The rising consumption of plant protein foods and the emergence of meat alternatives have prompted interest in the health benefits of such products, which contain fiber in addition to protein. This review investigates the effect of fiber on plant-based protein metabolism and evaluates its contribution to gut-derived health impacts. Plant proteins, which often come with added fiber, can have varying health outcomes. Factors such as processing and the presence of fiber and starch influence the digestibility of plant proteins, potentially leading to increased proteolytic fermentation in the gut and the production of harmful metabolites. However, fermentable fiber can counteract this effect by serving as a primary substrate for gut microbes, decreasing proteolytic activity. The increased amount of fiber, rather than the protein source itself, plays a significant role in the observed health benefits of plant-based diets in human studies. Differences between extrinsic and intrinsic fiber in the food matrix further impact protein fermentation and digestibility. Thus, in novel protein products without naturally occurring fiber, the health impact may differ from conventional plant protein sources. The influence of various fibers on plant-based protein metabolism throughout the gastrointestinal tract is not fully understood, necessitating further research.

BACKGROUND: Alcohol-associated liver disease (ALD) is a leading cause of liver-related morbidity and mortality, but there are no therapeutic targets and modalities to prevent ALD-related liver fibrosis. Peroxisome proliferator activated receptor (PPAR) α and δ play a key role in lipid metabolism and intestinal barrier homeostasis, which are major contributors to the pathological progression of ALD. Meanwhile, elafibranor (EFN), which is a dual PPARα and PPARδ agonist, has reached a phase III clinical trial for the treatment of metabolic dysfunction-associated steatotic liver disease and primary biliary cholangitis. However, the benefits of EFN for ALD treatment is unknown.
OBJECTIVE: To evaluate the inhibitory effects of EFN on liver fibrosis and gut-intestinal barrier dysfunction in an ALD mouse model.
METHODS: ALD-related liver fibrosis was induced in female C57BL/6J mice by feeding a 2.5% ethanol (EtOH)-containing Lieber-DeCarli liquid diet and intraperitoneally injecting carbon tetrachloride thrice weekly (1 mL/kg) for 8 weeks. EFN (3 and 10 mg/kg/day) was orally administered during the experimental period. Histological and molecular analyses were performed to assess the effect of EFN on steatohepatitis, fibrosis, and intestinal barrier integrity. The EFN effects on HepG2 lipotoxicity and Caco-2 barrier function were evaluated by cell-based assays.
RESULTS: The hepatic steatosis, apoptosis, and fibrosis in the ALD mice model were significantly attenuated by EFN treatment. EFN promoted lipolysis and β-oxidation and enhanced autophagic and antioxidant capacities in EtOH-stimulated HepG2 cells, primarily through PPARα activation. Moreover, EFN inhibited the Kupffer cell-mediated inflammatory response, with blunted hepatic exposure to lipopolysaccharide (LPS) and toll like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling. EFN improved intestinal hyperpermeability by restoring tight junction proteins and autophagy and by inhibiting apoptosis and proinflammatory responses. The protective effect on intestinal barrier function in the EtOH-stimulated Caco-2 cells was predominantly mediated by PPARδ activation.
CONCLUSIONS: EFN reduced ALD-related fibrosis by inhibiting lipid accumulation and apoptosis, enhancing hepatocyte autophagic and antioxidant capacities, and suppressing LPS/TLR4/NF-κB-mediated inflammatory responses by restoring intestinal barrier function.

The interactions of different dietary doses of copper with fructose contribute to the development of metabolic dysfunction-associated steatotic liver disease (MASLD) via the gut-liver axis. The underlying mechanisms remain elusive. The aim of this study was to identify the specific pathways leading to gut barrier dysfunction in the ileum using a proteomics approach in a rat model. Male weanling Sprague Dawley rats were fed diets with adequate copper (CuA), marginal copper (CuM), or supplemented copper (CuS) in the absence or presence of fructose supplementation (CuAF, CuMF, and CuSF) for 4 weeks. Ileum protein was extracted and analyzed with an LC-MS. A total of 2847 differentially expressed proteins (DEPs) were identified and submitted to functional enrichment analysis. As a result, the ileum proteome and signaling pathways that were differentially altered were revealed. Of note, the CuAF is characterized by the enrichment of oxidative phosphorylation and ribosome as analyzed with the KEGG; the CuMF is characterized by an enriched arachidonic acid metabolism pathway; and focal adhesion, the regulation of the actin cytoskeleton, and tight junction were significantly enriched by the CuSF. In conclusion, our proteomics analysis identified the specific pathways in the ileum related to the different dietary doses of copper-fructose interactions, suggesting that distinct mechanisms in the gut are involved in the development of MASLD.

