SERUM IRON CONCENTRATION (SI) AND TRANSFERRIN SATURATION (SAT) ARE LOWER IN NORMAL CHILDREN THAN IN ADULTS

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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Serum iron concentration and transferrin saturation in the diagnosis of iron deficiency in children: Normal developmental changes

The Journal of Pediatrics ◽

10.1016/s0022-3476(77)80879-2 ◽

1977 ◽

Vol 91 (6) ◽

pp. 870-874 ◽

Cited By ~ 45

Author(s):

Marion A. Koerper ◽

Peter R. Dallman

Keyword(s):

Iron Deficiency ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Developmental Changes ◽

Serum Iron Concentration

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Effect of Phenylhydrazine and Bone Marrow Inhibitors on Red Cell Destruction and Serum Iron Concentration

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1958.193.1.92 ◽

1958 ◽

Vol 193 (1) ◽

pp. 92-94

Author(s):

Alfred Chanutin

Keyword(s):

Bone Marrow ◽

Serum Iron ◽

Iron Concentration ◽

Hemoglobin Concentration ◽

Moderate Increase ◽

Serum Iron Concentration ◽

Moderate Anemia ◽

Sublethal Doses ◽

Slight Depression ◽

Marrow Activity

The administration of sublethal doses of bone marrow depressants (nitrogen mustard, triethylene melamine and thioguanine) causes a temporary, moderate increase in serum iron concentration, a slight depression of bone marrow activity and no change in hemoglobin concentration. A combination of any of these drugs with a small dose of phenylhydrazine causes a temporary marked hyperferremia, a moderate anemia and a marked reticulocytosis. The results indicate that hyperferremia is not necessarily associated with bone marrow activity.

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Iron Absorption after Single Pharmacological Oral Iron Loading Test in Patients on Chronic Peritoneal Dialysis and in Healthy Volunteers

Peritoneal Dialysis International ◽

10.1177/089686080002000614 ◽

2000 ◽

Vol 20 (6) ◽

pp. 662-666 ◽

Cited By ~ 5

Author(s):

Bahar Bastani ◽

Shah Islam ◽

Nasser Boroujerdi

Keyword(s):

Serum Iron ◽

Iron Absorption ◽

Iron Concentration ◽

Significant Rise ◽

Oral Iron ◽

Iron Sulfate ◽

Chronic Peritoneal Dialysis ◽

Dialysis Patients ◽

Control Subjects ◽

Serum Iron Concentration

Objective Oral iron is poorly absorbed in chronic dialysis patients. We tested the hypothesis that a superpharmacologic dose of iron sulfate (260 mg elemental iron) administered on an empty stomach results in significant iron absorption in these patients. Design A prospective open controlled trial. Setting Outpatient department of a university hospital. Patients Nine stable chronic peritoneal dialysis (PD) patients and seven normal control subjects. Method All subjects ingested a single dose of 4 tablets of iron sulfate (260 mg elemental iron total) in the morning while fasting. Outcome Measures Serum iron concentrations at baseline, and at 2 and 4 hours after the oral dose were compared between the two groups. Results The control group showed a significant rise in mean [± standard error (SE)] serum iron concentration, from a baseline value of 76.5 ± 7 μg/dL to 191 ± 10.5 μg/dL at 2 hours and to 190 ± 24 μg/dL at 4 hours. This result represents a percentage rise of 164% ± 32% at 2 hours and 152% ± 28.5% at 4 hours. In the PD patients, a significant rise in serum iron concentration was also seen, from a baseline value of 64 ± 8 μg/dL to 130 ± 3 μg/dL at 2 hours and 111 ± 18 μg/dL at 4 hours. This result represents a percentage rise of 105% ± 29% at 2 hours and 77% ± 23.5% at 4 hours. However, the absolute change in serum iron concentration in PD patients at 2 and 4 hours was approximately equal to 50% of the change in control subjects at those time points. None of the PD patients experienced gastrointestinal side effects; 4 control subjects experienced mild side effects. Conclusion Despite impaired oral iron absorption in chronic dialysis patients, a large pharmacologic dose given orally can result in significant iron absorption and may prove to be a more efficient means of oral iron supplementation therapy in these patients.

