Selenoprotein P in plasma in relation to cancer morbidity in middle-aged Swedish men.

The premorbid level of selenoprotein P in plasma from subjects with cancer at different sites was compared with that from control subjects in a nested case-control study. A health screening of 12,500 middle-aged men was performed during 1974-1982 in Malmö, Sweden, and from the 400 cancer cases that were identified during follow-up until the end of 1988, 302 plasma samples were available for analysis of selenoprotein P. Two living controls per case of the same screening day and age were chosen. Selenoprotein P levels in subgroups of major cancer sites were lower in cases than in controls for the respiratory tract (1.20 and 1.30 arbitrary units, respectively; p < 0.05) cancer group. The odds ratio for overall cancer risk in the lowest quintile of selenoprotein P level compared with that in the highest was 5.2 [p (for trend) = 0.01]. In subgroups of major cancer sites, the odds ratios for cancer risk in the lowest tertile compared with the highest were 6.0 [p (for trend) = 0.004] in the respiratory tract and 3.4 [p (for trend) = 0.002] in the digestive tract. In cases + controls, selenoprotein P was lower in smokers than in nonsmokers (p < 0.05). Selenoprotein P was significantly correlated to plasma albumin, fasting blood glucose, and body mass index and inversely correlated to plasma alpha 1-antitrypsin and gamma-glutamyl transferase. The results suggest that a low plasma selenoprotein P level is associated with higher future risk of respiratory and digestive tract cancer in middle-aged men.

Plasma levels of selenium, selenoprotein P and glutathione peroxidase and their correlations to fish intake and serum levels of thyrotropin and thyroid hormones: a study on Latvian fish consumers.

OBJECTIVE: To study the relationships between fish intake and different markers of selenium status and thyroid hormone function. DESIGN: Cross-sectional study. SETTING AND SUBJECTS: Sixty-eight men (age 24-79 years) were recruited among coastal fishermen and inland subjects from Latvia. None of the subjects was on selenium medication or had any known endocrine disease. MAIN OUTCOME MEASURES: Correlations between fish intake, plasma levels of selenium, selenoprotein P, glutathione peroxidase, organic mercury in erythrocytes and TSH in serum. RESULTS: Selenium in plasma ranged from 0.30 to 1.56 micromol/l, selenoprotein P from 0.54 to 2.21 arbitrary units relative to pooled plasma, and glutathione peroxidase from 1.20 to 5.73 mg/l. The number of fish meals per month was correlated with plasma selenium, selenoprotein P and glutathione peroxidase (r = 0.63, r = 0.62 and r = 0.50, respectively; P<0.001). Plasma selenium was correlated with selenoprotein P and glutathione peroxidase (r = 0.88 and r = 0.67, respectively; P < 0.001), and also selenoprotein P and glutathione peroxidase were correlated (r = 0.63, P < 0.001). The mean plasma selenium level in those with a high fish intake (21-50 fish meals/month), was 81% higher than in those with lowest fish intake. TSH in serum was inversely correlated with plasma selenium and selenoprotein P. Thyroid hormone levels were not correlated with plasma selenium, selenoproteins or fish intake. CONCLUSIONS: In this study group, selenium from fish intake had a marked impact on all variables studied on selenium status. No impact of selenium status on T3 and T4 levels was observed. The slightly negative correlation of selenium status with TSH levels might indicate a higher TSH secretion at low selenium status.

Plasma selenoprotein P levels of healthy males in different selenium status after oral supplementation with different forms of selenium.

OBJECTIVE: To assess changes in selenoprotein P levels in plasma from subjects who had received oral supplements of different selenium forms. DESIGN: The same study group participated in two similar selenium supplementation trials, Trial I in 1981 (Levander et al, 1983) and Trial II in 1987 (Alfthan et al, 1991). During Trial II the mean baseline intake of selenium in Finland was higher compared to that during Trial I (100 and 40 microg/d, respectively), due to a nationwide supplementation of fertilisers which started in 1985. SUBJECTS: Fifty healthy Finnish men, 36-60 y old. INTERVENTION: The study group received daily placebo or oral supplements consisting of 200 microg selenium as selenium-enriched yeast, sodium selenate or selenium-enriched wheat (Trial I) or selenium-enriched yeast, sodium selenate or sodium selenite (Trial II). The duration of supplementation periods was 11 (Trial I) and 16 (Trial II) weeks. RESULTS: In Trial I the mean plasma selenoprotein P values in all the supplemented groups increased significantly, approaching a plateau at 2 weeks and reaching maxima at 4 weeks (mean increase 34%, P < 0.05). In Trial II the mean selenoprotein P levels of the supplemented groups were not significantly different from each other or from the placebo group at the start or at any time point of the supplementation period. CONCLUSIONS: At a low selenium status the selenoprotein P levels increased in a similar fashion after supplementation with different forms of selenium, but at a high selenium status no significant effects of supplementation with the same amount of selenium were observed. No differences in selenoprotein P levels were observed for inorganic and organic selenium supplements.

