Indicator Of Selenium Status Research Articles

Functional Biomarkers for the Selenium Status in a Human Nutritional Intervention Study.

Soils in Germany are commonly low in selenium; consequently, a sufficient dietary supply is not always ensured. The extent of such provision adequacy is estimated by the optimal effect range of biomarkers, which often reflects the physiological requirement. Preceding epidemiological studies indicate that low selenium serum concentrations could be related to cardiovascular diseases. Inter alia, risk factors for cardiovascular diseases are physical inactivity, overweight, as well as disadvantageous eating habits. In order to assess whether these risk factors can be modulated, a cardio-protective diet comprising fixed menu plans combined with physical exercise was applied in the German MoKaRi (modulation of cardiovascular risk factors) intervention study. We analyzed serum samples of the MoKaRi cohort (51 participants) for total selenium, GPx activity, and selenoprotein P at different timepoints of the study (0, 10, 20, 40 weeks) to explore the suitability of these selenium-associated markers as indicators of selenium status. Overall, the time-dependent fluctuations in serum selenium concentration suggest a successful change in nutritional and lifestyle behavior. Compared to baseline, a pronounced increase in GPx activity and selenoprotein P was observed, while serum selenium decreased in participants with initially adequate serum selenium content. SELENOP concentration showed a moderate positive monotonic correlation (r = 0.467, p < 0.0001) to total Se concentration, while only a weak linear relationship was observed for GPx activity versus total Se concentration (r = 0.186, p = 0.021). Evidently, other factors apart from the available Se pool must have an impact on the GPx activity, leading to the conclusion that, without having identified these factors, GPx activity should not be used as a status marker for Se.

Timing of supplementation of selenium and isoflavones determines prostate cancer risk factor reduction in rats

BackgroundHigh dietary intake of selenium or isoflavones reduces risk factors for prostate cancer. We tested whether combined supplementation of these two dietary components would reduce prostate cancer risk factors in rats more than supplementation of each component individually.MethodsMale Noble rat pups were exposed from conception to diets containing an adequate (0.33–0.45 mg/kg diet) or high (3.33–3.45 mg/kg) concentration of selenium as Se-methylselenocysteine and a low (10 mg/kg) or high (600 mg/kg) level of isoflavones in a 2 × 2 factorial design. Pups consumed their respective diets until sacrifice at 35, 100, or 200 days. Male Noble rat breeders, whose exposure to the diets began after puberty, were sacrificed at 336 days. Rats were weighed biweekly. Blood was collected at the time of sacrifice and body fat and prostates were dissected and weighed. Serum levels of leptin, IGF-1, and testosterone were determined using ELISA kits. Serum levels of isoflavones were assayed by GC/MS. Liver activity of selenium-dependent glutathione peroxidase 1 was measured as an indicator of selenium status.ResultsSerum isoflavone concentrations were nearly 100-fold higher at 35 days of age (1187.1 vs. 14.4 ng/mL, mean ± SD) in pups fed the high vs. low isoflavone diets, and remained so at 100 and 200 days, and in breeders. There were no dietary differences in liver glutathione peroxidase activity in pups or breeders. High isoflavone intake significantly (p = 0.001–0.047) reduced body weight in rat pups from 35 days onward, but not in breeders. Body fat and leptin were likewise significantly reduced by high isoflavones in pups while effects in breeders were less pronounced but still significant. High intake of Se and isoflavones each decreased serum IGF-1 in pups at 100 and 200 days, but not in breeders. No consistent dietary effects were observed on serum testosterone or relative weights of prostates. In pups, the combination of high isoflavones and high selenium produced the lowest weight gain, the lowest serum leptin, and the lowest serum IGF-1 concentrations of all four diets.ConclusionCombined intake of high selenium and high isoflavones may achieve greater chemopreventive effects than either compound individually. The timing of supplementation may determine the significance of its effects.

Selenium status, sex hormones, and thyroid function in young women

The aim of the study was to identify those parameters characterising selenium status and sex hormones secretion, which are responsible for the changes in indicators of thyroid function, and to reveal the correlation structure of parameters expressing selenium status, sex hormones secretion and thyroid function, if any exist. The general approach in this work was essentially the same as in our previous report (cf. [Zagrodzki P, Ratajczak R, Wietecha-Posłuszny R. The interaction between selenium status, sex hormones, and thyroid metabolism in adolescent girls during the luteal phase of their menstrual cycle. Biol Trace Elem Res 2007; 120: 51–60]), but the study group and parameters’ spectrum were different. Thirty-six women aged 23.5±0.6 years were investigated. The parameters of interest were: plasma selenium concentration (Se) and plasma glutathione peroxidase activity (GPX3) (indicators of selenium status); serum estradiol (E2), progesterone (P4), follicle-stimulating hormone (FSH), luteotropic hormone (LH), and age of menarche (indicators of sex hormones secretion); thyroid-stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), anti-thyroid peroxidase antibodies in serum (anti-TPO), and thyroid volume (indicators of thyroid function). Our findings show that Se, GPX3, P4, LH, FSH, TSH and fT4 were interrelated. The pairs of parameters: GPX3 and P4; LH and FSH exhibited the strongest associations. The thyroid function parameters were mainly influenced by GPX3 and P4. Partial least-squares method corroborated our hypothesis about the existence of complex interactions among selenium status, sex hormones secretion, and thyroid function in healthy young women in the luteal phase.

