Early effects of gliadin on enterocyte intracellular signalling involved in intestinal barrier function

Exploring the role of gut microbiome in autoimmune diseases: A comprehensive review

As the industrialized society advances, there has been a gradual increase in the prevalence of autoimmune disorders. A probe into the fundamental causes has disclosed several factors in modern society that have an influence on the gut microbiome. These dramatic shifts in the gut microbiome are likely to be one of the reasons for the disarray in the immune system, and the relationship between the immune system and the gut microbiome emerging as a perennial hot topic of research. This review enumerates the findings from sequencing studies of gut microbiota on seven autoimmune diseases (ADs): Rheumatoid Arthritis (RA), Systemic Lupus Erythematosus (SLE), Ankylosing Spondylitis (AS), Systemic Sclerosis (SSc), Sjögren's Syndrome (SjS), Juvenile Idiopathic Arthritis (JIA), and Behçet's Disease (BD). It aims to identify commonalities in changes in the gut microbiome within the autoimmune disease cohort and characteristics specific to each disease. The dysregulation of the gut microbiome involves a disruption of the internal balance and the balance between the external environment and the host. This dysregulation impacts the host's immune system, potentially playing a role in the development of ADs. Damage to the gut epithelial barrier allows potential pathogens to translocate to the mucosal layer, contacting epithelial cells, disrupting tight junctions, and being recognized by antigen-presenting cells, which triggers an immune response. Primed T-cells assist B-cells in producing antibodies against pathogens; if antigen mimicry occurs, an immune response is generated in extraintestinal organs during immune cell circulation, clinically manifesting as ADs. However, current research is limited; advancements in sequencing technology, large-scale cohort studies, and fecal microbiota transplantation (FMT) research are expected to propel this field to new peaks.

Fecal calprotectin levels in patients with non-celiac wheat sensitivity: a proof of concept

Some data suggest the existence of intestinal inflammation in patients with non-celiac wheat sensitivity (NCWS). We aimed to verify whether fecal calprotectin (FCP), a marker of intestinal inflammation, could be used to confirm this inflammatory status and to test its diagnostic performance in differentiating NCWS from irritable bowel syndrome/functional dyspepsia (IBS/FD). We conducted a multicenter study, comparing NCWS patients, diagnosed by a double-blind placebo-controlled wheat challenge, with IBS/FD subjects. In the retrospective phase, FCP values were analyzed to define the prevalence of its positivity and its role as a NCWS diagnostic biomarker. In the prospective phase we tested the effects of a strict 6-month wheat-free diet (WFD) on FCP values. 31.3% (n = 63/201) of NCWS patients had above normal FCP values (NCWS FCP +), whereas all IBS/FD patients proved negative (P = 0.0001). FCP using a cut-off value > 41 µg/g showed a 58.6% sensitivity and a 98.0% specificity (AUC 0.755, 95% C.I. 0.702-0.837) in distinguishing NCWS from IBS/FD patients. Of the 63 NCWS FCP+, 65.1% had negative FCP values after ≥ 6 months of WFD, with a significant reduction in FCP values (P < 0.0001). All NCWS FCP- subjects still preserved negative FCP values after ≥ 6 months of WFD. Our study showed that FCP can be a useful but supplementary diagnostic marker for differentiating between NCWS and IBS/FD. Strict WFD adherence reduced FCP values, normalizing them in 65.1% of NCWS FCP + subjects. These data suggest the existence of two NCWS subgroups: NCWS FCP + characterized by a probable predominantly inflammatory/immunologic pattern and NCWS FCP- featuring non-immuno-mediated etiopathogenetic mechanisms. (Registration number NCT01762579).

Re-evaluation of dietary interventions in rheumatoid arthritis: can we improve patient conversations around food choices?

Rheumatoid arthritis (RA) is one of over 100 different types of autoimmune conditions. In RA, the cells of the immune system attack the tissue lining the joints, triggering inflammation. A large body of research suggests that the underlying trigger(s) of RA are unique to an individual. For example, increased risk of RA can be driven by smoking tobacco in one individual and mercury exposure in another. Due to the development of next-generation sequencing technology, the critical role of the microbiota in shaping RA risk has been elucidated. Therefore, it is surprising that diet, arguably the most important lever in shaping the gut microbiota, is ineffective in the treatment of RA, even in a sub-set of patients. To attempt to rationalise this apparent paradox, we conducted an umbrella review to address the question as to whether diet can affect outcomes in RA.

Association of celiac disease with eosinophilic esophagitis: Nationwide register-based cohort study with sibling analyses

Background

Celiac disease (CeD) is associated with several immune-mediated disorders, but it is unclear whether it is associated with eosinophilic esophagitis (EoE).

Objective

We sought to examine the risk of EoE in patients with biopsy-verified CeD compared with matched controls and siblings.

Methods

Using nationwide population-based histopathology data, we identified 27,338 patients with CeD diagnosed in the period 2002 to 2017 in Sweden. Patients with CeD were age- and sex-matched with up to 5 reference individuals (n = 134,987) from the general population. Cox Regression was used to estimate hazard ratios (HRs) for developing biopsy-verified EoE. In a secondary analysis, we used unaffected siblings of patients with CeD as comparators to adjust for intrafamilial confounding.

Results

The median age at CeD diagnosis was 27 years, and 63.3% were female patients. During a median follow-up of 8.1 years, 17 patients with CeD and 13 matched reference individuals were diagnosed with EoE. This corresponded to incidence rates of 0.08 versus 0.01 per 1000 person-years, respectively, and an adjusted HR for EoE of 6.65 (95% CI, 3.26-13.81). Compared with their siblings without CeD, patients with CeD were however at a no increased risk of EoE (HR, 1.39; 95% CI, 0.55-3.51).

Conclusions

In this study, individuals with CeD were at a 6.6-fold increased risk of later EoE compared with the general population. This association might be explained by an altered health-seeking behavior or through shared genetic or early environmental factors because the excess risk disappeared in sibling analyses.

Zonulin as Gatekeeper in Gut-Brain Axis: Dysregulation in Glioblastoma

Novel biomarkers and therapeutic strategies for glioblastoma, the most common malignant brain tumor with an extremely unfavorable prognosis, are urgently needed. Recent studies revealed a significant upregulation of the protein zonulin in glioblastoma, which correlates with patient survival. Originally identified as pre-haptoglobin-2, zonulin modulates both the intestinal barrier and the blood-brain barrier by disassembling tight junctions. An association of zonulin with various neuroinflammatory diseases has been observed. It can be suggested that zonulin links a putative impairment of the gut-brain barrier with glioblastoma carcinogenesis, leading to an interaction of the gut microbiome, the immune system, and glioblastoma. We therefore propose three interconnected hypotheses: (I) elevated levels of zonulin in glioblastoma contribute to its aggressiveness; (II) upregulated (serum-) zonulin increases the permeability of the microbiota-gut-brain barrier; and (III) this creates a carcinogenic and immunosuppressive microenvironment preventing the host from an effective antitumor response. The role of zonulin in glioblastoma highlights a promising field of research that could yield diagnostic and therapeutic options for glioblastoma patients and other diseases with a disturbed microbiota-gut-brain barrier.

