Novel players in coeliac disease pathogenesis: role of the gut microbiota

Microbial transglutaminase: A new potential player in celiac disease

Microbial transglutaminase is heavily used in the food processing industries to improve food qualities. Being a protein's glue, by cross-linking it creates neoepitope complexes that are immunogenic and potentially pathogenic in celiac disease. Despite low sequence identity, it imitates functionally its family member, the endogenous tissue transglutaminase, which is the autoantigen of celiac disease. The present comprehensive review highlights the enzyme characteristics, endogenous and exogenous intestinal sources, its cross-talks with gluten and gliadin, its immunogenicity and potential pathogenicity and risks for the gluten induced conditions. If substantiated, it might represent a new environmental inducer of celiac disease. The present findings might affect nutritional product labeling, processed food additive policies and consumer health education.

Probiotics in Celiac Disease

Recently, the interest in the human microbiome and its interplay with the host has exploded and provided new insights on its role in conferring host protection and regulating host physiology, including the correct development of immunity. However, in the presence of microbial imbalance and particular genetic settings, the microbiome may contribute to the dysfunction of host metabolism and physiology, leading to pathogenesis and/or the progression of several diseases. Celiac disease (CD) is a chronic autoimmune enteropathy triggered by dietary gluten exposure in genetically predisposed individuals. Despite ascertaining that gluten is the trigger in CD, evidence has indicated that intestinal microbiota is somehow involved in the pathogenesis, progression, and clinical presentation of CD. Indeed, several studies have reported imbalances in the intestinal microbiota of patients with CD that are mainly characterized by an increased abundance of Bacteroides spp. and a decrease in Bifidobacterium spp. The evidence that some of these microbial imbalances still persist in spite of a strict gluten-free diet and that celiac patients suffering from persistent gastrointestinal symptoms have a desert gut microbiota composition further support its close link with CD. All of this evidence gives rise to the hypothesis that probiotics might play a role in this condition. In this review, we describe the recent scientific evidences linking the gut microbiota in CD, starting from the possible role of microbes in CD pathogenesis, the attempt to define a microbial signature of disease, the effect of a gluten-free diet and host genetic assets regarding microbial composition to end in the exploration of the proof of concept of probiotic use in animal models to the most recent clinical application of selected probiotic strains.

First Insights into the Gut Microbiota of Mexican Patients with Celiac Disease and Non-Celiac Gluten Sensitivity

Gluten-related disorders (GRDs) are common chronic enteropathies and increasing evidence suggests an involvement of the gut microbiota. We examined the gut microbiota in Mexican people afflicted with GRDs. Ultra-high-throughput 16S marker sequencing was used to deeply describe the duodenal and fecal microbiota of patients with celiac disease (CD, n = 6), non-celiac gluten sensitivity (NCGS, n = 12), and healthy subjects (n = 12) from our local area. Additionally, we also investigated the changes in gut microbiota after four weeks on a gluten-free diet (GFD) in a subset of patients from whom paired samples were available. Despite a high inter-individual variability, significant differences in various microbial populations were identified. The linear discriminant analysis (LDA) effect size (LEfSe) method revealed that the genus Actinobacillus and the family Ruminococcaceae were higher in the duodenal and fecal microbiota of NCGS patients, respectively, while Novispirillum was higher in the duodenum of CD patients (p < 0.05, LDA score > 3.5). Interestingly, paired samples from NCGS patients showed a significant difference in duodenal Pseudomonas between the baseline period (median: 1.3%; min/max: 0.47⁻6.8%) and the period after four weeks on GFD (14.8%; 2.3⁻38.5%, p < 0.01, Wilcoxon signed-rank test). These results encourage more research on GRDs in México.

Commensal microbiota induces colonic barrier structure and functions that contribute to homeostasis

The intestinal barrier encompasses structural, permeability and immune aspects of the gut mucosa that, when disrupted, may contribute to chronic inflammation. Although gnotobiotic studies have demonstrated the effects of microbiota on mucosal and systemic immunity, as well as intestinal barrier architecture and innate immune characteristics, its impact on barrier function remains unclear. We compared germ-free and conventional mice, as well as mice colonized with human fecal microbiota that were followed for 21 days post-colonization. Colonic barrier structure was investigated by immunohistochemistry, molecular and electron microscopy techniques. Permeability was assessed in colon tissue by Ussing chambers, and by serum LPS and MDP detection using TLR4- and NOD2-NFκB reporter assays. Microbiota profile was determined by Illumina 16S rRNA gene sequencing. Low dose dextran sodium sulfate was administered to assess microbiota-induced barrier changes on resistance to colonic injury. Permeability to paracellular probes and mucus layer structure resembled that of conventional mice by day 7 post-colonization, coinciding with reduced claudin-1 expression and transient IL-18 production by intestinal epithelial cells. These post-colonization adaptations were associated with decreased systemic bacterial antigen exposure and reduced susceptibility to intestinal injury. In conclusion, commensal colonization promotes physiological barrier structural and functional adaptations that contribute to intestinal homeostasis.

Celiac Disease Autoimmunity

Celiac disease is an autoimmune condition triggered by the ingestion of gluten, the protein fraction of wheat, barley and rye. It is not simply an intestinal disease; it is multifactorial caused by many different genetic factors acting together with non-genetic causes. Similar to other autoimmune diseases, celiac disease is a polygenic disorder for which the major histocompatibility complex locus is the most important genetic factor, and is the result of an immune response to self-antigens leading to tissue destruction and the autoantibodies production. Celiac disease exemplifies how an illness can have autoimmune-like features having to be driven by exogenous antigen and how can be reasonably considered as a model of organ-specific autoimmunity.

Akkermansia muciniphila in the Human Gastrointestinal Tract: When, Where, and How?

Akkermansia muciniphila is a mucin-degrading bacterium of the phylum Verrucomicrobia. Its abundance in the human intestinal tract is inversely correlated to several disease states. A. muciniphila resides in the mucus layer of the large intestine, where it is involved in maintaining intestinal integrity. We explore the presence of Akkermansia-like spp. based on its 16S rRNA sequence and metagenomic signatures in the human body so as to understand its colonization pattern in time and space. A. muciniphila signatures were detected in colonic samples as early as a few weeks after birth and likely could be maintained throughout life. The sites where Akkermansia-like sequences (including Verrucomicrobia phylum and/or Akkermansia spp. sequences found in the literature) were detected apart from the colon included human milk, the oral cavity, the pancreas, the biliary system, the small intestine, and the appendix. The function of Akkermansia-like spp. in these sites may differ from that in the mucosal layer of the colon. A. muciniphila present in the appendix or in human milk could play a role in the re-colonization of the colon or breast-fed infants, respectively. In conclusion, even though A. muciniphila is most abundantly present in the colon, the presence of Akkermansia-like spp. along the digestive tract indicates that this bacterium might have more functions than those currently known.

