Advances in understanding the potential therapeutic applications of gut microbiota and probiotic mediated therapies in celiac disease

Celiac Disease: The Importance of Studying the Duodenal Mucosa-Associated Microbiota

There is increasing evidence indicating that changes in both the composition and functionality of the intestinal microbiome are closely associated with the development of several chronic inflammatory diseases, with celiac disease (CeD) being particularly noteworthy. Thanks to the advent of culture-independent methodologies, the ability to identify and quantify the diverse microbial communities residing within the human body has been significantly improved. However, in the context of CeD, a notable challenge lies in characterizing the specific microbiota present on the mucosal surfaces of the intestine, rather than relying solely on fecal samples, which may not fully represent the relevant microbial populations. Currently, our comprehension of the composition and functional importance of mucosa-associated microbiota (MAM) in CeD remains an ongoing field of research because the limited number of available studies have reported few and sometimes contradictory results. MAM plays a crucial role in the development and progression of CeD, potentially acting as both a trigger and modulator of the immune response within the intestinal mucosa, given its proximity to the epithelial cells and direct interaction. According to this background, this review aims to consolidate the existing literature specifically focused on MAM in CeD. By elucidating the complex interplay between the host immune system and the gut microbiota, we aim to pave the way for new interventions based on novel therapeutic targets and diagnostic biomarkers for MAM in CeD.

Reducing Immunoreactivity of Gluten Peptides by Probiotic Lactic Acid Bacteria for Dietary Management of Gluten-Related Diseases

Immunoreactive gluten peptides that are not digested by peptidases produced by humans can trigger celiac disease, allergy and non-celiac gluten hypersensitivity. The aim of this study was to evaluate the ability of selected probiotic strains to hydrolyze immunoreactive gliadin peptides and to identify peptidase-encoding genes in the genomes of the most efficient strains. Residual gliadin immunoreactivity was measured after one- or two-step hydrolysis using commercial enzymes and bacterial peptidase preparations by G12 and R5 immunoenzymatic assays. Peptidase preparations from Lacticaseibacillus casei LC130, Lacticaseibacillus paracasei LPC100 and Streptococcus thermophilus ST250 strains significantly reduced the immunoreactivity of gliadin peptides, including 33-mer, and this effect was markedly higher when a mixture of these strains was used. In silico genome analyses of L. casei LC130 and L. paracasei LPC100 revealed the presence of genes encoding peptidases with the potential to hydrolyze bonds in proline-rich peptides. This suggests that L. casei LC130, L. paracasei LPC100 and S. thermophilus ST250, especially when used as a mixture, have the ability to hydrolyze immunoreactive gliadin peptides and could be administered to patients on a restricted gluten-free diet to help treat gluten-related diseases.

Efficacy of probiotics supplementation in amelioration of celiac disease symptoms and enhancement of immune system

Patients with celiac disease (CD) have a mucosal layer that is unable to regulate the gut microbiota, leaving the host vulnerable to dangerous infections and antigens. When compared to healthy people, this dysbiosis is marked by a decrease in intra- and intergeneric biodiversity, which demonstrates an imbalance between helpful bacteria and possibly harmful or proinflammatory species. The early gut microbiota is influenced by the genotype of newborns with the HLA-DQ2 haplotypes, and this may modify how gluten is handled in the intestinal lumen, polarize innate or adaptive immune responses, and result in glutensensitive enteropathy. The outcome of gluten digestion can vary depending on the composition of the intestinal gut bacteria and the partial conversion of gluten into peptides larger than ten amino acids in the small intestines, which can be immunogenic. In the small intestine, 114 different bacterial strains belonging to 32 different species have 27 of them exhibiting peptidolytic activity. Thus, the individual risk of developing a gluten-related illness is further influenced by microbial composition and gluten degrading capacity. The conclusion that lactobacilli and Bifidobacterium spp. may be used as a probiotic supplement in CD patients is based on their shared possession of the most extensive peptidolytic and proteolytic activity thought to be engaged in the breakdown of gluten among all potential bacterial genera present in the gut microbiota. In children with CD autoimmunity, daily oral dose of Lactobacillus. plantarum HEAL9 and Lactobacillus. paracasei 8700:2 was found to modify the peripheral immune response. Bifidobacterium. breve strains have demonstrated a beneficial effect on reducing pro-inflammatory cytokine TNF- production in CD children on gluten-free diets.

