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Arita A, Kita I, Shinoda S. Internalization and Decrease of Duodenal DMT1 Involved in Transient Suppression of Iron Uptake in Short-Acting Mucosal Block. Biol Trace Elem Res 2022; 200:4795-4806. [PMID: 34997531 DOI: 10.1007/s12011-021-03053-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 11/27/2021] [Indexed: 12/30/2022]
Abstract
Mucosal block (MB) is induced by the oral administration of excess iron (10 mg) and suppresses intestinal iron absorption for 3-72 h. The inhibition of iron absorption is accompanied by the downregulation of molecules associated with intestinal iron absorption. Recently, we found that a smaller amount of iron (1 mg) also induced a transient suppression of iron uptake without affecting gene expression levels (short-acting mucosal block, SAMB), which is specific to iron-deficient rats. In this study, we investigated how the nonheme iron transporters divalent metal transporter 1 (DMT1) and ferroportin (FPN) are involved in the transient suppression of iron uptake in SAMB. To induce SAMB, a test solution containing 1 mg iron was infused into the duodenum loop in iron-sufficient and iron-deficient rats. Total duodenal DMT1 and DMT1-IRE expression were increased during iron deficiency. After 15 min of 1 mg iron loading, the fluorescence intensity of duodenal DMT1 in iron-deficient rats was decreased and was comparable to that in iron-sufficient rats. Internalized DMT1-IRE as puncta was observed at 15 and 60 min after 1 mg iron loading, and the number of punctas was significantly increased after 60 min compared with control. There was no effect of 1 mg iron loading on the intracellular distribution of duodenal FPN. Our results suggest that the decrease and internalization of DMT1-IRE protein may be related, at least in part, to iron uptake suppression in SAMB.
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Affiliation(s)
- Anna Arita
- Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan.
- Institute of Food, Nutrition, and Health, Jumonji University, Niiza, Saitama, Japan.
| | - Ichiro Kita
- Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Shoko Shinoda
- Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
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2
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Khan AZ, Badar S, O'Callaghan KM, Zlotkin S, Roth DE. Fecal Iron Measurement in Studies of the Human Intestinal Microbiome. Curr Dev Nutr 2022; 6:nzac143. [PMID: 36475017 PMCID: PMC9718653 DOI: 10.1093/cdn/nzac143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/09/2022] [Accepted: 09/09/2022] [Indexed: 04/22/2024] Open
Abstract
Iron is an essential micronutrient for humans and their intestinal microbiota. Host intestinal cells and iron-dependent bacteria compete for intraluminal iron, so the composition and functions of the gut microbiota may influence iron availability. Studies of the effects of the microbiota or probiotic interventions on host iron absorption may be particularly relevant to settings with high burdens of iron deficiency and gastrointestinal infections, since inflammation reduces iron bioavailability and unabsorbed intraluminal iron may modify the composition of the microbiota. The quantification of stool iron content may serve as an indicator of the amount of intraluminal iron to which the intestinal microbiota is exposed, which is particularly relevant for studies of the effect of iron on the intestinal microbiome, where fecal samples collected for purposes of microbiome characterization can be leveraged for stool iron analysis. However, few studies are available to guide researchers in the selection and implementation of stool iron assays, particularly because cross-comparison of available methods is limited in literature. This review aims to describe the available stool iron quantification methods and highlight their potential application in studies of iron-microbiome relationships, with a focus on pediatric research. MS-based methods offer high sensitivity and precision, but the need for expensive equipment and the high per-sample and maintenance costs may limit their widespread use. Conversely, colorimetric assays offer lower cost, ease of use, and rapid turnaround times but have thus far been optimized primarily for blood-derived matrices rather than stool. Further research efforts are needed to validate and standardize methods for stool iron assessment and to determine if the incorporation of such analyses in human microbiome studies 1) yields insights into the interactions between intestinal microbiota and iron and 2) contributes to the development of interventions that mitigate iron deficiency and promote a healthy microbiome.
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Affiliation(s)
- Afreen Z Khan
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Canada
- Centre for Global Child Health and SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada
| | - Sayema Badar
- Centre for Global Child Health and SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada
- Faculty of Health Sciences, Simon Fraser University, Burnaby, Canada
| | - Karen M O'Callaghan
- Centre for Global Child Health and SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada
| | - Stanley Zlotkin
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Canada
- Centre for Global Child Health and SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada
- Department of Paediatrics, The Hospital for Sick Children and University of Toronto, Toronto, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
| | - Daniel E Roth
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Canada
- Centre for Global Child Health and SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada
- Department of Paediatrics, The Hospital for Sick Children and University of Toronto, Toronto, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
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3
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Four AAs increase DMT1 abundance in duodenal brush-border membrane vesicles and enhance iron absorption in iron-deprived mice. Blood Adv 2022; 6:3011-3021. [PMID: 35061889 PMCID: PMC9131898 DOI: 10.1182/bloodadvances.2021005111] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 01/09/2022] [Indexed: 11/20/2022] Open
Abstract
Oral iron supplementation is usually recommended to treat iron-deficiency anemia; however, excess enteral iron has negative side effects. We identified 4 AAs that stimulate intestinal iron absorption and may potentiate iron repletion at lower effective supplemental doses.
Iron-deficiency anemia is common worldwide and typically treated by oral iron supplementation. Excess enteral iron, however, may cause pathological outcomes. Developing new repletion approaches is thus warranted. Previous experimentation revealed that select amino acids (AAs) induce trafficking of transporters onto the enterocyte brush-border membrane (BBM) and enhance electrolyte absorption/secretion. Here, we hypothesized that certain AAs would increase the abundance of the main intestinal iron importer, divalent metal-ion transporter 1 (DMT1), on the BBM of duodenal enterocytes, thus stimulating iron absorption. Accordingly, all 20 AAs were screened using an ex vivo duodenal loop/DMT1 western blotting approach. Four AAs (Asp, Gln, Glu, and Gly) were selected for further experimentation and combined into a new formulation. The 4 AAs stimulated 59Fe transport in mouse duodenal epithelial sheets in Ussing chambers (∼4-fold; P < .05). In iron-deprived mice, oral intragastric administration of the 4 AA formulation increased DMT1 protein abundance on the enterocyte BBM by ∼1.5-fold (P < .05). The 4 AAs also enhanced in vivo 59Fe absorption by ∼2-fold (P < .05), even when ∼26 µg of cold iron was included in the transport solution (equal to a human dose of ∼73 mg). Further experimentation using DMT1int/int mice showed that intestinal DMT1 was required for induction of iron transport by the 4 AAs. Select AAs thus enhance iron absorption by inducing DMT1 trafficking onto the apical membrane of duodenal enterocytes. We speculate that further refinement of this new 4 AA formulation will ultimately allow iron repletion at lower effective doses (thus mitigating negative side effects of excess enteral iron).
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Wang X, Zhang M, Woloshun RR, Yu Y, Lee JK, Flores SRL, Merlin D, Collins JF. Oral Administration of Ginger-Derived Lipid Nanoparticles and Dmt1 siRNA Potentiates the Effect of Dietary Iron Restriction and Mitigates Pre-Existing Iron Overload in Hamp KO Mice. Nutrients 2021; 13:1686. [PMID: 34063414 PMCID: PMC8157040 DOI: 10.3390/nu13051686] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 12/28/2022] Open
Abstract
Intestinal iron transport requires an iron importer (Dmt1) and an iron exporter (Fpn1). The hormone hepcidin regulates iron absorption by modulating Fpn1 protein levels on the basolateral surface of duodenal enterocytes. In the genetic, iron-loading disorder hereditary hemochromatosis (HH), hepcidin production is low and Fpn1 protein expression is elevated. High Fpn1-mediated iron export depletes intracellular iron, causing a paradoxical increase in Dmt1-mediated iron import. Increased activity of both transporters causes excessive iron absorption, thus initiating body iron loading. Logically then, silencing of intestinal Dmt1 or Fpn1 could be an effective therapeutic intervention in HH. It was previously established that Dmt1 knock down prevented iron-loading in weanling Hamp (encoding hepcidin) KO mice (modeling type 2B HH). Here, we tested the hypothesis that Dmt1 silencing combined with dietary iron restriction (which may be recommended for HH patients) will mitigate iron loading once already established. Accordingly, adult Hamp KO mice were switched to a low-iron (LFe) diet and (non-toxic) folic acid-coupled, ginger nanoparticle-derived lipid vectors (FA-GDLVs) were used to deliver negative-control (NC) or Dmt1 siRNA by oral, intragastric gavage daily for 21 days. The LFe diet reduced body iron burden, and experimental interventions potentiated iron losses. For example, Dmt1 siRNA treatment suppressed duodenal Dmt1 mRNA expression (by ~50%) and reduced serum and liver non-heme iron levels (by ~60% and >85%, respectively). Interestingly, some iron-related parameters were repressed similarly by FA-GDLVs carrying either siRNA, including 59Fe (as FeCl3) absorption (~20% lower), pancreatic non-heme iron (reduced by ~65%), and serum ferritin (decreased 40-50%). Ginger may thus contain bioactive lipids that also influence iron homeostasis. In conclusion, the combinatorial approach of FA-GDLV and Dmt1 siRNA treatment, with dietary iron restriction, mitigated pre-existing iron overload in a murine model of HH.
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Affiliation(s)
- Xiaoyu Wang
- Key Laboratory of Precision Nutrition and Food Quality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China;
- Food Science & Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA; (R.R.W.); (Y.Y.); (J.K.L.); (S.R.L.F.)
| | - Mingzhen Zhang
- Center for Diagnostics and Therapeutics, Institute for Biomedical Science, Georgia State University, Atlanta, GA 30303, USA; (M.Z.); (D.M.)
- School of Basic Medical Science, Health Science Center, Institute of Medical Engineering, Xi’an Jiaotong University, Xi’an 710049, China
| | - Regina R. Woloshun
- Food Science & Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA; (R.R.W.); (Y.Y.); (J.K.L.); (S.R.L.F.)
| | - Yang Yu
- Food Science & Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA; (R.R.W.); (Y.Y.); (J.K.L.); (S.R.L.F.)
| | - Jennifer K. Lee
- Food Science & Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA; (R.R.W.); (Y.Y.); (J.K.L.); (S.R.L.F.)
| | - Shireen R. L. Flores
- Food Science & Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA; (R.R.W.); (Y.Y.); (J.K.L.); (S.R.L.F.)
| | - Didier Merlin
- Center for Diagnostics and Therapeutics, Institute for Biomedical Science, Georgia State University, Atlanta, GA 30303, USA; (M.Z.); (D.M.)