OBJECTIVE: Sepsis has a high incidence, morbidity, and mortality rate and is a great threat to human safety. Gut health plays an important role in sepsis development. Qi Huang Fang (QHF) contains astragalus, rhubarb, zhishi, and atractylodes. It is used to treat syndromes of obstructive qi and deficiency of righteousness. This study aimed to investigate whether QHF improves intestinal barrier function and microorganisms in mice through NLRP3 inflammatory vesicle-mediated cellular focal death.
METHODS: A mouse model of sepsis was constructed by cecal ligation and puncture (CLP) of specific pathogen-free (SPF)-grade C57BL/6 mice after continuous gavage of low, medium, and high doses of astragalus formula or probiotics for 4 weeks. Twenty-four hours postoperatively, the mechanism of action of QHF in alleviating septic intestinal dysfunction and restoring intestinal microecology, thereby alleviating intestinal injury, was evaluated by pathological observation, immunohistochemistry, western blotting, ELISA, and 16S rDNA high-throughput sequencing.
RESULTS: Different doses of QHF and probiotics ameliorated intestinal injury and reduced colonic apoptosis in mice to varying degrees (P < 0.05). Meanwhile, different doses of QHF and probiotics were able to reduce the serum levels of IL-6, IL-1β, and TNF-α (P < 0.05); down-regulate the protein expression of NLRP3, caspase-1, and caspase-11 (P < 0.05); and up-regulate the protein expression of zonula occluden-1 (ZO-1) and occludin (P < 0.05), which improved the intestinal barrier function in mice. In addition, QHF decreased the relative abundance of harmful bacteria (Firmicutes, Muribaculaceae, Campilobacterota, Helicobacter, and Alistipes) and increased the relative abundance of beneficial bacteria (Bacteroidetes and Actinobacteria) (P < 0.05).
CONCLUSIONS: QHF improves intestinal barrier function and gut microbiology in mice via NLRP3 inflammasome-mediated cellular pyroptosis.

In this study, an in vitro co-culture model using an electric cell-substrate impedance sensing system (ECIS) for testing the impact of real-time fermentation of non-digestible carbohydrates (NDCs) by the intestinal microbiota on gut barrier function was established. We applied Lactobacillus plantarum WCFS1 as a model intestinal bacterium and alginate-pectin as immobilization polymers as well as a source of NDCs to determine the impact of pectin fermentation on the barrier function of T84 gut epithelial cells. In the first design, L. plantarum WCFS1 was encapsulated in an alginate capsule followed by embedding in an agar layer to mimic a firm mucus layer that might be present in the colon. In this experimental design, the presence of the agar layer interfered with the transepithelial electrical resistance (TEER) measurement of T84 cells. Subsequently, we removed the agar layer and used encapsulated bacteria in an alginate gel and found that the TEER measurement was adequate. The encapsulation of the L. plantarum WCFS1 does avoid direct contact with cells. Also, the encapsulation system allows higher amounts of packing densities of L. plantarum WCFS1 in a limited space which can limit the oxygen concentration within the capsule and therefore create anaerobic conditions. To test this design, T84 cells were co-incubated with L. plantarum alginate-capsules supplemented with graded loads of fermentable pectin (0, 4, and 8 mg/ml per capsule) to investigate the effect of pectin fermentation on gut barrier function. We observed that as the pectin content in the L. plantarum capsules increased, pectin showed a gradually stronger protective effect on the TEER of the gut epithelium. This could partly be explained by enhanced SCFA production as both lactate and acetate were enhanced in L. plantarum containing alginate capsules with 8 mg/ml pectin. Overall, this newly designed in vitro co-culture model allows for studying the impact of bacteria-derived fermentation products but also for studying the direct effects of NDCs on gut barrier function in a relatively high-throughput way.