The effects of probiotics on gastrointestinal symptoms and microbiota in patients with celiac disease: a systematic review and meta-analysis on clinical trials

Gluten-free diet (GFD) is the most effective method to manage celiac disease (CD). Many patients do not reach the complete symptom alleviation, even by strict GFD. Recent studies have reported inconsistent results regarding the beneficial benefits of taking probiotics. Therefore, we aimed to evaluate the effects of probiotics on gastrointestinal (GI) symptoms and the possible underlying causes in CD and celiac disease autoimmunity (CDA) patients. Databases, including PubMed, Scopus, Embase, Web of Science and Google Scholar, were searched for clinical trials published until July 2022 about assessing the effects of probiotics or synbiotics on CD or CDA patients. We collected data on GI symptoms, CD markers, inflammatory and immune responses, adverse events, and gut microbiota. A random effect meta-analysis was used to estimate the pooled standardized mean difference (SMD) and confidence interval (CI). We screened 7234 articles, of which 14 were included in the qualitative analysis and 5 in the quantitative analysis. Probiotics might alleviate GI symptoms, especially in the highly symptomatic patients, and improve immune response in CD and CDA patients. Results of the meta-analysis showed that probiotics increased the abundance of Bifidobacterium (SMD: 0.72, 95%CI (0.13, 1.30) and Lactobacillus (SMD: 0.49, 95%CI (0.18, 0.80) as compared with placebo. Probiotics did not increase the adverse events compared to the placebo. Probiotics might alleviate GI symptoms and immune response and improve dysbiosis in CD and CDA patients. However, high-quality clinical trials are needed to increase the level of evidence. Also, the most suitable combination of probiotics is yet to find.

Gut Microbiota Alteration and Its Modulation with Probiotics in Celiac Disease

Celiac disease (CD) is a chronic inflammation of the small intestine triggered by gluten ingestion in genetically predisposed people. Recent literature studies highlight the possible role of the gut microbiota in the pathogenesis of this disease. The gut microbiota is a complex community of microorganisms that can interact with the innate and adaptative immune systems. A condition of dysbiosis, which refers to an alteration in the composition and function of the human gut microbiota, can lead to a dysregulated immune response. This condition may contribute to triggering gluten intolerance, favoring the development and/or progression of CD in genetically susceptible patients. Interestingly, studies on children and adults with CD showed a different microbiome profile in fecal samples, with a different degree of "activity" for the disease. From this point of view, our review aimed to collect and discuss modern evidence about the alteration of the gut microbiota and its modulation with probiotics, with possible future indications in the management of patients affected by CD.

Interaction between Gut Microbiota and Celiac Disease: From Pathogenesis to Treatment

