Colonic Permeability Research Articles

Anti-inflammatory and glial response maintain normal colon function in trimethyltin-treated rats.

Studies on the contribution of enteric neuropathy and intestinal homeostasis to central nervous system degeneration using animal models have reported varying results. Recently, colonic myenteric plexus degeneration was observed in trimethyltin-treated rats. Further characterization of this animal model is necessary to determine its potential for investigating the relationship between the enteric nervous system and central nervous system degeneration. In this study, trimethyltin-treated rats (8mg/kg body weight, i.p.) were used to measure colonic function, structure, and possible colon abnormalities. The colonic function was assessed by measuring fecal pellet output and transit time. Hematoxylin and eosin staining and immunohistochemistry were performed to evaluate inflammatory profiles and intestinal epithelial cell homeostasis. The expression of mRNA encoding tight junction proteins was quantified with quantitative PCR to determine colon permeability. Histological examination of the colon revealed mucosal immune cell infiltration, crypt damage, and high iNOS and arginase-1 expression in the mucosal layer of trimethyltin-treated rats. At the same time, trimethyltin induced high expression of iNOS, arginase-1, and GFAP and increased cell death in the colonic myenteric plexus. The low cell proliferation and low goblet cell distribution suggested altered intestinal epithelial cell homeostasis in trimethyltin-treated rats. Trimethyltin also upregulated claudin 1 expression. However, normal colon function was preserved. In conclusion, the results show that trimethyltin induces colon inflammation and cell death in the colonic myenteric plexus, and disrupts intestinal epithelial cell homeostasis. However, the balance between anti-inflammatory and pro-inflammatory responses maintains normal colon function in trimethyltin-treated rats.

Splenectomy prevents brain orexin, ghrelin, or oxytocin but not GLP-1-induced improvement of intestinal barrier function in rats.

Accumulating evidence has suggested that neuropeptides such as orexin, ghrelin, or oxytocin act centrally in the brain to regulate intestinal barrier function through the vagus nerve. It has been reported that the vagal cholinergic anti-inflammatory pathway was blocked by splenectomy. In the present study, we therefore examined the effect of splenectomy on neuropeptides-induced improvement of increased intestinal permeability. Colonic permeability was determined invivo by quantifying the absorbed Evans blue in colonic tissue for 15 min spectrophotometrically in rats. Splenectomy increased colonic permeability. The increased permeability by splenectomy was significantly blocked by vagal activation induced by carbachol or 2-deoxy-d-glucose which was prevented by atropine, suggesting vagal activation could prevent colonic hyperpermeability in splenectomized rats. In the splenectomized rats, intracisternal injection of orexin, ghrelin, oxytocin, or butyrate failed to inhibit increased colonic permeability while intracisternal glucagon-like peptide-1 (GLP-1) analogue, liraglutide, potently blocked the increased colonic permeability in a dose-dependent manner. The liraglutide-induced improvement of increased colonic permeability was blocked by atropine in splenectomized rats. Intracisternal injection of GLP-1 receptor antagonist attenuated 2-deoxy-d-glucose-induced improvement of colonic hyperpermeability in splenectomized rats. The present results suggested that the spleen is important in the improvement of intestinal barrier function by brain orexin, ghrelin or oxytocin, and butyrate. On the other hand, GLP-1 acts centrally in the brain to improve colonic hyperpermeability in a spleen-independent manner. All these results suggest that dual mechanisms (spleen dependent or independent) may exist for the brain-gut regulation in intestinal barrier function.

A microphysiological system for studying barrier health of live tissues in real time

Epithelial cells create barriers that protect many different components in the body from their external environment. Increased gut barrier permeability (leaky gut) has been linked to several chronic inflammatory diseases. Understanding the cause of leaky gut and effective interventions are elusive due to the lack of tools that maintain tissue’s physiological environment while elucidating cellular functions under various stimuli ex vivo. Here we present a microphysiological system that records real-time barrier permeability of mouse colon in a physiological environment over extended durations. The system includes a microfluidic chamber; media composition that preserves microbiome and creates necessary oxygen gradients across the barrier; and integrated sensor electrodes for acquiring transepithelial electrical resistance (TEER). Our results demonstrate that the system can maintain tissue viability for up to 72 h. The TEER sensors can distinguish levels of barrier permeability when treated with collagenase and low pH media and detect different thickness in the tissue explant.

The neurotensin receptor 1 agonist PD149163 alleviates visceral hypersensitivity and colonic hyperpermeability in rat irritable bowel syndrome model.