Celiac Disease and Liver Disorders: From Putative Pathogenesis to Clinical Implications

Immunologically mediated liver diseases belong to the common extraintestinal manifestations of celiac disease. We have reviewed the current literature that addresses the association between celiac disease and liver disorders. We searched relevant articles on MEDLINE/PubMed up to 15 June 2018. The objective of the article is to provide a comprehensive and up-to-date review on the latest hypotheses explaining the pathogenetic relationship between celiac disease and liver injury. Besides the involvement of gut–liver axis, tissue transglutaminase antibodies, and impairment of intestinal barrier, we integrate the latest achievements made in elucidation of the role of gut microbiota in celiac disease and liver disorders, that has not yet been sufficiently discussed in the literature in this context. The further objective is to provide a complete clinical overview on the types of liver diseases frequently found in celiac disease. In conclusion, the review highlights the clinical implication, recommend a rational approach for managing elevated transaminases in celiac patients, and underscore the importance of screening for celiac disease in patients with associated liver disease.

Effects of long-term Bacillus subtilis CGMCC 1.921 supplementation on performance, egg quality, and fecal and cecal microbiota of laying hens

This study evaluated the effects of long-term Bacillus subtilis CGMCC 1.921 supplementation on the performance, egg quality, and fecal/cecal microbiota of laying hens. A total of 360 28-week-old Hy-Line Brown laying hens were randomly allocated into 5 treatments with 6 replicates of 12 birds each for 24 weeks. The experimental treatments included a basal diet without additions (Con) and the basal diet supplemented with 1.0 × 105 (B1), 1.0 × 106 (B2), 1.0 × 107 (B3), and 1.0 × 108 (B4) cfu/g B. subtilis CGMCC 1.921. The results showed that feed:egg ratio significantly decreased (P < 0.05) in groups B1 (wk 13 to 16, 17 to 20, 21 to 24, and one to 24), B2 (wk 13 to 16, 17 to 20, and 21 to 24), B3 (wk 13 to 16, 17 to 20, 21 to 24, and one to 24), and B4 (wk 13 to 16, 17 to 20, 21 to 24, and one to 24). However, egg production, egg weight, and feed intake were not significantly different (P > 0.05) among treatments. Eggshell strength significantly improved (P < 0.05) in groups B1 (wk 8, 16, 20, and 24), B2 (wk 20 and 24), and B3 (wk 8, 16, 20, and 24). Fecal E. coli counts significantly decreased (P < 0.05) in groups B1 (wk 16), B2 (wk 12, 16, 20, and 24), B3 (wk 12, 20, and 24), and B4 (wk 16, 20, and 24). Lactobacillus in cecal digesta of groups B1, B3, and B4 increased significantly (P < 0.01). Bifidobacterium in cecal digesta of groups B1, B2, B3, and B4 increased significantly (P < 0.05). Bifidobacterium counts increased linearly (P = 0.015) and quadratically (P = 0.004) as B. subtilis CGMCC 1.921 supplementation increased. Compared with Con, E. coli in the cecal digesta of groups B2 and B4 decreased significantly (P < 0.01). C. perfringens in the cecal digesta of groups B3 and B4 decreased significantly (P < 0.05). E. coli:Lactobacillus ratio decreased in group B1 (P < 0.05) and B2, B3, and B4 (P < 0.01). Therefore, the probiotic B. subtilis CGMCC 1.921 effectively improved performance and egg quality via the reduction of fecal E. coli and beneficial modulation of cecal microbiota.

Clinical intervention using Bifidobacterium strains in celiac disease children reveals novel microbial modulators of TNF-α and short-chain fatty acids

BACKGROUND & AIMS

Celiac disease (CD) is an immune-mediated systemic disease, caused by ingestion of gluten in genetically predisposed individuals. Gut microbiota dysbiosis might play a significant role in pathogenesis of chronic enteropathies and its modulation can be used as an intervention strategy in CD as well. In this study, we aimed to identify correlations between fecal microbiota, serum tumor necrosis factor alpha (TNF-α) and fecal short-chain fatty acids (SCFAs) in healthy children and children with CD after administration of probiotic Bifidobacterium breve BR03 and B632.

METHODS

A double-blind placebo-controlled study enrolled 40 children with CD (CD) and 16 healthy children (HC). CD children were randomly allocated into two groups, of which 20 belonged to the placebo (PL) group and 20 to the Probiotic (PR) group. The PR group received a probiotic formulation containing a mixture of 2 strains, B. breve BR03 (DSM 16604) and B. breve B632 (DSM 24706) in 1:1 ratio for 3 months. Subsequently, for statistical analysis, blood and fecal samples from CD children (on enrolment - T0 and after 3 months, at the end of intervention with probiotic/placebo - T1) and HC children were used. The HC group was sampled only once (T0).

RESULTS

Verrucomicrobia, Parcubacteria and some yet unknown phyla of Bacteria and Archaea may be involved in the disease, indicated by a strong correlation to TNF-α. Likewise, Proteobacteria strongly correlated with fecal SCFAs concentration. The effect of probiotic administration has disclosed a negative correlation between Verrucomicrobia, some unknown phyla of Bacteria, Synergistetes, Euryarchaeota and some SCFAs, turning them into an important target in microbiome restoration process. Synergistetes and Euryarchaeota may have a role in the anti-inflammatory process in healthy human gut.

CONCLUSIONS

Our results highlight new phyla, which may have an important relation to disease-related parameters, CD itself and health.

Gut Microbiota Composition in Mid-Pregnancy Is Associated with Gestational Weight Gain but Not Prepregnancy Body Mass Index

Background: Pregnancy is a time of numerous hormonal, metabolic, and immunological changes for both the mother and the fetus. Furthermore, maternal gut microbiota composition (GMC) is altered during pregnancy. One major factor affecting GMC in pregnant and nonpregnant populations is obesity. The aim was to analyze associations between maternal overweight/obesity, as well as gestational weight gain (GWG) and GMC. Moreover, the modifying effect of depression and anxiety symptom scores on weight and GMC were investigated.

Methods: Study included 46 women from the FinnBrain Birth Cohort study, of which 36 were normal weight, and 11 overweight or obese according to their prepregnancy body mass index (BMI). Stool samples were collected in gestational week 24, and the GMC was sequenced with Illumina MiSeq approach. Hierarchical clustering was executed to illuminate group formation according to the GMC. The population was divided according to Firmicutes and Bacteroidetes dominance. Symptoms of depression, general anxiety, and pregnancy-related anxiety were measured by using standardized questionnaires.

Results: Excessive GWG was associated with distinct GMC in mid-pregnancy as measured by hierarchical clustering and grouping according to Firmicutes or Bacteroidetes dominance, with Bacteroidetes being prominent and Firmicutes being less prominent in the GMC among those with increased GWG. Reduced alpha diversity was observed among the Bacteroidetes-dominated subjects. There were no zero-order effects between the abundances of bacterial genera or phyla, alpha or beta diversity, and prepregnancy BMI or GWG.

