Protein kinase C δ signaling is required for dietary prebiotic-induced strengthening of intestinal epithelial barrier function

Fructooligosaccharides slow colonic motility and activate myenteric neurons via calcium sensing and 5-HT3 receptors in the proximal colon

Calcium-sensing receptors (CaSR) regulate a variety of functions in the gastrointestinal tract. Recently, prebiotic-independent effects of fructooligosaccharides (FOS) on epithelial barrier function were found to be mediated by CaSR. Here, we tested the hypothesis that FOS acts via the CaSR to regulate colonic motility and neuronal activity in the enteric nervous system. Using immunohistochemistry, we determined that CaSR were localized on the colonic epithelium of the mouse proximal colon and that a small proportion of enterochromaffin cells coexpress CaSR. We demonstrated that intraluminal administration of FOS slows colonic motility in vivo in male and female mice, an effect that is mediated by both CaSR and 5-HT3 receptors. We assessed neuronal activity in response to luminally perfused FOS in intact segments of the proximal colon from male and female mice expressing a genetically encoded fluorescent calcium reporter in intrinsic primary afferent neurons (Calb1-GCaMP6 mice) or in all enteric neurons (Wnt1-GCaMP6 mice) using live cell confocal imaging. In both Calb1-GCaMP6 mice and Wnt1-GCaMP6 mice, intraluminal FOS perfusion induced a sustained elevation of intracellular Ca2+ in neurons of the myenteric plexus. This effect was sensitive to tetrodotoxin and mediated by CaSR and 5-HT3 receptors. Serosal application of FOS was without effect. Our results demonstrate that FOS acts acutely to slow colonic motility in vivo and activates the enteric nervous system via CaSR and 5-HT3 receptors.NEW & NOTEWORTHY Calcium-sensing receptors regulate a variety of functions in the gastrointestinal tract. Here, we demonstrate a novel action of fructooligosaccharides to regulate colonic motility in vivo and activate the enteric nervous system. These effects are mediated by calcium-sensing and 5-HT3 receptors.

Intestinal Microbiota and Vaccinations: A Systematic Review of the Literature

Background: Vaccination constitutes a low-cost, safe, and efficient public health measure that can help prevent the spread of infectious diseases and benefit the community. The fact that vaccination effectiveness varies among populations, and that the causes of this are still unclear, indicates that several factors are involved and should be thoroughly examined. The "intestinal microbiota" is the most crucial of these elements. Numerous clinical studies demonstrate the intestinal microbiota's significance in determining the alleged "immunogenicity" and efficacy of vaccines. This systematic review aimed to review all relevant scientific literature and highlight the role of intestinal microbiota in COVID-19, Salmonella typhi, Vibrio cholerae, and rotavirus vaccinations. Materials and Methods: The MESH terms "vaccines" and "microbiota" were used to search the major scientific databases PubMed, SciVerse Scopus, Web of Knowledge, and the Cochrane Central Register of Controlled Clinical Trials. Results: Between February 2024 and October 2024, the analysis was conducted using electronic databases, yielding a total of 235 references. Finally, 24 RCTs were chosen after meeting all inclusion criteria: eight studies of COVID-19, two studies of Salmonella typhi, three studies of Vibrio cholerae, and eleven studies of rotavirus. Only six of these demonstrated good study quality with a Jadad score of three or four. Conclusions: According to the review's results, the intestinal microbiota surely plays a role in vaccinations' enhanced immunogenicity, especially in younger people. As it is still unclear what mechanisms underlie this effect, more research is needed to better understand the role of the intestinal microbiota.

Methyl-esterification, degree of polymerization and ∆4,5-unsaturation of galacturonic acid oligosaccharides as determinants of immunomodulation

In recent years, immunomodulation by pectin and pectin-derived galacturonic acid oligosaccharides has been the subject of wide-spread scientific research due to the potential of different pectin structures as bioactive biomolecules. Yet, gaps remain in understanding the structure-dependent immunomodulation of galacturonic acid. This study describes in vitro immunomodulatory effects of well-characterized galacturonic acid oligosaccharides. Both methyl-esterified and non-methyl-esterified galacturonic acid oligosaccharides with a saturated non-reducing end (degree of polymerization 1-10) significantly induced cytokine production by THP-1 macrophages and directly activated TLR2 and TLR4 in transfected HEK-293 cells, even when accounting for minor endotoxin contamination. In contrast, both methyl-esterified and non-methyl-esterified galacturonic acid oligosaccharides with a Δ4,5-unsaturated non-reducing end (degree of polymerization 1-7) did not activate TLR2 and TLR4 and led to significantly reduced cytokine production (p < 0.05), suggesting Δ4,5-(un)saturation as a pivotal factor for immunomodulation by galacturonic acid oligosaccharides. Exposure to non-methyl-esterified saturated galacturonic acid oligosaccharides resulted in significantly lower TNF-α production, IL-1β production and TLR4 activation (p < 0.05) compared to methyl-esterified saturated galacturonic acid oligosaccharides, while IL-10 production and TLR2 activation remained unchanged. These findings establish galacturonic acid oligosaccharides as versatile immunomodulators with TLR2 and TLR4 binding capacity, fit for different immunomodulatory applications depending on their structural characteristics.

Nondigestible stachyose binds membranous HSP90β on small intestinal epithelium to regulate the exosomal miRNAs: A new function and mechanism

Oligosaccharides are conventionally recognized as "passersby" in the small intestine. However, our research has reframed this understanding by uncovering a new function of oligosaccharide stachyose, which binds hydrophobic residues of membranous HSP90β on small intestinal epithelial cells, thus reprograming the exosomal miRNA profile. CRISPR-Cas9-mediated HSP90β knockout abolished the accumulation of stachyose on cell membrane and its regulatory effects on these miRNAs. Notably, stachyose's regulation on these miRNAs is independent of its prebiotic role, as evidenced by the observation of stachyose-altered fecal miRNAs in pseudo-germ-free mice. These stachyose-altered miRNAs further shaped colonic microbiome, especially harboring Lactobacillus in mice. Thereinto, miR-30a-5p that was downregulated (Log2FC < -2) in both mice and human feces following stachyose treatment could specifically suppress the growth of Lactobacillus reuteri. These findings build a new regulatory axis of stachyose-intestinal miRNAs-gut microbiota and unveil a previously unknown mechanism underlying the direct "talk" of oligosaccharides to intestine epithelium via membranous HSP90β.

Rhamnogalacturonan promotes intestinal mucosal repair through increased cell migration

Mucosal healing is the primary goal for inflammatory bowel disease (IBD) treatment. We previously showed the direct beneficial effects of rhamnogalacturonan (RGal) on intestinal epithelial barrier function. Here, we aimed to evaluate the effect of RGal in intestinal epithelial wound healing. Confluent cancer cell lines and colonoid monolayers were wounded, treated with RGal for 48 h, and assessed using a live cell imaging system. Proliferation and apoptosis of cells were evaluated using 5-ethynyl-2'-deoxyuridine (EdU) and TUNEL assays, respectively. Inhibitors were used to determine the receptor and signaling pathways involved. Female and male mice with DSS-induced colitis were treated orally with RGal for 7 days during the recovery phase. RGal enhanced wound healing in Caco-2, T84, and primary cells by increasing cell migration. Inhibition of pretranscriptional signaling pathways FAK, Src, PI3K, Rho family, and JNK reversed the RGal-induced wound healing. RNAseq data from Caco-2 and primary cells treated with RGal showed the upregulation of the NF-κB pathway at 12 h. Actinomycin D, Bay 11-7082 or JSH-23, and NS-398 treatment significantly reversed the effect of RGal on wound healing, confirming that the response was also transcriptionally dependent and involved NF-κB signaling and downstream COX-2 protein activity. RGal treatment of male mice enhanced recovery from DSS colitis. RGal promoted wound healing in cancer and primary cells by increasing cell migration and accelerated epithelial mucosal healing in male mice. Our findings show a novel mechanism of action of RGal in wound healing that could help in mucosal healing and the resolution of intestinal inflammation.NEW & NOTEWORTHY RGal increases wound healing in colon cancer cell lines and primary cells through increased cell migration and participation of important pretranscriptional signaling pathways and the transcription factor NF-κB. In addition, RGal also accelerates intestinal mucosal healing of male mice with DSS-induced colitis.