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Effect of Phenylhydrazine and X-Irradiation on Red Cell Destruction and Serum Iron Concentration

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1953.173.3.474 ◽

1953 ◽

Vol 173 (3) ◽

pp. 474-480 ◽

Cited By ~ 2

Author(s):

Alfred Chanutin ◽

Elizabeth A. Lentz ◽

Stephan Ludewig

Keyword(s):

Serum Iron ◽

Iron Concentration ◽

Red Cell ◽

Cell Destruction ◽

Serum Iron Concentration ◽

X Irradiation

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RNAi-Mediated Inhibition of Tmprss6 Elevates Hamp1 Expression and Reduces Serum Iron Levels in Mice

Blood ◽

10.1182/blood.v118.21.1045.1045 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1045-1045 ◽

Cited By ~ 1

Author(s):

Ivanka Toudjarska ◽

Zuhua Cai ◽

Tim Racie ◽

Stuart Milstein ◽

Brian R Bettencourt ◽

...

Keyword(s):

Iron Overload ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Elevated Serum ◽

High Serum ◽

Therapeutic Modality ◽

Deficiency Anemia ◽

Loss Of Function ◽

Hepcidin Expression

Abstract Abstract 1045 The liver hormone Hepcidin (encoded by Hamp1) regulates serum iron levels by controlling the efflux of iron from intestinal enterocytes and macrophages. Maintaining sufficient iron levels to support erythropoiesis while preventing iron overload requires tight control of Hepcidin expression. Transcription of Hamp1 in hepatocytes is stimulated by high serum iron levels, via Transferrin Receptor signaling, as well as by activation of the BMP/SMAD pathway. The membrane serine protease Matriptase-2 (encoded by Tmprss6) inhibits BMP induced Hamp1 induction through the regulation of the BMP co-receptor, Hemojuvelin. In humans, loss of function mutations in TMPRSS6 lead to elevated Hepcidin levels resulting in iron-resistant iron-deficiency anemia (IRIDA). In diseases associated with iron overload, such as Thalassemia intermedia (TI) and Familial Hemochromatosis (FH), Hepcidin levels are low despite elevated serum iron concentrations. Studies in murine models of TI and FH have shown that elevating Hepcidin levels by genetic inactivation of Tmprss6 can prevent iron overload and correct aspects of the disease phenotype. Therefore, therapeutic strategies aimed at specifically inhibiting Tmprss6 expression could prove efficacious in these, and other, iron overloading diseases. Here we show that systemic administration of a potent lipid nanoparticle (LNP) formulated siRNA directed against Tmprss6 leads to durable inhibition of Tmprss6 mRNA in the mouse liver, with concomitant elevation of Hamp1 expression. This leads to significant decreases in serum iron concentration and Transferrin saturation, along with changes in hematologic parameters consistent with iron restriction. Further testing in mouse genetic models of TI and FH will support the rationale for developing LNP formulated Tmprss6 siRNA as a novel therapeutic modality. Disclosures: Toudjarska: Alnylam Pharmaceuticals, Inc.: Employment. Cai:Alnylam Pharmaceuticals, Inc.: Employment. Racie:Alnylam Pharmaceuticals, Inc.: Employment. Milstein:Alnylam Pharmaceuticals, Inc.: Employment. Bettencourt:Alnylam Pharmaceuticals, Inc.: Employment. Hettinger:Alnylam Pharmaceuticals, Inc.: Employment. Sah:Alnylam Pharmaceuticals, Inc.: Employment. Vaishnaw:Alnylam Pharmaceuticals, Inc.: Employment. Bumcrot:Alnylam Pharmaceuticals, Inc.: Employment.

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Targeting TMPRSS6 Using Antisense Technology for the Treatment of Beta-Thalassemia

Blood ◽

10.1182/blood.v126.23.753.753 ◽

2015 ◽

Vol 126 (23) ◽

pp. 753-753 ◽

Cited By ~ 2

Author(s):

Shuling Guo ◽

Mariam Aghajan ◽

Carla Casu ◽

Sara Gardenghi ◽

Sheri Booten ◽

...

