Increased Intestinal Permeability in Relatives of Patients With Crohn's Disease Is Not Associated With Small Bowel Ulcerations

Healthy First-Degree Relatives From Multiplex Families vs Simplex Families Have a Higher Subclinical Intestinal Inflammation, a Distinct Fecal Microbial Signature, and Harbor a Higher Risk of Developing Crohn's Disease

BACKGROUND & AIMS

Unaffected first-degree relatives (FDRs) from families with ≥2 affected FDRs with Crohn's disease (CD, multiplex families) have a high risk of developing CD, although the underlying mechanisms driving this risk are poorly understood. We aimed to identify differences in biomarkers between FDRs from multiplex vs simplex families and investigate the risk of future CD onset accounting for potential confounders.

METHODS

We assessed the Crohn's and Colitis Canada Genetic Environmental Microbial cohort of healthy FDRs of patients with CD. Genome-wide CD-polygenic risk scores, urinary fractional excretion of lactulose-to-mannitol ratio, fecal calprotectin (FCP), and fecal 16S ribosomal RNA microbiome were measured at recruitment. Associations between CD multiplex status and baseline biomarkers were determined using generalized estimating equations models. Cox models were used to assess the risk of future CD onset.

RESULTS

There were 4051 participants from simplex families and 334 from CD multiplex families. CD multiplex status was significantly associated with higher baseline FCP (P = .026) but not with baseline CD-polygenic risk scores or the lactulose-to-mannitol ratio. Three bacterial genera were found to be differentially abundant between both groups. CD multiplex status at recruitment was independently associated with an increased risk of developing CD (adjusted hazard ratio, 3.65; 95% confidence interval, 2.18-6.11, P < .001).

CONCLUSION

Within FDRs of patients with CD, participants from multiplex families had a 3-fold increased risk of CD onset, a higher FCP, and an altered bacterial composition, but not genetic burden or altered gut permeability. These results suggest that putative environmental factors might be enriched in FDRs from multiplex families.

Spontaneous episodic inflammation in the intestines of mice lacking HNF4A is driven by microbiota and associated with early life microbiota alterations

The inflammatory bowel diseases (IBD) occur in genetically susceptible individuals who mount inappropriate immune responses to their microbiota leading to chronic intestinal inflammation. Whereas IBD clinical presentation is well described, how interactions between microbiota and host genotype impact early subclinical stages of the disease remains unclear. The transcription factor hepatocyte nuclear factor 4 alpha (HNF4A) has been associated with human IBD, and deletion of Hnf4a in intestinal epithelial cells (IECs) in mice (Hnf4aΔIEC) leads to spontaneous colonic inflammation by 6-12 mo of age. Here, we tested if pathology in Hnf4aΔIEC mice begins earlier in life and if microbiota contribute to that process. Longitudinal analysis revealed that Hnf4aΔIEC mice reared in specific pathogen-free (SPF) conditions develop episodic elevated fecal lipocalin 2 (Lcn2) and loose stools beginning by 4-5 wk of age. Lifetime cumulative Lcn2 levels correlated with histopathological features of colitis at 12 mo. Antibiotic and gnotobiotic tests showed that these phenotypes in Hnf4aΔIEC mice were dependent on microbiota. Fecal 16S rRNA gene sequencing in SPF Hnf4aΔIEC and control mice disclosed that genotype significantly contributed to differences in microbiota composition by 12 mo, and longitudinal analysis of the Hnf4aΔIEC mice with the highest lifetime cumulative Lcn2 revealed that microbial community differences emerged early in life when elevated fecal Lcn2 was first detected. These microbiota differences included enrichment of a novel phylogroup of Akkermansia muciniphila in Hnf4aΔIEC mice. We conclude that HNF4A functions in IEC to shape composition of the gut microbiota and protect against episodic inflammation induced by microbiota throughout the lifespan. IMPORTANCE The inflammatory bowel diseases (IBD), characterized by chronic inflammation of the intestine, affect millions of people around the world. Although significant advances have been made in the clinical management of IBD, the early subclinical stages of IBD are not well defined and are difficult to study in humans. This work explores the subclinical stages of disease in mice lacking the IBD-associated transcription factor HNF4A in the intestinal epithelium. Whereas these mice do not develop overt disease until late in adulthood, we find that they display episodic intestinal inflammation, loose stools, and microbiota changes beginning in very early life stages. Using germ-free and antibiotic-treatment experiments, we reveal that intestinal inflammation in these mice was dependent on the presence of microbiota. These results suggest that interactions between host genotype and microbiota can drive early subclinical pathologies that precede the overt onset of IBD and describe a mouse model to explore those important processes.

