Polyphenols and phenolic acids from strawberry and apple decrease glucose uptake and transport by human intestinal Caco‐2 cells

The effect of polyphenols, phenolic acids and tannins (PPTs) from strawberry and apple on uptake and apical to basolateral transport of glucose was investigated using Caco‐2 intestinal cell monolayers. Substantial inhibition on both uptake and transport was observed by extracts from both strawberry and apple. Using sodium‐containing (glucose transporters SGLT1 and GLUT2 both active) and sodium‐free (only GLUT2 active) conditions, we show that the inhibition of GLUT2 was greater than that of SGLT1. The extracts were analyzed and some of the constituent PPTs were also tested. Quercetin‐3‐O‐rhamnoside (IC₅₀=31 μM), phloridzin (IC₅₀=146 μM), and 5‐caffeoylquinic acid (IC₅₀=2570 μM) contributed 26, 52 and 12%, respectively, to the inhibitory activity of the apple extract, whereas pelargonidin‐3‐O‐glucoside (IC₅₀=802 μM) contributed 26% to the total inhibition by the strawberry extract. For the strawberry extract, the inhibition of transport was non‐competitive based on kinetic analysis, whereas the inhibition of cellular uptake was a mixed‐type inhibition, with changes in both V_max and apparent K_m. The results in this assay show that some PPTs inhibit glucose transport from the intestinal lumen into cells and also the GLUT2‐facilitated exit on the basolateral side.     

The (193–209) 17‐residues peptide of bovine β‐casein is transported through Caco‐2 monolayer

Although the bioavailability of large peptides with biological activity is of great interest, the intestinal transport has been described for peptides up to only nine residues. β‐casein (β‐CN, 193–209) is a long and hydrophobic peptide composed of 17 amino acid residues (molecular mass 1881 Da) with immunomodulatory activity. The present work examined the transport of the β‐CN (193–209) peptide across Caco‐2 cell monolayer. In addition, we evaluated the possible routes of the β‐CN (193–209) peptide transport, using selective inhibitors of the different routes for peptide transfer through the intestinal barrier. The results showed that the β‐CN (193–209) peptide resisted the action of brush‐border membrane peptidases, and that it was transported through the Caco‐2 cell monolayer. The main route involved in transepithelial transport of the β‐CN (193–209) peptide was transcytosis via internalized vesicles, although the paracellular transport via tight‐junctions could not be excluded. Our results demonstrated the transport of an intact long‐chain bioactive peptide in an in vitro model of intestinal epithelium, as an important step to prove the evidence for bioavailability of this peptide.     

The antioxidant activity and transcellular pathway of Asp‐Leu‐Glu‐Glu in a Caco‑2 cell monolayer

Asp‐Leu‐Glu‐Glu (DLEE) is one of the antioxidant peptides purified from Chinese dry‐cured Xuanwei ham in our previous study. In the current work, the stability in a simulated digestion system, the transportation pathway and the antioxidant ability of DLEE were further investigated in a Caco‐2 cell monolayer. In the simulated gastrointestinal digestion system, no oligopeptides were generated. In the transport trial, the inhibitors cytochalasin D increased the transport of DLEE across the Caco‐2 cell monolayer, with P_app values of 3.22 × 10^?6 cm s^?1. A decreased expression occludin was observed with the DLEE incubation in the cell monolayer, and the antioxidant activity showed to be increased gradually in basolateral side. This study indicates that the absorption of DLEE could mainly occur via paracellular transport and provides information about its antioxidant activity after being absorbed across a cell monolayer.     

