Microbiomarkers Discovery in Inflammatory Bowel Diseases using Network-Based Feature Selection

ABSTRACTBackground and AimsIrritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and celiac disease (CeD) present with similar gastrointestinal (GI) symptoms. DNA methylation‐based biomarkers have not been investigated as diagnostic biomarkers to classify these disorders. We aimed to study DNA methylation profiles of IBS, IBD, CeD, and healthy controls (HC), develop machine learning‐based classifiers, and identify associated gene ontology (GO) terms.MethodsGenome‐wide DNA methylation of peripheral blood mononuclear cells from 315 patients with IBS, IBD, CeD, and HC was measured using Illumina's 450K or EPIC arrays. A methylation dataset on 304 IBD and HC samples was used for external validation. Differential methylation was measured using general linear models. Classifiers were developed using penalized generalized linear models using double cross‐validation controlling for confounders. Functional enrichment was assessed using GO.ResultsThree hundred and fifteen participants (148 IBS, 47 IBD, 34 CeD, and 86 HC) had DNA methylation data. IBS‐IBD and IBD‐CeD showed the highest number of differentially methylated CpG sites followed by IBD‐HC, CeD‐HC, and IBS‐HC. IBS‐associated genes were enriched in cell adhesion and neuronal pathways, while IBD‐ and CeD‐associated markers were enriched in inflammation and MHC class II pathways, respectively (p < 0.05). Classification performances assessed using area under the receiver operating characteristic curves (AUC) for IBS‐IBD, IBS‐CeD, and IBD‐CeD were 0.80 (95% CI = 0.7–0.87, p = 6.75E‐10), 0.78 (95% CI = 0.68–0.86, p = 4.57E‐10), and 0.73 (95% CI = 0.62–0.83, p = 0.03), respectively. The performance of IBD‐HC was successfully validated using external data (AUC = 0.74 [95% CI = 68–0.80, p < 0.001]).ConclusionsBlood‐based DNA methylation biomarkers can potentially distinguish chronic GI disorders that present with similar symptoms. GO suggested functional significance of the classifiers in disease‐specific pathology.

IntroductionThe incidence of inflammatory bowel disease (IBD) among US Hispanics is rising. Adoption of an American diet and/or US acculturation may help explain this rise.AimsTo measure changes in diet occurring with immigration to the USA in IBD patients and controls, and to compare US acculturation between Hispanics with versus without IBD. Last, we examine the current diet of Hispanics with IBD compared to the diet of Hispanic controls.MethodsThis was a cross-sectional study of Hispanic immigrants with and without IBD. Participants were recruited from a university-based GI clinic. All participants completed an abbreviated version of the Stephenson Multi-Group Acculturation Scale and a 24-h diet recall (the ASA-24). Diet quality was calculated using the Healthy Eating Index (HEI-2010).ResultsWe included 58 participants: 29 controls and 29 IBD patients. Most participants were Cuban or Colombian. Most participants, particularly those with IBD, reported changing their diet after immigration (72% of IBD and 57% of controls). IBD participants and controls scored similarly on US and Hispanic acculturation measures. IBD patients and controls scored equally poorly on the HEI-2010, although they differed on specific measures of poor intake. IBD patients reported a higher intake of refined grains and lower consumption of fruits, whereas controls reported higher intake of empty calories (derived from fat and alcohol).ConclusionThe majority of Hispanics change their diet upon immigration to the USA and eat poorly irrespective of the presence of IBD. Future studies should examine gene–diet interactions to better understand underlying causes of IBD in Hispanics.

