Changes In Intestinal Barrier Function Research Articles

Transcriptome analysis suggests broad jejunal alterations in Linghu’s obesity-diarrhea syndrome: A pilot study

BACKGROUND Obesity is associated with a significantly increased risk for chronic diarrhea, which has been proposed as Linghu’s obesity-diarrhea syndrome (ODS); however, its molecular mechanisms are largely unknown. AIM To reveal the transcriptomic changes in the jejunum involved in ODS. METHODS In a cohort of 6 ODS patients (JOD group), 6 obese people without diarrhea (JO group), and 6 healthy controls (JC group), high-throughput sequencing and bioinformatics analyses were performed to identify jejunal mucosal mRNA expression alterations and dysfunctional biological processes. In another cohort of 16 ODS patients (SOD group), 16 obese people without diarrhea (SO group), and 16 healthy controls (SC group), serum diamine oxidase (DAO) and D-lactate (D-LA) concentrations were detected to assess changes in intestinal barrier function. RESULTS The gene expression profiles of jejunal mucosa in the JO and JC groups were similar, with only 1 differentially expressed gene (DEG). The gene expression profile of the JOD group was significantly changed, with 411 DEGs compared with the JO group and 211 DEGs compared with the JC group, 129 of which overlapped. The enrichment analysis of these DEGs showed that the biological processes such as digestion, absorption, and transport of nutrients (especially lipids) tended to be up-regulated in the JOD group, while the biological processes such as rRNA processing, mitochondrial translation, antimicrobial humoral response, DNA replication, and DNA repair tended to be down-regulated in the JOD group. Eight DEGs (CDT1 , NHP2 , EXOSC5 , EPN3 , NME1 , REG3A , PLA2G2A , and PRSS2 ) may play a key regulatory role in the pathological process of ODS, and their expression levels were significantly decreased in ODS patients (P < 0.001). In the second cohort, compared with healthy controls, the levels of serum intestinal barrier function markers (DAO and D-LA) were significantly increased in all obese individuals (P < 0.01), but were higher in the SOD group than in the SO group (P < 0.001). CONCLUSION Compared with healthy controls and obese individuals without diarrhea, patients with Linghu’s ODS had extensive transcriptomic changes in the jejunal mucosa, likely affecting intestinal barrier function and thus contributing to the obesity and chronic diarrhea phenotypes.

Whole-protein enteral nutrition formula supplementation reduces Escherichia and improves intestinal barrier function in HIV-infected immunological nonresponders.

People living with human immunodeficiency virus (PLWH) have persistent malnutrition, intestinal barrier dysfunction, and gut microbial imbalance. The interplay between gut microbiota and nutrients is involved in the immune reconstitution of PLWH. To evaluate the effects of whole-protein enteral nutrition formula supplementation on T-cell levels, intestinal barrier function, nutritional status, and gut microbiota composition in human immunodeficiency virus (HIV)-infected immunological nonresponders (INRs) who failed to normalize CD4+ T-cell counts, with a number<350 cells/µL, a pilot study was carried out in 13 HIV-infected INRs undergoing antiretroviral therapy who received a 3-month phase supplementation of 200mL/200kcal/45g whole-protein enteral nutrition formula once daily. Our primary endpoint was increased CD4+ T-cell counts. Secondary outcome parameters were changes in intestinal barrier function, nutritional status, and gut microbiota composition. We showed that CD4+ T-cell counts of HIV-infected INRs increased significantly after the 3-month supplementation. Dietary supplementation for 3 months improved the intestinal barrier function and nutritional status of HIV-infected INRs. Furthermore, the enteral nutrition formula significantly decreased the relative abundance of Escherichia at the genus level and increased the alpha diversity of gut microbiota in HIV-infected INRs. The findings demonstrated that the whole-protein enteral nutrition formula aids in reducing Escherichia and improving intestinal barrier function in HIV-infected INRs. This study provides insight into the role of nutrients in the improvement of immune reconstitution in HIV-infected INRs. This study is registered in the Chinese Clinical Trial Registry (Document No. ChiCTR2000037839; http://www.chictr.org.cn/index.aspx).