Absorption of anthocyanins through intestinal epithelial cells – Putative involvement of GLUT2

Anthocyanins bioavailability is a major issue regarding their biological effects and remains unclear due to few data available on this matter. This work aimed to evaluate the absorption of anthocyanins at the intestine using Caco‐2 cells. Anthocyanin extract, rich in malvidin‐3‐glucoside, was obtained from red grape skins and tested on Caco‐2 cells. The absorption of anthocyanins, in absence or presence of 1% ethanol, was detected by HPLC/DAD/LC‐MS. Our results showed that this transport was significantly increased in the presence of ethanol especially after 60 min of incubation. In addition, cells that were pretreated for 96 h with anthocyanins (200 μg/mL) showed an increase of their own transport (about 50% increase). Expression of glucose transporters sodium‐dependent glucose transporter 1, facilitative glucose transporters 5, and facilitative glucose transporters 2 was assessed by RT‐PCR. It was found that facilitative glucose transporters 2 expression was increased (60%) in Caco‐2 cells pretreated with anthocyanins, by comparison with controls. When the effect of anthocyanin extract on ³H‐2‐deoxy‐D ‐glucose uptake was tested, an inhibitory effect was observed (about 60% decrease). However, the malvidin aglycone was tested and had no effect. In conclusion, anthocyanins could be absorbed through Caco‐2 cells, and can interfere with their own transport and also with glucose intestinal uptake.     

Efficacy of Combined Sous Vide‐Microwave Cooking for Foodborne Pathogen Inactivation in Ready‐to‐Eat Chicory Stems

There is a variety of different food processing methods, which can be used to prepare ready‐to‐eat foods. However, the need to preserve the freshness and nutritional qualities leads to the application of mild technologies which may be insufficient to inactivate microbial pathogens. In this work, fresh chicory stems were packed under a vacuum in films, which were transparent to microwaves. These were then exposed to microwaves for different periods of time. The application of sous vide microwave cooking (SV‐MW, 900 W, 2450 MHz), controlled naturally occurring mesophilic aerobic bacteria, yeasts and molds for up to 30 d when vacuum‐packed vegetables were stored at 4 °C. In addition, the process lethality of the SV‐MW 90 s cooking was experimentally validated. This treatment led to 6.07 ± 0.7 and 4.92 ± 0.65 log cfu/g reduction of Escherichia coli and Listeria monocytogenes inoculated over the chicory stems (100 g), respectively. With an initial load of 9 log cfu/g for both pathogens, less than 10 cfu/g of surviving cells were found after 90 s cooking. This shows that short‐time microwave cooking can be used to effectively pasteurize vacuum‐packed chicory stems, achieving >5 log cfu/g reduction of E. coli and L. monocytogenes.     

Esterification of Quercetin Increases Its Transport Across Human Caco‐2 Cells

Plant polyphenols showed useful biochemical characteristics in vitro; however, the assessments of their clinical applications in vivo are restricted by their limited bioavailability due to their strong resistance to 1st‐pass effects during absorption. In order to improve the bioavailability of quercetin (QU), the ester derivative of QU (3,3′,4′,5,7‐pentahydroxy flavones, TAQU) was synthesized, followed by examining the oil–water partition coefficient as well as the transport mechanisms of QU and its ester derivative (TAQU) using human Caco‐2 cells. The transport characteristics of QU and TAQU transport under different conditions (different concentrations, time, pH, temperature, tight junctions, and potential transporters) were systematically investigated. Results showed that QU had a lower permeability coefficient (2.82 × 10^?6 cm/s) for apical‐to‐basolateral (AP‐BL) transport over 5 to 50 μM, whereas the transport rate for AP to BL flux of TAQU (5.23 × 10^?6 cm/s) was significantly greater than that of QU. Paracellular pathways were not involved during the transport of both QU and TAQU. QU was poorly absorbed by active transport, whereas TAQU was mostly absorbed by passive diffusion. Efflux transporters, P‐glycoproteins, multidrug resistance proteins were proven to participate in the transport process of QU, but not in that of TAQU. These results suggested that improving the lipophicity of QU by esterification could increase the transport of QU across Caco‐2 cells.     