Inter- and Transgenerational Effects of In Ovo Stimulation with Bioactive Compounds on Cecal Tonsils and Cecal Mucosa Transcriptomes in a Chicken Model

Exploring how early-life nutritional interventions may impact future generations, this study examines the inter- and transgenerational effects of in ovo injection of bioactive compounds on gene expression in the cecal tonsils and cecal mucosa using a chicken model. Synbiotic PoultryStar® (Biomin) and choline were injected in ovo on the 12th day of egg incubation. Three experimental groups were established in the generation F1: (1) a control group (C) receiving 0.9% physiological saline (NaCl), (2) a synbiotic group (SYN) receiving 2 mg/embryo, and (3) a combined synbiotic and choline group (SYNCH) receiving 2 mg synbiotic and 0.25 mg choline per embryo. For the generations F2 and F3, the SYN and SYNCH groups were each divided into two subgroups: (A) those injected solely in F1 (SYNs and SYNCHs) and (B) those injected in each generation (SYNr and SYNCHr). At 21 weeks posthatching, cecal tonsil and cecal mucosa samples were collected from F1, F2, and F3 birds for transcriptomic analysis. Gene expression profiling revealed distinct intergenerational and transgenerational patterns in both tissues. In cecal tonsils, a significant transgenerational impact on gene expression was noted in the generation F3, following a drop in F2. In contrast, cecal mucosa showed more gene expression changes in F2, indicating intergenerational effects. While some effects carried into F3, they were less pronounced, except in the SYNs group, which experienced an increase compared to F2. The study highlights that transgenerational effects of epigenetic modifications are dynamic and unpredictable, with effects potentially re-emerging in later generations under certain conditions or fading or intensifying over time. This study provides valuable insights into how epigenetic nutritional stimulation during embryonic development may regulate processes in the cecal tonsils and cecal mucosa across multiple generations. Our findings provide evidence supporting the phenomenon of epigenetic dynamics in a chicken model.

From Structure to Function: How Prebiotic Diversity Shapes Gut Integrity and Immune Balance

The microbiota stability, diversity, and composition are pillars for an efficient and beneficial symbiotic relationship between its host and itself. Microbial dysbiosis, a condition where a homeostatic bacterial community is disturbed by acute or chronic events, is a predisposition for many diseases, including local and systemic inflammation that leads to metabolic syndrome, diabetes, and some types of cancers. Classical dysbiosis occurs in the large intestine. During this period, pathogenic strains can multiply, taking advantage of the compromised environment. This overgrowth triggers an exaggerated inflammatory response from the human immune system due to the weakened integrity of the intestinal barrier. Such inflammation can also directly influence higher polyp formation and/or tumorigenesis. Prebiotics can be instrumental in preventing or correcting dysbiosis. Prebiotics are molecules capable of serving as substrates for fermentation processes by gut microorganisms. This can promote returning the intestinal environment to homeostasis. Effective prebiotics are generally specific oligo- and polysaccharides, such as FOS or inulin. However, the direct effects of prebiotics on intestinal epithelial and immune cells must also be taken into consideration. This interaction happens with diverse prebiotic nondigestible carbohydrates, and they can inhibit or decrease the inflammatory response. The present work aims to elucidate and describe the different types of prebiotics, their influence, and their functionalities for health, primarily focusing on their ability to reduce and control inflammation in the intestinal epithelial barrier, gut, and systemic environments.

Diagnosing and engineering gut microbiomes

The microbes, nutrients and toxins that we are exposed to can have a profound effect on the composition and function of the gut microbiome. Thousands of peer-reviewed publications link microbiome composition and function to health from the moment of birth, right through to centenarians, generating a tantalizing glimpse of what might be possible if we could intervene rationally. Nevertheless, there remain relatively few real-world examples where successful microbiome engineering leads to beneficial health effects. Here we aim to provide a framework for the progress needed to turn gut microbiome engineering from a trial-and-error approach to a rational medical intervention. The workflow starts with truly understanding and accurately diagnosing the problems that we are trying to fix, before moving on to developing technologies that can achieve the desired changes.

Supplemental Psyllium Fiber Increases Antimicrobial Proteins via the Tuft Cell-ILC2 Circuit and Type II Immune Response in the Mouse Small Intestine

Dietary fibers regulate intestinal barrier function; however, the precise mechanisms remain unclear. This study investigated the effects of psyllium fibers on antimicrobial protein expression, focusing on the type II immunity and tuft cell-group 2 innate lymphoid cell (ILC2) circuit in the small intestine of the mouse. Supplemental psyllium fiber upregulated antimicrobial proteins, such as small proline-rich protein 2A (SPRR2A) and resistin-like beta (RELMβ), in mouse small intestine, evidently affecting cecal microbiota composition. The psyllium fibers also increased the RNA and protein expression of molecules related to ILC2 and tuft cells, such as IL-13, IL-25, DCLK1, Gfi-1b, SH2 domain-containing protein 3C, and Spi-B. In addition, ILC2 inhibitor (disulfiram) and bitter taste receptor blocker administration reduced psyllium-induced SPRR2A and RELMβ expression. Collectively, psyllium supplementation upregulates antimicrobial proteins such as SPRR2A and RELMß via the type II immune response and tuft cell-ILC2 circuit in the mouse small intestine.

The Degree of Inulin Polymerization Is Important for Short-Term Amelioration of High-Fat Diet (HFD)-Induced Metabolic Dysfunction and Gut Microbiota Dysbiosis in Rats

Inulin, a non-digestible polysaccharide, has gained attention for its prebiotic properties, particularly in the context of obesity, a condition increasingly understood as a systemic inflammatory state linked to gut microbiota composition. This study investigates the short-term protective effects of inulin with different degrees of polymerization (DPn) against metabolic health deterioration and gut microbiota alterations induced by a high-fat diet (HFD) in Sprague Dawley rats. Inulin treatments with an average DPn of 7, 14, and 27 were administered at 1 g/kg of bodyweight to HFD-fed rats over 21 days. Body weight, systemic glucose levels, and proinflammatory markers were measured to assess metabolic health. Gut microbiota composition was analyzed through 16S rRNA gene sequencing. The results showed that inulin27 significantly reduced total weight gain and systemic glucose levels, suggesting a DPn-specific effect on metabolic health. The study also observed shifts in gut microbial populations, with inulin7 promoting several beneficial taxa from the Bifidobacterium genera, whilst inducing a unique microbial composition compared to medium-chain (DPn 14) and long-chain inulin (DPn: 27). However, the impact of inulin on proinflammatory markers and lipid metabolism parameters was not statistically significant, possibly due to the short study duration. Inulin with a higher DPn has a more pronounced effect on mitigating HFD-induced metabolic health deterioration, whilst inulin7 is particularly effective at inducing healthy microbial shifts. These findings highlight the benefits of inulin as a dietary adjuvant in obesity management and the importance of DPn in optimizing performance.

Inulin diet uncovers complex diet-microbiota-immune cell interactions remodeling the gut epithelium

BACKGROUND

The continuous proliferation of intestinal stem cells followed by their tightly regulated differentiation to epithelial cells is essential for the maintenance of the gut epithelial barrier and its functions. How these processes are tuned by diet and gut microbiome is an important, but poorly understood question. Dietary soluble fibers, such as inulin, are known for their ability to impact the gut bacterial community and gut epithelium, and their consumption has been usually associated with health improvement in mice and humans. In this study, we tested the hypothesis that inulin consumption modifies the composition of colonic bacteria and this impacts intestinal stem cells functions, thus affecting the epithelial structure.

