Contribution of IL23R but not ATG16L1 to Crohn's disease susceptibility in Koreans

A Systematic Review on the Increasing Incidence of Inflammatory Bowel Disease in Southeast Asia: Looking Beyond the Urbanization Phenomenon

The incidence of inflammatory bowel disease (IBD) has been increasing in Southeast Asia (SEA) in tandem with its economic growth and urbanization over the past 2 decades. Specific characteristics of IBD in SEA are similar to East Asia and the West, such as the declining ratio of ulcerative colitis to Crohn's disease. However, exceptionally low familial aggregation is seen. Smoking is also not a common risk factor in patients with Crohn's disease. The incidence of perianal disease is higher in SEA than in Australia and is comparable to the West. In a multiracial population, such as Singapore and Malaysia, Indians have the highest incidence and prevalence rates, which are likely to be due to important putative mutations. For instance, a higher frequency of the NOD2 predisposing mutation SNP5 and IBD risk allele IGR2198a and IGR2092a were found in Indians. Although differences in the genetic constitution play an important role in the epidemiology and prognosis of IBD in SEA, the emergence of this disease offers a unique opportunity to identify potential exposomes that contribute to its pathogenesis.

ATG16L1 rs2241880/T300A increases susceptibility to perianal Crohn's disease: An updated meta-analysis on inflammatory bowel disease risk and clinical outcomes

BACKGROUND

ATG16L1 plays a fundamental role in the degradative intracellular pathway known as autophagy, being a mediator of inflammation and microbial homeostasis. The variant rs2241880 can diminish these capabilities, potentially contributing to inflammatory bowel disease (IBD) pathogenesis.

OBJECTIVES

To perform an updated meta-analysis on the association between ATG16L1 rs2241880 and IBD susceptibility by exploring the impact of age, ethnicity, and geography. Moreover, to investigate the association between rs2241880 and clinical features.

METHODS

Literature searches up until September 2022 across 7 electronic public databases were performed for all case-control studies on ATG16L1 rs2241880 and IBD. Pooled odds ratios (ORP ) and 95% CI were calculated under the random effects model.

RESULTS

Our analyses included a total of 30,606 IBD patients, comprising 21,270 Crohn's disease (CD) and 9336 ulcerative colitis (UC) patients, and 33,329 controls. ATG16L1 rs2241880 was significantly associated with CD susceptibility, where the A allele was protective (ORP : 0.74, 95% CI: 0.72-0.77, p-value: <0.001), while the G allele was a risk factor (ORP : 1.23, 95% CI: 1.09-1.39, p-value: 0.001), depending on the minor allele frequencies observed in this multi-ancestry study sample. rs2241880 was predominantly relevant in Caucasians from North America and Europe, and in Latin American populations. Importantly, CD patients harbouring the G allele were significantly more predisposed to perianal disease (ORP : 1.21, 95% CI: 1.07-1.38, p-value: 0.003).

CONCLUSIONS

ATG16L1 rs2241880 (G allele) is a consistent risk factor for IBD in Caucasian cohorts and influences clinical outcomes. As its role in non-Caucasian populations remains ambiguous, further studies in under-reported populations are necessary.

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.

How autophagy, a potential therapeutic target, regulates intestinal inflammation

Inflammatory bowel disease (IBD) is a group of disorders that cause chronic inflammation in the intestines, with the primary types including ulcerative colitis and Crohn's disease. The link between autophagy, a catabolic mechanism in which cells clear protein aggregates and damaged organelles, and intestinal health has been widely studied. Experimental animal studies and human clinical studies have revealed that autophagy is pivotal for intestinal homeostasis maintenance, gut ecology regulation and other aspects. However, few articles have summarized and discussed the pathways by which autophagy improves or exacerbates IBD. Here, we review how autophagy alleviates IBD through the specific genes (e.g., ATG16L1, IRGM, NOD2 and LRRK2), crosstalk of multiple phenotypes with autophagy (e.g., Interaction of autophagy with endoplasmic reticulum stress, intestinal antimicrobial defense and apoptosis) and autophagy-associated signaling pathways. Moreover, we briefly discuss the role of autophagy in colorectal cancer and current status of autophagy-based drug research for IBD. It should be emphasized that autophagy has cell-specific and environment-specific effects on the gut. One of the problems of IBD research is to understand how autophagy plays a role in intestinal tract under specific environmental factors. A better understanding of the mechanism of autophagy in the occurrence and progression of IBD will provide references for the development of therapeutic drugs and disease management for IBD in the future.

Biomarkers for the Prediction and Diagnosis of Fibrostenosing Crohn's Disease: A Systematic Review

BACKGROUND AND AIMS

Intestinal strictures are a common complication of Crohn's disease (CD). Biomarkers of intestinal strictures would assist in their prediction, diagnosis, and monitoring. Herein we provide a comprehensive systematic review of studies assessing biomarkers that may predict or diagnose CD-associated strictures.

METHODS

We performed a systematic review of PubMed, EMBASE, ISI Web of Science, Cochrane Library, and Scopus to identify citations pertaining to biomarkers of intestinal fibrosis through July 6, 2020, that used a reference standard of full-thickness histopathology or cross-sectional imaging or endoscopy. Studies were categorized based on the type of biomarker they evaluated (serum, genetic, histopathologic, or fecal).

RESULTS

Thirty-five distinct biomarkers from 3 major groups were identified: serum (20 markers), genetic (9 markers), and histopathology (6 markers). Promising markers include cartilage oligomeric matrix protein, hepatocyte growth factor activator, and lower levels of microRNA-19-3p (area under the curves were 0.805, 0.738, and 0.67, respectively), and multiple anti-flagellin antibodies (A4-Fla2 [odds ratio, 3.41], anti Fla-X [odds ratio, 2.95], and anti-CBir1 [multiple]). Substantial heterogeneity was observed and none of the markers had undergone formal validation. Specific limitations to acceptance of these markers included failure to use a standardized definition of stricturing disease, lack of specificity, and insufficient relevance to the pathogenesis of intestinal strictures or incomplete knowledge regarding their operating properties.

CONCLUSIONS

There is a lack of well-defined studies on biomarkers of intestinal stricture. Development of reliable and accurate biomarkers of stricture is a research priority. Biomarkers can support the clinical management of CD patients and aid in the stratification and monitoring of patients during clinical trials of future antifibrotic drug candidates.

The Risk of Systemic Diseases in Those with Psoriasis and Psoriatic Arthritis: From Mechanisms to Clinic

Psoriasis and psoriatic arthritis (PsA) have been recently considered as chronic systemic inflammatory disorders. Over the past decades, enormous evidence indicates that patients with psoriasis and PsA have a higher risk of developing various comorbidities including cardiovascular disease, metabolic disease, cancers, infections, autoimmune disease, and psychiatric diseases. However, reported risks of some comorbidities in those with psoriasis and PsA are somewhat different according to the research design. Moreover, pathomechanisms underlying comorbidities of those with psoriasis and PsA remain poorly elucidated. The purpose of this review is to provide the most updated comprehensive view of the risk of systemic comorbidities in those with psoriasis and PsA. Molecular mechanisms associated with the development of various comorbidities in those with psoriasis and PsA are also reviewed based on recent laboratory and clinical investigations. Identifying the risk of systemic comorbidities and its associated pathomechanisms in those with psoriasis and PsA could provide a sufficient basis to use a multi-disciplinary approach for treating patients with psoriasis and PsA.

Genetic polymorphisms of ATG16L1 and IRGM genes in Malaysian patients with Crohn's disease

OBJECTIVE

To investigate the association between genetic polymorphisms in ATG16L1 and IRGM genes and the development of Crohn's disease (CD) in Malaysian patients.

METHODS

Altogether 335 participants were recruited, including 85 patients with CD and 250 unrelated healthy controls, and their informed consent was obtained. Genomic DNA was extracted via a conventional phenol-chloroform extraction method. Six single nucleotide polymorphisms (SNPs) in ATG16L1 and IRGM genes were genotyped using TaqMan SNP genotyping assays. Associations between SNP and CD were determined using Fisher's exact test, odds ratio, and 95% confidence interval. Statistical power and the Hardy-Weinberg equilibrium were also calculated.

