DIETARY MODULATION OF OBESITY-RELATED CANCER BY SELENIUM
Location: Grand Forks Human Nutrition Research Center
Title: A human model of selenium that integrates metabolism from selenite and selenomethionine
Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 2011
Publication Date: April 1, 2011
Citation: Wastney, M.E., Combs, G.F., Canfield, W.K., Taylor, P.R., Patterson, K.K., Hill, A.D., Moler, J.E., Patterson, B.H. 2011. A human model of selenium that integrates metabolism from selenite and selenomethionine. Journal of Nutrition. 141:708-717.
Interpretive Summary: This study compares the kinetics of metabolism of two forms of selenium, selenite (a form widely used for supplementation) and selenomethionine (the dominant form of selenium in foods) in healthy adults. Different stable isotopic tracers of both forms of selenium were administered orally after which both isotopes were determined in urine and feces collected for 12 days and in blood collected over 4 months. The results were fitted to a multi-compartmental model. This showed that within 30 min of ingestion, selenium from both forms entered a common pool, and metabolism was similar for several days after which it diverged, with selenium from selenomethionine entering slowly turning-over pools in tissues and plasma including its three-fold greater incorporation into red blood cells selenium from selenite. The final model will be used to evaluate changes in Se metabolism following long-term (2 years) of selenium supplementation.
Selenium (Se) metabolism is determined by the various chemical forms of the element in foods and diets, by the incorporation of the element both specifically and non-specifically into multiple proteins, and by gender. Modeling may help clarify these issues. While the kinetics of Se forms have been compared in different subjects, or the same subjects at different times, direct comparisons of their respective metabolism have not been made. The aim of this study was to compare the kinetics of absorbed Se from inorganic selenite (Sel) and selenomethionine (SeMet) simultaneously in healthy subjects (n=31). After PO administration of stable isotopic tracers of each form, urine and feces were collected for 12 d and blood was sampled over 4 mo. Tracer enrichment was determined by isotope-dilution-gas chromatography/mass spectrometry. Using WinSAAM, a compartmental model was fitted to the data. Within 30 min of ingestion, Se from both forms entered a common pool, and metabolism was similar for several days before diverging. Slowly turning-over pools were required in tissues and plasma for Se derived from SeMet to account for its three-fold higher incorporation into RBC compared to Se from Sel; these presumably represent non-specific incorporation of SeMet into proteins. Pool sizes and transport rates were determined and compared by form and gender. The final model consisted of eleven plasma pools, two pools and a delay in RBC, and extravascular pools for recycling of Se back into plasma. This model will be used to evaluate changes in Se metabolism following long-term (2 y) Se supplementation.