Gut Bacteria-derived Membrane Vesicles Induce Colonic Dysplasia by Inducing DNA Damage in Colon Epithelial Cells.

BACKGROUND & AIMS: Colorectal cancer (CRC) is the third most common cancer in the world. Gut microbiota has recently been implicated in the development of CRC. Actinomyces odontolyticus is one of the most abundant bacteria in the gut of patients with very early stages of CRC. A odontolyticus is an anaerobic bacterium existing principally in the oral cavity, similar to Fusobacterium nucleatum, which is known as a colon carcinogenic bacterium. Here we newly determined the biological functions of A odontolyticus on colonic oncogenesis. METHODS: We examined the induction of intracellular signaling by A odontolyticus in human colonic epithelial cells (CECs). DNA damage levels in CECs were confirmed using the human induced pluripotent stem cell-derived gut organoid model and mouse colon tissues in vivo. RESULTS: A odontolyticus secretes membrane vesicles (MVs), which induce nuclear factor kappa B signaling and also produce excessive reactive oxygen species (ROS) in colon epithelial cells. We found that A odontolyticus secretes lipoteichoic acid-rich MVs, promoting inflammatory signaling via TLR2. Simultaneously, those MVs are internalized into the colon epithelial cells, co-localize with the mitochondria, and cause mitochondrial dysfunction, resulting in excessive ROS production and DNA damage. Induction of excessive DNA damage in colonic cells by A odontolyticus-derived MVs was confirmed in the gut organoid model and also in mouse colon tissues. CONCLUSIONS: A odontolyticus secretes MVs, which cause chronic inflammation and ROS production in colonic epithelial cells, leading to the initiation of CRC.

Effects of probiotic supplementation on chronic inflammatory process modulation in colorectal carcinogenesis.

The current study investigated the potential effects of probiotic supplementation on colorectal carcinogenesis chemically induced with 1,2-dimethylhydrazine (DMH) and treated with 5-fluorouracil (5FU)-based chemotherapy in mice. Animals were randomly allocated in five different groups: Control: which not receive any treatment throughout the experimental course; Colitis model group (DMH): treated with DMH; DMH+ 5FU: animals received I.P. (intraperitoneal) dose of chemotherapy on a weekly basis; DMH+PROB: animals received daily administrations (via gavage) of probiotics (Lactobacillus: acidophilus and paracasei, Bifidobacterium lactis and bifidum); and DMH+ PROB+ 5FU: animals received the same treatment as the previous groups. After ten-week treatment, mice's large intestine was collected and subjected to colon length, histopathological, periodic acid-schiff (PAS) staining and immunohistochemistry (TLR2, MyD88, NF-κB, IL-6, TLR4, TRIF, IRF-3, IFN-γ, Ki-67, KRAS, p53, IL-10, and TGF-ß) analyzes. Variance (ANOVA) and Kruskal-Wallis tests were used for statistical analysis, at significance level p 0.05. Probiotics' supplementation has increased the production of Ki-67 cell-proliferation marker, reduced body weight, and colon shortening, as well as modulated the chronic inflammatory process in colorectal carcinogenesis by inhibiting NF-κB expression and mitigating mucin depletion. Thus, these findings lay a basis for guide future studies focused on probiotics' action mechanisms in tumor microenvironment which might have implications in clinical practice.

Diet-induced shifts in the gut microbiota influence anastomotic healing in a murine model of colonic surgery.

Host diet and gut microbiota interact to contribute to perioperative complications, including anastomotic leak (AL). Using a murine surgical model of colonic anastomosis, we investigated how diet and fecal microbial transplantation (FMT) impacted the intestinal microbiota and if a predictive signature for AL could be determined. We hypothesized that a Western diet (WD) would impact gut microbial composition and that the resulting dysbiosis would correlate with increased rates of AL, while FMT from healthy, lean diet (LD) donors would reduce the risk of AL. Furthermore, we predicted that surgical outcomes would allow for the development of a microbial preclinical translational tool to identify AL. Here, we show that AL is associated with a dysbiotic microbial community characterized by increased levels of Bacteroides and Akkermansia. We identified several key taxa that were associated with leak formation, and developed an index based on the ratio of bacteria associated with the absence and presence of leak. We also highlight a modifiable connection between diet, microbiota, and anastomotic healing, potentially paving the way for perioperative modulation by microbiota-targeted therapeutics to reduce AL.

