We carried out a genome-wide association study of hemoglobin levels in 16,001 individuals of European and Indian Asian ancestry. The most closely associated SNP (rs855791) results in nonsynonymous (V736A) change in the serine protease domain of TMPRSS6 and a blood hemoglobin concentration 0.13 (95% CI 0.09–0.17) g/dl lower per copy of allele A (P = 1.6 × 10−13). Our findings suggest that TMPRSS6, a regulator of hepcidin synthesis and iron handling, is crucial in hemoglobin level maintenance.

Resveratrol has been widely investigated for its potential health properties, although little is known about its metabolism in vivo. Here we investigated the distribution of metabolic products of [ 3 H]trans-resveratrol, following gastric administration. At 2 h, plasma concentrations reached 1·7 % of the administered dose, whilst liver and kidney concentrations achieved 1·0 and 0·6 %, respectively. Concentrations detected at 18 h were lower, being only 0·5 % in plasma and a total of 0·35 % in tissues. Furthermore, whilst kidney and liver concentrations fell to 10 and 25 %, respectively, of concentrations at 2 h, the brain retained 43 % of that measured at 2 h. Resveratrol-glucuronide was identified as the major metabolite, reaching 7 mM in plasma at 2 h. However, at 18 h the main form identified in liver, heart, lung and brain was native resveratrol aglycone, indicating that it is the main form retained in the tissues. No phenolic degradation products were detected in urine or tissues, indicating that, unlike flavonoids, resveratrol does not appear to serve as a substrate for colonic microflora. The present study provides additional information about the nature of resveratrol metabolites and which forms might be responsible for its in vivo biological effects.

The Ity/Lsh/Bcg locus encodes the macrophage protein Slc11a1/Nramp1, which protects inbred mice against infection by diverse intracellular pathogens including Leishmania, Mycobacterium, and Salmonella. Human susceptibility to infectious and inflammatory diseases, including rheumatoid arthritis, inflammatory bowel disease, and tuberculosis, shows allelic association with a highly polymorphic regulatory, Z-DNA-forming microsatellite of (GT/AC) n dinucleotides within the proximal SLC11A1 promoter. We surmised that cis-acting allelic polymorphisms may underlie heritable differences in SLC11A1 expression and phenotypic variation in disease risk. However, it is unclear what may underlie such variation in SLC11A1 allele expression. Here we show that hypoxia-inducible Factor 1 (HIF-1) regulates allelic variation in SLC11A1 expression by binding directly to the microsatellite during macrophage activation by infection or inflammation. Targeted Hif-1␣ ablation in murine macrophages attenuated Slc11a11 expression and responsiveness to S typhimurium infection. Our data also showed that HIF-1 may be functionally linked to complex prototypical inflammatory diseases associated with certain SLC11A1 alleles. As these alleles are highly polymorphic, our finding suggests that HIF-1 may influence heritable variation in SLC11A1-dependent innate resistance to infection and inflammation within and between populations. This report also suggests that microsatellites may play critical roles in the directional evolution of complex heritable traits by regulating gene expression phenotypes. IntroductionA genetic basis for resistance to infection by intracellular pathogens was proposed several years ago. [1][2][3][4][5][6] This concept was confirmed upon the positional cloning of the dominant autosomal gene Ity/Lsh/Bcg based on its ability to confer on inbred mice an innate resistance to infection by diverse intracellular pathogens. 7 These include Salmonella typhimurium, 2 Leishmania donovani, 3 and some species of Mycobacterium such as M bovis 5 and M intracellulare. 8 Targeted ablation of Ity/Lsh/ Bcg 9 or allelic exchange in susceptible mice 10 confirmed its requirement for resistance to infection. Ity/Lsh/Bcg encodes the phagocyte-specific solute carrier 11a1 protein Slc11a1 (formerly Nramp1), 11-13 which restricts pathogen replication by inducing the expression of major histocompatibility complex (MHC) class II molecules, cytokines (eg, TNF␣), and chemokines. 14 SLC11A1/Slc11a1 belongs to a family of polytopic membrane proteins whose functions include divalent cation acquisition in mammals (DCT1/DMT1/NRAMP2), 15 taste perception in the fruit fly (malvolio), 16 and stress signal transduction in plants (EIN2). 17 In mice, a single nonsynonymous mutation in Slc11a1 codon 169 determines resistance (Gly169) or susceptibility (Asp169) to intracellular bacterial and leishmanial infections. 7 Compared with susceptible mice, macrophages from mice that are resistant to infection also show increased oxidative burst and expression of the MHC class...

