Hemolysate Thioredoxin Reductase and Glutathione Peroxidase Activities Correlate with Serum Selenium in a Group of New Zealand Men at High Prostate Cancer Risk

Abstract

The study provides data relating serum selenium concentration to activities of 2 key selenoenzymes, hemolysate thioredoxin reductase (TR) and glutathione peroxidase (GPx), measured by spectrophotometry, in a group of men at high risk for prostate cancer. This trial enrolled 43 patients with elevated prostate-specific antigen but negative biopsy for prostate cancer. Such individuals have a high risk of developing prostate cancer in the succeeding 5 y. In the men with baseline serum selenium concentrations ranging from 0.74-1.62 micromol/L (59-128 microg/L), hemolysate TR (r = 0.359, P < 0.05) and GPx (r = 0.341, P < 0.05) activities increased with increasing serum selenium. Furthermore, after a run-in period of 1 mo, men participated in a randomized, double-blind, placebo-controlled selenium supplementation trial for 6 mo and received a placebo, or 200 or 400 microg of Se per day, in the form of a seleno yeast. This study is a subsidiary of an ongoing Phase III cancer chemoprevention trial and, as such, randomization groups have not yet been revealed. After 6 mo of being on trial and with an estimated 66% of the group being supplemented with seleno yeast, the TR activity of the group increased by 80% relative to baseline. In contrast, 6 mo of selenium supplementation did not affect GPx activity. This study presents, to our knowledge for the first time, both measurements of human hemolysate TR activity and its relation to serum selenium.

Understanding Heterogeneity in Supplementation Effects of Selenium in Men: A Study of Stratification Variables and Human Genetics in a Prospective Sample from New Zealand

“…However, the RBC TR activity in this group showed a significant increase upon supplementation [52]. These observations indicate that RBC GPx activity is prioritised under low serum Se levels while RBC TR activity is compromised.…”

“…GPx and TR activities were measured following procedures given in Karunasinghe et al [52]. In brief, erythrocyte lysates were prepared from 100µl aliquots of EDTA bloods, as described for the Calbiochem Cellular glutathione peroxidase assay kit (Catalog No.…”

“…The upper estimated requirement considered the Se level necessary to produce maximal activity of plasma GPx, whereas the lower estimated requirement was based on the level required for two thirds of the maximal plasma GPx activity [49][50][51]. However, since these estimations were made, there have been studies that showed GPx activity plateau at a lower Se level compared to some other selenoproteins [52,53]. This indicates the danger of Se level requirement estimations based on GPx activity level alone.…”

Prostate Disease Risk Factors among a New Zealand Cohort

“…GPx and TR activities were measured in a subset of samples following procedures given in Karunasinghe et al [25]. Briefly, erythrocyte lysates were prepared from 100 µl aliquots of EDTA blood, as described for the Calbiochem Cellular glutathione peroxidase assay kit (catalog No.…”

O papel das selenoproteínas no câncer

“…However, GPx activity was not affected. 57 Observing the effect of selenium supplementation on GPx expression in different lung cancer cell lines (H460, H1703, H1944), Romanowska et al58 found that the full expression of GPx-1 and GPx-4 in these cells requires the presence of at least 100 nM of selenium. The impact of selenium supplementation varied according to the type of lung cancer cell and the type of GPx.…”