2005 Annual Report
Year 1 (Addressed in FY2005) Complete 1st yr of wheat & buckwheat Se accumulation studies (1.1) Complete transgenic wheat accumulation of Se study (1.1) Develop cells lines and constructs for antioxidants & gene expression study (1.5) Develop Se speciation methodology (1.1) Complete interim blood analyses for Fe excretion study & write initial paper (1.9) Enroll subjects in elemental Fe powder study (2.1) Complete antibody prep & perform studies on up/down regulation of mineral transport in Caco-2 cells (3.1). Complete studies on Cu transporter trafficking in Caco-2 cells given high Zn media (3.2).
Year 2 (Addressed in FY2006) Complete 2nd yr of wheat & buckwheat Se accumulation studies (1.1) Complete anti-oxidants & gene expression study (1.5) Complete 1st yr of organic/conventional foods study (1.1) Report transgenic wheat study (1.1) Complete Se speciation in wheat study (1.1) Develop Zn algorithm & prepare paper (1.7) Enroll subjects in Zn requirement study (1.6) Complete elemental Fe powders study (2.1) Wrap up studies on up/down regulation of mineral transport in Caco-2 cells. Write manuscripts (3.1) Wrap up studies on Cu transporter trafficking. Write manuscripts (3.2)
Year 3 (Addressed in FY2007) Complete feeding portion of human high-Se beef study (1.3) Report antioxidants & gene expression study (1.5) Report wheat & buckwheat accumulation studies (1.1) Complete 2nd yr of organic/conventional foods study (1.1) Complete high-Se beef and aberrant crypt study (1.3) Complete Zn requirement study (1.6) Report elemental Fe powders study (2.1) Complete studies on low mineral intakes, metal transporters, and cadmium accumulation in intestinal cells (3.3) Complete studies on relationship between Cu deprivation & Hephestin activity (3.4)
Year 4 (Addressed in FY2008) Complete analyses for human high-Se beef study (1.4) Complete differences in bioavailability of mineral nutrients from organic/conventional broccoli (1.2) Report high-Se beef and aberrant crypt study (1.3) Complete study of phytate X Ca & Zn bioavailability (1.8) Report Zn requirement study (1.6) Complete microencapsulated Fe study (2.2) Wrap up Cu/Heph/Fe absorption studies. Write manuscripts (3.4) Complete study on marginal mineral & Cd exposure, analyze data (3.5).
Year 5 (Addressed in FY2009) Report human high-Se beef study (1.4) Complete comparison of high-Se foods aberrant crypt study (1.2) Report comparison of high-Se foods and aberrant crypt study (1.3) Report organic & conventional foods study (1.1) Report study of phytate X Ca & Zn bioavailability (1.8) Complete final report of Fe excretion data (1.9) Report microencapsulated Fe study (2.2) Wrap up studies in objective 3.5. Write manuscripts. Complete new 5-year proposal.
c. Showed that copper deficiency impairs red blood cell formation in addition to impairing iron absorption. In most mammalian species, dietary copper deficiency leads to iron deficiency anemia. One of the reasons for this phenomenon is reduced iron absorption from the gut caused by reduced protein concentration of a copper-dependent iron ferroxidase protein in the intestinal absorptive cells. However, copper deficiency is known to affect blood cell formation in pigs and humans. A recent study in our laboratory showed that injections of iron into copper-deficient, anemic rats did not raise serum iron concentration and did not cure the anemia; however, liver iron was elevated 3-fold. These data suggest that copper is required for red cell formation and/or hemoglobin synthesis. An enhanced understanding of the role of copper in blood cell formation and hemoglobin synthesis will help set recommendations for dietary copper intakes.
