Iron Bioavailability Research Articles

Strategic design and development of a siderophore mimic: pioneering anticancer therapy via ROS generation and ferroptosis.

We designed a tris-catecholate-based siderophore mimic, H6-T-CATL, to selectively chelate iron(III) from mitochondrial cytochromes and other iron-containing proteins within cellular matrices. This strategic sequestration aims to trigger apoptosis or ferroptosis in cancer cells through the glutathione (GSH)-dependent release of reduced iron and subsequent ROS-mediated cytotoxicity. Synthesis of H6-T-CATL involved precise peptide coupling reactions. Using the Fe(III)-porphyrin model (Fe-TPP-Cl), akin to cytochrome c, we studied H6-T-CATL's ability to extract iron(III), yielding a binding constant (Krel) of 1014 for the resulting iron(III) complex (FeIII-T-CATL)3-. This complex readily underwent GSH-mediated reduction to release bioavailable iron(II), which catalyzed Fenton-like reactions generating hydroxyl radicals (˙OH), confirmed by spectroscopic analyses. Our research underscores the potential of H6-T-CATL to induce cancer cell death by depleting iron(III) from cellular metalloproteins, releasing pro-apoptotic iron(II). Evaluation across various cancer types, including normal cells, demonstrated H6-T-CATL's cytotoxicity through ROS production, mitochondrial dysfunction, and activation of ferroptosis and DNA damage pathways. These findings propose a novel mechanism for cancer therapy, leveraging endogenous iron stores within cells. H6-T-CATL emerges as a promising next-generation anticancer agent, exploiting iron metabolism vulnerabilities to induce selective cancer cell death through ferroptosis induction.

Millets in India: Current Scenario and the Way Forward

Millets are small-seeded plants with a short growing season, low water requirements and high disease resistance. Millet cultivation can potentially improve food security of marginal farmers in areas affected by drought due to climate change. But they are not the preferred crops in other areas because of low yield, short shelf life, low demand and non-remunerative selling price. There had been a progressive reduction in millet consumption over decades partly due to ready availability of subsidized rice and wheat through Public Distribution System (PDS) and partly because of the drudgery in processing of millets and difficulty in making tasty millet preparations. Industrial level processing methods to improve organoleptic properties often result in reduction in fiber content. Carbohydrate protein and fat content of millets are similar to cereals; they are gluten-free. Millets have higher vitamins, calcium, iron, phyto-nutrients and anti-oxidant content as compared to rice and wheat. Bio-availability of calcium and iron in millet-based diets is low because of the high fibre and phytate content. Millet-based meals with high fibre contents lows intestinal transit and provides satiety. Millets contain resistant starch which gets digested and absorbed slowly. The high phytonutrient and anti-oxidant content of millets has been shown to have a protective role in the prevention of non-communicable diseases in animals and may help in reducing CVD risk in human beings. Reintroducing millets into habitual Indian diets may help in the dietary management of over-nutrition, blood sugar in diabetic persons, halt the rise in lipid levels and reduce the risk of cardiovascular diseases.

COMPREHENSIVE ASSESSMENT OF THE QUALITY AND BIOLOGICAL VALUE OF APPLE FRUIT OF DIFFERENT VARIETIES GROWN IN THE CONDITIONS OF THE REPUBLIC OF ADYGEA

