Submitted to: Nutrition Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2012
Publication Date: 1/4/2013
Citation: Tako, E.N., Hoekenga, O., Kochian, L.V., Glahn, R.P. 2013. High bioavailable iron maize (Zea mays L.) developed through molecular breeding provides more absorbable iron in vitro and in vivo. Nutrition Journal. 12:3.
Interpretive Summary: Iron-deficiency is the most common micronutrient-deficiency worldwide. Iron-biofortification is a preventative strategy that alleviates iron-deficiency by improving the amount of absorbable-iron in staple food crops. In the present study, we used an in vitro system that simulates the human stomach and small intestine (using cultured human cells) for measuring Fe bioavailability in food crops and diets. This in vitro system was employed as the guiding tool for breeding and development of two maize lines with contrasting Fe-bioavailability (i.e., Low and High). Poultry feeding trials were then used to confirm that the maize provides more iron to living animals. Diets were made with 75% maize of either low (“Low”) or-high (“High”) iron-bioavailability maize, with (+) or without (-) added iron. Chicks were fed the diets for 6-weeks. Several physiological markers were used to assess the iron status of the birds; Hemoglobin (Hb), levels of the Fe storage protein ferritin in the liver, and the expression of iron-related transporter/enzyme genes whose expression increases in response to low Fe status. The bird’s ability to maintain their hemoglobin status and total-body-Hemoglobin-Fe values were used to estimate Fe-bioavailability from the diets. The expression of the iron related transporters was higher (P<0.05) in the “Low” vs. “High” groups, indicating lower iron-status and adaptation to less iron-bioavailability. In general, Hb-concentrations, Hb-Fe and liver-ferritin (markers for iron status) were higher in the “High“ vs. “Low” groups (P<0.05), indicating greater iron-absorption from the diet and improved iron-status. Hemoglobin maintenance ability was also higher in poultry fed the “High” variety (indicating increased iron bioavailability). We conclude that the “High” maize variety contains more bioavailable-iron than the “Low” maize. Since maize is a major staple food crop in countries that suffer from dietary iron deficiency and anemia, our findings are important to promote better nutrition and health in those regions. Maize shows promise for iron-biofortification; therefore, human trials should be conducted to determine the efficacy of consuming the high-bioavailable-Fe maize to reduce Fe-deficiency.
Technical Abstract: Iron (Fe) deficiency is the most common micronutrient deficiency worldwide. Fe biofortification is a preventative strategy that alleviates Fe deficiency by improving the amount of absorbable Fe in staple crops, such as maize. This approach reaches populations that fortification and supplementation programs may not address by creating new varieties for farmers with enhanced nutritional quality. Using the Caco-2 cell model as an evaluation tool, we developed new maize varieties predicted to differ significantly in Fe nutritional quality. Here, the maize varieties were tested with the Caco-2 cell model to estimate bioavailable Fe and then validated with the poultry (Gallus gallus) iron model. Diets made with 75% w/w maize of either the “Low” or “High” Fe bioavailability maize fed chicks (n=10) for 6 weeks. Raw and cooked maize were both evaluated. Fe homeostasis in chicks was estimated using hemoglobin (Hb), liver ferritin, reporter gene expression patterns and other assays. Reporter genes were expressed higher (P<0.05) in the “Low” fed groups than the “High” fed groups, indicating lower Fe status and adaptation to less Fe bioavailability. At times, Hb concentrations, Hb-Fe and liver ferritin were higher in the “High“ groups vs. the “Low” groups (P<0.05), indicating greater Fe absorption from the diet and improved Fe status. We conclude that the “High” variety contains more bioavailable Fe than the ”Low” and that maize shows promise for Fe biofortification. Human feeding trials should be conducted to determine the potential of the high bioavailable Fe maize to reduce Fe deficiency in susceptible populations.