Impaired Intestinal Permeability Assessed by Confocal Laser Endomicroscopy-A New Potential Therapeutic Target in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) represent a global phenomenon, with a continuously rising prevalence. The strategies concerning IBD management are progressing from clinical monitorization to a targeted approach, and current therapies strive to reduce microscopic mucosal inflammation and stimulate repair of the epithelial barrier function. Intestinal permeability has recently been receiving increased attention, as evidence suggests that it could be related to disease activity in IBD. However, most investigations do not successfully provide adequate information regarding the morphological integrity of the intestinal barrier. In this review, we discuss the advantages of confocal laser endomicroscopy (CLE), which allows in vivo visualization of histological abnormalities and targeted optical biopsies in the setting of IBD. Additionally, CLE has been used to assess vascular permeability and epithelial barrier function that could correlate with prolonged clinical remission, increased resection-free survival, and lower hospitalization rates. Moreover, the dynamic evaluation of the functional characteristics of the intestinal barrier presents an advantage over the endoscopic examination as it has the potential to select patients at risk of relapses. Along with mucosal healing, histological or transmural remission, the recovery of the intestinal barrier function emerges as a possible target that could be included in the future therapeutic strategies for IBD.

Altered Gut Microbiome Composition and Function Are Associated With Gut Barrier Dysfunction in Healthy Relatives of Patients With Crohn's Disease

BACKGROUND & AIMS

The gut microbiome has been suggested to play a role in gut barrier hemostasis, but data are scarce and limited to animal studies. We therefore aimed to assess whether alterations in gut microbial composition and functional pathways are associated with gut barrier function in a cohort of healthy first-degree relatives of patients with Crohn's disease.

METHODS

We used the Crohn's and Colitis Canada Genetic Environmental Microbial (CCC-GEM) cohort of healthy first-degree relatives of patients with Crohn's disease. Gut barrier function was assessed using the urinary fractional excretion of lactulose-to-mannitol ratio (LMR). Microbiome composition was assessed by sequencing fecal 16S ribosomal RNA. The cohort was divided into a discovery cohort (n = 2472) and a validation cohort (n = 655). A regression model was used to assess microbial associations with the LMR. A random forest classifier algorithm was performed to assess microbial community contribution to barrier function.

RESULTS

Individuals with impaired barrier function (LMR >0.025) had reduced alpha-diversity (Chao1 index, P = 4.0e-4) and altered beta-diversity (Bray-Curtis dissimilarity index, R² = 0.001, P = 1.0e-3) compared with individuals with an LMR ≤0.025. When taxa were assessed individually, we identified 8 genera and 52 microbial pathways associated with an LMR >0.025 (q < 0.05). Four genera (decreased prevalence of Adlercreutzia, Clostridia UCG 014, and Clostridium sensu stricto 1 and increased abundance of Colidextribacter) and 8 pathways (including decreased biosynthesis of glutamate, tryptophan, and threonine) were replicated in the validation cohort. The random forest approach revealed that the bacterial community is associated with gut barrier function (area under the curve, 0.63; P = 1.4e-6).

CONCLUSIONS

The gut microbiome community and pathways are associated with changes in gut barrier function. These findings may identify potential microbial targets to modulate gut barrier.

Mediterranean-Like Dietary Pattern Associations With Gut Microbiome Composition and Subclinical Gastrointestinal Inflammation

BACKGROUND & AIMS

Case-control studies have shown that patients with Crohn's disease (CD) have a microbial composition different from healthy individuals. Although the causes of CD are unknown, epidemiologic studies suggest that diet is an important contributor to CD risk, potentially via modulation of bacterial composition and gut inflammation. We hypothesized that long-term dietary clusters (DCs) are associated with gut microbiome compositions and gut inflammation. Our objectives were to identify dietary patterns and assess whether they are associated with alterations in specific gut microbial compositions and subclinical levels of gut inflammation in a cohort of healthy first-degree relatives (FDRs) of patients with CD.

METHODS

As part of the Genetic, Environmental, Microbial (GEM) Project, we recruited a cohort of 2289 healthy FDRs of patients with CD. Individuals provided stool samples and answered a validated food frequency questionnaire reflecting their habitual diet during the year before sample collection. Unsupervised analysis identified 3 dietary and 3 microbial composition clusters.

