High FE Research Articles

A Mouse Model of Cardiomyopathy Induced by Mutations in the Hemochromatosis HFE Gene

BackgroundThe heart is 1 of the organs most affected by hereditary hemochromatosis (HH). The clinical impact of cardiomyopathy in patients with HH requires a particular diagnosis and less invasive treatments. We developed a model of cardiomyopathy in knockout (KO) mice for the high-Fe (HFE) gene and assessed left ventricular (LV) function and structure from 7-20 months. MethodsMale wild-type (WT) heterozygous and KO SV129 mice for the HFE gene were used in this study. Twenty-four mice were used to assess LV function and structure by echocardiography at 7, 14, 18, and 20 months. Evaluations of LV function and structure and myocardial fibrosis were performed at 7 and 20 months. ResultsThe percent decrease of LV thickness-to-radius ratio between 7 and 20 months was higher in KO mice compared with WT mice (−30.2% ± 5.3% vs −10.5% ± 4.9%; P < 0.01). The LV diameters were higher in old mice compared with young mice (+13% at end-diastole; +33% at end-systole; P < 0.001). The LV ejection fraction values were lower in KO mice compared with WT mice between 7 and 20 months. The highest difference was found at 14 months (60.0% ± 7.6% vs 78.1% ± 3.5%; P < 0.001). Myocardial fibrosis was higher in old KO mice compared with old WT mice (+55%; P < 0.001), and myocardial iron deposition was slightly increased in old KO mice compared with old WT mice (1.31% ± 0.33% vs 0.84% ± 0.22%; P = 0.056). ConclusionsThe present mouse model has the potential to allow the determination of underlying mechanisms involved in the cardiomyopathy induced by HFE-related hemochromatosis.

Molecular epidemiology of HFE gene polymorphic variants (C282Y, H63D and S65C) in the population of Espírito Santo, Brazil.

Hereditary hemochromatosis (HH) is an autosomal recessive disorder that leads to progressive iron accumulation and may cause cirrhosis, hepatocellular carcinoma, diabetes, and heart failure. Most cases of HH have been linked to mutations in genes associated with iron homeostasis. There have been three major variants in the high Fe (HFE) gene associated with the disease: C282Y, H63D and S65C. In this context, we aimed to evaluate the prevalence of the polymorphic variants (C282Y, H63D and S65C) of the HFE gene in the population of the Espírito Santo State (ES), Brazil by analyzing three different groups: general population (N = 120), Pomeranian descendants (N = 59), and patients with HH (N = 20). Using genomic DNA extracted from peripheral blood, polymorphic variant identification was performed by polymerase chain reaction-restriction fragment length polymorphism. Statistically significant differences were observed for genotype distribution of C282Y (P < 0.001) and H63D (P = 0.013) between the general population and the patients diagnosed with HH. This is the first study to analyze HFE gene allele frequencies for the general population, Pomeranian subpopulation, and patients with HH of ES, Brazil.

Facilitation of blood donation amongst haemochromatosis patients.

The standard medical therapy for haemochromatosis is iron removal by regular phlebotomy. Current guidelines suggest that this blood should be made available through national blood services. Here, we describe a pilot facilitating the process of blood donation amongst uncomplicated haemochromatosis patients. At a dedicated clinic, patients with uncomplicated haemochromatosis interested in becoming blood donors were offered an information leaflet and self-referral application. Upon receipt, members of the local Blood Service contacted them to confirm eligibility to donate. Data on demographics and clinical characteristics, including HFE (high Fe) genotype, co-morbidities, alcohol consumption and body mass index, were collected. Since establishing the clinic, 140 patients have attended (93 male) with median age 57. Most (n = 125; 89%) had uncomplicated haemochromatosis. Of these, 55 were potentially eligible blood donors. Amongst those eligible, there are now 29 regular blood donors, including 23 new. There is an interest and willingness to donate blood through the Blood Service amongst uncomplicated haemochromatosis patients undergoing therapeutic phlebotomy. Since the introduction of this facilitation process, we have significantly increased the number of regular donors amongst this cohort. If this process was to be replicated more widely across the UK, this could have a significant impact on the blood donor pool.

Influence of lead on repetitive behavior and dopamine metabolism in a mouse model of iron overload.