Conclusion:Bacteroidetes-dominated GMC in mid-pregnancy is associated with increased GWG and reduced alpha diversity.

Occurrence of serum antibodies against wheat alpha-amylase inhibitor 0.19 in celiac disease

The alcohol-soluble fraction of wheat gluten (gliadins) induces in genetically susceptible individuals immunologically mediated celiac disease (CLD). However, gliadins and related cereal proteins are not unique foodstuff targets of CLD patients´ immune system. Non-gluten wheat alpha-amylase inhibitor 0.19 (AAI 0.19) has been found to be capable of activating human monocyte-derived dendritic cells and inducing pro-inflammatory status in intestinal mucosa of patients with celiac disease (CLD). The possible contribution of this reactivity in incomplete remission of CLD patients on a gluten-free diet (GFD) is matter of contention. In an attempt to characterize the antigenicity of AAI 0.19 in patients with active CLD, patients on a GFD and healthy controls we developed ELISA employing wheat recombinant AAI 0.19. Using this test we revealed a significant (P<0.001) elevation of IgA anti-AAI 0.19 antibodies (Ab) in patients with active CLD (12 out of 30 patients were seropositive) but also in CLD patients on a GFD (15/46), in contrast to healthy controls (2/59). Anti-AAI 0.19 IgG Ab levels were increased (P<0.001) only in patients with active CLD (14/30) in contrast to the controls. Interestingly, the levels of anti-AAI 0.19 IgG Ab were decreased in CLD patients on a GFD (P<0.001, 1/46) compared to the controls (1/59). Notably, 20 out of 30 patients with active CLD were positive either for IgA or for IgG anti-AAI 0.19 Ab. Thus, the majority of CLD patients developed a robust IgA and IgG Ab response against AAI 0.19. These findings may contribute to the broadening of the knowledge about CLD pathogenesis.

A Metagenome-Wide Association Study and Arrayed Mutant Library Confirm Acetobacter Lipopolysaccharide Genes Are Necessary for Association with Drosophila melanogaster

A metagenome wide association (MGWA) study of bacterial host association determinants in Drosophila predicted that LPS biosynthesis genes are significantly associated with host colonization. We were unable to create site-directed mutants for each of the predicted genes in Acetobacter, so we created an arrayed transposon insertion library using Acetobacter fabarum DsW_054 isolated from Drosophila. Creation of the A. fabarum DsW_054 gene knock-out library was performed by combinatorial mapping and Illumina sequencing of random transposon insertion mutants. Transposon insertion locations for 6,418 mutants were successfully mapped, including hits within 63% of annotated genes in the A. fabarum DsW_054 genome. For 45/45 members of the library, insertion sites were verified by arbitrary PCR and Sanger sequencing. Mutants with insertions in four different LPS biosynthesis genes were selected from the library to validate the MGWA predictions. Insertion mutations in two genes biosynthetically upstream of Lipid-A formation, lpxC and lpxB, show significant differences in host association, whereas mutations in two genes encoding LPS biosynthesis functions downstream of Lipid-A biosynthesis had no effect. These results suggest an impact of bacterial cell surface molecules on the bacterial capacity for host association. Also, the transposon insertion mutant library will be a useful resource for ongoing research on the genetic basis for Acetobacter traits.

Investigational drug therapies for coeliac disease - where to from here?

INTRODUCTION

Despite decades of research and a detailed knowledge of the immunopathological basis of coeliac disease (CD), adherence to a lifelong gluten-free diet (GFD) remains the single proven and available treatment. The increasing prevalence of CD combined with variable adherence to the GFD in a significant proportion of patients demands new therapeutic strategies.

AREAS COVERED

Trial registries, clinicaltrials.gov, pharmaceutical company website searches as well as published data from PubMed and conference proceedings were used to extract the most recent outcomes for CD therapeutics. This article aims to review the available therapies from a pathophysiological approach, and propose future directions in this interesting yet largely unfulfilled area of research.

EXPERT OPINION

Increasingly, the GFD is being challenged by its availability, palatability, practicality and now even efficacy in some populations. Whilst the causative antigens have been well described, it is clear that treatment based on the removal of these immunostimulatory peptides from the diet is far more complex than early experience in CD treatment implied. Despite burgeoning interest and research in experimental therapies for CD over the past twenty years, the only therapy showing promise as a true alternative to a GFD is that of the induction of tolerance via a vaccine.

Fecal microbiota transplantation and its potential therapeutic uses in gastrointestinal disorders

Typical human gut flora has been well characterized in previous studies and has been noted to have significant differences when compared with the typical microbiome of various disease states involving the gastrointestinal tract. Such diseases include Clostridium difficile colitis, inflammatory bowel disease, functional bowel syndromes, and various states of liver disease. A growing number of studies have investigated the use of a fecal microbiota transplant as a potential therapy for these disease states.

Celiac Disease: A Review of Current Concepts in Pathogenesis, Prevention, and Novel Therapies

Our understanding of celiac disease and how it develops has evolved significantly over the last half century. Although traditionally viewed as a pediatric illness characterized by malabsorption, it is now better seen as an immune illness with systemic manifestations affecting all ages. Population studies reveal this global disease is common and, in many countries, increasing in prevalence. These studies underscore the importance of specific HLA susceptibility genes and gluten consumption in disease development and suggest that other genetic and environmental factors could also play a role. The emerging data on viral and bacterial microbe-host interactions and their alterations in celiac disease provides a plausible mechanism linking environmental risk and disease development. Although the inflammatory lesion of celiac disease is complex, the strong HLA association highlights a central role for pathogenic T cells responding to select gluten peptides that have now been defined for the most common genetic form of celiac disease. What remains less understood is how loss of tolerance to gluten occurs. New insights into celiac disease are now providing opportunities to intervene in its development, course, diagnosis, and treatment.

Antibiotic and Modulation of Microbiota: A New Paradigm?

Recently new insights on gut microbiota have revolutionized many concepts of the modern medicine. The alteration of microbiota, which is called dysbiosis, has been associated with an expanding list of diseases and conditions. The development of next-generation sequencing techniques allowed comprehensive analysis of gut microbiota composition without the limitations of classic culture methods. Furthermore, introduction of functional techniques such as metabolomics and proteomics allowed for integrated analysis thus obtaining more robust insights on microbiota functions in health and disease. These tools allow to address the role of factors able to modify the gut microbiota, the so called "microbiota influencers." These data are useful to explain the physiopathology of several disease and thus to identify new potential therapeutic targets. Among microbiota influencers, many studies focused on the impact of antibiotic administration on the gut microbiota, because of their widespread use. Notably, beside the known beneficial effect of antibiotic in treating infectious diseases, these drugs have shown detrimental effects on gut microbiota which, in turn, might have long-term consequences on the host. Finally, therapeutic modulation of gut microbiota, by means of selected antibiotics with eubiotic effects, probiotics and with fecal microbiota transplantation seems of great interest as it might be able to prevent or even revert antibiotic-induced dysbiosis.