Celiac disease (CD) is a common systemic disorder that results from an abnormal response of human immunity to gluten intake, affecting the small intestine. In individuals who carry a genetic susceptibility, CD is triggered by environmental factors, including viral infections and dysbiosis of the gut microbiota. The gut microbiome is essential in controlling the immune system, and recent findings indicate that changes in the gut microbiome may contribute to various chronic immune disorders, such as CD through mechanisms that still require further exploration. Some bacteria exhibit epitopes that mimic gliadin and may enhance an immune response in the host. Other bacteria, including Pseudomonas aeruginosa, may work in conjunction with gluten to trigger and escalate intestinal inflammation. The microbiota may also directly influence antigen development through the production of immunogenic or tolerogenic gluten peptides or directly influence intestinal permeability through the release of zonulin. Finally, the gut microbiome can impact intestinal inflammation by generating proinflammatory or anti-inflammatory cytokines and metabolites. It is crucial to consider the impact of genetic factors (specifically, HLA-DQ haplotypes), perinatal elements such as birth mode, type of infant feeding, and antibiotic and infection exposure on the composition of the early intestinal microbiome. According to the available studies, the gut microbiome alterations associated with CD tend to exhibit a decreased presence of beneficial bacteria, including some anti-inflammatory Bifidobacterium species. However, some controversy remains as some reports have found no significant differences between the gut microbiomes of individuals with and without CD. A better understanding of the gut microbiome’s role in the development of CD would greatly benefit both prevention and treatment efforts, especially in complicated or treatment-resistant cases. Here, we have attempted to summarize the available evidence on the relationship between the gut microbiota and CD, with a particular focus on potential therapeutic targets.

Risk of obesity during a gluten-free diet in pediatric and adult patients with celiac disease: a systematic review with meta-analysis

CONTEXT

Obesity is a significant risk factor for many pathological conditions. Whether a gluten-free diet (GFD) is a risk factor for overweight or obesity remains controversial.

OBJECTIVE

The primary aim of this study was to assess the prevalence of body mass index (BMI) categories at disease presentation and the variation in BMI category from underweight/normal to overweight/obese and vice versa during a GFD.

DATA SOURCES

PubMed, Scopus, and Web of Science databases were searched through February 2021 for retrospective, cross-sectional, and prospective studies reporting BMI categories at disease diagnosis and during a GFD.

DATA EXTRACTION

Data were extracted by 2 reviewers independently. Disagreements were resolved by consensus; a third reviewer was consulted, if necessary. Risk of bias was assessed with the Cochrane ROBINS-I tool.

DATA ANALYSIS

Subgroup analysis based on age (pediatric/adult patients), study design (prospective, cross-sectional, retrospective), and duration of GFD was performed.. Forty-five studies were selected (7959 patients with celiac disease and 20 524 healthy controls). The mean BMI of celiac patients at presentation was significantly lower than that of controls (P < 0.001). During a GFD, the mean BMI increased significantly (mean difference = 1.14 kg/m2 [95%CI, 0.68-1.60 kg/m2]; I2 = 82.8%; P < 0.001), but only 9% of patients (95%CI, 7%-12%; I2 = 80.0%) changed from the underweight/normal BMI category to the overweight/obese category, while 20% (95%CI, 11%-29%; I2 = 85.8%) moved into a lower BMI category.

CONCLUSION

Most celiac patients had a normal BMI at presentation, although the mean BMI was significantly lower than that of controls. A GFD does not increase the risk of becoming overweight/obese, especially in children. The quality of several studies was suboptimal, with moderate or high overall risk of bias and heterogeneity.

Probiotics and gastrointestinal diseases

During the past decades, scientists have discovered the intimate role of the gut microbiome in human health, and since then, several papers have been published to investigate if the use of biotics (probiotics, prebiotics, synbiotics, and postbiotics) may have a beneficial impact on human health both in treatment and prevention. We now ask ourselves whether we have reached the finish line or just a new starting point, as the evidence supporting the use of biotics in several conditions still needs a lot of work. Many questions remain unanswered today because the evidence differs depending on the indication, used strain, and amount and duration of administration. Herein we will summarize the evidence on probiotics in some gastrointestinal diseases such as infantile colic, functional abdominal pain disorders, celiac disease, acute gastroenteritis, inflammatory bowel disease, and Helicobacter pylori infection.

