Pea Ferritin Stability under Gastric pH Conditions Determines the Mechanism of Iron Uptake in Caco-2 Cells

Wheat germ agglutinin modified mixed micelles overcome the dual barrier of mucus/enterocytes for effective oral absorption of shikonin and gefitinib

The combination of shikonin (SKN) and gefitinib (GFB) can reverse the drug resistance of lung cancer cells by affecting energy metabolism. However, the poor solubility of SKN and GFB limits their clinical application because of low bioavailability. Wheat germ agglutinin (WGA) can selectively bind to sialic acid and N-acetylglucosamine on the surfaces of microfold cells and enterocytes, and is a targeted biocompatible material. Therefore, we created a co-delivery micelle system called SKN/GFB@WGA-micelles with the intestinal targeting functions to enhance the oral absorption of SKN and GFB by promoting mucus penetration for nanoparticles via oral administration. In this study, Caco-2/HT29-MTX-E12 co-cultured cells were used to simulate a mucus/enterocyte dual-barrier environment, and HCC827/GR cells were used as a model of drug-resistant lung cancer. We aimed to evaluate the oral bioavailability and anti-tumor effect of SKN and GFB using the SKN/GFB@WGA-micelles system. In vitro and in vivo experimental results showed that WGA promoted the mucus penetration ability of micelles, significantly enhanced the uptake efficiency of enterocytes, improved the oral bioavailability of SKN and GFB, and exhibited good anti-tumor effects by reversing drug resistance. The SKN/GFB@WGA-micelles were stable in the gastrointestinal tract and provided a novel safe and effective drug delivery strategy.

Biofortification of common bean (Phaseolus vulgaris L.) with iron and zinc: Achievements and challenges

Micronutrient deficiencies (hidden hunger), particularly in iron (Fe) and zinc (Zn), remain one of the most serious public health challenges, affecting more than three billion people globally. A number of strategies are used to ameliorate the problem of micronutrient deficiencies and to improve the nutritional profile of food products. These include (i) dietary diversification, (ii) industrial food fortification and supplements, (iii) agronomic approaches including soil mineral fertilisation, bioinoculants and crop rotations, and (iv) biofortification through the implementation of biotechnology including gene editing and plant breeding. These efforts must consider the dietary patterns and culinary preferences of the consumer and stakeholder acceptance of new biofortified varieties. Deficiencies in Zn and Fe are often linked to the poor nutritional status of agricultural soils, resulting in low amounts and/or poor availability of these nutrients in staple food crops such as common bean. This review describes the genes and processes associated with Fe and Zn accumulation in common bean, a significant food source in Africa that plays an important role in nutritional security. We discuss the conventional plant breeding, transgenic and gene editing approaches that are being deployed to improve Fe and Zn accumulation in beans. We also consider the requirements of successful bean biofortification programmes, highlighting gaps in current knowledge, possible solutions and future perspectives.

Digestibility of Protein and Iron Availability from Enriched Legume Sprouts

Plant ferritin is suggested as a good source of iron for human. Usually present in trace amounts, it was induced in legumes seeds by their sprouting in FeSO₄ solution. Fortified sprouts were digested in the in vitro model of the human gastrointestinal tract. ~49% of lupine and ~ 45% of soy proteins were extracted into gastric fluid and next ~ 12% and only ~ 1% into intestine fluid from lupine and soybean, respectively. Gastric digestion released mainly ferrous iron (~ 85% from lupine and ~ 95% in soybean sprouts). Complexed iron constituted ~ 43% of total iron in intestine after lupine digestion and ~ 55% after soybean digestion. Intestine digestion doubled the total iron released from lupine sprouts (from ~ 21% up to 38%), while in soybean it increased from ~ 16% up to ~ 23%. Ferritin presence was confirmed by the specific antibodies in digestive fluids, but it is only partially extracted from sprouts during in vitro digestion.

Absorption of iron from Tegillarca granosa using an in vitro simulated digestion and Caco-2/HepG2 co-culture system

BACKGROUND

Iron-deficiency anemia is one severe micronutrient malnutrition and has captured worldwide attention. This study evaluated the in vitro iron absorption of two iron-binding proteins (hemoglobin and ferritin) from Tegillarca granosa. In addition, the protein structure-iron absorption relationship and the regulatory effect of hepcidin on cellular iron absorption were explored.

