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United States Department of Agriculture

Agricultural Research Service

Research Project: Absorption and Metabolism of Essential Mineral Nutrients in Children

Location: Children's Nutrition Research Center

2011 Annual Report


1a.Objectives (from AD-416)
The overall goal of our research is to develop nutritionally enhanced plant foods that provide increased nutrient bioavailability and absorption in children. Ultimately, this plant food research in combination with mineral nutrition research in children will allow researchers to provide guidance regarding food intake and fortification, specifically related to iron, zinc, Vitamin C and calcium. Specific objectives of this research include:.
1)use genetic, molecular, and physiological approaches to define the role of specific genes and gene products in the acquisition and whole-organism partitioning of minerals (iron, zinc, Vitamin C, calcium, and magnesium) and other factors that inhibit or promote absorption of these minerals in plant foods;.
2)Conduct animal and human feeding studies to determine mineral bioavailability of the nutritionally enhanced crops;.
3)develop new, cost-effective methods for the intrinsic labeling of plant foods for use in nutrient bioavailability studies;.
4)determine the absorption of dietary calcium, magnesium, iron, and zinc in children and the influence of other nutrients and dietary factors on the absorption;.
5)(deleted due to resignation of investigator);.
6)determine the effect of dietary components on the upregulation of intestinal iron transporter genes in human models;.
7)characterize dynamic indices of bone formation by quantitative histomorphometry and micro computed tomography in 7 mouse models;.
8)quantitate specific gene expression in calvarial osteoblasts derived from mouse models; and.
9)determine the effects of hormone ablation, iron loading, ASC feeding and plant derived antioxidants on bone parameters in vivo. These efforts will expand our capabilities for assessing the absorption and metabolism of various plant-derived minerals and phytochemicals and will provide novel information directly useful to government, industry and the consumer related to dietary requirements. The generation of new bioavailability data for various plant-derived nutrients will be established and such data will have global application and provide a strong basis for evidence-based nutritional recommendations to be developed.


1b.Approach (from AD-416)
These research studies will utilize diverse plant species, human cell culture systems, or human subjects. CNRC scientists will focus on characterizing plant genes and gene products that are involved with mineral transport in the plant, with a focus on iron, zinc, calcium, and magnesium. We will use specifically manipulated transgenic lines, various plant mutants, or unique plant genotypes to assess the impact of altered genes on mineral transport and storage throughout various plant tissues. In order to facilitate studies of bioavailability of plant-based nutrients, we will develop new, cost-effective methods for the intrinsic, stable-isotopic labeling of plant foods, by testing different hydroponic strategies and altered timings of isotope application to the plants. Food-based factors associated with the dietary delivery of the essential minerals calcium, iron, and zinc will be investigated using human in vitro cell culture and human subject-based experiments. We will conduct a controlled trial of vitamin D supplementation to assess the effects of vitamin D status on calcium absorption in small children. We will evaluate different types of whole diets (lacto-ovo vegetarian) on iron status and the effects of differing intakes of zinc on zinc and copper absorption. We will determine if benefits previously seen for prebiotic fibers in enhancing calcium absorption also occur for iron absorption. Low abundance stable isotopes of each element will be used to track absorption in each of these human studies. In vitro cell culture models will seek to identify the genetic basis for iron and zinc absorption in intestinal cells, by monitoring mineral absorption in combination with the differential expression of various metal transporter genes. We will explore the roles of aldose reductase and aldehyde reductase in modulating oxidative stress in cells, as well as their separate role in providing the starting substrates for the ascorbate synthesis pathway. Ultimately we will have a better understanding of the role of vitamin C in our diet.


