Total Se Levels Research Articles

Selenium in plant-based beverages: How can in vitro bioaccessibility contribute to an accurate daily intake?

BackgroundLactose intolerance, cow milk protein allergy, and environmental and ethical concerns drive the global market for plant-based beverages (PPBs). Despite this, data on the occurrence of selenium (Se) in these beverages are scarce. ObjectiveThe objectives of this study were to assess total selenium and determine the bioaccessible fractions in plant-based beverages (PBBs) from cereals, oilseeds, and pumpkin seeds, using an in vitro static method to simulate human digestion; and estimate the contribution these beverages have to the reference daily intake (RDI) for children and adults. MethodologyThe study involved beverages made under laboratory conditions. Samples and extracts were submitted to acid digestion (ultrasonic and block digester); total and bioaccessible Se levels were determined by ICP-MS. In vitro bioaccessibility was assessed using the INFOGEST protocol. ResultsThe results revealed a wide variation in Se content in the studied plant-based beverages from 10.3 µg kg−1 (sunflower seeds) to 3509 µg kg−1 (Brazil nuts). The bioaccessibility of Se was found only in PBBs made from oilseeds with macadamia, cashew and Brazil nut, with a variation in values from 86 to 96 %. The Se content and its bioaccessible fraction of Brazil nut PBB may contribute to 1276 % and 1218 % of the RDI for children and adults, respectively. ConclusionsThe Se content varied among samples of cereals, oilseeds and pumpkin seeds, reflecting the diversity in the studied PBBs. Only PBBs containing oilseeds (macadamia, cashews, and Brazil nuts) exhibited measurable amounts of bioaccessible Se, indicating an association with the raw material. However, the consumption of the PBB containing Brazil nuts may pose a risk of adverse effects, due to its high contribution to the RDI in both children and adults.

Selenium speciation studies in cancer patients to evaluate the responses of biomarkers of selenium status to different selenium compounds

This work presents the first systematic comparison of selenium (Se) speciation in plasma from cancer patients treated orally with three Se compounds (sodium selenite, SS; L-selenomethionine, SeMet; or Se-methylselenocysteine, MSC) at 400 µg/day for 28 days. The primary goal was to investigate how these chemical forms of Se affect the plasma Se distribution, aiming to identify the most effective Se compound for optimal selenoprotein expression. This was achieved using methodology based on HPLC-ICP-MS after sample preparation/fractionation approaches. Measurements of total Se in plasma samples collected before and after 4 weeks of treatment showed that median total Se levels increased significantly from 89.6 to 126.4 µg kg−1 Se (p < 0.001), particularly when SeMet was administered (190.4 µg kg−1 Se). Speciation studies showed that the most critical differences between treated and baseline samples were seen for selenoprotein P (SELENOP) and selenoalbumin after administration with MSC (p = 5.8 × 10−4) and SeMet (p = 6.8 × 10−5), respectively. Notably, selenosugar-1 was detected in all low-molecular-weight plasma fractions following treatment, particularly with MSC. Two different chromatographic approaches and spiking experiments demonstrated that about 45% of that increase in SELENOP levels (to ~ 8.8 mg L−1) with SeMet is likely due to the non-specific incorporation of SeMet into the SELENOP affinity fraction. To the authors’ knowledge, this has not been reported to date. Therefore, SELENOP is probably part of both the regulated (55%) and non-regulated (45%) Se pools after SeMet administration, whereas SS and MSC mainly contribute to the regulated one.Graphical abstract

Transfer of Se from sediments to the western mosquitofish Gambusia affinis: Tissue distribution, accumulation, and effects on the antioxidant physiology

