The influence of selenium-enriched milk proteins and selenium yeast on plasma selenium levels and rectal selenoprotein gene expression in human subjects

Abstract

Certain forms of dietary Se may have advantages for improving human Se status and regulating the risk for disease, such as cancers, including colorectal cancer (CRC). The present study compared the effects of a Se-enriched milk protein (dairy-Se) ith a Se-rich yeast (yeast-Se) on plasma Se levels and rectal selenoprotein gene expression since e reasoned that if these genes ere not regulated, there as little potential for regulating the risk for CRC in this organ. A total of t enty-three healthy volunteers ith plasma Se in the lo er half of the population range ere supplemented ith dairy-Se (150/d) or yeast-Se (150/d) for 6 eeks, follo ed by 6 eeks of ashout period. Blood as sampled every 2 eeks, and rectal biopsies ere obtained before and after Se supplementation and after the ashout period. Plasma Se levels and glutathione peroxidase (GPx) activity, and rectal mRNA of selenoprotein P (SeP), cytosolic GPx-1 (GPx-1), gastrointestinal GPx-2 (GPx-2) and thioredoxin reductase-1 (TrxR-1) ere measured. Plasma Se levels increased rapidly in both Se groups (P < 0•001); plasma GPx activity as not significantly changed. Rectal SeP mRNA increased at 6 eeks compared ith baseline in both Se groups (P < 0•05); only dairy-Se resulted in a sustained elevation of SeP after the ashout period (P < 0•05). Rectal GPx-1 and GPx-2 mRNA ere higher ith dairy-Se (P < 0•05) than ith yeast-Se at 6 eeks. In conclusion, three rectal selenoprotein mRNA ere differentially regulated by dairy-Se and yeast-Se. Changes in rectal selenoproteins are not predicted by changes in plasma Se; dairy-Se effectively regulates the expression of several rectal selenoproteins of relevance to the risk for CRC. © 2011 The Authors.