3.Progress Report
Project 1. We completed recruitment for the vitamin D supplementation trial in 4-8 yr old children and the absorption of calcium, zinc and magnesium in these subjects. All samples have been analyzed on the mass spectrometer and data entered. We completed IRB submission for the last phase of the study and began the recruitment process. We also conducted experiments in which we treated the mammalian cell line, Caco-2 cells, with different concentrations of iron for different durations of exposure at 6, 24, 48, 72 and 96 hrs. We measured DMT1 expression under different iron concentrations/exposures using a qPCR. We will measure the expression of two proteins located on the brush border of the cell, also involved in iron uptake called Dcytb1 and Dcytb2 under the same conditions when able. We also began to define the structures and mode of interactions of Osterix (which is a novel transcription factor that is essential for bone formation) with N066. N066 is an ascorbate dependent enzyme that acts as a repressor of Osterix. N066 is also a histone demethylase, a reaction which requires an ascorbate-dependent hydroxylation. Ascorbate deficiency leads to the accumulation of inactive Osterix in immature cells that are responsible for bone formation. Thus we hypothesize that N066-Osterix interaction is the key to cell differentiation for bone formation. We have now succeeded in expressing N066 and Osterix. Project 2. We have completed genetic and molecular studies directed toward identifying new genes required for crystal accumulation in Medicago truncatula. We have completed three back-crossings of two calcium oxalate crystal insertion mutants to allow easier identification of the defective genes. We have been able to isolate a small fragment of genomic DNA that contains an insertion in mutant gene 1. We are currently using this small fragment of DNA to screen a gene library to isolate mutant gene 1. We also completed mineral analysis on both back-crossed mutants and determined that their mineral composition is similar to control plants. We continued our work to understand how plant calcium transporters have evolved. We have used biochemical and genetic tools to show that a particular group of transporters work in tandem to perform specific functions. The concept of these transporters working in teams is novel. We used unique populations of soybean, bean, or other model plant species to study seed mineral concentrations and root processes that help the plant absorb nutrients, such as iron. We have initiated the seed mineral analysis of a large population of soybeans, grown in replicated field plots in Beltsville, MD. We have grown several plant species to assess root traits, leaf mineral, or seed mineral characteristics. Data have been analyzed to identify regions of the plant genome that are linked to specific seed or leaf mineral concentrations, or enhanced ability of the root system to absorb iron. Parent lines have now been crossed with unique genetic lines, to produce progeny with an altered genetic makeup. These lines will be used to test and confirm which regions of the DNA are most associated with the measured nutritional traits.


4.Accomplishments
1. Identifying new genes for enhancing calcium bioavailability in edible plants. Calcium, when present as the calcium oxalate crystal in foods, is unavailable for nutritional absorption. Such crystals are common in edible plant foods, thereby reducing their nutritional quality. Researchers at the Children's Nutrition Research Center in Houston, TX, have identified a small region of DNA within the genome of the model legume Medicago truncatula that contains a previously unidentified gene required for calcium oxalate crystal production. When this gene is "turned off" there is a dramatic reduction in the plants ability to produce these crystals. It is anticipated that the isolation of such a key gene will provide the molecular target that, when inactivated, will enhance the nutritional value of economically important crop plants.

2. Improved yield and nutritional content in melons. Grafting is a method of plant propagation where the tissues of one plant are encouraged to fuse with those of another. It is commonly used for the propagation of many melons grown commercially. Plant scientists at the Children's Nutrition Research Center have successfully used genetically modified rootstocks for grafting of melons. These modified rootstocks produced larger, more robust melons when compared with typical plants. Using genetically engineered rootstocks could be a means of boosting plant productivity for many commercial crops that use grafting techniques. This technique would be particularly compelling for the general public in that the genetic modifications do not enter the food supply.

3. Plant root responds to differing iron deficiency conditions. Plants acquire iron from soils via processes functioning in their roots, but the availability of iron in different soils can sometimes make it difficult for those roots to absorb enough iron to meet their needs. Soils that are alkaline (high pH) and contain high levels of calcium carbonate (also known as calcareous soils) are poor sources of iron, but some plants have found ways to acquire iron in these very challenging soils. Plant scientists at the Children's Nutrition Research Center have found that the roots of a certain legume plant could synthesize and release compounds that increased the levels of available iron in the soil. Moreover these plant roots could also change their internal biochemical properties to help them function more effectively with less iron. The identification of these changes and the identification of some of the genes responsible for them are providing tools and insights to help us develop new crops with improved abilities to acquire iron.


Review Publications
Sperotto, R.A., Boff, T., Duarte, G.L., Santos, L.S., Grusak, M.A., Fett, J.P. 2010. Identification of putative target genes to manipulate Fe and Zn concentrations in rice grains. Journal of Plant Physiology. 167(17):1500-1506.

Blair, M.W., Knewtson, S.J., Astudillo, C., Li, C.M., Fernandez, A.C., Grusak, M.A. 2010. Variation and inheritance of iron reductase activity in the roots of common vean (Phaseolus vulgaris L.) and association with seed iron accumulation QTL. Biomed Central (BMC) Plant Biology. 10:215.

