Identification of Three Novel Susceptibility Loci for Inflammatory Bowel Disease in Koreans in an Extended Genome-Wide Association Study

A Novel Microbial Dysbiosis Index and Intestinal Microbiota-Associated Markers as Tools of Precision Medicine in Inflammatory Bowel Disease Paediatric Patients

Recent evidence indicates that the gut microbiota (GM) has a significant impact on the inflammatory bowel disease (IBD) progression. Our aim was to investigate the GM profiles, the Microbial Dysbiosis Index (MDI) and the intestinal microbiota-associated markers in relation to IBD clinical characteristics and disease state. We performed 16S rRNA metataxonomy on both stools and ileal biopsies, metabolic dysbiosis tests on urine and intestinal permeability and mucosal immunity activation tests on the stools of 35 IBD paediatric patients. On the GM profile, we assigned the MDI to each patient. In the statistical analyses, the MDI was correlated with clinical parameters and intestinal microbial-associated markers. In IBD patients with high MDI, Gemellaceae and Enterobacteriaceae were increased in stools, and Fusobacterium, Haemophilus and Veillonella were increased in ileal biopsies. Ruminococcaceae and WAL_1855D were enriched in active disease condition; the last one was also positively correlated to MDI. Furthermore, the MDI results correlated with PUCAI and Matts scores in ulcerative colitis patients (UC). Finally, in our patients, we detected metabolic dysbiosis, intestinal permeability and mucosal immunity activation. In conclusion, the MDI showed a strong association with both severity and activity of IBD and a positive correlation with clinical scores, especially in UC. Thus, this evidence could be a useful tool for the diagnosis and prognosis of IBD.

Genome-Wide Meta-Analysis Identifies 11 Susceptibility Variants of Vitiligo in the Chinese Han Population

Vitiligo is an autoimmune disease involving loss of melanocytes. Although several genetic studies have confirmed that genetic factors play an important role, its pathogenesis remains incompletely characterized. In this study, a genome-wide meta-analysis was conducted to search for more susceptibility variants of vitiligo. Tang et al performed a GWAS for cohort I (1117 vitiligo cases and 1701 healthy controls) previously, and we conducted a GWAS for cohort II (3323 vitiligo cases and 7186 healthy controls) in this study, with the results subjected to a genome-wide meta-analysis and linkage disequilibrium analysis. We identify, to our knowledge, 11 previously unreported susceptibility variants, of which 6 variants are located in the intronic regions, and the remaining 5 variants are located within intergenic regions between genes. In addition, the results of polygenic risk score show that the best evaluated effect for target data is among significant SNVs of the base data. The susceptibility genes of vitiligo are mainly enriched in the immune-related functions and pathways. The susceptibility variants expand the role of genetic factors associated with vitiligo. The bioinformatics analysis for risk genes provides further insight into the pathogenesis of vitiligo.

Inflammatory Bowel Disease: A Comprehensive Analysis of Molecular Bases, Predictive Biomarkers, Diagnostic Methods, and Therapeutic Options

In inflammatory bowel diseases (IBDs), such as Crohn's disease (CD) and ulcerative colitis (UC), the immune system relentlessly attacks intestinal cells, causing recurrent tissue damage over the lifetime of patients. The etiology of IBD is complex and multifactorial, involving environmental, microbiota, genetic, and immunological factors that alter the molecular basis of the organism. Among these, the microbiota and immune cells play pivotal roles; the microbiota generates antigens recognized by immune cells and antibodies, while autoantibodies target and attack the intestinal membrane, exacerbating inflammation and tissue damage. Given the altered molecular framework, the analysis of multiple molecular biomarkers in patients proves exceedingly valuable for diagnosing and prognosing IBD, including markers like C reactive protein and fecal calprotectin. Upon detection and classification of patients, specific treatments are administered, ranging from conventional drugs to new biological therapies, such as antibodies to neutralize inflammatory molecules like tumor necrosis factor (TNF) and integrin. This review delves into the molecular basis and targets, biomarkers, treatment options, monitoring techniques, and, ultimately, current challenges in IBD management.

