Selenium speciation analysis in the cerebrospinal fluid of patients with Parkinson’s disease

BackgroundThe aim of the study was to investigate if speciation analysis by liquid chromatography coupled to mass spectrometry could be used to detect organic and inorganic binding forms of selenium in the cerebrospinal fluid (CSF) of patients with Parkinson’s disease (PD) and age-matched control subjects (AMC).MethodsPD patients and control subjects were enrolled from three different neurological departments. CSF samples were collected according to standardized biomarker protocols and subjected to inductively coupled plasma mass spectrometry (ICP-MS) for total selenium determination and ion exchange chromatography (IEC) hyphenated to ICP-MS for selenium speciation analysis.Results75 PD patients and 68 age-matched controls were enrolled for speciation analysis. 8 different species could be detected, but only selenoprotein P (SELENOP), human serum albumin-bound Se (Se-HSA), selenomethionine (Se-Met) and an unidentified Se-compound (U2) presented with more than 50% values above the limit of quantification, without showing significant differences between both groups (p > 0.05). The Se-HSA / Se-Met ratio yielded a significant difference between PD and AMC (p = 0.045). The inorganic species Se-IV and Se-VI were only detectable in a minor part of PD and AMC samples. A highly significant correlation between total selenium levels and SELENOP (PD p < 0.0001; AMC p < 0.0001) and Se-HSA (PD p < 0.0001; AMC p < 0.0001) could be demonstrated, respectively.ConclusionsSpeciation analysis yielded new insight into selenium homeostasis in PD but cannot be used to establish a diagnostic biomarker. The small number of detectable values for Se-IV and Se-VI suggests an inferior role of these potentially neurotoxic binding forms in PD pathology in contrast to other neurodegenerative disorders.     

Comparison of whole blood selenium values and erythrocyte glutathione peroxidase activities of normal individuals on supplementation with selenate,selenite,l-selenomethionine,and high selenium yeast

The selenium levels and the glutathione peroxidase activity GSH-PX of whole blood and of erythrocytes, respectively, were determined in 139 normal Danes and related to sex and smoking habits. No differences were found in relation to sex apart from a higher GSH-PX activity of females when assayed with tertiary butyl hydroperoxide. Smokers showed significantly lower selenium values than non-smokers (p<0.05), but the two groups had identical GSH-PX activities. Individuals from the above-mentioned group were divided into four groups, receiving daily oral doses of 200 μg of selenium in the form of selenite, selenate, L-selenomethionine, and selenium as contained in yeast. Whole blood selenium values and the erythrocyte glutathione peroxidase activities were determined during three months of supplementation followed by a withdrawal period of four months. Both the inorganic selenium compounds and the organic derivatives gave rise to steady state levels of GSH-PX after one month of supplementation. However, the selenium levels in the groups receiving organic selenium showed a steady rise during the whole period, whereas those supplemented with inorganic selenium leveled off after a period of one to three months. The data for smokers and non-smokers revealed identical results when organic selenium was supplemented. However, selenite gave rise to significantly higher selenium levels and GSH-PX activities in smokers than in non-smokers. Less significant (p<0.08) elevations of both parameters were also observed among the smokers in the selenate group. By taking both the selenium level and the GSH-PX activity into consideration, organic selenium (i.e.,l-(+) selenomethionine) was judged to be more bioavailable than selenite and selenate.     