- Atlanta Veterans Affairs Medical Center, Decatur, GA 30033, USA
| | - James F. Collins
- Food Science & Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA; (R.R.W.); (Y.Y.); (J.K.L.); (S.R.L.F.)
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Koiwa F, Yokoyama K, Fukagawa M, Akizawa T. Evaluation of changes in ferritin levels during sucroferric oxyhydroxide treatment. Clin Kidney J 2018; 12:294-299. [PMID: 30976411 PMCID: PMC6452212 DOI: 10.1093/ckj/sfy077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Indexed: 11/13/2022] Open
Abstract
Background A sub-analysis of a Phase III study was conducted to identify factors that might predict increased ferritin levels during long-term sucroferric oxyhydroxide (SO) treatment in hemodialysis patients. Methods The open-label, multicenter, Phase III study assessed the efficacy and safety of SO 750–3000 mg/day for 52 weeks in Japanese patients with chronic renal failure and hyperphosphatemia. A total of 125 of 161 patients from the Phase III trial, and who had data for ferritin levels after 28 weeks of SO treatment, were evaluated. Results Baseline ferritin was the strongest contributor (P < 0.0001) to ferritin increases during SO treatment. By Week 28, there were significant differences (P < 0.05/3) in ferritin increases between patients with higher [quartile 4 (Q4)] versus lower (Q1, Q2 and Q3) baseline ferritin. An erythropoiesis-stimulating agent dosage reduction was observed in patients with the lowest baseline ferritin level (Q1), and only slight reductions were noted in the other patient subsets. SO dosages administered to patients in baseline ferritin quartiles Q2, Q3 and Q4 were comparable throughout the study with slight fluctuations. SO dosages in Q1 were considerably lower than those in the other quartiles. Conclusions In summary, of the baseline variables found to predict increased ferritin, and changes in iron-related parameters, during SO treatment in Japanese chronic kidney disease patients undergoing hemodialysis, baseline ferritin was the most relevant variable.
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Affiliation(s)
- Fumihiko Koiwa
- Division of Nephrology, Department of Internal Medicine, Showa University Fujigaoka Hospital, Yokohama, Japan
| | - Keitaro Yokoyama
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Masafumi Fukagawa
- Division of Nephrology, Endocrinology and Metabolism, Department of Internal Medicine, Tokai University School of Medicine, Isehara, Japan
| | - Tadao Akizawa
- Division of Nephrology, Department of Medicine, Showa University School of Medicine, Tokyo, Japan
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6
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Doguer C, Ha JH, Collins JF. Intersection of Iron and Copper Metabolism in the Mammalian Intestine and Liver. Compr Physiol 2018; 8:1433-1461. [PMID: 30215866 DOI: 10.1002/cphy.c170045] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Iron and copper have similar physiochemical properties; thus, physiologically relevant interactions seem likely. Indeed, points of intersection between these two essential trace minerals have been recognized for many decades, but mechanistic details have been lacking. Investigations in recent years have revealed that copper may positively influence iron homeostasis, and also that iron may antagonize copper metabolism. For example, when body iron stores are low, copper is apparently redistributed to tissues important for regulating iron balance, including enterocytes of upper small bowel, the liver, and blood. Copper in enterocytes may positively influence iron transport, and hepatic copper may enhance biosynthesis of a circulating ferroxidase, ceruloplasmin, which potentiates iron release from stores. Moreover, many intestinal genes related to iron absorption are transactivated by a hypoxia-inducible transcription factor, hypoxia-inducible factor-2α (HIF2α), during iron deficiency. Interestingly, copper influences the DNA-binding activity of the HIF factors, thus further exemplifying how copper may modulate intestinal iron homeostasis. Copper may also alter the activity of the iron-regulatory hormone hepcidin. Furthermore, copper depletion has been noted in iron-loading disorders, such as hereditary hemochromatosis. Copper depletion may also be caused by high-dose iron supplementation, raising concerns particularly in pregnancy when iron supplementation is widely recommended. This review will cover the basic physiology of intestinal iron and copper absorption as well as the metabolism of these minerals in the liver. Also considered in detail will be current experimental work in this field, with a focus on molecular aspects of intestinal and hepatic iron-copper interplay and how this relates to various disease states. © 2018 American Physiological Society. Compr Physiol 8:1433-1461, 2018.
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Affiliation(s)
- Caglar Doguer
- Food Science and Human Nutrition Department, University of Florida, Florida, Gainesville, USA.,Nutrition and Dietetics Department, Namık Kemal University, Tekirdag, Turkey
| | - Jung-Heun Ha
- Food Science and Human Nutrition Department, University of Florida, Florida, Gainesville, USA.,Department of Food and Nutrition, Chosun University Note: Caglar Doguer and Jung-Heun Ha have contributed equally to this work., Gwangju, Korea
| | - James F Collins
- Food Science and Human Nutrition Department, University of Florida, Florida, Gainesville, USA
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Ballesteros C, Geary JF, Mackenzie CD, Geary TG. Characterization of Divalent Metal Transporter 1 (DMT1) in Brugia malayi suggests an intestinal-associated pathway for iron absorption. Int J Parasitol Drugs Drug Resist 2018; 8:341-349. [PMID: 29957332 PMCID: PMC6038845 DOI: 10.1016/j.ijpddr.2018.06.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 06/06/2018] [Accepted: 06/08/2018] [Indexed: 01/12/2023]
Abstract
Lymphatic filariasis and onchocerciasis are neglected parasitic diseases which pose a threat to public health in tropical and sub-tropical regions. Strategies for control and elimination of these diseases by mass drug administration (MDA) campaigns are designed to reduce symptoms of onchocerciasis and transmission of both parasites to eventually eliminate the burden on public health. Drugs used for MDA are predominantly microfilaricidal, and prolonged rounds of treatment are required for eradication. Understanding parasite biology is crucial to unravelling the complex processes involved in host-parasite interactions, disease transmission, parasite immune evasion, and the emergence of drug resistance. In nematode biology, large gaps still exist in our understanding of iron metabolism, iron-dependent processes and their regulation. The acquisition of iron from the host is a crucial determinant of the success of a parasitic infection. Here we identify a filarial ortholog of Divalent Metal Transporter 1 (DMT1), a member of a highly conserved family of NRAMP proteins that play an essential role in the transport of ferrous iron in many species. We cloned and expressed the B. malayi NRAMP ortholog in the iron-deficient fet3fet4 strain of Saccharomyces cerevisiae, performed qPCR to estimate stage-specific expression, and localized expression of this gene by immunohistochemistry. Results from functional iron uptake assays showed that expression of this gene in the iron transport-deficient yeast strain significantly rescued growth in low-iron medium. DMT1 was highly expressed in adult female and male B. malayi and Onchocerca volvulus. Immunolocalization revealed that DMT1 is expressed in the intestinal brush border, lateral chords, and reproductive tissues of males and females, areas also inhabited by Wolbachia. We hypothesize based on our results that DMT1 in B. malayi functions as an iron transporter. The presence of this transporter in the intestine supports the hypothesis that iron acquisition by adult females requires oral ingestion and suggests that the intestine plays a functional role in at least some aspects of nutrient uptake.
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Affiliation(s)
- Cristina Ballesteros
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, Quebec, H9X 3V9, Canada
| | - James F Geary
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Charles D Mackenzie
- Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - Timothy G Geary
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, Quebec, H9X 3V9, Canada.
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Xie L, Zhang L, Wang C, Wang X, Xu YM, Yu H, Wu P, Li S, Han L, Gunatilaka AAL, Wei X, Lin M, Molnár I, Xu Y. Methylglucosylation of aromatic amino and phenolic moieties of drug-like biosynthons by combinatorial biosynthesis. Proc Natl Acad Sci U S A 2018; 115:E4980-E4989. [PMID: 29760061 PMCID: PMC5984488 DOI: 10.1073/pnas.1716046115] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Glycosylation is a prominent strategy to optimize the pharmacokinetic and pharmacodynamic properties of drug-like small-molecule scaffolds by modulating their solubility, stability, bioavailability, and bioactivity. Glycosyltransferases applicable for "sugarcoating" various small-molecule acceptors have been isolated and characterized from plants and bacteria, but remained cryptic from filamentous fungi until recently, despite the frequent use of some fungi for whole-cell biocatalytic glycosylations. Here, we use bioinformatic and genomic tools combined with heterologous expression to identify a glycosyltransferase-methyltransferase (GT-MT) gene pair that encodes a methylglucosylation functional module in the ascomycetous fungus Beauveria bassiana The GT is the founding member of a family nonorthologous to characterized fungal enzymes. Using combinatorial biosynthetic and biocatalytic platforms, we reveal that this GT is a promiscuous enzyme that efficiently modifies a broad range of drug-like substrates, including polyketides, anthraquinones, flavonoids, and naphthalenes. It yields both O- and N-glucosides with remarkable regio- and stereospecificity, a spectrum not demonstrated for other characterized fungal enzymes. These glucosides are faithfully processed by the dedicated MT to afford 4-O-methylglucosides. The resulting "unnatural products" show increased solubility, while representative polyketide methylglucosides also display increased stability against glycoside hydrolysis. Upon methylglucosidation, specific polyketides were found to attain cancer cell line-specific antiproliferative or matrix attachment inhibitory activities. These findings will guide genome mining for fungal GTs with novel substrate and product specificities, and empower the efficient combinatorial biosynthesis of a broad range of natural and unnatural glycosides in total biosynthetic or biocatalytic formats.
