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Hepatic iron sensing genes

Paul A Sharp, Rachel Clarkson, Ahmed Hussain, Robert J Weeks, Ian M Morison
Production of the iron regulatory peptide hepcidin is tightly controlled by a network of proteins in hepatocytes that sense levels of iron in the circulation (as diferric-transferrin) and in tissues (in ferritin). Human studies show high variability in the normal range of serum hepcidin levels. We have postulated that this may, in part, be related to inter-individual variability in the expression of genes in the iron sensing pathway, potentially governed by epigenetic factors. Here, we have investigated whether genes encoding hepatic iron sensing proteins and hepcidin are regulated by DNA methylation...
2018: PloS One
Sadeesh K Ramakrishnan, Yatrik M Shah
Hepatic glucose production is regulated by hormonal and dietary factors. At fasting, 80% of glucose released into the circulation is derived from the liver, among which gluconeogenesis accounts for 55% and the rest by glycogenolysis. Studies suggest a complex mechanism involved in the regulation of hepatic glucose metabolism during fasting and post-absorptive phase. Oxygen plays a key role in numerous metabolic pathways such as TCA cycle, gluconeogenesis, glycolysis and fatty acid oxidation. Oxygenation of the gastrointestinal tract including liver and intestine is dynamically regulated by changes in the blood flow and metabolic activity...
December 7, 2017: Nutrition and Healthy Aging
Hiroshi Kawabata
Hereditary hemochromatosis (HH) is a group of genetic iron overload disorders that manifest with various symptoms, including hepatic dysfunction, diabetes, and cardiomyopathy. Classic HH type 1, which is common in Caucasians, is caused by bi-allelic mutations of HFE. Severe types of HH are caused by either bi-allelic mutations of HFE2 that encodes hemojuvelin (type 2A) or HAMP that encodes hepcidin (type 2B). HH type 3, which is of intermediate severity, is caused by bi-allelic mutations of TFR2 that encodes transferrin receptor 2...
January 2018: International Journal of Hematology
Julia Yue Cui, Curtis D Klaassen
The pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are well-known xenobiotic-sensing nuclear receptors with overlapping functions. However, there lacks a quantitative characterization to distinguish between the PXR and CAR target genes and signaling pathways in the liver. The present study performed a transcriptomic comparison of the PXR- and CAR-targets using RNA-Seq in livers of adult wild-type mice that were treated with the prototypical PXR ligand PCN (200mg/kg, i.p. once daily for 4days in corn oil) or the prototypical CAR ligand TCPOBOP (3mg/kg, i...
September 2016: Biochimica et Biophysica Acta
Wen Guo, Eric Bachman, Michelle Li, Cindy N Roy, Jerzy Blusztajn, Siu Wong, Stephen Y Chan, Carlo Serra, Ravi Jasuja, Thomas G Travison, Martina U Muckenthaler, Elizabeta Nemeth, Shalender Bhasin
Testosterone administration increases hemoglobin levels and has been used to treat anemia of chronic disease. Erythrocytosis is the most frequent adverse event associated with testosterone therapy of hypogonadal men, especially older men. However, the mechanisms by which testosterone increases hemoglobin remain unknown. Testosterone administration in male and female mice was associated with a greater increase in hemoglobin and hematocrit, reticulocyte count, reticulocyte hemoglobin concentration, and serum iron and transferrin saturation than placebo...
April 2013: Aging Cell
Emilio Ramos, Léon Kautz, Richard Rodriguez, Michael Hansen, Victoria Gabayan, Yelena Ginzburg, Marie-Paule Roth, Elizabeta Nemeth, Tomas Ganz
UNLABELLED: In response to iron loading, hepcidin synthesis is homeostatically increased to limit further absorption of dietary iron and its release from stores. Mutations in HFE, transferrin receptor 2 (Tfr2), hemojuvelin (HJV), or bone morphogenetic protein 6 (BMP6) prevent appropriate hepcidin response to iron, allowing increased absorption of dietary iron, and eventually iron overload. To understand the role each of these proteins plays in hepcidin regulation by iron, we analyzed hepcidin messenger RNA (mRNA) responsiveness to short and long-term iron challenge in iron-depleted Hfe, Tfr2, Hjv, and Bmp6 mutant mice...
