Biotransformation of l-Selenomethionine and Selenite in Rat Gut Contents

Abstract

L-selenomethionine (SeMet) and sodium selenite are widely used selenium nutritional supplements with potential benefit in preventing cancer. However, supplementation is not without risks of toxicity if intake is too high. The aim of the present study was to investigate SeMet and selenite metabolism in the gastrointestinal tract with particular focus on the formation of the volatile selenium excretion products, dimethylselenide (DMSe) and dimethyldiselenide (DMDSe). Adult male Wistar rats (n = 5) were euthanized, their intestinal tracts removed and the contents of jejunum, ileum, caecum and colon used to prepare 10% suspensions in saline. SeMet and selenite (0.5-0.6 mM) were then incubated with these suspensions at 37°C for 3 h. Caecum and colon contents were the most metabolically active towards SeMet with 30% and 15% metabolized over 3 h. DMDSe was the only volatile selenium metabolite detected accounting for 8.7 ± 1.3% of the selenium lost in caecum contents. Selenite was completely metabolized by caecum contents and 73% by colon contents under the same conditions forming DMSe (5.7 ± 0.9% of the selenium lost in caecum) and a precipitate of red amorphous elemental selenium. Based on previous literature and these results, we conclude that the gut microbiota contributes to the excretion of excess selenium through the production of methylated selenium compounds and elemental selenium.

Neurobehavioral changes in mice offspring induced by prenatal exposure to acute toxicity of sodium selenite

“…Receiving selenium as selenomethionine, the chief natural nutritional form present in grain crops is better than sodium selenite as a source (Schrauzer & Surai 2009). Selenomethionine and sodium selenite have risks of toxicity if intake is too high (Krittaphol et al 2010). Therefore, the general population should be warned against the employment of selenium supplements for prevention of hepatopathies, cardiovascular or cancer diseases.…”

“…The benefits of selenium supplementation are still uncertain, and their indiscriminate use could generate an increased risk of toxicity (Miguel & Carmen 2008). Although the gut microbiota contributes to the excretion of excess selenium through the production of methylated selenium compounds and elemental selenium (Krittaphol et al 2010), the high doses of this element are highly toxic.…”

Metabolism of l-Selenomethionine and Selenite by Probiotic Bacteria: In Vitro and In Vivo Studies

“…Selenite was analyzed by hydride generation atomic absorption spectrometry (HGAAS) [17,18] and DMSe and DMDSe by gas chromatography-mass spectrometry [8,19] as described elsewhere [4]. Serum selenium was determined by graphite furnace atomic absorption spectrometry based on a modification of the method of Jacobson and Lockitch [20].…”

“…Plasma selenium levels are low in patients with certain gastrointestinal disorders indicating a role for the gut microbiota in selenium disposition [2,3]. We previously showed that metabolism of SeMet and selenite in rat gut contents from normal rats [4] is similar to that mediated by microbial cultures (whole-cell suspensions of Enterobacter cloacae SLD, Escherichia coli or Pseudomonas syringae) in vitro [5,6]. Reported products of selenium metabolism include the volatile dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) as well as elemental selenium [7,8].…”

“…The most commonly reported benefits relate to improved gastrointestinal function [10] and include an improvement in selenium status of individuals taking selenium supplements [11][12][13]. Whether this is because probiotic cells remain viable and interact with selenium supplements in the gastrointestinal tract (GIT) is presently unknown [4,6]. An understanding of the metabolic fate of selenium supplements in the gut and the effect of probiotic treatment will help to determine how best to use selenium supplements to improve selenium status [14].…”