Gum Arabic-Derived Hydroxyproline-Rich Peptides Stimulate Intestinal Nonheme Iron Absorption via HIF2α-Dependent Upregulation of Iron Transport Proteins.

The stimulation of host iron absorption is a promising antianemia strategy adjunctive/alternative to iron intervention. Here, gum arabic (GA) containing 3.14 ± 0.56% hydroxyproline-rich protein with repetitive X-(Pro/Hyp)n motifs was found to increase iron reduction, uptake, and transport to upregulate duodenal cytochrome b (Dcytb), divalent metal transporter 1 (DMT1), ferroportin, and hephaestin to inhibit hypoxia-inducible factor (HIF) prolyl hydroxylase (PHD) and to stabilize HIF2α in polarized Caco-2 cell monolayers in a dose-dependent manner, and this was dependent on its protein fraction, rather than the polysaccharide fraction. Three abundant GA-derived hydroxyproline-containing dipeptides of Hyp-Hyp, Pro-Hyp, and Ser-Hyp were detected by liquid chromatography-mass spectrometry in the lysates of polarized Caco-2 cell monolayers at the maximum levels of  0.167 ± 0.021, 0.134 ± 0.017, and 0.089 ± 0.015 µg/mg of protein, respectively, and showed desirable docking affinity energy values of -7.53, - 7.91, and -7.39 kcal/mol, respectively, against human PHD3. GA-derived peptides also acutely increased duodenal HIF2α stability and Dcytb, DMT1, ferroportin, and hephaestin transcription in rats (P < 0.05). Overall, GA-derived hydroxyproline-rich peptides stimulated intestinal iron absorption via PHD inhibition, HIF2α stabilization, and subsequent upregulation of iron transport proteins.

Gum Arabic-Stabilized Ferric Oxyhydroxide Nanoparticles for Efficient and Targeted Intestinal Delivery of Bioavailable Iron.

Nanostructured iron(III) compounds are promising food fortificants with desirable iron bioavailability and food compatibility. Here, gum arabic (GA) solubilized 252 mg of iron(III) per g at neutral pH in the form of GA-stabilized ferric oxyhydroxide nanoparticles (GA-FeONPs) with Z-average size of 142.7 ± 5.9 nm and ζ-potential of -20.50 ± 1.25 mV. Calcein-fluorescence-quenching assay revealed well-absorbed iron from GA-FeONPs by polarized Caco-2 cells due to efficient macropinocytic internalization and asialoglycoprotein receptor-mediated specific endocytosis facilitated by the polypeptide and arabinogalactan fractions of GA, respectively, with endocytosed GA-FeONPs being in part basolaterally transcytosed and in another part degraded into cellular labile iron pool. GA-FeONPs showed good colloidal stability under varied pH, gastrointestinal, thermal processing, and spray/freeze drying conditions and displayed remarkably weaker pro-oxidant activity than FeSO4 in glyceryl trilinoleate emulsion (P < 0.05). Oral pharmacokinetics unveiled desirable iron bioavailability of GA-FeONPs relative to FeSO4, i.e., 124.27 ± 5.91% in aqueous solution and 161.64 ± 5.01% in milk. Overall, GA-FeONPs are a promising novel iron fortificant with food-compatible, efficient, and targeted intestinal iron delivery and sustained iron-release properties.

Chondroitin sulfate and its nanocomposites with protamine or chitosan stabilize and deliver available nanosized iron.

Nanostructured iron (III) compounds are promising candidates for iron fortification applications due to their good solubility, bioavailability, and redox inertia. The current study synthesized ferric oxyhydroxide nanoparticles (FeONPs) based on chondroitin sulfate (ChS) and its nanocomposites with protamine sulfate (PS) or chitosan (CS) in neutral aqueous solution under ambient conditions, and evaluated their iron availability to polarized human intestinal epithelial (Caco-2) cells. Ultraviolet-visible spectroscopy, dynamic light scattering, transmission electron microscopy and energy-dispersive X-ray spectroscopy showed that ChS-FeONPs were wave-like anionic particles where FeONPs attached on the polysaccharide chains and PS/ChS-FeONPs and CS/ChS-FeONPs were irregular anionic nanoparticles where FeONPs scattered across the entire region. The calcein-fluorescence-quenching assay in polarized Caco-2 cells showed good iron uptake from ChS-FeONPs, PS/ChS-FeONPs and CS/ChS-FeONPs mainly via endocytosis, with the latter two exhibiting better iron absorption. Overall, our study provides a more facile and greener alternative route to synthesize the bioavailable nano-sized iron.