Characteristics of gut microbiota and fecal metabolomes in patients with celiac disease in Northwest China

Celiac disease (CD) is an autoimmune small bowel disease. The pattern of gut microbiota is closely related to dietary habits, genetic background, and geographical factors. There is a lack of research on CD-related gut microbiota in China. This study aimed to use 16S rDNA sequencing and metabolomics to analyze the fecal microbial composition and metabolome characteristics in patients diagnosed with CD in Northwest China, and to screen potential biomarkers that could be used for its diagnosis. A significant difference in the gut microbiota composition was observed between the CD and healthy controls groups. At the genus level, the abundance of Streptococcus, Lactobacillus, Veillonella, and Allisonella communities in the CD group were increased (Q < 0.05). Furthermore, the abundance of Ruminococcus, Faecalibacterium, Blautia, Gemmiger, and Anaerostipes community in this group were decreased (Q < 0.05). A total of 222 different fecal metabolites were identified in the two groups, suggesting that CD patients have a one-carbon metabolism defect. Four species of bacteria and six metabolites were selected as potential biomarkers using a random forest model. Correlation analysis showed that changes in the gut microbiota were significantly correlated with changes in fecal metabolite levels. In conclusion, the patterns of distribution of gut microbiota and metabolomics in patients with CD in Northwest China were found to be unique to these individuals. This has opened up a new way to explore potential beneficial effects of supplementing specific nutrients and potential diagnostic and therapeutic targets in the future.

Investigation of Host-Microbe-Parasite Interactions in an In Vitro 3D Model of the Vertebrate Gut

In vitro models of the gut-microbiome axis are in high demand. Conventionally, intestinal monolayers grown on Transwell setups are used to test the effects of commensals/pathogens on the barrier integrity, both under homeostatic and pathophysiological conditions. While such models remain valuable for deepening the understanding of host-microbe interactions, often, they lack key biological components that mediate this intricate crosstalk. Here, a 3D in vitro model of the vertebrate intestinal epithelium, interfaced with immune cells surviving in culture for over 3 weeks, is developed and applied to proof-of-concept studies of host-microbe interactions. More specifically, the establishment of stable host-microbe cocultures is described and functional and morphological changes in the intestinal barrier induced by the presence of commensal bacteria are shown. Finally, evidence is provided that the 3D vertebrate gut models can be used as platforms to test host-microbe-parasite interactions. Exposure of gut-immune-bacteria cocultures to helminth "excretory/secretory products" induces in vivo-like up-/down-regulation of certain cytokines. These findings support the robustness of the modular in vitro cell systems for investigating the dynamics of host-microbe crosstalk and pave the way toward new approaches for systems biology studies of pathogens that cannot be maintained in vitro, including parasitic helminths.

How Metabolomics Provides Novel Insights on Celiac Disease and Gluten-Free Diet: A Narrative Review

Celiac disease (CD) is an inflammatory autoimmune disorder triggered by the ingestion of gluten from wheat and other cereals. Nowadays, its positive diagnosis is based on invasive approaches such as the histological examination of intestinal biopsies and positive serology screening of antibodies. After proven diagnosis, the only admissible treatment for CD individuals is strict life-long adherence to gluten-free diet (GFD), although it is not a conclusive therapy. Acting by different mechanisms and with different etiologies, both CD and GFD have a great impact on gut microbiota that result in a different taxa composition. Altered production of specific metabolites reflects these microbiota changes. In this light, the currently available literature reports some suggestions about the possible use of specific metabolites, detected by meta-omics analyses, as potential biomarkers for a CD non-invasive diagnosis. To highlight insights about metabolomics application in CD study, we conducted a narrative dissertation of selected original articles published in the last decade. By applying a systematic search, it clearly emerged how the metabolomic signature appears to be contradictory, as well as poorly investigated.

Lack of Effect of Gluten Challenge on Fecal Microbiome in Patients With Celiac Disease and Non-Celiac Gluten Sensitivity

INTRODUCTION

Celiac disease (CD) may be associated with gut microbial dysbiosis. Whether discrete gluten exposure in subjects with well-controlled disease on a gluten-free diet impacts the gut microbiome is unknown and may have implications for understanding disease activity and symptoms. We conducted a prospective study to evaluate the impact of gluten exposure on the gut microbiome in patients with CD and nonceliac gluten sensitivity (NCGS).