Background. Apple fruits are a valuable food product with a unique chemical composition that determines the taste and biological value. The chemical composition of fruits depends on the variety of apples, ripening terms, conditions and place of growth, which makes research relevant in the conditions of a certain region, including the Republic of Adygea, where horticulture not only has deep historical roots, but has been actively reviving and developing in recent decades. with the use of new technologies and the introduction of new varieties.
 Target. Carrying out a comprehensive assessment of the quality and biological value of apple fruits of different varieties grown in the conditions of the Republic of Adygea on the basis of a study of organoleptic, physicochemical and biochemical indicators.
 Materials and methods. The objects of the study were samples of apple fruits of the agricultural enterprise LLC “Yumiks” of 5 varieties: Braeburn, Granny Smith, Idared, Florina, Simirenko, grown in the conditions of the Republic of Adygea. In the samples under study, the determination of organoleptic, physicochemical and biochemical parameters was carried out: soluble solids (SS), titratable acids per malic acid, vitamin C, total sugars, iron, polyphenol oxidase activity, antioxidant activity (AOA). Statistical data processing was carried out in MS Excel 2016.
 Results. For the first time, on the basis of a complex of organoleptic, physicochemical and biochemical methods, studies of apple varieties grown in the Republic of Adygea were carried out: Florina, Idared, Granny Smith, Braeburn, Simirenko. It has been established that the highest index of sensory quality has apple varieties Braeburn and Simirenko, the Braeburn variety is distinguished by a high content of solids and sugars, more harmonious taste, i.e. the optimal ratio of sugar to acid is found in the Braeburn and Florina varieties. The highest content of vitamin C and bioavailable iron is characteristic of Braeburn and Simirenko apple varieties. Polyphenol oxidase activity in Simirenko, Idared and Florina varieties was higher than in samples of other varieties, while a higher AOA value was found in Granny Smith.
 Conclusion. The data obtained by us on the basis of a comprehensive study of apple varieties new to the Republic of Adygea, but already in a certain consumer demand, will allow us to give an objective assessment of their contribution to the biological value of the diets of various population groups, and also, subject to further monitoring studies, can be used gardeners of the Republic of Adygea when expanding the area under varieties with the highest taste and stable indicators of biological value.

NCOA4 requires a [3Fe-4S] to sense and maintain the iron homeostasis

NCOA4 is a selective cargo receptor for ferritinophagy, the autophagic turnover of ferritin (FTH), a process critical for regulating intracellular iron bioavailability. However, how ferritinophagy flux is controlled through NCOA4 in iron-dependent processes needs to be better understood. Here, we show that the C-terminal FTH-binding domain of NCOA4 harbors a [3Fe-4S] binding site with a stoichiometry of approximately one labile [3Fe-4S] cluster per NCOA4 monomer. By analyzing the interaction between NCOA4 and HERC2 ubiquitin ligase or NCOA4 and FTH, we demonstrate that NCOA4 regulates ferritinophagy by sensing the intracellular iron-sulfur-cluster levels. Under iron repletion conditions, HERC2 recognizes and recruits holo-NCOA4 as a substrate for polyubiquitination and degradation, favoring ferritin iron storage. Under iron depletion conditions, NCOA4 exists in the form of apo-protein and binds ferritin to promote the occurrence of ferritinophagy and release iron. Thus, we identify an iron-sulfur cluster [3Fe-4S] as a critical cofactor in determining the fate of NCOA4 in favoring iron storage in ferritin or iron release via ferritinophagy and provide a dual mechanism for selective interaction between HERC2 and [3Fe-4S]-NCOA4 for proteasomal degradation or between ferritin and apo-NCOA4 for ferritinophagy in the control of iron homeostasis.

Effect of Allium spices (garlic and onion) on the bioaccessibility of iron from Moringa oleifera leaves.

The aim of this study was to investigate the effect of garlic and onion, two Allium spices rich in sulfur compounds, on the bioaccessibility of iron from Moringa oleifera leaves. We first quantified anti-nutritional factors in various cooked mixtures of Moringa oleifera leaves and spices, with increasing level of incorporation of garlic or onion. We then assessed the iron bioaccessibility of the various mixtures using a simulated invitro digestion method. Finally, we studied the speciation of bioaccessible iron. Total phenols contents ranging from 801.44 to 903.07 and from 869.78 to 990.72 mg/100 g of dry matter in garlic and onion mixtures, respectively, increased (p < .05) with the level of incorporation of spices. Phytates contents followed the same tendency with values ranging from 1.84 to 2.12 and from 1.75 to 2.02 mg/100 g of dry matter in garlic and onion mixtures, respectively. Although the presence of garlic and onion significantly reduced (p < .05) the total iron content of the mixtures (11.56-11.96 mg/100 g of dry matter), we noticed that bioaccessible iron was significantly higher (p < .05) in spiced mixtures (36.35%-48.40%) compared to the control (23.28%), with the greatest amount found in the mixture containing 10 g of onion. The predominant specie of bioaccessible iron was organic iron, whose amounts in the spiced mixtures (0.59-0.69 mg/L) were all significantly higher (p < .05) than in the control (0.32 mg/L). Globally, the presence of spices produced no significant variation (p > .05) in amounts of ferrous iron, the major inorganic specie of bioaccessible iron. The use of garlic and onion as ingredients could help improving the iron status of populations consuming iron-rich leafy vegetables.

