By studying the effects of a fiber-free diet on the intestinal localization and metabolism of the pathobiont Mucispirillum schaedleri (Mucispirillum) and its role in preventing colitis, researchers investigate how EEN (exclusive enteral nutrition) aids in the treatment of Crohn’s disease (CD) in children.
Context
Childhood cases of inflammatory bowel disease, especially CD, are on the rise. An imbalance in the gut resulting from a mix of environmental and genetic factors can lead to chronic gastrointestinal disorders.
In pediatric CD, remission is frequently achieved with the restrictive liquid diet, known as EEN. This may be because of modifications in the composition of the gut microbiota. However, more investigation into gene nutrition and the gut microbiota is required to create customized dietary therapies for CD.
Concerning the study
In this work, the role of bacterial cultures in CD-like colitis was examined through culture under particular conditions. While Escherichia coli was grown aerobically in Lysogeny Broth (LB) medium and Ruminococcus torques in a specially prepared meat broth, Mucispirillum was cultured anaerobically in enriched Brain Heart Infusion (BHI) broth with additional nutrients.
For intestinal histopathology, mice free of specific pathogens were employed; their colon and cecum were removed and histologically analyzed. Dextran sodium sulfate was used to induce colitis and fluorescein isothiocyanate (FITC)-dextran was used to measure intestinal permeability.
The enzyme-linked immunosorbent assay was used to measure the levels of fecal lipocalin-2, a marker of inflammation (ELISA). Intestinal sections were subjected to fluorescence in situ hybridization (FISH) and immunofluorescence staining in order to visualize the mucus layer and bacteria.
Mouse cecal homogenates were used to examine the growth of E. coli or Mucispirillum. These samples’ nucleic acids were examined using the quantitative real-time polymerase chain reaction (qPCR) method.
The compositions of the microbiota were investigated using 16S ribosomal ribonucleic acid (rRNA) sequencing. Gene expression profiling was carried out using RNA-sequencing analysis.
A customized carbohydrate array was used to measure the growth of bacteria in the presence of various carbon sources. Mice were used in oral bacterial challenge experiments to examine inflammation and bacterial colonization.
Assays for hydrogen and ammonia were used to reveal metabolic activities in bacterial co-cultures, aiding in the analysis of interspecies interactions. The study’s reliability was guaranteed by the meticulous quantification and statistical analysis of the data.
Study results
Mice lacking the Nod2 and Cybb genes were subjected to spontaneous early-onset CD-like colitis induced by microbiota. In this experiment, a fiber-deficient diet (FD) and regular chow (RC) were contrasted. As demonstrated by a number of tests, including histological analysis and lower levels of inflammatory markers, the FD prevented the mice from developing colitis.
After more research, a specially designed control diet was employed, in which natural fiber sources were used to replace simple sugars in the FD to equal the fiber content in the RC. The mice developed diet-induced colitis, indicating a critical role for fiber in the development of CD. When administered therapeutically to mice with inflamed intestines, fiber also seems to successfully lessen disease symptoms.
The effect of FD on the gut microbiota, specifically on Mucispirillum abundance in the mucus layer, was one of the study’s key findings. Consequently, Mucispirillum moved from the mucus layer to the luminal compartment as a result of FD’s thinning of the mucus layer and increased gut permeability. This change was crucial because Mucispirillum’s pathogenicity in colitis is determined by where it is located in the mucus layer.
Subsequent research showed that Mucispirillum cannot colonize the intestine and cause inflammation without the intact mucus layer. It was also discovered that changes in the mucus layer brought on by diet had an impact on Mucispirillum’s vertical transmission during pregnancy.
The dissimilatory nitrate reduction to ammonia (DNRA) pathway by Mucispirillum within the mucus layer was found to be impacted by dietary fiber exclusion, which decreased its growth-promoting potential.
Moreover, the lack of fiber in the diet changed the number of fermentative hydrogen-producing bacteria, particularly those belonging to the Lachnospiraceae family. This had an impact on the bacteria’s ability to produce hydrogen and, in turn, on the interspecies hydrogen transfer that is necessary for Mucispirillum growth. This was especially true of the Lachnospiraceae member Ruminococcus torques (R. torques), which promoted Mucispirillum growth by hydrogen transfer.
In conclusion
The results of the study demonstrate the role of dietary fiber in the pathophysiology of CD-like colitis and offer significant new insights into the complex interactions between diet, gut microbiota, and intestinal disease. With an emphasis on the modification of particular microbial interactions in the gut, this research offers support for the creation of innovative dietary strategies for the management of CD.