METHODS

Subjects with CD (n = 9) and NCGS (n = 8) previously on a gluten-free diet were administered a 14-day gluten challenge (5 g of gluten per day) and compared with controls (n = 8) on a usual gluten-containing diet. Stool was collected for fecal microbiome analysis using 16S rRNA gene and metagenomic sequencing before, during, and after the gluten challenge. Symptoms were assessed using 2 validated clinical scales.

RESULTS

Among subjects with CD and NCGS, there were no significant fecal microbial changes in response to gluten challenge. Gut microbiome composition differed among controls, subjects with CD, and subjects with NCGS at baseline, and these differences persisted despite gluten exposure. Gastrointestinal and general health symptoms reported by subjects with CD and NCGS were worst in the middle of gluten challenge and lessened by its end, with no consistent associations with gut microbiome composition.

DISCUSSION

Pre-existing fecal microbiome diversity was unaffected by gluten challenge in adult subjects with CD and NCGS. These findings suggest that current microbiome status is unrelated to current disease activity and disease severity.

WHOLE-meal ancient wheat-based diet: Effect on metabolic parameters and microbiota

BACKGROUND & AIMS

Ancient wheat varieties are considered to be healthier than modern ones, but the data are not univocal. We investigated changes in hematochemical parameters and evaluated microbiota data before and after a set period on a diet containing a whole-meal ancient wheat mix.

PATIENTS AND METHODS

29 cloistered nuns were recruited. The study comprised two consecutive 30-day periods; during the first one (T1), the nuns received wheat-based foods produced with refined "modern" flour ("Simeto"); during the second one (T2) received wheat-based foods produced with an unrefined flour mix composed of "ancient" cultivars. At entry to the study (T0) and at the end of T1 and T2 hematochemical parameters and fecal microbiota and metabolome were evaluated.

RESULTS

At the end of T2, there was a significant reduction in serum iron, ferritin, creatinine, sodium, potassium, magnesium, total cholesterol, LDL- and HDL-cholesterol and folic acid. Furthermore, increased the abundance of cultivable enterococci, lactic acid bacteria and total anaerobes. The ability of the gut microbiome to metabolize carbohydrates increased after the period of diet containing ancient grain products. Several volatile organic compounds increased after the one month on the diet enriched with ancient grain products.

CONCLUSIONS

Our data showed the beneficial effects deriving from a diet including ancient whole-meal/unrefined wheat flours.

New Insights into Non-Dietary Treatment in Celiac Disease: Emerging Therapeutic Options

To date, the only treatment for celiac disease (CD) consists of a strict lifelong gluten-free diet (GFD), which has numerous limitations in patients with CD. For this reason, dietary transgressions are frequent, implying intestinal damage and possible long-term complications. There is an unquestionable need for non-dietary alternatives to avoid damage by involuntary contamination or voluntary dietary transgressions. In recent years, different therapies and treatments for CD have been developed and studied based on the degradation of gluten in the intestinal lumen, regulation of the immune response, modulation of intestinal permeability, and induction of immunological tolerance. In this review, therapeutic lines for CD are evaluated with special emphasis on phase III and II clinical trials, some of which have promising results.

In Vitro Selection of Probiotics, Prebiotics, and Antioxidants to Develop an Innovative Synbiotic (NatuREN G) and Testing Its Effect in Reducing Uremic Toxins in Fecal Batches from CKD Patients