d. Determined that excess cadmium retention in the intestines of animals marginally deficient in some minerals is independent of metallothionein protein. Marginal dietary deficiencies of zinc, iron, and calcium in mammals greatly enhance the absorption of the toxic element cadmium. With these deficiencies, cadmium fed at very low dietary levels accumulates in the intestinal absorptive cells, kidney, and liver. Intestinal metallothionein is a natural compound induced by high intakes of cadmium to detoxify the element. We found that accumulation of cadmium in the intestinal cells of these deficient animals was not associated with elevated metallothionein. In addition, mice genetically altered to be free of functional metallothionein and made marginally deficient in zinc, iron, and calcium, were found to have elevated intestinal cadmium. These data suggest that metallothionein is not induced or required to accumulate cadmium in the intestine when the metal is fed at low levels to animals marginally deficient in zinc, iron, and calcium, and that cadmium accumulation occurs by some other unknown mechanism.
e. Delineated mechanisms of antioxidant activity of the sulforaphane and selenium chemicals found in plant foods (especially cruciferous vegetables). A series of experiments established models and conditions for studying how sulforaphane and selenium affect oxidative stress and modulate expression of antioxidant genes. Molecular and chemical methods were used to demonstrate that thioredoxin reductase is regulated by multiple dietary components, especially selenium and sulforaphane, and that silencing thioredoxin reductase results in greatly increased oxidative stress. An improved understanding of how diet influences oxidative stress will help determine dietary recommendations that can reduce the risk of chronic diseases such as cancer.
f. Determined that selenium-enhancement of buckwheat reduced selenium bioavailability. Plants grown on soils high in selenium accumulate selenium in the edible tissue, and such foods have the potential to be a good dietary source of the nutrient. A series of studies have demonstrated that the edible flour of wheat and buckwheat grown on high-selenium soils will accumulate selenium as much as 20-times beyond the average. Human and animal studies have demonstrated that selenium from high-selenium processed wheat is bioavailable and able to induce selenoprotein production and replete tissue stores of selenium. Buckwheat selenium, however, was not as bioavailable to rodents as pure chemical sources of selenium. These studies demonstrate that wheat has potential to be a good source of supplemental selenium, but the low bioavailability of buckwheat selenium may decrease its potential value as a supplemental source of selenium. The selenium enhancement of grains would be useful for increasing dietary selenium intakes, with possible health benefits related to the risk of chronic diseases.
g. Determined that serum pro-hepcidin was not significantly correlated with iron absorption in premenopausal women. Comparisons with human iron absorption measurements can contribute to understanding the significance of hepcidin, a recently discovered peptide with antimicrobial properties, which is proposed to play a central role in the biological regulation of iron absorption. Serum pro-hepcidin concentrations were relatively stable in women assessed 16 weeks apart, and correlated directly with serum ferritin, an indicator of body iron stores. However, in contrast with serum ferritin, pro-hepcidin concentrations were unrelated to iron absorption in 28 healthy women. A better understanding of the biological control of iron absorption will help in developing recommendations for iron intake to prevent or treat iron disorders associated with altered absorption, especially those commonly associated with infection or inflammatory diseases.
h. Sensitively assessed iron excretion in women as well as men. For several decades, dietary recommendations for iron intake have relied substantially on a single study of iron excretion, sensitively measured by isotope dilution in men only nearly 50 years ago. An update of this work confirmed the iron excretion measurements in healthy men, and for the first time provided such measurements in women. The data suggested that iron excretion is unrelated to body iron status in men, but that it determines the iron status of pre-menopausal women, because of the substantial influence of menstrual iron losses. These are the first such iron excretion data from women, and will contribute to the data available for setting dietary recommendations for iron intake as affected by gender.
- Incorporated a selenium accumulation gene into wheat, and tested the effects of various growing conditions to increase the uptake of selenium by the transfected cultivars. (In collaboration with investigators at USDA/ARS, Albany, CA, and USDA/ARS, Houston, TX.) Development of selenium accumulating strain of wheat may someday allow production of wheat with extremely high concentrations of selenium which could be used as a source of supplemental Se or as a selenium-fortificant in cereal grain-based products.
