Subclinical intestinal inflammation in siblings of children with Crohn's disease

Deciphering the different phases of preclinical inflammatory bowel disease

Inflammatory bowel disease (IBD) is an immune-mediated inflammatory disease (IMID) of the gastrointestinal tract and includes two subtypes: Crohn's disease and ulcerative colitis. It is well-recognized that IBD is associated with a complex multifactorial aetiology that includes genetic predisposition and environmental exposures, with downstream dysregulation of systemic immune function and host-microbial interactions in the local environment in the gut. Evidence to support the notion of a multistage development of IBD is growing, as has been observed in other IMIDs such as rheumatoid arthritis and systemic lupus erythematosus. With the rising worldwide incidence of IBD, it is increasingly important to understand the complex interplay of pathological events during the different stages of disease development to enable IBD prediction and prevention strategies. In this article, we review comprehensively the current evidence pertaining to the preclinical phase of IBD, including at-risk, initiation and expansion phases. We also discuss the framework of preclinical IBD, expanding on underlying pathways in IBD development, future research directions and IBD development in the context of other IMIDs.

Performance of fecal S100A12 as a novel non-invasive diagnostic biomarker for pediatric inflammatory bowel disease: a systematic review and meta-analysis

OBJECTIVE

The incidence and prevalence of inflammatory bowel disease (IBD) in pediatric patients are increasing. Currently, the diagnostic method for IBD is inconvenient, expensive, and difficult. S100A12, a type of calcium-binding protein, detected in the feces of patients with IBD has recently been suggested as a promising diagnostic tool. Hence, the authors aimed to evaluate the accuracy of fecal S100A12 in diagnosing IBD in pediatric patients by performing a meta-analysis.

METHODS

The authors performed a systematic literature search in five electronic databases for eligible studies up to July 15, 2021. Pooled diagnostic accuracies of fecal S100A12 were analyzed as the primary outcomes. Secondary outcomes were standardized mean difference (SMD) of fecal S100A12 levels between IBD and non-IBD groups and a comparison of diagnostic accuracies between fecal S100A12 and fecal calprotectin.

RESULTS

Seven studies comprising 712 children and adolescents (474 non-IBD controls and 238 IBD cases) were included. Fecal S100A12 levels were higher in the IBD group than in the non-IBD group (SMD = 1.88; 95% confidence interval [CI] = 1.19-2.58; p < 0.0001). Fecal S100A12 could diagnose IBD in pediatric patients with a pooled sensitivity of 95% (95% CI = 88%-98%), specificity of 97% (95% CI = 95%-98%), and area under the receiver operating summary characteristics (AUSROC) curve of 0.99 (95% CI = 0.97-0.99). Fecal S100A12 specificity and AUSROC curve values were higher than those of fecal calprotectin (p < 0.05).

CONCLUSION

Fecal S100A12 may serve as an accurate and non-invasive tool for diagnosing pediatric IBD.

Preclinical Markers in Inflammatory Bowel Disease. A Nested Case-Control Study

Background

Our objective was to determine if patients who later develop inflammatory bowel disease (IBD) show signs of increased inflammatory activity in plasma measured with high sensitivity C-reactive protein (CRP), calprotectin, and albumin before the clinical onset of IBD.

Methods

We identified 96 subjects who later developed IBD (70 ulcerative colitis [UC] and 26 Crohn's disease [CD]). High sensitivity CRP, calprotectin, and albumin were analyzed in frozen plasma, donated from cases and sex-age matched controls 1-15 years before diagnosis.

Results

We found that subjects who later developed UC had lower albumin levels, and subjects who later developed CD had higher CRP levels than controls. Multivariable conditional logistic regression with albumin, calprotectin, and CRP showed a lower risk for developing IBD and UC with higher albumin levels (odds ratio [OR] 0.79, confidence interval [CI] 0.69-0.90; respective OR 0.77, CI 0.66-0.91). Higher CRP levels were associated with an increased risk of developing CD (OR 1.314, CI 1.060-1.630). When adjusting for body mass index or smoking in the logistic regression model, similar results were found. Plasma calprotectin levels in the preclinical period among patients with IBD did not differ from controls.

Conclusions

In this nested case-control study, subjects who later developed IBD had signs of low-grade systemic inflammation, indicated by significantly higher CRP plasma levels in CD and lower albumin plasma levels in UC, before the onset of clinical disease.

The Gut Microbial Profile of Preclinical Crohn's Disease Is Similar to That of Healthy Controls

BACKGROUND AND AIMS

It is unclear whether microbial dysbiosis plays an etiologic role in Crohn's disease (CD) or is the result of protracted inflammation. Here, we test the hypothesis that dysbiosis predates clinical CD in asymptomatic first-degree relatives (FDRs) of CD patients: normal (FDR1), with borderline inflammation (FDR2), and with frank, very early inflammation (FDR3).

