Profile of short-chain fatty acids and rectal proliferation in rats fed sucrose or cornstarch diets.

Rats were fed high fat (231 g/kg diet), low calcium (1.3 g/kg diet), low cellulose (20 g/kg diet) diets in which carbohydrates were represented by sucrose or starch (460 g/kg diet). A subgroup of animals was treated with 1,2-dimethylhydrazine (DMH) twice, 4 and 8 d before the beginning of the dietary treatments. Animals fed the starch diet, compared with those fed the sucrose diet, had higher concentrations of cecal and fecal short-chain fatty acids and a significantly lower acetic acid:butyric acid ratio in the cecal contents at d 105. Ratios were 14.7 +/- 1.7 and 6.8 +/- 0.4 for rats fed the sucrose and starch diets, respectively (P less than 0.01). Cecal pH was significantly lower in animals fed the starch diet for 105 d. At d 105, rectal proliferation was lower in rats fed the starch diet (labeled cells/crypt were 7.89 +/- 0.56 and 3.57 +/- 0.40 for rats fed the sucrose and starch diets, respectively, P less than 0.01); at d 30 the effect of starch on proliferation was evident in controls but not in DMH-treated rats. Rectal proliferation data were negatively correlated with the concentration and percentage of butyric acid and positively correlated with the percentage of acetic acid, the acetic acid:butyric acid ratio and cecal pH. These results suggest that low rectal proliferation in animals fed a high fat, high starch diet might be associated with a lower relative concentration of butyric acid in the cecal contents.