Colonic Mucin Research Articles

Impact of the Food Additive Titanium Dioxide (E171) on Gut Microbiota-Host Interaction.

The interaction between gut microbiota and host plays a central role in health. Dysbiosis, detrimental changes in gut microbiota and inflammation have been reported in non-communicable diseases. While diet has a profound impact on gut microbiota composition and function, the role of food additives such as titanium dioxide (TiO2), prevalent in processed food, is less established. In this project, we investigated the impact of food grade TiO2 on gut microbiota of mice when orally administered via drinking water. While TiO2 had minimal impact on the composition of the microbiota in the small intestine and colon, we found that TiO2 treatment could alter the release of bacterial metabolites in vivo and affect the spatial distribution of commensal bacteria in vitro by promoting biofilm formation. We also found reduced expression of the colonic mucin 2 gene, a key component of the intestinal mucus layer, and increased expression of the beta defensin gene, indicating that TiO2 significantly impacts gut homeostasis. These changes were associated with colonic inflammation, as shown by decreased crypt length, infiltration of CD8+ T cells, increased macrophages as well as increased expression of inflammatory cytokines. These findings collectively show that TiO2 is not inert, but rather impairs gut homeostasis which may in turn prime the host for disease development.

Structural weakening of the colonic mucus barrier is an early event in ulcerative colitis pathogenesis

ObjectiveThe colonic inner mucus layer protects us from pathogens and commensal-induced inflammation, and has been shown to be defective in active UC. The aim of this study was to determine...

Abstract TMP30: Mucin is a Novel Target for Gut Protective Immunity in Stroke

Introduction: Infections are a common cause of post-stroke morbidity and mortality. Recent studies suggest that gut microbiota are a major source of post-stroke infection. Gut mucus layers are a major area of communication between gut microbiota and host immune cells. To our knowledge there have been no studies evaluating the role of colonic epithelial mucins, where most of the gut bacteria reside, after ischemic stroke. Hypothesis: Epithelial mucin plays a protective role in stroke-induced colonic disruption. Methods: Mice were subjected to either sham or 60-minute middle cerebral artery occlusion (MCAO). Neurological deficit score (NDS) and levels of lipopolysaccharide-binding protein (LBP) in plasma were assessed at day 7 after stroke. Mice were sacrificed at day 7 after stroke and colonic epithelial cells (ECs) were isolated for a gene expression study. Tissues were used for histology and bacterial in situ hybridization. Fecal samples were collected for 16S sequencing and IgA ELISA. Results: Young female mice had lower NDS and LBP levels, with intact colonic structures (n=4/group, P <0.05). Young mice ECs significantly increased 1) regenerating islet-derived protein (Reg) family-specific antimicrobial proteins in males (24.3, 21.3 and 2.5 fold change in Reg3β, -γ and -4, respectively) and 2) mucin genes in females (1.8 and 1.4 fold change in Muc2 and -4, respectively, n=4-5/group, P <0.05). Young ovariectomized mice switched their protective strategies from enhanced expression of mucin genes to a “male-like” pattern in which Reg genes were increased after stroke (n=3-5/group, P <0.05). Aged mice failed to express these sex-specific genes after stroke. Interestingly, after stroke, bacteria from young female but not male mice were found at a farther distance from the colonic epithelium secondary to intact mucus layers. Finally, young female mice increased mucin-regulating Akkermansia bacteria and IgA in the feces after stroke (n=4/group, P <0.05). Conclusions: Our data demonstrates that 1) stroke provokes a colonic epithelial response and 2) mucin is critical for colonic protection in stroke. In conclusion, mucin should be considered as a novel target to improve post-stroke recovery as well as an important element in maintaining colonic structure.

Decreased electrogenic anionic secretory response in the porcine colon following in vivo challenge with Brachyspira spp. supports an altered mucin environment.