METHODS

Mice were fed with a diet containing 5% of the insoluble fiber cellulose or the same diet enriched with an additional 10% of inulin. Using a combination of histochemistry, host cell transcriptomics, 16S microbiome analysis, germ-free, gnotobiotic, and genetically modified mouse models, we analyzed the impact of inulin intake on the colonic epithelium, intestinal bacteria, and the local immune compartment.

RESULTS

We show that the consumption of inulin diet alters the colon epithelium by increasing the proliferation of intestinal stem cells, leading to deeper crypts and longer colons. This effect was dependent on the inulin-altered gut microbiota, as no modulations were observed in animals deprived of microbiota, nor in mice fed cellulose-enriched diets. We also describe the pivotal role of γδ T lymphocytes and IL-22 in this microenvironment, as the inulin diet failed to induce epithelium remodeling in mice lacking this T cell population or cytokine, highlighting their importance in the diet-microbiota-epithelium-immune system crosstalk.

CONCLUSION

This study indicates that the intake of inulin affects the activity of intestinal stem cells and drives a homeostatic remodeling of the colon epithelium, an effect that requires the gut microbiota, γδ T cells, and the presence of IL-22. Our study indicates complex cross kingdom and cross cell type interactions involved in the adaptation of the colon epithelium to the luminal environment in steady state. Video Abstract.

Different Structures of Arabinoxylan Hydrolysates Alleviated Caco-2 Cell Barrier Damage by Regulating the TLRs/MyD88/NF-κB Pathway

Arabinoxylan (AX) has been associated with alleviating intestinal barrier damage, and different structures of AX give rise to different effects on the intestinal barrier. This study investigated the main structural characteristics of AX, whose functional properties are attributed to alleviating intestinal barrier damage, and clarified their underlying mechanisms. An in vitro Caco-2 cell model was established to investigate the intestinal barrier effects of AX with various degrees of substitution (Ds) and molecular weight (Mw), with an added MyD88 inhibitor to verify the signaling pathways. Arabinoxylan treated with endo-1,4-β-xylanase (AXX) with higher Ds and Mw showed stronger physiological activity, which might be correlated with the uronic acid and bound ferulic acid contents in AXX. Moreover, AXX alleviated the intestinal barrier damage by upregulating the transepithelial electrical resistance (TER) and alleviating the decrease of claudin-1 (p < 0.05). AXX regulated the expression of inflammatory factors IL-2, TNF-α, IL-6 and IL-10 (p < 0.05). In addition, AXX reduced the intestinal barrier damage induced via inhibiting the TLRs/MyD88/NF-κB pathway and activating the TLRs/PKC pathway. Thus, AX with higher Ds and Mw might be better in alleviating intestinal barrier damage, and MyD88 might be the key point of AXX to identify these signaling pathways.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

Early-life galacto-oligosaccharides supplementation alleviates the small intestinal oxidative stress and dysfunction of lipopolysaccharide-challenged suckling piglets

BACKGROUND

Galacto-oligosaccharides (GOS) are non-digestible food ingredients that promote the growth of beneficial bacteria in the gut. This study investigated the protective effect of the early-life GOS supplement on the piglets' gut function against the oxidative stress induced by lipopolysaccharide (LPS)-challenge.

METHODS

Eighteen neonatal piglets were assigned to three groups including CON, LPS and LPS + GOS groups. The piglets in CON group and LPS group received physiological saline, while those in LPS + GOS group received GOS solution for 13 d after birth. On d 14, the piglets in LPS group and LPS + GOS group were injected with LPS solutions, while the piglets in CON group were injected with the same volume of physiological saline.

RESULTS

The results showed that the early-life GOS supplement blocked the LPS-induced reactive oxygen species (ROS) secretion, malondialdehyde (MDA) production and the increase of pro-apoptotic factor expression. Meanwhile, the early-life GOS supplement improved the activities of antioxidant enzymes, disaccharidase enzymes activities, and digestive enzymes activities, and increased the mRNA abundance of the gene related to nutrient digestion and absorption and the relative protein expression of tight junction. The study also showed that the early-life GOS supplement improved the expression of Hemeoxygenase-1 (HO-1) and NAD(P)H/quinone acceptor oxidoreductase-1 (NQO-1), and activated the AMP-activated protein kinase (AMPK).

CONCLUSIONS

These results suggested that GOS enhanced the gut function, reduced the ROS production and pro-apoptotic factors gene expression, and activated the AMPK signaling pathway in LPS-challenged piglets.

The effect of inulin-type fructans on the intestinal immune function of antibiotic-treated mice

This study aimed to evaluate the effect of supplementation with inulin-type fructans (ITFs) on the intestinal immune function in the context of dysbiosis resulting from antibiotic cocktail (ABx) treatment. BALB/c mice (8-9 weeks of age) were treated with an ABx for 3 weeks and then allowed to recover spontaneously or with ITF supplementation (5%) for 4 weeks. Our results showed that ABx treatment can induce gut microbiota dysbiosis and intestinal inflammation in mice. After 4 weeks of recovery, ITF supplementation restored the composition of the intestinal microbial community. However, compared with spontaneous recovery, ITF supplementation delayed inflammation recovery in the intestine and upregulated diamine oxidase (DAO) activity and increased lipopolysaccharide (LPS) content in serum. In addition, ITF supplementation delayed the regulatory T (Treg) cell and B cell recovery in the lamina propria (LP). Furthermore, compared with spontaneous recovery, ITF supplementation inhibited the relative expression of certain proinflammatory genes, such as for inducible nitric oxide synthase (iNOS) and tumour necrosis factor α (Tnf-α), in the colon, but it reduced the secretion of the anti-inflammatory mediator transforming growth factor β1 (TGF-β1) in serum, reduced the secretion of secretory immunoglobulin A (SIgA) in the colon and promoted the secretion of the proinflammatory cytokine interleukin (IL)-17A. In conclusion, these data supported the hypothesis that the influence of ITFs on the host's intestinal status is not always beneficial in the context of ABx-induced biological disorder. However, the significance of these findings needs to be determined by advanced studies KEY POINTS: • ITFs did not promote the recovery of microbial community composition. • ITFs delayed the recovery of ABx-induced colonic inflammation. • ITFs reduced the secretion of TGF-β1 and SIgA. • ITFs delayed the recovery of Treg and B cells in the LP.

Variations in the Composition of Human Milk Oligosaccharides Correlates with Effects on Both the Intestinal Epithelial Barrier and Host Inflammation: A Pilot Study

Background: Human milk oligosaccharides are complex, non-digestible carbohydrates that directly interact with intestinal epithelial cells to alter barrier function and host inflammation. Oligosaccharide composition varies widely between individual mothers, but it is unclear if this inter-individual variation has any impact on intestinal epithelial barrier function and gut inflammation. Methods: Human milk oligosaccharides were extracted from the mature human milk of four individual donors. Using an in vitro model of intestinal injury, the effects of the oligosaccharides on the intestinal epithelial barrier and select innate and adaptive immune functions were assessed. Results: Individual oligosaccharide compositions shared comparable effects on increasing transepithelial electrical resistance and reducing the macromolecular permeability of polarized (Caco-2Bbe1) monolayers but exerted distinct effects on the localization of the intercellular tight junction protein zona occludins-1 in response to injury induced by a human enteric bacterial pathogen Escherichia coli, serotype O157:H7. Immunoblots showed the differential effects of oligosaccharide compositions in reducing host chemokine interleukin 8 expression and inhibiting of p38 MAP kinase activation. Conclusions: These results provide evidence of both shared and distinct effects on the host intestinal epithelial function that are attributable to inter-individual differences in the composition of human milk oligosaccharides.