RESULTS

Two SNPs (rs2241880 and rs6754677) in the ATG16L1 gene were significantly associated with the onset of CD in the Malaysian population. The A allele and homozygous A/A genotype of the rs2241880 A/G polymorphism were protective against CD in the overall Malaysian and Malay population. The G allele and homozygous G/G genotype of the rs6754677 G/A polymorphism were protective in the Indian population, whereas the homozygous A/A genotype showed a risk of developing CD. The homozygous G/G genotype of IRGM rs11747270 was significantly present in the controls. However, this significance was not observed in a race-stratified analysis. All three ATG16L1 SNPs were associated with inflamed terminal ileum. IRGM rs4958847 and rs11747270 increased the risk of developing arthritis in patients with CD.

CONCLUSION

We found a significant association between SNP, which are located in autophagy-related genes, and CD in a Malaysian population.

ATG16L1 T300A polymorphism is associated with Crohn's disease in a Northwest Greek cohort, but ECM1 T130M and G290S polymorphisms are not associated with ulcerative colitis

Background:

Crohn’s disease (CD) and ulcerative colitis (UC) are well-described disease entities with unknown etiopathogenesis. Environmental, genetic, gut microbiota, and host immune response correlations have been implicated. The role of susceptibility gene polymorphisms, such as ATG16L1 T300A and ECM1 T130M and G290S, is well-described, although controversial findings have been reported.

Methods:

Two hundred five patients with inflammatory bowel disease (108 CD and 97 UC), and 223 healthy blood donors (control group) from the Northwest Greece region were genotyped for rs2241880 (T300A), rs3737240 (T130M) and rs13294 (G290S) single nucleotide polymorphisms. Genotyping was performed using the real-time polymerase chain reaction method.

Results:

The frequency of G allele was significantly higher in CD patients compared to the control group (P=0.029; odds ratio [OR] 1.45, 95% confidence interval [CI] 1.04-2.03). Carriers of two G alleles (T300A), compared to those carrying only one, were 1.3 times more susceptible to CD (P=0.022; OR 2.45, 95%CI 1.14-5.27). In CD patients, the presence of the T300A polymorphism indicates a possible protective effect against developing a penetrating (B3) phenotype, while in UC patients, presence of the T300A polymorphism, indicates a possible protective effect against developing joint-involving extraintestinal manifestations.

Conclusion:

Our study found a significant association of the T300A polymorphism with CD susceptibility, suggesting that CD occurrence in our population has a strong genetic background, with the T300A G allele having an additive effect.

Association of IL23R Variants With Crohn's Disease in Korean Children

Background: The interleukin 23 receptor gene (IL23R) is strongly associated with Crohn's disease (CD). It is unknown whether genetic variations in IL23R determine susceptibility for pediatric CD in Asian populations. Here, we investigated the association between IL23R variants and CD in Korean children. Methods: Four single nucleotide polymorphisms (SNPs) of IL23R [rs76418789 (G149R), rs1004819, rs7517847, and rs1495965] were genotyped in 141 children with CD and 150 controls using DNA direct sequencing. The risk allele and genotype frequencies were compared between patients and controls. The association between clinical phenotypes and genotypes of patients was also analyzed. Results: Two IL23R SNPs, rs76418789 (G149R), and rs1495965, were associated with CD in Korean pediatric patients as defense and risk loci, respectively. The odds ratio (OR) for rs76418789 (G149R) and rs1495965 was 0.409 (95% confidence interval [CI], 0.177-0.944; p = 0.031) and 1.484 (95% CI, 1.070-2.059; p = 0.018), respectively. Patients with the homozygous G allele of rs1495965 showed higher CD risk than those with other genotypes (GG vs. AA: OR, 2.256; 95% CI, 1.136-4.478; p = 0.019; GG vs. GA+AA: OR, 2.000; 95% CI, 1.175-3.404; p = 0.010). Additionally, they were more likely to have relatively invasive disease behavior of stenosis and/or penetration than simple inflammation (OR, 2.297; 95% CI, 1.065-4.950; p = 0.032). Conclusions: This is the first study reporting IL23R variants in Asian pediatric patients with CD. IL23R was significantly associated with Korean pediatric CD, and the rs1495965 may influence the clinical features of CD in Korean children.

Deep Resequencing of Ulcerative Colitis-Associated Genes Identifies Novel Variants in Candidate Genes in the Korean Population

BACKGROUND

Genome-wide association studies and meta-analyses have revealed the genetic background of ulcerative colitis (UC) by identifying common variants. However, these variants do not fully explain the disease variance in UC. To identify novel variants, we performed deep resequencing of UC-associated genes in Korean UC patients and subsequently investigated the functional roles of identified susceptibility genes.

METHODS

We performed targeted deep resequencing of 108 genes in 24 Korean UC patients and then performed association analysis with data from 126 healthy controls. We validated these variants using 2-stage replication studies including 793 UC patients and 783 controls. We performed in silico and pathway analyses and functional analyses.

RESULTS

The combined analysis including 2 replication studies identified 6 novel susceptibility loci and reconfirmed 10 previously reported loci. Among the novel single nucleotide variants (SNVs), rs10035653 in C5orf55 (P = 2.08 × 10-3; OR = 1.50), rs41417449 in BTNL2 (P = 1.27 × 10-2; OR = 1.32), rs3117099 in HCG23 (P = 9.98 × 10-6; OR = 1.40), rs7192 in HLA-DRA (P = 6.95 × 10-9; OR = 1.57), and rs3744246 in ORMDL3 (P = 2.21 × 10-2; OR = 1.21) were identified as causal variants, whereas rs713669 in IL17REL (P = 2.69 × 10-2; OR = 0.84) as a protective variant for UC. When correcting multiple testing, 3 novel SNVs (rs41417449 in BTNL2, rs3744246 in ORMDL3, and rs713669 in IL17REL) and 4 previously reported SNVs did not reach a statistical significance. Functional study suggested that SNVs of BTNL2 and C5orf55 exacerbated the inflammatory response both in vitro and in vivo.

CONCLUSIONS

This study identified 3 novel susceptibility loci and validated 6 previously reported SNVs for UC through deep resequencing in Koreans and revealed the functional roles of BTNL2 and C5orf55.

A novel susceptibility locus in MST1 and gene-gene interaction network for Crohn's disease in the Chinese population

The incidence of Crohn's disease is increasing in many Asian countries, but considerable differences in genetic susceptibility have been reported between Western and Asian populations. This study aimed to fine-map 23 previously reported Crohn's disease genes and identify their interactions in the Chinese population by Illumina-based targeted capture sequencing. Our results showed that the genetic polymorphism A>G at rs144982232 in MST1 showed the most significant association (P = 1.78 × 10-5 ; odds ratio = 4.87). JAK2 rs1159782 (T>C) was also strongly associated with Crohn's disease (P = 2.34 × 10-4 ; odds ratio = 3.72). Gene-gene interaction analysis revealed significant interactions between MST1 and other susceptibility genes, including NOD2, MUC19 and ATG16L1 in contributing to Crohn's disease risk. Main genetic associations and gene-gene interactions were verified using ImmunoChip data set. In conclusion, a novel susceptibility locus in MST1 was identified. Our analysis suggests that MST1 might interact with key susceptibility genes involved in autophagy and bacterial recognition. These findings provide insight into the genetic architecture of Crohn's disease in Chinese and may partially explain the disparity of genetic signals in Crohn's disease susceptibility across different ethnic populations by highlighting the contribution of gene-gene interactions.

Risk factors for postoperative recurrence after primary bowel resection in patients with Crohn’s disease

AIM

To evaluate the risk factors for postoperative recurrence after primary bowel resection in a cohort of Korean Crohn’s disease (CD) patients.

METHODS

This study included 260 patients with no history of previous bowel surgery who underwent primary surgery for CD between January 2000 and December 2010 at Asan Medical Center (Seoul, South Korea). The median follow-up period was 101 mo.

RESULTS

During the follow-up period, 66 patients (25.4%) underwent a second operation for disease recurrence. At 1, 5 and 10 years after the first operation, the cumulative rate of surgical recurrence was 1.1%, 8.3% and 35.9% and clinical recurrence occurred in 1.2%, 23.6% and 68.1%, respectively. In multivariate analysis, undergoing an emergency operation was a significant risk factor for surgical recurrence-free survival (SRFS) [HR = 2.431, 95%CI: 1.394-4.240, P = 0.002], as were the presence of perianal disease after the first operation (HR = 1.715, 95%CI: 1.005-2.926, P = 0.048) and history of smoking (HR = 1.798, 95%CI: 1.088-2.969, P = 0.022). The postoperative use of anti-tumor necrosis factor (TNF) agents reduced SRFS risk (HR = 0.521, 95%CI: 0.300-0.904, P = 0.02).

