High amylose corn starch retarded 7, 12-dimethylbenz[ a]anthracene - induced mammary tumor development in female rats

Abstract

The present study was planned to examine the effect of partial replacement of corn starch (CS) with high amylose corn starch (HAS) on mammary tumor progression. The first experiment was to evaluate the effects of HAS on 7, 12-dimethylbenz[ a]anthracene (DMBA)-induced mammary tumor progression. Two days after DMBA administration (31 mg/kg body weight of rat) at age of 49 days, rats were assigned into 3 groups and fed one of the three experimental diets including CS, 30% HAS and 13.6% wheat bran (WB), respectively. The rats were examined weekly for palpable mammary tumors for 112 days. In the middle of experimental period, cumulative palpable tumors per tumorbearing rat were significantly lower in rats fed the HAS and WB diets than in those fed the CS diet. At autopsy, both mean tumor number and weight per tumor bearing rat were reduced by 10∼30% in rats fed the HAS and WB diets compared with those in the CS diet, but these differences were not significant. Serum estradiol-17 β concentration did not differ among rats fed the CS, HAS and WB diets, although fecal excretion of estradiol-17 β in rats fed the WB diet was significantly higher than those in rats fed the CS and HAS diets. In the second experiment, digestibilities of HAS and CS were compared in ileorectostomized rats. The results showed that only 66% of HAS were digested in the small intestine, whereas CS was digested up to 99%. In the 3rd experiment, postprandial blood glucose concentrations in rats intubated HAS suspension were significantly depressed when compared with that in rats intubated CS suspension. These results suggest that a mild energy restriction in HAS feeding is effective in prevention of mammary tumor progression.