Microbial management is central to aquaculture\'s efficiency. Pediococcus acidilactici MA18/5M has shown promising results promoting growth, modulation of the immune response, and disease resistance in many fishes. However, the mechanisms through which this strain confers health benefits in fish are poorly understood, particularly in Pacific salmonid models. Briefly, the aims of this study were to i) assess the protective effects of P. acidilactici MA18/5M by examining gut barrier function and the expression of tight junction (TJ) and immune genes in vitro and in vivo, and ii) to determine the protective effects of this strain against a common saltwater pathogen, Vibrio anguillarum J382. An in vitro model of the salmonid gut was employed utilizing the cell line RTgutGC. Barrier formation and integrity assessed by TEER measurements in RTgutGC, showed a significant decrease in resistance in cells exposed only to V. anguillarum J382 for 24 h, but pre-treatment with P. acidilactici MA18/5M for 48 h mitigated these effects. While P. acidilactici MA18/5M did not significantly upregulate tight junction and immune molecules, pre-treatment with this strain protected against pathogen-induced insults to the gut barrier. In particular, the expression of ocldn was significantly induced by V. anguillarum J382, suggesting that this molecule might play a role in the host response against this pathogen. To corroborate these observations in live fish, the effects of P. acidilactici MA18/5M was evaluated in Chinook salmon reared in real aquaculture conditions. Supplementation with P. acidilactici MA18/5M had no effect on Chinook salmon growth parameters after 10 weeks. Interestingly, histopathological results did not show alterations associated with P. acidilactici MA18/5M supplementation, indicating that this strain is safe to be used in the industry. Finally, the expression pattern of transcripts encoding TJ and immune genes in all the treatments suggest that variation in expression is more likely to be due to developmental processes rather than P. acidilactici MA18/5M supplementation. Overall, our results showed that P. acidilactici MA18/5M is a safe strain for use in fish production, however, to assess the effects on growth and immune response previously observed in other salmonid species, an assessment in adult fish is needed.

Dietary fiber deprivation is linked to probiotic extinction, mucus barrier dysbiosis, and the overgrowth of mucin-degrading bacteria. However, whether and how mucin could rescue fiber deprivation-induced intestinal barrier defects remains largely unexplored. Here, we sought to investigate the potential role and mechanism by which exogenous mucin maintains the gut barrier function. The results showed that dietary mucin alleviated fiber deprivation-induced disruption of colonic barrier integrity and reduced spermine production in vivo. Importantly, we highlighted that microbial-derived spermine production, but not host-produced spermine, increased significantly after mucin supplementation, with a positive association with upgraded colonic Lactobacillus abundance. After employing an in vitro model, the microbial-derived spermine was consistently dominated by both mucin and Lactobacillus spp. Furthermore, Limosilactobacillus mucosae was identified as an essential spermine-producing Lactobacillus spp., and this isolated strain was responsible for spermine accumulation, especially after adhering to mucin in vitro. Specifically, the mucin-supplemented bacterial supernatant of Limosilactobacillus mucosae was verified to promote intestinal barrier functions through the increased spermine production with a dependence on enhanced arginine metabolism. Overall, these findings collectively provide evidence that mucin-modulated microbial arginine metabolism bridged the interplay between microbes and gut barrier function, illustrating possible implications for host gut health.
OBJECTIVE: Microbial metabolites like short-chain fatty acids produced by dietary fiber fermentation have been demonstrated to have beneficial effects on intestinal health. However, it is essential to acknowledge that certain amino acids entering the colon can be metabolized by microorganisms to produce polyamines. The polyamines can promote the renewal of intestinal epithelial cell and maintain host-microbe homeostasis. Our study highlighted the specific enrichment by mucin on promoting the arginine metabolism in Limosilactobacillus mucosae to produce spermine, suggesting that microbial-derived polyamines support a significant enhancement on the goblet cell proliferation and barrier function.

Anti-inflammatory activities of catechin-rich green tea extract (GTE) in obese rodents protect against metabolic endotoxemia by decreasing intestinal permeability and absorption of gut-derived endotoxin. However, translation to human health has not been established. We hypothesized that GTE would reduce endotoxemia by decreasing gut permeability and intestinal and systemic inflammation in persons with metabolic syndrome (MetS) compared with healthy persons. A randomized, double-blind, placebo-controlled, crossover trial in healthy adults (n = 19, 34 ± 2 years) and adults with MetS (n = 21, 40 ± 3 years) examined 4-week administration of a decaffeinated GTE confection (890 mg/d total catechins) on serum endotoxin, intestinal permeability, gut and systemic inflammation, and cardiometabolic parameters. Compared with the placebo, the GTE confection decreased serum endotoxin (P = .023) in both healthy persons and those with MetS, while increasing concentrations of circulating catechins (P < .0001) and γ-valerolactones (P = .0001). Fecal calprotectin (P = .029) and myeloperoxidase (P = .048) concentrations were decreased by GTE regardless of health status. Following the ingestion of gut permeability probes, urinary lactose/mannitol (P = .043) but not sucralose/erythritol (P > .05) was decreased by GTE regardless of health status. No between-treatment differences (P > .05) were observed for plasma aminotransferases, blood pressure, plasma lipids, or body mass nor were plasma tumor necrosis factor-α, interleukin-6, or the ratio of lipopolysaccharide-binding protein/soluble cluster of differentiation-14 affected. However, fasting glucose in both study groups was decreased (P = .029) by the GTE confection compared with within-treatment arm baseline concentrations. These findings demonstrate that catechin-rich GTE is effective to decrease circulating endotoxin and improve glycemic control in healthy adults and those with MetS, likely by reducing gut inflammation and small intestinal permeability but without affecting systemic inflammation.

