Ileal Explants Research Articles

Limosilactobacillus reuteri B1/1 modulated the intestinal immune response in preventing Salmonella Enteritidis PT4 infection in a chicken ileal explant model

In this study, we observed the effect of the newly isolated probiotic strain Limosilactobacillus reuteri B1/1 on the relative gene expression of selected cytokines (interleukin-15, transforming growth factor-β4), tight junction proteins (E-cadherin, occludin), biomarker active intestinal stem cells - LGR5 (leucine-rich repeat containing G protein-coupled receptor), markers of mucosal intestinal immunity (mucin-2, immunoglobulin A), as well as the creation of a new biomarker of inflammation in the intestine - calprotectin on an ex vivo model of chicken ileal explant in the prevention of Salmonella Enteritidis PT4 infection. The ability of L. reuteri B1/1 to effectively modulate the mucosal immune response under pretreatment conditions in S. Enteritidis PT4 infection in a chicken ileal explant model was confirmed. In addition, our obtained results point to the fact that the new chicken ileum explant model could be a suitable model to investigate or test the influence of natural substances such as probiotic bacteria in the interaction with the intestine as well as pathogenic microorganisms. In addition, the results of our study may contribute to a deeper understanding of the action of newly isolated probiotic bacteria at the intestinal level using ex vivo models such as chicken ileum explant, which are able to mimic in vivo conditions sufficiently.

Immunomodulatory properties of chicken cathelicidin-2 investigated on an ileal explant culture.

As the threat posed by antimicrobial resistance grows more crucial, the development of compounds that can replace antibiotics becomes increasingly vital. Chicken cathelicidin-2 (Cath-2) belongs to the group of Host Defense Peptides (HDPs), which could provide a feasible solution for the treatment of gastrointestinal infections in poultry. It is a small peptide produced by the heterophil granulocytes of chickens as part of the innate immune response, and its immunomodulatory activity has already been demonstrated in several cell types. In this study, the effects of Cath-2 on the intestinal immune response were examined using ileal explant cultures isolated from chicken. Regarding our results, Cath-2 displayed a potent anti-inflammatory effect as it alleviated the LTA-caused elevation of interleukin (IL)-6 and IL-2 concentrations, and that of the IFN-γ/IL-10 ratio, furthermore, it increased the concentration of IL-10, alleviating the LTA-evoked decreased level of the anti-inflammatory cytokine. Moreover, when applied alone, it elevated the concentrations of IL-6, CXCLi2, and IL-2, providing evidence of its complex immunomodulatory mechanisms. In summary, Cath-2 was able to modulate the immune response of the intestinal wall not only by reducing pro-inflammatory cytokine release, but also through immune stimulation, demonstrating that it has the ability to improve innate immunity via a complex mechanism that may make it a suitable candidate for the control of intestinal infections.

Discordant Effects of Janus Kinase Inhibition Ex Vivo on Inflammatory Responses in Colonic Compared to Ileal Mucosa.

Janus kinase [JAK] inhibitors are used for treating inflammatory bowel diseases [IBD]. We aimed to identify the molecular effects of JAK inhibition in human intestinal mucosa, considering IBD location and phenotype. Colonic and ileal explants from patients with ulcerative colitis [UC], Crohn's disease [CD], and non-IBD controls [NC] were assessed for levels of phosphorylated signal transducers and activators of transcription [p-STAT] and expression of inflammatory genes in response to an ex vivo JAK inhibitor [tofacitinib]. Cytokine production by lamina propria lymphocytes in response to tofacitinib was assessed. Human intestinal organoids were used to investigate the effects of JAK inhibitors on inducible nitric oxide synthase [iNOS] expression. Explants were collected from 68 patients [UC = 20, CD = 20, NC = 28]. p-STAT1/3/5 inhibition rates varied, being higher in colonic compared to ileal explants. p-STAT1/3 inhibition rates negatively correlated with levels of C-reactive protein [CRP]. While significant alterations in 120 of 255 inflammatory genes were observed in colonic explants, only 30 were observed in ileal NC explants. In colonic explants from UC, significant alterations were observed in five genes, including NOS2. JAK inhibition significantly decreased Th1/Th2/Th17-related cytokine production from lamina propria lymphocytes. Various JAK inhibitors reduced the interferon-γ-induced increase in iNOS expression in organoids. A site-specific anti-inflammatory effect of JAK inhibition by tofacitinib was noted, whereby the colon was more robustly affected than the ileum. The ex vivo response to tofacitinib is individual. JAK inhibition may attenuate inflammation by decreasing iNOS expression. Ex vivo mucosal platforms may be a valuable resource for studying personalized drug effects in patients with IBD.

