Author
PATTERSON, BLOSSOM - National Cancer Institute (NCI, NIH) | |
Combs, Gerald | |
CANFIELD, WESLEY - Cornell University | |
TAYLOR, PHILIP - National Cancer Institute (NCI, NIH) | |
Patterson, Kristine | |
HILL, A - Former ARS Employee | |
MOLER, JAMES - Information Management Services, Inc | |
WASTNEY, MERYL - Metabolic Modeling Services |
Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/5/2011 Publication Date: 2/2/2011 Citation: Patterson, B.H., Combs, G.F., Canfield, W.K., Taylor, P.R., Patterson, K.K., Hill, A.D., Moler, J.E., Wastney, M.E. 2011. A human model of selenium that integrates metabolism from selenite and selenomethionine. Journal of Nutrition. 141:708-717. Interpretive Summary: To gain insight into the metabolism of selenium during selenium-supplementation, we compared kinetics of metabolism of two forms, selenite (used in supplementation) and selenomethionine (a dominant form of selenium in foods) in healthy adults, using different stable isotopic tracers of each form. We evaluated selenium kinetics in each subject twice: before and after a two-year period of selenium supplementation (200 µg/day as selenomethionine). In each kinetic study we measured both tracers in urine and feces for 12 days, and in plasma, and red blood cells over 4 months. We used a multi-compartment model to estimate the rates of sizes and rates of transfer of selenium between these compartments. We found that supplementation did not affect the fractional absorption of either form of selenium, although in increased the total amounts that were absorbed and excreted. We also found that women and men showed different kinetic patterns of selenium metabolism, particularly for selenite. We identified pools that did not increase with selenomethionine supplementation; these may represent regulated selenoproteins. Technical Abstract: Increased selenium (Se) intake may improve health and reduce cancer incidence. To gain insight into Se metabolism during Se-supplementation, we compared Se kinetics in subjects (n=31) studied twice for 4 mo after oral tracer administration; initially (PK1), then after supplementation for 2 y with 200 µg/d of Se as selenomethionine (SeMet),(PK2). On each occasion, we administered 2 stable isotope tracers of Se; SeMet and Na276SeO3 an inorganic form,(selenite, Sel). Plasma and RBC were sampled throughout PK1 and PK2; urine and feces were collected for the initial 12 d of each period. Samples were analyzed for tracers and total Se by GC-MS. Data were analyzed using a compartmental model to estimate fractional transfer between pools and pool masses before and after supplementation. Fractional absorption did not change for either form in PK2, but total Se absorbed and excreted increased. Urine excretion increased from 7 of the 11 plasma pools in PK2 with gender differences in the contribution of specific pools. Recycling of Se from some plasma pools to tissues increased in PK2, including some gender-specific pool increases for Sel. Except for 2 plasma pools, masses of most pools increased in PK2. Because SeMet is incorporated into proteins in place of methionine, pools that did not increase with SeMet supplementation may represent proteins with few methionine residues and/or selenoproteins that are regulated. Kinetics identified the time of labeling and turnover times of pools for further experimental analyses. |