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PubMed2005

Hemochromatosis gene mutations, body iron stores, dietary iron, and risk of colorectal adenoma in women.

BACKGROUND: Some experimental evidence suggests that iron may play a role in colorectal carcinogenesis, but human data for this role have been conflicting, possibly because of problems related to study design or measurement of iron exposure. We assessed dietary iron intake and genetic and biochemical markers of iron status in a prospective, nested case-control study of women enrolled in the Nurses' Health Study. METHODS: Among 32 826 women who provided a blood specimen, we identified 527 women with colorectal adenoma and 527 matched control subjects who underwent endoscopy but were not diagnosed with adenoma after blood collection. We assessed iron intake, mutations in the HFE gene that are associated with hereditary hemochromatosis (i.e., H63D and C282Y), and plasma biochemical measures of total body iron, including transferrin saturation and the ratio of the concentrations of transferrin receptors to ferritin. Logistic regression models were used to estimate relative risks (RR) and 95% confidence intervals (CI). All statistical tests were two-sided. RESULTS: Women with any HFE gene mutation had higher total body iron stores, as reflected by higher transferrin saturations (P < .001) and lower levels of the ratio of transferrin receptors to ferritin (P = .02), than women with no HFE gene mutation. However, HFE gene mutations were not associated with risk of adenoma (multivariable RR = 1.08, 95% CI = 0.83 to 1.39; P = .58). Moreover, comparison of extreme categories showed no associations between adenoma and the extent of transferrin saturation (multivariable RR = 0.96, 95% CI = 0.63 to 1.47; Ptrend = .66), the ratio of transferrin receptors to ferritin (multivariable RR = 0.98, 95% CI, 0.60 to 1.60; Ptrend = .99), or dietary iron intake (multivariable RR = 1.04, 95% CI = 0.68 to 1.57; Ptrend = .94). CONCLUSIONS: Although our study used several distinct measures of iron status (i.e., genetic mutations, biochemical markers, and dietary intake) and a nested case-control design, we did not observe a role for iron in the pathogenesis of colorectal neoplasia in women.

Adenoma↗
PubMed2001

What's new in hemochromatosis.

Hereditary hemochromatosis (HHC) is an inherited disorder of iron metabolism affecting approximately 1 in 200-300 individuals of Northern European descent. Over time, the continued deposition of iron in parenchymal cells of many organs can eventually lead to diabetes mellitus, cardiomyopathy, and hepatic cirrhosis, the last of which is frequently followed by hepatocellular carcinoma. Although the complications of HHC can be devastating, its clinical management is simple and effective if the disease is identified early in its progression. The recent elucidation of the HFE gene has provided insight into the pathogenesis of HHC and provided a means for the early identification of individuals in whom HHC may develop. Two mutations have been implicated in HHC: C282Y and H63D. The former occurs in a homozygous state seen in 75-100% of patients with HHC. The high correlation of HFE to HHC has caused it to be considered as a candidate gene for population-based genetic testing for diagnosis and detection of predisposition to HHC. In addition, mechanisms of iron transport and metabolism are unfolding and are providing clues to the enigma of iron homeostasis and the pathophysiology of iron overload.

HLA Antigens↗
PubMedDate not supplied

Hereditary hemochromatosis: perspectives of public health, medical genetics, and primary care.

Hereditary hemochromatosis (HHC) is a condition characterized by excess iron in body tissues, resulting in complications such as cirrhosis, cardiomyopathy, diabetes, and arthritis. These complications usually manifest during adulthood. Two methods of screening for the detection of early stage of HHC are available: serum iron measures and molecular testing to detect mutations in the gene. These phenotypic and genotypic screening tests are of particular interest because a simple treatment-periodic phlebotomy-can be used to prevent iron accumulation and clinical complications. HHC might represent the first adult-onset genetic disorder for which universal population-based screening would be appropriate. Therefore, HHC has been proposed as a paradigm for the introduction of adult genetic diseases into clinical and public health practice. However, universal screening for HHC has not been recommended because of the uncertainty about the natural history of the iron overload or HHC and, in particular, uncertainty about the prevalence of asymptomatic iron overload and the likelihood that it will progress to clinical complications. If universal screening is not appropriate based on current data, what other measures might reduce the disease burden of iron overload? New studies provide more systematic information about the penetrance of the C282Y mutation and shed further light on the natural history of the disorder. The authors review these data and consider their implications for public health, medical genetics, and primary care.

