Review article: distinctions between ileal and colonic Crohn's disease: from physiology to pathology

From serum metabolites to the gut: revealing metabolic clues to susceptibility to subtypes of Crohn's disease and ulcerative colitis

Background and aims

Inflammatory bowel disease (IBD) is a common chronic inflammatory bowel disease characterized by diarrhea and abdominal pain. Recently human metabolites have been found to help explain the underlying biological mechanisms of diseases of the intestinal system, so we aimed to assess the causal relationship between human blood metabolites and susceptibility to IBD subtypes.

Methods

We selected a genome-wide association study (GWAS) of 275 metabolites as the exposure factor, and the GWAS dataset of 10 IBD subtypes as the outcome, followed by univariate and multivariate analyses using a two-sample Mendelian randomization study (MR) to study the causal relationship between exposure and outcome, respectively. A series of sensitivity analyses were also performed to ensure the robustness of the results.

Results

A total of 107 metabolites were found to be causally associated on univariate analysis after correcting for false discovery rate (FDR), and a total of 9 metabolites were found to be significantly causally associated on subsequent multivariate and sensitivity analyses. In addition we found causal associations between 7 metabolite pathways and 6 IBD subtypes.

Conclusion

Our study confirms that blood metabolites and certain metabolic pathways are causally associated with the development of IBD subtypes and their parenteral manifestations. The exploration of the mechanisms of novel blood metabolites on IBD may provide new therapeutic ideas for IBD patients.

Small bowel Crohn's disease: Proximal lesions linked to increased inflammation and biologic treatment needs

OBJECTIVE

Crohn's disease (CD) is heterogeneous, and proximal involvement in the small bowel (SB) is associated with worse outcomes. Nonetheless, studies on the impact of duodenal and jejunal lesions in SB CD are limited. This study aimed to investigate the clinical characteristics and outcomes of individuals diagnosed with SB CD, comparing those with and without proximal inflammation.

METHODS

A cohort of 53 treatment-naive SB CD patients that underwent Capsule Endoscopy at diagnosis were retrospectively selected. The inflammatory activity was quantified using the Lewis Score for each SB tertile.

RESULTS

Thirty-seven (69.8%) patients displayed inflammatory activity in the first and/or second tertile together with third tertile involvement (Proximal+T3 group). Sixteen (30.2%) had inflammation in the third tertile only (T3 group). Individuals in the Proximal+T3 group had a higher risk for moderate-to-severe inflammation (OR 4.93, 95% CI: 1.3-18.3, p=0.013). A subgroup analysis for those with mild inflammatory activity showed that individuals in the Proximal+T3 group initiated biologic drugs more often (OR 11, 95% CI: 1.1-109.7, p=0.036).

CONCLUSION

Proximal SB lesions are associated with increased inflammatory activity, necessitating more frequent use of biologics in patients with mild disease. Early detection of proximal SB CD with Capsule Endoscopy may contribute to timely treatment.

Real-world Clinical Effectiveness and Safety of Vedolizumab and Adalimumab in Biologic-naive Patients With Crohn's Disease: Results From the EVOLVE Study

GOALS

This study evaluated the real-world effectiveness and safety of vedolizumab versus adalimumab over 12 months of treatment in biologic-naive patients with Crohn's disease (CD), using data from the EVOLVE study.

BACKGROUND

A comparison of vedolizumab and adalimumab may help to better position them in the therapeutic algorithm for moderate-to-severe CD.

STUDY

Data were collected from medical records of patients with CD aged ≥18 years initiating treatment with adalimumab or vedolizumab between May 2014 and July 2017. Adjusted analyses were performed using inverse probability weighting to account for differences in baseline characteristics. Cumulative rates for clinical effectiveness outcomes and treatment persistence were estimated using Kaplan-Meier analyses. Disease-related exacerbations, serious adverse events (SAEs), and serious infections (SIs) were also assessed.