RESULTS

Our findings revealed that both hemoglobin and ferritin extracted from T. granosa contained abundant iron-binding sites, as evidenced by stronger peaks in amide I and II regions compared with the two proteins from humans. Less β-sheet (27.67%) structures were found in hemoglobin compared with ferritin (36.40%), probably contributing to its greater digestibility and more release of available iron. This was confirmed by the results of Caco-2/HepG2 cell culture system that showed iron absorption of hemoglobin was 26.10-39.31% higher than that of ferritin with an iron content of 50-150 μmol L^-1 . This high iron absorption of hemoglobin (117.86-174.10 ng mg^-1 ) could also be due to more hepcidin produced by HepG2 cells, thereby preventing ferroportin-mediated iron efflux from Caco-2 cells. In addition, the possible risk of oxidative stress was evaluated in cells post-iron exposure. In comparison with ferrous sulfate, a common iron supplement, Caco-2 cells treated with the iron-binding proteins had a 9.50-25.73% lower level of intracellular reactive oxygen species, indicating the safety of hemoglobin and ferritin.

CONCLUSION

Collectively, the data of this research would be helpful for understanding the key features and potential of developing hemoglobin and ferritin from T. granosa as novel iron supplements. © 2022 Society of Chemical Industry.

The internalization mechanisms and trafficking of the pea albumin in Caco-2 cells

Pea albumin (PA) can reach the intestine in the active form because it is highly resistant to gastric acid and proteolytic enzymes after their oral intake, which can supply various bioactivities. However, there is no detailed knowledge of the intestinal cell uptake about PA. The aim of this work was to study the internalization mechanism and intracellular trafficking route of PA. The uptake of PA-cyanine 5.5 NHS ester (Cy5.5) was a time-dependent and concentration-dependent process in Caco-2 cells. Endocytosis inhibitors or small interfering RNA (siRNA) techniques revealed that the internalization of PA-Cy5.5 was energy-dependent and mediated by caveolin-mediated endocytosis. Furthermore, we observed colocalization of PA-Cy5.5 and its subcellular localization in Caco-2 cells by using confocal laser scanning microscopy, which revealed that the intracellular trafficking process of PA-Cy5.5 was related to endoplasmic reticulum, Golgi, and lysosome. Interestingly, PA can alleviate lipopolysaccharide -induced ER stress, which may be the main reason why pea albumin is anti-inflammatory. Overall, our findings suggest caveolin may be critical for PA uptake in enterocytes and could contribute to explore the bioactivities mechanism of pea albumin in body.

Gastrointestinal Tract Stabilized Protein Delivery Using Disulfide Thermostable Exoshell System

Thermostable exoshells (tES) are engineered proteinaceous nanoparticles used for the rapid encapsulation of therapeutic proteins/enzymes, whereby the nanoplatform protects the payload from proteases and other denaturants. Given the significance of oral delivery as the preferred model for drug administration, we structurally improved the stability of tES through multiple inter-subunit disulfide linkages that were initially absent in the parent molecule. The disulfide-linked tES, as compared to tES, significantly stabilized the activity of encapsulated horseradish peroxidase (HRP) at acidic pH and against the primary human digestive enzymes, pepsin, and trypsin. Furthermore, the disulfide-linked tES (DS-tES) exhibited significant intestinal permeability as evaluated using Caco2 cells. In vivo bioluminescence assay showed that encapsulated Renilla luciferase (rluc) was ~3 times more stable in mice compared to the free enzyme. DS-tES collected mice feces had ~100 times more active enzyme in comparison to the control (free enzyme) after 24 h of oral administration, demonstrating strong intestinal stability. Taken together, the in vitro and in vivo results demonstrate the potential of DS-tES for intraluminal and systemic oral drug delivery applications.

Faba Bean: An Untapped Source of Quality Plant Proteins and Bioactives

Faba beans are emerging as sustainable quality plant protein sources, with the potential to help meet the growing global demand for more nutritious and healthy foods. The faba bean, in addition to its high protein content and well-balanced amino acid profile, contains bioactive constituents with health-enhancing properties, including bioactive peptides, phenolic compounds, GABA, and L-DOPA. Faba bean peptides released after gastrointestinal digestion have shown antioxidant, antidiabetic, antihypertensive, cholesterol-lowering, and anti-inflammatory effects, indicating a strong potential for this legume crop to be used as a functional food to help face the increasing incidences of non-communicable diseases. This paper provides a comprehensive review of the current body of knowledge on the nutritional and biofunctional qualities of faba beans, with a particular focus on protein-derived bioactive peptides and how they are affected by food processing. It further covers the adverse health effects of faba beans associated with the presence of anti-nutrients and potential allergens, and it outlines research gaps and needs.