Comparison of immune responses and intestinal flora in epicutaneously sensitized BALB/c or C57BL/6 mouse models of food allergy

Cutaneous exposure to food allergens through a disrupted skin barrier is recognized as an important cause of food allergy, and the cutaneous sensitized mouse model has been established to investigate relevant allergic disorders. However, the role of different genetic backgrounds of mice on immune responses to food allergens upon epicutaneous sensitization is largely unknown. In this study, two strains of mice, i.e., the BALB/c and C57BL/6 mice, were epicutaneously sensitized with ovalbumin on atopic dermatitis (AD)-like skin lesions, followed by intragastric challenge to induce IgE-mediated food allergy. Allergic outcomes were measured as clinical signs, specific antibodies and cytokines, and immune cell subpopulations, as well as changes in intestinal barrier function and gut microbiota. Results showed that both strains of mice exhibited typical food-allergic symptoms with a Th2-skewed response. The C57BL/6 mice, rather than the BALB/c mice, were fitter for establishing an epicutaneously sensitized model of food allergy since a stronger Th2-biased response and severer disruptions in the intestinal barrier and gut homeostasis were observed. This study provides knowledge for selecting an appropriate mouse model to study food-allergic responses associated with AD-like skin lesions and highlights the role of genetic variations in the immune mechanism underlying pathogenesis of food allergy.

Bacterial lipopolysaccharide with different administration routes affects intestinal mucosal morphological, immunological, and microbial barrier functions in goslings

The current study was conducted to evaluate the effects of different administration routes of bacterial lipopolysaccharide (LPS) on intestinal mucosal morphological, immunological, and microbial barrier functions in goslings. First, we compared intestinal villi morphology of goslings under intraperitoneal or oral LPS treatment through hematoxylin and eosin staining. Then, we determined the signatures of the microbiome in the ileum mucosa of goslings subjected to oral LPS treatment at 0, 2, 4, and 8 mg/kg BW by 16S sequencing, and analyzed the changes in intestinal barrier functions and permeability, levels of LPS in the ileum mucosa, plasma, and liver tissue, and the induced inflammatory response of Toll-like receptor 4 (TLR4). As a result, intraperitoneal LPS injection resulted in a thicker intestinal wall in the ileum within a short time, whereas villus height was less affected; in contrast, oral LPS treatment exerted a stronger influence on villus height but not on intestinal wall thickness. We also found that oral LPS treatment affected the structure of the intestinal microbiome, reflected by changes in the clustering of intestinal microbiota. The average abundance of Muribaculaceae showed an increasing trend with increasing LPS levels, and that of the genus Bacteroides decreased, compared with the control group. In addition, oral LPS treatment with 8 mg/kg BW affected the intestinal epithelial morphology, damage the mucosal immune barrier, downregulated the expression of tight junction proteins, increased circulating D-lactate levels, and stimulated the secretion of various inflammatory mediators and activation of the TLR4/MyD88/NFκB pathway. This study presented the injuries of intestinal mucosal barrier function induced by LPS challenges in goslings and provided a scientific model for searching the novel strategies to attenuate the immunological stress and gut injury caused by LPS.

Microbiota of the gastrointestinal tract: Friend or foe?

The gut microbiota is currently considered an external organ of the human body that provides important mechanisms of metabolic regulation and protection. The gut microbiota encodes over 3 million genes, which is approximately 150 times more than the total number of genes present in the human genome. Changes in the qualitative and quantitative composition of the microbiome lead to disruption in the synthesis of key bacterial metabolites, changes in intestinal barrier function, and inflammation and can cause the development of a wide variety of diseases, such as diabetes, obesity, gastrointestinal disorders, cardiovascular issues, neurological disorders and oncological concerns. In this review, I consider issues related to the role of the microbiome in the regulation of intestinal barrier function, its influence on physiological and pathological processes occurring in the body, and potential new therapeutic strategies aimed at restoring the gut microbiome. Herewith, it is important to understand that the gut microbiota and human body should be considered as a single biological system, where change of one element will inevitably affect its other components. Thus, the study of the impact of the intestinal microbiota on health should be considered only taking into account numerous factors, the role of which has not yet been fully elucidated.