Stephens, B.W., Cook, D.R., Grusak, M.A. 2011. Characterization of zinc transport by divalent metal transporters of the ZIP family from the model legume medicago truncatula. Biometals. 24(1):51-58.

Hill, K.M., McCabe, G.P., McCabe, L.D., Gordon, C.M., Abrams, S.A., Weaver, C.M. 2010. An inflection point of serum 25-hydroxyvitamin D for maximal suppression of parathyroid hormone is not evident from multi-site pooled data in children and adolescents. Journal of Nutrition. 140(11):1983-1988.

Ross, A.C., Manson, J.E., Abrams, S.A., Aloia, J.F., Brannon, P.M., Clinton, S.K., Durazo-Arvizu, R.A., Gallagher, J.C., Gallo, R.L., Jones, G., Kovacs, C.S., Mayne, S.T., Rosen, C.J., Shapses, S.A. 2011. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. Journal of Clinical Endocrinology and Metabolism. 96(1): 53-58.

Thacher, T.D., Abrams, S.A. 2010. Relationship of calcium absorption with 25(OH)D and calcium intake in children with rickets. Nutrition Reviews. 68(11):682-688.

Abrams, S.A. 2011. Dietary guidelines for calcium and vitamin D: a new era. Pediatrics. 127(3):566-568.

Thacher, T.D., Obadofin, M.O., O'Brien, K.O., Abrams, S.A. 2009. The effect of vitamin D2 and vitamin D3 on intestinal calcium absorption in Nigerian children with rickets. Journal of Clinical Endocrinology and Metabolism. 94(9):3314-3321.

Abrams, S.A. 2010. Setting dietary reference intakes with the use of bioavailability data: Calcium. American Journal of Clinical Nutrition. 91(5):1474S-1477S.

Venkatesh, M.P., Abrams, S.A. 2010. Oral lactoferrin for the prevention of sepsis and necrotizing enterocolitis in preterm infants. Cochrane Database Systematic Reviews. Issue 5:CD007137.

Kumari, M., Khazai, N.B., Ziegler, T.R., Nanes, M.S., Abrams, S.A., Tangpricha, V. 2010. Vitamin D-mediated calcium absorption in patients with clinically stable Crohn's disease: a pilot study. Molecular Nutrition and Food Research. 54(8):1085-1091.

Uenishi, K., Fujita, T., Ishida, H., Fujii, Y., Ohue, M., Kaji, H., Hirai, M., Kakumoto, M., Abrams, S.A. 2010. Fractional absorption of active absorbable algal calcium (AAACa) and calcium carbonate measured by a dual stable-isotope method. Nutrients. 2(7):752-761.

Abrams, S.A., Chen, Z. 2010. ICP-MS for isotope ratio measurement. In: Gross, M.L., Caprioli, R.M., editors-in-chief. The Encyclopedia of Mass Spectrometry: Elemental and Isotope Ratio Mass Spectrometry. Volume 5. Oxford, UK: Elsevier. p. 869-881.

Abrams, S.A. 2010. In vivo calcium metabolism by IRMS. In: Gross, M.L., Caprioli, R.M., editors-in-chief. The Encyclopedia of Mass Spectrometry: Elemental and Isotope Ration Mass spectrometry. Volume 5. Oxford, UK: Elsevier. p. 990-996.

Amaral, J.M., Abrams, S., Karaviti, L., Mckay, S.V. 2010. Effects of 1,25-dihydroxycholecalciferol on recovery and resolution of late transient neonatal hypocalcemia. International Journal of Pediatric Endocrinology. Available: http://www.hindawi.com/journals/ijpe/2010/409670.html

Hicks, P.D., Griffin, I.J. 2010. In vivo iron metabolism by IRMS. In: Gross, M.L., Caprioli, R.M., editors-in-chief. The Encyclopedia of Mass Spectrometry: Elemental and Isotope Ratio Mass Spectrometry. Volume 5. Oxford, UK: Elsevier. p. 996-1001.

Samarah, N., Abu-Yahya, A., Grusak, M.A. 2010. Effect of maturity stages for winter- and spring-sown chickpea (Cicer arietinum L.) on seed mineral content. Journal of Plant Nutrition. 33(14):2094-2103.

