Intestinal Barrier Function in Gluten-Related Disorders

The Frequently Used Industrial Food Process Additive, Microbial Transglutaminase: Boon or Bane

Microbial transglutaminase (mTG) is a frequently consumed processed food additive, and use of its cross-linked complexes is expanding rapidly. It was designated as a processing aid and was granted the generally recognized as safe (GRAS) classification decades ago, thus avoiding thorough assessment according to current criteria of toxicity and public health safety. In contrast to the manufacturer's declarations and claims, mTG and/or its transamidated complexes are proinflammatory, immunogenic, allergenic, pathogenic, and potentially toxic, hence raising concerns for public health. Being a member of the transglutaminase family and functionally imitating the tissue transglutaminase, mTG was recently identified as a potential inducer of celiac disease. Microbial transglutaminase and its docked complexes have numerous detrimental effects. Those harmful aspects are denied by the manufacturers, who claim the enzyme is deactivated when heated or by gastric acidity, and that its covalently linked isopeptide bonds are safe. The present narrative review describes the potential side effects of mTG, highlighting its thermostability and activity over a broad pH range, thus, challenging the manufacturers' and distributers' safety claims. The national food regulatory authorities and the scientific community are urged to reevaluate mTG's GRAS status, prioritizing public health protection against the possible risks associated with this enzyme and its health-damaging consequences.

Obeticholic acid attenuates the intestinal barrier disruption in a rat model of short bowel syndrome

BACKGROUND

Short bowel syndrome (SBS) features nutrients malabsorption and impaired intestinal barrier. Patients with SBS are prone to sepsis, intestinal flora dysbiosis and intestinal failure associated liver disease. Protecting intestinal barrier and preventing complications are potential strategies for SBS treatment. This study aims to investigate the effects of farnesoid X receptor (FXR) agonist, obeticholic acid (OCA), have on intestinal barrier and ecological environment in SBS.

METHODS AND RESULTS

Through testing the small intestine and serum samples of patients with SBS, impaired intestinal barrier was verified, as evidenced by reduced expressions of intestinal tight junction proteins (TJPs), increased levels of apoptosis and epithelial cell damage. The intestinal expressions of FXR and related downstream molecules were decreased in SBS patients. Then, global FXR activator OCA was used to further dissect the potential role of the FXR in a rat model of SBS. Low expressions of FXR-related molecules were observed on the small intestine of SBS rats, along with increased proinflammatory factors and damaged barrier function. Furthermore, SBS rats possessed significantly decreased body weight and elevated death rate. Supplementation with OCA mitigated the damaged intestinal barrier and increased proinflammatory factors in SBS rats, accompanied by activated FXR-related molecules. Using 16S rDNA sequencing, the regulatory role of OCA on gut microbiota in SBS rats was witnessed. LPS stimulation to Caco-2 cells induced apoptosis and overexpression of proinflammatory factors in vitro. OCA incubation of LPS-pretreated Caco-2 cells activated FXR-related molecules, increased the expressions of TJPs, ameliorated apoptosis and inhibited overexpression of proinflammatory factors.

CONCLUSIONS

OCA supplementation could effectively ameliorate the intestinal barrier disruption and inhibit overexpression of proinflammatory factors in a rat model of SBS and LPS-pretreated Caco-2 cells. As a selective activator of FXR, OCA might realize its protective function through FXR activation.

Prospective fecal microbiomic biomarkers for chronic wasting disease

Chronic wasting disease (CWD) is a naturally occurring prion disease in cervids that has been rapidly proliferating in the United States. Here, we investigated a potential link between CWD infection and gut microbiome by analyzing 50 fecal samples obtained from CWD-positive animals of different sexes from various regions in the USA compared to 50 CWD-negative controls using high throughput sequencing of the 16S ribosomal RNA and targeted metabolomics. Our analysis reveals promising trends in the gut microbiota that could potentially be CWD-dependent, including several bacterial taxa at each rank level, as well as taxa pairs, that can differentiate between CWD-negative and CWD-positive deer. Through machine-learning, these taxa and taxa pairs at each rank level could facilitate identification of around 70% of both the CWD-negative and the CWD-positive samples. Our results provide a potential tool for diagnostics and surveillance of CWD in the wild, as well as conceptual advances in our understanding of the disease.IMPORTANCEThis is a comprehensive study that tests the connection between the composition of the gut microbiome in deer in response to chronic wasting disease (CWD). We analyzed 50 fecal samples obtained from CWD-positive animals compared to 50 CWD-negative controls to identify CWD-dependent changes in the gut microbiome, matched with the analysis of fecal metabolites. Our results show promising trends suggesting that fecal microbial composition can directly correspond to CWD disease status. These results point to the microbial composition of the feces as a potential tool for diagnostics and surveillance of CWD in the wild, including non-invasive CWD detection in asymptomatic deer and deer habitats, and enable conceptual advances in our understanding of the disease.

Sustained control of recalcitrant chronic spontaneous urticaria after initiation of inflammatory airway diseases treatment: two case reports

BACKGROUND

Current classification of chronic urticaria is primarily based on clinical presentation of skin manifestations. Hence, therapeutic treatment is primarily aimed locally for immediate symptom relief. We reason that limiting therapeutic strategies to the skin pathology might be inadequate since cellular activation and inflammation might be triggered remotely.

CASE PRESENTATION

In this series two patients had exhausted all current treatments for recalcitrant urticaria but remained symptomatic. The first case was 26-year-old Caucasian female and the second was 63-year-old African American female. Both cases had frequent breakthrough urticaria requiring frequent pulsating courses of prednisone to control urticaria despite treatment with omalizumab and antihistamines. When inflammatory airway disease was discovered and managed with inhaled corticosteroid, urticaria is controlled much faster without the need of high dose immunosuppression over several years of observation. Coincidentally, autoimmune thyroiditis and anti-immunogobulin-E immunoglobulin-G titers dropped significantly in one case with sustained inhaled corticosteroid therapy.

CONCLUSIONS

We suggest a novel approach of controlling remote epithelial site inflammation in these two cases that resulted in sustained-control of urticaria symptoms without the need for systemic corticosteroids or immunosuppressant. The changes of autoimmune antibodies might be the consequences of tolerance breaking from chronic lower airway inflammation as observed in other epithelial inflammatory condition like in celiac disease and rheumatoid arthritis.

Dietary supplementation of ark clams protects gut health and modifies gut microbiota in d-galactose-induced aging rats

BACKGROUND

Ark clams, a seafood abundant in various nutrients, are widely consumed worldwide. This study aimed to investigate the protective benefits of two common ark clams in Korea, Scapharca subcrenata (SS) and Tegillarca granosa (TG), on gut health in d-galactose (d-gal)-induced aging rats.

RESULTS

Thirty-two Wistar rats (11 weeks old) were randomly allocated into four groups: a CON group (normal diet + saline intraperitoneal (i.p.) injection), a CD group (normal diet + d-gal i.p. injection), an SS group (normal diet with 5% SS supplementation + d-gal i.p. injection), and a TG group (normal diet with 5% TG supplementation + d-gal i.p. injection). After 12 weeks of treatment, histopathological results showed that gut barrier damage was alleviated in rats of the SS and TG groups, as evidenced by increases in mucus layer thickness and goblet cell numbers. Meanwhile, the two groups supplemented with ark clams showed an evident reduction in oxidative stress biomarkers (malondialdehyde and protein carbonyl content levels in the colon) and an increase in the immune-related factor (immunoglobulin A level in the plasma) in rats. The 16S ribosomal RNA analysis revealed that SS and TG ark clams significantly increased the proliferations of Bacteroidetes at the phylum level and Parabacteroides at the genus level. Additionally, the levels of the three main short-chain fatty acids in the cecal contents were also significantly increased in the SS and TG groups.

