Distribution of selenium: A case study of the Drava, Danube and associated aquatic biotopes.

This paper presents the results of the research on the overall distribution of selenium (Se) in various aquatic compartments (water, sediment, plankton and macrophytes) at six selected sites of the Croatian part of the Drava and Danube rivers, the connected floodplain lake and the melioration channel system carried out in two sampling periods (flooding in June and the drought period in September). In addition, the physicochemical water properties, plankton composition and biomass were analysed. Our study revealed low mean Se contents in sediments and water, indicating Se deficiency in the studied freshwater systems. The physicochemical environment, including Se distribution, was primarily influenced by hydrology rather than site-specific biogeochemical and morphological characteristics. The flooding period was characterised by higher Se content in water and higher transparency, nitrate and total nitrogen concentrations than drought conditions. At the river sites, sediment Se content was the highest during the flood period, while at all other sites, higher concentrations were found during the drought, reaching the maximum in the lake. Although Se concentrations were below the threshold for aquatic ecotoxicity, they increased in the following order: water (0.021-0.187 µg Se L-1) < sediments (0.005-0.352 mg Se kg-1) < macrophytes (0.010-0.413 mg Se kg-1) < plankton (0.044-0.518 mg Se kg-1) indicating its possible biomagnification at the bottom of the food chain. Species known for high Se accumulation potential dominated the biomass of the main plankton groups and the composition of the macrophyte community, which may provide a more sensitive and accurate steady-state compartment monitor for Se assessment in freshwater biotopes.

Biochemical and molecular responses of the ascorbate-glutathione cycle in wheat seedlings exposed to different forms of selenium.

Biofortification aims to increase selenium (Se) concentration and bioavailability in edible parts of crops such as wheat (Triticum aestivum L.), resulting in increased concentration of Se in plants and/or soil. Higher Se concentrations can disturb protein structure and consequently influence glutathione (GSH) metabolism in plants which can affect antioxidative and other detoxification pathways. The aim of this study was to elucidate the impact of five different concentrations of selenate and selenite (0.4, 4, 20, 40 and 400 mg kg-1) on the ascorbate-glutathione cycle in wheat shoots and roots and to determine biochemical and molecular tissue-specific responses. Content of investigated metabolites, activities of detoxification enzymes and expression of their genes depended both on the chemical form and concentration of the applied Se, as well as on the type of plant tissue. The most pronounced changes in the expression level of genes involved in GSH metabolism were visible in wheat shoots at the highest concentrations of both forms of Se. Obtained results can serve as a basis for further research on Se toxicity and detoxification mechanisms in wheat. New insights into the Se impact on GSH metabolism could contribute to the further development of biofortification strategies.

Consumption of Nutritionally Enriched Hen Eggs Enhances Endothelium-Dependent Vasodilation via Cyclooxygenase Metabolites in Healthy Young People-A Randomized Study.

OBJECTIVE: The present study aimed to evaluate the effects of enriched hen egg consumption on endothelium-dependent vasodilation (EDV) and the role of cyclooxygenases in EDV in the microcirculation of young healthy individuals. This study hypothesizes that Nutri4 eggs will improve endothelial function, which will be manifested by changes in microcirculatory flow measured by a laser Doppler flowmeter (LDF) during reactive hyperemia in response to vascular occlusion, in which n-3 PUFA plays an important role as well as its degradation pathway by cyclooxygenases. MATERIALS AND METHODS: Participants consumed three eggs per day for three weeks: The control group (CTRL, n = 14) consumed regular hen eggs (approximately 0.330 mg of lutein, 1.785 mg of vitamin E, 0.054 mg of selenium and 438 mg of n-3 PUFAs daily) and Nutri4 group (n = 20) consumed enriched eggs (approximately 1.85 mg of lutein, 0.06 mg of selenium, 3.29 mg of vitamin E, and 1026 mg of n-3 PUFAs daily). Skin microvascular blood flow in response to EDV (post-occlusive reactive hyperemia (PORH) and iontophoresis of acetylcholine (AChID)) and sodium nitroprusside (SNPID; endothelium-independent) was assessed by laser Doppler flowmetry before and after dietary protocol and in a separate group of participants who were administered perorally 100 mg of indomethacin before microvascular response assessment. Arterial blood pressure, heart rate, serum lipid, and liver enzymes, anthropometric measurements, protein expression of cyclooxygenase 1 (COX-1), cyclooxygenase 2 (COX-2), neuronal nitric oxide synthases (nNOS), inducible nitric oxide synthases (iNOS), and endothelial nitric oxide synthases (eNOS) were measured before and after dietary protocol. RESULTS: PORH and AChID were significantly enhanced, and SNPID remained unchanged in the Nutri4 group, while none was changed in the CTRL following a respective diet. PORH decreased after administration of indomethacin in Nutri4 after dietary protocol. Protein expression of COX-2 was significantly higher in the Nutri4 group compared to the CTRL after the dietary protocol. CONCLUSION: Consumption of enriched eggs improves microvascular EDV in healthy young subjects. Results suggest an element of n-3 PUFAs metabolites via the cyclooxygenases pathway in enhanced reactive hyperemia.

Selenium and Natural Zeolite Clinoptilolite Supplementation Increases Antioxidative Status and Immune Response in Growing Pigs.

