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

Amoxicillin-induced bacterial gut dysbiosis: A critical influence on mice reproduction and their offspring development

The use of antibiotics such as amoxicillin can induce intestinal dysbiosis leading to rupture the essential microbiota role in regulating immune, metabolic, and reproductive functions. This study assessed the effects of amoxicillin-induced intestinal dysbiosis on the female mice reproductive function and its repercussions on their offspring. Female mice were treated with amoxicillin for 15 days (AMOX) showed an increase in Proteobacteria and a decrease in Firmicutes and Bacteroidetes in feces and estrous cycle changes, with a predominance of the metestrus and diestrus phases in the treated mice. During gestation the AMOX group presented reduced number of implantations and decreased embryonic viability, resulting in a higher rate of resorption. Differential gene expression of reproductive hormones in AMOX-treated female mice suggested that intestinal dysbiosis interferes with hormonal regulation during pregnancy. The survival, body development, and intestinal microbiota composition of offspring showed significantly altered patterns in the AMOX mice. These findings indicate that amoxicillin-induced intestinal dysbiosis affects not only the estrous cycle and reproductive hormones but also has lasting impacts on offspring development. The study highlights the need for caution in the use of antibiotics during pregnancy to avoid potential harm to maternal and offspring health.

Mediterranean diet adherence and incident acute pancreatitis: a prospective cohort study

Background

The relationship between Mediterranean diet (MedDiet) adherence and acute pancreatitis (AP) risk is largely unknown.

Objectives

To investigate the associations between MedDiet adherence and AP risk and joint associations of genetic risk and MedDiet adherence with AP risk.

Design

A prospective cohort study using data from UK Biobank, a large population-based prospective study that recruited over 500,000 participants aged 40-69 between 2006 and 2010 across the United Kingdom.

Methods

We included 103,449 participants free of AP with typical dietary intake from 24-h dietary recalls. MedDiet adherence was measured via the Mediterranean Diet Adherence Screener (MEDAS) continuous score. Genetic predisposition to AP was estimated by polygenic risk score (PRS). Incident AP cases were identified via electronic medical records. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated by Cox proportional hazards models. Mediation analyses were further applied to explore the mediating effects of the low-grade inflammation (INFLA) score and metabolic status.

Results

Over a mean follow-up period of 10.4 years, 371 AP cases were documented. Higher MedDiet adherence defined by MEDAS continuous score was inversely associated with lower AP risk (highest vs lowest tertiles: HR 0.60, 95% CI 0.46-0.79, p < 0.001), with the INFLA score and metabolic status mediating 10% and 7.1% of the association, respectively. Although no interaction was observed between PRS and MedDiet adherence, participants with combined low genetic risk and the highest MedDiet adherence had the lowest risk of AP (HR 0.54, 95% CI 0.36-0.80, p = 0.002).

Conclusion

The study suggests that higher adherence to the MedDiet is associated with a decreased risk of AP, which is partially mediated by inflammation and metabolic status, and may attenuate the deleterious impact of genetics on AP risk.

Bioactive arabinoxylan oligomers via colonic fermentation and enzymatic catalysis: Evidence of interaction with toll-like receptors from in vitro, in silico and functional analysis

Dietary fibers (DF) from plant-based foods promote health benefits through their physicochemical properties and fermentation by the gut microbiota, often studied in relation to changes in gut microbiota profile and production of gut microbiota-derived metabolites. Here, we characterized structural motifs (i.e., oligomers) produced during DF breakdown upon colonic fermentation and explored their interaction with toll-like receptors (TLRs) present on the surface of human intestinal and immune system cells. Wheat arabinoxylan (WAX) was subjected to in vitro colonic fermentation, with its structural motifs identified and tracked throughout the fermentation process. Using carbohydrate-active enzymes, six well-defined fractions of arabinoxylans and linear xylans identified during colonic fermentation were produced and tested for interaction with tool-like receptors (TLR)2 and TLR4 via reporter cell assay. The results showed structure-dependent effects, with TLR2 inhibition and TLR4 activation varying based on the degree of polymerization and branching. Molecular docking confirmed that minor structural changes in oligomers structure significantly influenced these interactions. The study supports the hypothesis that oligomers and polysaccharides affect cell receptors through complex, multi-receptor interactions, and highlights the potential for enzymatic tailoring of DF to create functional ingredients with targeted effects on human health.