Characterization of Date (Deglet Nour) Seed Free and Bound Polyphenols by High‐Performance Liquid Chromatography‐Mass Spectrometry

Date (Pheonix dactylifera L.) seeds are a valuable and abundant by‐product with various potential food applications. Free polyphenols (FPPs) and bound polyphenols (BPPs) of date seeds from Deglet Nour variety grown in Australia were investigated using high‐performance liquid chromatography‐mass spectrometry. The FPP fraction contained the following main phenolic compounds per gram of date seed powder; procyanidin B1 (499.8 ± 7.8 μg), procyanidin B2 (288.6 ± 6.1 μg), catechin (167.6 ± 2.1 μg), epicatechin (39.44 ± 0.39 μg), and protocatechuic acid (1.77 ± 0.22 μg). Additionally, one of the 2 A‐type dimers was confirmed as procyanidin A2 (24.05 ± 0.12 μg/g). A‐type dimers have not been reported before in date seeds. The BPP fraction contained epicatechin (52.59 ± 0.76 μg/g) and procyanidin B2 (294.2 ± 3.7 μg/g), while several peaks exhibiting ESI^? m/z of 153 indicated dihydroxybenzoic acid isomers including protocatechuic acid (2.138 ± 0.025 μg/g). These findings contributed to our knowledge of date seed phytochemicals and understanding of their contribution to the reported bioactivities.     

Antioxidant activity in HepG2 cells,immunomodulatory effects in RAW 264.7 cells and absorption characteristics in Caco‐2 cells of the peptide fraction isolated from Dendrobium aphyllum

DA‐P, fraction of peptides with a molecular weight <1 kDa isolated from Dendrobium aphyllum, was analysed in three types of cell lines to verify its bioactivity and absorptivity. The cellular antioxidant activity of DA‐P in HepG2 cells was used and results revealed an EC50 of 2.88 ± 0.143 mg mL^?1 and a CAA unit of 63.46 ± 2.11 μm QE/100 g peptides. DA‐P treatment enhanced the secretion of cytokines in RAW 264.7 cells. After demonstrating the presence of tight junctions in Caco‐2 monolayers, the absorption was 25.57% ± 0.016% and 19.7% ± 0.012% from different sides. The relatively high absorption indicated that the antioxidant‐relevant immune functions of DA‐P had a greater possibility to be absorbed by Caco‐2 cells. Free amino acids and LC‐MS/MS analysis indicated the degradation and expulsion of components after the absorption of DA‐P, and Ser‐Ser‐Arg was able to come across the monolayers.     

Antioxidant effectiveness of coffee extracts and selected constituents in cell‐free systems and human colon cell lines

Scope: Epidemiological studies suggest that coffee can reduce the risk of degenerative diseases such as diabetes type 2, cardiovascular disease and cancer. These beneficial effects have partly been attributed to the antioxidant activity of coffee. We determined composition and antioxidant potential of differentially roasted coffee extracts and investigated the impact of selected original constituents and roast products. Methods and results: Parameters studied were direct antioxidant activity (trolox equivalent antioxidant capacity/oxygen radical absorbing capacity), cellular reactive oxygen species (ROS) level, DNA damage and protein expression of NAD(P)H: quinone oxidoreductase, γ‐glutamylcysteine ligase and glutathione reductase in HT‐29/Caco‐2 cells at 24‐h incubation. All extracts showed distinct direct antioxidant activity: medium roasts>light roast AB1 (caffeoylquinic acid (CQA)‐rich Arabica Brazil extract); dark roast AB2 (N‐methylpyridinium (NMP)‐rich Arabica Brazil extract), and diminished t‐butylhydroperoxide‐induced ROS level in HT‐29 cells (AB2>medium roasts>AB1). NAD(P)H:quinone oxidoreductase 1 expression and γ‐glutamylcysteine ligase expression were distinctly induced by AB1 and 5‐CQA, but not by AB2 and NMP. 5‐CQA and caffeic acid exhibited highest trolox equivalent antioxidant capacity/oxygen radical absorbing capacity values (5‐CQA: 1.3/3.5 mM and caffeic acid: 1.3/3.9 mM trolox); ROS level was distinctly diminished by 5‐CQA (≥3 μM), catechol (30 μM) and trigonelline (≥30 μM), whereas menadione‐induced DNA damage in Caco‐2 cells was reduced by NMP compounds (1–30 μM). Conclusion: The results emphasize that both original constituents and roast products contribute to the cellular antioxidant effectiveness of coffee.     

