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

Abstract

BackgroundIron deficiency is an enduring global health problem that requires new remedial approaches. Iron absorption from soybean-derived ferritin, an ∼550-kDa iron storage protein, is comparable to bioavailable ferrous sulfate (FeSO4). However, the absorption of ferritin is reported to involve an endocytic mechanism, independent of divalent metal ion transporter 1 (DMT-1), the transporter for nonheme iron.ObjectiveOur overall aim was to examine the potential of purified ferritin from peas (Pisum sativum) as a food supplement by measuring its stability under gastric pH treatment and the mechanisms of iron uptake into Caco-2 cells.MethodsCaco-2 cells were treated with native or gastric pH–treated pea ferritin in combination with dietary modulators of nonheme iron uptake, small interfering RNA targeting DMT-1, or chemical inhibitors of endocytosis. Cellular ferritin formation, a surrogate measure of iron uptake, and internalization of pea ferritin with the use of specific antibodies were measured. The production of reactive oxygen species (ROS) in response to equimolar concentrations of native pea ferritin and FeSO4 was also compared.ResultsPea ferritin exposed to gastric pH treatment was degraded, and the released iron was transported into Caco-2 cells by DMT-1. Inhibitors of DMT-1 and nonheme iron absorption reduced iron uptake by 26–40%. Conversely, in the absence of gastric pH treatment, the iron uptake of native pea ferritin was unaffected by inhibitors of nonheme iron absorption, and the protein was observed to be internalized in Caco-2 cells. Chlorpromazine (clathrin-mediated endocytosis inhibitor) reduced the native pea ferritin content within cells by ∼30%, which confirmed that the native pea ferritin was transported into cells via a clathrin-mediated endocytic pathway. In addition, 60% less ROS production resulted from native pea ferritin in comparison to FeSO4.ConclusionWith consideration that nonheme dietary inhibitors display no effect on iron uptake and the low oxidative potential relative to FeSO4, intact pea ferritin appears to be a promising iron supplement.

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

“…Iron is an essential micronutrient for seed embryo development, and a large proportion of the iron in pea seeds is stored as ferritin, which acts as a store for the seedling following germination ( Ravet et al, 2009 ). Plant ferritin is located in plastids, and so ferritin-iron in seeds is surrounded by multiple membranes, which can hinder the release of iron during digestion ( Moore et al, 2018 ); however, ferritin-iron in its purified form has been shown to exhibit good bioavailability in both pea and soybean ( Lönnerdal et al, 2006 ; Perfecto et al, 2018 ).…”

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

“…A large proportion of the iron in pea seeds is stored as ferritin, which acts as an iron store for the seedling following germination (Briat et al 2010). Plant ferritin is located in plastids, meaning that ferritin-iron is surrounded by several membranes, which can hinder the release of iron during digestion (Moore et al 2018); however, ferritin-iron in purified form has good bioavailability (L€ onnerdal et al 2006;Perfecto et al 2018).…”

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

“…Peas are a rich source of ferritin; however, the high phytic acid content within peas can lead to a low level of iron bioavailability [ 30 ]. Purified pea-ferritin iron could indeed provide a suitable alternative, and highly bioavailable, iron source [ 30 , 31 ]. The molecular structure of ferritin has provided inspiration for innovative nanoparticulate forms of iron [ 32 , 33 ].…”