Clostridioides difficile is a Gram-positive, anaerobic, spore-forming bacterium responsible for antibiotic-associated pseudomembranous colitis. Clostridioides difficile infection (CDI) symptoms can range from diarrhea to life-threatening colon damage. Toxins produced by C. difficile (TcdA and TcdB) cause intestinal epithelial injury and lead to severe gut barrier dysfunction, stem cell damage, and impaired regeneration of the gut epithelium. Current treatment options for intestinal repair are limited. In this study, we demonstrate that treatment with the microbial metabolite urolithin A (UroA) attenuates CDI-induced adverse effects on the colon epithelium in a preclinical model of CDI-induced colitis. Moreover, our analysis suggests that UroA treatment protects against C. difficile-induced inflammation, disruption of gut barrier integrity, and intestinal tight junction proteins in the colon of CDI mice. Importantly, UroA treatment significantly reduced the expression and release of toxins from C. difficile without inducing bacterial cell death. These results indicate the direct regulatory effects of UroA on bacterial gene regulation. Overall, our findings reveal a novel aspect of UroA activity, as it appears to act at both the bacterial and host levels to protect against CDI-induced colitis pathogenesis. This research sheds light on a promising avenue for the development of novel treatments for C. difficile infection.IMPORTANCETherapy for Clostridioides difficile infections includes the use of antibiotics, immunosuppressors, and fecal microbiota transplantation. However, these treatments have several drawbacks, including the loss of colonization resistance, the promotion of autoimmune disorders, and the potential for unknown pathogens in donor samples. To date, the potential benefits of microbial metabolites in CDI-induced colitis have not been fully investigated. Here, we report for the first time that the microbial metabolite urolithin A has the potential to block toxin production from C. difficile and enhance gut barrier function to mitigate CDI-induced colitis.

UNASSIGNED: Myopia is one of the most common eye diseases leading to blurred distance vision. Inflammatory diseases could trigger or exacerbate myopic changes. Although gut microbiota bacteria are associated with various inflammatory diseases, little is known about its role in myopia.
UNASSIGNED: The mice were randomly divided into control and model groups, with the model group being attached-30D lens onto the eyes for 3 weeks. Then, mouse cecal contents and plasma were collected to analyze their intestinal microbiota and plasma metabolome.
UNASSIGNED: We identified that the microbial composition differed considerably between the myopic and non-myopic mice, with the relative abundance of Firmicutes phylum decreased obviously while that of Actinobacteria phylum was increased in myopia. Furthermore, Actinobacteria and Bifidobacterium were positively correlated with axial lengths (ALs) of eyeballs while negatively correlated with refractive diopters. Untargeted metabolomic analysis identified 141 differentially expressed metabolites, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed considerable enrichment mainly in amino acid metabolism pathways. Notably, pathways involved glutamate metabolism including \"Glutamine and D-glutamate metabolism\" and \"Alanine, aspartate and glutamate metabolism\" was changed dramatically, which presented as the concentrations of L-Glutamate and L-Glutamine decreased obviously in myopia. Interestingly, microbiome dysbiosis and metabolites alternations in myopia have a disrupting gut barrier feature. We further demonstrated that the gut barrier function was impaired in myopic mice manifesting in decreased expression of Occludin, ZO-1 and increased permeation of FITC-dextran.
UNASSIGNED: Myopic mice had obviously altered gut microbiome and metabolites profiles compared to non-myopic mice. The dysbiosis and plasma metabolomics shift in myopia had an interrupting gut barrier feature. Our study provides new insights into the possible role of the gut microbiota in myopia and reinforces the potential feasibility of microbiome-based therapies in myopia.