Pyroptosis Tuning in Intestinal Cryptosporidiosis via the Natural Histone Deacetylase Inhibitor Romidepsin.

Cryptosporidium is an opportunistic protozoan, with many species of cross-human infectivity. It causes life-threatening diarrhoea in children and CD4-defective patients. Despite its limited efficacy, nitazoxanide remains the primary anti-cryptosporidial drug. Cryptosporidium infects the intestinal brush border (intracellular-extracytoplasmic) and down-regulates pyroptosis to prevent expulsion. Romidepsin is a natural histone deacetylase inhibitor that triggers pyroptosis. Romidepsin's effect on cryptosporidiosis was assessed in immunocompromised mice via gasdermin-D (GSDM-D) immunohistochemical expression, IFN-γ, IL-1β and IL-18 blood levels by ELISA, and via parasite scanning by modified Ziehl-Neelsen staining and scanning electron microscopy (SEM). Oocyst deformity and local cytokines were also assessed in ex vivo ileal explants. Following intraperitoneal injection of romidepsin, oocyst shedding significantly reduced at the 9th, 12th and 15th d.p.i. compared with infected-control and drug-control (nitazoxanide-treated) mice. H&E staining of intestinal sections from romidepsin-treated mice showed significantly low intestinal scoring with marked reduction in epithelial hyperplasia, villous blunting and cellular infiltrate. SEM revealed marked oocyst blebbing and paucity (in vivo and ex vivo) after romidepsin compared with nitazoxanide. Regarding pyroptosis, romidepsin triggered significantly higher intestinal GSDM-D expression in vivo, and higher serum/culture IFN-γ, IL-1β and IL-18 levels in romidepsin-treated mice than in the control groups. Collectively, in cryptosporidiosis, romidepsin succeeded in enhancing pyroptosis in the oocysts and infected epithelium, reducing infection and shifting the brush border towards normalisation.

Quantifying Forms and Functions of Enterohepatic Bile Acid Pools in Mice

Backgrounds & AimsBile acids (BAs) are core gastrointestinal metabolites with dual functions in lipid absorption and cell signaling. BAs circulate between the liver and distal small intestine (i.e., ileum), yet the dynamics through which complex BA pools are absorbed in the ileum and interact with host intestinal cells in vivo remain poorly understood. As ileal absorption is rate-limiting in determining which BAs in the intestinal lumen gain access to host intestinal cells and receptors, and at what concentrations, we hypothesized that defining the rates and routes of ileal BA absorption in vivo would yield novel insights into the physiological forms and functions of mouse enterohepatic BA pools. MethodsUsing ex vivo mass spectrometry, we quantified 88 BA species and metabolites in the intestinal lumen and superior mesenteric vein of individual wild type mice, as well as cage-mates lacking the ileal BA transporter, Asbt/Slc10a2. ResultsUsing these data, we calculated that the pool of BAs circulating through ileal tissue (i.e., the ‘ileal BA pool’) in fasting C57BL/6J female mice is ∼0.3 μmoles/g. Asbt-mediated transport accounted for ∼80% of this pool and amplified size. Passive permeability explained the remaining ∼20% and generated diversity. Compared with wild type mice, the ileal BA pool in Asbt-deficient mice was ∼5-fold smaller, enriched in secondary BA species and metabolites normally found in the colon, and elicited unique transcriptional responses upon addition to ex vivo-cultured ileal explants. ConclusionsThis study defines quantitative traits of the mouse enterohepatic BA pool and reveals how aberrant BA metabolism can impinge directly on host intestinal physiology.

