The gut-liver axis: impact of a mouse model of small-bowel bacterial overgrowth

Benign regulation of the gut microbiota: The possible mechanism through which the beneficial effects of manual acupuncture on cognitive ability and intestinal mucosal barrier function occur in APP/PS1 mice

Background

Gut microbiota dysbiosis and intestinal barrier injury play vital roles in Alzheimer’s disease (AD) onset and development. Our previous studies have demonstrated that manual acupuncture (MA) could improve the cognitive abilities of APP/PS1 mice. However, the effect of MA on the intestinal mucosal barrier and the gut microbiota mechanism through which this effect occurs remain to be clarified.

Methods

In the APP/PS1 manual acupuncture (Am) group, MA was applied in Baihui (GV20), Yintang (GV29), and Zusanli (ST36). Mice in the APP/PS1 antibiotic + manual acupuncture (Aa) group were treated with an antibiotic mixture and MA at the same time. Probiotics were delivered to the APP/PS1 probiotics (Ap) group. Alterations in spatial learning and memory, the gut microbiota, the intestinal barrier function, and the expression of glial fibrillary acidic protein (GFAP), lipopolysaccharide (LPS), and TNF-α were evaluated in each group.

Results

Compared with the C57BL/6 control (Cc) group, cognitive ability was significantly decreased, the gut microbiota structure was obviously disrupted, intestinal barrier integrity was drastically impaired, and the intestinal inflammatory response was enhanced in the APP/PS1 control (Ac) group (P < 0.01). These changes were reversed by MA and probiotics (P < 0.01 or P < 0.05), whereas antibiotics inhibited the benign regulation by MA (P < 0.01 or P < 0.05).

Conclusion

Manual acupuncture can benignly modulate gut microbiota dysbiosis, significantly reduce intestinal inflammation, and effectively alleviate the destruction of the intestinal mucosal barrier in APP/PS1 mice, and the effects are comparable to those of probiotics. The gut microbiota may play an important role in the improvement of the cognitive function and intestinal barrier function by MA.

Gut Microbiota at the Intersection of Alcohol, Brain, and the Liver

Over the last decade, increased research into the cognizance of the gut-liver-brain axis in medicine has yielded powerful evidence suggesting a strong association between alcoholic liver diseases (ALD) and the brain, including hepatic encephalopathy or other similar brain disorders. In the gut-brain axis, chronic, alcohol-drinking-induced, low-grade systemic inflammation is suggested to be the main pathophysiology of cognitive dysfunctions in patients with ALD. However, the role of gut microbiota and its metabolites have remained unclear. Eubiosis of the gut microbiome is crucial as dysbiosis between autochthonous bacteria and pathobionts leads to intestinal insult, liver injury, and neuroinflammation. Restoring dysbiosis using modulating factors such as alcohol abstinence, promoting commensal bacterial abundance, maintaining short-chain fatty acids in the gut, or vagus nerve stimulation could be beneficial in alleviating disease progression. In this review, we summarize the pathogenic mechanisms linked with the gut-liver-brain axis in the development and progression of brain disorders associated with ALD in both experimental models and humans. Further, we discuss the therapeutic potential and future research directions as they relate to the gut-liver-brain axis.

Wheat gluten intake increases the severity of experimental colitis and bacterial translocation by weakening of the proteins of the junctional complex

Gluten is only partially digested by intestinal enzymes and can generate peptides that can alter intestinal permeability, facilitating bacterial translocation, thus affecting the immune system. Few studies addressed the role of diet with gluten in the development of colitis. Therefore, we investigate the effects of wheat gluten-containing diet on the evolution of sodium dextran sulphate (DSS)-induced colitis. Mice were fed a standard diet without (colitis group) or with 4·5 % wheat gluten (colitis + gluten) for 15 d and received DSS solution (1·5 %, w/v) instead of water during the last 7 d. Compared with the colitis group, colitis + gluten mice presented a worse clinical score, a larger extension of colonic injury area, and increased mucosal inflammation. Both intestinal permeability and bacterial translocation were increased, propitiating bacteria migration for peripheral organs. The mechanism by which diet with gluten exacerbates colitis appears to be related to changes in protein production and organisation in adhesion junctions and desmosomes. The protein α-E-catenin was especially reduced in mice fed gluten, which compromised the localisation of E-cadherin and β-catenin proteins, weakening the structure of desmosomes. The epithelial damage caused by gluten included shortening of microvilli, a high number of digestive vacuoles, and changes in the endosome/lysosome system. In conclusion, our results show that wheat gluten-containing diet exacerbates the mucosal damage caused by colitis, reducing intestinal barrier function and increasing bacterial translocation. These effects are related to the induction of weakness and disorganisation of adhesion junctions and desmosomes as well as shortening of microvilli and modification of the endocytic vesicle route.

Effect of Peptides from Alaska Pollock on Intestinal Mucosal Immunity Function and Purification of Active Fragments

The intestinal mucosal barrier plays an important role in systemic immune functions. This study aimed to find the mechanism of peptide from Alaska Pollock (APP) on intestinal mucosal immunity in mice induced by cyclophosphamide (Cy). Cy-induced decreases of body weight and index of immune organ were significantly improved by APP as compared with Cy group (p < 0.05). APP could promote the secretion of SIgA and IgA on intestinal mucosa (p < 0.05) and mainly had an impact on the final differentiation of IgA⁺ B cell, thereby promoting the secretion of plasma cells, which can be corroborated by the increases of IL-6 and IL-10 (p < 0.05). APP with high immune activity was separated and two peptides were purified and identified as Gly–Val–Ile–Lys and Ala–Cys–Asn–Gly–Arg. Therefore, APP can be considered as beneficial ingredients to protect the intestinal barrier disruption induced by Cy.