High Selenium Group Research Articles

Association of dietary selenium intake and all-cause mortality of Parkinson’s disease and its interaction with blood cadmium level: a retrospective cohort study

BackgroundParkinson’s disease (PD) is a slowly progressive neurodegenerating disease that may eventually lead to disabling condition and pose a threat to the health of aging populations. This study aimed to explore the association of two potential risk factors, selenium and cadmium, with the prognosis of Parkinson’s disease as well as their interaction effect.MethodsData were obtained from the National Health and Nutrition Examination Survey (NHANES) 2005–2006 to 2015–2016 and National Death Index (NDI). Participants were classified as Parkinson’s patients by self-reported anti-Parkinson medications usage. Cox regression models and restricted cubic spline models were applied to evaluate the association between PD mortality and selenium intake level as well as blood cadmium level. Subgroup analysis was also conducted to explore the interaction between them.ResultsA total of 184 individuals were included. In full adjusted cox regression model (adjusted for age, gender, race, hypertension, pesticide exposure, smoking status and caffeine intake), compared with participants with low selenium intake, those with normal selenium intake level were significantly associated with less risk of death (95%CI: 0.18–0.76, P = 0.005) while no significant association was found between low selenium intake group and high selenium group (95%CI: 0.16–1.20, P = 0.112). Restricted cubic spline model indicated a nonlinear relationship between selenium intake and PD mortality (P for nonlinearity = 0.050). The association between PD mortality and blood cadmium level was not significant (95%CI: 0.19–5.57, P = 0.112). However, the interaction term of selenium intake and blood cadmium showed significance in the cox model (P for interaction = 0.048). Subgroup analysis showed that the significant protective effect of selenium intake existed in populations with high blood cadmium but not in populations with low blood cadmium.ConclusionModerate increase of selenium intake had a protective effect on PD mortality especially in high blood cadmium populations.

The protective role of selenium in an experimental high fructose corn syrup exposure

<b>Objective:</b> Nowadays, fructose is recognized as a significant health threat. Prepared foods containing fructose are consumed more because they do not create a feeling of satiety. Selenium is an essential trace element with antioxidant and cell protective properties. In this study, the effect of high fructose corn syrup, which is used as a sweetener in many foods and beverages and consumed during pregnancy, and the possible protective role of selenium in this effect were investigated and examined.<br /> <b>Methods:</b> Fertilized specific pathogen-free eggs were used in our study. These eggs were divided equally into four groups. Each group was allocated 10 eggs containing viable embryos. These groups are pre-process control, post-process control, high fructose corn syrup (HFCS-55), and high fructose corn syrup and selenium (HFCS-55+Se 10<sup>-6</sup>) groups. Pellets containing and containing no active substance (HFCS-55, HFCS-55+Se 10<sup>-6</sup>) were carefully placed on the chorioallantoic membrane (CAM) of each egg in these groups. Oxidative stress status in all groups was determined by total oxidative stress (TOS) and total antioxidant capacity (TAC) methods.<br /> <b>Results:</b> In our study, a significant increase in TOS levels and a significant decrease in TAC levels were observed in egg groups given HFCS compared to other groups (p<0.05). The OSI value was shown to be lower in the group given HFCS+Se.<br /> <b>Conclusion:</b> As a result, HFCS was shown to increase oxidative stress. In line with our data, it has been shown that Se, plays a protective role against oxidative stress.

The Relationship between Iodine and Selenium Levels with Anxiety and Depression in Patients with Euthyroid Nodular Goiter.