Lcn2 deficiency accelerates the infection of Escherichia coli O157:H7 by disrupting the intestinal barrier function.

Bacterial infections result in intestinal inflammation and injury, which affects gut health and nutrient absorption. Lipocalin 2 (Lcn2) is a protein that reacts to microbial invasion, inflammatory responses, and tissue damage. However, it remains unclear whether Lcn2 has a protective effect against bacterial induced intestinal inflammation. Therefore, this study endeavors to investigate the involvement of Lcn2 in the intestinal inflammation of mice infected with Enterohemorrhagic Escherichia coli O157:H7 (E. coli O157:H7). Lcn2 knockout (Lcn2-/-) mice were used to evaluate the changes of inflammatory responses. Lcn2 deficiency significantly exacerbated clinical symptoms of E. coli O157:H7 infection by reducing body weight and encouraging bacterial colonization of. Compared to infected wild type mice, infected Lcn2-/- mice had significantly elevated levels of pro-inflammatory cytokines in serum and ileum, including interleukin (IL)-6, IL-1ß, and tumor necrosis factor-α (TNF-α), as well as severe villi destruction in the jejunum. Furthermore, Lcn2 deficiency aggravated intestinal barrier degradation by significantly reducing the expression of tight junction proteins occludin and claudin 1, the content of myeloperoxidase (MPO) in the ileum, and the number of goblet cells in the colon. Our findings indicated that Lcn2 could alleviate inflammatory damage caused by E. coli O157:H7 infection in mice by enhancing intestinal barrier function.

Colon-Targeted Release of Gel Microspheres Loaded with Antioxidative Fullerenol for Relieving Radiation-Induced Colon Injury and Regulating Intestinal Flora.

Radiation-induced colitis is a serious clinical problem worldwide. However, the current treatment options for this condition have limited efficacy and can cause side effects. To address this issue, colon-targeted fullerenol@pectin@chitosan gel microspheres (FPCGMs) are developed, which can aggregate on colon tissue for a long time, scavenge free radicals generated in the process of radiation, and regulate intestinal flora to mitigate damage to colonic tissue. First, FPCGMs exhibit acid resistance and colon-targeted release properties, which reduce gastrointestinal exposure and extend the local colonic drug residence time. Second, fullerenol, which has a superior scavenging ability and chemical stability, reduces oxidative stress in colonic epithelial cells. Based on this, it is found that FPCGMs significantly reduce inflammation in colonic tissue, mitigated damage to tight junctions of colonic epithelial cells, and significantly relieved radiation-induced colitis in mice. Moreover, 16S ribosomal DNA (16S rDNA) sequencing results show that the composition of the intestinal flora is optimized after FPCGMs are utilized, indicating that the relative abundance of probiotics increases while harmful bacteria are inhibited. These findings suggest that it is a promising candidate for treating radiation-induced colitis.

Microbial experience through housing in a farmyard-type environment alters intestinal barrier properties in mouse colons.

To close the gap between ultra-hygienic research mouse models and the much more environmentally exposed conditions of humans, we have established a system where laboratory mice are raised under a full set of environmental factors present in a naturalistic, farmyard-type habitat-a process we have called feralization. In previous studies we have shown that feralized (Fer) mice were protected against colorectal cancer when compared to conventionally reared laboratory mice (Lab). However, the protective mechanisms remain to be elucidated. Disruption of the protective intestinal barrier is an acknowledged player in colorectal carcinogenesis, and in the current study we assessed colonic mucosal barrier properties in healthy, feralized C57BL/6JRj male mice. While we found no effect of feralization on mucus layer properties, higher expression of genes encoding the mucus components Fcgbp and Clca1 still suggested mucus enforcement due to feralization. Genes encoding other proteins known to be involved in bacterial defense (Itln1, Ang1, Retnlb) and inflammatory mechanisms (Zbp1, Gsdmc2) were also higher expressed in feralized mice, further suggesting that the Fer mice have an altered intestinal mucosal barrier. These findings demonstrate that microbial experience conferred by housing in a farmyard-type environment alters the intestinal barrier properties in mice possibly leading to a more robust protection against disease. Future studies to unravel regulatory roles of feralization on intestinal barrier should aim to conduct proteomic analyses and in vivo performance of the feralized mice intestinal barrier.

