Selenium and selenium species in feeds and muscle tissue of Atlantic salmon

Organ-specific mercury stable isotopes, speciation and particle measurements reveal methylmercury detoxification processes in Atlantic Bluefin Tuna

Identifying metabolism and detoxification mechanisms of Hg in biota has important implications for biomonitoring, ecotoxicology, and food safety. Compared to marine mammals and waterbirds, detoxification of MeHg in fish is understudied. Here, we investigated Hg detoxification in Atlantic bluefin tuna Thunnus thynnus using organ-specific Hg and Se speciation data, stable Hg isotope signatures, and Hg and Se particle measurements in multiple tissues. Our results provide evidence for in vivo demethylation and biomineralization of HgSe particles, particularly in spleen and kidney. We observed a maximum range of 1.83‰ for δ202Hg between spleen and lean muscle, whereas Δ199Hg values were similar across all tissues. Mean percent methylmercury ranged from 8% in spleen to 90% in lean muscle. The particulate masses of Hg and Se were higher in spleen and kidney (Hg: 61% and 59%, Se: 12% and 6%, respectively) compared to muscle (Hg: 2%, Se: 0.05%). Our data supports the hypothesis of an organ-specific, two-step detoxification of methylmercury in wild marine fish, consisting of demethylation and biomineralization, like reported for waterbirds. While mass dependent fractionation signatures were highly organ specific, stable mass independent fractionation signatures across all tissues make them potential candidates for source apportionment studies of Hg using ABFT.

Microflora structure and functional capacity in Tibetan kefir grains and selenium-enriched Tibetan kefir grains: A metagenomic analysis

Tibetan kefir grains (TKGs) are a complex protein-lipid-polysaccharide matrix composed of various microorganisms. Microorganisms have the benefit of being effective, secure, and controllable when used for selenium enrichment. In this study, selenium-enriched Tibetan kefir grains (Se-TKGs) were made, and the microbiology composition was analyzed through a metagenomic analysis, to explore the influence of selenium enrichment. The microbial composition of TKGs and Se-TKGs, as well as the probiotic species, quorum sensing system (QS) and functional genes were compared and evaluated. Lactobacillus kefiranofaciens was the most abundant microbial species in both communities. Compared with TKGs, Se-TKGs had a much higher relative abundance of acetic acid bacteria. Lactobacillus helveticus was the most common probiotic species both in TKGs and Se-TKGs. Probiotics with antibacterial and anti-inflammatory properties were more abundant in Se-TKGs. QS analysis revealed that Se-TKGs contained more QS system-associated genes than TKGs. Moreover, Kyoto Encyclopedia of Genes and Genomes analysis revealed that the pathway for human disease ko01501 had the greatest relative abundance in both TKGs and Se-TKGs. Compared with TKGs, Se-TKGs demonstrated a greater relative abundance of different drug resistance-related metabolic pathways. Additionally, linear discriminant analysis effect size was used to examine the biomarkers responsible for the difference between the two groups. In this study, we focused on the microbiological structure of TKGs and Se-TKGs, with the aim of establishing a foundation for a more thorough investigation of Se-TKGs and providing a basis for exploring potential future use.

Selenium nanoparticles in aquaculture: Unique advantages in the production of Se-enriched grass carp (Ctenopharyngodon idella)

The production of selenium-enriched fish can contribute to alleviating selenium deficiency in human diets. However, it is still unclear which selenium source, as an additive, can efficiently and cost-effectively produce high-quality selenium-enriched fish. This study evaluated the effects of selenium nanoparticles (SeNP), selenite, and selenomethionine (SeMet) on the growth, antioxidant capacity, selenium content, selenium speciation, and meat quality of grass carp. Ten diets were prepared, including a basal diet (BD) and three concentrations (0.1, 0.3, and 0.9 mg/kg) of SeNP, selenite, and SeMet. A total of 600 fish (250.79 ± 1.57 g) were randomly assigned to 30 tanks (3 tanks/group). Fish were fed the experimental diet three times daily for 60 d. In this study, SeNP most significantly promoted the growth and antioxidant capacity of grass carp, with 0.3 mg/kg SeNP identified as the optimal additive concentration. Additionally, SeNP demonstrated equally excellent bioavailability as SeMet and significantly increased the content of SeMet in grass carp (Ctenopharyngodon idella) muscle. Furthermore, compared to SeMet and selenite, dietary SeNP could more significantly enhance the content of selenocysteine (SeCys2) and methylselenocysteine (MeSeCys) in grass carp muscle tissue. In addition, we have demonstrated that SeCys2 and MeSeCys promote apoptosis of cancer cells (HeLa) through the mitochondrial apoptotic pathway (involving Bax and Bcl-2). Furthermore, as an additive, 0.3 mg/kg SeNP significantly improved the flesh quality of grass carp by reducing crude fat and heavy metal content, as well as increasing the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the ratio of n-3/n-6 polyunsaturated fatty acid (PUFA). In summary, SeNP is the most suitable additive for producing selenium-enriched fish.

Selenium yeast improve growth, serum biochemical indices, metabolic ability, antioxidant capacity and immunity in black carp Mylopharyngodnpiceus

