Systems genetic analysis of multivariate response to iron deficiency in mice

The aim of this study was to identify genes that influence iron regulation under varying dietary iron availability. Male and female mice from 20+ BXD recombinant inbred strains were fed iron-poor or iron-adequate diets from weaning until 4 mo of age. At death, the spleen, liver, and blood were harvested for the measurement of hemoglobin, hematocrit, total iron binding capacity, transferrin saturation, and liver, spleen and plasma iron concentration. For each measure and diet, we found large, strain-related variability. A principal-components analysis (PCA) was performed on the strain means for the seven parameters under each dietary condition for each sex, followed by quantitative trait loci (QTL) analysis on the factors. Compared with the iron-adequate diet, iron deficiency altered the factor structure of the principal components. QTL analysis, combined with PosMed (a candidate gene searching system) published gene expression data and literature citations, identified seven candidate genes, Ptprd, Mdm1, Picalm, lip1, Tcerg1, Skp2, and Frzb based on PCA factor, diet, and sex. Expression of each of these is cis-regulated, significantly correlated with the corresponding PCA factor, and previously reported to regulate iron, directly or indirectly. We propose that polymorphisms in multiple genes underlie individual differences in iron regulation, especially in response to dietary iron challenge. This research shows that iron management is a highly complex trait, influenced by multiple genes. Systems genetics analysis of iron homeostasis holds promise for developing new methods for prevention and treatment of iron deficiency anemia and related diseases.

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Vitamin A does not influence mRNA expression of hormone hepcidin but other biomarkers of iron homeostasis in young male Wistar rats

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000666 ◽

2020 ◽

pp. 1-8

Author(s):

Mauricio Restrepo-Gallego ◽

Luis E. Díaz

Keyword(s):

Iron Deficiency ◽

Vitamin A ◽

Mrna Expression ◽

Wistar Rats ◽

Iron Homeostasis ◽

Regulatory Protein ◽

Deficiency Anemia ◽

Control Group ◽

Dietary Iron ◽

Male Wistar Rats

Abstract. The effects of an adequate supply of vitamin A and iron, in comparison with diets low or absent in vitamin A and low in iron, on the mRNA expression of some biomarkers of iron homeostasis as hepcidin ( Hamp), transferrin receptor-1 ( Tfrc), iron regulatory protein-2 ( Ireb2) and ferritin ( Fth1) in rats were investigated. 35 male Wistar rats were randomly divided into 5 dietary groups: control, sufficient in iron and insufficient in vitamin A (FesvAi), sufficient in iron and depleted in vitamin A (FesvAd), insufficient in iron and sufficient in vitamin A (FeivAs) and insufficient in both iron and vitamin A (FeivAi). After 6 weeks rats showed no significant effects of variations in vitamin A on the expression of Hamp relative to the control group (FesvAi: 1.37-fold; FesvAd: 1.22-fold); however, iron deficiency showed significant reduction on it relative to the control group (FeivAs: 71.4-fold, P = 0.0004; FeivAi: 16.1-fold, P = 0.0008). Vitamin A deficiency (FesvAd) affects expression of Fth1 independent of low dietary iron in spleen (0.29-fold, P = 0.002) and duodenum (5.15-fold, P = 0.02). Variations of dietary iron and vitamin A showed significant effects relative to the control group for expression of Tfrc in spleen (FesvAd: 0.18-fold, P = 0.01; FeivAs: 0.24-fold, P < 0.0001; FeivAi: 0.42-fold, P = 0.014), Ireb2 in spleen (FeivAs: 3.7-fold, P < 0.0001; FeivAi: 2.9-fold, P < 0.0001) and Ireb2 in duodenum (FeivAs: 2.68-fold, P = 0.012; FeivAi: 2.60-fold, P = 0.014). These results show that vitamin A and iron must be supplied together to regulate some of the main biomarkers of iron metabolism as a strategy to reduce prevalence of iron deficiency anemia.