April 2011: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
Mitchell D Knutson
The human body cannot actively excrete excess iron. As a consequence, iron absorption must be strictly regulated to ensure adequate iron uptake and prevent toxic iron accumulation. Iron absorption is controlled chiefly by hepcidin, the iron-regulatory hormone. Produced by the liver and secreted into the circulation, hepcidin regulates iron metabolism by inhibiting iron release from cells, including duodenal enterocytes, which mediate the absorption of dietary iron. Hepcidin production increases in response to iron loading and decreases in iron deficiency...
August 21, 2010: Annual Review of Nutrition
Jolanta Malyszko
Hemojuvelin (HJV) is a membrane protein that is responsible for the iron overload condition known as juvenile hemochromatosis. HJV, highly expressed in the liver, skeletal muscle and heart, seems to play a role in iron absorption and release from cells and has anti-inflammatory properties. HJV is a bone morphogenetic protein (BMP) co-receptor and signals via the SMAD (human homolog of Drosophila mad--mother against decapentaplegic) pathway to regulate hepcidin expression. HJV acts as a BMP co-receptor. Moreover, HJV plays an essential role in the regulation of hepcidin expression, specifically in the iron-sensing pathway, although through unknown mechanisms...
2009: Kidney & Blood Pressure Research
Hana Cho, Hyung Chul Lee, Sung Key Jang, Yoon Ki Kim
Although increased liver iron in individuals with chronic hepatitis C virus (HCV) is associated with a poor response to interferon therapy, the underlying molecular mechanisms are poorly understood. In this study, we show that iron enhances the translation initiation mediated by the internal ribosome entry site (IRES) of HCV. We also demonstrate by UV cross-linking analysis that specific cellular proteins bind to HCV 5' untranslated region (5' UTR) in an iron-dependent manner. Notably, p85 and p110 are competed out for their binding to HCV 5' UTR when excess amounts of iron-responsive element (IRE) competitor RNAs are treated...
October 2008: Virus Genes
Elmar Aigner, Igor Theurl, Milan Theurl, Dieter Lederer, Heike Haufe, Otto Dietze, Michael Strasser, Christian Datz, Guenter Weiss
BACKGROUND: Mild iron overload is frequently observed in nonalcoholic fatty liver disease (NAFLD). OBJECTIVE: We aimed to study putative pathways underlying iron accumulation in NAFLD. DESIGN: Hepatic and duodenal expression of critical iron molecules in NAFLD patients with (n = 32) and without (n = 29) iron overload, hereditary hemochromatosis (n = 10), and controls (n = 20) were investigated. Phlebotomy treatment was performed in 14 NAFLD patients...
May 2008: American Journal of Clinical Nutrition
Jonathan M Flanagan, HongFan Peng, Ernest Beutler
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...
January 2007: Alcoholism, Clinical and Experimental Research
Ferga Gleeson, Eleanor Ryan, Sharon Barrett, Jennifer Russell, John Crowe
BACKGROUND: Individuals with pathogenic mutations in HFE, hemojuvelin (HJV) and transferrin receptor 2 (TfR2) have low levels of hepcidin, but little is known about the hepatic expression of these molecules in patients with physiological iron overload or HFE associated Hemochromatosis (HH). AIMS: To examine the hepatic mRNA expression of iron homeostasis genes in patients with HH, physiological iron overload and healthy controls. PATIENTS: Untreated C282Y homozygous HH patients (n=20) with elevated serum ferritin (SF) and patients with physiological iron overload (n=12) with positive hepatocellular iron staining and negative HFE mutation analysis were evaluated...
January 2007: Blood Cells, Molecules & Diseases
Kimr Bridle, Ting-Kin Cheung, Theresel Murphy, Margaretm Walters, Gregoryj Anderson, Darrellh G Crawford, Linda M Fletcher
BACKGROUND: Alcoholic liver disease is known to be associated with abnormal iron homeostasis, and iron metabolism itself is regulated by the liver-derived peptide hepcidin. Both CCAAT enhancer binding protein alpha (C/EBPalpha) and interleukin 6 (IL-6) have been shown to regulate hepcidin gene transcription. AIM: To investigate mechanisms underlying alcohol-induced disturbances in iron homeostasis by measuring the expression of hepcidin and C/EBPalpha mRNA using in vivo and in vitro models of alcoholic liver injury...
