Effects of Chemical Form of Selenium on Plasma Biomarkers in a High-Dose Human Supplementation Trial

Abstract

Intervention trials with different forms of selenium are under way to assess the effects of selenium supplements on the incidence of cancer and other diseases. Plasma selenium biomarkers respond to selenium administration and might be useful for assessing compliance and safety in these trials. The present study characterized the effects of selenium supplementation on plasma selenium biomarkers and urinary selenium excretion in selenium-replete subjects. Moderate (f200 Mg/d) to large (f600 Mg/d) selenium supplements in the forms sodium selenite, high-selenium yeast (yeast), and Lselenomethionine (selenomethionine) were administered. Subjects were randomized into 10 groups (placebo and three dose levels of each form of selenium). Plasma biomarkers (selenium concentration, selenoprotein P concentration, and glutathione peroxidase activity) were determined before supplementation and every 4 weeks for 16 weeks. Urinary selenium excretion was determined at 16 weeks. Supplementation with selenomethionine and yeast raised the plasma selenium concentration in a dose-dependent manner. Selenite did not. The increased selenium concentration correlated with the amount of selenomethionine administered. Neither glutathione peroxidase activity nor selenoprotein P concentration responded to selenium supplementation. Urinary selenium excretion was greater after selenomethionine than after selenite, with excretion after yeast being intermediate and not significantly different from either of the other two. We conclude that plasma selenium concentration is useful in monitoring compliance and safety of selenium supplementation as selenomethionine but not as selenite. Plasma selenium seems to reflect the selenomethionine content of yeast but not the other yeast selenium forms. As judged by urinary selenium excretion, selenium in the form of selenomethionine is better absorbed than selenite. (Cancer Epidemiol Biomarkers Prev 2006;15(4):804 -10)

Selenium biochemistry and its role for human health

“…Nevertheless, once the basal Se requirement is reached, additional increase of the element does not lead to an increase in GPx3 or SelP concentration, therefore such Se biomarkers have limited validity. 19 Plasma/serum selenoproteins, namely SelP and GPx3 are the most commonly used markers for the assessment of Se status also because they can be determined with a scarcely invasive procedure compared to tissue Se-proteins, which requires a biopsy. It is worth highlighting that the choice of Se-protein to be used as a biomarker must consider its specific biological function, which therefore provides partial information in terms of Se bioactivity.…”

Plasma Selenium Measurements in Subjects from Areas with Contrasting Gastric Cancer Risks in Colombia

“…Se has been studied in relation to this neoplasia due to its possible preventive effects on DNA damage. The chemical form of Se and the dose are determinants of its biological activities as an essential nutrient, chemopreventive agent, or toxicant (33,(35)(36)(37).…”

“…Briefly, the rate of NADPH (USB Corp., Cleveland, OH) oxidation was measured using hydrogen peroxide as the oxidizing substrate. Sepp1 levels were determined by ELISA as described (33). Monoclonal antibodies N11 and N22 were a generous gift of Dr. T. Naruse (Kaketsuken, Kumamoto, Japan).…”

“…Monoclonal antibodies N11 and N22 were a generous gift of Dr. T. Naruse (Kaketsuken, Kumamoto, Japan). Other Se pools, presumably mostly selenomethionine in albumin and other plasma proteins, were estimated as described (33). Briefly, the Se content (in µg/dL) in glutathione peroxidase was calculated to be 1.7 times the ratio of the subject's GPx activity to the reference plasma's GPx activity.…”

“…The other Se value was the total plasma Se measured minus the Se calculated to be in GPx and Sepp1. This calculation has been previously described (33). Laboratory personnel were blinded to the site of residence of the participants and to the histopathological diagnosis.…”