Cellular and nephrotoxicity of selenium species

ProjectBeside its useful functions at very low concentrations, selenium including supplementary Se sources pose a potential toxicological risk. The toxicity of selenium species was tested in HaCaT cell culture and related nephrotoxicity in mice.ProcedureThe apoptotic shrinkage and necrotic expansion of cells were measured by time-lapse image microscopy. Acute nephrotoxicity was estimated upon administration of various selenium species to mice for two weeks. To confirm or to refute the accumulation of Se in the kidney and its potential chronic effect, Se concentration in kidney tissue and histopathlology were tested.ResultsThe comparison of selenium species showed that organic lactomicroSe did not affect cell growth at 5 ppm, but inorganic nanoSe severely hampered it at lower concentration (1 ppm). The in vivo Se treatment (0.5, 5, 50 ppm, corresponding to 4, 40 and 400 μg/kg) was misleading as it did neither affect the outward appearance nor the weight of the kidney. Se accumulation was observed after selenate, selenite, SelPlex, selenite and nanoSe administration, while lactomicroSe caused no traceable accumulation. In vivo, ex vivo and in vitro experiments reflected this order of selenium toxicity: selenate > selenite > SelPlex = nanoSe > lactomicroSe.ConclusionWithin the tested species lactomicroSe was the only non-nephrotoxic selenium source recommended for nutritional Se supplementation.     

Absorption,distribution, metabolism and excretion (ADME) of oral selenium from organic and inorganic sources: A review

BackgroundSelenium is a trace element traditionally ingested either in its organic form via food or in its inorganic form through nutritional supplements, while selenium formulated as nanoparticles is a putative long-acting alternative. To understand the physiology and toxicology of the different selenium formulations, it is important to determine how their selenium content is absorbed, distributed, metabolised and excreted; therefore, we reviewed their biokinetics following oral exposure.MethodsWe retrieved and reviewed the literature on the absorption, distribution, metabolism, and excretion of oral exposure to different forms of selenium.ResultsSelenium in both the organic form (containing carbon to selenium chemical bonds) and the inorganic form is absorbed into the blood in humans. The mean normal blood level of many studies was 139 μg/L. There are indications that selenium from organic sources is more bioavailable than selenium from inorganic sources. Selenium is distributed throughout the body, including in breast milk. The elimination of selenium mainly involves the faecal and urinary pathways, whereas breath, saliva and hair are minor contributors. Urinary metabolites include trimethylselenium ions, selenosugars and Se-methylselenoneine.ConclusionSelenium is absorbed to a high extent, and selenium from organic sources is more bioavailable than from inorganic sources. Selenium, as expected as an essential trace element, is distributed throughout the body. Selenium is extensively metabolised, and various excretion metabolites have been identified in both urine and breath, while some selenium is also excreted via faeces.     

富硒条件下蜜环菌菌株硒耐受性及胞外酶生物活性的研究

[目的]通过对蜜环菌(Armillaria mellea)的富硒驯化,研究各菌株硒耐受性、有机硒含量及生物活性的变化规律,从而获得生物活性更强的蜜环菌,并对富硒蜜环菌的生物学特征进行初步研究.[方法]以Na2SeO3为无机硒试剂对蜜环菌进行富硒驯化;采用氢化物原子荧光光谱法测定蜜环菌的硒含量,热水浴法测定蜜环菌的无机硒...     

Evaluation of blood mercury and serum selenium levels in the pregnant population of the Community of Madrid,Spain

BackgroundThe main exposure route to methylmercury (MeHg) is from eating fish and shellfish containing this compound. Since 2004, women of childbearing age in Spain have been urged not to eat some species (eg, tuna, shark, and swordfish), instead choosing low-MeHg seafood as part of a healthy diet.ObjectiveTo describe maternal total blood mercury (THg) and serum selenium (Se) in a cohort of pregnant women living in Spain as it relates to fish intake during the three trimesters and to assess whether or not Spanish women of childbearing age follow the recommendations listed in fish advisories and choose fish species with lower mercury levels.MethodsWe studied 141 female volunteers of childbearing age (16–45 years), interviewing all participants about their overall eating habits and seafood intake. Hg and Se levels were tested using cold-vapor atomic absorption spectrometry (CVAAS) and electrothermal atomic absorption spectrometry (ETAAS), respectively.ResultsAverage THg levels in pregnant women were 2.89 μg/L (standard deviation [SD], 2.75 μg/L, geometric mean [GM], 2.19 μg/L), and THg GM was positively associated with fish intake. Mean Se levels in pregnant women were 73.06 μg/L (SD, 13.38 μg/L), and Se levels were found to increase with tuna intake. In 16 (12%) pregnant women, THg was higher than the level recommended by the U.S. Environmental Protection Agency (EPA) (6.4 μg/L). A positive association was also found between THg and serum Se.ConclusionWomen of childbearing age in Spain had higher THg levels than women in other Western studies. Our study observed that 12% of women had THg levels above the safety limit set by the EPA (6.4 μg/L), and 31% had levels above the relevant benchmark level of 3.5 μg/L suggested by various researchers.     

