Giada De Palma

Proton Pump Inhibitors Exacerbate NSAID-Induced Small Intestinal Injury by Inducing Dysbiosis

BACKGROUND & AIMS Proton pump inhibitors (PPIs) and nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used classes of drugs, with the former frequently coprescribed to reduce gastroduodenal injury caused by the latter. However, suppression of gastric acid secretion by PPIs is unlikely to provide any protection against the damage caused by NSAIDs in the more distal small intestine. METHODS Rats were treated with antisecretory doses of omeprazole or lanzoprazole for 9 days, with concomitant treatment with anti-inflammatory doses of naproxen or celecoxib on the final 4 days. Small intestinal damage was blindly scored, and changes in hematocrit were measured. Changes in small intestinal microflora were evaluated by denaturing gradient gel electrophoresis and reverse-transcription polymerase chain reaction. RESULTS Both PPIs significantly exacerbated naproxen- and celecoxib-induced intestinal ulceration and bleeding in the rat. Omeprazole treatment did not result in mucosal injury or inflammation; however, there were marked shifts in numbers and types of enteric bacteria, including a significant reduction (∼80%) of jejunal Actinobacteria and Bifidobacteria spp. Restoration of small intestinal Actinobacteria numbers through administration of selected (Bifidobacteria enriched) commensal bacteria during treatment with omeprazole and naproxen prevented intestinal ulceration/bleeding. Colonization of germ-free mice with jejunal bacteria from PPI-treated rats increased the severity of NSAID-induced intestinal injury, as compared with mice colonized with bacteria from vehicle-treated rats. CONCLUSIONS PPIs exacerbate NSAID-induced intestinal damage at least in part because of significant shifts in enteric microbial populations. Prevention or reversal of this dysbiosis may be a viable option for reducing the incidence and severity of NSAID enteropathy.

Intestinal dysbiosis and reduced immunoglobulin-coated bacteria associated with coeliac disease in children

BackgroundCoeliac disease is a chronic intestinal inflammatory disorder due to an aberrant immune response to dietary gluten proteins in genetically predisposed individuals. Mucosal immune response through IgA secretion constitutes a first line of defence responsible for neutralizing noxious antigens and pathogens. The aim of this study was the characterization of the relationships between immunoglobulin-coated bacteria and bacterial composition of faeces of coeliac disease (CD) patients, untreated and treated with a gluten-free diet (GFD) and healthy controls.ResultsIgA-coated faecal bacterial levels were significantly lower in both untreated and treated CD patients than in healthy controls. IgG and IgM-coated bacterial levels were also significantly lower in treated CD patients than in untreated CD patients and controls. Gram-positive to Gram-negative bacteria ratio was significantly reduced in both CD patients compared to controls. Bifidobacterium, Clostridium histolyticum, C. lituseburense and Faecalibacterium prausnitzii group proportions were less abundant (P < 0.050) in untreated CD patients than in healthy controls. Bacteroides-Prevotella group proportions were more abundant (P < 0.050) in untreated CD patients than in controls. Levels of IgA coating the Bacteroides-Prevotella group were significantly reduced (P < 0.050) in both CD patients in comparison with healthy controls.ConclusionsIn CD patients, reduced IgA-coated bacteria is associated with intestinal dysbiosis, which altogether provide new insights into the possible relationships between the gut microbiota and the host defences in this disorder.

Effects of a gluten-free diet on gut microbiota and immune function in healthy adult human subjects

