Reference Number: 55
Gut microbiota has been well recognized in regulation of intestinal homeostasis and pathogenesis of inflammatory bowel diseases. However, the mechanisms involved are still not completely understood. Further, the components of the microbiota which are critically responsible for such effects are also largely unknown. Accumulating evidence suggests that, in addition to pathogen-associated molecular patterns, nutrition and bacterial metabolites might greatly impact the immune response in the gut and beyond. Short chain fatty acids (SCFA), which are metabolized by gut bacteria from otherwise indigestible fiber-rich diets, have been shown to ameliorate diseases in animal models of inflammatory bowel diseases (IBD) and allergic asthma. Although the exact mechanisms for the action of SCFA are still not completely clear, most notable among the SCFA targets is the mammalian G protein-coupled receptor pair of GPR41 and GPR43. In addition to the well-documented inhibition of histone deacetylases activity mainly by butyrate and propionate, which causes anti-inflammatory activities on IEC, macrophages, and dendritic cells, SCFA has recently been implicated in promoting development of Treg cells and possibly other T cells. In addition to animal models, the beneficial effects have also been reported from the clinical studies that used SCFA therapeutically in controlled trial settings in inflammatory disease, in that application of SCFA improved indices of IBD and therapeutic efficacy was demonstrated in acute radiation proctitis.
SIGNIFICANCE OF THIS STUDY
The current review summarises recent the importance and role of SCFA in the regulation of intestinal stability as well as in underlying causes of IBD. Our gastrointestinal tract harbours huge amounts of diverse microbes which collectively is called the microbiota. The microbiota not only contributes to the regulation of various physiological functions in our body, but also participates in the breakdown of food and energy. The gut bacteria have special enzymes that we humans lack for breaking down carbohydrates and turning them into different useful components. Usually undigested dietary fibers, as well as proteins and peptides, can be fermented in colon by our gut bacteria and one of the major products of these fermentative reactions are short chain fatty acids (SCFA). The principal SCFA in the gut are acetate, propionate and butyrate which constitute more than 95 % of all the SCFA content that is produced. These SCFAs are absorbed by the cells lining the colon which help in maintaining the integrity and structure of the epithelial layer which acts as a protective barrier in preventing the invasion of pathogens or the ‘leakage’ of essential nutrients from the gut into the blood stream. If these cells are deprived of SCFA this may limit the cells from carrying out their functions effectively thereby resulting in increased epithelial permeability triggerng an inflammatory response as seen in conditions such as IBS.