Concurrent quantitative HPLC–mass spectrometry profiling of small selenium species in human serum and urine after ingestion of selenium supplements

Selenium metabolic patterns in the human body originating from five distinct selenium dietary sources, selenate, selenite, selenomethionine (SeMet), methylselenocysteine (MeSeCys) and selenized yeast, were investigated by performing concurrent HPLC–mass spectrometric analysis of human serum and urine. Total selenium and selenium species time profiles were generated by sampling and analyzing serum and urine from volunteers treated with selenium supplements, up to 5 and 24 h following ingestion, respectively. We found that an increase in total serum selenium levels, accompanied by elevated selenium urinary excretion, was the common pattern for all treatments, except for that of selenite supplementation. Selenosugar 1 was a universal serum metabolite in all treatments, indicating that ingested selenium is favorably metabolized to the sugar. Except for selenite and selenized yeast ingestion, these patterns were reflected in the urine time series of the different treatments. Selenosugar 1 was the major selenium species present in urine in all treatments except for the selenate treatment, accounting for about 80% of the identified excreted species within 24 h of ingestion. Furthermore, the urinary metabolite trimethylselenonium ion (TMSe) was detected for the first time in human background serum by using HPLC coupled to elemental and molecular mass spectrometry. The concurrent monitoring of non-protein selenium species in both body fluids provides the relation between bioavailability and excretion of the individual ingested species and of their metabolic products, while the combined use of elemental and molecular mass spectrometry enables the accurate quantitation of structurally confirmed species. This successfully applied approach is anticipated to be a useful tool for more extensive future studies into human selenium metabolism.     

Genetically predicted selenium is negatively associated with serum TC,LDL-C and positively associated with HbA1C levels

Background & AimsPervious epidemiological evidence on the associations of selenium, zinc with lipid profile and glycemic indices was contradictory. The aim of this study was to investigate whether selenium and zinc were casually associated with lipid profile and glycemic indices using mendelian randomization (MR) analysis.MethodA two-sample MR was used to evaluate the causal-effect estimations. Summary statistics for selenium, zinc, lipids and glycemic indices were retrieved from previous large-scale genome-wide association study (GWAS). Single nucleotide polymorphisms (SNPs) that independently and strongly associated with the selenium and zinc were selected as the instrumental variables. The casual estimates were calculated using inverse variance weighted method (IVW), with weighted median, MR-Egger, and MR-PRESSO test as sensitivity analysis, respectively.ResultsIn the standard IVW analysis, per SD increment in selenium was associated with an 0.077 mmol/L decrease of TC (95 %CI: −0.102,−0.052) and 0.074 mmol/L of LDL-C (95 %CI: −0.1,−0.048). Suggestive casual associations were found between selenium and insulin or HbA1c. With IVW method, per SD increase in selenium was associated with an 0.023 mmol/L increase of insulin (95 %CI: 0.001,0.045), and an 0.013 mmol/L increase of HbA1c (95 %CI: 0.003,0.023). The results were robust in the sensitivity analysis. Zinc was not casually associated with any of lipid and glycemic markers.ConclusionOur MR analysis provides evidence of the potential causal effect of Se on beneficial lipid profile, including decreased TC and LDL-C. Furthermore, suggestive casual evidence was suggested between Se and increased serum HbA1c levels. Careful consideration is required for the protective effects of Se supplementation. No casual-effect association was found between Zn and any indices of the lipid and glucose parameters.     

