype Analysis of Hemochromatosis Gene Polymorphisms in Chronic Hepatitis C Virus Infection: A Case Control Study

Background

Chronic hepatitis C virus (HCV) infection is frequently associated with elevated serum iron markers. Polymorphisms in the hemochromatosis (HFE) genes are responsible for iron accumulation in most cases of hemochromatosis, and may play a role in HCV infection.

Objectives

We aimed to assess the prevalence of HFE gene polymorphisms in a group of Iranian HCV-infected patients, and to explore the association of these polymorphisms with HCV infection.

Patients and Methods

HFE gene polymorphisms were examined in a total of 69 HCV patients and 69 healthy controls using polymerase chain reaction and restriction fragment length polymorphism techniques. Haplotype and diplotype analyses were performed using PHASE software.

Results

In a recessive analysis model of the His63Asp (H63D) locus (HH vs. HD + DD), the HH genotype was more common in patients compared to controls (adjusted P = 0.012; OR = 6.42 [95% CI: 1.51 - 27.33]). Also, in a recessive analysis model of the Cys282Tyr (C282Y) locus (CC vs. CY + YY), the CC genotype was more frequent in patients compared to controls (adjusted P = 0.03; OR = 5.06 [95% CI: 1.13 - 22.06]). In addition, there was a significant association between the HC haplotype and the HCDC diplotype and HCV infection.

Conclusions

Polymorphism in the hemochromatosis gene may confer some degree of risk for HCV infection, and individuals carrying the H and C alleles may be susceptible to this disease; however, a larger sample of HCV patients and healthy individuals may be necessary to further illustrate the role of these polymorphisms in HCV.

DNA methylation as a potential mediator of environmental risks in the development of childhood acute lymphoblastic leukemia

5-year survival rate for childhood acute lymphoblastic leukemia (ALL) has risen to approximately 90%, yet the causal disease pathway is still poorly understood. Evidence suggests multiple 'hits' are required for disease progression; an initial genetic abnormality followed by additional secondary 'hits'. It is plausible that environmental influences may trigger these secondary hits, and with the peak incidence of diagnosis between 2 and 5 years of age, early life exposures are likely to be key. DNA methylation can be modified by many environmental exposures and is dramatically altered in cancers, including childhood ALL. Here we explore the potential that DNA methylation may be involved in the causal pathway toward disease by acting as a mediator between established environmental factors and childhood ALL development.

Conditional and inducible transgene expression in endothelial and hematopoietic cells using Cre/loxP and tetracycline-off systems

In the present study, the tetracycline-off and Cre/loxP systems were combined to gain temporal and spatial control of transgene expression. Mice were generated that carried three transgenes: Tie2-tTA, tet-O-Cre and either the ZEG or ZAP reporter. Tie2-tTA directs expression of tetracycline-controlled transactivator (tTA) in endothelial and hematopoietic cells under the control of the Tie2 promoter. Tet-O-Cre produces Cre recombinase from a minimal promoter containing the tet-operator (tetO). ZEG or ZAP contains a strong promoter and a loxP-flanked stop sequence, followed by an enhanced green fluorescence protein (EGFP) or human placental alkaline phosphatase (hPLAP) reporter. In the presence of tetracycline, the tTA transactivator produced by Tie-2-tTA is disabled and Cre is not expressed. In the absence of tetracycline, the tTA binds tet-O-Cre to drive the expression of Cre, which recombines the loxP sites of the ZEG or ZAP transgene and results in reporter gene expression. In the present study, the expression of the ZEG or ZAP reporter genes in embryos and adult animals with and without tetracycline treatment was examined. In the presence of tetracycline, no reporter gene expression was observed. When tetracycline was withdrawn, Cre excision was activated and the reporter genes were detected in endothelial and hematopoietic cells. These results demonstrate that this system may be used to bypass embryonic lethality and access adult phenotypes.