Therapeutic efficacy and underlying mechanisms of Gastrodia elata polysaccharides on dextran sulfate sodium-induced inflammatory bowel disease in mice: Modulation of the gut microbiota and improvement of metabolic disorders.

Inflammatory bowel disease (IBD) is a chronic inflammatory gastrointestinal disease, and an imbalance in the gut microbiota is a critical factor in its development. Gastrodia elata (G. elata), an Orchidaceae plant, is recognized for its nutritional and medicinal value. Studies have shown that G. elata polysaccharides (GBP) have anti-inflammatory properties that may ameliorate IBD. However, the therapeutic effects of GBP on gut microbiota metabolism remain unknown. Therefore, we aimed to examine the therapeutic potential of G. elata extract and GBP in dextran sulfate sodium (DSS)-induced IBD mice. GBP demonstrated the best therapeutic effect by reducing IBD symptoms in mice to the greatest extent. Administering GBP resulted in significant increases in the relative abundances of bacteria with potential anti-inflammatory effects, such as Ligilactobacillus and Alloprevotella, and decreases in the levels of bacteria associated with proinflammatory responses, such as Bacteroides and Escherichia-Shigella. Furthermore, 36 significant differential metabolites between the model and GBP groups were identified in feces, which were mainly enriched in amino acid metabolism, including tryptophan and cysteine, vitamin B6 metabolism and steroid hormone biosynthesis. Consequently, investigating the metabolic regulation of the gut microbiota is a promising approach to evaluate the therapeutic effect of GBP on IBD.

Lactobacillus reuteri CCFM1175 and Lactobacillus paracasei CCFM1176 Could Prevent Capsaicin-Induced Ileal and Colonic Injuries.

Capsaicin (CAP) is usually reported to have many biological activities. However, a large intake of CAP may cause heartburn, gastrointestinal pain, and diarrhea. In this study, mice were gavaged with nine lactic acid bacteria (LAB) strains for two weeks, in which the mice were treated with CAP at the second week and lasted for one week. We tried to identify potential probiotics that could prevent CAP-induced intestinal injury and investigate the mechanisms. The modulation of transient receptor potential vanilloid 1 (TRPV1), levels of short-chain fatty acids (SCFAs), and the composition of gut microbiota were analyzed. The results showed that Lactobacillus reuteri CCFM1175 and Lactobacillus paracasei CCFM1176 effectively attenuated CAP-induced injuries to the ileum and colon, including relieving the damage to colonic crypt structures, increasing the number of goblet cells, decreasing levels of interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α), increasing levels of anti-inflammatory factors (IL-10), and reducing levels of substance P (SP) and calcitonin gene-related peptide (CGRP) in serum and colon tissue. Further analysis showed that L. reuteri CCFM1175 increased the relative abundance of Ruminococcaceae UCG_014 and Akkermansia. L. paracasei CCFM1176 downregulated the expression of TRPV1 in the ileal and colonic tissues and promoted the relative abundance of Ruminococcaceae UCG_014 and Lachnospiraceae UCG_006. These results indicate that L. reuteri CCFM1175 and L. paracasei CCFM1176 could prevent CAP-induced intestinal injury and be used as probiotics to improve the gastrointestinal health.

Evaluation of microbial and vancomycin treatments in ulcerative colitis in murine models.