RESULTS

Data from 218 vedolizumab- and 144 adalimumab-treated patients were analyzed. Adjusted cumulative rates of clinical remission were greater with vedolizumab than with adalimumab (66.3% vs. 46.4%; P=0.006). Probability of treatment persistence was higher with vedolizumab (89.3% vs. 77.5%; P=0.024); probabilities of clinical response (68.5% vs. 61.1%; P=0.586) and mucosal healing (67.7% vs. 56.0%; P=0.562) were similar. SAEs were less likely to occur with vedolizumab [hazard ratio, 0.45 (95% confidence interval, 0.22-0.93)]; however, the likelihood of SIs [0.27 (0.06-1.20)], CD exacerbations [0.91 (0.56-1.47)], and CD-related surgeries [1.55 (0.21-11.15)] was comparable between the 2 groups.

CONCLUSIONS

In a real-world setting, biologic-naive patients with CD treated with vedolizumab demonstrated a greater likelihood of drug persistence and achieving clinical remission, with equivalent rates of response and mucosal healing versus adalimumab-treated patients.

The utility of capsule endoscopy in the phenotype of Crohn's disease. Data from England 2016-2021

BACKGROUND AND STUDY AIMS

Isolated small bowel Crohn's disease (SBCD) is reported to have a worse prognosis compared to other CD phenotypes. The aim of this study was to understand the correlation between Isolated SBCD and ileocolonic disease with blood and faecal biomarkers and also to identify differences in outcome and management between the two phenotypes.

PATIENTS AND METHODS

Patients with ileocolonic or isolated small bowel Crohn's Disease (SBCD) were identified from an existing capsule endoscopy (CE) database. Harvey Bradshaw Index (HBI), biomarkers: c-reactive protein (CRP) and faecal calprotectin (FC), Lewis score and findings on CE and subsequent follow up data were collected. SPSS was used to analyse the data.

RESULTS

In total 248 patients were included in the study. Patients were split into two groups- Isolated SBCD with 178 patient (median age 44 years (IQR 31-56); 41.5 % male) and Ileocolonic Crohn's with 70 patients (median age 31 years (IQR 22.7-49); 31.5 % male). A new diagnosis of SBCD was made in 38.7 % (n = 96), whilst 60.0 % (n = 144) had established CD. Patients with ileocolonic disease had a higher HBI in comparison to isolated SBCD [HBI = 7 (IQR 5-10) vs HBI = 6(IQR 4-9); P = 0.04 ]. There was no significant difference in the FC levels between isolated SBCD and ileocolonic disease [136ug/g (IQR 53.8-363.3) vs 171ug/g (IQR 68.5-485.5); p = 0.98]. In isolated SBCD group, 30.3 % (n = 54) CE showed proximal disease, 96 % (n = 171) showed distal disease and 26.4 % (n = 47) showed extensive disease. SBCE was superior to MRI at diagnosing proximal SBCD (P < 0.01). On multivariate logistic regression, we did not identify any predictors of disease severity defined as Lewis score > 790. Following SBCE, 68.5 % (n = 170) of the total patients had a management change. This included commencement or dose escalation of corticosteroids in 123 (49.5 %) patients, azathioprine in 80 (33.3 %) patients, methotrexate in 22 (9.1 %) patients and biological therapy in 110 (44.3 %) patients. HBI predicted a change in management (p < 0.01).

CONCLUSION

CE is an important modality for the diagnosis of active SBCD. It also helps guide treatment in patients identified with active disease.

Serum proteome signatures associated with ileal and colonic ulcers in Crohn's disease