Exposures to lead (Pb) are associated with neurological problems including psychiatric disorders and impaired learning and memory. Pb can be absorbed by iron transporters, which are up-regulated in hereditary hemochromatosis, an iron overload disorder in which increased iron deposition in various parenchymal organs promote metal-induced oxidative damage. While dysfunction in HFE (High Fe) gene is the major cause of hemochromatosis, the transport and toxicity of Pb in Hfe-related hemochromatosis are largely unknown. To elucidate the relationship between HFE gene dysfunction and Pb absorption, H67D knock-in Hfe-mutant and wild-type mice were given drinking water containing Pb 1.6 mg/ml ad libitum for 6 weeks and examined for behavioral phenotypes using the nestlet-shredding and marble-burying tests. Latency to nestlet-shredding in Pb-treated wild-type mice was prolonged compared with non-exposed wild-types (p < 0.001), whereas Pb exposure did not alter shredding latency in Hfe-mutant mice. In the marble-burying test, Hfe-mutant mice showed an increased number of marbles buried compared with wild-type mice (p = 0.002), indicating more repetitive behavior upon Hfe mutation. Importantly, Pb-exposed wild-type mice buried more marbles than non-exposed wild-types, whereas the number of marbles buried by Hfe-mutant mice did not change whether or not exposed to Pb. These results suggest that Hfe mutation could normalize Pb-induced behavioral alteration. To explore the mechanism of repetitive behavior caused by Pb, western blot analysis was conducted for proteins involved in brain dopamine metabolism. The levels of tyrosine hydroxylase and dopamine transporter increased upon Pb exposure in both genotypes, whereas Hfe-mutant mice displayed down-regulation of the dopamine transporter and dopamine D1 receptor with D2 receptor elevated. Taken together, our data support the idea that both Pb exposure and Hfe mutation increase repetitive behavior in mice and further suggest that these behavioral changes could be associated with altered dopaminergic neurotransmission, providing a therapeutic basis for psychiatric disorders caused by Pb toxicity.

156 Regulation of LDL-cholesterol Associated Gene Expression by Iron Responsive Elements and Iron

Variants in 37 genes have been associated with low density lipoprotein cholesterol (LDL-C) levels, including HFE (High Fe) p.(C282Y), rs1800562. This variant is homozygous in ~90% patients with haemochromatosis. It...

Central ghrelin treatment stimulates ACTH cells in normal-fed, food-restricted and high-fed rats: An immunohistomorphometric and hormonal study

Changes in feeding regime represent serious stress, while ghrelin is considered a key player in energy balance. We investigated the effects of intracerebroventricular (ICV) ghrelin application on pituitary adrenocorticotropic (ACTH) cells in rats fed diets differing in energy content. Before the ICV treatment, male Wistar rats were subjected to three different feeding regimes for 4 weeks: normal-fed (NF), food-restricted (FR) or high-fed (HF) (n=3×14). At the age of 8 weeks, rats from each group were divided into two subgroups and given ICV, either ghrelin (G; 1μg ghrelin/5μl PBS, n=7) or solvent alone (5μl PBS, n=7) every 24h for 5 days. The immunohistochemical appearance and quantitative morphology of pituitary ACTH cells were evaluated, as well as peripheral ACTH and corticosterone levels. Central ghrelin administration increased (p<0.05) ACTH cell volumes in GNF, GFR and GHF rats by 8.1%, 11.8% and 9.1%, respectively, compared to the controls, while significant increases in ACTH cell volume density were observed in GNF and GHF rats. Circulating ACTH and corticosterone levels were elevated (p<0.05) in GNF and GFR rats by 72.8% and 80.8%, respectively, when compared to the corresponding controls. Thus, central ghrelin administration stimulated the pituitary-adrenal axis under preserved and negative energy balance states.

Iron Transporters Are Differentially Regulated by Dietary Iron, and Modifications Are Associated with Changes in Manganese Metabolism in Young Pigs1–3