Response of Selenium Status Indicators to Supplementation of Healthy North American Men with High-Selenium Yeast

The essential nutrient selenium is required in microgram amounts [recommended dietary allowance (RDA) = 55 microg/day, 699 nmol/day] and has a narrow margin of safety (upper tolerable intake limit = 400 microg/day, 5 micromol/day). We conducted a randomized placebo-controlled study of high-selenium yeast, the form used in most supplements (300 microg/day, 3.8 micromol/day), administered to 42 free-living healthy men for 48 weeks. Dietary intakes of selenium, macronutrients, and micronutrients were not different between groups and did not change during the study. Supplementation more than doubled urinary selenium excretion from 69 to 160 microg/day (876 to 2,032 nmol/day). Urinary excretion was correlated with recent selenium intake estimated from 3-day diet records: urinary selenium excretion = 42 microg/day (533 nmol/day) + 0.132 x dietary selenium intake, p < 0.001. Dietary selenium intake was not significantly correlated with the other indicators of selenium status, presumably because urinary selenium excretion reflected recent intake, and tissue selenium was homeostatically controlled. After 48 weeks of supplementation, plasma selenium was increased 60% from 142 to 228 microg/l (1.8 to 2.9 micromol/l), and erythrocyte selenium was approximately doubled from 261 to 524 microg/l (3.3 to 6.6 micromol/l). Selenium concentrations increased more modestly in hair (56%) and platelets (42%). Platelets were the only blood component in which glutathione peroxidase activity was significantly related to selenium content. Selenium levels decreased rapidly after the end of supplementation, and there were no significant differences in selenium status indicators between groups by week 96. The absorption, distribution, and excretion of selenium from high-Se yeast were similar to selenium in foods.

Measure of association between selenium status and sepsis in cattle

Odds ratio was used to evaluate relationship between sepsis in cattle less than 1 year old and mastitis in cows and erythrocyte glutathione peroxides (GSH-PX) activity as an indicator of selenium status. Data were from 178 blood samples collected from referred cases to Urmia University, Veterinary Teaching Hospital. Low activity of GSH-PX was significantly associated with higher odds of developing sepsis (P=0.005) in young cattle and mastitis (P=0.044) in adult cows. The odds ratios for the low activity of GSH-PX on incidence of sepsis and mastitis were 4.74 and 3.95, respectively. Selenium deficiency was associated with sepsis in young cattle and mastitis in cows, i.e., cattle with low activity of erythrocyte GSH-PX were at increased risk of sepsis and mastitis.

Determination of Selenium Concentration in Serum and Toenail as an Indicator of Selenium Status

Determination of Selenium Concentration in Serum and Toenail as an Indicator of Selenium Status

Mineral deficiencies in beef cattle from southern Brazil

Minerals play an important role in the cattle metabolism with great impact in productive and reproductive performance of animals raised on extensive grasslands. At present, there is a lack of information concerning mineral deficiency throughout the analysis of biological fluids in Rio Grande do Sul State (southern Brazil). The Central Valley region of this State is characterized by extensive production on natural pastures with poor mineral supplementation. The low levels of minerals found by previous studies on pastures in this area motivated this research. The aim of the present work was to detect possible mineral deficiencies in beef cows by determining concentrations of minerals in biological fluids and in pasture. There were determined concentrations of phosphorus, calcium, copper, zinc, glutathion peroxidase (as indicator of selenium status) and thyroxine (as indicator of iodine status) in blood, sodium and potassium in saliva, and calcium, phosphorus, potassium, zinc, copper, sodium and iron in pastures, in four different periods of the reproductive cycle as follows: service period (artificial insemination), clean up bulls period, end of gestation and early lactation. Four herds were selected in Cachoeira do Sul County for this study which included 112 animals. The results showed marginal deficiencies of phosphorus, copper, iodine and selenium. Calcium concentration was below normal level and could be related to the low protein content of pasture. Most critical periods were the end of gestation and the early lactation.