Uncovering the therapeutic potential of anti-tuberculoid agent Isoniazid in a model of microbial-driven Crohn's disease

AIMS

TNFα has long stood as a hallmark feature of both inflammatory bowel disease and arthritis with its therapeutic potential demonstrated in neutralizing monoclonal antibody treatments such as Infliximab. Due to the high global burden of latent Mycobacterium tuberculosis (TB) infections, prior to receiving anti-TNF therapy, patients testing positive for latent TB are given prophylactic treatment with anti-tuberculoid medications including the first described TB-selective antibiotic, Isoniazid. While this is common clinical practice to prevent the emergence of TB, little is known about whether Isoniazid modifies intestinal inflammation alone. The aim of this study, therefore, was to determine whether Isoniazid presents a novel TB-independent therapeutic option for the treatment of Crohn's disease (CD)-like ileitis and uncover new mechanisms predisposing the host to intestinal inflammation.

METHODS

The transgenic TNFΔARE mouse model of Crohn's-like terminal ileitis was used. The impact of Isoniazid administration (10 mg/kg/day dose in drinking water) on disease development was monitored between 8 and 12 weeks of age using a variety of behavioral and serological assays. Behavioral and motor functions were assessed using the LABORAS automated monitoring system while systemic and local tissue inflammation were determined at experimental termination using multiplex cytokine analysis. Whole-mount tissue immunofluorescence and fluorescent in situ hybridization were used to qualify changes within the host as well as the microbial compartment of the ileum and associated mesentery. Proposed cellular mechanisms of altered cytokine decay were performed on isolated primary splenocytes in vitro using selective pharmacological agents.

RESULTS

Compared to age-matched wild-type littermates, TNFΔARE mice display prominent progressive sickness behaviors from 8 through 12 weeks of age indicated by reduced movement, climbing, and rearing. Prophylactic administration of Isoniazid (10 mg/kg/day) is effectively able to protect TNFΔARE mice from this loss of function during the same period. Analysis revealed that Isoniazid was able to significantly reduce both systemic and intestinal inflammation compared to untreated vehicle controls impacting the epithelial colonization of known pathobiont segmented filamentous bacteria (SFB). Reduction in terminal ileal inflammation was also associated to the diminished formation of precursor-tertiary lymphoid organs within the associated ileal mesentery which were found to be associated with endospores derived SFB itself. Finally, we reveal that due to their genetic manipulation, TNFΔARE mice display accelerated posttranscriptional decay of IL-22 mRNA resulting in diminished IL-22 protein production and associated downstream antimicrobial peptide production.

CONCLUSIONS

Isoniazid protects against the development of intestinal and systemic inflammation in the TNFΔARE model of terminal ileitis by limiting the expansion of mucosal SFB and progression of the associated microbial-driven inflammation. This work highlights a possible mycobacterial-independent function of Isoniazid in limiting CD pathophysiology through limiting the mucosal establishment of pathobionts such as SFB and the association of such microbe-derived endospores linked to the formation of ectopic tertiary lymphoid organs seen commonly in patients.

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.

Diverse domains of raspberry pectin: critical determinants for protecting against IBDs

Inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic conditions characterized by periods of intestinal inflammation and have become global diseases. Dietary pectins have shown protective effects on IBD models. However, the development of pectin-based diet intervention for IBD individuals requires knowledge of both the bioactive structural patterns and the mechanisms underlying diet-microbiota-host interactions. Here, dextran sulfate sodium (DSS) induced colitis mice were fed with different pectins with various domain compositions, including AG, P37, P55 and P85, in order to understand why different structural patterns function differently on colitis mouse models. The structural diversity of pectin manifests in the different percentages of the homogalacturonan (HG) backbone, Ara sidechains, and Gal sidechains. AG comprises only neutral sugar chains consisting of 14% Ara and 86% Gal, and P85 is a commercial HG pectin mainly composed of 85% HG. P37 and P55 were isolated from raspberry pulps with different domain ratios (P37 = 37% HG + 22% Ara + 32% Gal; P55 = 55% HG + 16% Ara + 18% Gal). Compared to the monotonous structure of AG and P85, the domain-diverse pectins P37 and P55 show superior protective effects against colitis through inhibiting the proliferation of the mucin-consuming bacteria and the pro-inflammatory microorganisms, potentiating the MUC2 expression and the mucus layer and regulating the gut-spleen axis. The HG structure promoted the proliferation of the mucin-degrading microbiota and potentiated mucus erosion. AG enhanced the mucus thickness but increased the growth of the pro-inflammatory microbiota. Our study revealed that the specific domain composition of pectic fibers was a key factor on which the diet-induced alterations in the gut microbiota and the intestinal barrier function highly depended.