Gut-Bile Acid-Immune Axis Regulates T Cell Homeostasis in the Pathogenesis of Immune Thrombocytopenia

Introduction Immune thrombocytopenia (ITP) is an acquired autoimmune hemorrhagic disease characterized by isolated thrombocytopenia. In a previous study, we observed dysbiosis in the phylogenetic composition and function of the gut microbiome of patients with ITP [Sci China Life Sci, 2020]. It is suggested that impaired intestinal barrier as well as the gut microbiota-related metabolites may provide signaling molecules and facilitate communication between the intestinal tract and the immune system. For example, bile acids (BAs), which are synthesized in the liver and transformed into secondary BAs in the gut, have recently been considered to be important signaling metabolites for the immune system. The bile acid receptor FXR can also inhibit the TLR4/MAPK pathway and participate in the regulation of the immune response. Here, we provide evidence that the gut-bile acid-immune axis plays a role in the pathogenesis of ITP and that obeticholic acid (OCA) treatment can repair the gut barrier and restore the gut-bile acid balance to reduce the destruction of platelets. Methods After establishing an active ITP mouse model, pathological analyses of biopsies, 16S amplicon sequencing, targeted bile acid metabolomics and real-time fluorescent quantitative PCR were used to explore the changes in intestinal barrier function, gut microbiota composition, and bile acid metabolites in feces and plasma. OCA treatment of the ITP mouse model and bone marrow-derived dendritic cells was used to investigate the effect of OCA on gut bile acid metabolism and T cell differentiation. In a clinical sample study, 65 treatment-naïve ITP patients and 62 healthy controls were enrolled. Metagenomic sequencing, bile acid-targeted metabolomics and mass cytometry were used to explore the characteristics of the "gut-bile acid-immune” axis in the ITP patients. Results In the mouse model of ITP, the gut barrier was damaged, as shown by exfoliation of IECs according to H&E staining and greater FITC-dextran leakage from the intestinal mucosa into the peripheral circulation. RNA sequencing of the IEC transcriptome revealed that the expression of claudin-4 and claudin-8 was significantly diminished in ITP mice. As a result of the impaired gut barrier, plasma levels of LPS were elevated in ITP mice. Moreover, the Firmicutes:Bacteroidetes ratio was elevated in the gut microbiota according to 16S amplicon sequencing, and increased fecal levels of BAs were observed, which gave priority to primary BAs like β-MCA. The accumulation of β-MCA, which is an FXR antagonist, inhibited the activity of FXR in IECs, hepatocytes and immune cells such as DCs. After stimulation with LPS in vitro, murine bone marrow-derived DCs were observed to induce greater Th1 differentiation, which could be reversed by an FXR agonist (GW4064 or OCA). The secretion of IL-12 by DCs induced Th1 differentiation and was regulated by the TLR4/MAPK/p38 pathway, and this effect was inhibited by OCA through the activation of FXR. In vivo, OCA increased the expression of claudin-4 and claudin-8, and restored the balance of bile acid metabolism in the mice with ITP. After OCA treatment, the Th1/Th2 imbalance in the bone marrow of the mice with ITP was corrected, and reduced platelet destruction in the spleen and liver was observed with an in vivo imaging system. Clinical studies have shown that the gut microbiota in ITP patients is dysregulated, which showed an increased abundance of Firmicutes. Scanning electron microscopy showed that the gaps between IECs were increased in the ITP patients. The bile acid pool of the ITP patients was shown to have an increased proportion of primary BAs in the bone marrow. After in vitro treatment with OCA for 72 h, the proportion of human Th1 cells among human bone marrow mononuclear cells was significantly reduced, which suggested the therapeutic effect of OCA in ITP patients. Conclusions This study preliminarily revealed the characteristics of the "gut-bile acid-immune” axis in ITP patients and a mouse model. In vitro and in vivo studies confirmed that OCA could repair the intestinal barrier, correct gut microbiota dysbiosis and bile acid metabolism abnormalities, and decrease the proportion of peripheral Th1 cells via MAPK signaling in DCs, resulting in a decrease in the excessive destruction of platelets. This study provides a theoretical basis for targeting the gut microbiota in the clinical treatment of ITP.

Consumption of a multi-deficient diet causes dynamic changes in the intestinal morphofunctional barrier, body composition and impaired physical development in post-weaning mice.