Indicators of selenium status in Australian infants

To provide the first Australian data for the commonly used indicators of selenium (Se) status including plasma and erythrocyte Se and erythrocyte glutathione peroxidase (GSHPx) activity in newborn term and preterm infants from Adelaide, South Australia. Plasma Se levels from adults from Adelaide and Tasmania are also reported. Descriptive, cross-sectional study of the indicators of Se status of newborn Australian preterm and term infants. Mean (+/- SD) plasma Se concentrations in the first 5 days of life for term (n = 48) and preterm (n = 90) infants were similar at 33 +/- 11 and 29 +/- 14 microg/L, respectively. Glutathione peroxidase activity was lower in preterm than term infants (P < 0.001). Erythrocyte Se was lower in male (n = 74) compared with female (n = 57) infants (491 +/- 98 vs 561 +/- 134 ng/g Hb; P < 0.001). Adelaide adult plasma Se levels were 88 +/- 20 microg/L and higher than those of adult Tasmanian blood donors (77 +/- 13 microg/l, P < 0.05). These data indicate that values for indicators of Se status of Australian infants and adults are at the lower end of the international range. This article highlights the paucity of Australian data on the Se content in the food supply and the Se status of the Australian population. Given the increasing range and complexity of the biological roles of Se and the emerging evidence that Se may have important roles in prevention of cancer and other disorders, further data are required to clarify the Se status of Australians.

Urinary selenium concentrations

Urinary selenium concentrations are used as an indicator of selenium status. A strong correlation has been established between dietary selenium and daily urinary selenium excretion in a wide range of populations from all over the world with different dietary selenium intake. Data on urinary selenium concentrations in healthy individuals and patients with different pathological conditions are reviewed. Selenium excretion rates of 20-200 micrograms/day are not associated with deficiency or toxicity problems. Urinary Se excretion is decreased in children, elderly people, and pregnant women. Workers exposed to heavy metals, and cancer patients, have higher and lower urinary Se concentrations, respectively, than control groups. The trimethylselenonium ion, a minor metabolite of Se in urine, assumes a significant role only in the detoxification of excess Se intake. Studies of bioavailability and balance show the important role of the kidneys in homeostatic regulation of Se.

Effects of Dietary Selenium on DMBA-Induced Carcinogenesis in Rats Fed a Diet High in Mixed Fats

The effects of selenium intake on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis were examined in rats fed a diet high in mixed fats and representative of that consumed in North America. Six groups of 20 rats were fed an AIN-76 diet modified to contain 20% fat from lard:corn oil (3:1 wt/wt) and various amounts of selenium (0.1, 0.035, 0.1, 1.0, 2.0 or 4.0 mg Se/kg diet). At wk 5, animals in groups 2-6 were dosed with 4.32 mg of DMBA. Serum clinical parameters and the activities of plasma selenium-dependent and total glutathione peroxidase (GSHPx), erythrocyte GSHPx and superoxide dismutase (SOD) were determined every 4 wk for 25 wk. The extent of lipid peroxidation was determined by measuring urinary malondialdehyde during wk 13 and 24, and erythrocyte malondialdehyde at wk 25. Erythrocyte GSHPx was found to be a better indicator of selenium status than plasma activity, while SOD did not vary with dietary selenium. The group of animals fed 4.0 mg Se/kg diet had reduced numbers of tumors (P less than 0.01), but this reduction was associated with evidence of chronic selenium toxicity. Variations in GSHPx activity with dietary selenium did not result in differences in tumor incidence, nor in changes in lipid peroxidation in the other groups. Thus, nontoxic levels of selenium do not appear to offer any protective effect during carcinogenesis in rats fed a casein-based diet similar in fat content to that consumed by North Americans.

Glutathione peroxidase protein. Absence in selenium deficiency states and correlation with enzymatic activity.

Glutathione peroxidase (GSHPx) activity is an indicator of selenium status in selenium-deficient individuals. Utilizing polyclonal monospecific antibodies to purified erythrocyte GSHPx, we were able to determine the relationship between enzymatic activity and protein content. In erythrocytes from a selenium-deficient individual who was treated with selenium, and in HL-60 cells grown in the absence of selenium and then returned to selenium-containing medium, there was a direct relationship between enzymatic activity and protein content. Thus, selenium deficiency results not only in a decrease of GSHPx activity, but also in a decrease of GSHPx protein.

Glutathione peroxidase activity in liver and kidney as indicator of selenium status in swine

Glutathione peroxidase activity and selenium concentration were determined in liver and kidney samples from pigs randomly selected at a slaughterhouse. The average selenium concentration in the kidney was approximately four times higher than that in liver, while the glutathione peroxidase levels in the two tissues differed only slightly. A highly significant positive correlation between selenium concentration and glutathione peroxidase activity was found in the liver, but not in the kidney. It is concluded that liver glutathione peroxidase activity may be used as a measure of selenium status in swine. The range of both glutathione peroxidase activity and selenium concentration was considerable, and the possible existence of genetic variations is discussed.