RESULTS

DC3, resembling the Mediterranean diet, was strongly associated with a defined microbial composition, with an increased abundance of fiber-degrading bacteria, such as Ruminococcus, as well as taxa such as Faecalibacterium. The DC3 diet was also significantly associated with lower levels of subclinical gut inflammation, defined by fecal calprotectin, compared with other dietary patterns. No significant associations were found between individual food items and fecal calprotectin, suggesting that long-term dietary patterns rather than individual food items contribute to subclinical gut inflammation. Additionally, mediation analysis demonstrated that DC3 had a direct effect on subclinical inflammation that was partially mediated by the microbiota.

CONCLUSIONS

Overall, these results indicated that Mediterranean-like dietary patterns are associated with microbiome and lower intestinal inflammation. This study will help guide future dietary strategies that affect microbial composition and host gut inflammation to prevent diseases.

A Simple, Robust, and Convenient HPLC Assay for Urinary Lactulose and Mannitol in the Dual Sugar Absorption Test

Background: Heterogeneous laborious analytical methodologies for the determination of urinary lactulose and mannitol limit their utility in intestinal permeability testing. Methods: We developed an assay using a Shimadzu HPLC system, an Aminex HPX87C column, and refractive index detection. The test was calibrated using a series of dilutions from standard stock solutions of lactulose and mannitol ‘spiked’ into urine samples. The utility to quantify urinary excretion during the dual sugar absorption test over 6 h was also determined. Results: Lactulose and mannitol were eluted isocratically at 5.7 and 10.1 min, respectively, with water as a mobile phase at a flow rate of 0.3 mL min⁻¹, 858 psi, 60 °C. The calibration curves for both sugars were linear up to 500 µg mL⁻¹ with a limit of detection in standard solutions at 4 µg mL⁻¹ and in ‘spiked’ urine samples at 15 µg mL⁻¹. The intra-assay and inter-assay CVs were between 2.0–5.1% and 2.0–5.1% for lactulose and 2.5–4.4% and 2.8–3.9% for mannitol. The urinary profiles of the 6 h absorption of lactulose and mannitol showed similar peak-retention times to standard solutions and were well-resolved at 5.9 and 10.4 min, respectively. Conclusions: The assay was easy to automate, using commonly available equipment and convenient requiring no prior laborious sample derivatization. The simplicity, reproducibility, and robustness of this assay facilitates its use in routine clinical settings for the quantification of intestinal permeability.

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

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

Exploring the Early Phase of Crohn's Disease

The development of Crohn's disease (CD) is characterized by a breakdown of homeostatic immune-bacterial communication, which takes place at the intestinal mucosa when environmental triggers impact genetically predisposed individuals. Converging lines of evidence support the hypothesis that this pathogenetic model develops through sequential, although inter-related, steps that indicate failure of mucosal defense mechanisms at various stages. In this context, immunologic phenomena that mediate the initial appearance of inflammatory lesions across the intestinal tissue may differ substantially from those that mediate and perpetuate chronic inflammatory responses. A compromise in the integrity of the epithelial barrier is among the earliest events and leads to accelerated influx of intraluminal antigens and intact microorganisms within the immunologically rich lamina propria. Inadequate clearance of invading microorganisms also may occur as a result of defects in innate immunity, preventing the timely and complete resolution of acute inflammatory responses. The final step is the development of persistent adaptive responses, which also differ between early and late Crohn's disease. Current progress in our ability to delineate single-cell transcriptomics and proteomics has allowed the discovery of cellular and molecular mechanisms that participate in each sequential step of CD development. This not only will advance our understanding of CD pathogenesis, but also facilitate the design of targeted therapeutic approaches.

Leaky Gut Syndrome Is Associated with Endotoxemia and Serum (1→3)-β-D-Glucan in Severe Dengue Infection

The hallmark of severe dengue infection is the increased vascular permeability and hemodynamic alteration that might be associated with an intestinal permeability defect. However, the mechanisms underlying the gastrointestinal-related symptoms of dengue are not well characterized. A prospective observational study was conducted on patients with dengue who were categorized according to: (i) febrile versus critical phase and (ii) hospitalized patients with versus without the warning signs to evaluate the gut barrier using lactulose-to-mannitol excretion ratio (LEMR). Serum endotoxins, (1→3)-β-D-glucan (BG), and inflammatory parameters were measured. A total of 48 and 38 patients were enrolled in febrile illness and critical phase, respectively, while 22 and 64 patients presented with or without the warning signs, respectively. At enrollment, a positive LEMR test was found in 20 patients (91%) with warning signs, regardless of phase of infection. Likewise, serum endotoxins and BG, the indirect biomarkers for leaky gut, prominently increased in patients who developed severe dengue when compared with the non-severe dengue (endotoxins, 399.1 versus 143.4 pg/mL (p < 0.0001); BG, 123 versus 73.8 pg/mL (p = 0.016)). Modest impaired intestinal permeability occurred in dengue patients, particularly those with warning signs, and were associated with endotoxemia and elevated BG. Thus, leaky gut syndrome might be associated with severity of dengue infection.

