Alterations in short-chain fatty acids and serotonin in irritable bowel syndrome: a systematic review and meta-analysis

Abstract

Background Short-chain fatty acids (SCFAs) and serotonin (5-hydroxytryptamine, 5-HT) may be associated with the pathogenesis of irritable bowel syndrome (IBS). There are some reports of alterations in SCFAs and 5-HT in IBS, but their results are inconsistent. We aimed to perform a meta-analysis to assess alterations in SCFAs and 5-HT in IBS patients and their potential role in the abnormal brain-gut-microbiota (BGM) axis. Methods Case–control studies detecting SCFAs and 5-HT in IBS patients were identified from PubMed, Web of Science, Cochrane Library, and Scopus databases to identify relevant articles up to September 2018. The standardized mean differences (SMDs) with 95% confidence intervals (CIs) of SCFAs and 5-HT were calculated by REVIEW MANAGER 5.3 to evaluate the alterations of 5-HT and SCFAs in IBS. Results Five studies on SCFAs and 5 on 5-HT in IBS patients were included. As compared to healthy controls (HCs), the SMDs of 5-HT in IBS patients was 2.35 (95% CI 0.46–4.24) and the SMDs of total SCFAs, acetic acid, propionic acid, and butyric acid in IBS patients were − 0.01 (95% CI − 0.57–0.55), − 0.04 (95% CI − 0.55–0.47), 0.07 (95% CI − 0.45–0.60), and − 0.00 (95% CI − 0.49–0.49), respectively. Conclusions There was an increase in 5-HT in blood of IBS patients, indicating the increased 5-HT in blood may be involved in IBS pathogenesis. However, there were no significant differences in SCFAs in feces between IBS patients and HCs. But the study did not differentiate between subgroups of IBS. These findings might provide insight for future studies of the BGM axis in the pathogenesis of IBS. Mei Luo and Xiaojun Zhuang contributed equally to the writing of this article

Microbiome, Mycobiome and Related Metabolites Alterations in Patients with Metabolic Syndrome—A Pilot Study

“…Short chain fatty acids (SCFAs) such as butyrate, propionate, and acetate produced primarily from the microbial fermentation of dietary fiber are thought to be key mediators of the beneficial effects of the gut microbiome [ 33 , 34 ]. SCFA directly modulate host health through tissue-specific mechanisms related to glucose homeostasis, gut barrier function, immunomodulation, and appetite regulation [ 35 ].…”

Crosstalk Between Intestinal Serotonergic System and Pattern Recognition Receptors on the Microbiota–Gut–Brain Axis

“…Irritable bowel syndrome (IBS) has been described as a gut–brain disorder, where the serotonergic system may be altered in both the intestine and the CNS ( 357 ). Interestingly, intestinal microbiota ( 358 ), as well as SCFAs and 5-HT, are altered in IBS patients ( 359 ). In addition, TLRs and NLRs play a chief role in the pathogenesis of IBS.…”

Phenethylamine-producing gut bacteria induces diarrhea-predominant irritable bowel syndrome by increasing serotonin biosynthesis

“…Gut microbial metabolites including butyrate, propionate, tyramine, deoxycholate and p-aminobenzoate have been shown to stimulate 5-HT biosynthesis in vitro, which provide fundamental understanding to the regulatory mechanisms of gut microbiota in regulating 5-HT (Yano et al, 2015). However, these metabolites including short fatty acids (butyrate and propionate) and deoxycholate are not altered in IBS-D patients (Luo et al, 2021;Wei et al, 2020). Although tyramine was found increased in inflammatory bowel disease (Santoru et al, 2017) and colorectal cancer (Salahshouri et al, 2021), we could not detect significant changes of tyramine and tyrosine in stool samples and fecal batch culture from IBS-D patients (Supplement Figure .S2 F-H).…”