An impaired intestinal barrier with the activation of corticotropin-releasing factor (CRF), Toll-like receptor 4 (TLR4), and proinflammatory cytokine signaling, resulting in visceral hypersensitivity, is a crucial aspect of irritable bowel syndrome (IBS). The gut exhibits abundant expression of neurotensin; however, its role in the pathophysiology of IBS remains uncertain. This study aimed to clarify the effects of PD149163, a specific agonist for neurotensin receptor 1 (NTR1), on visceral sensation and gut barrier in rat IBS models. The visceral pain threshold in response to colonic balloon distention was electrophysiologically determined by monitoring abdominal muscle contractions, while colonic permeability was measured by quantifying absorbed Evans blue in colonic tissue invivo in adult male Sprague-Dawley rats. We employed the rat IBS models, i.e.,lipopolysaccharide (LPS)- and CRF-induced visceral hypersensitivity and colonic hyperpermeability, and explored the effects of PD149163. Intraperitoneal PD149163 (160, 240, 320 μg kg-1) prevented LPS (1 mg kg-1, subcutaneously)-induced visceral hypersensitivity and colonic hyperpermeability dose-dependently. It also prevented the gastrointestinal changes induced by CRF (50 μg kg-1, intraperitoneally). Peripheral atropine, bicuculline (a GABAA receptor antagonist), sulpiride (a dopamine D2 receptor antagonist), astressin2-B (a CRF receptor subtype 2 [CRF2] antagonist), and intracisternal SB-334867 (an orexin 1 receptor antagonist) reversed these effects of PD149163 in the LPS model. PD149163 demonstrated an improvement in visceral hypersensitivity and colonic hyperpermeability in rat IBS models through the dopamine D2, GABAA, orexin, CRF2, and cholinergic pathways. Activation of NTR1 may modulate these gastrointestinal changes, helping to alleviate IBS symptoms.

Somatostatin peptides prevent increased human colonic epithelial permeability induced by hypoxia.

Mesenteric ischemia increases gut permeability and bacterial translocation. In human colon, chemical hypoxia induced by 2,4-dinitrophenol (DNP) activates basolateral intermediate conductance K+ (IK) channels (designated KCa3.1 or KCNN4) and increases paracellular shunt conductance/permeability (GS), but whether this leads to increased macromolecule permeability is unclear. Somatostatin (SOM) inhibits IK channels and prevents hypoxia-induced increases in GS. Thus, we examined whether octreotide (OCT), a synthetic SOM analog, prevents hypoxia-induced increases GS in human colon and hypoxia-induced increases in total epithelial conductance (GT) and permeability to FITC-dextran 4000 (FITC) in rat colon. The effects of serosal SOM and OCT on increases in GS induced by 100 µM DNP were compared in isolated human colon. The effects of OCT on DNP-induced increases in GT and transepithelial FITC movement were evaluated in isolated rat distal colon. GS in DNP-treated human colon was 52% greater than in controls (P = 0.003). GS was similar when 2 µM SOM was added after or before DNP treatment, in both cases being less (P < 0.05) than with DNP alone. OCT (0.2 µM) was equally effective preventing hypoxia-induced increases in GS, whether added after or before DNP treatment. In rat distal colon, DNP significantly increased GT by 18% (P = 0.016) and mucosa-to-serosa FITC movement by 43% (P = 0.01), and 0.2 µM OCT pretreatment completely prevented these changes. We conclude that OCT prevents hypoxia-induced increases in paracellular/macromolecule permeability and speculate that it may limit ischemia-induced gut hyperpermeability during abdominal surgery, thereby reducing bacterial/bacterial toxin translocation and sepsis.NEW & NOTEWORTHY Somatostatin (SOM, 2 µM) and octreotide (OCT, 0.2 µM, a long-acting synthetic analog of SOM) were equally effective in preventing chemical hypoxia-induced increases in paracellular shunt permeability/conductance in isolated human colon. In rat distal colon, chemical hypoxia significantly increased total epithelial conductance and transepithelial movement of FITC-dextran 4000, changes completely prevented by 0.2 µM OCT. OCT may prevent or limit gut ischemia during abdominal surgery, thereby decreasing the risk of bacterial/bacterial toxin translocation and sepsis.

Effects of the N-Butanol Extract of Pulsatilla Decoction on Neutrophils in a Mouse Model of Ulcerative Colitis.

Ulcerative colitis (UC) is a chronic inflammatory disease, the incidence of which is increasing worldwide. However, the etiology and pathogenesis of UC remains unclear. The n-butanol extract of Pulsatilla decoction (BEPD), a traditional Chinese medicine, has been shown to be effective in treating UC. This study aimed to explore the molecular mechanism underlying the effects of BEPD on UC, in particular its effects on neutrophil extracellular trap (NET) formation by neutrophils. High-performance liquid chromatography was used to determine the principal compounds of BEPD. UC was induced in mice using dextran sodium sulfate, and mice were treated with 20, 40, or 80 mg/kg BEPD daily for seven days. Colonic inflammation was determined by assessing the disease activity index, histopathology, colonic mucosal damage index, colonic mucosal permeability, and pro- and anti-inflammatory cytokine levels. The infiltration and activation status of neutrophils in the colon were determined by analyzing the levels of chemokine (C-X-C motif) ligand (CXCL) 1 and CXCL2, reactive oxygen species, Ly6G, and numerous NET proteins. The findings suggest that BEPD improved the disease activity index, histopathology, and colonic mucosal damage index scores of mice with UC, and restored colonic mucosal permeability compared with untreated mice. The expression levels of the pro-inflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α in colon tissues were significantly decreased, while the expression levels of anti-inflammatory cytokines in colon tissues were significantly increased, exceeding those of control mice. In addition, BEPD reduced the expression of the neutrophil chemokines CXCL1 and CXCL2 in the colon tissue of mice with UC, reduced neutrophil infiltration, reduced reactive oxygen species levels, and significantly reduced the expression of NET proteins. BEPD also significantly reduced NET formation. The results of this study suggest that BEPD exerts therapeutic effects in a murine model of UC by inhibiting neutrophil infiltration and activation in the colon, as well as by inhibiting the expression of key proteins involved in NET formation and reducing NET formation, thereby alleviating local tissue damage and disease manifestations.

