Location: Immunity and Disease Prevention Research2010 Annual Report
1a. Objectives (from AD-416)
Objective 1: Conduct a controlled, vitamin D supplementation trial in volunteers with vitamin D insufficiency (VDI) to determine if supplementation to achieve the proposed level of >75 nmol/L for maintenance of bone health is also appropriate for maintenance of immune function. Sub-objective 1A. Determine if supplements decrease the production of proinflammatory and increase the production of anti-inflammatory cytokines and chemokines by innate immune cells stimulated ex vivo. Objective 1B. Determine if supplements decrease serum markers of inflammation and autoimmune activity, and increase serum levels of defensive molecules. Objective 1C. Determine if supplements decrease blood levels of proinflammatory T-helper type 1 (Th1) and Th17 cells and increase levels of anti-inflammatory T-regulatory (Treg) and Th2 cells. Objective 2: Determine the impact of plant polyphenols and polyphenol-rich foods on immune cell function using cell culture systems, mouse models, and human volunteers. Examine anti-inflammatory and anti-cancer activities of polyphenols in animal models, as well as inflammation and oxidative damage in studies with human volunteers, including overweight/obese individuals. Objective 2A. Analyze the effects of polyphenol-rich foods and individual plant polyphenols on immune cell function in vivo and ex vivo. Ojective 2B. Examine anti-inflammatory activities of polyphenol-rich foods, individual plant polyphenols and vitamin A in mice and humans who are at risk for developing inflammatory disease, such as autoimmune mice and obese humans. Objective 2C. Evaluate the anti-cancer activity of polyphenol-rich foods and individual plant polyphenols. Objective 3: Examine the absorption of B-cryptoxanthin (CX) from supplements and foods, its contribution to vitamin A stores, and the impact of CX, other carotenoids and vitamin A on immune function. Objective 3A. Measure the absorption and metabolism of CX from Satsuma mandarin juice fed to healthy adult humans. Objective 3B. Estimate the impact of daily consumption of food sources of CX or B-carotene (BC) on plasma and breast milk concentrations of CX, BC and retinol in lactating women. Objective 3C. Determine the impact of CX on immune and bone marker status in the Mongolian gerbil. Objective 4: Determine if high-level vitamin A intake is associated with higher Th2 and Treg responses and lower Th1 and Th17 responses relative to adequate and deficient intake. Objective 4A. Using dietary and targeted gene disruption approaches in mice, determine if vitamin A enhances Th2 and Treg responses by acting directly on T cells. Objective 4B. Using subjects recruited in the vitamin D supplementation trial described under Objective 1, determine if vitamin A status is associated with higher blood levels of NK, NK-T, Th2 and Treg cells, and lower levels of Th1 and Th17 cells. Objective 5: Identify the role of dietary selenium and selenoproteins in regulating cellular responses to oxidative stress. Objective 5A. Identify the pro-inflammatory and anti-inflammatory proteins S-glutathionylated by selenoprotein W. Objective 5B. Determine the role of selenoprotein W in key inflammatory pathways.
1b. Approach (from AD-416)
The impact of selenium, vitamins A and D, and plant polyphenols, on immune function will be examined using cell culture systems, mouse models, and human intervention trials. The anti-cancer activities of polyphenols will be examined in animal models. Absorption of beta-cryptoxanthin will be examined in gerbils and humans. The effect of selenium on cell division and cell signaling will be examined in cell culture. Replacing 5306-51530-013-00D (1/09).