Microscopic Colitis and Celiac Disease: Sharing More than a Diagnostic Overlap

Microscopic colitis (MC) is an emergent group of chronic inflammatory diseases of the colon, and celiac disease (CD) is a chronic gluten-induced immune-mediated enteropathy affecting the small bowel. We performed a narrative review to provide an overview regarding the relationship between both disorders, analyzing the most recent studies published at the epidemiological, clinical and pathophysiological levels. In fact, MC and CD are concomitantly prevalent in approximately 6% of the cases, mainly in the subset of refractory patients. Thus, physicians should screen refractory patients with CD against MC and vice versa. Both disorders share more than a simple epidemiological association, being multifactorial diseases involving innate and adaptive immune responses to known or unknown luminal factors based on a rather common genetic ground. Moreover, autoimmunity is a shared characteristic between the patients with MC and those with CD, with autoimmunity in the latter being quite well-established. Furthermore, CD and MC share some common clinical symptoms and risk factors and overlap with other gastrointestinal diseases, but some differences exist between both disorders. More studies are therefore needed to better understand the complex mechanisms involving the common pathogenetic ground contributing to the CD and MC epidemiological association.

Non-Host Factors Influencing Onset and Severity of Celiac Disease

Celiac disease (CeD) is a chronic autoimmune condition driven by gluten ingestion in genetically predisposed individuals, resulting in inflammatory lesions in the proximal small intestine. Although the presence of specific HLA-linked haplotypes and gluten consumption are necessary for disease development, they alone do not account for the variable onset of CeD in susceptible individuals. This review explores the multifaceted role of non-host factors in CeD development, including dietary and microbial influences. We discuss clinical associations and observations highlighting the impact of these factors on disease onset and severity. Furthermore, we discuss studies in CeD-relevant animal models that offer mechanistic insights into how diet, the microbiome, and enteric infections modulate CeD pathogenesis. Finally, we address the clinical implications and therapeutic potential of understanding these cofactors offering a promising avenue for preventive and therapeutic interventions in CeD management.

Celiac disease and depressive disorders as nutritional implications related to common factors - A comprehensive review

Celiac disease (CD) is an immune-mediated disease affecting the small intestine. The only treatment strategy for CD is the gluten-free diet (GFD). One of the more common mental disorders in CD patients is major depressive disorder (MDD). The influence of GFD on the occurrence of MDD symptoms in patients with CD will be evaluated. This diet often reduces nutritional deficiencies in these patients and also helps to reduce depressive symptoms. Both disease entities are often dominated by the same deficiencies of nutrients such as iron, zinc, selenium, iodine, or B and D vitamins. Deficiencies of particular components in CD can favor MDD and vice versa. Gluten can adversely affect the mental state of patients without CD. Also, intestinal microbiota may play an important role in the described process. This work aims to comprehensively assess the common factors involved in the pathomechanisms of MDD and CD, with particular emphasis on nutrient imbalances. Given the complexity of both disease entities, and the many common links, more research related to improving mental health in these patients and the implementation of a GFD would need to be conducted, but it appears to be a viable pathway to improving the quality of life and health of people struggling with CD and MDD. Therefore, probiotics, micronutrients, macronutrients, and vitamin supplements are recommended to reduce the risk of MDD, given that they may alleviate the symptoms of both these disease entities. In turn, in patients with MDD, it is worth considering testing for CD.

Microbial interventions in yak colibacillosis: Lactobacillus-mediated regulation of intestinal barrier

Introduction

The etiology of Escherichia coli in yaks, along with its drug resistance, results in economic losses within the yak breeding industry. The utilization of lactic acid bacteria treatment has emerged as a viable alternative to antibiotics in managing colibacillosis.

Methods

To elucidate the therapeutic mechanisms of Lactobacillus against Escherichia coli-induced intestinal barrier damage in yaks, we employed yak epithelial cells as the experimental model and established a monolayer epithelial barrier using Transwell. The study encompassed four groups: a control group, a model group (exposed to E. coli O78), a low-dose Lactobacillus group (E. coli O78 + 1 × 105CFU LAB), and a high-dose Lactobacillus group (E. coli O78 + 1 × 107CFU LAB). Various techniques, including transmembrane resistance measurement, CFU counting, RT-qPCR, and Western Blot, were employed to assess indicators related to cell barrier permeability and tight junction integrity.

Results

In the Model group, Escherichia coli O78 significantly compromised the permeability and tight junction integrity of the yak epithelial barrier. It resulted in decreased transmembrane resistance, elevated FD4 flux, and bacterial translocation. Furthermore, it downregulated the mRNA and protein expression of MUC2, Occludin, and ZO-1, while upregulating the mRNA expression and protein expression of FABP2 and Zonulin, thereby impairing intestinal barrier function. Contrastingly, Lactobacillus exhibited a remarkable protective effect. It substantially increased transmembrane resistance, mitigated FD4 flux, and reduced bacterial translocation. Moreover, it significantly upregulated the mRNA and protein expression of MUC2, Occludin, and ZO-1, while downregulating the mRNA and protein expression of FABP2 and Zonulin. Notably, high-dose LAB demonstrated superior regulatory effects compared to the low-dose LAB group.

Discussion

In conclusion, our findings suggest that Lactobacillus holds promise in treating yak colibacillosis by enhancing mucin and tight junction protein expression. Furthermore, we propose that Lactobacillus achieves these effects through the regulation of Zonulin.

Gluten and Wheat in Women's Health: Beyond the Gut

Since the rise of awareness of gluten/wheat-related disorders in the academic and clinical field in the last few decades, misinformation regarding the gluten-free diet (GFD) and its impact on health has been spreading among the general population. Despite the established link between gluten and celiac disease (CD), where a GFD is mandatory to reach clinical and histological remission, things are more complicated when it comes to non-celiac gluten/wheat sensitivity (NCGWS) and other autoimmune/dysimmune disorders. In the last conditions, a beneficial effect of gluten withdrawal has not been properly assessed, but still is often suggested without strong supporting evidence. In this context, women have always been exposed, more than men, to higher social pressure related to nutritional behaviors and greater engagement in controlling body weight. With this narrative review, we aim to summarize current evidence on the adherence to a GFD, with particular attention to the impact on women's health.

Zonulin as a Biomarker for the Development of Celiac Disease

OBJECTIVES

Increased intestinal permeability seems to be a key factor in the pathogenesis of autoimmune diseases, including celiac disease (CeD). However, it is unknown whether increased permeability precedes CeD onset. This study's objective was to determine whether intestinal permeability is altered before celiac disease autoimmunity (CDA) in at-risk children. We also examined whether environmental factors impacted zonulin, a widely used marker of gut permeability.

METHODS

We evaluated 102 children in the CDGEMM study from 2014-2022. We included 51 CDA cases and matched controls, who were enrolled for 12 months or more and consumed gluten. We measured serum zonulin from age 12 months to time of CDA onset, and the corresponding time point in controls, and examined clinical factors of interest. We ran a mixed-effects longitudinal model with dependent variable zonulin.

RESULTS

Children who developed CDA had a significant increase in zonulin in the 18.3 months (range 6-78) preceding CDA compared to those without CDA (slope differential = β = 0.1277, 95% CI: 0.001, 0.255). Among metadata considered, zonulin trajectory was only influenced by increasing number of antibiotic courses, which increased the slope of trajectory of zonulin over time in CDA subjects (P = .04).

CONCLUSIONS

Zonulin levels significantly rise in the months that precede CDA diagnosis. Exposure to a greater number of antibiotic courses was associated with an increase in zonulin levels in CDA subjects. This suggests zonulin may be used as a biomarker for preclinical CeD screening in at-risk children, and multiple antibiotic courses may increase their risk of CDA by increasing zonulin levels.

Intestinal proteases

PURPOSE OF REVIEW

Proteases constitute a group of enzymes that hydrolyze peptide bonds. Intestinal proteases are an integral part of gut homeostasis and digestion. This review discusses the broader classification of proteases, regulation of proteolytic activity (PA) in the intestinal tract, and how dysregulation of intestinal proteases contributes to the pathophysiology of conditions such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and celiac disease. We also discuss recent advancements in therapeutic modulation that directly or indirectly target intestinal proteases and can be utilized to treat these illnesses.