ObjectivesSelenium and iodine are essential microelements for normal body functions. These two elements play important roles in thyroid metabolism. The potential relationship between thyroid diseases and mental disorders have been demonstrated. We aimed to investigate the relationship between selenium and iodine levels with anxiety and depression in patients with euthyroid nodular goiter (ENG).MethodsIn this cross-sectional study, we enrolled 102 consecutive patients with ENG who attended the endocrine outpatient clinic between January 2018 and June 2018. We noted the patient’s demographics, thyroid ultrasound imaging, thyroid hormones, and urinary iodine concentration (UIC) results. We also obtained venous blood samples for serum selenium measurement. The same psychiatrist completed the Beck Anxiety Inventory (BAI) and Hamilton Depression Rating Scale (HDRS) for all participants. The study population was dichotomized according to the median values of selenium levels and UIC.ResultsBAI and HDRS scores were significantly higher in the low selenium group than the high selenium group (p = 0.032 and p = 0.042, respectively). BAI scores were significantly higher in the low UIC group than the high UIC group (p = 0.007).ConclusionsLow selenium and UIC levels may contribute to the development of anxiety and depression, independent of thyroid functions, in patients with ENG. In these patients, selenium and iodine replacement may be useful for the prevention of anxiety and depression, especially in deficient regions.

High serum selenium levels are associated with impaired fasting glucose and elevated fasting serum glucose in Linyi, China

BackgroundThe relationship between selenium level and impaired fasting glucose or elevated fasting serum glucose remains controversial. This study aimed to evaluate these associations in China. MethodsThis observational population study adopted a cluster sampling approach to enroll participants. Baseline information on selenium categories was tested using one-way analysis of variance and Kruskal–Wallis equality-of-populations rank tests. Multivariable logistic regression was used to investigate the association between serum selenium level and impaired fasting glucose or elevated fasting serum glucose. ResultsThe mean serum selenium concentration was 121.5μg/L which in a relatively high baseline Se status. Differences were observed among individuals with normal, impaired fasting glucose and elevated fasting serum glucose levels in their basic information, physical examination results and laboratory findings. After adjusting for their basic information, physical examination results and laboratory findings, compared with the low-selenium group, the high-selenium groups (124.9–143.9 and above 143.9μg/L) had ORs for elevated fasting serum glucose of 2.31 (1.37–3.90) and 2.67 (1.59–4.48), respectively (both P<0.05). A sex-difference was observed, and a significant association between selenium levels and impaired fasting glucose was observed for males but not for females. ConclusionsThe findings of this observational study suggest that relatively high selenium levels might be positively associated with elevated fasting serum glucose and relatively high selenium levels might be positively associated with impaired fasting glucose in men.

Supplementation with Selenium and Coenzyme Q10 Reduces Cardiovascular Mortality in Elderly with Low Selenium Status. A Secondary Analysis of a Randomised Clinical Trial.

BackgroundSelenium is needed by all living cells in order to ensure the optimal function of several enzyme systems. However, the selenium content in the soil in Europe is generally low. Previous reports indicate that a dietary supplement of selenium could reduce cardiovascular disease but mainly in populations in low selenium areas. The objective of this secondary analysis of a previous randomised double-blind placebo-controlled trial from our group was to determine whether the effects on cardiovascular mortality of supplementation with a fixed dose of selenium and coenzyme Q10 combined during a four-year intervention were dependent on the basal level of selenium.MethodsIn 668 healthy elderly individuals from a municipality in Sweden, serum selenium concentration was measured. Of these, 219 individuals received daily supplementation with selenium (200 μg Se as selenized yeast) and coenzyme Q10 (200 mg) combined for four years. The remaining participants (n = 449) received either placebo (n = 222) or no treatment (n = 227). All cardiovascular mortality was registered. No participant was lost during a median follow-up of 5.2 years. Based on death certificates and autopsy results, all mortality was registered.FindingsThe mean serum selenium concentration among participants at baseline was low, 67.1 μg/L. Based on the distribution of selenium concentration at baseline, the supplemented group was divided into three groups; <65 μg/L, 65–85 μg/L, and >85 μg/L (45 and 90 percentiles) and the remaining participants were distributed accordingly. Among the non-treated participants, lower cardiovascular mortality was found in the high selenium group as compared with the low selenium group (13.0% vs. 24.1%; P = 0.04). In the group with the lowest selenium basal concentration, those receiving placebo or no supplementation had a mortality of 24.1%, while mortality was 12.1% in the group receiving the active substance, which was an absolute risk reduction of 12%. In the middle selenium concentration group a mortality of 14.0% in the non-treated group, and 6.0% in the actively treated group could be demonstrated; thus, there was an absolute risk reduction of 8.0%. In the group with a serum concentration of >85 μg/L, a cardiovascular mortality of 17.5% in the non-treated group, and 13.0% in the actively treated group was observed. No significant risk reduction by supplementation could thus be found in this group.ConclusionsIn this evaluation of healthy elderly Swedish municipality members, two important results could be reported. Firstly, a low mean serum selenium concentration, 67 μg/L, was found among the participants, and the cardiovascular mortality was higher in the subgroup with the lower selenium concentrations <65 μg/L in comparison with those having a selenium concentration >85 μg/L. Secondly, supplementation was cardio-protective in those with a low selenium concentration, ≤85 at inclusion. In those with serum selenium>85 μg/L and no apparent deficiency, there was no effect of supplementation. This is a small study, but it presents interesting data, and more research on the impact of lower selenium intake than recommended is therefore warranted.Trial RegistrationClinicaltrials.gov NCT01443780