Growth of freshwater cyanobacterium Aphanizomenon sp. ULC602 in different growing and nutrient conditions.

Aphanizomenon sp. ULC602, recently isolated in a Belgian lake, is a filamentous, nitrogen-fixing, freshwater cyanobacterium that is one of the primary producers of cyanotoxins following its bloom formation, causing water contamination. This study aims to evaluate the effects of growing conditions and essential nutrients on the growth of Aphanizomenon sp. ULC602 via its production of chlorophyll-a (Chlo-a). Our results indicated that this bacterium could grow well at temperatures ranging from 18 to 25°C with an optimal pH of 6.0-7.5 under continuous lighting. It grew slowly in the absence of a carbon source or at lower carbon concentrations. The addition of nitrogen from nitrate and urea led to a less than 50% reduction of Chlo-a content compared to the medium lacking nitrogen. The iron bioavailability significantly stimulated the Chlo-a production, but it was saturated by an iron concentration of 0.115 mM. Moreover, a decrease in Chlo-a biomass was observed under sulfur deficiency. The bacterium could not grow well in media containing various phosphorus sources. In conclusion, as the growth and consequent forming bloom of cyanobacteria can be stimulated or inhibited by environmental conditions and eutrophication, our investigation could contribute to further studies to control the blooming of the target bacterium in freshwater.

Preparation, characterization, and bioavailability evaluation of antioxidant phosvitin peptide-ferrous complex.

Iron deficiency anemia (IDA) is one of the commonest global nutritional deficiency diseases, and the low bioavailability of iron is a key contributing factor. The peptide-iron complex could be used as a novel iron supplement to improve iron bioavailability. In this study, antioxidant low molecular weight (<3 kDa) phosvitin peptide (named PP-4) was separated to prepare a phosvitin peptide-ferrous complex (named PP-4-Fe); then the structural conformation of PP-4-Fe was characterized and its bioavailability by in vitro digestion was evaluated. The results showed that PP-4 had good ferrous-binding activity with 96.14 ± 2.86 μg Fe2+ mg-1 , and had a strong antioxidant effect with 995.61 ± 79.75 μmol TE mg-1 in 2,2'-azinobis'3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 62.3 ± 3.95 μmol FeSO4 mg-1 in ferric ion reducing antioxidant power (FRAP). After ferrous binding, the FRAP activity of PP-4-Fe, enhanced by 1.8 times, formed a more ordered structure with an increase in α-helix and decrease in γ-random coil. The ferrous binding sites of PP-4 involved were the amino, carboxyl, imidazole, and phosphate groups. The PP-4-Fe complex displayed excellent gastrointestinal stability and antioxidant effects during digestion. The iron dialysis percentage of PP-4-Fe was 74.59% ± 0.68%, and increased to 81.10% ± 0.89% with the addition of 0.25 times vitamin C (VC). This indicated that PP-4-Fe displayed excellent bioavailability and VC in sufficient quantities had a synergistic effect on improving bioavailability. This study demonstrated that antioxidant phosvitin peptide was an efficient delivery system to protect ferrous ions and suggested that the phosvitin peptide-ferrous complex has strong potential as a ferrous supplement. © 2023 Society of Chemical Industry.