RECENT FINDINGS

Host and microbiota derived proteases have been associated with symptoms in subsets of patients with IBS, IBD and celiac disease. Elevated PA mediates barrier dysfunction, visceral hypersensitivity as well as immune activation and inflammation. Recent mechanistic studies have revealed the nature of disease-associated proteases and mechanisms regulating their activity, particularly those driven by the microbiota. Advancements in activity-based probes have allowed novel ways of in vivo imaging of PA. Newer strategies targeting proteases include monoclonal antibodies, engineered microbiota as well as specific protease inhibitors.

SUMMARY

Significant progresses made in the detection as well as regulation of PA is likely to provide therapeutic advancements for gastrointestinal diseases.

Effect of altered human exposome on the skin and mucosal epithelial barrier integrity

Pollution in the world and exposure of humans and nature to toxic substances is continuously worsening at a rapid pace. In the last 60 years, human and domestic animal health has been challenged by continuous exposure to toxic substances and pollutants because of uncontrolled growth, modernization, and industrialization. More than 350,000 new chemicals have been introduced to our lives, mostly without any reasonable control of their health effects and toxicity. A plethora of studies show exposure to these harmful substances during this period with their implications on the skin and mucosal epithelial barrier and increasing prevalence of allergic and autoimmune diseases in the context of the "epithelial barrier hypothesis". Exposure to these substances causes an epithelial injury with peri-epithelial inflammation, microbial dysbiosis and bacterial translocation to sub-epithelial areas, and immune response to dysbiotic bacteria. Here, we provide scientific evidence on the altered human exposome and its impact on epithelial barriers.

Effectiveness of Anthocyanin-Rich Sour Cherry Extract on Gliadin-Induced Caco-2 Barrier Damage

Several types of gluten-related disorders are known, in which the common starting point is gluten-induced zonulin release. Zonulin results in varying degrees of increased permeability in certain gluten-related disorders but is largely responsible for the development of further pathogenic processes and symptoms. Therefore, it is important to know the barrier-modulating role of individual nutritional components and to what extent the antioxidant substance supports the protection of gliadin-induced membrane damage with its radical scavenging capacity. We investigated the pH dependence of the gliadin-anthocyanin interaction using UV photometry, during which a concentration-dependent interaction was observed at pH 6.8. The barrier modulatory effect of the anthocyanin-rich sour cherry extract (AC) was analyzed on Caco-2 cell culture with pepsin-trypsin-resistant gliadin (PT-gliadin) exposure by TEER measurement, zonula occludens-1 (ZO-1), and Occludin immunohistochemistry. In addition to the TEER-reducing and TJ-rearranging effects of PT-gliadin, NF-κB activation, an increase in cytokine (TNF-α, IFN-γ, and IL-8) release, and mitochondrial ROS levels were observed. We confirmed the anti-inflammatory, stabilizing, and restoring roles of AC extract during gliadin treatment on the Caco-2 monolayer. The extract was able to significantly reduce cytokine and ROS levels despite the known interaction of the main components of the extract with PT-gliadin.

A spotlight on intestinal permeability and inflammatory bowel diseases

INTRODUCTION

The intestinal barrier is a multi-faced structure lining the surface of the intestinal mucosa of the GI tract. To exert its main functions as a physical and immunological defense barrier, several components of the intestinal barrier act in a concerted and cooperative manner.

AREAS COVERED

Herein, we first introduce to the basic organization of the intestinal barrier and then summarize different methods to assess barrier function in and ex vivo. Finally, we provide an in-depth overview of the relevance of intestinal barrier dysfunction in inflammatory bowel diseases.

EXPERT OPINION

In parallel to a more fundamental understanding of the intestinal barrier as a key component for intestinal integrity is the notion that intestinal barrier defects are associated with a variety of diseases such as inflammatory bowel diseases. Recent research has fueled and perpetuated the concept that barrier defects are critical components of disease development, disease behavior, and potentially also an area of therapeutic intervention in IBD patients. Although being far away from standard, new technologies can be used to easily assess barrier healing in IBD and to derive clinical consequences from these findings such as more accurate forecasting of future disease behavior or the identification of novel therapeutic targets.

Zonulin as a Potential Therapeutic Target in Microbiota-Gut-Brain Axis Disorders: Encouraging Results and Emerging Questions

The relationship between dysbiosis and central nervous diseases has been proved in the last 10 years. Microbial alterations cause increased intestinal permeability, and the penetration of bacterial fragment and toxins induces local and systemic inflammatory processes, affecting distant organs, including the brain. Therefore, the integrity of the intestinal epithelial barrier plays a central role in the microbiota-gut-brain axis. In this review, we discuss recent findings on zonulin, an important tight junction regulator of intestinal epithelial cells, which is assumed to play a key role in maintaining of the blood-brain barrier function. In addition to focusing on the effect of microbiome on intestinal zonulin release, we also summarize potential pharmaceutical approaches to modulate zonulin-associated pathways with larazotide acetate and other zonulin receptor agonists or antagonists. The present review also addresses the emerging issues, including the use of misleading nomenclature or the unsolved questions about the exact protein sequence of zonulin.

IDP Force Fields Applied to Model PPII-Rich 33-mer Gliadin Peptides

The 33-mer gliadin peptide and its deamidated metabolite, 33-mer DGP, are the immunodominant peptides responsible for the adaptive immune response in celiac disease (CD). CD is a complex autoimmune chronic disorder triggered by gluten ingestion that affects the small intestine and affects ∼1% of the global population. The 33-mers are polyproline II-rich (PPII) and intrinsically disordered peptides (IDPs), whose structures remain elusive. We sampled the conformational ensembles of both 33-mer peptides via molecular dynamics simulations employing two force fields (FFs) (Amber ff03ws and Amber ff99SB-disp) specifically validated for other IDPs. Our results show that both FFs allow the extensive exploration of the conformational landscape, which was not possible with the standard FF GROMOS53A6 reported before. Clustering analysis of the trajectories showed that the five largest clusters (78-88% of the total structures) present elongated, semielongated, and curved conformations in both FFs. Large average radius of gyration and solvent-exposed surfaces characterized these structures. While the structures sampled are similar, the Amber ff99SB-disp trajectories explored folded conformations with a higher probability. In addition, PPII secondary structure was preserved throughout the trajectories (58-73%) together with a non-negligible content of β structures (11-23%), in agreement with previous experimental results. This work represents the initial step in studying further the interaction of these peptides with other biologically relevant molecules, which could lead to finally disclose the molecular events that lead to CD.

Protective effects of Acetobacter ghanensis against gliadin toxicity in intestinal epithelial cells with immunoregulatory and gluten-digestive properties

PURPOSE

The aim of this study was to establish whether Acetobacter ghanensis, the probiotic characteristics of which were evaluated previously, attenuates gliadin-induced toxicity in intestinal epithelial cells with gluten-digestive and immunoregulatory properties.

METHODS

A co-culture model of human intestinal epithelial cell (Caco-2) monolayers on top of peripheral blood mononuclear cells (PBMCs) obtained from patients with celiac disease (CD) was established. The gluten-digestive properties of A. ghanensis were determined by checking bacterial growth in a medium containing gluten as the main nitrogen source. The mRNA levels of genes encoding TJ-associated proteins were measured by quantitative real-time PCR (qRT-PCR). The concentrations of IL-6 and TNFα were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found that PT-gliadin disrupted intestinal barrier integrity by modulating the expression of TJ-associated genes encoding zonulin (increased by ~ 60%), zonula occludens-1 (ZO-1) (decreased by ~ 22%), and occludin (decreased by ~ 28%) in Caco-2 cells. Furthermore, PT-gliadin treatment in Caco-2 cells was associated with increased concentrations of IL-6 (~ 1.6-fold) and TNFα (~ twofold) from PBMCs. These modulatory effects of PT-gliadin, however, were suppressed when Caco-2 cells were subjected to A. ghanensis in the presence of PT-gliadin. As a factor underlying these protective effects, we showed that A. ghanensis could digest gluten peptides.