Miniature chicken ileal explant culture to investigate the inflammatory response induced by pathogen associated molecular patterns

Miniature chicken ileal explant culture to investigate the inflammatory response induced by pathogen associated molecular patterns

Commensal bacteria signal through TLR5 and AhR to improve barrier integrity and prevent allergic responses to food

The increasing prevalence of food allergies has been linked to reduced commensal microbial diversity. In this article, we describe two features of allergy-protective Clostridia that contribute to their beneficial effects. Some Clostridial taxa bear flagella (a ligand for TLR5) and produce indole (a ligand for the aryl hydrocarbon receptor [AhR]). Lysates and flagella from a Clostridia consortium induced interleukin-22 (IL-22) secretion from ileal explants. IL-22 production is abrogated in explants from mice in which TLR5 or MyD88 signaling is deficient either globally or conditionally in CD11c+ antigen-presenting cells. AhR signaling in RORγt+ cells is necessary for the induction of IL-22. Mice deficient in AhR in RORγt+ cells exhibit increased intestinal permeability and are more susceptible to an anaphylactic response to food. Our findings implicate TLR5 and AhR signaling in a molecular mechanism by which commensal Clostridia protect against allergic responses to food.

Investigating the Role of the NLRP3 Inflammasome Pathway in Acute Intestinal Inflammation: Use of THP-1 Knockout Cell Lines in an Advanced Triple Culture Model.

The NLRP3 inflammasome plays an important role in intestinal homeostasis as well as inflammation. However, in vivo studies investigating the role of the NLRP3 inflammasome in inflammatory bowel disease (IBD) report contrasting results, leaving it unclear if the NLRP3 inflammasome augments or attenuates intestinal inflammation. To investigate the role of the NLRP3/caspase-1 pathway in a model of acute intestinal inflammation, we modified a previously established in vitro triple culture model of the healthy and inflamed intestine (Caco-2/HT29-MTX-E12/THP-1). Using THP-1 knockout cell lines, we analyzed how the NLRP3 inflammasome and its downstream enzyme caspase-1 (CASP1) affect inflammatory parameters including barrier integrity and cytotoxicity, as well as gene expression and secretion of pro-inflammatory cytokines and mucus. Furthermore, we investigated differences in inflammation-mediated cytotoxicity towards enterocyte-like (Caco-2) or goblet-like (HT29-MTX-E12) epithelial cells. As a complementary approach, inflammation-related cytotoxicity and gene expression of cytokines was analyzed in intestinal tissue explants from wildtype (WT) and Nlrp3-/- mice. Induction of intestinal inflammation impaired the barrier, caused cytotoxicity, and altered gene expression of pro-inflammatory cytokines and mucins in vitro, while the knockout of NLRP3 and CASP1 in THP 1 cells led to attenuation of these inflammatory parameters. The knockout of CASP1 tended to show a slightly stronger attenuating effect compared to the NLRP3 knockout model. We also found that the inflammation-mediated death of goblet-like cells is NLRP3/caspase-1 dependent. Furthermore, inflammation-related cytotoxicity and upregulation of pro-inflammatory cytokines was present in ileal tissue explants from WT, but not Nlrp3-/- mice. The here presented observations indicate a pro-inflammatory and adverse role of the NLRP3 inflammasome in macrophages during acute intestinal inflammation.

Bile acid toxicity in Paneth cells contributes to gut dysbiosis induced by high-fat feeding.

