Selenium is an essential trace element in our diet, crucial for the composition of human selenoproteins, which include 25 genes such as glutathione peroxidases and thioredoxin reductases. The regulation of the selenoproteome primarily hinges on the bioavailability of selenium, either from dietary sources or cell culture media. This selenium-dependent control follows a specific hierarchy, with \"housekeeping\" selenoproteins maintaining constant expression while \"stress-regulated\" counterparts respond to selenium level fluctuations. This study investigates the variability in fetal bovine serum (FBS) selenium concentrations among commercial batches and its effects on the expression of specific stress-related cellular selenoproteins. Despite the limitations of our study, which exclusively used HEK293 cells and focused on a subset of selenoproteins, our findings highlight the substantial impact of serum selenium levels on selenoprotein expression, particularly for GPX1 and GPX4. The luciferase reporter assay emerged as a sensitive and precise method for evaluating selenium levels in cell culture environments. While not exhaustive, this analysis provides valuable insights into selenium-mediated selenoprotein regulation, emphasizing the importance of serum composition in cellular responses and offering guidance for researchers in the selenoprotein field.

Selenium (Se) agronomic biofortification of plants is effective for alleviating Se deficiencies in human and livestock populations. Less is known about how higher selenate amendment rates, or how foliar compared with granular selenate amendments affect forage Se concentrations. Therefore, we compared the effects of a higher sodium selenate foliar amendment rate (900 vs. 90 g Se ha-1), and two selenate amendment methods (liquid foliar sodium selenate vs. granular slow-release Selcote Ultra® at 0, 45, and 90 g Se ha-1) on Se concentrations and Se species in forages across Oregon. The 10 × amendment rate (900 g Se ha-1) resulted in 6.4 × higher forage Se concentrations in the first cut (49.19 vs. 7.61 mg Se kg-1 plant DM, respectively) compared with the 90 g ha-1 amendment rate, indicating that forages can tolerate higher selenate amendment rates. Most Se was incorporated as SeMet (75%) in the harvested portion of the forage (37 mg Se kg-1 forage DM of the first cut) and only a limited amount was stored in the selenate reserve pool in the leaves (~ 5 mg Se kg-1 forage DM). Higher application rates of selenate amendment increased forage Se concentrations in first and second cuts, but carry over in subsequent years was negligible. Application of foliar selenate vs. granular Selcote Ultra® amendments, between 0 and 90 g Se ha-1, both resulted in a linear, dose-dependent increase in forage Se concentration. Amendments differed in their Se incorporation pattern (Se%), in that, first cut forage Se concentrations were higher with foliar selenate amendment and second, third, and residual (following spring) cut forage Se concentrations were higher with granular Selcote Ultra® amendment. Given the linear relationship between forage Se concentrations and whole-blood Se concentrations in livestock consuming Se-biofortified forage, we conclude that targeted grazing or other forage feeding strategies will allow producers to adapt to either selenate-amendment form.

Selenized glucose (SeGlu) is a new type of organic selenium (Se) that is synthesized through the selenide reaction of glucose with sodium hydrogen selenide. This study aimed to clarify the influence of dietary SeGlu on the Se level and antioxidant capacity of the liver, oviduct, and spleen in laying hens. A total of 360, 60-week-old, Hy-Line Brown laying hens were randomly assigned to three treatment groups: a basal diet alone (control group, without adding exogenous Se) or the basal diet supplemented with 0.3 mg/kg of Se from sodium selenite (SS) or 5 mg/kg of Se from SeGlu. Diets with SeGlu increased Se levels in the liver, oviduct, and spleen of laying hens (P < 0.001). Compared with the control and SS groups, diet supplemented with SeGlu enhanced glutathione peroxidase (GSH-Px) activity and total antioxidant capacity (T-AOC) in the spleen and oviduct as well as the scavenging ability of 2, 2-diphenyl-1-picrylhydrazyl free radical (DPPH•) in the oviduct (P < 0.05). Compared with the control group, SeGlu treatment resulted in an increase (P < 0.05) in GSH-Px activity, T-AOC, and scavenging abilities of hydroxyl radical and DPPH• in the liver of hens. In addition, dietary SeGlu and SS decreased the hydrogen peroxide level in the oviduct in comparison to the control group (P < 0.05). Therefore, dietary SeGlu increased Se concentration and antioxidant ability in the liver, oviduct, and spleen of laying hens. Moreover, SeGlu may be used as a potential source of Se additive in laying hen production.

The present study was conducted to assess the relative bioavailability of selenium (Se) as Se yeast (SY) relative to sodium selenite (SS) for broilers fed a conventional corn-soybean meal diet. A total of 360 one-d-old Arbor Acres commercial broilers were randomly assigned to 5 treatments with 6 replicates per treatment in a completely randomized design involving a 2 (Se sources: SY and SS) × 2 (added Se levels: 0.20 and 0.40 mg Se/kg) factorial design of treatments plus 1 (a Se-unsupplemented control diet) for 42 days. The results showed that Se concentrations in plasma, liver, heart, breast muscle, pancreas and kidney of broilers on d 21 and 42, glutathione peroxidase (GSH-Px) activity in the pancreas on d 21 as well as in the breast muscle and pancreas on d 42, and GSH-Px mRNA levels in the liver, heart, breast muscle and pancreas on d 21 increased linearly (p < .03) as levels of added Se increased. Furthermore, a difference (p ≤ .05) between SY and SS was detected for Se concentrations in plasma, liver, heart, breast muscle, pancreas and kidney, GSH-Px activity in pancreas on both d 21 and 42, as well as pancreatic GSH-Px mRNA level on d 21. Based on slope ratios from the multiple linear regressions of the above indices, the Se bioavailabilities of SY relative to SS (100%) were 111%-394% (p ≤ .05) when calculated from the Se concentrations in plasma, liver, heart, breast muscle, pancreas, kidney and GSH-Px activities in pancreas on d 21 and 42, as well as GSH-Px mRNA level in pancreas on d 21. The results from this study indicated that the Se from SY was more available for enhancing the Se concentrations in plasma or tissues and the expression and activity of GSH-Px in pancreas of broilers than the Se from SS.

Edible fungi have strong ability to transform inorganic Se into organic forms. Therefore, different concentrations of selenite, selenate and Se-yeast were injected as Se-supplements into substrates to produce Se-enriched Lentinula edodes. The Se content and its speciation distribution in the fruit bodies of L. edodes were analysed at different harvest times. Results indicate that Se concentrations of L. edodes increased first and then decreased over time. Based on Se accumulation in L. edodes, selenium use efficiency was ranked as selenite > selenate > Se-yeast. SeMet was the predominant Se speciation in the fruit bodies of L. edodes. SeMet made up the biggest proportion of total Se content and increased with application time for selenite and selenate treatments, whereas no significant change was found for Se-yeast treatment. This study demonstrates that Se-enriched L. edodes is a good source of dietary Se.