Selenium (Se) has been shown to cause various toxicities in predatory species (i.e., fish and birds) in Se-contaminated aquatic environments. However, trophic transfer of Se from abiotic environments to freshwater fish has been relatively less addressed. In this study, 2-month-old mosquitofish (Gambusia affinis) were fed Se-enriched oligochaete (Lumbriculus variegatus, exposed to different concentrations of Se(IV) at 0.0, 3.0, 10.0, and 30.0 µg/g dry weight for 7 days) for 45 days. Tissue distribution, Se speciation, and effects on the antioxidant physiology in G. affinis were assessed. The results showed Se was rapidly accumulated in the oligochaete, with 6.30 ± 1.20, 16.20 ± 2.10, and 34.50 ± 2.40 µg/g dw of total Se levels in the worms exposed to 3.0, 10.0, and 30.0 µg/g of Se(IV), respectively. Total Se levels were increased in a dose-dependent manner in fish tissues and Se(IV) from sediments was maternally transferred to the fish embryos. Se-Met-and Se-Cys-were the predominant Se species in the worm and fish tissues, accounting for a minimum of 91.01% of the total Se. Furthermore, increased lipid peroxidation and altered the activities of antioxidant enzymes and levels of GSH were noticed in G. affinis fed the Se-enriched L. variegatus. This study has demonstrated that Se(IV) is transferred from an abiotic vector to freshwater organisms, disturbing the antioxidant physiology in G. affinis and potentially their offspring. This study highlights the importance of dietary exposure on the accumulation and toxicity of Se in aquatic organisms.

Selenium Biofortification of Grain Maize Through Foliar Application of Sodium Selenate: Selenium Accumulation and Recovery by the Grain

ABSTRACT The study was conducted to investigate the effects of sodium selenate foliar application on the biofortification of selenium (Se) compositions of grain maize (Zea mays L. cvs. DKC 5783 F1). The experiment was carried out in a randomized block design with three replications, and sodium selenate (Na2SeO4) was applied at eight different levels (0, 5, 10, 15, 25, 50, 75, 100 g Se ha−1) from the foliar when the maize plant reached 50–70 cm in height. Applications did not statistically affect yields and biomass, the contents of total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), boron (B), and molybdenum (Mo), but it affected Se content. The total Se levels varied between 27 and 523 µg kg−1, the highest value was obtained from 100 g Se ha−1 application. When the amount of foliar-applied Se was increased from 0 to 100 g Se ha−1, the Se content increased by 19.37-fold and Se accumulation increased by 19.30-fold. Se recovery showed no significant change across the Se rates with an average of 37.01%. Foliar selenium application showed a significantly greater potential for increasing the Se level in grain maize, with 1 g of Se ha−1 increasing the grains by 5.23 µg kg−1. In this study, the Se content of maize grain increased with foliar selenate application. For human Se nutrient, it would be necessary to consume more than 100 g of maize (dry weight) per day with the foliar selenate application to maize.

Selenium and Redox Enzyme Activity in Pregnant Women Exposed to Methylmercury.

Selenium (Se) is a micronutrient with essential physiological functions achieved through the production of selenoproteins. Adequate Se intake has health benefits and reduces mercury (Hg) toxicity, which is important due to its neurotoxicity. This study determined the Se status and redox enzyme, including selenoproteins', activity in pregnant women highly exposed to Hg (between 1 to 54 µg Hg/L blood) via fish consumption. A cross-sectional study enrolling 513 women between the first and third trimester of pregnancy from Madeira, Portugal was conducted, encompassing collection of blood and plasma samples. Samples were analyzed for total Se and Hg levels in whole blood and plasma, and plasma activity of redox-active proteins, such as glutathione peroxidase (GPx), thioredoxin reductase (TrxR) and thioredoxin (Trx). Enzyme activities were related to Se and Hg levels in blood. Se levels in whole blood (65.0 ± 13.1 µg/L) indicated this population had a sub-optimal Se status, which translated to low plasma GPx activity (69.7 ± 28.4 U/L). The activity of TrxR (12.3 ± 5.60 ng/mL) was not affected by the low Se levels. On the other hand, the decrease in Trx activity with an increase in Hg might be a good indicator to prevent fetal susceptibility.

Sex-Specific Association between Fasting Plasma Glucose and Serum Selenium Levels in Adults from Southern Mexico.

Selenium (Se) is an essential trace element that by its antioxidant properties has been studied to elucidate its participation in the development of obesity and type 2 diabetes. We evaluated the association between cardiometabolic traits and serum Se levels in a sample of adults from southern Mexico. In 96 nondiabetic individuals, anthropometric data and clinical biochemistry measurements were analyzed. Serum total Se levels were measured with inductively coupled plasma mass spectrometry (ICP-MS). Serum Se level in the whole sample was 10.309 ± 3.031 μg mL−1 and no difference between the women and men was observed (p = 0.09). Additionally, fasting plasma glucose (FPG) was significantly associated with serum Se level (β = −0.07 ± 0.03, p = 0.02, analysis adjusted for age, sex and BMI). Furthermore, sex shows significant interaction with FPG on the serum Se levels (p = 0.01). A follow-up analysis revealed the particular association between FPG and Se levels in women (β = −0.10 ± 0.04, p = 0.01). In conclusion, our data evidenced a women-specific association between FPG and serum Se levels in a sample of adults from southern Mexico.