Genetic Testing↗
PubMed2006

Hemochromatosis (HFE) gene mutations and peripheral neuropathy during antiretroviral therapy.

OBJECTIVE: Peripheral neuropathy (PN) often complicates nucleoside reverse transcriptase inhibitor (NRTI) therapy of HIV infection and may involve mitochondrial dysfunction. Since iron deficiency is associated with some types of PN, and iron is essential for mitochondrial function, we tested the hypothesis that hemochromatosis (HFE) gene mutations influence susceptibility to NRTI-induced PN. DESIGN: Case-control study involving multicenter, AIDS Clinical Trials Group (ACTG) protocol 384 and ACTG Human DNA Repository specimens. METHODS: Study participants were randomized to receive three- or four-drug antiretroviral therapy with didanosine (ddI) plus stavudine (d4T) or zidovudine plus lamivudine, given with efavirenz, nelfinavir, or both, with up to three years of follow-up. PN was ascertained based on signs and symptoms. HFE C282Y and H63D genotypes were determined, and associations with PN were assessed using logistic regression. RESULTS: : Of 509 participants, 147 (29%) developed PN, 73% of whom had been randomized to receive ddI plus d4T. Among ddI/d4T-ever-treated individuals, HFE C282Y heterozygotes developed PN on ddI/d4T significantly less often than C282Y non-carriers, adjusting for age, CD4 lymphocyte count and viral load at baseline, and concomitant antiretroviral drugs [6% vs. 35%, respectively, in whites; adjusted odds ratio (OR), 0.17; 95% confidence interval (CI) 0.03-0.83; P = 0.021]. Regardless of race/ethnicity, ddI/d4T-associated PN was uncommon in C282Y heterozygotes [race-adjusted OR, 0.30; 95% CI 0.09-0.96); P = 0.042]. CONCLUSIONS: Iron-loading HFE mutations such as C282Y are associated with a decreased risk of PN during antiretroviral therapy. This finding has potential implications for the prediction and prevention of NRTI-associated PN, particularly in populations at risk of iron deficiency.

Adolescent↗
PubMed2004

Frequency of HFE mutations among Turkish blood donors according to transferrin saturation: genotype screening for hereditary hemochromatosis among voluntary blood donors in Turkey.

BACKGROUND AND GOALS: The C282Y and H63D mutations of HFE gene are associated with hereditary hemochromatosis (HH), the most common autosomal recessive disorder in European population. This is the first Turkish population study of, the prevalence of these mutations. STUDY: 2677 healthy volunteer blood donors were screened by means of transferrin saturation (TS) with the cutoff value of 45. As study group, 86 donors with a TS 45 or higher and as control group 57 donors with TS less than 45 were tested for these mutations, ferritin, and alanin aminotransferase (ALT) levels. RESULTS: The mean age of donors were 33+/-9 and 94.1% of them were male. The number of donors with TS 45 or higher was 265 (9.9%). C282Y mutation was not detected. The frequency of H63D mutation in the study, control and general groups were 27.32%, 21.05%, and 24.83%, respectively. As a result, the H63D mutation was present in 60 out of 143 participants in whom 49 were heterozygote (frequency of heterozygote allele 49/286 = 17.13%), 11 were homozygote (frequency of homozygote allele 22/286 = 7.69%). Serum ALT and TS were not affected from the type of H63D mutation. There was no difference in ferritin levels according to type of H63D mutations among 143 blood donors. CONCLUSION: This study revealed the absence of C282Y mutation in our population. Although the frequency of H63D heterozygosity seems to be higher than the other population, the genetic screening for the HFE gene mutation is inadequate and the phenotypic screening with TS and ferritin seems to be preferable in Turkish population.

Adult↗
PubMedDate not supplied

Hereditary hemochromatosis: population screening based on phenotype in Brazilian blood donors.