High-fat feeding (HFF) leads to gut dysbiosis through unclear mechanisms. We hypothesize that bile acids secreted in response to high-fat diets (HFDs) may act on intestinal Paneth cells, leading to gut dysbiosis. We found that HFF resulted in widespread taxonomic shifts in the bacteria of the ileal mucosa, characterized by depletion of Lactobacillus and enrichment of Akkermansia muciniphila, Clostridium XIVa, Ruminococcaceae, and Lachnospiraceae, which were prevented by the bile acid binder cholestyramine. Immunohistochemistry and in situ hybridization studies showed that G protein–coupled bile acid receptor (TGR5) expressed in Paneth cells was upregulated in the rats fed HFD or normal chow supplemented with cholic acid. This was accompanied by decreased lysozyme+ Paneth cells and α-defensin 5 and 6 and increased expression of XBP-1. Pretreatment with ER stress inhibitor 4PBA or with cholestyramine prevented these changes. Ileal explants incubated with deoxycholic acid or cholic acid caused a decrease in α-defensin 5 and 6 and an increase in XBP-1, which was prevented by TGR5 antibody or 4PBA. In conclusion, this is the first demonstration to our knowledge that TGR5 is expressed in Paneth cells. HFF resulted in increased bile acid secretion and upregulation of TGR5 expression in Paneth cells. Bile acid toxicity in Paneth cells contributes to gut dysbiosis induced by HFF.

OR31-3 Role of a Novel Short Chain Fatty Acid Receptor OLFR78 in Mediating Gluco-metabolic Hormone Secretion

Olfactory receptor OLFR78 is a G protein-coupled receptor (GPCR) which is activated by short chain fatty acids (SCFAs), especially propionate. OLFR78 is expressed in islets as well as intestinal epithelial cells. Based on these properties, we hypothesized its role in the regulation of metabolic hormone secretion. Our emerging data shows that OLFR78 signaling regulates GLP-1 secretion from murine enteroendocrine cells in vitro and ex vivo. We demonstrate that knockdown of Olfr78 through siRNA in the murine enteroendocrine cell line STC-1 results in a significant reduction in propionate-induced GLP-1 secretion. Utilizing constitutive and cyclic AMP inducible transcriptional luciferase promoters in addition to G protein pathway modulators, we further demonstrate that the signaling pathway downstream of active OLFR78 involves the activation of a Gαs subunit. As GLP-1 is an insulinotropic factor, we sought to determine the role of OLFR78 in insulin secretion and β cell mass maintenance. Using islets isolated from both wildtype and global OLFR78 knockout mice, we show that OLFR78 signaling in islets does not have a significant effect on insulin secretion. Additionally, we observed no differences in beta cell mass in wildtype versus OLFR78 knockout mice. Furthermore, no differences are observed in incretin secretion in response to oral glucose challenge between wildtype and knockout mice fed normal chow. However, ileal explants prepared from wildtype mice reveal higher secretion of GLP-1 in response to propionate challenge. These data suggest that specific activation of the receptor, rather than its presence alone, affects GLP-1 secretion. We have previously shown that the activity of other SCFA-sensing GPCRs, such as FFA2 and FFA3, are dependent on gut microbiota-derived metabolites which fluctuate with physiological stress. Similarly, we believe that the function of OLFR78 will be more evident under conditions of dietary stress, which is a crucial determinant of gut microbial activity.

Cellular immune response and scanning electron microscopy in the evaluation of Moringa leaves aqueous extract effect on Cryptosporidium parvum in buffalo intestinal tissue explants.