Evaluation of Zn, Cu, and Se Levels in the North American Autism Spectrum Disorder Population

Metal ion dyshomeostasis and disparate levels of biometals like zinc (Zn), copper (Cu), and selenium (Se) have been implicated as a potential causative factor for Autism Spectrum Disorder (ASD). In this study, we have enrolled 129 children (aged 2–4 years) in North America, of which 64 children had a diagnosis of ASD and 65 were controls. Hair, nail, and blood samples were collected and quantitatively analyzed for Zn, Cu and Se using inductively coupled plasma mass spectrometry (ICP-MS). Of the analyzed biometals, serum Se (116.83 ± 14.84 ng/mL) was found to be significantly lower in male ASD cases compared to male healthy controls (128.21 ± 9.11 ng/mL; p < 0.005). A similar trend was found for nail Se levels in ASD (1.01 ± 0.15 mcg/g) versus that of controls (1.11 ± 0.17 mcg/g) with a p-value of 0.0132 using a stratified Wilcoxon rank sum testing. The level of Se in ASD cohort was co-analyzed for psychometric correlation and found a negative correlation between total ADOS score and serum Se levels. However, we did not observe any significant difference in Zn, Cu, and Zn/Cu ratio in ASD cases versus controls in this cohort of North American children. Further studies are recommended to better understand the biology of the relationship between Se and ASD status.

Serum Selenium Levels in Glaucoma: a Pilot Study.

Trace elements are assumed to be involved in glaucoma pathogenesis via changes in oxidative stress. Especially serum selenium (Se) has been linked to this neurodegenerative disease. Serum Se levels differ between countries due to nutrition and ethnicity. It was the aim of the present study to investigate serum Se levels in primary open-angle glaucoma (POAG) patients and controls in Germany and to consider potential age and gender effects. The Se concentration of 39 serum samples (22 patients with POAG, 17 controls) were analyzed by inductively coupled plasma-sector field mass spectrometry (ICP-sf-MS) in high resolution mode. Covariance and percentile regression were analyzed. Age and gender were defined as confounding factors and their different trends were investigated. Moreover, age was examined across different quantiles of Se levels. Total serum least-squares means (LS-means) Se levels were 132.02 µg/L (controls) and 134.86 µg/L (POAG). Total serum Se levels did not differ between the study groups (p > 0.05). Significant age and gender effects of serum Se were observed. Quantile analysis showed that the 1st serum Se quantile decreased with increasing age in POAG patients in contrast to controls. The odds ratios of the 1st serum Se were 1.3 (with 2nd quantile) and 1.3 (with 3rd quantile), respectively. The serum Se level of the German cohort was almost half of those of the published US cohort (glaucoma 209.11 ng/mL; control 194.45 ng/mL). Age and gender effects were observed; the serum Se level increased with age in women (controls and POAG), however, Se levels decreased with age in men (controls and POAG).

Tissue localization of selenium of parental or dietary origin in rainbow trout (Oncorhynchus mykiss) fry using LA-ICP MS bioimaging

Abstract In relation to the decrease of selenium (Se) content in aquafeeds, the impact of level and form of parental and dietary Se supplementation was investigated in rainbow trout fry using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP MS) bioimaging. The offspring of rainbow trout broodstock, fed either a control diet without any Se supplementation (0.3 mg Se/kg diet) or a diet supplemented with Se (0.6 mg Se/kg diet) either as sodium selenite or hydroxy-selenomethionine, were sampled at swim-up fry stage or after 11 weeks of cross-feeding. Total body Se levels were influenced by parental Se nutrition in swim-up fry and by direct Se feeding in 11-week fry with higher levels in the Se-supplemented groups compared with the control and the highest levels in the hydroxy-selenomethionine treatment. The Se retention was lower for dietary sodium selenite. Selenomethionine levels increased when Se was provided as hydroxy-selenomethionine. LA-ICP MS maps revealed yolk in swim-up fry and intestine, liver, and kidney in 11-week fed fry as tissues with high Se abundance. In swim-up fry, muscle Se was the highest abundant when parents were fed hydroxy-selenomethionine. In 11-week fed fry, muscle Se abundance was higher in the head part of fry fed both Se-supplemented diets, but only in the tail part of fry fed hydroxy-selenomethionine. Liver Se abundance was higher in fry fed sodium selenite compared with the control diet supporting the hypothesis that tissue Se distribution can be influenced by parental and dietary Se forms and levels.