The role of legume peptides released during different digestion stages in modulating the bioaccessibility of exogenous iron and zinc: An in-vitro study

The effects of legume protein fractions on Fe and Zn bioaccessibility remain equivocal to date, largely due to the protein’s structure and the presence of anti-nutritional compounds. We administered Fe and Zn salts with legume concentrates consisting mainly of albumin or globulin from lupin, pea and faba to in vitro gastrointestinal digestion. Under the fasted intestinal state, faba globulins were found to enhance Fe²⁺ and Zn solubility compared to control salts without legume proteins. Meanwhile, other fractions had no effect or significantly lowered Fe and Zn solubility. Under the fed intestinal state, the presence globulins enhanced Fe solubility versus the control, where protein solubilization due to high bile concentration likely played a role in circumventing precipitation. The lupin albumin fraction significantly enhanced Fe²⁺ and Zn solubility, whilst other fractions generally reduced Zn solubility under fed state. Our results highlight the complex role of legume proteins towards Fe and Zn solubility.

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Bioaccessibility of Fe/Zn mineral salts were examined with and without legume protein fractions.

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Bile concentrations and/or digestion time affected Fe³⁺/Fe²⁺ and Zn solubility in presence of legume protein fractions.

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Globulins consistently enhanced Fe²⁺, but not Fe³⁺ solubility during the high-bile (fed state) intestinal digestion phase.

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Both enhancements and reductions in Zn solubility were reflected by different legume fractions.

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A non-linear relationship was observed between soluble protein and Fe/Zn bioaccessibility during simulated digestion.

Iron

Iron deficiency anemia affects approximately one-third of the world's population, and about half the cases are due to iron deficiency. The latest research on iron metabolism published in original articles and systematic reviews is described, and references to recent reviews provided. The topics include dietary sources and bioavailability, iron homeostasis, functions of iron in the body, and biomarkers of status. The consequences of iron deficiency and excess are discussed, with particular focus on vulnerable populations such as pregnant women, infants and the elderly. The newest dietary recommendations, including dietary reference values and food based dietary guidelines, are briefly summarized, followed by the latest developments in food fortification and iron supplementation.

Perspectives on the genetic improvement of health- and nutrition-related traits in pea

Pea (Pisum sativum L.) is a widely grown pulse crop that is a source of protein, starch and micronutrients in both human diets and livestock feeds. There is currently a strong global focus on making agriculture and food production systems more sustainable, and pea has one of the smallest carbon footprints of all crops. Multiple genetic loci have been identified that influence pea seed protein content, but protein composition is also important nutritionally. Studies have previously identified gene families encoding individual seed protein classes, now documented in a reference pea genome assembly. Much is also known about loci affecting starch metabolism in pea, with research especially focusing on improving concentrations of resistant starch, which has a positive effect on maintaining blood glucose homeostasis. Diversity in natural germplasm for micronutrient concentrations and mineral hyperaccumulation mutants have been discovered, with quantitative trait loci on multiple linkage groups identified for seed micronutrient concentrations. Antinutrients, which affect nutrient bioavailability, must also be considered; mutants in which the concentrations of important antinutrients including phytate and trypsin inhibitors are reduced have already been discovered. Current knowledge on the genetics of nutritional traits in pea will greatly assist with crop improvement for specific end uses, and further identification of genes involved will help advance our knowledge of the control of the synthesis of seed compounds.

Biofortification and bioavailability of Zn, Fe and Se in wheat: present status and future prospects

Knowledge of genetic variation, genetics, physiology/molecular basis and breeding (including biotechnological approaches) for biofortification and bioavailability for Zn, Fe and Se will help in developing nutritionally improved wheat. Biofortification of wheat cultivars for micronutrients is a priority research area for wheat geneticists and breeders. It is known that during breeding of wheat cultivars for productivity and quality, a loss of grain micronutrient contents occurred, leading to decline in nutritional quality of wheat grain. Keeping this in view, major efforts have been made during the last two decades for achieving biofortification and bioavailability of wheat grain for micronutrients including Zn, Fe and Se. The studies conducted so far included evaluation of gene pools for contents of not only grain micronutrients as above, but also for phytic acid (PA) or phytate and phytase, so that, while breeding for the micronutrients, bioavailability is also improved. For this purpose, QTL interval mapping and GWAS were carried out to identify QTLs/genes and associated markers that were subsequently used for marker-assisted selection (MAS) during breeding for biofortification. Studies have also been conducted to understand the physiology and molecular basis of biofortification, which also allowed identification of genes for uptake, transport and storage of micronutrients. Transgenics using transgenes have also been produced. The breeding efforts led to the development of at least a dozen cultivars with improved contents of grain micronutrients, although land area occupied by these biofortified cultivars is still marginal. In this review, the available information on different aspects of biofortification and bioavailability of micronutrients including Zn, Fe and Se in wheat has been reviewed for the benefit of those, who plan to start work or already conducting research in this area.