Examination of HFE associations with childhood leukemia risk and extension to other iron regulatory genes

Hereditary hemochromatosis (HFE) variants correlating with body iron levels have shown associations with cancer risk, including childhood acute lymphoblastic leukemia (ALL). Using a multi-ethnic sample of cases and controls from Houston, TX, we examined two HFE variants (rs1800562 and rs1799945), one transferrin receptor gene (TFRC) variant (rs3817672) and three additional iron regulatory gene (IRG) variants (SLC11A2 rs422982; TMPRSS6 rs855791 and rs733655) for their associations with childhood ALL. Being positive for either of the HFE variants yielded a modestly elevated odds ratio (OR) for childhood ALL risk in males (1.40, 95% CI=0.83-2.35), which increased to 2.96 (95% CI=1.29-6.80) in the presence of a particular TFRC genotype for rs3817672 (P interaction=0.04). The TFRC genotype also showed an ethnicity-specific association, with increased risk observed in non-Hispanic Whites (OR=2.54, 95% CI=1.05-6.12; P interaction with ethnicity=0.02). The three additional IRG SNPs all showed individual risk associations with childhood ALL in males (OR=1.52-2.60). A polygenic model based on the number of variant alleles in five IRG SNPs revealed a linear increase in risk among males with the increasing number of variants possessed (OR=2.0 per incremental change, 95% CI=1.29-3.12; P=0.002). Our results replicated previous HFE risk associations with childhood ALL in a US population and demonstrated novel associations for IRG SNPs, thereby strengthening the hypothesis that iron excess mediated by genetic variants contributes to childhood ALL risk.

Therapeutic complications in a patient with high-risk acute lymphoblastic leukemia and undiagnosed hereditary hemochromatosis

Hereditary hemochromatosis (HH) is an autosomal-recessive disorder of iron metabolism that most commonly manifests in the fourth or fifth decade of life. Here, we describe a 14-year-old male who presented with high-risk acute lymphoblastic leukemia and previously undiagnosed HH. His treatment course was remarkable for significant therapeutic complications, including iron overload, hepatic failure, cardiac dysfunction, and death. Postmortem testing revealed homozygosity for the C282Y mutation, confirming the diagnosis of HH. Since HH mutations occur commonly in select populations, screening patients with leukemia for HH may better inform treatment decisions regarding chemotherapy, transfusions, and/or iron chelation therapy.

The use of a reverse hybridization strip assay for the study of hemochromatosis-associated gene mutations in Lebanon

AIMS

Hereditary hemochromatosis (HHC) is the most commonly identified autosomal recessive genetic disorder in the Caucasian population and HFE gene mutations are highly concentrated among European populations. This is the first study that screens for HHC-related gene mutations in a healthy Lebanese sample population.

METHODS

Using the reverse hybridization Hemochromatosis StripAssay A from ViennaLab, the DNA extracted from a total of 116 healthy volunteers (59 males and 57 females) was analyzed, looking for 18 different mutations in the HFE, ferroportin, and transferrin genes.

RESULTS

For the HFE gene, the C282Y mutation was not detected, but the H63D mutation was found with an overall carrier frequency of 25.8% (24.1% heterozygous and 1.7% homozygous). None of the mutations in the transferrin and ferroportin genes was identified.

CONCLUSIONS

The Hemochromatosis StripAssay A from ViennaLab provides an easy and reliable technique for simultaneous screening of the different HFE gene mutations. This first study in Lebanon represents a baseline report for further future studies in the field using this easy technique with a reasonable turnaround time for diagnosis. We also note that ferroportin and transferrin gene mutations have not been detected in this population sample and larger clinical studies will be needed to better estimate their prevalence.