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Tmprss6 Is a Genetic Modifier of the Hfe-Hemochromatosis Phenotype in Mice.

Blood ◽

10.1182/blood.v114.22.625.625 ◽

2009 ◽

Vol 114 (22) ◽

pp. 625-625

Author(s):

Karin E. Finberg ◽

Rebecca Whittlesey ◽

Mark D. Fleming ◽

Nancy C. Andrews

Keyword(s):

Iron Deficiency ◽

Iron Content ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Heme Iron ◽

Deficiency Anemia ◽

Wild Type ◽

Non Heme Iron ◽

Serum Iron Concentration

Abstract Abstract 625 HFE-associated hereditary hemochromatosis is an autosomal recessive disorder characterized by inappropriately elevated absorption of dietary iron by the gastrointestinal mucosa, resulting in excessive storage of iron in multiple organs. A significant proportion of individuals who are homozygous for HFE mutations fail to develop clinical symptoms, suggesting that environmental and/or genetic factors may influence the penetrance of this disorder. In vitro and animal studies have revealed that HFE promotes the expression of hepcidin, a circulating hormone produced by the liver that acts to inhibit iron absorption by the duodenum. In contrast, TMPRSS6, a transmembrane serine protease produced by the liver, acts to inhibit hepcidin expression; both humans and mice harboring TMPRSS6 mutations display impaired intestinal iron absorption, resulting in a phenotype of iron-refractory iron deficiency anemia (IRIDA). Here we asked if heterozygous or homozygous loss of Tmprss6 function could modify the iron overload phenotype of Hfe null (Hfe-/-) mice, a mouse model of human HFE-hemochromatosis. To test this, we bred Hfe-/- mice to Tmprss6-/- mice; the latter harbor a targeted disruption of the Tmprss6 serine protease domain and exhibit an IRIDA phenotype. We generated Hfe-/-Tmprss6+/+, Hfe-/-Tmprss6+/-, and Hfe-/-Tmprss6-/- female mice (6-10 mice per genotype), in which parameters of systemic iron homeostasis were compared at eight weeks of age by Student's t test. Consistent with previous study of Hfe-/- mice, Hfe-/- mice harboring two wild type Tmprss6 alleles (Hfe-/-Tmprss6+/+ mice) showed serum iron concentration, transferrin saturation, and hepatic non-heme iron content that were significantly elevated compared to wild type mice of similar genetic background. Heterozygosity for Tmprss6 mutation, however, markedly reduced the severity of the hemochromatosis phenotype of Hfe-/- mice. Compared to Hfe-/- mice with two wild type Tmprss6 alleles, Hfe-/- mice that were heterozygous for Tmprss6 mutation (Hfe-/-Tmprss6+/- mice) showed significant reductions in serum iron concentration (p<0.01), transferrin saturation (p<0.005), and non-heme iron content of liver (p<10-4). Furthermore, homozygosity for Tmprss6 mutation completely ameliorated the iron overload phenotype of Hfe-/- mice and in fact led to systemic iron deficiency. Compared to both Hfe-/-Tmprss6+/+ and Hfe-/-Tmprss6+/- mice, Hfe-/-Tmprss6-/- mice showed markedly reduced serum iron concentration (p<10-7), transferrin saturation (p<10-10), and non-heme iron content of liver (p<10-4). Hfe-/-Tmprss6-/- mice also displayed iron deficiency anemia and appeared phenotypically similar to previously characterized Tmprss6-/- mice harboring two wild type copies of Hfe. In summary, these results demonstrate that Tmprss6 is a genetic modifier of the Hfe-hemochromatosis phenotype in mice. These findings suggest that natural genetic variation in the human ortholog TMPRSS6 might modify the clinical penetrance of HFE-hemochromatosis and raise the possibility that pharmacological inhibition of TMPRSS6 activity might prove an effective therapy in this disorder. Disclosures: No relevant conflicts of interest to declare.

