Gastric digestion of pea ferritin and modulation of its iron bioavailability by ascorbic and phytic acids in caco-2 cells.
OBJECTIVE
To understand the digestive stability and mechanism of release and intestinal uptake of pea ferritin iron in caco-2 cell line model.


METHODS
Pea seed ferritin was purified using salt fractionation followed by gel filtration chromatography. The bioavailability of ferritin iron was assessed using coupled in vitro digestion/Caco-2 cell model in the presence or absence of ascorbic acid and phytic acid. Caco-2 cell ferritin formation was used as a surrogate marker of iron uptake. Structural changes of pea ferritin under simulated gastric pH were characterized using electrophoresis, gel filtration and circular dichroism spectroscopy.


RESULTS
The caco-2 cell ferritin formation was significantly increased (P<0.001) with FeSO(4) (19.3 +/- 9.8 ng/mg protein) and pea ferritin (13.9 +/- 6.19 ng/mg protein) compared to the blank digest (3.7 +/- 1.8 ng/mg protein). Ascorbic acid enhanced while phytic acid decreased the pea ferritin iron bioavailability. However, either in the presence or absence of ascorbic acid, the ferritin content of caco-2 cells was significantly less with pea ferritin than with FeSO(4). At gastric pH, no band corresponding to ferritin was observed in the presence of pepsin either on native PAGE or SDS-PAGE. Gel filtration chromatography and circular dichroism spectroscopy revealed a pH dependent loss of quaternary and secondary structure.


CONCLUSIONS
Under gastric conditions, the iron core of pea ferritin is released into the digestive medium due to acid induced structural alterations and dissociation of protein. The released iron interacts with dietary factors leading to modulation of pea ferritin iron bioavailability, resembling the typical characteristics of non-heme iron.
Bejjani
Satyanarayana
S
Micronutrient Research Group, National Institute of Nutrition, Indian Council of Medical Research, Jamai Osmania, Hyderabad 500007, India.
Pullakhandam
Raghu
R
Punjal
Ravinder
R
Nair
K Madhavan
KM
D001205:Ascorbic Acid / Q000494:pharmacology*; D001682:Biological Availability; D018938:Caco-2 Cells; D005293:Ferritins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D007501:Iron / Q000493:pharmacokinetics*; D008954:Models, Biological; D018532:Pisum sativum; D010833:Phytic Acid / Q000494:pharmacology*; D012639:Seeds
D010833:Phytic Acid; D005293:Ferritins; D007501:Iron; D001205:Ascorbic Acid