CONCLUSIONS

To our knowledge, the current study is the first to demonstrate that A. ghanensis improves intestinal barrier functions by attenuating the modulatory effects of PT-gliadin with immunoregulatory and gluten-digestive properties.

Restorative effects of Acetobacter ghanensis on the pathogenicity of gliadin-induced modulation of tight junction-associated gene expression in intestinal epithelial cells

Background/Aim: At present, a gluten-free diet is the only efficient way to treat celiac disease (CD). The development of novel approaches to lessen or counteract the pathogenic effects of gluten remains crucial for the treatment of CD. The aim in this investigation was to examine the restorative effects of Acetobacter ghanensis as a novel probiotic against gliadin-induced modulation in the barrier integrity of an intestinal epithelial cell (IEC) model (Caco-2). Methods: Fully differentiated Caco-2 cell monolayers were subjected to enzymatically digested gliadin with a pepsin and trypsin (PT) in the presence or absence of A. ghanensis for 90 min. The relative amounts of zonulin, zonula occludens-1 (ZO-1), claudin-1, and occludin mRNA expression were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Transepithelial electrical resistance (TEER) was evaluated to monitor the barrier integrity of cell monolayers. Statistical analyses were carried out using one- or two-way ANOVA followed by Tukey’s post-hoc analysis for multiple pairwise comparisons. Results: A significant upregulation (4.7-fold) of zonulin was noted in the PT-gliadin treated Caco-2 cells in comparison with the untreated controls (P<0.001). Conversely, gliadin-induced zonulin expression was markedly downregulated in the Caco-2 cells following exposure to A. ghanensis in the presence of PT-gliadin (P<0.001). Furthermore, prominent decreases in the mRNA expression levels of ZO-1 (45%) and occludin (40%) were seen in the PT-gliadin exposed Caco-2 cells compared to the untreated control cells (P<0.001). PT-gliadin in the Caco-2 cells did not significantly alter the mRNA levels of claudin-1 (P=0.172). Similarly to zonulin expression, the decreasing effect of PT-gliadin on ZO-1 was completely attenuated in the PT-gliadin-administrated Caco-2 cells following exposure to A. ghanensis (P<0.001). Conclusion: A. ghanensis restored the pathogenicity of PT-gliadin on intestinal barrier integrity.

Predictive and Prognostic Value of Plasma Zonulin for Gestational Diabetes Mellitus in Women at 24-28 Weeks of Gestation

OBJECTIVE

We aimed to examine the predictive and prognostic value of plasma zonulin for gestational diabetes mellitus (GDM) in women at 24-28 weeks of gestation.

METHODS

This retrospective study was carried out with pregnant women with GDM (n=98) and normal glucose tolerance (control group) (n=132). GDM was diagnosed according to American Diabetes Association (ADA) criteria with a one-step 75-g OGTT at 24-28 gestational weeks. Their serum zonulin levels measured during one-step 75-g OGTT and perinatal outcomes were compared, and the cut-off value of plasma zonulin for the prediction of GDM was calculated with receiver operating characteristic curve analysis.

RESULTS

Plasma zonulin level was significantly higher in women with GDM compared to controls (28.8±24.9 and 7.3±11.3 ng/mL, respectively). According to logistic regression analysis, plasma zonulin levels and GDM were statistically significant. The plasma zonulin cut-off value was>45.2 ng/mL. The rate of cesarean section, the rate of meconium in the amniotic fluid, and the need for admission to the neonatal intensive care unit significantly differed between women with GDM and controls.

CONCLUSION

In pregnant women with GDM, plasma zonulin increases, and with the cut-off level of>45.2 ng/mL, it can predict GDM with values of sensitivity and specificity levels significantly higher in pregnant women with GDM, suggesting that it can be used as a tool for its screening and early diagnosis.

Impact of Biometric Patient Data, Probiotic Supplementation, and Selected Gut Microorganisms on Calprotectin, Zonulin, and sIgA Concentrations in the Stool of Adults Aged 18-74 Years

Alterations to the intestinal barrier may be involved in the pathogenesis of various chronic diseases. The diagnosis of mucosal barrier disruption has become a new therapeutic target for disease prevention. The aim of this study was to determine whether various patient demographic and biometric data, often not included in diagnostic analyses, may affect calprotectin, zonulin, and sIgA biomarker values. Stool markers' levels in 160 samples were measured colorimetrically. The analysis of twenty key bacteria (15 genera and 5 species) was carried out on the basis of diagnostic tests, including cultures and molecular tests. The concentrations of selected markers were within reference ranges for most patients. The sIgA level was significantly lower in participants declaring probiotics supplementation (p = 0.0464). We did not observe differences in gastrointestinal discomfort in participants. We found significant differences in the sIgA level between the 29-55 years and >55 years age-related intervals groups (p = 0.0191), together with a significant decreasing trend (p = 0.0337) in age-dependent sIgA concentration. We observed complex interdependencies and relationships between their microbiota and the analyzed biomarkers. For correct clinical application, standardized values of calprotectin and sIgA should be determined, especially in elderly patients. We observed a correlation between the composition of the gut community and biomarker levels, although it requires further in-depth analysis.

Morphological Assessment and Biomarkers of Low-Grade, Chronic Intestinal Inflammation in Production Animals

Simple Summary

Production animals are continuously exposed to environmental and dietary factors that might induce a state of low-grade, chronic intestinal inflammation. This condition compromises the productive performance and well-fare of these animals, requiring studies to understand what causes it and to develop control strategies. An intestinal inflammatory process is generally associated with alterations in the structure and functionality of its wall, resulting in the release of cellular components into the blood and/or feces. These components can act as biomarkers, i.e., they are measured to identify and quantify an inflammatory process without requiring invasive methods. In this review we discuss the mechanisms of low-grade inflammation, its effects on animal production and sustainability, and the identification of biomarkers that could provide early diagnosis of this process and support studies of useful interventional strategies.

Abstract

The complex interaction between the intestinal mucosa, the gut microbiota, and the diet balances the host physiological homeostasis and is fundamental for the maximal genetic potential of production animals. However, factors such as chemical and physical characteristics of the diet and/or environmental stressors can continuously affect this balance, potentially inducing a state of chronic low-grade inflammation in the gut, where inflammatory parameters are present and demanding energy, but not in enough intensity to provoke clinical manifestations. It’s vital to expand the understanding of inflammation dynamics and of how they compromise the function activity and microscopic morphology of the intestinal mucosa. These morphometric alterations are associated with the release of structural and functional cellular components into the feces and the blood stream creating measurable biomarkers to track this condition. Moreover, the identification of novel, immunometabolic biomarkers can provide dynamic and predictors of low-grade chronic inflammation, but also provide indicators of successful nutritional or feed additive intervention strategies. The objective of this paper is to review the mechanisms of low-grade inflammation, its effects on animal production and sustainability, and the biomarkers that could provide early diagnosis of this process and support studies of useful interventional strategies.