This experiment was conducted to investigate the impacts of dietary selenium yeast (SeY) on the growth performance, fish body composition, metabolic ability, antioxidant capability, immunity and inflammatory responses in juvenile black carp (Mylopharyngodn piceus). The base diet was supplemented with 0.00, 0.30 and 0.60 g/kg SeY (0.04, 0.59 and 1.15 mg/kg of selenium) to form three isonitrogenous and isoenergetic diets for juvenile black carp with a 60-day. Adequate dietary SeY (0.30 and 0.60 g/kg) could significantly increase the weight gain (WG), special growth rate (SGR) compared to the SeY deficient groups (0.00 g/kg) (P < 0.05). Meanwhile, 0.30 and 0.60 g/kg SeY elevated the mRNA levels of selenoprotein T2 (SEPT2), selenoprotein H (SEPH), selenoprotein S (SEPS) and selenoprotein M (SEPM) in the liver and intestine compared with the SeY deficient groups (P < 0.05). Adequate dietary SeY could promote glucose catabolism and utilization through activating glucose transport (GLUT2), glycolysis (GCK, HK, PFK, PK, PDH), tricarboxylic acid cycle (ICDH and MDH), glycogen synthesis (LG, GCS and GBE) and IRS/PI3K/AKT signal pathway molecules (IRS2b, PI3Kc and AKT1) compared with the SeY deficient groups (P < 0.05). Similarly, adequate dietary SeY could improve lipid transport and triglycerides (TG) synthesis through increasing transcription amounts of CD36, GK, DGAT, ACC and FAS in the fish liver compared with the SeY deficient groups (P < 0.05). In addition, adequate SeY could markedly elevate activities of antioxidant enzymes (T-SOD, CAT, GR, GPX) and contents of T-AOC and GSH, while increased transcription amounts of Nrf2, Cu/Zn-SOD, CAT, and GPX in fish liver and intestine (P < 0.05). However, adequate SeY notably decreased contents of MDA, and the mRNA transcription levels of Keap1 in the intestine compared with the SeY deficient groups (P < 0.05). Adequate SeY markedly increased amounts or levels of the immune factors (ALP, ACP, LZM, C3, C4 and IgM) and the transcription levels of innate immune-related functional genes in the liver and intestine (LZM, C3 and C9) compared to the SeY deficient groups (P < 0.05). Moreover, adequate SeY could notably reduce levels of IL-8, IL-1β, and IFN-γ and elevate TGF-1β levels in fish intestine (P < 0.05). The transcription levels of MAPK13, MAPK14 and NF-κB p65 were notably reduced in fish intestine treated with 0.30 and 0.60 g/kg SeY (P < 0.05). In conclusion, these results suggested that 0.30 and 0.60 g/kg SeY could not only improve growth performance, increase Se, glucose and lipid metabolic abilities, enhance antioxidant capabilities and immune responses, but also alleviate inflammation, thereby supplying useful reference for producing artificial feeds in black carp.

Selenium Health Benefit Values and Hg and Se speciation studies for elucidating the quality and safety of highly consumed fish species and fish-derived products

Nowadays, there has been an increase in the consumption of fish-derived products that constitute alternative ways of introducing fish into the diet, such as fish roe and products made from fish (crab sticks andsurimi-derived products). However, there is no data available considering selenium and mercury total contents along with speciation studies in these kinds of samples, which are mandatory for a proper safety and quality assessment. In this study,Selenium Health Benefit Values (HBVSe) in fish and fish-derived products were evaluated, resulting inpositivein all cases. Selenium speciation studies performed by HPLC-ICP-MS and confirmed by HPLC-ESI-MS/MS revealed that SeMet and SeMeSeCys are present in fish and fish-derived products. Finally, Hg speciation studiesshow that the percentage of Hg2+ increases in fishes lower in the food chain as well as in fish-derived products.

Selenium Nanoparticles Ameliorate Adverse Impacts of Aflatoxin in Nile Tilapia with Special Reference to Streptococcus agalactiae Infection

Aflatoxin B1 (AFB1) is a plant-origin toxin that could induce oxidative stress in fish. The micromineral selenium (Se) possesses well-documented antioxidant properties. To assess the ameliorative effects of SeNPs (1 mg/kg fish feed) on oxidative stress induced by AFB1 (500 μg/kg fish feed), Nile tilapia (32.2±1.7 g body weight) were distributed randomly and even in six groups for 8-week feeding trial. Live enzymes, AST, ALT, and ALP levels were increased in the serum of fish fed AFB1-contaminated diet, and the addition of SeNPs could restore normal values compared to the control. The gene expression of antioxidant enzymes, superoxide dismutase (SOD) enzyme and catalase (CAT) enzyme, and DNA fragmentation were significantly increased in response to aflatoxin exposure, while dietary SeNPs could mitigate the generated oxidative stress. The innate immunity, serum antibacterial activity (SAA), oxidative burst activity (OBA), phagocytic activities (PA and PI), and gene expression of cytokines (interleukin (IL)-1β, heat shock protein70 (Hsp), and tumor necrosis factor (TNF)-α) revealed a status of immunosuppression in Nile tilapia fed on AFB1-contaminated diet. These findings showed that fish became more vulnerable to Streptococcus agalactiae infection with a high mortality rate while dietary SeNPs provided a high relative protection level (RPL). From the obtained findings, SeNPs could mitigate the oxidative stress induced by feeding the AFB1 diet and could boost the immunity of stressed Nile tilapia.

Simultaneous speciation analysis of Hg and Se in fish by high-performance liquid chromatography and inductively coupled plasma-mass spectrometry following microwave-assisted enzymatic hydrolysis

This study reports the development and validation of a new analytical method for simultaneous speciation analysis of Se and Hg in fish muscle. For this purpose, four Se species (selenite/Se(IV), selenate/Se(VI), selenomethionine/SeMet, and selenocysteine/SeCys) and two Hg species (inorganic mercury/iHg and methylmercury/MeHg) were extracted simultaneously by microwave-assisted enzymatic hydrolysis and then separated by HPLC in less than 15 min by using a column with both anion and cation exchange mechanisms and a mobile phase consisting of a mixture of methanol 5% (v/v), 45 mM HNO3, 0.015% 2-mercaptoethanol, and 1.5 mM sodium 3-mercapto-1-propanesulfonate. The separated species of Hg and Se were detected online by inductively coupled plasma-mass spectrometry (ICP-MS). The speciation analysis method was validated by means of the accuracy profile approach by carrying out three series of measurements in duplicate on three different days over a time-span of 3 weeks. The limits of quantification (LOQ) are in the range of 0.010-0.013 mg/kg wet weight (ww) for all selenium species, except for Se(IV) (0.15 mg/kg ww), while the coefficient of variation in terms of intermediate reproducibility (CVR) was < 7%. The LOQ for MeHg was 0.006 mg/kg ww, while the CVR was 3%. The method was successfully applied to the analysis of muscle samples from four different fish species: rainbow trout, tuna, swordfish, and dogfish.

Metal-amino acid complexes (Zn, Se, Cu, Fe, and Mn) enhance immune response, antioxidant capacity, liver function enzymes, and expression of cytokine genes in Nile Tilapia reared under field conditions

OBJECTIVES

In the present study, we investigated the effects of partial or total replacement of dietary inorganic trace materials (ITM) with metal-amino acid complexes (MAACs) on immune response, antioxidant capacity, cytokine genes expression, and overall health status of Nile Tilapia Oreochromis niloticus reared in in-pond hapas (mesh cages) under field conditions.

