Electro-acupuncture promotes gut motility and alleviates functional constipation by regulating gut microbiota and increasing butyric acid generation in mice

Objective: Abnormalities in the gut microbiota and intestinal short-chain fatty acid(SCFA) levels are implicated in the pathogenesis of functional constipation(FC). Electro-acupuncture(EA) has been shown to improve constipation-related symptoms and rebalance the gut microbiota. However, it is currently unknown whether the gut microbiota is a key mechanistic target for EA or how EA promotes gut motility by regulating the gut microbiota and SCFAs. Therefore, we assessed the effects of EA in FC mice and pseudo-germfree(PGF) mice to address these questions.Methods: Forty female Kunming mice were randomly separated into a normal control group(n = 8), an FC group(n = 8), an FC + EA group(n = 8), a PGF group(n = 8) and a PGF + EA group(n = 8). The FC group and FC + EA group were treated with diphenoxylate to establish the FC model; the PGF group and PGF + EA group were given an antibiotic cocktail to initiate the PGF model. After maintaining the model for 14 d, mice in the FC + EA and PGF + EA groups received EA stimulation at the ST25 and ST37 acupoints, once a day, 5 times per week, for 2 weeks. Fecal parameters and intestinal transit rate were calculated to assess the efficacy of EA on constipation and gastrointestinal motility. Colonic contents were used to quantify gut microbial diversity using 16S r RNA sequencing, and measure SCFA concentrations using gas chromatography-mass spectrometry.Results: EA significantly shortened the first black stool defecation time(P < 0.05) and increased the intestinal transit rate(P < 0.01), and fecal pellet number(P < 0.05), wet weight(P < 0.05) and water content(P < 0.01) over 8 h, compared with the FC group, showing that EA promoted gut motility and alleviated constipation. However, EA treatment did not reverse slow-transit colonic motility in PGF mice(P > 0.05), demonstrating that the gut microbiota may play a mechanistic role in the EA treatment of constipation. In addition, EA treatment restored the Firmicutes to Bacteroidetes ratio and significantly increased butyric acid generation in FC mice(P < 0.05), most likely due to the upregulation of Staphylococcaceae microorganisms(P < 0.01).Conclusion: EA-mediated resolution of constipation occurs through rebalancing the gut microbiota and promoting butyric acid generation.