Apple extract induces increased epithelial resistance and claudin 4 expression in Caco-2 cells

BACKGROUND: The small intestinal epithelium functions both to absorb nutrients, and to provide a barrier between the outside, luminal, world and the human body. One of the passageways across the intestinal epithelium is paracellular diffusion, which is controlled by the properties of tight junction complexes. We used a differentiated Caco‐2 monolayer as a model for small intestinal epithelium to study the effect of crude apple extracts on paracellular permeability. RESULTS: Exposure of crude apple homogenate to the differentiated Caco‐2 cells increased the paracellular resistance, determined as trans‐epithelial electrical resistance (TEER). This increase was linearly related to the concentration of apple present. The TEER‐enhancing effect of apple extract was due to factors mainly present in the cortex, and the induction was not inhibited by protein kinase inhibitors. Apple‐induced resistance was accompanied by increased expression of several tight junction related genes, including claudin 4 (CLDN4). CONCLUSION: Crude apple extract induces a higher paracellular resistance in differentiated Caco‐2 cells. Future research will determine whether these results can be extrapolated to human small intestinal epithelia. Copyright © 2011 Society of Chemical Industry     

Absorption and metabolism of the mycotoxin zearalenone and the growth promotor zeranol in Caco-2 cells in vitro

Scope: Zearalenone (ZEN) and α‐zearalanol (α‐ZAL, zeranol) were studied in differentiated Caco‐2 cells and in the Caco‐2 Millicell^® system in vitro to simulate their in vivo intestinal absorption and metabolism in humans. Methods and results: In addition to metabolic reduction/oxidation, extensive conjugation with glucuronic acid and sulfate of the parent compounds and their phase I metabolites was observed. The positional isomers of the glucuronides and sulfates were unambiguously identified: Sulfonation occurred specifically at the 14‐hydroxyl group, whereas glucuronidation was less specific and, in addition to the preferred 14‐hydroxyl group, involved the 16‐ and 7‐hydroxyl groups. Using the Caco‐2 Millicell^® system, an efficient transfer of the glucuronides and sulfates of ZEN and α‐ZAL and their phase I metabolites into both the basolateral and the apical compartment was observed after apical administration. The apparent permeability coefficients (P_app values) of ZEN, α‐ZAL and the ZEN metabolite α‐zearalenol were determined, using an initial apical concentration of 20 μM and a permeation time of 1 h. Conclusion: According to the P_app values, the three compounds are expected to be extensively and rapidly absorbed from the intestinal lumen in vivo and reach the portal blood both as aglycones and as glucuronide and sulfate conjugates in humans.     

Characterization,Anti‐Inflammatory and Antiproliferative Activities of Natural and Sulfonated Exo‐Polysaccharides from Streptococcus thermophilus ASCC 1275

