This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Vitamin B12 (B12) is an essential dietary nutrient required as a coenzyme for two major metabolic reactions. A deficiency of B12 may result from dietary inadequacies but more commonly results from B12 malabsorption, which may lead to anemia, irreversible neurological damage, and birth defect-affected pregnancies. Improved clinical diagnostic tests are needed to detect B12 malabsorption so that effective B12 therapy can be implemented. This study is designed to provide pilot data related to changes in a B12 transport protein, transcobalamin (TC) in response to oral B12 doses that may be used to design a new diagnostic test for B12 malabsorption. B12 binds to TC (holo-TC) rapidly after uptake by the mucosal epithelial cell, has a short half-life, and is more sensitive to changes in B12 intake and short-term status than serum B12 concentration. It is hypothesized that holo-TC concentration may be used as an indicator of B12 absorption. The primary objective of this study is to evaluate changes in holo-TC concentration in response to oral doses of B12. Healthy individuals with high-normal (serum B12 =444 pmol/L) vitamin B12 status will have blood drawn at timed intervals prior to and following three separate oral doses (9 ?g/dose) on Day 1 followed by one fasting blood sample drawn on Days 2 and 3. Holo-TC and other B12 response indices will be measured to evaluate changes in holo-TC in response to supplemental B12. The data from this pilot study will be useful in designing future studies with the long-term goal of developing new and improved diagnostic absorption tests for B12.
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