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Zinc Protoporphyrin Is a Reliable Marker of Functional Iron Deficiency in Patients with Inflammatory Bowel Disease

Diagnostics ◽

10.3390/diagnostics11020366 ◽

2021 ◽

Vol 11 (2) ◽

pp. 366

Author(s):

Eleni Leventi ◽

Aysegül Aksan ◽

Carl Thomas Nebe ◽

Jürgen Stein ◽

Karima Farrag

Keyword(s):

Inflammatory Bowel Disease ◽

Iron Deficiency ◽

Chronic Inflammation ◽

Bowel Disease ◽

Iron Homeostasis ◽

Transferrin Saturation ◽

Deficiency Anemia ◽

Zinc Protoporphyrin ◽

Anemia Of Chronic Disease ◽

Inflammatory Bowel

Iron deficiency (ID) is a common manifestation of inflammatory bowel disease (IBD), arising primarily due to chronic inflammation and/or blood loss. There is no gold standard for ID diagnosis, which is often complicated by concomitant inflammation. Zinc protoporphyrin (ZnPP) correlates with parameters of iron homeostasis and has been identified as a promising marker for ID, irrespective of inflammation. We investigated the diagnostic performance of ZnPP in ID, iron deficiency anemia, anemia of chronic disease and mixed anemia in a cross-sectional study in 130 patients with IBD. Different parameters were compared by receiver operator characteristic (ROC) analysis as detectors of iron-restricted erythropoiesis (IRE). IRE was detected in 91 patients (70.0%); fifty-nine (64.8%) had absolute ID and 23 (25.4%) functional ID. When inflammation was present, ZnPP was a more reliable sole biomarker of IRE than MCV, transferrin saturation (TSAT) or ferritin (AUC; 0.855 vs. 0.763, 0.834% and 0.772, respectively). The specificity of TSAT was significantly lower than ZnPP when inflammation was present (38% vs. 71%, respectively). We conclude that ZnPP is a reliable biomarker of functional ID in patients with IBD and more dependable than ferritin or TSAT, which are influenced by chronic inflammation. We propose that ZnPP may also have utility in patients with other chronic diseases.

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Ceruloplasmin Is Essential for the Mobilization of Tissue Iron Stores.

Blood ◽

10.1182/blood.v106.11.3581.3581 ◽

2005 ◽

Vol 106 (11) ◽

pp. 3581-3581

Author(s):

Seth Rivera ◽

Miguel Lopez ◽

Dina Farshidi ◽

Victoria Gabayan ◽

Tomas Ganz

Keyword(s):

Iron Deficiency ◽

Serum Iron ◽

Iron Homeostasis ◽

Extracellular Fluid ◽

Deficiency Anemia ◽

Dietary Iron ◽

Deficient Diet ◽

Iron Stores ◽

High Iron ◽

Iron Deficient

Abstract In extracellular fluid, iron is in the ferric (oxidized form) but the intracellular form is ferrous iron (reduced). The outflow of iron from cells is dependent on oxidase activity that converts ferrous to ferric iron. Iron-absorbing enterocytes possess a unique iron oxidase, hephaestin. It is presumed that the circulating hephaestin paralog ceruloplasmin fulfils this role in hepatocytes and macrophages. The DiSnA mouse lacks ceruloplasmin. We hypothesized that iron homeostasis in this mouse would be unusually dependent on dietary iron because the mouse would not be able to mobilize iron from tissue stores in hepatocytes and macrophages. We fed 4-week-old DiSnA and wildtype (WT) mice a high iron (1%) diet for 4 weeks to load tissue stores. We then switched them to an iron-deficient diet and analyzed them weekly to measure iron and hemoglobin concentrations. Even on the high iron diet, DiSnA mice had lower serum iron concentrations than WT control (32.9±17.9 vs. 53.5±17.6 μM, p=0.05) but after two weeks on the iron deficient diet, the DiSnA mice had almost undetectable serum iron (4.2±1.8 μM) whereas the WT controls had only declined slightly (43.2±9.6 μM, p<0.001). Iron saturation followed a similar trend. Neither WT nor DiSnA mice were anemic at baseline (Hgb = 13.9±0.3 and 13.9±1.1 g/dL, respectively; p=0.994) but by the end of two weeks, the DiSnA mice had developed anemia whereas the WT mice had not (Hgb = 10.4±0.5 vs. 12.6±0.5 g/dL; p<0.001). The difference in hemoglobin concentrations persisted to the 6-week timepoint (Hgb = 8.4±0.5 vs. 12.6±1.4; p<0.001). After 6-weeks on a low iron diet, iron was still present in livers and spleens of both groups. Ceruloplasmin is essential for the mobilization of iron stores to protect against iron deficiency anemia in response to periods of dietary iron deficiency.