January 2006: Alcoholism, Clinical and Experimental Research
Dan-Qing Lou, Jeanne-Claire Lesbordes, Gaël Nicolas, Lydie Viatte, Myriam Bennoun, Nico Van Rooijen, Axel Kahn, Laurent Renia, Sophie Vaulont
Hepcidin, a recently discovered iron regulatory peptide, is believed to inhibit the release of iron from absorptive enterocytes and macrophages. Liver hepcidin synthesis is induced in vivo by iron stores and inflammation. The molecular basis of the regulation of hepcidin gene expression by these effectors in hepatocytes is currently unknown, although there is strong evidence that indirect mechanisms are involved. The aims of this study were to gain insight into these mechanisms and to determine to what extent other liver cell types are responsible for transducing the signal by which hepcidin expression is regulated in mouse hepatocytes...
May 2005: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
Susanne Ludwiczek, Igor Theurl, Siamak Bahram, Klaus Schümann, Günter Weiss
Although the recent identification of several genes has extended our knowledge on the maintenance of body iron homeostasis, their tissue specific expression patterns and the underlying regulatory networks are poorly understood. We studied C57black/Sv129 mice and HFE knockout (HFE -/-) variants thereof as a model for hemochromatosis, and investigated the expression of iron metabolism genes in the duodenum, liver, and kidney as a function of dietary iron challenge. In HFE +/+ mice dietary iron supplementation increased hepatic expression of hepcidin which was paralleled by decreased iron regulatory protein (IRP) activity, and reduced expression of divalent metal transporter-1 (DMT-1) and duodenal cytochrome b (Dcytb) in the enterocyte...
August 2005: Journal of Cellular Physiology
An-Sheng Zhang, Shigang Xiong, Hidekazu Tsukamoto, Caroline A Enns
The mRNAs of proteins involved in iron metabolism were measured in isolated hepatocytes, Kupffer cells, sinusoidal endothelial cells (SECs), and hepatic stellate cells (HSCs). Levels of type I hereditary hemochromatosis gene (HFE), transferrin, hepcidin, transferrin receptors 1 and 2 (TfR1, TfR2), ferroportin 1 (FPN1), divalent metal transporter 1 (DMT1), natural resistance-associated macrophage protein 1 (Nramp1), ceruloplasmin, hephaestin, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), were measured by quantitative reverse-transriptase polyerase chain reaction (qRT-PCR)...
February 15, 2004: Blood
Françoise Dupic, Séverine Fruchon, Mounia Bensaid, Nicolas Borot, Mirjana Radosavljevic, Olivier Loreal, Pierre Brissot, Susan Gilfillan, Siamak Bahram, Hélène Coppin, Marie-Paule Roth
BACKGROUND & AIMS: Hfe knockout mice, like patients with hereditary hemochromatosis, have augmented duodenal iron absorption and increased iron deposition in hepatic parenchymal cells. The goals of the present study were to gain further insight into the control of iron absorption by comparing the transcript levels of iron-related genes in the duodenum of DBA/2 Hfe-/- mice, susceptible to iron loading, and wild-type controls, and to test whether variations in the duodenal expression of these messengers contribute to the DBA/2 and C57BL/6 strain differences in the severity of hepatic iron loading...
March 2002: Gastroenterology
H F Bunn, J Gu, L E Huang, J W Park, H Zhu
The physiological regulation of the red cell mass depends upon enhanced transcription of the erythropoietin (Epo) gene in response to hypoxia. Studies of Epo gene expression have been useful in investigating the mechanism by which cells and tissues sense hypoxia and respond with biologically appropriate alterations in gene expression. It is likely that oxygen sensing involves a heme protein in which cobalt and nickel can substitute for iron in the porphyrin ring. Indirect evidence suggests that the sensor is present in all cells and is a multi-subunit assembly containing an NAD(P)H oxidase capable of generating peroxide and reactive oxygen intermediates, which serve as signaling molecules...
April 1998: Journal of Experimental Biology
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