The dietary fibre rhamnogalacturonan improves intestinal epithelial barrier function in a microbiota-independent manner

BACKGROUND AND PURPOSE

Dietary fibre comprises a complex group of polysaccharides that are indigestible but are fermented by gut microbiota, promoting beneficial effects to the intestinal mucosa indirectly through the production of short chain fatty acids. We found that a polysaccharide, rhamnogalacturonan (RGal), from the plant Acmella oleracea, has direct effects on intestinal epithelial barrier function. Our objective was to determine the mechanism whereby RGal enhances epithelial barrier function.

EXPERIMENTAL APPROACH

Monolayers of colonic epithelial cell lines (Caco-2, T84) and of human primary cells from organoids were mounted in Ussing chambers to assess barrier function. The cellular mechanism of RGal effects on barrier function was determined using inhibitors of TLR-4 and PKC isoforms.

KEY RESULTS

Apically applied RGal (1000 μg/ml) significantly enhanced barrier function as shown by increased transepithelial electrical resistance (TER) and reduced fluorescein isothiocyanate (FITC)-dextran flux in Caco-2, T84 and human primary cell monolayers, and accelerated tight junction reassembly in Caco-2 cells in a calcium switch assay. RGal also reversed the barrier-damaging effects of inflammatory cytokines on FITC-dextran flux and preserved the tight junction distribution of occludin. RGal activated TLR4 in TLR4-expressing HEK reporter cells, an effect that was significantly inhibited by the TLR4 inhibitor, C34. The effect of RGal was also dependent on PKC, specifically the isoforms PKCd and PKCζ.

CONCLUSION AND IMPLICATIONS

RGal enhances intestinal epithelial barrier function through activation of TLR4 and PKC signaling pathways. Elucidation of RGal mechanisms of action could lead to new, dietary approaches to enhance mucosal healing in inflammatory bowel diseases.

Baseline Fecal Microbiota in Pediatric Patients With Celiac Disease Is Similar to Controls But Dissimilar After 1 Year on the Gluten-Free Diet

The objectives of this pilot study were to examine fecal microbiota composition of pediatric patients with celiac disease (CD) before and after a 1-year gluten-free diet (GFD) and to determine the association with symptoms and anti-tissue transglutaminase (aTTG) antibody.

Methods

Stool samples were obtained from pediatric patients with CD and from healthy controls. Patients were classified by the presence (diarrhea, abdominal pain, weight loss) or absence (asymptomatic, headache, fatigue, etc.) of typical CD gastrointestinal symptoms and by aTTG normalization post-GFD intervention (< 7 U/mL). Fecal microbial composition was measured using 16S ribosomal RNA gene amplicon sequencing of the V3-V4 region.

Results

At diagnosis, 13 of 22 patients with CD had typical gastrointestinal symptoms, the remaining patients having atypical or asymptomatic presentations. After a 1-year GFD, all symptomatic patients improved and 9 of 19 had normalized aTTG. Prior to GFD, no distinct microbial signature was observed between patients and controls (P = 0.39). Post-GFD, patients with CD had a unique microbial signature with reductions in known fiber-degrading bacteria, including Blautia, Dorea, Lactobacillus, and Prevotella compared with controls. Within the patients with CD, microbial composition was not associated with reported symptom presentation or aTTG normalization.

Conclusions

Pediatric patients with CD only had a unique microbial signature compared with healthy controls when placed on the GFD. These results suggest that pediatric patients with CD may not have a unique fecal microbial signature indicative of inherent dysbiosis, in contrast to that suggested for older patients. In children with CD, diet may play a role in shaping microbial composition more so than disease status.

Anti-Microbial Antibody Response is Associated With Future Onset of Crohn's Disease Independent of Biomarkers of Altered Gut Barrier Function, Subclinical Inflammation, and Genetic Risk

BACKGROUND AND AIMS

Altered host immune reactivity to microbial antigens is hypothesized to trigger the onset of Crohn's disease (CD). We aimed to assess whether increased serum anti-microbial antibody response in asymptomatic first-degree relatives (FDRs) of CD patients is an independent risk factor for future CD development.