Selenoprotein P in patients on home parenteral nutrition.

BACKGROUND: The purpose of this study was to evaluate the use of selenoprotein P as an indicator of selenium status in patients receiving home parenteral nutrition. METHODS: Adult patients (n = 38) who had been on parenteral nutrition with no addition of selenium for 3 to 216 months were included in the study. Plasma samples were analyzed for selenium, selenoprotein P, and extracellular glutathione peroxidase (eGSHPx) using fluorimetry and newly developed radioimmunoassays. RESULTS: The mean plasma (+/- SD) eGSHPx and selenoprotein P in the patients were 1.9 +/- 1.2 mg/L and 0.7 +/- 0.4 arbitrary units, respectively, which corresponds to about 50% of the concentration measured in the plasma of the reference subjects (4.0 +/- 1.0 mg/L and 1.50 +/- 0.17 arbitrary units). The mean plasma selenium concentration was 0.5 +/- 0.4 mumol/L, which was approximately half of the concentration measured in the healthy subjects (1.1 +/- 0.2 mumol/L). Thirty-four (89%) and 20 (53%) patients, respectively, had selenoprotein P and eGSHPx values lower than mean - 2 SD of the reference material. The lowest values observed for selenoprotein P and eGSHPx were 3% and 2% of the reference mean. Selenoprotein P levels correlated significantly to eGSHPx (p = 0.88, p < .0001) and plasma selenium (p = 0.91, p < .0001). CONCLUSIONS: The positive correlations between selenoprotein P and eGSHPX and plasma selenium indicates that selenoprotein P may be used as a marker of selenium status in selenium-depleted patients.

Selenoprotein P in serum as a biochemical marker of selenium status.

Some characteristics of a radioimmunoassay of selenoprotein P (a major selenoprotein in human serum) are described. Polyclonal antibodies generated in rabbits were used and goat anti-rabbit-IgG antiserum was used as a second antibody. Depending on the concentration of selenoprotein P, 1-10 microliters of human serum were used in the assay. The relative standard deviation for the concentration of selenoprotein P was 6.3% between assays and 7.7% within assays. Different animal sera gave no significant interference, indicating that the antibodies did not react with non-human analogues of selenoprotein P. No indication of cross-reactivity could be found concerning extracellular glutathione peroxidase (another selenoprotein in serum). Addition of increasing amounts of normal human serum and partially purified selenoprotein P to the radioimmunoassay resulted in parallel curves. Incubation at 4 degrees C gave somewhat higher binding of labelled selenoprotein P than incubation at room temperature. The epitope, recognized by the antibodies, was apparently stable after storage of serum (in the frozen state for years, and in the cold for months). No significant amount of selenoprotein P could be demonstrated in red blood cells, and analysis of haemolysed whole blood gave expected data. Investigations of selenium status in different study groups indicated that in most cases the concentration of selenoprotein P in serum was positively correlated to that of glutathione peroxidase and serum selenium. In an intervention study, where subjects decreased their selenium intake to 50%, the serum levels of glutathione peroxidase and selenium decreased, but no significant decrease of selenoprotein P could be demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Variation in selenoprotein P concentration in serum from different European regions.

OBJECTIVE: To study the variation in selenoprotein P levels in serum among healthy subjects from 17 European regions representing nine countries. SUBJECTS: Survey of 414 37-70-year-old subjects (197/217 males/females) from 17 regions. RESULTS: The level of selenoprotein P varied significantly among regions and countries. When the highest concentration of selenoprotein P encountered in samples from Maldegem (Belgium), was set at 100%, the mean concentration for other regions was: 92% Barcelona; 91% Ipswich and London; 89% Malmö and Vosselaan; 86% Lisbon; 85% Netherlands; 83% Umeå; 82% Uppsala; 80% Paris; 79% Heidelberg; 78% Gothenburg and Grenoble; 74% Giessen; 71% Ioannina and 69% Epirus. When the data were pooled for the nine countries the highest selenoprotein P concentration was observed for subjects from Spain. When this concentration was set at 100%, the mean concentration for other countries was: 99% Belgium and United Kingdom, 94% Portugal, 92% Netherlands and Sweden, 86% France, 83% Germany and 76% Greece. The linear correlation between serum selenium and serum selenoprotein P in the whole sample was 0.68, P < 0.001 (n = 414), and it was similar in men and women. Despite this high correlation the mean ratio between selenoprotein P and selenium varied 1.3-fold among regions. CONCLUSIONS: Both the concentration of selenoprotein P as well as its proportion of total serum selenium in adult subjects vary among different European regions. Further studies are necessary to evaluate the physiological or medical implications of these differences.