Abrams, S.A. 2011. Vitamin D deficiency and calcium absorption during childhood. In: Feldman, D., Pike, J.W., Adams, J.S., editors. Vitamin D. Third Edition. Volume 1. Oxford, UK: Elsevier. p. 647-656.

Hicks, P.D., Rogers, S.P., Hawthorne, K.M., Chen, Z., Abrams, S.A. 2011. Calcium absorption in very low birth weight infants with and without bronchopulmonary dysplasia. Journal of Pediatrics. 158(6):885-890.

Rodriguez-Celma, J., Lattanzio, G., Grusak, M.A., Abadia, A., Abadia, J., Lopez-Millan, A. 2011. Root responses of Medicago truncatula plants grown in two different iron deficiency conditions: changes in root protein profile and riboflavin biosynthesis. Journal of Proteome Research. 10(5):2590-2601.

Muzhingi, T., Gadaga, T.H., Siwela, A.H., Grusak, M.A., Russell, R.M., Tang, G. 2011. Yellow maize with high beta-carotene is an effective source of vitamin A in healthy Zimbabwean men. American Journal of Clinical Nutrition. 94(2):510-519.

Durmaz, E., Coruh, C., Dinler, G., Grusak, M.A., Peleg, Z., Saranga, Y., Fahima, T., Yazici, A., Ozturk, L., Cakmak, I., Budak, H. 2011. Expression and cellular localization of ZIP1 transporter under zinc-deficiency in wild emmer wheat. Plant Molecular Biology Reporter. 29(3):582-596.

Abrams, S.A. 2011. What are the risks and benefits to increasing dietary bone minerals and vitamin D intake in infants and small children?. Annual Review of Nutrition. 31:285-297.

Ross, A.C., Manson, J.E., Abrams, S.A., Aloia, J.F., Brannon, P.M., Clinton, S.K., Durazo-Arvizu, R.A., Gallagher, J.C., Gallo, R.L., Jones, G., Kovacs, C.S., Mayne, S.T., Rosen, C.J., Shapses, S.A. 2011. The 2011 dietary reference intakes for calcium and vitamin D: what dietetics practitioners need to know. Journal of American Dietetic Association. 111(4):524-527.

Abrams, S.A. 2011. Vitamin D requirements in adolescents: what is the target? American Journal of Clinical Nutrition. 93(3):483-484.

Connorton, J.M., Hirschi, K.D., Pittman, J.K. 2011. Mechanism and evolution of calcium transport across the plant plasma membrane, Section II: Plasma membrane transporters. In: Murphy, A.S., Peer W., Schultz, B. editors. The Plant Plasma Membrane, Plant Cell Monographs 19. Heidelberg, Germany: Springer-Verlag Berlin. p. 275-289.

Manohar, M., Shigaki, T., Mei, H., Park, S., Marshall, J., Aguilar, J., Hirschi, K.D. 2011. Characterization of "Arabidopsis" Ca(2+)/H(+) exchanger CAX3. Biochemistry. 50(28):6189-6195.

Wu, Q., Shigaki, T., Williams, K.A., Han, J., Kim, C., Hirschi, K.D., Park, S. 2011. Expression of an "Arabidopsis" Ca(2+)/H(+) antiporter CAX1 variant in petunia enhances cadmium tolerance and accumulation. Journal of Plant Physiology. 168(2):167-173.

Shigaki, T., Mei, H., Marshall, J., Li, X., Manohar, M., Hirschi, K.D. 2010. The expression of the open reading frame of "Arabidopsis" CAX1, but not its cDNA, confers metal tolerance in yeast. Plant Biology. 12(6):935-939.

Conn, S.J., Gilliham, M., Athman, A., Schreiber, A.W., Baumann, U., Moller, I., Cheng, N., Stancombe, M.A., Hirschi, K.D., Webb, A.A. 2011. Cell-specific vacuolar calcium storage mediated by "CAX1" regulates apoplastic calcium concentration, gas exchange, and plant productivity in "Arabidopsis". The Plant Cell. 23(1):240-257.

Manohar, M., Shigaki, T., Hirschi, K. 2011. Plant cation/H(+) exchangers (CAXs): biological functions and genetic manipulations. Plant Biology. 13(4):561-569.

Last Modified: 4/16/2014
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