CONCLUSION

History of smoking, postoperative perianal disease and undergoing an emergency operation were independent risk factors for surgical recurrence. Using anti-TNF agents may reduce surgical recurrence.

Management of Crohn's disease in Taiwan: consensus guideline of the Taiwan Society of Inflammatory Bowel Disease

Crohn's disease (CD) is a chronic relapsing and remitting inflammatory disease of the gastrointestinal tract. CD is rare in Taiwan and other Asian countries, but its prevalence and incidence have been steadily increasing. A steering committee was established by the Taiwan Society of Inflammatory Bowel Disease to formulate statements on the diagnosis and management of CD taking into account currently available evidence and the expert opinion of the committee. Thorough clinical, endoscopic, and histological assessments are required for accurate diagnosis of CD. Computed tomography and magnetic resonance imaging are complementary to endoscopic evaluation for disease staging and detecting complications. The goals of CD management are to induce and maintain remission, reduce the risk of complications, and improve quality of life. Corticosteroids are the mainstay for inducing re-mission. Immunomodulating and biologic therapies should be used to maintain remission. Patients should be evaluated for hepatitis B virus and tuberculosis infection prior to treatment and receive regular surveillance for cancer. These consensus statements are based on current local evidence with consideration of factors, and could be serve as concise and practical guidelines for supporting clinicians in the management of patients with CD in Taiwan.

Association of ATG16L1 gene haplotype with inflammatory bowel disease in Indians

Inflammatory bowel disease (IBD) is characterized by multigenic inheritance. Defects in autophagy related genes are considered to show genetic heterogeneity between populations. We evaluated the association of several single nucleotide polymorphisms (SNPs) in the autophagy related 16 like 1 (ATG16L1) gene with IBD in Indians. The ATG16L1 gene was genotyped for ten different SNPs using DNA extracted from peripheral blood of 234 patients with Crohn's disease (CD), 249 patients with ulcerative colitis (UC) and 393 healthy controls The SNPs rs2241880, rs4663396, rs3792106, rs10210302, rs3792109, rs2241877, rs6737398, rs11682898, rs4663402 and rs4663421 were genotyped using the Sequenom MassArray platform. PLINK was used for the association analysis and pairwise linkage disequilibrium (LD) values. Haplotype analysis was done using Haploview. All SNPs were in Hardy Weinberg equilibrium in cases and controls. The G allele at rs6737398 exhibited a protective association with both CD and UC. The T allele at rs4663402 and C allele at rs4663421 were positively associated with CD and UC. The T allele at rs2241877 exhibited protective association with UC only. The AA genotype at rs4663402 and the GG genotype at rs4663421 were protectively associated with both CD and UC. Haplotype analysis revealed that all the SNPs in tight LD (D' = 0.76-1.0) and organized in a single haplotype block. Haplotype D was positively associated with IBD (P = 5.8 x 10-6 for CD and 0.002 for UC). SNPs in ATG16L1 were associated with IBD in Indian patients. The relevance to management of individual patients requires further study.

Genetic variation in IBD: progress, clues to pathogenesis and possible clinical utility

Epidemiological and clinical studies have suggested that the pathogenesis of inflammatory bowel disease (IBD) is strongly influenced by genetic predisposition. Beyond the limitations of linkage analysis, multiple genome-wide association studies, their meta-analyses, and targeted genotyping array techniques have broadened our understanding of the genetic architecture of IBD. Currently, over 200 single nucleotide polymorphisms are known to be associated with susceptibility to IBD and through functional analysis of genes and loci, a substantial proportion of pathophysiologic mechanisms have been revealed. However, because only a modest fraction of predicted heritability can be explained by known genes/loci, additional strategies are needed including the identification of rare variants with large effect sizes to help explain the missing heritability. Considerable progress is also being made on applying outcomes of genetic research in diagnostics, classification, prognostics, and the development of new therapeutics of IBD.

Genetic Influences on the Development of Fibrosis in Crohn's Disease

Fibrostenotic strictures are an important complication in patients with Crohn’s disease (CD), very often necessitating surgery. This fibrotic process develops in a genetically susceptible individual and is influenced by an interplay with environmental, immunological, and disease-related factors. A deeper understanding of the genetic factors driving this fibrostenotic process might help to unravel the pathogenesis, and ultimately lead to development of new, anti-fibrotic therapy. Here, we review the genetic factors that have been associated with the development of fibrosis in patients with CD, as well as their potential pathophysiological mechanism(s). We also hypothesize on clinical implications, if any, and future research directions.

Deep resequencing of 131 Crohn's disease associated genes in pooled DNA confirmed three reported variants and identified eight novel variants

OBJECTIVE

Genome wide association studies (GWAS) and meta-analyses for Crohn's disease (CD) have not fully explained the heritability of CD, suggesting that additional loci are yet to be found and that the known loci may contain high effect rare risk variants that have thus far gone undetected by GWAS. While the cost of deep sequencing remains too high to analyse many samples, targeted sequencing of pooled DNA samples allows the efficient and cost effective capture of all variations in a target region.

DESIGN

We performed pooled sequencing in 500 Korean CD cases and 1000 controls to evaluate the coding exon and 5' and 3' untranslated regions of 131 CD associated genes. The identified genetic variants were validated using genotyping in an independent set of 500 CD cases and 1000 controls.

RESULTS

Pooled sequencing identified 30 common/low single nucleotide variants (SNVs) in 12 genes and 3 rare SNVs in 3 genes. Our results confirmed a significant association of CD with the following previously reported risk loci: rs3810936 in TNFSF15 (OR=1.83, p<2.2×10(-16)), rs76418789 in IL23R (OR=0.47, p=1.14×10(-8)) and rs2241880 in ATG16L1 (OR=1.30, p=5.28×10(-6)). In addition, novel loci were identified in TNFSF8 (rs3181374, OR=1.53, p=1.03×10(-14)), BTNL2 (rs28362680, OR=1.47, p=9.67×10(-11)), HLA-DQA2 (rs3208181, OR=1.36, p=4.66×10(-6)), STAT3 (rs1053004, OR=1.29, p=2.07×10(-5)), NFKBIA (rs2273650, OR=0.80, p=3.93×10(-4)), NKX2-3 (rs888208, OR=0.82, p=6.37×10(-4)) and DNAH12 (rs4462937, OR=1.13, p=3.17×10(-2)). A novel rare SNV, rs200735402 in CARD9, was shown to have a protective effect (OR=0.09, p=5.28×10(-5)).

CONCLUSIONS

Our deep resequencing of 131 CD associated genes confirmed 3 reported risk loci and identified 8 novel risk loci for CD in Koreans, providing new insights into the genetic architecture of CD.

ATG16L1: A multifunctional susceptibility factor in Crohn disease

Genetic variations in the autophagic pathway influence genetic predispositions to Crohn disease. Autophagy, the major lysosomal pathway for degrading and recycling cytoplasmic material, constitutes an important homeostatic cellular process. Of interest, single-nucleotide polymorphisms in ATG16L1 (autophagy-related 16-like 1 [S. cerevisiae]), a key component in the autophagic response to invading pathogens, have been associated with an increased risk of developing Crohn disease. The most common and well-studied genetic variant of ATG16L1 (rs2241880; leading to a T300A conversion) exhibits a strong association with risk for developing Crohn disease. The rs2241880 variant plays a crucial role in pathogen clearance, resulting in imbalanced cytokine production, and is linked to other biological processes, such as the endoplasmic reticulum stress/unfolded protein response. In this review, we focus on the importance of ATG16L1 and its genetic variant (T300A) within the elementary biological processes linked to Crohn disease.

Asia Pacific Consensus Statements on Crohn's disease. Part 1: Definition, diagnosis, and epidemiology: (Asia Pacific Crohn's Disease Consensus--Part 1)

Inflammatory bowel disease (IBD) was previously thought to be rare in Asia, but emerging data indicate rising incidence and prevalence of IBD in the region. The Asia Pacific Working Group on Inflammatory Bowel Disease was established in Cebu, Philippines, at the Asia Pacific Digestive Week conference in 2006 under the auspices of the Asian Pacific Association of Gastroenterology with the goal of developing best management practices, coordinating research, and raising awareness of IBD in the region. The consensus group previously published recommendations for the diagnosis and management of ulcerative colitis with specific relevance to the Asia-Pacific region. The present consensus statements were developed following a similar process to address the epidemiology, diagnosis, and management of Crohn's disease. The goals of these statements are to pool the pertinent literature specifically highlighting relevant data and conditions in the Asia-Pacific region relating to the economy, health systems, background infectious diseases, differential diagnoses, and treatment availability. It does not intend to be all comprehensive and future revisions are likely to be required in this ever-changing field.