METHODS

All-male Nile Tilapia with an average initial weight of about 90 g fish-1 were stocked into the hapas, in quadruplicates, at a density of 60 fish per hapa (30 fish m-3 ). The fish in each hapa were acclimatized to culture conditions and test diets for 1 week. Water quality parameters, including temperature (°C), pH, dissolved oxygen (mg L-1 ), and total ammonia (mg L-1 ), were monitored regularly. The MAACs were formulated to contain the same mineral concentrations found in the inorganic premix. Metal-amino acid complexes replaced the ITM premix at 0 (control), 25, 50, 75, and 100% levels (Table 1). The diets were fed to caged Nile Tilapia twice a day, for 80 days, at a daily rate of 3% of their body weights. The fish were weighed every 10 days, and the daily rations were readjusted. At harvest, fish in each hapa were collected, counted, and weighed collectively. Five fish from each hapa were rapidly anesthetized, and used for chemical and physiological analyses, including antioxidant and immune response analyses, liver function analysis, and gene expression.

RESULT

The activities of lysozyme, respiratory burst (%), alternative complement (ACH50), phagocytic cells, phenoloxidase, superoxide dismutase, glutathione peroxidase, and liver function enzymes were all improved with increasing supplemental MAACs up to the 50% substitution level. The expression of cytokine genes, including interferon, tumor necrosis factor, interleukin-1, serum alkaline phosphatase, the integrated microbial genomes, chloramphenicol acetyltransferase, and transforming growth factor genes, was significantly upregulated in fish fed on MAAC-supplemented diets compared with the control group. The 50% MAAC level produced the highest upregulation of these genes, whereas gene expression decreased with increasing dietary MAAC levels to 75% and 100%. The quadratic regression analysis indicated that about 60-65% MAAC is required for maximum promotion of immunological and oxidative stress responses, gene expression, and overall health status of Nile Tilapia reared in in-pond hapas under field conditions.

CONCLUSION

Replacement of the ITM premix with a MAAC premix enhanced the immune and antioxidant responses of Nile Tilapia.

Research Progress of Selenium-Enriched Foods

Selenium is an essential micronutrient that plays a crucial role in maintaining human health. Selenium deficiency is seriously associated with various diseases such as Keshan disease, Kashin-Beck disease, cataracts, and others. Conversely, selenium supplementation has been found to have multiple effects, including antioxidant, anti-inflammatory, and anticancer functions. Compared with inorganic selenium, organic selenium exhibits higher bioactivities and a wider range of safe concentrations. Consequently, there has been a significant development of selenium-enriched foods which contain large amounts of organic selenium in order to improve human health. This review summarizes the physiological role and metabolism of selenium, the development of selenium-enriched foods, the physiological functions of selenium-enriched foods, and provides an analysis of total selenium and its species in selenium-enriched foods, with a view to laying the foundation for selenium-enriched food development.

Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts

The aquafeed ingredient inventory is ever changing, from marine to plant based, and recently evolving to incorporate increasing amounts of low trophic, side stream and circular economy based raw materials, each one contributing with variable amounts and qualities of macro- and micronutrients. Meeting the micronutrient requirement of farmed fish for healthy and efficient growth under normal and challenging conditions is of paramount importance. In this study we run a trial based on a 2 × 4 factorial design with three replications for each dietary treatment, where Atlantic salmon smolt were fed one of 8 experimental diets supplemented with either organic or inorganic mineral premixes (copper, iron, manganese, selenium, and zinc) at four dietary inclusion levels. We saw a trend for higher growth rate in the organic mineral groups irrespective of the dietary mineral levels. Mineral digestibility was negatively correlated with increasing mineral supplementation levels for all tested minerals but Se which increased with the increasing supplementation in the inorganic and up to the 2nd inclusion level in the organic mineral groups. Increasing mineral supplementation affected retention efficiency of Zn, Mn, Cu and Fe while mineral source affected only the retention of Se which was higher in the organic mineral groups. Moreover, fish obtained higher EPA and DHA in their body and increased slaughter yield in the organic as compared to the inorganic mineral groups and corroborated that trace mineral inclusion levels play a key role on salmon fillet's technical quality. More effects from different origin and dietary inclusion levels of trace minerals were seen on fillet yield, fillet technical and nutritional quality, bone strength, skin morphology, organ mineralization and midgut transcriptome.

Human serum albumin-bound selenium (Se-HSA) in serum and its correlation with other selenium species

INTRODUCTION

Selenium (Se) is a trace element with different toxicological and nutritional properties according to its chemical forms. Among the wide range of selenium species, human serum albumin-bound selenium (Se-HSA) has still uncertain composition in terms of organic or inorganic selenium species. This study aimed at investigating the relation between Se-HSA levels with total selenium and the specific organic and inorganic selenium species.

METHODS

We determined levels of total selenium and selenium species in serum of participants enrolled in two populations of the Emilia-Romagna region, in Northern Italy. Anion exchange chromatography coupled with inductively coupled plasma dynamic reaction cell mass spectrometry was used as quantification method. Correlations between Se-HSA and the other selenium compounds were analyzed using linear regression and restricted cubic spline regression models, adjusted for potential confounders.

RESULTS

The first cohort comprised 50 participants (men/women: 26/24) with median (interquartile range, IQR) age 50 (55-62) years, while the second was composed of 104 participants (M/W: 50/54), median (IQR) age 48 (44-53) years. Median (IQR) levels of total selenium were 118.5 (109-136) µg/L and 116.5 (106-128) µg/L, respectively, while Se-HSA was 25.5 µg/L (16.2-51.5) and 1.1 (0.03-3.1) µg/L, respectively. In both populations, Se-HSA was positively associated with inorganic selenium species. Conversely, Se-HSA was inversely associated with organic selenium, especially with selenoprotein P-bound-Se (Se-SELENOP) and less strongly with selenomethionine-bound-Se (Se-Met), while the relation was null or even positive with other organic species. Evaluation of non-linear trends showed a substantially positive association with inorganic selenium, particularly selenite, until a concentration of 30 µg/L, above which a plateau was reached. The association with Se-SELENOP was inverse and strong until 100 µg/L, while it was almost null at higher levels.