Novel bioanalytical strategy using isotope pattern deconvolution and ICP-QMS for the study of iron incorporation in erythrocytes: An insight to better assessment

Iron is an essential element for human life and its nutritional status in the human body is directly linked to human health. More than 1015 atoms of iron per second are necessary for the maintenance of haemoglobin formation. To predict iron bioavailability three approaches are normally employed: (a) faecal recovery; (b) plasma appearance; and (c) erythrocyte incorporation (the most used). Isotope Pattern Deconvolution (IPD) is a mathematical tool that allows the isolation of distinct isotope signatures from mixtures of natural abundance and enriched tracers. In this work we propose a novel strategy to assess erythrocyte iron incorporation, based on the use of an iron stable isotope (57Fe) and the IPD concept. This strategy allows direct calculation of the exogenous concentration of 57Fe incorporated into RBCs after supplementation. In this way, to determine the mass of iron incorporated into erythrocytes, the unique prediction that must be made is the blood volume, estimate to reproduce the natural dilution of the tracer (57Fe) in the blood. This novel bioanalytical approach was applied for the measurements of iron incorporation and further iron absorption studies in humans, using a group of twelve healthy participants, that should be further evaluated for the assessment of other chemical elements that could be of health concerns and directly impact society.

Effects of iron concentration and DFB (Desferrioxamine-B) on transcriptional profiles of an ecologically relevant marine bacterium

Research into marine iron cycles and biogeochemistry has commonly relied on the use of chelators (including siderophores) to manipulate iron bioavailability. To test whether a commonly used chelator, desferrioxamine B (DFB) caused effects beyond changing the iron-status of cells, cultures of the environmentally relevant marine heterotrophic bacterium, Ruegeria pomeroyii, were grown in media with different concentrations of iron and/or DFB, resulting in a gradient of iron availability. To determine how cells responded, transcriptomes were generated for cells from the different treatments and analyzed to determine how cells reacted to these to perturbations. Analyses were also performed to look for cellular responses specific to the presence of DFB in the culture medium. As expected, cells experiencing different levels of iron availability had different transcriptomic profiles. While many genes related to iron acquisition were differentially expressed between treatments, there were many other genes that were also differentially expressed between different sample types, including those related to the uptake and metabolism of other metals as well as genes related to metabolism of other types of molecules like amino acids and carbohydrates. We conclude that while DFB certainly altered iron availability to cells, it also appears to have had a general effect on the homeostasis of other metals as well as influenced metabolic processes outside of metal acquisition.

Bioaccessibility of iron and zinc content of a traditional pearl millet gruel acidulated with extracts of roselle calyces and tamarind pulp

Iron and zinc deficiencies are a public health concern in the Far-north region of Cameroon, where diets are based on cereals containing inhibitors of minerals’ absorption. This work investigated the effect of acidulating a traditional pearl millet gruel with extracts of roselle calyces and tamarind pulp on iron and zinc bioaccessibility. We first determined pH, titratable acidity, phytates and polyphenols content of decoction and maceration extracts. Phytates, polyphenols and minerals content of the acidulated gruels as well as the bioaccessibility of iron and zinc using a simulated in vitro digestion method were then assessed. Finally, we evaluated the acceptability of the acidulated gruels. The pHs of roselle calyces extracts (2.59 – 2.71) were the lowest (p < 0.05) while phytates (114.61 – 115.72 µg.mL−1) and polyphenols (100.80 – 116.32 µg.mL−1) were more abundant (p < 0.05) in tamarind pulp extracts. There were no significant differences (p ˃ 0.05) in the titratable acidity of all extracts (0.20 – 0.24 g .100 mL−1). Gruels acidulated with decoction and maceration extracts of tamarind pulp were more concentrated (p < 0.05) in phytates (469.66 mg .100 g−1 DM), polyphenols (70.91 mg .100 g−1 DM) and Iron (5.70 mg .100 g−1 DM), respectively. All the acidulated gruels exhibited higher (p < 0.05) bioaccessible minerals with the greatest increases (22.28% for iron and 61.41% for zinc) being found in decoction and maceration extracts of roselle calyces, respectively. No acidulated gruels had a general acceptability score inferior to that of the control. The acidulation of pearl millet gruels with roselle calyces and tamarind pulp extracts could be an efficient and affordable food-based strategy to fight against iron and zinc deficiencies in at-risk populations.