Effects of dietary excess of vitamin e and selenium on some production traits, lipid peroxide state and amount/activity of the glutathione redox system in African catfish Clarias gariepinus (siluriformes, clariidae) fingerlings

Purpose of present study was to investigate the effect of excess dietary amount of vitamin E and selenium also short-term starvation on some production traits and parameters of the lipid peroxide state and glutathione redox system in African catfish fingerlings. Three purified diets were formulated: diet 1 (control) contained 114 mg.kg -1 tocopherol and 0.43 mg.kg -1 selenium, diet 2 contained high level of tocopherol (245mg kg -1 ) and control level of selenium (0.5 mg kg -1 ), while diet 3 contained high level of selenium (2.5 mg kg -1 ) and control level of tocopherol (170 mg kg -1 ). Fingerlings of C. gariepinus (3.16-3.93 g) were investigated in four groups, three consumed the above mentioned diets and the fourth served as unfed control. The experiment lasted 30 days except in the case of the unfed group which was terminated on the 15 th day because of high mortality. The vitamin E / selenium treated groups showed significantly (P£0.001) lower final body weight and specific growth rate as compared to the control. Vitamin E and selenium content of the fish body in diet 2 group increased significantly (P£0.001) as compared to the control. Vitamin E content did not changed in the unfed group, but selenium content decreased significantly (P£0.001) during the 15-days starvation period. Reduced glutathione (GSH) content increased significantly (P£0.05) only in the high selenium group. Glutathione-disulphide (GSSG) content, and glutathione peroxidase activity did not changed neither during the period of investigation and nor as effect of treatments, but the value of GSH/GSSG ratio was significantly higher (P£0.05) in the high selenium as compared to the high vitamin E group. Lipid peroxide state of the body, as was measured by the malondialdehyde content, changed as effect of age and/or maturation but not as effect of the treatments.

Growth and gut health in chickens on diets varying in fatty acid composition and selenium content

Chicken feed composition is essential to chicken health and meat composition. Fatty acids of the n-6 and n-3 families and selenium are of high importance to inflammatory processes. The effect of varying chicken dietary compositions in saturated and unsaturated oil sources with varying n-6 and n-3 levels combined with two levels of organic selenium on chicken growth, gizzard and gut health was studied.Wheat-based chicken diets supplemented with either 0.1 mg Se/kg feed or 1.0 mg Se/kg feed in combinations with rendered fat, soybean oil, rapeseed oil, linseed oil, palm oil, and red palm oil were used.Altering the fatty acid profile and selenium level did not significantly affect gizzard or gut health in broiler chickens, but increased early growth in chickens was seen for the red palm oil, linseed oil, and high selenium groups. Increased selenium levels lead to fewer incidences of loose digesta and higher gizzard weights.