HFE polymorphisms influence the response to chemotherapeutic agents via induction of p16INK4A

HFE is a protein that impacts cellular iron uptake. HFE gene variants are identified as risk factors or modifiers for multiple diseases. Using HFE stably transfected human neuroblastoma cells, we found that cells carrying the C282Y HFE variant do not differentiate when exposed to retinoic acid. Therefore, we hypothesized HFE variants would impact response to therapeutic agents. Both the human neuroblastoma and glioma cells that express the C282Y HFE variant are resistant to Temodar, geldanamycin and γ-radiation. A gene array analysis revealed that p16INK4A (p16) expression was increased in association with C282Y expression. Decreasing p16 protein by siRNA resulted in increased vulnerability to all of the therapeutic agents suggesting that p16 is responsible for the resistance. Decreasing HFE expression by siRNA resulted in a 85% decrease in p16 expression in the neuroblastoma cells but not the astrocytoma cells. These data suggest a potential direct relationship between HFE and p16 that may be cell specific or mediated by different pathways in the different cell types. In conclusion, the C282Y HFE variant impacts the vulnerability of cancer cells to current treatment strategies apparently by increasing expression of p16. Although best known as a tumor suppressor, there are multiple reports that p16 is elevated in some forms of cancer. Given the frequency of the HFE gene variants, as high as 10% of the Caucasian population, these data provide compelling evidence that the C282Y HFE variant should be part of a pharmacogenetic strategy for evaluating treatment efficacy in cancer cells.

Gender-related variations in iron metabolism and liver diseases

The regulation of iron metabolism involves multiple organs including the duodenum, liver and bone marrow. The recent discoveries of novel iron-regulatory proteins have brought the liver to the forefront of iron homeostasis. The iron overload disorder, genetic hemochromatosis, is one of the most prevalent genetic diseases in individuals of Caucasian origin. Furthermore, patients with non-hemochromatotic liver diseases, such as alcoholic liver disease, chronic hepatitis C or nonalcoholic steatohepatitis, often exhibit elevated serum iron indices (ferritin, transferrin saturation) and mild to moderate hepatic iron overload. Clinical data indicate significant differences between men and women regarding liver injury in patients with alcoholic liver disease, chronic hepatitis C or nonalcoholic steatohepatitis. The penetrance of genetic hemochromatosis also varies between men and women. Hepcidin has been suggested to act as a modifier gene in genetic hemochromatosis. Hepcidin is a circulatory antimicrobial peptide synthesized by the liver. It plays a pivotal role in the regulation of iron homeostasis. Hepcidin has been shown to be regulated by iron, inflammation, oxidative stress, hypoxia, alcohol, hepatitis C and obesity. Sex and genetic background have also been shown to modulate hepcidin expression in mice. The role of gender in the regulation of human hepcidin gene expression in the liver is unknown. However, hepcidin may play a role in gender-based differences in iron metabolism and liver diseases. Better understanding of the mechanisms associated with gender-related differences in iron metabolism and chronic liver diseases may enable the development of new treatment strategies.

Hereditary hemochromatosis gene (HFE) variants are associated with birth weight and childhood leukemia risk

BACKGROUND

Our original studies reported an association between the iron-metabolism gene HFE and risk of childhood acute lymphoblastic leukemia (ALL), and a birth weight association in ALL. Through its effect on cell proliferation, iron is involved in both fetal development and cancer. We hypothesize that HFE links higher infant birth weight with leukemia risk and that maternal HFE genotype modifies this association.

PROCEDURE

Nine hundred ninety-five infants and their mothers from the North Cumbria Community Genetics Project, and 163 incident childhood ALL cases from the Newcastle Haematology Biobank were genotyped for HFE, HAMP, TFRC variants and 21 genomic control loci. Cord blood iron levels were measured in 217 control infants.

RESULTS

Three HFE variants showed correlations with birth weight with a gene-dosage relationship in males (gender effect). The association was stronger in homozygotes for TFRC S142G and when the mother was positive for any HFE variant (maternal effect). The genotypes expected to increase fetal iron levels correlated with birth weight in males and their association with ALL was stronger in females who, we postulate, could not offset iron excess by increasing their weight.

CONCLUSIONS

Certain materno-fetal genotype combinations that increase fetal iron exposure showed associations with higher birth weight in males and somewhat higher ALL risk in females. Gender-specific use of iron during fetal growth may lead to this dichotomy in birth weight change. Only the materno-fetal genotype combinations that increase iron levels most extremely correlated with birth weight and ALL risk in males.