Brachyspira spp. cause diarrheal disease in multiple animal species by colonization of the colon, resulting in colitis, mucus induction, and disrupted ion transport. Unique to spirochete pathogenesis is the immense production of mucus, resulting in a niche mucin environment likely favoring spirochete colonization. Mucin rheological properties are heavily influenced by anionic secretion, and loss of secretory function has been implicated in diseases such as cystic fibrosis. Here, the effects on the agonist-induced electrogenic anionic secretory response by infectious colonic spirochete bacteria Brachyspira hyodysenteriae and Brachyspira hampsonii were assessed in the proximal, apex, and distal sections of colon in Ussing chambers. Activation of secretion via isoproterenol, carbachol, and forskolin/3-isobutyl-1-methylxanthine demonstrated a significantly decreased change in short-circuit current ( Isc) in Brachyspira-infected pigs in all sections. Tissue resistances did not account for this difference, rather, it was attributed to a decrease in anionic secretion as indicated by a decrease in bumetanide inhibitable Isc. Quantitative RT-PCR and Western blot analyses determined that the major anionic channels of the epithelium were downregulated in diarrheic pigs paired with altered mucin gene expression. The investigated cytokines were not responsible for the downregulation of anion channel gene transcripts. Although IL-1α was upregulated in all segments, it did not alter cystic fibrosis transmembrane conductance regulator (CFTR) mRNA expression in Caco-2 monolayers. However, a whole cell Brachyspira hampsonii lysate significantly reduced CFTR mRNA expression in Caco-2 monolayers. Together, these findings indicate that these two Brachyspira spp. may directly cause a decreased anionic secretory response in the porcine colon, supporting an altered mucin environment likely favoring spirochete colonization. NEW & NOTEWORTHY This research demonstrates for the first time that the niche mucin environment produced by two infectious spirochete spp. is supported by a decrease in the electrogenic anionic secretory response throughout the porcine colon. Our findings suggest that the host's cytokine response is not likely responsible for the decrease in anionic secretory function. Rather, it appears that Brachyspira spp. directly impede ion channel transcription and translation, potentially altering colonic mucin rheological properties, which may favor spirochete colonization.

Defining cooperative roles for colonic microbiota and Muc2 mucin in mediating innate host defense against Entamoeba histolytica.

Amebiasis is caused by the protozoan parasite Entamoeba histolytica (Eh), a potentially fatal disease occurring mainly in developing countries. How Eh interacts with innate host factors in the gut is poorly understood. Eh resides and feed in/on the outer colonic mucus layer and thus share an ecological niche with indigenous microbiota. As gut microbiota regulates innate immune responses, in this study we characterized the cooperative roles that microbiota and the mucus layer play in Eh-induced pro-inflammatory responses in the colon. To study this, we used antibiotics treated and non-treated specific pathogen free Muc2-/- and Muc2+/+ littermates and germ-free mice inoculated with Eh in colonic loops as a short infection model. In antibiotic treated Muc2-/- and Muc2+/+ littermates, Eh elicited robust mucus and water secretions, enhanced pro-inflammatory cytokines and chemokine expression with elevated MPO activity and higher pathology scores as compared to the modest response observed in non-antibiotic treated littermates. Host responses were microbiota specific as mucus secretion and pro-inflammatory responses were attenuated following homologous fecal microbial transplants in antibiotic-treated Muc2+/+ quantified by secretion of 3H-glucosamine newly synthesized mucin, Muc2 mucin immunostaining and immunohistochemistry. Eh-elicited pro-inflammatory responses and suppressed goblet cell transcription factor Math1 as revealed by in vivo imaging of Eh-colonic loops in Math1GFP mice, and in vitro using Eh-stimulated LS174T human colonic goblet cells. Eh in colonic loops increased bacterial translocation of bioluminescent E. coli and indigenous bacteria quantified by FISH and quantitative PCR. In germ-free animals, Eh-induced mucus/water secretory responses, but acute pro-inflammatory responses and MPO activity were severely impaired, allowing the parasite to bind to and disrupt mucosal epithelial cells. These findings have identified key roles for intestinal microbiota and mucus in regulating innate host defenses against Eh, and implicate dysbiosis as a risk factor for amebiasis that leads to exacerbated immune responses to cause life-threatening disease.

Oral Nutrition Modulates the Intestinal Barrier Following Cytotoxic Therapy Via the Microbiome