We aimed to develop an innovative synbiotic formulation for use in reducing dysbiosis, uremic toxins (e.g., p-cresol and indoxyl sulfate), and, consequently, the pathognomonic features of patients with chronic kidney disease (CKD). Twenty-five probiotic strains, belonging to lactobacilli and Bifidobacterium, were tested for their ability to grow in co-culture with different vegetable (pomegranate, tomato, and grapes) sources of antioxidants and prebiotics (inulin, fructo-oligosaccharides, and β-glucans). Probiotics were selected based on the acidification rates and viable cell counts. Inulin and fructo-oligosaccharides reported the best prebiotic activity, while a pomegranate seed extract was initially chosen as antioxidant source. The investigation was also conducted in fecal batches from healthy and CKD subjects, on which metabolomic analyses (profiling volatile organic compounds and total free amino acids) were conducted. Two out of twenty-five probiotics were finally selected. After the stability tests, the selective innovative synbiotic formulation (named NatuREN G) comprised Bifidobacterium animalis BLC1, Lacticaseibacillus casei LC4P1, fructo-oligosaccharides, inulin, quercetin, resveratrol, and proanthocyanidins. Finally, NatuREN G was evaluated on fecal batches collected from CKD in which modified the viable cell densities of some cultivable bacterial patterns, increased the concentration of acetic acid and decane, while reduced the concentration of nonanoic acid, dimethyl trisulfide, and indoxyl sulfate.

Probiotics and gut health

BACKGROUND

Gut microbiota is a complex ecosystem of bacteria, viruses, archea, protozoa and yeasts in our intestine. It has several functions maintaining human body equilibrium. Microbial " dysbiosis " can be responsible for several gastrointestinal diseases.

METHODS

to build a narrative review we performed a Pubmed, Medline, EMBASE search for English language papers, reviews, meta-analyses, case series, and randomized controlled trials (RCTs) by keywords and their associations: gut microbiota, dysbiosis, gastrointestinal diseases, probiotics.

RESULTS

gut microbiota is altered in several gastrointestinal diseases with very different pathophysiology. They range from multi-factorial diseases such as irritable bowel syndrome (IBS), non-alcoholic fatty liver disease (NAFLD) and gastric and colorectal cancers, immunemediated such as celiac disease, inflammatory bowel diseases (IBD), antibioticrelated such as Clostridium Difficile infection (CDI). Microbial dysbiosis re-modulation by probiotics is feasible and safe in some of them.

CONCLUSIONS

gut microbial dysbiosis is statistically associated with several gastro-intestinal diseases, affecting their pathophysiology. Its reverse by probiotics has some promising evidences of efficacy.

Selection of Gut-Resistant Bacteria and Construction of Microbial Consortia for Improving Gluten Digestion under Simulated Gastrointestinal Conditions

This work aimed to define the microbial consortia that are able to digest gluten into non-toxic and non-immunogenic peptides in the human gastrointestinal tract. Methods: 131 out of 504 tested Bacillus and lactic acid bacteria, specifically Bacillus (64), lactobacilli (63), Pediococcus (1), and Weissella (3), showed strong gastrointestinal resistance and were selected for their PepN, PepI, PepX, PepO, and PepP activities toward synthetic substrates. Based on multivariate analysis, 24 strains were clearly distinct from the other tested strains based on having the highest enzymatic activities. As estimated by RP-HPLC and nano-ESI–MS/MS, 6 cytoplasmic extracts out of 24 selected strains showed the ability to hydrolyze immunogenic epitopes, specifically 57–68 of α9-gliadin, 62–75 of A-gliadin, 134–153 of γ-gliadin, and 57–89 (33-mer) of α2-gliadin. Live and lysed cells of selected strains were combined into different microbial consortia for hydrolyzing gluten under gastrointestinal conditions. Commercial proteolytic enzymes (Aspergillusoryzae E1, Aspergillusniger E2, Bacillussubtilis Veron HPP, and Veron PS proteases) were also added to each microbial consortium. Consortium activity was evaluated by ELISA tests, RP-HPLC-nano-ESI–MS/MS, and duodenal explants from celiac disease patients. Results: two microbial consortia (Consortium 4: Lactiplantibacillus (Lp.) plantarum DSM33363 and DSM33364, Lacticaseibacillus (Lc.) paracasei DSM33373, Bacillussubtilis DSM33298, and Bacilluspumilus DSM33301; and Consortium 16: Lp. plantarum DSM33363 and DSM33364, Lc. paracasei DSM33373, Limosilactobacillusreuteri DSM33374, Bacillusmegaterium DSM33300, B.pumilus DSM33297 and DSM33355), containing commercial enzymes, were able to hydrolyze gluten to non-toxic and non-immunogenic peptides under gastrointestinal conditions. Conclusions: the results of this study provide evidence that selected microbial consortia could potentially improve the digestion of gluten in gluten-sensitive patients by hydrolyzing the immunogenic peptides during gastrointestinal digestion.