METHODS

The gut microbial diversity was tested in ileocecal biopsies through next generation sequencing of the 16S rRNA gene in 10 healthy controls (HCs), 22 patients with active, untreated CD, and 25 FDRs (9 FDR1; 12 FDR2; 4 FDR3). The metagenomic functions of 41 microbiome-related processes were inferred by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis.

RESULTS

Compared with HCs, alpha diversity in CD patients was decreased, with an observed decrease in Faecalibacterium prausnitzii and increase in Bacteroides fragilis. In FDRs, microbial diversity was unchanged compared with HCs. In Operational Taxonomic Units and PICRUSt Principal coordinates and component analyses, the ellipse centroid of FDRs was diagonally opposed to that of CD patients, but close to the HC centroid. In both analyses, statistically significant differences in terms of beta diversity were found between CD and HC but not between FDR and HC.

CONCLUSIONS

In FDRs (including FDR3-who bear preclinical/biologic onset disease), we found that the microbial profile is remarkably similar to HC. If confirmed in larger studies, this finding suggests that clinical CD-associated dysbiosis could result from the changed microenvironment due to disease evolution over time.

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.

Fecal biomarkers in inflammatory bowel disease

Over the last two decades, knowledge on fecal biomarkers has substantially increased. Nowadays, these non-invasive markers of inflammation have significant clinical utility in the management of inflammatory bowel disease. Their use informs the decision to perform endoscopy before diagnosis is made right through to influencing therapeutic choices and the need for interval endoscopic assessment. In this review, the roles of two S100 proteins, calprotectin, and S100A12 are described along with that of lactoferrin, in the context of inflammatory bowel disease.

Management Strategies to Improve Outcomes of Patients With Inflammatory Bowel Diseases

Strategies for management of inflammatory bowel diseases are shifting from simple control of symptoms toward full control of these diseases (clinical and endoscopic remission), with the final aim of blocking their progression and preventing bowel damage and disability. New goals have been proposed for treatment, such as treat to target and tight control based on therapeutic monitoring and early intervention. For patients who achieve clinical remission, there is often interest in discontinuation of therapy due to safety or economic concerns. We review the evidence supporting these emerging paradigms, the reasons that early effective treatment can alter progression of inflammatory bowel diseases, the importance of examining objective signs of inflammation, and the safety of reducing treatment dosage. We also discuss recent findings regarding personalization of care, including factors that predict patient outcomes and response to therapies, as well as preventative strategies.

Infliximab Selectively Modulates the Circulating Blood Monocyte Repertoire in Crohn's Disease

BACKGROUND

Infliximab (IFX), an anti-tumour necrosis factor alpha (TNFα) monoclonal antibody, provides clinical benefits in treating Crohn's disease (CD) but its mechanisms of action are not fully elucidated. This study investigated blood monocyte repertoires and the acute effects of IFX infusion on monocyte subset phenotype and function in IFX-treated patients with CD.

METHODS

Monocytes and monocyte subsets were enumerated and phenotypically characterized by multicolor flow cytometry in freshly isolated blood from healthy controls (n = 21) and patients with CD treated with (IFX, n = 24) and without (non-IFX, n = 20) IFX. For the IFX-CD group, blood was sampled immediately before (tough-IFX) and after (peak-IFX) infusion. Monocyte responses to lipopolysaccharide were analyzed by whole-blood intracellular cytokine staining.

RESULTS

Non-IFX and IFX-CD patients had increased numbers of intermediate (CD14CD16) monocytes compared with healthy controls, whereas classical (CD14CD16) and nonclassical (CD14CD16) monocytes were numerically reduced in the IFX-CD group alone. In all groups, monocyte subsets expressed high surface levels of transmembrane (tm)TNFα. After IFX infusion, a significant reduction in monocyte numbers occurred. Post-IFX monocytopenia was proportionately greatest for classical and intermediate subsets, correlated with postinfusion IFX levels and was not associated with monocyte apoptosis. In contrast, lipopolysaccharide-induced production of TNFα and IL-12 by monocytes was significantly reduced in peak-IFX compared with trough-IFX blood samples.

CONCLUSIONS

Actively managed CD is associated with monocyte repertoire skewing suggestive of chronic inflammatory stimulation. Infused IFX acutely targets monocytes, likely by binding to tmTNFα, resulting in a non-apoptosis-related decline in circulating monocyte numbers and blunting of the inflammatory response of monocytes remaining in the blood.

Vitamin D and the Pathogenesis of Inflammatory Bowel Disease

Vitamin D has traditionally been known for its role in bone metabolism, but emerging evidence has suggested a broader role for vitamin D in immune regulation. Vitamin D deficiency has been associated with the pathogenesis of diverse autoimmune disorders and has similarly been implicated as a contributor to inflammatory bowel disease. In this review, we discuss animal, in vitro, genetic, and epidemiologic studies that have linked vitamin D deficiency with inflammatory bowel disease pathogenesis or severity. Nonetheless, we present the caveat in interpreting these studies in the context of reverse causation: Does vitamin D deficiency lead to gastrointestinal disease, or does gastrointestinal disease (with related changes in dietary choices, intestinal absorption, nutritional status, lifestyle) lead to vitamin D deficiency?

