Iron and zinc bioavailability in Caco-2 cells: Influence of caseinophosphopeptides

Recent progress in the preparation of bioactive peptides using simulated gastrointestinal digestion processes

Bioactive peptides (BAPs) represent a unique class of peptides known for their extensive physiological functions and their role in enhancing human health. In recent decades, owing to their notable biological attributes such as antioxidant, antihypertensive, antidiabetic, and anti-inflammatory activities, BAPs have received considerable attention. Simulated gastrointestinal digestion (SGD) is a technique designed to mimic physiological conditions by adjusting factors such as digestive enzymes and their concentrations, pH levels, digestion duration, and salt content. Initially established for analyzing the gastrointestinal processing of foods or their constituents, SGD has recently become a preferred method for generating BAPs. The BAPs produced via SGD often exhibit superior biological activity and stability compared with those of BAPs prepared via other methods. This review offers a comprehensive examination of the recent advancements in BAP production from foods via SGD, addressing the challenges of the method and outlining prospective directions for further investigation.

A Comprehensive Review of Self-Assembled Food Protein-Derived Multicomponent Peptides: From Forming Mechanism and Structural Diversity to Applications

Food protein-derived multicomponent peptides (FPDMPs) are a natural blend of numerous peptides with various bioactivities and multiple active sites that can assume several energetically favorable conformations in solutions. The remarkable structural characteristics and functional attributes of FPDMPs make them promising codelivery carriers that can coassemble with different bioactive ingredients to induce multidimensional structures, such as fibrils, nanotubes, and nanospheres, thereby producing specific health benefits. This review offers a prospective analysis of FPDMPs-based self-assembly nanostructures, focusing on the mechanism of formation of self-assembled FPDMPs, the internal and external stimuli affecting peptide self-assembly, and their potential applications. In particular, we introduce the exciting prospect of constructing functional materials through precursor template-induced self-assembly of FPDMPs, which combine the bioactivity and self-assembly capacity of peptides and could dramatically broaden the functional utility of peptide-based materials.

Novel Casein-Derived Peptide-Zinc Chelate: Zinc Chelation and Transepithelial Transport Characteristics

Casein-derived peptides are recognized as promising candidates for improving zinc bioavailability through the form of a peptide-zinc chelate. In the present work, a novel 11-residue peptide TEDELQDKIHP identified from casein hydrolysate in our previous study was synthesized to investigate the zinc chelation characteristics. Meanwhile, the digestion stability and transepithelial transport of TEDELQDKIHP-Zn were also investigated. The obtained results indicated that the carboxyl groups (from Asp and Glu), amino groups (from Lys and His), pyrrole nitrogen group of Pro, and imidazole nitrogen group of His were responsible for zinc chelation. The complexation with zinc resulted in a more ordered structure of TEDELQDKIHP-Zn. In terms of digestion stability, the chelate of TEDELQDKIHP-Zn could remain stable to a large extent after gastric (78.54 ± 0.14%) and intestinal digestion (70.18 ± 0.17%). Moreover, TEDELQDKIHP-Zn was proven to be a well-absorbed biological particle with a P_app value higher than 1 × 10^-6 cm/s, and it could be transported across the intestine epithelium through transcytosis. TEDELQDKIHP-Zn exhibited more bioavailable effects on zinc absorption and ALP activity than inorganic zinc sulfate.

Zinc nutrition and dietary zinc supplements

As the second most abundant trace element in the human body, zinc nutrition is constantly a hot topic. More than one-third population is suffering zinc deficiency, which results in various types of diseases or nutritional deficiencies. Traditional ways of zinc supplementation seem with low absorption rates and significant side effects. Zinc supplements with dietary components are easily accessible and improve zinc utilization rate significantly. Also, mechanisms of maintaining zinc homeostasis are of broad interest. The present review focuses on zinc nutrition in human health in inductive methods. Mainly elaborate on different diseases relating to zinc disorder, highlighting the impact on the immune system and the recent COVID-19. Then raise food-derived zinc-binding compounds, including protein, peptide, polysaccharide, and polyphenol, and also analyze their possibilities to serve as zinc complementary. Finally, illustrate the way to maintain zinc homeostasis and the corresponding mechanisms. The review provides data information for maintaining zinc homeostasis with the food-derived matrix.

