Abstract A74: Inhibition of azoxymethane-induced preneoplastic lesions in the rat colon by a novel resistant starch cooked by different methods

Abstract

Abstract The purpose of this study was to test the inhibitory effects of a novel resistant starch cooked by two different methods on azoxymethane (AOM)-induced colon carcinogenesis in rats. The novel resistant starch (RS)(patent pending) was processed from commercial high amylose cornstarch. A normal cornstarch (CS) and the high amylose cornstarch (HA) were used as negative and positive control starch groups, respectively. Two cooking methods were applied to all the three starches: (1) making each starch into bread using a standard bakery procedure (cB). (2) using boiling water, high moisture cooking method (cW). Then the starches were mixed with other ingredients based on AIN-93 formulations into 6 rat diets: bread normal-cornstarch diet (cB-CS), bread high-amylose-cornstarch diet (cB-HA), bread novel-resistant-starch diet (cB-RS), boiling-water-high-moisture normal-cornstarch diet (cW-CS), boiling-water-high-moisture high-amylose-cornstarch diet (cW-HA), and boiling-water-high-moisture novel-resistant-starch diet (cW-RS). Six groups of 5-week-old male Fischer 344 rats including 15 animals each were injected with two doses of 20 mg/kg bw AOM one week apart and fed the above diets respectively. Another six groups of male Fischer 344 rats with 5 animals in each group were injected with saline and fed the same six kinds of diets as the AOM treated groups. The rats were fed for 8 weeks after the second injection and then killed. Caecum weight and pH, Aberrant Crypt Foci (ACF) and Mucin Depleted Foci (MDF) were investigated. ACF and MDF were only seen with AOM treatment. The ACF numbers for cB-CS, cB-HA, cB-RS, cW-CS, cW-HA, and cW-RS groups were 29, 29, 17, 225, 256, and 121, respectively. The MDF numbers for the above diet groups were 6.1, 4.9, 1.9, 10.7, 8.7 and 2.1, respectively. ACF and MDF numbers were significantly reduced in rats fed novel resistant starch diet in comparison with rats fed the other two diets (P<0.0001). When comparing the two cooking methods, the cB diet groups also showed a significantly decrease in preneoplastic lesion numbers compared with the cW diet groups (P<0.0003). Increased caecum weight and decreased caecum pH were also observed in the novel resistant starch diet group in comparison with the other two diet groups (P<0.05). These results suggested that the novel resistant starch, which is less digestible than regular cornstarch or commercial high amylose cornstarch, may inhibit colonic carcinogenesis. The cooking method could also be important since the bread baking procedure showed significantly more effectiveness in the inhibition than the boiling water high moisture method. The inhibition might be related to increased caecal fermentation. Citation Information: Cancer Prev Res 2010;3(1 Suppl):A74.