Old Fashioned vs. Ultra-Processed-Based Current Diets: Possible Implication in the Increased Susceptibility to Type 1 Diabetes and Celiac Disease in Childhood

Ultra-processed foods are ready-to-heat and ready-to-eat products created to replace traditional homemade meals and dishes due to convenience and accessibility. Because of their low-fiber and high-fat and sugar composition, these foodstuffs could induce a negative impact on health. They are partially responsible for obesity and chronic non-transmissible diseases; additionally, they could impact in the prevalence of autoimmune diseases such as type 1 diabetes and celiac disease. The rationale is that the nutritional composition of ultra-processed foodstuffs can induce gut dysbiosis, promoting a pro-inflammatory response and consequently, a “leaky gut”. These factors have been associated with increased risk of autoimmunity in genetically predisposed children. In addition, food emulsifiers, commonly used in ultra-processed products could modify the gut microbiota and intestinal permeability, which could increase the risk of autoimmunity. In contrast, unprocessed and minimally processed food-based diets have shown the capacity to promote gut microbiota eubiosis, anti-inflammatory response, and epithelial integrity, through bacterial butyrate production. Thus, to decrease the susceptibility to autoimmunity, genetically predisposed children should avoid ultra-processed food products and encourage the consumption of fresh and minimally processed foods.

Prevalence of positive coeliac disease serology and HLA risk genotypes in a multiethnic population of adults in Canada: a cross-sectional study

OBJECTIVES

Coeliac disease (CD) is a complex autoimmune disorder with known genetic risk factors. Approximately 1% of individuals of European ancestry have CD, but the prevalence among different ethnicities living in Canada remains unknown. The objective of the present study was to determine the prevalence of positive CD serology in a population of Canadian adults living in Toronto, and to determine whether the prevalence of CD seropositivity and predisposing human leucocyte antigen (HLA)-DQ2/DQ8 risk genotypes differ between major ethnocultural groups.

DESIGN

Cross-sectional screening study of participants from the Toronto Nutrigenomics and Health and the Toronto Healthy Diet studies.

SETTING

University campus and households across Toronto, Canada.

PARTICIPANTS FREE-LIVING

Adults (n=2832) of diverse ethnocultural backgrounds.

MAIN OUTCOME MEASURES

Prevalence of positive CD serology was determined by screening for antitissue transglutaminase antibodies in individuals with predisposing HLA-DQ2/DQ8 genotypes. HLA genotypes were determined using six single nucleotide polymorphisms in the HLA gene region.

RESULTS

Of the 2832 individuals screened, a total of 25 (0.88%; 95% CI 0.57% to 1.30%) were determined to have positive CD serology. The majority of seropositive CD cases were undiagnosed (87%). Prevalence was highest among Caucasians (1.48%; 95% CI 0.93% to 2.23%), and similar in those of 'Other' (0.74%; 95% CI 0.09% to 2.63%) or 'Unknown' (0.43; 95% CI 0.01% to 2.36%) ethnicity. No cases of positive CD serology were identified among East Asian or South Asian individuals. East Asians had a lower prevalence of HLA risk genotypes than Caucasians and South Asians (p<0.005).

CONCLUSIONS

The prevalence of positive CD serology among Canadian adults living in Toronto is likely ~1%, with 87% of cases being undiagnosed. These findings suggest the need for better screening in high genetic risk groups.

TRIAL REGISTRATION NUMBER

NCT00516620; Post-results.

Bifidobacterium infantis NLS Super Strain Reduces the Expression of α-Defensin-5, a Marker of Innate Immunity, in the Mucosa of Active Celiac Disease Patients

BACKGROUND

We have previously shown a reduction of gastrointestinal symptoms after the oral administration of Bifidobacterium infantis Natren Life Start super strain (NLS-SS) in untreated celiac disease (CD) patients. The symptomatic improvement was not associated with changes in intestinal permeability or serum levels of cytokines, chemokines, or growth factors. Therefore, we hypothesized that the beneficial symptomatic effect observed previously in patients with CD treated with B. infantis may be related to the modulation of innate immunity.

GOALS

To investigate the potential mechanisms of a probiotic B. infantis Natren Life Start super strain on the mucosal expression of innate immune markers in adult patients with active untreated CD compared with those treated with B. infantis×6 weeks and after 1 year of gluten-free diet (GFD).

METHODS

Numbers of macrophages and Paneth cells and α-defensin-5 expression were assessed by immunohistochemistry in duodenal biopsies.

RESULTS

We showed that GFD decreases duodenal macrophage counts in CD patients more effectively than B. infantis. In contrast, B. infantis decreases Paneth cell counts and expression of α-defensin-5 in CD (P<0.001).

CONCLUSIONS

The results identify differential innate immune effects of treatment with B. infantis compared with 1 year of GFD. Further studies are needed to investigate synergistic effects of GFD and B. infantis supplementation in CD.

The potential role of gut microbiota in pancreatic disease: A systematic review

BACKGROUND

Several studies have suggested a link between microbiota imbalance and some gastrointestinal, inflammatory and neoplastic diseases. However, the role in pancreatic diseases remain unclear. To evaluate the available evidence for pancreatic diseases, we undertook a systematic review.

METHODS

OVID Medline (1946-2017), EMBASE (1980-2017) and the Cochrane Central Register of Controlled Trials (CENTRAL Issue 3, 2017) were searched for studies on microbiota in pancreatic disease. We also searched the reference lists of retrieved papers, and conference proceedings. We excluded animal studies, reviews, and case reports.

RESULTS

A total of 2833 articles were retrieved. After screening and applying the exclusion criteria, 10 studies were included. Three studies showed lower levels of Bifidobacterium or Lactobacillus and higher levels of Enterobacteriaceae in chronic pancreatitis. Two of these studies were uncontrolled, and the third (controlled) study which compared patients with endocrine and exocrine insufficiency, reported that Bacteroidetes levels were lower in those patients without diabetes, while Bifidobacteria levels were higher in those without exocrine insufficiency. Only one study investigated acute pancreatitis, showing higher levels of Enterococcus and lower levels of Bifidobacterium versus healthy participants. There was an overall association between pancreatic cancer and lower levels of Neisseria elongate, Streptococcus mitis and higher levels of Porphyromonas gingivalis and Granulicatella adiacens.

CONCLUSIONS

Current evidence suggests a possible link between microbiota imbalance and pancreatic cancer. Regarding acute and chronic pancreatitis, data are scarce, dysbiosis appears to be present in both conditions. However, further investigation is required to confirm these findings and to explore therapeutic possibilities.