Cryptosporidium is an apicomplexan parasite of human and animals and is considered as an important co-factor in neonatal diarrhea. In this study, an explant culture was usedas an in vitro model of buffalo intestine to evaluate the effect of Moringa leaves extract on Cryptosporidium parvum (C. parvum) oocysts using light and scanning electron microscopy and measuring IFN-γ, IL-12 and IL-14 in the culture supernatants. C. parvum oocysts were collected from naturally-infected calf feces, isolated, excysted and then co-inoculated with ileal tissue explants culture medium. The prepared Moringa leaves extract was then introduced to the infected tissues in the concentrations of 100mg/ml and 300mg/ml. After 24h, tissues were collected and processed for light and scanning electron microscopy. Also, culture supernatants were collected for cytokines measurement. C. parvum parasitophorous vacuoles were found attached to the surface of tissue in Cryptosporidium-infected ileal tissue explants. High magnification imaging of ileal tissue explants using scanning electron microscopy showed that Moringa leaves extracts had a great effect on Cryptosporidium-infected ileal tissue explants. There was a high significant (P < 0.001) increase in IFN-γ, IL-12 and IL-14 (375, 275 and 90pg/ml, respectively) in the supernatants of infected non-treated ileal tissue explant culture plate wells compared to the control non-infected ones (74.66, 75 and 50pg/ml, respectively). A concentration of 100mg/ml Moringa extract exhibited the highest anticryptosporidial effect causing a significant decrease in IFN-γ, IL-12 and IL-14 levels (225, 150 and 65pg/ml, respectively) compared with supernatants of infected non-treated ileal explant culture plate wells. In this study, explant culturing of buffalo ileal tissues allowed investigating the pathogenesis of cryptosporidiosis using light and scanning electron microscopy and studying changes in cytokine levels in tissues with and without Moringa leaves extract treatment. This model could helpto understand the regulation of intestinal secretory and inflammatory responses, and could be useful for the screening of potential anticryptosporidial candidate compounds.

Schistosoma mansoni Coinfection Attenuates Murine Toxoplasma gondii-Induced Crohn's-Like Ileitis by Preserving the Epithelial Barrier and Downregulating the Inflammatory Response.

Background and aims: Mice orally infected with T. gondii develop Crohn's disease (CD)-like enteritis associated with severe mucosal damage and a systemic inflammatory response, resulting in high morbidity and mortality. Previously, helminthic infections have shown therapeutic potential in experimental colitis. However, the role of S. mansoni in T. gondii-induced CD-like enteritis has not been elucidated. Our study investigated the mechanisms underlying T. gondii-induced ileitis and the potential therapeutic effect of S. mansoni coinfection.Methods: C57BL/6 mice were infected by subcutaneous injection of cercariae of the BH strain of S. mansoni, and 7–9 weeks later, they were orally infected with cysts of the ME49 strain of T. gondii. After euthanasia, the ileum was removed for histopathological analysis; staining for goblet cells; immunohistochemistry characterizing mononuclear cells, lysozyme expression, apoptotic cells, and intracellular pathway activation; and measuring gene expression levels by real-time PCR. Cytokine concentrations were measured in the serial serum samples and culture supernatants of the ileal explants, in addition to myeloperoxidase (MPO) activity.Results: T. gondii-monoinfected mice presented dense inflammatory cell infiltrates and ulcerations in the terminal ileum, with abundant cell extrusion, apoptotic bodies, and necrosis; these effects were absent in S. mansoni-infected or coinfected animals. Coinfection preserved goblet cells and Paneth cells, remarkably depleted in T. gondii-infected mice. Densities of CD4- and CD11b-positive cells were increased in T. gondii- compared to S. mansoni-infected mice and controls. MPO was significantly increased among T. gondii-mice, while attenuated in coinfected animals. In T. gondii-infected mice, the culture supernatants of the explants showed increased concentrations of TNF-alpha, IFN-gamma, and IL-17, and the ileal tissue revealed increased expression of the mRNA transcripts for IL-1 beta, NOS2, HMOX1, MMP3, and MMP9 and activation of NF-kappa B and p38 MAPK signaling, all of which were counterregulated by S. mansoni coinfection.Conclusion: S. mansoni coinfection attenuates T. gondii-induced ileitis by preserving mucosal integrity and downregulating the local inflammatory response based on the activation of NF-kappa B and MAPK. The protective function of prior S. mansoni infection suggests the involvement of innate immune mechanisms and supports a conceptually new approach to the treatment of chronic inflammatory diseases, including CD.