BACKGROUND: Despite the number of available therapies for ulcerative colitis (UC), severe side effects and high cost has limited their clinical application. Thus, finding new alternative strategies with minimal side effects is inevitable. Therefore, this study aimed to compare the effectiveness of different therapeutic approaches in DSS-induced colitis. METHODS: Firstly, we designed oral bio-therapeutic products, Live Bacterial Products (LBP), which include a mixture of fecal bacteria strains isolated from healthy mice and prepared by microencapsulation and freeze-dried techniques. Then we investigated the efficiency of 7 days of freeze-dried FMT, LBP, and vancomycin treatments in DSS-induced colitis. Secondly, we compared the effect of 15 days of microbial therapies (freeze-dried powder of FMT and LBP microcapsules) and seven days of oral vancomycin on the severity of colitis in mice. Furthermore, the levels of IL-1ß and TNF-α were measured in serum by ELISA, and the fecal microbiota diversity was analyzed by high-throughput sequencing for all mice groups. RESULTS: After seven days of treatments, our results indicated that oral vancomycin reduced the severity of DSS-induced colitis in mice, where weight gain and a decrease in IL-1 ß and TNF-α levels were observed in the vancomycin group compared with other treatment groups. While after two weeks of treatment, the LBP microcapsules were able to reduce the severity of colitis. And at the end of the treatment period, weight gain and a decrease in the DAI scores and the levels of IL-1ß and TNF-α were noted in the LBP treatment group compared to other treatment groups. By high-throughput sequencing of the 16S rRNA gene, our results showed that while the microcapsules LBP treatment increased the fecal microbial diversity, after vancomycin therapy, most of the fecal microbiota genera and operational taxonomic units (OTUs) were depleted. CONCLUSION: Our results concluded that treatment duration and preparation methods affect the microbial therapies' efficiency in UC. Furthermore, this study highlighted the negative consequences of oral vancomycin administration on gut health that should be known before using this medication.

Anti-Inflammatory and Gut Microbiota Modulating Effects of Probiotic Lactobacillus paracasei MSMC39-1 on Dextran Sulfate Sodium-Induced Colitis in Rats.

Probiotics have been shown to possess several properties, depending on the strain. Some probiotics have important roles in preventing infection and balancing the immune system due to the interaction between the intestinal mucosa and cells in the immune system. This study aimed to examine the properties of three probiotic strains using the tumor necrosis factor-alpha (TNF-α) inhibition test in colorectal adenocarcinoma cells (Caco-2 cells). It was revealed that the viable cells and heat-killed cells of the probiotic L. paracasei strain MSMC39-1 dramatically suppressed TNF-α secretion in Caco-2 cells. The strongest strains were then chosen to treat rats with colitis induced by dextran sulfate sodium (DSS). Viable cells of the probiotic L. paracasei strain MSMC39-1 reduced aspartate transaminase and alanine transaminase in the serum and significantly inhibited TNF-α secretion in the colon and liver tissues. Treatment with the probiotic L. paracasei strain MSMC39-1 alleviated the colon and liver histopathology in DSS-induced colitis rats. Furthermore, supplementation with probiotic L. paracasei strain MSMC39-1 increased the genus Lactobacillus and boosted the other beneficial bacteria in the gut. Thus, the probiotic L. paracasei strain MSMC39-1 exhibited an anti-inflammation effect in the colon and modulated the gut microbiota.

Characterization of Gut Microbiota Compositions along the Intestinal Tract in CD163/pAPN Double Knockout Piglets and Their Potential Roles in Iron Absorption.

The gut microbiota is known to play a role in regulating host metabolism, yet the mechanisms underlying this regulation are not well elucidated. Our study aimed to characterize the differences in gut microbiota compositions and their roles in iron absorption between wild-type (WT) and CD163/pAPN double-gene-knockout (DKO) weaned piglets. A total of 58 samples along the entire digestive tract were analyzed for microbial community using 16S rRNA gene sequencing. The colonic microbiota and their metabolites were determined by metagenomic sequencing and untargeted liquid chromatography-mass spectrometry (LC-MS), respectively. Our results showed that no alterations in microbial community structure and composition were observed between DKO and WT weaned piglets, with the exception of colonic microbiota. Interestingly, the DKO piglets had selectively increased the relative abundance of the Leeia genus belonging to the Neisseriaceae family and decreased the Ruminococcaceae_UCG_014 genus abundance. Functional capacity analysis showed that organic acid metabolism was enriched in the colon in DKO piglets. In addition, the DKO piglets showed increased iron levels in important tissues compared with WT piglets without any pathological changes. Pearson's correlation coefficient indicated that the specific bacteria such as Leeia and Ruminococcaceae_UCG_014 genus played a key role in host iron absorption. Moreover, the iron levels had significantly (P < 0.05) positive correlation with microbial metabolites, particularly carboxylic acids and their derivatives, which might increase iron absorption by preventing iron precipitation. Overall, this study reveals an interaction between colonic microbiota and host metabolism and has potential significance for alleviating piglet iron deficiency. IMPORTANCE Iron deficiency is a major risk factor for iron deficiency anemia, which is among the most common nutritional disorders in piglets. However, it remains unclear how the gut microbiota interacts with host iron absorption. The current report provides the first insight into iron absorption-microbiome connection in CD163/pAPN double knockout piglets. The present results showed that carboxylic acids and their derivatives contributed to the absorption of nonheme iron by preventing ferric iron precipitation.

