Selenium-enriched milk proteins and selenium yeast affect selenoprotein activity and expression differently in mouse colon

Abstract

Certain forms of dietary Se may have an advantage in improving Se status and reducing cancer risk. The present study compared the effects of an Se-enriched milk protein product (dairy-Se) with an Se yeast (yeast-Se) on selenoprotein activity and expression in the mouse colon. Mice were fed four diets for 4 weeks: a control milk protein diet (Se at 0·068 parts per million (ppm)), dairy-Se diets with Se at 0·5 and 1 ppm, and a yeast-Se diet with Se at 1 ppm. Cytosolic glutathione peroxidase-1 (GPx-1) activity, mRNA of selenoprotein P (SeP),GPx-1, gastrointestinal glutathione peroxidase-2 (GPx-2) and thioredoxin reductase-1 (TrxR-1) were examined in the mouse colon. Dairy-Se diets did not significantly affectGPx-1mRNA and GPx-1 activity but produced a dose-dependent increase inSePandGPx-2mRNA, with a significantly higher level achieved at 1 ppm Se (P < 0·05). Yeast-Se at 1 ppm significantly increasedGPx-1mRNA and GPx-1 activity (P < 0·01) but notGPx-2mRNA. Neither Se supplement had any effect onTrxR-1. The present study indicates that selenoprotein levels in the mouse colon are regulated differently depending on the Se supplement. As we have previously shown that dairy-Se at 1 ppm was protective against colorectal cancer (CRC) in an azoxymethane-induced CRC mouse model, this up-regulation of colonicGPx-2andSePwith Se supplementation may be crucial to its chemopreventive action.