Association of Interleukin-23 receptor gene polymorphisms with susceptibility to Crohn's disease: A meta-analysis

Studies investigating the association between Interleukin-23 receptor (IL-23R) gene polymorphisms and Crohn’s disease (CD) report conflicting results. Thus, a meta-analysis was carried out to assess the association between the IL-23R polymorphisms and CD. A systematic literature search was conducted to identify all relevant studies. Pooled odds ratio (ORs) with 95% confidence interval (CIs) was used to estimate the strength of association. Finally, a total of 60 case-control studies in 56 articles, involving 22,820 CD patients and 27,401 healthy controls, were included in the meta-analysis. Overall, a significant association was found between all CD and the rs7517847 polymorphism (OR = 0.699, 95% CI = 0.659 ~ 0.741, P < 0.001). Meta-analysis of the rs11209026, rs1343151, rs10489629 and rs11465804 polymorphisms indicated the same pattern as for rs7517847. Meta-analysis showed an association between the rs10889677A allele and CD (OR = 1.393, 95% CI = 1.328 ~ 1.461, P < 0.001). Similarly, meta-analysis of the rs2201840, rs1004819, rs1495965 and rs11209032 polymorphisms revealed the same pattern as that shown by meta-analysis of rs10889677. Stratification by ethnicity revealed that IL-23R gene polymorphisms were associated with CD in the Caucasian group, but not in Asians. In summary, the meta-analysis suggests a significant association between IL-23R polymorphisms and CD, especially in Caucasians.

Risk of Major Abdominal Surgery in an Asian Population-based Crohn's Disease Cohort

BACKGROUND

Crohn's disease (CD) is increasing in incidence and prevalence in Asia, but there is a paucity of population-based studies on risk factors for surgery in Asian patients with CD. This will be useful to identify patients who may benefit from top-down treatment. This study describes the rates of abdominal surgery and identifies associated risk factors in Singaporean patients with CD.

METHODS

This was a retrospective observational study. The medical records of Singaporeans diagnosed with CD from 1970 to 2013 were reviewed from 8 different hospitals in Singapore. The cumulative probability of CD-related abdominal surgery was estimated using the Kaplan-Meier method. The logistic regression model was used to assess associations between independent risk factors and surgery.

RESULTS

The cohort of 430 Singaporean patients with CD included 63.5% Chinese, 11.9% Malay, and 24.7% Indians, with a male to female ratio of 1.6; median follow-up was 7.3 years (range, 2.9-13.0 yr) and median age at diagnosis 30.5 years (range, 19.5-43.7 yr). One hundred twelve patients (26.0%) required major abdominal surgery: the cumulative risk of surgery was 14.9% at 90 days, 21.2% at 5 years, 28.8% at 10 years, 38.3% at 20 years, and 50.6% at 30 years from diagnosis. Of the surgical patients, 75.0% were Chinese, 10.7% Malays, and 14.3% Indians; 21.4% underwent surgery for inflammatory disease, 40.2% for stricturing disease, and 38.4% for penetrating disease. Age at diagnosis (A2 17-40 yr, OR: 2.75, 95% confidence interval [CI], 1.14-7.76), ileal disease (L1 location, OR: 2.35, 95% CI, 1.14-5.0), stricturing (B2 OR: 6.09, 95% CI, 3.20-11.8), and penetrating behavior (B3 OR: 21.6, 95% CI, 9.0-58.8) were independent risk factors for CD-related abdominal surgery. Indian patients were less likely to require surgery (OR: 0.40, 95% CI, 0.19-0.78).

CONCLUSIONS

Age at diagnosis, L1 location, B2, and B3 disease behavior are independent risk factors for abdominal surgery. Interestingly, despite a higher prevalence of CD in Indians, a smaller proportion of Indian patients required surgery. These findings suggest that both environmental and genetic factors contribute to the risk of surgery in Asian patients with CD.

Genetic Polymorphisms in Autophagy-Associated Genes in Korean Children With Early-Onset Crohn Disease

OBJECTIVE

The aim of the present study was to investigate the genetic polymorphisms of the autophagy-associated genes autophagy-related 16-like 1 (ATG16L1), immunity-related GTPase M (IRGM), Unc-51-like kinase 1 (ULK1), and NOD2 with respect to early-onset Crohn disease (CD) among Korean children.

METHODS

A total of 65 patients with CD from the Seoul National University Children's Hospital, from January 2000 to May 2012, and 72 unaffected controls were selected. Twelve different single nucleotide polymorphisms (SNPs) were analyzed (TaqMan assay: ATG16L1 rs2241880, IRGM SNPs [rs13361189, rs4958847, rs1000113, rs10065172, and rs72553867], ULK1 SNPs [rs12303764, rs10902469, and rs7488085], NOD2 SNPs [Arg702Trp and Gly908Arg]; direct sequencing: NOD2 leu1007fsinsC). The onset age of patients was 8.6 ± 4.7 years. Twelve patients (18.5%) had an onset age of <1 year.

RESULTS

Two of the 12 SNPs showed significant results. IRGM rs1000113 exhibited an association with CD with respect to its minor allele frequency (odds ratio [OR] 1.71, 95% confidence interval [CI] 1.05-2.79, P = 0.03) and genotype distribution (dominant model: OR 2.17, 95% CI 1.07-4.39, P = 0.03). IRGM rs72553867 exhibited association with CD with respect to its minor allele frequency (OR 0.50, 95% CI 0.27-0.91, P = 0.02) and genotype distribution (dominant model: OR 0.50, 95% CI 0.23-0.94, P = 0.03). The 3 SNPs of NOD2 existed only as wild types for both groups. In the genotype-phenotype analysis, the onset age, disease location, and disease behavior exhibited no association.

CONCLUSIONS

IRGM rs1000113 and IRGM rs72553867 exhibited associations with early-onset CD as risk loci and defense loci, respectively. This suggests that the autophagy pathway plays an important role in early-onset CD.

ATG16L1: A multifunctional susceptibility factor in Crohn disease

Genetic variations in the autophagic pathway influence genetic predispositions to Crohn disease. Autophagy, the major lysosomal pathway for degrading and recycling cytoplasmic material, constitutes an important homeostatic cellular process. Of interest, single-nucleotide polymorphisms in ATG16L1 (autophagy-related 16-like 1 [S. cerevisiae]), a key component in the autophagic response to invading pathogens, have been associated with an increased risk of developing Crohn disease. The most common and well-studied genetic variant of ATG16L1 (rs2241880; leading to a T300A conversion) exhibits a strong association with risk for developing Crohn disease. The rs2241880 variant plays a crucial role in pathogen clearance, resulting in imbalanced cytokine production, and is linked to other biological processes, such as the endoplasmic reticulum stress/unfolded protein response. In this review, we focus on the importance of ATG16L1 and its genetic variant (T300A) within the elementary biological processes linked to Crohn disease.

ATG16L1 and IL23R variants and genetic susceptibility to crohn's disease: mode of inheritance based on meta-analysis of genetic association studies

BACKGROUND

Autophagy and regulation of IL-23 signaling pathways have been implicated in the pathogenesis of Crohn's disease (CD). We studied the mode of inheritance and reviewed the association of 2 polymorphic variants of ATG16L1 and IL23R with CD.

METHODS

We searched the PubMed and ISI Web of Science databases (up to May 2014) for pertinent articles. We included all studies that had a case-control design, with cases having CD and controls being healthy and reported full genotype frequencies for the ATG16L1 and/or IL23R variant of interest. We quantified the relative genetic risk using the model-free approach of the generalized odds ratio metric (ORG) and reported 95% precision estimates. Also, we explored the mode of inheritance using the degree of dominance h-index.