GOALS: A population of blood donors was screened for hereditary hemochromatosis (HH) based on the phenotype strategy in accordance with the European consensus. STUDY: Nonfasting serum samples were obtained from 1,050 donors. Transferrin saturation (TS) was measured using a threshold of 45%. Donors with a TS > or = 45% were retested in a fasting sample. If TS was elevated, the participants were tested for iron overload by ferritin measurement followed by genetic testing. All donors underwent clinical and laboratory workup for expression of the disease. RESULTS: A total of 775 (74.6%) of the donors were men, 749 (72.1%) white, and had a mean age of 30 years (range, 8-60 years). Mean +/- SD TS was 25.9% +/- 13.1% (range, 2.1%-85.8%), and there were 58 (5.6%) donors with a TS > or = 45%. Fifty-four subjects had a repeat TS in a fasting serum sample with a mean +/- SD TS of 32.1% +/-16.1% (range, 15.4%-63.0%), and 12 donors had a TS > or = 45%. Ten complied with genetic testing and ferritin measurement. The study found four donors with HH-related mutations (C282Y and/or H63D); therefore, a gene allele frequency of 0.4%. Only the C282Y homozygote had diagnostic criteria for HH, defining a disease frequency of 0.1%. None of the donors who were mutations carriers had clinical or laboratory manifestations of organic injury. CONCLUSION: We conclude that this is a feasible screening strategy that, by timely diagnosing HH, allows patients not only to benefit from effective treatment but also to have disease progression halted.

Adolescent↗
PubMed1997

A 1.1-Mb transcript map of the hereditary hemochromatosis locus.

In the process of positionally cloning a candidate gene responsible for hereditary hemochromatosis (HH), we constructed a 1.1-Mb transcript map of the region of human chromosome 6p that lies 4.5 Mb telomeric to HLA-A. A combination of three gene-finding techniques, direct cDNA selection, exon trapping, and sample sequencing, were used initially for a saturation screening of the 1.1-Mb region for expressed sequence fragments. As genetic analysis further narrowed the HH candidate locus, we sequenced completely 0.25 Mb of genomic DNA as a final measure to identify all genes. Besides the novel MHC class 1-like HH candidate gene HLA-H, we identified a family of five butyrophilin-related sequences, two genes with structural similarity to a type 1 sodium phosphate transporter, 12 novel histone genes, and a gene we named RoRet based on its strong similarity to the 52-kD Ro/SSA lupus and Sjogren's syndrome auto-antigen and the RET finger protein. Several members of the butyrophilin family and the RoRet gene share an exon of common evolutionary origin called B30-2. The B30-2 exon was originally isolated from the HLA class 1 region, yet has apparently "shuffled" into several genes along the chromosome telomeric to the MHC. The conservation of the B30-2 exon in several novel genes and the previously described amino acid homology of HLA-H to MHC class 1 molecules provide further support that this gene-rich region of 6p21.3 is related to the MHC. Finally, we performed an analysis of the four approaches for gene finding and conclude that direct selection provides the most effective probes for cDNA screening, and that as much as 30% of ESTs in this 1.1-Mb region may be derived from noncoding genomic DNA.

Amino Acid Sequence↗
PubMed2005

HJV gene mutations in European patients with juvenile hemochromatosis.

A large variety of mutations within the genes encoding hepcidin (HAMP) and hemojuvelin (HJV) have been identified in patients with the severe iron overload disorder juvenile hemochromatosis (JH). The aim of the present study was to evaluate the molecular background of JH in patients from central parts of Europe. Sequence analyses of HAMP and HJV were performed in seven JH patients from six families from Germany, Slovakia, and Croatia. For detection of the G320V mutation in HJV, a rapid polymerase chain reaction-based assay was developed. No mutations were found within the HAMP gene. Six of seven (86%) JH patients carried at least one copy of the G320V mutation within the HJV gene. Four of these patients were homozygous for the G320V mutation. In addition, two novel HJV mutations were identified (C119F and S328fsX337). Taken together, the present study demonstrates that molecular analysis of the HJV gene is a powerful tool for an early and reliable diagnosis of JH. As in affected patients from Greece, the G320V mutation seems to be widely distributed among JH patients from central parts of Europe. Therefore, detection of the G320V mutation could identify the majority of JH cases from these regions non-invasively.

