Iron bioavailability of maize hemoglobin in a Caco-2 cell culture model

A systematic in silico report on iron and zinc proteome of Zea mays

Zea mays is an essential staple food crop across the globe. Maize contains macro and micronutrients but is limited in essential mineral micronutrients such as Fe and Zn. Worldwide, serious health concerns have risen due to the deficiencies of essential nutrients in human diets, which rigorously jeopardizes economic development. In the present study, the systematic in silico approach has been used to predict Fe and Zn binding proteins from the whole proteome of maize. A total of 356 and 546 putative proteins have been predicted, which contain sequence and structural motifs for Fe and Zn ions, respectively. Furthermore, the functional annotation of these predicted proteins, based on their domains, subcellular localization, gene ontology, and literature support, showed their roles in distinct cellular and biological processes, such as metabolism, gene expression and regulation, transport, stress response, protein folding, and proteolysis. The versatile roles of these shortlisted putative Fe and Zn binding proteins of maize could be used to manipulate many facets of maize physiology. Moreover, in the future, the predicted Fe and Zn binding proteins may act as relevant, novel, and economical markers for various crop improvement programs.

Mass spectrometry-based analytical developments to link iron speciation to iron bioavailability in maize

A sequential fractionation procedure based on (i) water extraction, (ii) hexane extraction, (iii) saccharification, and (iv) proteolysis was developed to provide the first ever data on the molecular distribution of iron in maize. This was completed by the operational determination of the iron bioavailability using an in-vitro simulated model for gastro-intestinal digestion. The coupling of hydrophilic interaction chromatography (HILIC) and size exclusion chromatography (SEC) with the parallel detection by inductively coupled plasma mass spectrometry (ICP-MS) and high resolution electrospray mass spectrometry (HR-ESI-MS) allowed the identification of water-soluble Fe(III)-mugineate, Fe(III)-(citrate)₂, and Fe(III)₂-(phytate)₂. The procedures were applied to study some well characterized maize varieties having shown previously differences in iron bioavailability during cell culture and animal model feeding studies. The combined analytical methods developed in this work could unambiguously discriminate low from high Fe bioavailable seeds in these closely related maize varieties.

Evaluation of iron transport from ferrous glycinate liposomes using Caco-2 cell model

Background

Iron fortification of foods is currently a strategy employed to fight iron deficiency in countries. Liposomes were assumed to be a potential carrier of iron supplements.

Objective

The objective of this study was to investigate the iron transport from ferrous glycinate liposomes, and to estimate the effects of liposomal carriers, phytic acid, zinc and particle size on iron transport using Caco-2 cell models.

Methods

Caco-2 cells were cultured and seeded in DMEM medium. Minimum essential medium was added to the basolateral side. Iron liposome suspensions were added to the apical side of the transwell.

Results

The iron transport from ferrous glycinate liposomes was significantly higher than that from ferrous glycinate. In the presence of phytic acid or zinc ion, iron transport from ferrous glycinate liposomes and ferrous glycinate was evidently inhibited, and iron transport decreased with increasing phytic acid concentration. Iron transport was decreased with increase of particle size increasing of ferrous glycinate liposome.

Conclusion

Liposomes could behave as more than a simple carrier, and iron transport from liposomes could be implemented via a mechanism different from the regulated non-heme iron pathway.

Biomimetic Gastrointestinal Tract Functions for Metal Absorption Assessment in Edible Plants: Comparison to In Vivo Absorption

A biomimetic gastrointestinal tract, including in vitro digestion and biomimetic biomembrane extraction, has been proposed for absorption assessment of metals from edible plants. However, its validity is still unknown. Herein, two species of edible plants, Anoectochilus roxburghii and Radix astragali, were selected and digested in a bionic mouth, stomach, and intestine, and then trace metals (Cr, Mn, Fe, Ni, Cu, Zn, Se, Sr, As, and Pb) were transformed to their final metal species. To check model predictability, in vitro and in vivo metal absorption were imitated and tested by monolayer liposome extraction and rat stomach or single-pass duodenal intestine, respectively. A strong correlation was established between in vivo and in vitro metal absorption ratios, with 0.89 > R² > 0.66, and a significant relationship (p < 0.05) was exhibited for stomach, intestine, two plant species, and 10 metal species. Our biomimetic system could be used as low-cost alternatives to animal and clinical studies for multi-metal absorption.

In Vitro Iron Availability from Insects and Sirloin Beef

Interest in the consumption of insects (entomophagy) as an alternative environmentally sustainable source of protein in the diet of humans has recently witnessed a surge. Knowledge of the nutrient composition and, in particular, the bioavailability of minerals from insects is currently sparse. This study evaluated the availability of Fe, Ca, Cu, Mg, Mn, and Zn from four commonly eaten insects and compared these to sirloin beef. Soluble iron from the samples was measured by inductively coupled plasma optical emission spectrometry (ICP-OES). Iron bioavailability was determined using an in vitro simulated peptic-pancreatic digestion, followed by measurement of ferritin (a surrogate marker for iron absorption) in Caco-2 cells. Cricket and sirloin beef had comparably higher levels of Fe, Ca, and Mn than grasshopper, meal, and buffalo worms. However, iron solubility was significantly higher from the insect samples than from beef. The complementation of whole-wheat flour with insect or beef protein resulted in overall decreases in mineral content and iron solubility in the composite mixtures. Collectively, the data show that grasshopper, cricket, and mealworms contain significantly higher chemically available Ca, Cu, Mg, Mn, and Zn than sirloin. However, buffalo worms and sirloin exhibited higher iron bioavailability comparable to that of FeSO₄. Commonly consumed insect species could be excellent sources of bioavailable iron and could provide the platform for an alternative strategy for increased mineral intake in the diets of humans.

Micromilling enhances iron bioaccessibility from wholegrain wheat

Cereals constitute important sources of iron in human diet; however, much of the iron in wheat is lost during processing for the production of white flour. This study employed novel food processing techniques to increase the bioaccessibility of naturally occurring iron in wheat. Iron was localized in wheat by Perl's Prussian blue staining. Soluble iron from digested wheat flour was measured by a ferrozine spectrophotometric assay. Iron bioaccessibility was determined using an in vitro simulated peptic-pancreatic digestion, followed by measurement of ferritin (a surrogate marker for iron absorption) in Caco-2 cells. Light microscopy revealed that iron in wheat was encapsulated in cells of the aleurone layer and remained intact after in vivo digestion and passage through the gastrointestinal tract. The solubility of iron in wholegrain wheat and in purified wheat aleurone increased significantly after enzymatic digestion with Driselase, and following mechanical disruption using micromilling. Furthermore, following in vitro simulated peptic-pancreatic digestion, iron bioaccessibility, measured as ferritin formation in Caco-2 cells, from micromilled aleurone flour was significantly higher (52%) than from whole aleurone flour. Taken together our data show that disruption of aleurone cell walls could increase iron bioaccessibility. Micromilled aleurone could provide an alternative strategy for iron fortification of cereal products.