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Affiliation(s)
- Linan Xie
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China
| | - Liwen Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China
| | - Chen Wang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China
- Natural Products Center, University of Arizona, Tucson, AZ 85706
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, People's Republic of China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, People's Republic of China
| | - Xiaojing Wang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China
- Natural Products Center, University of Arizona, Tucson, AZ 85706
| | - Ya-Ming Xu
- Natural Products Center, University of Arizona, Tucson, AZ 85706
| | - Hefen Yu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Capital Medical University, 100069 Beijing, People's Republic of China
| | - Ping Wu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, People's Republic of China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, People's Republic of China
| | - Shenglan Li
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Capital Medical University, 100069 Beijing, People's Republic of China
| | - Lida Han
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China
| | | | - Xiaoyi Wei
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, People's Republic of China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, People's Republic of China
| | - Min Lin
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China;
| | - István Molnár
- Natural Products Center, University of Arizona, Tucson, AZ 85706;
| | - Yuquan Xu
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081 Beijing, People's Republic of China;
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Zhang LY, Liao XD, Zhang LY, Lu L, Luo XG. Kinetics of iron absorption by in situ ligated small intestinal loops of broilers involved in iron transporters. J Anim Sci 2017; 94:5219-5229. [PMID: 28046154 DOI: 10.2527/jas.2016-0713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Two experiments were conducted with 28-d-old commercial male broilers to study the kinetics of iron (Fe) absorption and the effect of Fe treatment on divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) mRNA levels in in situ ligated segments from different small intestinal regions of broilers. In Exp. 1, we compared Fe absorption in 3 small intestinal segments at different post-perfusion time points after perfusion with 0.45 m of Fe as Fe sulfate (FeSO ∙ 7HO), and found that the Fe absorption in the duodenum at 30, 45, and 60 min was greater ( < 0.006) than that in the jejunum, and at 60 min, the Fe absorption in the duodenum was greater ( = 0.034) than that in the ileum. In addition, the Fe absorption at 30 min was more than 85.0% of the maximum absorption in each segment. In Exp. 2, a kinetic study of Fe absorption was performed with the duodenal, jejunal, and ileal loops perfused with solutions containing 0 (control), 0.11, 0.22, 0.45, 0.80, 1.79, or 3.58 m of Fe as FeSO 7HO. The Fe concentrations in perfusates were measured at 30 min after perfusion, and in the control group and the group treated with 0.45 m Fe as FeSO 7HO, the DMT1 and FPN1 mRNA levels in the ligated duodenum, jejunum, and ileum were analyzed. The kinetic curves of Fe absorption showed that Fe absorption in the duodenum and jejunum depended on a saturated carrier-mediated process. The maximum absorption rate in the duodenal segment was greater ( < 0.0001) than that in the jejunum (42.75 vs. 8.16 nmol × cm × min), and the Michaelis-Menten constant value was higher ( < 0.0001) in the duodenum than in the jejunum (6.16 vs. 1.31 m). In the ileum, however, the Fe absorption was a non-saturated diffusion process, and the diffusive constant was 3.54 × 10 cm × min. The DMT1 and FPN1 mRNA levels in the duodenum were greater ( < 0.0001) than those in the jejunum and ileum, and greater ( < 0.009) in the jejunum than in the ileum. No differences ( > 0.25) were detected in the DMT1 and FPN1 mRNA levels of the duodenum or jejunum and the DMT1 mRNA level of the ileum between the control and the 0.45 m Fe group, but Fe perfusion increased ( < 0.03) FPN1 mRNA level in the ileum. The above results indicate that the duodenum is the main site of Fe absorption in the small intestine of broilers, and Fe absorption in the duodenum and jejunum is a saturated carrier-mediated process, but a non-saturated diffusion process in the ileum.
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10
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Tan GZH, Das Bhowmik SS, Hoang TML, Karbaschi MR, Johnson AAT, Williams B, Mundree SG. Finger on the Pulse: Pumping Iron into Chickpea. FRONTIERS IN PLANT SCIENCE 2017; 8:1755. [PMID: 29081785 PMCID: PMC5646179 DOI: 10.3389/fpls.2017.01755] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 09/25/2017] [Indexed: 05/21/2023]
Abstract
Iron deficiency is a major problem in both developing and developed countries, and much of this can be attributed to insufficient dietary intake. Over the past decades several measures, such as supplementation and food fortification, have helped to alleviate this problem. However, their associated costs limit their accessibility and effectiveness, particularly amongst the financially constrained. A more affordable and sustainable option that can be implemented alongside existing measures is biofortification. To date, much work has been invested into staples like cereals and root crops-this has culminated in the successful generation of high iron-accumulating lines in rice and pearl millet. More recently, pulses have gained attention as targets for biofortification. Being secondary staples rich in protein, they are a nutritional complement to the traditional starchy staples. Despite the relative youth of this interest, considerable advances have already been made concerning the biofortification of pulses. Several studies have been conducted in bean, chickpea, lentil, and pea to assess existing germplasm for high iron-accumulating traits. However, little is known about the molecular workings behind these traits, particularly in a leguminous context, and biofortification via genetic modification (GM) remains to be attempted. This review examines the current state of the iron biofortification in pulses, particularly chickpea. The challenges concerning biofortification in pulses are also discussed. Specifically, the potential application of transgenic technology is explored, with focus on the genes that have been successfully used in biofortification efforts in rice.
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Affiliation(s)
- Grace Z. H. Tan
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, Australia
| | - Sudipta S. Das Bhowmik
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, Australia
| | - Thi M. L. Hoang
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, Australia
| | - Mohammad R. Karbaschi
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, Australia
| | | | - Brett Williams
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, Australia
| | - Sagadevan G. Mundree
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, Australia
- *Correspondence: Sagadevan G. Mundree
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11
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Abstract
In recent years, a number of components of the iron absorption pathway have been identified, greatly increasing our understanding of this important process. These include two molecules involved in brush border iron uptake, the ferric reductase DcytB and the iron transporter DMT1, and two mediating iron transfer to the body, the iron transporter Ireg1 and the ferroxidase hephaestin (Hp). Analysis of the regulation of these molecules has provided us with valuable insights into how the body responds to changes in iron requirements, and has enabled us to re-examine how iron absorption is controlled, and in particular the mucosal block phenomenon. Evidence suggests that the block to absorption that follows a priming dose of iron is the result of elevated intracellular iron levels decreasing the expression of the brush border iron transporter DMT1. Based on these observations, it is possible to propose a general model for the regulation of iron absorption whereby the basolateral transfer step involving Ireg1 and Hp controls the rate of absorption. In this model, DMT1 expression, and hence, brush border uptake, is regulated by local iron levels that are, in turn, determined by the rate of basolateral transfer.
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Affiliation(s)
- D M Frazer
- a Joint Clinical Sciences Program, The Queensland Institute of Medical Research and The University of Queensland, PO Royal Brisbane Hospital , Brisbane , Qld 4029 , Australia
| | - G J Anderson
- a Joint Clinical Sciences Program, The Queensland Institute of Medical Research and The University of Queensland, PO Royal Brisbane Hospital , Brisbane , Qld 4029 , Australia
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12
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Geng L, Duan X, Wang Y, Zhao Y, Gao G, Liu D, Chang YZ, Yu P. Quantum dots-hemin: Preparation and application in the absorption of heme iron. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2016; 12:1747-1755. [PMID: 27112306 DOI: 10.1016/j.nano.2016.04.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 03/21/2016] [Accepted: 04/11/2016] [Indexed: 10/21/2022]
Abstract
The absorption mechanism of heme iron remains unclear due to the limit of labeling techniques. Quantum dots (QDs) are powerful fluorescent probes resistant to photobleaching, however, there is no data about the application of QDs in heme iron absorption. Herein, we prepared hemin-coated CdSe/ZnS (QDs-hemin), and studied their absorption in vitro and in vivo. Results showed that QDs-hemin had uniform particle sizes, physiological stability and high joint efficiency. Moreover, QDs-hemin could be successfully absorbed gradually into the duodenum with the time using synchrotron radiation micro X-ray fluorescence and confocal laser scanning microscopy. Furthermore, QDs-hemin were observed to degrade in lysosomes, and their absorption was blocked by Heme Carrier Protein 1 (HCP1) antibody and HCP1 siRNA. All the results demonstrate that QDs can be a good tracer for heme iron and that HCP1 pathway is critical and predominant over the endocytosis pathway in the absorption mechanism.
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Affiliation(s)
- Lina Geng
- College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang, China
| | - Xianglin Duan
- Key Laboratory of Animal Physiology, Biochemistry & Molecular Biology of Hebei Province, Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Laboratory of Molecular Iron Metabolism, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Yan Wang
- Key Laboratory of Animal Physiology, Biochemistry & Molecular Biology of Hebei Province, Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Laboratory of Molecular Iron Metabolism, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Yashuo Zhao
- Key Laboratory of Animal Physiology, Biochemistry & Molecular Biology of Hebei Province, Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Laboratory of Molecular Iron Metabolism, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Guofen Gao
- Key Laboratory of Animal Physiology, Biochemistry & Molecular Biology of Hebei Province, Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Laboratory of Molecular Iron Metabolism, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Delong Liu
- College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang, China
| | - Yan-Zhong Chang
- Key Laboratory of Animal Physiology, Biochemistry & Molecular Biology of Hebei Province, Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Laboratory of Molecular Iron Metabolism, College of Life Science, Hebei Normal University, Shijiazhuang, China.
| | - Peng Yu
- Key Laboratory of Animal Physiology, Biochemistry & Molecular Biology of Hebei Province, Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Laboratory of Molecular Iron Metabolism, College of Life Science, Hebei Normal University, Shijiazhuang, China.
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13
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Matsuo-Tezuka Y, Noguchi-Sasaki M, Kurasawa M, Yorozu K, Shimonaka Y. Quantitative analysis of dietary iron utilization for erythropoiesis in response to body iron status. Exp Hematol 2016; 44:491-501. [PMID: 26911670 DOI: 10.1016/j.exphem.2016.02.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 02/08/2016] [Accepted: 02/09/2016] [Indexed: 12/18/2022]
Abstract
Erythropoiesis requires large amounts of iron for hemoglobin synthesis. There are two sources of iron for erythropoiesis, dietary and stored iron; however, their relative contributions to erythropoiesis remain unknown. In this study, we used the stable iron isotope (57)Fe to quantify synthesis of hemoglobin derived from dietary iron. Using this method, we investigated the activities of dietary iron absorption and the utilization of dietary iron for erythropoiesis in responses to stimulated erythropoiesis and to interventions to alter body iron status. Under iron-loaded conditions, the activity of dietary iron absorption was clearly lowered in response to up-regulation of hepcidin, although the estimated activity of iron release from stored iron was not compared with that under control conditions. This result was supported by the observation that two duodenal iron transporters, divalent metal transporter 1 (DMT1) and ferroportin, were downregulated by iron loading, although the levels of expression of ferroportin in iron storage tissues were not changed by iron loading under erythropoietic stimulation by epoetin-β pegol (C.E.R.A., a long-acting erythropoiesis-stimulating agent). These results indicate that the dietary iron absorption system is more sensitive to body iron status than are reticuloendothelial iron- release mechanisms. Our data indicated that there could be a regulatory mechanism favoring use of stored iron over dietary iron under iron-loaded conditions.