Investigating the effects of differently produced synthetic amorphous silica (E 551) on the integrity and functionality of the human intestinal barrier using an advanced in vitro co-culture model

E 551, also known as synthetic amorphous silica (SAS), is the second most produced food additive. However, according to the re-evaluation of E 551 by the European Food Safety Authority (EFSA) in 2018, the amount of available data on the oral toxicity of food grade E 551 is still insufficient for reliable risk assessment. To close this gap, this study aimed to investigate six food-grade SAS with distinct physicochemical properties on their interaction with the intestinal barrier using advanced in vitro intestinal co-cultures and to identify potential structure-activity relationships. A mucus-secreting Caco-2/HT-29/Raji co-culture model was treated with up to 50 µg/ml SAS for 48 h, which represents a dose range relevant to dietary exposure. No effects on cell viability, barrier integrity, microvilli function or the release of inflammatory cytokine were detected after acute exposure. Slight biological responses were observed for few SAS materials on iron uptake and gene expression levels of mucin 1 and G-protein coupled receptor 120 (GPR120). There was no clear correlation between SAS properties (single or combined) and the observed biological responses. Overall, this study provides novel insights into the short-term impact of food-relevant SAS with distinct characteristics on the intestinal epithelium including a range of intestine-specific functional endpoints. In addition, it highlights the importance of using advanced intestinal co-cultures embracing relevant cell types as well as a protective mucus barrier to achieve a comprehensive understanding of the biological response of food additives at the intestinal barrier in vitro.

The Impact of Low-Level Iron Supplements on the Faecal Microbiota of Irritable Bowel Syndrome and Healthy Donors Using In Vitro Batch Cultures

Ferrous iron supplementation has been reported to adversely alter the gut microbiota in infants. To date, the impact of iron on the adult microbiota is limited, particularly at low supplementary concentrations. The aim of this research was to explore the impact of low-level iron supplementation on the gut microbiota of healthy and Irritable Bowel Syndrome (IBS) volunteers. Anaerobic, pH-controlled in vitro batch cultures were inoculated with faeces from healthy or IBS donors along with iron (ferrous sulphate, nanoparticulate iron and pea ferritin (50 μmol⁻¹ iron)). The microbiota were explored by fluorescence in situ hybridisation coupled with flow cytometry. Furthermore, metabolite production was assessed by gas chromatography. IBS volunteers had different starting microbial profiles to healthy controls. The sources of iron did not negatively impact the microbial population, with results of pea ferritin supplementation being similar to nanoparticulate iron, whilst ferrous sulphate led to enhanced Bacteroides spp. The metabolite data suggested no shift to potentially negative proteolysis. The results indicate that low doses of iron from the three sources were not detrimental to the gut microbiota. This is the first time that pea ferritin fermentation has been tested and indicates that low dose supplementation of iron is unlikely to be detrimental to the gut microbiota.

Genetically Modified Plants: Nutritious, Sustainable, yet Underrated

Combating malnutrition is one of the greatest global health challenges. Plant-based foods offer an assortment of nutrients that are essential for adequate nutrition and can promote good health. Unfortunately, the majority of widely consumed crops are deficient in some of these nutrients. Biofortification is the umbrella term for the process by which the nutritional quality of food crops is enhanced. Traditional agricultural breeding approaches for biofortification are time consuming but can enhance the nutritional value of some foods; however, advances in molecular biology are rapidly being exploited to biofortify various crops. Globally, genetically modified organisms are a controversial topic for consumers and governmental agencies, with a vast majority of people apprehensive about the technology. Golden Rice has been genetically modified to contain elevated β-carotene concentrations and is the bellwether for both the promise and angst of agricultural biotechnology. Although there are numerous other nutritional targets of genetically biofortified crops, here I briefly summarize the work to elevate iron and folate concentrations. In addition, the possibility of using modified foods to affect the gut microbiota is examined. For several decades, plant biotechnology has measured changes in nutrient concentrations; however, the bioavailability of nutrients from many biofortified crops has not been demonstrated.