Development of a chicken ileal explant culture model for measurement of gut inflammation induced by lipopolysaccharide

Gut mucosa holds a single layer of epithelial cells and the largest mass of lymphoid tissue in the body. Although the epithelial cell culture model is widely used to assess intestinal barrier function, it has limitations for studying cellular interactions, in particular those of the immune system. In this study, a chicken ileal explant culture model was developed for investigating short-term gut inflammatory and secretory responses in an ex vivo environment. Initially, ileal explants from broilers at 21 d of age were cultured ex vivo up to 6 h. Explants cultured for a maximum of 2 h remained over 90% viable, based on lactate dehydrogenase (LDH) release assay. Morphologically, explants cultured for 2 h displayed normal morphology compared to those cultured longer, further confirming that short-term culture for up to 2 h duration is an acceptable model for studying ex vivo regulation of inflammation. Subsequently, lipopolysaccharide (LPS) dose-related responses were determined for explants cultured for 2 h. Results from LDH activity assay showed that the viability of explants was decreased (P ≤ 0.05) at an LPS dose higher than 50 μg/mL. A significant (P ≤ 0.05) nitric oxide release was observed at LPS concentrations of 10 and 20 μg/mL. In addition, the highest inflammatory and secretory responses were detected at 20 μg/mL LPS based on gene expression of TLR-4, IL-1β, IL-8, MUC2, IgA, and pIgR (P ≤ 0.05). However, the gene expression of claudin-1 and claudin-4 were not increased at the determined LPS concentrations (P > 0.05). These results demonstrated the potential usefulness of this intestinal explant culture model for short-term study of biological factors in gut inflammatory and secretory responses, but not a sufficient duration for evaluation of tight junction responsiveness.

Effect of threonine on secretory immune system using a chicken intestinal ex vivo model with lipopolysaccharide challenge

Secretory IgA (sIgA) and its transcytosis receptor, polymeric immunoglobulin receptor (pIgR), along with mucus, form the first lines of intestinal defense. Threonine (Thr) is a major component of intestinal mucins and IgA, which are highly secreted under lipopolysaccharide (LPS) induced inflammation. In the current study, the effect of Thr on the secretory immune system was determined in an ex vivo chicken ileal explant model. Results showed that a 2-hour Thr-deprivation of culture medium induced a compensatory increase in the mRNA expression of interleukin-8 (IL-8), mucin 2 (MUC2), and IgA during LPS challenge, and this increase was suppressed with Thr addition to the media (P ≤ 0.05), suggesting that Thr was required for mucin and IgA production after exposure to LPS. Similarly, a 2-hour culture of explants from birds fed a Thr adequate diet showed an increase in the mRNA abundance of IL-8, MUC2, and IgA with LPS treatment (P ≤ 0.003), which had a trend to be attenuated with Thr supplementation in the media (P ≤ 0.10). In contrast, explants from birds fed a Thr deficient diet had no response to LPS treatment. These results indicated that in vivo Thr deficiency induced impaired inflammatory and secretory immune responses in broiler chicks. Furthermore, our results revealed that induction of MUC2 and pIgR gene expression required nuclear factor-κB (NF-κB) activation. Additionally, IgA transcytosis may be dependent on extracellular-regulated protein kinase (ERK) activation, which may indirectly impact pIgR gene expression.

Bile Acid Administration Elicits an Intestinal Antimicrobial Program and Reduces the Bacterial Burden in Two Mouse Models of Enteric Infection.

In addition to their chemical antimicrobial nature, bile acids are thought to have other functions in the homeostatic control of gastrointestinal immunity. However, those functions have remained largely undefined. In this work, we used ileal explants and mouse models of bile acid administration to investigate the role of bile acids in the regulation of the intestinal antimicrobial response. Mice fed on a diet supplemented with 0.1% chenodeoxycholic acid (CDCA) showed an upregulated expression of Paneth cell α-defensins as well as an increased synthesis of the type-C lectins Reg3b and Reg3g by the ileal epithelium. CDCA acted on several epithelial cell types, by a mechanism independent from farnesoid X receptor (FXR) and not involving STAT3 or β-catenin activation. CDCA feeding did not change the relative abundance of major commensal bacterial groups of the ileum, as shown by 16S analyses. However, administration of CDCA increased the expression of ileal Muc2 and induced a change in the composition of the mucosal immune cell repertoire, decreasing the proportion of Ly6G+ and CD68+ cells, while increasing the relative amount of IgGκ+ B cells. Oral administration of CDCA to mice attenuated infections with the bile-resistant pathogens Salmonella enterica serovar Typhimurium and Citrobacter rodentium, promoting lower systemic colonization and faster bacteria clearance, respectively. Our results demonstrate that bile acid signaling in the ileum triggers an antimicrobial program that can be potentially used as a therapeutic option against intestinal bacterial infections.