Reduced oral intake (ROI) is common in patients that have received cytotoxic therapy for hematologic malignancies. Here we examine the interplay between nutrition, intestinal bacteria and intestinal barrier function, focusing on preclinical mouse models.By 3 days following 9 Gy of total body irradiation (TBI), individually-housed C57BL/6 mice were observed to have an approximately 40-60% reduction in oral intake (Fig A), and 3 days later displayed marked changes in the microbiome by 16S deep sequencing, including an expansion of Bacteroides thetaiotaomicron (Fig B). These mice also had lost roughly 20% of their body weight (Fig C), and showed compromise of their intestinal barrier assayed by oral challenge with FITC-dextran (Fig M). We hypothesized that the ROI could be a driving factor behind the microbiome changes. To assess this, we limited the access of unirradiated mice to 2 grams of normal chow a day for 7 days (an approximately 50% reduction in oral intake) with unlimited water. Microbiome profiling by 16S sequencing showed many changes that were similar to those seen in irradiated mice, including an expansion of Bacteroides thetaiotaomicron (Fig D). Because Bacteroides thetaiotaomicron has been shown to utilize glycans derived from colonic mucin, we evaluated the consumption of porcine gastric mucin by intestinal bacteria in vitro with a colorimetric assay that quantifies polysaccharides. We found that following ROI, mice harbored intestinal bacteria that were significantly more efficient at utilizing mucin glycans (Fig E). Corroborating this, a histological characterization of the colonic mucus thickness following fixation with Carnoy's solution showed that after a week of ROI, unirradiated mice developed significant thinning of the colonic mucus layer (Fig F), though intestinal barrier function otherwise remained intact as assayed by FITC-dextran gavage (data not shown).We asked how ROI could favor mucolytic bacteria and hypothesized that ROI could reduce bacterial fermentation of dietary carbohydrates which largely results in production of short-chain fatty acids. Evaluating the pH of the colonic lumen showed that ROI led to a significant elevation in pH (Fig G). Ion-chromatography mass spectrometry of colonic stool samples showed a reduction in acetate, propionate, butyrate, and lactate following ROI, and interestingly an increase in succinate (Fig I). Corroborating this, RNA sequencing of intestinal bacteria following ROI demonstrated a downregulation of phosphoenolpyruvate carboxykinase, a metabolic enzyme that in Bacteroides species has been previously been found to be associated with conversion of succinate to propionate (Fig H).Finally, we evaluated in our ROI model the impact of administration of oral sugars by supplementing a well-absorbed sugar (glucose), and a poorly-absorbed prebiotic sugar in the drinking water of mice. We found that compared with glucose, supplementation with the prebiotic more effectively acidified the colonic lumen of normal mice (Fig J), and completely prevented thinning of the mucus layer in mice undergoing ROI (Fig K). Additionally, in mice following 9 Gy of total body irradiation, daily administration of the prebiotic was highly effective in preventing weight loss (Fig L) and nearly completely abrogated compromise of intestinal barrier function (Fig M).Conclusions:Reduced oral intake following cytotoxic therapy contributes to thinning of the colonic mucus layer, an effect that appears to be independent of the cytotoxic effects on the host and is rather mediated by changes in the intestinal microbiome, including reduced metabolism of organic acids. Strategies to restore colonic acidity with prebiotic sugars may successfully target this phenomenon with potential clinical benefits, particularly in preventing disruption to the intestinal barrier. DisclosuresJenq:MicrobiomeDx: Consultancy; Seres Therapeutics, Inc.: Patents & Royalties; Ziopharm Oncology: Consultancy; Seres Therapeutics, Inc.: Membership on an entity's Board of Directors or advisory committees.

Consumption of non-digestible oligosaccharides elevates colonic alkaline phosphatase activity by up-regulating the expression of IAP-I, with increased mucins and microbial fermentation in rats fed a high-fat diet.

We have recently reported that soluble dietary fibre, glucomannan, increased colonic alkaline phosphatase (ALP) activity and the gene expression without affecting the small-intestinal activity and that colonic ALP was correlated with gut mucins (index of intestinal barrier function). We speculated that dietary fermentable carbohydrates including oligosaccharides commonly elevate colonic ALP and gene expression as well as increase mucin secretion and microbial fermentation. To test this hypothesis, male Sprague-Dawley rats were fed a diet containing 30 % lard with or without 4 % fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), raffinose (RAF) and lactulose (LAC), which are non-digestible oligosaccharides or isomalto-oligosaccharides (IMOS; some digestible oligosaccharides) for 2 weeks. Colon ALP activity, the gene expression and gut luminal variables including mucins, organic acids and microbiota were measured. Colonic ALP was significantly elevated in the FOS, RAF and LAC groups, and a similar trend was observed in the GOS group. Colonic expression of intestinal alkaline phosphatase (IAP -I), an ALP gene, was significantly elevated in the FOS, GOS and RAF groups and tended to be increased in the LAC group. Dietary FOS, GOS, RAF and LAC significantly elevated faecal mucins, caecal n-butyrate and faecal ratio of Bifidobacterium spp. Dietary IMOS had no effect on colonic ALP, mucins, organic acids and microbiota. Colon ALP was correlated with mucins, caecal n-butyrate and faecal Bifidobacterium spp. This study demonstrated that non-digestible and fermentable oligosaccharides commonly elevate colonic ALP activity and the expression of IAP-I, with increasing mucins and microbial fermentation, which might be important for protection of gut epithelial homoeostasis.