High stability of plant-expressed virus-like particles of an insect virus in artificial gastric and intestinal fluids

The harsh conditions of the gastro-intestinal (GI) milieu pose a major barrier to the oral delivery of protein nanocages. Here we studied the stability of Nudaurelia capensis omega virus (NωV) virus-like particles (VLPs) in simulated GI fluids. NωV VLPs capsids and procapsids were transiently expressed in plants, the VLPs were incubated in various simulated GI fluids and their stability was determined by gel electrophoresis, density gradient ultracentrifugation and transmission electron microscopy (TEM). The results showed that the capsids were highly resistant to simulated gastric fluids at pH ≥ 3. Even under the harshest conditions, which consisted of a pepsin solution at pH 1.2, NωV capsids remained assembled as VLPs, though some digestion of the coat protein occurred. Moreover, 80.8% (±10.2%) stability was measured for NωV capsids upon 4 h incubation in simulated intestinal fluids. The high resistance of this protein cage to digestion and denaturation can be attributed to its distinctively compact structure. The more porous form of the VLPs, the procapsid, was less stable under all conditions. Our results suggest that NωV VLPs capsids are likely to endure transit through the GI tract, designating them as promising candidate protein nanocages for oral drug delivery.

Reminiscences of my life as a nutritionist-and looking to the future

In this invited article for the Crystal Ball series, I have tried to briefly cover my undergraduate and post-graduate training and subsequent career in nutrition, and end with some thoughts about the future. It has not been possible to give a comprehensive account of my many years of nutrition research, so I have selected a few events that might amuse readers. Also, due to the lack of space, I have been unable to mention all the wonderful colleagues and friends with whom I have interacted, but, if they read this article, they know who they are. Unfortunately, a growing number are no longer with us and I would like to pay tribute to them and their important contribution to human nutrition.

Structural Requirement of Casein Peptides for Transcytosis through the Caco-2 Cell Monolayer: Hydrophobicity and Charge Property Affect the Transport Pathway and Efficiency

Casein is a rich source of bioactive peptides with complete amino acid composition. In this study, the casein peptides identified in our previous study with different hydrophobicities and charge properties were employed to investigate the transport efficiency via the transcytosis pathway across Caco-2 cell monolayers. Results revealed that the apparent permeability coefficient (P_app) values of transcytosis exhibited a linear correlation with a pI of positively charged peptides during bidirectional transport. A similar law was found as for the peptides with different hydrophobicities. The transcytosis route of Pep-II to Pep-VII appears to be the clathrin- and caveolin-independent transcytosis pathway as well as caveolae-mediated transcytosis pathway, showing a linear correlation with P_app values, respectively. Additionally, no direct correlation was shown between the hydrophobicity of peptides and clathrin-mediated transcytosis. Our results help to increase the bioaccessibility of peptide drugs across intestinal mucosa by developing strategies to alter the physicochemical properties without changing bioactivity.

Improving pulse crops as a source of protein, starch and micronutrients

Pulse crops have been known for a long time to have beneficial nutritional profiles for human diets but have been neglected in terms of cultivation, consumption and scientific research in many parts of the world. Broad dietary shifts will be required if anthropogenic climate change is to be mitigated in the future, and pulse crops should be an important component of this change by providing an environmentally sustainable source of protein, resistant starch and micronutrients. Further enhancement of the nutritional composition of pulse crops could benefit human health, helping to alleviate micronutrient deficiencies and reduce risk of chronic diseases such as type 2 diabetes. This paper reviews current knowledge regarding the nutritional content of pea (Pisum sativum L.) and faba bean (Vicia faba L.), two major UK pulse crops, and discusses the potential for their genetic improvement.

Iron Biofortification of Staple Crops: Lessons and Challenges in Plant Genetics

Plants are the ultimate source of iron in our diet, either directly as staple crops and vegetables or indirectly via animal fodder. Increasing the iron concentration of edible parts of plants, known as biofortification, is seen as a sustainable approach to alleviate iron deficiency which is a major global health issue. Advances in sequencing and gene technology are accelerating both forward and reverse genetic approaches. In this review, we summarize recent progress in iron biofortification using conventional plant breeding or transgenics. Interestingly, some of the gene targets already used for transgenic approaches are also identified as genetic factors for high iron in genome-wide association studies. Several quantitative trait loci and transgenes increase both iron and zinc, due to overlap in transporters and chelators for these two mineral micronutrients. Research efforts are predominantly aimed at increasing the total concentration of iron but enhancing its bioavailability is also addressed. In particular, increased biosynthesis of the metal chelator nicotianamine increases iron and zinc levels and improves bioavailability. The achievements to date are very promising in being able to provide sufficient iron in diets with less reliance on meat to feed a growing world population.