Urinary Se Research Articles

Differential responses to selenomethionine supplementation by sex and genotype in healthy adults.

A year-long intervention trial was conducted to characterise the responses of multiple biomarkers of Se status in healthy American adults to supplemental selenomethionine (SeMet) and to identify factors affecting those responses. A total of 261 men and women were randomised to four doses of Se (0, 50, 100 or 200 μg/d as L-SeMet) for 12 months. Responses of several biomarkers of Se status (plasma Se, serum selenoprotein P (SEPP1), plasma glutathione peroxidase activity (GPX3), buccal cell Se, urinary Se) were determined relative to genotype of four selenoproteins (GPX1, GPX3, SEPP1, selenoprotein 15), dietary Se intake and parameters of single-carbon metabolism. Results showed that supplemental SeMet did not affect GPX3 activity or SEPP1 concentration, but produced significant, dose-dependent increases in the Se contents of plasma, urine and buccal cells, each of which plateaued by 9-12 months and was linearly related to effective Se dose (μg/d per kg0·75). The increase in urinary Se excretion was greater for women than men, and for individuals of the GPX1 679 T/T genotype than for those of the GPX1 679 C/C genotype. It is concluded that the most responsive Se-biomarkers in this non-deficient cohort were those related to body Se pools: plasma, buccal cell and urinary Se concentrations. Changes in plasma Se resulted from increases in its non-specific component and were affected by both sex and GPX1 genotype. In a cohort of relatively high Se status, the Se intake (as SeMet) required to support plasma Se concentration at a target level (Se(pl-target)) is: Se(in) = [(Se(pl - target) - Se(pl))/(18.2ng d kg⁰.⁷⁵/ml per mu g)] .

Correlations of Trace Element Levels in the Diet, Blood, Urine, and Feces in the Chinese Male

In order to explore the associations between trace elements in dietary intake and the other three biological media (blood, urine, or feces) and inter-element interactions among the latter, we simultaneously collected 72-h diet duplicates, whole blood, and 72-h urine and feces from 120 free-living healthy males in China. Correlations among the toxic (cadmium [Cd], lead [Pb]), and nutritionally essential (zinc [Zn], copper [Cu], iron [Fe], manganese [Mn], selenium [Se], iodine [I]) elements were evaluated using Spearman rank correlation analysis based on analytical data determined by inductively coupled plasma-mass spectrometry. Dietary Cd intakes were highly correlated with the fecal Cd and blood Cd levels. Inverse correlations were found for Fe-Cd and Fe-Pb in both diet versus blood and diet versus feces. Cd-Zn and Cd-Se were significantly directly correlated in the urine and feces. Cd-Se and Pb-Se were negatively correlated in blood. In addition, there existed an extremely significant association between urinary Se and urinary I. Moreover, the other two highly direct correlations were found for Se-Fe and for I-Fe in urine. Improved knowledge regarding their mutual associations is considered to be of fundamental importance to understand more the complex interrelationships in trace element metabolism.

Determinants of selenium status in healthy adults

BackgroundSelenium (Se) status in non-deficient subjects is typically assessed by the Se contents of plasma/serum. That pool comprises two functional, specific selenoprotein components and at least one non-functional, non-specific components which respond differently to changes in Se intake. A more informative means of characterizing Se status in non-deficient individuals is needed.MethodsMultiple biomarkers of Se status (plasma Se, serum selenoprotein P [SEPP1], plasma glutathione peroxidase activity [GPX3], buccal cell Se, urinary Se) were evaluated in relation to selenoprotein genotypes (GPX1, GPX3, SEPP1, SEP15), dietary Se intake, and parameters of single-carbon metabolism in a cohort of healthy, non-Se-deficient men (n = 106) and women (n = 155).ConclusionsPlasma Se concentration was 142.0 ± 23.5 ng/ml, with GPX3 and serum-derived SEPP1 calculated to comprise 20% and 34%, respectively, of that total. The balance, comprised of non-specific components, accounted for virtually all of the interindividual variation in total plasma Se. Buccal cell Se was associated with age and plasma homocysteine (hCys), but not plasma Se. SEPP1 showed a quadratic relationship with body mass index, peaking at BMI 25-30. Urinary Se was greater in women than men, and was associated with metabolic body weight (kg0.75), plasma folate, vitamin B12 and hCys (negatively). One GPX1 genotype (679T/T) was associated with significantly lower plasma Se levels than other allelic variants. Selenium intake, estimated from food frequency questionnaires, did not predict Se status as indicated by any biomarker. These results show that genotype, methyl-group status and BMI contribute to variation in Se biomarkers in Se-adequate individuals.

