P-0179 Effects of γ-Oryzanol and Unsaponifiable Matter from Rice Bran Oil on Colon Carcinogenesis in Rats

Abstract

ABSTRACT Introduction Our previous study showed that rice bran oil (RBO) inhibited chemically induced colon carcinogenesis in rats. γ-Oryzanol, a major component in unsaponifiable matter (UM) of RBO, was reported to have an anti-cancer activity in vitro. However, the in vivo effect of γ-oryzanol and UM obtained from RBO on cancer has not been well known. The present study investigated the effect of γ-oryzanol and UM from RBO on colon carcinogenesis in rats. Methods Male F344 rats were fed control diet (C group), diets containing 0.8% γ-oryzanol (O group) or 0.8% UM (U group). 1,2-Dimethylhydrazine (DMH) and dextran sodium sulphate (DSS) were used to induce colon carcinogenesis. After 16 weeks, colons were examined for preneoplastic lesions including aberrant crypt foci (ACF) and mucin-depleted foci (MDF). Catalase and superoxide dismutase (SOD) activities in livers and colons, as well as total antioxidant capacity (TAC) in plasma were measured. Colonic expression of cyclooxygenase-2 (COX-2), a pro-inflammatory protein, was also assessed. Results ACF and MDF were induced by DMH/DSS treatment in all rats of C group. U group had lower MDF incidence and lower numbers of ACF and MDF than did C group; O group had lower number of MDF than did C group. DMH/DSS treatment caused a decrease in colonic catalase and SOD activities, a decrease in TAC and an increase in COX-2 expression, which were improved in U group compared with C group. Colonic SOD activity and COX-2 expression were improved in O group compared with C group. Conclusion γ-Oryzanol and unsaponifiable matter obtained from rice bran oil may suppress chemically induced colon carcinogenesis in rats via mechanisms related to anti-oxidation and anti-inflammation. Unsaponifiable matter from rice bran oil may be more effective than γ-oryzanol.