Gut Bacterial Indole-3-acetic Acid Induced Immune Promotion Mediates Preventive Effects of Fu Brick Tea Polyphenols on Experimental Colitis.

Ulcerative colitis has been consistently associated with gut microbiota imbalance and disturbed immune system. Emerging research suggests a protective function of polyphenols on prevention and treatment of ulcerative colitis, yet underlying mechanisms remain unclear. Fu brick tea, a postfermented tea, contains abundant polyphenols with anti-inflammatory and antioxidant properties. In the present study, we found that prophylactic supplementation of polyphenols extracted from Fu brick tea (FBTP) dose-dependently alleviated colitis symptoms, immune cells infiltration, and pro-inflammatory cytokines secretion in mice suffering dextran sulfate sodium induced murine colitis. FBTP substantially reshaped gut microbiota and promoted microbial transformation of tryptophan into indole-3-acetic acid (I3A), thereafter leading to aryl hydrocarbon receptor (AHR)-mediated protection from colitis through enhanced expressions of IL-22 and tight junction proteins (i.e., ZO-1, occluding and claudin-1) in colon. Multiomics integration analyses revealed strong connections between I3A, tryptophan-metabolizing bacteria, AHR activity, and pathological phenotypes of colitis. Notably, FBTP failed to significantly alleviate colitis symptoms in the absence of gut microbiota, while intragastric administration of I3A could imitate benefits of FBTP on colitis alleviation and intestinal epithelial homeostasis through a direct enhancement in AHR activity in microbiota-depleted mice. These findings further determine the key role of gut microbiota controlled I3A-AHR signaling in mediating the FBTP on colitis alleviation. This study provides the first data proposing the FBTP as a natural prebiotic for colitis alleviation through the gut microbiota-dependent modulation of the AHR pathway. Most importantly, we also identified I3A as a key microbial metabolite targeted by FBTP for exhibiting health-promoting effects.

2-deoxy-D-glucose mitigates Citrobacter rodentium and dibenzazepine-induced gastrointestinal damage and colitis: novel implications of 2-DG polypharmacopea.

PURPOSE: Citrobacter rodentium (CR) infection coupled with blocking Notch/Wnt signaling via γ-secretase inhibitor dibenzazepine (DBZ) disrupts the gastro-intestinal (GI) barrier and induces colitis, akin to ionizing radiation (IR)-induced GI-injury. We investigated the effects of 2-deoxy-D-glucose (2-DG) to ameliorate the CR-DBZ-induced GI damage. MATERIALS AND METHODS: NIH:Swiss outbred mice were inoculated with 109CFUs of CR orally. DBZ was administered intraperitoneally (10 µM/kg b.wt; for 10 days 2 days post-CR infection). Mice were fed with 0.4% 2-DG (w/v) daily in drinking water. For microbiota depletion, antibiotics (Abx), 1 g/l metronidazole, and 0.2 g/l ciprofloxacin were administered for 10 days in drinking water. Oxidative stress, survival assay, colonic crypt hyperplasia, Notch/Wnt downstream signaling, immunomodulation, and bacterial dysbiosis were measured. RESULTS: We show that real-time visualization of reactive oxygen species (ROS) is similar during CR-induced colonic infection and IR-induced GI-damage. The histology revealed that dietary 2-DG mitigates CR + DBZ-induced colitis and improves survival compared with CR + DBZ alone. These changes were phenocopied in Abx-treated mice. Both 2-DG and Abx reduced dysbiosis, increased proliferation, inhibited pro-inflammatory response, and restored Hes-1 and ß-catenin protein levels, in the crypts. CONCLUSION: The energy disruptor 2-DG mitigates bacterial infection and its responsive hyperplasia/colitis, indicating its utility as a mitigator of infection/IR-induced GI-damage.

