Alterations in the amounts of microbial metabolites in different regions of the mouse large intestine using variably fermentable fibres

Abstract

Understanding the fermentation profiles of dietary fibres in the different regions of the large intestine is needed to design dietary strategies for desired outcomes related to health such as targeting region-specific diseases. In order to test how variably fermentable dietary fibres affect microbial fermentation metabolites in different regions of the large intestine, mice were fed with fructooligosaccharides (FOS, fast fermentation rate), resistant starch type 2 (native potato, RS2, moderate fermentation rate), starch-entrapped microspheres (SM, very slow fermentation rate), and lignin (control) for 14 days. Analysis of intestinal contents obtained from the cecum, proximal colon, and distal colon revealed that short-chain fatty acid (SCFA) metabolites as well as branched-chain fatty acids (BCFA) levels in different regions of the large intestine were influenced by fibre type and rate of fermentation. Slower fermenting resistant starch-based fibres (RS2 and SM) produced more butyrate than FOS in the proximal and distal colon regions. SM substantially lowered the amount of total BCFAs in the distal colon compared to FOS, suggesting that SM promotes delayed saccharolytic activity throughout the colon. Moreover, the microbial analysis done with length-heterogeneity-PCR showed that all fermentable substrates shifted the microbial community with respect to the control group. Overall, our findings show that the type and amount of SCFAs and BCFAs generated in different regions of the large intestine is dietary fibre type and fermentation rate dependent, which should be considered for increasing the health promoting effects of dietary fibres.