An extensive analysis of the hereditary hemochromatosis gene HFE and neighboring histone genes: associations with childhood leukemia

The most common mutation of the HFE gene C282Y has shown a risk association with childhood acute lymphoblastic leukemia (ALL) in Welsh and Scottish case-control studies. This finding has not been replicated outside Britain. Here, we present a thorough analysis of the HFE gene in a panel of HLA homozygous reference cell lines and in the original population sample from South Wales (117 childhood ALL cases and 414 newborn controls). The 21 of 24 variants analyzed were from the HFE gene region extending 52 kb from the histone gene HIST1H1C to HIST1H1T. We identified the single-nucleotide polymorphism (SNP) rs807212 as a tagging SNP for the most common HFE region haplotype, which contains wild-type alleles of all HFE variants examined. This intergenic SNP rs807212 yielded a strong male-specific protective association (per allele OR = 0.38, 95% CI = 0.22-0.64, P (trend) = 0.0002; P = 0.48 in females), which accounted for the original C282Y risk association. In the HapMap project data, rs807212 was in strong linkage disequilibrium with 25 other SNPs spanning 151 kb around HFE. Minor alleles of these 26 SNPs characterized the most common haplotype for the HFE region, which lacked all disease-associated HFE variants. The HapMap data suggested positive selection in this region even in populations where the HFE C282Y mutation is absent. These results have implications for the sex-specific associations observed in this region and suggest the inclusion of rs807212 in future studies of the HFE gene and the extended HLA class I region.

Design, synthesis, screening, and molecular modeling study of a new series of ROS1 receptor tyrosine kinase inhibitors

A series of rationally designed ROS1 tyrosine kinase inhibitors was synthesized and screened. Compound 12b has showed good potency with IC50 value of 209 nM, which is comparable with that of the reference lead compound 1. Molecular modeling studies have been performed, that is, a homology model for ROS1 was built, and the screened inhibitors were docked into its major identified binding site. The docked poses along with the activity data have revealed a group of the essential features for activity. Overall, simplification of the lead compound 1 into compound 12b has maintained the activity, while facilitated the synthetic advantages. A molecular interaction model for ROS1 kinase and inhibitors has been proposed.

HFE C282Y mutation as a genetic modifier influencing disease susceptibility for chronic myeloproliferative disease

Iron metabolism has been implicated in carcinogenesis and several studies assessed the potential role of genetic variants of proteins involved in iron metabolism (HFE C282Y, TFR S142G) in different malignancies. Few reports addressed this issue with relation to chronic myeloproliferative disorders (CMPD). The aims of our study were (a) to examine the potential associations of CMPD development with genetic modifiers of iron metabolism in a large cohort of CMPD patients; (b) to examine associations of genetic variants of proteins involved in iron metabolism; and acquired JAK2 V617F mutation with clinical characteristics of CMPD. HFE C282Y was genotyped in 328 CMPD patients and 996 blood donors as controls, HFE H63D, and TFR S142G were tested in CMPD patients and 171 first time blood donors. JAK2 V617F mutation was tested in CMPD patients and in 122 repeated blood donors. Decreased C282Y allele frequency (allele frequency+/-95% confidence interval) was found in the CMPD group (1.8%+/-1.0%) compared with controls (3.4%+/-0.8%; P=0.048). TFR S142G allele frequency was reduced among V617F-negative CMPD patients (34.8%+/-7.6%) compared with controls (47.8%+/-5.4%; P=0.02). The frequency of JAK2 V617F was 75.9% (249 of 328) in the CMPD group. At presentation, elevated hemoglobin levels were found in V617F-positive patients compared with V617F-negative counterparts (P<0.000). Vascular complications (26.6% versus 15.2%; P=0.039) as well as female gender (57.4% versus 41.8%; P=0.019) were more common in V617F-positive patients. We found that HFE C282Y might be associated with a protective role against CMPD. Because chronic iron deficiency or latent anemia may trigger disease susceptibility for CMPD, HFE C282Y positivity may be a genetic factor influencing this effect.