Characterization of a synthetic zinc-chelating peptide from sea cucumber (Stichopus japonicus) and its gastrointestinal digestion and absorption in vitro

BACKGROUND

Zinc absorption in intestinal system could be strongly affected by the gastrointestinal digestion and absorption of zinc-chelating peptides serving as zinc carriers. In this study, a novel zinc-chelating sea cucumber synthetic peptide (SCSP) was synthesized to estimate its gastrointestinal digestion and promotive effect of zinc absorption in vitro.

RESULTS

Analysis of isothermal titration calorimetry suggested that the binding of SCSP and zinc (N ≈ 1) was exothermic, with relatively weak binding affinity (K = 1.0 × 10^-3  mol L^-1 ). The formation of SCSP-Zn complexes brought morphological changes to the peptides confirmed by scanning electron microscopy (SEM), which also indicated 6.88% of the existence of zinc element. In addition, the SCSP-Zn complexes remained stable under simulated human gastrointestinal digestion. In an in vitro study, the SCSP-Zn complex could successfully transport through the intestinal membrane in the model of everted rat gut sacs (nearly 7.5 μM cm^-2 ) as well as Caco-2 cells where the zinc transport reached 0.0014 mg mL^-1 carried by SCSP. Fluorescence staining experiments revealed free zinc accumulation inside the tissues and cells treated with the SCSP-Zn complex.

CONCLUSIONS

The chelation SCSP-Zn had the promotion ability of zinc absorption in vitro and ex vivo experiments, which suggested a theoretical basis for the design and production of effective zinc chelating peptides as zinc carriers to improve zinc bioavailability. © 2022 Society of Chemical Industry.

Iron delivery systems for controlled release of iron and enhancement of iron absorption and bioavailability

Iron deficiency is a global nutritional problem, and adding iron salts directly to food will have certain side effects on the human body. Therefore, there is growing interest in food-grade iron delivery systems. This review provides an overview of iron delivery systems, with emphasis on the controlled release of iron during gastrointestinal digestion, as well as the enhancement of iron absorption and bioavailability. Iron-bearing proteins are easily degraded by digestive enzymes and absorbed through receptor-mediated endocytosis. Instead, protein aggregates are slowly degraded in the stomach, which delays iron release and serves as a potential iron supplement. Amino acids, peptides and polysaccharides can bind iron through iron binding sites, but the formed compounds are prone to dissociation in the stomach. Moreover, peptides and polysaccharides can deliver iron by mediating the formation of ferric oxyhydroxide which is absorbed through endocytosis or bivalent transporter 1. In addition, liposomes are unstable during gastric digestion and iron is released in large quantities. Complexes formed by polysaccharides and proteins, and microcapsules formed by polysaccharides can delay the release of iron in the gastric environment and prolong iron release in the intestinal environment. This review is conducive to the development of iron functional ingredients and dietary supplements.

Preparation of casein phosphopeptides calcium complex and the promotion in calcium cellular uptake through transcellular transport pathway

This study evaluated the stability of casein phosphopeptides (CPP) and obtained peptide-calcium complex by heating and chelating the peptide with CaCl₂ in a neutral solution. To assess the bioavailability of various calcium formulations, the calcium transport models were established in Caco-2 cells, and the transcellular transport pathways of various calcium formulations were studied by RT-PCR and Western blotting. Results of circular dichroism showed that CPP was a stable polypeptide. The ultraviolet absorption spectrum and Fourier transform-infrared spectrum (FT-IR) indicated that calcium could be chelated by carboxyl oxygen and amino nitrogen atoms of CPP to form peptide calcium chelate, and the calcium bioavailability of peptide calcium chelate was significantly higher than that of CaCl₂ , calcium l-aspartate, and casein phosphopeptides mixed with CaCl₂ . Four calcium sources increased the expression of TRPV5 and TRPV6 genes and proteins. The study intended to provide a basis for developing a novel calcium supplement. PRACTICAL APPLICATIONS: This paper examined the bioavailability of casein phosphopeptides calcium complex, CaCl₂ , calcium l-aspartate, and casein phosphopeptides mixed with CaCl₂ in Caco-2 cells, and the mechanisms were detected by western blotting. The results provide theoretical knowledge for the selection of calcium supplement raw materials and lay a foundation for the development of compound calcium preparations and drugs in the future.