METHODS

We measured host serum antibody response to 6 microbial antigens at enrollment (Prometheus enzyme-linked immunosorbent assay test: anti-Saccharomyces cerevisiae antibodies immunoglobulin A/immunoglobulin G, anti-OmpC, anti-A4-Fla2, anti-FlaX, anti-CBir1) and derived the sum of positive antibodies (AS). We used samples at enrollment of prospectively followed healthy FDRs from a nested case-control cohort of the Crohn's and Colitis Canada Genetics Environment Microbial Project. Those who later developed CD (n = 77) were matched 1:4 by age, sex, follow-up duration, and geographic location with control FDRs remaining healthy (n = 307). To address our research aims, we fitted a multivariable conditional logistic regression model and performed causal mediation analysis.

RESULTS

High baseline AS (≥2) (43% of cases, 11% of controls) was associated with higher risk of developing CD (adjusted odds ratio, 6.5; 95% confidence interval, 3.4-12.7; P < .001). Importantly, this association remained significant when adjusted for markers of gut barrier function, fecal calprotectin, C-reactive protein, and CD-polygenic risk score, and in subjects recruited more than 3 years before diagnosis. Causal mediation analysis showed that the effect of high AS on future CD development is partially mediated (42%) via preclinical gut inflammation.

CONCLUSIONS

Our results suggest that increased anti-microbial antibody responses are associated with risk of future development of CD, independent of biomarkers of abnormal gut barrier function, subclinical inflammation, and CD-related genetic risks. This suggests that anti-microbial antibody responses are an early predisease event in the development of CD.

Results of the Seventh Scientific Workshop of ECCO: Precision Medicine in IBD-Prediction and Prevention of Inflammatory Bowel Disease

Inflammatory bowel disease [IBD] is a complex chronic disorder with no clear aetiology and no known cure. Despite recent advances in overall disease management and improved therapeutics, patients with IBD still experience a substantial burden. Furthermore, as the incidence continues to increase in developing areas of the world, it is expected that the burden of IBD to society will increase and exert tremendous pressure on health care systems worldwide. Therefore, new strategies to prevent the global increase of IBD are urgently required. Data are being progressively acquired on the period preceding disease diagnosis, which support the concept that IBD has a preclinical period that may reveal the triggers of disease and may be amenable to early intervention. Having a better knowledge of this preclinical period will increase the potential not only for improved understanding of disease pathogenesis and improved therapeutics, but also for disease prediction and prevention.

Biomarkers for assessment of intestinal permeability in clinical practice

Intestinal permeability is an important diagnostic marker, yet its determination by established tests, which measure the urinary excretion of orally administered tracer molecules, is time consuming and can only be performed prospectively. Here, we aim to validate proposed surrogate biomarkers, which allow measuring intestinal permeability more easily. In this cross-sectional study, we included two independent cohorts comprising nonobese (Healthy cohort, n = 51) and individuals with obesity (Obesity cohort, n = 27). The lactulose/mannitol (lac/man) ratio was determined in all individuals as an established marker of intestinal permeability. Furthermore, we measured six potential surrogate biomarkers, being albumin, calprotectin, and zonulin, measured in feces, as well as intestinal fatty acid binding protein (I-FABP), lipopolysaccharide binding protein (LBP) and zonulin, measured in plasma. Correlation analyses and multiple linear regression models were conducted to assess possible associations between the established lac/man ratio and the proposed biomarkers by also evaluating a potential effect of age, body mass index (BMI), and sex. The lac/man ratio correlated with plasma LBP levels in all cohorts consistently and with the amount of fecal zonulin in overweight and obese individuals. Multiple linear regression models showed that the association between the lac/man ratio and plasma LBP was independent of age, BMI, and sex. Fecal zonulin levels were associated with the lac/man ratio as well as BMI, but not age and sex. Our data suggest plasma LBP as a promising biomarker for intestinal permeability in adults and fecal zonulin as a potential biomarker in overweight and obese individuals.NEW & NOTEWORTHY This study shows that biomarkers from blood and fecal samples are associated with the cumbersome established tests of intestinal permeability throughout different cohorts. Therefore, such biomarkers could be used to assess gut barrier function in prospective cohort studies and large-scale clinical trials for which tracer-based tests may not be feasible.