Exo‐polysaccharides (EPS) isolated from Streptococcus thermophilus ASCC 1275 were sulfated (31%). High‐performance liquid chromatography identified that EPS was composed of mannose (30.19%), galactose (20.10%), glucose (18.05%), glucosamine (16.04%), galactosamine (9.06%), glucuronic acid (3.55%), and ribose (3.01%). Pro‐/anti‐inflammatory cytokine secretion ratios (IL‐1β/IL‐10, IL‐6/IL‐10, and TNF‐α/IL‐10) of lipopolysaccharide stimulated RAW 264.7 macrophages were significantly decreased by EPS and S.EPS treatments in a dose dependent manner. Furthermore, anti‐inflammatory activities of S.EPS improved 49.3% and 24.0% than those of EPS before or after LPS treatment. The reactive oxygen species were inhibited by EPS and S.EPS by 49.6% and 55.1% at 50 μg/mL, respectively. Inhibition activities of S.EPS on nitric oxide production were 12.9% and 55.4% higher than those of EPS at 10 and 50 μg/mL. Additionally, S.EPS exhibited stronger antiproliferative activity on Caco‐2 and HepG2 cells. Our results indicated that anti‐inflammatory and antiproliferative activities of EPS were significantly (P < 0.01) improved by sulfonation.     

Vitamin D intestinal absorption is not a simple passive diffusion: evidences for involvement of cholesterol transporters

Scope : It is assumed that vitamin D is absorbed by passive diffusion. However, since cholecalciferol (vitamin D₃) and cholesterol display similar structures, we hypothesized that common absorption pathways may exist. Methods and results : Cholecalciferol apical transport was first examined in human Caco‐2 and transfected Human embryonic kidney (HEK) cells. Cholecalciferol uptake was then valuated ex vivo and in vivo, using either wild‐type mice, mice overexpressing Scavenger Receptor class B type I (SR‐BI) at the intestinal level or mice treated or not with ezetimibe. Cholecalciferol uptake was concentration‐, temperature‐ and direction‐dependent, and was significantly impaired by a co‐incubation with cholesterol or tocopherol in Caco‐2 cells. Moreover Block Lipid Transport‐1 (SR‐BI inhibitor) and ezetimibe glucuronide (Niemann‐Pick C1 Like 1 inhibitor) significantly decreased cholecalciferol transport. Transfection of HEK cells with SR‐BI, Cluster Determinant 36 and Niemann‐Pick C1 Like 1 significantly enhanced vitamin D uptake, which was significantly decreased by the addition of Block Lipid Transport‐1, sulfo‐N‐succinimidyl oleate (Cluster Determinant 36 inhibitor) or ezetimibe glucuronide, respectively. Similar results were obtained in mouse intestinal explants. In vivo, cholecalciferol uptake in proximal intestinal fragments was 60% higher in mice overexpressing SR‐BI than in wild‐type mice (p<0.05), while ezetimibe effect remained non‐significant. Conclusion: These data show for the first time that vitamin D intestinal absorption is not passive only but involves, at least partly, some cholesterol transporters.     

Carotenoids,but Not Vitamin A,Improve Iron Uptake and Ferritin Synthesis by Caco‐2 Cells from Ferrous Fumarate and NaFe‐EDTA

Due to the high prevalence of iron and vitamin A deficiencies and to the controversy about the role of vitamin A and carotenoids in iron absorption, the objectives of this study were to evaluate the following: (1) the effect of a molar excess of vitamin A as well as the role of tannic acid on iron uptake by Caco‐2 cells; (2) iron uptake and ferritin synthesis in presence of carotenoids without pro‐vitamin A activity: lycopene, lutein, and zeaxantin; and (3) iron uptake and ferritin synthesis from ferrous fumarate and NaFe‐EDTA. Cells were incubated 1 h at 37 °C in PBS pH 5.5, containing ⁵⁹Fe and different iron compounds. Vitamin A, ferrous fumarate, β‐carotene, lycopene, lutein, zeaxantin, and tannic acid were added to evaluate uptake. Ferritin synthesis was measured 24 h after uptake experiments. Vitamin A had no effect on iron uptake by Caco‐2 cells, and was significantly lower from NaFe‐EDTA than from ferrous fumarate (15.2 ± 2.5 compared with 52.5 ± 8.3 pmol Fe/mg cell protein, respectively). Carotenoids increase uptake up to 50% from fumarate and up to 300% from NaFe‐EDTA, since absorption from this compound is low when administered alone. We conclude the following: (1) There was no effect of vitamin A on iron uptake and ferritin synthesis by Caco‐2cells. (2) Carotenoids significantly increased iron uptake from ferrous fumarate and NaFe‐EDTA, and were capable of partially overcoming the inhibition produced by tannic acid. (3) Iron uptake by Caco‐2 cell from NaFe‐EDTA was significantly lower compared to other iron compounds, although carotenoids increased and tannic acid inhibited iron uptake comparably to ferrous fumarate.     

