Yam (Dioscorea batatas Decne.) has long been used as a health food and oriental
folk medicine because of its nutritional fortification, tonic, anti-diarrheal, anti-inflammatory,
antitussive, and
expectorant effects.
Reactive oxygen species (ROS), which are known to be implicated in a range of diseases, may be important progenitors of
carcinogenesis. The aim of this study was to investigate the modulatory effect of yam on
antioxidant status and inflammatory conditions during
azoxymethane (AOM)-induced colon
carcinogenesis in male F344 rats. We measured the formation of
aberrant crypt foci (ACF), hemolysate
antioxidant enzyme activities, colonic mucosal
antioxidant enzyme gene expression, and colonic mucosal inflammatory mediator gene expression. The feeding of yam prior to
carcinogenesis significantly inhibited AOM-induced colonic ACF formation. In yam-administered rats, erythrocyte levels of
glutathione,
glutathione peroxidase (GPx), and
catalase were increased and colonic mucosal gene expression of
Cu/Zn-superoxide dismutase (SOD),
Mn-SOD, and GPx were up-regulated compared to the AOM group. Colonic mucosal gene expression of inflammatory mediators (i.e.,
nuclear factor kappaB,
inducible nitric oxide synthase,
cyclooxygenase-2,
tumor necrosis factor alpha, and
interleukin-1beta) was suppressed by the yam-supplemented diet. These results suggest that yam could be very useful for the prevention of
colon cancer, as they enhance the
antioxidant defense system and modulate inflammatory mediators.