Negotiating the complexities of exocrine and endocrine dysfunction in chronic pancreatitis

Chronic pancreatitis is a chronic inflammatory disease of the pancreas characterised by irreversible morphological change and typically causing pain and/or permanent loss of function. This progressive, irreversible disease results in destruction of healthy pancreatic tissue and the development of fibrous scar tissue. Gradual loss of exocrine and endocrine function follows, along with clinical manifestations such as steatorrhoea, abdominal pain and diabetes. Nutrition in chronic pancreatitis has been described as a problem area and, until recently, there was little research on the topic. It is often asserted that >90 % of the pancreas must be damaged before exocrine insufficiency occurs; however, an exploration of the original studies from the 1970s found that the data do not support this assertion. The management of steatorrhoea with pancreatic enzyme replacement therapy is the mainstay of nutritional management, and early identification and treatment is a key. The presence of steatorrhoea, coupled with poor dietary intake (due to intractable abdominal pain, gastrointestinal side effects and often alcoholism) renders the chronic pancreatitis patients at considerable risk for undernutrition, muscle depletion and fat-soluble vitamin deficiency. Premature osteoporosis/osteopenia afflicts two-thirds of patients as a consequence of poor dietary intake of calcium and vitamin D, low physical activity, low sunlight exposure, heavy smoking, as well as chronic low-grade inflammation. Bone metabolism studies show increased bone formation as well as bone resorption in chronic pancreatitis, indicating that bone turnover is abnormally high. Loss of the pancreatic islet cells occurs later in the disease process as the endocrine cells are diffusely distributed throughout the pancreatic parenchyma. Patients may develop type 3c (pancreatogenic) diabetes, which is complicated by concurrent decreased glucagon secretion, and hence an increased risk of hypoglycaemia. Diabetes control is further complicated by poor diet, malabsorption and (for some) alcoholism, and therefore those with type 3c diabetes have clinical characteristics and therapeutic goals that are different from that of type 1 and type 2 diabetes patients. This review describes emerging research and clinical guidelines for nutrition in chronic pancreatitis.

Recent advances in pediatric celiac disease

The incidence of celiac disease (CD) has increased over the last half-century, resulting in rising interest in identifying risk factors for CD. The necessity of duodenal biopsies in the diagnosis of CD has recently been challenged. Areas covered: This review covers the recent literature regarding the role of infant feeding practices, including breastfeeding and timing of gluten introduction, and the microbiota in the development of CD. Additionally, the application of the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for a non-biopsy approach to the diagnosis of CD is reviewed. Expert commentary: Recent investigations have not revealed any significant effect of breastfeeding or timing of gluten introduction on the risk of CD in at-risk populations. There are alterations in the microbiota of CD patients. However, the role of the microbiome and whether its manipulation has a clinical effect are unknown. Preliminary data suggests a non-biopsy approach to diagnosis of pediatric CD can be applied to several populations, although additional studies are needed. Prospective investigations are underway to examine the interplay of infant feeding practices and the microbiome and to identify particular CD-specific biomarkers that may aid in the diagnosis and ultimately prevention of CD.

Significantly higher faecal counts of the yeasts candida and saccharomyces identified in people with coeliac disease

Background

Coeliac disease is an autoimmune disorder resulting from an interaction between diet, genome and immunity. The treatment of CoeD is lifelong adherence to a gluten free diet, which is associated with clinical and histological improvements. However, a substantive number of individuals report only partial symptom improvement despite both compliance with a strict gluten free diet and improvements in serological and histological biomarkers of disease activity. The role of the intestinal microbiota is an area of interest in this sub-group.

Aims

To investigate the role of yeasts and parasites in individuals reporting persistent symptoms of Coeliac disease (CoeD).

Methods

Forty-five people who met the ESPGHAN diagnostic criteria for CoeD were recruited via the Australian Coeliac Association. The faecal measures of the DNA of yeasts and parasites from the CoeD group were compared to data obtained from the medical records of non-coeliac controls with gastrointestinal symptoms from other causes.

Results

Candida sp. was detected in 33% of the CoeD group compared 0% of the control group (p = 0.000) and Saccharomyces sp. was detected in 33% of the CoeD group compared to 10% of the control group (p = 0.026). There were no differences in the presence of any of the parasite species measured.

Conclusion

Further research is required to understand the significance of Candida and Saccharomyces species in both the aetiology of CoeD and of persistent symptoms in this sub-group.

Trial Registration Clinical Trial Registration—ANZCTR Number: 12610000630011

Mode of Delivery and Risk of Celiac Disease: Risk of Celiac Disease and Age at Gluten Introduction Cohort Study

OBJECTIVE

To determine whether the mode of delivery is associated with the risk of celiac disease (CD) in a cohort of children genetically predisposed to CD prospectively followed from birth.

STUDY DESIGN

By telephone interview, we recorded information on the mode of delivery of children participating in the Risk of Celiac Disease and Age at Gluten Introduction study, a multicenter, prospective intervention trial that compared early and delayed introduction of gluten in infants with at least 1 first-degree relative affected with CD. The human leukocyte antigen genotype was determined at 15 months of age, and serologic screening for CD was performed at 15, 24, and 36 months of age and at 5, 8, and 10 years of age. Patients with positive serologic findings underwent intestinal biopsy. The primary outcome of the current study was the prevalence of CD autoimmunity and overt CD at 5 years of age, according to the mode of delivery.

RESULTS

The study-group included 553 children at CD risk because of positivity for human leukocyte antigen-DQ2, -DQ8, or both. We obtained data on the mode of delivery from 431 of 553 children; 233 of 431 children were born by vaginal delivery (54%). At 5 years of age, the prevalence of CD autoimmunity or overt CD was not different between children born by cesarean or vaginal delivery (24% and 19%, P = .2; 19% and 14%, P = .2 respectively, by the log-rank test).

CONCLUSIONS

In this cohort of children genetically predisposed to CD, the mode of delivery did not influence the risk of developing CD.

Impaired intestinal cholecystokinin secretion, a fascinating but overlooked link between coeliac disease and cholesterol gallstone disease

BACKGROUND

Coeliac disease is a chronic, small intestinal, immune-mediated enteropathy caused by a permanent intolerance to dietary gluten in genetically predisposed individuals. Clinical studies have found that intestinal cholecystokinin secretion and gallbladder emptying in response to a fatty meal are impaired before coeliac patients start the gluten-free diet (GFD).

DESIGN

However, it was never really appreciated whether coeliac disease is associated with gallstones because there were very few studies investigating the mechanism underlying the impact of coeliac disease on the pathogenesis of gallstones.

RESULTS

We summarize recent progress on the relationship between coeliac disease and gallstones and propose that coeliac disease is an important risk factor for gallstone formation because defective intestinal cholecystokinin secretion markedly increases susceptibility to cholesterol gallstones via a mechanism involving dysmotility of both the gallbladder and the small intestine. Because GFD can significantly improve the coeliac enteropathy, early diagnosis and therapy in coeliac patients is crucial for preventing the long-term impact of cholecystokinin deficiency on the biliary and intestinal consequences. When gluten is reintroduced, clinical and histologic relapse often occurs in coeliac patients. Moreover, some of the coeliac patients do not respond well to GFD.