CONCLUSION

Our results indicated a potent preventive effect of SS and TG ark clams on d-gal-induced gut injury, suggesting that ark clams may be a promising dietary component for intervening in aging. © 2023 Society of Chemical Industry.

Understanding the potential causes of gastrointestinal dysfunctions in multiple system atrophy

Multiple system atrophy (MSA) is a rare, progressive neurodegenerative disorder characterised by autonomic, pyramidal, parkinsonian and/or cerebellar dysfunction. Autonomic symptoms of MSA include deficits associated with the gastrointestinal (GI) system, such as difficulty swallowing, abdominal pain and bloating, nausea, delayed gastric emptying, and constipation. To date, studies assessing GI dysfunctions in MSA have primarily focused on alterations of the gut microbiome, however growing evidence indicates other structural components of the GI tract, such as the enteric nervous system, the intestinal barrier, GI hormones, and the GI-driven immune response may contribute to MSA-related GI symptoms. Here, we provide an in-depth exploration of the physiological, structural, and immunological changes theorised to underpin GI dysfunction in MSA patients and highlight areas for future research in order to identify more suitable pharmaceutical treatments for GI symptoms in patients with MSA.

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.

Prevalence of autoimmune, cholestatic and nonalcoholic fatty liver disease in celiac disease

BACKGROUND

While there is higher prevalence of autoimmune, cholestatic and fatty liver disease in celiac disease (CeD), most data is from small-scale studies. We evaluated the prevalence and risk factors of the same using large cohort data.

METHODS

A population-based cross-sectional study was conducted using Explorys, a multi-institutional database. Prevalence and risk factors of autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and nonalcoholic fatty liver disease (NAFLD) in CeD were assessed.

RESULTS

Out of 70 352 325 subjects, 136 735 had CeD (0.19%). The prevalence of AIH (0.32%), PBC (0.15%), PSC (0.004%) and NAFLD (0.7%) were high in CeD. After adjusting for age, gender, Caucasian race and anti-tissue transglutaminase antibody (anti-TTG), CeD subjects had higher odds of AIH [adjusted odds ratio (aOR) 7.06, 95% confidence interval (CI) 6.32-7.89] and PBC (aOR 4.16, 95% CI 3.46-5.0). Even after adjusting for CeD, anti-TTG positivity concurred with higher odds of AIH (aOR 4.79, 95% CI 3.88-5.92) and PBC (aOR 9.22, 95% CI 7.03-12.1). After adjusting for age, gender, Caucasian race, diabetes mellitus (DM), obesity, hypothyroidism and metabolic syndrome, there was higher prevalence of NAFLD in CeD, with the aOR in the presence of DM type 1 being 2.1 (95% CI 1.96-2.25), and in the presence of DM type 2 being 2.92 (95% CI 2.72-3.14).

CONCLUSION

Subjects with CeD are more likely to have AIH, PBC, PSC and NAFLD. AIH and PBC have higher odds in the presence of anti-TTG. The odds of NAFLD in CeD are high regardless of type of DM.

The emerging paradigm of Unconventional T cells as a novel therapeutic target for celiac disease

Celiac disease (CD) is an organ-specific autoimmune disorder that occurs in genetically predisposed individuals when exposed to exogenous dietary gluten. This exposure to wheat gluten and related proteins from rye and barley triggers an immune response which leads to the development of enteropathy associated with symptoms of bloating, diarrhea, or malabsorption. The sole current treatment is to follow a gluten-free diet for the rest of one's life. Intestinal barriers are enriched with Unconventional T cells such as iNKT, MAIT, and γδ T cells, which lack or express only a limited range of rearranged antigen receptors. Unconventional T cells play a crucial role in regulating mucosal barrier function and microbial colonization. Unconventional T cell populations are widely represented in diseased conditions, where changes in disease activity related to iNKT and MAIT cell reduction, as well as γδ T cell expansion, are demonstrated. In this review, we discuss the role and potential employment of Unconventional T cells as a therapeutic target in the pathophysiology of celiac disease.

Bacillus coagulans MZY531 alleviates intestinal mucosal injury in immunosuppressive mice via modulating intestinal barrier, inflammatory response, and gut microbiota

Bacillus coagulans has a potential role in improving intestinal injury. However, the specific mechanism is still unclear. In this study, the protective effect of B. coagulans MZY531 on intestinal mucosa injury in cyclophosphamide (CYP)-induced immunosuppressed mice were investigated. The results indicated that the immune organ (thymus and spleen) indices of B. coagulans MZY531 treatment groups were significantly increased compared to the CYP group. B. coagulans MZY531 administration promotes the expression of immune proteins (IgA, IgE, IgG, and IgM). B. coagulans MZY531 could upregulate the ileum levels of IFN-γ, IL-2, IL-4, and IL-10 in immunosuppressed mice. Moreover, B. coagulans MZY531 restores the villus height and crypt depth of the jejunum and alleviates injury of intestinal endothelial cells caused by CYP. Furthermore, the western blotting results showed that B. coagulans MZY531 ameliorated CYP-induced intestinal mucosal injury and inflammatory via up-regulates the ZO-1 pathway and down-regulates the expression of the TLR4/MyD88/NF-κB pathway. After treatment with B. coagulans MZY531, the relative abundance of Firmicutes phylum was dramatically increased, as well as the genera of Prevotella and Bifidobacterium, and reducing harmful bacteria. These findings suggested that B. coagulans MZY531 has a potential immunomodulatory activity on chemotherapy-induced immunosuppression.

Assessing the Prevalence of HLA-DQ2 and HLA-DQ8 in Lipedema Patients and the Potential Benefits of a Gluten-Free Diet

Objective The aim of this study is to assess the prevalence of HLA-DQ2 and HLA-DQ8 in women diagnosed with lipedema. Methods Leukocyte histocompatibility antigen (HLA) tests of 95 women diagnosed with lipedema were analyzed using non-probabilistic sampling for convenience. The prevalence of HLA-DQ2 and HLA-DQ8 was compared to the general population. Results The prevalence of HLA-DQ2+ was 47.4%, that of HLA-DQ8+ was 22.2%, the presence of any celiac disease associated HLA (HLA-DQ2+ or HLA-DQ8+) was 61.1%, both HLA (HLA-DQ2+ and HLA-DQ8+) was 7.4%, and the absence of celiac disease associated HLA was 39%. Compared to the general population, there was a significantly higher prevalence of HLA-DQ2, HLA-DQ8, any HLA, and both HLAs in lipedema patients. The mean weight of patients with HLA-DQ2+ was significantly lower than the overall study population, and their mean BMI significantly differed from the overall mean BMI. Conclusion Lipedema patients seeking medical assistance have a higher prevalence of HLA-DQ2 and HLA-DQ8. Considering the role of gluten in inflammation, further research is needed to establish if this association supports the benefit of gluten withdrawal from the diet in managing lipedema symptoms.

Skin gluten-related disorders: new and old cutaneous manifestations to be considered

The term gluten-related disorders (GRD) refer to a spectrum of different clinical manifestations triggered by the ingestion of gluten in genetically susceptible individuals, including coeliac disease (CD), wheat allergy and non-celiac gluten sensitivity (NCGS). GRD are characterized by a large variety of clinical presentations with both intestinal and extra-intestinal manifestations. The latter may affect almost every organ of the body, including the skin. Besides the well-known association between CD and dermatitis herpetiformis, considered as the cutaneous specific manifestation of CD, many other muco-cutaneous disorders have been associated to GRD. In this review, we analyzed the main features of dermatological diseases with a proven association with GRD and those that improve after a gluten-free diet, focusing on the newly described cutaneous manifestations associated with NCGS. Our main hypothesis is that a "cutaneous-gluten sensitivity," as specific cutaneous manifestation of NCGS, may exist and could represent a diagnostic marker of NCGS.