Butyrate-producing colonic clostridia: picky glycan utilization specialists.

Butyrate-producing human gut microbiota members are recognized for their strong association with a healthy immune-homeostasis and protection from inflammatory disorders and colorectal cancer. These effects are attributed to butyrate, the terminal electron sink of glycan fermentation by prevalent and abundant colonic Firmicutes from the Lachnospiraceae and Oscillospiraceae families. Remarkably, our insight into the glycan utilization mechanisms and preferences of butyrogenic Firmicutes remains very limited as compared with other gut symbionts, especially from the Bacteroides, Bifidobacterium, and Lactobacillus genera. Here, we summarize recent findings on the strategies that colonic butyrate producers have evolved to harvest energy from major dietary fibres, especially plant structural and storage glycans, such as resistant starch, xylans, and mannans. Besides dietary fibre, we also present the unexpected discovery of a conserved protein apparatus that confers the growth of butyrate producers on human milk oligosaccharides (HMOs), which are unique to mother's milk. The dual dietary fibre/HMO utilization machinery attests the adaptation of this group to both the infant and adult guts. These finding are discussed in relation to the early colonization of butyrogenic bacteria and the maturation of the microbiota during the transition from mother's milk to solid food. To date, the described butyrogenic Firmicutes are glycan utilization specialists that target only a few glycans in a highly competitive manner relying on co-regulated glycan utilization loci. We describe the common pillars of this machinery, highlighting butyrate producers as a source for discovery of biochemically and structurally novel carbohydrate active enzymes.

ASSESSMENT OF COLON MICROBIOCENOSIS DISORDERS IN PATIENTS WITH CHRONIC HEPATITIS C.

OBJECTIVE: The aim: To investigate the peculiarities of colon microbiocenosis disorders in patients with chronic hepatitis C. PATIENTS AND METHODS: Materials and methods: 142 patients with CHC were under observation, determination of the degree of liver fibrosis (FibroMax), bacteriological examination of stools and pancreatic elastase was performed. RESULTS: Results: It was found that 59.2% of patients with CHC had gut dysbiosis (DB), of which 61.9% had increased body weight. Intestinal microbiocenosis disorders were manifested by constipation in 57.1% of patients, diarrhea in 31% of patients, and alternating constipation and diarrhea in 11.9% of patients. Bacteriologically, gut dysbiosis was character¬ized by suppression of the growth of normal microflora: Escherichia coli in 47.6%, bifidobacteria in 61.9%, lactobacilli in 53.6%, complete absence of bifidobacteria in 20.2% of cases. In patients with CHC combined with DB deep stages of liver fibrosis (F2-3 and F3-4) are registered 3.6 times more often compared to patients without intestinal dysbiosis (53.6% versus 24.1% and 11.9% versus 3.4%). The degree of gut DB increased in proportion to the stage of liver fibrosis (p<0.05). 32.1% of patients with CHC with dysbiosis were diagnosed with exocrine insufficiency of the pancreas. CONCLUSION: Conclusions: Gut dysbiosis occurs more often in CHC patients with increased body weight and is characterized by constipation in 59.2% of patients. Intestinal microbiocenosis is characterized by suppression of the growth of normal microflora. In 32.1% of CHC patients with intestinal dysbiosis, according to the results of the pancreatic elastase-1 test, pancreatic exocrine insufficiency of various degrees was found.

Plasticity of the adult human small intestinal stoma microbiota.