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Affiliation(s)
- Yukari Matsuo-Tezuka
- Product Research Department, Chugai Pharmaceutical Company, Ltd., Kamakura, Japan.
| | | | - Mitsue Kurasawa
- Product Research Department, Chugai Pharmaceutical Company, Ltd., Kamakura, Japan
| | - Keigo Yorozu
- Product Research Department, Chugai Pharmaceutical Company, Ltd., Kamakura, Japan
| | - Yasushi Shimonaka
- Product Research Department, Chugai Pharmaceutical Company, Ltd., Kamakura, Japan
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14
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Glahn RP, Tako E, Cichy K, Wiesinger J. The cotyledon cell wall and intracellular matrix are factors that limit iron bioavailability of the common bean (Phaseolus vulgaris). Food Funct 2016; 7:3193-200. [DOI: 10.1039/c6fo00490c] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Strategies that enhance the Fe bioavailability of the bean are of keen interest to nutritionists, bean breeders and growers.
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Affiliation(s)
- Raymond P. Glahn
- United States Department of Agriculture
- Agricultural Research Service
- Robert Holley Center for Agriculture and Health
- Ithaca
- USA
| | - Elad Tako
- United States Department of Agriculture
- Agricultural Research Service
- Robert Holley Center for Agriculture and Health
- Ithaca
- USA
| | - Karen Cichy
- United States Department of Agriculture
- Agricultural Research Service
- Sugarbeet and Bean Research Unit
- East Lansing
- USA
| | - Jason Wiesinger
- Department of Plant Soil and Microbial Sciences
- Michigan State University
- East Lansing
- USA
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15
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Aregbesola A, Voutilainen S, Virtanen JK, Aregbesola A, Tuomainen TP. Serum hepcidin concentrations and type 2 diabetes. World J Diabetes 2015; 6:978-982. [PMID: 26185605 PMCID: PMC4499531 DOI: 10.4239/wjd.v6.i7.978] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Revised: 12/22/2014] [Accepted: 03/20/2015] [Indexed: 02/05/2023] Open
Abstract
Hepcidin is a peptide hormone with both paracrine and endocrine functions that help in maintaining body iron stores. Type 2 diabetes (T2D) is one of the sequelae of excess body iron stores; thus, iron regulatory hormone hepcidin may have a direct or at least an indirect role in the aetiopathogenesis of T2D. Both human and animal studies at molecular and genetic levels have attempted to establish a role for hepcidin in the development of T2D, and a few epidemiologic studies have also showed a link between hepcidin and T2D at population level, but the findings are still inconclusive. Recent data have suggested different pathways in which hepcidin could be associated with T2D with much emphasis on its primary or secondary role in insulin resistance. Some of the suggested pathways are via transcription modulator of hepcidin (STAT3); ferroportin 1 expression on the cells involved in iron transport; transmembrane protease 6 enzyme; and pro-inflammatory cytokines, interleukin (IL)-1, IL-6, tumor necrosis factor-α and IL-10. This review briefly reports the existing evidence on the possible links between hepcidin and T2D and concludes that more data are needed to confirm or refute hepcidin’s role in the development of T2D. Examining this role could provide a further evidence base for iron in the aetiopathogenesis of T2D.
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16
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Nakanishi T, Hasuike Y, Nanami M, Yahiro M, Kuragano T. Novel iron-containing phosphate binders and anemia treatment in CKD: oral iron intake revisited. Nephrol Dial Transplant 2015; 31:1588-94. [PMID: 26142396 DOI: 10.1093/ndt/gfv268] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/05/2015] [Indexed: 01/01/2023] Open
Abstract
Recent reports have shown that novel phosphate binders containing iron are not only efficacious for the treatment of hyperphosphatemia but also may reduce the need for erythropoiesis-stimulating agents and intravenous (IV) iron for anemia management in patients on maintenance hemodialysis (MHD). Possible healthcare cost savings, which have not been demonstrated in a long-term study, may be an additional advantage of using such multi-pronged treatment strategies for the control of both hyperphosphatemia and iron needs. It is currently assumed that oral iron supplementation is less efficient than the IV route in patients with chronic kidney disease (CKD). The unexpected efficacy of novel iron-containing phosphate binders, such as ferric citrate, in repleting insufficient iron stores and improving the anemia of CKD could change this view. Previous assumptions of self-controlled iron uptake by 'mucosal block' or hepcidin, or else by impaired intestinal iron absorption due to CKD-associated inflammation cannot be reconciled with recent observations of the effects of ferric citrate administration. Citrate in the intestinal lumen may partly contribute to the acceleration of iron absorption. Animal experiments and clinical studies have also shown that oral iron overload can cause excessive iron accumulation despite high hepcidin levels, which are not able to block iron absorption completely. However, like with IV iron agents, no long-term safety data exist with respect to the effects of iron-containing phosphate binders on 'hard' patient outcomes. Future randomized prospective studies in patients with CKD are necessary to establish the safety of oral iron-containing phosphate binders for the control of both hyperphosphatemia and renal anemia.
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Affiliation(s)
- Takeshi Nakanishi
- Department of Internal Medicine, Division of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan
| | - Yukiko Hasuike
- Department of Internal Medicine, Division of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan
| | - Masayoshi Nanami
- Department of Internal Medicine, Division of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan
| | - Mana Yahiro
- Department of Internal Medicine, Division of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan
| | - Takahiro Kuragano
- Department of Internal Medicine, Division of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan
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17
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Abstract
The experimental and epidemiological evidence demonstrating that Ca inhibits Fe absorption was reviewed, with the objectives of estimating the potential impact of variations in Ca intake on dietary Fe bioavailability and of providing some guidelines for predicting the effects on Fe status of recent recommendations for higher dietary Ca intake. In animal models Ca salts reduced both haem- and non-haem-Fe absorption, the effect being dependent on the amount of Ca administered rather than the Ca:Fe molar ratio; dairy products had a variable effect; factors other than Ca may have been important. In single-meal human absorption studies, both haem- and non-haem-Fe absorption was inhibited by Ca supplements and by dairy products, the effect depending on the simultaneous presence of Ca and Fe in the lumen of the upper small intestine and also occurring when Ca and Fe were given in the fasting state. The quantitative effect, although dose dependent, was modified by the form in which Ca was administered and by other dietary constituents (such as phosphate, phytate and ascorbic acid) known to affect Fe bioavailability. The mechanism by which Ca influences Fe absorption has not been elucidated. The effects of factors that modulate Fe bioavailability are known to be exaggerated in single-meal studies, and measurements based on several meals are more likely to reflect the true nutritional impact. The results of most multiple-meal human studies suggest that Ca supplementation will have only a small effect on Fe absorption unless habitual Ca consumption is very low. Outcome analyses showed that Ca supplements had no effect on Fe status in infants fed Fe-fortified formula, lactating women, adolescent girls and adult men and women. However it should be noted that the subjects studied had adequate intakes of bioavailable Fe and, except in one study, had relatively high habitual Ca intakes. Although cross-sectional analyses in Europe have shown a significant inverse correlation between Ca intake (derived primarily from dairy foods) and Fe stores, the quantitative effect was relatively small. The general conclusion is that dietary Ca supplements are unlikely to have a biologically significant impact on Fe balance in Western societies unless Ca consumption is habitually very low; however, increased consumption of dairy products may have a small negative effect that could be functionally important in pregnancy if Fe supplements are not taken. It is uncertain whether the inverse relationship between consumption of dairy products and Fe status is due entirely to increased Ca intake; substitution of milk proteins for meat may also have negative effects on Fe balance.
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Affiliation(s)
- S R Lynch
- Eastern Virginia Medical School, Medical Service, Hampton Veterans Affairs Medical Center, Hampton, Virginia 23667, USA
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18
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Abstract
Iron is universally abundant and no life can exist without it. However, iron levels should be maintained within a narrow range. Iron deficiency causes anaemia, whereas excessive iron increases cancer risk, presumably by free radical generation. Several pathological conditions such as genetic haemochromatosis, chronic viral hepatitis B and C, conditions related to asbestos fibre exposure and ovarian endometriosis have been recognized as iron overload-associated conditions that also increase human cancer risks. Iron's carcinogenicity has been documented in animal experiments. Surprisingly, these studies have revealed that the homozygous deletion of CDKN2A/2B is a major hallmark of iron-induced carcinogenesis. Recently, the hormonal regulation of iron metabolism has been elucidated. A commonly hypothesized mechanism may be the lack of any iron disposal pathway other than for bleeding and a mechanism of iron re-uptake as catechol chelate has been discovered. Iron overload in neurons via the ferroportin block may play a role in Alzheimer's disease. Furthermore, a recent epidemiological study reported that iron reduction by phlebotomy was associated with decreased cancer risks in a general population. Given that the required amounts of iron decrease during ageing, the fine control of body iron stores would be a wise strategy for chemoprevention of several diseases.
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Affiliation(s)
- Shinya Toyokuni
- Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
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19
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Garrick MD. Human iron transporters. GENES AND NUTRITION 2010; 6:45-54. [PMID: 21437029 DOI: 10.1007/s12263-010-0184-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 08/24/2010] [Indexed: 01/17/2023]
Abstract
Human iron transporters manage iron carefully because tissues need iron for critical functions, but too much iron increases the risk of reactive oxygen species. Iron acquisition occurs in the duodenum via divalent metal transporter (DMT1) and ferroportin. Iron trafficking depends largely on the transferrin cycle. Nevertheless, non-digestive tissues have a variety of other iron transporters that may render DMT1 modestly redundant, and DMT1 levels exceed those needed for the just-mentioned tasks. This review begins to consider why and also describes advances after 2008 that begin to address this challenge.