Intestinal Barrier Function in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. The mechanisms involved in NAFLD onset are complicated and multifactorial. Recent literature has indicated that altered intestinal barrier function is related to the occurrence and progression of liver disease. The intestinal barrier is important for absorbing nutrients and electrolytes and for defending against toxins and antigens in the enteric environment. Major mechanisms by which the intestinal barrier influences the development of NAFLD involve the altered epithelial layer, decreased intracellular junction integrity, and increased intestinal barrier permeability. Increased intestinal permeability leads to luminal dysbiosis and allows the translocation of pathogenic bacteria and metabolites into the liver, inducing inflammation, immune response, and hepatocyte injury in NAFLD. Although research has been directed to NAFLD in recent decades, the pathophysiological changes in NAFLD initiation and progression are still not completely understood, and the therapeutic targets remain limited. A deeper understanding on the correlation between NAFLD pathogenesis and intestinal barrier regulation must be attained. Therefore, in this review, the components of the intestinal barrier and their respective functions and disruptions during the progression of NAFLD are discussed.

Intestinal mucus components and secretion mechanisms: what we do and do not know

Damage to the colon mucus barrier, the first line of defense against microorganisms, is an important determinant of intestinal diseases such as inflammatory bowel disease and colorectal cancer, and disorder in extraintestinal organs. The mucus layer has attracted the attention of the scientific community in recent years, and with the discovery of new mucosal components, it has become increasingly clear that the mucosal barrier is a complex system composed of many components. Moreover, certain components are jointly involved in regulating the structure and function of the mucus barrier. Therefore, a comprehensive and systematic understanding of the functional components of the mucus layer is clearly warranted. In this review, we summarize the various functional components of the mucus layer identified thus far and describe their unique roles in shaping mucosal structure and function. Furthermore, we detail the mechanisms underlying mucus secretion, including baseline and stimulated secretion. In our opinion, baseline secretion can be categorized into spontaneous Ca²⁺ oscillation-mediated slow and continuous secretion and stimulated secretion, which is mediated by massive Ca²⁺ influx induced by exogenous stimuli. This review extends the current understanding of the intestinal mucus barrier, with an emphasis on host defense strategies based on fortification of the mucus layer.

Food, gut barrier dysfunction, and related diseases: A new target for future individualized disease prevention and management

Dysfunction of gut barrier is known as "leaky gut" or increased intestinal permeability. Numerous recent scientific evidences showed the association between gut dysfunction and multiple gastrointestinal tract (GI) and non-GI diseases. Research also demonstrated that food plays a crucial role to cause or remedy gut dysfunction related to diseases. We reviewed recent articles from electronic databases, mainly PubMed. The data were based on animal models, cell models, and human research in vivo and in vitro models. In this comprehensive review, our aim focused on the relationship between dietary factors, intestinal permeability dysfunction, and related diseases. This review synthesizes currently available literature and is discussed in three parts: (a) the mechanism of gut barrier and function, (b) food and dietary supplements that may promote gut health, and food or medication that may alter gut function, and (c) a table that organizes the synthesized information by general mechanisms for diseases related to leaky gut/intestinal permeability and associated dietary influences. With future research, dietary intervention could be a new target for individualized disease prevention and management.

Dietary Supplement, Containing the Dry Extract of Curcumin, Emblica and Cassia, Counteracts Intestinal Inflammation and Enteric Dysmotility Associated with Obesity

Intestinal epithelial barrier (IEB) impairment and enteric inflammation are involved in the onset of obesity and gut-related dysmotility. Dietary supplementation with natural plant extracts represents a useful strategy for the management of body weight gain and systemic inflammation associated with obesity. Here, we evaluate the efficacy of a food supplement containing the dry extract of Curcumin, Emblica and Cassia in counteracting enteric inflammation and motor abnormalities in a mouse model of obesity, induced by a high-fat diet (HFD). Male C57BL/6 mice, fed with standard diet (SD) or HFD, were treated with a natural mixture (Curcumin, Emblica and Cassia). After 8 weeks, body weight, BMI, liver and spleen weight, along with metabolic parameters and colonic motor activity were evaluated. Additionally, plasma LBP, fecal calprotectin, colonic levels of MPO and IL-1β, as well as the expression of occludin, TLR-4, MYD88 and NF-κB were investigated. Plant-based food supplement administration (1) counteracted the increase in body weight, BMI and metabolic parameters, along with a reduction in spleen and liver weight; (2) showed strengthening effects on the IEB integrity; and (3) reduced enteric inflammation and oxidative stress, as well as ameliorated the colonic contractile dysfunctions. Natural mixture administration reduced intestinal inflammation and counteracted the intestinal motor dysfunction associated with obesity.

Biomarkers of gut barrier dysfunction in obstructive sleep apnea: A systematic review and meta-analysis

We conducted this systematic review and meta-analysis to evaluate the impact of obstructive sleep apnea (OSA) on gut barrier dysfunction as represented by the following biomarkers: zonulin, lipopolysaccharide, lipopolysaccharide binding protein, intestinal fatty acid binding protein, and lactic acid. A comprehensive search of the literature was conducted in Ovid MEDLINE, Embase, Scopus, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov without language restrictions from inception to October 2022. The analysis of all outcomes was performed using a random-effects model. We included eight studies (seven cross sectional and one case control) in the final quantitative synthesis with a total of 897 patients. We concluded that OSA was associated with higher levels of gut barrier dysfunction biomarkers [Hedges' g = 0.73 (95%CI 0.37-1.09, p < 0.01). Biomarker levels were positively correlated with the apnea-hypopnea index [r = 0.48 (95%CI 0.35-0.6, p < 0.01)] and oxygen desaturation index [r = 0.30 (95%CI 0.17-0.42, p < 0.01)], and negatively correlated with the nadir oxygen desaturation values [r = -0.45 (95%CI - 0.55 - - 0.32, p < 0.01). Our systematic review and meta-analysis suggests that OSA is associated with gut barrier dysfunction. Furthermore, OSA severity appears to be correlated with higher biomarkers of gut barrier dysfunction. PROSPERO REGISTRATION NUMBER: CRD42022333078.

The gut microbiota of people with asthma influences lung inflammation in gnotobiotic mice

The gut microbiota in early childhood is linked to asthma risk, but may continue to affect older patients with asthma. Here, we profile the gut microbiota of 38 children (19 asthma, median age 8) and 57 adults (17 asthma, median age 28) by 16S rRNA sequencing and find individuals with asthma harbored compositional differences from healthy controls in both adults and children. We develop a model to aid the design of mechanistic experiments in gnotobiotic mice and show enterotoxigenic Bacteroides fragilis (ETBF) is more prevalent in the gut microbiota of patients with asthma compared to healthy controls. In mice, ETBF, modulated by community context, can increase oxidative stress in the lungs during allergic airway inflammation (AAI). Our results provide evidence that ETBF affects the phenotype of airway inflammation in a subset of patients with asthma which suggests that therapies targeting the gut microbiota may be helpful tools for asthma control.

Replacing the Burden of the Gluten Free Diet: Then, Now, and the Future

Without a doubt, a majority of diseases are food-pattern-related. However, one disease stands out as an increasingly more common autoimmune-mediated enteropathy triggered by the ingestion of gluten. Celiac disease (CD) is an old disease, with changing clinical patterns, affecting any age, including infancy and adolescence, and becoming more frequent among the elderly. The gluten-free diet (GFD) has been the sole provider of clinical, serological, and histological improvement for patients with CD for more than seven decades. Nowadays, complete avoidance of dietary gluten is rarely possible because of the wide availability of wheat and other processed foods that contain even more gluten, to the detriment of gluten-free products. Undeniably, there is a definite need for replacing the burdensome GFD. An add-on therapy that could control the dietary transgressions and inadvertent gluten consumption that can possibly lead to overt CD should be considered while on GFD. Nevertheless, future drugs should be able to provide patients some freedom to self-manage CD and increase food independence, while actively reducing exposure and mucosal damage and alleviating GI symptoms. Numerous clinical trials assessing different molecules have already been performed with favorable outcomes, and hopefully they will soon be available for patient use.