Few studies have focused on nutrient-deficient diets and associated pathobiological dynamics of body composition and intestinal barrier function. This study evaluated the impact of a nutrient-deficient diet on physical development and intestinal morphofunctional barrier in mice. C57BL/6 (21 days of age) mice were fed a Northeastern Brazil regional basic diet (RBD) or a control diet for 21 d. The animals were subjected to bioimpedance analysis, lactulose test, morphometric analysis and quantitative reverse transcription-PCR to evaluate tight junctions and intestinal transporters. RBD feeding significantly reduced weight (P < 0·05) from day 5, weight gain from day 3 and tail length from day 14. The intake of RBD reduced total body water, extracellular fluid, fat mass and fat-free mass from day 7 (P < 0·05). RBD induced changes in the jejunum, with an increase in the villus:crypt ratio on day 7, followed by reduction on days 14 and 21 (P < 0·05). Lactulose:mannitol ratio increased on day 14 (P < 0·05). Changes in intestinal barrier function on day 14 were associated with reductions in claudin-1 and occludin, and on day 21, there was a reduction in the levels of claudin-2 and occludin. SGLT-1 levels decreased on day 21. RBD compromises body composition and physical development with dynamic changes in intestinal barrier morphofunctional. RBD is associated with damage to intestinal permeability, reduced levels of claudin-1 and occludin transcripts and return of bowel function in a chronic period.

Changes in intestinal barrier functions and gut microbiota in rats exposed to zearalenone

Zearalenone (ZEN) is a mycotoxin that causes serious health problems in humans and animals. However, few studies have focused on the destruction of the intestinal barrier caused by ZEN. In this study, rats were exposed to different dosages of ZEN (0, 0.2, 1.0 and 5.0 mg/kg bw) by gavage for 4 weeks. The results showed that 1.0 and 5.0 mg/kg ZEN impaired gut morphology, induced the inflammatory response, reduced mucin expression, increased intestinal permeability, decreased the expression of TJ proteins and activated the RhoA/ROCK pathway. However, 0.2 mg/kg ZEN had no significant effect on intestinal barrier except for reducing the expression of some TJ proteins and mucins. Moreover, exposure to ZEN led to slight imbalance in microbiota. In conclusion, ZEN exposure resulted in intestinal barrier dysfunction by inducing intestinal microbiota dysbiosis, decreasing the expression of TJ proteins, activating the RhoA/ROCK pathway, and inducing the inflammatory response.

An Amino Acid–Based Oral Rehydration Solution Regulates Radiation-Induced Intestinal Barrier Disruption in Mice

Radiotherapy inadvertently affects gastrointestinal (GI) epithelial cells, causing intestinal barrier disruption and increased permeability. We examined the effect of amino acid-based oral rehydration solution (AA-ORS) on radiation-induced changes of intestinal barrier function and epithelial tight junctions (TJs) in a randomized experimental study using a total-body irradiation (TBI) mouse model. Eight-week-old male Swiss mice received a single-dose TBI (0, 1, 3, or 5Gy), and subsequent gastric gavage with AA-ORS (threonine, valine, serine, tyrosine, and aspartic acid) or saline for 2 or 6 d. Intestinal barrier function of mouse ileum was characterized by electrophysiological analysis of conductance, anion selectivity, and paracellular permeability [fluorescein isothiocyanate (FITC)-dextran]. Ultrastructural changes of TJs were evaluated by transmission electron microscopy. Membrane protein and mRNA expression of claudin-1, -2, -3, -5, and -7, occludin, and E-cadherin were analyzed with western blot, qPCR, and immunohistochemistry. Nonparametric tests were used to compare treatment-dose differences for each time point. Saline-treated mice had a higher conductance at doses as low as 3Gy, and as early as 2 d post-TBI compared with 0Gy (P<0.001). Paracellular permeability and dilution potential were increased 6 d after 5Gy TBI (P<0.001). Conductance decreased with AA-ORS after 2 d in 3-Gy and 5-Gy mice (P<0.05 and P<0.001), and on day 6 after 5Gy TBI (P<0.001). Anion selectivity and FITC permeability decreased from 0.73±0.02 to 0.61±0.03 pCl/pNa (P<0.01) and from 2.7±0.1×105 to 2.1±0.1×105 RFU (P<0.001) in 5-Gy mice treated with AA-ORS for 6 d compared with saline. Irradiation-induced ultrastructural changes of TJs characterized by decreased electron density and gap formation improved with AA-ORS. Reduced claudin-1, -3, and -7 membrane expression after TBI recovered with AA-ORS within 6d, whereas claudin-2 decreased indicating restitution of TJ proteins. Radiation-induced functional and structural disruption of the intestinal barrier in mice is reversed by AA-ORS rendering AA-ORS a potential treatment option in prospective clinical trials in patients with gastrointestinal barrier dysfunction.

Intestinal barrier function in morbid obesity: results of a prospective study on the effect of sleeve gastrectomy.

