Cysteine supplementation reduces the bioavailability of selenomethionine in mice

SummaryBackground & aimsSelenomethionine, a common form of dietary selenium that is sometimes used to supplement patients with selenium deficiency, must be degraded to an inorganic form of selenium for incorporation into selenium-specific proteins (selenoprotein), and cysteine, which is occasionally added in the total parenteral nutrition preparation, might influence the degradation of selenomethionine. The purpose of this research is to study the influence of cysteine on the metabolism of selenomethionine.MethodsAn animal study was conducted. Mice were fed a selenomethionine diet with or without cysteine. The control mice were fed a selenite diet. The total selenium concentration and glutathione peroxidase (GPx) activity were measured.ResultsThe mouse experiment showed that the selenium contents in liver, plasma, red blood cells, muscle, and brain were higher in the selenomethionine groups than in the selenite control group. However, the activities of GPx, which were measured in liver, red blood cells, and blood plasma, were lower in the group fed selenomethionine with the addition of cysteine than in the other groups, especially in red blood cells, where the activities were significantly lower than those in mice fed a diet containing only selenomethionine or selenite.ConclusionsThe results show that the addition of cysteine to a selenomethionine diet may inhibit the selenium metabolism from selenomethionine to selenoproteins, such as extracellular GPx.