CONCLUSIONS

Our findings seem to indicate that Se-HSA incorporates more selenium when circulating levels of inorganic compounds are higher, thus supporting its mainly inorganic nature, particularly at high circulating levels of selenite.

Selenium nanoparticles coated with polysaccharide-protein complexes from abalone viscera improve growth and enhance resistance to diseases and hypoxic stress in juvenile Nile tilapia (Oreochromis niloticus)

The use of selenium nanoparticles (SeNPs) in aquaculture has been increasing gradually over the past few years. SeNPs enhance immunity, are highly effective against pathogens, and have low toxicity. In this study, SeNPs were prepared using polysaccharide-protein complexes (PSP) from abalone viscera. The acute toxicity of PSP-SeNPs to juvenile Nile tilapia and their effect on growth performance, intestinal tissue structure, antioxidation capacity, hypoxic stress, and Streptococcus agalactiae infection were investigated. The results showed that the spherical PSP-SeNPs were stable and safe, with an LC₅₀ of 13.645 mg/L against tilapia, which was about 13-fold higher than that of sodium selenite (Na₂SeO₃). A basal diet supplemented with 0.1-1.5 mg/kg PSP-SeNPs improved the growth performance of tilapia juveniles to a certain extent, increased the intestinal villus length, and significantly enhanced the activities of liver antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and catalase (CAT). PSP-SeNPs also enhanced the resistance of tilapia to hypoxic stress and Streptococcus agalactiae infection, with supplementation at 0.1-0.3 mg/kg exerting more obvious effects than 1.5 mg/kg. However, PSP-SeNPs at a concentration of 4.5 mg/kg and Na₂SeO₃ at 0.3 mg/kg negatively affected the growth, gut health, and the activity of the antioxidant enzymes of tilapia. Quadric polynomial regression analysis revealed that 0.1-1.2 mg/kg was the optimal PSP-SeNP supplementation concentration for tilapia feeds. The findings of this study lay a foundation for the application of PSP-SeNPs in aquaculture.

Selenium Content in Freshwater and Marine Fish from Southern Brazil Coastal Plain: a Comparative Analysis on Environmental and Dietary Aspects

The coastal plain of Rio Grande do Sul is considered to be a Se-deficient region in terms of its population dietary habit, making it the focus of this study. Selenium dietary deficiency is a concern when we consider its potential critical health effects on the local population. Therefore, this study contributes new information on the levels of Se in several species of marine and freshwater fish in the region of the Patos-Mirim Lagoon system, coupled with a comparative analysis of the metalloid contents between both fish groups. The Se contents in the fish species ranged from 88 ± 13 to 688 ± 19 μg.kg^-1. The average Se concentration in the muscle tissue of the freshwater species (251 ± 96 μg kg^-1) was significantly lower than that of the marine species (412 ± 143 μg kg^-1). Likewise, no evidence of Se biomagnification was found among the fish from both the marine and freshwater environments, suggesting the absence of trophic transfer of Se. We note that to ensure that the RDA (Recommended Daily Allowance, 55 μg day^-1) of Se dietary intake for adults is met, at least 134 g of freshwater or 82 g of marine fish fillet could be incorporated into the diet of the population of Rio Grande do Sul. According to target hazard quotients (THQ) and the permissible safety limits, consumption of the fish species analyzed is safe for human health.

Effect of phosphorus limitation on Se uptake efficiency in the microalga Nannochloropsis oceanica

Microalgae are considered an efficient accumulator and promising source of Se for feed additive purposes. This study aimed at investigating, for the first time, the effect of phosphorus limitation on Se accumulation and uptake efficiency in N.oceanica. A range of phosphorus concentrations (0-2470 µM) were tested in either the presence or absence of sodium selenite (0, 5, 30 µM). Se accumulation was increased up to 16-fold and Se uptake efficiency was increased up to 3.6-fold under phosphorus growth-limiting concentrations. N.oceanica was then cultivated in a 1.8L flat-panel photobioreactor in batch operation under two phosphorus growth-limiting concentrations (250 and 750 µM) where the accumulation of Se in the microalgal biomass, as well as its presence in the spent medium were analysed. This study is the first to investigate the effect of phosphorus limitation for increasing Se accumulation in microalgae, and to prevent the release of Se in wastewater.

Scientific opinion on the tolerable upper intake level for selenium

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for selenium. Systematic reviews of the literature were conducted to identify evidence regarding excess selenium intake and clinical effects and potential biomarkers of effect, risk of chronic diseases and impaired neuropsychological development in humans. Alopecia, as an early observable feature and a well-established adverse effect of excess selenium exposure, is selected as the critical endpoint on which to base a UL for selenium. A lowest-observed-adverse-effect-level (LOAEL) of 330 μg/day is identified from a large randomised controlled trial in humans (the Selenium and Vitamin E Cancer Prevention Trial (SELECT)), to which an uncertainty factor of 1.3 is applied. A UL of 255 μg/day is established for adult men and women (including pregnant and lactating women). ULs for children are derived from the UL for adults using allometric scaling (body weight0.75). Based on available intake data, adult consumers are unlikely to exceed the UL, except for regular users of food supplements containing high daily doses of selenium or regular consumers of Brazil nuts. No risk has been reported with the current levels of selenium intake in European countries from food (excluding food supplements) in toddlers and children, and selenium intake arising from the natural content of foods does not raise reasons for concern. Selenium-containing supplements in toddlers and children should be used with caution, based on individual needs.

Dietary Selenomethionine Reduce Mercury Tissue Levels and Modulate Methylmercury Induced Proteomic and Transcriptomic Alterations in Hippocampi of Adolescent BALB/c Mice

Methylmercury (MeHg) is a well-known environmental contaminant, particularly harmful to the developing brain. The main human dietary exposure to MeHg occurs through seafood consumption. However, seafood also contains several nutrients, including selenium, which has been shown to interact with MeHg and potentially ameliorate its toxicity. The aim of this study was to investigate the combined effects of selenium (as selenomethionine; SeMet) and MeHg on mercury accumulation in tissues and the effects concomitant dietary exposure of these compounds exert on the hippocampal proteome and transcriptome in mice. Adolescent male BALB/c mice were exposed to SeMet and two different doses of MeHg through their diet for 11 weeks. Organs, including the brain, were sampled for mercury analyses. Hippocampi were collected and analyzed using proteomics and transcriptomics followed by multi-omics bioinformatics data analysis. The dietary presence of SeMet reduced the amount of mercury in several organs, including the brain. Proteomic and RNA-seq analyses showed that both protein and RNA expression patterns were inversely regulated in mice receiving SeMet together with MeHg compared to MeHg alone. Several pathways, proteins and RNA transcripts involved in conditions such as immune responses and inflammation, oxidative stress, cell plasticity and Alzheimer’s disease were affected inversely by SeMet and MeHg, indicating that SeMet can ameliorate several toxic effects of MeHg in mice.

