Impaired uptake of β-carotene by Caco-2 human intestinal cells in the presence of iron

Iron, Catechin, and Ferulic Acid Inhibit Cellular Uptake of β-Carotene by Reducing Micellization

Green leafy vegetables have low β-carotene bioavailability, which we hypothesized to be, at least in part, due to high contents of fiber, minerals, and phenolics. We investigated the effects of pectin (40-120 μg/mL), iron (50-150 μg/mL), ferulic acid (30-90 μg/mL), and catechin (50-150 μg/mL), in a model system, on β-carotene micellization (in vitro digestion) and intestinal absorption (Caco-2 cell model). Iron, pectin, ferulic acid, and catechin on average reduced ( p < 0.05) β-carotene micellization (1.49 ± 0.05 μmol/L) by 66.9, 59.3, 43.2, and 51.7%, respectively. Iron reduced micellization by precipitating bile salts from solution and ferulic acid and catechin by inhibition of pancreatic lipase. β-Carotene uptake by Caco-2 cells (2.63 ± 0.22%) was reduced ( p < 0.05) by 37.4, 70.1, 77.0, and 75.1%, respectively, when it was digested with pectin, iron, ferulic acid, or catechin. However, when individual test compounds were added to already micellized β-carotene, they did not inhibit β-carotene uptake. The large reductions in β-carotene micellization observed in vitro warrant further investigation in humans using model green leafy vegetable systems to elucidate their relevance under real-life conditions.

Nanoparticulate iron(III) oxo-hydroxide delivers safe iron that is well absorbed and utilised in humans

Iron deficiency is the most common nutritional disorder worldwide with substantial impact on health and economy. Current treatments predominantly rely on soluble iron which adversely affects the gastrointestinal tract. We have developed organic acid-modified Fe(III) oxo-hydroxide nanomaterials, here termed nano Fe(III), as alternative safe iron delivery agents. Nano Fe(III) absorption in humans correlated with serum iron increase (P < 0.0001) and direct in vitro cellular uptake (P = 0.001), but not with gastric solubility. The most promising preparation (iron hydroxide adipate tartrate: IHAT) showed ~80% relative bioavailability to Fe(II) sulfate in humans and, in a rodent model, IHAT was equivalent to Fe(II) sulfate at repleting haemoglobin. Furthermore, IHAT did not accumulate in the intestinal mucosa and, unlike Fe(II) sulfate, promoted a beneficial microbiota. In cellular models, IHAT was 14-fold less toxic than Fe(II) sulfate/ascorbate. Nano Fe(III) manifests minimal acute intestinal toxicity in cellular and murine models and shows efficacy at treating iron deficiency anaemia.

FROM THE CLINICAL EDITOR

This paper reports the development of novel nano-Fe(III) formulations, with the goal of achieving a magnitude less intestinal toxicity and excellent bioavailability in the treatment of iron deficiency anemia. Out of the tested preparations, iron hydroxide adipate tartrate met the above criteria, and may become an important tool in addressing this common condition.

High pressure homogenization increases the in vitro bioaccessibility of α- and β-carotene in carrot emulsions but not of lycopene in tomato emulsions

The correlation between food microstructure and in vitro bioaccessibility of carotenes was evaluated for tomato and carrot emulsions (5% olive oil) subjected to high pressure homogenization (HPH) at varying degrees of intensity. The aim was to investigate whether additional mechanical disruption of the food matrix could be utilized to further increase the carotene bioaccessibility of an already pre-processed material. The carotene bioaccessibility of the samples was measured after simulated in vitro digestion, carotene release to the oil phase was estimated by Confocal Raman spectroscopy and, to measure active uptake of carotenes, Caco-2 cells were incubated with the digesta of selected samples. HPH did not notably affect the retention of carotenes or ascorbic acid but significantly increased both the release and micellar incorporation of α- and β-carotene in carrot emulsions 1.5- to 1.6-fold. On the other hand, in vitro bioaccessibility of lycopene from tomato was not increased by HPH under any of the conditions investigated. Instead, the results suggested that lycopene bioaccessibility was limited by a combination of the low solubility of lycopene in dietary lipids and entrapment in the cellular network. Carotene uptake by Caco-2 cells appeared to be mainly dependent upon the carotene concentration of the digesta, but cis-trans isomerization had a significant impact on the micellarization efficiency of carotenes. We therefore conclude that HPH is an interesting option for increasing the bioaccessibility of carotenes from fruits and vegetables while maintaining a high nutrient content, but that the results will depend on both food source and type of carotene.

PRACTICAL APPLICATION

A better understanding of the correlation between the processing of fruits and vegetables, microstructure and nutrient bioaccessibility can be directly applied in the production of food products with an increased nutritional value.

Application of in vitro bioaccessibility and bioavailability methods for calcium, carotenoids, folate, iron, magnesium, polyphenols, zinc, and vitamins B(6), B(12), D, and E

A review of in vitro bioaccessibility and bioavailability methods for polyphenols and selected nutrients is presented. The review focuses on in vitro solubility, dialyzability, the dynamic gastrointestinal model (TIM)™, and Caco-2 cell models, the latter primarily for uptake and transport, and a discussion of how these methods have been applied to generate data for a range of nutrients, carotenoids, and polyphenols. Recommendations are given regarding which methods are most justified for answering bioaccessibility or bioavailability related questions for specific nutrients. The need for more validation studies in which in vivo results are compared to in vitro results is also discussed.