Rapid speciation and quantification of selenium compounds by HPLC-ICP MS using multiple standards labelled with different isotopes

Speciation analysis using high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP MS) is now commonly used to investigate metabolic and toxicological aspects of some metals and metalloids. We have developed a rapid method for simultaneous identification and quantification of metabolites of selenium (Se) compounds using multiple standards labelled with different isotopes. A mixture of the labelled standards was spiked in a selenised garlic extract and the sample was subjected to speciation analysis by HPLC-ICP MS. The selenised garlic contains γ-glutamyl-methylselenocysteine, methylselenocysteine, and selenomethionine and the concentrations of those Se compounds were 723.8, 414.8, and 310.7 ng Se ml−1, respectively. The isotopically labelled standards were also applied to the speciation of Se in rat urine. Selenate, methylselenonic acid, selenosugar, and trimethyselenium ions were found to be excreted by the present speciation procedure. Multiple standards labelled with different stable isotopes enable high-throughput identification and quantitative measurements of Se metabolites.

Investigation and analysis of trace element levels in children with osteomalacia malformation from endemic fluorosis area in Shuicheng, Guizhou

Objective To investigate the levels of trace elements such as fluorine(F), and aluminium (Al)etc. of osteomalacia malformation children and to make etiological diagnosis in reference with clinical manifestations.Methods Urine and occipitalia hairs of 14 diseased children(patient group) from endemic fluorosis area and 13 healthy children(control group) from non-endemic area were included in the study on November, 2008, and contents of 10 elements of fluorine(F), aluminum(Al), chromium(Cr), manganese(Mn), ferrum(Fe), cuprum(Cu), zinc(Zn), arsenic (As), selenium(Se), strontium(Sr), and barium(Ba) were tested. The data were analyzed with medical soft package PEMS 3.1. Results Urinary contents of F, Al, Mn, Cu, Sr, and Se(1.18 mg/L, 112.6 μg/L,6.62,29.86 mg/L, 177.5,4.23 ng/L) in patient group were significantly different from those in control group (0.48,47.1,2.04,16.61 mg/L, 55.17,15.52 ng/L, t = 4.592,2.486,4.850,2.210 2.078,2.912, all P＜ 0.05); Hair contents of Al, Mn, As, Sr, Ba, Fe, and Se in patient group(59.27,5.26,0.96,1.50,1.29,297.13,0.45 mg/kg)were significantly different from those of control group( 18.69,0.72,1.09,0.62,0.68,69.02,1.323 mg/kg, t = 4.583,6.318,3.309,2.704,5.606,6.294, all P ＜ 0.05); in patient group, the correlation coefficients of urinary Fe to Al,Zn, As, and Se were all bigger tan 0.662(all P＜ 0.05), those of urinary Se to Mn, Ba, Cu, Zn, Sr, and As were all bigger than 0.694(all P＜ 0.05), those among urinary Mn, Sr, As, and Ba were bigger than 0.550(all P＜0.05), those of hair Al to Mn, Cr, Fe, and Cu were bigger than 0.732(all P＜ 0.05), those of hair Ba to Mn,Cr, Fe, and Sr, and of hair Mn to Cr and Fe, and those between Cr and As, between Cu and Sr were all bigger than 0.686 (all P ＜ 0.05). In control group, the correlation coefficients of urinary Cu to Zn, Se, and Ba, those of Zn to Se and Ba, and those of Cr to Mn and Ba were all bigger than 0.516(all P ＜ 0.05), those of hair Al to Mn,Fe, Cu, As, and Se, and those of hair Se to Fe, Cu, and As, those of hair Fe to Mn, Cu, and As, those of hair Cu to Zn and As, and that between Zn and As were bigger than 0.739(all P ＜ 0.05). The correlation coefficient of urinary F to Se in patient group(0.762) was significantly different from that in control group( - 0.469, u = 2.079,P ＜ 0.05). Conclusions The burden of F and Al of osteomalacia malformation children in endemic fluorosis area of Shuicheng county is too high. The contents of multi-elements in urine and hairs and their correlation are coincident with high levels of Al and F and they cause network increase of multi-element content changes and their correlation. According to bone X-ray features combining with the living environment, the diagnosis of endemic Al-F fluorosis can be made. The biological significance of reducing urinary and hair Se levels and the correlations of F and Al need to be further studied. Key words: Fluoride poisoning; Aluminum compounds; Selenium; Osteomalacia; Endemic diseases