Effects of Selenium Intervention on Chronic Fluorosis-Induced Renal Cell Apoptosis in Rats

This study aims to explore the effect of selenium in fluoride-induced renal cell apoptosis in rats and determine the optimal level of selenium in drinking water to prevent fluorosis. Experimental animals were divided into a control group, a sodium fluoride-treated group (NaF, 50mg/L), three sodium selenite-treated groups (Na2SeO3, 0.375, 0.75, and 1.5mg/L), and three selenium + NaF-treated groups (Na2SeO3, 0.375, 0.75, and 1.5mg/L; NaF, 50mg/L). Ultrastructural changes in the kidney tissues of each group were observed by transmission electron microscopy. Apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and the expressions of Bcl-2 and Bax proteins were detected by immunohistochemical methods. The expressions of Bcl-2 and Bax mRNA were detected by reverse transcription-polymerase chain reaction. The results showed that Bcl-2, Bax, and Bax/Bcl-2 protein expressions in the fluoride and high selenium groups were highly elevated compared with the control group (P < 0.01). Bax expression in the low selenium group and Bcl-2, Bax, and Bax/Bcl-2 protein expressions in the moderate selenium groups were observably elevated (P < 0.05). Bax and Bax/Bcl-2 expressions in the fluoride group and Bax mRNA expression in the high selenium group were highly elevated (P < 0.01). Bax/Bcl-2 mRNA expression in the high selenium group was also highly elevated (P < 0.05). Compared with the fluoride group, the group treated with low selenium has Bax protein expression that was observably reduced (P < 0.05); the group treated with moderate selenium has Bcl-2 protein expression that was observably elevated (P < 0.05), Bax protein expression that was highly reduced (P < 0.01), and Bax/Bcl-2 protein expression that was observably reduced (P < 0.05); the group treated with high selenium has Bcl-2 protein expression that was highly elevated (P < 0.01), Bax protein expression that was highly elevated (P < 0.01), and Bax/Bcl-2 protein expression that was highly reduced (P < 0.01); the groups treated with moderate selenium and high selenium have Bax mRNA expression that was highly reduced (P < 0.01), and the groups treated with high selenium have Bax/Bcl-2 mRNA expression that was observably reduced (P < 0.05). Selenium may inhibit the apoptosis of renal cells in fluorosis rats by regulating the expressions of Bcl-2 and Bax. The optimal dose of Na2SeO3 to protect against fluoride-induced renal cell apoptosis was determined to be 1.5mg/L.

Comparative study of p38 MAPK signal transduction pathway of peripheral blood mononuclear cells from patients with coal-combustion-type fluorosis with and without high hair selenium levels

Coal-combustion-type fluorosis has only been reported in China and its pathogenesis has not been fully understood. Fluoride causes chronic toxic effects and selenium modulates cellular activities through signal transduction in human cells. The present study enrolled three groups of subjects with well-defined serum and urine fluoride and hair selenium: high fluoride+high selenium group, high fluoride group and normal control group. The expressions of p38, NF-kB p65, caspase-3 and p53 genes at both protein and mRNA levels in peripheral blood mononuclear cells (PBMCs) were determined by Western blotting and quantitative real-time RT-PCR, respectively. The results showed that the expressions of p38, NF-kB p65, and caspase-3 protein in high fluoride group were higher than those in the other two groups. The mRNA level of NF-kB p65 and caspase-3 was significantly higher in high fluoride+high selenium group than control and lower than high fluoride group. The mRNA and protein level of p53 was significantly higher in high fluoride+high selenium group than that in other two groups. These results suggest that selenium may influence the protein and gene expression associated with p38 signal transduction pathway and up-regulate p53 expression in PBMCs from patients with coal-combustion-type fluorosis.