The Epidemiology of Childhood Leukemia with a Focus on Birth Weight and Diet

Leukemia is the most common childhood cancer and a major source of morbidity and mortality. The etiology of childhood leukemia remains largely unknown. Cytogenetic abnormalities determine disease subtypes, prognosis, clinical presentation, and course and may help in discovering etiological factors. Epidemiologic investigations of leukemia are complicated by many factors, including the rarity of the disease, necessitating careful study design. Two emerging areas of interest in leukemia etiology are birth weight and diet. High birth weight has been associated with increased risk of childhood leukemia. The biological mechanism behind this association may involve insulin-like growth factor I (IGF-I), which is associated with high birth weight. IGF-I may act by increasing the absolute number of stem cells available for transformation, stimulating the growth of cells that are already transformed, or a combination of effects. Diet has been linked with leukemia. Maternal dietary DNA topoisomerase II (DNAt2) inhibitor intake is associated with infant acute myeloid leukemia (AML) with the MLL gene translocation. Increased intake of fruits and vegetables has been associated with decreased leukemia risk and, relatedly, lack of maternal folate supplementation has been associated with increased childhood leukemia risk, possibly by causing DNA hypomethylation and increased DNA strand breaks. Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms modify this risk.

HFE genotypes in patients with chronic pancreatitis and pancreatic adenocarcinoma

PURPOSE

The homozygous p.C282Y variant of the HFE gene is a major risk factor for hereditary hemochromatosis, a disorder of iron metabolism resulting in progressive iron accumulation in a variety of organs including the pancreas. Heterozygosity of p.C282Y and p.H63D may increase susceptibility to chronic liver and pancreatic disease. This study determines the frequencies of p.C282Y and p.H63D alterations in patients with chronic pancreatitis and pancreatic adenocarcinoma.

METHODS

In total, 958 patients (349 with alcoholic pancreatitis, 343 with idiopathic pancreatitis, 64 with familial chronic pancreatitis, 34 with acute pancreatitis, and 168 with pancreatic adenocarcinoma) were enrolled and compared with 681 healthy and 100 alcoholic controls. Furthermore, 45 parent-offspring trios were included for segregation analysis. Genotyping of p.C282Y and p.H63D was performed by restriction fragment length polymorphism or melting curve analyses.

RESULTS

No significant differences were found in heterozygosity for p.C282Y and p.H63D when patients with alcoholic (8.0/21.5%), idiopathic (7.3/24.5%), or familial (9.8/23.0%) pancreatitis, or pancreatic adenocarcinoma (5.4/28.6%) were compared with healthy (6.2/24.8%) and alcoholic (7.0/25.0%) controls. Neither genotype was associated with the presence of secondary diabetes mellitus in patients with chronic pancreatitis.

CONCLUSION

Although hemochromatosis is associated with pancreatic pathology, the p.C282Y and p.H63D variants do not play a significant role in the pathogenesis of chronic pancreatitis or pancreatic adenocarcinoma.

HFE gene mutations in patients with acute leukemia

An increased incidence of HFE gene mutations has been described in hematologic malignancies. In the present study, we investigated the allelic frequency of HFE gene mutations in 154 adult patients with acute leukemia (AL) [107 acute myeloid leukemia (AML), 20 acute promyelocytic leukemia (APL) and 27 acute lymphoblastic leukemia (ALL)]. The allelic frequency of the H63D mutation was 29% in AL patients and 25% in the healthy controls [P = 0.41; odds ratio (OR) = 1.20; 95% confidence interval (CI) = 0.77 - 1.93]. No difference was found between controls and AML or APL patients, whereas the H63D mutation was significantly more frequent in ALL than controls (44% vs. 25%, P = 0.04; OR = 2.37; 95% CI = 1.05 - 5.36). The overall comparison of the mutation among the three subtypes of AL demonstrated a higher allelic frequency in ALL (P = 0.02). In conclusion, our data demonstrate a correlation between the presence of the H63D mutation and the occurrence of ALL in adult patients.