Effect of inorganic and organic forms of selenium supplementation on development of larval Heliothis virescens

Selenium (Se) is an essential micronutrient for vertebrates though little is known about the effects on insects. Herbivorous insect larvae acquire Se from plant tissues in the inorganic form of sodium selenate and sodium selenite, and in the organic form of selenoamino acids, selenomethionine, and selenocystine. In this study, we document the effects of dietary supplementation with sodium selenite, sodium selenate, selenocystine, selenomethionine, and selenized yeast on the developmental rate of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae). Larvae tolerated high levels of Se (500 µg g^?1 Se) as sodium selenate and to a lesser extent as selenocystine. Lower levels of sodium selenite (>1 µg g^?1 Se) caused increased mortality, reduced rates of pupation, more pupal/adult intermediates, and reduced adult emergence. Selenomethionine proved toxic to larvae at levels above 25 µg g^?1 Se, significantly delaying pupation and raising mortality. Provision of Se as selenized yeast, which contains primarily selenomethionine, was also extremely detrimental to larval development and survival. The results indicate that the impact of dietary Se supplement for insects may differ from vertebrates.     

Determination of eleven small selenium species in human urine by chromatographic-coupled ICP-MS methods

BackgroundThe determination of various selenium species in urine enables a specific biomonitoring of the exposure to different selenium compounds.MethodsFor this task a coupling of three chromatographic techniques with ICP-MS was developed for the separate quantification of eleven species in urine. The first procedure was based on reverse phase chromatography and was designed for the separate determination of methyl-2-acetamido-2-deoxy-1-seleno-b-d-galactopyranoside (SeSug1), methyl-2-acetamido-2-deoxy-1-seleno-b-d-glucopyranoside (SeSug2), selenomethionine (SeMet), methylselenocysteine (MeSeC), seleno-D,L-ethionine (SeEt), methylselenic acid (MeSeA) and methylselenoglutathione (MeSeG); the second procedure was based on anion exchange chromatography and measured selenate (Se (VI)) and selenite (Se (IV)); the third procedure was based on cationic exchange chromatography and determined methyl-2-amino-2-deoxy-1-seleno-b-d-galactopyranoside (SeSug3) and the trimethylselenium ion (TMSe). A fourth method for the more sensitive determination of TMSe was upgraded by an on-line after-column reaction process.ResultsThe validation of the methods yielded sensitive detection limits of the species between 0.03 and 0.10 μg Se/L. For TMSe a detection limit of 0.02 μg Se/L resulted by the fourth method. An intra-day precision of 2.7–10.6% and a relative recovery between 87 % and 108 % confirm the robustness of the methods.ConclusionThe developed procedures enable a separate and sensitive determination of eleven selenium species in urine and thus permit the exploring of metabolic factors in the general population and particularly exposed individuals.     

The effects of organic selenium supplementation on the rumen ciliate population in sheep

The effect of selenium supplementation on the rumen protozoan population of sheep was demonstrated. Both the total and generic counts of rumen ciliates in sheep fed a diet with basal Se content (70 microg/kg dry matter) were compared to those of animals given feed supplemented with inorganic (disodium selenite) or organic Se (selenized yeast) (310 microg/kg dry matter). The genera of Entodinium, Isotricha, Dasytricha, Ophryoscolex, Diploplastron and Polyplastron occurred in all sheep except for the control, in which Ophryoscolex was not observed. The population of Ophryoscolex caudatus f. tricoronatus was significantly higher in sheep supplemented with organic Se than in animals given inorganic Se (by 160 %). Supplementation of feed with selenized yeast induced significant growth in the Diploplastron population (by 63 %) while no change occurred in sheep given selenite. The populations of Dasytricha ruminantium and Polyplastron multivesiculatum were higher than control in both Se-supplemented groups. The ciliate population of Entodinium spp. was not influenced by Se supplements. Our results suggest a protective effect of Se feed supplementation on the development of some rumen ciliate species in young ruminants.     