Inflammatory Bowel Disease Clinical

Although the main treatments of inflammatory bowel disease (IBD) aim at the induction and maintenance of clinical remission, several studies have demonstrated inflammation still present in clinical remission. The goal of this study was to analyze the gene expression profiles between the pediatric IBD and control samples, aiming to further investigate the underlying therapeutic target in remission. Gene expression profiles data of GSE33943 were downloaded from Gene Expression Omnibus, which included 45 pediatric IBD samples and 13 control samples. The differentially expressed genes (DEGs) between IBD and control samples were identified by LIMMA package in R and the function of DEGs were predicted by Gene Ontology and KEGG pathway enrichment analyses using GeneAnswer package. Furthermore, a protein-protein interaction (PPI) network was constructed through the STRING database and functional module was obtained using ClusterONE. A total of 224 DEGs were screened between IBD and control samples. These DEGs (e.g. up-regulated FAS and down-regulated CCL5) were mainly enriched in cytokine‒cytokine receptor interaction and chemokine signaling pathway. In addition, some hub genes (e.g. up-regulated PSMA2 and PSMA6) were obtained through PPI network and functional module. These two genes were involved in Proteasome alpha-subunit and conserved site by functional module analysis. The immune and Proteasome mechanisms are still active during remission and FAS, PMSF6 and PMSF2 may be underlying targets for therapy of this disease.

Inflammatory bowel disease (IBD) involves dysregulation of mucosal immunity in response to environmental factors such as the gut microbiota. The bacterial microbiota is often altered in IBD, but the connection to disease is not fully clarified and gut fungi have recently been suggested to play a role as well. In this study, we compared microbes from all 3 domains of life-bacteria, archaea, and eukaryota-in pediatric patients with IBD and healthy controls. A stool sample was collected from patients with IBD (n = 32) or healthy control subjects (n = 90), and bacterial, archaeal, and fungal communities were characterized by deep sequencing of rRNA gene segments specific to each domain. Patients with IBD (Crohn's disease or ulcerative colitis) had lower bacterial diversity and distinctive fungal communities. Two lineages annotating as Candida were significantly more abundant in patients with IBD (P = 0.0034 and P = 0.00038, respectively), whereas a lineage annotating as Cladosporium was more abundant in healthy subjects (P = 0.0025). There were no statistically significant differences in archaea, which were rare in pediatric samples compared with those from adults. Pediatric IBD is associated with reduced diversity in both fungal and bacterial gut microbiota. Specific Candida taxa were found to be increased in abundance in the IBD samples. These data emphasize the potential importance of fungal microbiota signatures as biomarkers of pediatric IBD, supporting their possible role in disease pathogenesis.

Background Inflammatory Bowel Disease (IBD) affects about 7 million people worldwide. People with active disease often experience symptoms of abdominal pain, fatigue and incontinence which may persist even in remission. We assess the impact of these symptoms, and the further contribution of anxiety and depression, on health-related quality of life (QoL) of people with IBD. Methods In the IBD-BOOST survey, over 12,500 people with IBD in the UK were approached across outpatient clinics, the IBD-BioResource participants and the Crohn’s and Colitis UK charity membership; 8486 self-completed surveys were returned. Participants’ QoL was measured using the EQ-5D-5L questionnaire, a generic health-related QoL instrument. Patients’ QoL, ranging from 1 (perfect health) to -0.594 (worst health) was calculated using UK value set. Our approach involved three pre-specified stages of linear regression model development to assess the effects of symptoms on QoL. At stage 1 the model included IBD type, IBD activity score, IBD control score, socio-demographic characteristics and co-morbidities. At stage 2, the three key IBD symptoms: pain, fatigue and bowel incontinence were added. At stage 3, anxiety and depression were also included. Results Table 1 presents selected characteristics of the 8486 IBD-BOOST survey participants (mean age 50 years, 58% women, 49% Crohn’s disease). The EQ-5D-5L questionnaire was completed by 8114 (96%) participants reporting problems across QoL domains (Figure 1: 30% problems with mobility, 13% with self-care, 43% with usual activities, 60% pain/discomfort and 50% anxiety/depression). The mean QoL was 0.76 (SD 0.22). Health-related QoL was substantially reduced in respondents reporting higher IBD activity or worse IBD control (Table 2; stage 1). These associations weakened substantially following adjustment for the key IBD symptoms of pain, fatigue and bowel incontinence for which strong and graded associations with higher symptom severity associated with lower QoL were observed (Table 2; stage 2). The further inclusion of adjustments for anxiety and depression only moderately weakened previous associations and strong and graded associations between more severe anxiety or depression and lower QoL were also observed (Table 3; stage 3). Being male, obese, unemployed/retired, or having physical or mental health comorbidity were associated with lower QoL, and being in a relationship with higher QoL (results not shown). Conclusion We report graded associations between symptoms of pain, fatigue, bowel incontinence, anxiety and depression and QoL in IBD. These estimates could inform assessments of interventions to improve IBD management.