The human distal small intestine (ileum) has a distinct microbiota, but human studies investigating its composition and function have been limited by the inaccessibility of the ileum without purging and/or deep intubation. We investigated inherent instability, temporal dynamics, and the contribution of fed and fasted states using stoma samples from cured colorectal cancer patients as a non-invasive access route to the otherwise inaccessible small and large intestines. Sequential sampling of the ileum before and after stoma formation indicated that ileostoma microbiotas represented that of the intact small intestine. Ileal and colonic stoma microbiotas were confirmed as distinct, and two types of instability in ileal host-microbial relationships were observed: inter-digestive purging followed by the rapid postprandial blooming of bacterial biomass and sub-strain appearance and disappearance within individual taxa after feeding. In contrast to the relative stability of colonic microbiota, the human small intestinal microbiota biomass and its sub-strain composition can be highly dynamic.

Alginate Alleviates Dextran Sulfate Sodium-Induced Colitis by Promoting Bifidobacterium animalis and Intestinal Hyodeoxycholic Acid Synthesis in Mice.

Alginate (ALG) is known to alleviate intestinal inflammation in inflammatory bowel disease, but its mechanism of action remains elusive. In the present study, we studied the involvement of the intestinal microbiota and bile acid (BA) metabolism in ALG-mediated anti-inflammatory effects in mice. A combination of 16S rRNA gene amplicon sequencing, shotgun metagenomic sequencing, and targeted BA metabolomic profiling was employed to investigate structural and functional differences in the colonic microbiota and BA metabolism in dextran sulfate sodium (DSS)-treated mice with or without dietary supplementation of ALG. We further explored the role of the intestinal microbiota as well as a selected ALG-enriched bacterium and BA in DSS-induced colitis. Dietary ALG alleviated DSS-mediated intestinal inflammation and enriched a small set of bacteria including Bifidobacterium animalis in the colon (P < 0.05). Additionally, ALG restored several bacteria carrying secondary BA-synthesizing enzymes such as 7α-hydroxysteroid dehydrogenase and BA hydrolase to healthy levels in DSS-treated mice. Although a majority of BAs were suppressed by DSS, a few secondary BAs such as hyodeoxycholic acid (HDCA) were markedly enriched by ALG. Furthermore, ALG significantly upregulated the expression of a major BA receptor, the farnesoid X receptor, while suppressing NF-κB and c-Jun N-terminal kinase (JNK) activation. Depletion of the intestinal microbiota completely abrogated the protective effect of ALG in DSS-treated mice. Similar to ALG, B. animalis and HDCA exerted a strong anti-inflammatory effect in DSS-induced colitis by downregulating inflammatory cytokines (interleukin-1ß [IL-1ß], IL-6, and tumor necrosis factor alpha [TNF-α]). Taken together, these results indicated that ALG achieves its alleviating effect on intestinal inflammation through regulation of the microbiota by enriching B. animalis to promote the biosynthesis of specific secondary BAs such as HDCA. These findings have revealed intricate interactions among the intestinal microbiota, BA metabolism, and intestinal health and further provided a novel strategy to improve intestinal health through targeted manipulation of the intestinal microbiota and BA metabolism. IMPORTANCE ALG has been shown to ameliorate inflammatory bowel disease (IBD), but little is known about the mechanism of its anti-inflammatory action. This study was the first to demonstrate that ALG provided a preventive effect against colitis in an intestinal microbiota-dependent manner. Furthermore, we confirmed that by selectively enriching intestinal B. animalis and secondary BA (HDCA), ALG contributed to the attenuation of DSS-induced colitis. These findings contribute to a better understanding of the mechanism of action of ALG on the attenuation of colitis and provide new approaches to IBD therapy by regulating gut microbial BA metabolism.

Differential analysis of microbiomes in mucus and tissues obtained from colorectal cancer patients.