Effects of climate, soil and water source on the distribution of bioavailable iron in low-land paddy soils of Sri Lanka

Iron (Fe) is an essential mineral element of plants. However, the current status of bioavailable Fe in lowland paddy fields in Sri Lanka is not known. This study was conducted to examine the (i) spatial distribution of bioavailable Fe concentration, and (ii) interactive effects of agro-climatic zone (ACZ), soil order, and water source in determining the bioavailable Fe concentration in lowland paddy fields in Sri Lanka. A total of 6003 soil samples representing six ACZs, six soil orders, and three water sources were collected using a stratified random sampling approach. Bioavailable Fe was extracted using 0.01 M CaCl2 and measured using Inductively Coupled Plasma Mass Spectrophotometry. Bioavailable Fe concentration ranged between 0.0003 and 339 mg kg−1 with a mean of 49.4 mg kg−1. Samples collected from the Wet zone, particularly the Wet zone Low country, had higher Fe concentrations than those reported in other ACZs (p < 0.05). Among the soil orders, Histosols, Inceptisols and Ultisols had higher Fe concentrations while Entisols, Alfisols and Vertisols reported lower values (p < 0.05). Paddy fields receiving water from major irrigation systems in Wet zone Low country had more Fe. Moreover, Fe concentration was not correlated with rice crop productivity (p > 0.05). The spatial maps of bioavailable Fe generated in this study could be useful for making area-specific agronomic and administrative decisions based on ACZs, soil orders and water sources used in paddy cultivation in Sri Lanka.

Nutritional Modulation of Hepcidin in the Treatment of Various Anemic States.

Twenty years after its discovery, hepcidin is still considered the main regulator of iron homeostasis in humans. The increase in hepcidin expression drastically blocks the flow of iron, which can come from one's diet, from iron stores, and from erythrophagocytosis. Many anemic conditions are caused by non-physiologic increases in hepcidin. The sequestration of iron in the intestine and in other tissues poses worrying premises in view of discoveries about the mechanisms of ferroptosis. The nutritional treatment of these anemic states cannot ignore the nutritional modulation of hepcidin, in addition to the bioavailability of iron. This work aims to describe and summarize the few findings about the role of hepcidin in anemic diseases and ferroptosis, as well as the modulation of hepcidin levels by diet and nutrients.

Aerobic iron-oxidizing bacteria secrete metabolites that markedly impede abiotic iron oxidation.

Iron is one of the Earth's most abundant elements and is required for essentially all forms of life. Yet, iron's reactivity with oxygen and poor solubility in its oxidized form (Fe3+) mean that it is often a limiting nutrient in oxic, near-neutral pH environments like Earth's ocean. In addition to being a vital nutrient, there is a diversity of aerobic organisms that oxidize ferrous iron (Fe2+) to harness energy for growth and biosynthesis. Accordingly, these organisms rely on access to co-existing Fe2+ and O2 to survive. It is generally presumed that such aerobic iron-oxidizing bacteria (FeOB) are relegated to low-oxygen regimes where abiotic iron oxidation rates are slower, yet some FeOB live in higher oxygen environments where they cannot rely on lower oxygen concentrations to overcome abiotic competition. We hypothesized that FeOB chemically alter their environment to limit abiotic interactions between Fe2+ and O2. To test this, we incubated the secreted metabolites (collectively known as the exometabolome) of the deep-sea iron- and hydrogen-oxidizing bacterium Ghiorsea bivora TAG-1 with ferrous iron and oxygen. We found that this FeOB's iron-oxidizing exometabolome markedly impedes the abiotic oxidation of ferrous iron, increasing the half-life of Fe2+ 100-fold from ∼3 to ∼335 days in the presence of O2, while the exometabolome of TAG-1 grown on hydrogen had no effect. Moreover, the few precipitates that formed in the presence of TAG-1's iron-oxidizing exometabolome were poorly crystalline, compared with the abundant iron particles that mineralized in the absence of abiotic controls. We offer an initial exploration of TAG-1's iron-oxidizing exometabolome and discuss potential key contributors to this process. Overall, our findings demonstrate that the exometabolome as a whole leads to a sustained accumulation of ferrous iron in the presence of oxygen, consequently altering the redox equilibrium. This previously unknown adaptation likely enables these microorganisms to persist in an iron-oxidizing and iron-precipitating world and could have impacts on the bioavailability of iron to FeOB and other life in iron-limiting environments.