Correlation between selenium concentrations and glutathione peroxidase activity in serum and human prostate tissue

Low serum selenium concentration has been associated with increased risk of prostate cancer. A possible mechanism is through the antioxidant activity of selenoenzymes. However, the effect of selenium intake on selenoenzymes at target tissues is not well established. Hence, we investigated the correlation between serum and prostate tissue selenium concentrations and prostate tissue activity of glutathione peroxidase (GPX), a major selenoenzyme with antioxidant properties. In an ongoing study investigating gene expression in prostate tissue, we measured serum selenium concentration in 98 men using atomic absorption spectrometry. Of these men, we selected 12 men with the highest and 12 men with the lowest serum selenium concentrations and measured selenium concentration and GPX activity in fresh frozen prostate tissue using the cyclic neutron activation analysis and a direct spectrophotometric procedure, respectively. The mean serum selenium concentrations among low and high selenium groups were 123.7 +/- 5.9 and 196.7 +/- 16.6 microg/L (P < 0.0001), respectively. The corresponding mean prostate tissue selenium concentrations were 1.39 +/- 0.28 and 1.65 +/- 0.42 microg/g (P = 0.08), resulting in a positive correlation between serum and prostate tissue selenium concentrations (r = 0.56, P = 0.02). The mean prostate tissue GPX activity was non-significantly greater in the low serum selenium group (32.2 +/- 8.4 U/g protein) than in the high serum selenium group (29.6 +/- 5.9 U/g protein) (P = 0.39) and it was not correlated with serum or prostate tissue selenium concentrations (r = -0.22, P = -0.37 for serum and r = -0.33, P = 0.18 for prostate tissue). Serum and prostate tissue selenium concentrations were moderately correlated. In this population with relatively high selenium concentration, neither prostate tissue nor serum selenium concentrations were associated with prostate tissue GPX activity.

Effects of long-term selenium yeast supplementation on selenium status studied in the rat

To investigate the selenium status during long-term dietary supply of selenium yeast, 30-day-old male rats were fed for 379 days a methionine-adequate low-selenium diet supplemented with 0.2 mg Se/kg (selenium-adequate diet) or 1.5 mg Se/kg (high-selenium diet) in the form of selenium yeast that contained 60% of the element as l-selenomethionine. Their selenium load was determined at several intervals by neutron activation analysis of the selenium concentrations in the main selenium body pools, skeletal muscle and liver. After 64 days the tissue selenium concentrations plateaued in both groups and then stayed at that level. Compared with the selenium-adequate group, elevated tissue selenium concentrations were found in the high-selenium group, but the increase by a factor of 3.5 in the muscle and by a factor of 2.3 in the liver was smaller than the 7.5-fold increase in the selenium intake. In the selenium-adequate group about 50% of the muscle selenium and 30% of the liver selenium and in the high-selenium group about 85% of the muscle selenium and 70% of the liver selenium were estimated to be present in non-selenoprotein forms. During selenium depletion the liver glutathione peroxidase activity in the high-selenium group remained unaffected for 4 weeks and then decreased more slowly than that in the selenium-adequate group. From these results it can be concluded that selenium incorporated from the selenium yeast diet into non-selenoprotein forms can serve as an endogenous selenium source to maintain selenoprotein levels in periods of insufficient selenium supply.

Histological and ultrastructural changes induced by selenium in early experimental gastric carcinogenesis

To investigate the effect and significance of selenium in early experimental gastric carcinogenesis. Weaning male Wistar rats were divided randomly into normal control group, experiment control group, low selenium (2 mg/L) group and high selenium (4 mg/L) group. Wistar rat gastric carcinogenesis was induced by N-methyl-N-nitro-N-nitroso guanidine (MNNG) (20 mg/kg) gavage daily for 10 d. Na2SeO3 was given by piped drinking 1 wk prior to MNNG gavage. The rats were killed at the 43rd wk. The surface characteristics of gastric mucosa were observed with naked eyes. Histopathologic changes of rat gastric mucosa were observed by HE staining and AB-PAS methods. The changes of cellular ultrastructure were observed under transmission electron microscope. Statistical analysis was carried out by SPSS. The incidence rate of gastric mucosa erosion, hemorrhage and intestinal metaplasia was 0, 45.5%, 66.7%, and 92.9%, respectively (92.9% vs 45.5%, P < 0.05) in the normal control group, experiment control group, low selenium group, and high selenium group. Leiomyoma formed in the process of inducement of rat gastric carcinoma. Dietary Na2SeO3 (2 and 4 mg/L) slightly increased the incidence rate of leiomyoma (0, 23%, 46.6%, and 46.6%). gastric mucosa did not change in the course of rat gastric carcinogenesis. Dietary Na2SeO3 by pipe drinking could expand the intracellular secretory canaliculus of parietal cells and increase the number of endocrine cells and lysosomes. Dietary Na2SeO3 by pipe drinking aggravates gastric erosion, hemorrhage and promotes intestinal metaplasia of gastric mucosa. The mechanism may be related with the function of parietal cells.