Translational evaluation of Gelsectan® effects on gut barrier dysfunction and visceral pain in animal models and irritable bowel syndrome with diarrhoea.

Gelsectan® is a formulation of xyloglucan (XG), pea protein, grape seed extract (PPGS) and xylo-oligosaccharides (XOS). Our aim was to examine the effect of Gelsectan® on rectal sensitivity in an animal model, abdominal pain in irritable bowel syndrome with diarrhoea (IBS-D) subjects and intestinal permeability in both conditions. Animals: Wistar rats received gavage with XOS, XG+PPGS or XG+PPGS+XOS, as a single dose or for 7days before a partial restraint stress (PRS). Visceromotor response to rectal distension and total gut paracellular permeability to 51Cr-EDTA were assessed. Humans: IBS-D and control patients were involved. After initial colonoscopy with biopsy sampling Gelsectan® was administered to IBS-D patients for 12weeks. Stool count and pain scores were documented. After treatment, colonoscopy was repeated. The permeability of biopsy samples was measured in Ussing-chambers. Adherent mucus layer, Muc-2 expression as well as TNFα, Interferon IFNγ were evaluated by histology/immunohistochemistry and ELISA assays, respectively. Animal studies: In control rats, PRS significantly increased visceromotor response as well as gut paracellular permeability. Single dose administration of XG+PPGS+XOS failed to reverse PRS, but 7days of oral treatment reversed PRS-induced rectal hypersensitivity and gut hyperpermeability. Human studies: Gelsectan® treatment significantly reduced and abdominal pain. Intestinal permeability in IBS-D patients was elevated compared with controls, Gelsectan® restored permeability in the ascendent colon. Periodic acid-Schiff-stained mucus layer was significantly thinner in IBS-D patients compared with controls, In both segments, mucus thickness and the proportion of Muc-2 positive cells were not affected by Gelsectan® treatment. IFNγ tissue level in the sigmoid colon shows modest mucosal inflammation in IBS-D. Gelsectan® prevented rectal hypersensitivity in rats, abdominal pain in human and intestinal hyperpermeability in rat and human studies respectively. These effects involve restoration of gut permeability. Based on this translational study, Gelsectan® can be considered as an effective therapy for IBS-D symptoms.

Dietary Milk Phospholipids Increase Body Fat and Modulate Gut Permeability, Systemic Inflammation, and Lipid Metabolism in Mice

The study aimed at how dietary milk polar lipids affect gut permeability, systemic inflammation, and lipid metabolism during diet-induced obesity (DIO). C57BL/6J mice (n = 6x3) were fed diets with 34% fat as energy for 15 weeks: (1) modified AIN-93G diet (CO); (2) CO with milk gangliosides (GG); (3) CO with milk phospholipids (MPL). Gut permeability was assessed by FITC-dextran and sugar absorption tests. Intestinal tight junction proteins were evaluated by Western blot. Plasma cytokines were measured by immunoassay. Body composition was assessed by magnetic resonance imaging. Tissue lipid profiles were obtained by thin layer chromatography. Hepatic expression of genes associated with lipid metabolism was assessed by RT-qPCR. MPL increased the efficiency of converting food into body fat and facilitated body fat accumulation compared with CO. MPL and GG did not affect fasting glucose or HOMA-IR during DIO. MPL increased while GG decreased plasma TG compared with CO. MPL decreased phospholipids subclasses in the muscle while increased those in the liver compared with CO. GG and MPL had little effect on hepatic expression of genes associated with lipid metabolism. Compared with CO, MPL decreased polar lipids content in colon mucosa. Small intestinal permeability decreased while colon permeability increased and then recovered during the feeding period. High-fat feeding increased plasma endotoxin after DIO but did not affect plasma cytokines. MPL and GG did not affect plasma endotoxin, adipokines and inflammatory cytokines. After the establishment of obesity, MPL increased gut permeability to large molecules but decreased intestinal absorption of small molecules while GG tended to have the opposite effects. MPL and GG decreased mannitol and sucralose excretions, which peaked at d 45 in the CO group. MPL decreased occludin in jejunum mucosa compared with CO. GG and MPL did not affect zonula occludens-1 in gut mucosa. In conclusion, during DIO, milk GG decreased gut permeability, and had little effect on systemic inflammation and lipid metabolism; MPL facilitated body fat accumulation, decreased gut permeability, did not affect systemic inflammation.

Protective properties of Ophiopogonin D in DSS-induced colitis: insights into microbiota modulation.