Zonulin — regulation of tight contacts in the brain and intestine — facts and hypotheses

In recent years, the interrelationship between the brain and the gut has become an area of high scientific interest. The intestine is responsible not only for digestion, as it contains millions of neurons, its own immune system, and affects the emotional and cognitive processes. The relationship between the gut and the brain suggests that the processes carried out by the gut microbiota play a significant role in the regulation of brain function, and vice versa. A special role here is played by intercellular tight junctions (TJ), where the zonulin protein holds an important place. Zonulin, an unprocessed precursor of mature haptoglobin, is the only physiological modulator of intercellular TJ that can reversibly regulate the permeability of the intestinal (IB) and blood-brain (BBB) barriers in the human body. BBB disruption and altered microbiota composition are associated with many diseases, including neurological disorders and neuroinflammation. That is, there is a gut-brain axis (GBA) — a communication system through which the brain modulates the functions of the gastrointestinal tract (GIT) and vice versa. GBA is based on neuronal, endocrine, and immunological mechanisms that are interconnected at the organismal, organ, cellular, and molecular levels.

Neuroprotective Effects of Sodium Butyrate and Monomethyl Fumarate Treatment through GPR109A Modulation and Intestinal Barrier Restoration on PD Mice

Research has connected Parkinson's disease (PD) with impaired intestinal barrier. The activation of G-protein-coupled receptor 109A (GPR109A) protects the intestinal barrier by inhibiting the NF-κB signaling pathway. Sodium butyrate (NaB), which is a GPR109A ligand, may have anti-PD effects. The current study's objective is to demonstrate that NaB or monomethyl fumarate (MMF, an agonist of the GPR109A) can treat PD mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) via repairing the intestinal barrier. Male C57BL/6J mice were divided into four groups randomly: control, MPTP + vehicle, MPTP + NaB, and MPTP + MMF. Modeling mice received MPTP (20 mg/kg/day, i.p.) for a week, while control mice received sterile PBS. Then, four groups each received two weeks of sterile PBS (10 mL/kg/day, i.g.), sterile PBS (10 mL/kg/day, i.g.), NaB (600 mg/kg/day, i.g.), or MMF (100 mg/kg/day, i.g.). We assessed the expression of tight junction (TJ) proteins (occludin and claudin-1), GPR109A, and p65 in the colon, performed microscopic examination via HE staining, quantified markers of intestinal permeability and proinflammatory cytokines in serum, and evaluated motor symptoms and pathological changes in the substantia nigra (SN) or striatum. According to our results, MPTP-induced defected motor function, decreased dopamine and 5-hydroxytryptamine levels in the striatum, decreased tyrosine hydroxylase-positive neurons and increased activated microglia in the SN, and systemic inflammation were ameliorated by NaB or MMF treatment. Additionally, the ruined intestinal barrier was also rebuilt and NF-κB was suppressed after the treatment, with higher levels of TJ proteins, GPR109A, and decreased intestinal permeability. These results show that NaB or MMF can remedy motor symptoms and pathological alterations in PD mice by restoring the intestinal barrier with activated GPR109A. We demonstrate the potential for repairing the compromised intestinal barrier and activating GPR109A as promising treatments for PD.

Zonulin, as a marker of intestinal permeability, is elevated in IgA nephropathy and IgA vasculitis with nephritis

Background

Immunoglobulin A nephropathy (IgAN) and IgA vasculitis with nephritis (IgAV-N) are considered related diseases and share some similar clinicopathologic phenotypes. Elevated circulating galactose-deficient IgA1 (Gd-IgA1)-containing immune complexes and mucosal immunity were associated with the pathogenesis of IgAN and IgAV-N. Recently, studies have identified that the zonulin level, as a modulator of intestinal permeability, is significantly elevated in several inflammatory and autoimmune-related diseases. However, whether zonulin also plays a role in IgAN and IgAV-N is not clear.

Methods

A total of 73 IgAV-N patients, 68 IgAN patients and 54 healthy controls were assessed for circulating zonulin and Gd-IgA1 levels by enzyme-linked immunosorbent assay. The diagnostic efficiency of the combination of zonulin with Gd-IgA1 was evaluated by the area under the receiver operating characteristic curve (AUC) and integrated discrimination improvement (IDI) analysis.

Results

Compared with healthy controls, we found that both IgAV-N and IgAN patients had elevated zonulin and Gd-IgA1 levels (P < .001). Additionally, patients with IgAV-N presented with even higher circulating zonulin levels than patients with IgAN (P = .020). The addition of zonulin to Gd-IgA1 showed better predictive performance than Gd-IgA1 alone in the diagnosis of both IgAN and IgAV-N, as illustrated by a significantly increased AUC (IgAN: 0.805 versus 0.708, P = .0021; IgAV-N: 0.886 versus 0.673, P < .001) and significant IDI (IgAN: IDI 0.136, P < .001; IgAV-N: IDI 0.281, P < .001).

Conclusion

Elevated circulating zonulin levels were detected in both patients with IgAV-N and those with IgAN. Combined detection of circulating zonulin and Gd-IgA1 is recommended as a noninvasive diagnostic biomarker for IgAV-N and IgAN.

Intestinal fatty acid binding protein (I-FABP) and CXC3L1 evaluation as biomarkers for patients at high-risk for coeliac disease in Johannesburg, South Africa

Coeliac disease (CD) is an autoimmune disorder and one of the few gastroenteropathies with accurate serological testing. CD serology has decreased accuracy for patients on a gluten-free diet and for monitoring mucosal healing. New ancillary tests would, therefore, be useful. Intestinal Fatty Acid Binding Protein (I-FABP) and CX3CL1 (Fractalkine) are two promising biomarkers for CD but haven't been examined in patients who are at a high-risk for CD such as patients with type one diabetes (TID). This study, therefore, aimed to investigate serum levels of I-FABP and CX3CL1 in a cohort of South African patients with TID at a high-risk of developing CD. The serum I-FABP levels were significantly higher in CD-positive patients compared to CD-negative individuals (p = 0.03). No significant differences in the serum CX3CL1 levels were detected although this may reflect the impact of the comorbid autoimmune diseases had on the serum CX3CL1 levels. In conclusion, this study is the first to assess the levels of these biomarkers in a multiethnic population with comorbid autoimmune disease and determined I-FABP to be the more promising biomarker in such clinical contexts. Future research should focus on a diverse biomarker panel and longitudinal follow-up of patients at a high-risk for CD.

Celiac Disease and Targeting the Molecular Mechanisms of Autoimmunity in COVID Pandemic

Celiac disease (CD) comprises over 1% of the world’s population and is a chronic multisystem immune-mediated condition manifested by digestive and/or extradigestive symptoms caused by food intake of gluten. This review looked at the risk of children diagnosed with CD developing SARS-CoV-2 infection and possible severe forms of COVID-19. A better understanding of the interaction and effects of SARS-CoV-2 infection in CD is very important, as is the role of environmental and genetic factors, but especially the molecular mechanisms involved in modulating intestinal permeability with impact on autoimmunity. CD inspired the testing of a zonulin antagonist for the fulminant form of multisystem inflammatory syndrome in children (MIS-C) and paved the way for the discovery of new molecules to regulate the small intestine barrier function and immune responses. Original published works on COVID-19 and CD, new data and points of view have been analyzed because this dangerous virus SARS-CoV-2 is still here and yet influencing our lives. Medical science continues to focus on all uncertainties triggered by SARS-CoV-2 infection and its consequences, including in CD. Although the COVID-19 pandemic seems to be gradually extinguishing, there is a wealth of information and knowledge gained over the last two years and important life lessons to analyze, as well as relevant conclusions to be drawn to deal with future pandemics. Zonulin is being studied extensively in immunoengineering as an adjuvant to improving the absorption of new drugs and oral vaccines.