Nano-selenium Supplementation Increases Selenoprotein (Sel) Gene Expression Profiles and Milk Selenium Concentration in Lactating Dairy Cows

Supplementation with selenium is common for dairy cows, but the importance of selenium source is not clear. This study aimed to compare nano-selenium (Nano-Se) and sodium selenite supplements for dairy cows on lactation performance, milk Se levels and selenoprotein (Sel) gene expression. Twelve multiparous Holstein cows were randomly divided into two groups: a control group fed a basal diet plus 0.30 mg Se/kg of DM as sodium selenite or Nano-Se for 30 days. Dry matter intake, milk yield and composition were not affected by dietary Se source (P > 0.05); however, the milk total Se levels and milk glutathione peroxidase (GSH-Px) activities were higher with Nano-Se supplementation than sodium selenite (P < 0.05). At the end of the experiment, Nano-Se supplementation significantly increased plasma Se levels and GSH-Px activity, compared with the sodium selenite supplement. The mRNA expression levels of glutathione peroxidase 1, 2 and 4; thioredoxin reductase 2 and 3; and selenoproteins W, T, K and F were markedly upregulated (P < 0.05) in the mammary gland of the Nano-Se group. Thus, the source of selenium plays an important role in the antioxidant status and in particular the Sel gene expression in the mammary glands of dairy cows, both being stimulated by nano sources.

Determination of trace amounts of selenium in natural spring waters and tea samples by catalytic kinetic spectrophotometry

In this work, a new kinetic method is described for the determination of trace Se(IV) in natural spring waters and commercial tea samples. The method is based on the activation of Se(IV) onto the indicator reaction in acidic medium. The reaction was monitored using a fixed time approach of 20 min at 680 nm. The variables affecting the reaction rate were evaluated and optimized. The method allows the determination of Se(IV) in the range of 0.0125-1.0 mg L-1 with a detection limit of 3.6 µg L-1. The precision was in range of 0.63-3.15% (as RSD %) with a higher recovery than 98.6%. The method has been found to be selective against matrix effect. The method was applied to the speciation analysis of inorganic Se species present in the selected samples. The method was statistically validated by analysis of two certified samples and comparing the obtained results to those of HG-AAS analysis. Also, the total Se levels of the samples were determined by using both methods after conversion of Se(VI) into Se(IV) in ultrasonic bath in acidic medium for 30 min at 85-90 °C. The results were in good agreement with those of HG-AAS. The Se(VI) level of the samples was calculated from the difference between amounts of total Se and Se(IV).

Selenium and mercury concentration in drinking water and food samples from a coal mining area in Brazil.

Selenium (Se) is an essential element for human health and can also alleviate the toxicity of elements such as mercury (Hg), which is considered deleterious to health. The study area is an important coal mineral region in Brazil, generating 40% of all Brazilian coal. During the coal mining process, Se and Hg are released, which can induce potential human health risks via the food chain. The purpose of the present study is to determine total Se and its species and total Hg in drinking water and food locally produced from a coal mining area, to assess the impact of coal mining. The samples were collected in two cities, with and without coal mining influence. Total Se levels in drinking water and food were assessed by inductively coupled plasma mass spectrometry (ICP-MS) and its species by high-performance liquid-ICP-MS, while total Hg was determined by cold vapor atomic fluorescence spectrometry. Drinking water (1.1 ± 0.2 mg L-1 dry weight) (p = 0.02) and tomatoes (1.5 ± 0.1 mg kg-1 dry weight) (p = 0.01) from the coal mining area had higher total Se concentration than the control area. The highest Se concentrations were found in animal-based food (6.4 ± 0.8 mg kg-1 dry weight) with an important contribution of Se IV (65%). The analyzed sample did not accumulate a significant amount of Hg. Future studies on the estimates of daily intake of these elements and dietary pattern of the population are needed to make appropriate dietary recommendations and support public health action.