Ulcerative colitis (UC), a chronic inflammatory gastrointestinal disorder, is becoming increasingly prevalent worldwide. Ophiopogonin D, which is derived from Ophiopogon japonicus, exhibits anti-inflammatory and antioxidant properties, yet its therapeutic potential in UC remains unclear. In this study, we employed a mouse model of DSS-induced colitis to assess the impact of Ophiopogonin D on various parameters, including weight loss, bloody stools, and inflammation in the colon. Ophiopogonin-D treatment significantly mitigated these DSS-induced effects, improved colon permeability, and modulated inflammatory markers like ZO-1, MUC-2, TNF-α, and IL-1β in mice compared with the control. Furthermore, compared to the DSS-treatment group, Ophiopogonin-D treatment improved the α- and β-diversity indices of the mouse intestinal microbiota, along with an increase in the abundance of genera such as Akkermansia (AKK) and a decrease in the abundance of genera such as Enterobacter. Notably, propionic acid, a metabolite of AKK, demonstrated significant improvement in the symptoms of DSS-induced colitis in mice compared to the control. Moreover, propionic-acid administration also resulted in alterations in the levels of inflammatory factors and calreticulin within the intestinal tissues. Overall, Ophiopogonin D significantly affects intestinal microbiota composition, thereby improving symptoms of DSS-induced colitis in mice. These findings present promising therapeutic strategies and potential pharmaceutical candidates for the treatment of ulcerative colitis.

Mathematical Modeling of Vedolizumab Treatment's Effect on Microbiota and Intestinal Permeability in Inflammatory Bowel Disease Patients.

Growing evidence suggests that impaired gut permeability and gut microbiota alterations are involved in the pathogenesis of Inflammatory Bowel Diseases (IBDs), which include Ulcerative Colitis (UC) and Crohn's Disease (CD). Vedolizumab is an anti-α4β7 antibody approved for IBD treatment, used as the first treatment or second-line therapy when the first line results in inadequate effectiveness. The aim of this study is to develop a mathematical model capable of describing the pathophysiological mechanisms of Vedolizumab treatment in IBD patients. In particular, the relationship between drug concentration in the blood, colonic mucosal permeability and fecal microbiota composition was investigated and modeled to detect and predict trends in order to support and tailor Vedolizumab therapies. To pursue this aim, clinical data from a pilot study on a cluster of 11 IBD patients were analyzed. Enrolled patients underwent colonoscopy in three phases (before (t0), after 24 weeks of (t1) and after 52 weeks of (t2 ) Vedolizumab treatment) to collect mucosal biopsies for transepithelial electrical resistance (TEER) evaluation (permeability to ions), intestinal permeability measurement and histological analysis. Moreover, fecal samples were collected for the intestinal microbiota analysis at the three time points. The collected data were compared to those of 11 healthy subjects at t0, who underwent colonoscopy for screening surveillance, and used to implement a three-compartmental mathematical model (comprising central blood, peripheral blood and the intestine). The latter extends previous evidence from the literature, based on the regression of experimental data, to link drug concentration in the peripheral blood compartment with Roseburia abundance and intestinal permeability. The clinical data showed that Vedolizumab treatment leads to an increase in TEER and a reduction in intestinal permeability to a paracellular probe, improving tissue inflammation status. Microbiota analysis showed increasing values of Roseburia, albeit not statistically significant. This trend was adequately reproduced by the mathematical model, which offers a useful tool to describe the pathophysiological effects of Vedolizumab therapy on colonic mucosal permeability and fecal microbiota composition. The model's satisfactory predictive capabilities and simplicity shed light on the relationship between the drug, the microbiota and permeability and allow for its straightforward extension to diverse therapeutic conditions.

Transcriptomic and Metabolomic Correlates of Increased Colonic Permeability in Postinfection Irritable Bowel Syndrome

Background and aimPost-infection irritable bowel syndrome (PI-IBS) is well-known epidemiologically; however, its physiological and molecular characteristics are not well studied. We aimed to determine the physiological phenotypes, colonic transcriptome, fecal microbiome, and metabolome in PI-IBS. MethodsFifty-one Rome III Campylobacter PI-IBS patients and 39 healthy volunteers (HV) were enrolled. Participants completed questionnaires, in vivo intestinal permeability, gastrointestinal transit, and rectal sensation. Fecal samples were collected for shotgun metagenomics, untargeted metabolomics, and sigmoid colonic biopsies for bulk RNAseq. Differential gene expression, differences in microbiota composition and metabolite abundance were determined. Gene and metabolite clusters were identified via weighted gene correlation network analysis and correlations with clinical and physiological parameters determined. ResultsPI-IBS (59% F, 46±2 yrs.) and HV (64% F, 42±2 yrs.) demographics were comparable. Mean IBS-symptom severity score was 227; 94% were non-constipation. 2-24h lactulose excretion was increased in PI-IBS, suggesting increased colonic permeability (4.4±0.5 mg vs. 2.6±0.3 mg, p=0.01). Colonic transit and sensory thresholds were similar between the two groups. Overall, expression of 2036 mucosal genes and 223 fecal metabolites were different, with changes more prominent in females. Fecal N-acetylputrescine was increased in PI-IBS and associated with colonic permeability, worse diarrhea, and negatively correlated with abundance of Collinsella aerofaciens. Histamine and N-acetyl histamine positively associated with 2-24 hr lactulose excretion. Eight weighted gene coexpression modules significantly correlated with phenotypes (sex, stool frequency, colonic permeability, transit). ConclusionsCampylobacter PI-IBS patients demonstrate higher colonic permeability which associated with changes in polyamine and histamine metabolites. Female patients demonstrated greater molecular changes.