The outer mucus layer of the colorectal epithelium is easily removable and colonized by commensal microbiota, while the inner mucus layer is firmly attached to the epithelium and devoid of bacteria. Although the specific bacteria penetrating the inner mucus layer can contact epithelial cells and trigger cancer development, most studies ignore the degree of mucus adhesion at sampling. Therefore, we evaluated whether bacteria adhering to tissues could be identified by removing the outer mucus layer. Our 16S rRNA gene sequencing analysis of 18 surgical specimens of human colorectal cancer revealed that Sutterella (P = 0.045) and Enterobacteriaceae (P = 0.045) were significantly enriched in the mucus covering the mucosa relative to the mucosa. Rikenellaceae (P = 0.026) was significantly enriched in the mucus covering cancer tissues compared with those same cancer tissues. Ruminococcaceae (P = 0.015), Enterobacteriaceae (P = 0.030), and Erysipelotrichaceae (P = 0.028) were significantly enriched in the mucus covering the mucosa compared with the mucus covering cancers. Fusobacterium (P = 0.038) was significantly enriched in the mucus covering cancers compared with the mucus covering the mucosa. Comparing the microbiomes of mucus and tissues with mucus removed may facilitate identifying bacteria that genuinely invade tissues and affect tumorigenesis.

Linarin ameliorates dextran sulfate sodium-induced colitis in C57BL/6J mice via the improvement of intestinal barrier, suppression of inflammatory responses and modulation of gut microbiota.

Linarin is a natural flavonoid compound found in Chrysanthemum indicum, Mentha species and other plants with various biological activities. The study aimed to investigate the protective effect of linarin supplementation on dextran sulfate sodium (DSS)-induced colitis in C57BL/6J mice and its potential mechanisms. The results showed that doses of linarin at 25 and 50 mg kg-1 day-1 alleviated the DSS-induced histopathological damage, and improved the mucosal layer and intestinal barrier function. Importantly, Linarin significantly suppressed the levels of myeloperoxidase activity and pro-inflammatory cytokines (IL-6, TNF-α, IFN-γ and IL-1ß) in the colon, and enhanced the mRNA level of anti-inflammatory cytokine (IL-10). Moreover, 50 mg kg-1 day-1 linarin reversed the gut microbiota damaged by DSS, including Alistipes, Rikenella and Clostridia UCG-014_norank. Linarin also partly increased the relative abundance of short-chain fatty acids (SCFAs)-producing bacteria, including Lactobacillus, Roseburia, Parabacteroides and Blautia, and elevated the contents of SCFAs. Collectively, linarin attenuates DSS-induced colitis in mice, suggesting that linarin may be a promising nutritional strategy for reducing inflammatory bowel disease.

Akkermansia muciniphila Reduces Peritonitis and Improves Intestinal Tissue Wound Healing after a Colonic Transmural Defect by a MyD88-Dependent Mechanism.

Anastomotic leakage is a major complication following colorectal surgery leading to peritonitis, complications, and mortality. Akkermansia muciniphila has shown beneficial effects on the gut barrier function. Whether A. muciniphila reduces peritonitis and mortality during colonic leakage is unknown. Whether A. muciniphila can directly modulate the expression of genes in the colonic mucosa in humans has never been studied. We investigated the effects of a pretreatment (14 days) with live A. muciniphila prior to surgical colonic perforation on peritonitis, mortality, and wound healing. We used mice with an inducible intestinal-epithelial-cell-specific deletion of MyD88 (IEC-MyD88 KO) to investigate the role of the innate immune system in this context. In a proof-of-concept pilot study, healthy humans were exposed to A. muciniphila for 2 h and colonic biopsies taken before and after colonic instillation for transcriptomic analysis. Seven days after colonic perforation, A.-muciniphila-treated mice had significantly lower mortality and severity of peritonitis. This effect was associated with significant improvements of wound histological healing scores, higher production of IL22, but no changes in the mucus layer thickness or genes involved in cell renewal, proliferation, or differentiation. All these effects were abolished in IEC-MyD88 KO mice. Finally, human subjects exposed to A. muciniphila exhibited an increased level of the bacterium at the mucus level 2 h after instillation and significant changes in the expression of different genes involved in the regulation of cell cycling, gene transcription, immunity, and inflammation in their colonic mucosa. A. muciniphila improves wound healing during transmural colonic wall defect through mechanisms possibly involving IL22 signaling and requiring MyD88 in the intestinal cells. In healthy humans, colonic administration of A. muciniphila is well tolerated and changes the expression of genes involved in the immune pathways.