Bidirectional causal link between inflammatory bowel disease and celiac disease: A two-sample mendelian randomization analysis

Background: Observational research has shown a correlation between inflammatory bowel disease (IBD) [comprising ulcerative colitis (UC) and Crohn’s disease (CD)] and celiac disease. However, the relationship between these two diseases remains uncertain.

Methods: We utilized two-sample Mendelian randomization (MR) to estimate the bidirectional causal relationships between IBD and celiac disease. This study utilized data on single nucleotide polymorphisms (SNPs) from genome-wide association studies (GWASs). Heterogeneity, pleiotropy, and sensitivity analyses were also performed to evaluate the MR results.

Results: There was a significant causal relationship between IBD and CD and celiac disease (e.g., IBD and celiac disease, inverse variance weighting (IVW) odds ratio (OR) = 1.0828, 95% CI = 1.0258–1.1428, p = 0.0039; CD and celiac disease, IVW OR = 1.0807, 95% CI = 1.0227–1.1420, p = 0.0058). However, in the reverse direction, we found only suggestive positive causality between celiac disease and CD (e.g., IVW OR = 1.0366, 95% CI = 1.0031–1.0711, p = 0.0319). No evidence of heterogeneity between genetic variants was found (e.g., IBD vs. celiac disease, MR-Egger Q = 47.4391, p = 0.6159). Horizontal pleiotropy hardly influenced causality (e.g., IBD vs. celiac disease, MR-Egger test: p = 0.4340). Leave-one-out analysis showed that individual SNPs did not influence the general results.

Conclusion: Our MR analysis revealed a positive causal link between IBD and celiac disease in the European population. In addition, several recommendations for disease prevention and clinical management have been discussed.

Differential Protective Effect of Resveratrol and Its Microbial Metabolites on Intestinal Barrier Dysfunction is Mediated by the AMPK Pathway

The effectiveness of resveratrol (RES) on intestinal barrier dysfunction and colitis has been extensively studied. However, the specific effects of its microbial metabolites on gut barrier function remain unclear. Hence, we compared the protective effects of RES and its microbial metabolites dihydroresveratrol (DHR) and 3-(4-hydroxyphenyl)-propionic acid (4HPP) against intestinal barrier injury and colitis. Only 4HPP and RES significantly reduced paracellular permeability and the secretion of proinflammatory cytokines in lipopolysaccharides (LPS)-treated intestinal Caco-2 cells, which was consistent with the upregulation in tight junction (TJ) proteins. Furthermore, RES and 4HPP ameliorated intestinal barrier dysfunction and colonic inflammation in colitis mice, while DHR did not. In particular, the expressions of intestinal TJ proteins and Muc2 were restored by RES and 4HPP. The molecular mechanism involved the adenosine monophosphate-activated protein kinase (AMPK)-mediated activation of CDX2 and the regulation of the SIRT1/NF-κB pathway. These findings provide new insights into understanding the protective effects of RES against intestinal barrier damage and colitis.

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.

Non-Celiac Gluten Sensitivity and Protective Role of Dietary Polyphenols

Pathogenetically characterized by the absence of celiac disease and wheat allergy, non-celiac gluten sensitivity (NCGS) is a clinical entity triggered by the consumption of gluten-containing foods that relieved by a gluten-free diet. Since it is very difficult to maintain a complete gluten-free diet, there is a high interest in discovering alternative strategies aimed at reducing gluten concentration or mitigating its toxic effects. Plant-based dietary models are usually rich in bioactive compounds, such as polyphenols, recognized to prevent, delay, or even reverse chronic diseases, including intestinal disorders. However, research on the role of polyphenols in mitigating the toxicity of gluten-containing foods is currently limited. We address the metabolic fate of dietary polyphenols, both as free and bound macromolecule-linked forms, with particular reference to the gastrointestinal compartment, where the concentration of polyphenols can reach high levels. We analyze the potential targets of polyphenols including the gluten peptide bioavailability, the dysfunction of the intestinal epithelial barrier, intestinal immune response, oxidative stress and inflammation, and dysbiosis. Overall, this review provides an updated overview of the effects of polyphenols as possible dietary strategies to counteract the toxic effects of gluten, potentially resulting in the improved quality of life of patients with gluten-related disorders.

NLRX1 Deficiency Alters the Gut Microbiome and Is Further Exacerbated by Adherence to a Gluten-Free Diet

Patients with gluten sensitivities present with dysbiosis of the gut microbiome that is further exacerbated by a strict adherence to a gluten-free diet (GFD). A subtype of patients genetically susceptible to gluten sensitivities are Celiac Disease (CeD) patients, who are carriers of the HLA DR3/DQ2 or HLA DR4/DQ8 haplotypes. Although 85-95% of all CeD patients carry HLA DQ2, up to 25-50% of the world population carry this haplotype with only a minority developing CeD. This suggests that CeD and other gluten sensitivities are mediated by factors beyond genetics. The contribution of innate immune system signaling has been generally understudied in the context of gluten sensitivities. Thus, here we examined the role of NOD-like receptors (NLRs), a subtype of pattern recognition receptors, in maintaining the composition of the gut microbiome in animals maintained on a GFD. Human transcriptomics data revealed significant increases in the gene expression of multiple NLR family members, across functional groups, in patients with active CeD compared to control specimens. However, NLRX1 was uniquely down-regulated during active disease. NLRX1 is a negative regulatory NLR that functions to suppress inflammatory signaling and has been postulate to prevent inflammation-induced dysbiosis. Using Nlrx1^-/- mice maintained on either a normal or gluten-free diet, we show that loss of NLRX1 alters the microbiome composition, and a distinctive shift further ensues following adherence to a GFD, including a reciprocal loss of beneficial microbes and increase in opportunistic bacterial populations. Finally, we evaluated the functional impact of an altered gut microbiome by assessing short- and medium-chain fatty acid production. These studies revealed significant differences in a selection of metabolic markers that when paired with 16S rRNA sequencing data could reflect an overall imbalance and loss of immune system homeostasis in the gastrointestinal system.

Inhibition of LncRNA-NEAT1 alleviates intestinal epithelial cells (IECs) dysfunction in ulcerative colitis by maintaining the homeostasis of the glucose metabolism through the miR-410-3p-LDHA axis

Dysfunction of intestinal epithelial cells (IECs) leads to intestinal epithelial barrier damage and critically involves in the pathogenesis and development of ulcerative colitis (UC). Accumulating studies revealed essential functions of non-coding RNAs in UC. LncRNA NEAT1 (long non-coding RNA nuclear paraspeckle assembly transcript 1) is frequently dysregulated in diverse human diseases. Currently, the precise roles of NEAT1 in the dysfunction of IECs during UC remain unclear. We report NEAT1 was significantly upregulated in IECs from UC patients. In addition, microRNA-410-3p was remarkedly suppressed in IECs from UC patients. Silencing NEAT1 effectively ameliorates the LPS-induced IECs dysfunction. Bioinformatical analysis, RNA pull-down and luciferase assays illustrated that NEAT1 sponged miR-410-3p to downregulate its expression in IECs. Interestingly, the glucose metabolism was obviously elevated in IECs from UC compared with normal colon tissues. Furthermore, NEAT1 promoted and miR-410-3p suppressed glucose metabolism of IECs. We identified lactate dehydrogenase A (LDHA), a glucose metabolism key enzyme, was a direct target of miR-410-3p in IECs. Rescue experiments verified that restoration of miR-410-3p in NEAT1-overexpressing IECs successfully overcame the NEAT1-promoted cell death under LPS treatment by targeting LDHA. In summary, these results unveiled new roles and molecular mechanisms for the NEAT1-mediated IECs dysfunction during the ulcerative colitis.