At a clinical level, ileal and colonic Crohn's disease (CD) are considered as separate entities. These subphenotypes need to be better supported by biological data to develop personalised medicine in CD. To this end, we combined different technologies (proximity extension assay, selected reaction monitoring, and high-sensitivity turbidimetric immunoassay (hsCRP)) to measure 207 immune-related serum proteins in CD patients presenting no endoscopic lesions (endoscopic remission) (n = 23), isolated ileal ulcers (n = 17), or isolated colonic ulcers (n = 16). We showed that isolated ileal ulcers and isolated colonic ulcers were specifically associated with 6 and 18 serum proteins, respectively: (high level: JUN, CNTNAP2; low level: FCRL6, LTA, CLEC4A, NTF4); (high level: hsCRP, IL6, APCS, CFB, MBL2, IL7, IL17A, CCL19, CXCL10, CSF3, IL10, CLEC4G, MMP12, VEGFA; low level: CLEC3B, GSN, TNFSF12, TPSAB1). Isolated ileal ulcers and isolated colonic ulcers were detected by hsCRP with an area under the receiver operating characteristics curve of 0.64 (p-value = 0.07) and 0.77 (p-value = 0.001), respectively. We highlighted distinct serum proteome profiles associated with ileal and colonic ulcers in CD, this finding might support the development of therapeutics and biomarkers tailored to disease location. SIGNIFICANCE: Although ileal and colonic Crohn's disease present important clinical differences (eg, progression, response to treatment and reliability of biomarkers), these two entities are managed with the same therapeutic strategy. The biological specificities of ileal and colonic Crohn's disease need to be better characterised to develop more personalised approaches. The present study used robust technologies (selected reaction monitoring, proximity extension assays and turbidimetric immunoassay) to quantify precisely 207 serum immune-related proteins in three groups of Crohn's disease patients presenting: 1) no endoscopic lesions (endoscopic remission) (n = 23); 2) isolated ileal ulcers (n = 17); 3) isolated colonic ulcers (n = 16). We found distinct serum proteome signatures associated with ileal and colonic ulcers. Our findings could foster the development of biomarkers and treatments tailored to Crohn's disease location.

Spatial features of skip lesions in Crohn's disease

Skip lesions are an enigmatic spatial feature characterizing Crohn's disease (CD). They comprise inflamed and adjacent non-inflamed tissue sections with a clear demarcation. Currently, spatial features of the human gastrointestinal (GI) system lack clarity regarding the organization of microbes, mucus, tissue, and host cells during inflammation. New technologies with multiplexing abilities and innovative approaches provide ways of examining the spatial organization of inflamed and non-inflamed tissues in CD, which may open new avenues for diagnosis, prognosis, and treatment. In this review, we present evidence of the relevance of spatial context in patients with CD and the methods and ideas recently published in studies of spatiality during inflammation. With this review, we aim to provide inspiration for further research to address existing gaps.

Matrix gla protein, a potential marker of tissue remodelling and physiological ageing of the gut in crohn's disease

BACKGROUND

The inactive dephosphorylated and uncarboxylated form of the matrix Gla protein (dp-ucMGP) has been shown to be increased in plasma of inflammatory bowel disease (IBD) patients. Our aim was to assess if the plasmatic level of dp-ucMGP could reflect disease endoscopic activity, presence of strictures and cumulative structural bowel damage in Crohn's disease (CD) patients.

METHODS

The plasmatic level of dp-ucMGP was measured in a monocentric cohort of prospectively recruited patients. The analysis was done by chemiluminescent immunoassay on blood samples collected the day of a planned ileocolonoscopy. In addition to classical clinical data (gender, age, body mass index (BMI), disease duration, current treatment), endoscopic data (disease location, Crohn's Disease Endoscopic Index of Severity (CDEIS), mucosal healing (MH), presence of 9 CD lesion types) and biological markers (faecal calprotectin and C-reactive protein (CRP)) were collected. The association between dp-ucMGP level and Lémann index was also investigated. Univariate linear regression was used to investigate the relationship between dp-ucMGP level and different parameters collected.

RESULTS

A total of 82 ileocolonoscopies and dp-ucMGP assays were performed in 75 CD patients (45 females; 37 ileocolonic, 19 ileal and 19 colonic diseases) between October 2012 and November 2019. A total of 24 patients (29.3%) showed MH. The dp-ucMGP levels were not associated with MH, CDEIS, faecal calprotectin or CRP levels. Plasmatic dp-ucMGP levels increased significantly with age (p = 0.0032), disease duration (p = 0.0033), corticosteroids use (p = 0.019) and tended to increase in patients with intestinal strictures (p = 0.086) but not with the Lémann index.

CONCLUSION

The significant increase of plasmatic dp-ucMGP levels with age, disease duration and the trend observed in patients with non-ulcerated strictures may suggest that this extracellular matrix protein could be a marker of tissue remodelling and physiological ageing of the gut.

