Comparison of bacterial composition, concentration, and metabolism of short chain fatty acid in inflammatory bowel disease: A systematic review

Inflammatory bowel disease (IBD), which consists of Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory disorder of the intestine. The etiology is heterogeneous and multifactorial, including genetic susceptibility, immune-mediated tissue damage, and changes of lumen microenvironment, especially short-chain fatty acid (SCFA) producing bacteria. Several studies reported a decrease in SCFA concentration in both CD and UC. In fact, SCFAs has important roles in accelerating disease remission. This systematic review aimed to evaluate the changes in SCFA concentration, the composition of SCFA-producing bacteria, and SCFA metabolism in IBD. A literature search was conducted via PubMed, Scopus, and CENTRAL by selecting studies according to inclusion and exclusion criteria. The quality and risk of bias assessment were performed using the Newcastle-Ottawa Scale (NOS). Overall, 160 UC and 127 CD patients from 5 studies were reviewed. The SCFA concentration was significantly reduced (p <0.05) in both PC and UC. Moreover, there was a decrease in major SCFA-producing bacteria. Clostridium coccoides were significantly decreased in the feces of active UC (p = 0.015) and CD (p = 0.04). Clostridium leptum was decreased on intestinal mucosal biopsy of active CD and UC (p <0.0001). Faecalibacterium prausnitzii were decreased in active CD faeces (p <0.0001) and UC (p = 0.0001). Butyrate oxidation rate was also reported to decrease in UC compared to control (p<0.0001). In conclusion, the ability of major SCFA-producing bacterial production in IBD was diminished, which implies a decreased protective and anti-inflammatory effect of SCFA that altered its metabolism.