Adolescent↗
PubMed1998

HFE codon 63/282 (H63D/C282Y) dimorphism in German patients with genetic hemochromatosis.

Genetic hemochromatosis (GH) is closely associated with genes of the major histocompatibility complex (MHC) on chromosome 6. Recently, a candidate gene for GH, with structural similarities to MHC class I genes, designated HLA-H and presently named HFE, has been cloned. The HFE gene is localized telomeric to the MHC and several reports have indicated that the HFE gene is mutated in GH patients. In the present study we have analyzed the relationship of HFE gene variants and disease manifestation in GH patients and family members. Fifty-seven patients with GH, 73 family members and 153 healthy blood donors were studied for the amino acid dimorphism at codon 63 (His63Asp=H63D) and codon 282 (Cys282Tyr= C282Y) of the HFE gene. The codon 63 and 282 dimorphism were defined by PCR amplification of genomic DNA samples and restriction enzyme digestion using RsaI/SnaBI for C282Y and BclI/MboI for H63D. Ferritin, transferrin serum levels and total iron-binding capacity were determined prior to therapeutic intervention. The Tyr-282 substitution occurred in 53 (93%) of patients compared with 8 (5.2%) of controls (OR=169, P<0.0001). Fifty-one (90%) patients were Tyr-282 homozygous. In contrast, the Asp-63 substitution was present in 5 (8.8%) of the patients compared with 34 (22%) of controls (OR=0.39, P=NS) with none of the patients being homozygous. In Tyr-282 homozygous GH patients serum ferritin levels, transferrin saturation, liver iron and liver iron index were elevated significantly compared to Tyr-282-negative patients, whereas no difference was observed between Tyr/Cys-282 heterozygous and Tyr-282-negative patients.

Aspartic Acid↗
PubMed2004

Hemochromatosis (HFE) gene mutations and hepatitis C virus infection as risk factors for porphyria cutanea tarda in Hungarian patients.

AIM: It is not clear whether the mutations in hemochromatosis (HFE) gene and hepatitis C virus (HCV) infection act independently in the pathogenesis of porphyria cutanea tarda (PCT). The prevalence of both risk factors varies greatly in different parts of the world. PCT patients from Hungary were evaluated to assess both factors. METHODS: The prevalence of C282Y and H63D mutations in the HFE gene was determined in 50 PCT patients and compared with the reported control frequencies. Furthermore, the presence of HCV infection was determined and related to the patients' HFE gene status. RESULTS: The C282Y mutation was found in 8/50 cases (three homozygotes and five heterozygotes), with an 11% allele frequency (vs. 3.8% control) (P<0.05). Seventeen patients were heterozygous, one was homozygous for the H63D mutation, allele frequency 19%, which did not differ significantly from the reported control prevalence of 12.3%. Twenty-two patients (44%) were HCV-RNA positive; six out of them were heterozygous for H63D mutation, one only for the C282Y mutation and one was compound heterozygous for both mutations. CONCLUSION: HCV infection and HFE C282Y mutation may probably be independent predisposing factors for development of PCT in Hungarian patients.

Adult↗
PubMed2005

Hepatic iron overload in alcoholic end-stage liver disease is associated with iron deposition in other organs in the absence of HFE-1 hemochromatosis.

BACKGROUND: End-stage cirrhosis in the absence of hereditary hemochromatosis (HHC) can be associated with moderate to marked hepatic iron overload, especially in liver disease as a result of alcohol and/or hepatitis C. However, no published studies have addressed extrahepatic iron deposition in this setting. METHOD: A retrospective case series from three autopsied patients who died from end-stage cirrhosis associated with significant hepatic iron overload. Histology of vital organs was performed to detect extrahepatic iron deposition. HFE genotyping for the C282Y and H63D mutations was determined from archival tissue. Hepatic iron index and hepatic iron concentration (HIC) were quantified from formalin-fixed, paraffin-embedded tissue. Medical records were reviewed for possible causes of iron overload. RESULTS: Two patients were H63D heterozygous (H63D +/-) and one was wild type (C282Y -/-, H63D -/-). Histology revealed evidence of stainable iron in the heart and pancreas of all three subjects. Additionally, stainable iron was seen in the stomach in one subject and in the thyroid, pituitary, choroid plexus and testes in another subject. HIC ranged from 4354 to 6834 microg/g dry weight and HII from 1.8 to 2.2 (micromol/g/years). CONCLUSION: Iron overload secondary to end-stage liver disease can be associated with iron deposition in other organs in the absence of HFE-1 HHC.