Background Sexual dysfunction (SD) is common in patients with Inflammatory Bowel Disease (IBD), yet previous research identified depression as a key confounding factor. This is the first study to exclude participants with depression, aiming to isolate the impact of IBD on sexual health. Methods Adults with confirmed IBD and non-IBD controls were enrolled. A Hospital Anxiety and Depression Scale1 (HADS) score &amp;gt;16 was an exclusion criteria. Sexual function was assessed with validated tools: the Sexual Desire Inventory2 (SDI) for all participants, Female Sexual Function Index3 (FSFI, cut off ≤26 for dysfunction) for women and the International Index of Erectile Function4 (IIEF, cut off ≤43 for dysfunction and ≤25 for erectile function). Disease activity was measured with Harvey-Bradshaw Index (HBI) for Crohn’s disease and Simple Clinical Colitis Activity Index (SCCAI) for Ulcerative Colitis. Results We screened 916 individuals, of whom 597 met inclusion criteria: 435 IBD and 162 non-IBD (Table 1). No overall differences were observed in SDI domains between IBD and non-IBD. However, among patients with active IBD, particularly in those aged 36 to 50, solitary desire was significantly lower compared to those in remission (P = 0.034). In women, SD was more common in IBD versus non-IBD (37.6% vs 21.5%), with impairments in FSFI domains of arousal and pain (P = 0.023; P = 0.017). Women with active IBD had more SD (66.7% vs 34.1%), more pain and lower desire compared to those in remission (P &amp;lt;.001; P = 0.006). Pain was especially common in IBD women aged 26 to 35 compared to non-IBD, regardless of disease activity (P =0.010). In addition, women aged 51 to 80 with active disease experienced pain, impairment in arousal and desire (P = 0.014; P = 0.031; P = 0.029). Furthermore, women with IBD showed a decrease in solitary sexual desire and dyadic sexual desire compared to women without IBD, with the decline in solitary desire being particularly significant in the 36-50 age group (P = 0.001; P = 0.023). In men, no SD was observed overall. However, IIEF scores revealed that erectile dysfunction was more prevalent in men with active IBD versus remission (45% vs. 15.3%). Interestingly, solitary desire by SDI was higher in IBD men than those with non-IBD in the 36-50 age group (P = 0.050). Conclusion SD occurs in IBD patients regardless of disease activity and in the absence of depression. Women with IBD experience significant impairment in sexual function, including reduced desire, arousal, and increased pain. In men, IBD primarily impacts erectile function during active disease. These findings highlight the need for a tailored approach to sexual health in IBD that considers both gender and disease activity.