Current findings support the potential use of bioactive peptides in enhancing zinc absorption in humans

More than two billion people around the world are affected by zinc deficiency, mainly due to the inadequate intake and absorption of zinc. Based on recent research findings, the bioactive peptides could potentially be used to combat zinc deficiency particularly due to their Zinc chelating ability. The main aim of this review was to present current findings, supporting the potential use of bioactive peptides based on their ability to enhance zinc absorption. In-vivo, in-vitro, and ex-vivo studies have demonstrated that zinc chelating peptides can enhance the retention, transportation, and absorption of zinc. Comparative studies on zinc bioavailability from protein hydrolysates and zinc salts have demonstrated that the protein hydrolysates-zinc complexes are more bioavailable than the zinc salts. Data from the structure-function relationship of zinc chelating peptides suggest that the zinc chelating capacities of peptides increase in the following order; the position of zinc chelator > zinc chelator strength > abundance of zinc chelators > net charge > molecular weight. In addition, the transport mechanism of peptide-zinc complex is hypothesized, and the potential use of bioactive peptides based on their safety and taste and limitations to their commercialization are also discussed.

Antarctic krill-derived peptides with consecutive Glu residues enhanced iron binding, solubility, and absorption

Three peptides containing three glutamic acid (Glu) residues at different positions derived from Antarctic krill were obtained to investigate their iron-binding properties, digestive stability, and effectiveness on enhancing iron solubility and absorption. Results indicated that Fe2+ bound to the carbonyl, carboxyl, or hydroxyl groups of DELEDSLER, EEEFDATR, and DTDSEEEIR at stoichiometric ratios of 0.453, 0.466, and 0.490, respectively. DTDSEEEIR with three consecutive Glu in the middle of the sequence possessed higher iron-binding ability and iron release potential than EEEFDATR with three consecutive Glu in the N-terminal, and DELEDSLER with three discontinuous Glu showed the lowest values. Although EEEFDATR showed remarkably lower digestion stability than DTDSEEEIR, the effect of EEEFDATR-iron on iron solubility and absorption was comparable to that of DTDSEEEIR-iron, but better than that of DELEDSLER-iron and FeSO4. Thus, peptides with consecutive Glu have the potential as an effective iron carrier to improve iron absorption.

Prevalence and approaches to manage iron deficiency anemia (IDA)

Iron is a vital micronutrient required for growth and development at all stages of human life. Its deficiency is the primary cause of anemia that poses a significant global health problem and challenge for developing countries. Various risks are involved during iron deficiency anemia (IDA), such as premature delivery, low birth weight, etc. Further, it affects children's cognitive functioning, delays motor development, hampers physical performance and quality of life. It also speeds up the morbidity and mortality rate among women. The major reasons accountable are elevated iron demand in diet, socio-economic status, and disease condition. Various strategies have been adopted to reduce the IDA occurrence, such as iron supplementation, iron fortificants salts, agronomic practices, dietary diversification, biofortification, disease control measures, and nutritional education. Usually, the staple food groups for fortification are considered, but the selection of food fortificants and their combination must be safe for the consumers and not alter the finished product's stability and acceptability. Genetically modified breeding practices also increase the micronutrient levels of cereal crops. Therefore, multiple strategies could be relied on to combat IDA.

Delivery systems for improving iron uptake in anemia

Anemia poses a threat to a broad population globally as depleted hemoglobin leads to a plethora of conditions, and the most common cause includes iron deficiency. Iron is an essential element important for erythropoiesis, DNA synthesis, protection of the immune system, energy production, and cognitive function and hence should be maintained at appropriate levels. Various proteins are involved in transporting and absorption of iron, activation of heme synthesis, and RBC production that could be possible targets to improve iron delivery. Oral supplementation of iron either from dietary or synthetic sources has been the frontline therapy for treating iron deficiency in anemia. At the same time, intravenous administration is provided in chronic anemia, such as chronic kidney diseases (CKD). This review focuses on the strategies developed to overcome the disadvantages of available iron therapies and increase iron absorption and uptake in the body to restore iron content. Nanotechnology combined with the food fortification processes gained attention as they help develop new delivery systems to improve iron uptake by enterocytes. Furthermore, naturally obtained products such as polysaccharides, peptides, proteins, and new synthetic molecules have been used in fabrication of iron-carrier systems. The establishment of transdermal iron delivery systems such as microneedle arrays or iontophoresis, or the discovery of new molecules also proved to be an effective way for delivering iron in patients non-compliant to oral therapy.