Micronutrient Improvement of Epithelial Barrier Function in Various Disease States: A Case for Adjuvant Therapy

The published literature makes a very strong case that a wide range of disease morbidity associates with and may in part be due to epithelial barrier leak. An equally large body of published literature substantiates that a diverse group of micronutrients can reduce barrier leak across a wide array of epithelial tissue types, stemming from both cell culture as well as animal and human tissue models. Conversely, micronutrient deficiencies can exacerbate both barrier leak and morbidity. Focusing on zinc, Vitamin A and Vitamin D, this review shows that at concentrations above RDA levels but well below toxicity limits, these micronutrients can induce cell- and tissue-specific molecular-level changes in tight junctional complexes (and by other mechanisms) that reduce barrier leak. An opportunity now exists in critical care—but also medical prophylactic and therapeutic care in general—to consider implementation of select micronutrients at elevated dosages as adjuvant therapeutics in a variety of disease management. This consideration is particularly pointed amidst the COVID-19 pandemic.

Managing Symptom Profile of IBS-D Patients With Tritordeum-Based Foods: Results From a Pilot Study

In the past few years, increasing attention has been given to the pathologic role of specific foods in IBS, like wheat and other cereals. Recent literature describes IBS patients who may experience gastrointestinal (GI) and extra-GI symptoms precipitated by the ingestion of cereals. Tritordeum is a cereal of Spanish origin derived from the hybridization of durum wheat and wild barley. It is different from classic wheat for its gluten protein composition, with fewer carbohydrates and fructans and a higher content of proteins, dietary fibers, and antioxidants. This pilot study aimed to investigate the effects of a 12-week diet with Tritordeum-based foods in substitution of other cereals on the profile of GI symptoms (evaluated by appropriate questionnaire) and the health of the GI barrier (assessed by sugar absorption test and different markers of integrity and functions) in 16 diarrhea-predominant IBS (IBS-D) patients. The diet with Tritordeum-based foods (bread, bakery products, and pasta) significantly reduced IBS-D patients' symptoms. This amelioration appears to occur through an overall improvement of the GI barrier, as demonstrated by the reduced intestinal permeability and the decreased levels of markers of intestinal mucosal integrity, mucosal inflammation, and fermentative dysbiosis.

Healthy and pro-inflammatory gut ecology plays a crucial role in the digestion and tolerance of a novel Gluten Friendly™ bread in celiac subjects: a randomized, double blind, placebo control in vivo study

Gluten Friendly™ (GF) is a new gluten achieved through a physicochemical process applied to wheat kernels. The goal of this research was to assess the in vivo effects of Gluten Friendly™ bread on celiac gut mucosa and microbiota. In a double-blind placebo-controlled intervention study, 48 celiac disease (CD) patients were randomized into 3 groups to eat 100 g of bread daily, containing different doses (0; 3 g; 6 g) of GF for 12 weeks. The small-bowel morphology (VH/CrD), intraepithelial densities of CD3+, celiac serology, MUC2, CB1, gut permeability, proinflammatory cytokines, gluten in stools, symptoms, and gut microbial composition were assessed. All 48 CD subjects experienced no symptoms. K-means analysis evidenced celiac subjects clustering around unknown parameters independent of GF dosage: K1 35%; K2 30%; K3 35%. VH/CrD significantly decreased in K1 and K2. VH/CrD did not correlate with IEL increase in K2. 33-mer was not detected in 47% and 73% of patients in both K1 and K2, respectively. VH/CrD and IEL did not change significantly and strongly correlated with the absence of 33-mer in K3. Inflammation and VH/CrD decrease are strongly related with the presence of proinflammatory species at the baseline. A boost in probiotic, butyrate-producing genera, is strongly related with GF tolerance at the end of the trial. Our research suggests that a healthy and proinflammatory ecology could play a crucial role in the digestion and tolerance of the new gluten molecule in celiac subjects. However, GF can be completely digested by gut microbiota of CD subjects and shapes it toward gut homeostasis by boosting healthy butyrate-producing populations. The clinical trial registry number is NCT03137862 (https://clinicaltrials.gov).

The Pivotal Role of Microbiota in Modulating the Neuronal-Glial-Epithelial Unit

The enteric nervous system (ENS) consists of enteric neurons and enteric glial cells (EGCs) and controls the function of the epithelial barrier. Thus, a novel concept of neuronal–glial–epithelial unit in the gut was put forward by analogy with neuronal–glial–endothelial unit in the brain. The environment in the gastrointestinal (GI) tract is complex as it harbours millions of bacteria, which extensively attach with intestinal epithelium. The cross-talk between the neuronal–glial–endothelial unit and microbiota plays a pivotal role in modulating the epithelial barrier's permeability, intestinal development and immune response. And evidence shows dysbiosis is the potent risk factor in the pathologic process of Parkinson’s disease (PD) and inflammatory bowel disease (IBD). In this review, we summarize the compelling results in favor of microbiota serving as the key modulator in the neuronal–glial–epithelial unit development and function, with profound effects on intestinal homeostasis.

Scientific Opinion on development needs for the allergenicity and protein safety assessment of food and feed products derived from biotechnology

This Scientific Opinion addresses the formulation of specific development needs, including research requirements for allergenicity assessment and protein safety, in general, which is urgently needed in a world that demands more sustainable food systems. Current allergenicity risk assessment strategies are based on the principles and guidelines of the Codex Alimentarius for the safety assessment of foods derived from 'modern' biotechnology initially published in 2003. The core approach for the safety assessment is based on a 'weight-of-evidence' approach because no single piece of information or experimental method provides sufficient evidence to predict allergenicity. Although the Codex Alimentarius and EFSA guidance documents successfully addressed allergenicity assessments of single/stacked event GM applications, experience gained and new developments in the field call for a modernisation of some key elements of the risk assessment. These should include the consideration of clinical relevance, route of exposure and potential threshold values of food allergens, the update of in silico tools used with more targeted databases and better integration and standardisation of test materials and in vitro/in vivo protocols. Furthermore, more complex future products will likely challenge the overall practical implementation of current guidelines, which were mainly targeted to assess a few newly expressed proteins. Therefore, it is timely to review and clarify the main purpose of the allergenicity risk assessment and the vital role it plays in protecting consumers' health. A roadmap to (re)define the allergenicity safety objectives and risk assessment needs will be required to inform a series of key questions for risk assessors and risk managers such as 'what is the purpose of the allergenicity risk assessment?' or 'what level of confidence is necessary for the predictions?'.

Duodenal mast cells and eosinophils in children with celiac disease: occurrence and distribution pattern

OBJECTIVE

The aim of this study was to characterize duodenal mast cell (MC) and eosinophil (EO) numbers, their distribution within the lamina propria and possible impact on disease severity of paediatric celiac patients compared to children without celiac disease (CD).

METHODS

We analysed duodenal samples of 215 children (109 CD, 106 controls) who underwent esophagogastroduodenoscopy from 2010 to 2018. After immunohistochemical staining, average MC and EO counts were histologically examined in ten high-power-fields. Additionally, cell-distribution within the lamina propria was analysed. Possible influence of relevant clinical parameters was evaluated.

STATISTICS

Student's-t-test, Mann-Whitney U-test, Chi-square-test, ANOVA, significance-level <.05. Trial registration-number: DRKS00024669.

RESULTS

MC-density was higher in CD-patients compared to the control-group (23.7 (±12.1)/HPF versus 19.7 (±9.1)/HPF; p = .008), varying in number interindividually. Eosinophils were also increased in the duodenum of celiac patients (23.3 (±9.3)/HPF versus 12.2 (±6.3)/HPF; p= <.001). MCs were distributed more often homogenously in all parts of CD lamina propria (44 biopsies (40.4%), residing more distant from the intestinal lumen in controls (0 biopsies with homogenous distribution-pattern (0%); p= <.001). Regarding EOs no polarity was observable. Atopic diseases did not occur significantly more often in patients with elevated EO-counts.