Diet influences the composition of the gut microbiota and hosts health, particularly in patients suffering from food-related diseases. Coeliac disease (CD) is a permanent intolerance to cereal gluten proteins and the only therapy for the patients is to adhere to a life-long gluten-free diet (GFD). In the present preliminary study, the effects of a GFD on the composition and immune function of the gut microbiota were analysed in ten healthy subjects (mean age 30.3 years) over 1 month. Faecal microbiota was analysed by fluorescence in situ hybridisation (FISH) and quantitative PCR (qPCR). The ability of faecal bacteria to stimulate cytokine production by peripheral blood mononuclear cells (PBMC) was determined by ELISA. No significant differences in dietary intake were found before and after the GFD except for reductions (P = 0.001) in polysaccharides. Bifidobacterium, Clostridium lituseburense and Faecalibacterium prausnitzii proportions decreased (P = 0.007, P = 0.031 and P = 0.009, respectively) as a result of the GFD analysed by FISH. Bifidobacterium, Lactobacillus and Bifidobacterium longum counts decreased (P = 0.020, P = 0.001 and P = 0.017, respectively), while Enterobacteriaceae and Escherichia coli counts increased (P = 0.005 and P = 0.003) after the GFD assessed by qPCR. TNF-alpha, interferon-gamma, IL-10 and IL-8 production by PBMC stimulated with faecal samples was also reduced (P = 0.021, P = 0.037, P = 0.002 and P = 0.007, respectively) after the diet. Therefore, the GFD led to reductions in beneficial gut bacteria populations and the ability of faecal samples to stimulate the hosts immunity. Thus, the GFD may constitute an environmental variable to be considered in treated CD patients for its possible effects on gut health.

The microbiota–gut–brain axis in gastrointestinal disorders: stressed bugs, stressed brain or both?

The gut–brain axis is the bidirectional communication between the gut and the brain, which occurs through multiple pathways that include hormonal, neural and immune mediators. The signals along this axis can originate in the gut, the brain or both, with the objective of maintaining normal gut function and appropriate behaviour. In recent years, the study of gut microbiota has become one of the most important areas in biomedical research. Attention has focused on the role of gut microbiota in determining normal gut physiology and immunity and, more recently, on its role as modulator of host behaviour (‘microbiota–gut–brain axis’). We therefore review the literature on the role of gut microbiota in gut homeostasis and link it with mechanisms that could influence behaviour. We discuss the association of dysbiosis with disease, with particular focus on functional bowel disorders and their relationship to psychological stress. This is of particular interest because exposure to stressors has long been known to increase susceptibility to and severity of gastrointestinal diseases.

Unraveling the Ties between Celiac Disease and Intestinal Microbiota

Celiac disease is a multifactorial disorder that involves interactions between genetic and environmental factors. Gluten proteins are responsible for the symptoms of celiac disease, but other environmental factors that influence the intestinal ecosystem, including the milk-feeding type and gastrointestinal infections, may also play a role. Moreover, intestinal dysbiosis, characterized by increased Gram-negative bacteria and reduced bifidobacteria, has been detected in celiac disease patients. This review summarizes current knowledge of the associations between the intestinal microbiota and celiac disease and its possible modes of action in pathogenesis. Deeper understanding of these interactions can help redefine how this disorder is investigated.

FODMAPs alter symptoms and the metabolome of patients with IBS: a randomised controlled trial

Objective To gain mechanistic insights, we compared effects of low fermentable oligosaccharides, disaccharides and monosaccharides and polyols (FODMAP) and high FODMAP diets on symptoms, the metabolome and the microbiome of patients with IBS. Design We performed a controlled, single blind study of patients with IBS (Rome III criteria) randomised to a low (n=20) or high (n=20) FODMAP diet for 3 weeks. Symptoms were assessed using the IBS symptom severity scoring (IBS-SSS). The metabolome was evaluated using the lactulose breath test (LBT) and metabolic profiling in urine using mass spectrometry. Stool microbiota composition was analysed by 16S rRNA gene profiling. Results Thirty-seven patients (19 low FODMAP; 18 high FODMAP) completed the 3-week diet. The IBS-SSS was reduced in the low FODMAP diet group (p<0.001) but not the high FODMAP group. LBTs showed a minor decrease in H2 production in the low FODMAP compared with the high FODMAP group. Metabolic profiling of urine showed groups of patients with IBS differed significantly after the diet (p<0.01), with three metabolites (histamine, p-hydroxybenzoic acid, azelaic acid) being primarily responsible for discrimination between the two groups. Histamine, a measure of immune activation, was reduced eightfold in the low FODMAP group (p<0.05). Low FODMAP diet increased Actinobacteria richness and diversity, and high FODMAP diet decreased the relative abundance of bacteria involved in gas consumption. Conclusions IBS symptoms are linked to FODMAP content and associated with alterations in the metabolome. In subsets of patients, FODMAPs modulate histamine levels and the microbiota, both of which could alter symptoms. Trial registration number NCT01829932.