Colonic Epithelial Permeability to Ions Is Restored after Vedolizumab Treatment and May Predict Clinical Response in Inflammatory Bowel Disease Patients.

Vedolizumab (VDZ) is used for treating inflammatory bowel disease (IBD) patients. A study investigating colonic epithelial barrier function ex vivo following VDZ is lacking. This work aims to evaluate ex vivo the colonic epithelial barrier function in IBD patients at baseline and during VDZ treatment, and to investigate the relationships between barrier function and clinical parameters. Colonic specimens were obtained from 23 IBD patients before, and at 24 and 52 weeks after VDZ treatment, and from 26 healthy volunteers (HV). Transepithelial electrical resistance (TEER, permeability to ions) and paracellular permeability were measured in Ussing chambers. IBD patients showed increased epithelial permeability to ions (TEER, 13.80 ± 1.04 Ω × cm2 vs. HV 20.70 ± 1.52 Ω × cm2, p < 0.001) without changes in paracellular permeability of a 4 kDa probe. VDZ increased TEER (18.09 ± 1.44 Ω × cm2, p < 0.001) after 52 weeks. A clinical response was observed in 58% and 25% of patients at week 24, and in 62% and 50% at week 52, in ulcerative colitis and Crohn's disease, respectively. Clinical and endoscopic scores were strongly associated with TEER. TEER < 14.65 Ω × cm2 predicted response to VDZ (OR 11; CI 2-59). VDZ reduces the increased permeability to ions observed in the colonic epithelium of IBD patients before treatment, in parallel to a clinical, histological (inflammatory infiltrate), and endoscopic improvement. A low TEER predicts clinical response to VDZ therapy.

Role of CRF1 and CRF2 Receptors in Stress-induced Increase of Intestinal Epithelial Permeability in the Mouse Colon

Background and Aims: Stress is known to increase intestinal permeability, which may contribute to the development of irritable bowel syndrome (IBS) and other intestinal disorders. Corticotropin releasing factor (CRF) has been proven to mediate stress-induced changes in gut function, such as increased colonic motility, ion secretion, and intestinal permeability. Actions of CRF are mediated by two G-protein coupled receptors, CRF1 and CRF2; both are expressed in the intestine. However, the roles of the CRF1 and CRF2 receptors in stress-induced increase of intestinal epithelial permeability remain unknown. Methods: Adult male and female C57BL/6 mice were restrained (1h/d) for five consecutive days. The selective CRF1 and CRF2 receptor antagonists were injected intraperitoneally 15 min prior to the restraint stress. Control mice were kept in their home cages without restraint. After the last restraint stress/control session, the proximal colon was removed, and the mucosa/submucosa preparations were dissected and mounted onto the Ussing Chamber System for the measurement of intestinal permeability. Transepithelial resistance (TER) and FITC-inulin (4kD) flux across the colonic epithelium were used as indicators of paracellular permeability. Horseradish peroxidase (HRP, 40kD) flux was used to measure transcellular permeability. Results: Restraint stress did not alter TER or FITC-inulin flux in male mice. Pretreatment with the CRF1 receptor antagonist NBI 27914 or the CRF2 receptor antagonist antisauvagine-30 had no effect on TER or FITC-inulin flux in male mice. In female mice, restraint stress significantly reduced TER and increased FITC-inulin flux in the proximal colon, which were blocked by NBI 27914 but not by antisauvagine-30. Restraint stress significantly increased HRP flux in both male and female mice. In male mice, pretreatment with NBI 27914 significantly reduced stress-evoked increase of HRP flux, while antisauvagine-30 had no effect. In female mice, both NBI 27914 and antisauvagine-30 significantly reduced stress-evoked increase of HRP flux. Conclusions: Stress evokes different changes in epithelial permeability in the proximal colon of male and female mice. In male mice, stress does not influence paracellular permeability but increases transcellular permeability, which is mediated by the CRF1 receptor. In female mice, stress increases both transcellular and paracellular permeability. Stress-induced increase of paracellular permeability was mediated by the CRF1 receptor, but the increased transcellular permeability was mediated by both CRF1 and CRF2 receptors. University of Wisconsin-La Crosse Undergraduate Research Grant (CS and LB). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Gastrointestinal Permeability After Bariatric Surgery: A Systematic Review.

