Influences of transcutaneous neuromodulation on fecal microbiota and short chain fatty acids in patients with functional constipation.

OBJECTIVES: Transcutaneous neuromodulation (TN) has been reported effective for functional constipation (FC). The underlying mechanism remains unclear. In this study, we aimed to investigate the gut microbiota (GM) and short chain fatty acids (SCFAs) metabolism changed in FC patients due to TN treatment. The correlation between GM and 5-HT was evaluated. METHODS: Fourteen FC patients were recruited, and the FC related symptoms were evaluated by questionnaires before and after 4-week TN treatment. Blood and fecal samples were collected to assess the fecal microbiome and SCFAs. RESULTS: The richness and diversity of fecal microbiota were both found to be increased in FC patients before TN treatment. Fecal metabolomic differences between FC patients and healthy controls were observed at baseline, including elevated branched-chain SCFAs (isobutyric, isovaleric, and valeric acids) in FC. TN treatment did not significantly alter SCFA levels but improved constipation symptoms and increased plasma 5-HT. The correlation of Blautia-serotonin and 5-HT was observed in FC patients (r = 0.574, P = 0.035) and disappeared after TN treatment (r = 0.160, P = 0.584). CONCLUSION: TN treatment significantly improved the symptoms of FC patients and increased their plasma 5-HT expression levels. The correlation between 5-HT and Blautia-serotonin (which changed after TN treatment) indicated that the 5-HT changes caused by TN treatment might have a potential interaction with the dynamic changes of the intestinal microbiota.