The dietary fibre rhamnogalacturonan improves intestinal epithelial barrier function in a microbiota-independent manner

BACKGROUND AND PURPOSE

Dietary fibre comprises a complex group of polysaccharides that are indigestible but are fermented by gut microbiota, promoting beneficial effects to the intestinal mucosa indirectly through the production of short chain fatty acids. We found that a polysaccharide, rhamnogalacturonan (RGal), from the plant Acmella oleracea, has direct effects on intestinal epithelial barrier function. Our objective was to determine the mechanism whereby RGal enhances epithelial barrier function.

EXPERIMENTAL APPROACH

Monolayers of colonic epithelial cell lines (Caco-2, T84) and of human primary cells from organoids were mounted in Ussing chambers to assess barrier function. The cellular mechanism of RGal effects on barrier function was determined using inhibitors of TLR-4 and PKC isoforms.

KEY RESULTS

Apically applied RGal (1000 μg/ml) significantly enhanced barrier function as shown by increased transepithelial electrical resistance (TER) and reduced fluorescein isothiocyanate (FITC)-dextran flux in Caco-2, T84 and human primary cell monolayers, and accelerated tight junction reassembly in Caco-2 cells in a calcium switch assay. RGal also reversed the barrier-damaging effects of inflammatory cytokines on FITC-dextran flux and preserved the tight junction distribution of occludin. RGal activated TLR4 in TLR4-expressing HEK reporter cells, an effect that was significantly inhibited by the TLR4 inhibitor, C34. The effect of RGal was also dependent on PKC, specifically the isoforms PKCd and PKCζ.

CONCLUSION AND IMPLICATIONS

RGal enhances intestinal epithelial barrier function through activation of TLR4 and PKC signaling pathways. Elucidation of RGal mechanisms of action could lead to new, dietary approaches to enhance mucosal healing in inflammatory bowel diseases.

Anti-Inflammatory Properties of Fructo-Oligosaccharides in a Calf Lung Infection Model and in Mannheimia haemolytica-Infected Airway Epithelial Cells

Emerging antimicrobial-resistant pathogens highlight the importance of developing novel interventions. Here, we investigated the anti-inflammatory properties of Fructo-oligosaccharides (FOS) in calf lung infections and in airway epithelial cells stimulated with pathogens, and/or bacterial components. During a natural exposure, 100 male calves were fed milk replacer with or without FOS for 8 weeks. Then, immune parameters and cytokine/chemokine levels in the bronchoalveolar lavage fluid (BALF) and blood were measured, and clinical scores were investigated. Calf primary bronchial epithelial cells (PBECs) and human airway epithelial cells (A549) were treated with Mannheimia haemolytica, lipopolysaccharides (LPS), and/or flagellin, with or without FOS pretreatment. Thereafter, the cytokine/chemokine levels and epithelial barrier function were examined. Relative to the control (naturally occurring lung infections), FOS-fed calves had greater macrophage numbers in BALF and lower interleukin (IL)-8, IL-6, and IL-1β concentrations in the BALF and blood. However, FOS did not affect the clinical scores. At slaughter, FOS-fed calves had a lower severity of lung lesions compared to the control. Ex vivo, FOS prevented M. haemolytica-induced epithelial barrier dysfunction. Moreover, FOS reduced M. haemolytica- and flagellin-induced (but not LPS-induced) IL-8, TNF-α, and IL-6 release in PBECs and A549 cells. Overall, FOS had anti-inflammatory properties during the natural incidence of lung infections but had no effects on clinical symptoms.

Maternal Nutritional Status and Development of Atopic Dermatitis in Their Offspring

Atopic dermatitis (AD) is the leading chronic skin inflammatory disease and the initial manifestation of atopic march. Available evidence supports the notion that primary prevention early in life leads to a decreased incidence of AD, thus possibly decreasing the subsequent occurrence of atopic march. Nutritional status is essential to a proper functioning immune system and is valued for its important role in AD. Essential nutrients, which include carbohydrates, proteins, lipids, vitamins, and minerals, are transferred from the mother to the fetus through the placenta during gestation. Various nutrients, such as polyunsaturated fatty acids (PUFAs) and vitamin D, were studied in relation to maternal status and offspring allergy. However, no strong evidence indicates that a single nutrient or food in mothers' diet significantly affects the risk of childhood AD. In the light of current evidence, mothers should not either increase nor avoid consuming these nutrients to prevent or ameliorate allergic diseases in their offspring. Each essential nutrient has an important role in fetal development, and current government recommendations suggest specific intake amounts for pregnant women. This review discusses evidence on how various nutrients, including lipids (monounsaturated fatty acids, PUFAs, saturated fatty acids, and short-chain fatty acids), carbohydrates (oligosaccharides and polysaccharides), proteins, vitamins (A, B, C, D, and E), and trace minerals (magnesium, iron, zinc, copper, selenium, and strontium) in maternal status are associated with the development of AD and their possible mechanisms.

Fermentation Supernatants of Pleurotus eryngii Mushroom Ameliorate Intestinal Epithelial Barrier Dysfunction in Lipopolysaccharide-Induced Caco-2 Cells via Upregulation of Tight Junctions

In recent years, modulation of gut microbiota through prebiotics has garnered interest as a potential to ameliorate intestinal barrier dysfunction. The aim of the study was to examine the in vitro effect of fermentation supernatants (FSs) from rich in β-glucan Pleurotus eryngii mushrooms on the expression levels of tight junctions (TJs) genes in Caco-2 cells stimulated by bacterial lipopolysaccharides (LPS). Mushrooms were fermented using fecal inocula in an in vitro batch culture model. Caco-2 cells were subjected to LPS and FS treatment under three different conditions: pre-incubation with FS, co- and post-incubation. Reverse transcription PCR was applied to measure the expression levels of zonulin-1, occludin and claudin-1 genes. FSs from P. eryngii mushrooms led to a significant upregulation of the TJs gene expression in pre-incubation state, indicating potential preventive action. Down-regulation of all TJs gene expression levels was observed when the cells were challenged with LPS. The FS negative control (gut microbiota of each donor with no carbohydrate source) exhibited a significant upregulation of TJs expression levels compared to the cells that were challenged with LPS, for all three conditions. Overall, our data highlighted the positive and potential protective effects of P. eryngii mushrooms in upregulation of TJs’ genes.

Unraveling enterohemorrhagic Escherichia coli infection: the promising role of dietary compounds and probiotics in bacterial elimination and host innate immunity boosting

The innate immune system has developed sophisticated strategies to defense against infections. Host cells utilize the recognition machineries such as toll-like receptors and nucleotide binding and oligomerization domain-like receptors to identify the pathogens and alert immune system. However, some pathogens have developed tactics to evade host defenses, including manipulation of host inflammatory response, interference with cell death pathway, and highjack of phagocytosis signaling for a better survival and colonization in host. Enterohemorrhagic Escherichia coli (EHEC) is a notorious foodborne pathogen that causes severe tissue damages and gastrointestinal diseases, which has been reported to disturb host immune responses. Diverse bioactive compounds such as flavonoids, phenolic acids, alkaloids, saccharides, and terpenoids derived from food varieties and probiotics have been discovered and investigated for their capability of combating bacterial infections. Some of them serve as novel antimicrobial agents and act as immune boosters that harness host immune system. In this review, we will discuss how EHEC, specifically E. coli O157:H7, hijacks the host immune system and interferes with host signaling pathway; and highlight the promising role of food-derived bioactive compounds and probiotics in harnessing host innate immunity and eliminating E. coli O157:H7 infection with multiple strategies.