Dietary Selenium Intake Modulates Thyroid Hormone and Energy Metabolism in Men

Most studies of selenium and thyroid hormone have used sodium selenite in rats. However, rats regulate thyroid hormone differently, and selenite, which has unique pharmacologic activities, does not occur in foods. We hypothesized that selenium in food would have different effects in humans. Healthy men were fed foods naturally high or low in selenium for 120 d while confined to a metabolic research unit. Selenium intake for all subjects was 47 microg/d (595 nmol/d) for the first 21 d, and then changed to either 14 (n = 6) or 297 (n = 5) microg/d (177 nmol/d or 3.8 micromol/d) for the remaining 99 d, causing significant changes in blood selenium and glutathione peroxidase. Serum 3,3',5-triiodothyronine (T3) decreased in the high selenium group, increased in the low selenium group, and was significantly different between groups from d 45 onward. A compensatory increase of thyrotropin occurred in the high selenium group as T3 decreased. The changes in T3 were opposite in direction to those reported in rats, but were consistent with other metabolic changes. By d 64, the high selenium group started to gain weight, whereas the low selenium group began to lose weight, and the weight changes were significantly different between groups from d 92 onward. Decreases of serum T3 and compensatory increases in thyrotropin suggest that a subclinical hypothyroid response was induced in the high selenium group, leading to body weight increases. Increases of serum T3 and serum triacylglycerol accompanied by losses of body fat suggest that a subclinical hyperthyroid response was induced in the low selenium group, leading to body weight decreases.

Absorption, Distribution and Excretion of Selenium from Beef and Rice in Healthy North American Men

Previous metabolic studies of selenium used pure selenium compounds with pharmacologic activities unrelated to selenium nutrition. Healthy men were fed foods naturally high or low in selenium while confined to a metabolic research unit. Selenium intake was 47 microg/d (595 nmol/d) for 21 d while energy intakes and body weights were stabilized and selenium excretion and intake came into metabolic balance. On d 22, selenium intake was changed to either 14 microg/d (177 nmol/d, low selenium) or 297 microg/d (3.8 micromol, high selenium) for the remaining 99 d. The absorption, distribution and excretion of selenium in food were similar to selenomethionine, and distinctly different from sodium selenite. Daily urinary selenium excretion and selenium concentrations in plasma and RBC showed the largest responses to selenium intake relative to interindividual variation. Urinary selenium and plasma selenium responded most rapidly to changes in selenium intake, whereas RBC reflected longer-term selenium intake. Given the difficulty of 24-h urine collections outside a metabolic research unit, RBC and plasma selenium seem to be the most useful indicators of selenium intake. During the intervention period, the high selenium group retained 15 mg (190 micromol) of selenium, with approximately 5 mg (63 micromol) going into skeletal muscle. The low selenium group lost only 0.9 mg (11 micromol) of whole-body selenium but lost 3.3 mg (42 micromol) from muscle, indicating that selenium was redistributed from muscle to tissues that have a higher metabolic priority for selenium such as testes. Fecal excretion decreased by half, representing an important but previously underappreciated adaptation to selenium restriction.

The effects of dietary selenium on the immune system in healthy men.