Combination of High Zn Density and Low Phytic Acid for Improving Zn Bioavailability in Rice (Oryza stavia L.) Grain

BACKGROUND

Zn deficiency is one of the leading public health problems in the world. Staple food crop, such as rice, cannot provide enough Zn to meet the daily dietary requirement because Zn in grain would chelate with phytic acid, which resulted in low Zn bioavailability. Breeding new rice varieties with high Zn bioavailability will be an effective, economic and sustainable strategy to alleviate human Zn deficiency.

RESULTS

The high Zn density mutant LLZ was crossed with the low phytic acid mutant Os-lpa-XS110-1, and the contents of Zn and phytic acid in the brown rice were determined for the resulting progenies grown at different sites. Among the hybrid progenies, the double mutant always displayed significantly higher Zn content and lower phytic acid content in grain, leading to the lowest molar ratio of phytic acid to Zn under all environments. As assessed by in vitro digestion/Caco-2 cell model, the double mutant contained the relatively high content of bioavailable Zn in brown rice.

CONCLUSIONS

Our findings suggested pyramiding breeding by a combination of high Zn density and low phytic acid is a practical and useful approach to improve Zn bioavailability in rice grain.

Antarctic Krill Derived Nonapeptide as an Effective Iron-Binding Ligand for Facilitating Iron Absorption via the Small Intestine

A novel nonapeptide DTDSEEEIR identified from Antarctic krill (Euphausia superba) iron-binding peptides was used in this study to analyze its iron-binding sites and structural changes after iron coordination. The enzymatic resistance and transport of DTDSEEEIR-iron during gastrointestinal digestion and absorption as well as the relationship between the DTDSEEEIR stability and the enhancement of iron absorption were further explored. Results revealed that iron ions spontaneously bound to the carboxyl, hydroxyl, and amino groups of the DTDSEEEIR peptide, which induced the folding of DTDSEEEIR to form a more orderly structure. The DTDSEEEIR peptide remained stable to a certain extent (79.60 ± 0.19%) after gastrointestinal digestion and the coordination of iron improved the digestive stability of the DTDSEEEIR peptide (93.89 ± 1.37%). Moreover, the stability of DTDSEEEIR across intestinal epithelium had a positive effect on iron absorption, which implied that DTDSEEEIR might carry iron ions through intestinal epithelial cells.

Peptide-Mineral Complexes: Understanding Their Chemical Interactions, Bioavailability, and Potential Application in Mitigating Micronutrient Deficiency

Iron, zinc, and calcium are essential micronutrients that play vital biological roles to maintain human health. Thus, their deficiencies are a public health concern worldwide. Mitigation of these deficiencies involves micronutrient fortification of staple foods, a strategy that can alter the physical and sensory properties of foods. Peptide-mineral complexes have been identified as promising alternatives for mineral-fortified functional foods or mineral supplements. This review outlines some of the methods used in the determination of the mineral chelating activities of food protein-derived peptides and the approaches for the preparation, purification and identification of mineral-binding peptides. The structure-activity relationship of mineral-binding peptides and the potential use of peptide-mineral complexes as functional food ingredients to mitigate micronutrient deficiency are discussed in relation to their chemical interactions, solubility, gastrointestinal digestion, absorption, and bioavailability. Finally, insights on the current challenges and future research directions in this area are provided.