Exploring the intestinal ecosystem: from gut microbiota to associations with subtypes of inflammatory bowel disease

Objective

Significant differences have been discovered between subtypes of Crohn's disease (CD) and ulcerative colitis (UC). The role of gut microbiota in promoting the onset of UC and CD is established, but conclusions regarding subtype-specific analyses remain limited.

Methods

This study aims to explore the influence of gut microbiota on subtypes of UC and CD, offering novel insights into the pathogenesis and treatment of UC and CD.Two-sample Mendelian randomization (MR) analysis was employed to examine the causal relationship between subtypes of UC and CD and gut microbiota composition. Gut microbiota data were sourced from the International Consortium MiBioGen, while UC and CD data were obtained from FINNGEN. Eligible single nucleotide polymorphisms (SNPs) were selected as instrumental variables. Multiple analytical approaches such as inverse variance-weighted (IVW), MR-Egger regression, weighted median, weighted mode, and MR-RAPS were utilized. Sensitivity analyses including MR-Egger intercept test, Cochran's Q test, and leave-one-out analysis were conducted for quality control. Subsequently, we employed multivariable IVW, MR-Egger, weighted median, and LASSO regression methods to identify independently significant genera or families and conducted sensitivity analyses.

Results

We have determined that Hungatella, Acidaminococcaceae, and 15 other microbial taxa act as protective factors for various CD and UC subtypes, while Terrisporobacter, Anaerostipes, and 23 other microbial taxa are associated with increased risk for different CD and UC subtypes. Furthermore, through multivariable MR analysis, we have identified significant genera or families with independent effects.

Conclusion

Our study confirms a causal relationship between dysbiosis of gut microbiota and the occurrence of CD and UC subtypes. Furthermore, it validates etiological distinctions among different subtypes of CD and UC. A novel approach to adjunctive therapy involving distinct UC or CD subtypes may involve the use of probiotics and represents a potential avenue for future treatments.

Dysregulation of intestinal epithelial electrolyte transport in canine chronic inflammatory enteropathy and the role of the renin-angiotensin-aldosterone-system

Chronic diarrhea is a hallmark sign of canine chronic inflammatory enteropathy (CIE), leading to fluid and electrolyte losses. Electrolyte homeostasis is regulated by the renin-angiotensin-aldosterone-system (RAAS), which might be involved in (counter-)regulating electrolyte losses in canine CIE. Whether and which electrolyte transporters are affected or if RAAS is activated in canine CIE is unknown. Thus, intestinal electrolyte transporters and components of the RAAS were investigated in dogs with CIE. Serum RAAS fingerprint analysis by mass spectrometry was performed in 5 CIE dogs and 5 healthy controls, and mRNA levels of intestinal electrolyte transporters and local RAAS pathway components were quantified by RT-qPCR in tissue biopsies from the ileum (7 CIE, 10 controls) and colon (6 CIE, 12 controls). Concentrations of RAAS components and mRNA expression of electrolyte transporters were compared between both groups of dogs and were tested for associations among each other. In dogs with CIE, associations with clinical variables were also tested. Components of traditional and alternative RAAS pathways were higher in dogs with CIE than in healthy controls, with statistical significance for Ang I, Ang II, and Ang 1-7 (all p < 0.05). Expression of ileal, but not colonic electrolyte transporters, such as Na+/K+-ATPase, Na+/H+-exchanger 3, Cl- channel 2, down-regulated in adenoma, and Na+-glucose-cotransporter (all p < 0.05) was increased in CIE. Our results suggest that the dys- or counter-regulation of intestinal electrolyte transporters in canine CIE might be associated with a local influence of RAAS. Activating colonic absorptive reserve capacities may be a promising therapeutic target in canine CIE.

Predicting diagnostic biomarkers associated with immune infiltration in Crohn's disease based on machine learning and bioinformatics

OBJECTIVE

The objective of this study is to investigate potential biomarkers of Crohn's disease (CD) and the pathological importance of infiltration of associated immune cells in disease development using machine learning.