CONCLUSION

MC- and EO-numbers were increased in the duodenum of CD-patients and MCs showed a different distribution-pattern in the lamina propria of celiac patients. These findings support the concept that both cell-types contribute to disease-pathogenesis. However, functional studies highlighting both cell-types' and their mediators' role regarding mucosal alterations during the course of the inflammatory process in celiac patients are needed.

TRIAL REGISTRATION NUMBER AND URL

DRKS00024669; https://www.drks.de/drks_web/.

The Role of the Tumor Microenvironment and Treatment Strategies in Colorectal Cancer

Colorectal cancer (CRC) has the second highest mortality rate among all cancers worldwide. Surgery, chemotherapy, radiotherapy, molecular targeting and other treatment methods have significantly prolonged the survival of patients with CRC. Recently, the emergence of tumor immunotherapy represented by immune checkpoint inhibitors (ICIs) has brought new immunotherapy options for the treatment of advanced CRC. As the efficacy of ICIs is closely related to the tumor immune microenvironment (TME), it is necessary to clarify the relationship between the immune microenvironment of CRC and the efficacy of immunotherapy to ensure that the appropriate drugs are selected. We herein review the latest research progress in the immune microenvironment and strategies related to immunotherapy for CRC. We hope that this review helps in the selection of appropriate treatment strategies for CRC patients.

Assessment of Markers of Gut Integrity and Inflammation in Non-Celiac Gluten Sensitivity After a Gluten Free-Diet

Purpose

Markers for gut integrity and inflammation have received increasing interest as intestinal permeability and innate immune system activation are suggested as possible pathophysiological mechanisms in non-celiac gluten sensitivity (NCGS). We aimed to assess relevant biomarkers in NCGS by analyzing serum levels of gut integrity and permeability markers, pro-inflammatory cytokines and antigliadin IgG in patients with suspected NCGS on a gluten-free diet (GFD), and compare them to serum levels in patients with irritable bowel syndrome (IBS) and healthy controls (HC).

Patients and Methods

Serum samples collected from patients with suspected NCGS on a GFD (n=20, 14 women, 21–62 years), IBS (n=20, 16 women, 24–67 years) and HC (n=20, 14 women, 21–54 years) were analyzed. IBS severity scoring system (IBS-SSS) was applied to evaluate gastrointestinal symptoms.

Results

The IBS-SSS score was higher in subjects with suspected NCGS and IBS patients compared to HC (p<0.0001). No significant differences were found in the serum levels of any of the gut integrity and permeability markers, cytokines or antigliadin IgG antibodies between the three groups. However, positive correlations were observed between claudin-1 and i-FABP, and between claudin-1 and antigliadin IgG antibodies.

Conclusion

No differences in serum levels of gut integrity and permeability markers, pro-inflammatory cytokines or antigliadin IgG antibodies were found among patients with suspected NCGS on a GFD, IBS and HC.

(-)-Epigallocatechin-3-gallate mitigates cyclophosphamide-induced intestinal injury by modulating the tight junctions, inflammation and dysbiosis in mice

Cyclophosphamide (CTX) is an antitumor drug commonly used to treat various cancer types. Unfortunately, its toxic side effects, including gastrointestinal (GI) toxicity, affect treatment compliance and patients' prognosis. Thus, there is a critical need of evaluating strategies that may improve the associated GI toxicity induced by CTX. In this work, we evaluated the capacity of epigallocatechin-3-gallate (EGCG), a major constituent of green tea, to improve the recovery of gut injury induced by CTX in mice. Treatment with CTX for 5 days severely damaged the intestinal structure, increased immune-related cytokines (TNFα, IL-10 and IL-21), reduced the expression levels of tight junction proteins (ZO-1, occludin, claudin-1), induced reactive oxygen species, altered the composition of gut microbiota, and reduced short chain fatty acid levels. EGCG treatment, starting one day after the last CTX dose, significantly improved the intestinal structure, ameliorated gut permeability, and restored ZO-1, occludin and claudin-1 levels. Moreover, EGCG reduced TNFα, IL-10 and IL-21 levels and decreased oxidative stress by regulating the activities of the antioxidant enzymes catalase, superoxide dismutase and glutathione peroxidase. Finally, EGCG treatment restored the composition of gut microbiota and the levels of the short chain fatty acids. In conclusion, these findings indicate that EGCG may function as an effective bioactive compound to minimize CTX-induced GI tract toxicity.

Gualou Xiebai Decoction ameliorates increased Caco-2 monolayer permeability induced by bile acids via tight junction regulation, oxidative stress suppression and apoptosis reduction

Gualou Xiebai Decoction (GXD), a classic prescription, is widely used to dealing with inflammatory diseases in China for thousands of years. Abnormal metabolic state of bile acids (BAs) is confirmed to cause intestinal epithelial barrier dysfunction. In preliminary work, we observed that GXD could decrease intestinal permeability in hyperlipidemia mice. The present study aimed to explore the protective effect of GXD on intestinal mucosa in vitro. Caco-2 cell monolayer permeability among different groups was determined by measuring the concentrations of FITC-dextran in the lower compartments and transepithelial electrical resistance (TEER). Meanwhile, mRNA and protein expressions of tight junctions (TJs) were investigated. Generation of intracellular reactive oxygen species (ROS) and the ratio of cell apoptosis induced by BAs were assessed by fluorescence probe and flow cytometry. GXD was shown to keep the cell monolayer in low permeable status, increase TEER and mRNA and protein expressions of occludin (Ocln) and zonula occluden 2 (ZO2) remarkably in cells challenged with cholic acid (CA), deoxycholic acid (DCA) and glycocholic acid (GCA). However, no significant effects were uncovered against the pathological effects of taurocholic acid (TCA). Meanwhile, generation of ROS and increased levels of apoptotic cells caused by CA, DCA and GCA were dramatically decreased by GXD, which were not observed on TCA. GXD could significantly attenuate intestinal barrier dysfunction induced by BAs via TJs regulation, oxidative stress suppression and cell apoptosis decrease, but such effects and behind mechanisms differed among different kinds of BAs.

New Insights into Intestinal Permeability in Irritable Bowel Syndrome-Like Disorders: Histological and Ultrastructural Findings of Duodenal Biopsies

BACKGROUND AND AIM

Diarrhea, abdominal pain, and bloating are frequent in irritable bowel syndrome (IBS)-like disorders, although little is known about their intestinal ultrastructural alterations. The aim of the present study was to study duodenal biopsies from IBS-like patients to find ultrastructural alterations.

MATERIALS AND METHODS

Study design: descriptive comparative pilot study. Thirty outpatients (9 male and 21 female; median age 37.7 years; range, 20 to 65 years) complaining of IBS-like symptoms were enrolled between January 2015 to May 2019 and were divided into 6 groups, each equally consisting of 5 patients: (A) untreated celiac disease (uCD); (B) treated celiac disease (tCD); (C) wheat allergy (WA); (D) Non-celiac gluten sensitivity (NCGS); (E) Nickel allergic contact mucositis (Ni ACM); (F) controls affected by GERD. Transmission electron microscopy (TEM) morphological characteristics were: microvilli length, intermicrovillar distance, junctional complexes (JC) gap width, autophagic bodies, apoptosis, altered mitochondria, lipid/chylomicron droplets, and mast cells. Regarding JC, we focused on tight junctions (TJ), adherens junctions (AJ), and desmosomes.