Selenium Accumulation, Antioxidant Enzyme Levels, and Amino Acids Composition in Chinese Mitten Crab (Eriocheir sinensis) Fed Selenium-Biofortified Corn.

The effects of selenium (Se)-biofortified corn on the total Se contents, the antioxidant enzyme levels, and the amino acids composition in Chinese mitten crab (Eriocheir sinensis) during the stage of the fifth shelling to maturity were investigated in the present study. The culture density of crabs was 600 per 667 m2, and they were continuously fed 120.4 mg Se from Se-biofortified corn per 667 m2 every two days for 90 days. The results showed that the total muscle Se levels in the crabs were significantly increased (p < 0.05). Activities of hemolymph supernatant enzymes including alkaline phosphatase (AKP), lysozyme (LZM), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were also enhanced (p < 0.05). The protein and crude fat levels at maturity were higher than those at the fourth molt. The levels of total essential amino acids (∑EAAs) and total delicious amino acids (∑DAAs) were significantly increased (p < 0.05). We demonstrate that the feeding of Se-biofortified corn could significantly improve total muscle Se concentrations and hemolymph supernatant antioxidant enzyme activities in Chinese mitten crab, and slow down the rapid decline of ∑EAAs and ∑DAAs at maturity, thus improving the nutritional quality of Chinese mitten crab.

Bioaccessibility of selenium from cooked rice as determined in a simulator of the human intestinal tract (SHIME).

As an essential but also potentially toxic element, both overexposure and underexposure to selenium (Se) can significantly affect public health. Rice is a common source of Se, especially in Asia. Not all Se may be released from the rice and become available for absorption into the bloodstream upon digestion in the gastrointestinal tract. Therefore, the bioaccessibility of Se in cooked white (polished) rice was assessed in vitro using the static gastrointestinal simulator SHIME (Simulator of the Human Intestinal Microbial Ecosystem). The common cooking procedure in China prior to consumption [i.e. boiling at low rice:water ratios (1:3) until all of the water is absorbed into the rice] did not change total Se levels in the rice. Gastrointestinal digestion of the cooked rice matrix revealed a Se bioaccessibility of 67-76% of total Se. Subsequent microbial activity in the colon reduced the accessibility of Se in the cooked rice to 51-62%. Not all Se present in cooked white rice should be considered as being bioavailable in the small intestine. A minor part is transferred with the remaining food matrix to the colon, where it is available for the microbial metabolism. © 2017 Society of Chemical Industry.

Do the dietary ingredients of low-protein formulated diet provide a sufficient selenium source in Australian snapper Pagrus auratus diet (Bloch & Schneider 1801)?

A 10-week feeding trial was conducted to evaluate the necessity of supplementing selenium (Se) in a low-protein basal diet for Australian snapper Pagrus auratus, a slower-growing fish species. Dietary Se supplementation was tested against commercial barramundi diet, most commonly fed to Australian snapper. Se-yeast was added to a reconstituted commercial diet and to a formulated basal diet at 0, 0.8 and 1.0mg/kg Se to form six isoenergetic test diets to evaluate the effects of diet types, dietary Se supplementation and their interaction on the growth, feed utilisation, body composition and liver morphology of juvenile Australian snapper. These Se supplementation levels resulted in total dietary Se levels of 0.92, 1.68, 1.76, 1.67, 2.59 and 2.77mg/kg, respectively. Each test diet was fed to triplicate groups of Australian snapper in a flow-through seawater system. There were no significant interaction between diet types and Se supplementation on all tested parameters of the snapper. Regardless of the diet types, snapper fed 1.0mg/kg Se-supplemented diet attained significantly lower growth rate than the fish fed diets supplemented with 0 and 0.8mg/kg of Se. Feed conversion ratio was significantly increased in snapper fed diets supplemented with 1.0mg/kg Se. There were no effects of both diet types and Se supplementation on the proximate composition of the muscle and whole-body except the reduced moisture and gross energy levels in the whole-body of snapper fed 1.0mg/kg Se-supplemented diet. The Se contents in the muscle and liver tissues showed positive linear relationships with dietary Se levels. Fish fed diet supplemented with 1.0mg/kg Se showed increased hepatic lipid compared with the fish fed 0 and 0.8mg/kg Se-supplemented diets. Histopathological alterations were observed in liver tissues of snapper fed the basal diet containing 2.77mg/kg Se. The results concluded that the protein and Se requirements of Australian snapper are low and can be met by lower protein ingredients with the endogenous Se. Further, the dietary Se threshold level in Australian snapper fed a basal diet was 2.77mg/kg, whereas this level was only 1.76mg/kg in the reconstituted commercial diet.