Mucin degradation niche as a driver of microbiome composition and Akkermansia muciniphila abundance in a dynamic gut model is donor independent

Akkermansia muciniphila, an abundant mucin degrading intestinal bacterium, has been correlated with human health in various studies. The in vitro SHIME model was used to reach a mechanistic understanding of A. muciniphila's colonization preferences and its response to environmental parameters such as colon pH and mucins. These insight can help to identify the optimal conditions for successful in vivo application. After a period of mucin deprivation, we found that mucin supplementation resulted in significantly different microbial communities, with more Akkermansia, Bacteroides and Ruminococcus. Mucin treatment accounted for 26% of the observed variation in the microbial community at OTU level (P = 0.001), whereas the donor effect was limited (8%) (P = 0.035), indicating mucins to constitute an important ecological niche shaping the microbiota composition. The effect of colonic pH had a less profound impact on the microbiome with both pH and donor origin explaining around 10% of the variability in the dataset. Yet, higher simulated colonic pH had a positive impact on Akkermansia abundance while short chain fatty acid analysis displayed a preference for propionate production with higher colonic pH. Our results show that mucins as nutritional resource are a more important modulator of the gut microbiome than colon pH as environmental factor.

Reduced colonic mucin degradation in breastfed infants colonized by Bifidobacterium longum subsp. infantis EVC001

Mucin glycoproteins play an important role in protecting the gut epithelium by keeping gut microbes from direct contact with the gut epithelium while allowing for diffusion of small molecules from the lumen to the epithelium. The mucin glycocalyx can be degraded by gut bacteria such as Bacteroides and Akkermansia, but other bacteria, such as Bifidobacterium longum subsp. Infantis, cannot consume mucin glycans. Untargeted mass spectrometry profiles were compared to microbiome profiles to assess how different gut microbiomes affect colonic mucin degradation. Samples obtained from nine infants colonized by Bifidobacterium infantis EVC001 and from 10 infants colonized by higher levels of mucolytic taxa (controls), including Bacteroides, were compared. Previously performed untargeted nano‐high‐performance liquid chromatography‐chip/time‐of‐flight mass spectrometry was used to detect and quantify glycans originating from colonic mucin. Colonic mucin‐derived O‐glycans from control infants composed 37.68% (± 3.14% SD) of the total glycan structure pool, whereas colonic mucin‐derived O‐glycans made up of only 1.78% (± 0.038% SD) of the total in B. infantis EVC001 samples. The relative abundance of these colonic mucin‐derived O‐glycans in the total glycan pool was higher among control, 26.98% (± 8.48% SD), relative to B. infantis‐colonized infants, 1.68% (± 1.12% SD). Key taxa, such as Bacteroidaceae, were significantly and positively correlated with the abundance of these structures, while Bifidobacteriaceae were significantly and negatively associated with these structures. These results suggest that colonization of infants by B. infantis may diminish colonic glycan degradation and help maintain barrier function in the gastrointestinal tract of infants.

Sodium butyrate ameliorates insulin resistance and renal failure in CKD rats by modulating intestinal permeability and mucin expression.

BackgroundThe associated increase in the lipopolysaccharide (LPS) levels and uremic toxins in chronic kidney disease (CKD) has shifted the way we focus on intestinal microbiota. This study shows that a disruption of the intestinal barrier in CKD promotes leakage of LPS from the gut, subsequently decreasing insulin sensitivity. Butyrate treatment improved the intestinal barrier function by increasing colonic mucin and tight junction (TJ) proteins. This modulation further ameliorated metabolic functions such as insulin intolerance and improved renal function.MethodsRenal failure was induced by 5/6th nephrectomy (Nx) in rats. A group of Nx and control rats received sodium butyrate in drinking water. The Nx groups were compared with sham-operated controls.ResultsThe Nx rats had significant increases in serum creatinine, urea and proteinuria. These animals had impaired glucose and insulin tolerance and increased gluconeogenesis, which corresponded with decreased glucagon-like peptide-1 (GLP-1) secretion. The Nx animals suffered significant loss of intestinal TJ proteins, colonic mucin and mucin 2 protein. This was associated with a significant increase in circulating LPS, suggesting a leaky gut phenomenon. 5′adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, known to modulate epithelial TJs and glucose metabolism, was significantly reduced in the intestine of the Nx group. Anti-inflammatory cytokine, interleukin 10, anti-bacterial peptide and cathelicidin-related antimicrobial peptide were also lowered in the Nx cohort. Butyrate treatment increased AMPK phosphorylation, improved renal function and controlled hyperglycemia.ConclusionsButyrate improves AMPK phosphorylation, increases GLP-1 secretion and promotes colonic mucin and TJ proteins, which strengthen the gut wall. This decreases LPS leakage and inflammation. Taken together, butyrate improves metabolic parameters such as insulin resistance and markers of renal failure in CKD animals.

Entamoeba histolytica Alters Ileal Paneth Cell Functions in Intact and Muc2 Mucin Deficiency.

