2004 Annual Report 1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? This CRIS includes research conducted in the Mineral Bioavailability Laboratory. The major problems being addressed are: (1) identification of risk factors of low calcium absorption, (2) determination of the specificity of intestinal vitamin D resistance in age-associated calcium malabsorption, and (3) determination of the molecular mechanism of vitamin D-mediated calcium absorption. Calcium absorption is addressed by studies that investigate vitamin D-induced calcium absorption in young and elderly women, as well as experimental animals, and complimentary studies on the molecular mechanisms of vitamin D-induced gene expression and calcium transport are conducted in Caco-2 cells, a human intestinal cell line. This work is relevant to deepening our understanding of the factors affecting calcium handling in the body, which will be important in developing appropriate diet-based preventative strategies to ameliorate these risk factors for chronic disease. Twenty percent of women in the United States (US) have osteoporosis. Forty percent of persons 80 years and older in the US have had a bone fracture. Decreased intestinal calcium absorption is an important mineral-related problem commonly associated with the aging process. Relative calcium malabsorption contributes to the age-related bone loss and increasing prevalence of osteoporosis in the aged. Persons with lower fractional calcium absorption are at increased risk of a future hip fracture. Besides the obvious personal costs of increased mortality and morbidity of the older patient with osteoporotic bone fracture, this increasingly prevalent chronic bone disease adds a multi-billion dollar cost to the nation's annual health care bill. Research conducted within this CRIS falls under National Program 107 Human Nutrition, Action Plan components 2: Diet, Genetics, Lifestyle and the Prevention of Obesity and Disease and 7: Bioavailability of nutrients and food components. 2.List the milestones (indicators of progress) from your Project Plan. 1a. Calcium/strontium absorption study in young and old persons treated with 1,25-dihydroxyvitamin D. 1b. FokI vitamin D receptor polymorphism study in humans. 1c. 1,25-dihydroxyvitamin D-responsive gene expression in human immune cells. 2a. Intestinal vitamin D resistance in senescent rats. 2b. Effect of 24-hydroxylase inhibitors on 1,25-dihydroxyvitamin D-mediated gene expression in senescent rats. 2c. Vitamin D resistance in non-intestinal tissues in the senescent rat. 3a. TRPV6/CaT1 expression controls calcium influx across the apical membrane of Caco-2 cells. 3b. Calbindin D expression controls the rate of transcellular calcium transport at high external calcium concentrations in Caco-2 cells. 3c. Gene silencing of TRPV6/CaT1 and calbindin D blocks 1,25-dihydroxyvitamin D-induced calcium transport. 3.Milestones: A. List the milestones that were scheduled to be addressed in FY 2004. Since the replacement project has been recently certified by OSQR and began in May 2004, none of the goals of the new project have been finished. Please see the report for 1950-51520-006-00D B. List the milestones that you expect to address over the next 3 years. Year 1 - 2 (FY2005-06): 1a. Calcium/strontium absorption study in young and old persons treated with 1,25-dihydroxyvitamin D. These studies will demonstrate if the strontium absorption test can be used as a simple screening method to detect persons with calcium malabsorption or intestinal resistance to 1,25-dihydroxyvitamin D. These studies may help to better target nutritional prevention of bone loss and thereby lower the risk osteoporosis. 2a. Intestinal vitamin D resistance in senescent rats. These studies in old rats will help to identify the molecular mechanism of vitamin D resistance in the intestine and will provide potential molecular targets to improve calcium absorption and lower rates of bone loss. 3a. TRPV6/CaT1 expression controls calcium influx across the apical membrane of Caco-2 cells. These studies will provide definitive information on the extent to which TRPV6 acts as a gatekeeper of calcium influx into the enterocyte. Year 2 - 4 (FY2006-07): 3b. Calbindin D expression controls the rate of transcellular calcium transport at high external calcium concentrations in Caco-2 cells. These studies will determine to what extent calbindin D is needed to achieve optimal rates of calcium absorption. Year 4 - 5 (FY2007-08): 1c. 1,25-dihydroxyvitamin D-responsive gene expression in human immune cells. These studies will identify novel vitamin D-responsive genes that are important in vitamin D-dependent modulation of the immune system. 3c. Gene silencing of TRPV6/CaT1 and calbindin D blocks 1,25-dihydroxyvitamin D-induced calcium transport. These studies will determine whether TRPV6 and calbindin D work together to bring about an increase in calcium absorption in response to an increase in 1,25-dihydroxyvitamin D. 4.What were the most significant accomplishments this past year? The replacement project has been recently certified by OSQR. Please see the report for 1950-51520-006-00D. 5.Describe the major accomplishments over the life of the project, including their predicted or actual impact. The replacement project has been recently certified by OSQR. Please see the report for 1950-51520-006-00D. 6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The replacement project has been recently certified by OSQR. Please see the report for 1950-51520-006-00D. 7.List your most important publications in the popular press and presentations to organizations and articles written about your work. The replacement project has been recently certified by OSQR. Please see the report for 1950-51520-006-00D.