RESULTS

Fifty-one studies fulfilled these requirements and were included in the analysis. These studies involved 12,762 patients and 16,735 controls evaluating the association of ATG16L1 (rs2241880 p.Thr300Ala) and 8110 patients and 11,900 controls evaluating the association of IL23R (rs11209026 p.Arg381Gln) with CD. The ATG16L1 variant rs2241880 was associated with increased susceptibility to CD (combined ORG = 1.38; 95% confidence interval, 1.29-1.48) and a nondominant mode of inheritance (suggesting that the effect of heterozygosity lies exactly in the middle of extreme homozygotes, h = 0). The IL23R variant rs11209026 was associated with significant protection (ORG = 0.46; 95% confidence interval, 0.41-0.53) and a recessive mode of inheritance, indicating that the effect of a heterozygous genotype would lie close to the wild-type homozygous genotype. In subgroup analysis, the significant effects persisted across Caucasian ancestry studies and pediatric populations but were lacking across studies in Asian populations.

CONCLUSIONS

The ATG16L1 variant rs2241880 was associated with 38% increase in the risk for CD for higher mutational load, whereas IL23R variant rs11209026 decreased the risk by 54% for higher mutational load. The mode of inheritance for ATG16L1 variant demonstrated perfect additivity for genetic risk, whereas it showed recessiveness for the IL23R variant. This analysis permits risk stratification for CD based on the mutational status and highlight the need for additional studies in certain populations.

CNTNAP3 associated ATG16L1 expression and Crohn's disease

Autophagy is a common physiological process in cell homeostasis and regulation. Autophagy-related gene mutations and autophagy disorders are important in Crohn's disease (CD). The nucleotide oligomerization domain 2–autophagy genes autophagy 16-like 1 (NOD2–ATG16L1) signaling axis disorder contributes to the dysfunction of autophagy. This paper is focused on the relationship between contactin associated protein-like 3 (CNTNAP3) and ATG16L1 expression in Crohn's disease. The results indicated that the expression of ATG16L1 is higher in some CD patients compared to normal controls. ATG16L1 was well correlated with the C-reactive protein (CRP) in some CD patients. In vitro study revealed that CNTNAP3 could upregulate the expression of ATG16L1 and increase autophagy vacuoles.

Emerging leadership lecture: Inflammatory bowel disease in Asia: emergence of a "Western" disease

More than a decade ago, inflammatory bowel disease (IBD) is rare in Asia. Today, the importance of IBD in Asia is exemplified by its rapidly increasing incidence, complicated disease behavior, and substantial morbidity. In the first large-scale population-based epidemiologic study in Asia, the incidence of IBD varied from 0.60 to 3.44 per 100,000. There has been a twofold to threefold increase in the incidence of IBD in several countries in Asia. Ulcerative colitis (UC) is more prevalent than Crohn's disease (CD), although CD incidence is rapidly increasing. A positive family history is much less common than in the West, as are extra-intestinal disease manifestations. Complicated and penetrating CD are common in Asia. These epidemiologic changes may relate to increased contact with the West, westernization of diet, improved hygiene, increasing antibiotics use, or changes in the gut microbiota. Asian patients with CD have altered gut microbiota compared with their healthy counterparts and Caucasian CD subjects. Mucosa-associated microbiota in IBD may differ geographically. In a population-based case-control study, breast-feeding, having pets, and better sanitary conditions were protective of IBD, suggesting that childhood environment plays an important role in modulating disease development. Genetic factors also differ between Asians and Caucasians. Nucleotide oligomerization domain-2 (NOD2) and autophagy variants were not associated with CD, but tumor necrosis factor superfamily gene-15 polymorphisms were strongly associated with CD in East Asians. Research in Asia, an area of rapidly changing IBD epidemiology, may lead to the discovery of critical etiologic factors that lead to the development of IBD.

Smoking behaviour modifies IL23r-associated disease risk in patients with Crohn's disease

BACKGROUND AND AIM

The etiology of Crohn's disease (CD) implicates both genetic and environmental factors. Smoking behavior is one environmental risk factor to play a role in the development of CD. The study aimed to assess the contribution of the interleukin 23 receptor (IL23R) in determining disease susceptibility in two independent cohorts of CD, and to investigate the interactions between IL23R variants, smoking behavior, and CD-associated genes, NOD2 and ATG16L1.

METHODS

Ten IL23R single-nucleotide polymorphisms (SNPs) were genotyped in 675 CD cases, and 1255 controls from Brisbane, Australia (dataset 1). Six of these SNPs were genotyped in 318 CD cases and 533 controls from Canterbury, New Zealand (dataset 2). Case-control analysis of genotype and allele frequencies, and haplotype analysis for all SNPs was conducted.

RESULTS

We demonstrate a strong increased CD risk for smokers in both datasets (odds ratio 3.77, 95% confidence interval 2.88-4.94), and an additive interaction between IL23R SNPs and cigarette smoking. Ileal involvement was a consistent marker of strong SNP-CD association (P ≤ 0.001), while the lowest minor allele frequencies for location were found in those with colonic CD (L2). Three haplotype blocks were identified across the 10 IL23R SNPs conferring different risk of CD. Haplotypes conferred no further risk of CD when compared with single SNP analyses.

CONCLUSION

IL23R gene variants determine CD susceptibility in the Australian and New Zealand population, particularly ileal CD. A strong additive interaction exists between IL23R SNPs and smoking behavior resulting in a dramatic increase in disease risk depending upon specific genetic background.

Risk and clinical characteristics of lymphoma in Korean patients with inflammatory bowel diseases: a multicenter study

BACKGROUND AND AIMS

Studies of lymphoma risk in Western inflammatory bowel disease (IBD) patients show conflicting results; however, none have examined the lymphoma risk and clinical characteristics of Asian IBD patients.

METHODS

Patients with lymphoma were identified in an IBD database from 3 tertiary referral centers in Seoul, Korea. The standardized incidence ratio (SIR) of lymphoma was estimated using data from the Korea Central Cancer Registry of the National Cancer Center. The risk of lymphoma in relation to specific medications was also explored.

RESULTS

Seven cases of lymphoma (0.1%) were identified in 6585 IBD patients. The median age at lymphoma diagnosis was 43 years (range, 33 to 70 y) and the median duration of IBD at lymphoma diagnosis was 96.1 months (range, 15.1 to 171.6 mo). Three patients had underlying ulcerative colitis and 4 had Crohn's disease (CD). Non-Hodgkin lymphoma was diagnosed in 5 patients (71.4%) and Hodgkin disease (HD) in 2 patients (28.6%). The SIR of lymphoma was 2.03 [95% confidence interval (CI), 0.81-4.18] in the entire IBD patients. Both the SIR of lymphoma in CD patients (9.31; 95% CI, 1.13-33.62) and the SIR of HD (13.16; 95% CI, 1.59-47.53) in IBD patients were increased. The SIR of lymphoma in patients who were exposed to thiopurines was 5.93 (95% CI, 1.61-15.18).

CONCLUSIONS

The risk of lymphoma in CD patients and the risk of HD in IBD patients seem to be increased in Korea. Thiopurine may be related with the risk of lymphoma in Korean IBD patients.

Immunochip analysis identification of 6 additional susceptibility loci for Crohn's disease in Koreans

BACKGROUND

Crohn's disease (CD) is an intractable inflammatory bowel disease of unknown cause. Recent genome-wide association studies of CD in Korean and Japanese populations suggested marginal sharing of susceptibility loci between Caucasian and Asian populations. As the 7 identified loci altogether explain 5.31% of the risk for CD, the objective of this study was to identify additional CD susceptibility loci in the Korean population.

METHODS

Using the ImmunoChip custom single-nucleotide polymorphism array designed for dense genotyping of 186 loci identified through GWAS, we analyzed 722 individuals with CD and 461 controls for 96,048 SNP markers in the discovery stage, followed by validation in an additional 948 affected individuals and 977 controls.

RESULTS

We confirmed 6 previously reported loci in Caucasian: GPR35 at 2q37 (rs3749172; P = 5.30 × 10, odds ratio [OR] = 1.45), ZNF365 at 10q21 (rs224143; P = 2.20 × 10, OR = 1.38), ZMIZ1 at 10q22 (rs1250569; P = 3.05 × 10, OR = 1.30), NKX2-3 at 10q24 (rs4409764; P = 7.93 × 10, OR = 1.32), PTPN2 at 18p11 (rs514000; P = 9.00 × 10, OR = 1.33), and USP25 at 21q11 (rs2823256; P = 2.49 × 10, OR = 1.35), bringing the number of known CD loci (including 3 in the HLA) in Koreans to 15. The 6 additional loci increased the total genetic variance for CD risk from 5.31% to 7.27% in Koreans.