Antioxidant Properties of Casein Phosphopeptides (CPP) and Maillard-Type Conjugated Products

A casein phosphopeptide (CPP) fraction derived from tryptic hydrolysis of bovine casein was evaluated for antioxidant activity. Conjugations or mixtures of CPP with polysaccharide, galactomannan (Gal), or xyloglucan (Xyl) were prepared to evaluate potential enhancement of CPP antioxidant activity. The effect of calcium was also investigated. The CPP preparation alone was effective at scavenging hydroxyl radicals and sequestering Fe2+ to protect against Fenton reaction-induced deoxyribose oxidation in non-site-specific (up 63.3% inhibition) and site-specific (up 32.1% inhibition) binding assays, respectively. CPP also effectively quenched 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid radicals (ABTS•+) to an extent of 67.6% scavenging in an aqueous system. In a soybean lecithin liposome system, CPP exhibited effective protection against peroxyl radical-induced liposomal peroxidation (38.3% of control in terms of rate of propagation). Conjugating CPP with Gal or Xyl polysaccharides using Maillard reaction conditions significantly reduced activity in the Fenton reaction-deoxyribose assays, while exhibiting no effect on the antioxidant activity of native CPP in both the ABTS and liposome assays, respectively. These results represent comparative antioxidant capacity of the native CPP and associated conjugates in phases that varied in relative hydrophilic and hydrophobic character. We conclude that CPP has the potential to act as both a primary and secondary antioxidant by displaying transition metal ion sequestering activity and free radical quenching activity. Improvements in antioxidant activity of CPP by Maillard-type conjugation with Xyl or Gal were relatively small and model-specific.

Peptide-metal complexes: obtention and role in increasing bioavailability and decreasing the pro-oxidant effect of minerals

Bioactive peptides derived from food protein sources have been widely studied in the last years, and scientific researchers have been proving their role in human health, beyond their nutritional value. Several bioactivities have been attributed to these peptides, such as immunomodulatory, antimicrobial, antioxidant, antihypertensive, and opioid. Among them, metal-binding capacity has gained prominence. Mineral chelating peptides have shown potential to be applied in food products so as to decrease mineral deficiencies since peptide-metal complexes could enhance their bioavailability. Furthermore, many studies have been investigating their potential to decrease the Fe pro-oxidant effect by forming a stable structure with the metal and avoiding its interaction with other food constituents. These complexes can be formed during gastrointestinal digestion or can be synthesized prior to intake, with the aim to protect the mineral through the gastrointestinal tract. This review addresses: (i) the amino acid residues for metal-binding peptides and their main protein sources, (ii) peptide-metal complexation prior to or during gastrointestinal digestion, (iii) the function of metal (especially Fe, Ca, and Zn)-binding peptides on the metal bioavailability and (iv) their reactivity and possible pro-oxidant and side effects.

Bioavailability assessment of zinc enriched lactobacillus biomass in a human colon carcinoma cell line (Caco-2)

The present study utilizes lactobacilli strains having the potential to accumulate a significant amount of Zinc (Zn) in their biomass and ability to deliver the same mineral in a highly bioavailable form. A human origin Lactobacillus fermentum SR4 and Lactobacillus rhamnosus GG (LGG) were studied for their ability to accumulate Zn by growing them in the medium containing Zn salt. Further, Zn enriched cell lysates were prepared by Ultrasonication, as an organic Zn source. Various functional groups involved in bacterial Zn binding were identified by FT-IR spectroscopy and elemental Zn in bio-chelated cell lysate complex was confirmed by SEM and Energy Dispersive X-ray Spectrometry (EDX). Experimental data demonstrated a significantly higher (P < 0.05) bioavailability of Zn chelated by SR4 followed by LGG i.e., 57% and 48%, as compared to the commercially available inorganic (ZnSo₄) and even organic (Zinc gluconate) forms tested which has 15.6% and 21.7% respectively.

The Functional Power of the Human Milk Proteome

Human milk is the most complete and ideal form of nutrition for the developing infant. The composition of human milk consistently changes throughout lactation to meet the changing functional needs of the infant. The human milk proteome is an essential milk component consisting of proteins, including enzymes/proteases, glycoproteins, and endogenous peptides. These compounds may contribute to the healthy development in a synergistic way by affecting growth, maturation of the immune system, from innate to adaptive immunity, and the gut. A comprehensive overview of the human milk proteome, covering all of its components, is lacking, even though numerous analyses of human milk proteins have been reported. Such data could substantially aid in our understanding of the functionality of each constituent of the proteome. This review will highlight each of the aforementioned components of human milk and emphasize the functionality of the proteome throughout lactation, including nutrient delivery and enhanced bioavailability of nutrients for growth, cognitive development, immune defense, and gut maturation.