Commensal and probiotic bacteria influence intestinal barrier function and susceptibility to colitis in Nod1-/-; Nod2-/- mice.

Background: The intestinal microbiota regulates key host functions. It is unknown whether modulation of the microbiota can affect a genetically determined host phenotype. Polymorphisms in the Nucleotide oligomerization domain (Nod)‐like receptor family confer genetic risk for inflammatory bowel disease (IBD). We investigated whether the intestinal microbiota and the probiotic strain Bifidobacterium breve NCC2950 affect intestinal barrier function and responses to intestinal injury in Nod1−/−;Nod2−/− mice. Methods: Specific pathogen‐free (SPF) Nod1−/−;Nod2−/− mice and mice gnotobiotically derived with altered Schaedler flora (ASF) biota were used. SPF Nod1+/−;Nod2+/−littermates (generated by crossing SPF Nod1−/−;Nod2−/− and germ‐free C57BL/6 mice) and ASF Nod1+/−;Nod2+/− mice were used as controls. SPF mice were gavaged daily with 109‐CFU B. breve for 14 days before colitis induction. Denaturing gradient gel electrophoresis (DGGE) and real‐time polymerase chain reaction (PCR) were used to assess microbiota composition. Intestinal permeability was assessed by in vitro and in vivo techniques. Expressions of epithelial apical junction proteins, mucin, and antimicrobial proteins were assessed by quantitative reverse‐transcription PCR (qRT‐PCR) and immunofluorescence. Responses to intestinal injury were investigated using an acute experimental model of colitis. Results: Under SPF conditions, Nod1−/−;Nod2−/− mice had increased paracellular permeability, decreased E‐cadherin, and lower colonic antimicrobial RegIII‐&ggr; expression compared to Nod1+/−;Nod2+/− littermate controls. These changes were associated with increased susceptibility to colitis. ASF colonization or B. breve supplementation normalized RegIII‐&ggr; expression and decreased susceptibility to dextran sodium sulfate (DSS) colitis in Nod1−/−;Nod2−/− mice. Conclusions: The intestinal microbiota influences colitis severity in Nod1−/−;Nod2−/− mice. The results suggest that colonization strategies with defined commensals or exogenous specific probiotic therapy may prevent intestinal inflammation in a genetically predisposed host. (Inflamm Bowel Dis 2012)

Role of Intestinal Bacteria in Gliadin-Induced Changes in Intestinal Mucosa: Study in Germ-Free Rats

Background and Aims Celiac disease (CD) is a chronic inflammatory disorder of the small intestine that is induced by dietary wheat gluten proteins (gliadins) in genetically predisposed individuals. The overgrowth of potentially pathogenic bacteria and infections has been suggested to contribute to CD pathogenesis. We aimed to study the effects of gliadin and various intestinal bacterial strains on mucosal barrier integrity, gliadin translocation, and cytokine production. Methodology/Principal Findings Changes in gut mucosa were assessed in the intestinal loops of inbred Wistar-AVN rats that were reared under germ-free conditions in the presence of various intestinal bacteria (enterobacteria and bifidobacteria isolated from CD patients and healthy children, respectively) and CD-triggering agents (gliadin and IFN-γ) by histology, scanning electron microscopy, immunofluorescence, and a rat cytokine antibody array. Adhesion of the bacterial strains to the IEC-6 rat cell line was evaluated in vitro. Gliadin fragments alone or together with the proinflammatory cytokine interferon (IFN)-γ significantly decreased the number of goblet cells in the small intestine; this effect was more pronounced in the presence of Escherichia coli CBL2 and Shigella CBD8. Shigella CBD8 and IFN-γ induced the highest mucin secretion and greatest impairment in tight junctions and, consequently, translocation of gliadin fragments into the lamina propria. Shigella CBD8 and E. coli CBL2 strongly adhered to IEC-6 epithelial cells. The number of goblet cells in small intestine increased by the simultaneous incubation of Bifidobacterium bifidum IATA-ES2 with gliadin, IFN-γ and enterobacteria. B. bifidum IATA-ES2 also enhanced the production of chemotactic factors and inhibitors of metalloproteinases, which can contribute to gut mucosal protection. Conclusions Our results suggest that the composition of the intestinal microbiota affects the permeability of the intestinal mucosa and, consequently, could be involved in the early stages of CD pathogenesis.

