Location: Children's Nutrition Research Center2012 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:
Significant research progress was accomplished during the year. To review the progress, please refer to project 6250-51000-051-10S (Project 1) and 6250-51000-051-20S (Project 2).
1. Effects of vitamin D supplementation in children. The importance of vitamin D for ensuring the health of children has long been understood. Over time, however, dietary recommendations for vitamin D intake have varied, with some eras seeing higher levels recommended and some lower. Researchers at the Children's Nutrition Research Center in Houston, Texas, analyzed data and have shown conclusively that giving healthy children an extra 1000 IU/day of vitamin D, although likely safe, has no benefit to calcium absorption and therefore cannot be advocated on bone health grounds. This means that caregivers do not need to emphasize the use of high-dose supplements above the recommended daily amounts (RDA) for children. This information has benefits to the dairy industry whose products are key in providing adequate, but not excessive, vitamin D for children.
2. Long-term trends in the mineral nutritional quality of broccoli florets. Crop breeding is often focused on yield improvement, rather than nutritional improvement. Thus, researchers asked the question whether long-term breeding efforts in broccoli had resulted in diminished concentrations of various essential minerals. Scientists at the Children's Nutrition Research Center in Houston, Texas, grew 14 broccoli cultivars released over 50 years, and harvested market-sized florets for the analysis of mineral concentrations. We demonstrated that there were significant cultivar differences in floret concentrations for several minerals, but no clear downward trends between concentration and year of cultivar release. These results confirm that broccoli mineral concentrations have not declined over the years, and provide a guide for mineral levels in broccoli that should be maintained as other characteristics are manipulated by breeders in the future.
3. Engineering calcium oxalate crystal formation in plants. Calcium oxalate crystals can help protect plants from chewing insects but not all plants make these crystals. Research conducted at the Children's Nutrition Research Center in Houston, Texas, has shown that it is now possible to engineer a non-calcium oxalate crystal accumulating plant, such as Arabidopsis, to form crystals of calcium oxalate. Thus, engineering this form of plant protection in important crop plants appears possible. Such a feat would help reduce the need for chemical pesticides in producing food stuffs and other plant goods.Zhai, J., Jeong, D.-H., De Paoli, E., Park, S., Rosen, B.D., Li, Y., Gonzalez, A.J., Yan, Z., Kitto, S.L., Grusak, M.A., Jackson, S.A., Stacey, G., Cook, D.R., Green, P.J., Sherrier, D.J., Meyers, B.C. 2011. MicroRNAs as master regulators of the plant NB-LRR defense gene family via the production of phased, trans-acting siRNAs. Genes and Development. 25:2540-2553.