还原亚硒酸盐产生红色单质硒光合细菌菌株的筛选与鉴定

从实验室保藏的光合细菌中筛选出一株对亚硒酸钠还原效率较高的菌株S3,其亚硒酸钠还原产物通过透射电子显微镜及EDX(Electron-Dispersive X-ray)分析确定为红色单质硒。菌株S3的形态学特征、生理生化特征及光合色素扫描结果与固氮红细菌(Rhodobacter azotoformans)的特征基本一致;16S rDNA序列(GenBank登录号为DQ402051)在系统发育树中与固氮红细菌同属一个类群,序列同源性为99%。根据上述结果将菌株S3鉴定为固氮红细菌。初步研究了该菌株还原亚硒酸钠的特性,首次报道固氮红细菌具有还原亚硒酸盐产生红色单质硒的能力,为今后利用微生物方法治理环境中硒污染、利用微生物方法获得活性红色单质硒以及对微生物还原亚硒酸盐产生红色单质硒的机理研究奠定了良好的基础。     

Supplemental selenium and coenzyme Q10 reduce glycation along with cardiovascular mortality in an elderly population with low selenium status – A four-year,prospective, randomised,double-blind placebo-controlled trial

BackgroundA low intake of selenium has been shown to increase the risk of cardiovascular mortality, and supplementation of selenium and coenzyme Q10 influences this. The mechanism behind is unclear although effects on inflammation, oxidative stress and microRNA expression have been reported.Fructosamine, a marker of long-term glycaemic control, is also a marker of increased risk of heart disease and death, even in non-diabetics.ObjectiveTo analyse the impact of selenium and coenzyme Q10 supplementation on the concentration of fructosamine. Also, the relation between pre-intervention serum selenium concentration and the effect on fructosamine of the intervention was studied.MethodsFructosamine plasma concentration was determined in 219 participants after six and 42 months of intervention with selenium yeast (200 μg/day) and coenzyme Q10 (200 mg/ day) (n = 118 of which 20 had diabetes at inclusion), or placebo (n = 101 of which 18 had diabetes at inclusion). Pre-intervention, the serum selenium levels were 67 μg/L (active treatment group: 66.6 μg/L; placebo group: 67.4 μg/L), corresponding to an estimated intake of 35 μg/day. Changes in concentrations of fructosamine following intervention were assessed by the use of T-tests, repeated measures of variance, and ANCOVA analyses.ResultsPost-intervention selenium concentrations were 210 μg/L in the active group and 72 μg/L in the placebo group. A lower concentration of fructosamine could be seen as a result of the intervention in the total population (P = 0.001) in both the males (P = 0.04) and in the females (P = 0.01) in the non-diabetic population (P = 0.002), and in both the younger (<76 years) (P = 0.01) and the older (≥76 years) participants (P = 0.03). No difference could be demonstrated in fructosamine concentration in the diabetic patients, but the total sample was small (n = 38). In subjects with a low pre-intervention level of serum selenium the intervention gave a more pronounced decrease in fructosamine compared with those with a higher baseline selenium level.ConclusionA significantly lower concentration of fructosamine was observed in the elderly community-living participants supplemented with selenium and coenzyme Q10 for 42 months compared to those on the placebo. As oxidative mechanisms are involved in the glycation of proteins, less glycoxidation could be a result of the supplementation of selenium and coenzyme Q10, which could have contributed to lower cardiac mortality and less inflammation, as has earlier been reported.This study was registered at Clinicaltrials.gov, and has the identifier NCT01443780.     