Identification in human urine and blood of a novel selenium metabolite, Se-methylselenoneine, a potential biomarker of metabolization in mammals of the naturally occurring selenoneine, by HPLC coupled to electrospray hybrid linear ion trap-orbital ion trap MS

Speciation analysis of selenium in human urine allowed for the first time the identification of a novel selenium metabolite, Se-methylselenoneine. Despite a concentration at low ppb level, its characterization was achieved after sample purification by solid phase extraction (SPE) followed by the parallel coupling of the bidimensional RP/HILIC chromatography with ICP-MS and ESI-LTQ Orbitrap MS detection. To confirm its biological significance with regards to selenoneine, the recently discovered analog of ergothioneine, and to discard the possibility of sample preparation artifacts, a new method was developed to monitor its actual presence, as well as the occurrence of its sulfur and/or non-methylated analogs, in non-preconcentrated urine and blood samples of non-supplemented humans. It consisted in a HILIC ESI-MS(3) method in high resolution mode (resolution 30 000 at m/z 400) with large isolation width windows for precursor ions. These two particular settings allowed respectively to keep observing the specific mass defect of selenium- and sulfur-containing molecules and to maintain the characteristic selenium pattern in product ions created through MS(n) fragmentations. As a result, all four metabolites were detected in blood and three of them in urine. Moreover, different ratios "methylated/non-methylated" were observed between urine and blood samples, which seemed to indicate their active metabolization. The analytical tool developed here will be of a great importance to further study the occurrence and the potential metabolic role in mammalian organelles, cells and fluids of these very particular and promising redox metabolites.

Output of selenium in milk, urine, and feces is proportional to selenium intake in dairy cows fed a total mixed ration supplemented with selenium yeast

Fifteen rumen fistulated Holstein cows in late lactation and fed a total mixed ration offered ad libitum were supplemented with Se yeast to provide 0, 11, 20, 30, or 42mg of supplemental Se/day to test the hypothesis that amounts of Se secreted in milk, excreted in urine and feces, and apparently retained in tissues would increase in direct proportion to Se intake. One-half of the yeast supplement was placed directly into the rumen through the fistula of each cow just before milking in the morning and again in the evening, and estimates of average daily excretion of Se were made using total collections of urine and feces from 25 to 31 d after treatments commenced. Amounts of Se secreted daily in milk and apparently retained in tissues increased linearly with average daily intake of Se. The amount of Se excreted in feces and total excretion of Se in urine plus feces increased curvilinearly with Se intake, such that proportionately less Se was excreted as the amount of Se fed increased. On average, total Se excretion accounted for 66%, Se secretion in milk accounted for 17%, and Se apparently retained in tissues accounted for 17% of total Se intake by cows. Thus, in herds fed large amounts of Se yeast, most of the Se will be excreted and retained on-farm. High concentrations of Se will be found where urine and feces accumulate (e.g., yards and effluent ponds), and effluent management practices must be tailored to avoid environmental issues.