Celiac Disease and Targeting the Molecular Mechanisms of Autoimmunity in COVID Pandemic

Celiac disease (CD) comprises over 1% of the world's population and is a chronic multisystem immune-mediated condition manifested by digestive and/or extradigestive symptoms caused by food intake of gluten. This review looked at the risk of children diagnosed with CD developing SARS-CoV-2 infection and possible severe forms of COVID-19. A better understanding of the interaction and effects of SARS-CoV-2 infection in CD is very important, as is the role of environmental and genetic factors, but especially the molecular mechanisms involved in modulating intestinal permeability with impact on autoimmunity. CD inspired the testing of a zonulin antagonist for the fulminant form of multisystem inflammatory syndrome in children (MIS-C) and paved the way for the discovery of new molecules to regulate the small intestine barrier function and immune responses. Original published works on COVID-19 and CD, new data and points of view have been analyzed because this dangerous virus SARS-CoV-2 is still here and yet influencing our lives. Medical science continues to focus on all uncertainties triggered by SARS-CoV-2 infection and its consequences, including in CD. Although the COVID-19 pandemic seems to be gradually extinguishing, there is a wealth of information and knowledge gained over the last two years and important life lessons to analyze, as well as relevant conclusions to be drawn to deal with future pandemics. Zonulin is being studied extensively in immunoengineering as an adjuvant to improving the absorption of new drugs and oral vaccines.

Hallmarks of Severe COVID-19 Pathogenesis: A Pas de Deux Between Viral and Host Factors

Two years into Coronavirus Disease 2019 (COVID-19) pandemic, a comprehensive characterization of the pathogenesis of severe and critical forms of COVID-19 is still missing. While a deep dysregulation of both the magnitude and functionality of innate and adaptive immune responses have been described in severe COVID-19, the mechanisms underlying such dysregulations are still a matter of scientific debate, in turn hampering the identification of new therapies and of subgroups of patients that would most benefit from individual clinical interventions. Here we review the current understanding of viral and host factors that contribute to immune dysregulation associated with COVID-19 severity in the attempt to unfold and broaden the comprehension of COVID-19 pathogenesis and to define correlates of protection to further inform strategies of targeted therapeutic interventions.

Loss of Gut Barrier Integrity In Lupus

Systemic Lupus Erythematosus is a complex autoimmune disease and its etiology remains unknown. Increased gut permeability has been reported in lupus patients, yet whether it promotes or results from lupus progression is unclear. Recent studies indicate that an impaired intestinal barrier allows the translocation of bacteria and bacterial components into systemic organs, increasing immune cell activation and autoantibody generation. Indeed, induced gut leakage in a mouse model of lupus enhanced disease characteristics, including the production of anti-dsDNA antibody, serum IL-6 as well as cell apoptosis. Gut microbiota dysbiosis has been suggested to be one of the factors that decreases gut barrier integrity by outgrowing harmful bacteria and their products, or by perturbation of gut immune homeostasis, which in turn affects gut barrier integrity. The restoration of microbial balance eliminates gut leakage in mice, further confirming the role of microbiota in maintaining gut barrier integrity. In this review, we discuss recent advances on the association between microbiota dysbiosis and leaky gut, as well as their influences on the progression of lupus. The modifications on host microbiota and gut integrity may offer insights into the development of new lupus treatment.

No effects of a 4-week post-exercise sauna bathing on targeted gut microbiota and intestinal barrier function, and hsCRP in healthy men: a pilot randomized controlled trial

Background

Body temperature fluctuations induced by acute exercise bouts may influence the intestinal barrier with related effects on epithelial permeability, immune responses, and release of metabolites produced by the gut microbiota. This study evaluated the effects of post-exercise sauna bathing in young men undergoing endurance training on gut bacteria inflammation and intestinal barrier function.

Methods

Fifteen (15) untrained males aged 22 ± 1.5 years were randomly assigned to exercise training (ET) with or without post-exercise sauna treatments (S). Participants in the group ET + S (n = 8) exercised 60 min, 3 times per week, on a bicycle ergometer followed by a 30-min dry Finish sauna treatment. The control group (ET, n = 7) engaged in the same exercise training program without the sauna treatments. Blood and stool samples were collected before and after the 4-week training program. Blood samples were analysed for the concentration of high-sensitivity C-reactive protein (hsCRP) and complete blood counts. Stool samples were analysed for pH, quantitative and qualitative measures of targeted bacteria, zonulin, and secretory immunoglobulin A.

Results

Interaction effects revealed no differences in the pattern of change over time between groups for the abundance of selected gut microbiome bacteria and stool pH, zonulin, sIgA, and hsCRP. Pre- and post-study fecal concentrations of Bifidobacterium spp., Faecalibacterium prausnitzii, and Akkermansia muciniphila were below reference values for these bacteria in both groups.

Conclusions

The combination of 4-weeks exercise followed by passive heat exposure did not have a measurable influence on targeted gut microbiota, intestinal barrier function, and hsCRP levels in young males.

Trial registration

The study was retrospectively registered in the clinical trials registry (Clinicaltrials.gov) under the trial registration number: NCT05277597. Release Date: March 11, 2022.

Assessing Hydrolyzed Gluten Content in Dietary Enzyme Supplements Following Fermentation

Partially digested gluten fragments from grains including wheat, rye, spelt and barley are responsible for triggering an inflammatory response in the intestinal tract of Celiac Disease (CD) and Non-Celiac Gluten Sensitive (NCGS) individuals. Fermentation is an effective method to metabolize gluten, with enzymes from bacterial or fungal species being released to help in this process. However, the levels of gluten in commercially available enzymes, including those involved in gluten fermentation, are unknown. In this study we investigated gluten levels in commercially available dietary enzymes combined with assessing their effect on inflammatory response in human cell culture assays. Using antibodies that recognize different gluten epitopes (G12, R5, 2D4, MloBS and Skerritt), we employed ELISA and immunoblotting methodologies to determine gluten content in crude gluten, crude gliadin, pepsin-trypsin digested gluten and a selection of commercially available enzymes. We further investigated the effect of these compounds on inflammatory response in immortalized immune and intestinal human cell lines, as well as in peripheral blood mononuclear cells (PBMCs) from coeliac individuals. All tested supplemental enzyme products reported a gluten concentration that was equivalent to or below 20 parts per million (ppm) as compared with an intact wheat reference standard and a pepsin-trypsin digested standard. Similarly, the inflammatory response to IL-8 and TNF-α inflammatory cytokines in mammalian cell lines and PBMCs from coeliac individuals to the commercial enzymes was not significantly different to 20 ppm of crude gluten, crude gliadin or pepsin-trypsin digested gluten. This combined approach provides insight into the extent of gluten breakdown in the fermentation process and the safety of these products to gluten-sensitive individuals.

In vitro Effects of Bacterial Exposure on Secretion of Zonulin Family Peptides and Their Detection in Human Tissue Samples

Commercially available ELISAs for zonulin (pre-haptoglobin 2), a protein with tight junction regulatory activity in the epithelia, were recently shown to recognize other proteins that are structurally and functionally related to zonulin, termed zonulin family peptides (ZFPs). With little or no information about the identity and property of ZFPs, various commercial zonulin ELISA kits are widely utilized in research as a marker of intestinal permeability. Bacterial exposure is a known trigger for the secretion of zonulin, but it remains unclear whether distinct bacteria differ in their capability to stimulate zonulin secretion. We hypothesized that ZFPs are similar to zonulin regarding response to bacterial exposure and aimed to compare the effects of non-pathogenic, Gram-negative bacteria (Escherichia coli RY13 and E. coli K12 DH5α) and probiotic, Gram-positive bacteria (Lactobacillus rhamnosus GG and Bifidobacterium bifidum) on ZFP secretion in an in vitro model. Additionally, utilizing samples from human clinical trials, we correlated circulating levels of ZFPs to the gut bacteria and determined the presence of ZFPs in various human tissues. Unexpectedly, we found that the ZFPs quantified by the widely used IDK® Zonulin ELISA kits are specifically triggered by the exposure to live Lactobacillus rhamnosus GG in HT-29 cells, associated with absolute abundances of intestinal Lactobacillus and Bifidobacterium in adults, and are copious in the small intestine but undetectable in the liver or adipose tissue. These characteristics appear to be different from zonulin and highlight the need for further characterization of ZFPs recognized by commercially available and widely used “zonulin” ELISAs.