Gastrointestinal permeabilityrefers to the movement of substances across the gut wall. This is mediated by endotoxemia (bacterial products entering the systemic circulation), and is associated with metabolic disease. The effect of bariatric surgery on permeability remains uncertain; the associated dietary, metabolic and weight changes are suggested to influence, or trigger, altered permeability. The primary aim of this study is to synthesize evidence and analyze the effect of bariatric surgery on permeability. A systematic review was performed, searching MEDLINE, EMBASE, and Scopus until February 2023, using MESH terms "intestinal permeability", "bariatric", for studies reporting in vivo assessment of permeability. Three cohort studies and two case series were identified (n=96). Data was heterogeneous; methodology and controls preclude meta-analysis. Gastroduodenal permeability reduced post-sleeve gastrectomy (SG). Two studies showed an increase in small intestinal permeabilityafter biliopancreatic diversion. Two studies revealed a decrease in post-Roux-en-Y gastric bypass. One study identified increased colonic permeability six months post-SG. Evidence regarding permeability change after bariatric surgery is conflicting, notably for the small intestine. Impaired colonic permeability post-SG raises concerns regarding colonic protein fermentation and harmful dietary sequelae. There are multiple interacting variables confounding gastrointestinal permeability change; procedure type, altered microbiotaand metabolic response to surgery. Further understanding of this important aspect of obesity is required, both before and after bariatric surgery.

Paneth Cell-Specific TRPV6 Channel Plays a Crucial Role in Alcohol-Associated Dysbiosis of Gut Microbiota and Tissue Injury at the Gut-Liver Axis

Introduction: Endotoxemia plays an essential role in alcohol-associated tissue injury. Two factors contributing to endotoxemia are gut microbiota dysbiosis and epithelial barrier dysfunction. Previous studies indicated that TRPV6 channel-mediated Ca2+ influx plays a crucial role in alcohol-induced epithelial tight junction (TJ) disruption, mucosal barrier dysfunction, and endotoxemia. Trpv6 knockout mice were resistant to alcohol-induced intestinal barrier dysfunction and modulated microbiota dysbiosis, raising the question of how TRPV6 regulates microbiota composition. In this study, we investigated the role of Paneth cell-specific TRPV6 in alcohol-induced microbiota dysbiosis and barrier dysfunction. Methods: Adult Trpv6fl/fl (WT) and Trpv6fl/fl-Defa6Cre (KO; Paneth cell-specific TRPV6 knockout) mice were fed a Lieber-DiCarli liquid diet with EtOH (0% 2d, 1% 2d, 2% 2d, 4% 1wk, 5% 1wk, &amp; 6% 1wk). Control groups were pair-fed an isocaloric EtOH-free diet. Intestinal permeability was measured by vascular-to-luminal flux of FITC-inulin in vivo, and mucosal inflammation was assessed by RT-PCR for cytokines/chemokines. Plasma lipopolysaccharide (LPS) was measured to evaluate endotoxemia. Gut microbiota was analyzed by 16S rRNA sequencing of colonic flushing. Lipidome in colonic flushing was analyzed using nontargeted liquid chromatography-mass spectrometry. Microbiome and lipidome data were processed by bioinformatic analyses. Results and conclusion: Data show that colon length was reduced, and colonic mucosal permeability in vivo was elevated by EtOH in WT mice. The increase in mucosal permeability was associated with increased plasma LPS levels. EtOH feeding elevated the expression of IL-6, IL-1β, and TNFα in the colon. EtOH-induced changes in colon length, mucosal permeability, cytokine expression, and plasma LPS were absent in KO mice. 16S rRNA sequencing data indicated that the microbiota composition in KO mice differed from that of WT mice. The relative abundance of Prevotellaceae, Xanthomonadaceae, and Streptococaceae were higher, and Psuedomonadaceae and Verrucomicrobiaceae abundance were lower in KO mice compared to WT mice. EtOH-induced increase in the abundance of Norcardiaceae and Psuedomonadaceae was low or absent in KO mice. EtOH increased Rhodococcus, Odoribacter, and Pseudomonas abundance at the genus level in WT but not KO mice. On the other hand, Clostridium, Turicibacter, and Helicobacter abundance were increased by EtOH in KO but not WT mice. Lipidomic analysis of colonic flushing showed that phospholipid contents were higher in KO mice than WT mice, irrespective of sex and treatments. A cluster of sphingolipids was dramatically high in KO female mice, which was reduced by EtOH feeding. Short-chain fatty acid esters of hydroxy fatty acids (AAHFA 3:0/24:0;O) were elevated by EtOH in male WT mice but not in female WT and male or female KO mice. In conclusion, these data indicate that Paneth cell-specific deletion of TRPV6 attenuates alcohol-induced changes in gut microbiota, colonic luminal lipids, mucosal barrier function, and endotoxemia in mice. NIH/NIAAA, RO1-AA029270; Veterans Administration IO1-BX003014. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Luminal Polyamines Disrupt Intestinal Barrier and Undergo Complex Regulation by Host and Commensal Microbiota