Serum Zonulin Measured by Commercial Kit Fails to Correlate With Physiologic Measures of Altered Gut Permeability in First Degree Relatives of Crohn's Disease Patients

Intestinal epithelial cell tight junctions (TJs) contribute to the integrity of the intestinal barrier allowing for control of the physical barrier between external antigens or bacterial products and the internal environment. Zonula occludens-1 (ZO-1) is a protein that modulates intestinal TJs, and serum levels of ZO-1 has been suggested as a biomarker of disrupted barrier function in humans. Previous studies suggested that increased intestinal permeability was associated with evidence of TJ abnormalities. However, there is limited information on the serological measurement of ZO-1 and its relation to other tests of barrier function in healthy subjects. We investigated the correlation of serum ZO-1, with physiologic measures of intestinal permeability (as the ratio of the fractional excretion of lactulose-mannitol or LMR) in a cohort of 39 healthy FDRs of Crohn's disease (CD) patients. No significant correlation was found between LMR and ZO-1 levels (r2 = 0.004, P < 0.71), or intestinal fatty acid binding proteins (I-FABP) (r2 = 0.004, P < 0.71). In conclusion, our data show that ZO-1 and I-FABP are not a marker of gut permeability as defined by LMR.

Are hospitalized patients with inflammatory bowel disease at increased risk of invasive bacterial infections? Results from POLIBD 3-year cohort study

The aim of this study was to determine the dominant species of bacteria found in blood cultures collected from patients under treatment in the tertiary inflammatory bowel disease (IBD) center in Poland. The dominant pathogen isolated from blood in patients with IBD was Staphylococcus epidermidis MRCNS (MRCNS—methicillin-resistant coagulase-negative Staphylococcus), a strain resistant to all beta-lactam antibiotics (penicillins, penicillins with B-lactamase inhibitor, cephalosporins and carbapenems). The second most commonly isolated pathogen found in the blood samples was Escherichia coli. Blood cultures were found to be positive for these pathogens more frequently in male patients (90.0%). An increased risk of bacteremia in IBD patients was associated with prolonged hospitalization.

Functional Food Components, Intestinal Permeability and Inflammatory Markers in Patients with Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are characterized by a chronic inflammatory process that affects the intestinal barrier structure. Recent evidence suggests that some food components can influence the integrity of the intestinal barrier and thus its permeability. We aimed at assessing the effect of food components on the intestinal permeability (IP) and on inflammatory markers in individuals with IBD by a single-blind randomized clinical study. Of the 53 individuals included, 47% (n = 25) had been diagnosed with IBD. The participants were divided into 4 groups. IBD patients were allocated to intervention group (n = 14) vs. no intervention group (n = 11), and the same happened with 28 control participants without disease (n = 14 in intervention group vs. n = 14 without intervention). Symptomatology, nutritional status, biochemical parameters (specifically serum zonulin (ZO) to measure IP) were evaluated on all individuals on an eight week period following a diet plan with/without potentially beneficial foods for the IP. At the beginning of the study, there were no significant differences in ZO values between individuals with and without IBD (p > 0.05). The effect of specific food components was inconclusive; however, a trend in the reduction of inflammatory parameters and on the prevalence of gastrointestinal symptomatology was observed. More controlled intervention studies with diet plans, including food components potentially beneficial for the integrity of the intestinal barrier, are of the utmost importance.

Diagnosis and natural history of preclinical and early inflammatory bowel disease

Inflammatory bowel disease is a chronic and progressive disorder of the gastrointestinal tract. A relevant proportion of patients develop complicated lesions, defined as strictures, fistulas and/or abscesses already at diagnosis, and this proportion increases over time. The preclinical phase defines the period of time from the appearance of the first immune disturbances until the development of overt disease, and it may be present months to years before the diagnosis. Multiple biomarkers (e.g., C-reactive protein, interleukin-6, fecal calprotectin) and cellular mechanisms (e.g., complement cascade, lysosomes, innate immunity, and glycosaminoglycan metabolism) are already altered during this period. Research in this area allows the description of the initial immune disturbances that may identify potential targets and lead to the development of new drug therapies. During this period, different interventions in high-risk individuals, including drugs or environmental factors, will open the possibility of innovative strategies focused on the reduction of complications, or even prevention trials for inflammatory bowel disease. Here, we review the most relevant findings regarding the characteristics, prevalence and biomarkers associated with preclinical disease, along with their possible use in our future clinical practice.

Genetic and Inflammatory Biomarkers Classify Small Intestine Inflammation in Asymptomatic First-degree Relatives of Patients With Crohn's Disease

BACKGROUND & AIMS

Relatives of individuals with Crohn's disease (CD) carry CD-associated genetic variants and are often exposed to environmental factors that increase their risk for this disease. We aimed to estimate the utility of genotype, smoking status, family history, and biomarkers can calculate risk in asymptomatic first-degree relatives of patients with CD.