Hepcidin is the presumed negative regulator of systemic iron levels; its expression is induced in iron overload, infection, and inflammation, and by cytokines, but is suppressed in hypoxia and anemia. Although the gene is exquisitely sensitive to changes in iron status in vivo, its mRNA is devoid of prototypical ironresponse elements, and it is therefore not obvious how it may be regulated by iron flux. The multiplicity of effectors of its expression also suggests that the transcriptional circuitry controlling the gene may be very complex indeed. In delineating enhancer elements within both the human and mouse hepcidin gene promoters, we show here that members of the basic helix-loop-helix leucine zipper (bHLH-ZIP) family of transcriptional regulators control hepcidin expression. The upstream stimulatory factor 2 (USF2), previously linked to hepcidin through gene ablation in inbred mice, appears to exert a polar or cis-acting effect, while USF1 may act in trans to control hepcidin expression. In mice, we found variation in expression of both hepcidin genes, driven by these transcription factors. In addition, c-Myc and Max synergize to control the expression of this hormone, supporting previous findings for the role of this couple in regulating iron metabolism. Transcriptional activation by both USF1/ USF2 and c-Myc/Max heterodimers occurs through E-boxes within the promoter. Site-directed mutagenesis of these elements rendered the promoter unresponsive to USF1/USF2 or c-Myc/Max. Dominant-negative mutants of USF1 and USF2 reciprocally attenuated promoter transactivation by both wild-type USF1 and USF2. Promoter occupancy by the transcription factors was confirmed by DNA-binding and chromatin immunoprecipitation assays. Taken IntroductionHepcidin is a small liver-derived acute-phase cationic peptide that is induced by iron overload, infection, and proinflammatory cytokines; on the other hand, its expression is attenuated in hypoxia and anemia. [1][2][3][4][5][6][7][8][9] The relationship between this peptide hormone and iron is analogous to the link between blood glucose levels and insulin in that iron overload is accompanied by increased hepcidin expression by the liver, while the converse is true in iron deficiency. Initially isolated from urine and by subtraction cloning of its mRNA, 1-3 this peptide has evolved as the primary regulator of iron homeostasis and a probable mediator of the anemia of chronic disease or inflammation. This role has been amply proven in a number of recent reports either by direct or indirect approaches. For example, in a study to define the role of upstream stimulatory factor 2 (USF2) in energy/glucose metabolism in mice, 10,11 hepcidin was also surprisingly identified in association with an iron overload phenotype similar to hemochromatosis, as these mice produced diminished levels of hepcidin. 12 On the other hand, transgenic mice that constitutively expressed hepcidin were severely anemic, thereby suggesting a role for this peptide in preventing iron overload. 13,14 A frame-shift ...

Hephaestin was implicated in mammalian iron homeostasis following its identification as the defective gene in murine sex-linked anaemia. It is a member of the family of copper oxidases that includes mammalian ceruloplasmin, factors V and VIII, yeast fet3 and fet5 and bacterial ascorbate oxidase. Hephaestin is different from ceruloplasmin, a soluble ferroxidase, in having a membrane-spanning region towards the C-terminus. Here we report the gene structure, spanning approximately 100 kb, of the human homologue of mouse hephaestin. The sequence was assembled from the cDNA clones and the chromosome X genomic sequence data available at the Sanger Centre. It has an open reading frame that encodes a protein of 1158 residues, 85% identical with the murine homologue. A model of the N-terminal ecto-domain has been built based on the known three-dimensional structure of human ceruloplasmin. The overall tertiary structure for the hephaestin and the putative residues involved in binding copper and iron appear to be highly conserved between these proteins, which suggests they share the same fold and a conserved function.

TNFa has dramatic effects on iron metabolism contributing to the generation of hypoferraemia in the anaemia of chronic disease. Interestingly, TNFa is also synthesised and released within the intestinal mucosa, suggesting that this proinflammatory cytokine may play a role in regulating dietary iron absorption. To investigate this possibility, we stimulated intestinal Caco-2 cells with TNFa (10 ng/ml). In TNFa-treated cells, apical iron uptake was significantly decreased and this was accompanied by a reduction in divalent metal transporter protein and mRNA expression. Our data suggest that TNFa could regulate dietary iron absorption and that the apical transport machinery is the target for these actions.

Edited by Stuart FergusonKeywords: Zinc Iron Hepcidin MRE-binding transcription factor-1 Metal response element a b s t r a c t Hepcidin is a small acute phase peptide that regulates iron absorption. It is induced by inflammation and infection, but is repressed by anaemia and hypoxia. Here we further reveal that hepcidin transcription also involves interactions between functional metal response elements (MREs) in its promoter, and the MRE-binding transcription factor-1. Analysis of hepcidin mRNA and protein levels in hepatoma cells suggests that its expression may be regulated by divalent metal ions, with zinc inducing maximal effects on hepcidin levels. These data suggest that this peptide may be a pleiotropic sensor of divalent metals, some of which are xenobiotic environmental toxins.

BackgroundIron metabolism during pregnancy maintains fetal iron levels at the expense of the mother. The mechanism behind this regulation is still not clear despite recent advances. Here we examine the role of maternal and fetal Hfe, its downstream signaling molecule, hepcidin and dietary iron in the regulation of placental iron transfer. Design and MethodsHfe wild-type, knockout and heterozygote dams were fed iron deficient (12.5 ppm), adequate (50 ppm) and replete (150 ppm) iron diets and mated with heterozygote males to produce pups of all genotypes. Dams and pups were sacrificed at Day 18 of gestation; serum, placenta, body and liver iron parameters were measured. Protein and mRNA levels of various iron transporter genes were determined in duodenum, liver and placenta by Western blotting and real time PCR. ResultsMaternal liver iron levels were dependent on both dietary iron intake and Hfe genotype. Increasing iron levels in the maternal diet resulted in increased total iron in the fetus, primarily in the liver. However, fetuses of Hfe-knockout mothers showed further elevation of liver iron levels, concomitant with elevated expression of Tfr1, Dmt1 and Fpn in the placenta. Hfe-knockout fetuses that express low levels of liver hepcidin accumulated more iron in their liver than wild-type fetuses due to increased ferroportin levels in the placenta. ConclusionsMaternal and fetal status, as well as dietary iron, is important in regulating iron transfer across placenta. Maternal Hfe regulates iron transfer by altering gene expression in the placenta. Fetal Hfe is important in regulating placental iron transfer by modulating fetal liver hepcidin expression.