CONCLUSIONS

It is imperative to routinely examine by ultrasonography whether gallbladder motility function is preserved in coeliac patients and monitor whether biliary sludge (a precursor of gallstones) appears in the gallbladder, regardless of whether they are under the GFD programme. To prevent gallstones in coeliac patients, it is urgently needed to investigate the prevalence and pathogenesis of gallstones in these patients.

Environmental Enteric Dysfunction and the Fecal Microbiota in Malawian Children

Environmental enteric dysfunction (EED) is often measured with a dual sugar absorption test and implicated as a causative factor in childhood stunting. Disturbances in the gut microbiota are hypothesized to be a mechanism by which EED is exacerbated, although this supposition lacks support. We performed 16S ribosomal RNA gene sequencing of fecal samples from 81 rural Malawian children with varying degrees of EED to determine which bacterial taxa were associated with EED. At the phyla level, Proteobacteria abundance is reduced with severe EED. Among bacterial genera, Megasphaera, Mitsuokella, and Sutterella were higher in EED and Succinivibrio, Klebsiella, and Clostridium_XI were lower in EED. Bacterial diversity did not vary with the extent of EED. Though EED is a condition that is typically believed to affect the proximal small bowel, and our focus was on stool, our data do suggest that there are intraluminal microbial differences that reflect, or plausibly lead to, EED.

Gata4 is critical to maintain gut barrier function and mucosal integrity following epithelial injury

The intestinal epithelial barrier is critical to limit potential harmful consequences from exposure to deleterious luminal contents on the organism. Although this barrier is functionally important along the entire gut, specific regional regulatory mechanisms involved in the maintenance of this barrier are poorly defined. Herein, we identified Gata4 as a crucial regulator of barrier integrity in the mouse proximal intestinal epithelium. Conditional deletion of Gata4 in the intestine led to a drastic increase in claudin-2 expression that was associated with an important increase of gut barrier permeability without causing overt spontaneous inflammation. Administration of indomethacin, a non-steroidal anti-inflammatory drug (NSAID) that causes enteritis, led to rapid and restricted proximal small intestinal injuries in Gata4 mutant mice as opposed to control mice. Comparative analysis of gene transcript profiles from indomethacin-challenged control and Gata4 mutant mice identified defects in epithelial cell survival, inflammatory cell recruitment and tissue repair mechanisms. Altogether, these observations identify Gata4 as a novel crucial regulator of the intestinal epithelial barrier and as a critical epithelial transcription factor implicated in the maintenance of proximal intestinal mucosal integrity after injury.

Coeliac disease: a unique model for investigating broken tolerance in autoimmunity

Coeliac disease, a prevalent immune-mediated enteropathy driven by dietary gluten, provides an exceptional human model to dissect the genetic, environmental and immunologic factors operating in autoimmunity. Despite the causative antigen being an exogenous food protein, coeliac disease has many features in common with autoimmune disease including a strong HLA class II association and the presence of pathogenic CD4⁺ T cells and autoantibodies. CD8⁺ intraepithelial lymphocytes specifically target and destroy intestinal epithelium in response to stress signals and not a specific antigen. A unique feature of coeliac disease is the ability to remove gluten to induce disease remission and reintroduce it to trigger a memory response. This provides an unparalleled opportunity to study disease-relevant CD4⁺ T cells that have been expanded in vivo. As a result, the causative peptides have been characterised at a level unprecedented for any autoimmune disease. Despite the complexity of the gluten proteome, resistance to gastrointestinal proteolysis and susceptibility to post-translational modification by transglutaminase help shape a restricted repertoire of immunogenic gluten peptides that have high affinity for disease-associated HLA. The critical steps in coeliac disease pathogenesis have been broadly elucidated and provide the basis for experimental therapies in pre-clinical or clinical development. However, little is known about how and why tolerance to gluten sometimes breaks or fails to develop. Understanding the interactions between genes, the environment, gluten immunity and the microbiome may provide novel approaches for the prevention and treatment of disease.

Recent Advances in Celiac Disease

Recent diagnostic advances have demonstrated that celiac disease is relatively common although most patients have less florid symptoms than previously recognised. The mucosal lesion of this autoimmune disorder depends on both adaptive and innate immune responses. The characteristic antibodies to tissue transglutaminase-2 (tTG-2) and deamidated gliadin peptides may be produced in persons possessing the relevant HLA-DQ genotypes if intact gliadin peptides can penetrate the epithelial barrier to reach antigen presenting cells. Progression from celiac autoimmunity to overt disease may depend on innate immune mechanisms, not HLA-restricted, where IL-15 is generated within the epithelial compartment. A specific innate immune response previously thought restricted to invertebrates, the encapsulation reaction, may contribute to mucosal volume expansion through recruitment of syndecan-expressing leukocytes and stimulated matrix production. It is notable that tissue transglutaminase is critical in this reaction in insects, and that the very few insects that can predate wheat, possess specific salivary or intestinal enzymes that degrade gluten. Animal models in HLA-DQ transgenic mice suggest that the microbial flora of the intestine may play a role in host responses and modulate the evolution of the disease. This suggests that therapeutic modulation of the microbiome may contribute to management of celiac disease. In developing world countries, there is a potential difficulty in histological diagnosis because of the widespread incidence of environmental enteropathy amongst apparently healthy children. Thus, recognition of local patterns of enteropathy will be important for histopathologists, and high titre tTG-2 autoantibody titres may hold considerable diagnostic significance.

Circadian Rhythm Shapes the Gut Microbiota Affecting Host Radiosensitivity

Modern lifestyles, such as shift work, nocturnal social activities, and jet lag, disturb the circadian rhythm. The interaction between mammals and the co-evolved intestinal microbiota modulates host physiopathological processes. Radiotherapy is a cornerstone of modern management of malignancies; however, it was previously unknown whether circadian rhythm disorder impairs prognosis after radiotherapy. To investigate the effect of circadian rhythm on radiotherapy, C57BL/6 mice were housed in different dark/light cycles, and their intestinal bacterial compositions were compared using high throughput sequencing. The survival rate, body weight, and food intake of mice in diverse cohorts were measured following irradiation exposure. Finally, the enteric bacterial composition of irradiated mice that experienced different dark/light cycles was assessed using 16S RNA sequencing. Intriguingly, mice housed in aberrant light cycles harbored a reduction of observed intestinal bacterial species and shifts of gut bacterial composition compared with those of the mice kept under 12 h dark/12 h light cycles, resulting in a decrease of host radioresistance. Moreover, the alteration of enteric bacterial composition of mice in different groups was dissimilar. Our findings provide novel insights into the effects of biological clocks on the gut bacterial composition, and underpin that the circadian rhythm influences the prognosis of patients after radiotherapy in a preclinical setting.