The role of dietary fibre in intestinal heat shock protein regulation

The gastrointestinal tract serves as a pivotal physical barrier that prevents the translocation of exogenous substances from the intestinal lumen into the systemic circulation. Dysfunction of intestinal barrier function has been implicated in the pathogenesis of several diseases, such as metabolic disorders. Heat shock proteins (HSPs) play a critical role in maintaining the resilience and viability of epithelial cells when exposed to stressors. Evidence suggests that dietary fibre (DF), a known inducer of HSP production, may be a promising candidate for strengthening the intestinal barrier. Understanding the regulation of intestinal HSPs and the protective effect of DF is critical to defending against environmental threats and preserving human health. To date, six DFs—pectin, chicory, psyllium, guar gum, partially hydrolysed guar gum, and xylooligosaccharide—have been reported to have promotive effects on intestinal HSP induction. DF promotes intestinal HSP induction through gut microbiota-dependent and independent mechanisms. DF is fermented by gut microbiota to produce short-chain fatty acids, specifically butyrate and propionate, to promote HSP production. Meanwhile, DF also promotes intestinal HSP induction through direct interaction with intestinal epithelial cells, independent of gut microbiota activity, although the precise mechanism is still unclear. Regulation of intestinal HSP occurs by transcriptional modulation through activation of heat shock transcription factors, primarily heat shock factor 1, or at the post-transcriptional level by modulation of the translation process. This review highlights recent advances in understanding the role of DF in improving intestinal barrier function, with particular emphasis on the regulatory mechanisms of intestinal HSPs.

The impact of daily supplementation with rhamnogalacturonan-I on the gut microbiota in healthy adults: A randomized controlled trial

Pectin and its derivatives have been shown to modulate immune signaling as well as gut microbiota in preclinical studies, which may constitute the mechanisms by which supplementation of specific pectic polysaccharides confers protection against viral respiratory infections. In a double-blind, placebo-controlled rhinovirus (RV16) challenge study, healthy volunteers were randomized to consume placebo (0.0 g/day) (N = 46), low-dose (0.3 g/day) (N = 49) or high-dose (1.5 g/day) (N = 51) of carrot derived rhamnogalacturonan-I (cRG-I) for eight weeks and they were subsequently challenged with RV-16. Here, the effect of 8-week cRG-I supplementation on the gut microbiota was studied. While the overall gut microbiota composition in the population was generally unaltered by this very low dose of fibre, the relative abundance of Bifidobacterium spp. (mainly B. adolescentis and B. longum) was significantly increased by both doses of cRG-1. Moreover, daily supplementation of cRG-I led to a dose-dependent reduction in inter- and intra-individual microbiota heterogeneity, suggesting a stabilizing effect on the gut microbiota. The severity of respiratory symptoms did not directly correlate with the cRG-I-induced microbial changes, but several dominant groups of the Ruminococcaceae family and microbiota richness were positively associated with a reduced and hence desired post-infection response. Thus, the present results on the modulation of the gut microbiota composition support the previously demonstrated immunomodulatory and protective effect of cRG-I during a common cold infection.

Xylobiose treatment strengthens intestinal barrier function by regulating claudin 2 and heat shock protein 27 expression in human Caco-2 cells

BACKGROUND

Xylobiose, a non-digestible disaccharide, largely contributes to the beneficial physiological effects of xylooligosaccharides. However, there is insufficient evidence to assess the direct effect of xylobiose on intestinal barrier function. Here, we investigated the intestinal barrier function in human intestinal Caco-2 cells treated with xylobiose.

RESULTS

In total, 283 genes were upregulated and 256 genes were downregulated in xylobiose-treated Caco-2 cells relative to the controls. We focused on genes related to intestinal barrier function, such as tight junction (TJ) and heat shock protein (HSP). Xylobiose decreased the expression of the TJ gene Claudin 2 (CLDN2) and increased the expression of the cytoprotective HSP genes HSPB1 and HSPA1A, which encode HSP27 and HSP70, respectively. Immunoblot analysis confirmed that xylobiose suppressed CLDN2 expression and enhanced HSP27 and HSP70 expression. A quantitative reverse transcription-PCR and promoter assays indicated that xylobiose post-transcriptionally regulated CLDN2 and HSPB1 levels. Additionally, selective inhibition of phosphatidyl-3-inositol kinase (PI3K) inhibited xylobiose-mediated CLDN2 expression, whereas HSP27 expression induced by xylobiose was sensitive to the inhibition of PI3K, mitogen-activated protein kinase kinase and Src.

CONCLUSION

The results of the present study reveal that xylobiose suppresses CLDN2 and increases HSP27 expression in intestinal Caco-2 cells via post-transcriptional regulation, potentially strengthening intestinal barrier integrity; however, these effects seem to occur via different signaling pathways. Our findings may help to assess the physiological role of xylobiose. © 2023 Society of Chemical Industry.