Characterizing Factors Associated With Differences in FGF19 Blood Levels and Synthesis in Patients With Primary Bile Acid Diarrhea.

Chronic diarrhea caused by primary bile acid diarrhea (PBAD) is a common condition. We have previously shown PBAD is associated with low fasting serum levels of the ileal hormone, fibroblast growth factor 19 (FGF19). FGF19 is a negative regulator of hepatic bile acid synthesis and is stimulated by farnesoid X receptor agonists, which produce symptomatic improvement in PBAD. We aimed to assess possible causes for low serum FGF19 in patients with PBAD. Patients with PBAD, defined by reduced (75)Se-labelled homocholic acid taurine (SeHCAT) retention, and idiopathic diarrhea controls had measurements of fasting lipids and fasting/post-prandial FGF19 serum profiles. Specific functional variants in candidate genes were investigated in exploratory studies. In further groups, basal and bile acid-stimulated transcript expression was determined in ileal biopsies and explant cultures by quantitative PCR. FGF19 profiles in PBAD patients included low fasting and meal-stimulated responses, which were both strongly correlated with SeHCAT. A subgroup of 30% of PBAD patients had fasting hypertriglyceridemia and higher FGF19. No clear significant differences were found for any genetic variant but there were borderline associations with FGFR4 and KLB. SeHCAT retention significantly correlated with the basal ileal transcript expression of FGF19 (rs=0.59, P=0.03) and apical sodium-dependent bile acid transporter (ASBT) (rs=0.49, P=0.04), and also with the degree of stimulation by chenodeoxycholic acid at 6 h for transcripts of FGF19 (median 184-fold, rs=0.50, P=0.02) and ileal bile acid binding protein (IBABP) (median 2.2-fold, rs=0.47, P=0.04). Median stimulation of FGF19 was lower in patients with SeHCAT retention <10% (P=0.01). These studies demonstrate a complex, multifactorial etiology of PBAD, including impairments in ileal FGF19 expression and responsiveness.

The Effect of Divergence in Feed Efficiency on the Intestinal Microbiota and the Intestinal Immune Response in Both Unchallenged and Lipopolysaccharide Challenged Ileal and Colonic Explants.

Feed efficiency is an important trait in pig production, with evidence to suggest that the efficiencies of a variety of biological systems contribute to variation in this trait. Little work has been conducted on the contribution of the intestinal innate immune response to divergence in feed efficiency. Hence, the objective of this study was to examine select bacterial populations and gene expression profiles of a range of targets relating to gut health and immunity in the intestine of pigs phenotypically divergent in feed efficiency in: a) the basal state; and (b) following an ex-vivo lipopolysaccharide (LPS) challenge of ileal and colonic tissue. Male pigs (initial BW 22.4 kg (SD = 2.03)) were fed a standard finishing diet for the final 43 days prior to slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). On day 115, 16 animals (average weight 85 kg, SEM 2.8 kg), designated high RFI (HRFI) and low RFI (LRFI) were slaughtered. The LRFI pigs had increased lactobacillus spp. in the caecum compared to HRFI pigs (P < 0.05). RFI groups did not differ in the expression of the measured genes involved in the innate immune system in the basal ileal or colonic tissues (P > 0.10). Interestingly, there was an interaction between RFI and LPS for the cytokines IL-8, IL-1, IL-6, TNF-α, Interferon-γ (IFN-γ) and SOCS3, with the LRFI group having consistently lower gene expression in the colon following the LPS challenge, compared to the HRFI group. The lower gene expression of SOCS and cytokines following an ex vivo LPS challenge supports the theory that a possible energy saving mechanism exists in the intestinal innate immune response to an immune challenge in more feed efficient pigs.