Impact of Bacterial Metabolites on Gut Barrier Function and Host Immunity: A Focus on Bacterial Metabolism and Its Relevance for Intestinal Inflammation

The diverse and dynamic microbial community of the human gastrointestinal tract plays a vital role in health, with gut microbiota supporting the development and function of the gut immune barrier. Crosstalk between microbiota-gut epithelium and the gut immune system determine the individual health status, and any crosstalk disturbance may lead to chronic intestinal conditions, such as inflammatory bowel diseases (IBD) and celiac disease. Microbiota-derived metabolites are crucial mediators of host-microbial interactions. Some beneficially affect host physiology such as short-chain fatty acids (SCFAs) and secondary bile acids. Also, tryptophan catabolites determine immune responses, such as through binding to the aryl hydrocarbon receptor (AhR). AhR is abundantly present at mucosal surfaces and when activated enhances intestinal epithelial barrier function as well as regulatory immune responses. Exogenous diet-derived indoles (tryptophan) are a major source of endogenous AhR ligand precursors and together with SCFAs and secondary bile acids regulate inflammation by lowering stress in epithelium and gut immunity, and in IBD, AhR expression is downregulated together with tryptophan metabolites. Here, we present an overview of host microbiota-epithelium- gut immunity crosstalk and review how microbial-derived metabolites contribute to host immune homeostasis. Also, we discuss the therapeutic potential of bacterial catabolites for IBD and celiac disease and how essential dietary components such as dietary fibers and bacterial tryptophan catabolites may contribute to intestinal and systemic homeostasis.

Protective effects of lactic acid bacteria on gut epithelial barrier dysfunction are Toll like receptor 2 and protein kinase C dependent

Lactic acid bacteria (LAB) are recognized for support of host gut homeostasis but the precise mechanisms remain to be identified. LABs interact with Toll-like receptors (TLRs) which might stimulate barrier function of gut epithelial cells. We previously identified six TLR2-signalling LAB strains. As TLR2 is involved in barrier-function enhancement in gut-epithelium, the epithelial barrier-protective effect of these TLR2-signalling strains was studied by using T84 human colorectal cancer cell monolayer as an in vitro gut epithelial barrier model. The protein kinase C (PKC) dependent barrier disruptor A23187 and mitogen-activated protein kinase dependent barrier stressor deoxynivalenol were tested to determine which pathways LAB influenced. We found that exclusively the PKC dependent disruption was prevented by the selected TLR2-signalling LAB strains. This study suggests that TLR2 is a pivotal epithelial barrier modulator, and provides novel insight in the molecular mechanisms by which LAB contribute to intestinal health.

Human Milk Oligosaccharides Protect against Necrotizing Enterocolitis by Activating Intestinal Cell Differentiation

SCOPE

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal emergency and currently the leading cause of mortality in preterm infants. Recent studies show that human milk oligosaccharides (HMOs) reduce the frequency and incidence of NEC; however, the molecular mechanisms for their protection are largely unexplored.

METHODS AND RESULTS

To address this gap, a genome-wide profiling of the intestinal epithelial transcriptome in response to HMOs using RNA-sequencing is performed. It is found that HMOs alter the host transcriptome in 225 unique target genes pertaining to cell proliferation and differentiation, including upregulation of stem cell differentiation marker HMGCS2. To validate these results, differentiation in Caco-2Bbe1 (Caco-2) intestinal cells is verified by Alcian Blue staining and transepithelial electrical resistance (TER) recordings. Furthermore, an in vivo model of NEC is also employed whereby neonatal pups are gavage fed HMOs. Interestingly, HMOs-fed pups show enhanced cell MUC2 differentiation and HMGCS2 expression.

CONCLUSIONS

These findings demonstrate HMOs protect against NEC in part by altering the differentiation of the crypt-villus axis. In addition, this study suggests that pooled HMOs directly induce a series of biological processes, which provide mechanistic insights to how HMOs protect the host intestine.

Health promoting microbial metabolites produced by gut microbiota after prebiotics metabolism

Human gut microbiota (HGM) is a microbial complex where dynamic mutualistic interactions related to digestion and absorption of dietary components take place. The consumption of specific food ingredients, such as prebiotics and dietary fibers, constituted mainly by carbohydrates polymers, can modulate the HGM composition and metabolism serving as a fermentable substrate to produce bacterial metabolites with beneficial effects on host health. Especially, bacterial short-chain fatty acids, tryptophan and organic acids have shown positive effects on pathogenic bacteria control, mineral absorption, weight control and obesity, immune response homeostasis, gut barrier improvement, brain modulation and anticancer activity. Despite the fact that these effects vary between individuals due to personal HGM richness, the information presented in this review contributes to understanding the effects of prebiotics and dietary fibers consumption on the generation of HGM metabolites and the mechanisms by which these metabolites interact with host cells improving host health.

From Beef to Bees: High-Throughput Kinome Analysis to Understand Host Responses of Livestock Species to Infectious Diseases and Industry-Associated Stress

Within human health research, the remarkable utility of kinase inhibitors as therapeutics has motivated efforts to understand biology at the level of global cellular kinase activity (the kinome). In contrast, the diminished potential for using kinase inhibitors in food animals has dampened efforts to translate this research approach to livestock species. This, in our opinion, was a lost opportunity for livestock researchers given the unique potential of kinome analysis to offer insight into complex biology. To remedy this situation, our lab developed user-friendly, cost-effective approaches for kinome analysis that can be readily incorporated into most research programs but with a specific priority to enable the technology to livestock researchers. These contributions include the development of custom software programs for the creation of species-specific kinome arrays as well as comprehensive deconvolution and analysis of kinome array data. Presented in this review are examples of the application of kinome analysis to highlight the utility of the technology to further our understanding of two key complex biological events of priority to the livestock industry: host immune responses to infectious diseases and animal stress responses. These advances and examples of application aim to provide both mechanisms and motivation for researchers, particularly livestock researchers, to incorporate kinome analysis into their research programs.

In Vitro Evaluation of the Effects of Commercial Prebiotic GOS and FOS Products on Human Colonic Caco-2 Cells

Prebiotic oligosaccharides are widely used as human and animal feed additives for their beneficial effects on the gut microbiota. However, there are limited data to assess the direct effect of such functional foods on the transcriptome of intestinal epithelial cells. The purpose of this study is to describe the differential transcriptomes and cellular pathways of colonic cells directly exposed to galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS). We have examined the differential gene expression of polarized Caco–2 cells treated with GOS or FOS products and their respective mock-treated cells using mRNA sequencing (RNA-seq). A total of 89 significant differentially expressed genes were identified between GOS and mock-treated groups. For FOS treatment, a reduced number of 12 significant genes were observed to be differentially expressed relative to the control group. KEGG and gene ontology functional analysis revealed that genes up-regulated in the presence of GOS were involved in digestion and absorption processes, fatty acids and steroids metabolism, potential antimicrobial proteins, energy-dependent and -independent transmembrane trafficking of solutes and amino acids. Using our data, we have established complementary non-prebiotic modes of action for these frequently used dietary fibers.

Beyond Heat Stress: Intestinal Integrity Disruption and Mechanism-Based Intervention Strategies

The current climate changes have increased the prevalence and intensity of heat stress (HS) conditions. One of the initial consequences of HS is the impairment of the intestinal epithelial barrier integrity due to hyperthermia and hypoxia following blood repartition, which often results in a leaky gut followed by penetration and transfer of luminal antigens, endotoxins, and pathogenic bacteria. Under extreme conditions, HS may culminate in the onset of “heat stroke”, a potential lethal condition if remaining untreated. HS-induced alterations of the gastrointestinal epithelium, which is associated with a leaky gut, are due to cellular oxidative stress, disruption of intestinal integrity, and increased production of pro-inflammatory cytokines. This review summarizes the possible resilience mechanisms based on in vitro and in vivo data and the potential interventions with a group of nutritional supplements, which may increase the resilience to HS-induced intestinal integrity disruption and maintain intestinal homeostasis.