- Developed methods to determine the chemical form of the selenium in foods, especially selenium in methylated forms that may be especially anticarcinogenic. The selenium compounds in dried vegetable powder were extracted and analyzed by HPLC coupled to inductively coupled plasma mass spectrometry. Further development of this methodology will allow us to better predict the bio-activity of selenium from numerous common plant foods.
- Demonstrated the potential antioxidant properties of selenium-enriched broccoli, which in rat diets was associated with decreased risk of some cancers. Extracts of selenium-enriched broccoli or of broccoli rich in sulforaphane effectively reduced DNA strand breaks in cultured liver cells of rats. Because DNA strand breaks are a major initiating event of many cancers, these results suggest that some of the cancer protective effects of sulforaphane and selenium may be protection against oxidative stress.
- Discovered a novel role for selenium in the up-regulation of cell cycle related genes, that may lead to a better understanding of the essentiality of selenium as a nutrient and its involvement in cancer prevention.
- Demonstrated that, compared to a conventional farming technique, an organic farming method had limited influence on several nutritional characteristics of broccoli, including trace minerals, multiple individual glucosinolates, primary glucosinolate breakdown products, vitamin C and phenolic acids.
- Discovered that enhancing the selenium content of broccoli decreased total glucosinolate content, specifically sulforaphane, and changed the phenolic profile, especially reducing the content of hydroxy-cinnamic acids, suggesting that it may not be possible to simultaneously maximize all bioactive ingredients in a food, as enrichment with one compound may cause a concomitant decrease in another.
- Determined that zinc interference with copper transport appears unrelated to the expression of the human copper transporter, ATP7b. An understanding of the interaction between copper and zinc absorption will be useful in setting recommendations for balanced dietary intakes of the two elements.
- Confirmed that copper deficiency reduces iron absorption in rats of both sexes, resolving some mixed results from other laboratories. An understanding of the role of copper in iron absorption will be useful in setting recommendations for balanced dietary intakes and addressing the causes of nutritional anemias.
- Discovered that marginal intakes of zinc, iron, and calcium greatly enhanced the accumulation of cadmium in the upper small intestine, leading to a higher accumulation of the toxic metal in the liver and kidneys, which suggests that populations with these nutrient deficiencies are especially susceptible to cadmium toxicity.
- Demonstrated that the 10% of people of Northern European origin who inherited the hemochromatosis mutation from one parent (heterozygous carriers) absorbed both heme and nonheme iron similar to those without the mutation, even from a meal highly fortified with iron and vitamin C, suggesting that current food iron fortification policies do not place this large group at increased health risk.
- Demonstrated that elemental iron powders commonly used to fortify staple foods with iron were less bioavailable to rats than iron from ferrous sulfate, and commercial versions differed considerably, suggesting that higher concentrations of these forms may be needed if they are used in international iron fortification programs.
- Showed that reduced and electrolytic iron sources were approximately 50 and 85% as effective as ferrous sulfate and 5 mg iron in the heme form was half as effective as 50 mg of iron from ferrous sulfate for improving body iron in premenopausal women. This research with humans will help to determine the most useful forms of iron to use in supplementation and fortification programs to reduced iron deficiency anemia worldwide.
JR Hunt began service as member of the National Academies, Institute of Medicine, Food and Nutrition Board Committee on Mineral Requirements for Cognitive and Physical Performance of Military Personnel, April 2005-February, 2006.
Hunt, J.R. 2005. Letter to the editor: absorption of iron from ferritin. American Journal of Clinical Nutrition. 81(5):1178-79.
Combs, G.F., Jr. 2005. Geological Impacts on Nutrition (Chapter 7). In: Stone, D. Essentials of Medical Geology. Elsevier Publishers, Sweden. pp 161-177.
Hunt, J.R. 2005. Iron: physiology, requirements, and dietary sources. In: Cabellero, B., Allen, L. and Prentice, A., editors. Encyclopedia of Human Nutrition, 2nd Ed. Elsevier Limited. p. 82-90.