CONCLUSIONS

Although the different genetic backgrounds of CD between Asian and Western countries has been well established for the major susceptibility genes, our findings of overlapping associations offer new insights into the genetic architecture of CD.

Association of IL23R and ATG16L1 with susceptibility of Crohn's disease in Chinese population

OBJECTIVES

To investigate whether gene polymorphisms of ATG16L1 and IL23R are associated with the susceptibility of Crohn's disease (CD) in Chinese population.

METHODS

A total of 420 patients with CD and 450 age- and sex-matched healthy volunteers from Chinese Han population were included in this study. Single nucleotide polymorphisms (SNPs) rs2241880 of ATG16L1 and rs11209026, rs1004819, and rs1495965 of IL23R were genotyped. The differences of genotype and allele distributions between CD patients and healthy controls were assessed using the Chi-squared test. Besides, subgroup analysis of disease groups was performed using the Chi-squared test.

RESULTS

For ATG16L1, patients were found to have significantly higher proportion of genotype GG (18.3%), when compared with the normal controls (12.4%). Allele G was found to be the risk allele for the disease (34.3% vs. 29.0%, p = 0.016) with an odds ratio of 1.18. For IL23R, all three SNPs were found not to be associated with the development of CD. None of these four SNPs was found to be associated with the clinical features of the patients, including age at diagnosis, disease location, and behavior.

CONCLUSION

The original genome-wide association studies finding on ATG16L1 gene should be robust and this gene does play a role in the pathogenesis of CD in the Chinese population. However, the role of IL23R gene in the occurrence of CD remains obscure.

Crohn's disease in Korea: past, present, and future

The epidemiology, genetics, and clinical manifestations of Crohn's disease (CD) vary considerably among geographic areas and ethnic groups. Thus, identifying the characteristics of Korean CD is important for establishing management strategies appropriate for Korean patients. Since the mid-2000s, many studies have investigated the characteristic features of Korean CD. The incidence and prevalence rates of CD have been increasing rapidly in Korea, especially among the younger population. Unlike Western data, Korean CD shows a male predominance and a lower proportion of isolated colonic disease. Perianal lesions are more prevalent than in Western countries. Genome-wide association studies have confirmed that genetic variants in TNFSF15, IL-23R, and IRGM, but not ATG16L1, are associated with CD susceptibility in the Korean population. Studies of the associations between genetic mutations and the clinical course of CD are underway. Although it has been generally accepted that the clinical course of Korean CD is milder than that in Western countries, recent studies have shown a comparable rate of intestinal resection in Korean and Western CD patients. An ongoing nationwide, hospital-based cohort study is anticipated to provide valuable information on the natural history and prognosis of Korean CD in the near future.

Advances in IBD genetics

IBD is a spectrum of chronic disorders that constitute an important health problem worldwide. The hunt for genetic determinants of disease onset and course has culminated in the Immunochip project, which has identified >160 loci containing IBD susceptibility genes. In this Review, we highlight how genetic association studies have informed our understanding of the pathogenesis of IBD by focusing research efforts on key pathways involved in innate immunity, autophagy, lymphocyte differentiation and chemotaxis. Several of these novel genetic markers and cellular pathways are promising candidates for patient stratification and therapeutic targeting.

Biomarkers of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic disease mostly involved with intestine with unknown etiology. Diagnosis, evaluation of severity, and prognosis are still present as challenges for physicians. An ideal biomarker with the characters such as simple, easy to perform, noninvasive or microinvasive, cheap, rapid, and reproducible is helpful for patients and clinicians. Currently biomarkers applied in clinic include CRP, ESR, pANCA, ASCA, and fecal calprotectin. However, they are far from ideal. Lots of studies are focused on seeking for ideal biomarker for IBD. Herein, the paper reviewed recent researches on biomarkers of IBD to get advances of biomarkers in inflammatory bowel disease.

Interleukin and interleukin receptor gene polymorphisms in inflammatory bowel diseases susceptibility

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), represents a group of chronic inflammatory disorders caused by dysregulated immune responses in genetically predisposed individuals. Genetic markers are associated with disease phenotype and long-term evolution, but their value in everyday clinical practice is limited at the moment. IBD has a clear immunological background and interleukins play key role in the process. Almost 130 original papers were revised including meta-analysis. It is clear these data are very important for understanding the base of the disease, especially in terms of clinical utility and validity, but text often do not available for the doctors use these in the clinical practice nowadays. We conducted a systematic review of the current literature on interleukin and interleukin receptor gene polymorphisms associated with IBD, performing an electronic search of PubMed Database from publications of the last 10 years, and used the following medical subject heading terms and/or text words: IBD, CD, UC, interleukins and polymorphisms.

Long-term prognosis of crohn's disease and its temporal change between 1981 and 2012: a hospital-based cohort study from Korea

BACKGROUND

To date, no large-scale studies have evaluated the prognosis of Crohn's disease (CD) over a period of 3 decades in non-Caucasian populations. The aims of this study were to update the current information on the long-term prognosis of CD using a large series of patients and to evaluate changes in treatment paradigms over time and their impact on the prognosis of CD in Korea.

METHODS

We retrospectively analyzed 2043 Korean patients with CD who visited the Asan Medical Center. The study subjects were divided into 3 groups according to the year of diagnosis (cohort 1: 1981-2000, cohort 2: 2001-2005, and cohort 3: 2006-2012).

RESULTS

Azathioprine/6-mercaptopurine and anti-tumor necrosis factor agents have been used increasingly more frequently and earlier over the past 30 years, with a 5-year cumulative probability of prescription of 28.9% and 1.4%, respectively, in cohort 1 and 88.1% and 23.7%, respectively, in cohort 3 (P < 0.001). A total of 726 patients (35.5%) underwent intestinal resection, with a cumulative probability of intestinal resection 10, 20, and 30 years after diagnosis of 43.5%, 70.0%, and 76.1%, respectively. The cumulative probability of surgery was significantly lower in cohort 3 than in cohort 1 (P = 0.012). Early use of azathioprine/6-mercaptopurine was significantly associated with delayed need for intestinal resection by multivariate Cox analysis (hazard ratio: 0.63, 95% confidence interval: 0.46-0.85).

CONCLUSIONS

Korean patients with CD may have a similar clinical course to Westerners, as indicated by the intestinal resection rate. The surgery rate has decreased over time, and early use of azathioprine/6-mercaptopurine was related to its decrease.

Genome-wide association study of Crohn's disease in Koreans revealed three new susceptibility loci and common attributes of genetic susceptibility across ethnic populations

OBJECTIVE

Crohn's disease (CD) is an intractable inflammatory bowel disease (IBD) of unknown cause. Recent meta-analysis of the genome-wide association studies (GWAS) and Immunochip data identified 163 susceptibility loci to IBD in Caucasians, however there are limited studies in other populations.

METHODS

We performed a GWAS and two validation studies in the Korean population comprising a total of 2311 patients with CD and 2442 controls.

RESULTS

We confirmed four previously reported loci: TNFSF15, IL23R, the major histocompatibility complex region, and the RNASET2-FGFR1OP-CCR6 region. We identified three new susceptibility loci at genome-wide significance: rs6856616 at 4p14 (OR=1.43, combined p=3.60×10(-14)), rs11195128 at 10q25 (OR=1.42, combined p=1.55×10(-10)) and rs11235667 at 11q13 (OR=1.46, combined p=7.15×10(-9)), implicating ATG16L2 and/or FCHSD2 as novel susceptibility genes for CD. Further analysis of the 11q13 locus revealed a non-synonymous single nucleotide polymorphism (SNP) (R220W/rs11235604) in the evolutionarily conserved region of ATG16L2 with stronger association (OR=1.61, combined p=2.44×10(-12)) than rs11235667, suggesting ATG16L2 as a novel susceptibility gene for CD and rs11235604 to be a potential causal variant of the association. Two of the three SNPs (rs6856616 (p=0.00024) and rs11195128 (p=5.32×10(-5))) showed consistent patterns of association in the International IBD Genetics Consortium dataset. Together, the novel and replicated loci accounted for 5.31% of the total genetic variance for CD risk in Koreans.

CONCLUSIONS

Our study provides new biological insight to CD and supports the complementary value of genetic studies in different populations.