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Cancer Related Anemia: An Integrated Multitarget Approach and Lifestyle Interventions

Nutrients ◽

10.3390/nu13020482 ◽

2021 ◽

Vol 13 (2) ◽

pp. 482

Author(s):

Valentina Natalucci ◽

Edy Virgili ◽

Federica Calcagnoli ◽

Giacomo Valli ◽

Deborah Agostini ◽

...

Keyword(s):

Iron Homeostasis ◽

Iron Concentration ◽

Transferrin Saturation ◽

Intravenous Iron ◽

Complex Problem ◽

Low Grade ◽

Inflammatory Status ◽

Line Of Therapy ◽

Cancer Related Anemia ◽

Low Grade Inflammation

Cancer is often accompanied by worsening of the patient’s iron profile, and the resulting anemia could be a factor that negatively impacts antineoplastic treatment efficacy and patient survival. The first line of therapy is usually based on oral or intravenous iron supplementation; however, many patients remain anemic and do not respond. The key might lie in the pathogenesis of the anemia itself. Cancer-related anemia (CRA) is characterized by a decreased circulating serum iron concentration and transferrin saturation despite ample iron stores, pointing to a more complex problem related to iron homeostatic regulation and additional factors such as chronic inflammatory status. This review explores our current understanding of iron homeostasis in cancer, shedding light on the modulatory role of hepcidin in intestinal iron absorption, iron recycling, mobilization from liver deposits, and inducible regulators by infections and inflammation. The underlying relationship between CRA and systemic low-grade inflammation will be discussed, and an integrated multitarget approach based on nutrition and exercise to improve iron utilization by reducing low-grade inflammation, modulating the immune response, and supporting antioxidant mechanisms will also be proposed. Indeed, a Mediterranean-based diet, nutritional supplements and exercise are suggested as potential individualized strategies and as a complementary approach to conventional CRA therapy.

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IRON-FORTIFIED FORMULAS

PEDIATRICS ◽

10.1542/peds.47.4.786 ◽

1971 ◽

Vol 47 (4) ◽

pp. 786-786

Author(s):

L. J. Filer ◽

Lewis A. Barness ◽

Richard B. Goldbloom ◽

Malcolm A. Holliday ◽

Robert W. Miller ◽

...

Keyword(s):