Ferritinophagy Is a Druggable Vulnerability of Quiescent Leukemic Stem Cells

Acute myeloid leukemia (AML) poses significant challenges in terms of prognosis and treatment options. Leukemic stem cells (LSCs) contribute to therapy resistance, relapse and adverse outcomes. This study aimed to explore one of the major features of LSCs (e.g. quiescence) and its underlying molecular mechanisms, as well as identify potential targets for therapeutic intervention. Using in vivo cell labeling in patient-derived xenograft (PDX) assays, we identified a quiescent cell subpopulation with high LSC potential. Transcriptomics experiments conducted separately on quiescent and cycling cell subsets revealed gene signatures characteristic of quiescent (Q_AML_UP) and cycling cells (C_AML_UP). Using single-cell RNA sequencing, we identified clusters of quiescent leukemic cell that were highly enriched in gene signatures related to LSCs (Figure 1A). Through a machine learning approach, we identified a gene set highly specific of quiescent cells (named the QS35 gene signature) that emerged as a significant prognostic factor for poor outcomes in independent cohorts of AML patients (Figure 1B). Next, we aimed to identify new vulnerabilities of LSCs by investigating the quiescent subset of leukemic cells. Transcriptomics and proteomics approaches on quiescent vs cycling cells revealed enhanced autophagy within the quiescent subset. Additionally, the transferrin receptor TFRC and ferritin, two key regulators of iron metabolism, exhibited lower expression in the quiescent subpopulations. As intracellular iron availability is tightly regulated by ferritinophagy, a specific form of autophagy leading to the degradation of ferritin, we investigated the coordinated regulation of autophagy and iron metabolism in the quiescent LSC subset. Intriguingly, the intracellular iron pool was lower in quiescent LSCs, particularly in the CD34+CD38- compartment compared to more mature leukemic cells. Moreover, autophagy inhibition selectively induced cytotoxicity in the CD34+CD38- compartment and reduced the frequency of long-term culture-initiating cells (LTC-IC), and these effects were rescued by exogenous iron supply, underscoring the critical role of autophagy in iron bioavailability within the quiescent LSC subpopulation. To target ferritinophagy in this compartment, we depleted NCOA4, the main carrier in ferritinophagy responsible for delivering ferritin-bound iron to the autophagosome, using shRNAs in primary AML samples. Interestingly, NCOA4 was found more expressed in quiescent compared to cycling AML cells. In ex vivo assays, NCOA4 downregulation significantly reduced the frequency of LTC-IC and inhibited the clonogenic capacities of leukemic cells. Furthermore, NCOA4 invalidation abrogated leukemia initiation and self-renewal in serial transplantation experiments in vivo, particularly within the quiescent LSC population (Figure 2A). Additionally, treatment with a novel small molecule inhibitor named compound 9a that disrupts the NCOA4-ferritin interaction, depleted intracellular iron in primary AML cells, reduced their clonogenic potential and LTC-IC frequency ex vivo, and induced cell death specifically within the quiescent CD34+CD38- subset. Importantly, the viability of LSCs treated with compound 9a was rescued by the addition of iron, demonstrating that the cytotoxic effects of this compound were dependent on iron depletion. Notably, compound 9a exhibited minimal toxicity to normal hematopoietic cells ex vivo. In PDX models, in vivo short-term treatment with compound 9a decreased tumor burden and induced cell death within the CD34+CD38- LSC population (Figure 2B). Mechanistically, genetic of chemical inhibition of NCOA4 led to the accumulation of dysfunctional mitochondria, and to the generation of reactive oxygen species especially within the LSCs population. Furthermore, inhibition of NCOA4 by compound 9a decreased mitophagy, strongly suggesting that NCOA4 coordinates ferritinophagy and mitophagy pathways to increase intracellular iron, thereby specifically promoting the survival of LSCs. These findings highlight the critical vulnerability of quiescent LSCs to ferritinophagy. Thus, NCOA4 inhibition represents an innovative therapeutic approach for AML patients.