RESULTS

Major alterations in microvilli length and intermicrovillar distance have been observed in the subjects affected by uCD. Microvilli of tCD patients showed marked recovery after adequate GFD, although not comparable to controls. Intermediate microvillar alterations were instead observed in NCGS and Ni ACM, while characteristics of WA subjects appeared more similar to tCD. Regarding JC, TJ did not show significant differences between all groups studied, including controls. The AJ were significantly more dilated in all groups compared to controls, while no significant differences were found between the pathological groups. The distance between desmosomes was greater in uCD, NCGS, and Ni ACM than in tCD, WA, and controls. Finally, intracellular alterations have been detected in most of the groups studied although they seemed more unspecific.

CONCLUSIONS

TEM analysis confirmed damages to the intestinal barrier and defense mechanisms by enterocytes in IBS-like patients, probably linked to low-grade inflammation or adverse reactions triggered by food allergens, heavy metals, or other unknown. On the other hand, our study needs confirmation and further investigations with larger populations to facilitate diagnosis, therapy, and prevention of IBS-like disorders in the future.

Microbial Transglutaminase Is a Very Frequently Used Food Additive and Is a Potential Inducer of Autoimmune/Neurodegenerative Diseases

Microbial transglutaminase (mTG) is a heavily used food additive and its industrial transamidated complexes usage is rising rapidly. It was classified as a processing aid and was granted the GRAS (generally recognized as safe) definition, thus escaping full and thorough toxic and safety evaluations. Despite the manufacturers claims, mTG or its cross-linked compounds are immunogenic, pathogenic, proinflammatory, allergenic and toxic, and pose a risk to public health. The enzyme is a member of the transglutaminase family and imitates the posttranslational modification of gluten, by the tissue transglutaminase, which is the autoantigen of celiac disease. The deamidated and transamidated gliadin peptides lose their tolerance and induce the gluten enteropathy. Microbial transglutaminase and its complexes increase intestinal permeability, suppresses enteric protective pathways, enhances microbial growth and gliadin peptide’s epithelial uptake and can transcytose intra-enterocytically to face the sub-epithelial immune cells. The present review updates on the potentially detrimental side effects of mTG, aiming to interest the scientific community, induce food regulatory authorities’ debates on its safety, and protect the public from the mTG unwanted effects.

Association of Emulsifier and Highly Processed Food Intake with Circulating Markers of Intestinal Permeability and Inflammation in the Cancer Prevention Study-3 Diet Assessment Sub-Study

Compelling animal studies report increased intestinal permeability, inflammation, and colorectal carcinogenesis with exposure to certain emulsifiers commonly added to processed foods, but human data are lacking. Highly processed food consumption is also associated with obesity and higher risk of chronic diseases. We cross-sectionally examined the association of emulsifier and highly processed food consumption estimated from six 24-h dietary recalls among 588 U.S. men and women over one year, with biomarkers of intestinal permeability and inflammation measured from two fasting blood samples collected six months apart. In multivariable-adjusted generalized linear models, greater emulsifier intake (g/d) was not associated with antibodies to flagellin (P-trend = 0.88), lipopolysaccharide (LPS) (P-trend = 0.56), or the combined total thereof (P-trend = 0.65) but was positively associated with an inflammatory biomarker, glycoprotein acetyls (GlycA) (P-trend = 0.02). Highly processed food intake (% kcal/d) was associated with higher anti-LPS antibodies (P-trend = 0.001) and total anti-flagellin and anti-LPS antibodies (P-trend = 0.005) but not with other biomarkers, whereas processed food intake expressed as % g/d was associated with higher GlycA (P-trend = 0.02). Our findings suggest that, broadly, highly processed food consumption may be associated with intestinal permeability biomarkers, and both emulsifier and highly processed food intakes may be associated with inflammation. Additional studies are warranted to further evaluate these relationships.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1957947.

Multifaceted Impacts of Periodontal Pathogens in Disorders of the Intestinal Barrier

Periodontal disease, a common inflammatory disease, is considered a hazardous factor that contributes to the development of diseases of the digestive system as well as other systems. The bridge between periodontitis and systemic diseases is believed to be periodontal pathogens. The intestine, as part of the lower gastrointestinal tract, has a close connection with the oral cavity. Within the intestine, the intestinal barrier acts as a multifunctional system including microbial, mucous, physical and immune barrier. The intestinal barrier forms the body's first line of defense against external pathogens; its breakdown can lead to pathological changes in the gut and other organs or systems. Reports in the literature have described how oral periodontal pathogens and pathobiont-reactive immune cells can transmigrate to the intestinal mucosa, causing the destruction of intestinal barrier homeostasis. Such findings might lead to novel ideas for investigating the relationship between periodontal disease and other systemic diseases. This review summarizes studies on the effects of periodontal pathogens on the intestinal barrier, which might contribute to understanding the link between periodontitis and gastrointestinal diseases.

Role of Goblet Cells in Intestinal Barrier and Mucosal Immunity

Goblet cells and the mucus they secrete serve as an important barrier, preventing pathogens from invading the mucosa to cause intestinal inflammation. The perspective regarding goblet cells and mucus has changed, with current evidence suggesting that they are not passive but play a positive role in maintaining intestinal tract immunity and mucosal homeostasis. Goblet cells could obtain luminal antigens, presenting them to the underlying antigen-presenting cells (APCs) that induces adaptive immune responses. Various immunomodulatory factors can promote the differentiation and maturation of goblet cells, and the secretion of mucin. The abnormal proliferation and differentiation of goblet cells, as well as the deficiency synthesis and secretion of mucins, result in intestinal mucosal barrier dysfunction. This review provides an extensive outline of the signaling pathways that regulate goblet cell proliferation and differentiation and control mucins synthesis and secretion to elucidate how altering these pathways affects goblet functionality. Furthermore, the interaction between mucins and goblet cells in intestinal mucosal immunology is described. Therefore, the contribution of goblet cells and mucus in promoting gut defense and homeostasis is illustrated, while clarifying the regulatory mechanisms involved may allow the development of new therapeutic strategies for intestinal disorders.

Non-Celiac Gluten/Wheat Sensitivity: Clinical Characteristics and Microbiota and Mycobiota Composition by Response to the Gluten Challenge Test

The aims of this observational “proof-of-concept” study were to analyze the clinical/psychological characteristics and gut microbiota/mycobiota composition of individuals with suspected non-celiac gluten/wheat sensitivity (NCGS/WS) according to responses to the double-blind-placebo-controlled (DBPC) crossover gluten challenge test. Fifty individuals with suspected NCGS/WS were subjected to the DBPC challenge test; anthropometric measurements, psychometric questionnaires, and fecal samples were collected. Twenty-seven (54%) participants were gluten responsive (NCGS), and 23 were placebo responsive, with an order effect. NCGS individuals displayed a significantly lower risk of eating disorders and a higher mental health score when compared to placebo-responsive participants, confirmed by multiple logistic regression analyses (OR = 0.87; 95% CI 0.76–0.98, p = 0.021, and OR = 1.30; 95% CI 1.06–1.59, p = 0.009, respectively). Principal coordinate analyses based on microbiota composition showed a separation by the DBPC response (p = 0.039). For Bacteroides (p = 0.05) and Parabacteroides (p = 0.007), the frequency of amplicon sequence variants was lower, and that for Blautia (p = 0.009) and Streptococcus (p = 0.004) was higher in NCGS individuals at multiple regression analyses. No difference in the mycobiota composition was detected between the groups. In conclusion, almost half of the individuals with suspected gluten sensitivity reported symptoms with placebo; they showed lower mental health scores, increased risk for eating disorders, and a different gut microbiota composition.