Regulatory Variants on the Leukocyte Immunoglobulin-Like Receptor Gene Cluster are Associated with Crohn's Disease and Interact with Regulatory Variants for TAP2

BACKGROUND AND AIMS

Crohn's disease [CD] has a complex polygenic aetiology with high heritability. There is ongoing effort to identify novel variants associated with susceptibility to CD through a genome-wide association study [GWAS] in large Korean populations.

METHODS

Genome-wide variant data from 902 Korean patients with CD and 72 179 controls were used to assess the genetic associations in a meta-analysis with previous Korean GWAS results from 1621 patients with CD and 4419 controls. Epistatic interactions between CD-risk variants of interest were tested using a multivariate logistic regression model with an interaction term.

RESULTS

We identified two novel genetic associations with the risk of CD near ZBTB38 and within the leukocyte immunoglobulin-like receptor [LILR] gene cluster [p < 5 × 10-8], with highly consistent effect sizes between the two independent Korean cohorts. CD-risk variants in the LILR locus are known quantitative trait loci [QTL] for multiple LILR genes, of which LILRB2 directly interacts with various ligands including MHC class I molecules. The LILR lead variant exhibited a significant epistatic interaction with CD-associated regulatory variants for TAP2 involved in the antigen presentation of MHC class I molecules [p = 4.11 × 10-4], showing higher CD-risk effects of the TAP2 variant in individuals carrying more risk alleles of the LILR lead variant (odds ratio [OR] = 0.941, p = 0.686 in non-carriers; OR = 1.45, p = 2.51 × 10-4 in single-copy carriers; OR = 2.38, p = 2.76 × 10-6 in two-copy carriers).

CONCLUSIONS

This study demonstrated that genetic variants at two novel susceptibility loci and the epistatic interaction between variants in LILR and TAP2 loci confer a risk of CD.

The potential clinical impact of cell type-specific genetic regulation: Crohn's disease

Complex diseases are heterogenous due to variation in their genetic and environmental underpinnings, leading to varied treatment responses. Genome-wide association studies (GWAS) integrated with single-cell expression quantitative trait loci analyses (eQTL) can pinpoint cell-type specific candidate disease-relevant genes and pathways. This knowledge can be applied to patient stratification and novel therapeutic target identification. Here, we describe the translational potential of cell-type specific genetic regulation, using Crohn's disease as an example.

The latest breakthrough on genetic characteristics of inflammatory bowel disease in Chinese and other East Asian ancestries

Inflammatory bowel diseases (IBDs) are complex chronic disorders of the gastrointestinal tract with the following two subtypes: Crohn's disease and ulcerative colitis. Disease presentation and progression within and across IBDs, especially Crohn's disease, are highly heterogeneous in the location, severity of inflammation, intestinal stenosis and obstruction, and extraintestinal manifestations. Clinical classifications fail to accurately predict the disease course and response to therapies. To date, most IBD genetic associations are derived from individuals of European ancestries, leading to a limitation of the discovery and application of IBD genetics in the rest of the world populations. In this mini-review, we summarize the latest progress of genome-wide association studies of IBD across global ancestries especially the Chinese population, the similarities and differences in genetic architecture between European and East Asian ancestries, as well as, the clinical significances relevant to IBD genetic study.

Treatment of inflammatory bowel disease-Asian perspectives: the results of a multinational web-based survey in the 8th Asian Organization for Crohn's and Colitis meeting

BACKGROUND/AIMS

As the characteristics of inflammatory bowel disease (IBD) differ between Asians and Westerners, it is necessary to determine adequate therapeutic strategy for Asian IBD patients. We evaluated the current treatment of IBD in Asian countries/regions using a web-based survey.

METHODS

The Korean Association for the Study of Intestinal Diseases conducted a multinational web-based survey for current IBD care in Asia between September 16, 2020, and November 13, 2020.