SAT-331 - Cafestol but Not Resveratrol is a Partial Agonist of Farnesoidx Receptor and Stimulates FGF19 in Human Ileal Explants

SAT-331 - Cafestol but Not Resveratrol is a Partial Agonist of Farnesoidx Receptor and Stimulates FGF19 in Human Ileal Explants

FRI-395 - Ursodeoxycholic Acid Increases Obeticholic Acid Stimulation of FGF19 in Human Ileal Explants

FRI-395 - Ursodeoxycholic Acid Increases Obeticholic Acid Stimulation of FGF19 in Human Ileal Explants

OC-036 Stimulated expression of ileal fibroblast growth factor 19 by bile acids is impaired in patients with primary and secondary bile acid diarrhoea

<h3>Introduction</h3> Bile acid diarrhoea (BAD) results from excess luminal bile acids (BA) in the colon. Most BAs are reabsorbed at the terminal ileum. Increased colonic BA occur secondary to ileal disease or resection (common in Crohn’s disease [CD]) leading to BA malabsorption and secondary BAD (SBAD). Primary BAD (PBAD) occurs in the absence of overt ileal disease or malabsorption. The peptide FGF19 is produced from enterocytes in response to BA absorption and maintains homeostasis of the BA pool size by inhibiting hepatic BA synthesis. Impaired ileal FGF19 production may underlie the excess faecal BA observed in PBAD and may be contributory in CD as a result of increased hepatic BA synthesis. We aimed to investigate whether BA-induced expression of FGF19 in the ileum is reduced in patients with PBAD or CD. <h3>Method</h3> Patients attending for colonoscopy (n = 58) were prospectively recruited and gave informed consent to give additional ileal biopsies. 14 patients had CD (4 with previous right hemi colectomy and 10 without), 16 patients had unexplained diarrhoea and had SeHCAT tests, and 28 controls. Groups of 2–3 biopsies (explants) were incubated separately for 6 h with either BA-free culture media (unstimulated controls), chenodeoxycholate (CDCA) or glyco-CDCA (GCDCA), both at 50 µM. After RNA extraction and cDNA synthesis, FGF19 expression was quantified relative to GAPDH by RT-PCR. <h3>Results</h3> In patients with unexplained diarrhoea SeHCAT 7d retention values were &lt;15% in 7 patients, indicating primary BAD, and &gt;15% in 9 who were normal diarrhoea controls. A positive correlation was found between SeHCAT retention and the magnitude of the fold change in FGF19 expression stimulated by either CDCA (r = 0.50, n = 16, p = 0.02) or by GCDCA (r = 0.76, n = 7, p = 0.02). The median CDCA stimulated fold change in FGF19 expression was significantly lower in CD compared to controls (87, n = 12 vs 251, n = 28, p = 0.03) and a similar non-significant trend was observed for median GCDCA stimulated expression (97, n = 10 vs 156, n = 13, p = 0.18). <h3>Conclusion</h3> Ileal explants from patients with lower SeHCAT 7d retention had a lower response to both CDCA and GCDCA. Patients with CD had lower responses to CDCA. As uptake of GCDCA is dependent on carrier-mediated apical BA uptake but CDCA is not, this implies abnormalities in the intracellular ileal FGF19 response to BA. A reduced capacity to induce ileal FGF19 expression in response to absorbed BA is proposed to increase faecal BA due to increased hepatic BA synthesis in primary BAD. In secondary BAD an impaired ileal BA FGF19 response may lead to an increase in BA synthesis and faecal BA that is disproportionate to the degree of ileal BA malabsorption. <h3>Disclosure of interest</h3> None Declared.