Hydrophilic Food-Borne Nanoparticles from Beef Broth as Novel Nanocarriers for Zinc

Food-borne nanoparticles (FNs) may be used as nanocarriers for metal ion chelation in micronutrient supplements. In this paper, the preparation and characterization of hydrophilic FNs were reported from beef broth cooked with a pressure cooker at 117 °C for different periods (30, 50, and 70 min) and their potential application as nanocarriers for zinc was investigated. The broth FNs are quasi-spherical with good water solubility and ultrasmall size, which can emit a strong sapphire color under 365 nm ultraviolet irradiation. X-ray photoelectron spectroscopy (XPS) analysis showed that there are carboxyl, amino, and hydroxyl groups on the FNs, which are useful for Zn(II) chelation. The vibration band of C═O at 1688 cm^-1 in the infrared spectrum of FNs shifted to 1718 cm^-1 after binding with Zn(II) ions, suggesting the participation of the carbonyl group in Zn(II) ion chelation. The appearance of Zn_2p XPS peaks, at 1021.6 and 1045 eV for Zn(II)-FNs, clearly demonstrated the formation of Zn-O between the FNs and zinc ions. Biodistribution of FNs and the Zn(II)-FN complex in normal rat kidney cells demonstrated that they could easily enter normal rat kidney cells. A downfield was found for the signals of Zn(II)-FNs in ¹H nuclear magnetic resonance spectroscopy and strongly suggested the binding of Zn(II) ions to FNs through carboxylic acid, hydroxyl, and amine groups. In addition, no obvious cytotoxicity was found for Zn(II)-FNs compared to zinc (ZnSO₄) and commercial zinc gluconate. The results revealed that the FNs from beef broth may have a potential as nanocarriers for zinc chelation.

Purification of an iron-binding peptide from scad (Decapterus maruadsi) processing by-products and its effects on iron absorption by Caco-2 cells

This work was aimed at producing peptides containing iron-binding capabilities from scad (Decapterus maruadsi) processing by-product with alcalase hydrolysis. The chelating peptides were purified by ultrafiltration, immobilized-metal affinity chromatography, gel filtration chromatography, and reversed-phase high-performance liquid chromatography. A novel iron-binding peptide was purified with 1,386.63 Da molecular weight and amino acid sequence of QKGTYDDYVEGL. The peptide binds to iron mainly through carboxyl and hydroxyl oxygen bonds. The iron-binding peptide can significantly promote the absorption of inorganic iron in Caco-2 cells. These results have contributed to development of the peptide from scad processing by-products hydrolyzate in iron supplementations. PRACTICAL APPLICATIONS: Iron deficiency is one of the most common and widespread nutritional disorders in the world. Iron-peptide chelates may be suitable for iron-fortification. Our study shows that a peptide purified from scad processing by-product has iron-chelating activity, and significantly increases iron absorption by Caco-2 cells. Hence, this peptide has potential application as a novel carrier for enhancing iron absorption.

Cryptides: latent peptides everywhere

Proteomic surveys with top-down platforms are today revealing thousands of naturally occurring fragments of bigger proteins. Some of them have not functional meaning because they derive from pathways responsible for protein degradation, but many have specific functions, often completely different from that one of the parent proteins. These peptides encrypted in the protein sequence are nowadays called cryptides. They are frequent in the animal and plant kingdoms and represent a new interesting -omic field of investigation. To point out how much widespread is their presence, we describe here the most studied cryptides from very common sources such as serum albumin, immunoglobulins, hemoglobin, and from saliva and milk proteins. Given its vastness, it is unfeasible to cover the topic exhaustively, therefore only several selected examples of cryptides from other sources are thereafter reported. Demanding is the development of new -omic platforms for the functional screening of new cryptides, which could provide suggestion for peptides and peptido-mimetics with variegate fields of application.

In vitrodigestion profile and calcium absorption studies of a sea cucumber ovum derived heptapeptide–calcium complex

A novel sea cucumber ovum derived heptapeptide (NDEELNK) could bind one calcium ionviaits carboxyl oxygen and amino nitrogen atoms, and the formed complex underwent disaggregation and self aggregation during simulated gastrointestinal digestion.