Clinical features and predictors of clinical outcomes in Korean patients with Crohn's disease: a Korean association for the study of intestinal diseases multicenter study

BACKGROUND AND AIM

Although differences in genetic susceptibility and the clinical features of Crohn's disease (CD) have been reported between Asian and Caucasian patients, the disease course and predictors of CD in Asians remains poorly defined. The study therefore aimed to investigate factors predictive of the clinical outcomes of patients with CD in a Korean population.

METHODS

This retrospective multicenter cohort study included 728 Korean CD patients from 13 university hospitals. The first CD-related surgery or need for immunosuppressive or biological agents were regarded as the clinical outcomes of interest.

RESULTS

A total of 126 (17.3%) CD patients underwent CD-related surgery, while 473 (65.0%) and 196 (26.9%) were prescribed thiopurine drugs and infliximab, respectively. Multivariate Cox regression analysis identified current (hazard ratio [HR] = 1.86; P = 0.018) and former smoking habits (HR = 1.78; P = 0.049), stricturing (HR = 2.24; P < 0.001), and penetrating disease behavior at diagnosis (HR = 3.07; P < 0.001) as independent predictors associated with the first CD-related surgery. With respect to immunosuppressive and biological agents, younger age (< 40 years) (HR = 2.17; P < 0.001 and HR = 2.10; P = 0.006, respectively), ileal involvement (HR = 1.36; P = 0.035 and HR = 2.17; P = 0.006, respectively), and perianal disease (HR = 1.42; P = 0.001 and HR = 1.38; P = 0.038, respectively) at diagnosis were significant predictors for the need of these medications.

CONCLUSIONS

In Korean patients with CD, stricturing, penetrating disease behavior, and smoking habits at the time of diagnosis are independent predictors for CD-related surgery. It was also identified that younger age (< 40 years), ileal involvement, and perianal disease at diagnosis are predictive of a need for immunosuppressive or biological agents.

Marked differences of haplotype tagging SNP distribution, linkage, and haplotype profile of IL23 receptor gene in Roma and Hungarian population samples

Polymorphisms of the interleukin-23 receptor (IL23R) gene have been found to play an important role in the development of several autoimmune diseases. We examined five susceptible (rs10889677, rs1004819, rs2201841, rs11805303, rs11209032), one protective (rs7517847) and two neutral variants (rs7530511, rs1884444) of the IL23R gene in pooled DNA of healthy Roma (Gipsy) and Hungarian population samples. Our aim was to determine the genetic variability of the major haplotype tagging polymorphisms, and the haplotype profile of IL23R between the two groups. We analyzed 273 healthy Roma and 253 Hungarian DNA samples using PCR/RFLP assay. Comparing the five susceptible conferring alleles, there were significant increase (p<0.05), while in the protective alleles, there were decrease in the allele frequencies in Roma population (p<0.05). One of the neutral alleles showed increase, the another one did not differ between the two groups. The haplotype analysis of the SNPs revealed fundamentally different association types of SNPs in the two groups; moreover, the frequencies of the various haplotypes also exhibited strong differences, as of ht4 and ht5 haplotypes were significantly higher, whereas the frequencies of ht2 and ht3 haplotypes were significantly lower in the Roma population than in Hungarians (p<0.05). The data presented here show profound differences in the IL23R genetic profiles in the Roma population, that likely has also clinical implications in respect their possible role in the development of certain immunological diseases.

Long-term prognosis of the jejunal involvement of Crohn's disease

GOALS

We investigated the prognosis of Crohn's disease (CD) in Korean patients with jejunal involvement.

BACKGROUND

Although jejunal involvement is considered a poor prognostic factor of CD in whites, it has never been validated in Asian populations.

METHODS

We retrospectively reviewed the medical records of 1403 Korean CD patients (median age at diagnosis, 23 years; male patients, 72.3%; median follow-up duration, 65 mo). Probabilities of medication use, surgery, and hospitalization were analyzed by a Cox proportional hazards model and a Poisson regression model.

RESULTS

Jejunal involvement was observed in 198 of 1403 (14.1%) patients at diagnosis. There were more ileal location (28.3% vs. 20.6%, P<0.001) and stricturing behavior (16.7% vs. 9.4%, P=0.001) in the jejunal group than in the non-jejunal group. In univariate analyses, the cumulative probabilities of treatment with corticosteroids (P=0.014) and thiopurines (P=0.008), the first major surgery (P=0.021), and the first hospitalization (P=0.015) were significantly higher in the jejunal than in the non-jejunal group. In multivariate analyses, jejunal involvement was independently associated with the more common use of corticosteroids [hazard ratio, 1.24; 95% confidence interval (CI), 1.02-1.50] and thiopurines (hazard ratio, 1.26; 95% CI, 1.06-1.49), higher incidence rates of strictureplasties [relative risk (RR), 2.52; 95% CI, 1.60-3.96] and hospitalizations (RR, 1.29; 95% CI, 1.14-1.47), and longer hospitalization duration (RR, 1.30; 95% CI, 1.25-1.34).

CONCLUSIONS

Korean CD patients are more likely to have jejunal involvement than western patients. Jejunal involvement is one of the poor prognostic factors in Korean CD patients, as it is in westerners.

Genome-wide association study of ulcerative colitis in Koreans suggests extensive overlapping of genetic susceptibility with Caucasians

BACKGROUND

Recent genome-wide association studies and meta-analyses have identified 47 susceptibility loci for ulcerative colitis (UC) in Caucasian populations. A previous genome-wide association study of UC in a Japanese population suggested marginal sharing of susceptibility loci between Caucasian and Asian populations. We performed a genome-wide association studies to identify UC susceptibility loci in a Korean population and further comparative study.

METHODS

We analyzed 581,060 autosomal single-nucleotide polymorphisms (SNPs) in 388 individuals with UC and 739 control subjects in the discovery stage. For the validation, 64 suggestive SNPs were analyzed in an additional 417 affected individuals and 732 control subjects.

RESULTS

Three genetic loci were validated for significant association, and all were previously reported in Caucasians including the major histocompatibility complex region (top SNP, rs9271366; P = 1.03 × 10(-18), odds ratio [OR] = 2.10), 16q24.1 (rs16940186; P = 4.39 × 10(-10), OR = 1.56), and RNF186-OTUD3-PLA2G2E at chromosome arm 1p36.13 (top SNP, rs4654903 in OTUD3; P = 7.43 × 10(-9), OR = 0.64). Although failed to reach genome-wide statistical significance, 2 additional loci previously reported in Caucasians including rs17085007 at chromosome arm 13q12 and JAK2 at chromosome arm 9p24 were significant after Bonferroni correction (P(corrected) = 0.0016 and P(corrected) = 0.0056, respectively). FOS, UBE2L3, the JAK2 gene region, and rs1297265 at chromosome arm 21q21.1 likely play a role in both Crohn's disease and UC.

CONCLUSIONS

Our data support the biologic significance of the overlapping loci for UC between Caucasian and Korean populations. Our data suggest that genetic associations for UC tend to overlap more extensively among different ethnic groups than those for Crohn's disease, which shows well-established dependence on ethnicity.

Genetics of inflammatory bowel diseases: a comparison between Western and Eastern perspectives

Inflammatory bowel disease (IBD) is a chronic relapsing intestinal inflammatory disorder with unidentified causes. Currently, studies indicate that IBD results from a complex interplay between various genetic and environmental factors that produce intestinal inflammation. However, these factors may differ for Asians and Caucasians. Thus, differences in epidemiology, genetic variants, and clinical phenotypes of IBD have been observed between the two populations. Understanding the discrepancies between data from populations with different genetic backgrounds and environmental factors may reveal fundamental aspects of IBD pathogenesis. Accordingly, this review will summarize the current knowledge of IBD genetics studied in Asian countries and compare it with that from Western countries, with special focus on innate bacterial sensing, autophagy, and the interleukin-23 receptor-T helper cell 17 pathway. The epigenetic nature of IBD pathogenesis as well as the pharmacogenetics related to the use of immunomodulators will also be briefly covered.

Phenotype-genotype profiles in Crohn's disease predicted by genetic markers in autophagy-related genes (GOIA study II)

BACKGROUND

About 70 loci are associated with susceptibility to Crohn's disease (CD), particularly in pathways of innate immunity, autophagy, and pathogen recognition. Phenotype-genotype associations are inconsistent.

METHODS

CD susceptibility polymorphisms ATG16L1 rs2241880, ICAM1 rs5498, IL4 rs2070874, IL17F rs763780, IRGM rs13361189, ITLN1 rs2274910, LRRK2 rs11175593, and TLR4 rs4986790 were genotyped in a Portuguese population (511 CD patients, 626 controls) and assessed for association with CD clinical characteristics.