METHODS

We recruited 480 healthy first-degree relatives (full siblings, offspring or parents) of patients with CD through the Guy's and St Thomas' NHS Foundation Trust and from members of Crohn's and Colitis, United Kingdom. DNA samples were genotyped using the Immunochip. We calculated a risk score for 454 participants, based on 72 genetic variants associated with CD, family history, and smoking history. Participants were assigned to highest and lowest risk score quartiles. We assessed pre-symptomatic inflammation by capsule endoscopy and measured 22 markers of inflammation in stool and serum samples (reference standard). Two machine-learning classifiers (elastic net and random forest) were used to assess the ability of the risk factors and biomarkers to identify participants with small intestinal inflammation in the same dataset.

RESULTS

The machine-learning classifiers identified participants with pre-symptomatic intestinal inflammation: elastic net (area under the curve, 0.80; 95% CI, 0.62-0.98) and random forest (area under the curve, 0.87; 95% CI, 0.75-1.00). The elastic net method identified 3 variables that can be used to calculate odds for intestinal inflammation: combined family history of CD (odds ratio, 1.31), genetic risk score (odds ratio, 1.14), and fecal calprotectin (odds ratio, 1.04). These same 3 variables were among the 5 factors associated with intestinal inflammation in the random forest model.

CONCLUSION

Using machine learning classifiers, we found that genetic variants associated with CD, family history, and fecal calprotectin together identify individuals with pre-symptomatic intestinal inflammation who are therefore at risk for CD. A tool for detecting people at risk for CD before they develop symptoms would help identify the individuals most likely to benefit from early intervention.

Increased Gut Permeability in First-degree Relatives of Children with Irritable Bowel Syndrome or Functional Abdominal Pain

BACKGROUND & AIMS

Increased gut permeability might contribute to the pathogenesis of irritable bowel syndrome or functional abdominal pain (IBS or FAP). We investigated whether siblings and parents of children with IBS or FAP have increased gut permeability.

METHODS

We performed permeability tests (using sucrose, lactulose, mannitol, and sucralose) on 29 siblings and 43 parents of children with IBS or FAP, and 43 children (controls) and 42 parents of controls, from primary and secondary care. Permeability studies were repeated in 7 siblings and 37 parents of children with IBS or FAP and 23 controls and 36 parents of controls following ingestion of 400 mg of ibuprofen. Percent recovery of sucrose was calculated based on analyses of urine collected overnight; the lactulose/mannitol ratio and percent recovery of sucralose were based on analyses of urine samples collected over a 24-hour period.

RESULTS

When we controlled for age, sex, and family membership, siblings of children with IBS or FAP had increased small bowel permeability (urinary lactulose/mannitol ratio) vs controls (P = .004). There was no difference in gastroduodenal (percent sucrose recovery) or colonic (percent sucralose recovery) permeability between groups. Similarly, parents of children with IBS or FAP also had increased small bowel permeability, compared with parents of controls (P = .015), with no differences in gastric or colonic permeability. After administration of ibuprofen, gastroduodenal and small bowel permeability tended to be greater in IBS or FAP siblings (P = .08) and gastroduodenal permeability tended to be greater in IBS or FAP parents (P = .086).

CONCLUSIONS

Siblings and parents of children with IBS or FAP have increased baseline small intestinal permeability compared with control children and their parents. These results indicate that there are familial influences on gastrointestinal permeability in patients with IBS or FAP.

Transdermal fluorescence detection of a dual fluorophore system for noninvasive point-of-care gastrointestinal permeability measurement

The intestinal mucosal barrier prevents macromolecules and pathogens from entering the circulatory stream. Tight junctions in this barrier are compromised in inflammatory bowel diseases, environmental enteropathy, and enteric dysfunction. Dual sugar absorption tests are a standard method for measuring gastrointestinal integrity, however, these are not clinically amenable. Herein, we report on a dual fluorophore system and fluorescence detection instrumentation for which gastrointestinal permeability is determined in a rat small bowel disease model from the longitudinal measured transdermal fluorescence of each fluorophore. This fluorophore technology enables a specimen-free, noninvasive, point-of-care gastrointestinal permeability measurement which should be translatable to human clinical studies.

Studies on patients establish Crohn's disease as a manifestation of impaired innate immunity