Iron Deficiency ◽

Iron Deficiency Anemia ◽

Deficiency Anemia ◽

Dietary Iron ◽

Iron Intake ◽

Feeding Problems ◽

Whole Milk ◽

Dietary Component ◽

Recent Statement ◽

Marketing Information

In its recent statement on iron,1 the Committee on Nutrition emphasized the value of iron-fortified, proprietary milk formulas for the prevention of iron-deficiency anemia of infancy. Despite this recommendation, the most recent marketing information available to the Committee shows that more than 70% of the proprietary formulas currently prescribed by physicians do not contain added iron. The reasons for continuing routine use of formulas not fortified with iron are not entirely clear. One reason may be that some physicians still believe iron additives increase the incidence of feeding problems or gastrointestinal disturbances. There is no documented evidence that this is a significant problem. The Committee strongly recommends when proprietary formulas are prescribed that iron-supplemented formulas be used routinely as the standard–that is, that this be the rule rather than the exception. There seems to be little justification for continued general use of proprietary formulas not fortified with iron. The Committee is fully aware that only a small percentage of American infants are fed proprietary formulas after 6 months of age. Fluid whole milk (available in bottle or carton ) or evaporated milk, both of which contain only trace amounts of iron, are substituted at the time of greatest iron need and highest prevalence of iron-deficiency anemia. The infant's diet is usually deficient in iron, unless other foods are carefully selected to insure adequate iron intake. Since the major dietary component during infancy is milk, two courses of action should be taken: (1) Pediatricians and other health professionals should engage in a program of public education to convince American mothers to provide their infants with a source of dietary iron.

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Iron Homeostasis and Disorders in Dogs and Cats: A Review

Journal of the American Animal Hospital Association ◽

10.5326/jaaha-ms-5553 ◽

2011 ◽

Vol 47 (3) ◽

pp. 151-160 ◽

Cited By ~ 27

Author(s):

Jennifer L. McCown ◽

Andrew J. Specht

Keyword(s):

Iron Deficiency ◽

Iron Overload ◽

Iron Homeostasis ◽

Diagnostic Testing ◽

Clinical Manifestations ◽

Essential Element ◽

The Body ◽

Deficiency Anemia ◽

Enzyme Systems ◽

Living Organisms

Iron is an essential element for nearly all living organisms and disruption of iron homeostasis can lead to a number of clinical manifestations. Iron is used in the formation of both hemoglobin and myoglobin, as well as numerous enzyme systems of the body. Disorders of iron in the body include iron deficiency anemia, anemia of inflammatory disease, and iron overload. This article reviews normal iron metabolism, disease syndromes of iron imbalance, diagnostic testing, and treatment of either iron deficiency or excess. Recent advances in diagnosing iron deficiency using reticulocyte indices are reviewed.

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Modulation of intestinal sulfur assimilation metabolism regulates iron homeostasis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1715302115 ◽

2018 ◽

Vol 115 (12) ◽

pp. 3000-3005 ◽

Cited By ~ 7

Author(s):

Benjamin H. Hudson ◽

Andrew T. Hale ◽

Ryan P. Irving ◽

Shenglan Li ◽

John D. York

Keyword(s):

Iron Deficiency ◽

Iron Deficiency Anemia ◽

Iron Reduction ◽

Genetic Basis ◽

Iron Homeostasis ◽

Deficiency Anemia ◽

Sulfur Assimilation ◽

Nucleotide Hydrolysis ◽

Evolutionarily Conserved ◽

Organismal Development

Sulfur assimilation is an evolutionarily conserved pathway that plays an essential role in cellular and metabolic processes, including sulfation, amino acid biosynthesis, and organismal development. We report that loss of a key enzymatic component of the pathway, bisphosphate 3′-nucleotidase (Bpnt1), in mice, both whole animal and intestine-specific, leads to iron-deficiency anemia. Analysis of mutant enterocytes demonstrates that modulation of their substrate 3′-phosphoadenosine 5′-phosphate (PAP) influences levels of key iron homeostasis factors involved in dietary iron reduction, import and transport, that in part mimic those reported for the loss of hypoxic-induced transcription factor, HIF-2α. Our studies define a genetic basis for iron-deficiency anemia, a molecular approach for rescuing loss of nucleotidase function, and an unanticipated link between nucleotide hydrolysis in the sulfur assimilation pathway and iron homeostasis.

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Intestinal expression of genes involved in iron absorption in humans

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00371.2001 ◽

2002 ◽

Vol 282 (4) ◽

pp. G598-G607 ◽

Cited By ~ 58

Author(s):

Andreas Rolfs ◽

Herbert L. Bonkovsky ◽

James G. Kohlroser ◽

Kristina McNeal ◽

Ashish Sharma ◽

...