HSF1-SELENOS pathway mediated dietary inorganic Se-induced lipogenesis via the up-regulation of PPARγ expression in yellow catfish

At present, studies involved in the effects of dietary Se sources on lipid metabolism were very scarce and the underlying mechanism remains unknown. Previous studies reported that dietary Se sources differentially affected selenoprotein S (SELENOS) expression and SELENOS affected lipid metabolism via the inositol-requiring enzyme 1α (IRE1α)- spliced X-box binding protein 1 (XBP1s) pathway. Thus, we used yellow catfish as an experimental model to explore whether dietary selenium sources affected the hepatic lipid metabolism, and further determined the role of SELENOS-IRE1α-XBP1s pathway in dietary selenium sources affecting hepatic lipid metabolism. Compared with the selenomethionine (S-M) group, sodium selenite (SS) group possessed higher liver triglycerides (TGs) (34.7%), lipogenic enzyme activities (57.9-70.6%), and lower antioxidant enzyme activities (23.3-35.5%), increased protein levels of heat shock transcription factor 1 (HSF1) and SELENOS (1.17-fold and 47.4%, respectively), and XBP1s- peroxisome proliferators-activated receptor γ (PPARγ) pathway. Blocking SELENOS and PPARγ by RNA interference demonstrated that the SELENOS/XBP1s/PPARγ axis was critical for S-S-induced lipid accumulation. Moreover, S-S-induced upregulation of SELENOS was via the increased DNA binding capacity of HSF1 to SELENOS promoter, which activated the XBP1s/PPARγ pathway and promoted lipogenesis and lipid accumulation. XBP1s is required for S-S-induced upregulation of PPARγ expression. Our finding elucidated the mechanism of dietary Se sources affecting the lipid metabolism in the liver of yellow catfish and demonstrated novel function of SELENOS in metabolic regulation. Our study also suggested that seleno-methionine was a better Se source than selenite against abnormal lipid deposition in the liver of yellow catfish.

Analysis of Se and Hg biomolecules distribution and Se speciation in poorly studied protein fractions of muscle tissues of highly consumed fishes by SEC-UV-ICP-MS and HPLC-ESI-MS/MS

Distribution of Se and Hg in sarcoplasmic, myofibrillar and alkali-soluble protein fractions extracted from muscle tissue of tuna, swordfish and salmon (wild vs. farmed) is investigated for the first time. SEC-UV-ICP-MS analyses revealed that Se and Hg are mostly bound to proteins of 2-12 kDa and up to 574 kDa, respectively. Moreover, Se and Hg appeared associated to proteins of same molecular weight, evidencing that Se-Hg interaction may occur at the level of the fish tissue evaluated. Important differences were found between farmed and wild salmon, suggesting the effect of the type of feed and growing conditions on Se and Hg content and their distribution through protein fractions. Finally, Se speciation studies performed by HPLC-ICP-MS and confirmed by HPLC-ESI-MS/MS showed SeMeSeCys as the only Se specie found in soluble, sarcoplasmic, myofibrillar and alkali-soluble proteins of all fishes analysed, except in soluble proteins extracted from tuna, where SeMet was also identified.

Biofortified Diets Containing Algae and Selenised Yeast: Effects on Growth Performance, Nutrient Utilization, and Tissue Composition of Gilthead Seabream (Sparus aurata)

Efforts have been made to find natural, highly nutritious alternatives to replace fish meal (FM) and fish oil (FO), which can simultaneously promote fish health and improve the nutritional quality of filets for human consumption. This study evaluated the impact of biofortified diets containing microalgae (as replacement for FM and FO), macroalgae (as natural source of iodine) and selenised yeast (organic source of selenium) on gilthead seabream growth, nutrient utilization, tissue composition and gene expression. A control diet (CTRL) with 15% FM and 5.5% FO was compared with three experimental diets (AD1, AD2, and AD3), where a microalgae blend (Chlorella sp., Tetraselmis sp., and DHA-rich Schizochytrium sp.) replaced 33% of FM. Diet AD1 contained 20% less FO. Diets were supplemented with Laminaria digitata (0.4% AD1 and AD2; 0.8% AD3) and selenised yeast (0.02% AD1 and AD2; 0.04% AD3). After feeding the experimental diets for 12 weeks, growth was similar in fish fed AD1, AD2, and CTRL, indicating that microalgae meal can partially replace both FM and FO in diets for seabream. But AD3 suppressed fish growth, suggesting that L. digitata and selenised yeast supplementation should be kept under 0.8 and 0.04%, respectively. Despite lower lipid intake and decreased PUFAs bioavailability in fish fed AD3, compared to CTRL, hepatic elovl5 was upregulated resulting in a significant increase of muscle EPA + DHA. Indeed, filets of fish fed AD2 and AD3 provided the highest EPA + DHA contents (0.7 g 100 g^–1), that are well above the minimum recommended values for human consumption. Fish consuming the AD diets had a higher retention and gain of selenium, while iodine gain remained similar among diets. Upregulation of selenoproteins (gpx1, selk, and dio2) was observed in liver of fish fed AD1, but diets had limited impact on fish antioxidant status. Overall, results indicate that the tested microalgae are good sources of protein and lipids, with their LC-PUFAs being effectively accumulated in seabream muscle. Selenised yeast is a good fortification vehicle to increase selenium levels in fish, but efforts should be placed to find new strategies to fortify fish in iodine.

