Location: Obesity and Metabolism Research2012 Annual Report
1a. Objectives (from AD-416):
The overall goal of the proposed research is to identify foods, nutrients, and food components that promote health and prevent disease in at-risk populations; where possible diet-gene interactions will be explored. Over the next 5 years we will focus on the following objectives: OBJECTIVE 1: Determine the effects of specific foods, fortified foods, and nutrients on bone health of at-risk population groups. Sub-objective 1.A. Determine the effects of carbonated beverages and milk on calcium kinetics and calcium efflux from the skeleton of women and girls. Sub-objective 1.B. Determine the effects of vitamin B12 deficiency on markers of calcium kinetics, bone health, and calcium metabolism in postmenopausal women. OBJECTIVE 2: Investigate vitamin B12 and zinc intestinal absorption and metabolism in at-risk populations. Sub-objective 2.A. Determine the absorption of 14C-vitamin B12 from fortified foods in elderly with gastric atrophy and H. pylori infection, pre- and post H. pylori treatment. Sub-objective 2.B. Determine the impact of SNPs in a major Zn uptake gene (ZIP4) on dietary Zn absorption using ZIP4-expressing cell lines. OBJECTIVE 3. Investigate the effect of Zn supplementation on the development of prostate cancer, a cancer common in African-Americans, using a mouse prostate cancer model (TRAMP).
1b. Approach (from AD-416):
The overall goal is to identify foods, nutrients, and food components that promote health and prevent disease in at-risk populations and to identify diet gene interactions where possible. To achieve this goal, human studies will be conducted investigating the effects of carbonated beverages and milk on calcium kinetics and calcium efflux from the skeleton of women and girls; effects of vitamin B12 deficiency on markers of calcium kinetics, bone health, and calcium metabolism in postmenopausal women; and determine the absorption of 14C-vitamin B12 from fortified foods in elderly with gastric atrophy and H. pylori infection, pre- and post H. pylori treatment. Animal models will be used to investigate the impact of SNPs in a major Zn uptake gene (ZIP4) on dietary Zn absorption using ZIP4-expressing cell lines and to investigate the effect of Zn supplementation on the development of prostate cancer, common in African-American men. There is a need to devise effective nutrition interventions to prevent the progress of chronic disease in at-risk populations.
3. Progress Report:
Two manuscripts from the dairy study have been submitted for peer review. Other progress made on the current objectives falls under the National Program 107. For objective 1: 13 women were enrolled; 10 completed the protocol to date. A grant was written and funds secured for additional sample analysis of the kinetics of change in bone metabolism with the interventions (Dairy Research Institute: 5306-51000-003-14T). 41Ca in urine from 6 women was processed, shipped to Lawrence Livermore National Laboratory (LLNL) and analyzed by accelerator mass spectrometry (AMS). All dietary data have been entered into the nutrient data base and are up to date. Funds have been secured from the California Dairy Research Foundation (5306-51000-003-15T) to examine the effect of other nutrients, e.g. protein, magnesium, on bone metabolism. Also relevant to objective 1, a study to examine calcium flux from bone in B12-insufficient postmenopausal women had 9 women complete the study. Recruitment will continue in FY2012. Urine samples will be analyzed at LLNL in October 2012 and if B12 supplements improved bone kinetics, funds will be sought to expand the study in a population with greater prevalence of B12 deficiency. Objective 2A: what percent of vitamin B12 added as a fortificant to flour is absorbed by healthy people and those with low gastric acid secretion? Labeled vitamin B12 (14C) was added to flour followed by 14C analysis with AMS. Samples from the 5 healthy subjects were analyzed and showed B12 survived the fermentation and baking process and on average was 48% bioavailable when 0.8 ug were fed, but was highly variable across individuals, from 28.4 to 63.4%. These data will be used by the global Flour Fortification Initiative and potentially the US government to base recommendations for B12 fortification levels in flour. The study is now recruiting volunteers with low gastric acid secretion to compare their ability to absorb 14C-B12 from fortified foods. Studies related to Objective 2B were terminated due to lack of effect; no further work in this area has been conducted. Objective 3: The proposed project was not initiated due to lack of funding. A project to identify molecule(s) that underlie aggressive prostate cancer was initiated. Based on previous work ZnT7 deficiency alters the interaction between immune defenses and prostate cancer cells. A signal protein that mediates a broad variety of immune and inflammatory responses was found bound to ZnT7. To confirm the interaction, cDNA of the signal gene was cloned into a bacterial expression plasmid tagged with a bacterial protein GST. Additionally, Znt7 cDNA and its deletion derivatives were cloned into a bacterial expression plasmid tagged with a polyhistidine tag. Fusion proteins were expressed, harvested, and purified. Immunoprecipitation analyses were done using purified fusion proteins. The results showed that ZnT7 physically interacts with this immune function regulator and the C-terminal of ZnT7 was critical for the interaction.
1. Dairy foods maintain bone health during weight loss. It is well known that bone loss occurs during weight loss. Given the obesity epidemic and the need to lose weight an unexpected consequence may be loss of bone mineral density, so nutritional interventions that thwart this effect would be of high value. In clinical studies, it was found that the inclusion of 3-4 servings of calcium-rich dairy foods during weight loss maintains bone metabolism and bone density compared to weight loss diets with less than 1 serving of dairy foods. These results support the U.S. Dietary Guidelines for adequate dairy intake.
2. New, efficient analytical methods for multiple micronutrients in breast milk. Little information exists on the vitamin or mineral content of human milk, and how the composition of breast milk from women consuming poor quality diets differs from that of well-nourished women. To address this question, new methods were developed for simultaneous analysis of thiamin, riboflavin, flavin adenine dinucleotide, nicotinide and pyridoxal in human milk using mass spectrometry. The method was used to analyze 1200 breast milk samples from a maternal micronutrient intervention study in Malawi that revealed the concentrations of thiamin, riboflavin and nicotinamide are only 5 to 35% of those reported in well-nourished populations. This research has important public health implications concerning the need to adequately supplement lactating women who consume poor quality diets with vitamins.
3. Zinc modulates immune function and inflammatory responses. It is well known that dietary zinc deficiency affects immune function leading to frequent respiratory infections, pneumonia, and diarrhea. However, the underlying mechanism is not understood. Studies in cell culture models revealed that a zinc transporter (ZnT7) interacts with a signal protein involved in activating immune macrophage antigen presenting cells, T cell-dependent immunoglobulin class switching of B cells, resting B cell activation, and memory B cell development. The finding that zinc ions can directly affect immune function and its regulation through its transporter is novel and significantly contributes to the fundamental understanding of how zinc affects immune function.
Allen, L.H. 2012. Vitamin B-12. Advances in Nutrition. 3:54-55.