Effect of Bifidobacterium breve on the Intestinal Microbiota of Coeliac Children on a Gluten Free Diet: A Pilot Study

Coeliac disease (CD) is associated with alterations of the intestinal microbiota. Although several Bifidobacterium strains showed anti-inflammatory activity and prevention of toxic gliadin peptides generation in vitro, few data are available on their efficacy when administered to CD subjects. This study evaluated the effect of administration for three months of a food supplement based on two Bifidobacterium breve strains (B632 and BR03) to restore the gut microbial balance in coeliac children on a gluten free diet (GFD). Microbial DNA was extracted from faeces of 40 coeliac children before and after probiotic or placebo administration and 16 healthy children (Control group). Sequencing of the amplified V3-V4 hypervariable region of 16S rRNA gene as well as qPCR of Bidobacterium spp., Lactobacillus spp., Bacteroides fragilis group Clostridiumsensu stricto and enterobacteria were performed. The comparison between CD subjects and Control group revealed an alteration in the intestinal microbial composition of coeliacs mainly characterized by a reduction of the Firmicutes/Bacteroidetes ratio, of Actinobacteria and Euryarchaeota. Regarding the effects of the probiotic, an increase of Actinobacteria was found as well as a re-establishment of the physiological Firmicutes/Bacteroidetes ratio. Therefore, a three-month administration of B. breve strains helps in restoring the healthy percentage of main microbial components.

The Role of the Intestinal Microbiome in Type 1 Diabetes Pathogenesis

The gastrointestinal system represents one of the largest interfaces between the human internal microenvironment and the external world. This system harbors trillions of commensal bacteria that reside in symbiosis with the host. Intestinal bacteria play a crucial role in maintaining systemic and intestinal immune and metabolic homeostasis because of their effect on nutrient absorption and immune development and function. Recently, altered gut bacterial composition (dysbiosis) was hypothesized to be involved in mechanisms through which islet autoimmunity is triggered. Evidence from animal models indicates that alterations in the gut bacterial composition precede disease onset, thus implicating a causal role for the gut microbiome in islet destruction. However, it remains unclear whether dysbiosis is directly linked to the mechanisms of human type 1 diabetes (T1D). In this review, we discuss data implicating the gut microbiota in disease progression with an emphasis on our recent studies performed in humans and in rodent models of T1D.

Duodenal Bacteria From Patients With Celiac Disease and Healthy Subjects Distinctly Affect Gluten Breakdown and Immunogenicity

BACKGROUND & AIMS

Partially degraded gluten peptides from cereals trigger celiac disease (CD), an autoimmune enteropathy occurring in genetically susceptible persons. Susceptibility genes are necessary but not sufficient to induce CD, and additional environmental factors related to unfavorable alterations in the microbiota have been proposed. We investigated gluten metabolism by opportunistic pathogens and commensal duodenal bacteria and characterized the capacity of the produced peptides to activate gluten-specific T-cells from CD patients.

METHODS

We colonized germ-free C57BL/6 mice with bacteria isolated from the small intestine of CD patients or healthy controls, selected for their in vitro gluten-degrading capacity. After gluten gavage, gliadin amount and proteolytic activities were measured in intestinal contents. Peptides produced by bacteria used in mouse colonizations from the immunogenic 33-mer gluten peptide were characterized by liquid chromatography tandem mass spectrometry and their immunogenic potential was evaluated using peripheral blood mononuclear cells from celiac patients after receiving a 3-day gluten challenge.

RESULTS

Bacterial colonizations produced distinct gluten-degradation patterns in the mouse small intestine. Pseudomonas aeruginosa, an opportunistic pathogen from CD patients, exhibited elastase activity and produced peptides that better translocated the mouse intestinal barrier. P aeruginosa-modified gluten peptides activated gluten-specific T-cells from CD patients. In contrast, Lactobacillus spp. from the duodenum of non-CD controls degraded gluten peptides produced by human and P aeruginosa proteases, reducing their immunogenicity.

CONCLUSIONS

Small intestinal bacteria exhibit distinct gluten metabolic patterns in vivo, increasing or reducing gluten peptide immunogenicity. This microbe-gluten-host interaction may modulate autoimmune risk in genetically susceptible persons and may underlie the reported association of dysbiosis and CD.

Interleukin-15 promotes intestinal dysbiosis with butyrate deficiency associated with increased susceptibility to colitis

Dysbiosis resulting in gut-microbiome alterations with reduced butyrate production are thought to disrupt intestinal immune homeostasis and promote complex immune disorders. However, whether and how dysbiosis develops before the onset of overt pathology remains poorly defined. Interleukin-15 (IL-15) is upregulated in distressed tissue and its overexpression is thought to predispose susceptible individuals to and have a role in the pathogenesis of celiac disease and inflammatory bowel disease (IBD). Although the immunological roles of IL-15 have been largely studied, its potential impact on the microbiota remains unexplored. Analysis of 16S ribosomal RNA-based inventories of bacterial communities in mice overexpressing IL-15 in the intestinal epithelium (villin-IL-15 transgenic (v-IL-15tg) mice) shows distinct changes in the composition of the intestinal bacteria. Although some alterations are specific to individual intestinal compartments, others are found across the ileum, cecum and feces. In particular, IL-15 overexpression restructures the composition of the microbiota with a decrease in butyrate-producing bacteria that is associated with a reduction in luminal butyrate levels across all intestinal compartments. Fecal microbiota transplant experiments of wild-type and v-IL-15tg microbiota into germ-free mice further indicate that diminishing butyrate concentration observed in the intestinal lumen of v-IL-15tg mice is the result of intrinsic alterations in the microbiota induced by IL-15. This reconfiguration of the microbiota is associated with increased susceptibility to dextran sodium sulfate-induced colitis. Altogether, this study reveals that IL-15 impacts butyrate-producing bacteria and lowers butyrate levels in the absence of overt pathology, which represent events that precede and promote intestinal inflammatory diseases.

The Role of the Microbiota in Shaping Infectious Immunity

Humans are meta-organisms that maintain a diverse population of microorganisms on their barrier surfaces, collectively named the microbiota. Since most pathogens either cross or inhabit barrier surfaces, the microbiota plays a critical and often protective role during infections, both by modulating immune system responses and by mediating colonization resistance. However, the microbiota can also act as a reservoir for opportunistic microorganisms that can 'bloom', significantly complicating diseases of barrier surfaces by contributing to inflammatory immune responses. This review discusses our current understanding of the complex interactions between the host, its microbiota, and pathogenic organisms, focusing in particular on the intestinal mucosa.