Assessment of the mercury-selenium antagonism in rainbow trout fish

This study aims at the assessment of mercury (Hg)-selenium (Se) antagonism in fish. For this purpose, rainbow trout fish (Oncorhynchus mykiss) were exposed to methylmercury (MeHg) under controlled conditions, in the presence or absence of selenomethionine (SeMet) using an in-house prepared diet (enriched with MeHg and SeMet at 0.2 μg/g and 5.0 μg/g, respectively). The total duration of the exposure study was 3 months. Fish was sampled and analysed for total Se (Se_T) and total mercury (Hg_T) content after 1, 2 and 3 months of exposure. Six feeding protocols were compared, depending on the exposure type: (i) no MeHg nor SeMet exposure (control group); (ii) exposure to SeMet solely; (iii) exposure to MeHg solely; (iv) exposure to both MeHg and SeMet; (v) exposure first to MeHg during 1 month and then to SeMet during 2 months and (vi), exposure to SeMet during 1 month and then to MeHg for 2 months. The levels of Se_T and Hg_T in the fish (control and supplemented with MeHg/SeMet) were measured by inductively coupled plasma-mass spectrometry (ICPMS). Steadily (linear) bioaccumulation of MeHg in the fish muscle occurred when the fish were exposed individually to this species during the period. The bioaccumulation of MeHg is diminished when the fish are firstly exposed to SeMet and then to MeHg, hence indicating the MeHg detoxification due to SeMet supplementation.

New Method for Simultaneous Arsenic and Selenium Speciation Analysis in Seafood and Onion Samples

This paper presents a new method for the simultaneous speciation analysis of arsenic (As(III)-arsenite, As(V)-arsenate, DMA-dimethylarsinic acid, MMA-methylarsonic acid, and AsB-arsenobetaine) and selenium (Se(IV)-selenite, Se(VI)-selenate, Se-Methionine, and Se-Cystine), which was applied to a variety of seafood and onion samples. The determination of the forms of arsenic and selenium was undertaken using the High-Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS) analytical technique. The separation of both organic and inorganic forms of arsenic and selenium was performed using two analytical columns: an anion exchange column, Dionex IonPac AS22, containing an alkanol quaternary ammonium ion, and a double bed cation-anion exchange guard column, Dionex Ion Pac CG5A, containing, as a first layer, fully sulfonated latex for cation exchange and a fully aminated layer for anion exchange as the second layer. The ammonium nitrate, at pH = 9.0, was used as a mobile phase. The method presented here allowed us to separate the As and Se species within 10 min with a suitable resolution. The applicability was presented with different sample matrix types: seafood and onion.

Survival of Embryos and Fry of Sea Trout (Salmo trutta m. trutta) Growing from Eggs Exposed to Different Concentrations of Selenium during Egg Swelling

Adequate selenium (Se) availability enhances the health and growth of organisms, but overdose of it can be harmful and pathogenic. The study's objective was to analyse the impact of short-term exposure of sea trout fertilised eggs to inorganic selenium (SeO₂) at concentrations from 0 to 32 mg Se L^-1 to find the optimal and toxic dose of Se on early fish development. Se accumulated in the body, embryos' survival rate, and growth in the first four months of life was examined. Swelling of fertilised eggs in water supplemented with Se at a concentration from 0.5 to 8 mg Se L^-1 was associated with a slightly positive impact on the hatching rate. At higher Se concentration, a harmful effect on the survival of the embryo was observed. The survival of fry was similar in all groups, while the fry length and weight correlated positively with Se concentration in its body. Immersion of fertilised eggs in water enriched with Se during egg swelling can constitute a method to supplement the element to non-feeding stages of fish. In selenium-poor areas, this innovative method can be implemented in aquaculture to improve breeding outcomes. Se concentration should be adjusted to the chemical compound, fish species, and Se's content in the yolk.

Nutrition and Metabolism of Minerals in Fish

Simple Summary

Our aim is to introduce the mineral nutrition of fish and explain the complexity of determining requirements for these elements, which are absorbed and excreted by the fish into the surrounding water. To date, only the requirements for nine minerals have been investigated. The review is focused on the absorption and the dietary factors that reduce their absorption from feed ingredients of plant and animal origin. Some diseases, such as cataracts, anemia and bone deformity, have been linked to dietary deficiency of minerals.

Abstract

Aquatic animals have unique physiological mechanisms to absorb and retain minerals from their diets and water. Research and development in the area of mineral nutrition of farmed fish and crustaceans have been relatively slow and major gaps exist in the knowledge of trace element requirements, physiological functions and bioavailability from feed ingredients. Quantitative dietary requirements have been reported for three macroelements (calcium, phosphorus and magnesium) and six trace minerals (zinc, iron, copper, manganese, iodine and selenium) for selected fish species. Mineral deficiency signs in fish include reduced bone mineralization, anorexia, lens cataracts (zinc), skeletal deformities (phosphorus, magnesium, zinc), fin erosion (copper, zinc), nephrocalcinosis (magnesium deficiency, selenium toxicity), thyroid hyperplasia (iodine), muscular dystrophy (selenium) and hypochromic microcytic anemia (iron). An excessive intake of minerals from either diet or gill uptake causes toxicity and therefore a fine balance between mineral deficiency and toxicity is vital for aquatic organisms to maintain their homeostasis, either through increased absorption or excretion. Release of minerals from uneaten or undigested feed and from urinary excretion can cause eutrophication of natural waters, which requires additional consideration in feed formulation. The current knowledge in mineral nutrition of fish is briefly reviewed.

Dietary selenium sources differentially regulate selenium concentration, mRNA and protein expression of representative selenoproteins in various tissues of yellow catfish Pelteobagrus fulvidraco

The study was conducted to determine the effects of three dietary Se sources, such as sodium-selenite (S-S), seleno-yeast (S-Y) and seleno-methionine (S-M), on Se concentration, glutathione peroxidase (GPX) and TXNRD activities, and mRNA expression of fifteen representative selenoproteins, and protein expression of four endoplasmic reticulum-resided selenoproteins in a wide range of tissues of yellow catfish. Compared with S-S and S-M groups, dietary S-Y significantly decreased growth performance and feed utilisation of yellow catfish. Dietary Se sources significantly influenced Se contents in the spleen, dorsal muscle and the kidney, GPX activities in spleen, kidney, intestine, muscle and mesenteric fat, and TXNRD activities in the heart, intestine and mesenteric fat. Among ten tested tissues, dietary Se sources influenced mRNA expression of GPX4 and SELENOK in three tissues; GPX3, SELENOS and TXNRD2 in four tissues; SELENOF, SELENON and DIO2 in five tissues; SELENOM, GPX1/2 and TXNRD3 in six tissues; SELENOW in seven tissue and SELENOP and SELENOT in eight tissues. Based on these observations above, S-S and S-M seem to be suitable Se sources for improving growth performance and feed utilisation of yellow catfish. Dietary Se sources differentially influence the expression of selenoproteins in various tissues of yellow catfish. For the first time, we determined the expression of selenoproteins in fish in responses to dietary Se sources, which contributes to a better understanding of the functions and regulatory mechanisms of selenoporteins.