SELENIUM: TOXICITY AND TOLERANCE IN HIGHER PLANTS

1. Different plant species show considerable variation in their selenium content. Primary indicators, also termed selenium accumulators, many of which are members of the genus Astragalus, are highly tolerant of selenium; they are known to contain tissue levels of several thousand µg selenium/g. Secondary indicators, tolerant to low concentrations of the element, may absorb up to 1000 µg selenium/g. Non-accumulators are poisoned by selenium. 2. The toxicity of selenate (SeO₄^-) and selenite (SeO₃^-) to most plants can be attributed to a combination of three factors. Firstly, selenate and selenite are readily absorbed from the soil by roots and translocated to other parts of the plant. Secondly, metabolic reactions convert these anions into organic forms of selenium. Thirdly, the organic selenium metabolites, which act as analogues of essential sulphur compounds, interfere with cellular biochemical reactions. 3. Incorporation into proteins of the amino acid analogues selenocysteine and selenomethionine, in place of the equivalent sulphur amino acids, is considered to be the underlying cause of selenium toxicity. The physical and chemical differences between selenium and sulphur will result in small, but significant, changes in the biological properties of a selenium-substituted protein. 4. Selenium-tolerant accumulator plants differ in at least two respects from sensitive species. Large quantities of Se-methylselenocysteine and selenocystathionine, two non-protein selenoamino acids rarely detected in non-accumulators, have been isolated from the tissues of selenium accumulators. In addition, selenium is kept from entering proteins so that the selenium levels in proteins of accumulator plants is significantly lower than the levels in selenium-sensitive plants. 5. Exclusion of selenium from the proteins of accumulators is thought to be the basis of selenium tolerance. Discrimination against selenocysteine during protein synthesis seems to prevent incorporation of this selenoamino acid into proteins of accumulators. Furthermore, synthesis of Se-methylselenocysteine and selenocystathionine, which results in diversion of selenium away from the synthesis of selenomethionine, will restrict the amount of this compound available for protein synthesis. 6. Selenium accumulation among unrelated plant genera is a striking example of convergent evolution. The possibility that accumulation of this element is associated with a nutritional requirement for selenium, although explored in the past, is still in need of further clarification.     

Differential effects of selenium compounds on glucose synthesis in rabbit kidney-cortex tubules and hepatocytes. In vitro and in vivo studies

Although selenium is taken with diet mainly as selenoamino acids, its hypoglycaemic action on hepatic gluconeogenesis has been studied with the use of inorganic selenium derivatives. The aim of the present investigation was to compare relative efficacies of inorganic and organic selenium compounds in reducing glucose synthesis in hepatocytes and renal tubules, significantly contributing to the glucose homeostasis. In contrast to hepatocytes, both selenite and methylselenocysteine inhibited renal gluconeogenesis by about 40-45% in control rabbits. Selenate did not affect this process, whereas selenomethionine inhibited gluconeogenesis by about 20% in both hepatocytes and renal tubules. In contrast to methylselenocysteine, selenite decreased intracellular ATP content, glutathione reduced/glutathione oxidized (GSH/GSSG) ratio and pyruvate carboxylase, PEPCK and FBPase activities, while methylselenocysteine diminished PEPCK activity due to elevation of intracellular 2-oxoglutarate and GSSG, inhibitors of this enzyme. Experiments in vivo indicate that in 3 of 9 alloxan-diabetic rabbits treated for 14 days with methylselenocysteine (0.182mg/kg body weight) blood glucose level was normalized, whereas in all diabetic rabbits plasma creatinine and urea levels decreased from 2.52+/-0.18 and 87.4+/-9.7 down to 1.63+/-0.11 and 39.0+/-2.8, respectively. In view of these data selenium supplementation might be beneficial for protection against diabetes-induced nephrotoxicity despite selenium accumulation in kidneys and liver.     

The bioavailability of various selenium compounds to a marine wading bird

The uptake of dietary selenium (about 3.5 mg/kg AF dry wt) as selenomethionine, selenocystine, selenite, selenate, and fish selenium in the plasma and red blood cells (RBC) of the oystercatcher has been investigated. The birds received the various selenium compounds subsequently, for at least 9 wk. After dietary supplementation of selenocystine, selenite, and selenate, plasma selenium was about 350 μg/L and RBC selenium 2.1 mg/kg dry wt. After supplementation of selenomethionine, the plasma concentration increased to 630 μg/L, and the RBC concentration to 4.1 mg/kg dry wt. When the fodder contained 3.1 mg/kg fish Se, an average plasma and RBC concentration of 415 μg/L and 14.4 mg/kg dry wt, respectively, was measured. The maximal increase of the selenium concentration in the plasma was attained at first sampling, 14 d after a change in dietary selenium (selenomethione or fish Se); the uptake seemed to be a concentration-regulated process. RBC concentrations (γ in mg/kg dry wt) increased with time (X in d) according toY=a?be^?cX . Fifty percent of the total increase was attained within 17d, suggesting that diffusion into the RBC played a role. The selenium concentration in the plasma was positively correlated with the (fish) Se concentration in the fodder; the RBC concentration (60 d after the change in diet) was positively correlated with the plasma concentration. When the diet contained fish Se, the blood selenium concentrations of the captive birds were similar to the concentrations measured in field birds. Fish Se is a yet undetermined selenium compound. The present experiment showed that fish Se differed from selenomethionine, selenocystine, selenite, or selenate in uptake from the food and uptake in the RBC.     

