Intestinal microflora in the diabetes-prone bio-breeding rat and its possible relationship to the development of Type I diabetes

Bacteria play an important role in the development of the gut immune system and the development of gastro-intestinal disease, yet relatively few studies have focused on the role of the intestinal flora in the outcome of Type 1 diabetes. There is some evidence that exposing the Bio-Breeding diabetes-prone rat (BB rat) to food and bacterial antigens early in life delays and even suppresses later development of diabetes. This study used a culture-independent approach based on sequence variability in the 16S rDNA gene to analyse bacterial communities along different parts of the gastro-intestinal tract of the BB rat and their possible relationship to the development of diabetes. Several primers sets were evaluated to identify potential bias caused by primer length and PCR cycles.Primers for variable regions 6-8 of the 16S rDNA gene were found to accurately represent the distribution of bacteria when compared to full-length sequence data. We observed a difference in the gut bacterial communities between control and diabetic-prone BB rats. An uncultured bacterium was predominant in the lymph nodes of the young diabetic-prone BB rat, but was absent from the lymph node of young control animals. Denaturing gradient gel electrophoresis profiling and non-metric multi-dimensional scaling (NMDS) showed age-related differences in the gut microbiota. NMDS and analysis of the shared operational taxonomic units suggest that the gut-associated lymphoid tissue is sampling bacteria from both the small intestine and the distal colon. The age and condition associated differences found between the experimental groups suggest that the intestinal flora has a role in the development of type 1 diabetes. Factors influencing composition of the intestinal flora could be a target for studies of therapeutic interventions.