3. Progress Report
Objective 1: (1) A pilot study was completed involving six subjects to evaluate newly implemented methods for testing antigen-specific T-cell responses that should be influenced by vitamin D status. This involved implementing new methods in our laboratory. (2) Donation of vitamin D supplements was arranged and the supplements analyzed to assure appropriate content. The intervention will begin before December, 2010. Objective 2: (1) The California Strawberry Commission funded a human study to determine the anti-inflammatory effects of strawberries in obese individuals. The data show dietary strawberries inhibited T cell proliferation, and beneficially altered several serum lipid fractions. California Table Grape Commission funded a human study to understand the anti-inflammatory role of dietary grape powder in obese human volunteers. (2) A mouse model was used to determine whether dietary strawberry powder inhibited inflammation associated with diet-induced obesity and measurements of inflammation are being completed. (3) Mice engrafted human leukemia cells were fed or injected with resveratol and curcumin to determine if these phytochemicals could slow the progression of the leukemia. Neither treatment was effective. Objective 3: (1) 3-hydroxyretinol and didehydroretinol, major metabolites of beta-cryptoxanthin were synthesized. A rapid, high-performance liquid chromatography method was developed for measuring beta-cryptoxanthin and its metabolites. In vitro methods for analyzing stomach digestion of carotenoids and other nutrients from foods were tested. Analysis of metabolites in human blood and tissues has begun. (2) Standard operating procedures for dietary and clinical analysis were developed, and a collaborative study to assess the impact of daily consumption of food sources of beta-cryptoxanthin and beta-carotene on vitamin A status was begun. (3) Methods to determine the impact of beta-cryptoxanthin on immune and bone marker status in the Mongolian gerbil are being selected and optimized for our laboratory conditions. Objective 4: These objectives have not been pursued because funds are not available. Extramural funds are required to pursue these objectives. Objective 5: We tried three different methods to show that selenoprotein W (SEPW1) affected global protein glutathionylation and none of them worked. Immunoprecipitation of p53 failed to reveal glutathionylation of this protein. We ruled out ER stress and the unfolded protein response as mediators of cell cycle arrest induced by SEPW1 depletion. We determined that p53 and p21 levels are not different in RWPE-1 cell lines stably under- or over-expressing SEPW1. We showed that SEPW1 knockdown induced a G1 arrest in MCF-7 breast cancer cells. We showed that G1 arrest from SEPW1 knockdown is abolished in MCF-7 mutant cells in which p53 expression is silenced and in RWPE-1 and MCF-7 cells in which p21 expression was silenced. We showed that SEPW1 knockdown causes p53 to be phosphorylated on serine 33, consistent with involvement of the p38 stress activated MAP kinase, glycogen synthase kinase beta, cyclin-dependent kinase 7 and/or 9.
1. Fish oil for African Americans to decrease risk of heart disease: Both diet and genes contribute to one’s risk of heart disease and in the case of omega-3 fatty acids and the ALOX5 gene the two factors may interact. ARS researchers at Davis, CA found that African Americans with a variant of the ALOX5 gene that is associated with a high risk of heart disease produce lower levels of potentially heart-healthy omega-3 metabolites than did subjects with the low-risk ALOX5 variant. Subjects with the high-risk variant also responded to fish oil supplements with a smaller increase in these metabolites than did subjects with the low-risk variant. These data suggest that dietary recommendations for lowering risk of heart disease may need to be tailored by genotype to maximize their impact.
2. Strawberries decrease cardiovascular risk: The risk of heart disease is higher among obese than non-obese Americans but this risk can be decreased by dietary interventions. ARS reseachers at Davis, CA demonstrated that freeze-dried strawberry powder consumed by obese individuals decreased serum cholesterol and improved other serum lipid indicators that are linked to risk of heart disease and stroke. These results indicate that consuming strawberries should decrease the risk of heart disease by improving lipid metabolism and will thus help form the scientific basis of dietary guidelines for all Americans.
3. Carotenoid bioavailability and food-based interventions: Studies show low correlations between dietary intake and serum concentrations of lycopene and other carotenoids, indicating that serum concentrations alone are a poor biomarker for assessing the effectiveness of dietary interventions with these phytonutrients. ARS researchers at Davis, CA showed that combining dietary intake methods (food-frequency questionnaires and 3-d diet records) using the triads method improved the validity of this relationship. Furthermore, correcting dietary information for differences in lycopene absorption from its most important food matrices further improved validity, to a relatively strong level. Thus, using the triads method with bioavailability estimates should make it possible to determine whether food-based interventions for increasing lycopene or other carotenoids are effective.
4. Selenium and the cell cycle: Although selenium supplements prevent cancer in animals, human cancer-prevention trials have failed, perhaps because we do not understand what most of the 25 selenium-containing proteins (“selenoproteins”) do in the body. Selenoprotein W (SEPW1) is the most ancient and widely distributed selenoprotein in Nature but its function is unknown. ARS researchers at Davis, CA have discovered that SEPW1 controls the stability of p53, a tumor suppressor protein that plays a central role in controlling the cell-division cycle, which is required for all cells to replicate themselves and is thus fundamental to growth and development for all organisms. This new knowledge adds to our understanding of selenium biology and will help form a solid scientific basis for dietary recommendations for Americans with regard to maintaining optimal health.
5. Resveratrol and curcumin do not improve leukemia outcome: Plant polyphenols and other dietary components may slow the development or progression of certain cancers but results vary by cancer type. ARS researchers at Davis, CA found that feeding resveratrol and curcumin to leukemic mice was not effective in decreasing the growth of leukemia cells, nor were these polyphenols able to increase the effectiveness of vincristine, a standard chemotherapeutic agent. These results do not support a role for these compounds for slowing progression of established leukemia and thus help form a better scientific basis for dietary recommendations to individuals with this form of cancer.
5. Significant Activities that Support Special Target Populations
The research described under the first accomplishment has particular importance for African Americans because of the high risk of heart disease in that group and because of the high prevalence in African Americans of the ALOX5 gene variant examined in that study, which is associated with a high risk of heart disease.