Plasma levels of selenium-containing proteins in Inuit adults from Nunavik

Selenium (Se) is highly abundant in marine foods traditionally consumed by Inuit of Nunavik (Northern Quebec, Canada) and accordingly, their Se intake is among the highest in the world. However, little is known regarding the biological implications of this high Se status in this Arctic indigenous population. We used a method combining affinity chromatography and inductively coupled plasma-mass spectrometry with quantification by post-column isotope dilution to determine total Se levels and concentrations of Se-containing proteins in archived plasma samples of Inuit adults who participated to the 2004 Nunavik Inuit Health Survey (N = 852). Amounts of mercury (Hg) associated with Se-containing proteins were also quantified. Results show that glutathione peroxidase 3 (GPx3), selenoprotein P (SelP) and selenoalbumin (SeAlb) represented respectively 25%, 52% and 23% of total plasma Se concentrations. In addition, small amounts of Hg co-eluted with each Se-containing protein and up to 50% of plasma Hg was associated to SelP. Total plasma Se concentrations (median = 139 μg L−1; interquartile range (IQR) = 22.7 μg L−1) were markedly lower and less variable than whole blood Se concentration (median = 261 μg L−1, IQR = 166 μg L−1). A non linear relation was observed between whole blood Se and plasma Se levels, with plasma Se concentrations leveling off at approximately 200 μg L−1, whereas 16% and 3% of individuals exhibited whole blood concentrations higher than 500 μg L−1 and 1000 μg L−1, respectively. In contrast, a linear relationship was previously reported in communities consuming Brazil nuts which are rich Se, mainly present as selenomethionine. This suggests that a different selenocompound, possibly selenoneine, is present in the Arctic marine food chain and accumulates in the blood cellular fraction of Inuit.

Separation/preconcentration of ultra-trace levels of inorganic Sb and Se from different sample matrices by charge transfer sensitized ion-pairing using ultrasonic-assisted cloud point extraction prior to their speciation and determination by hydride generation AAS

In the existing study, a new, simple and low cost process for separation/preconcentration of ultra-trace level of inorganic Sb and Se from natural waters, beverages and foods using ultrasonic-assisted cloud point extraction (UA-CPE) prior to their speciation and determination by hydride generation AAS, is proposed. The process is based on charge transfer sensitized complex formations of Sb(III) and Se(IV) with 3-amino-7-dimethylamino-2-methylphenazine hydrochloride (Neutral red, NRH+) in presence of pyrogallol and cetyltrimethylammonium bromide (CTAB) as both sensitivity enhancement and counter ion at pH 6.0. Under the optimized reagent conditions, the calibration curves were highly linear in the ranges of 8–300ngL−1 and 12–250ngL−1 (r2≥0.993) for Se(IV) and Sb(III), respectively. The limits of detection were 2.45 and 3.60ngL−1 with sensitivity enhancement factors of 155 and 120, respectively. The recovery rate was higher than 96% with a relative standard deviation lower than 5.3% for five replicate measurements of 25, 75 and 150ngL−1 Se(IV) and Sb(III), respectively. The method was validated by analysis of two certified reference materials (CRMs), and was successfully applied to the accurate and reliable speciation and determination of the contents of total Sb/Sb(III), and total Se/Se(IV) after UA-CPE of the pretreated sample matrices with and without pre-reduction with a mixture of l-cysteine and tartaric acid. Their Sb(V) and Se(VI) contents were calculated from the differences between total Sb and Sb(III) and/or total Se and Se(IV) levels.