Genetic factors may play a role in determining the development of extraintestinal manifestations (EIMs) and autoimmune diseases (AD) in patients with inflammatory bowel disease (IBD). We sought to determine the association between EIMs and AD in patients with first-degree familial IBD and sporadic IBD. All patients evaluated in the IBD Clinic at the Mayo Clinic between January and September 1999 were offered enrollment. One clinic patient who was matched on age, gender, and geographic area of residence to each case served as controls. Information regarding EIMs and AD was obtained from a questionnaire completed by all IBD patients and controls. The adjusted odds ratios (95% CIs) for EIM as a function of first-degree familial IBD compared with sporadic IBD and AD as a function of first-degree familial IBD compared with sporadic IBD were estimated with a matched one-to-one conditional logistic regression model. Two hundred forty-three patients with IBD (47 first-degree familial IBD, 196 sporadic IBD) were enrolled. Forty percent of IBD patients had one or more EIMs compared with 14% matched controls [p < 0.001; OR = 3.1 (95% CI: 1.8 to 5.2)]. A total of 259 of the 1122 IBD patients and their first-degree family members indicated one or more EIM diagnoses (23%). The association between "familial versus sporadic" status and any EIM diagnosis was not significant [p = 0.59, the odds for an individual from a familial IBD family relative to an individual from a sporadic IBD family was 1.2 (95% CI: 0.8 to 1.7)]. Ten percent of IBD patients had one or more AD diagnoses compared with 19% matched controls [p = 0.04; OR = 0.4 (95% CI: 0.1 to 0.96)]. A total of 153 of the 1122 IBD patients and their first-degree family members indicated one or more AD diagnoses (14%). The association between disease status ("familial or sporadic") versus any AD diagnosis was not significant [p = 0.68, the odds for any AD in an individual from a familial IBD family relative to an individual from a sporadic IBD family was 1.4 (95% CI: 0.9 to 2.3)]. There was a positive association between IBD status (patient vs control) versus EIM, but not AD. A significant positive association between disease type (familial or sporadic) versus either EIM or AD was not detected.

Background The inflammatory bowel diseases (IBD), Crohn’s disease (CD) and ulcerative colitis (UC) are chronic inflammatory conditions with a polygenic and multifactorial pathogenesis. Intensified treatment early in the disease course of IBD results in better outcomes. This is, however, challenged by the diagnostic delay faced in IBD, and especially in CD. Therefore, markers supporting early and differential diagnosis are needed. In this study, we aimed to discriminate IBD patients from non-IBD controls, and CD from UC patients, using serum protein profiles combined with an IBD polygenic risk score. Methods Patients naïve for immunosuppressives and biologicals, and without previous IBD-related surgery were prospectively included within 3 months after diagnosis, across three Belgian IBD referral centres (PANTHER study). We collected serum from 127 patients (88 CD, 39 UC) and 66 age- and gender-matched non-IBD controls. Relative serum levels of 576 unique proteins were quantified (OLINK). Proteins were ranked according to (1) adjusted (adj.) p values obtained from differential expression analysis; (2) importance scores from machine-learning feature-selection algorithms (univariate feature selection, logistic regression with L2 penalty and Random Forest). For all individuals, a weighted IBD polygenic risk score (PRS) was calculated (PRSice 2.0) for the 242 known IBD risk loci. Receiver operating characteristics (ROC) and area under the curve (AUC) analysis were performed to measure the performance of top-ranked proteins and the IBD PRS (R package ROCR). Results Following statistical analysis, 243 serum proteins were found to be differentially expressed (adj. p &amp;lt; 0.05) between IBD patients and controls. Three top-ranked markers were also identified as top 10 ranked proteins by all feature-selection algorithms, and resulted in a significant AUC of 93% (95% CI: 89–97%) to distinguish IBD from controls. While adding the IBD PRS did not further contribute (AUC 93% [95% CI: 89–97%]), the top-ranked protein on its own had a strong discriminative power with an AUC of 87% (95% CI: 82–92%). When comparing UC and CD, we found 15 differentially expressed proteins. Two proteins ranked within the top 10 across all feature-selection algorithms. This two-marker panel could discriminate UC from CD with an accuracy of 88% (95% CI: 82–96%). Adding the IBD PRS did not further improve the prediction model (AUC=88% [95% CI: 81–96%]). Conclusion Machine learning approaches validated top differentially expressed serum proteins with diagnostic potential in IBD. We identified a three-marker panel classifying IBD patients and non-IBD controls, and a two-marker panel discriminating UC from CD.