Reeves, P.G., Chaney, R.L., Simmons, R.W., Cherian, M.G. 2005. Metallothionein induction is not involved in cadmium accumulation in the duodenum of mice and rats fed diets containing high-cadmium rice or sunflower kernels and a marginal supply of zinc, iron, and calcium. Journal of Nutrition. 135:99-108.
Reeves, P.G., DeMars, L.C.S., Johnson, W.T., Lukaski, H.C. 2005. Dietary copper deficiency reduces iron absorption and duodenal enterocyte hephaestin protein in male and female rats. Journal of Nutrition. 135:92-98.
Reeves, P.G., DeMars, L.C.S. 2005. Repletion of copper-deficient rats with dietary copper restores duodenal hephaestin protein and iron absorption. Experimental Biology and Medicine. 230:320-325.
Chaney, R.L., Reeves, P.G., Ryan, J.A., Simmons, R.W., Welch, R.M., Angle, J.S. 2004. An improved understanding of soil cd risk to humans and low cost methods to remediate soil cd risks. Biometals. 17(5):549-553.
Finley, J.W. 2005. Selenium accumulation in plant foods. Nutrition Reviews. 63(6):196-202.
Hintze, K.J., Wald, K., Finley, J.W. 2005. Phytochemicals in broccoli transcriptionally induce thioredoxin reductase. Journal of Agricultural and Food Chemistry. 53:5535-40.
Hunt, J.R. 2004. Combating iron deficiency - supplementation, fortification, and dietary tactics [abstract]. The Journal of Trace Elements in Experimental Medicine. 17(4):259.
Beiseigel, J.M., Hunt, J.R. 2005. Algorithms for estimating zinc absorption from whole diets [abstract]. The Federation of American Societies for Experimental Biology Journal. 19(4):A456.
Hunt, J.R., Swain, J.H. 2005. Bioavailability to humans of an electrolytic elemental iron fortificant, assessed after radiolabeling by neutron activation [abstract]. The Federation of American Societies for Experimental Biology Journal. 19(5):A1468.
Hadley, K.B., Johnson, L.K., Hunt, J.R. 2005. Serum prohepcidin does not predict iron absorption in healthy women [abstract]. The Federation of American Societies for Experimental Biology Journal. 19(5):A1481.
Hunt, J.R., Hadley, K.B., Johnson, L.K. 2005. Serum prohepcidin was not associated with iron absorption by healthy women in a dose-response assessment of elemental iron powders [abstract]. First Congress of the International BioIron Soiety. p. 57.
Reeves, P.G., DeMars, L.C. 2005. A chronological study on the effects of Cu deficiency on Fe absorption and metabolism in male rats [abstract]. The Federation of American Societies for Experimental Biology Journal. 19(5):A1485.
Reeves, P.G., DeMars, L.C. 2005. Low Fe absorption and signs of anemia in Cu-deficient rats are reversed by short-term dietary supplementation with Cu [abstract]. The Federation of American Societies for Experimental Biology Journal. 19(5):A1485.
Chaney, R.L., Reeves, P.G., Ryan, J.A. 2004. Risk assessment for cadmium in phosphate fertilizers [abstract]. American Chemical Society Abstracts. (228th ACS National Meeting, Philadelphia, Pennsylvania, August 22-26, 2004).
Park, S.Y., Woodward, C.L., Birkhold, S.G., Kubena, L.F., Nisbet, D.J., Ricke, S.C. 2004. The combination of zinc compounds and acidic pH limits aerobic growth of a Salmonella typhimurium poultry marker strain in rich and minimal media. Journal of Environmental Science and Health. B39:199-207.
Reeves, P.G. 2005. Iron absorption and intestinal hephaestin protein in copper-deficient rats [abstract]. Presented at Gordon Research Conference on Cell Biology of Metals. Bates College, Lewiston, ME. July 3-8, 2005.