Adult↗
PubMed2007

Effects of alcohol consumption on iron metabolism in mice with hemochromatosis mutations.

BACKGROUND: Alcoholic liver disease is associated with increased hepatic iron accumulation. The liver-derived peptide hepcidin is the central regulator of iron homeostasis and recent animal studies have demonstrated that exposure to alcohol reduces hepcidin expression. This down-regulation of hepcidin in vivo implies that disturbed iron sensing may contribute to the hepatosiderosis seen in alcoholic liver disease. Alcohol intake is also a major factor in expression of the hemochromatosis phenotype in patients homozygous for the C282Y mutation of the HFE gene. METHODS: To assess the effect of alcohol in mice with iron overload, alcohol was administered to mice with disrupted Hfe and IL-6 genes and Tfr2 mutant mice and their respective 129x1/SvJ, C57BL/6J, and AKR/J wild-type congenic strains. Iron absorption, serum iron levels, and hepcidin expression levels were then measured in these mice compared with water-treated control mice. RESULTS: Alcohol was shown to have a strain-specific effect in 129x1/SvJ mice, with treated 129x1/SvJ mice showing a significant increase in iron absorption, serum iron levels, and a corresponding decrease in hepcidin expression. C57BL/6J and AKR/J strain mice showed no effect from alcohol treatment. 129x1/SvJ mice heterozygous or homozygous for the Hfe knockout had a diminished response to alcohol. All 3 strains were shown to have high blood alcohol levels. CONCLUSIONS: The effect of alcohol on iron homeostasis is dependent on the genetic background in mice. In an alcohol-susceptible strain, mutation of the Hfe gene diminished the response of the measured iron indices to alcohol treatment. This indicates that either maximal suppression of hepcidin levels had already occurred as a result of the Hfe mutation or that Hfe was a component of the pathway utilized by EtOH in suppressing hepcidin production and increasing iron absorption.

Alcohol Drinking↗
PubMed2002

Physiology of iron transport and the hemochromatosis gene.

Iron is essential for fundamental cell functions but is also a catalyst for chemical reactions involving free radical formation, potentially leading to oxidative stress and cell damage. Cellular iron levels are therefore carefully regulated to maintain an adequate substrate while also minimizing the pool of potentially toxic "free iron." The main control of body iron homeostasis in higher organisms is placed in the duodenum, where dietary iron is absorbed, whereas no controlled means of eliminating unwanted iron have evolved in mammals. Hereditary hemochromatosis, the prototype of deregulated iron homeostasis in humans, is due to inappropriately increased iron absorption and is commonly associated to a mutated HFE gene. The HFE protein is homologous to major histocompatibility complex class I proteins but is not an iron carrier, whereas biochemical and cell biological studies have shown that the transferrin receptor, the main protein devoted to cellular uptake of transferrin iron, interacts with HFE. This review focuses on recent advances in iron research and presents a model of HFE function in iron metabolism.

Animals↗
PubMed2005

Prevalence of three hereditary hemochromatosis mutant alleles in the Michigan Caucasian population.

OBJECTIVE: To investigate the prevalence in the Michigan non-Hispanic Caucasian population of the C282Y, H63D and S65C mutations in the HFE gene associated with hereditary hemochromatosis. METHODS: Polymerase chain reaction and restriction fragment length polymorphism analysis were performed on 3,532 blood samples from newborn screening cards provided by the state of Michigan. RESULTS: More than 30% of Michigan Caucasians carry one HFE mutation, while 6% have two mutations. The allele frequency of the C282Y mutation is 5.7%, significantly higher than expected (p < 0.05), while the frequency of the H63D mutation is 14%, significantly lower than expected (p < 0.01). CONCLUSIONS: This is the first publication to examine HFE allele frequencies in an unbiased sample of the Caucasian population. Results indicate that the C282Y mutation may be more common in the non-Hispanic Caucasian population than previously reported, and medical problems related to iron overload may be a health concern for Michigan non-Hispanic Caucasians. Additional studies of penetrance for the C282Y allele are required to fully understand the impact of this information.

