Suppression of azoxymethane-induced colon cancer development in rats by dietary resistant starch

Abstract

Resistant starch is a complex carbohydrate that reaches the colon where it can be fermented by the colonic microflora resulting in production of short chain fatty acids (SCFA), in particular butyrate. RS effects on colorectal tumourigenesis are contrasting and protection remains controversial. Butyrate has an important role as the preferred metabolic fuel and regulator of colonocyte proliferation, differentiation and apoptosis and may play a role in cancer prevention. Thus variation in butyrate production from different substrates might explain the variation in effect of RS. This study evaluated the hypothesis that feeding dietary resistant starch (as high amylose maize starch) would protect against azoxymethane (AOM)-colon carcinogenesis and favourably influence the colonic luminal environment. Male Sprague-Dawley rats (n = 90 were provided one of three diets: Control (without added dietary fibre or RS), 10% HAS (contained 100 g/kg raw high amylose maize starch) or 20% HAS (contained 200 g/kg high amylose maize starch). Rats were fed their experimental diets for 4 weeks after which they were injected with AOM (15 mg/kg) during the fifth and six week. Colons were resected (25 weeks post second injection) for evaluation of tumour formation, apoptosis, proliferating cell nuclear antigen (PCNA) labelling index and short chain fatty acid levels. Feeding resistant starch significantly reduced the incidence (P