Plasma and fecal zonulin are not altered by a high green leafy vegetable dietary intervention: secondary analysis of a randomized control crossover trial

BACKGROUND

Zonulin is observed in animal models to regulate intestinal permeability and influenced by dietary intake, gut microbiota, and inflammation. We conducted a secondary analysis of a randomized controlled crossover trial (NCT03582306) in individuals with a BMI greater than 30 kg/m² and high habitual red meat intake and low habitual green leafy vegetable (GLV) intake.

METHODS

Participants were provided with frozen GLV during the first or last four weeks (immediate or delayed intervention) of the twelve-week trial. Biological and anthropometric measures were taken at the beginning and at each four-week interval. A subset of 20 participants was selected for this secondary analysis of the intestinal permeability and inflammation-related biomarkers: serum and fecal zonulin; serum lipopolysaccharide binding protein (LBP), Alpha-1-acid glycoprotein 1 (ORM-1), tumor necrosis factor α (TNFα), interleukin-6 (IL-6), and C-reactive protein; 8-hydroxy-2'-deoxyguanosine (8OHdG) and plasma Vitamin K1 as a marker of protocol adherence. Nutrient and food group intake from two-24-h dietary recalls collected at each time point were assessed. Fecal microbiota was measured by 16 s rRNA PCR sequencing. Changes in biological markers, dietary factors, and microbial taxa were assessed with Wilcoxon Sign Ranks Tests. Exploratory analyses of the relationship between changes in outcome variables were conducted with Spearman correlations.

RESULTS

No changes in serum and fecal zonulin and serum LBP were observed. Plasma Vitamin K (p = 0.005) increased, while plasma 8OHdG (p = 0.023) decreased during the intervention compared to the control. The only dietary factors that changed significantly were increases during intervention in Vitamin K and Dark GLV (p < 0.001 for both) compared to control. Fecal microbiota did not change significantly across all times points; however, change in serum zonulin was associated with change in Proteobacteria (ρ = - 0.867, p = 0.001) in females and Bifidobacterium (ρ = - 0.838, p = 0.009) and Bacteroidaceae (ρ = 0.871, p = 0.005) in men.

CONCLUSIONS

A high GLV dietary intervention increased serum zonulin levels and had no effect on fecal zonulin. Lack of concordance between several inflammation-associated biomarkers and zonulin corroborate recent reports of limited utility of zonulin in obese adults free of lower gastrointestinal disease. Trial Registration information: https://clinicaltrials.gov/ct2/show/NCT03582306 (NCT03582306) registered on 07/11/2018.

Implication of Intestinal Barrier Dysfunction in Gut Dysbiosis and Diseases

The intestinal mucosal barrier, also referred to as intestinal barrier, is widely recognized as a critical player in gut homeostasis maintenance as it ensures the complex crosstalk between gut microbes (both commensals and pathogens) and the host immune system. Highly specialized epithelial cells constantly cope with several protective and harmful agents to maintain the multiple physiological functions of the barrier as well as its integrity. However, both genetic defects and environmental factors can break such equilibrium, thus promoting gut dysbiosis, dysregulated immune-inflammatory responses, and even the development of chronic pathological conditions. Here, we review and discuss the molecular and cellular pathways underlying intestinal barrier structural and functional homeostasis, focusing on potential alterations that may undermine this fine balance.

The Gluten-Free Diet for Celiac Disease and Beyond

The gluten-free diet (GFD) has gained popularity beyond its main medical indication as the treatment for gluten-induced immune-mediated disorders such as celiac disease (CD), dermatitis herpetiformis, gluten ataxia, wheat allergy, and non-celiac gluten sensitivity. However, the diet carries some disadvantages such as elevated costs, nutritional deficiencies, and social and psychological barriers. The present work aims to review indications, proven benefits, and adverse events of a gluten-free diet. Close follow-up with patients following the diet is recommended. More data is needed to assess the effectiveness of the diet in managing mental and cognitive disorders and to establish a connection between the brain and gluten.

Does the epithelial barrier hypothesis explain the increase in allergy, autoimmunity and other chronic conditions?

There has been a steep increase in allergic and autoimmune diseases, reaching epidemic proportions and now affecting more than one billion people worldwide. These diseases are more common in industrialized countries, and their prevalence continues to rise in developing countries in parallel to urbanization and industrialization. Intact skin and mucosal barriers are crucial for the maintenance of tissue homeostasis as they protect host tissues from infections, environmental toxins, pollutants and allergens. A defective epithelial barrier has been demonstrated in allergic and autoimmune conditions such as asthma, atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, coeliac disease and inflammatory bowel disease. In addition, leakiness of the gut epithelium is also implicated in systemic autoimmune and metabolic conditions such as diabetes, obesity, multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis and autoimmune hepatitis. Finally, distant inflammatory responses due to a 'leaky gut' and microbiome changes are suspected in Alzheimer disease, Parkinson disease, chronic depression and autism spectrum disorders. This article introduces an extended 'epithelial barrier hypothesis', which proposes that the increase in epithelial barrier-damaging agents linked to industrialization, urbanization and modern life underlies the rise in allergic, autoimmune and other chronic conditions. Furthermore, it discusses how the immune responses to dysbiotic microbiota that cross the damaged barrier may be involved in the development of these diseases.

From celiac disease to coccidia infection and vice-versa: The polyQ peptide CXCR3-interaction axis

Zonulin is a physiological modulator of intercellular tight junctions, which upregulation is involved in several diseases like celiac disease (CeD). The polyQ gliadin fragment binds to the CXCR3 chemokine receptor that activates zonulin upregulation, leading to increased intestinal permeability in humans. Here, we report a general hypothesis based on the structural connection between the polyQ sequence of the immunogenic CeD protein, gliadin, and enteric coccidian parasites proteins. Firstly, a novel interaction pathway between the parasites and the host is described based on the structural similarities between polyQ gliadin fragments and the parasite proteins. Secondly, a potential connection between coccidial infections as a novel environmental trigger of CeD is hypothesized. Therefore, this report represents a promising breakthrough for coccidian research and points out the potential role of coccidian parasites as a novel trigger of CeD that might define a preventive strategy for gluten-related disorders in general. Also see the video abstract here: https://youtu.be/oMaQasStcFI.

The Effect of Bacterial Infections, Probiotics and Zonulin on Intestinal Barrier Integrity

The intestinal barrier plays an extremely important role in maintaining the immune homeostasis of the gut and the entire body. It is made up of an intricate system of cells, mucus and intestinal microbiota. A complex system of proteins allows the selective permeability of elements that are safe and necessary for the proper nutrition of the body. Disturbances in the tightness of this barrier result in the penetration of toxins and other harmful antigens into the system. Such events lead to various digestive tract dysfunctions, systemic infections, food intolerances and autoimmune diseases. Pathogenic and probiotic bacteria, and the compounds they secrete, undoubtedly affect the properties of the intestinal barrier. The discovery of zonulin, a protein with tight junction regulatory activity in the epithelia, sheds new light on the understanding of the role of the gut barrier in promoting health, as well as the formation of diseases. Coincidentally, there is an increasing number of reports on treatment methods that target gut microbiota, which suggests that the prevention of gut-barrier defects may be a viable approach for improving the condition of COVID-19 patients. Various bacteria-intestinal barrier interactions are the subject of this review, aiming to show the current state of knowledge on this topic and its potential therapeutic applications.