Preclinical and Undiagnosed Crohn's Disease: The Submerged Iceberg

Little is known on the natural history of Crohn's disease (CD) before diagnosis. By the time the patient is diagnosed, the disease has often produced considerable damage to the intestinal mucosa and sometimes other organs. Such period before diagnosis might involve both a silent and a symptomatic phase. The silent phase, or preclinical CD, might last several years after the biological disease onset. Evidence is accumulating that the symptomatic phase might also go undiagnosed for months or years. In fact, for each established case of CD, there are probably several undiagnosed cases, a classic iceberg phenomenon of disease. Such status quo--lagging behind diagnostic standards for many other diseases--effectively hampers efforts to block disease evolution and the development of complications. This is no longer tenable because CD is a debilitating, severe, and costly affection, whose incidence is rapidly rising worldwide. Here, we will review what is currently known on preclinical and undiagnosed CD and what could be done to improve accuracy and timeliness of diagnosis.

Host-microbiome interaction in Crohn’s disease: A familiar or familial issue?

An impaired interaction between the gut and the intestinal microbiome is likely to be the key element in the pathogenesis of Crohn’s disease (CD). Family studies have provided invaluable information on CD pathogenesis and on its etiology. Relatives share the same genetic risk of developing the disease as affected subjects. Relatives also exhibit similar features relating to their host-microbiome interaction, namely genetic variants in loci involved in detecting bacteria, a greater sero-reactivity to microbial components, and an impaired intestinal permeability. The burden of environmental factors such as cigarette smoking and dysbiosis also seems to be particularly relevant in these genetically predisposed subjects. Diet is emerging as an important factor and could account for the changing epidemiology of CD in recent years. Despite the pivotal role of genetics in the disease’s pathogenesis (especially in familial CD), screening tests in healthy relatives cannot be recommended.

Tissue studies in screened first-degree relatives reveal a distinct Crohn's disease phenotype

BACKGROUND

First-degree relatives of patients with Crohn's disease (CD) are at risk of developing the disease with 5% to 15% reported to be affected over time. Yet, a much greater proportion of them (>40%) shows features of "subclinical inflammation" with elevated intestinal inflammatory markers such as fecal calprotectin. The meaning of these findings is unclear in the absence of tissue data.

METHODS

Thirty-eight asymptomatic first-degree relatives of patients with CD underwent ileocolonoscopy and other tests including fecal calprotectin. All known causes of intestinal inflammation were carefully excluded. Age and gender-matched controls consisted of 10 individuals who underwent colonoscopy for other reasons. Histology was scored based on known methods.

RESULTS

Compared with controls, the relatives had significantly greater median values for fecal calprotectin and histological scores. In relatives, endoscopy identified 3 different phenotypes: (1) normal, (2) with minor lesions (aphthae or small superficial erosions), and (3) with typical CD inflammation. Based on the histological scores, the clustering analysis produced 3 corresponding highly separated clusters (61%, 26%, and 13% of the total, respectively) with divisive coefficient D = 0.94. When followed up (on the average for 53 mo), individuals in the second cluster had histological scores similar to baseline values (P = 0.12).

CONCLUSIONS

Tissue studies in first-degree relatives of patients with CD reveal 3 distinct groups: normal, with minimal inflammation, and with frank disease. The second cluster represents a novel phenotype, which does not seem to develop the disease over time. These findings explain previous observations of "subclinical inflammation" in such population.

S100A12: a noninvasive marker of inflammation in inflammatory bowel disease

Inflammatory bowel diseases are incurable conditions that feature gut inflammation. Standard markers have inadequate sensitivity and specificity. S100A12 is a new fecal marker that has promise as a non-invasive indicator of gut inflammation. This article reviews recent studies focusing on S100A12 and highlights the current and potential roles of this biomarker.

Crohn disease: recognition is key

Crohn disease (CD) is an autoimmune disease that affects people across the lifespan. Patients with CD are predisposed to other autoimmune illnesses, such as psoriasis or arthritis, and suffer from complications including infection and malnutrition. This article will focus on the diagnosis and treatment of CD.

Abnormal intestinal permeability in Crohn's disease pathogenesis

Increased small intestinal permeability is a longstanding observation in both Crohn's disease patients and in their healthy, asymptomatic first-degree relatives. However, the significance of this compromised gut barrier function and its place in the pathogenesis of the disease remains poorly understood. The association between abnormal small intestinal permeability and a specific mutation in the NOD2 gene, which functions to modulate both innate and adaptive immune responses to intestinal bacteria, suggests a common, genetically determined pathway by which an abnormal gut barrier could result in chronic intestinal inflammation. Furthermore, rodent colitis models show that gut barrier defects precede the development of inflammatory changes. However, it remains possible that abnormal permeability is simply a consequence of mucosal inflammation. Further insight into whether abnormal barrier function is the cause or consequence of chronic intestinal inflammation will be crucial to understanding the role of intestinal permeability in the pathogenesis of Crohn's disease.