Background: Polyamines produced by host cells and intestinal microbiota and are critical to overall health. Studies have shown putrescine, a polyamine, can strengthen, or in some instances disrupt, gastrointestinal (GI) barrier integrity, yet the regulation of polyamine concentrations in the GI tract is unknown. Host colonocytes and microbiota both metabolize polyamines, and in GI diseases like irritable bowel syndrome (IBS) where intestinal microbiota is significantly altered, polyamine metabolism may be affected. Aim: Determine regulation of luminal polyamine concentration and its effects on intestinal barrier integrity. Hypothesis: Luminal polyamine concentration is suppressed by commensal intestinal microbiota and increasing concentration of putrescine results in intestinal barrier disruption. Methods: Microbiota effects on luminal polyamine concentrations were assessed by humanizing germ-free (GF) mice with a single oral gavage of commensal human microbiota. Polyamine effect on barrier integrity was assessed in vitro using Caco-2 cells and ex vivo on Ussing using mouse colonic tissue with 300Da fluorescein and 4kDa FITC-Dextran tracers. Changes in transepithelial resistance (TER) and rate of tracer flux was recorded. Untargeted metabolomics with shotgun metagenomics was completed on human fecal samples and sigmoid colonic biopsies were collected for bulk RNAseq. Bray-Curtis distance was determined at the species level using the PERMANOVA method and used to test relationships between beta-diversity and fecal polyamine concentration. Results: Humanization with human commensal microbiota (1.2% C. aerofaciens) lead to a 20-fold increase in cecal putrescine and a 20-fold decrease in fecal putrescine compared to GF controls. In vitro addition of putrescine (100mM) caused increased fluorescein flux (3.50±0.24 vs 1.44±0.04 mg/mL) and a rapid loss of transepithelial resistance compared to controls (% of Baseline TER, 36.6±8.2 vs 102.8±5.4, 3h postexposure). Ex vivo addition of putrescine caused a loss of TER (57% vs 89% of baseline by 3h) and an increased rate of 4kDa FITC-Dextran flux compared to untreated controls (1236±131 vs 562±70 ng/hr/cm2). Transcriptomic profiles show decreased expression of ornithine decarboxylase antienzyme (OAZ1, FDR=0.018) in IBS which inhibits the rate limiting enzyme for putrescine production. Increased lactulose excretion (2-24h), suggestive of increased distal colonic permeability, correlated with N-acetylputrescine concentration (p=0.07). N-acetylputrescine also correlated positively with increased stool frequency (p=0.009) and looser consistency (p=0.013). C. aerofaciens, a polyamine consumer, negatively correlated with n-acetylputrescine (FDR=0.02) suggesting a loss of specific taxa may lead to insuffcient polyamine metabolism. Conclusion: Polyamines, namely putrescine, disrupts intestinal barrier integrity, correlate with in vivo permeability, and are decreased in the colon by commensal microbiota. These observations identify putrescine as a negative effector of barrier function and suggest a novel role for the commensal microbiome in regulating barrier integrity through polyamine metabolism. Further work investigating host and microbiota mechanisms of polyamine metabolism, signaling and the specific taxa involved is needed to better understand the effects polyamines have on GI physiology. NIH DK 127998 (MG), support from Mayo Clinic Center for Individualized Medicine (CIM), and Mayo Clinic Center for Cell Signalling in Gastroenterology (C-Sig) P30DK084567. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Modulation of intestinal epithelial permeability by chronic small intestinal helminth infections.

Increased permeability of the intestinal epithelial layer is linked to the pathogenesis and perpetuation of a wide range of intestinal and extra-intestinal diseases. Infecting humans with controlled doses of helminths, such as human hookworm (termed hookworm therapy), is proposed as a treatment for many of the same diseases. Helminths induce immunoregulatory changes in their host which could decrease epithelial permeability, which is highlighted as a potential mechanism through which helminths treat disease. Despite this, the influence of a chronic helminth infection on epithelial permeability remains unclear. This study uses the chronically infecting intestinal helminth Heligmosomoides polygyrus to reveal alterations in the expression of intestinal tight junction proteins and epithelial permeability during the infection course. In the acute infection phase (1 week postinfection), an increase in intestinal epithelial permeability is observed. Consistent with this finding, jejunal claudin-2 is upregulated and tricellulin is downregulated. By contrast, in the chronic infection phase (6 weeks postinfection), colonic claudin-1 is upregulated and epithelial permeability decreases. Importantly, this study also investigates changes in epithelial permeability in a small human cohort experimentally challenged with the human hookworm, Necator americanus. It demonstrates a trend toward small intestinal permeability increasing in the acute infection phase (8 weeks postinfection), and colonic and whole gut permeability decreasing in the chronic infection phase (24 weeks postinfection), suggesting a conserved epithelial response between humans and mice. In summary, our findings demonstrate dynamic changes in epithelial permeability during a chronic helminth infection and provide another plausible mechanism by which chronic helminth infections could be utilized to treat disease.