Influence of Environmental and Genetic Factors Linked to Celiac Disease Risk on Infant Gut Colonization by Bacteroides Species

ABSTRACT Celiac disease (CD) is an immune-mediated enteropathy involving genetic and environmental factors whose interaction might influence disease risk. The aim of this study was to determine the effects of milk-feeding practices and the HLA-DQ genotype on intestinal colonization of Bacteroides species in infants at risk of CD development. This study included 75 full-term newborns with at least one first-degree relative suffering from CD. Infants were classified according to milk-feeding practice (breast-feeding or formula feeding) and HLA-DQ genotype (high or low genetic risk). Stools were analyzed at 7 days, 1 month, and 4 months by PCR and denaturing gradient gel electrophoresis (DGGE). The Bacteroides species diversity index was higher in formula-fed infants than in breast-fed infants. Breast-fed infants showed a higher prevalence of Bacteroides uniformis at 1 and 4 months of age, while formula-fed infants had a higher prevalence of B. intestinalis at all sampling times, of B. caccae at 7 days and 4 months, and of B. plebeius at 4 months. Infants with high genetic risk showed a higher prevalence of B. vulgatus, while those with low genetic risk showed a higher prevalence of B. ovatus, B. plebeius, and B. uniformis. Among breast-fed infants, the prevalence of B. uniformis was higher in those with low genetic risk than in those with high genetic risk. Among formula-fed infants, the prevalence of B. ovatus and B. plebeius was increased in those with low genetic risk, while the prevalence of B. vulgatus was higher in those with high genetic risk. The results indicate that both the type of milk feeding and the HLA-DQ genotype influence the colonization process of Bacteroides species, and possibly the disease risk.

Bifidobacterium strains suppress in vitro the pro-inflammatory milieu triggered by the large intestinal microbiota of coeliac patients.

BackgroundCoeliac disease (CD) is an enteropathy characterized by an aberrant immune response to cereal-gluten proteins. Although gluten peptides and microorganisms activate similar pro-inflammatory pathways, the role the intestinal microbiota may play in this disorder is unknown. The purpose of this study was to assess whether the faecal microbiota of coeliac patients could contribute to the pro-inflammatory milieu characteristic of CD and the possible benefits of bifidobacteria.MethodsThe effect of faeces of 26 CD patients with active disease (mean age 5.5 years, range 2.1–12.0 years), 18 symptom-free coeliac disease (SFCD) patients (mean age 5.5 years, range 1.0–12.3 years) on a gluten-free diet for 1–2 years; and 20 healthy children (mean age 5.3 years, range 1.8–10.8 years) on induction of cytokine production and surface antigen expression in peripheral blood mononuclear cells (PBMCs) were determined. The possible regulatory roles of Bifidobacterium longum ES1 and B. bifidum ES2 co-incubated with faecal samples were also assessed in vitro.ResultsFaeces of both active CD and SFCD patients, representing an imbalanced microbiota, significantly increased TNF-α production and CD86 expression in PBMCs, while decreased IL-10 cytokine production and CD4 expression compared with control samples. Active CD-patient samples also induced significantly higher IFN-γ production compared with controls. However, Bifidobacterium strains suppressed the pro-inflammatory cytokine pattern induced by the large intestinal content of CD patients and increased IL-10 production. Cytokine effects induced by faecal microbiota seemed to be mediated by the NFκB pathway.ConclusionThe intestinal microbiota of CD patients could contribute to the Th1 pro-inflammatory milieu characteristic of the disease, while B. longum ES1 and B. bifidum ES2 could reverse these deleterious effects. These findings hold future perspectives of interest in CD therapy.