H-ferritin in sows' colostrum- and milk-derived extracellular vesicles: a novel iron delivery concept

Iron deficiency anemia is a significant problem in piglets, as they are born with insufficient iron stores for supporting their rapid body growth. Further, sows' milk contains inadequate iron levels for meeting the demands of piglet rapid growth in the pre-wean stage. The forms of iron present in the milk are essential to understanding bioavailability and potential routes for supplementing iron to mitigate iron deficiency anemia in piglets. Recently, our studies showed that H-ferritin (FTH1) is involved in iron transport to different tissues and can be used as an oral iron supplement to correct iron deficiency in rats and monkeys. In this study, we investigate the FTH1 levels in colostrum and milk in Yorkshires-crossbred sows (n = 27) and collected samples at the 1st, 15th, and 28th days of lactation to measure FTH1. Colostrum and milk were found to have FTH1, but there is no significant difference between the different days of lactation. FTH1 has been observed to be enriched in extracellular vesicles (EVs) of other species, and therefore examined the EVs in the samples. Colostrum-derived EVs were enriched with L-ferritin compared to FTH1, while in milk-derived EVs, only FTH1 was detected (P = 0.04). In milk-derived EVs, FTH1 was significantly higher (P = 0.021; P = 006) than FTH1 in colostrum-derived EVs. Furthermore, FTH1 levels of milk-derived EVs were significantly higher (P = 0.0002; P = 0004) than whole milk and colostrum FTH1. These results indicate that FTH1 is enriched in the milk-derived EVs and suggest that EVs play a predominant role in the FTH1 delivery mechanism for the piglet. The extent to which FTH1 in EVs accounts for the overall iron delivery mechanism in piglets is yet to be determined.