The use of peripheral blood mononuclear cells in celiac disease diagnosis and treatment

Introduction: Celiac disease is characterized by an abnormal immune activation driven by the ingestion of gluten from wheat, barley, and rye. Gluten-specific CD4⁺ T cells play an important role in disease pathogenesis and are detectable among peripheral blood mononuclear cells (PBMCs). Areas covered: This review summarizes the use of celiac disease patient PBMCs in clinical applications focusing on their exploitation in the development of diagnostic approaches and novel drugs to replace or complement gluten-free diet. Expert opinion: The most used PBMC-based methods applied in celiac disease research include ELISpot and HLA-DQ:gluten tetramer technology. ELISpot has been utilized particularly in research aiming to develop a celiac disease vaccine and in studies addressing the toxicity of different grains in celiac disease. HLA-DQ:gluten tetramer technology on the other hand initially focused on improving current diagnostics but in combination with additional markers it is also a useful outcome measure in clinical trials to monitor the efficacy of drug candidates. In addition, the technology serves well in the more detailed characterization of celiac disease-specific T cells, thereby possibly revealing novel therapeutic targets. Future studies may also reveal clinical applications for PBMC microRNAs and/or dendritic cells or monocytes present among PBMCs.

Anti-Inflammatory and Immunomodulatory Effects of Probiotics in Gut Inflammation: A Door to the Body

Hosting millions of microorganisms, the digestive tract is the primary and most important part of bacterial colonization. On one side, in cases of opportunistic invasion, the abundant bacterial population inside intestinal tissues may face potential health problems such as inflammation and infections. Therefore, the immune system has evolved to sustain the host-microbiota symbiotic relationship. On the other hand, to maintain host immune homeostasis, the intestinal microflora often exerts an immunoregulatory function that cannot be ignored. A field of great interest is the association of either microbiota or probiotics with the immune system concerning clinical uses. This microbial community regulates some of the host's metabolic and physiological functions and drives early-life immune system maturation, contributing to their homeostasis throughout life. Changes in gut microbiota can occur through modification in function, composition (dysbiosis), or microbiota-host interplays. Studies on animals and humans show that probiotics can have a pivotal effect on the modulation of immune and inflammatory mechanisms; however, the precise mechanisms have not yet been well defined. Diet, age, BMI (body mass index), medications, and stress may confound the benefits of probiotic intake. In addition to host gut functions (permeability and physiology), all these agents have profound implications for the gut microbiome composition. The use of probiotics could improve the gut microbial population, increase mucus-secretion, and prevent the destruction of tight junction proteins by decreasing the number of lipopolysaccharides (LPSs). When LPS binds endothelial cells to toll-like receptors (TLR 2, 4), dendritic cells and macrophage cells are activated, and inflammatory markers are increased. Furthermore, a decrease in gut dysbiosis and intestinal leakage after probiotic therapy may minimize the development of inflammatory biomarkers and blunt unnecessary activation of the immune system. In turn, probiotics improve the differentiation of T-cells against Th2 and development of Th2 cytokines such as IL-4 and IL-10. The present narrative review explores the interactions between gut microflora/probiotics and the immune system starting from the general perspective of a biological plausibility to get to the in vitro and in vivo demonstrations of a probiotic-based approach up to the possible uses for novel therapeutic strategies.

