Expression pattern of gastrointestinal selenoproteins - Targets for selenium supplementation

There is experimental and epidemiological evidence for an association betwe en low selenium levels and gastrointestinal cancer incidence, prevalence, a nd mortality. To identify targets for selenium supplementation in the human digestive tract, we examined mRNA expression of various selenocysteine-con taining proteins in normal mucosa biopsy specimens. Tissue samples from the esophagus and from different sites of the stomach, small bowel, and colon were obtained during endoscopies of the upper and lower gastrointestinal tr act Northern blot analyses revealed a lack of cytosolic glutathione peroxid ase mRNA bur a differential mRNA expression pattern of gastrointestinal and plasma glutathione peroxidase, selenoprotein P, and thioredoxin reductase. Glutathione peroxidase and thioredoxin reductase activities were detected in the mucosa of all biopsies, but the differential pattern did not reflect the differential mRNA steady-state levels. In addition to gastrointestinal glutathione peroxidase, which was found to play a role in colon cancer res istance, we identified further gastrointestinal selenoproteins, which may b e involved in gastrointestinal cell defense and cell differentiation.