Differential Effects of Organic and Inorganic Selenium on Oxidative Stress and Metal Homeostasis in Mouse Brain and Liver

This study aimed to evaluate and compare the effects of different selenium compounds on levels of glutathione and metallothionein levels, as well as on markers of lipid peroxidation and micronutrient status, in brain and liver tissues of mice. Mice were orally administered either inorganic sodium selenite or organic L-selenomethionine at a dose of 0.4 mg Se/kg body weight for eight weeks. Blood, brain, and liver tissues were collected for analysis. Antioxidant markers: content of reduced glutathione (GSH), metallothioneins (MT), and malondialdehyde (MDA) from lipid peroxidation were evaluated spectrophotometrically; micronutrient levels (Se, Zn, Cu, and Fe) determined by inductively coupled plasma mass spectrometry. SeMet supplementation significantly reduced liver MT concentration compared to control. Na₂SeO₃ lowered blood GSH levels. Both selenium compounds significantly increased MDA, with SeMet raising blood and liver levels, and Na₂SeO₃ having a stronger effect. Substantial Se accumulation was observed in both groups: SeMet elevated liver and brain Se as well as liver Fe, while Na₂SeO₃ boosted liver and brain Se. Additionally, Na₂SeO₃ reduced brain Cu, Zn, and Fe, yet increased liver Fe compared to controls. Overall, the findings suggest that prolonged selenium supplementation, whether organic or inorganic, can have complex and sometimes adverse effects on antioxidant defenses and trace element homeostasis. These results underscore the critical role of selenium form, dose, and exposure duration in determining its benefits, as excessive intake may lead to oxidative stress rather than protection.