Investigation of the selenium metabolism in cancer cell lines

The aim of this work was to compare different selenium species for their ability to induce cell death in different cancer cell lines, while investigating the underlying chemistry by speciation analysis. A prostate cancer cell line (PC-3), a colon cancer cell line (HT-29) and a leukaemia cell line (Jurkat E6-1) were incubated with five selenium compounds representing inorganic as well as organic Se compounds in different oxidation states. Selenomethionine (SeMet), Se-methylselenocysteine (MeSeCys), methylseleninic acid (MeSeA), selenite and selenate in the concentration range 5-100 μM were incubated with cells for 24 h and the induction of cell death was measured using flow cytometry. The amounts of total selenium in cell medium, cell lysate and the insoluble fractions was determined by ICP-MS. Speciation analysis of cellular fractions was performed by reversed phase, anion exchange and size exclusion chromatography and ICP-MS detection. The selenium compounds exhibited large differences in their ability to induce cell death in the three cell lines and the susceptibilities of the cell lines were different. Full recovery of selenium in the cellular fractions was observed for all Se compounds except MeSeA. Speciation analysis showed that MeSeA was completely transformed during the incubations, while metabolic conversion of the other Se compounds was limited. Production of volatile dimethyl diselenide was observed for MeSeA and MeSeCys. MeSeA, MeSeCys and selenite showed noticeable protein binding. Correlations between cell death induction and the Se compounds transformations could not be demonstrated.     

Performance,carcass characteristics and meat quality of Nellore cattle supplemented with supranutritional doses of sodium selenite or selenium-enriched yeast

The enrichment of meat with selenium is important to improve the intake of selenium by humans. The effects of supranutritional doses of sodium selenite or selenium-enriched yeast on performance, carcass characteristics and meat quality were evaluated using 63 Nellore cattle in a completely randomized design with two sources (sodium selenite and selenium-enriched yeast), three levels (0.3, 0.9 and 2.7 mg Se/kg DM) and control treatment (without addition of selenium). Final body weight (BW), average daily gain, dry matter intake and gain to feed ratio (G : F) at the end of 84 days of supplementation were not influenced by treatments (P>0.05). Values of pH, ribeye area, back fat thickness and marbling score were also not influenced by treatments (P>0.05). Dressing percentage was greater (P=0.02) in Nellore cattle supplemented with organic Se (58.70%) compared to animals supplemented with inorganic Se (57.94%). Hot carcass weight increased (P=0.05) with the increasing of Se levels in the diet. Colour, shear force (SF), cooking and drip loss remained unchanged (P>0.05); however thiobarbituric acid reactive substances was 15.51% higher with inorganic Se compared with organic Se. The selenium concentration in the meat of animals receiving organic selenium was higher (P<0.001) than that of animals receiving sodium selenite, at all levels (0.3; 0.9 and 2.7 mg/kg DM). The meat of animals receiving 2.7 mg of organic Se/kg of DM presented concentration of 372.7 μg Se/kg in the L.dorsi muscle, and the intake of 150 g of this meat by humans provides approximately 100% of the recommended Se intake (55 μg Se/day for adults). Therefore, the use of supranutritional doses of 2.7 mg Se/kg of DM, regardless of source, is a way of naturally producing selenium-enriched meat without compromising performance, carcass characteristics and quality of Nellore bovine meat.