Background The early life period is suggested to be important in development of Inflammatory Bowel Disease (IBD). Studies in babies from mothers with IBD observed increased faecal calprotectin and changes in the microbial compartments compared to babies from healthy mothers1,2, which suggests that changes in early life might be associated with later disease development. Prospective studies of IBD risk following early life changes at the molecular level are sparse. We aimed to investigate if individuals with early onset (EO) IBD had changes in systemic inflammatory markers shortly after birth. Methods We measured the concentration of 9 cytokines in a cohort of 464 neonatal dried blood spot samples stored at the Danish National Biobank from individuals who later developed EO IBD (median age of diagnosis 11 years), as well as matched controls. Individuals who developed IBD were identified through the use of the Danish National Patient Registry. Uni- and multivariate logistic regression with adjustment for birth year, sex, and gestational age was conducted to assess the association between 6 of the inflammatory markers with later disease development (INF-γ, TNF-α, IL-1β, IL-4, IL-6 and IL-17a). Further exploratory analyses were performed investigating risk of very early onset (VEO) IBD (onset from 0-5 years) in 88 cases and their matched controls. Results No significant association with EO IBD was observed for any of the cytokines in uni- and multivariate models when adjusting for multiple testing. In the exploratory analysis of VEO IBD, increased IL-4 was associated with significantly reduced risk of IBD (OR=0.992, p-value=0.023) and increased IL-17a was borderline-significantly associated with increased risk of IBD (OR=1.002, p-value=0.063) in a multivariate logistic model including all 6 cytokines. This association did not remain significant when adjusting for multiple testing, which may reflect limited power. Conclusion In our unique study of 464 dried blood spots from later IBD patients and controls, we could not find an association between measured cytokines and EO IBD. In contrast, patients with VEO IBD had decreased levels of IL-4 and increased levels of IL-17a. This sub-cohort was small, and significance disappeared after adjusting for multiple testing. Still, we find it important to report these findings, as they are novel and may inspire future studies into the aetiology of VEO IBD. 1. Kim, E. S. et al. Longitudinal Changes in Fecal Calprotectin Levels Among Pregnant Women With and Without Inflammatory Bowel Disease and Their Babies. Gastroenterology (2021) 2. Torres, J. et al. Infants born to mothers with IBD present with altered gut microbiome that transfers abnormalities of the adaptive immune system to germ-free mice. Gut (2020)

Microbial diversity is typically characterized by clustering ribosomal RNA (SSU-rRNA) sequences into operational taxonomic units (OTUs). Targeted sequencing of environmental SSU-rRNA markers via PCR may fail to detect OTUs due to biases in priming and amplification. Analysis of shotgun sequenced environmental DNA, known as metagenomics, avoids amplification bias but generates fragmentary, non-overlapping sequence reads that cannot be clustered by existing OTU-finding methods. To circumvent these limitations, we developed PhylOTU, a computational workflow that identifies OTUs from metagenomic SSU-rRNA sequence data through the use of phylogenetic principles and probabilistic sequence profiles. Using simulated metagenomic data, we quantified the accuracy with which PhylOTU clusters reads into OTUs. Comparisons of PCR and shotgun sequenced SSU-rRNA markers derived from the global open ocean revealed that while PCR libraries identify more OTUs per sequenced residue, metagenomic libraries recover a greater taxonomic diversity of OTUs. In addition, we discover novel species, genera and families in the metagenomic libraries, including OTUs from phyla missed by analysis of PCR sequences. Taken together, these results suggest that PhylOTU enables characterization of part of the biosphere currently hidden from PCR-based surveys of diversity?