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Affiliation(s)
- Michael D Garrick
- Department of Biochemistry, 140 Farber Hall, SUNY at Buffalo, 3435 Main St., Buffalo, NY 14214 USA
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20
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Intestinal ferritin H is required for an accurate control of iron absorption. Cell Metab 2010; 12:273-82. [PMID: 20816093 DOI: 10.1016/j.cmet.2010.08.003] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 05/08/2010] [Accepted: 06/16/2010] [Indexed: 12/26/2022]
Abstract
To maintain appropriate body iron levels, iron absorption by the proximal duodenum is thought to be controlled by hepcidin, a polypeptide secreted by hepatocytes in response to high serum iron. Hepcidin limits basolateral iron efflux from the duodenal epithelium by binding and downregulating the intestinal iron exporter ferroportin. Here, we found that mice with an intestinal ferritin H gene deletion show increased body iron stores and transferrin saturation. As expected for iron-loaded animals, the ferritin H-deleted mice showed induced liver hepcidin mRNA levels and reduced duodenal expression of DMT1 and DcytB mRNA. In spite of these feedback controls, intestinal ferroportin protein and (59)Fe absorption were increased more than 2-fold in the deleted mice. Our results demonstrate that hepcidin-mediated regulation alone is insufficient to restrict iron absorption and that intestinal ferritin H is also required to limit iron efflux from intestinal cells.
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21
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Chua ACG, Klopcic B, Lawrance IC, Olynyk JK, Trinder D. Iron: An emerging factor in colorectal carcinogenesis. World J Gastroenterol 2010; 16:663-72. [PMID: 20135713 PMCID: PMC2817053 DOI: 10.3748/wjg.v16.i6.663] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The carcinogenic potential of iron in colorectal cancer (CRC) is not fully understood. Iron is able to undergo reduction and oxidation, making it important in many physiological processes. This inherent redox property of iron, however, also renders it toxic when it is present in excess. Iron-mediated generation of reactive oxygen species via the Fenton reaction, if uncontrolled, may lead to cell damage as a result of lipid peroxidation and oxidative DNA and protein damage. This may promote carcinogenesis through increased genomic instability, chromosomal rearrangements as well as mutations of proto-oncogenes and tumour suppressor genes. Carcinogenesis is also affected by inflammation which is exacerbated by iron. Population studies indicate an association between high dietary iron intake and CRC risk. In this editorial, we examine the link between iron-induced oxidative stress and inflammation on the pathogenesis of CRC.
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22
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Schümann K, Herbach N, Kerling C, Seifert M, Fillebeen C, Prysch I, Reich J, Weiss G, Pantopoulos K. Iron absorption and distribution in TNF(DeltaARE/+) mice, a model of chronic inflammation. J Trace Elem Med Biol 2010; 24:58-66. [PMID: 20122582 DOI: 10.1016/j.jtemb.2009.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 08/14/2009] [Accepted: 10/13/2009] [Indexed: 12/11/2022]
Abstract
Hemizygous TNF(DeltaARE/+) mice are a murine model for chronic inflammation. We utilized these animals to study iron-kinetics and corresponding protein expression in an iron-deficient and iron-adequate setting. (59)Fe-absorption was determined in ligated duodenal loops in vivo. Whole body distribution of i.v. injected (59)Fe was analysed, and the organ specific expression of ferroportin, transferrin receptor-1, hepcidin and duodenal DMT-1 was quantified by real-time PCR and Western blotting. Duodenal (59)Fe-lumen-to-body transport was not affected by the genotype. Duodenal (59)Fe-retention was increased in TNF(DeltaARE/+) mice, suggesting higher (59)Fe-losses with defoliated enterocytes. Iron-deficiency increased duodenal (59)Fe-lumen-to-body transport, and higher duodenal (59)Fe-tissue retention went along with higher duodenal DMT-1, ferroportin, and liver hepcidin expression. TNF(DeltaARE/+) mice significantly increase their (59)Fe-content in inflamed joints and ilea, and correspondingly reduce splenic (59)Fe-content. Leukocyte infiltrations in the joints suggest a substantial shift of iron-loaded RES cells to inflamed tissues as the underlying mechanism. This finding was paralleled by increased non-haem iron content in joints and reduced haemoglobin and haematocrit concentrations in TNF(DeltaARE/+) mice. In conclusion, erythropoiesis in inflamed TNF(DeltaARE/+) mice could be iron-limited due to losses with exfoliated iron-loaded enterocytes and/or to increased iron-retention in RES cells that shift from the spleen to inflamed tissues.
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Affiliation(s)
- Klaus Schümann
- Science Centre Weihenstephan, Technical University Munich, 85350 Freising, Germany.
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23
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24
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Khomenko T, Szabo S, Deng X, Ishikawa H, Anderson GJ, McLaren GD. Role of iron in the pathogenesis of cysteamine-induced duodenal ulceration in rats. Am J Physiol Gastrointest Liver Physiol 2009; 296:G1277-86. [PMID: 19342511 PMCID: PMC3834006 DOI: 10.1152/ajpgi.90257.2008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cysteamine induces perforating duodenal ulcers in rats within 24-48 h. This reducing aminothiol generates hydrogen peroxide in the presence of transition metals (e.g., ferric iron), producing oxidative stress, which may contribute to organ-specific tissue damage. Since most intestinal iron absorption takes place in the proximal duodenum, we hypothesized that cysteamine may disrupt regulation of mucosal iron transport, and iron may facilitate cysteamine-induced duodenal ulceration. We show here that cysteamine-induced ulceration was aggravated by pretreatment of rats with Fe(3+) or Fe(2+) compounds, which elevated iron concentration in the duodenal mucosa. In contrast, feeding rats an iron-deficient diet was associated with a 4.6-fold decrease in ulcer formation, accompanied by a 34% decrease (P < 0.05) in the duodenal mucosal iron concentration. Administration of deferoxamine inhibited ulceration by 65%. We also observed that the antiulcer effect of H2 receptor antagonist cimetidine included a 35% decrease in iron concentration in the duodenal mucosa. Cysteamine-induced duodenal ulcers were also decreased in iron-deficient Belgrade rats (P < 0.05). In normal rats, cysteamine administration increased the iron concentration in the proximal duodenal mucosa by 33% in the preulcerogenic stage but at the same time decreased serum iron (P < 0.05). Cysteamine also enhanced activation of mucosal iron regulatory protein 1 and increased the expression of divalent metal transporter 1 mRNA and protein. Transferrin receptor 1 protein expression was also increased, although mucosal ferroportin and ferritin remained almost unchanged. These results indicate an expansion of the intracellular labile iron pool in the duodenal mucosa, increasing its susceptibility to oxidative stress, and suggest a role for iron in the pathogenesis of organ-specific tissue injury such as duodenal ulcers.
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Affiliation(s)
- Tetyana Khomenko
- Diagnostic and Molecular Medicine and Medical Health Care Groups, Veterans Affairs Medical Center, Long Beach, California and Departments of Pathology, Pharmacology and Medicine, University of California, Irvine, California
| | - Sandor Szabo
- Diagnostic and Molecular Medicine and Medical Health Care Groups, Veterans Affairs Medical Center, Long Beach, California and Departments of Pathology, Pharmacology and Medicine, University of California, Irvine, California
| | - Xiaoming Deng
- Diagnostic and Molecular Medicine and Medical Health Care Groups, Veterans Affairs Medical Center, Long Beach, California and Departments of Pathology, Pharmacology and Medicine, University of California, Irvine, California
| | - Hideki Ishikawa
- Diagnostic and Molecular Medicine and Medical Health Care Groups, Veterans Affairs Medical Center, Long Beach, California and Departments of Pathology, Pharmacology and Medicine, University of California, Irvine, California
| | - Gregory J. Anderson
- Iron Metabolism Laboratory, Queensland Institute of Medical Research, Brisbane, Australia
| | - Gordon D. McLaren
- Diagnostic and Molecular Medicine and Medical Health Care Groups, Veterans Affairs Medical Center, Long Beach, California and Departments of Pathology, Pharmacology and Medicine, University of California, Irvine, California
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25
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26
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27
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Brookes MJ, Hughes S, Turner FE, Reynolds G, Sharma N, Ismail T, Berx G, McKie AT, Hotchin N, Anderson GJ, Iqbal T, Tselepis C. Modulation of iron transport proteins in human colorectal carcinogenesis. Gut 2006; 55:1449-60. [PMID: 16641131 PMCID: PMC1856421 DOI: 10.1136/gut.2006.094060] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
BACKGROUND AND AIMS Total body iron and high dietary iron intake are risk factors for colorectal cancer. To date there is no comprehensive characterisation of iron transport proteins in progression to colorectal carcinoma. In this study, we examined expression of iron import (duodenal cytochrome b (DCYTB), divalent metal transporter 1 (DMT1), and transferrin receptor 1 (TfR1)) and export (hephaestin (HEPH) and ferroportin (FPN)) proteins in colorectal carcinoma. METHODS Perl's staining was used to examine colonocyte iron content. Real time polymerase chain reaction (PCR) and western blotting were used to examine mRNA and protein levels of the molecules of interest in 11 human colorectal cancers. Semiquantitative immunohistochemistry was used to verify protein levels and information on cellular localisation. The effect of iron loading on E-cadherin expression in SW480 and Caco-2 cell lines was examined by promoter assays, real time PCR and western blotting. RESULTS Perl's staining showed increased iron in colorectal cancers, and there was a corresponding overexpression of components of the intracellular iron import machinery (DCYTB, DMT1, and TfR1). The iron exporter FPN was also overexpressed, but its intracellular location, combined with reduced HEPH levels, suggests reduced iron efflux in the majority of colorectal cancers examined. Loss of HEPH and FPN expression was associated with more advanced disease. Iron loading Caco-2 and SW480 cells caused cellular proliferation and E-cadherin repression. CONCLUSIONS Progression to colorectal cancer is associated with increased expression in iron import proteins and a block in iron export due to decreased expression and aberrant localisation of HEPH and FPN, respectively. This results in increased intracellular iron which may induce proliferation and repress cell adhesion.