Examination of gender effect in birth weight and miscarriage associations with childhood cancer (United Kingdom)

BACKGROUND

Higher birth weight and maternal history of miscarriage has been associated with an increased risk of childhood leukemia. The possibility that this association may be sex-specific has not been explored in detail in previous studies.

METHODS

In a retrospective case-control study, 732 childhood (< or =14 years) cancer cases from a population-based Registry in Northern England whose hospital birth records could be accessed and 3,723 controls matched for date and hospital of birth to the cases were compared. We examined birth weight for sex-specific associations with childhood cancer. Conditional logistic regression analysis was used for statistical evaluation of associations.

RESULTS

In acute lymphoblastic leukemia (ALL) (225 cases and 1,163 matched controls), birth weight and sex showed a strong interaction (P = 0.003). In boys with ALL, but not in girls, there was a nonlinear association with birth weight (P for trend = 0.008; OR = 3.05 for the highest quintile compared to the second lowest quintile, 95% CI = 1.40-6.64; P = 0.005). When birth weights were adjusted using UK standards for gestational age and sex, the risk associations were similar in statistical significance and magnitude. Maternal history of miscarriage showed an association with all cancers and individually with ALL. The miscarriage association with ALL was statistically significant in boys only (OR = 1.91, 95% CI = 1.07-3.42; P = 0.03). A multivariable model for ALL containing other examined maternal and reproductive variables confirmed the independence of the birth weight and miscarriage associations. There was no birth weight or miscarriage associations in other cancers.

CONCLUSIONS

This study confirmed the risk associations with birth weight and miscarriages in childhood ALL. Statistically significant association of size at birth suggested marked differences in etiology between girls and boys.

HFE H63D mutation frequency shows an increase in Turkish women with breast cancer

BACKGROUND

The hereditary hemochromatosis gene HFE plays a pivotal role in iron homeostasis. The association between cancer and HFE hetero- or homozygosity has previously been shown including hepatocellular and nonhepatocellular malignancies. This study was performed to compare frequencies of HFE C282Y and H63D variants in Turkish women with breast cancer and healthy controls.

METHODS

Archived DNA samples of Hacettepe University Oncology Institute were used in this study. The HFE gene was investigated by PCR-RFLP.

RESULTS

All subjects studied were free from C282Y mutation. Thirty-nine patients had H63D mutation and were all heterozygous. H63D allele frequency was 22.2% (39/176) in the breast cancer patients, and 14% (28/200) in the healthy volunteers. Statistical analysis of cases with HFE H63D phenotype showed significant difference between breast cancer and healthy volunteers (P = 0.02).

CONCLUSION

Our results suggest that HFE H63D mutation frequencies were increased in the breast cancer patients in comparison to those in the general population. Also, odds ratios (odds ratio = 2.05) computed in this study suggest that H63D has a positive association with breast cancer.

[Iron overload and insulin resistance]

There is increasing evidence that moderately elevated body iron stores, below levels commonly found in genetic hemochromatosis, may be associated with adverse health outcomes. Genetic hemochromatosis, characterized by transferrin saturation (TS) greater than 45%, is most often linked to homozygosity of the HFE C282Y allele. The phenotype is also modulated by mutations of more recently discovered genes (including ferroportin, hemojuvelin, hepcidin, and transferrin receptor) and environmental factors (including alcohol, viruses, diet, blood loss). Iron overload without hemochromatosis is characterized by high levels of serum ferritin and normal TS, as seen in dysmetabolic hepatosiderosis. Elevated serum ferritin levels predict incident type 2 diabetes in prospective studies and have been associated with hypertension, dyslipidemia, glucose tolerance disturbances, central adiposity, and metabolic syndrome. High ferritin levels are not synonymous with iron overload and may in some cases be a simple marker of insulin resistance.