Mutation of megalin leads to urinary loss of selenoprotein P and selenium deficiency in serum, liver, kidneys and brain

Distribution of selenium (Se) within the mammalian body is mediated by SePP (selenoprotein P), an Se-rich glycoprotein secreted by hepatocytes. Genetic and biochemical evidence indicate that the endocytic receptors ApoER2 (apolipoprotein E receptor 2) and megalin mediate tissue-specific SePP uptake. In the present study megalin-mutant mice were fed on diets containing adequate (0.15 p.p.m.) or low (0.08 p.p.m.) Se content and were analysed for tissue and plasma Se levels, cellular GPx (glutathione peroxidase) activities and protein expression patterns. Megalin-mutant mice displayed increased urinary Se loss, which correlated with SePP excretion in their urine. Accordingly, serum Se and SePP levels were significantly reduced in megalin-mutant mice, reaching marginal levels on the low-Se diet. Moreover, kidney Se content and expression of renal selenoproteins were accordingly reduced, as was SePP internalization along the proximal tubule epithelium. Although GPx4 expression was not altered in testis, Se and GPx activity in liver and brain were significantly reduced. When fed on a low-Se diet, megalin-mutant mice developed impaired movement co-ordination, but no astrogliosis. These findings suggest that megalin prevents urinary SePP loss and participates in brain Se/SePP uptake.

The Selenium Status of Pediatric Patients With Burn Injuries

Dietary selenium (Se) requirements during critical illness are not well known. The objective of this study was to assess the longitudinal Se status of pediatric patients with burns. Twenty patients admitted to our hospital with burns exceeding 10% of their total body surface area were studied longitudinally during the first 8 weeks of admission or until 95% wound closure was achieved. Dietary Se intake was calculated daily, and plasma and urine samples were collected weekly for analyses of plasma Se, urinary Se, and glutathione peroxidase activity. Patients included in this study were individuals with an average age of 6.5 years ± 5.3 years and with burn injury of a mean total body surface area of 42% ± 21%. Dietary Se intake throughout the study (mean = 60 μg/d ± 39 μg/d) was consistent with established standards for healthy children and did not change throughout the study. Plasma Se (mean = 1.08 μmol/L ± 0.34 μmol/L) and plasma glutathione peroxidase (mean = 3.2 U/g protein ± 1.42 U/g protein) were below reported normal values for healthy American children. Mean urinary Se excretion (65.9 μg/L ± 50 μg/L) exceed dietary Se intake. Plasma Se was inversely related to incidence of total infection (p = 0.04). Results from this study indicate that Se status is depressed among pediatric patients with burns and that recommended Se intake for healthy children is likely insufficient for this population. Further studies are necessary to elucidate the amount of dietary Se required to maximize Se stores among pediatric patients with burn injuries.

Speciation Analysis of Selenium Metabolites in Urine and Breath by HPLC- and GC-Inductively Coupled Plasma-MS after Administration of Selenomethionine and Methylselenocysteine to Rats

Selenium is an essential trace element found in vegetables as selenomethionine (SeMet) and methylselenocysteine (MeSeCys). In the present study, we used stable isotopes of Se to investigate differences between how SeMet and MeSeCys are metabolized, using methylseleninic acid (MSA) as a reference methylselenol source. A mixture containing (76)Se-SeMet, (77)Se-MeSeCys, and (82)Se-MSA (each 25 microg Se/kg b.w.) was orally administered to rats, and then, speciation analyses of Se in urine and exhaled gas were conducted using HPLC-inductively coupled plasma (ICP)-MS and GC-ICP-MS, respectively. The proportions of (76)Se-, (77)Se-, and (82)Se-selenosugar (Se-sugar) to total urinary Se metabolites originating from each tracer were very similar, while the proportion of (77)Se-tirmethylselenonium (TMSe) was much less than that of(76)Se- and (82)Se-TMSe in urine, suggesting that(77)Se-SeMet is less efficiently metabolized to TMSe. Similarly, there was significantly less (77)Se-dimethylselenide (DMSe) originating from (77)Se-SeMet than(76)Se- and (82)Se-DMSe originating from (76)Se-MeSeCys and (82)Se-MSA in exhaled gas. It is generally accepted that DMSe and TMSe are metabolites of methylselenol, a putative metabolic intermediate in Se metabolism. Methylselenol is believed to be responsible for the cancer chemoprevention effects of Se. These results suggest that MeSeCys is converted to methylselenol more efficiently than is SeMet and that urinary TMSe and exhaled DMSe might be useful biomarkers for the generation of cancer chemopreventive forms of Se.