Short-term acidification promotes diverse iron acquisition and conservation mechanisms in upwelling-associated phytoplankton

Coastal upwelling regions are among the most productive marine ecosystems but may be threatened by amplified ocean acidification. Increased acidification is hypothesized to reduce iron bioavailability for phytoplankton thereby expanding iron limitation and impacting primary production. Here we show from community to molecular levels that phytoplankton in an upwelling region respond to short-term acidification exposure with iron uptake pathways and strategies that reduce cellular iron demand. A combined physiological and multi-omics approach was applied to trace metal clean incubations that introduced 1200 ppm CO2 for up to four days. Although variable, molecular-level responses indicate a prioritization of iron uptake pathways that are less hindered by acidification and reductions in iron utilization. Growth, nutrient uptake, and community compositions remained largely unaffected suggesting that these mechanisms may confer short-term resistance to acidification; however, we speculate that cellular iron demand is only temporarily satisfied, and longer-term acidification exposure without increased iron inputs may result in increased iron stress.

Frozen Clay Minerals as a Potential Source of Bioavailable Iron and Magnetite.

Iron (Fe) is an essential micronutrient that affects biological production. Iron-containing clay minerals are an important source of bioavailable iron. However, the dissolution of iron-containing clay minerals at temperatures below the freezing point has not been investigated. Here, we demonstrate the enhanced reductive dissolution of iron from a clay mineral in ice in the presence of iodide (I-) as the electron donor. The accelerated production of dissolved iron in the frozen state was irreversible, and the freeze concentration effect was considered the main driving force. Furthermore, the formation of magnetite (Fe3O4) after the freezing process was observed using transmission electron microscopy analysis. Our results suggest a new mechanism of accelerated abiotic reduction of Fe(III) in clay minerals, which may release bioavailable iron, Fe(II), and reactive iodine species into the natural environment. We also propose a novel process for magnetite formation in ice. The freezing process can serve as a source of bioavailable iron or act as a sink, leading to the formation of magnetite.

Impact of dust deposition on the growth of marine autotrophic and heterotrophic microorganisms: Evidence from the South China Sea

Aeolian dust can provide nutrients for the ocean and affect the growth of phytoplankton. However, the impacts of dust deposition on autotrophic and heterotrophic microorganisms have rarely been studied. In this study, we conducted two microcosm experiments in the low-nutrient and low-chlorophyll environment of the South China Sea and found that dust did not stimulate the abundance of autotrophic and heterotrophic microorganisms. Our results show that dust contains most of the unreacted iron-bearing minerals, and thus provides limited bioavailable iron and nitrogen for bacterioplankton and phytoplankton growth. These results elucidate the overlooked impacts of the properties of the iron-bearing minerals in aeolian dust on microbial communities, which may play an important role in marine ecosystems and climate change.

Iron Bioavailability in the Extracellular Environment Is More Relevant Than the Intracellular One in Viability and Gene Expression: A Lesson from Oligodendroglioma Cells.

Oligodendroglioma (OG) is a brain tumor that contributes to <1% of brain tumor diagnoses in the pediatric population. Unfortunately, pediatric OG remains without definitive molecular characteristics to aid in diagnosis, and little is known about the tumor microenvironment. Tumor cells' metabolism and proliferation rate are generally higher than those of healthy cells, so their iron demand is also significantly higher. This consideration underlines the great importance of iron for tumor development and progression. In this context, this study aims to evaluate the effect of iron in a cellular in vitro model of human oligodendroglioma brain tumor. Cell morphology, the effect of siderotic medium on cell growth, iron uptake, and the expression of iron-metabolism-related genes were evaluated via optic microscopy, ICP-MS, confocal microscopy, and real-time PCR, respectively. This study underlines the great importance of iron for tumor development and progression and also the possibility of reducing the available iron concentration to determine an antiproliferative effect on OG. Therefore, every attempt can be promising to defeat OG for which there are currently no long-term curative therapies.