Long-term effect of parental selenium supplementation on the one-carbon metabolism in rainbow trout (Oncorhynchus mykiss) fry exposed to hypoxic stress

This study evaluated how different forms of selenium (Se) supplementation into rainbow trout broodstock diets modified the one-carbon metabolism of the progeny after the beginning of exogenous feeding and followed by hypoxia challenge. The progeny of three groups of rainbow trout broodstock fed either a control diet (Se level: 0·3 µg/g) or a diet supplemented with inorganic sodium selenite (Se level: 0·6 µg/g) or organic hydroxy-selenomethionine (Se level: 0·6 µg/g) was cross-fed with diets of similar Se composition for 11 weeks. Offspring were sampled either before or after being subjected to an acute hypoxic stress (1·7 mg/l dissolved oxygen) for 30 min. In normoxic fry, parental Se supplementation allowed higher glutathione levels compared with fry originating from parents fed the control diet. Parental hydroxy-selenomethionine treatment also increased cysteine and cysteinyl-glycine concentrations in fry. Dietary Se supplementation decreased glutamate-cysteine ligase (cgl) mRNA levels. Hydroxy-selenomethionine feeding also lowered the levels of some essential free amino acids in muscle tissue. Supplementation of organic Se to parents and fry reduced betaine-homocysteine S-methyltransferase (bhmt) expression in fry. The hypoxic stress decreased whole-body homocysteine, cysteine, cysteinyl-glycine and glutathione levels. Together with the higher mRNA levels of cystathionine beta-synthase (cbs), a transsulphuration enzyme, this suggests that under hypoxia, glutathione synthesis through transsulphuration might have been impaired by depletion of a glutathione precursor. In stressed fry, S-adenosylmethionine levels were significantly decreased, but S-adenosylhomocysteine remained stable. Decreased bhmt and adenosylmethionine decarboxylase 1a (amd1a) mRNA levels in stressed fry suggest a nutritional programming by parental Se also on methionine metabolism of rainbow trout.

Advantages and prospective challenges of nanotechnology applications in fish cultures: a comparative review

Applications of nanotechnology in fish cultures have participated in getting over various difficulties that hinder fish productivity. They can achieve growth performance after adding some important minerals and vitamins in the form of nano-feed supplements like selenium, zinc, iron, and vitamin C. Also, they have an important role in reproduction, and fish medicine as antimicrobial, drug delivery, nano-vaccination, and rapid disease diagnosis. Moreover, their roles in water remediation and purification, and fish packaging are documented. On the other hand, some nanoparticles exhibit toxic effects on living organisms, which return to their tiny size, high reactivity, and permeability. They can alter many physiological functions and cause cytotoxicity, DNA damage, and histopathological changes. Also, nanotechnology applications cause new secondary pollutants to be introduced into the environment that can negatively affect fish health and the surrounding living organisms. So, in spite of the promising applications of nanotechnology to fulfill high growth performance and pathogen-free fish, there are a lot of debates about the potential toxicity of nanomaterials, their reactivity with the surrounding environment, and bioaccumulation. The present review aims to elucidate and discuss various advantages and challenges of nanotechnology applications in fish cultures. Also, it points to green nanotechnology as a promising alternative to chemical ones.

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

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.

Lean-seafood intake increases urinary iodine concentrations and plasma selenium levels: a randomized controlled trial with crossover design

PURPOSE

Iodine deficiency due to insufficient nutritional intake is a public health challenge in several European countries, including Norway. Lean-seafood has a high iodine and arsenic (As) content and is a good source of selenium (Se). Evidence of a direct effect of increased intake of lean-seafood on iodine status is limited. The main aims were to determine the iodine status at baseline and to investigate possible dietary effects on urinary iodine concentration (UIC) after intervention with lean-seafood versus non-seafood. Plasma Se, and plasma and urinary As concentrations were also measured.

METHODS

A randomized controlled crossover study comprising two 4 weeks experimental periods with two balanced diets varied in main proteins (60% of total dietary proteins) of lean-seafood and non-seafood, separated by a 5 week washout period.

RESULTS

Twenty participants (7 males, 13 females) were included and the mean ± SD age was 50.6 ± 15.3 years for all participants. Fasting UIC was median (25th, 75th percentile) 70 (38, 110) and 79 (49, 94) µg/L in the lean-seafood and non-seafood intervention at baseline, respectively. UIC increased after 4 weeks of the lean-seafood intervention to 135 (110, 278) µg/L, but not after the non-seafood intervention [58 (33, 91) µg/L] (P diet-effect < 0.001). Fasting plasma Se increased in the lean-seafood intervention and decreased in the non-seafood intervention (P diet-effect = 0.001). Fasting urinary and plasma As increased in the lean-seafood intervention and was unchanged in the non-seafood intervention (P diet-effect < 0.001).

CONCLUSION

The participant's UIC was below the recommended median (100 µg/L) at baseline, but increased sufficiently after a 4 week intervention with lean-seafood.

Determination of Selenium Species in Muscle, Heart, and Liver Tissues of Lambs Using Mass Spectrometry Methods

Simple Summary

The objective of the project was to evaluate speciation of selenium (Se) in various tissues (the liver, heart, or muscles) obtained from lambs fed with a diet enriched with an inorganic and organic chemical form of Se (i.e., selenite and Se-enriched yeast, respectively).

