Enhancement of butyrate production in the rat caecocolonic tract by long-term ingestion of resistant potato starch

Some data suggest that the colonic microflora may adapt to produce more but yrate if given time and the proper substrate. To test this hypothesis, we i nvestigated the effect of prolonged feeding of resistant potato starch on b utyrate production. Rats were fed on either a low-fibre diet (basal) or the same diet supplemented with 90 g resistant potato starch/kg (PoS) for 0.5, 2 and 6 months. Short-chain fatty acid (SCFA) concentrations were determin ed in caecal and colonic contents at the end of each ingestion period. Tota l SCFA concentration increased over time throughout the caecocolonic tract with PoS, but was not modified with the basal diet. While propionate concen tration was unchanged, butyrate concentration was highly increased by PoS a t each time period in both the caecum and colon. Moreover, the butyrogenic effect of PoS increased over time, and the amount of butyrate was increased 6-fold in the caecum and proximal colon and 3-fold in the distal colon aft er 6 months compared with 0.5 months. Accordingly, the ratio butyrate:total SCFA increased over time throughout the caecocolonic tract (12.6 (SE 2.8) v. 28 (SE 1.8)% in the caecum, 10.5 (SE 1.4) v. 26.8 (SE 0.9)% in the proxi mal colon, and 7.3 (SE 2.4) v. 23.9 (SE 2.7)% in the distal colon at 0.5 v. 6 months respectively), while the proportion of acetate decreased. Neither the proportion nor the concentration of butyrate was modified over time wi th the basal diet. Butyrate production was thus promoted by long-term inges tion of PoS, from the caecum towards the distal colon, which suggests that a slow adaptive process occurs within the digestive tract in response to a chronic load of indigestible carbohydrates.