Enteric α-defensins, termed cryptdins (Crps) in mice, and lysozymes secreted by Paneth cells contribute to innate host defense in the ileum. Antimicrobial factors, including lysozymes and β-defensins, are often embedded in luminal glycosylated colonic Muc2 mucin secreted by goblet cells that form the protective mucus layer critical for gut homeostasis and pathogen invasion. In this study, we investigated ileal innate immunity against Entamoeba histolytica, the causative agent of intestinal amebiasis, by inoculating parasites in closed ileal loops in Muc2+/+ and Muc2-/- littermates and quantifying Paneth cell localization (lysozyme expression) and function (Crp secretion). Relative to Muc2+/+ littermates, Muc2-/- littermates showed a disorganized mislocalization of Paneth cells that was diffusely distributed, with elevated lysozyme secretion in the crypts and on villi in response to E. histolytica Inhibition of E. histolytica Gal/GalNAc lectin (Gal-lectin) binding with exogenous galactose and Entamoeba histolytica cysteine proteinase 5 (EhCP5)-negative E. histolytica had no effect on parasite-induced erratic Paneth cell lysozyme synthesis. Although the basal ileal expression of Crp genes was unaffected in Muc2-/- mice in response to E. histolytica, there was a robust release of proinflammatory cytokines and Crp peptide secretions in luminal exudates that was also present in the colon. Interestingly, E. histolytica-secreted cysteine proteinases cleaved the proregion of Crp4 but not the active form. These findings define Muc2 mucin as an essential component of ileal barrier function that regulates the localization and function of Paneth cells critical for host defense against microbes.

Binding of Helicobacter pylori to Human Gastric Mucins Correlates with Binding of TFF1.

Helicobacter pylori binds to the gastric mucin, MUC5AC, and to trefoil factor, TFF1, which has been shown to interact with gastric mucin. We examined the interactions of TFF1 and H. pylori with purified gastrointestinal mucins from different animal species and from humans printed on a microarray platform to investigate whether TFF1 may play a role in locating H. pylori in gastric mucus. TFF1 bound almost exclusively to human gastric mucins and did not interact with human colonic mucins. There was a strong correlation between binding of TFF1 and H. pylori to human gastric mucins, and between binding of both TFF1 and H. pylori to gastric mucins with that of Griffonia simplicifolia lectin-II, which is specific for terminal non-reducing α- or β-linked N-acetyl-d-glucosamine. These results suggest that TFF1 may help to locate H. pylori in a discrete layer of gastric mucus and hence restrain their interactions with epithelial cells.

Effect of Different Doses of Herbal Cake-partitioned Moxibustion on Histopathological Changes of Colon Tissue in Ulcerative Colitis Rats

To observe the effect of different-doses of herbal cake-partitioned moxibustion (Moxi) on histopathological changes of the damaged colon tissue in rats with ulcerative colitis (UC), so as to select an optimal dosage of Moxi in the treatment of UC. Sixty-three male Sprague Dawley (SD) rats were randomized into 7 groups: normal control, model, medication, and 1, 2, 3 and 4 moxa-cone Moxi (n＝9 rats per group). The UC model was developed by subcutaneous injection of emulsion (1 mL) containing colon mucosa-prepared protein suspension and complete Freund's adjuvant into the toes, groin and back. On the 38th day, enema of 3% formalin and the aforementioned emulsion was used. Herbal-cake (composed of monkshood, cinnamon, etc.) partitioned Moxi with 1 or 2 moxa-cones (about 5 min/cone) was applied to bilateral "Tianshu" (ST 25) once daily or once every other day. The rat's general conditions (diet, movement, response ability, stool, and body weight) were observed, and histopathological changes (adhesion, ulcer formation and inflammation) of colon tissues were examined after hematoxylin-eosin (HE) staining, and scored (histopathological score). Gross score was given according to the severity of adhesion, ulcer formation and inflammation of colonic tissues under stereo microscope. The average optical density (AOD) values of colonic mucins were detected after periodic acid-schiff (PAS) staining, and those of the sulfated mucus content detected after high iron dia-mine-alcian blue (HID-AB) staining. Compared with the normal group, rats in the model group presented loose stool, or with pus and blood, and slowly increased body weight (P<0.01), obvious congestion of colon with ulcer spots or continuous superficial ulcer regions which had irregular glandular cavities, swelling and serious inflammatory infiltration in lamina propria and submucosa, and increased score of colon tissue damage (P<0.01). PAS and HID-AB staining showed a marked decrease of AOD values of colonic mucins and sulfated mucus in the model group relevant to the normal control group (P<0.01), suggesting a reduction of mucus secretion of intestinal glands. Following the intervention, rats in the Moxi groups presented an increase of the body weight, formed feces, and an improvement of the damaged colon tissues as mucosal healing and inflammatory reduction, and a marked decrease of the damage score relevant to the model rats. No significant differences were found in the gross scores among the medication, 1, 2, 3 and 4 moxa-cone groups (P>0.05). The histopathological scores were significantly lower in the 1 and 4 moxa-cone Moxi groups than in the medication group (P<0.05, P<0.01); and significantly lower in the 1, 3, 4 moxa-cone Moxi groups than in the 2 moxa-cone Moxi group (P<0.05, P<0.01). PAS staining showed a significant increase of the AOD values of colonic mucins in the 1, 2, 3 and 4 moxa-cone and medication groups relevant to the model group (P<0.01); and the AOD values of colonic mucins in the 1, 3, 4 moxa-cone Moxi groups were significantly increased than that in the 2 moxa-cone Moxi group (P<0.05, P<0.01). HID-AB staining showed that the AOD values of sulfated mucus content were significantly higher in the 2 and 4 moxa-cone Moxi groups than in the 3 moxa-cone Moxi group (P<0.01). The two-level two-factor factorial analysis showed an interaction existed between the moxa-cone number and Moxi frequency in reducing the gross score and histopathological score and in facilitating colonic mucin and sulfated mucus secretion. The histopathological score of the 4 moxa-cone Moxi group was significantly lower than that of the 2 moxa-cone Moxi group (P<0.05), and the sulfated mucus content was significantly higher in the 4 moxa-cone group than in the 3 moxa-cone group (P<0.01). The effect of Moxi given on alternate days was superior to that of daily Moxi in improving colonic histological damage. Herbal cake-partitioned moxibustion at ST 25 can promote repair of the damaged colonic tissue and secretion of mucin in UC rats. The number of moxa cones and intervention frequency affect the efficacy of Moxi in improving histopathological changes. The Moxi intervention on alternate days and with 2 moxa-cones every time is recommended.