Keyword(s):

Iron Deficiency ◽

Iron Deficiency Anemia ◽

Iron Absorption ◽

Genetic Disorders ◽

Hereditary Hemochromatosis ◽

Transferrin Saturation ◽

High Serum ◽

Deficiency Anemia ◽

Dependent Manner ◽

Expression Levels

Hereditary hemochromatosis (HHC) is one of the most frequent genetic disorders in humans. In healthy individuals, absorption of iron in the intestine is tightly regulated by cells with the highest iron demand, in particular erythroid precursors. Cloning of intestinal iron transporter proteins provided new insight into mechanisms and regulation of intestinal iron absorption. The aim of this study was to assess whether, in humans, the two transporters are regulated in an iron-dependent manner and whether this regulation is disturbed in HHC. Using quantitative PCR, we measured mRNA expression of divalent cation transporter 1 (DCT1), iron-regulated gene 1 (IREG1), and hephaestin in duodenal biopsy samples of individuals with normal iron levels, iron-deficiency anemia, or iron overload. In controls, we found inverse relationships between the DCT1 splice form containing an iron-responsive element (IRE) and blood hemoglobin, serum transferrin saturation, or ferritin. Subjects with iron-deficiency anemia showed a significant increase in expression of the spliced form, DCT1(IRE) mRNA. Similarly, in subjects homozygous for the C282Y HFE mutation, DCT1(IRE) expression levels remained high despite high serum iron saturation. Furthermore, a significantly increased IREG1 expression was observed. Hephaestin did not exhibit a similar iron-dependent regulation. Our data show that expression levels of human DCT1 mRNA, and to a lesser extent IREG1 mRNA, are regulated in an iron-dependent manner, whereas mRNA of hephaestin is not affected. The lack of appropriate downregulation of apical and basolateral iron transporters in duodenum likely leads to excessive iron absorption in persons with HHC.

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Ferroportin-Hepcidin Axis in Prepubertal Obese Children with Sufficient Daily Iron Intake

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph15102156 ◽

2018 ◽

Vol 15 (10) ◽

pp. 2156 ◽

Cited By ~ 6

Author(s):

Joanna Gajewska ◽

Jadwiga Ambroszkiewicz ◽

Witold Klemarczyk ◽

Ewa Głąb-Jabłońska ◽

Halina Weker ◽

...

Keyword(s):

Iron Deficiency ◽

Iron Status ◽

Hematological Parameters ◽

Daily Intake ◽

Normal Weight ◽

Deficiency Anemia ◽

Dietary Iron ◽

Iron Intake ◽

Obese Children ◽

Iron Concentrations

Iron metabolism may be disrupted in obesity, therefore, the present study assessed the iron status, especially ferroportin and hepcidin concentrations, as well as associations between the ferroportin-hepcidin axis and other iron markers in prepubertal obese children. The following were determined: serum ferroportin, hepcidin, ferritin, soluble transferrin receptor (sTfR), iron concentrations and values of hematological parameters as well as the daily dietary intake in 40 obese and 40 normal-weight children. The ferroportin/hepcidin and ferritin/hepcidin ratios were almost two-fold lower in obese children (p = 0.001; p = 0.026, respectively). Similar iron concentrations (13.2 vs. 15.2 µmol/L, p = 0.324), the sTfR/ferritin index (0.033 vs. 0.041, p = 0.384) and values of hematological parameters were found in obese and control groups, respectively. Iron daily intake in the obese children examined was consistent with recommendations. In this group, the ferroportin/hepcidin ratio positively correlated with energy intake (p = 0.012), dietary iron (p = 0.003) and vitamin B12 (p = 0.024). In the multivariate regression model an association between the ferroportin/hepcidin ratio and the sTfR/ferritin index in obese children (β = 0.399, p = 0.017) was found. These associations did not exist in the controls. The results obtained suggest that in obese children with sufficient iron intake, the altered ferroportin-hepcidin axis may occur without signs of iron deficiency or iron deficiency anemia. The role of other micronutrients, besides dietary iron, may also be considered in the iron status of these children.

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