Selenium (Se), an essential trace element for human and animal health, is covalently incorporated into amino acids, acts as a cofactor for antioxidant enzymes, and is involved in the maintenance of the immune system. The main goal of this investigation was to show the effect of Se supplementation, at levels slightly higher than the recommended values, combined with natural zeolite clinoptilolite on Se deposition in tissues (muscle and liver) and on the immune and antioxidative status of supplemented growing pigs. The experiment was carried out during a 98 d period on 60 pigs. Pigs were fed a standard feed mixture based on corn and soybean and were divided into four groups, according to the level of dietary selenium supplementation as follows: C-0.3 mg/kg DM organic Se, E1-0.5 mg/kg DM sodium selenite, E2-0.5 mg/kg DM organic selenium; E3-0.5 mg/kg DM organic Se+0.2% zeolite. Higher (P < 0.05) selenium concentrations were determined in the muscle and liver in growing pigs fed with higher organic Se in combination with zeolite compared to the lower organic Se concentration. Addition of organic Se increased (P < 0.05) Se deposition in muscle and liver compared to the equal amount of inorganic Se (E2 vs. E1). Higher organic Se in combination with natural zeolite addition increases (P < 0.05) proportion of pigs' cluster of differentiation (CD)45+ compared to the same amount of inorganic Se and lower organic Se addition. The proportion of CD45+ and CD4+ lymphocytes was higher (P < 0.05) in E3 group compared to the other groups. Higher (P < 0.05) proportion of CD21+ lymphocytes were measured in the E2 and E3 groups compared with the other groups. The highest (P < 0.01) activity of glutathione peroxidase (GSH-Px) in pig erythrocytes was observed in the E3 group, while higher (P < 0.05) activity of glutathione reductase (GR) was in all experimental groups related to the control one. A dietary addition of 0.5 mg/kg DM of organic Se in combination with zeolite (0.2% DM) has increased (P < 0.05) Se deposition in liver, muscle, and blood, compared to the dietary addition of 0.3 mg/kg DM of the organic Se.

The effect of dietary selenium addition on the concentrations of heavy metals in the tissues of fallow deer (Dama dama L.) in Croatia.

The aim of this research was to determine the concentrations of cadmium, lead, mercury, and arsenic and the essential elements iron and selenium in the tissues (muscle, kidney, liver, spleen, and fat) of fallow deer (Dama dama L.) without and with supplemental selenium addition. Another aim was to determine the effect of selenium addition on the indicators of oxidative stress, namely, the levels of superoxide dismutase, glutathione peroxidase, glutathione, and vitamin E. The research was carried out with 40 fallow deer during two research periods. Supplemental feed without selenium addition was provided during the first research period, and supplemental feed with added selenium (3 mg/kg) was provided for 60 days during the second research period. The concentration of selenium in tissues was higher in the second research period than in the first research period (in kidney tissue, 0.957 vs. 0.688 mg/kg, P < 0.05). The dietary addition of selenium decreased (P < 0.05) the concentrations of some heavy metals (lead in the spleen = 0.06 vs. 0.27 mg/kg and in the fatty tissue = 0.17 vs. 0.69 mg/kg; arsenic in the muscle tissue = 0.005 vs. 0.014 mg/kg, liver = 0.003 vs. 0.009 mg/kg, spleen = 0.004 vs. 0.013 mg/kg, and fat = 0.008 vs. 0.016 mg/kg). The activity of glutathione peroxidase was significantly higher (P < 0.05) in the second research period than in the first research period (1375.36 vs. 933.23 U/L).

Reduced Dietary Selenium Impairs Vascular Function by Increasing Oxidative Stress in Sprague-Dawley Rat Aortas.

This study aimed to determine whether low dietary Se content affects the function and mechanisms mediating the vascular relaxation of rat aortas, and to test the role of oxidative stress in observed differences. Male Sprague Dawley (SD) rats were maintained for 10 weeks on low Se (low-Se group; N = 20) or normal Se content (norm-Se group; N = 20) rat chow. Dose responses to acetylcholine (ACh; 10-9-10-5M) and the response to reduced pO2 were tested in noradrenaline-precontracted aortic rings in the absence/presence of the nitric oxide synthase (NOS) inhibitor nitro-l-arginine methyl ester (l-NAME), the cyclooxygenase 1 and 2 (COX-1, 2) inhibitor Indomethacin, and the antioxidative agent Tempol in tissue bath. mRNA expression of glutathione peroxidase 1 (GPx1), catalase (CAT), and Cu/Zn superoxide dismutase (SOD) was measured in rat aortas. Oxidative stress (Thiobarbituric Acid Reactive Substances; TBARS), antioxidative plasma capacity (ferric reducing ability of plasma assay; FRAP), and protein levels of GPx1 were measured in plasma and serum samples, respectively. Reduced ACh-induced relaxation (AChIR) (dominantly mediated by NO) in the low-Se group compared to the norm-Se group was restored by Tempol administration. Hypoxia-induced relaxation (HIR) (dominantly mediated by COX-1, 2), TBARS, and FRAP as well as GPx1 serum concentrations were similar between the groups. mRNA GPx1 expression in rat aortas was significantly decreased in the low-Se compared to the norm-Se group. These data suggest that low dietary Se content increases the local oxidative stress level, which subsequently affects the NO-mediated vascular response.