METHODS

Three publicly accessible CD gene expression profiles were obtained from the GEO database. Inflammatory tissue samples were selected and differentiated between colonic and ileal tissues. To determine the differentially expressed genes (DEGs) between CD and healthy controls, the larger sample size was merged as a training unit. The function of DEGs was comprehended through disease enrichment (DO) and gene set enrichment analysis (GSEA) on DEGs. Promising biomarkers were identified using the support vector machine-recursive feature elimination and lasso regression models. To further clarify the efficacy of potential biomarkers as diagnostic genes, the area under the ROC curve was observed in the validation group. Additionally, using the CIBERSORT approach, immune cell fractions from CD patients were examined and linked with potential biomarkers.

RESULTS

Thirty-four DEGs were identified in colon tissue, of which 26 were up-regulated and 8 were down-regulated. In ileal tissues, 50 up-regulated and 50 down-regulated DEGs were observed. Disease enrichment of colon and ileal DEGs primarily focused on immunity, inflammatory bowel disease, and related pathways. CXCL1, S100A8, REG3A, and DEFA6 in colon tissue and LCN2 and NAT8 in ileum tissue demonstrated excellent diagnostic value and could be employed as CD gene biomarkers using machine learning methods in conjunction with external dataset validation. In comparison to controls, antigen processing and presentation, chemokine signaling pathway, cytokine-cytokine receptor interactions, and natural killer cell-mediated cytotoxicity were activated in colonic tissues. Cytokine-cytokine receptor interactions, NOD-like receptor signaling pathways, and toll-like receptor signaling pathways were activated in ileal tissues. NAT8 was found to be associated with CD8 T cells, while CXCL1, S100A8, REG3A, LCN2, and DEFA6 were associated with neutrophils, indicating that immune cell infiltration in CD is closely connected.

CONCLUSION

CXCL1, S100A8, REG3A, and DEFA6 in colonic tissue and LCN2 and NAT8 in ileal tissue can be employed as CD biomarkers. Additionally, immune cell infiltration is crucial for CD development.

Faecal Myeloperoxidase as a Biomarker of Endoscopic Activity in Inflammatory Bowel Disease

BACKGROUND AND AIMS

Inflammatory bowel disease [IBD], consisting of Crohn's disease [CD] and ulcerative colitis [UC], is a relapsing-remitting illness. Treat-to-target IBD management strategies require monitoring of gastrointestinal inflammation. This study aimed to investigate faecal myeloperoxidase [fMPO], a neutrophil granule enzyme, as a biomarker of IBD activity.

METHODS

Prospectively recruited participants with IBD, undergoing ileocolonoscopy for disease assessment, provided biological samples and completed symptom questionnaires prior to endoscopy. fMPO, C-reactive protein [CRP], and faecal calprotectin [fCal] were compared with validated endoscopic indices [simple endoscopic score for CD and UC endoscopic index of severity]. Receiver operating characteristic [ROC] curves assessed the performance of fMPO, CRP, and fCal in predicting endoscopic disease activity. Baseline biomarkers were used to predict a composite endpoint of complicated disease at 12 months [need for escalation of biologic/immunomodulator due to relapse, steroid use, IBD-related hospitalisation, and surgery].

RESULTS

A total of 172 participants were recruited [91 female, 100 with CD]. fMPO was significantly correlated with endoscopic activity in both CD [r = 0.53, p < 0.01] and UC [r = 0.63, p < 0.01], and with fCal in all patients with IBD [r = 0.82, p < 0.01]. fMPO was effective in predicting moderate-to-severely active CD [AUROC 0.86, p < 0.01] and UC [AUROC 0.92, p < 0.01]. Individuals with a baseline fMPO > 26 µg/g were significantly more likely to reach the composite outcome at 12 months (hazard ratio [HR] 3.71, 95% confidence interval [CI] 2.07-6.64, p < 0.01).

CONCLUSIONS

Faecal myeloperoxidase is an accurate biomarker of endoscopic activity in IBD and predicted a more complicated IBD course during follow-up.