Molecular basis for intestinal mucin recognition by galectin-3 and C-type lectins.

Intestinal mucins trigger immune responses upon recognition by dendritic cells via protein–carbohydrate interactions. We used a combination of structural, biochemical, biophysical, and cell-based approaches to decipher the specificity of the interaction between mucin glycans and mammalian lectins expressed in the gut, including galectin (Gal)-3 and C-type lectin receptors. Gal-3 differentially recognized intestinal mucins with different O-glycosylation profiles, as determined by mass spectrometry (MS). Modification of mucin glycosylation, via chemical treatment leading to a loss of terminal glycans, promoted the interaction of Gal-3 to poly-N-acetyllactosamine. Specific interactions were observed between mucins and mouse dendritic cell-associated lectin (mDectin)-2 or specific intercellular adhesion molecule–grabbing nonintegrin-related-1 (SIGN-R1), but not mDectin-1, using a cell-reporter assay, as also confirmed by atomic force spectroscopy. We characterized the N-glycosylation profile of mouse colonic mucin (Muc)-2 by MS and showed that the interaction with mDectin-2 was mediated by high-mannose N-glycans. Furthermore, we observed Gal-3 binding to the 3 C-type lectins by force spectroscopy. We showed that mDectin-1, mDectin-2, and SIGN-R1 are decorated by N-glycan structures that can be recognized by the carbohydrate recognition domain of Gal-3. These findings provide a structural basis for the role of mucins in mediating immune responses and new insights into the structure and function of major mammalian lectins.—Leclaire, C., Lecointe, K., Gunning, P. A., Tribolo, S., Kavanaugh, D. W., Wittmann, A., Latousakis, D., MacKenzie, D. A., Kawasaki, N., Juge, N. Molecular basis for intestinal mucin recognition by galectin-3 and C-type lectins.

Co-supplementation of isomalto-oligosaccharides potentiates metabolic health benefits of polyphenol-rich cranberry extract in high fat diet-fed mice via enhanced gut butyrate production.

Cranberries are a rich source of polyphenolic antioxidants. Purified sugars or artificial sweeteners are being added to cranberry-based food products to mask tartness. Refined sugar and artificial sweeteners intake modulate gut microbiota and result in metabolic complications. We evaluated effects of isomalto-oligosaccharides (IMOs; sweet tasting non-digestible oligosaccharides) with cranberry extract (CRX) on high fat diet (HFD)-induced metabolic alterations in mice. Male Swiss albino mice were fed normal chow or HFD (58% fat kcal), and were administered either CRX (200mg/kg) alone or in combination with IMOs (1g/kg). Cecal short-chain fatty acids, abundances of selected (1) butyrate producing, (2) metabolically beneficial, and (3) selective lipopolysaccharides producing gram negative gut bacteria were studied. Further, gut-related histological, biochemical, genomic changes along with circulating pro-/anti-inflammatory markers and systemic obesity-associated metabolic changes were studied. Co-supplementation of CRX and IMOs significantly improved cecal SCFAs, especially butyrate levels, selected butyrate-producing bacteria (clostridial cluster XIVa bacteria) and butyrate kinase expression in HFD-fed mice. The combination also significantly improved gut beneficial bacterial abundance, gut histology and related changes (colon mucin production, gut permeability) as compared to individual agents. It also prevented HFD-induced systemic and tissue inflammation, glucose intolerance and systemic obesity-associated metabolic changes in adipose tissue and liver. The combination of CRX and IMOs appeared more effective in the prevention of HFD-induced gut derangements. Combination of CRX and IMOs could be advantageous for normalization of metabolic alterations seen in diet-induced obesity via beneficial modulation of gastrointestinal health.

