Location: Plant, Soil and Nutrition Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1. Determine the genes affecting iron level and bioavailability in edible portions of maize by utilizing quantitative trait loci (QTL) mapping and an in-vitro digestion/Caco-2 cell culture model system. Confirm this QTL information via in-vitro and in-vivo studies and transfer this information to plant breeders. Objective 2. Investigate the role and mechanisms of action of prebiotic compounds, beneficial bacteria, and plant phenolic constituents on the bioavailability of iron and zinc from the diet.
1b. Approach (from AD-416):
This project seeks to improve the bioavailability of iron (Fe) and zinc (Zn) in plant foods by two distinct strategies. First, a multidisciplinary, genomics-based approach will be used to identify the genes and chemical factors that modulate Fe bioavailability in maize grain, using maize as the model to demonstrate proof of concept for this work. The second approach defines how prebiotic (non-digestible carbohydrates) and polyphenolic compounds in plant foods influence Fe and Zn bioavailability and thereby enhance absorption of Fe and Zn from plant foods in the intestine. Maize Fe Bioavailability: The goal here is to improve the nutritional quality of maize with respect to Fe via identifying the genetic factors that contribute to improved seed-iron concentration and bioavailability. This will be accomplished by building on current genetic mapping of maize seed-Fe bioavailability using a simulated intestinal digestion/Caco-2 cell assay. Animal models will then be used to confirm the cell culture results before definitive testing in humans. By identifying the genes that contribute to seed-iron accumulation and bioavailability, plant breeders will be able to improve the nutritional quality of maize. Prebiotics, Beneficial Bacteria, Polyphenols and Fe/Zn Bioavailability: The gastrointestinal microflora is increasingly becoming recognized as a major factor in human health via systemic effects on gut health and nutrient absorption. Prebiotic compounds such as inulin dramatically alter the profile of intestinal microflora and this alteration may enhance absorption of Fe and Zn. Therefore, one of the goals here is to determine if prebiotics enhance Fe and Zn absorption via changes in gut microflora. The second subobjective is to determine if polyphenolic compounds play a significant role in Fe absorption in long term feeding trials. This will be accomplished via animal feeding trials and cell culture models, whereby foods will be compared that have low and high amounts of prebiotics (eg. inulin, raffinose, stachyose) and polyphenols (e.g., kaempferol, quercitin, chlorogenic acid, ferulic acid). In these studies Fe and Zn absorption from these foods will be measured, as well as their effect on the bacterial profile. By understanding the role of prebiotics and polyphenols in the absorption of these two essential minerals, plant foods and food products can be improved to provide more optimal nutrition.
3. Progress Report:
In previous years we utilized our screening tools to collaborate with a maize breeder within our research unit (Project1907-21000-032-00D) to identify regions of the maize genome that are linked to Fe bioavailability. Our initial efforts indicated that this was a very promising approach to improve the nutritional quality of maize and possibly other staple food crops. However, this part of the research has been put on hold while issues regarding the genetic analysis of these lines are addressed. As a complementary strategy we have completed phenotyping for seed Fe availability of a maize association (diversity) panel assembled by a collaborator, Dr. Ed Buckler of our USDA-ARS Robert Holley Center. Compounds present in seed coats of beans are known to be antioxidants and also inhibitors of iron absorption. Over the past year we have continued to investigate compounds that are inhibitors of iron absorption, and identified at least 2 compounds that appear to be promoters of Fe absorption. We are now working to publish these results and further define the mechanism(s) as to how these compounds interact with Fe and influence its bioavailability. Defining these mechanisms should contribute to our ability to significantly improve the nutritional quality of iron in beans and other staple food crops.
1. Low iron concentration in a majority of plant food staples is the main reason for iron deficiency in humans, especially in the developing world. ARS researchers at Ithaca, New York, identified the polyphenolic compounds that influence Fe bioavailability in black beans. One of these is myricetin which is a major inhibitor of Fe bioavailability. However, caffeic acid and epicatechin were also found to promote Fe bioavailability. These results are valuable to bean breeders allowing them to modify the concentration of these compounds to improve Fe bioavailability in black beans and thus combat Fe deficiency in humans. The impact of these findings can be extended to other crops such as lentils, peas, red beans and maize.
Pebsworth, P.A., Seim, G., Huffman, M.A., Glahn, R.P., Tako, E.N., Young, S.L. 2013. Soil consumed by chacma baboons is low in bioavailable iron and high in clay. Journal of Chemical Ecology. http://www.springerlink.com/openurl.asp?genre=article&id=DOI: 10.1007/s10886-013-0258-3.