RESULTS

There is a significant association of CD with the single nucleotide polymorphisms (SNPs) in ATG16L1 (odds ratio [OR] 1.36 [1.15-1.60], P = 2.7 × 10(-6) for allele G), IRGM (OR 1.56 [1.21-1.93], P = 3.9 × 10(-4) for allele C), and ITLN1 (OR 1.55 [1.28-1.88], P = 4.9 × 10(-4) for allele C). These SNPs are associated with ileal location (OR, respectively, 1.49, 1.52, and 1.70), ileocolonic location (OR, respectively, 1.31, 1.57, and 1.68), and involvement of the upper digestive tract (OR, respectively for ATG16L1 and IRGM, 1.96 and 1.95). The risk genotype GG in ATG16L1 is associated with patients who respond to steroids (OR 1.89), respond to immunosuppressants (OR 1.77), and to biologic therapy (OR 1.89). The SNPs in ITLN1 and IRGM are both associated with a positive response to biologic therapy. The risk for ileal, ileocolonic, and upper digestive tract locations increases with the number of risk alleles (OR for three alleles, respectively, 7.10, 3.54, and 12.07); the OR for positive response to biologic therapy is 3.66.

CONCLUSIONS

A multilocus approach using autophagy-related genes provides insight into CD phenotype-genotype associations and genetic markers for predicting therapeutic responses.

Associations between genetic variants in the IRGM gene and inflammatory bowel diseases in the Korean population

BACKGROUND

Recent European ancestry genome-wide association studies have identified genetic variants of IRGM as significant susceptibility loci for Crohn's disease (CD). Therefore, we investigated whether genetic variants of IRGM confer genetic susceptibility to CD or ulcerative colitis (UC) and evaluated the genotype-phenotype associations in the Korean population.

METHODS

This study included 510 inflammatory bowel disease (IBD) patients (253 patients with CD and 257 with UC) and 520 healthy controls in Koreans. Initially, we performed direct sequencing analysis to identify unique IRGM single nucleotide polymorphisms (SNPs). Three selected haplotype-tagging SNPs and one risk locus (rs72553867, rs10065172, rs4958847, and rs12654043) within the IRGM were then geno-typed in patients and controls.

RESULTS

IRGM SNP rs10065172 was significantly associated with CD susceptibility in terms of allelic frequency (P = 0.004; odds ratio [OR] = 1.42) and genotype frequency (dominant model, P = 0.008; OR = 1.62). We also found a relationship between SNP rs72553867 and CD susceptibility in the analysis of allelic frequency (P = 0.0117; OR = 0.67) and genotype frequency (dominant model, P = 0.002; OR = 0.55). In addition, we observed that the association of CD with rs10065172 became stronger in patients with younger age at diagnosis (≤ 20 years) or male gender. However, there was no significant association between the four SNPs and UC susceptibility.

CONCLUSIONS

This is the first study to identify SNP rs10065172 and rs72553867 in IRGM as principal CD susceptibility loci in an Asian population.

The role of autophagy in Crohn's disease

(Macro)-autophagy is a homeostatic process by which eukaryotic cells dispose of protein aggregates and damaged organelles. Autophagy is also used to degrade micro-organisms that invade intracellularly in a process termed xenophagy. Genome-wide association scans have recently identified autophagy genes as conferring susceptibility to Crohn’s disease (CD), one of the chronic inflammatory bowel diseases, with evidence suggesting that CD arises from a defective innate immune response to enteric bacteria. Here we review the emerging role of autophagy in CD, with particular focus on xenophagy and enteric E. coli strains with an adherent and invasive phenotype that have been consistently isolated from CD patients with ileal disease.

Inflammatory bowel disease in Asia: a systematic review

The incidence and prevalence of inflammatory bowel diseases (IBD), Crohn's disease (CD) and ulcerative colitis (UC), are lower in Asia than in the West. However, across Asia the incidence and prevalence of IBD has increased rapidly over the last two to four decades. These changes may relate to increased contact with the West, westernization of diet, increasing antibiotics use, improved hygiene, vaccinations, or changes in the gut microbiota. Genetic factors also differ between Asians and the Caucasians. In Asia, UC is more prevalent than CD, although CD incidence is rapidly increasing in certain areas. There is a male predominance of CD in Asia, but a trend towards equal sex distribution for UC. IBD is diagnosed at a slightly older age than in the West, and there is rarely a second incidence peak as in the West. A positive family history is much less common than in the West, as are extra-intestinal disease manifestations. There are clear ethnic differences in incidence within countries in Asia, and an increased incidence in IBD in migrants from Asia to the West. Research in Asia, an area of rapidly changing IBD epidemiology, may lead to the discovery of critical etiologic factors that lead to the development of IBD.

Genetics of inflammatory bowel disease in Asia: systematic review and meta-analysis

BACKGROUND

Inflammatory bowel diseases (IBD) result from an interaction between genetic and environmental factors. Preliminary findings suggest that susceptibility genes differ between IBD patients in Asia and the West. We aimed to evaluate disease-predisposing genes in Asian IBD patients.

METHODS

A systematic review and meta-analysis were performed of published studies from 1950 to 2010 using keyword searches in MEDLINE, EMBASE, EBM Reviews, and BIOSIS Previews.

RESULTS

In all, 477 abstracts were identified and data extracted from 93 studies, comprising 17,976 IBD patients and 27,350 age- and sex-matched controls. Major nucleotide oligomerization domain (NOD)-2 variants in Western Crohn's disease (CD) patients were not associated with CD in Han Chinese, Japanese, South Korean, Indian, and Malaysian populations. New NOD2 mutations were, however, associated with CD in Malaysians (JW1), Han Chinese, and Indians (P268S). Autophagy-related protein 16-linked 1 (ATG16L1) was not associated with CD in East Asians (odds ratio [OR] 0.97; 95% confidence interval [CI] 0.84-1.13). Interleukin (IL)-23R was associated with CD in South Koreans (OR 1.8; 95% CI 1.16-2.82) and a single nucleotide polymorphism in IL-23R (Gly149Arg) was protective of CD in Han Chinese (OR 0.3; 95% CI 0.15-0.60). Tumor necrosis factor (TNF) superfamily gene-15 (SF15) polymorphisms were associated with CD (OR 2.68; 95% CI 1.86-3.86), while TNF-308 polymorphisms (OR 1.82; 95% CI 1.15-2.9), cytotoxic T lymphocyte antigen (CTLA)-4 (OR 2.75; 95% CI 1.22-6.22) and MICA allele (OR 2.41; 95% CI 1.89-3.07) were associated with ulcerative colitis in Asians.

CONCLUSIONS

Genetic mutations of IBD in Asians differ from Caucasians. New mutations and susceptibility genes identified in Asian IBD patients provide an opportunity to explore new disease-associated mechanisms in this population of rising incidence.

Potential role of a navigator gene NAV3 in colorectal cancer

Background:

The recently described navigator proteins have a multifaceted role in cytoskeletal dynamics. We report here on the relevance of one of them, navigator 3 (NAV3), in colorectal cancer (CRC).

Methods:

We analysed changes in chromosome 12 and NAV3 copy number in CRC/adenoma samples of 59 patients and in 6 CRC cell lines, using fluorescence in situ hybridisation, loss of heterozygosity, and array-CGH. NAV3 target genes were identified by siRNA depletion, expression arrays, and immunohistochemistry.

Results:

NAV3 deletion and chromosome 12 polysomy were detected in 30 and 70% of microsatellite stability (MSS) carcinomas, in 23 and 30% of adenomas and in four of six CRC cell lines. NAV3 amplification was found in 25% of MSS samples. NAV3 alterations correlated with lymph node metastasis. In normal colon cells, NAV3 silencing induced upregulation of interleukin 23 receptor (IL23R) and gonadotropin releasing hormone receptor. In MSS and microsatellite instability tumours, IL23R immunoreactivity correlated with Dukes’ staging and lymph node metastases, whereas nuclear beta-catenin correlated with lymph node metastases only.

Conclusion:

NAV3 copy number changes are frequent in CRC and in adenomas, and upregulation of IL23R, following NAV3 silencing, strongly correlates with Dukes’ staging and lymph node metastases. This suggests that NAV3 has a role in linking tissue inflammation to cancer development in the colon.