Genetic Determinants of Responses to Selenium Supplementation

In a cohort of healthy adults (106 M, 155 W) in eastern North Dakota, we determined the relationships of five biomarkers of selenium (Se) status (plasma Se, serum selenoprotein P [SePP], plasma glutathione peroxidase [GPX3] activity, buccal cell Se, urine Se) to genotype for four selenoproteins (cytosolic glutathione peroxidase [GPX1], phospholipid hydroperoxide glutathione peroxidase [GPX4], the 15 kD selenoprotein [SeP15], SePP) and two glutathione S‐transferases (GST‐M1, GST‐T1). The cohort had plasma Se of 141.5±23.7 (SD) ng/ml, SePP lof 3.55 (CI 2.61, 4.51) mg/L, GPX3 activities of 3.64±0.54 nmoles NADPH/min/mg protein, buccal cell Se of 10.2±6.5 ng Se/mg protein, and urinary Se of 58.2±21.5 ng Se/mg creatinine. Plasma Se was significantly related to GPX3 genotype (198Leu/Leu: 135.7a±19.0 ng/ml; 198Leu/Pro: 139.2a,b±23.8 ng/ml; 198 Pro/Pro: 145.9b±24.4 ng/ml; P<0.05). Buccal cell Se was significantly related to SeP15 genotype (C/C: 8.77a [5.85, 13.14]; T/C: 7.65b [5.06, 11.57]; T/T: 8.27a,b [6.16, 11.10] P<0.05). SePP was significantly related to SePP genotype at a polymorphism in the 3′‐UTR region (A/A: 3.49a,b [2.91, 4.18]; G/A: 3.24 a [2.44, 4.31]; G/G: 3.62 b [2.75, 4.76]), but not one in the coding region (A234T). No other effects were detected. These results show that genetic polymorphisms can significantly affect some biomarkers used to assess Se status.

Selenium Deficiency as a Possible Contributor of Goiter in Schoolchildren of Isfahan, Iran

The prevalence of goiter still remains high in some areas of Iran in spite of iodine supplementation. In the present study, we investigated the role of selenium (Se) deficiency in the etiology of goiter in Isfahan. Two thousand three hundred thirty-one schoolchildren were selected by multistage random sampling. Thyroid size was estimated in each child by inspection and palpation. Urinary iodine concentration (UIC) and plasma Se were measured. Overall, 32.9% of the 2,331 children had goiter. The median UIC was 19.55 microg/dl. Plasma Se was measured in 96 goitrous and 72 nongoitrous children. The mean +/- SD of plasma Se in goitrous and nongoitrous children was 66.86 +/- 21.82 and 76.67 +/- 23.33 microg/l, respectively (P = 0.006). Goitrous girls had lower plasma Se level than nongoitrous girls (65.62 +/- 21.64 vs. 76.51 +/- 22.61 microg/dl, P = 0.02). Goitrous boys had lower plasma Se level than nongoitrous boys (68.45 +/- 22.21 vs. 76.91 +/- 24.76 microg/l, P = 0.14). The prevalence of Se deficiency was significantly higher in goitrous boys and girls than nongoitrous children. Se deficiency is among the contributors of goiter in Isfahan goitrous schoolchildren. However, the role of other micronutrient deficiencies or goitrogens should be investigated in this region.

