A short-term intervention trial with selenate, selenium-enriched yeast and selenium-enriched milk: effects on oxidative defence regulation

Abstract

Increased Se intakes have been associated with decreased risk of cancer and CVD. Several mechanisms have been proposed, including antioxidant effects through selenoproteins, induction of carcinogen metabolism and effects on the blood lipid profile. In a 4 £ 1 week randomised, double-blind cross-over study, healthy young men supplemented their usual diet with selenate, Se-enriched yeast, Se-enriched milk or placebo (Se dose was 300 mg/d for selenate and Se-enriched yeast, and about 480 mg/d for Se-enriched milk) followed by 8-week washout periods. All Se sources increased serum Se levels after supplementation for 1 week. The effect of the organic forms did not differ significantly and both increased serum Se more than selenate. Conversely, thrombocyte glutathione peroxidase (GPX) was increased in the periods where subjects were supplemented with selenate but not in those where they were given Se-enriched yeast or Se-enriched milk. We found no effect on plasma lipid resistance to oxidation, total cholesterol, TAG, HDL-and LDL-cholesterol, GPX, glutathione reductase (GR) and glutathione S-transferase (GST) activities measured in erythrocytes, GPX and GR activities determined in plasma, or GR and GST activities in thrombocytes. Leucocyte expression of genes encoding selenoproteins (GPX1, TrR1 and SelP), and of electrophile response element-regulated genes (GCLC, Fra1 and NQO1) were likewise unaffected at all time points following intervention. We conclude that thrombocyte GPX is specifically increased by short-term selenate supplementation, but not by short-term supplementation with organic Se. Short-term Se supplementation does not seem to affect blood lipid markers or expression and activity of selected enzymes and a transcription factor involved in glutathione-mediated detoxification and antioxidation.

Increased consumption of wheat biofortified with selenium does not modify biomarkers of cancer risk, oxidative stress, or immune function in healthy Australian males

“…There was a weak negative correlation with CRP at baseline and at the end of the trial but no impact of Se supplementation on this biomarker of inflammation and cardiovascular disease. Our results are in agreement with those of Ravn-Haren et al [2008] who also showed no benefit of Se supplementation on conventional biomarkers of cardiovascular disease. In another study in patients with coronary artery disease there was no impact of Se supplementation (as selenite) on endothelial function, biomarkers of inflammation, or oxidative stress even though GPx activity was increased [Schnabel et al, 2008].…”

“…In a study of men at high risk for prostate cancer, DNA damage in lymphocytes measured by Comet assay was shown to be inversely associated with serum Se concentration for those with serum Se less than 98 lg/L but not for those with higher concentrations [Karunasinghe et al, 2004]. Increased Se intake has been associated with decreased risk for cardiovascular disease (CVD) but it is unknown whether this is due to Se-mediated reduction in lipid peroxidation, inhibition of inflammation, or an improved lipid profile in the blood [Ravn-Haren et al, 2008]. There is also a need to know that both CVD and cancer risk biomarkers are affected favorably and thus verify that benefits, if present, occur across multiple conditions of degenerative disease.…”

Level of selenoprotein transcripts in peripheral leukocytes of patients with bladder cancer and healthy individuals

“…Correlation between mRNA hGPx1, hGPx3, hSep15, hSeP1 and Se status showed no significant association in patients with TCC of the urinary bladder or healthy controls. Recent results by RavnHaren et al (23,24) also indicated lack of alterations in selenoprotein mRNA expression in WBCs after short-and long-term supplementation with Se. Following one week of non-organic or organic forms of Se supplementation in healthy young Danish men, there were no differences in expression of GPx1, cytosolic TrR1 and SeP1 in leukocytes.…”

“…This readily accessible human biological material can be easily used and is supposed to be a biomarker of nutritional status (24,25). The study performed on rats by Evenson et al (12) indicated that WBC rGPx1 mRNA concentrations can be a useful biomarker of the effects of Se exposure.…”

Speciation of selenium dietary supplements; formation of S-(methylseleno)cysteine and other selenium compounds

“…Due to the low abundance of selenium in some natural and common processed foods [7], a variety of selenium-enriched materials including yeast [23,24], milk [9], broccoli [25,26], garlic [27,28], green onions [29,30], green tea [31,32] and mushrooms [33,34] have been commercialized or proposed as selenium dietary supplements. Baker's yeast (Saccharomyces cerevisiae) is most commonly used for the production of supplements; selenized or 'high selenium yeasts' are prepared by growing yeast in a sodium selenite-enriched medium [35][36][37].…”