Effects of inulin supplementation on intestinal barrier function and immunity in specific pathogen-free chickens with Salmonella infection

We investigated the effects of inulin on intestinal barrier function and mucosal immunity in Salmonella enterica serovar Enteritidis (SE)-infected specific pathogen-free (SPF) chickens. SPF chickens (n = 240, 1-d-old) were divided into 4 groups (6 replicates per group, 10 chickens per replicate): a control group (CON) fed a basal diet without inulin supplementation and 3 SE-infected groups fed a basal diet supplemented with inulin 0% (SE group), 0.5% (0.5% InSE group), and 1% (1% InSE group), respectively. At 28 d of age, the chickens in SE-infected groups were orally infected with SE and in CON group were administrated with phosphated-buffered saline (PBS). Intestinal morphology, mucosal immunity, and intestinal barrier function-related gene expression were analyzed at 1- and 3-d post-infection (dpi). SE challenge significantly increased the mucosal gene expression, such as interleukin-1β (IL-1β), lipopolysaccharide-induced tumor necrosis factor factor (LITAF), interferon-γ (IFN-γ), and interleukin-6 (IL-6), and increased serum IFN-γ, secretory IgA (sIgA), and IgG concentration, and significantly decreased the gene expression levels of mucin 2 (MUC2) and claudin-1 at 3 dpi compared with the CON group (P < 0.05). Inulin supplementation improved the expression levels of these immunity- and intestinal barrier function-related genes, increased villus height (VH), and decreased crypt depth (CD) in the duodenum, jejunum, and ileum at 1 and 3 dpi within the SE-challenged groups (P < 0.05). SE challenge significantly increased ileal Toll-like receptor 4 (TLR4) mRNA at 1 and 3 dpi, suppressor of cytokine signaling 3 (SOCS3) mRNA at 1 dpi, and phospho-signal transducer and activator of transcription 3 (p-STAT3) and Janus kinase1 (JAK1) protein expression at 3 dpi compared with the CON group (P < 0.05). Inulin supplementation suppressed p-STAT3 and JAK1 protein expression and promoted ileal TLR4 and SOCS3 mRNA expression at 3 dpi compared with SE group (P < 0.05). In conclusion, inulin alleviated SE-induced gut injury by decreasing the proinflammatory response and enhancing mucosal immunity in chickens.

The use of inulin and wheat bran only during the starter period or during the entire rearing life of broilers: effects on growth performance, small intestinal maturation, and cecal microbial colonization until slaughter age

Inulin and wheat bran were added to broiler diets during the starter period or during the entire rearing period to investigate whether the effects of using these ingredients remained until slaughter age. Diets containing no inulin and no wheat bran (CON), 2% inulin (IN), 10% wheat bran (WB), or 2% inulin + 10% wheat bran (IN+WB) were provided until day 11. Thereafter, each dietary treatment was further divided into a continued diet with supplementation or a control diet, resulting in 7 groups (CON, IN/IN, IN/CON, WB/WB, WB/CON, IN+WB/IN+WB, or IN+WB/CON). On day 40, 12 chickens per group were euthanized. The IN/IN group increased the cecal molar ratio of butyrate but had a lower relative abundance of Lactobacillus (P < 0.05). Additionally, the cecal molar ratio of propionate was higher in the IN/CON group compared to the IN/IN group (P = 0.034). The WB/CON group had the best results on BW and feed conversion ratio (FCR) (P < 0.05). Only the cecal molar ratio of iso-butyrate was higher in the WB/WB group (P = 0.013). Moreover, compared to the CON group, both WB/WB and WB/CON groups reduced the relative abundances of Bifidobacterium and Escherichia coli, and only the WB/WB group reduced the relative abundance of Enterobacteriaceae (P < 0.05). Both IN+WB/IN+WB and IN+WB/CON groups increased BW until day 21 and lowered the relative abundance of Bifidobacterium (P < 0.05). The IN+WB/IN+WB group increased the cecal molar ratio of butyrate but reduced the molar ratio of propionate with a higher relative abundance of Enterobacteriaceae (P < 0.05). In conclusion, the lack of positive effects induced by inulin might be explained by the dose being too high. The beneficial effects on BW, FCR, and microbiota induced by wheat bran during the starter period were lasting when supplementation was stopped, suggesting that wheat bran could be a favorable ingredient during the starter period.

Effect of a Synbiotic Mix on Intestinal Structural Changes, and Salmonella Typhimurium and Clostridium Perfringens Colonization in Broiler Chickens

Synbiotics can prevent gastrointestinal infections in broilers. This work studies the effect of a Synbiotic on broilers. One-day-old male broilers were divided into groups: Control; Synbiotic; Synbiotic + S. Typhimurium; Synbiotic + C. perfringens; Synbiotic + S. Typhimurium + C. perfringens; S. Typhimurium; C. perfringens; and S. Typhimurium + C. perfringens. Histopathological analysis revealed that the Synbiotic promoted longer villi, less deep crypts, and better villi-crypt ratio. Broilers treated with the Synbiotic, infected with pathogens or not, had healthier mucosa. In groups infected with pathogens, the frequency and intensity of histopathologic lesions were lessened often in groups treated with the Synbiotic. The Synbiotic group had higher lactic acid bacteria counts than the Control group on day 39, and the isolation frequency of S. Typhimurium was lower (p < 0.05) in the Synbiotic-treated groups. On day 18, mucosa, villi, villi-crypt ratio, crypt, and feed intake were influenced by Enterobacteriaceae. However, on day 39 (end of the trial), those parameters were influenced by lactic acid bacteria. The Synbiotic influenced morphological modifications in the duodenal mucosa, which in turn gave the broilers the ability to resist infections caused by S. Typhimurium and C. perfringens, by inhibiting their growth and decreasing the intensity and frequency of histopathological injuries.

Prebiotics: Mechanisms and Preventive Effects in Allergy

Allergic diseases now affect over 30% of individuals in many communities, particularly young children, underscoring the need for effective prevention strategies in early life. These allergic conditions have been linked to environmental and lifestyle changes driving the dysfunction of three interdependent biological systems: microbiota, epithelial barrier and immune system. While this is multifactorial, dietary changes are of particular interest in the altered establishment and maturation of the microbiome, including the associated profile of metabolites that modulate immune development and barrier function. Prebiotics are non-digestible food ingredients that beneficially influence the health of the host by 1) acting as a fermentable substrate for some specific commensal host bacteria leading to the release of short-chain fatty acids in the gut intestinal tract influencing many molecular and cellular processes; 2) acting directly on several compartments and specifically on different patterns of cells (epithelial and immune cells). Nutrients with prebiotic properties are therefore of central interest in allergy prevention for their potential to promote a more tolerogenic environment through these multiple pathways. Both observational studies and experimental models lend further credence to this hypothesis. In this review, we describe both the mechanisms and the therapeutic evidence from preclinical and clinical studies exploring the role of prebiotics in allergy prevention.

Human Milk Oligosaccharides Increase Mucin Expression in Experimental Necrotizing Enterocolitis

SCOPE

Necrotizing enterocolitis (NEC) is a leading cause of morbidity and death in preterm infants, occurring more often in formula-fed than breastfed infants. Studies in both rats and humans show that human milk oligosaccharides (HMOs) lower the incidence of NEC, but the mechanism underlying such protection is currently unclear.

METHODS AND RESULTS

By extracting HMOs from pooled human breastmilk, the impact of HMOs on the intestinal mucin levels in a murine model of NEC are investigated. To confirm the results, the findings are validated by exposing human intestinal epithelial cells and intestinal organoids to HMOs and evaluated for mucin expression. HMO-gavage to pups increases Muc2 levels and decreases intestinal permeability to macromolecular dextran. HMO-treated cells have increased Muc2 expression, decreased bacterial attachment and dextran permeability during challenge by enteric pathogens. To identify the mediators involved in HMO induction of mucins, it is demonstrated that HMOs directly induce the expression of chaperone proteins including protein disulfide isomerase (PDI). Suppression of PDI activity removes the protective effects of HMOs on barrier function in vitro as well as NEC protection in vivo.

CONCLUSIONS

Taken together, the results provide insights to the possible mechanisms by which HMOs protect the neonatal intestine through upregulation of mucins.