Bioavailability of iron from a heat treated glucose‐lysine model food system: assays in rats and in Caco‐2 cells

The influence of Maillard reaction products (MRP) from glucose–lysine on iron bioavailability was investigated. Equimolar glucose–lysine mixtures (GL, 40% moisture) were heated (150 °C, for 30, 60 and 90 min) to prepare samples GL30, GL60 and GL90, respectively, and were used to study the influence of MRP on iron solubility, iron uptake and transport in Caco‐2 cells and iron balance in rats. After an initial increase with GL30, in vitro iron solubility decreased in the presence of most of the heated samples. The Caco‐2 cell experiments showed that Fe cell content increased in the presence of heated mixtures with respect to GL, whereas transport was less affected. Iron balance was determined in rats fed diets containing the GL30 and GL90 samples (3%) for a 21 day period and compared with that measured in a control group. Consumption of glucose–lysine heated mixtures increased total iron retention, although hemoglobin values decreased. Iron accumulations in organs such as the spleen, kidney and small intestine were observed. Copyright © 2004 Society of Chemical Industry     

A novel mechanism underlying phytate‐mediated biological action‐phytate hydrolysates induce intracellular calcium signaling by a Gαq protein‐coupled receptor and phospholipase C‐dependent mechanism in colorectal cancer cells

Phytate (inositol hexa‐phosphate, IP6) possesses multiple biological functions including anticancer activity. IP6 is converted to inositol di‐, tri‐, and tetra‐phosphates (IP2, IP3, and IP4) by phytase in large intestinal microbes; however, their contribution to the IP6‐mediated functions has not been investigated. We have developed the preparations of IP2–4 and IP3‐rich phytate hydrolysate (IP3‐RPH) by IP6 digestion using microbial phytase, and examined the induction of intracellular Ca²⁺ signaling in response to the preparations in colorectal cancer cells. IP2–4, but not inositol (IP0) and IP6, induced increases in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in Caco‐2 cells with the following rank order: IP3>IP2=IP4. Inositol tri‐phosphate (IP3)‐RPH induced increases in [Ca²⁺]_i in both undifferentiated Caco‐2 and HT‐29 cells, but not in differentiated Caco‐2. The IP3‐RPH‐induced [Ca²⁺]_i increase was resistant to extracellular Ca²⁺ depletion, however, it was impaired by inhibitors of phospholipase C, inositol 1, 4, 5 tri‐phosphate receptor, ryanodine receptor, and Gαq protein. These results show that the putative G protein‐coupled receptor on the plasma membrane senses the IP6 hydrolysates and activates phospholipase Cβ, resulting in Ca²⁺ mobilization through Ca²⁺ channels coupled with the inositol 1, 4, 5 tri‐phosphate and ryanodine receptors on the sarco‐endoplasmic reticulum Ca²⁺ store in colorectal cancer cells.     

