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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Plant, Soil and Nutrition Research » Research » Publications at this Location » Publication #309548
Title: Higher iron pearl millet (Pennisetum glaucum L.) provides more absorbable iron that is limited by increased polyphenolic content

Author
item Tako, Elad
item REED, SPENSER - Cornell University
item BUDIMAN, JESSICA - Cornell University
item Hart, Jonathan
item Glahn, Raymond

Submitted to: Nutrition Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2014
Publication Date: 1/23/2015
Citation: Tako, E.N., Reed, S.M., Budiman, J., Hart, J.J., Glahn, R.P. 2015. Higher iron pearl millet (Pennisetum glaucum L.) provides more absorbable iron that is limited by increased polyphenolic content. Nutrition Journal. 14:11.

Interpretive Summary: The objective of this study was to compare the capacity of iron (Fe) biofortified and standard pearl millet (Pennisetum glaucum L.) to deliver Fe for hemoglobin (Hb) synthesis. Pearl millet is the most widely grown type of millet. It is common primarily in West Africa and the Indian subcontinent, and is well adapted to growing areas characterized by drought, low soil fertility, and high temperature. Because of its tolerance to difficult growing conditions, it can be grown in areas where other cereal crops, such as maize or wheat, would not survive. It accounts for approximately 50% of the total world production of millet. Given the pervasive nature of Fe deficiency, and the widespread use of pearl millet in areas of the world affected by Fe deficiency, it is important to establish whether biofortified pearl millet can improve Fe nutriture. Two lines of pearl millet, a low Fe control ( “Low Fe”) and Fe biofortified (“High Fe”) (Fe concentrations were 26ug and 85ug Fe/g, respectively) were used. Pearl millet based diets were formulated to meet the nutrient requirements for the broiler (Gallus gallus) except for Fe (dietary Fe concentrations were 22.1+/-0.52 and 78.6+/-0.51 mg/kg for the Low-Fe and High-Fe diets, respectively). For 6 weeks, Hb, feed-consumption and body weight were measured (n=12). Final total Hb-Fe contents (PARAMETER FOR Fe status) differed between the Low-Fe and High-Fe (26.7+/-1.4 and 15.5+/-0.8 mg, respectively) pearl millet groups (P<0.05). DMT-1, DcytB, and ferroportin mRNA expression (proteins that participate in Fe metabolism) was higher (P<0.05) and liver ferritin (cellular Fe storage unit) was lower (P<0.05) in the Low-Fe group versus High-Fe group. In vitro (intestinal cell culture) comparisons indicated that the High Fe pearl millet should provide more absorbable Fe; however, the cell ferritin values of the in vitro bioassay were very low. Such low values in this bioassay typically indicate the presence of high levels of polyphenolic compounds or/and phytic acid that inhibit Fe absorption. LC/MS analysis yielded 15 unique parent aglycone polyphenolic compounds elevated in the High-Fe line, corresponding to a m/z = 431.09. We concluded that the High-Fe diet appeared to deliver more absorbable Fe as evidenced by the increased Hb and Hb-Fe status. Our results suggest that some pearl millet varieties with higher iron contents also contain elevated polyphenolic concentrations, which inhibit Fe bioavailability. Our observations are important as these polyphenols compounds represent potential targets which can perhaps be manipulated during the breeding process to yield improved dietary Fe bioavailability. Therefore, the polyphenolic and phytate profiles of pearl millet must be carefully evaluated in order to further improve the nutritional benefit of this crop.

Technical Abstract: Background: Our objective was to compare the capacity of iron (Fe) biofortified and standard pearl millet (Pennisetum glaucum L.) to deliver Fe for hemoglobin (Hb) synthesis. Pearl millet is the most widely grown type of millet. It is common primarily in West Africa and the Indian subcontinent, and is well adapted to growing areas characterized by drought, low soil fertility, and high temperature. Because of its tolerance to difficult growing conditions, it can be grown in areas where other cereal crops, such as maize or wheat, would not survive. It accounts for approximately 50% of the total world production of millet. Given the pervasive nature of Fe deficiency, and the widespread use of pearl millet in areas of the world affected by Fe deficiency, it is important to establish whether biofortified pearl millet can improve Fe nutriture. Methods: Two isolines of pearl millet, a low Fe control ( “DG-9444”, Low Fe) and biofortified (“ICTP 8203 Fe”, High Fe) in Fe (26ug and 85ug Fe/g, respectively) were used. Pearl millet based diets were formulated to meet the nutrient requirements for the broiler (Gallus gallus) except for Fe (dietary Fe concentrations were 22.1+/-0.52 and 78.6+/-0.51 mg/kg for the Low-Fe and High-Fe diets, respectively). For 6 weeks, Hb, feed-consumption and body weight were measured (n=12). Results: Final total Hb-Fe contents differed between the Low-Fe and High-Fe (26.7+/-1.4 and 15.5+/-0.8 mg, respectively) pearl millet groups (P<0.05). DMT-1, DcytB, and ferroportin mRNA expression was higher (P<0.05) and liver ferritin was lower (P<0.05) in the Low-Fe group versus High-Fe group. In vitro comparisons indicated that the High Fe pearl millet should provide more absorbable Fe; however, the cell ferritin values of the in vitro bioassay were very low. Such low values in this bioassay typically indicate the presence of high levels of polyphenolic compounds or/and phytic acid that inhibit Fe absorption. LC/MS analysis yielded 15 unique parent aglycone polyphenolic compounds elevated in the High-Fe line, corresponding to a m/z = 431.09. Conclusions: The High-Fe diet appeared to deliver more absorbable Fe as evidenced by the increased Hb and Hb-Fe status. Our results suggest that some pearl millet varieties with higher iron contents also contain elevated polyphenolic concentrations, which inhibit Fe bioavailability. Our observations are important as these polyphenols compounds represent potential targets which can perhaps be manipulated during the breeding process to yield improved dietary Fe bioavailability. Therefore, the polyphenolic and phytate profiles of pearl millet must be carefully evaluated in order to further improve the nutritional benefit of this crop.