Eleven men were fed foods naturally high or low in selenium for 120 d. Selenium intake was stabilized at 47 microg/d for 21 d, then changed to either 13 or 297 microg/d for 99 d, leading to significantly different blood selenium and glutathione peroxidase concentrations. Serum immunoglobulins, complement components, and primary antibody responses to influenza vaccine were unchanged. Antibody titers against diphtheria vaccine were 2.5-fold greater after reinoculation in the high selenium group. White blood cell counts decreased in the high-selenium group and increased in the low-selenium group, resulting primarily from changes in granulocytes. Apparent increases in cytotoxic T-lymphocytes and activated T-cells in the high-selenium group only approached statistical significance. Lymphocyte counts increased on d 45 in the high-selenium group. In vitro proliferation of peripheral lymphocytes in autologous serum in response to pokeweed mitogen was stimulated in the high-selenium group by d 45 and remained elevated throughout the study, whereas proliferation in the low selenium group did not increase until d 100. This study indicates that the immune-enhancing properties of selenium in humans are the result, at least in part, of improved activation and proliferation of B-lymphocytes and perhaps enhanced T-cell function.

Selenate fortification of infant formulas improves the selenium status of preterm infants

The purpose of this study was to determine whether selenate fortification of infant formula would improve the selenium status of relatively well, growing, preterm infants during the first 12 wk of enteral feeding. A high-selenium group (n = 7, mean body weight = 1312 g) received selenate-fortified preterm and full-term infant formulas containing 0.36 and 0.22 mumol Se/L, respectively, and a low-selenium group (n = 10, mean body weight = 1262 g) received non-selenium-fortified preterm and full-term infant formulas containing 0.12 and 0.11 mumol Se/L, respectively. There were no significant differences in growth between the two groups throughout the study. The high-selenium group had significantly greater mean selenium intakes than did the low-selenium group from weeks 2 to 12. Plasma selenium concentrations decreased over the study period in the low-selenium group. Plasma selenium-dependent glutathione peroxidase activity was greater in the high-selenium group at week 12 only. Red blood cell selenium concentrations decreased over time in both groups and were significantly greater in the high-selenium group at weeks 4, 8, and 12. Plasma selenium concentrations were significantly correlated with plasma glutathione peroxidase activity for all infants on study day 1 and at weeks 4 and 12. Selenium intake of all infants was significantly correlated with plasma glutathione peroxidase activity at 12 wk. Selenate fortification of infant formulas can improve the selenium status of preterm infants. Current selenium contents of infant formulas and recommendations for dietary intakes of selenium for some preterm infants may be inadequate.

Selenium and difluoromethylornithine additively inhibit DMH-induced distal colon tumor formation in rats fed a fiber-free diet.

We investigated the effects of difluoromethylornithine, an inhibitor of ornithine decarboxylase (ODC) and selenium supplementation on tumor formation induced by the carcinogen 1,2-dimethylhydrazine (DMH) in Sprague-Dawley rats. A biochemical link between polyamine biosynthesis and selenium metabolism to its cancer preventative form has been suggested by the common requirement of S-adenosylmethionine. One-hundred and twenty male Sprague-Dawley rats were divided into experimental (n = 80) and control (n = 40) groups. Experimental animals received DMH 20 mg/kg s.c. for 20 weeks. Animals were fed either a regular diet (selenium content 0.2 p.p.m.) or a high selenium diet (5 p.p.m.) with or without 0.2% DFMO in the drinking water. At death, week 30, animal weights within experimental or control groups were not different between the four diet treatment groups. Tumor number and incidence in the proximal colon was not affected by DFMO treatment, selenium supplementation or the combined treatment. In contrast, in the distal colon, 19 tumors developed in the DFMO treated group, 22 tumors in the high selenium group and only 12 tumors in the combined high selenium/DFMO treatment group compared to 32 tumors in the regular diet group. Similarly, tumor incidence was decreased by DFMO and selenium supplementation and their effects were additive. In control animals, ODC activity was decreased by DFMO treatment and selenium supplementation in the distal colon and liver, but not the proximal colon. ODC activity of tumor tissue was greater than normal colon tissue from diet paired animals for proximal and distal colon, except for distal colonic tumors in the high selenium/DFMO treatment group. Polyamine content, however, did not correlate with ODC activity in normal or neoplastic tissue. In general, S-adenosylmethionine levels from normal colon and liver tissue were unaffected by diet treatment. Selenium supplementation in combination with DFMO treatment selectively inhibited distal colon tumor formation in rats fed a fiber-free diet.