Lifestyle, behaviour, and environmental modification for the management of patients with inflammatory bowel diseases: an International Organization for Study of Inflammatory Bowel Diseases consensus

Environmental and lifestyle factors play an important role in the natural history of Crohn's disease and ulcerative colitis. A group of international experts from the International Organization for the Study of Inflammatory Bowel Diseases voted on a series of consensus statements to inform the management of inflammatory bowel disease (IBD). The recommendations include avoiding traditional cigarette smoking in patients with Crohn's disease or ulcerative colitis, screening for symptoms of depression, anxiety, and psychosocial stressors at diagnosis and during flares (with referral to mental health professionals when appropriate), and encouraging regular physical activity as tolerated. Patients using dietary approaches for treatment of their IBD should be encouraged to adopt diets that are best supported by evidence and involve monitoring for the objective resolution of inflammation. We recommend formal assessment for obesity and nutritional deficiencies, and patients should be encouraged to maintain a normal body-mass index. A shared decision-making approach to contraception should include the consideration of IBD-related factors, and risk factors for venous thromboembolism. Long-term or frequent use of high-dose non-steroidal anti-inflammatory drugs should be avoided. For primary prevention of disease in the offspring of patients with IBD, we recommend avoiding passive exposure to tobacco, using antibiotics judiciously, and considering breastfeeding when able.

Ileal and colonic Crohn'´s disease: Ddoes location makes a difference in therapy efficacy?

Within the IBD entity of Crohn's disease, there is currently no differentiation between ileal and colonic manifestation for recruitment of patients in clinical trials, well-powered analysis of study results or therapeutic decisions in daily clinical practice. However, there is accumulating evidence from epidemiological, genetic, microbial, immunological, and clinical characteristics that clearly indicate that ileal Crohn's disease represents a distinct disease entity, which differentiates itself from colonic Crohn's disease. This is also reflected by lower efficacy of targeted therapies in isolated ileal compared to colonic Crohn's disease. The distinct site-specific mechanisms that drive heightened non-response in ileal disease need to be analysed in-depth in the future, to enable optimized therapy in the individual Crohn's disease patient.

Efficacy of Biologic Drugs in Short-Duration Versus Long-Duration Inflammatory Bowel Disease: A Systematic Review and an Individual-Patient Data Meta-Analysis of Randomized Controlled Trials

BACKGROUND AND AIMS

Starting biologic treatment early in the course of inflammatory bowel disease (IBD) may be associated with higher efficacy, especially in Crohn's disease (CD).

METHODS

This was a systematic review and individual-patient data meta-analysis of all placebo-controlled trials of biologics approved for IBD at study inception (October 2015), using Vivli data-sharing platform. The primary outcome was the proportional biologic/placebo treatment effect on induction of remission in patients with short-duration (≤18 months) vs long-duration disease (>18 months) analyzed separately for CD and ulcerative colitis (UC). We used meta-regression to examine the impact of patients' characteristics on the primary outcome.

RESULTS

We included 25 trials, testing infliximab, adalimumab, certolizumab, golimumab, natalizumab, or vedolizumab (6168 patients with CD and 3227 patients with UC). In CD, remission induction rates were higher in pooled placebo and patients in active arms with short-duration disease of ≤18 months (41.4% [244 of 589]) compared with disease duration of >18 months (29.8% [852 of 2857], meta-analytically estimated odds ratio, 1.33; 95% confidence interval, 1.09-1.64). The primary outcome, proportional biologic/placebo treatment effect on induction of remission, was not different in short-duration disease of ≤18 months (n = 589, odds ratio, 1.47; 95% confidence interval, 1.01-2.15) compared with longer disease duration (n = 2857, odds ratio, 1.43; 95% confidence interval, 1.19-1.72). In UC trials, both the proportional biologic/placebo remission-induction effect and the pooled biologic-placebo effect were stable, regardless of disease duration. Primary outcome results remained unchanged when tested using alternative temporal cutoffs and when modeled for individual patient's covariates, including prior anti-tumor necrosis factor exposure.

CONCLUSIONS

There are higher rates of induction of remission with biologics and with placebo in early CD, resulting in a treatment to placebo effect ratio that is similar across disease durations. No such relationships between disease duration and outcomes was found in UC. PROSPERO registration: CRD42018041961.