Human intestinal organoids: Modeling gastrointestinal physiology and immunopathology - current applications and limitations

Human intestinal organoids are an ideal model system for studying gastrointestinal physiology and immunopathology. Altered physiology and mucosal immune response are hallmarks of numerous intestinal functional and inflammatory diseases, including inflammatory bowel disease (IBD), coeliac disease, irritable bowel syndrome (IBS), and obesity. These conditions impact the normal epithelial functions of the intestine, such as absorption, barrier function, secretion, and host-microbiome communication. They are accompanied by characteristic intestinal symptoms and have significant societal, economic, and healthcare burdens. To develop new treatment options, cutting-edge research is required to investigate their etiology and pathology. Human intestinal organoids derived from patient tissue recapitulate the key physiological and immunopathological aspects of these conditions, providing a promising platform for elucidating disease mechanisms. This review will summarize recent reports on patient-derived human small intestinal and colonic organoids and highlight how these models have been used to study intestinal epithelial functions in the context of inflammation, altered physiology, and immune response. Furthermore, it will elaborate on the various organoid systems in use and the techniques/assays currently available to study epithelial functions. Finally, it will conclude by discussing the limitations and future perspectives of organoid technology.

Rice-derived arabinoxylan fibers are particle size-dependent inducers of trained immunity in a human macrophage-intestinal epithelial cell co-culture model

Arabinoxylans have been identified for a wide range of purported health-promoting applications, primarily attributed to its immunomodulatory effects. Previously, we have reported the ability of arabinoxylans to induce non-specific memory in innate immune cells, commonly referred to as "trained innate immunity". In the present study, we investigated the effect of particle size on innate immune training and resilience in primary human macrophages as well as in a more physiologically relevant macrophage-intestinal epithelial cell co-culture model. We demonstrated that smaller (>45 & < 90 μm) compared to larger (>90 μm) particle size fractions of rice bran-derived arabinoxylan preparations have a higher enhancing effect on training and resilience in both models. Smaller particle size fractions elevated TNF-α production in primary macrophages and enhanced Dectin-1 receptor activation in reporter cell lines compared to larger particles. Responses were arabinoxylan source specific as only the rice-derived arabinoxylans showed these immune-supportive effects. This particle size-dependent induction of trained immunity was confirmed in the established co-culture model. These findings demonstrate the influence of particle size on the immunomodulatory potential of arabinoxylans, provide further insight into the structure-activity relationship, and offer new opportunities to optimize the immune-enhancing effects of these dietary fibers.

In-depth insight into correlations between gut microbiota and dietary fiber elucidates a dietary causal relationship with host health

Dietary fiber exerts a wide range of biological benefits on host health, which not only provides a powerful source of nutrition for gut microbiota but also supplies key microbial metabolites that directly affect host health. This review mainly focuses on the decomposition and metabolism of dietary fiber and the essential genera Bacteroides and Bifidobacterium in dietary fiber fermentation. Dietary fiber plays an essential role in host health by impacting outcomes related to obesity, enteritis, immune health, cancer and neurodegenerative diseases. Additionally, the gut microbiota-independent pathway of dietary fiber affecting host health is also discussed. Personalized dietary fiber intake combined with microbiome, genetics, epigenetics, lifestyle and other factors has been highlighted for development in the future. A higher level of evidence is needed to demonstrate which microbial phenotype benefits from which kind of dietary fiber. In-depth insights into the correlation between gut microbiota and dietary fiber provide strong theoretical support for the precise application of dietary fiber, which elucidates a dietary causal relationship with host health.

Higher dietary fibre intake is associated with lower risk of inflammatory bowel disease: prospective cohort study

BACKGROUND

Limited prospective studies that have examined the association of dietary fibre with IBD have provided inconsistent evidence.

AIM

To examine any associations between dietary fibre intake and subsequent incidence of IBD, Crohn's disease (CD) and ulcerative colitis (UC) METHODS: We conducted a prospective cohort study of 470,669 participants from the UK Biobank and estimated dietary fibre intake from a valid food frequency questionnaire at baseline. Incident IBD was ascertained from primary care data and inpatient data. Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between dietary fibre intake and the risk of IBD, CD and UC.

RESULTS

During an average follow-up of 12.1 years, we ascertained 1473 incident IBD cases, including 543 cases of CD and 939 cases of UC. Comparing the lowest quintiles, an inverse association was observed between dietary fibre intake and risk of IBD (HR 0.74, 95% CI 0.58-0.93, p = 0.011) and CD (HR 0.48, 95% CI 0.32-0.72, p < 0.001), but not UC (HR 0.92, 95% CI 0.69-1.24, p = 0.595). For specified sources, dietary fibre intake from fruit and bread decreased the risk of CD, while dietary fibre intake from cereal decreased the risk of UC.

CONCLUSIONS

Higher consumption of dietary fibre was associated with a lower risk of IBD and CD, but not UC. Our findings support current recommendations to increase the intake of dietary fibre.

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.