Entamoeba histolytica-Induced Mucin Exocytosis Is Mediated by VAMP8 and Is Critical in Mucosal Innate Host Defense.

ABSTRACTIntestinal mucus secretion is critical in maintaining mucosal host defense against a myriad of pathogens by preventing direct association with the epithelium. Entamoeba histolytica specifically binds colonic MUC2 mucin and also induces potent hypersecretion from goblet cells; however, characterization of the nature of the mechanisms controlling mucus release remains elusive. In this report, we identify vesicle SNARE vesicle-associated membrane protein 8 (VAMP8) present on mucin granules as orchestrating regulated exocytosis in human goblet cells in response to the presence of E. histolytica. VAMP8 was specifically activated during E. histolytica infection, and ablation of VAMP8 led to impaired mucin secretion. As a consequence, loss of VAMP8 increased E. histolytica adherence to epithelial cells associated with enhanced cell death through apoptosis characterized by caspase 3 and 9 cleavages and DNA fragmentation. With the mucosal barrier compromised in Vamp8−/− animals, E. histolytica induced an aggressive proinflammatory response with elevated levels of interleukin-1 alpha (IL-1α), IL-1β, and tumor necrosis factor alpha (TNF-α) secretion. This report is the first to characterize regulated mucin exocytosis in intestinal goblet cells in response to a pathogen and the downstream consequences of improper mucin secretion in mucosal barrier defense.

Bifidobacterium bifidum Extracellular Sialidase Enhances Adhesion to the Mucosal Surface and Supports Carbohydrate Assimilation.

ABSTRACTBifidobacterium is a natural inhabitant of the human gastrointestinal (GI) tract. We studied the role of the extracellular sialidase (SiaBb2, 835 amino acids [aa]) from Bifidobacterium bifidum ATCC 15696 in mucosal surface adhesion and carbohydrate catabolism. Human milk oligosaccharides (HMOs) or porcine mucin oligosaccharides as the sole carbon source enhanced B. bifidum growth. This was impaired in a B. bifidum ATCC 15696 strain harboring a mutation in the siabb2 gene. Mutant cells in early to late exponential growth phase also showed decreased adhesion to human epithelial cells and porcine mucin relative to the wild-type strain. These results indicate that SiaBb2 removes sialic acid from HMOs and mucin for metabolic purposes and may promote bifidobacterial adhesion to the mucosal surface. To further characterize SiaBb2-mediated bacterial adhesion, we examined the binding of His-tagged recombinant SiaBb2 peptide to colonic mucins and found that His-SiaBb2 as well as a conserved sialidase domain peptide (aa 187 to 553, His-Sia) bound to porcine mucin and murine colonic sections. A glycoarray assay revealed that His-Sia bound to the α2,6-linked but not to the α2,3-linked sialic acid on sialyloligosaccharide and blood type A antigen [GalNAcα1-3(Fucα1-2)Galβ] at the nonreducing termini of sugar chains. These results suggest that the sialidase domain of SiaBb2 is responsible for this interaction and that the protein recognizes two distinct carbohydrate structures. Thus, SiaBb2 may be involved in Bifidobacterium-mucosal surface interactions as well as in the assimilation of a variety of sialylated carbohydrates.