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Affiliation(s)
- M J Brookes
- Cancer Research UK Institute for Cancer Studies, University of Birmingham, Vincent Drive, Birmingham B15 2TH, UK
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28
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Collins JF. Gene chip analyses reveal differential genetic responses to iron deficiency in rat duodenum and jejunum. Biol Res 2006; 39:25-37. [PMID: 16629162 PMCID: PMC1458503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023] Open
Abstract
Previous studies revealed novel genetic changes in the duodenal mucosa of iron-deprived rats during postnatal development. These observations are now extended to compare the genetic response to iron deficiency in the duodenum versus jejunum of 12-wk-old rats. cRNA samples were prepared from the duodenal and jejunal mucosa of three groups each of control and iron-deficient rats and hybridized with RAE 230A and 230B gene chips (Affymetrix). Stringent data reduction strategies were employed. Results showed that several genes were similarly induced in both gut segments, including DMT1, Dcytb, transferrin receptor 1, heme oxygenase 1, metallothionein, the Menkes copper ATPase (ATP7A), tripartitie motif protein 27, and the sodium-dependent vitamin C transporter. However, a subset of genes showed regulation in only one or the other gut segment. In duodenum only, gastrokine 1, trefoil factor 1 and claudin 2 were induced by iron-deficiency. Other genes previously identified were only regulated in the duodenum. Overall, these studies demonstrate similarities and distinct differences in the genetic response to iron deprivation in the duodenum versus jejunum and provide evidence that more distal gut segments also may play a role in increasing iron absorption in iron-deficiency anemia.
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Affiliation(s)
- James F Collins
- Department of Pediatrics and Nutritional Sciences, Steele Children's Research Center, University of Arizona, Tucson, Arizona, USA.
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Collins JF, Franck CA, Kowdley KV, Ghishan FK. Identification of differentially expressed genes in response to dietary iron deprivation in rat duodenum. Am J Physiol Gastrointest Liver Physiol 2005; 288:G964-71. [PMID: 15637178 DOI: 10.1152/ajpgi.00489.2004] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We sought to identify novel genes involved in intestinal iron absorption by inducing iron deficiency in rats during postnatal development from the suckling period through adulthood. We then performed comparative gene chip analyses (RAE230A and RAE230B chips; Affymetrix) with cRNA derived from duodenal mucosa. Real-time PCR was used to confirm changes in gene expression. Genes encoding the apical iron transport-related proteins [divalent metal transporter 1 (DMT1) and duodenal cytochrome b] were strongly induced at all ages studied, whereas increases in mRNA encoding the basolateral proteins iron-regulated gene 1 and hephaestin were observed only by real-time PCR. In addition, transferrin receptor 1 and heme oxygenase 1 were induced. We also identified induction of novel genes not previously associated with intestinal iron transport. The Menkes copper ATPase (ATP7a) and metallothionein were strongly induced at all ages studied, suggesting increased copper absorption by enterocytes during iron deficiency. We also found significantly increased liver copper levels in 7- to 12-wk-old iron-deficient rats. Also upregulated at most ages examined were the sodium-dependent vitamin C transporter, tripartite motif protein 27, aquaporin 4, lipocalin-interacting membrane receptor, and the breast cancer-resistance protein (ABCG2). Some genes also showed decreased expression with iron deprivation, including several membrane transporters, metabolic enzymes, and genes involved in the oxidative stress response. We speculate that dietary iron deprivation leads to increased intestinal copper absorption via DMT1 on the brush-border membrane and the Menkes copper ATPase on the basolateral membrane. These findings may thus explain copper loading in the iron-deficient state. We also demonstrate that many other novel genes may be differentially regulated in the setting of iron deprivation.
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Affiliation(s)
- James F Collins
- Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona, 1501 N. Campbell Ave., Tucson, Arizona 85724, USA.
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Affiliation(s)
- Silvia Miret
- Department of Life Sciences, King's College London, The Franklin-Wilkins Building, London
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Chen H, Su T, Attieh ZK, Fox TC, McKie AT, Anderson GJ, Vulpe CD. Systemic regulation of Hephaestin and Ireg1 revealed in studies of genetic and nutritional iron deficiency. Blood 2003; 102:1893-9. [PMID: 12730111 DOI: 10.1182/blood-2003-02-0347] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Hephaestin is a membrane-bound multicopper ferroxidase necessary for iron egress from intestinal enterocytes into the circulation. Mice with sex-linked anemia (sla) have a mutant form of Hephaestin and a defect in intestinal basolateral iron transport, which results in iron deficiency and anemia. Ireg1 (SLC11A3, also known as Ferroportin1 or Mtp1) is the putative intestinal basolateral iron transporter. We compared iron levels and expression of genes involved in iron uptake and storage in sla mice and C57BL/6J mice fed iron-deficient, iron-overload, or control diets. Both iron-deficient wild-type mice and sla mice showed increased expression of Heph and Ireg1 mRNA, compared to controls, whereas only iron-deficient wild-type mice had increased expression of the brush border transporter Dmt1. Unlike iron-deficient mice, sla mouse enterocytes accumulated nonheme iron and ferritin. These results indicate that Dmt1 can be modulated by the enterocyte iron level, whereas Hephaestin and Ireg1 expression respond to systemic rather than local signals of iron status. Thus, the basolateral transport step appears to be the primary site at which the small intestine responds to alterations in body iron requirements.
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Affiliation(s)
- Huijun Chen
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA
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Pizarro F, Olivares M, Hertrampf E, Mazariegos DI, Arredondo M. Heme-iron absorption is saturable by heme-iron dose in women. J Nutr 2003; 133:2214-7. [PMID: 12840181 DOI: 10.1093/jn/133.7.2214] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In developed countries where meat is an important constituent of the diet, much of the dietary iron is in the heme-iron form as hemoglobin and myoglobin. Heme-iron is absorbed more efficiently than inorganic iron by the human intestine. Thus, it is important to know how the dose of heme-iron affects iron absorption. The purpose of this study was to establish the dose-effect of heme-iron on the percentage and absolute amount of iron absorbed. Twenty-seven healthy women (28- to 50-y-old) were selected to participate in two iron absorption studies. Through the use of iron isotopes ((59)Fe and (55)Fe), the studies were performed to characterize the dose-response curve of non-heme-iron absorption (ferrous sulfate), and to establish the dose-response curve of heme-iron absorption (hemoglobin). The labeled hemoglobin was prepared by use of red blood cells from rabbits. The geometric means (+/-1 SEM range) of non-heme iron absorbed were 0.2 (0.2-0.3), 1.2 (1.0-1.5), 6.7 (5.7-8.0) and 13.0 (11.5-14.6) mg of iron for doses of 0.5, 5, 50 and 100 mg of iron as ferrous sulfate, respectively; and 0.1 (0.1-0.2), 0.4 (0.3-0.4), 2.2 (2.0-2.4) and 2.2 (1.7-3.0) mg of iron for doses of 0.5, 3, 15 and 30 mg of heme-iron as hemoglobin, respectively. The fitted curves for heme and non-heme iron differed (P < 0.04). These results strongly suggest that the heme-iron absorption pathway is saturable.
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Affiliation(s)
- Fernando Pizarro
- Institute of Nutrition and Food Technology (INTA) of University of Chile, Santiago, Chile.
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Frazer DM, Wilkins SJ, Becker EM, Murphy TL, Vulpe CD, McKie AT, Anderson GJ. A rapid decrease in the expression of DMT1 and Dcytb but not Ireg1 or hephaestin explains the mucosal block phenomenon of iron absorption. Gut 2003; 52:340-6. [PMID: 12584213 PMCID: PMC1773562 DOI: 10.1136/gut.52.3.340] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/11/2002] [Indexed: 12/18/2022]
Abstract
BACKGROUND A large oral dose of iron will reduce the absorption of a subsequent smaller dose of iron in a phenomenon known as mucosal block. Molecular analysis of this process may provide insights into the regulation of intestinal iron absorption. AIMS To determine the effect of an oral bolus of iron on duodenal expression of molecules associated with intestinal iron transport in rats and to relate this to changes in iron absorption. METHODS Rats were given an oral dose of iron and duodenal expression of divalent metal transporter 1 (DMT1), Dcytb, Ireg1, and hephaestin (Hp) was determined using the ribonuclease protection assay, western blotting, and immunofluorescence. Iron absorption was measured using radioactive (59)Fe. RESULTS A decrease in intestinal iron absorption occurred following an oral dose of iron and this was associated with increased enterocyte iron levels, as assessed by iron regulatory protein activity and immunoblotting for ferritin. Reduced absorption was also accompanied by a rapid decrease in expression of the mRNAs encoding the brush border iron transport molecules Dcytb and the iron responsive element (IRE) containing the splice variant of DMT1. No such change was seen in expression of the non-IRE splice variant of DMT1 or the basolateral iron transport molecules Ireg1 and Hp. Similar changes were observed at the protein level. CONCLUSIONS These data indicate that brush border, but not basolateral, iron transport components are regulated locally by enterocyte iron levels and support the hypothesis that systemic stimuli exert their primary effect on basolateral transport molecules.
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Affiliation(s)
- D M Frazer
- Joint Clinical Sciences Program, the Queensland Institute of Medical Research and the University of Queensland, PO Royal Brisbane Hospital, Brisbane, Queensland 4029, Australia
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McKie AT, Marciani P, Rolfs A, Brennan K, Wehr K, Barrow D, Miret S, Bomford A, Peters TJ, Farzaneh F, Hediger MA, Hentze MW, Simpson RJ. A novel duodenal iron-regulated transporter, IREG1, implicated in the basolateral transfer of iron to the circulation. Mol Cell 2000; 5:299-309. [PMID: 10882071 DOI: 10.1016/s1097-2765(00)80425-6] [Citation(s) in RCA: 1011] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Iron absorption by the duodenal mucosa is initiated by uptake of ferrous Fe(II) iron across the brush border membrane and culminates in transfer of the metal across the basolateral membrane to the portal vein circulation by an unknown mechanism. We describe here the isolation and characterization of a novel cDNA (Ireg1) encoding a duodenal protein that is localized to the basolateral membrane of polarized epithelial cells. Ireg1 mRNA and protein expression are increased under conditions of increased iron absorption, and the 5' UTR of the Ireg1 mRNA contains a functional iron-responsive element (IRE). IREG1 stimulates iron efflux following expression in Xenopus oocytes. We conclude that IREG1 represents the long-sought duodenal iron export protein and is upregulated in the iron overload disease, hereditary hemochromatosis.
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Affiliation(s)
- A T McKie
- Department of Molecular Medicine, King's College London, Guy's, King's, St Thomas' School of Medicine, United Kingdom.