Biomarkers of selenium status in the amazonian context: Blood, urine and sequential hair segments

Selenium (Se) is an essential element and deficit or excess of dietary Se is associated with health disorders. Relatively elevated Se levels have been reported in the Brazilian Amazon, where there are also important annual variations in the availability of different foods. The present study was conducted among six riparian communities of the Tapajós River to evaluate seasonal variations in blood and sequential hair cm Se concentrations, and to examine the relationships between Se in blood and hair, and blood and urine. Two cross-sectional studies were conducted, at the descending water (DWS, n=259) and the rising water (RWS, n=137) seasons, with repeated measures for a subgroup (n=112). Blood Se (B-Se), hair Se (H-Se) and urine Se (U-Se) were determined. Match-paired analyses were used for seasonal comparisons and the method of best fit was used to describe the relationships between biomarkers. B-Se levels presented a very large range (142-2447 microg/l) with no overall seasonal variation (median 284 and 292 microg/l, respectively). Sequential analysis of 13 cm hair strands showed significant variations over time: Se concentrations at the DWS were significantly lower compared with the rising water season (medians: 0.7 and 0.9 microg/g; ranges: 0.2-4.3 microg/g and 0.2-5.4 microg/g, respectively). At both seasons, the relationships between B-Se and H-Se were linear and highly significant (r(2)=67.9 and 63.6, respectively), while the relationship between B-Se and U-Se was best described by a sigmoid curve. Gender, age, education and smoking did not influence Se status or biomarker relationships. Variations in H-Se suggest that there may be seasonal availability of Se sources in local food. For populations presenting a large range and/or elevated Se exposure, sequential analyses of H-Se may provide a good reflection of variations in Se status.

Sequential Hair Analysis as a Seasonal Biomarker of Variations in Selenium Status

ISEE-591 Objective: In the Brazilian Amazon, where there is high mercury (Hg) exposure, there is much interest in possible Hg-Se interactions. Se is ingested through a number of food sources, whose content is dependent on soil Se concentrations and plant accumulation. Intraindividual variations over time can occur through changes in dietary habits and seasonal availability of different foods. The present study was conducted among 6 riparian communities of the Tapajós River (Brazil) to evaluate variations in whole blood and sequential hair cm Se biomarkers, and to examine blood-hair and blood-urine relations. Materials and Methods: Two cross-sectional studies were conducted, at the descending water (n=259) and the rising water (n=137) seasons, with repeated measures for a subgroup (n=112). Blood Se (B-Se), hair Se (H-Se), and urine Se (U-Se) were assessed. Sociodemographic information was collected using an interview-administered questionnaire. Results: Blood Se (B-Se) levels presented a large range (142.1 to 2447.8 mg/L) with no overall interseasonal variation (median 284.3 and 292.2 mg/L respectively). Sequential analysis of 13 cm hair strands showed significant variations over time, where Se levels associated to the descending water season were lower compared to the that of rising water season (median 0.7 and 0.9 mg/g, range 0.2–4.3 and 0.2–5.4 mg/g respectively), possibly reflecting seasonal availability of Se sources in local food. No individuals presented Se deficiency, but 10 participants had high Se status, potentially a threat to their health. At both seasons, relations between B-Se and H-Se were linear and highly significative, while the best relation between B-Se and U-Se was described by a sigmoid curve. Gender, age, education, and smoking had no influence on Se status or biomarker relations. Conclusions: While blood represents a single measure in time, sequential analyses of H-Se provides a good reflection of varying Se status and should be useful to study Se-Hg relations.