Endoscopic Ultrasound Findings of Colitis Cystica Profunda With Literature Review

Introduction: Colitis Cystica Profunda (CCP) is a rare benign disease of the colon and rectum of uncertain etiology. Its recognition is important since it often mimics malignant processes. We review a case of CCP in a 50-year-old patient, with emphasis on endoscopic ultrasound findings and present review of the current literature. Case description: 50-year-old male with no past medical history was referred to our institution for further evaluation of a large multilobulated mass in the left proximal colon found on screening colonoscopy. We performed colonoscopy with endoscopic ultrasound and fine needle aspiration and snare polypectomy. Colonoscopy up to the transverse colon revealed a large multilobulated submucosal mass with normal overlying mucosa that extends from 50 cm to 70 cm from the anal verge (fig.1). The endosonographic examination revealed anechoic, round, well demarcated lesions with a hyperechoic rim and hypoechoic foci within (fig.2). They were located within the deep mucosa and submucosal layer. The muscularis propria was intact. The largest submucosal lesion measured 18.6 mm x11.4 mm. Small amount of fluid was aspirated by FNA from two lesions. Snare polypectomy of one of the lesions was then performed. The polypectomy site was closed with two endoclips. Histological examination showed multinucleate giant cells in a background of benign colonic elements and mucin consistent with a diagnosis of CCP. Discussion: CCP is an uncommon benign entity that mimics malignancy on endoscopic views but histologically characterized by mucin-filled cysts beneath the muscularis mucosa. It can present in a localized form with a polypoid lesion or more diffusely along the gastrointestinal tract. Endoscopically, CCP are polypoid lesions covered by normal, edematous or ulcerated mucosa. There are few case reports of the endosonographic features of CCP. They were described as hypoechoic or anechoic lesions involving the mucosa or submucosa, with areas of echorefringent fibrosis between lesions by Hulsmans, F.J., et al. In another case report by Sultan et al. the EUS findings of CCP were described as hypoechoic lesion with cystic/spongy features involving the mucosa and submucosa. Our case depicted similar features of well demarcated mucosal and submucosal anechoic lesions with hypoechoic foci surrounded by hyperechoic rim. Colonic EUS can be a useful tool to assist in establishing the diagnosis of CCP.Figure: Colonoscopy showing large multilobulated submucosal mass with overlying normal looking mucosa.Figure: Endosonographic imaging showing anechoic, round, well demarcated lesions.

Brachyspira hyodysenteriae Infection Regulates Mucin Glycosylation Synthesis Inducing an Increased Expression of Core-2 O-Glycans in Porcine Colon.

Brachyspira hyodysenteriae causes swine dysentery (SD), leading to global financial losses to the pig industry. Infection with this pathogen results in an increase in B. hyodysenteriae binding sites on mucins, along with increased colonic mucin secretion. We predict that B. hyodysenteriae modifies the glycosylation pattern of the porcine intestinal mucus layer to optimize its host niche. We characterized the swine colonic mucin O-glycome and identified the differences in glycosylation between B. hyodysenteriae-infected and noninfected pigs. O-Glycans were chemically released from soluble and insoluble mucins isolated from five infected and five healthy colon tissues and analyzed using porous graphitized carbon liquid chromatography tandem mass spectrometry. In total, 94 O-glycans were identified, with healthy pigs having higher interindividual variation, although a larger array of glycan structures was present in infected pigs. This implied that infection induced loss of individual variation and that specific infection-related glycans were induced. The dominating structures shifted from core-4-type O-glycans in noninfected pigs toward core-2-type O-glycans in infected animals, which correlated with increased levels of the C2GnT glycosyl transferase. Overall, glycan chains from infected pigs were shorter and had a higher abundance of structures that were neutral or predominantly contained NeuGc instead of NeuAc, whereas they had a lower abundance of structures that were fucosylated, acidic, or sulfated than those from noninfected pigs. Therefore, we conclude that B. hyodysenteriae plays a major role in regulating colonic mucin glycosylation in pigs during SD. The changes in mucin O-glycosylation thus resulted in a glycan fingerprint in porcine colonic mucus that may provide increased exposure of epitopes important for host-pathogen interactions. The results from this study provide potential therapeutic targets and a platform for investigations of B. hyodysenteriae interactions with the host via mucin glycans.

Chickpea-supplemented diet alters the gut microbiome and enhances gut barrier integrity in C57Bl/6 male mice

Pulses are rich in fermentable fibre and phenolic compounds that have the potential to modify baseline function within the gut microenvironment (microbiota and epithelial barrier), thereby mitigating gut-associated diseases. The objective was to assess the gut health promoting effects of dietary chickpea in C57BL/6 mice consuming a 20% cooked chickpea flour diet (CK) or an isocaloric control diet for 3weeks. Gut health was enhanced by CK including (i) colon crypt mucus content and mucin mRNA expression, (ii) crypt length, proliferation, and epithelial barrier junctional components expression, (iii) anti-microbial defenses, and (iv) altered cecal and fecal microbiota community structure (e.g. increased Prevotella) with enhanced metagenomic functions (e.g. increased flavonoid biosynthesis, butanoate metabolism), and microbial activity (increased short chain fatty acid production). Collectively, CK modulated the baseline function of the colonic microenvironment (microbiome and epithelial barrier), thereby priming colonic function such that the severity of gut-associated diseases could be mitigated.