Ketoanalogs' Effects on Intestinal Microbiota Modulation and Uremic Toxins Serum Levels in Chronic Kidney Disease (Medika2 Study)

Nutritional therapy (NT) is a therapeutic option in the conservative treatment of chronic kidney disease (CKD) patients to delay the start of dialysis. The aim of this study was to evaluate the specific effect of ketoanalogs (KA)-supplemented diets for gut microbiota modulation. In a previous study we observed that the Mediterranean diet (MD) and a KA-supplemented very-low-protein diet (VLPD) modulated beneficially gut microbiota, reducing indoxyl- and p-cresyl-sulfate (IS, PCS) serum levels, and ameliorating the intestinal permeability in CKD patients. In the current study, we added a third diet regimen consisting of KA-supplemented MD. Forty-three patients with CKD grades 3B–4 continuing the crossover clinical trial were assigned to six months of KA-supplemented MD (MD + KA). Compared to MD, KA-supplementation in MD + KA determined (i) a decrease of Clostridiaceae, Methanobacteriaceae, Prevotellaceae, and Lactobacillaceae while Bacteroidaceae and Lachnospiraceae increased; (ii) a reduction of total and free IS and PCS compared to a free diet (FD)—more than the MD, but not as effectively as the VLPD. These results further clarify the driving role of urea levels in regulating gut integrity status and demonstrating that the reduction of azotemia produced by KA-supplemented VLPD was more effective than KA-supplemented MD in gut microbiota modulation mainly due to the effect of the drastic reduction of protein intake rather than the effect of KA.

Immunopathology of Type 1 Diabetes and Immunomodulatory Effects of Stem Cells: A Narrative Review of the Literature

Type 1 Diabetes (T1D) is a complex autoimmune disorder which occurs as a result of an intricate series of pathologic interactions between pancreatic β-cells and a wide range of components of both the innate and the adaptive immune systems. Stem-cell therapy, a recently-emerged potentially therapeutic option for curative treatment of diabetes, is demonstrated to cause significant alternations to both different immune cells such as macrophages, natural killer (NK) cells, dendritic cells, T cells, and B cells and non-cellular elements including serum cytokines and different components of the complement system. Although there exists overwhelming evidence indicating that the documented therapeutic effects of stem cells on patients with T1D is primarily due to their potential for immune regulation rather than pancreatic tissue regeneration, to date, the precise underlying mechanisms remain obscure. On the other hand, immune-mediated rejection of stem cells remains one of the main obstacles to regenerative medicine. Moreover, the consequences of efferocytosis of stem-cells by the recipients' lung-resident macrophages have recently emerged as a responsible mechanism for some immune-mediated therapeutic effects of stem-cells. This review focuses on the nature of the interactions amongst different compartments of the immune systems which are involved in the pathogenesis of T1D and provides explanation as to how stem cell-based interventions can influence immune system and maintain the physiologic equilibrium.

Molecular Biomarkers for Celiac Disease: Past, Present and Future

Celiac disease (CeD) is a complex immune-mediated disorder that is triggered by dietary gluten in genetically predisposed individuals. CeD is characterized by inflammation and villous atrophy of the small intestine, which can lead to gastrointestinal complaints, malnutrition, and malignancies. Currently, diagnosis of CeD relies on serology (antibodies against transglutaminase and endomysium) and small-intestinal biopsies. Since small-intestinal biopsies require invasive upper-endoscopy, and serology cannot predict CeD in an early stage or be used for monitoring disease after initiation of a gluten-free diet, the search for non-invasive biomarkers is ongoing. Here, we summarize current and up-and-coming non-invasive biomarkers that may be able to predict, diagnose, and monitor the progression of CeD. We further discuss how current and emerging techniques, such as (single-cell) transcriptomics and genomics, can be used to uncover the pathophysiology of CeD and identify non-invasive biomarkers.