Tranilast alleviates visceral hypersensitivity and colonic hyperpermeability by suppressing NLRP3 inflammasome activation in irritable bowel syndrome rat models

Visceral hypersensitivity resulting from compromised gut barrier with activated immune system is a key feature of irritable bowel syndrome (IBS). Corticotropin-releasing factor (CRF) and Toll-like receptor 4 (TLR4) activate proinflammatory cytokine signaling to induce these changes, which is one of the mechanisms of IBS. As activation of the NLRP3 inflammasome by lipopolysaccharide (LPS) or TLR4 leads to release interleukin (IL)-1β, the NLRP3 inflammasome may be involved in the pathophysiology of IBS. Tranilast, an anti-allergic drug has been demonstrated to inhibit the NLRP3 inflammasome, and we evaluated the impact of tranilast on visceral hypersensitivity and colonic hyperpermeability induced by LPS or CRF (IBS rat model). Visceral pain threshold caused by colonic balloon distention was measured by monitoring abdominal muscle contractions electrophysiologically. Colonic permeability was determined by quantifying the absorbed Evans blue within the colonic tissue. Colonic protein levels of NLRP3 and IL-1β were assessed by immunoblot or ELISA. Intragastric administration of tranilast (20–200 mg/kg) for 3 days inhibited LPS (1 mg/kg)-induced visceral hypersensitivity and colonic hyperpermeability in a dose-dependent manner. Simultaneously, tranilast also abolished these alterations induced by CRF (50 µg/kg). LPS increased colonic protein levels of NLRP3 and IL-1β, and tranilast inhibited these changes. β-hydroxy butyrate, an NLRP3 inhibitor, also abolished visceral hypersensitivity and colonic hyperpermeability caused by LPS. In contrast, IL-1β induced similar GI alterations to LPS, which were not modified by tranilast. In conclusion, tranilast improved visceral pain and colonic barrier by suppression of the NLRP3 inflammasome in IBS rat models. Tranilast may be useful for IBS treating.

Brain histamine improves colonic hyperpermeability through the basal forebrain cholinergic neurons, adenosine A2B receptors and vagus nerve in rats

Intestinal barrier dysfunction, leaky gut, is implicated in various diseases, including irritable bowel syndrome (IBS) and neurodegenerative conditions like Alzheimer's disease. Our recent investigation revealed that basal forebrain cholinergic neurons (BFCNs), critical for cognitive function, receive signals from butyrate and orexin, playing a role in regulating intestinal barrier function through adenosine A2B signaling and the vagus. This study explores the involvement and function of brain histamine, linked to BFCNs, in the regulation of intestinal barrier function. Colonic permeability, assessed by quantifying absorbed Evans blue in rat colonic tissue, showed that histamine did not affect increased colonic permeability induced by LPS when administered subcutaneously. However, intracisternal histamine administration improved colonic hyperpermeability. Elevating endogenous histamine levels in the brain with SKF91488, a histamine N-methyltransferase inhibitor, also improved colonic hyperpermeability. This effect was abolished by intracisternal chlorpheniramine, an histamine H1 receptor antagonist, not ranitidine, an H2 receptor antagonist. The SKF91488-induced improvement in colonic hyperpermeability was blocked by vagotomy, intracisternal pirenzepine (suppressing BFCNs activity), or alloxazine (an adenosine A2B receptor antagonist). Additionally, intracisternal chlorpheniramine injection eliminated butyrate-induced improvement in colonic hyperpermeability. These findings suggest that brain histamine, acting via the histamine H1 receptor, regulates intestinal barrier function involving BFCNs, adenosine A2B signaling, and the vagus. Brain histamine appears to centrally regulate intestinal barrier function influenced by butyrate, differentiating its actions from peripheral histamine in conditions like IBS, where mast cell-derived histamine induces leaky gut. Brain histamine emerges as a potential pharmacological target for diseases associated with leaky gut, such as dementia and IBS.

Increased Intestinal Permeability and Decreased Resiliency of the Intestinal Barrier in Alcoholic Liver Disease.

Only 20%-30% of individuals with alcohol use disorder (AUD) develop alcoholic liver disease (ALD). While the development of gut-derived endotoxemia is understood to be a required cofactor, increased intestinal permeability in ALD is not completely understood. We recruited 178 subjects-58 healthy controls (HCs), 32 with ALD, 53 with AUD but no liver disease (ALC), and 35 with metabolic dysfunction-associated steatotic liver disease (MASLD). Intestinal permeability was assessed by a sugar cocktail as a percentage of oral dose. The permeability test was repeated after an aspirin challenge in a subset. Five-hour urinary lactulose/mannitol ratio (primarily representing small intestinal permeability) was not statistically different in HC, ALC, ALD, and MASLD groups ( P = 0.40). Twenty-four-hour urinary sucralose (representing whole gut permeability) was increased in ALD ( F = 5.3, P < 0.01) and distinguished ALD from ALC; 24-hour sucralose/lactulose ratio (primarily representing colon permeability) separated the ALD group ( F = 10.2, P < 0.01) from the MASLD group. After aspirin challenge, intestinal permeability increased in all groups and ALD had the largest increase. In a group of patients, we confirmed that (i) the ALD group has increased intestinal permeability compared with the HC, ALC, or MASLD group. In addition, because small bowel permeability (lactulose/mannitol ratio) is normal, the disruption of intestinal barrier seems to be primarily in the large intestine; (ii) decreased resiliency of intestinal barrier to injurious agents (such as NSAID) might be the mechanism for gut leak in subset of AUD who develop ALD.