Obesity has been associated with impaired intestinal barrier function. It is not known whether bariatric surgery leads to changes in intestinal barrier function. We hypothesized that obesity is associated with disturbances in gastrointestinal barrier function, and that after bariatric surgery barrier function will improve. Prospective single center study in which we assessed segmental gut permeability by urinary recovery of a multisugar drink in 27 morbidly obese (BMI 43.3 ± 1.1 kg/m2) and 27 age and gender matched lean subjects (BMI 22.9 ± 0.43 kg/m2). Fecal calprotectin, SCFAs, plasma cytokines, and hsCRP were assessed as inflammatory and metabolic markers. Comparisons: (a) morbidly obese subjects vs. controls and (b) 2 and 6 months postsleeve vs. presleeve gastrectomy (n = 14). In another group of 10 morbidly obese and 11 matched lean subjects colonic and ileal biopsies were obtained in order to measure gene transcription of tight junction proteins. Gastroduodenal permeability (urinary sucrose recovery) was significantly increased in obese vs. lean controls (p < 0.05). Small intestinal and colonic permeability (urinary recovery of lactulose/L-rhamnose and sucralose/erythritol, respectively) in obese subjects were not significantly different from controls. Morbidly obese subjects had a proinflammatory systemic and intestinal profile compared with lean subjects. After sleeve gastrectomy BMI decreased significantly (p < 0.001). Postsleeve gastroduodenal permeability normalized to values that do not differ from lean controls. Gastroduodenal permeability, but not small intestinal or colonic permeability, is significantly increased in morbidly obese patients. After sleeve gastrectomy, gastroduodenal permeability normalized to values in the range of lean controls. Thus, the proximal gastrointestinal barrier is compromised in morbid obesity and is associated with a proinflammatory intestinal and systemic profile.

Effect of stocking density and dietary tryptophan on growth performance and intestinal barrier function in broiler chickens

The objective of the present experiment was to investigate the effect of stocking density (SD) and dietary supplementation of crystalline tryptophan (Trp) on growth performance and intestinal barrier function in broiler chickens raised in a floor pen. The experiment was conducted using a completely randomized design with a 2 × 2 factorial arrangement consisting of 2 different SD and 2 supplemental levels of dietary Trp. A total of 1,140 Ross 308 broiler chickens at 21 d of age were allotted to 1 of 4 treatments with 5 replicates. Low SD (9 birds/m2) and high SD (18 birds/m2) were achieved by raising different number of birds per identical floor pen (2.0m × 2.4m). The basal diet was formulated with no supplemental Trp in diets to meet or exceed nutrient recommendation of the Ross 308 manual. The calculated concentrations of total Trp and digestible Trp in the basal diet were 0.19 and 0.16%, respectively. The other diet was prepared by adding 0.16% crystalline Trp to the basal diet. Diets were fed to birds for 21 d. At the end of the experiment, 2 birds per replicate were euthanized to collect tissue samples for further analyses. Results indicated that there were no interactions between SD and dietary Trp for all measurements. For the main effects, birds raised at a low SD had greater (P < 0.01) body weight gain, feed intake, and feed efficiency than those raised at a high SD. However, supplementation of dietary Trp had no effect on broiler performance. Furthermore, there were no main effects of SD and dietary Trp on intestinal barrier functions. In conclusion, broiler chickens raised in a floor pen with a high SD (18 birds/m2) have decreased growth performance with little changes in intestinal barrier functions. Supplementation of dietary Trp at 0.16% has no positive effect on broiler chickens raised in a floor pen with either a low or high SD.

Changes of intestinal mucosal barrier function and effects of early enteral nutrition in patients with severe organophosphorus poisoning