Abstract

Identification and quantification of the selenium species in biological tissues is imperative, considering the need to properly understand its metabolism and its importance in various field of sciences, especially nutrition science. Although a number of studies deals with the speciation of selenium, speciation analysis is still far from being a routine task, and so far strongly depends on the type of the samples. We present a study aimed to examine speciation analysis of Se in tissues of livers, muscles, and hearts obtained from lambs, namely in liver, muscle, and heart. The studied lambs were fed with the diet enriched with an inorganic (as sodium selenate) and organic chemical form of Se (as Se-enriched yeast) compounds with simultaneous addition of fish oil (FO) and carnosic acid (CA). The first part of the work was focused on the optimization of the extraction procedure of selenium compounds from tissues. Next, hyphenated high performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC–ICP–MS) was used for the identification of five seleno-compounds—Se-methionine (SeMet), Se-cystine (SeCys2), Se-methyl-Se-cysteine (SeMetSeCys), and Se(IV) and Se(VI). Verification of the identified seleno-compounds was achieved using triple-quadrupole mass spectrometer coupled to high performance liquid chromatography (HPLC–ESI–MS/MS). The applied procedure allowed for quantitative analysis of SeMet, SeCys2, and SeMetSeCys, in biological tissues. The developed analytical protocol is feasible for speciation analysis of small molecular seleno-compounds in animals samples.

In vitro digestion method to evaluate solubility of dietary zinc, selenium and manganese in salmonid diets

BACKGROUND

The determination of dietary mineral solubility is one of the main steps in the evaluation of their availability for a given species.

METHODS

This study proposed an in vitro digestion method (acidic and alkaline hydrolysis). The method was applied to evaluate the solubility of inorganic and organic forms of zinc (Zn), selenium (Se) and manganese (Mn) in salmonid diets. An inorganic mineral (IM) diet was supplemented with zinc sulphate, sodium selenite and manganous sulphate and an organic mineral (OM) diet was supplemented with zinc chelate of glycine, l-selenomethionine and manganese chelate of glycine.

RESULTS

The solubility of Zn was similar in both diets tested. The amount of soluble Zn was low in the acidic hydrolysis (3-8%) and lower in the alkaline hydrolysis (0.4-2%). The solubility of Se was higher in the OM diet (7-34%) compared with the IM diet (3-12%). Regarding Mn, after the acidic hydrolysis the solubility was higher in the IM diet (6-25%) than the OM diet (4-17%). The in vitro solubility were compared with in vivo availability of Zn, Se and Mn. Data obtained for solubility (%) of Zn, Se and Mn was lower when compared with apparent availability (%) of Zn, Se and Mn.

CONCLUSION

Data obtained demonstrated that solubility of Zn, Se and Mn was influenced by the mineral chemical form supplemented to the diet and by the gastrointestinal environment. The solubility of Zn, Se and Mn was not comparable with the apparent availability of Zn, Se and Mn. Nevertheless, the effect of the chemical form of the minerals was similar for the solubility of Zn, Se and Mn and the apparent availability of Zn, Se and Mn. Considering the overall results of this study, the in vitro method could replace some of the in vivo studies for a qualitative evaluation but not for a quantitative evaluation.

Feed-to-Fillet Transfer of Selenite and Selenomethionine Additives to Plant-Based Feeds to Farmed Atlantic Salmon Fillet

This study investigated the transfer kinetics of dietary selenite and selenomethionine (SeMet) to the fillet of farmed Atlantic salmon (Salmo salar). The uptake and elimination rate constants of the two selenium (Se) forms were determined in Atlantic salmon fed either selenite- or SeMet-supplemented diets followed by a depuration period. The fillet half-life of selenite and SeMet was 779 ± 188 and 339 ± 103 days, respectively. The elimination and uptake rates were used in a simple one-compartmental kinetic model to predict levels in fillet based on long-term (whole production cycle) feeding with given dietary Se levels. Model predictions for Atlantic salmon fed plant-based feeds low in natural Se and supplemented with either 0.2 mg of selenite or SeMet kg^-1 gave a predicted fillet level of 0.042 and 0.058 mg Se kg^-1 wet weight, respectively. Based on these predictions and the European Food Safety Authority risk assessment of Se feed supplementation for food-producing terrestrial farm animals, the supplementation with 0.2 mg of selenite kg^-1 would likely be safe for the most sensitive group of consumers (toddlers). However, supplementing feed to farm animals, including salmon, with 0.2 mg of SeMet kg^-1 would give a higher (114%) Se intake than the safe upper intake limit for toddlers.

Selenium Analysis and Speciation in Dietary Supplements Based on Next-Generation Selenium Ingredients

Selenium is essential for humans and the deficit of Se requires supplementation. In addition to traditional forms such as Se salts, amino acids, or selenium-enriched yeast supplements, next-generation selenium supplements, with lower risk for excess supplementation, are emerging. These are based on selenium forms with lower toxicity, higher bioavailability, and controlled release, such as zerovalent selenium nanoparticles (SeNPs) and selenized polysaccharides (SPs). This article aims to focus on the existing analytical systems for the next-generation Se dietary supplement, providing, at the same time, an overview of the analytical methods available for the traditional forms. The next-generation dietary supplements are evaluated in comparison with the conventional/traditional ones, as well as the analysis and speciation methods that are suitable to reveal which Se forms and species are present in a dietary supplement. Knowledge gaps and further research potential in this field are highlighted. The review indicates that the methods of analysis of next-generation selenium supplements should include a step related to chemical species separation. Such a step would allow a proper characterization of the selenium forms/species, including molecular mass/dimension, and substantiates the marketing claims related to the main advantages of these new selenium ingredients.

Diet composition and serum levels of selenium species: A cross-sectional study

Selenium is a trace element of both nutritional and toxicological interest, depending on its dose and chemical form. Diet is the primary source of exposure for most individuals. We sought to investigate the influence of food intake on serum levels of selenium species. Among fifty subjects randomly selected from a Northern Italian population, we assessed dietary habits using a validated semi-quantitative food frequency questionnaire. We also measured circulating levels of selenium species in serum using high pressure liquid chromatography associated with inductively-coupled plasma dynamic reaction cell mass spectrometer. Circulating levels of inorganic selenium, the most toxic selenium species, were positively associated with intake of fish, legumes and dry fruits, and inversely associated with intake of dairy products and mushrooms. Concerning the organic selenium species, selenoproteinP-bound selenium was inversely associated with intake of fish, fresh fruits, vegetables, and legumes, while selenocysteine-bound selenium positively associated with intake of fresh fruit, potato, legume and mushroom. In the present study, intakes of different foods were correlated with different types of selenium species. These results have important public health implications when assessing the nutritional and toxicological potential of diet composition with reference to selenium exposure.