Persistent Intraepithelial Lymphocytosis in Celiac Patients Adhering to Gluten-Free Diet Is Not Abolished Despite a Gluten Contamination Elimination Diet

The gluten-free diet (GFD) is the only validated treatment for celiac disease (CD), but despite strict adherence, complete mucosal recovery is rarely obtained. The aim of our study was to assess whether complete restitutio ad integrum could be achieved by adopting a restrictive diet (Gluten Contamination Elimination Diet, GCED) or may depend on time of exposure to GFD. Two cohorts of CD patients, with persisting Marsh II/Grade A lesion at duodenal biopsy after 12–18 months of GFD (early control) were identified. Patients in Cohort A were re-biopsied after a three-month GCED (GCED control) and patients in Cohort B were re-biopsied after a minimum of two years on a standard GFD subsequent to early control (late control). Ten patients in Cohort A and 19 in Cohort B completed the study protocol. There was no change in the classification of duodenal biopsies in both cohorts. The number of intraepithelial lymphocytes, TCRγδ+ (T-Cell Receptor gamma delta) T cell and eosinophils significantly decreased at GCED control (Cohort A) and at late control (Cohort B), compared to early control. Duodenal intraepithelial lymphocytosis persisting in CD patients during GFD is not eliminated by a GCED and is independent of the length of GFD. [NCT 02711696]

Gastrointestinal Symptoms in Celiac Disease Patients on a Long-Term Gluten-Free Diet

Experience suggests that many celiac patients suffer from persistent symptoms despite a long-term gluten-free diet (GFD). We investigated the prevalence and severity of these symptoms in patients with variable duration of GFD. Altogether, 856 patients were classified into untreated (n = 128), short-term GFD (1–2 years, n = 93) and long-term GFD (≥3 years, n = 635) groups. Analyses were made of clinical and histological data and dietary adherence. Symptoms were evaluated by the validated GSRS questionnaire. One-hundred-sixty healthy subjects comprised the control group. Further, the severity of symptoms was compared with that in peptic ulcer, reflux disease, inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). Altogether, 93% of the short-term and 94% of the long-term treated patients had a strict GFD and recovered mucosa. Untreated patients had more diarrhea, indigestion and abdominal pain than those on GFD and controls. There were no differences in symptoms between the short- and long-term GFD groups, but both yielded poorer GSRS total score than controls (p = 0.03 and p = 0.05, respectively). Furthermore, patients treated 1–2 years had more diarrhea (p = 0.03) and those treated >10 years more reflux (p = 0.04) than controls. Long-term treated celiac patients showed relatively mild symptoms compared with other gastrointestinal diseases. Based on our results, good response to GFD sustained in long-term follow-up, but not all patients reach the level of healthy individuals.

Novel diagnostic techniques for celiac disease

The diagnosis of celiac disease has long been based on the demonstration of gluten-induced small-bowel mucosal damage. However, due to the constantly increasing disease prevalence and limitations in the histology-based criteria there is a pressure towards more serology-based diagnostics. The serological tools are being improved and new non-invasive methods are being developed, but the constantly refined endoscopic and histologic techniques may still prove helpful. Moreover, growing understanding of the disease pathogenesis has led researchers to suggest completely novel approaches to celiac disease diagnostics regardless of disease activity. In this review, we will elucidate the most recent development and possible future innovations in the diagnostic techniques for celiac disease.

Lack of endogenous cholecystokinin promotes cholelithogenesis in mice

BACKGROUND

Celiac disease is an autoimmune enteropathy caused by a permanent intolerance to dietary gluten in genetically predisposed individuals. Cholecystokinin (CCK) release from the proximal small intestine and gallbladder emptying in response to a fatty meal are greatly reduced in celiac patients before they start the gluten-free diet, showing a genetic predisposition to gallstones.

METHODS

To elucidate the complex pathophysiological mechanisms determining the biliary characteristic of celiac disease, we investigated the effect of the absence of endogenous CCK on cholesterol crystallization and gallstone formation in mice fed a lithogenic diet for 28 days.

KEY RESULTS

Fasting gallbladder volumes were increased and the response of gallbladder emptying to the high-fat diet was impaired in CCK knockout (KO) mice compared to wild-type mice. Because of the absence of CCK, small intestinal transit time was prolonged and intestinal cholesterol absorption was increased. During 28 days of feeding, elevated biliary cholesterol concentrations and gallbladder stasis promoted the growth and agglomeration of solid cholesterol crystals into microlithiasis and stones. Thus, cholesterol crystallization and gallstone formation were accelerated in CCK KO mice. In contrast, daily intraperitoneal administration of CCK-8 reduced gallstone formation in CCK KO mice even on the lithogenic diet.

CONCLUSIONS & INFERENCES

The lack of endogenous CCK enhances susceptibility to gallstones by impairing gallbladder contractile function and small intestinal motility function. These findings show that celiac disease is an important risk factor for gallstone formation and the gallbladder motility function should be routinely examined by ultrasonography and gallbladder stasis should be prevented in celiac patients.

The Role of Environmental Factors in the Development of Celiac Disease: What Is New?

Celiac disease (CD) is a systemic immune-mediated disorder caused by the ingestion of gluten-containing grains in genetically susceptible persons. It is one of the most common lifelong disorders, affecting approximately 1% of the general population. The prevalence of CD has increased in developed countries over recent decades, pointing to the role of additional environmental triggers other than gluten. It has been hypothesized that intestinal infections, the amount and quality of gluten, the intestinal microbiota, and early nutrition are all possible triggers of the switch from tolerance to an immune response to gluten. Two recent randomized controlled trials have been performed to clarify the relationship between the age at which gluten is introduced to a child’s diet and the risk of CD, showing that timing of gluten introduction does not modify the risk of CD. Both trials also showed that breastfeeding compared with no breastfeeding or breastfeeding duration or breastfeeding during gluten introduction have no effect on the risk of CD. The two trials, although not designed to address this issue, have shown that intestinal infections seem not to influence the risk of CD. Further studies are still needed to explore the missing environmental factors of CD for future prevention.

Intestinal microbiota modulates gluten-induced immunopathology in humanized mice

Celiac disease (CD) is an immune-mediated enteropathy triggered by gluten in genetically susceptible individuals. The recent increase in CD incidence suggests that additional environmental factors, such as intestinal microbiota alterations, are involved in its pathogenesis. However, there is no direct evidence of modulation of gluten-induced immunopathology by the microbiota. We investigated whether specific microbiota compositions influence immune responses to gluten in mice expressing the human DQ8 gene, which confers moderate CD genetic susceptibility. Germ-free mice, clean specific-pathogen-free (SPF) mice colonized with a microbiota devoid of opportunistic pathogens and Proteobacteria, and conventional SPF mice that harbor a complex microbiota that includes opportunistic pathogens were used. Clean SPF mice had attenuated responses to gluten compared to germ-free and conventional SPF mice. Germ-free mice developed increased intraepithelial lymphocytes, markers of intraepithelial lymphocyte cytotoxicity, gliadin-specific antibodies, and a proinflammatory gliadin-specific T-cell response. Antibiotic treatment, leading to Proteobacteria expansion, further enhanced gluten-induced immunopathology in conventional SPF mice. Protection against gluten-induced immunopathology in clean SPF mice was reversed after supplementation with a member of the Proteobacteria phylum, an enteroadherent Escherichia coli isolated from a CD patient. The intestinal microbiota can both positively and negatively modulate gluten-induced immunopathology in mice. In subjects with moderate genetic susceptibility, intestinal microbiota changes may be a factor that increases CD risk.