Location: Children's Nutrition Research Center2013 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 6250-5100-051-20S (Project #2).
1. Magnesium in bone health. An important, but poorly investigated mineral for bone health in children is magnesium. Researchers at the Children's Nutrition Research Center in Houston, Texas, determined that there was a significant relationship between the amount of magnesium in the diet and the amount of mineral in bone. This relationship was such that increasing the amount of magnesium in the diet led to substantially more dense and thus likely stronger bones. These findings may be important in developing dietary recommendations for children that include emphasis on key sources of magnesium such as dairy products, vegetables, and nuts.
2. Calcium fertilizer is important for seed nutritional quality in peanut. Peanuts are grown in sandy soils, which often have low levels of plant-required mineral nutrients such as calcium. For many soil types, peanut farmers apply a calcium fertilizer (gypsum) to improve peanut yields and the quality of the harvested seeds; however, there is little information on the effect of soil calcium application on the plant's uptake of other minerals, or the delivery of these minerals to the pod walls and seeds. Using different peanut varieties and different calcium fertilizer treatments, plant researchers at the Children's Nutrition Research Center in Houston, Texas, found that calcium applications resulted in higher concentrations of calcium, sulfur, and zinc in seeds, but showed slight decreases in phosphorus and sodium concentrations. There were no effects on any other minerals studied. These results provide useful information on the growing conditions and agricultural methods needed to maintain peanut yield and seed nutritional quality in the future.
3. Location, Location, Location - where a protein resides within a plant cell. Determining where a given protein is located within a cell often provides clues about its function. To help determine where a given protein is located within a cell, Children's Nutrition Research Center researchers in Houston, Texas, have generated a set of green fluorescence protein (GFP) marker lines in the plant Medicago truncatula that allows visualization of the different parts of the plant cell. It is expected that this marker set will prove to be a useful resource in the study of any given biological pathway, and thus a germplasm release has been completed for the entire marker set so it can be available for use to the plant research community. Currently, we are utilizing this marker set to uncover the function of proteins that are required for calcium oxalate crystal formation. The calcium bound in the crystals of calcium oxalate has been shown to be unavailable for nutritional absorption by humans and other animals. By gaining a better understanding of how plants form these crystals we can design strategies to decrease the amount of calcium bound in these crystals and improve the nutritional quality of plant foods.
Lopez-Millan, A.-F., Grusak, M.A., Abadia, J. 2012. Carboxylate metabolism changes induced by Fe deficiency in barley, a Strategy II plant species. Journal of Plant Physiology. 169(11):1121-1124.