Introduction: Patients with inflammatory bowel disease (IBD) are at higher risk of developing colorectal cancer (CRC). Guidelines recommend periodic endoscopic surveillance to detect and manage dysplasia. We aimed to explore patient knowledge and perceptions of CRC risk and colonoscopic surveillance. Methods: A 44-item questionnaire was administered to IBD patients with colonic involvement attending gastroenterology clinics between July 2021 and April 2022. Results: Of 418 respondents, 266 (64%) had ulcerative colitis and 145 (34%) had Crohn’s disease, with 176 (42%) diagnosed for ≥10 years. Two hundred and sixty-five (66%) patients rated their IBD control moderate/good (score ≥7/10), and 314 (75%) self-rated their understanding of IBD as good/excellent. Two hundred and ninety-eight patients (71%) recognised that CRC risk is higher in IBD but 83 (20%) felt the risk of CRC was lower in IBD or were unsure. Age (p=0.02), being a Crohn’s and Colitis UK (CCUK) member (p< 0.001), patient rated IBD control (p=0.04) and self-rated understanding (p=0.01) were associated with better CRC risk awareness. One hundred and forty-nine (36%) respondents stated that their IBD healthcare professional (HCP) had previously discussed CRC risk with them; this was associated with better CRC knowledge (p=0.001). On multivariate analysis CCUK membership (OR 2.75; 95% CI 1.57- 4.83; p< 0.001), prior HCP discussion (OR 1.57; 95% CI 0.85-2.87; p=0.01) and age ≥65 years (OR 0.3; 95% CI 0.09- 0.99; p=0.05) were predictive of greater CRC risk awareness. Concerning the most appropriate screening test for dysplasia, 369 patients (88%) stated colonoscopy, but only 29 (7%) were aware that colonic surveillance should commence 8-10 years after diagnosis; 153 (37%) recognised that optimal timing is when IBD is in remission. Patient reported information sources included gastroenterology HCPs (43%), patient support groups (28%), and patient leaflets (17%). The majority (78%) stated they would agree to have surveillance colonoscopy. Bowel preparation (50%) and discomfort (45%) were factors most likely to dissuade them from agreeing to surveillance. Conclusion: Patient knowledge of CRC risk and surveillance practice in IBD is variable. Modifiable factors associated with improved knowledge are discussion with HCPs and CCUK membership. Our findings underscore the need for better patient education to aid informed decision-making between patients and HCPs and improve adherence to colonoscopic surveillance.

Clostridium difficile infection (CDI) has been associated with an increased mortality risk among patients with inflammatory bowel disease (IBD) in multiple observational studies. We performed a systematic review and meta-analysis to help clearly define the magnitude of risk in IBD patients with and without CDI, and to assess the risk in individual IBD subtypes. A systematic search of multiple electronic databases was conducted for observational studies reporting the risk of mortality in IBD, stratified by the presence of CDI. Weighted summary estimates were calculated using generalized inverse variance with random-effects model. Study quality was assessed using the Newcastle-Ottawa scale. Ten observational studies were identified (8 from North America and 2 from Europe) and included 40,700 IBD patients with CDI and 1,320,764 IBD controls without CDI. Overall, IBD patients with CDI had a higher risk of mortality compared with IBD patients without CDI [odds ratios (OR), 4.39; 95% confidence interval (CI), 3.56-5.42; I=93%]. The results were stable in high-quality studies and in hospitalized patients. When patients were stratified by IBD type, CDI was associated with increased mortality in patients with ulcerative colitis (7 studies) (OR, 4.39; 95% CI, 3.44-5.61; I), but not in patients with Crohn's disease (4 studies) (OR, 2.21; 95% CI, 0.84-5.77; I). Individual studies were limited by an inability to control for IBD disease activity and therapeutic interventions. On the basis of 10 observational studies with at least moderate quality, CDI seems to increase mortality risk in IBD, particularly in ulcerative colitis. These findings are a cause for concern and suggest that CDI should be managed aggressively in patients with IBD.