Objective: To observe the changes of intestinal barrier function in patients with acute severe organophosphorus pesticide poisoning (ASOPP) and the effect of early enteral nutrition on them. Methods: A single-center, single-sample, prospective, randomized controlled clinical trial was conducted. A total of 50 patients with ASOPP were divided into 24 h enteral nutrition group (group A) and 48 h (48-72 h) enteral nutrition group (B group) according to the order of hospitalization. The two groups received equal calorie nutritional support, and Serum D-lactic acid (D-LA) and serum human diamine oxidase (DAO) were detected immediately after admission and at 48 h, 72 h and 144 h. At the same time, the worst value of APACHE-Ⅱ score was recorded, and the correlation between DAO, D-LA and APACHE-Ⅱ score was analyzed. The serum concentration of D-LA and DAO in 15 healthy adults were detected as healthy control group. Results: There was no statistical difference in gender, age, poisoning time and organophosphorus pesticide components between group A and B (P>0.05). The distribution of D-LA concentration in group A poisoned patients at admission, 48 h, 72 h and 144 h was (66±19) μg/L, (68±21) μg/L, (66±19) μg/L, (63±17) μg/L, while in group B they were (62±15) μg/L, (58±17) μg/L, (58±16) μg/L, (67±9) μg/L. There was no statistical difference between the two groups in D-LA concentration and that of healthy people [(67±17) μg/L, P>0.05]. The distribution of DAO concentration in group A poisoned patients at admission, 48 h, 72 h and 144 h was (2.1±0.6) μg/ml, (2.1±0.5) μg/ml, (2.2±0.4) μg/ml, (2.2±0.5) μg/ml, while in group B they were (2.1±0.5) μg/ml, (2.1±0.5) μg/ml, (2.2±0.5) μg/ml, (2.1±0.4) μg/ml. DAO concentration in the early stage of the intoxication of the two groups were higher than that of healthy people (0.1±0.0 μg/ml) (P<0.05). There is no statistical difference in DAO concentration between group A and B at different time points (P>0.05). The APACHEE-Ⅱ score of 48 hours and 72 hours in group A (12.2+1.7, 5.5+2.1) was significantly lower than that in group B (14.1+2.4, 8.2+2.6) (P<0.05). D-LA, DAO concentration at different time points was not correlated with APACHE-Ⅱ score (P>0.05). D-LA (r, P) was immediate admission (-0.17, 0.24), 48 h (0.04, 0.79), 72 h (0.32, 0.06), 144 h (0.29, 0.07), and DAO (r, P) was immediate admission (-0.12, 0.43), 48 h (0.02, 0.92), 72 h (0.03, 0.85), 144 h (0.03, 0.82). Conclusions: Patients with ASOPP may have obvious injury at intestinal mucosa at early stage (144 h), but the intestinal permeability is normal. Early enteral nutrition therapy can promote the recovery of patients, but has low correlation with intestinal barrier function improvement.

Adaptation of exercise-induced stress in well-trained healthy young men.

What is the central question of this study? Exercise is known to induce stress-related physiological responses, such as changes in intestinal barrier function. Our aim was to determine the test-retest repeatability of these responses in well-trained individuals. What is the main finding and its importance? Responses to strenuous exercise, as indicated by stress-related markers such as intestinal integrity markers and myokines, showed high test-retest variation. Even in well-trained young men an adapted response is seen after a single repetition after 1 week. This finding has implications for the design of studies aimed at evaluating physiological responses to exercise. Strenuous exercise induces different stress-related physiological changes, potentially including changes in intestinal barrier function. In the Protégé Study (ISRCTN14236739; www.isrctn.com), we determined the test-retest repeatability in responses to exercise in well-trained individuals. Eleven well-trained men (27±4 years old) completed an exercise protocol that consisted of intensive cycling intervals, followed by an overnight fast and an additional 90min cycling phase at 50% of maximal workload the next morning. The day before (rest), and immediately after the exercise protocol (exercise) a lactulose and rhamnose solution was ingested. Markers of energy metabolism, lactulose-to-rhamnose ratio, several cytokines and potential stress-related markers were measured at rest and during exercise. In addition, untargeted urine metabolite profiles were obtained. The complete procedure (Test) was repeated 1week later (Retest) to assess repeatability. Metabolic effect parameters with regard to energy metabolism and urine metabolomics were similar for both the Test and Retest period, underlining comparable exercise load. Following exercise, intestinal permeability (1h plasma lactulose-to-rhamnose ratio) and the serum interleukin-6, interleukin-10, fibroblast growth factor-21 and muscle creatine kinase concentrations were significantly increased compared with rest only during the first test and not when the test was repeated. Responses to strenuous exercise in well-trained young men, as indicated by intestinal markers and myokines, show adaptation in Test-Retest outcome. This might be attributable to a carry-over effect of the defense mechanisms triggered during the Test. This finding has implications for the design of studies aimed at evaluating physiological responses to exercise.