The effects of inulin on the mucosal morphology and immune status of specific pathogen-free chickens

This study investigated the effects of inulin on mucosal morphology and immune function of specific pathogen-free (SPF) chickens. A total of 200 one-day-old White Leghorns SPF chickens were divided into 5 groups of 4 replicates of 10 chickens each. All SPF chickens were fed a basal diet supplemented with 0, 0.25, 0.5, 1.0, or 2.0% inulin. The mucosal morphology and immune indexes were analyzed on days 7, 14, and 21, respectively. Our results showed that the concentrations of acetate and propionate in the cecum and serum had increased with dietary inulin supplementation on day 21 (P < 0.05). Butyrate could not be detected in the cecal digesta, but was increased in the serum of 1 and 2% groups, as compared with the control group (P < 0.05). The villi height was increased (P < 0.05) and the crypt depth was decreased (P < 0.05) in the duodenum and ileum of SPF chickens fed inulin, as compared with the control group. Also, inulin at a low concentration (0.25 or 0.5%) significantly decreased (P < 0.05) the gene expression of nuclear factor-κB (NF-κB), lipopolysaccharide-induced tumor necrosis factor (LITAF) at 7, 14, and 21 d, and of interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) at 7 and 14 d, and increased that of mucin 2 (MUC2) and claudin-1 in the ileum of SPF chickens at 7, 14, and 21 d. High inulin supplementation (2%) significantly increased the gene expression of NF-κB, LITAF, IL-6, iNOS, and Claudin-1 at 14 and 21 d compared to low inulin concentration (0.25 or 0.5%). The results indicated that the effects of inulin on mucosal immune function occurred in a dose-dependent manner. A low concentration (0.25 or 0.5%) of inulin may be beneficial in promoting intestinal immune function.

Ground flaxseed reverses protection of a reduced-fat diet against Citrobacter rodentium-induced colitis

Flaxseed is high in ω-3 polyunsaturated fatty acids, fiber, and lignans known to lower cholesterol levels. However, its use for prevention or treatment of inflammatory bowel diseases has yielded mixed results, perhaps related to dietary interactions. In this study, we evaluated the impact of ground flaxseed supplementation on the severity of Citrobacter rodentium-induced colitis in the setting of either a high-fat (HF, ~36%kcal) or reduced-fat (RF, ~12%kcal) diet. After weaning, C57BL/6 mice ( n = 8-15/treatment) were fed ground flaxseed (7 g/100 g diet) with either HF (HF Flx) or RF (RF Flx) diets for 4 wk before infection with C. rodentium or sham gavage. Weight changes, mucosal inflammation, pathogen burden, gut microbiota composition, tissue polyunsaturated fatty acids, and cecal short-chain fatty acids were compared over a 14-day infection period. The RF diet protected against C. rodentium-induced colitis, whereas the RF Flx diet increased pathogen burden, exacerbated gut inflammation, and promoted gut dysbiosis. When compared with the RF diet, both HF and HF Flx diets resulted in more severe pathology in response to C. rodentium infection. Our findings demonstrate that although an RF diet protected against C. rodentium-induced colitis and associated gut dysbiosis in mice, beneficial effects were diminished with ground flaxseed supplementation. NEW & NOTEWORTHY Our results demonstrate a strong protective effect of a reduced-fat diet against intestinal inflammation, dysbiosis, and pathogen burden during Citrobacter rodentium-induced colitis. However, ground flaxseed supplementation in the setting of a reduced-fat diet exacerbated colitis despite higher levels of intestinal n-3 polyunsaturated fatty acids and cecal short-chain fatty acids.

The effect of inulin and wheat bran on intestinal health and microbiota in the early life of broiler chickens

Inulin and wheat bran were added to the starter diets of broiler chickens to investigate the potential of these ingredients to improve the host's health and growth performance, as well as the underlying mechanisms of their effects. A total of 960 1-day-old chicks were assigned to 4 treatments: control (CON), 2% inulin (IN), 10% wheat bran (WB), and 10% wheat bran +2% inulin (WB+IN). On day 11, 6 chicks per treatment were euthanized. A general linear model procedure with Tukey's multiple range test was performed to compare a series of parameters between treatments. The WB-containing treatments improved BW on day 7, day 11, day 35, and BW gain until day 11 (P < 0.05), but only the WB+IN treatment showed a lower feed conversion ratio than the CON treatment (P = 0.011). Furthermore, the WB+IN treatment showed the highest villus height in the jejunum and ileum (P < 0.05), and the highest jejunal ratio villus height/crypt depth (P = 0.035). The concentration of acetate in the ceca was higher in the CON treatment compared to the IN treatment (P = 0.040). The IN treatment increased the concentration (P = 0.003) and ratio (P = 0.004) of iso-butyrate compared to the WB+IN and the CON treatments (P < 0.05). A clustering result exhibited similar intestinal microbiota profiles in the chicks receiving the IN and the WB+IN diets (P > 0.05), but these profiles were different from those found in chicks receiving the WB and the CON diets (P < 0.05). In conclusion, wheat bran and the combination of wheat bran and inulin ameliorated the growth performance and gut morphology of the starter chicks, which resulted in a higher BW until day 35. Inulin, on the other hand, had a greater ability to influence the microbiota profile. The beneficial results found in relation to BW and gut morphology during the starter period suggested a synergistic effect of inulin and wheat bran.

Rhamnogalacturonan, a chemically-defined polysaccharide, improves intestinal barrier function in DSS-induced colitis in mice and human Caco-2 cells

Natural polysaccharides have emerged as an important class of bioactive compounds due their beneficial biological effects. Here we investigated the protective and healing effects of rhamnogalacturonan (RGal) isolated from Acmella oleracea (L.) R.K. Jansen leaves in an experimental model of intestinal inflammation in mice and in heterogeneous human epithelial colorectal adenocarcinoma cells (Caco-2). The findings demonstrated that RGal treatment for 7 days reduced the severity of DSS-induced colitis by protecting mice from weight loss, macroscopic damage and reduction of colon length. When compared to the DSS group, RGal also protected the colon epithelium and promoted the maintenance of mucosal enterocytes and mucus secreting goblet cells, in addition to conserving collagen homeostasis and increasing cell proliferation. In an in vitro barrier function assay, RGal reduced the cellular permeability after exposure to IL-1β, while decreasing IL-8 secretion and claudin-1 expression and preserving the distribution of occludin. Furthermore, we also observed that RGal accelerated the wound healing in Caco-2 epithelial cell line. In conclusion, RGal ameliorates intestinal barrier function in vivo and in vitro and may represent an attractive and promising molecule for the therapeutic management of ulcerative colitis.

The epithelial barrier-protecting properties of a soy hydrolysate

Enhancing the epithelial barrier function could be a possible strategy to prevent food allergy or reduce its symptoms. Soy hydrolysates containing bioactive peptides could be instrumental in this. In this study, the protective effects of pretreatment with 6 soy hydrolysates on calcium ionophore A23187-induced TEER reduction were studied in T84 cells. The effects of the most potent soy hydrolysate on tight junction gene expression were studied. In order to identify the underlying pathways involved, the barrier disruptor specificity of the effect was studied by comparing the protective effects on TEER and Lucifer Yellow flux after the exposure to barrier disruptors that work via different intracellular pathways, i.e. the disruptors A23187, mellitin, and deoxynivalenol (DON). Preincubation with one of the six hydrolysates protected the epithelial cells from a decrease in TEER induced by A23187 (restored to 105% of the starting point, while A23187 alone decreased to 53% of the starting value) and mellitin (restored to 11% of the starting point, while mellitin alone decreased to 3.8% of the starting value). This soy hydrolysate was found to increase claudin-1 and decrease claudin-2 expression. The protective effect of the hydrolysate on TEER was specific for the barrier disruptors A23187 and mellitin, but was not observed for DON. This observation suggests that the soy hydrolysate may act via PKC isoforms, which are known to lead to changes in the expression of claudin-1 and 2. Our data suggest that specific soy hydrolysates may be designed to strengthen the epithelial barrier which might be instrumental in the management of the barrier function in individuals at risk of developing food allergy.

