The function of the gut microbiota-bile acid-TGR5 axis in diarrhea-predominant irritable bowel syndrome.

Imbalanced gut microbiota (GM) and abnormal fecal bile acid (BA) are thought to be the key factors for diarrhea-predominant irritable bowel syndrome (IBS-D), but the underlying mechanism remains unclear. Herein, we explore the influence of the GM-BA-Takeda G-protein-coupled receptor 5 (TGR5) axis on IBS-D. Twenty-five IBS-D patients and fifteen healthy controls were recruited to perform BA-related metabolic and metagenomic analyses. Further, the microbiota-humanized IBS-D rat model was established by fecal microbial transplantation (FMT) to investigate the GM-BA-TGR5 axis effects on the colonic barrier and visceral hypersensitivity (VH) in IBS-D. Finally, we used chenodeoxycholic acid (CDCA), an important BA screened out by metabolome, to evaluate whether it affected diarrhea and VH via the TGR5 pathway. Clinical research showed that GM associated with bile salt hydrolase (BSH) activity such as Bacteroides ovatus was markedly reduced in the GM of IBS-D, accompanied by elevated total and primary BA levels. Moreover, we found that CDCA not only was increased as the most important primary BA in IBS-D patients but also could induce VH through upregulating TGR5 in the colon and ileum of normal rats. TGR5 inhibitor could reverse the phenotype, depression-like behaviors, pathological change, and level of fecal BSH in a microbiota-humanized IBS-D rat model. Our findings proved that human-associated FMT could successfully induce the IBS-D rat model, and the imbalanced GM-BA-TGR5 axis may promote colonic mucosal barrier dysfunction and enhance VH in IBS-D. IMPORTANCE: Visceral hypersensitivity and intestinal mucosal barrier damage are important factors that cause abnormal brain-gut interaction in diarrhea-predominant irritable bowel syndrome (IBS-D). Recently, it was found that the imbalance of the gut microbiota-bile acid axis is closely related to them. Therefore, understanding the structure and function of the gut microbiota and bile acids and the underlying mechanisms by which they shape visceral hypersensitivity and mucosal barrier damage in IBS-D is critical. An examination of intestinal feces from IBS-D patients revealed that alterations in gut microbiota and bile acid metabolism underlie IBS-D and symptom onset. We also expanded beyond existing knowledge of well-studied gut microbiota and bile acid and found that Bacteroides ovatus and chenodeoxycholic acid may be potential bacteria and bile acid involved in the pathogenesis of IBS-D. Moreover, our data integration reveals the influence of the microbiota-bile acid-TGR5 axis on barrier function and visceral hypersensitivity.

Shenling Baizhu Powder Alleviates TNBS-Induced Colitis in Rats by Improving Intestinal Epithelial Permeability and Inhibiting Inflammation Through the TLR5/MyD88/NF-κB Pathway.

Aim of the study: To evaluate the protective effect and mechanism of shenling baizhu powder (SBP) on TNBS-induced colitis. Methods: Rats were given TNBS to establish the model of colitis and subsequently treated with different doses of SBP or mesalamine (MES). In addition, the expression of the TLR5/MyD88/NF-κB signaling pathway and critical targets of the intestinal mucosal barrier was detected by immunochemical analysis techniques. Results: SBP significantly ameliorated the symptoms of TNBS-induced colitis in rats and reduced the secretion of pro-inflammatory cytokines. SBP could effectively strengthen epithelial barrier integrity in TNBS-induced colitis by increasing the secretion of mucin and tight junction and inhibiting apoptosis. Furthermore, we identified the crucial role of the TLR5/MyD88/NF-κB signaling pathway in exerting the therapeutic effect of SBP. Conclusion: The results of our study suggest that SBP has therapeutic effects on TNBS-induced colitis and potential value in treating and maintaining remission of colitis.

Comparison of five diarrhea-predominant irritable bowel syndrome (IBS-D) rat models in the brain-gut-microbiota axis.