RESULTS

A total of 384 doctors treating IBD patients from 24 Asian countries/regions responded to the survey. Anti-tumor necrosis factor (TNF) agents, anti-integrins, and anti-interleukin-12/23 agents were available for use by 93.8%, 72.1%, and 70.1% of respondents in Asian countries/regions. Compared with a previous survey performed in 2014, an increased tendency for treatment with biologics, including anti-TNF agents, was observed. In the treatment of corticosteroid-refractory acute severe ulcerative colitis, 72.1% of respondents chose anti-TNF agents, followed by tacrolimus (11.7%). In the treatment of corticosteroid-refractory Crohn's disease, 90.4% chose anti-TNF agents, followed by thiopurines (53.1%), anti-interleukin-12/23 agents (39.3%), and anti-integrin agents (35.7%). In the treatment of Crohn's disease patients refractory to anti-TNF agents, the most preferred strategy was to measure serum levels of anti-TNF and anti-drug antibodies (40.9%), followed by empiric dose escalation or shortening of dosing intervals (25.3%).

CONCLUSIONS

Although there were some differences, treatment strategies for patients with IBD were mostly similar among Asian doctors. Based on the therapeutic outcomes, it is necessary to identify the most appropriate therapeutic strategy for Asian IBD patients.

Crohn’s disease: Why the ileum?

Crohn’s disease (CD) is an inflammatory bowel disease characterized by immune-mediated flares affecting any region of the intestine alternating with remission periods. In CD, the ileum is frequently affected and about one third of patients presents with a pure ileal type. Moreover, the ileal type of CD presents epidemiological specificities like a younger age at onset and often a strong link with smoking and genetic susceptibility genes. Most of these genes are associated with Paneth cell dysfunction, a cell type found in the intestinal crypts of the ileum. Besides, a Western-type diet is associated in epidemiological studies with CD onset and increasing evidence shows that diet can modulate the composition of bile acids and gut microbiota, which in turn modulates the susceptibility of the ileum to inflammation. Thus, the interplay between environmental factors and the histological and anatomical features of the ileum is thought to explain the specific transcriptome profile observed in CD ileitis. Indeed, both immune response and cellular healing processes harbour differences between ileal and non-ileal CD. Taken together, these findings advocate for a dedicated therapeutic approach to managing ileal CD. Currently, interventional pharmacological studies have failed to clearly demonstrate distinct response profiles according to disease site. However, the high rate of stricturing disease in ileal CD requires the identification of new therapeutic targets to significantly change the natural history of this debilitating disease.

Multi-omics in Crohn's disease: New insights from inside

Crohn's disease (CD) is an inflammatory bowel disease (IBD) with complex clinical manifestations such as chronic diarrhea, weight loss and hematochezia. Despite the increasing incidence worldwide, cure of CD remains extremely difficult. The rapid development of high-throughput sequencing technology with integrated-omics analyses in recent years has provided a new means for exploring the pathogenesis, mining the biomarkers and designing targeted personalized therapeutics of CD. Host genomics and epigenomics unveil heredity-related mechanisms of susceptible individuals, while microbiome and metabolomics map host-microbe interactions in CD patients. Proteomics shows great potential in searching for promising biomarkers. Nonetheless, single omics technology cannot holistically connect the mechanisms with heterogeneity of pathological behavior in CD. The rise of multi-omics analysis integrates genetic/epigenetic profiles with protein/microbial metabolite functionality, providing new hope for comprehensive and in-depth exploration of CD. Herein, we emphasized the different omics features and applications of CD and discussed the current research and limitations of multi-omics in CD. This review will update and deepen our understanding of CD from integration of broad omics spectra and will provide new evidence for targeted individualized therapeutics.