The fruitless search for the cause of Crohn's disease has been conducted for more than a century. Various theories, including autoimmunity, mycobacterial infection and aberrant response to food and other ingested materials, have been abandoned for lack of robust proof. This review will provide the evidence, obtained from patients with this condition, that the common predisposition to Crohn's is a failure of the acute inflammatory response to tissue damage. This acute inflammation normally attracts large numbers of neutrophil leucocytes which engulf and clear bacteria and autologous debris from the inflamed site. The underlying predisposition in Crohn's disease is unmasked by damage to the bowel mucosa, predominantly through infection, which allows faecal bowel contents access to the vulnerable tissues within. Consequent upon failure of the clearance of these infectious and antigenic intestinal contents, it becomes contained, leading to a chronic granulomatous inflammation, producing cytokine release, local tissue damage and systemic symptoms. Multiple molecular pathologies extending across the whole spectrum of the acute inflammatory and innate immune response lead to the common predisposition in which defective monocyte and macrophage function plays a central role. Family linkage and exome sequencing together with GWAS have identified some of the molecules involved, including receptors, molecules involved in vesicle trafficking, and effector cells. Current therapy is immunosuppressant, which controls the symptoms but accentuates the underlying problem, which can only logically be tackled by correcting the primary lesion/s by gene therapy or genome editing, or through the development of drugs that stimulate innate immunity.

Capturing the Biologic Onset of Inflammatory Bowel Diseases: Impact on Translational and Clinical Science

While much progress has been made in the last two decades in the treatment and the management of inflammatory bowel diseases (IBD)-both ulcerative colitis (UC) and Crohn's Disease (CD)-as of today these conditions are still diagnosed only after they have become symptomatic. This is a major drawback since by then the inflammatory process has often already caused considerable damage and the disease might have become partially or totally unresponsive to medical therapy. Late diagnosis in IBD is due to the lack of accurate, non-invasive indicators that would allow disease identification during the pre-clinical stage-as it is often done in many other medical conditions. Here, we will discuss what is known about the biologic onset and pre-clinical CD with an emphasis on studies conducted in patients' first degree relatives. We will then review the possible strategies to diagnose IBD very early in time including screening, available disease markers and imaging, and the possible clinical implications of treating these conditions at or close to their biologic onset. Later, we will review the potential impact of conducting translational research in IBD during the pre-clinical stage, especially focusing on the role of the microbiome in disease etiology and pathogenesis. Finally, we will highlight possible future developments in the field and how they can impact IBD management and our scientific knowledge of these conditions.

Evolving role of diet in the pathogenesis and treatment of inflammatory bowel diseases

Recent advances in basic and clinical science over the last 3 years have dramatically altered our appreciation of the role of diet in inflammatory bowel diseases (IBD). The marked increase in incidence of these diseases along with the important role of non-genetic susceptibility among patients with IBD has highlighted that these diseases have a strong environmental component. Progress in the field of microbiome and IBD has demonstrated that microbiome appears to play an important role in pathogenesis, and that diet may in turn impact the composition and functionality of the microbiome. Uncontrolled clinical studies have demonstrated that various dietary therapies such as exclusive enteral nutrition and newly developed exclusion diets might be potent tools for induction of remission at disease onset, for patients failing biologic therapy, as a treatment for disease complications and in reducing the need for surgery. We review these advances from bench to bedside, along with the need for better clinical trials to support these interventions.

Inter-kingdom effect on epithelial cells of the N-Acyl homoserine lactone 3-oxo-C12:2, a major quorum-sensing molecule from gut microbiota

Background and aims

N-acyl homoserine lactones (AHLs), which are autoinducer quorum-sensing molecules involved in the bacterial communication network, also interact with eukaryotic cells. Searching for these molecules in the context of inflammatory bowel disease (IBD) is appealing. The aims of our study were to look for AHL molecules in faecal samples from healthy subjects (HS) and IBD patients to correlate AHL profiles with the microbiome and investigate the effect of AHLs of interest on epithelial cells.

Methods

Using mass spectrometry, we characterised AHL profiles in faecal samples from HS (n = 26) and IBD patients in remission (n = 24) and in flare (n = 25) and correlated the presence of AHLs of interest with gut microbiota composition obtained by real-time qPCR and 16S sequencing. We synthesised AHLs of interest to test the inflammatory response after IL1β stimulation and paracellular permeability on Caco-2 cells.

Results

We observed 14 different AHLs, among which one was prominent. This AHL corresponded to 3-oxo-C12:2 and was found significantly less frequently in IBD patients in flare (16%) and in remission (37.5%) versus HS (65.4%) (p = 0.001). The presence of 3-oxo-C12:2 was associated with significantly higher counts of Firmicutes, especially Faecalbacterium prausnitzii, and lower counts of Escherichia coli. In vitro, 3-oxo-C12:2 exerted an anti-inflammatory effect on Caco-2 cells. Interestingly, although 3-oxo-C12, the well-known AHL from Pseudomonas aeruginosa, increased paracellular permeability, 3-oxo-C12:2 did not.

Conclusions

We identified AHLs in the human gut microbiota and discovered a new and prominent AHL, 3-oxo-C12:2, which correlates with normobiosis and exerts a protective effect on gut epithelial cells.