Variability in zinc:phosphorous and zinc:silicon ratios and zinc isotope fractionation in Southern Ocean diatoms: Observations from laboratory and field experiments

We studied the impact of iron limitation on zinc uptake and the zinc isotope (δ66Zn) composition for Southern Ocean phytoplankton. We undertook laboratory culture and field incubation experiments, and linked these to in situ depth profiles of dissolved (dZn) and particulate (pZn) zinc collected from three sites in the Southern Ocean. For the laboratory experiments, diatom growth rates, cellular zinc accumulation, and δ66Zn all responded to changes in iron and zinc bioavailability. A significant increase in the cellular quota for zinc (expressed as zinc:phosphorous (Zn:P)) occurred upon iron limitation and zinc enrichment. At the same time, δ66Zn for organic tissues became isotopically light under high zinc and low iron concentrations. The opposite occurred for frustule δ66Zn values. Here δ66Znfrustule-organic for cultured phytoplankton became isotopically heavier under high zinc and low iron concentrations. For senescing and dead cells, Zn:P declined and δ66Zn increased, indicating a loss of isotopically light zinc from organic matter. For field incubation experiments, δ66Znfrustule was isotopically heavier than seawater, except for added zinc treatments. The percentage of zinc associated with frustule material for laboratory and field incubations encompassed a wide range with values between 1 and 57%. Depth profiles of δ66Zn for dZn and pZn varied, with dZn being isotopically lighter than pZn in low dZn concentration subantarctic waters, whereas the opposite occurred in polar waters where dZn was isotopically heavier than pZn at higher dZn concentrations. Our results show that iron and zinc availability regulates the zinc content of phytoplankton and the δ66Zn composition of the Southern Ocean, which is propagated to other parts of the world ocean.

A microalgae docosahexaenoic acid supplement does not modify the influence of sex and diet on iron status in Spanish vegetarians or omnivores: A randomized placebo-controlled crossover study

ObjectivePlant-based diets are accepted as healthy, provided that are well-planned and include supplements. In this context, iron deficiency is a threat, and data from Spanish vegetarians are scarce. The aim of this study was to determine if a microalgae ω-3 supplement rich in docosahexaenoic acid (DHA) affected iron status in this population. MethodsIron biomarkers and nutrient intake (72-h dietary records) were analyzed in 204 usual consumers of lacto-ovo vegetarian (LOV), vegan (VEG), or omnivorous (OMN) diets. A randomized double-blind, placebo-controlled crossover trial was performed in a subgroup (n = 98) to test if a microalgae DHA supplement (250 mg/d for 5 wk) changed iron status. ResultsIron intake was higher in vegetarians than omnivores (P= 0.002), fiber intake was highest in vegans followed by lacto-ovo vegetarians and omnivores, whereas calcium intake was lower in vegans than both lacto-ovo vegetarians and omnivores (all P < 0.001). Women, regardless of diet type, showed lower iron status than men. Erythrocytes, hemoglobin, hematocrit, and serum ferritin were lower in lacto-ovo vegetarians and vegans than omnivores. The prevalence of iron deficiency anemia was low (<10%), but iron depletion (ferritin <15 ng/mL) was higher in lacto-ovo vegetarians than omnivores (P = 0.003). Iron biomarkers were similar in lacto-ovo vegetarians and vegans. The DHA supplementation did not change iron status compared with placebo. ConclusionsSpanish vegetarians had lower iron status than omnivores. Consumption of eggs and dairy products increased the risk for iron deficiency, but a microalgae DHA supplement had no effect. Dietary strategies to increase iron bioavailability in vegetarians, particularly in lacto-ovo vegetarians and women, are recommended.