Amino Acid Substitution↗
PubMed1999

Heterozygosity for a hereditary hemochromatosis gene is associated with cardiovascular death in women.

Background-The genetic background of hereditary hemochromatosis (HH) is homozygosity for a cysteine-to-tyrosine transition at position 282 in the HFE gene. Heterozygosity for HH is associated with moderately increased iron levels and could be a risk factor for cardiovascular death. Methods and Results-We studied the relation between HH heterozygosity and cardiovascular death in a cohort study among 12 239 women 51 to 69 years of age residing in Utrecht, the Netherlands. Women were followed for 16 to 18 years (182 976 follow-up years). The allele prevalence of the HH gene in the reference group was 4.0 (95% CI 2.9 to 5.4). The mortality rate ratios for HH heterozygotes compared with wild types was 1.5 (95% CI 0.9 to 2.5) for myocardial infarction (n=242), 2.4 (95% CI 1.3 to 3. 5) for cerebrovascular disease (n=118), and 1.6 (95% CI 1.1 to 2.4) for total cardiovascular disease (n=530). The population-attributable risks of HH heterozygosity for myocardial infarction and cerebrovascular and total cardiovascular death were 3. 3%, 8.8%, and 4.0%, respectively. In addition, we found evidence for effect modification by hypertension and smoking. Conclusions-We found important evidence that inherited variation in iron metabolism is involved in cardiovascular death in postmenopausal women, especially in women already carrying classic risk factors.

Aged↗
PubMed2003

Co-localization of the mammalian hemochromatosis gene product (HFE) and a newly identified transferrin receptor (TfR2) in intestinal tissue and cells.

Mutations in the HFE gene and a newly identified second transferrin receptor gene, TfR2, cause hemochromatosis. The cognate proteins, HFE and TfR2, are therefore of key importance in human iron homeostasis. HFE is expressed in small intestinal crypt cells where transferrin-iron entry may determine subsequent iron absorption by mature enterocytes, but the physiological function of TfR2 is unknown. Using specific peptide antisera, we examined the duodenal localization of HFE and TfR2 in humans and mice, with and without HFE deficiency, by confocal microscopy. We also investigated potential interactions of these proteins in human intestinal cells in situ. Duodenal expression of HFE and TfR2 (but not TfR1) in wild-type mice and humans was restricted to crypt cells, in which they co-localized. HFE deficiency disrupted this interaction, altering the cellular distribution of TfR2 in human crypts. In human Caco-2 cells, HFE and TfR2 co-localized to a distinct CD63-negative vesicular compartment showing marked signal enhancement on exposure to iron-saturated transferrin ligand, indicating that HFE preferentially interacts with TfR2 in a specialized early endosomal transport pathway for transferrin-iron. This interaction occurs specifically in small intestinal crypt cells that differentiate to become iron-absorbing enterocytes. Our immunohistochemical findings provide evidence for a novel mechanism for the regulation of iron balance in mammals.

Animals↗
PubMed2003

Hepcidin, a candidate modifier of the hemochromatosis phenotype in mice.

Hereditary hemochromatosis (HH) type I is a disorder of iron metabolism caused by a mutation in the HFE gene. Whereas the prevalence of the mutation is very high, its penetrance seems very low. The goal of our study was to determine whether hepcidin, a recently identified iron-regulatory peptide, could be a genetic modifier contributing to the HH phenotype. In mice, deficiency of either HFE (Hfe(-/-)) or hepcidin (Usf2(-/-)) is associated with the same pattern of iron overload observed in patients with HH. We intercrossed Hfe(-/-) and Usf2(+/-) mice and asked whether hepcidin deficiency increased the iron burden in Hfe(-/-) mice. Our results showed that, indeed, liver iron accumulation was greater in the Hfe(-/-)Usf2(+/-) mice than in mice lacking Hfe alone. This result, in agreement with recent findings in humans, provides a genetic explanation for some variability of the HH phenotype.

Animals↗