Selenium and goiter prevalence in borderline iodine sufficiency

Selenium (Se) is required for the biosynthesis of selenocysteine-containing proteins. Several selenoenzymes, e.g. glutathione peroxidases and thioredoxin reductases, are expressed in the thyroid. Selenoenzymes of the deiodinase family regulate the levels of thyroid hormones. For clinical investigators, it is difficult to determine the role of Se in the etiology of (nodular-)goiter, because there are considerable variations of Se concentrations in different populations as reflected by dietary habits, bioavailability of Se compounds, and racial differences. Moreover, most previous clinical trials which investigated the influence of Se on thyroid volume harbored a bias due to the coexistence of severe iodine deficiency in the study populations. Therefore, we investigated the influence of Se on thyroid volume in an area with borderline iodine sufficiency. First, we investigated randomly selected probands for urinary iodine (UI) and creatinine excretion in spot urine samples and determined the prevalence of goiter and thyroid nodules by high-resolution ultrasonography. After this, we determined urinary Se excretion (USe) in probands with goiter as well as in matched probands without goiter. Adjustments between the two compared groups were made for age, gender, history of thyroid disorders, smoking, and UI excretion. The mean USe and UI rates of all 172 probands were 24 micro g Se/l or 27 micro g Se/g creatinine and 96 micro g I/l or 113 micro g I/g creatinine indicating borderline selenium (20-200 micro g/l) and iodine (100-200 micro g/l) sufficiency of the study population. Probands with goiter (n=89) showed significantly higher USe levels than probands with normal thyroid volume (n=83; P < 0.05). USe rates were not influenced by present smoking or pregnancy. In our investigation, USe was not an independent risk factor for the development of goiter. The higher USe in probands with goiter in comparison with probands with normal thyroid volume is most likely a coincidence. Se does not significantly influence thyroid volume in borderline iodine sufficiency because the iodine status is most likely the more important determinant.

Selenium absorption, distribution, and excretion in white sturgeon orally dosed with L‐selenomethionine

The usefulness of a newly developed, combined technique consisting of esophageal intubation, dorsal aortic cannulation, and urinary catheterization to deliver Se orally and to monitor Se uptake, accumulation, and excretion in white sturgeon (Acipenser transmontanus) was explored. Groups of five yearling sturgeon (1-2 kg) each were intubated with 0 (sham), 250, 500, or 1,000 microg Se/kg body weight in the form of L-selenomethionine, an ecologically relevant organic form of Se. Selenium concentrations in whole blood, plasma, and red blood cells did not change in the sham group but began to rise within 2 h postintubation in the other groups, and levels remained near maximum concentrations throughout the 48-h sampling period. Average urinary Se excretion rates over the entire 48-h period were 0.05, 0.46, 0.61, and 2.15 microg Se/kg/h in sturgeon intubated with 0, 250, 500, and 1,000 microg Se/kg, respectively. Selenium excretion rates were highest within the first 6 h in all treatment groups except the sham group. Selenium concentrations in the liver were positively correlated with the intubated Se dosage.

Selenium metabolism in humans: Response of kinetic pools in plasma to 2 yr of Se supplementation

Selenium (Se) is a particularly promising cancer chemopreventive agent. We have been investigating the effects of oral Se supplementation on the metabolism of two forms of Se, selenomethionine (SeMet) and selenite (Sel), by comparing kinetics for 4-mo before (PK1) and after (PK2) 2 yrs of supplementation with 200 ug of Se as SeMet. For each pharmacokinetic study, thirty free-living subjects (15 M, 15 F) received 2 oral doses of 2 stable isotope tracers, 150 ug of 74Se as SeMet and 150 ug of 76Se as sodium selenite (Sel). A compartmental model requiring ten kinetically distinct compartments in plasma and recirculation of tracer through liver and tissues was developed using data from PK1. The model was then applied to data from PK2. By using the relative absorption of Sel to Se Met and excretion rates of total Se in urine and feces, we were able to combine information on the kinetics of each form and predict the size of each plasma pool in each study. Based on data from 7 subjects, Se-supplementation increased total plasma Se from 132ng/ml to 252 ng/ml with notable increases in five of the plasma pools. Insights into Se metabolism from this investigation will be crucial to interpreting Se-intervention results, such as those of the 35,000+ male subject SELECT prostate cancer prevention trial.