The effects of fermentation products of prebiotic fibres on gut barrier and immune functions in vitro

The beneficial effects of prebiotic fibres on human health have been related to their capacities to alter the gut microbiota and modify the growth of beneficial microorganisms. It is long appreciated that bacterial metabolites affect the host’s physiology. The inner lining of the intestinal tract is the first level of interaction between the host and bacteria and their metabolites. Therefore, we set out to test the effects of five common dietary fibres (oat β-glucan 28%; oat β-glucan 94%; dried chicory root containing inulin 75%; xylo-oligosaccharide; inulin 90%) and maltodextrin, after fermentation by human gut microbiota in vitro, on measures of gut barrier integrity using a Caco-2/HT29-MTX co-culture as well as mucus production and immune parameters using HT29-MTX and HT29 cell models, respectively. Our data show that all fibres, fermentation products increased the tightness of the gut barrier with oat β-glucan 28% having the largest effect. Fermentation supernatants were tested also in models of the compromised gut barrier (leaky gut). After the addition of ethanol as basolateral stressor, only fermentation supernatant of oat β-glucan 28%, oat β-glucan 94% and maltodextrin improved the gut barrier integrity, while oat β-glucan 28% and dried chicory root containing inulin 75% significantly improved the gut barrier integrity after addition of rhamnolipids as apical stressor. Using the Luminex Technology, we demonstrated an important role of oat β-glucan fermentation products in modulating cytokine and chemokine productions. Furthermore, treating the goblet cells with effluent from xylo-oligosaccharide fermentation significantly increased mucus production. In summary, our data emphasize the potential positive effects of fermentation supernatant of dietary fibres on gut-related physiological outcomes and show that prebiotic fibres may have promising potential to induce specific gut health benefits.

Metabolism of Caprine Milk Carbohydrates by Probiotic Bacteria and Caco-2:HT29⁻MTX Epithelial Co-Cultures and Their Impact on Intestinal Barrier Integrity

The development and maturation of the neonatal intestine is generally influenced by diet and commensal bacteria, the composition of which, in turn, can be influenced by the diet. Colonisation of the neonatal intestine by probiotic Lactobacillus strains can strengthen, preserve, and improve barrier integrity, and adherence of probiotics to the intestinal epithelium can be influenced by the available carbon sources. The goal of the present study was to examine the role of probiotic lactobacilli strains alone or together with a carbohydrate fraction (CF) from caprine milk on barrier integrity of a co-culture model of the small intestinal epithelium. Barrier integrity (as measured by trans epithelial electrical resistance (TEER)), was enhanced by three bacteria/CF combinations (Lactobacillus rhamnosus HN001, L. plantarum 299v, and L. casei Shirota) to a greater extent than CF or bacteria alone. Levels of occludin mRNA were increased for all treatments compared to untreated co-cultures, and L. plantarum 299v in combination with CF had increased mRNA levels of MUC4, MUC2 and MUC5AC mucins and MUC4 protein abundance. These results indicate that three out of the four probiotic bacteria tested, in combination with CF, were able to elicit a greater increase in barrier integrity of a co-culture model of the small intestinal epithelium compared to that for either component alone. This study provides additional insight into the individual or combined roles of microbe–diet interactions in the small intestine and their beneficial contribution to the intestinal barrier.

Lactobacillus acidophilus Attenuates Salmonella-Induced Stress of Epithelial Cells by Modulating Tight-Junction Genes and Cytokine Responses

Scope: Salmonellosis is a prevalent food-borne illness that causes diarrhea in over 130 million humans yearly and can lead to death. There is an urgent need to find alternatives to antibiotics as many salmonellae are now multidrug resistant. As such, specific beneficial bacteria and dietary fibers can be an alternative as they may prevent Salmonella Typhimurium (STM) infection and spreading by strengthening intestinal barrier function. Methods and Results: We tested whether immune active long-chain inulin-type fructans and/or L. acidophilus W37, L. brevis W63, and L. casei W56 can strengthen barrier integrity of intestinal Caco-2 cells in the presence and absence of a STM. Effects of the ingredients on intestinal barrier function were first evaluated by quantifying trans-epithelial electric resistance (TEER) and regulation of gene expression by microarray. Only L. acidophilus had effects on TEER and modulated a group of 26 genes related to tight-junctions. Inulin-type fructans, L. brevis W63 and L. casei W56 regulated other genes, unrelated to tight-junctions. L. acidophilus also had unique effects on a group of six genes regulating epithelial phenotype toward follicle-associated epithelium. L. acidophilus W37 was therefore selected for a challenge with STM and prevented STM-induced barrier disruption and decreased secretion of IL-8. Conclusion:L. acidophilus W37 increases TEER and can protect against STM induced disruption of gut epithelial cells integrity in vitro. Our results suggest that selection of specific bacterial strains for enforcing barrier function may be a promising strategy to reduce or prevent STM infections.

Epithelial Barrier Function in Gut-Bone Signaling

The intestinal epithelial barrier plays an essential role in maintaining host homeostasis. The barrier regulates nutrient absorption as well as prevents the invasion of pathogenic bacteria in the host. It is composed of epithelial cells, tight junctions, and a mucus layer. Several factors, such as cytokines, diet, and diseases, can affect this barrier. These factors have been shown to increase intestinal permeability, inflammation, and translocation of pathogenic bacteria. In addition, dysregulation of the epithelial barrier can result in inflammatory diseases such as inflammatory bowel disease. Our lab and others have also shown that barrier disruption can have systemic effects including bone loss. In this chapter, we will discuss the current literature to understand the link between intestinal barrier and bone. We will discuss how inflammation, aging, dysbiosis, and metabolic diseases can affect intestinal barrier-bone link. In addition, we will highlight the current suggested mechanism between intestinal barrier and bone.

Separation and Purification of Fructo-Oligosaccharide by High-Speed Counter-Current Chromatography Coupled with Precolumn Derivatization

High-speed counter-current chromatography (HSCCC) coupled with precolumn derivatization was developed for isolating and purifying fructo-oligosaccharides (FOSs). Firstly, the total FOSs were precolumn derivatized and then separated by high-speed counter-current chromatography (HSCCC) with two-phase solvent system petroleum ether–n-butanol–methanol–water (3:2:1:4, v/v). Secondly, the obtained compounds were deacetylated and the fructo-oligosaccharides (FOSs) with high purity were obtained. Their structures were identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). This research successfully established a novel strategy for separation and purification of FOS. There is no doubt that the application of the research will be beneficial for the quantitative and qualitative analysis of products containing FOSs.

Non-digestible oligosaccharides directly regulate host kinome to modulate host inflammatory responses without alterations in the gut microbiota

BACKGROUND

Prebiotics are non-digestible food ingredients that enhance the growth of certain microbes within the gut microbiota. Prebiotic consumption generates immune-modulatory effects that are traditionally thought to reflect microbial interactions within the gut. However, recent evidence suggests they may also impart direct microbe-independent effects on the host, though the mechanisms of which are currently unclear.

METHODS

Kinome arrays were used to profile the host intestinal signaling responses to prebiotic exposures in the absence of microbes. Identified pathways were functionally validated in Caco-2Bbe1 intestinal cell line and in vivo model of murine endotoxemia.

RESULTS

We found that prebiotics directly regulate host mucosal signaling to alter response to bacterial infection. Intestinal epithelial cells (IECs) exposed to prebiotics are hyporesponsive to pathogen-induced mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) activations, and have a kinome profile distinct from non-treated cells pertaining to multiple innate immune signaling pathways. Consistent with this finding, mice orally gavaged with prebiotics showed dampened inflammatory response to lipopolysaccharide (LPS) without alterations in the gut microbiota.

CONCLUSIONS

These findings provide molecular mechanisms of direct host-prebiotic interactions to support prebiotics as potent modulators of host inflammation.