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Research: HU and COLLEAGUES,
Listed in Issue 196
Abstract
HU and COLLEAGUES, Flinders Centre for Cancer Prevention and Control, Flinders University of South Australia, Adelaide, SA, Australia. ying.hu@flinders.edu.au compared the effects of a Se-enriched milk protein (dairy-Se) with a Se-rich yeast (yeast-Se) on plasma Se levels and rectal selenoprotein gene expression to evaluate colorectal cancer (CRC).
Background
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) with a Se-rich yeast (yeast-Se) on plasma Se levels and rectal selenoprotein gene expression since the authors reasoned that if these genes were not regulated, there was little potential for regulating the risk for CRC in this organ.
Methodology
A total of twenty-three healthy volunteers with plasma Se in the lower half of the population range were supplemented with dairy-Se (150 mug/d) or yeast-Se (150 mug/d) for 6 weeks, followed by 6 weeks of washout period. Blood was sampled every 2 weeks, and rectal biopsies were obtained before and after Se supplementation and after the washout 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) were measured.
Results
Plasma Se levels increased rapidly in both Se groups (P < 0.001); plasma GPx activity was not significantly changed. Rectal SeP mRNA increased at 6 weeks compared with baseline in both Se groups (P < 0.05); only dairy-Se resulted in a sustained elevation of SeP after the washout period (P < 0.05). Rectal GPx-1 and GPx-2 mRNA were higher with dairy-Se (P < 0.05) than with yeast-Se at 6 weeks.
Conclusion
In conclusion, three rectal selenoprotein mRNA were 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.
References
Hu Y, McIntosh GH, Le Leu RK, Upton JM, Woodman RJ, Young GP. The influence of selenium-enriched milk proteins and selenium yeast on plasma selenium levels and rectal selenoprotein gene expression in human subjects. British Journal of Nutrition. 106(4):572-82. Aug 2011.