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Abstract
Iron is vital for living organisms because it is essential for multiple metabolic processes to include oxygen transport, DNA synthesis, and electron transport. However, iron must be bound to proteins to prevent tissue damage from free radical formation. Thus, its concentrations in body organs must be regulated carefully. Intestinal absorption is the primary mechanism regulating iron concentrations in the body. Three pathways for intestinal iron uptake have been proposed and reported. These are the mobilferrin-integrin pathway, the divalent cation transporter 1 (DCT-1) [or natural resistance-associated macrophage protein (Nramp2)] pathway, and a separate pathway for uptake of heme by absorptive cells. Each of these pathways are incompletely described. However, studies with blocking antibodies, observations in rodents with disorders of iron metabolism, and studies in tissue culture cells suggest that the DCT-1 pathway is dominant in embryonic cells and is involved with cellular uptake of ferrous iron, whereas the mobilferrin-integrin pathway facilitates absorption of dietary inorganic ferric iron. Thus, there are separate pathways for cellular uptake of ferric and ferrous inorganic iron. Body iron can enter intestinal cells from plasma via basolateral membranes containing the classical transferrin receptor pathway with a high affinity for holotransferrin. This keeps the absorptive cell informed of the state of iron repletion of the host. Intestinal mucosal cell iron seems to exit the cell via a distinct apotransferrin receptor and a newly described protein named hephaestin. Unlike the absorptive surface of intestinal cells, most other cells possess transferrin receptors on their surfaces and the vast majority of iron entering these cells is transferrin associated. There seem to be 2 distinct pathways by which transferrin iron enters nonintestinal cells. In the classical clathrin-coated pitendosome pathway, iron accompanies transferrin into the cell to enter a vesicle, which releases the iron to the cytosol with acidification (high affinity, low capacity). Under physiological conditions, a second transferrin associated pathway (low affinity, high capacity) exists which has been named the transferrin receptor independent pathway (TRIP). How the TRIP delivers iron to cells is incompletely described. In addition, tissue culture studies show that nonintestinal cells can accept iron from soluble iron salts. This occurs via the mobilferrin-integrin and probably the DCT-1 pathways. Cellular uptake of iron from iron salts probably occurs in iron overloading disorders and may be responsible for free radical damage when the iron binding capacity of plasma is exceeded. Radioiron entering the cell via the heme and transferrin associated pathways can be found in isolates of mobilferrin/paraferritin and hemoglobin. This interaction probably occurs to permit NADPH dependent ferrireduction so iron can be used for synthesis of heme proteins. Production of heme from iron delivered via these routes indicates functional specificity for the pathways.
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Affiliation(s)
- M E Conrad
- USA Cancer Center, University of South Alabama, Mobile 36688, USA.
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Schümann K, Elsenhans B, Forth W. Kinetic analysis of 59Fe movement across the intestinal wall in duodenal rat segments ex vivo. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:G431-40. [PMID: 9950817 DOI: 10.1152/ajpgi.1999.276.2.g431] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Duodenal segments from iron-deficient and iron-adequate rats were luminally perfused ex vivo with solutions containing 1, 10, 50, 100, 200 and 500 micromol 59Fe/l. When duodenal tissue load and mucosal-to-serosal transport had reached a steady state, perfusion was continued without luminal 59Fe supply. Mobilization of 59Fe from the duodenal tissue into the serosally released absorbate followed first-order rate kinetics, which permitted calculation of the asymptotic maximum, the rate constant, and the initial mobilization rate for tissue-to-absorbate transfer. There was no evidence for adaptation of 59Fe tissue binding in iron-deficient segments. 59Fe tissue-to-absorbate transfer increased in proportion to the mobilizable fraction of recently absorbed iron in the tissue, which is indicative of simple diffusion or carrier-mediated transport below saturation. Regulation of the mucosal uptake step appears to determine the mobilizable 59Fe fraction and thus the adaptation of the overall iron absorption process to the demand. Iron retention in the duodenal tissue and iron transfer from here into the body appear not to be either regulated or rate limited.
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Affiliation(s)
- K Schümann
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität, D-80336 Munich, Germany
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Kramer W, Corsiero D, Friedrich M, Girbig F, Stengelin S, Weyland C. Intestinal absorption of bile acids: paradoxical behaviour of the 14 kDa ileal lipid-binding protein in differential photoaffinity labelling. Biochem J 1998; 333 ( Pt 2):335-41. [PMID: 9657973 PMCID: PMC1219590 DOI: 10.1042/bj3330335] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Photoaffinity labelling of brush border membrane vesicles from rabbit ileum with radiolabelled 3,3-azo and 7,7-azo derivatives of taurocholate identified integral membrane proteins of molecular masses 93 and 46 kDa, as well as a 14 kDa peripheral membrane protein, as components of the ileal Na+/bile acid transport system [Kramer, Girbig, Gutjahr, Kowalewski, Jouvenal, Müller, Tripier and Wess (1993) J. Biol. Chem. 268, 18035-18046]. Differential photoaffinity labelling in the presence of non-radiolabelled bile acid derivatives led, as expected, to a concentration-dependent decrease in the extent of labelling of the 93 and 46 kDa transmembrane proteins, which are the monomeric and dimeric forms of the ileal bile acid transporter protein. The extent of labelling of the 14 kDa ileal lipid-binding protein (ILBP), however, increased on the addition of unlabelled bile acids, the increase being dependent on the structure of the bile acid added. The possibility of artifacts was excluded by photoaffinity labelling experiments in the frozen state as well as by model calculations. The experimental results suggest that the binding of bile acids to ILBP can increase the affinity of ILBP for bile acids. These results would be in accordance with a substrate-load modification of transport activity and a positive-feedback regulation mechanism for active uptake of bile acid in the ileum.
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Affiliation(s)
- W Kramer
- Research Metabolic Diseases, Hoechst Marion Roussel Deutschland GmbH, D-65926 Frankfurt am Main, Federal Republic of Germany
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Rabie A, Simpson RJ, Bomford A, Cunninghame-Graham D, Peters TJ. Relationship between duodenal cytosolic aconitase activity and iron status in the mouse. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1245:414-20. [PMID: 8541321 DOI: 10.1016/0304-4165(95)00120-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cytosolic aconitase activity was assayed in duodenal mucosa from mice subjected to a variety of manipulations known to modulate duodenal iron status and duodenal iron absorption. No changes in cytosolic aconitase activity were observed 1 h after oral FeSO4 dosing or intramuscular desferrioxamine treatment. Three days of hypoxic exposure and two weeks treatment with intramuscular iron dextran also had no effect on cytosolic aconitase. Three weeks growth on an iron deficient diet significantly reduced cytosolic aconitase activity. In no situation was there any evidence for significant amounts of inactive aconitase which could be activated in vitro with FeSO4/cysteine. These data suggest that duodenal cytosolic aconitase is not sensitive to acute changes in mucosal iron levels and is generally much less sensitive to body iron status than is duodenal iron absorption. There is evidence that chronic iron depletion reduces cytosolic aconitase to a relatively small degree but generally activity is maintained, consistent with an important metabolic role for the enzyme.
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Affiliation(s)
- A Rabie
- Department of Clinical Biochemistry, King's College School of Medicine and Dentistry, London, UK
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Carpenter CE, Ummadi M. Iron status alters the adsorption, uptake, and absorption capacities of rat duodenum for ferrous and ferric iron. Nutr Res 1995. [DOI: 10.1016/0271-5317(95)00072-q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Takahashi H, Yang SI, Ueda Y, Kim M, Yamamoto T. Influence of intact and partially hydrolysed guar gum on iron utilization in rats fed on iron-deficient diets. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PHYSIOLOGY 1994; 109:75-82. [PMID: 8076455 DOI: 10.1016/0300-9629(94)90313-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Effects of partially hydrolysed guar gum (PHGG) or intact guar gum (GG) on iron utilization in rats fed on several iron-deficient diets were examined. Hemoglobin, serum iron and iron storage in liver of rats fed on iron-deficient diets as a control group (without PHGG and GG) significantly decreased, while those of the test group fed together with PHGG or GG were unchanged. In an iron balance test for 3 days, administration of PHGG or GG caused an increase in iron absorption. The results suggested that PHGG or its metabolites increase the bioavailability of dietary iron in deficiency.
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Affiliation(s)
- H Takahashi
- Central Research Laboratories, Taiyo Kagaku Co. Ltd., Yokkaichi, Japan
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Batey RG, Johnston R. Effects of alcohol, carbon tetrachloride, and choline deficiency on iron metabolism in the rat. Alcohol Clin Exp Res 1993; 17:931-4. [PMID: 8279676 DOI: 10.1111/j.1530-0277.1993.tb05643.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effects of alcohol on hepatic iron uptake and intestinal iron transport were studied in rats fed a nutritionally replete liquid diet containing varying quantities of ethanol. Results were compared with those from animals exposed to carbon tetrachloride (CCl4) to produce hepatocellular necrosis or a choline-deficient diet to produce steatosis and cirrhosis. A high ethanol intake for 4 or 10 weeks produced hepatic steatosis. CCl4 produced hepatocellular necrosis. Choline deficiency was associated with steatosis +/- cirrhosis. Intestinal iron transport was unaffected by ethanol, CCl4, or choline deficiency. Hepatic iron uptake was significantly depressed in rats consuming 11.7 g/kg/day ethanol (p < 0.01) for 4 weeks. Choline-deficient animals studied at 14 weeks also had significantly decreased hepatic iron uptake (p < 0.01); results were similar in the cirrhotic and noncirrhotic animals. Conversely, CCl4 exposure produced a significant 5-fold increase in hepatic iron uptake (p < 0.001). Results suggest that ethanol consumption, fatty liver, and cirrhosis are not responsible for any increase in iron absorption or of hepatic iron uptake in the rat model. Acute hepatocellular injury is followed by increased hepatic iron uptake.