Maintaining tissue selenium species distribution as a potential defense mechanism against methylmercury toxicity in juvenile white sturgeon (Acipenser transmontanus)

Selenium (Se) has been shown to antagonize mercury (Hg) toxicity. We have previously demonstrated that orally intubated selenomethionine (SeMet) and methylmercury (MeHg) reduced tissue Se accumulation, as well as blood and kidney Hg concentrations in juvenile white sturgeon (Acipenser transmontanus). However, the form of Se accumulated is not known. In this study, three organoseleniums: selenocysteine (Sec), Se-methyl-selenocysteine (MSeCys), and SeMet and two inorganic Se species: selenate and selenite were determined and quantified in the blood at different post-intubation periods (12, 24, 48h) and in the muscle, liver, and kidneys at 48h in white sturgeon orally intubated with a single dose of control (carrier), SeMet (500μg Se/kg body weight; BW), MeHg (850μg Hg/kg BW), and both (Se+Hg; at 500μg Se/kg and 850μg Hg/kg BW). When only SeMet was intubated, the accumulative/unmodified pathway took precedent in the blood, white muscle, liver, and kidneys. In the presence of MeHg, however, active metabolic transformation and de novo synthesis of biologically active Se forms are seen in the liver and kidneys, as indicated by a gradual increase in blood Sec:SeMet ratios and Se metabolites. In the white muscle, mobilization of endogenous Se storage by MeHg is supported by the absence of tissue SeMet and detectable levels of blood SeMet. In contrast, co-intubation with SeMet increased muscle SeMet. The high levels of unknown Se metabolites and detectable levels of selenite in the kidney reflect its role as the major excretory organ for Se. Selenium metabolism is highly regulated in the kidneys, as Se speciation was not affected by MeHg or by its co-intubation with SeMet. In the Se+Hg group, the proportion of SeMet in the liver has decreased to nearly 1/8th of that of the SeMet only group, resulting in a more similar selenocompound distribution profile to that of the MeHg only group. This is likely due to the increased need for Se metabolites necessary for MeHg demethylation in the liver. Our study demonstrated that in the presence of MeHg, regulating tissue Se speciation, hence, Se bioavailability, is more an important strategy than maintaining total Se levels in major organs of juvenile white sturgeon.

Comparing the effects of dietary selenium and mannan oligosaccharide supplementation on the growth, immune function, and antioxidant enzyme activity in the cultured marron Cherax cainii (Austin, 2002)

This study was conducted to compare the effects of dietary supplementation of selenium (Se, both inorganic and organic) and mannan oligosaccharide (MOS) on the growth, immune function, and antioxidant enzyme activities in the haemolymph of the marron Cherax cainii (Austin, 2002); 0.4 mg kg−1 of sodium selenate, 0.2 g kg−1 Sel-Plex®, or 0.4 % Bio-MOS® was added to the basal diet as sources of inorganic selenium (IS), organic selenium (OS), and MOS, respectively. After 90 days, marron fed all 3 supplemented test diets had significantly higher final weight, specific growth rate (SGR), survival, total haemocyte count (THC), percentage of hyaline cells, glutathione-S-transferase (GST), and glutathione peroxidase (GPx) activities than marron fed without any supplements. The marron fed OS showed significantly higher THC and percentage of hyaline cells than those fed IS and MOS. Marron fed MOS showed the highest final weight, SGR, and percentage of granular cells; however, there was no significant difference in the neutral red time retention between marron fed IS and OS, whereas marron fed OS resulted in the highest GPx activity and total Se levels in the haemolymph but the lowest lipid peroxidase activity; therefore, it is suggested that dietary supplementation with any source of Se and MOS is beneficial to improving growth, survival, and antioxidant activity.

Blood dynamics of mercury and selenium in northern elephant seals during the lactation period

The effects of reproduction and maternal investment (i.e., milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of mercury (Hg) and selenium (Se) during lactation in the northern elephant seal (Mirounga angustirostris), a top predator from the North Pacific Ocean. Total Hg and Se levels were measured in whole blood and milk of 10 mother–pup pairs on days 5 and 22 of lactation. Both Hg and Se were transferred to offspring through the milk. Results suggested that the maternal transfer of Se was prominent during lactation, whereas the Hg transfer was larger during gestation. The lactation period affected Hg and Se levels in the blood of elephant seal mothers and pups. Physiological processes and their relationship to body condition should be considered carefully when interpreting trace element levels in the framework of biomonitoring.