In vitro assessment of bio-augmented minerals from peanut oil cakes fermented by Aspergillus oryzae through Caco-2 cells

Present study was carried out to assess the significances of solid state fermentation of peanut oil cakes (POC) by Aspergillus oryzae on in vitro bioavailability of minerals (iron, zinc and calcium) and cellular transport, retention and uptake from POC through Caco-2 cells. Bioavailability of iron, zinc and calcium of POC was examined by means of a combined simulated gastrointestinal digestion/Caco-2 cell system. Bio-augmentation of minerals of fermented POC attributed a positive, statistically significant increased influence on minerals retention, transport and uptake values when compared with that of respective inorganic salts as reference. Results revealed increased cellular ferritin content from fermented POC digests than the digests of free form of respective inorganic salt. In prospect of the present investigation the fermented POC samples showed significantly higher iron, zinc and calcium bioavailability and enormous possible health benefits.

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.

Protein Hydrolysates as Promoters of Non-Haem Iron Absorption

Iron (Fe) is an essential micronutrient for human growth and health. Organic iron is an excellent iron supplement due to its bioavailability. Both amino acids and peptides improve iron bioavailability and absorption and are therefore valuable components of iron supplements. This review focuses on protein hydrolysates as potential promoters of iron absorption. The ability of protein hydrolysates to chelate iron is thought to be a key attribute for the promotion of iron absorption. Iron-chelatable protein hydrolysates are categorized by their absorption forms: amino acids, di- and tri-peptides and polypeptides. Their structural characteristics, including their size and amino acid sequence, as well as the presence of special amino acids, influence their iron chelation abilities and bioavailabilities. Protein hydrolysates promote iron absorption by keeping iron soluble, reducing ferric iron to ferrous iron, and promoting transport across cell membranes into the gut. We also discuss the use and relative merits of protein hydrolysates as iron supplements.

The transepithelial transport mechanism of polybrominated diphenyl ethers in human intestine determined using a Caco-2 cell monolayer

Oral ingestion plays an important role in human exposure to polybrominated diphenyl ethers (PBDEs). The uptake of PBDEs primarily occurs in the small intestine. The aim of the present study is to investigate the transepithelial transport characteristics and mechanisms of PBDEs in the small intestine using a Caco-2 cell monolayer model. The apparent permeability coefficients of PBDEs indicated that tri- to hepta-BDEs were poorly absorbed compounds. A linear increase in transepithelial transport was observed with various concentrations of PBDEs, which suggested that passive diffusion dominated their transport at the concentration range tested. In addition, the pseudo-first-order kinetics equation can be applied to the transepithelial transport of PBDEs. The rate-determining step in transepithelial transport of PBDEs was trans-cell transport including the trans-pore process. The significantly lower transepithelial transport rates at low temperature for bidirectional transepithelial transport suggested that an energy-dependent transport mechanism was involved. The efflux transporters (P-glycoprotein, multidrug resistance-associated protein, and breast cancer resistance protein) and influx transporters (organic cation transporters) participated in the transepithelial transport of PBDEs. In addition, the transepithelial transport of PBDEs was pH sensitive; however, more information is required to understand the influence of pH.

Effect of Caseinophosphopeptides from αs- and β-Casein on Iron Bioavailability in HuH7 Cells

Two pools of caseinophosphopeptides (CPPs) obtained from αs- and β-casein fractions (α-CPPs and β-CPPs) were characterized. A total of 16 CPPs were identified in the α-CPPs pool, 9 of them derived from αs1-casein and 7 from αs2-casein. A total of 18 CPPs were identified in the β-CPPs pool. Four of the identified CPPs contained the characteristic phosphoseryl-glutamic acid cluster SpSpSpEE. Calcein assay was used to compare the iron-binding capacity of the α- and β-CPPs pools. At the concentration of 12.5 μM CPPs used in the iron bioavailability assays, β-CPPs pools show greater iron-binding capacity than α-CPPs pools. HuH7 human hepatoma cells show many differentiated functions of liver cells in vivo and can be used to evaluate iron bioavailability (ferritin content and soluble transferrin receptor) from Fe-α-CPPs and Fe-β-CPPs complexes. The α-CPPs and β-CPPs pools did not improve ferritin content or soluble transferrin receptor in HuH7 cells.