Keyword(s):

Mouse Model ◽

Targeted Delivery ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Beta Thalassemia ◽

Control Group ◽

Mrna Levels ◽

Antisense Technology ◽

Wide Range

Abstract Antisense technology is a powerful drug discovery approach for identifying oligonucleotide analogs that can specifically modify RNA expression through multiple mechanisms including RNase H-mediated degradation of RNA and modulation of RNA splicing. We have successfully applied this technology towards targeting a number of transcripts in a wide-range of therapeutic areas. Beta-thalassemia, one of the most common genetic disorders worldwide, is characterized by reductions in beta-globin and ineffective erythropoiesis. This in turn leads to suppression of hepcidin, a peptide hormone that serves as the master regulator of iron homeostasis. Inappropriately low levels of hepcidin trigger increased dietary iron absorption resulting in iron overload, which is the major cause of morbidity and mortality in beta-thalassemia patients. TMPRSS6 is a transmembrane serine protease mainly produced by hepatocytes that negatively regulates hepcidin expression. Previous mouse and human genetic data from multiple groups suggest that lowering TMPRSS6 expression could up-regulate hepcidin and ameliorate many of the disease symptoms associated with β-thalassemia. We identified potent antisense oligonucleotides (ASOs) against mouse TMPRSS6. Downregulation of TMPRSS6 with ASO treatment resulted in dose-dependent hepcidin upregulation and reduction in serum iron and transferrin saturation in normal mice. In a mouse model of beta-thalassemia (th3/+ mice), which effectively recapitulates beta-thalassemia intermedia in humans, TMPRSS6 reduction resulted in induction of hepcidin and dramatic reductions of serum transferrin saturation (from 55-63% in control group down to 20-26% in treatment group). Liver iron concentration (LIC) was also greatly reduced (40-50%). Moreover, anemia endpoints were significantly improved with ASO treatment, including increases in red blood cells (~30-40%), hemoglobin (~2 g/dl), and hematocrit (~20%); reduction of splenomegaly; decreases in serum erythropoietin levels; improved erythroid maturation as indicated by a strong reduction in reticulocyte number and a normalized proportion between the pool of erythroblasts and enucleated erythroid cells. Encouraged by the strong pharmacology of TMPRSS6 suppression in animal models, we initiated an effort to identify a human TMPRSS6 clinical candidate with a liver-targeted delivery strategy. Over 2000 ASOs were screened in cell lines and the most active compounds were evaluated in rodent tolerability studies. A human TMPRSS6 transgenic mouse model was established enabling evaluation of ASO activity toward human TMPRSS6 transcript in vivo. Furthermore, lead compounds were tested in a 3-month study in normal monkeys. With repeated dosing, TMPRSS6 mRNA levels in monkey liver were reduced by >90%, accompanied by time-dependent reductions of serum iron (from ~100-120ug/dl to <40ug/dl), transferrin saturation (from ~30-35% to <10%), and hemoglobin. These compounds were well tolerated in rodents and in monkeys. Collectively, our data demonstrate that TMPRSS6 ASO could be an effective therapeutic for patients with beta-thalassemia and related disorders. A Phase 1 clinical trial is planned to initiate in 2016. Disclosures Guo: Isis Pharmaceuticals: Employment, Other: Shareholder. Aghajan:Isis Pharmaceuticals: Employment, Other: Shareholder. Booten:Isis Pharmaceuticals: Employment, Other: Shareholder. Monia:Isis Pharmaceuticals: Employment, Other: Shareholder.

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Effect of Thermal Injury and X-Irradiation on Serum Iron Concentration and on Iron Contents of Liver, Spleen and Kidney of Rats

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1952.169.1.203 ◽

1952 ◽

Vol 169 (1) ◽

pp. 203-207

Author(s):

Alfred Chanutin ◽

Stephan Ludewig ◽

Elizabeth A. Lentz

Keyword(s):

Serum Iron ◽

Thermal Injury ◽

Iron Concentration ◽

Serum Iron Concentration ◽

X Irradiation

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Serum Iron Determinations

Clinical Chemistry ◽

10.1093/clinchem/4.4.290 ◽

1958 ◽

Vol 4 (4) ◽

pp. 290-295 ◽

Cited By ~ 5

Author(s):

Harold L Rosenthal ◽

Mari Lou Pfluke ◽

Lois Jud

Keyword(s):

Serum Iron ◽

Iron Concentration ◽

Serum Samples ◽

Serum Iron Concentration ◽

Control Serum ◽

Control Samples

Abstract The inclusion of control serum samples for the estimation of serum iron by the Kingsley-Getchell bathophenanthroline and the Ramsay dipyridyl methods is necessary in order to correct for nonspecific absorption of serum pigments. In the absence of control samples, serum iron concentration may be from 25 to 90 per cent too high.

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