Abstract 645: Curcumin Modulates the Function(s) of Intestinal Epithelial Cells: Role in the Development of Diet-Induced Metabolic Diseases

Association between circulating lipopolysaccharide (LPS) and metabolic diseases (such as Type 2 Diabetes and atherosclerosis) has shifted the focus from high fat high cholesterol containing western type diet (WD)-induced changes in gut microbiota per se to release of gut bacteria-derived products into circulation as the possible mechanism for the chronic inflammatory state underlying the development of these diseases. We demonstrated earlier that WD-induced changes in intestinal barrier function increases the release of LPS into systemic circulation and oral supplementation with curcumin not only reduces the levels of systemic LPS but also attenuates the subsequent development of glucose intolerance and atherosclerosis. Although curcumin is reported to exert potent anti-inflammatory effects in vitro , its poor bioavailability has raised doubts about a causal relationship between oral supplementation and the in vivo effects. It is hypothesized that curcumin attenuates WD-induced chronic inflammation and associated metabolic diseases by modulating the function of intestinal epithelial cells (IECs) and the objective of the present study was to delineate the underlying mechanisms. Human IEC lines, Caco-2, HT-29 and T-84 were used for these studies and modulation of direct as well as indirect effects of LPS on tight junctions as well as intracellular signaling were examined. Pre-treatment with Curcumin prevented LPS-induced disruption of tight junctions. LPS-induced secretion of master cytokine IL-1β was also dramatically reduced by pre-treatment with curcumin. Furthermore, curcumin also attenuated IL-1β induced activation of p-38 MAPK involved in the phosphorylation of tight junction proteins and subsequent disruption of their normal arrangement. Based on these data, the sites of curcumin actions leading to preservation of intestinal barrier function are shown in the Figure (activation and inhibition denoted by + and - symbols in green circles).

The long-term functional consequences of acute infectious diarrhea.

The study reviews recent publications that build on previous studies showing that acute enteric infection can produce persistent dysfunction in the lower gut (postinfectious irritable bowel syndrome) and proximal gut (postinfectious functional dyspepsia). The review addresses risk factors, the pathophysiological basis of persistent gut dysfunction, and the factors that initiate and maintain it. Recent work has identified several loci of host genetic predisposition to these syndromes that focus attention on host immune responses that may lead to gut dysfunction, including changes in intestinal barrier function and cytokine responses to the initial infection. Human and animal studies identify changes in the serotonergic and cannabinoid pathways regulating visceral pain responses and gut motility. Recent work has also focused attention on the putative role of the intestinal microbiota or dysbiosis in maintaining gut dysfunction and this is reviewed in depth. The development of long-term consequences following an acute episode of gastroenteritis reflects a convergence of host factors that include genetic predisposition and psychological factors, as well as the development of intestinal dysbiosis. It is anticipated that future research will generate biomarkers of susceptibility as well as novel microbiota-directed preventive and therapeutic strategies.

Changes in intestinal barrier function and gut microbiota in high-fat diet-fed rats are dynamic and region dependent.

A causal relationship between the pathophysiological changes in the gut epithelium and altered gut microbiota with the onset of obesity have been suggested but not defined. The aim of this study was to determine the temporal relationship between impaired intestinal barrier function and microbial dysbiosis in the small and large intestine in rodent high-fat (HF) diet-induced obesity. Rats were fed HF diet (45% fat) or normal chow (C, 10% fat) for 1, 3, or 6 wk; food intake, body weight, and adiposity were measured. Barrier function ex vivo using FITC-labeled dextran (4,000 Da, FD-4) and horseradish peroxidase (HRP) probes in Ussing chambers, gene expression, and gut microbial communities was assessed. After 1 wk, there was an immediate but reversible increase in paracellular permeability, decrease in IL-10 expression, and decrease in abundance of genera within the class Clostridia in the ileum. In the large intestine, HRP flux and abundance of genera within the order Bacteroidales increased with time on the HF diet and correlated with the onset of increased body weight and adiposity. The data show immediate insults in the ileum in response to ingestion of a HF diet, which were rapidly restored and preceded increased passage of large molecules across the large intestinal epithelium. This study provides an understanding of microbiota dysbiosis and gut pathophysiology in diet-induced obesity and has identified IL-10 and Oscillospira in the ileum and transcellular flux in the large intestine as potential early impairments in the gut that might lead to obesity and metabolic disorders.

The intestinal barrier function and its involvement in digestive disease.

