Changes in fecal short-chain fatty acids following fecal microbiota transplantation in patients with irritable bowel syndrome

Background: Short-chain fatty acids (SCFAs) may play a role in the pathophysiology of irritable bowel syndrome (IBS). This study analyzed fecal SCFAs after performing fecal microbiota transplantation (FMT) in the IBS patients who were included in our previous study of the efficacy of FMT.

Methods: This study included 142 of the 164 IBS patients who participated in our previous study. They were belonging to three groups: placebo (own feces), 30-g (superdonor feces), and 60-g (superdonor feces) FMT. The patients completed the IBS Severity Scoring System (IBS-SSS) Birmingham IBS Symptom, Fatigue Assessment Scale (FAS), the IBS Quality of Life (IBS-QoL) and Short-Form Nepean Dyspepsia Index (SF-NDI) questionnaires and delivered fecal samples at the baseline and 1 month after FMT. The SCFA levels were determined by vacuum distillation followed by gas chromatography.

Key results: The fecal butyric acid level was significantly increased after FMT in both the 30-g and 60-g groups (both P ≤ 0.001). In the 60-g group, the levels of total SCFAs and isobutyric, isovaleric, and valeric acids increased after FMT. Butyric acid levels in the responders in both the 30-g and 60-g FMT groups were significantly inversely correlated with IBS-SSS and FAS scores (P = 0.001, r = -0.3 and P = 0.0001. r=- 0.3, respectively). There were no differences in the SCFA levels in the placebo group after FMT.

Conclusion and inferences: FMT increases the fecal SCFA levels in IBS patients. The increase in the butyric acid level is inversely correlated with symptoms in IBS patients following FMT, suggesting that SCFAs might play a role in the pathophysiology of IBS.