The effect of co‐administered flavonoids on the metabolism of hesperetin and the disposition of its metabolites in Caco‐2 cell monolayers

Metabolism by phase II enzymes and transport from intestinal cells back into the lumen by ATP binding cassette (ABC) transporters limits the bioavailability of the flavanone hesperetin, the aglycone of hesperidin. This study investigates to what extent other flavonoids modulate the metabolism and transport of hesperetin by characterizing the effect of co‐administrating a series of flavonoids using Caco‐2 cell monolayers in a two‐compartment transwell system. Flavonoids may interfere with hesperetin metabolism and can also inhibit the apically located ABC transporter breast cancer resistance protein (ABCG2) which was previously shown to be responsible for the apical transport of hesperetin metabolites. Co‐exposure of Caco‐2 cell monolayers to hesperetin with specific flavonoids reduced the ratio of apical efflux to basolateral transport of hesperetin metabolites, and in some cases, also reduced the amount of hesperetin metabolites detected extracellularly. As intracellular accumulation of hesperetin metabolites did not account for this decrease, inhibition of metabolism of hesperetin is likely the underlying mechanism for the reduced metabolite formation and excretion. In spite of the reduction in metabolism the amount of hesperetin metabolites transported to the basolateral side significantly increased upon co‐exposure with specific flavonoids and therefore co‐administration of specific flavonoids could be a strategy to improve the bioavailability of hesperetin.     

Characterization of the Saccharomyces bayanus‐type AGT1 transporter of lager yeast

Transport of maltose and maltotriose into the yeast cell is thought to be rate‐limiting in the utilization of these sugars. The maltose and maltotriose transporters Malx1, Agt1, Mtt1 and Mphx are present in different combinations in brewer's yeast strains, conferring different maltose and maltotriose transport characteristics on the strains. A new putative maltose/maltotriose transporter ORF was identified during whole genome sequencing of the lager strain WS34/70 (Y. Nakao et al., DNA Res., 2009, 16, 115–129). Sequence comparisons suggested that this putative α‐glucoside transporter might be a Saccharomyces bayanus counterpart of the Agt1 (Saccharomyces cerevisiae type) transporter. In the present work, the transporter coded by a SbAGT1 gene from a lager strain, A15 (and with the same sequence as the corresponding gene in WS34/70) was characterized. It is shown that this SbAGT1 encodes a functional α‐glucoside transporter with a wide‐substrate range, including maltose and maltotriose. Trehalose, α‐methylglucoside and sucrose were inhibitors, suggesting they are also substrates. The SbAgt1 transporter had similar affinities for maltose and maltotriose (17 ± 7 and 22 ± 2 m m , respectively) and a higher V_max for maltose than maltotriose (21 ± 7 and 12 ± 2 µmol min^?1 g dry yeast^?1, respectively). Copyright © 2012 The Institute of Brewing & Distilling     

Development of a three‐tier in vitro system,using Caco‐2 cells,to assess the effects of lactate on iron uptake and transport from rye bread following in vitro digestion

A three‐tier Caco‐2 cell system was developed to assess simultaneously iron dialysability, uptake and transport across the Caco‐2 monolayer from an in vitro digested food matrix. The effect of lactate (0–200 mmol L⁻¹) on iron absorption from rye bread subjected to simulated peptic (pH 5.5) and pancreatic digestion (pH 6.5) was investigated to model absorption pre and post the sphincter of Oddi. Lactate increased dialysability (11.8%, P < 0.05) in peptic digests whereas it reduced it in pancreatic digests (4.9%, P < 0.001). Iron uptake from the peptic digests was in the region of 39–76 pmol mg⁻¹ protein whereas it decreased from 281 to 51 pmol mg⁻¹ protein in pancreatic digests. Iron transport was calculated for the peptic digests from [¹⁴C]polyethylene glycol movement and only at 200 mmol L⁻¹ lactate was there any detectable transcellular transport (180 pmol mg⁻¹ protein, P < 0.05). Iron absorption was positively correlated to dialysable iron for both digests (R² = 0.48 and 0.41, respectively, P < 0.01) and the effect of lactate was therefore associated mainly with iron bioaccessibility. The three‐tier system showed the potential to obtain detailed insight into each step involved in iron transport across the monolayer from a food mixture. Copyright © 2006 Society of Chemical Industry