The gastrointestinal mucosal surface is lined with epithelial cells representing an effective barrier made up with intercellular junctions that separate the inner and the outer environments, and block the passage of potentially harmful substances. However, epithelial cells are also responsible for the absorption of nutrients and electrolytes, hence a semipermeable barrier is required that selectively allows a number of substances in while keeping others out. To this end, the intestine developed the "intestinal barrier function", a defensive system involving various elements, both intra- and extracellular, that work in a coordinated way to impede the passage of antigens, toxins, and microbial byproducts, and simultaneously preserves the correct development of the epithelial barrier, the immune system, and the acquisition of tolerance against dietary antigens and the intestinal microbiota. Disturbances in the mechanisms of the barrier function favor the development of exaggerated immune responses; while exact implications remain unknown, changes in intestinal barrier function have been associated with the development of inflammatory conditions in the gastrointestinal tract. This review details de various elements of the intestinal barrier function, and the key molecular and cellular changes described for gastrointestinal diseases associated with dysfunction in this defensive mechanism.

Arctigenin from Fructus Arctii (Seed of Burdock) Reinforces Intestinal Barrier Function in Caco-2 Cell Monolayers.

Fructus Arctii is used as a traditional herbal medicine to treat inflammatory diseases in oriental countries. This study aimed to investigate effect of F. Arctii extract on intestinal barrier function in human intestinal epithelial Caco-2 cells and to reveal the active component of F. Arctii. We measured transepithelial electrical resistance (TEER) value (as an index of barrier function) and ovalbumin (OVA) permeation (as an index of permeability) to observe the changes of intestinal barrier function. The treatment of F. Arctii increased TEER value and decreased OVA influx on Caco-2 cell monolayers. Furthermore, we found that arctigenin as an active component of F. Arctii increased TEER value and reduced permeability of OVA from apical to the basolateral side but not arctiin. In the present study, we revealed that F. Arctii could enhance intestinal barrier function, and its active component was an arctigenin on the functionality. We expect that the arctigenin from F. Arctii could contribute to prevention of inflammatory, allergic, and infectious diseases by reinforcing intestinal barrier function.

Oral Supplementation with Non-Absorbable Antibiotics or Curcumin Attenuates Western Diet-Induced Atherosclerosis and Glucose Intolerance in LDLR−/− Mice – Role of Intestinal Permeability and Macrophage Activation

Association between circulating lipopolysaccharide (LPS) and metabolic diseases (such as Type 2 Diabetes and atherosclerosis) has shifted the focus from Western diet-induced changes in gut microbiota per se to release of gut bacteria-derived products into circulation as the possible mechanism for the chronic inflammatory state underlying the development of these diseases. Under physiological conditions, an intact intestinal barrier prevents this release of LPS underscoring the importance of examining and modulating the direct effects of Western diet on intestinal barrier function. In the present study we evaluated two strategies, namely selective gut decontamination and supplementation with oral curcumin, to modulate Western-diet (WD) induced changes in intestinal barrier function and subsequent development of glucose intolerance and atherosclerosis. LDLR−/− mice were fed WD for 16 weeks and either received non-absorbable antibiotics (Neomycin and polymyxin) in drinking water for selective gut decontamination or gavaged daily with curcumin. WD significantly increased intestinal permeability as assessed by in vivo translocation of FITC-dextran and plasma LPS levels. Selective gut decontamination and supplementation with curcumin significantly attenuated the WD-induced increase in plasma LPS levels (3.32 vs 1.90 or 1.51 EU/ml, respectively) and improved intestinal barrier function at multiple levels (restoring intestinal alkaline phosphatase activity and expression of tight junction proteins, ZO-1 and Claudin-1). Consequently, both these interventions significantly reduced WD-induced glucose intolerance and atherosclerosis in LDLR−/− mice. Activation of macrophages by low levels of LPS (50 ng/ml) and its exacerbation by fatty acids is likely the mechanism by which release of trace amounts of LPS into circulation due to disruption of intestinal barrier function induces the development of these diseases. These studies not only establish the important role of intestinal barrier function, but also identify oral supplementation with curcumin as a potential therapeutic strategy to improve intestinal barrier function and prevent the development of metabolic diseases.

PP032-SUN: Observation of Changes of Intestinal Barrier Function in Critically Ill Patients along with Enteral Nutrition

PP032-SUN: Observation of Changes of Intestinal Barrier Function in Critically Ill Patients along with Enteral Nutrition