Implication of Human Bacterial Gut Microbiota on Immune-Mediated and Autoimmune Dermatological Diseases and Their Comorbidities: A Narrative Review

During the last decade, the advent of modern sequencing methods (next generation techniques, NGS) has helped describe the composition of the human gut microbiome, enabling us to understand the main characteristics of a healthy gut microbiome and, conversely, the magnitude of its disease-related changes. This new knowledge has revealed that healthy gut microbiota allow the maintenance of several crucial physiological functions, such as the ability to regulate the innate and adaptive immune systems. Increasing evidence has pointed out a condition of dysbiosis in several autoimmune/immune mediated dermatological conditions and specific gut microbial signatures have also been reported to correlate with clinical and prognostic parameters of such diseases. Based on a literature search of relevant published articles, this review debates the current knowledge and the possible pathogenic implications of bacterial gut microbiota composition assessed through NGS techniques in systemic lupus erythematosus, atopic dermatitis, psoriasis, and alopecia areata. Evidence of a potential role of specific gut microbiota signatures in modulating the clinical course of such diseases and their main comorbidities has been also reviewed.

"Let Food Be Thy Medicine": Gluten and Potential Role in Neurodegeneration

Wheat is a most favored staple food worldwide and its major protein is gluten. It is involved in several gluten dependent diseases and lately was suggested to play a role in non-celiac autoimmune diseases. Its involvement in neurodegenerative conditions was recently suggested but no cause-and-effect relationship were established. The present narrative review expands on various aspects of the gluten-gut-brain axes events, mechanisms and pathways that connect wheat and gluten consumption to neurodegenerative disease. Gluten induced dysbiosis, increased intestinal permeabillity, enteric and systemic side effects, cross-reactive antibodies, and the sequence of homologies between brain antigens and gluten are highlighted. This combination may suggest molecular mimicry, alluding to some autoimmune aspects between gluten and neurodegenerative disease. The proverb of Hippocrates coined in 400 BC, "let food be thy medicine," is critically discussed in the frame of gluten and potential neurodegeneration evolvement.

Butyrate Alleviates Cytokine-Induced Barrier Dysfunction by Modifying Claudin-2 Levels

Simple Summary

The influence of Short-chain fatty acids (SCFAs) on barrier function under pathological conditions has not been assessed, and the regulation of the tight junction (TJ) proteins by SCFAs under pathological conditions has not been fully elucidated. We therefore aimed to evaluate the effect of SCFAs on intestinal barrier function under cytokine-stimulated conditions. Butyrate, but not acetate, propionate, or succinate, ameliorated the tumor necrosis factor-alpha (TNF-α)/interferon-gamma (IFN-γ)-induced decrease in transepithelial electrical resistance (TEER). TNF-α/IFN-γ stimulation significantly increased the protein level of claudin-2 and decreased the level of claudin-3. Butyrate significantly attenuated the upregulation of claudin-2 induced by TNF-α/IFN-γ. Similarly, butyrate blocked the decrease in TEER and the upregulation of claudin-2 induced by interleukin-13, without changing the level of other TJ proteins. Our results suggested that butyrate is the main component of SCFAs to alleviate barrier dysfunction and that claudin-2 is the major target of this SCFA. It is hoped that these results will facilitate the development of treatments for diseases related to intestinal barrier impairment.

Abstract

Gastrointestinal (GI) disorders such as celiac disease and inflammatory bowel disease are attributed to intestinal barrier disruption. Imbalance of cytokines has been reported in the intestinal epithelium of patients with GI disorders. Short-chain fatty acids (SCFAs), derived from the fermentation of dietary fiber in the intestine, have been reported to benefit the intestinal barrier. Accordingly, we evaluated the effect of specific SCFAs on intestinal barrier function under cytokine-stimulated conditions. Caco-2 cells were cultured on insert membranes to generate monolayers, which then were used to investigate the effects of SCFAs. Tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), or interleukin-13 (IL-13) was added to the basolateral side of the membrane while SCFAs were added to the apical side. After a 24 h stimulation, transepithelial electrical resistance (TEER) was measured, and the protein levels of claudin-1, claudin-2, claudin-3, claudin-4, occludin, and zonula occludens-1 (ZO-1) were evaluated by Western blot. Butyrate, but not acetate, propionate, or succinate, ameliorated the TNF-α/IFN-γ-induced decrease in TEER. TNF-α/IFN-γ stimulation significantly increased the protein level of claudin-2 and decreased the level of claudin-3. Butyrate significantly attenuated the upregulation of claudin-2 induced by TNF-α/IFN-γ. Butyrate blocked the decrease in TEER and the upregulation of claudin-2 induced by IL-13 without changing the level of other tight junction proteins. Our results suggested that butyrate is the main component of SCFAs to alleviate barrier dysfunction and that claudin-2 is the major target of this SCFA.

Pediatric Celiac Disease Patients Show Alterations of Dendritic Cell Shape and Actin Rearrangement

Celiac disease (CD) is a frequent intestinal inflammatory disease occurring in genetically susceptible individuals upon gluten ingestion. Recent studies point to a role in CD for genes involved in cell shape, adhesion and actin rearrangements, including a Rho family regulator, Rho GTPase-activating protein 31 (ARHGAP31). In this study, we investigated the morphology and actin cytoskeletons of peripheral monocyte-derived dendritic cells (DCs) from children with CD and controls when in contact with a physiological substrate, fibronectin. DCs were generated from peripheral blood monocytes of pediatric CD patients and controls. After adhesion on fibronectin, DCs showed a higher number of protrusions and a more elongated shape in CD patients compared with controls, as assessed by immunofluorescence actin staining, transmitted light staining and video time-lapse microscopy. These alterations did not depend on active intestinal inflammation associated with gluten consumption and were specific to CD, since they were not found in subjects affected by other intestinal inflammatory conditions. The elongated morphology was not a result of differences in DC activation or maturation status, and did not depend on the human leukocyte antigen (HLA)-DQ2 haplotype. Notably, we found that ARH-GAP31 mRNA levels were decreased while RhoA-GTP activity was increased in CD DCs, pointing to an impairment of the Rho pathway in CD cells. Accordingly, Rho inhibition was able to prevent the cytoskeleton rearrangements leading to the elongated morphology of celiac DCs upon adhesion on fibronectin, confirming the role of this pathway in the observed phenotype. In conclusion, adhesion on fibronectin discriminated CD from the controls' DCs, revealing a gluten-independent CD-specific cellular phenotype related to DC shape and regulated by RhoA activity.

Tight Junctions as a Key for Pathogens Invasion in Intestinal Epithelial Cells

Tight junctions play a major role in maintaining the integrity and impermeability of the intestinal barrier. As such, they act as an ideal target for pathogens to promote their translocation through the intestinal mucosa and invade their host. Different strategies are used by pathogens, aimed at directly destabilizing the junctional network or modulating the different signaling pathways involved in the modulation of these junctions. After a brief presentation of the organization and modulation of tight junctions, we provide the state of the art of the molecular mechanisms leading to permeability breakdown of the gut barrier as a consequence of tight junctions’ attack by pathogens, including bacteria, viruses, fungi, and parasites.

Current and emerging therapies for coeliac disease

Coeliac disease is a common enteropathy that occurs in genetically susceptible individuals in response to the ingestion of gluten proteins present in wheat, rye and barley. Currently, the only available treatment for the condition is a strict, life-long gluten-free diet that, despite being safe and often effective, is associated with several challenges. Due to the high cost, particularly restrictive nature and perception of decreased quality of life associated with the diet, some patients are continuously exposed to gluten, which prevents an adequate disease control. Moreover, a subgroup of patients does not respond to the diet adequately, and healing of the small-bowel mucosa can be incomplete. Thus, there is a need for alternative treatment forms. The increasingly understood pathogenetic process of coeliac disease has enabled the identification of various targets for future therapies. Multiple investigational therapies ranging from tolerogenic to immunological approaches are in the pipeline, and several drug candidates have entered phase II/III clinical trials. This Review gives a broad overview of the different investigative treatment modalities for coeliac disease and summarizes the latest advances in this field.