The brain-gut-microbiota (BGM) axis is known to be essential for diarrhea-predominant irritable bowel syndrome (IBS-D). In order to evaluate the effects of IBS-D rat models (the central sensitization model, the peripheral sensitization model and the compound model) on the BGM axis, five models were induced in Wistar rats with 4% acetic acid (AD, dissolved 0.4 ml of AD in 9.6 ml of ultrapure water) + wrap restrain stress (WRS), 4% AD, colorectal distention (CRD), WRS, and neonatal maternal separation (NMS). Abdominal withdrawal reflex (AWR) scale scores and the moisture content of feces (MCF) were evaluated on the day of completing modeling. Body weight was measured every 7 days during modeling. Brain gut peptides, cytokine levels, the activity of spinal cord neurons, intestinal mucosal barrier function, and gut microbiota were determined after induction of IBS-D. We found intervention with 4% AD + WRS, 4% AD, CRD, WRS, and NMS induced a similar course of effects on the BGM axis. Among the five models, AWR scores (60 mmHg, 80 mmHg) were all increased. The levels of 5-hydroxytryptamine, corticotropin-releasing factor, substance P, and calcitonin gene-related protein in serum rapidly increased, whereas that of neuropeptide Y decreased. C-fos in the spinal cord showed increased neuronal activity. The intestinal permeability was increased and the composition and structure of gut microbiota were changed. In conclusion, the five models could cause changes in BGM axis, but the 4% AD + WRS model was closer to the changes BGM axis of post-inflammatory models of IBS-D.

Clinical evidence of acupuncture and moxibustion for irritable bowel syndrome: A systematic review and meta-analysis of randomized controlled trials.

Background: Acupuncture and moxibustion have been widely used in the treatment of Irritable Bowel Syndrome (IBS). But the evidence that acupuncture and moxibustion for IBS reduction of symptom severity and abdominal pain, and improvement of quality of life is scarce. Methods: PubMed, Embase, Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure (CNKI), Chinese Scientific Journals Database (VIP), Wanfang Database, China Biomedical Literature Service System (SinoMed), and unpublished sources were searched from inception until June 30, 2022. The quality of RCTs was assessed with the Cochrane Collaboration risk of bias tool. The strength of the evidence was evaluated with the Grading of Recommendations Assessment, Development and Evaluation system (GRADE). Trial sequential analysis (TSA) was conducted to determine whether the participants in the included trials had reached optimal information size and whether the cumulative data was adequately powered to evaluate outcomes. Results: A total of 31 RCTs were included. Acupuncture helped reduce the severity of symptoms more than pharmaceutical drugs (MD, -35.45; 95% CI, -48.21 to -22.68; I 2 = 71%). TSA showed the cumulative Z score crossed O'Brien-Fleming alpha-spending significance boundaries. Acupuncture wasn't associated with symptom severity reduction (SMD, 0.03, 95% CI, -0.25 to 0.31, I 2 = 46%), but exhibited therapeutic benefits on abdominal pain (SMD, -0.24; 95% CI, -0.48 to -0.01; I 2 = 8%) compared to sham acupuncture. Moxibustion show therapeutic benefits compared to sham moxibustion on symptom severity (SMD, -3.46, 95% CI, -5.66 to -1.27, I 2 = 95%) and abdominal pain (SMD, -2.74, 95% CI, -4.81 to -0.67, I 2 = 96%). Acupuncture (SMD, -0.46; 95% CI, -0.68 to -0.24; I 2 = 47%) and the combination of acupuncture and moxibustion (SMD, -2.00; 95% CI, -3.04 to -0.96; I 2 = 90%) showed more benefit for abdominal pain compared to pharmacological medications as well as shams. Acupuncture (MD, 4.56; 95% CI, 1.46-7.67; I 2 = 79%) and moxibustion (MD, 6.97; 95% CI, 5.78-8.16; I 2 = 21%) were more likely to improve quality of life than pharmaceutical drugs. Conclusion: Acupuncture and/or moxibustion are beneficial for symptom severity, abdominal pain and quality of life in IBS. However, in sham control trials, acupuncture hasn't exhibited robust and stable evidence, and moxibustion's results show great heterogeneity. Hence, more rigorous sham control trials of acupuncture or moxibustion are necessary. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=262118, identifier CRD42021262118.