Genetic architecture of the inflammatory bowel diseases across East Asian and European ancestries

Inflammatory bowel diseases (IBDs) are chronic disorders of the gastrointestinal tract with the following two subtypes: Crohn's disease (CD) and ulcerative colitis (UC). To date, most IBD genetic associations were derived from individuals of European (EUR) ancestries. Here we report the largest IBD study of individuals of East Asian (EAS) ancestries, including 14,393 cases and 15,456 controls. We found 80 IBD loci in EAS alone and 320 when meta-analyzed with ~370,000 EUR individuals (~30,000 cases), among which 81 are new. EAS-enriched coding variants implicate many new IBD genes, including ADAP1 and GIT2. Although IBD genetic effects are generally consistent across ancestries, genetics underlying CD appears more ancestry dependent than UC, driven by allele frequency (NOD2) and effect (TNFSF15). We extended the IBD polygenic risk score (PRS) by incorporating both ancestries, greatly improving its accuracy and highlighting the importance of diversity for the equitable deployment of PRS.

Case-case genome-wide association analysis identifying genetic loci with divergent effects on Crohn's disease and ulcerative colitis

Crohn's disease (CD) and ulcerative colitis (UC), two major subtypes of inflammatory bowel disease, show substantial differences in their clinical course and treatment response. To identify the genetic factors underlying the distinct characteristics of these two diseases, we performed a genome-wide association study (GWAS) between CD (n = 2359) and UC (n = 2175) in a Korean population, followed by replication in an independent sample of 772 CD and 619 UC cases. Two novel loci were identified with divergent effects on CD and UC: rs9842650 in CD200 and rs885026 in NCOR2. In addition, the seven established susceptibility loci [major histocompatibility complex (MHC), TNFSF15, OTUD3, USP12, IL23R, FCHSD2 and RIPK2] reached genome-wide significance. Of the nine loci, six (MHC, TNFSF15, OTUD3, USP12, IL23R and CD200) were replicated in the case-case GWAS of European populations. The proportion of variance explained in CD-UC status by polygenic risk score analysis was up to 22.6%. The area under the receiver-operating characteristic curve value was 0.74, suggesting acceptable discrimination between CD and UC. This CD-UC GWAS provides new insights into genetic differences between the two diseases with similar symptoms and might be useful in improving their diagnosis and treatment.

Real-world effectiveness and safety of ustekinumab induction therapy for Korean patients with Crohn's disease: a KASID prospective multicenter study

BACKGROUND/AIMS

We investigated the real-world effectiveness and safety of ustekinumab (UST) as induction treatment for Koreans with Crohn's disease (CD).

METHODS

CD patients who started UST were prospectively enrolled from 4 hospitals in Korea. All enrolled patients received intravenous UST infusion at week 0 and subcutaneous UST injection at week 8. Clinical outcomes were assessed using Crohn's Disease Activity Index (CDAI) scores at weeks 8 and 20 among patients with active disease (CDAI ≥150) at baseline. Clinical remission was defined as a CDAI <150, and clinical response was defined as a reduction in CDAI ≥70 points from baseline. Safety and factors associated with clinical remission at week 20 were also analyzed.

RESULTS

Sixty-five patients were enrolled between January 2019 and December 2020. Among 49 patients with active disease at baseline (CDAI ≥150), clinical remission and clinical response at week 8 were achieved in 26 (53.1%) and 30 (61.2%) patients, respectively. At week 20, 27 (55.1%) and 35 (71.4%) patients achieved clinical remission and clinical response, respectively. Twenty-seven patients (41.5%) experienced adverse events, with serious adverse events in 3 patients (4.6%). One patient (1.5%) stopped UST therapy due to poor response. Underweight (body mass index <18.5 kg/m2) (odds ratio [OR], 0.085; 95% confidence interval [CI], 0.014-0.498; P=0.006) and elevated C-reactive protein at baseline (OR, 0.133; 95% CI, 0.022-0.823; P=0.030) were inversely associated with clinical remission at week 20.

CONCLUSIONS

UST was effective and well-tolerated as induction therapy for Korean patients with CD.