To investigate the effects of dietary iron (Fe) on manganese (Mn) metabolism, 24 weaned pigs (21 d old) were blocked by litter and weight and randomly assigned to the following treatments: 1) no supplemental Fe [low Fe (L-Fe)]; 2) 100 mg supplemental Fe/kg [adequate Fe (A-Fe)]; and 3) 500 mg supplemental Fe/kg [high Fe (H-Fe)]. The basal diet was analyzed to contain 20 mg Fe/kg. Tissues were harvested after 32 d of feeding. Daily gain (least square means ± SEM) was greater in A-Fe pigs (328.3 ± 29.9 g/d) than in L-Fe pigs (224.0 ± 11.2 g/d). Hemoglobin concentrations on d 32 were lower in L-Fe pigs (62 ± 3.5 g/L) than in A-Fe pigs (128 ± 5.6 g/L) and did not differ between pigs fed A-Fe and H-Fe (133 ± 12.0 g/L). Liver Fe increased with increasing dietary Fe. Relative hepatic hepcidin expression was greater in pigs fed A-Fe and H-Fe than in those fed L-Fe. Relative expressions of duodenal divalent metal transporter 1 (DMT1) and solute carrier family 39 member 14 (ZIP14) were increased in L-Fe pigs compared with H-Fe pigs. Liver copper (Cu) was higher in L-Fe (0.56 ± 0.04 mmol/kg) and H-Fe (0.58 ± 0.04 mmol/kg) pigs than in A-Fe pigs (0.40 ± 0.04 mmol/kg). Liver Mn was lower in H-Fe pigs (0.15 ± 0.01 mmol/kg) than in A-Fe (0.23 ± 0.02 mmol/kg) or L-Fe pigs (0.20 ± 0.02 mmol/kg). Duodenal Mn concentrations were greater in L-Fe pigs than in A-Fe or H-Fe pigs. Fe deficiency in pigs increased gene expression of duodenal metal transporters (DMT1 and ZIP14) and supplementation with H-Fe reduced expression of DMT1 and ZIP14, which may have decreased absorption of Mn.

HFE gene in primary and secondary hepatic iron overload.

Distinct from hereditary haemochromatosis, hepatic iron overload is a common finding in several chronic liver diseases. Many studies have investigated the prevalence, distribution and possible contributory role of excess hepatic iron in non-haemochromatotic chronic liver diseases. Indeed, some authors have proposed iron removal in liver diseases other than hereditary haemochromatosis. However, the pathogenesis of secondary iron overload remains unclear. The High Fe (HFE) gene has been implicated, but the reported data are controversial. In this article, we summarise current concepts regarding the cellular role of the HFE protein in iron homeostasis. We review the current status of the literature regarding the prevalence, hepatic distribution and possible therapeutic implications of iron overload in chronic hepatitis C, hepatitis B, alcoholic and non-alcoholic fatty liver diseases and porphyria cutanea tarda. We discuss the evidence regarding the role of HFE gene mutations in these liver diseases. Finally, we summarize the common and specific features of iron overload in liver diseases other than haemochromatosis.

Effect of Feeding Level and Nitrogen Source of the Diet on GH, IGF-T, and Prolactin Receptors in Mammary and Liver Tissue from Pre-pubertal Heifers

Pre-pubertal (86-220 kg BW) Finnish Ayrshire heifers were used to study the effect of feeding level and nitrogen source on GH, IGF-I, and prolactin (PRL) receptors in mammary and liver parenchymal tissue. The heifers were fed a hay-barley diet supplemented with either urea or rapeseed meal. The treatments were: (1) LU, low feeding level+urea; (2) LR, low feeding level+rapeseed meal; (3) HU, high feeding+urea; (4) HR, high feeding level+rapeseed meal. The average daily gains of the heifers on LU, LR, HU and HR diets were 692, 655, 805 and 890 g. At slaughter, mammary and liver parenchymal tissue was collected for preparation of crude membranes, and ligand-binding assays were performed. Specific binding of bGH to mammary membranes could not be detected. Linear Scatchard plots were obtained showing the presence of a single class of high-affinity binding sites for IGF-I in mammary tissue. Specific binding of IGF-I to mammary membranes was unaffected by feeding level and nitrogen source. Furthermore, Scatchard analysis showed unchanged binding capacities and binding affinities of the IGF-I receptors in mammary tissue from low and high fed heifers. Specific binding of prolactin to mammary membranes was increased by high feeding level (P<0.02) and by rapeseed meal (P<0.01). No interaction between feeding level and nitrogen source was identified. Hepatic binding of bGH, IGF-I and prolactin was unaffected by feeding level and nitrogen source. However, specific binding of prolactin tended to be lower (P<0.07) in liver tissue from heifers fed rapeseed meal as diet nitrogen source. The present study shows that the previously reported negative effect of high feeding level on pubertal mammary development (Mäntysaari et al., 1995), cannot be explained by changes in binding to GH and IGF-I receptors. The importance of the increase in prolactin binding to mammary membranes from heifers at high feeding level and with rapeseed meal needs further investigation.