Inflammatory and Microbiota-Related Regulation of the Intestinal Epithelial Barrier

The intestinal epithelial barrier (IEB) is one of the largest interfaces between the environment and the internal milieu of the body. It is essential to limit the passage of harmful antigens and microorganisms and, on the other side, to assure the absorption of nutrients and water. The maintenance of this delicate equilibrium is tightly regulated as it is essential for human homeostasis. Luminal solutes and ions can pass across the IEB via two main routes: the transcellular pathway or the paracellular pathway. Tight junctions (TJs) are a multi-protein complex responsible for the regulation of paracellular permeability. TJs control the passage of antigens through the IEB and have a key role in maintaining barrier integrity. Several factors, including cytokines, gut microbiota, and dietary components are known to regulate intestinal TJs. Gut microbiota participates in several human functions including the modulation of epithelial cells and immune system through the release of several metabolites, such as short-chain fatty acids (SCFAs). Mediators released by immune cells can induce epithelial cell damage and TJs dysfunction. The subsequent disruption of the IEB allows the passage of antigens into the mucosa leading to further inflammation. Growing evidence indicates that dysbiosis, immune activation, and IEB dysfunction have a role in several diseases, including irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and gluten-related conditions. Here we summarize the interplay between the IEB and gut microbiota and mucosal immune system and their involvement in IBS, IBD, and gluten-related disorders.

The Role of Intestinal Permeability in Gastrointestinal Disorders and Current Methods of Evaluation

An increased intestinal permeability has been described in various gastrointestinal and non-gastrointestinal disorders. Nevertheless, the concept and definition of intestinal permeability is relatively broad and includes not only an altered paracellular route, regulated by tight junction proteins, but also the transcellular route involving membrane transporters and channels, and endocytic mechanisms. Paracellular intestinal permeability can be assessed in vivo by using different molecules (e.g., sugars, polyethylene glycols, ⁵¹Cr-EDTA) and ex vivo in Ussing chambers combining electrophysiology and probes of different molecular sizes. The latter is still the gold standard technique for assessing the epithelial barrier function, whereas in vivo techniques, including putative blood biomarkers such as intestinal fatty acid-binding protein and zonulin, are broadly used despite limitations. In the second part of the review, the current evidence of the role of impaired barrier function in the pathophysiology of selected gastrointestinal and liver diseases is discussed. Celiac disease is one of the conditions with the best evidence for impaired barrier function playing a crucial role with zonulin as its proposed regulator. Increased permeability is clearly present in inflammatory bowel disease, but the question of whether this is a primary event or a consequence of inflammation remains unsolved. The gut-liver axis with a crucial role in impaired intestinal barrier function is increasingly recognized in chronic alcoholic and metabolic liver disease. Finally, the current evidence does not support an important role for increased permeability in bile acid diarrhea.

The use of biomarkers associated with leaky gut as a diagnostic tool for early intervention in autism spectrum disorder: a systematic review

Background

Innovative research highlighted the probable connection between autism spectrum disorder (ASD) and gut microbiota as many autistic individuals have gastrointestinal problems as co-morbidities. This review emphasizes the role of altered gut microbiota observed frequently in autistic patients, and the mechanisms through which such alterations may trigger leaky gut.

Main body

Different bacterial metabolite levels in the blood and urine of autistic children, such as short-chain fatty acids, lipopolysaccharides, beta-cresol, and bacterial toxins, were reviewed. Moreover, the importance of selected proteins, among which are calprotectin, zonulin, and lysozyme, were discussed as biomarkers for the early detection of leaky gut as an etiological mechanism of ASD through the less integrative gut–blood–brain barriers. Disrupted gut–blood–brain barriers can explain the leakage of bacterial metabolites in these patients.

Conclusion

Although the cause-to-effect relationship between ASD and altered gut microbiota is not yet well understood, this review shows that with the consumption of specific diets, definite probiotics may represent a noninvasive tool to reestablish healthy gut microbiota and stimulate gut health. The diagnostic and therapeutic value of intestinal proteins and bacterial-derived compounds as new possible biomarkers, as well as potential therapeutic targets, are discussed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00448-y.

Diagnosing coeliac disease: A literature review

Coeliac disease (CD) is an autoimmune gastroenteropathy triggered by gliadin and gliadin-tissue transglutaminase (tTG) complexes. CD is one of the few autoimmune diseases with an accurate, non-invasive serological test. Anti-endomysial, anti-tTG and anti-deaminated gliadin peptides (DGP) antibodies are currently used for serological tests with tTG ELISAs being the superior test. Duodenal biopsy, although invasive, is the gold standard for CD diagnosis. HLA genotyping and flow cytometry can also be used as supplementary tests. The incidence of CD is rising globally although the reasons for this remain unclear. In addition, the true incidence of coeliac disease in African populations remains unknown although recent work suggests that South African populations express the alleles associated with this disease. This review examines the pathogenesis and diagnosis of coeliac disease and considers novel and innovative biomarkers in its diagnosis specifically in an African population.

Advances in quantification and analysis of the celiac-related immunogenic potential of gluten

Gluten-free products have emerged in response to the increasing prevalence of gluten-related disorders, namely celiac disease. Therefore, the quantification of gluten in products intended for consumption by individuals who may suffer from these pathologies must be accurate and reproducible, in a way that allows their proper labeling and protects the health of consumers. Immunochemical methods have been the methods of choice for quantifying gluten, and several kits are commercially available. Nevertheless, they still face problems such as the initial extraction of gluten in complex matrices or the use of a standardized reference material to validate the results. Lately, other methodologies relying mostly on mass spectrometry-based techniques have been explored, and that may allow, in addition to quantitative analysis, the characterizationof gluten proteins. On the other hand, although the level of 20 mg/kg of gluten detected by these methods is sufficient for a product to be considered gluten-free, its immunogenic potential for celiac patients has not been clinically validated. In this sense, in vitro and in vivo models, such as the organoid technology applied in gut-on-chip devices and the transgenic humanized mouse models, respectively, are being developed for investigating both the gluten-induced pathogenesis and the treatment of celiac disease. Due to the ubiquitous nature of gluten in the food industry, as well as the increased prevalence of gluten-related disorders, here we intend to summarize the available methods for gluten quantification in food matrices and for the evaluation of its immunogenic potential concerning the development of novel therapies for celiac disease to highlight active research and discuss knowledge gaps and current challenges in this field.

Interplay Between Gluten, HLA, Innate and Adaptive Immunity Orchestrates the Development of Coeliac Disease

Several environmental, genetic, and immune factors create a "perfect storm" for the development of coeliac disease: the antigen gluten, the strong association of coeliac disease with HLA, the deamidation of gluten peptides by the enzyme transglutaminase 2 (TG2) generating peptides that bind strongly to the predisposing HLA-DQ2 or HLA-DQ8 molecules, and the ensuing unrestrained T cell response. T cell immunity is at the center of the disease contributing to the inflammatory process through the loss of tolerance to gluten and the differentiation of HLA-DQ2 or HLA-DQ8-restricted anti-gluten inflammatory CD4⁺ T cells secreting pro-inflammatory cytokines and to the killing of intestinal epithelial cells by cytotoxic intraepithelial CD8⁺ lymphocytes. However, recent studies emphasize that the individual contribution of each of these cell subsets is not sufficient and that interactions between these different populations of T cells and the simultaneous activation of innate and adaptive immune pathways in distinct gut compartments are required to promote disease immunopathology. In this review, we will discuss how tissue destruction in the context of coeliac disease results from the complex interactions between gluten, HLA molecules, TG2, and multiple innate and adaptive immune components.