Dietary resistant and butyrylated starches have different effects on the faecal bacterial flora of azoxymethane-treated rats.
Journal - The British journal of nutrition
Epidemiological studies have suggested that dietary fibre lowers the risk of colorectal cancer, which may be due to increased butyrate production from colonic fermentation of a type of fibre, resistant starch (RS). The present study investigated the effects of dietary RS and butyrylated RS on the faecal microbiota of rats treated with azoxymethane. A total of four groups of nine rats were fed diets containing either standard maize starch (low-amylose maize starch (LAMS), low RS), LAMS with 3 % tributyrin (LAMST), cooked 10 % high-amylose maize starch (HAMS, high RS) or cooked 10 % butyrylated HAMS (HAMSB). Faecal samples were examined by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments. Multivariate analysis demonstrated no differences between faecal microbiota before treatment but revealed differences in DGGE patterns between diet groups, with the exception of the two low-RS groups (LAMS and LAMST). Subsequent analysis identified eleven DGGE bands contributing significantly to the differentiation between diets. These phylotypes belonged to Clostridiales (five), Lactobacillus (one) and Bacteroidetes (five) lineages. Rats fed HAMS had increased concentration of propionate in their distal colonic digesta and developed faecal populations containing Ruminococcus bromii-like bacteria. HAMSB increased propionate and butyrate concentrations in distal colonic digesta and was associated with the appearance of two non-butyrate-producing bacteria, Lactobacillus gasseri and Parabacteroides distasonis. In conclusion, supplementation with specific dietary RS leads to changes in faecal microbiota profiles that may be associated with improved bowel health.
Phylotypes related to Ruminococcus bromii are abundant in the large bowel of humans and increase in response to a diet high in resistant starch.
Journal - FEMS microbiology ecology (England )
To further understand how diets containing high levels of fibre protect against colorectal cancer, we examined the effects of diets high in nonstarch polysaccharides (NSP) or high in NSP plus resistant starch (RS) on the composition of the faecal microbial community in 46 healthy adults in a randomized crossover intervention study. Changes in bacterial populations were examined using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. Bacterial profiles demonstrated changes in response to the consumption of both RS and NSP diets [analysis of similarities (ANOSIM): R=0.341-0.507, P<0.01]. A number of different DGGE bands with increased intensity in response to dietary intervention were attributed to as-yet uncultivated bacteria closely related to Ruminococcus bromii. A real-time PCR assay specific to the R. bromii group was applied to faecal samples from the dietary study and this group was found to comprise a significant proportion of the total community when individuals consumed their normal diets (4.4+/-2.6% of total 16S rRNA gene abundance) and numbers increased significantly (+/-67%, P<0.05) with the RS, but not the NSP, dietary intervention. This study indicates that R. bromii-related bacteria are abundant in humans and may be significant in the fermentation of complex carbohydrates in the large bowel.
|ISSN : ||0168-6496|
|Mesh Heading : ||Adult Aged Bacteria Diet Dietary Carbohydrates Fatty Acids Feces Female Humans Intestine, Large Male Middle Aged Molecular Sequence Data Phylogeny RNA, Ribosomal, 16S Ruminococcus Starch genetics growth & development analysis chemistry microbiology genetics|
|Mesh Heading Relevant : ||classification drug effects pharmacology microbiology classification drug effects pharmacology|