Background Inflammatory bowel disease (IBD) is a chronic inflammatory disorders of the gastrointestinal tract. Up to 30% of people with active IBD experience mood disorders such as depression. Our objective was to identify the pathways associated with the interplay between IBD and depression Methods Detailed information on IBD and depression was gathered from 204 countries and territories spanning 1990 to 2021, sourced from the GBD 2021. Calculations were performed for incidence rates, prevalence rates, disease-adjusted life years (DALYs), years lived with disability (YLDs) and estimated annual percentage changes (EAPCs). In addition, we constructed an age–period–cohort model. We selected three GEO datasets (GSE87473, GSE92415, and GSE112366), Differential expression analysis was performed on the batch-corrected data using the limma package. Furthermore, we curated a list of 153 depression-associated genes from published studies and executed intersection analysis with the identified DEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were carried out to investigate biological pathways potentially linking IBD and depression. Finally, GSVA enrichment analysis investigate the underlying molecular biological alterations. Results The incidence of both IBD and depression has been increasing annually globally. Over the past 30 years, the incidence of IBD in China has shown a marked upward trend, while the incidence of depression has exhibited a downward trend. The DALY and YLD rates for both IBD and depression have declined over time. A strong positive correlation between IBD and depression was observed in high-SDI regions and developed countries such as the United States; however, partial correlation analysis controlling for the effect of year revealed no strong linear association between the two. The APC models for IBD and depression indicated that age and period effects play a significant role in the incidence of both diseases. We identified 2560 upregulated and 2593 downregulated genes between IBD and healthy control groups. Intersection of these DEGs with a curated list of 153 depression-related genes revealed 25 overlapping core genes. Then, GO and KEGG enrichment and GSVA analyses highlighted α-Linolenic acid metabolism as a potential key pathway in the IBD-depression comorbidity. Conclusion Although significant progress has been made in the diagnosis and treatment of IBD in China, issues such as delayed identification of depressive symptoms may still persist. Our study discovered α-Linolenic acid metabolism may constitute a critical biological link between IBD and depression, providing novel insights for investigating the shared pathophysiological mechanisms underlying this comorbidity. Reference: none Conflict of interest: Mr. Zhou, Ziru: The authors declare that they have no conflicts of interest. None of the authors have financial, employment, or personal relationships with organizations that could influence the research presented. Zhan, Qiang: The authors declare that they have no conflicts of interest. None of the authors have financial, employment, or personal relationships with organizations that could influence the research presented. Sun, Jing: The authors declare that they have no conflicts of interest. None of the authors have financial, employment, or personal relationships with organizations that could influence the research presented.

This study aimed to explore the causal association between inflammatory bowel disease (IBD) and the risk of type 2 diabetes (T2D) based on a two-sample Mendelian randomization (MR) study. Summary single nucleotide polymorphism (SNP)-phenotype association data were obtained from published two genome-wide association studies (GWAS) including SNPs related to IBD, UC, or CD in European participants (n = 71,997) and East Asian participants (n = 16,805). Two GWAS including SNPs associated with T2D included 655,666 Europeans and 433,540 East Asians. A series of screening processes were performed to select qualified instrumental SNPs strongly related to exposure. We applied the inverse variance weighted (IVW), the MR-Egger regression, and the weighted median to estimate the causal effects of IBD, ulcerative colitis (UC) or Crohn' disease (CD) on T2D. Cochran's Q test was conducted to evaluate the statistical heterogeneity between SNPs in the IVW method. The leave-one-out analysis was employed to assess whether the results were caused by any single SNP associated with IBD, UC, or CD. Odds ratio (OR) and 95% confidence interval (CI) were calculated. The IVW results demonstrated that IBD could increase the risk of T2D in the European population (OR = 1.0230, 95%CI: 1.0073-1.0390). UC was positively associated with the risk of T2D according to the weighted median (OR = 1.0274, 95%CI: 1.0009-1.0546) and IVW (OR = 1.0244, 95%CI: 1.0071-1.0421) results in the European population. The IVW results indicated that the CD was positively associated with the risk of T2D in the European population (OR = 1.0187, 95%CI: 1.0045-1.0330). In the East Asian population, there are no associations between the IBD, UC, or CD and the risk of T2D (all P > 0.05). MVMR results revealed that the causal effect UC on T2D was still statistically significant after including body mass index (BMI) or low-density lipoprotein (LDL). IBD, UC, or CD had causal effects on the risk of T2D in the European population, which might provide evidence for the prevention of T2D in patients with IBD, UC, or CD.