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Affiliation(s)
- R G Batey
- Department of Medicine, Westmead Hospital, New South Wales, Australia
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Lillienau J, Crombie DL, Munoz J, Longmire-Cook SJ, Hagey LR, Hofmann AF. Negative feedback regulation of the ileal bile acid transport system in rodents. Gastroenterology 1993; 104:38-46. [PMID: 8419260 DOI: 10.1016/0016-5085(93)90833-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND Active transport of conjugated bile acids by ileal enterocytes is a key mechanism for conservation of the bile acid pool. Experiments were performed to determine whether such transport is regulated by substrate load. METHODS Using anesthetized biliary fistula guinea pigs or rats, the ileum was perfused with ursodeoxycholyltaurine at a concentration causing maximal ileal transport of this bile acid; absorption was assessed by biliary recovery. Before ileal perfusion, animals ingested one of three diets: chow, chow with added conjugated bile acid, or chow with added cholestyramine. RESULTS In the guinea pig, ingestion of a taurocholate-enriched diet resulted in a 75% decrease in the absorption rate of ursodeoxycholyltaurine. Similar results were obtained with cholylsarcosine (a deconjugation-dehydroxylation resistant analogue) or with chenodeoxycholylglycine, the endogenous bile acid of the guinea pig. In contrast, cholestyramine ingestion caused an increase in ursodeoxycholyltaurine absorption. In the rat, cholyltaurine or cholylsarcosine ingestion also caused decreased ileal transport. In the guinea pig, maximal down-regulation of active ileal bile acid transport occurred after 2-3 days of bile acid feeding; up-regulation required 3-4 days. CONCLUSIONS Bile acid metabolism is regulated by feedback inhibition of active ileal transport in addition to the well-established feedback inhibition of bile acid biosynthesis in the liver. Together, these two regulatory mechanisms ensure constancy of bile acid secretion.
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Affiliation(s)
- J Lillienau
- Department of Physiological Chemistry, University of Lund, Sweden
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Abstract
Iron (Fe) absorption by three segments (duodenum, jejunum, and ileum) of the small intestine of chickens was studied by a perfusion technique in vivo in closed circuit using 59Fe Cl3 and was related to the histological characteristics of each segment. The serosal transfers of Fe for the duodenum and jejunum were the same (14%/cm), but significantly different (p < 0.05) from those of the ileum (9%/cm), which may be explained by the morphological and histological properties of the gut of chickens. However, the presence of Fe in blood and in liver was significantly lower after perfusion of the jejunum and ileum than after perfusion of the duodenum. It is concluded that chickens show an early adaptation of small intestine to Fe absorption in response to the considerable loss of Fe suffered during the laying process.
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Affiliation(s)
- M P Sáiz
- Department de Bioqumica i Fisiologia, Universitat de Barcelona, Spain
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Chowrimootoo G, Gillett M, Debnam ES, Srai SK, Epstein O. Iron-transferrin binding to isolated guinea pig enterocytes and the regional localisation of intestinal iron transfer during ontogeny. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1116:256-60. [PMID: 1610881 DOI: 10.1016/0304-4165(92)90037-u] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Neonatal animals are iron replete but in comparison with adults they display increased intestinal iron absorption. In order to examine possible mechanisms for this developmental adaptation we have measured the appearance of iron in peripheral blood following 30 min exposure of duodenal and ileal segments of adult and neonatal guinea pigs in vivo to 59Fe-ascorbate. Parallel experiments have determined the kinetics of 125I-labelled diferric transferrin binding to villus enterocytes isolated from duodenum and ileum. In adult animals the rate of appearance of 59Fe in peripheral blood was 11-fold greater following duodenal, compared to ileal exposure to the radioligand. No such regional difference was detected in the neonate. Isolated cells showed saturable binding of [125I]transferrin which was maximal between 30 and 60 min. The kinetics of specific transferrin binding by adult duodenal and ileal enterocytes were similar and were also not significantly different to respective values in neonatal duodenal and ileal cells. Thus, it is likely that increased iron absorption in the neonate is due in part to enhanced ileal iron transfer. The interaction of transferrin with its receptor, however, is not involved in this developmental change in uptake.
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Affiliation(s)
- G Chowrimootoo
- Department of Medicine, Royal Free Hospital School of Medicine, London, UK
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Abstract
Dietary iron is present in food both in inorganic forms as ferrous and ferric compounds, and in organic forms, the most important of these being heme iron. The purpose of this review is to evaluate the contributions of both heme and nonheme iron in establishing and maintaining a healthful iron status. The human requirement for iron, bioavailability of heme and nonheme iron, and amounts of heme and nonheme iron in the diet are individually estimated after reviewing the relevant literature in Sections II, III, and IV, respectively. In Section V, the contribution of heme and nonheme iron to human nutrition, as compared to the human requirement for iron (Section II), is estimated after attenuating the amounts of heme and nonheme iron found in the diet (Section IV) by their bioavailabilities (Section III).
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Affiliation(s)
- C E Carpenter
- Department of Nutrition and Food Sciences, Utah State University, Logan 84322-8700
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Sanyal AJ, Shiffmann ML, Hirsch JI, Moore EW. Premicellar taurocholate enhances ferrous iron uptake from all regions of rat small intestine. Gastroenterology 1991; 101:382-9. [PMID: 2065914 DOI: 10.1016/0016-5085(91)90015-d] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Inorganic iron is virtually insoluble at the pH of small intestinal contents. This severe solubility limitation has been partly overcome by intraluminal substances that bind and solubilize iron, thus increasing availability for absorption. While several dietary ligands capable of solubilizing Fe2+ in intestinal lumen have been described, an endogenous binding ligand has not been previously described. It has recently been shown that certain trihydroxy bile acids (taurocholate and glycocholate) show high-affinity premicellar and low-affinity micellar Fe(2+)-binding properties, resulting in the formation of soluble Fe(2+)-bile salt complexes. It was hypothesized that this binding would increase the intraluminal pool of soluble iron, increase delivery of soluble iron to mucosal carriers, and thus enhance intestinal Fe2+ uptake. As a first step toward testing this hypothesis, the effect of taurocholate on Fe2+ uptake from all regions of in vivo rat small intestine is reported. It is shown that taurocholate, at premicellar concentrations, produces a marked, stepwise increase in Fe2+ uptake from all regions of small bowel, with little further increase above the critical micellar concentration. Enhancement of intestinal Fe2+ uptake is a newly described effect, and potential physiological function, of premicellar bile salts.
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Affiliation(s)
- A J Sanyal
- Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond
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Snape S, Simpson RJ. Iron binding to, and release from, the basolateral membrane of mouse duodenal enterocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1074:159-66. [PMID: 2043666 DOI: 10.1016/0304-4165(91)90055-l] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The basolateral membrane of mouse duodenal enterocytes can be selectively labelled in vitro with 59Fe by incubating intact enterocytes with 59Fe(III)-nitrilotriacetate at 0-4 degrees C. It has been proposed that this labelling represents binding to a site important in the transfer of intracellular Fe to the portal plasma (Snape, S., Simpson, R.J. and Peters, T.J. (1990) Cell Biochem. Funct. 8, 107-115). Studies presented here show binding to intact enterocytes in vitro was complete within 1 h and was proportional to enterocyte protein concentration. Binding to enterocytes isolated from both normal and chronically hypoxic mice showed a hyperbolic dependence on medium Fe(III) concentration, consistent with a single class of binding sites. Neither apparent binding constant nor maximal binding were increased by hypoxic exposure of mice, suggesting that the increased in vivo labelling of this site in hypoxia is not due to an increase in affinity or capacity of this site for iron. Release of iron from intact enterocytes, labelled at 0-4 degrees C, was measured at 37 degrees C and 0-4 degrees C. Release of 59Fe was extensive and more rapid at 37 degrees C with highest release to mouse serum. Iron released to serum was found to be bound to transferrin. Prior dialysis of serum against buffer led to complete failure of enterocytes to release iron. Reconstituting serum by adding back the dialysate restores release to levels seen in fresh serum, suggesting that low molecular weight serum components, notably bicarbonate, mediate iron transfer from the basolateral membrane to serum transferrin. The properties of the basolateral membrane iron binding site described here are consistent with a role in the iron transfer process.
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Affiliation(s)
- S Snape
- Department Clinical Biochemistry, Kings College School of Medicine and Dentistry, London, U.K
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Conrad ME, Umbreit JN, Moore EG, Peterson RD, Jones MB. A newly identified iron binding protein in duodenal mucosa of rats. Purification and characterization of mobilferrin. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)34117-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Schümann K. [The role of iron as a deficient element]. ZEITSCHRIFT FUR ERNAHRUNGSWISSENSCHAFT 1989; 28:279-99. [PMID: 2694640 DOI: 10.1007/bf02019391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Iron is an essential trace element. In its heme-form as well as in its non heme-form it is a part of enzymes and hemoproteins. For a safe and adequate dietary intake 10-18 mg of iron are recommended daily. Frequently, this quantity is not available: approximately 20% of the world population is iron-deficient. In this state the enteral transfer capacity for toxic metals, e.g., Cd and Pb, is increased and the adaptation to physical strain as well as the immunological responses are depressed. Alterations of body iron-stores are almost exclusively balanced by adequate adaptation of the enteral iron-transfer capacity. The mechanism of this adaptation process can neither be satisfactorily explained by the "mucosal block hypothesis", nor by the "mucosal transferrin hypothesis". When the time-course of iron storage and its relation to intestinal iron transfer was investigated after i.v. iron administration to iron-deficient rats, the results indicated that the process of adaptation is located in the intestinal mucosa. Intestinal iron loading is decreased in iron deficiency, whereas the iron transfer into the organism is increased. Further investigation is necessary to find out by which mechanism the iron manages to bypass existing mucosal storage capacity in this situation. The geographical distribution of iron deficiency is influenced by a variety of local factors. Still, the paramount causes of iron-deficiency are unbalanced iron losses and the lack of bioavailable iron in the diet. The bioavailability of non heme iron is influenced by the composition of the diet. The effect of promotors of iron absorption, such as meat, amino acids, polycarbonic acids and ascorbate is opposed by the influence of inhibitors, such as bran, soya products, vegetables and egg-dishes. Iron losses are mainly due to blood losses. Thus, the wide distribution of hookworm diseases in tropical areas contributes significantly to the endemic iron-deficiency in these regions. A more physiological loss of iron is caused by menstruation and pregnancy. In small infants the iron-demand of the organism is increased by rapid growth, which in turn increases the intestinal iron transfer. An increased iron-demand can be balanced by an iron-supplemented diet or by pharmaceutical iron compounds. Acute intoxications can be caused by an overdose of such preparations. The pathophysiology and symptoms of acute iron intoxication are summarized. Their frequency has markedly decreased since "childproof" packaging has been introduced for iron-preparations. To meet the increased iron demand of young children, commercial infant formulas are frequently fortified with iron, preferentially with heme-iron.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- K Schümann
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität, München, FRG
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