Selenium and goiter prevalence in borderline iodine sufficiency

It is difficult to determine the role of Selenium (Se) in the etiology of (nodular-)goiter, because there are considerable variations of Se concentrations in different populations as reflected by dietary habits, bioavailability of Se compounds and racial differences. Moreover, most previous clinical trials, which investigated the influence of Se on thyroid volume, harboured a bias due to the coexistence of severe iodine deficiency in the study populations. Therefore, we investigated the influence of Se on thyroid volume in a mildly iodine deficient area. First, we investigated randomly selected probands for iodine (UI) and creatinine excretion in spot urine samples and determined the prevalence of goiter and thyroid nodules by high resolution ultrasonography. Iodine concentration was measured manually according to the protocol described by Sandell and Kolthoff and Creatinine as described by Jaffe. Thyroid volume determination was performed using a high resolution real-time instrument. Thyroid volumes were calculated according to the spherical ellipsoid formula. After this, we determined urinary Se excretion (USe) in probands with goiter as well as in matched probands without goiter. Urinary selenium excretion was measured according to the method previously described by Vezina et al. Adjustments between the 2 compared groups were made for age, gender, history of thyroid disorders, smoking and urinary iodine excretion. The mean USe and UI rates of all 172 probands were 24µg Se/l or 27µg Se/g creatinine and 96µg I/l or 113µg I/g creatinine indicating borderline selenium (20–200µg/l) and iodine (100–200µg/l) sufficiency of the study population. Probands with goiter (n=89) showed significantly higher USe levels than probands with normal thyroid volume (n=83; p<0.05). USe rates were not influenced by current smoking or pregnancy. In our investigation, USe was not an independent risk factor for development of goiter. Se does not significantly influence thyroid volume in borderline iodine sufficiency because the iodine status is the more important determinant.

The determination of total Se in urine and serum by graphite furnace atomic absorption spectrometry using Ir as permanent modifier and in situ oxidation for complete trimethylselenonium recovery

The present work evaluated the use of iridium (Ir) as permanent modifier for the determination of total selenium in urine and serum by graphite furnace atomic absorption spectrometry. Concerning urine, the presence of trimethylselenonium (TMSe(+)) was especially considered. Pyrolysis and atomization temperatures of 1,000 and 2,100 degrees C, respectively, were used. For nondigested urine and serum samples, 0.2% v/v HNO(3) and Triton X-100 were used as diluents, respectively, and the same initial platform Ir treatment was effective for up to 1,100 atomization cycles. Good precision [less than 5% relative standard deviation (RSD)] can be achieved with the proposed method. Low TMSe(+) recovery was observed for nondigested urine samples. Thus, if this species is to be considered in urine analysis, a previous external mineralization step was found to be necessary. Alternatively, an in situ oxidation treatment was developed. Detection limits of 8, 10, and 7 mug l(-1) were obtained after dilution, microwave-assisted digestion, and in situ oxidation procedures, respectively. The accuracy of the method was validated by the analysis of certified reference or commercial quality control materials and spiked samples.

Serum and Urine Levels of Zinc and Selenium in Diabetics in Calabar, Nigeria

The study aimed to determine the serum and urine zinc (Zn) and selenium (Se) in diabetics and non-diabetics in Calabar, Nigeria. Fasting plasma glucose (FPG), urine creatinine and serum and urine zinc and selenium levels were determined in 60 diabetic subjects aged between 35-75 years and 40 age-matched non-diabetic subjects using colorimetric methods and Atomic Absorption Spectrometry. The FPG, urine Zn and Se levels were significantly higher and serum Zn and urine creatinine levels lower in diabetics than those of non-diabetics. No significant difference was observed in the serum Se levels of both groups. A significant positive correlation (p < 0.01) was observed between serum Zn and serum Se (r = 0.368), urine Zn and urine Se (r = 0.446) and a negative correlation (p < 0.05, r = -0.287) between serum Se and urine Se levels of diabetics. There was no association between serum and urine zinc levels of diabetics. Diabetes alters the metabolism of zinc and selenium by increasing their urinary excretion. Key words: serum, urine, selenium zinc and diabetes Journal of Medical Laboratory Science Vol.13(1) 2004: 17 - 22