Inhibition by selenium of intrahepatic cholangiocarcinoma induction in Syrian golden hamsters by N'-nitrosobis(2-oxopropyl)amine.

The effects of selenium supplementation on induction of cholangiocarcinomas and related precancerous lesions in female Syrian Golden hamsters by N'-nitrosobis(2-oxopropyl)amine (BOP) were investigated. Four-week-old animals were divided into two groups according to the selenium level contained in the drinking water (0.1 ppm or 4.0 ppm) and fed a purified diet containing less than 0.05 ppm of the trace element. Starting at Week 4 of the experiment, hamsters were administered 10 weekly injections of BOP (10 mg/kg body wt) and then killed 18 weeks after the last carcinogen administration. Animals receiving physiological saline alone served as controls. Cholangiocellular carcinomas tended to be reduced, and putative preneoplastic lesions of cholangiofibrosis were significantly decreased in the high-as opposed to the low-selenium groups in terms of both incidence rate and number per effective animal. The respective high and low selenium values for incidence and number were 24/38% and 0.34/0.66, respectively, for cholangiocarcinomas and 50/89% and 1.21/8.44, respectively, for cholangiofibroses. Proliferation of intrahepatic bile ducts was also significantly inhibited in the high-selenium group along with cyst formation. Biochemical investigation revealed both selenium level and glutathione peroxidase activity to be significantly greater in the high-than in the low-selenium group livers. The results thus suggest that selenium may inhibit BOP-induction of bile duct lesions, possibly via glutathione peroxidase-mediated alteration of carcinogenesis.

Inhibitory effect of selenium on hamster pancreatic cancer induction by n′‐nitrosobis(2‐oxopropyl)amine

The effect of selenium intake on the development of pancreatic cancer was investigated in female Syrian golden hamsters. Four-week-old hamsters were divided into 2 groups according to the selenium level in their drinking water and were fed a purified diet containing less than 0.05 ppm selenium. Starting 4 weeks later, groups received 10 s.c. injections at weekly intervals of N'-nitrosobis(2-oxopropyl)amine (BOP) dissolved in saline, while controls received saline alone. When the animals were killed 18 weeks after the last injection, palpable tumors were less frequent in the high-selenium group than in animals receiving low-selenium supplement, the numbers of histologically diagnosed cancerous lesions also being significantly reduced by high selenium intake. The selenium level and glutathione peroxidase activity in serum and pancreas were significantly greater in the high-selenium group. Moreover, selenium levels and glutathione peroxidase activity were both significantly higher in tumor-bearing tissue. The results suggest that glutathione peroxidase is involved as an intermediate factor in prevention of carcinogenesis by selenium.

Comparative Utilization of Fish Selenium and Inorganic Selenite by Rats of Normal Selenium Status

Rats of a normal selenium status were fed diets based on fish (rainbow trout) as the main protein source. A 4-week experiment with three dietary groups (low fish selenium, high fish selenium and selenite supplementation) was performed, and the selenium absorption, excretion and retention were recorded. Samples of blood serum, liver, kidneys, testes, hairs, spleen, lungs, heart, brain and skeletal muscle were collected for analysis of selenium. Glutathione peroxidase activity was measured in the blood serum. A selenium supplementation of approximately 1 mg/kg (high fish selenium and selenite group) yielded a selenium retention of only 7% of the intake, while in the group with a dietary selenium concentration of approximately 0.1 mg/kg (low fish selenium group) the selenium retention was 50%, resulting in almost the same absolute selenium retention in all three groups. The liver and kidneys showed the highest accumulations of selenium, reflecting the participation of these organs in the excretion of surplus selenium. The highest relative uptake of selenium was recorded in the testes, which increased equally in all dietary groups. The selenium concentration in the other tissues investigated, as well as the glutathione peroxidase activity in the blood serum responded little to the selenium supplementations. These results showed that the selenium levels normally found in fish were sufficient to satisfy the need for this element in rats of a good selenium status, and that inorganic selenite was absorbed and excreted at a high rate already after 1 week.